1.
Micrograph
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A micrograph or photomicrograph is a photograph or digital image taken through a microscope or similar device to show a magnified image of an item. This is opposed to an image, which is at a scale that is visible to the naked eye. Micrography is the practice or art of using microscopes to make photographs, a micrograph contains extensive details that form the features of a microstructure. The neuropathologist Solomon C. Fuller designed and created the first photomicrograph in 1900, micrographs are widely used in all fields of microscopy. A light micrograph or photomicrograph is a micrograph prepared using an optical microscope, at a basic level, photomicroscopy may be performed simply by hooking up a regular camera to a microscope, thereby enabling the user to take photographs at reasonably high magnification. Roman Vishniac was a pioneer in the field of photomicroscopy, specializing in the photography of living creatures in full motion and he also made major developments in light-interruption photography and color photomicroscopy. An electron micrograph is a micrograph prepared using an electron microscope, however, the term electron micrograph is not used in electron microscopy. Digital micrography is a digital picture obtained either directly with a microscope or by scanning of a photomicrograph, digital micrographs are now commonly obtained using a USB microscope attached directly to a home computer or laptop. Today, an add-on three-in-one macro lens which has capability to take wide-angle, fish-eye and macro with 7x, 14x, micrographs usually have micron bars, or magnification ratios, or both. Magnification is a ratio between size of object on a picture and its real size, unfortunately, magnification is somewhat a misleading parameter. It depends on a size of a printed picture. Editors of journals and magazines routinely resize a figure to fit the page, a scale bar, or micron bar, is a bar of known length displayed on a picture. The bar can be used for measurements on a picture, when a picture is resized a bar is also resized. If a picture has a bar, the magnification can be easily calculated, ideally, all pictures destined for publication/presentation should be supplied with a scale bar, the magnification ratio is optional. All but one of the micrographs presented on this page do not have a bar, supplied magnification ratios are likely incorrect. The microscope has been used for scientific discovery. It has also linked to the arts since its invention in the 17th century. At first scientists used the microscope to view and draw objects not visible with the unaided eye, early adopters of the microscope, such as Robert Hooke and Antonie van Leeuwenhoek, were excellent illustrators
2.
Paper
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Paper is a thin material produced by pressing together moist fibres of cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets. It is a material with many uses, including writing, printing, packaging, cleaning. The modern pulp and paper industry is global, with China leading its production, the oldest known archaeological fragments of the immediate precursor to modern paper, date to the 2nd century BC in China. The pulp papermaking process is ascribed to Cai Lun, a 2nd-century AD Han court eunuch, with paper as an effective substitute for silk in many applications, China could export silk in greater quantity, contributing to a Golden Age. Because of papers introduction to the West through the city of Baghdad, in the 19th century, industrial manufacture greatly lowered its cost, enabling mass exchange of information and contributing to significant cultural shifts. In 1844, the Canadian inventor Charles Fenerty and the German F. G. Keller independently developed processes for pulping wood fibres, before the industrialisation of the paper production the most common fibre source was recycled fibres from used textiles, called rags. The rags were from hemp, linen and cotton, a process for removing printing inks from recycled paper was invented by German jurist Justus Claproth in 1774. Today this method is called deinking and it was not until the introduction of wood pulp in 1843 that paper production was not dependent on recycled materials from ragpickers. The word paper is etymologically derived from Latin papyrus, which comes from the Greek πάπυρος, although the word paper is etymologically derived from papyrus, the two are produced very differently and the development of the first is distinct from the development of the second. Papyrus is a lamination of natural plant fibres, while paper is manufactured from fibres whose properties have changed by maceration. To make pulp from wood, a chemical pulping process separates lignin from cellulose fibres and this is accomplished by dissolving lignin in a cooking liquor, so that it may be washed from the cellulose, this preserves the length of the cellulose fibres. Paper made from chemical pulps are also known as wood-free papers–not to be confused with paper, this is because they do not contain lignin. The pulp can also be bleached to produce paper, but this consumes 5% of the fibres, chemical pulping processes are not used to make paper made from cotton. There are three main chemical pulping processes, the process dates back to the 1840s and it was the dominant method extent before the second world war. Most pulping operations using the process are net contributors to the electricity grid or use the electricity to run an adjacent paper mill. Another advantage is that this process recovers and reuses all inorganic chemical reagents, soda pulping is another specialty process used to pulp straws, bagasse and hardwoods with high silicate content. There are two major mechanical pulps, thermomechanical pulp and groundwood pulp, in the TMP process, wood is chipped and then fed into steam heated refiners, where the chips are squeezed and converted to fibres between two steel discs. In the groundwood process, debarked logs are fed into grinders where they are pressed against rotating stones to be made into fibres
3.
Ultraviolet
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Ultraviolet is an electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays. UV radiation constitutes about 10% of the light output of the Sun. It is also produced by electric arcs and specialized lights, such as lamps, tanning lamps. Consequently, the effects of UV are greater than simple heating effects. Suntan, freckling and sunburn are familiar effects of over-exposure, along with risk of skin cancer. Living things on dry land would be damaged by ultraviolet radiation from the Sun if most of it were not filtered out by the Earths atmosphere. More-energetic, shorter-wavelength extreme UV below 121 nm ionizes air so strongly that it is absorbed before it reaches the ground, Ultraviolet is also responsible for the formation of bone-strengthening vitamin D in most land vertebrates, including humans. The UV spectrum thus has both beneficial and harmful to human health. Ultraviolet rays are invisible to most humans, the lens in a human eye ordinarily filters out UVB frequencies or higher, and humans lack color receptor adaptations for ultraviolet rays. Under some conditions, children and young adults can see ultraviolet down to wavelengths of about 310 nm, near-UV radiation is visible to some insects, mammals, and birds. Small birds have a fourth color receptor for ultraviolet rays, this gives birds true UV vision, reindeer use near-UV radiation to see polar bears, who are poorly visible in regular light because they blend in with the snow. UV also allows mammals to see urine trails, which is helpful for animals to find food in the wild. The males and females of some species look identical to the human eye. Ultraviolet means beyond violet, violet being the color of the highest frequencies of visible light, Ultraviolet has a higher frequency than violet light. He called them oxidizing rays to emphasize chemical reactivity and to them from heat rays. The terms chemical and heat rays were eventually dropped in favour of ultraviolet and infrared radiation, in 1878 the effect of short-wavelength light on sterilizing bacteria was discovered. By 1903 it was known the most effective wavelengths were around 250 nm, in 1960, the effect of ultraviolet radiation on DNA was established. The discovery of the ultraviolet radiation below 200 nm, named vacuum ultraviolet because it is absorbed by air, was made in 1893 by the German physicist Victor Schumann
4.
Mitochondrion
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The mitochondrion is a double membrane-bound organelle found in all eukaryotic organisms. Some cells in multicellular organisms may however lack them. A number of organisms, such as microsporidia, parabasalids. To date, only one eukaryote, Monocercomonoides, is known to have completely lost its mitochondria, the word mitochondrion comes from the Greek μίτος, mitos, thread, and χονδρίον, chondrion, granule or grain-like. Mitochondria generate most of the supply of adenosine triphosphate, used as a source of chemical energy. Mitochondria are commonly between 0.75 and 3 μm in diameter but vary considerably in size and structure, unless specifically stained, they are not visible. Mitochondrial biogenesis is in turn temporally coordinated with these cellular processes, Mitochondria have been implicated in several human diseases, including mitochondrial disorders, cardiac dysfunction, heart failure and autism. The number of mitochondria in a cell can vary widely by organism, tissue, for instance, red blood cells have no mitochondria, whereas liver cells can have more than 2000, The organelle is composed of compartments that carry out specialized functions. These compartments or regions include the outer membrane, the space, the inner membrane. Although most of a cells DNA is contained in the cell nucleus, mitochondrial proteins vary depending on the tissue and the species. In humans,615 distinct types of protein have been identified from cardiac mitochondria, the mitochondrial proteome is thought to be dynamically regulated. The first observations of structures that probably represented mitochondria were published in the 1840s. Richard Altmann, in 1890, established them as cell organelles, the term mitochondria was coined by Carl Benda in 1898. Leonor Michaelis discovered that Janus green can be used as a stain for mitochondria in 1900. Benjamin F. Kingsbury, in 1912, first related them with cell respiration, in 1913, particles from extracts of guinea-pig liver were linked to respiration by Otto Heinrich Warburg, which he called grana. Warburg and Heinrich Otto Wieland, who had postulated a similar particle mechanism. It was not until 1925, when David Keilin discovered cytochromes, in the following years, the mechanism behind cellular respiration was further elaborated, although its link to the mitochondria was not known. The introduction of tissue fractionation by Albert Claude allowed mitochondria to be isolated from other cell fractions, in 1946, he concluded that cytochrome oxidase and other enzymes responsible for the respiratory chain were isolated to the mitchondria
5.
Lysosome
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A lysosome is a membrane-bound organelle found in nearly all animal cells. They are spherical vesicles which contain hydrolytic enzymes that can break down all kinds of biomolecules. Simply stated, a lysosome is a type of vesicle with specific composition, the lumens pH is optimal for the enzymes involved in hydrolysis, analogous to the activity of the stomach. Besides degradation of polymers, the lysosome is involved in cell processes, including secretion, plasma membrane repair, cell signaling. The lysosomes also act as the disposal system of the cell by digesting unwanted materials in the cytoplasm. Material from the outside of the cell is taken-up through endocytosis and their sizes can be very different—the biggest ones can be more than 10 times bigger than the smallest ones. They were discovered and named by Belgian biologist Christian de Duve, lysosomes are known to contain more than 60 different enzymes. Enzymes of the lysosomes are synthesised in the endoplasmic reticulum. The enzymes are imported from the Golgi apparatus in small vesicles, enzymes destined for a lysosome are specifically tagged with the molecule mannose 6-phosphate, so that they are properly sorted into acidified vesicles. Synthesis of lysosomal enzymes is controlled by nuclear genes, mutations in the genes for these enzymes are responsible for more than 30 different human genetic diseases, which are collectively known as lysosomal storage diseases. These diseases result from an accumulation of specific substrates, due to the inability to break them down and these genetic defects are related to several neurodegenerative disorders, cancer, cardiovascular diseases, and ageing-related diseases. By 1949, he and his team had focused on the enzyme called glucose 6-phosphatase, which is the first crucial enzyme in sugar metabolism and they already suspected that this enzyme played a key role in regulating blood sugar levels. However, even after a series of experiments, they failed to purify, therefore, they tried a more arduous procedure of cell fractionation, by which cellular components are separated based on their sizes using centrifugation. They succeeded in detecting the activity from the microsomal fraction. This was the step in the serendipitous discovery of lysosomes. To estimate this enzyme activity, they used that of standardised enzyme acid phosphatase, one day, the enzyme activity of purified cell fractions which had been refrigerated for five days was measured. Surprisingly, the activity was increased to normal of that of the fresh sample. They described this membrane-like barrier as a saclike structure surrounded by a membrane, Novikoff from the University of Vermont visited de Duve´s laboratory, and successfully obtained the first electron micrographs of the new organelle
6.
Fluorophore
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A fluorophore is a fluorescent chemical compound that can re-emit light upon light excitation. Fluorophores typically contain several combined aromatic groups, or planar or cyclic molecules with several π bonds, fluorophores are sometimes used alone, as a tracer in fluids, as a dye for staining of certain structures, as a substrate of enzymes, or as a probe or indicator. More generally they are bonded to a macromolecule, serving as a marker for affine or bioactive reagents. Fluorophores are notably used to stain tissues, cells, or materials in a variety of methods, i. e. fluorescent imaging. Fluorescein, by its amine reactive isothiocyanate derivative FITC, has one of the most popular fluorophores. From antibody labeling, the applications have spread to nucleic acids thanks to, other historically common fluorophores are derivatives of rhodamine, coumarin, and cyanine. The fluorophore absorbs light energy of a wavelength and re-emits light at a longer wavelength. Wavelengths of maximum absorption and emission are the terms used to refer to a given fluorophore. The excitation wavelength spectrum may be a narrow or broader band. The emission spectrum is usually sharper than the spectrum, and it is of a longer wavelength. Excitation energies range from ultraviolet through the spectrum, and emission energies may continue from visible light into the near infrared region. Quantum yield, efficiency of the transferred from incident light to emitted fluorescence Lifetime. It refers to the time taken for a population of excited fluorophores to decay to 1/e of the original amount, stokes shift, difference between the maximum excitation and maximum emission wavelengths. These characteristics drive other properties, including the photobleaching or photoresistance, other parameters should be considered, as the polarity of the fluorophore molecule, the fluorophore size and shape, and other factors can change the behavior of fluorophores. Fluorophores can also be used to quench the fluorescence of other fluorescent dyes or to relay their fluorescence at longer wavelength See more on fluorescence principle. Fluorescence particles are not considered fluorophores, the size of the fluorophore might sterically hinder the tagged molecule, and affect the fluorescence polarity. Fluorophore molecules could be either utilized alone, or serve as a fluorescent motif of a functional system, fluorescent proteins GFP, YFP and RFP can be attached to other specific proteins to form a fusion protein, synthesized in cells after transfection of a suitable plasmid carrier. Oxazine derivatives, Nile red, Nile blue, cresyl violet, oxazine 170, acridine derivatives, proflavin, acridine orange, acridine yellow, etc
7.
Flavin group
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Flavin is the common name for a group of organic compounds based on pteridine, formed by the tricyclic heterocycle isoalloxazine. The biochemical source is the vitamin riboflavin and it is in one or the other of these forms that flavin is present as a prosthetic group in flavoproteins. The flavin group is capable of undergoing oxidation-reduction reactions, and can accept one electron in a two-step process or two electrons at once. In the form of FADH2, it is one of the cofactors that can transfer electrons to the electron transfer chain, FADH and FADH2 are reduced forms of FAD. FADH2 is produced as a group in succinate dehydrogenase, an enzyme involved in the citric acid cycle. In oxidative phosphorylation, two molecules of FADH2 typically yield 1.5 ATP each, or three ATP combined, flavin mononucleotide is a prosthetic group found in, among other proteins, NADH dehydrogenase, E. coli nitroreductase and old yellow enzyme. Pteridine Pterin Deazaflavin Voet, D. Voet, J. G
8.
Collagen
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Collagen /ˈkɒlədʒᵻn/ is the main structural protein in the extracellular space in the various connective tissues in animal bodies. As the main component of tissue, it is the most abundant protein in mammals. Depending upon the degree of mineralization, collagen tissues may be rigid, compliant, Collagen, in the form of elongated fibrils, is mostly found in fibrous tissues such as tendons, ligaments and skin. It is also abundant in corneas, cartilage, bones, blood vessels, the gut, intervertebral discs, in muscle tissue, it serves as a major component of the endomysium. Collagen constitutes one to two percent of muscle tissue, and accounts for 6% of the weight of strong, tendinous muscles, the fibroblast is the most common cell that creates collagen. Gelatin, which is used in food and industry, is collagen that has been irreversibly hydrolyzed, Collagen also has many medical uses in treating complications of the bones and skin. The name collagen comes from the Greek κόλλα, meaning glue and this refers to the compounds early use in the process of boiling the skin and sinews of horses and other animals to obtain glue. Collagen occurs in places throughout the body. Over 90% of the collagen in the body, however, is type I. So far,28 types of collagen have been identified and described, type IV, forms basal lamina, the epithelium-secreted layer of the basement membrane. Type V, cell surfaces, hair and placenta The collagenous cardiac skeleton which includes the four valve rings, is histologically, elastically and uniquely bound to cardiac muscle. The cardiac skeleton also includes the separating septa of the heart chambers – the interventricular septum, Collagen contribution to the measure of cardiac performance summarily represents a continuous torsional force opposed to the fluid mechanics of blood pressure emitted from the heart. With support from collagen, atrial fibrillation should never deteriorate to ventricular fibrillation, Collagen is layered in variable densities with cardiac muscle mass. The mass, distribution, age and density of collagen all contribute to the required to move blood back. Individual cardiac valvular leaflets are folded into shape by specialized collagen under variable pressure, gradual calcium deposition within collagen occurs as a natural function of aging. Pathology of the underpinning of the heart is understood within the category of connective tissue disease. Collagen has been used in cosmetic surgery, as a healing aid for burn patients for reconstruction of bone and a wide variety of dental, orthopedic. Both human and bovine collagen is used as dermal fillers for treatment of wrinkles
9.
Amino acid
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Amino acids are organic compounds containing amine and carboxyl functional groups, along with a side chain specific to each amino acid. The key elements of an acid are carbon, hydrogen, oxygen. About 500 amino acids are known and can be classified in many ways, in the form of proteins, amino acids comprise the second-largest component of human muscles, cells and other tissues. Outside proteins, amino acids perform critical roles in such as neurotransmitter transport. In biochemistry, amino acids having both the amine and the acid groups attached to the first carbon atom have particular importance. They are known as 2-, alpha-, or α-amino acids and they include the 22 proteinogenic amino acids, which combine into peptide chains to form the building-blocks of a vast array of proteins. These are all L-stereoisomers, although a few D-amino acids occur in bacterial envelopes, as a neuromodulator, twenty of the proteinogenic amino acids are encoded directly by triplet codons in the genetic code and are known as standard amino acids. The other two are selenocysteine, and pyrrolysine, pyrrolysine and selenocysteine are encoded via variant codons, for example, selenocysteine is encoded by stop codon and SECIS element. N-formylmethionine is generally considered as a form of methionine rather than as a separate proteinogenic amino acid, codon–tRNA combinations not found in nature can also be used to expand the genetic code and create novel proteins known as alloproteins incorporating non-proteinogenic amino acids. Many important proteinogenic and non-proteinogenic amino acids also play critical roles within the body. Nine proteinogenic amino acids are called essential for humans because they cannot be created from other compounds by the human body, others may be conditionally essential for certain ages or medical conditions. Essential amino acids may also differ between species, because of their biological significance, amino acids are important in nutrition and are commonly used in nutritional supplements, fertilizers, and food technology. Industrial uses include the production of drugs, biodegradable plastics, the first few amino acids were discovered in the early 19th century. In 1806, French chemists Louis-Nicolas Vauquelin and Pierre Jean Robiquet isolated a compound in asparagus that was subsequently named asparagine, cystine was discovered in 1810, although its monomer, cysteine, remained undiscovered until 1884. Glycine and leucine were discovered in 1820, usage of the term amino acid in the English language is from 1898. Proteins were found to yield amino acids after enzymatic digestion or acid hydrolysis, in the structure shown at the top of the page, R represents a side chain specific to each amino acid. The carbon atom next to the group is called the α–carbon. Amino acids containing an amino group bonded directly to the alpha carbon are referred to as amino acids
10.
Tryptophan
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Tryptophan is an α-amino acid that is used in the biosynthesis of proteins. It contains a group, an α-carboxylic acid group. It is essential in humans, meaning the body cannot synthesize it, tryptophan is also a precursor to the neurotransmitters serotonin and melatonin. Like other amino acids, tryptophan is a zwitterion at physiological pH where the group is protonated. The isolation of tryptophan was first reported by Frederick Hopkins in 1901 through hydrolysis of casein, from 600 grams of crude casein one obtains 4-8 grams of tryptophan. As an essential amino acid, tryptophan is not synthesized from more basic substances in humans and other animals, the ring of the ribose moiety is opened and subjected to reductive decarboxylation, producing indole-3-glycerinephosphate, this, in turn, is transformed into indole. In the last step, tryptophan synthase catalyzes the formation of tryptophan from indole and these strains carry either mutations that prevent the reuptake of aromatic amino acids or multiple/overexpressed trp operons. The conversion is catalyzed by the tryptophan synthase. For many organisms, tryptophan is needed to prevent illness or death, amino acids, including tryptophan, act as building blocks in protein biosynthesis, and proteins are required to sustain life. In addition, tryptophan functions as a precursor for the following compounds, Serotonin. Serotonin, in turn, can be converted to melatonin, via N-acetyltransferase and 5-hydroxyindole-O-methyltransferase activities, niacin, also known as vitamin B3, is synthesized from tryptophan via kynurenine and quinolinic acids as key biosynthetic intermediates. The disorder fructose malabsorption causes improper absorption of tryptophan in the intestine, reduced levels of tryptophan in the blood, some studies did not find reduced tryptophan in cases of lactose maldigestion. In bacteria that synthesize tryptophan, high levels of this amino acid activate a repressor protein. Binding of this repressor to the tryptophan operon prevents transcription of downstream DNA that codes for the involved in the biosynthesis of tryptophan. So high levels of tryptophan prevent tryptophan synthesis through a feedback loop and. The genetic organisation of the trp operon thus permits tightly regulated, tryptophan is a routine constituent of most protein-based foods or dietary proteins. Contrary to the belief that turkey contains an abundance of tryptophan. A common assertion in the US is that consumption of turkey meat results in drowsiness
11.
Tyrosine
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Tyrosine or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is an amino acid with a polar side group. Its codons are UAC and UAU, the word tyrosine is from the Greek tyros, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese. It is called tyrosyl when referred to as a group or side chain. Aside from being an amino acid, tyrosine has a special role by virtue of the phenol functionality. It occurs in proteins that are part of signal transduction processes and it functions as a receiver of phosphate groups that are transferred by way of protein kinases. Phosphorylation of the group changes the activity of the target protein. A tyrosine residue plays a important role in photosynthesis. In chloroplasts, it acts as a donor in the reduction of oxidized chlorophyll. In this process, it loses the hydrogen atom of its phenolic OH-group and this radical is subsequently reduced in the photosystem II by the four core manganese clusters. The Recommended Dietary Allowance for phenylalanine and tyrosine is 33 mg per kilogram of body weight, for a 70 kg person this is 2310 mg. For example, the white of an egg has about 250 mg per egg, in plants and most microorganisms, tyr is produced via prephenate, an intermediate on the shikimate pathway. Mammals synthesize tyrosine from the amino acid phenylalanine, which is derived from food. The conversion of phe to tyr is catalyzed by the enzyme phenylalanine hydroxylase and this enzyme catalyzes the reaction causing the addition of a hydroxyl group to the end of the 6-carbon aromatic ring of phenylalanine, such that it becomes tyrosine. Some of the residues can be tagged with a phosphate group by protein kinases. In its phosphorylated form, tyrosine is called phosphotyrosine, tyrosine phosphorylation is considered to be one of the key steps in signal transduction and regulation of enzymatic activity. Phosphotyrosine can be detected through specific antibodies, tyrosine residues may also be modified by the addition of a sulfate group, a process known as tyrosine sulfation. Tyrosine sulfation is catalyzed by tyrosylprotein sulfotransferase, like the phosphotyrosine antibodies mentioned above, antibodies have recently been described that specifically detect sulfotyrosine
12.
Phenylalanine
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Phenylalanine is an α-amino acid with the formula C 9H 11NO2. It can be viewed as a benzyl group substituted for the group of alanine. This essential amino acid is classified as neutral, and nonpolar because of the inert, the L-isomer is used to biochemically form proteins, coded for by DNA. The codons for L-phenylalanine are UUU and UUC, Phenylalanine is a precursor for tyrosine, the monoamine neurotransmitters dopamine, norepinephrine, and epinephrine, and the skin pigment melanin. Phenylalanine is found naturally in the breast milk of mammals and it is used in the manufacture of food and drink products and sold as a nutritional supplement for its reputed analgesic and antidepressant effects. It is a precursor to the neuromodulator phenethylamine, a commonly used dietary supplement. The first description of phenylalanine was made in 1879, when Schulze and Barbieri identified a compound with the formula, C9H11NO2. In 1882, Erlenmeyer and Lipp first synthesized phenylalanine from phenylacetaldehyde, hydrogen cyanide, the genetic codon for phenylalanine was first discovered by J. Heinrich Matthaei and Marshall W. Nirenberg in 1961. This discovery helped to establish the nature of the relationship that links information stored in genomic nucleic acid with protein expression in the living cell. As an essential amino acid, phenylalanine is not synthesized de novo in humans and other animals, good sources of phenylalanine are eggs, chicken, liver, beef, milk, and soybeans. L-Phenylalanine is biologically converted into L-tyrosine, another one of the DNA-encoded amino acids, L-tyrosine in turn is converted into L-DOPA, which is further converted into dopamine, norepinephrine, and epinephrine. The latter three are known as the catecholamines, Phenylalanine uses the same active transport channel as tryptophan to cross the blood–brain barrier. The corresponding enzymes in for those compounds are the amino acid hydroxylase family. Phenylalanine is the compound used in the synthesis of flavonoids. Lignan is derived from phenylalanine and from tyrosine, Phenylalanine is converted to cinnamic acid by the enzyme phenylalanine ammonia-lyase. The genetic disorder phenylketonuria is the inability to metabolize phenylalanine because of a lack of the enzyme phenylalanine hydroxylase, individuals with this disorder are known as phenylketonurics and must regulate their intake of phenylalanine. A variant form of phenylketonuria called hyperphenylalaninemia is caused by the inability to synthesize a cofactor called tetrahydrobiopterin, pregnant women with hyperphenylalaninemia may show similar symptoms of the disorder but these indicators will usually disappear at the end of gestation. Pregnant women with PKU must control their blood phenylalanine levels even if the fetus is heterozygus for the defective gene because the fetus could be affected due to hepatic immaturity
13.
Mouse
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A mouse is a small rodent characteristically having a pointed snout, small rounded ears, a body-length scaly tail and a high breeding rate. The best known species is the common house mouse. It is also a popular pet, in some places, certain kinds of field mice are locally common. They are known to invade homes for food and shelter, domestic mice sold as pets often differ substantially in size from the common house mouse. This is attributable both to breeding and to different conditions in the wild, the most well known strain, the white lab mouse, has more uniform traits that are appropriate to its use in research. The American white-footed mouse and the mouse, as well as other common species of mouse-like rodents around the world. These, however, are in other genera, cats, wild dogs, foxes, birds of prey, snakes and even certain kinds of arthropods have been known to prey heavily upon mice. Nevertheless, because of its adaptability to almost any environment. Mice, in contexts, can be considered vermin which are a major source of crop damage, causing structural damage. In North America, breathing dust that has come in contact with mouse excrement has been linked to hantavirus, primarily nocturnal animals, mice compensate for their poor eyesight with a keen sense of hearing, and rely especially on their sense of smell to locate food and avoid predators. Mice build intricate burrows in the wild and these burrows typically have long entrances and are equipped with escape tunnels or routes. In at least one species, the design of a burrow is a genetic trait. Breeding onset is at about 50 days of age in females and males, although females may have their first estrus at 25–40 days. Mice are polyestrous and breed year round, ovulation is spontaneous, the duration of the estrous cycle is 4–5 days and estrus itself lasts about 12 hours, occurring in the evening. Vaginal smears are useful in timed matings to determine the stage of the estrous cycle, mating is usually nocturnal and may be confirmed by the presence of a copulatory plug in the vagina up to 24 hours post-copulation. The presence of sperm on a smear is also a reliable indicator of mating. Female mice housed together tend to go into anestrus and do not cycle, if exposed to a male mouse or the pheromones of a male mouse, most of the females will go into estrus in about 72 hours. This synchronization of the cycle is known as the Whitten effect
14.
Fluorescence microscope
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The specimen is illuminated with light of a specific wavelength which is absorbed by the fluorophores, causing them to emit light of longer wavelengths. The illumination light is separated from the much weaker emitted fluorescence through the use of an emission filter. Typical components of a microscope are a light source, the excitation filter, the dichroic mirror. The filters and the dichroic beamsplitter are chosen to match the spectral excitation and emission characteristics of the used to label the specimen. In this manner, the distribution of a fluorophore is imaged at a time. Multi-color images of types of fluorophores must be composed by combining several single-color images. Most fluorescence microscopes in use are epifluorescence microscopes, where excitation of the fluorophore and these microscopes are widely used in biology and are the basis for more advanced microscope designs, such as the confocal microscope and the total internal reflection fluorescence microscope. The majority of fluorescence microscopes, especially used in the life sciences, are of the epifluorescence design shown in the diagram. Light of the wavelength is focused on the specimen through the objective lens. Fluorescence microscopy requires intense, near-monochromatic, illumination which some widespread light sources, four main types of light source are used, including xenon arc lamps or mercury-vapor lamps with an excitation filter, lasers, supercontinuum sources, and high-power LEDs. In order for a sample to be suitable for fluorescence microscopy it must be fluorescent, there are several methods of creating a fluorescent sample, the main techniques are labelling with fluorescent stains or, in the case of biological samples, expression of a fluorescent protein. Alternatively the intrinsic fluorescence of a sample can be used, as a result, there is a diverse range of techniques for fluorescent staining of biological samples. Many fluorescent stains have been designed for a range of biological molecules, some of these are small molecules which are intrinsically fluorescent and bind a biological molecule of interest. Major examples of these are nucleic acid stains like DAPI and Hoechst and DRAQ5 and DRAQ7 which all bind the minor groove of DNA, others are drugs or toxins which bind specific cellular structures and have been derivatised with a fluorescent reporter. A major example of class of fluorescent stain is phalloidin which is used to stain actin fibres in mammalian cells. Immunofluorescence is a technique which uses the specific binding of an antibody to its antigen in order to label specific proteins or other molecules within the cell. A sample is treated with an antibody specific for the molecule of interest. A fluorophore can be conjugated to the primary antibody
15.
Staining
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Staining is an auxiliary technique used in microscopy to enhance contrast in the microscopic image. Stains and dyes are used in biology and medicine to highlight structures in biological tissues for viewing. Stains may be used to define and examine bulk tissues, cell populations, in biochemistry it involves adding a class-specific dye to a substrate to qualify or quantify the presence of a specific compound. Staining and fluorescent tagging can serve similar purposes, biological staining is also used to mark cells in flow cytometry, and to flag proteins or nucleic acids in gel electrophoresis. Simple staining is staining with only one stain/dye, there are various kinds of multiple staining, many of which are examples of counterstaining, differential staining, or both, including double staining and triple staining. In vivo staining is the process of dyeing living tissues—in vivo means in life, by causing certain cells or structures to take on contrasting colour, their form or position within a cell or tissue can be readily seen and studied. In vitro staining involves colouring cells or structures that have removed from their biological context. Certain stains are often combined to reveal more details and features than a single stain alone, combined with specific protocols for fixation and sample preparation, scientists and physicians can use these standard techniques as consistent, repeatable diagnostic tools. A counterstain is stain that makes cells or structures more visible, for example, crystal violet stains only Gram-positive bacteria in Gram staining. A safranin counterstain is applied that stains all cells, allowing identification of Gram-negative bacteria, while ex vivo, many cells continue to live and metabolize until they are fixed. Some staining methods are based on this property and those stains excluded by the living cells but taken up by the already dead cells are called vital stains. Those that enter and stain living cells are called supravital stains, however, these stains are eventually toxic to the organism, some more so than others. To achieve desired effects, the stains are used in very dilute solutions ranging from 1,5000 to 1,500000, note that many stains may be used in both living and fixed cells. The preparatory steps involved depend on the type of analysis planned, fixation–which may itself consist of several steps–aims to preserve the shape of the cells or tissue involved as much as possible. Sometimes heat fixation is used to kill, adhere, and alter the specimen so it accepts stains, most chemical fixatives generate chemical bonds between proteins and other substances within the sample, increasing their rigidity. Common fixatives include formaldehyde, ethanol, methanol, and/or picric acid, pieces of tissue may be embedded in paraffin wax to increase their mechanical strength and stability and to make them easier to cut into thin slices. Permeabilization involves treatment of cells with a mild surfactant and this treatment dissolves cell membranes, and allows larger dye molecules into the cells interior. Mounting usually involves attaching the samples to a microscope slide for observation
16.
Antibody
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An antibody, also known as an immunoglobulin, is a large, Y-shaped protein produced mainly by plasma cells that is used by the immune system to neutralize pathogens such as bacteria and viruses. The antibody recognizes a molecule of the harmful agent, called an antigen. Each tip of the Y of an antibody contains a paratope that is specific for one particular epitope on an antigen, allowing these two structures to bind together with precision. Using this binding mechanism, an antibody can tag a microbe or a cell for attack by other parts of the immune system. Depending on the antigen, the binding may impede the process causing the disease or may activate macrophages to destroy the foreign substance. The ability of an antibody to communicate with the components of the immune system is mediated via its Fc region. The production of antibodies is the function of the humoral immune system. Antibodies are secreted by B cells of the immune system. In most cases, interaction of the B cell with a T helper cell is necessary to produce full activation of the B cell and, therefore, soluble antibodies are released into the blood and tissue fluids, as well as many secretions to continue to survey for invading microorganisms. Antibodies are glycoproteins belonging to the immunoglobulin superfamily and they constitute most of the gamma globulin fraction of the blood proteins. They are typically made of basic structural units—each with two heavy chains and two small light chains. There are several different types of heavy chains that define the five different types of crystallisable fragments that may be attached to the antigen-binding fragments. The five different types of Fc regions allow antibodies to be grouped into five isotypes, each Fc region of a particular antibody isotype is able to bind to its specific Fc Receptor, thus allowing the antigen-antibody complex to mediate different roles depending on which FcR it binds. The ability of an antibody to bind to its corresponding FcR is further modulated by the structure of the present at conserved sites within its Fc region. The ability of antibodies to bind to FcRs helps to direct the immune response for each different type of foreign object they encounter. For example, IgE is responsible for an allergic response consisting of mast cell degranulation, igEs Fab paratope binds to allergic antigen, for example house dust mite particles, while its Fc region binds to Fc receptor ε. The allergen-IgE-FcRε interaction mediates allergic signal transduction to induce conditions such as asthma and this region is known as the hypervariable region. Each of these variants can bind to a different antigen and this enormous diversity of antibody paratopes on the antigen-binding fragments allows the immune system to recognize an equally wide variety of antigens
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Sample (material)
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In general, a sample is a limited quantity of something which is intended to be similar to and represent a larger amount of that thing. The things could be countable objects such as individual items available as units for sale, an act of obtaining a sample is called sampling, which can be done by a person or automatically. Samples of material can be taken or provided for testing, analysis, inspection, investigation, demonstration, sometimes, sampling may be continuously ongoing. The material may be solid, liquid, gas, material of some characteristics such as gel or sputum, tissue, organisms. Even if a sample is not countable as individual items. A solid sample can come in one or a few pieces, or can be fragmented, granular. A section of a rod, wire, cord, sheeting, samples which are not a solid piece are commonly kept in a container of some sort. In the field of science, a liquid sample taken from a larger amount of liquid is sometimes called an aliquot
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Confocal microscopy
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It enables the reconstruction of three-dimensional structures from sets of images obtained at different depths within a thick object. This technique has gained popularity in the scientific and industrial communities and typical applications are in life sciences, semiconductor inspection, a conventional microscope sees as far into the specimen as the light can penetrate, while a confocal microscope only sees images one depth level at a time. In effect, the CLSM achieves a controlled and highly limited depth of focus, the principle of confocal imaging was patented in 1957 by Marvin Minsky and aims to overcome some limitations of traditional wide-field fluorescence microscopes. In a conventional microscope, the entire specimen is flooded evenly in light from a light source. However, as much of the light from sample fluorescence is blocked at the pinhole, as only one point in the sample is illuminated at a time, 2D or 3D imaging requires scanning over a regular raster in the specimen. The beam is scanned across the sample in the plane by using one or more oscillating mirrors. This scanning method usually has a low latency and the scan speed can be varied. Slower scans provide a better signal-to-noise ratio, resulting in better contrast, the thin optical sectioning possible makes these types of microscopes particularly good at 3D imaging and surface profiling of samples. Successive slices make up a z-stack which can either be processed by software to create a 3D image. Biological samples are treated with fluorescent dyes to make selected objects visible. However, the actual dye concentration can be low to minimize the disturbance of biological systems, also, transgenic techniques can create organisms that produce their own fluorescent chimeric molecules. Spinning-disk confocal microscopes use a series of moving pinholes on a disc to scan spots of light, decreased excitation energy reduces photo-toxicity and photo-bleaching of a sample often making it the preferred system for imaging live cells or organisms. Every pinhole has an associated micro-lens, microlens enhanced confocal microscopes are therefore significantly more sensitive than standard spinning disk systems. Yokogawa Electric invented this technology in 1992, programmable array microscopes use an electronically controlled spatial light modulator that produces a set of moving pinholes. The SLM is a device containing an array of pixels with some property of the pixels that can be adjusted electronically. The SLM contains microelectromechanical mirrors or liquid crystal components, the image is usually acquired by a charge coupled device camera. Each of these classes of confocal microscope have particular advantages and disadvantages, most systems are either optimized for recording speed or high spatial resolution. Confocal laser scanning microscopes can have a programmable sampling density and very high resolutions while Nipkow, imaging frame rates are typically slower for single point laser scanning systems than spinning-disk or PAM systems
19.
Excited state
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In quantum mechanics, an excited state of a system is any quantum state of the system that has a higher energy than the ground state. Excitation is an elevation in energy level above a baseline energy state. In physics there is a technical definition for energy level which is often associated with an atom being raised to an excited state. The temperature of a group of particles is indicative of the level of excitation and this return to a lower energy level is often loosely described as decay and is the inverse of excitation. Long-lived excited states are called metastable. Long-lived nuclear isomers and singlet oxygen are two examples of this, a simple example of this concept comes by considering the hydrogen atom. The ground state of the hydrogen atom corresponds to having the single electron in the lowest possible orbit. By giving the additional energy, the electron is able to move into an excited state. If the photon has too much energy, the electron will cease to be bound to the atom, after excitation the atom may return to the ground state or a lower excited state, by emitting a photon with a characteristic energy. Emission of photons from atoms in excited states leads to an electromagnetic spectrum showing a series of characteristic emission lines An atom in a high excited state is termed Rydberg atom. A system of highly excited atoms can form a long-lived condensed excited state e. g. a condensed phase made completely of excited atoms, hydrogen can also be excited by heat or electricity. This phenomenon has been studied in the case of a gas in some detail. These calculations are more difficult than non-excited state calculations, a further consequence is reaction of the atom in the excited state, as in photochemistry. Excited states give rise to chemical reaction, Rydberg formula Stationary state Repulsive state NASA background information on ground and excited states
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Skin
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Skin is the soft outer tissue covering vertebrates. Other animal coverings, such as the arthropod exoskeleton have different developmental origin, structure, the adjective cutaneous means of the skin. In mammals, the skin is an organ of the system made up of multiple layers of ectodermal tissue. Skin of a different nature exists in amphibians, reptiles, all mammals have some hair on their skin, even marine mammals like whales, dolphins, and porpoises which appear to be hairless. The skin interfaces with the environment and is the first line of defense from external factors, for example, the skin plays a key role in protecting the body against pathogens and excessive water loss. Its other functions are insulation, temperature regulation, sensation, severely damaged skin may heal by forming scar tissue. This is sometimes discoloured and depigmented, the thickness of skin also varies from location to location on an organism. The skin on the palms and the soles of the feet is 4 mm thick, the speed and quality of wound healing in skin is promoted by the reception of estrogen. Primarily, fur augments the insulation the skin provides but can serve as a secondary sexual characteristic or as camouflage. On some animals, the skin is hard and thick. Reptiles and fish have hard scales on their skin for protection. Amphibian skin is not a barrier, especially regarding the passage of chemicals via skin and is often subject to osmosis. For example, a sitting in an anesthetic solution would be sedated quickly. Amphibian skin plays key roles in everyday survival and their ability to exploit a range of habitats. Keratinocytes are the cells, constituting 95% of the epidermis, while Merkel cells, melanocytes. Keratinocytes from the stratum corneum are eventually shed from the surface, the epidermis contains no blood vessels, and cells in the deepest layers are nourished by diffusion from blood capillaries extending to the upper layers of the dermis. The epidermis and dermis are separated by a sheet of fibers called the basement membrane. The dermis is the layer of skin beneath the epidermis consists of connective tissue and cushions the body from stress
21.
Advanced glycation end-product
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Advanced glycation end products are proteins or lipids that become glycated as a result of exposure to sugars. They can be a factor in aging and in the development or worsening of many diseases, such as diabetes, atherosclerosis, chronic kidney disease. AGEs affect nearly every type of cell and molecule in the body and are thought to be one factor in aging and they are also believed to play a causative role in the vascular complications of diabetes mellitus. Under certain pathologic conditions, such as oxidative stress due to hyperglycemia in patients with diabetes, AGEs are now known to play a role as proinflammatory mediators in gestational diabetes as well. In the context of disease, AGEs can induce crosslinking of collagen which can cause vascular stiffening. AGEs can also cause glycation of LDL which can promote its oxidation, oxidized LDL is one of the major factors in the development of atherosclerosis. Finally, AGEs can bind to RAGE and cause oxidative stress as well as activation of pathways in vascular endothelial cells. The formation and accumulation of advanced glycation endproducts has been implicated in the progression of age-related diseases, AGEs have been implicated in Alzheimers Disease, cardiovascular disease, and stroke. The mechanism by which AGEs induce damage is through a process called cross-linking that causes intracellular damage and they form photosensitizers in the crystalline lens, which has implications for cataract development. Reduced muscle function is associated with AGEs. AGEs have a range of effects, such as, Increased vascular permeability. Increased arterial stiffness Inhibition of vascular dilation by interfering with nitric oxide, binding cells—including macrophage, endothelial, and mesangial—to induce the secretion of a variety of cytokines. Proteins are usually glycated through their lysine residues, in humans, histones in the cell nucleus are richest in lysine, and therefore form the glycated protein N-Carboxymethyllysine. The pathogenesis of this process hypothesized to activation of the nuclear factor kappa B following AGE binding, nF-κB controls several genes which are involved in inflammation. These latter, after being released into the plasma, can be excreted in the urine, nevertheless, the resistance of extracellular matrix proteins to proteolysis renders their advanced glycation end products less conducive to being eliminated. It is thought that these acids are then returned to the kidneys inside space, or lumen, AGE free adducts are the major form through which AGEs are excreted in urine, with AGE-peptides occurring to a lesser extent but accumulating in the plasma of patients with chronic kidney failure. Larger, extracellularly derived AGE proteins cannot pass through the basement membrane of the renal corpuscle and must first be degraded into AGE peptides and AGE free adducts. Peripheral macrophage as well as liver sinusoidal cells and Kupffer cells have been implicated in this process
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Disease
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A disease is a particular abnormal condition, a disorder of a structure or function, that affects part or all of an organism. The study of disease is called pathology which includes the study of cause, Disease is often construed as a medical condition associated with specific symptoms and signs. When caused by pathogens, even in the literature, the term disease is often misleadingly used in the place of its causal agent. This language habitat can cause confusion in the communication of the principle in epidemiology. Diseases can affect not only physically, but also emotionally. Death due to disease is called death by natural causes, there are four main types of disease, infectious diseases, deficiency diseases, genetic diseases, and physiological diseases. Diseases can also be classified as communicable and non-communicable, the deadliest diseases in humans are coronary artery disease, followed by cerebrovascular disease and lower respiratory infections. In many cases, terms such as disease, disorder, morbidity, there are situations, however, when specific terms are considered preferable. Disease The term disease broadly refers to any condition that impairs the normal functioning of the body, for this reason, diseases are associated with dysfunctioning of the bodys normal homeostatic processes. The term disease has both a count sense and a noncount sense, by contrast, an infection that is asymptomatic during its incubation period, but expected to produce symptoms later, is usually considered a disease. Non-infectious diseases are all other diseases, including most forms of cancer, heart disease, acquired disease disease that began at some point during ones lifetime, as opposed to disease that was already present at birth, which is congenital disease. Acquired sounds like it could mean caught via contagion, but it simply means acquired sometime after birth and it also sounds like it could imply secondary disease, but acquired disease can be primary disease. It is often, genetic and can be inherited and it can also be the result of a vertically transmitted infection from the mother such as HIV/AIDS. Genetic disease disease that is caused by genetic mutation and it is often inherited, but some mutations are random and de novo. Hereditary or inherited disease a type of disease caused by mutation that is hereditary Iatrogenic disease A disease condition caused by medical intervention. Idiopathic disease disease whose cause is unknown, as medical science has advanced, many diseases whose causes were formerly complete mysteries have been somewhat explained or even extensively explained. Bacterial infections can be primary or secondary to a viral infection or burn. Terminal disease disease with death as an inevitable result Illness Illness is generally used as a synonym for disease, however, this term is occasionally used to refer specifically to the patients personal experience of his or her disease
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Multiplexing
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In telecommunications and computer networks, multiplexing is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share an expensive resource, for example, in telecommunications, several telephone calls may be carried using one wire. Multiplexing originated in telegraphy in the 1870s, and is now applied in communications. In telephony, George Owen Squier is credited with the development of telephone carrier multiplexing in 1910, the multiplexed signal is transmitted over a communication channel such as a cable. The multiplexing divides the capacity of the channel into several logical channels. A reverse process, known as demultiplexing, extracts the original channels on the receiver end, a device that performs the multiplexing is called a multiplexer, and a device that performs the reverse process is called a demultiplexer. Multiple variable bit rate digital bit streams may be transferred efficiently over a fixed bandwidth channel by means of statistical multiplexing. This is an asynchronous mode time-domain multiplexing which is a form of time-division multiplexing, digital bit streams can be transferred over an analog channel by means of code-division multiplexing techniques such as frequency-hopping spread spectrum and direct-sequence spread spectrum. In wired communication, space-division multiplexing, also known as Space-division multiple access is the use of separate point-to-point electrical conductors for each transmitted channel, in wireless communication, space-division multiplexing is achieved with multiple antenna elements forming a phased array antenna. Examples are multiple-input and multiple-output, single-input and multiple-output and multiple-input and single-output multiplexing, different antennas would give different multi-path propagation signatures, making it possible for digital signal processing techniques to separate different signals from each other. These techniques may also be utilized for space diversity or beamforming rather than multiplexing Frequency-division multiplexing is inherently an analog technology, FDM achieves the combining of several signals into one medium by sending signals in several distinct frequency ranges over a single medium. In FDM the signals are electrical signals, one of the most common applications for FDM is traditional radio and television broadcasting from terrestrial, mobile or satellite stations, or cable television. Only one cable reaches a customers residential area, but the provider can send multiple television channels or signals simultaneously over that cable to all subscribers without interference. Receivers must tune to the frequency to access the desired signal. A variant technology, called wavelength-division multiplexing is used in optical communications, time-division multiplexing is a digital technology which uses time, instead of space or frequency, to separate the different data streams. TDM involves sequencing groups of a few bits or bytes from each individual input stream, one after the other, if done sufficiently quickly, the receiving devices will not detect that some of the circuit time was used to serve another logical communication path. Consider an application requiring four terminals at an airport to reach a central computer, each terminal communicated at 2400 baud, so rather than acquire four individual circuits to carry such a low-speed transmission, the airline has installed a pair of multiplexers. A pair of 9600 baud modems and one dedicated analog communications circuit from the ticket desk back to the airline data center are also installed
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Super-resolution microscopy
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Super-resolution microscopy is a form of light microscopy. Due to the diffraction of light, the resolution of conventional light microscopy is limited, Super-resolution techniques allow images to be taken with a higher resolution than the diffraction limit. However, the majority of techniques of importance in biological imaging fall into the functional category and these methods include STED, GSD, RESOLFT and SSIM. These methods include Super-resolution optical fluctuation imaging and all single-molecule localization methods such as SPDM, SPDMphymod, PALM, FPALM, on October 8,2014, the Nobel Prize in Chemistry was awarded to Eric Betzig, W. E. Moerner and Stefan Hell for the development of super-resolved fluorescence microscopy, some of the following information was gathered from a chemistry blogs review of sub-diffraction microscopy techniques Part I and Part II. For a review, see also reference, in 1986, the super-resolution optical microscope based on stimulated emission was patented by Okhonin. NORM microscopy is a method of optical near-field acquisition by a microscope through the observation of nanoparticles Brownian motion in an immersion liquid. NORM utilizes object surface scanning by stochastically moving nanoparticles, through the microscope, nanoparticles look like symmetric round spots. The spot width is equivalent to the point spread function and is defined by the microscope resolution, lateral coordinates of the given particle can be evaluated with a precision much higher than the resolution of the microscope. By collecting the information from many frames one can map out the field intensity distribution across the whole field of view of the microscope. In comparison with NSOM and ANSOM this method does not require any equipment for tip positioning and has a large field of view. Due to the number of scanning sensors one can get shorter time of image acquisition. A 4Pi microscope is a laser scanning microscope with an improved axial resolution. The typical value of 500–700 nm can be improved to 100–150 nm, the improvement in resolution is achieved by using two opposing objective lenses, both of which are focused to the same geometrical location. Also, the difference in path length through each of the two objective lenses is carefully aligned to be minimal. The solid angle Ω that is used for illumination and detection is increased, in this case the sample is illuminated and detected from all sides simultaneously. Up to now, the best quality in a 4Pi microscope was reached in conjunction with the STED principle in fixed cells, there is also the wide-field structured-illumination approach. SI enhances spatial resolution by collecting information from frequency space outside the observable region, the reverse FT returns the reconstructed image to a super-resolution image
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Vertico spatially modulated illumination
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Vertico spatially modulated illumination is the fastest light microscope for the 3D analysis of complete cells in the nanometer range. It is based on two technologies developed in 1996, SMI and SPDM, the effective optical resolution of this optical nanoscope has reached the vicinity of 5 nm in 2D and 40 nm in 3D and surpasses the 200 nm resolution limit predicted by Abbe‘s law. Abbe postulated in 1873 the theoretical limit of resolution of optical microscopy, a particularity of this technology compared with focusing techniques such as 4Pi microscopy, is the wide field exposures which allow entire cells to be depicted at the nano scale. Such a 3D exposure of a cell with a typical object size of 20 µm ×20 µm require only 2 minutes. Wide field exposures signify that the object is illuminated and detected simultaneously. SMI microscopy is a light optical process of the point spread function-engineering. The principle of the modulated wave field was developed in 1993 by Bailey et al. This results in an improved axial size and distance resolution, SMI can be combined with other super resolution technologies, for instance with 3D LIMON or LSI-TIRF as a total internal reflection interferometer with laterally structured illumination. This SMI technique allowed to acquire images of autofluorophore distributions in the sections from human eye tissue with previously unmatched optical resolution. Use of three different excitation wavelengths, enables to gather information about the autofluorescence signal. This has been used for of human eye tissue affected by macular degeneration AMD, however, this approach does not work when there are too many sources close to each other, The sources all blur together. SPDM is a family of techniques in fluorescence microscopy which gets around this problem by measuring just a few sources at a time, then, the above technique can be used. If the molecules have a variety of different spectra, then it is possible to look at light from just a few molecules at a time by using the light sources. Molecules can also be distinguished in more subtle ways based on fluorescent lifetime, an important area of application is genome research. Another important area of use is research into the structure of membranes, by combining many thousands of images of the same cell, it was possible using laser optical precision measurements to record localization images with significantly improved optical resolution. Using this so-called SPDMphymod technology a single wavelength of suitable intensity is sufficient for nanoimaging. In contrast other localization microscopies need two laser wavelengths when special photo-switchable/photo-activatable fluorescence molecules are used, the GFP gene has been introduced and expressed in many procaryotic and eucaryotic cells and the Nobel Prize in Chemistry 2008 was awarded to Martin Chalfie, Osamu Shimomura, and Roger Y. Tsien for their discovery and development of the fluorescent protein
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Banana
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The banana is an edible fruit – botanically a berry – produced by several kinds of large herbaceous flowering plants in the genus Musa. In some countries, bananas used for cooking may be called plantains, in contrast to dessert bananas. The fruit is variable in size, color and firmness, but is elongated and curved, with soft flesh rich in starch covered with a rind which may be green, yellow, red, purple. The fruits grow in clusters hanging from the top of the plant, almost all modern edible parthenocarpic bananas come from two wild species – Musa acuminata and Musa balbisiana. The scientific names of most cultivated bananas are Musa acuminata, Musa balbisiana, the old scientific name Musa sapientum is no longer used. Musa species are native to tropical Indomalaya and Australia, and are likely to have been first domesticated in Papua New Guinea. They are grown in 135 countries, primarily for their fruit, worldwide, there is no sharp distinction between bananas and plantains. Especially in the Americas and Europe, banana usually refers to soft, sweet, dessert bananas, particularly those of the Cavendish group, by contrast, Musa cultivars with firmer, starchier fruit are called plantains. In other regions, such as Southeast Asia, many kinds of banana are grown and eaten. The term banana is used as the common name for the plants which produce the fruit. This can extend to members of the genus Musa like the scarlet banana, pink banana. It can also refer to members of the genus Ensete, like the snow banana, both genera are classified under the banana family, Musaceae. The banana plant is the largest herbaceous flowering plant, all the above-ground parts of a banana plant grow from a structure usually called a corm. Plants are normally tall and fairly sturdy, and are mistaken for trees. Bananas grow in a variety of soils, as long as the soil is at least 60 cm deep, has good drainage and is not compacted. The leaves of plants are composed of a stalk and a blade. The base of the petiole widens to form a sheath, the tightly packed sheaths make up the pseudostem, the edges of the sheath meet when it is first produced, making it tubular. As new growth occurs in the centre of the pseudostem the edges are forced apart, cultivated banana plants vary in height depending on the variety and growing conditions
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Fluorescence
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Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence, in most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation. Fluorescent materials cease to glow immediately when the radiation source stops, unlike phosphorescence, Fluorescence also occurs frequently in nature in some minerals and in various biological states in many branches of the animal kingdom. An early observation of fluorescence was described in 1560 by Bernardino de Sahagún and it was derived from the wood of two tree species, Pterocarpus indicus and Eysenhardtia polystachya. The chemical compound responsible for this fluorescence is matlaline, which is the product of one of the flavonoids found in this wood. The name was derived from the fluorite, some examples of which contain traces of divalent europium. In a key experiment he used a prism to isolate ultraviolet radiation from sunlight, the specific frequencies of exciting and emitted light are dependent on the particular system. S0 is called the state of the fluorophore, and S1 is its first excited singlet state. A molecule in S1 can relax by various competing pathways and it can undergo non-radiative relaxation in which the excitation energy is dissipated as heat to the solvent. Excited organic molecules can also relax via conversion to a triplet state, relaxation from S1 can also occur through interaction with a second molecule through fluorescence quenching. Molecular oxygen is an extremely efficient quencher of fluorescence just because of its unusual triplet ground state, in most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation, this phenomenon is known as the Stokes shift. The emitted radiation may also be of the wavelength as the absorbed radiation. Molecules that are excited through light absorption or via a different process can transfer energy to a second sensitized molecule, the fluorescence quantum yield gives the efficiency of the fluorescence process. It is defined as the ratio of the number of photons emitted to the number of photons absorbed, Φ = Number of photons emitted Number of photons absorbed The maximum fluorescence quantum yield is 1.0, each photon absorbed results in a photon emitted. Compounds with quantum yields of 0.10 are still considered quite fluorescent, thus, if the rate of any pathway changes, both the excited state lifetime and the fluorescence quantum yield will be affected. Fluorescence quantum yields are measured by comparison to a standard, the quinine salt quinine sulfate in a sulfuric acid solution is a common fluorescence standard. The fluorescence lifetime refers to the time the molecule stays in its excited state before emitting a photon. This is an instance of exponential decay, various radiative and non-radiative processes can de-populate the excited state
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Nicotinamide adenine dinucleotide
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Nicotinamide adenine dinucleotide is a coenzyme found in all living cells. The compound is a dinucleotide, because it consists of two nucleotides joined through their phosphate groups, one nucleotide contains an adenine base and the other nicotinamide. Nicotinamide adenine dinucleotide exists in two forms, an oxidized and reduced form abbreviated as NAD+ and NADH respectively, in metabolism, nicotinamide adenine dinucleotide is involved in redox reactions, carrying electrons from one reaction to another. The coenzyme is, therefore, found in two forms in cells, NAD+ is an oxidizing agent – it accepts electrons from other molecules and becomes reduced and this reaction forms NADH, which can then be used as a reducing agent to donate electrons. These electron transfer reactions are the function of NAD. However, it is used in other cellular processes, the most notable one being a substrate of enzymes that add or remove chemical groups from proteins. Because of the importance of these functions, the involved in NAD metabolism are targets for drug discovery. In organisms, NAD can be synthesized from simple building-blocks from the amino acids tryptophan or aspartic acid, in an alternative fashion, more complex components of the coenzymes are taken up from food as the vitamin called niacin. Similar compounds are released by reactions that break down the structure of NAD and these preformed components then pass through a salvage pathway that recycles them back into the active form. Some NAD is also converted into nicotinamide adenine dinucleotide phosphate, the chemistry of this related coenzyme is similar to that of NAD, nicotinamide adenine dinucleotide, like all dinucleotides, consists of two nucleosides joined by a pair of bridging phosphate groups. The nucleosides each contain a ring, one with adenine attached to the first carbon atom. The nicotinamide moiety can be attached in two orientations to this carbon atom. Because of these two structures, the compound exists as two diastereomers. It is the diastereomer of NAD+ that is found in organisms. These nucleotides are joined together by a bridge of two groups through the 5 carbons. In metabolism, the compound accepts or donates electrons in redox reactions, such reactions involve the removal of two hydrogen atoms from the reactant, in the form of a hydride ion, and a proton. The proton is released into solution, while the reductant RH2 is oxidized, the midpoint potential of the NAD+/NADH redox pair is −0.32 volts, which makes NADH a strong reducing agent. The reaction is reversible, when NADH reduces another molecule and is re-oxidized to NAD+
29.
Chlorophyll
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Chlorophyll is any of several closely related green pigments found in cyanobacteria and the chloroplasts of algae and plants. Its name is derived from the Greek words χλωρός, chloros and φύλλον, chlorophyll is essential in photosynthesis, allowing plants to absorb energy from light. Chlorophyll absorbs light most strongly in the portion of the electromagnetic spectrum. Conversely, it is a poor absorber of green and near-green portions of the spectrum, chlorophyll molecules are specifically arranged in and around photosystems that are embedded in the thylakoid membranes of chloroplasts. Two types of chlorophyll exist in the photosystems of green plants, chlorophyll was first isolated and named by Joseph Bienaimé Caventou and Pierre Joseph Pelletier in 1817. Chlorophyll is vital for photosynthesis, which plants to absorb energy from light. Chlorophyll molecules are arranged in and around photosystems that are embedded in the thylakoid membranes of chloroplasts. In these complexes, chlorophyll serves two primary functions, the two currently accepted photosystem units are photosystem II and photosystem I, which have their own distinct reaction centres, named P680 and P700, respectively. These centres are named after the wavelength of their red-peak absorption maximum, the identity, function and spectral properties of the types of chlorophyll in each photosystem are distinct and determined by each other and the protein structure surrounding them. Once extracted from the protein into a solvent, these chlorophyll pigments can be separated into chlorophyll a, the function of the reaction center of chlorophyll is to absorb light energy and transfer it to other parts of the photosystem. The absorbed energy of the photon is transferred to an electron in a process called charge separation, the removal of the electron from the chlorophyll is an oxidation reaction. The chlorophyll donates the high energy electron to a series of molecular intermediates called a transport chain. The charged reaction center of chlorophyll is reduced back to its ground state by accepting an electron stripped from water. The electron that reduces P680+ ultimately comes from the oxidation of water into O2 and this reaction is how photosynthetic organisms such as plants produce O2 gas, and is the source for practically all the O2 in Earths atmosphere. Electron transfer reactions in the membranes are complex, however. NADPH is an agent used to reduce CO2 into sugars as well as other biosynthetic reactions. Thus, the other chlorophylls in the photosystem and antenna pigment proteins all cooperatively absorb, besides chlorophyll a, there are other pigments, called accessory pigments, which occur in these pigment–protein antenna complexes. Chlorophyll is a pigment, which is structurally similar to
30.
Retinol
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Retinol, also known as Vitamin A1, is a vitamin found in food and used as a dietary supplement. As a supplement it is used to treat and prevent vitamin A deficiency, in areas where deficiency is common a single large dose is recommended to those at high risk a couple of times a year. It is also used to prevent further issues in those who have measles and it is used by mouth or injection into a muscle. Retinol at normal doses is well tolerated, high doses may result in an enlarged liver, dry skin, or hypervitaminosis A. High doses during pregnancy may result in harm to the baby, Retinol is in the vitamin A family. It or other forms of vitamin A are needed for eye sight, maintenance of the skin and it is converted in the body to retinal and retinoic acid through which it acts. Dietary sources include fish, dairy products, and meat, Retinol was discovered in 1909, isolated in 1931, and first made in 1947. It is on the World Health Organizations List of Essential Medicines, Retinol is available as a generic medication and over the counter. The wholesale cost in the world is about 0.02 to 0.30 USD per 50,000 units. In the United States it is not very expensive, Retinol is used to treat vitamin A deficiency. The Tolerable Upper Intake Level for vitamin A, for a 25-year-old male, is 3,000 micrograms/day, too much vitamin A in retinoid form can be harmful or fatal, resulting in what is known as hypervitaminosis A. The body converts the dimerized form, carotene, into vitamin A as it is needed, the livers of certain animals, especially those adapted to polar environments, often contain amounts of vitamin A that would be toxic to humans. Thus, vitamin A toxicity is typically reported in Arctic explorers, Vitamin A acute toxicity occurs when an individual ingests vitamin A in large amounts more than the daily recommended value in the threshold of 25,000 IU/kg or more. Often, the individual consumes about 3–4 times the RDAs specification, the former occurs few hours or days after ingestion of large amounts of vitamin A accidentally or via inappropriate therapy. The later toxicity takes place when about 4,000 IU/kg or more of vitamin A is consumed for a period of time. Symptoms associated with both toxicities include nausea, blurred vision, fatigue, weight-loss, menstrual abnormalities etc, excess vitamin A has also been suspected to be a contributor to osteoporosis. This seems to happen at lower doses than those required to induce acute intoxication. Only preformed vitamin A can cause problems, because the conversion of carotenoids into vitamin A is downregulated when physiological requirements are met
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Cholecalciferol
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Cholecalciferol, also known as vitamin D3 and colecalciferol, is a type of vitamin D found in food and used as a dietary supplement. As a supplement it is used to treat and prevent vitamin D deficiency including rickets and it is also used for familial hypophosphatemia, hypoparathyroidism that is causing low blood calcium, and Fanconi syndrome. Excessive doses can result in vomiting, constipation, weakness, normal doses are safe in pregnancy. It may not be effective in people with kidney disease. After being converted into 1, 25-dihydroxyvitamin D, it works by increasing the uptake of calcium by the intestines, food in which it is found include some fish, cheese, and eggs. Cholecalciferol was first described in 1936 and it is on the World Health Organizations List of Essential Medicines, the most effective and safe medicines needed in a health system. Cholecalciferol is available as a medication and over the counter. The wholesale cost in the world is about 2.14 USD per 30 ml bottle. In the United States treatment costs less than 25 USD per month, certain foods such as milk have cholecalciferol added to them in some countries. One gram is 40,000,000 IU, equivalently 1 IU is 0.025 µg, recommendations vary depending on the country, In the US,15 µg/d for all individuals between the ages of 1 and 70 years old, inclusive. For all individuals older than 70 years,20 µg/d is recommended, in the EU,20 µg/d In France,25 µg/d Many question whether the current recommended intake is sufficient to meet physiological needs. Individuals without regular sun exposure, the obese, and darker skinned individuals all have lower blood levels, patients with severe vitamin D deficiency will require treatment with a loading dose, its magnitude can be calculated based on the actual serum 25-hydroxy-vitamin D level and body weight. Also, there is a therapy for rickets utilizing a single dose, called stoss therapy in Europe, taking from 300,000 IU to 500,000 IU, in a single dose, or in two to four divided doses. There are conflicting reports concerning the absorption of cholecalciferol versus ergocalciferol, with studies suggesting less efficacy of D2. At present, D2 and D3 doses are considered interchangeable. A meta-analysis of 2007 concluded that intake of 1000 to 2000 IU per day of vitamin D3 could reduce the incidence of colorectal cancer with minimal risk. In humans, with 400 IU daily, there was no effect of cholecalciferol supplements on the risk of colorectal cancer, supplements are not recommended for prevention of cancer as any effects of cholecalciferol are very small. It is a secosteroid, that is, a molecule with one ring open
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Folic acid
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Folic acid, another form of which is known as folate, is one of the B vitamins. The recommended daily level of folate is 400 micrograms from foods or dietary supplements. Folic acid is used to treat anemia caused by folic acid deficiency and it is also used as a supplement by women during pregnancy to prevent neural tube defects in the baby. Low levels in early pregnancy are believed to be the cause of more than half of babies born with neural tube defects, more than 50 countries use fortification of certain foods with folic acid as a measure to decrease the rate of NTDs in the population. Long term supplementation is also associated with reductions in the risk of stroke. It may be taken by mouth or by injection, there are no common side effects. It is not known whether high doses over a period of time are of concern. There are concerns that large amounts of folic acid might hide vitamin B12 deficiency, folic acid is essential for the body to make DNA, RNA, and metabolise amino acids which are required for cell division. As humans cannot make folic acid, it is required from the diet, not consuming enough folate can lead to folate deficiency. This may result in a type of anemia in which low numbers of red blood cells occur. Symptoms may include feeling tired, heart palpitations, shortness of breath, open sores on the tongue, deficiency in children may develop within a month of poor dietary intake. In adults normal total body folate is between 10, 000–30,000 micrograms with blood levels of greater than 7 nmol/L, folic acid was discovered between 1931 and 1943. It is on the World Health Organizations List of Essential Medicines, the wholesale cost of supplements in the developing world is between 0.001 and 0.005 USD per dose as of 2014. The term folic is from the Latin word folium, which means leaf, folates occur naturally in many foods especially dark green leafy vegetables and liver. Other names include vitamin B9, vitamin Bc, vitamin M, folacin, folic acid intake during pregnancy has been linked to a lessened risk of neural tube defects. Likewise, a meta-analysis of folic acid supplementation during pregnancy reported a 28% lower risk of congenital heart defects. The United States Preventive Services Task Force recommends folic acid supplementation for all able to become pregnant. Prenatal supplementation did not appear to reduce the risk of pre-term births, and there does not appear to be a correlation between maternal folic acid supplementation and an increased risk for asthma in the child
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Indolamine
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Indolamines are a family of neurotransmitters that share a common molecular structure. Indolamines are a classification of monoamine neurotransmitter, along with catecholamines, a common example of an indolamine is the tryptophan derivative serotonin, a neurotransmitter involved in mood and sleep. Another example of an indolamine is melatonin, which regulates the sleep-wake cycle in humans, in biochemistry, indolamines are substituted indole compounds that contain an amino group. Examples of indoleamines include the lysergamides, in humans, neurotransmitters in the indolamine family are believed to be produced in the pineal gland. Indolamines are biologically synthesized from the amino acid tryptophan
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Lipofuscin
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Lipofuscin is the name given to finely granular yellow-brown pigment granules composed of lipid-containing residues of lysosomal digestion. It is considered to be one of the aging or wear-and-tear pigments, found in the liver, kidney, heart muscle, retina, adrenals, nerve cells and it is specifically arranged around the nucleus, and is a type of lipochrome. It appears to be the product of the oxidation of unsaturated fatty acids and may be symptomatic of membrane damage, or damage to mitochondria and lysosomes. Aside from a large lipid content, lipofuscin is known to contain sugars and metals, including mercury, aluminum, iron, copper, however, this result is controversial, as it is questionable if the leupeptin-induced material is true lipofuscin. There exists evidence that true lipofuscin is not degradable in vitro, lipofuscin accumulation is a major risk factor implicated in macular degeneration, a degenerative disease of the eye, as well as Stargardt disease, an inherited juvenile form of macular degeneration. Accumulation of lipofuscin in the colon is the cause of the condition melanosis coli, calorie restriction, vitamin E, and increased glutathione appear to reduce or halt the production of lipofuscin. The nootropic drug piracetam appears to significantly reduce accumulation of lipofuscin in the tissue of rats. The technique is used as a skin treatment to remove tattoos, liverspots. This ability to selectively target lipofuscin has opened up opportunities in the field of Anti-aging medicine. A tetrahydropyridoether can remove lipofuscin from retinal pigment epithelial cells and this opens up a new therapy option for the treatment of dry age-related macular degeneration and Stargardt disease, for which there is currently no treatment. The drug has now been granted orphan designation for the treatment of Stargardt disease by the European Medicines Agency. Lipofuscin quantification is used for age determination in various such as lobsters. Since these animals lack bony parts, they cannot be aged in the way as bony fish. Age determination of fish and shellfish is a step in generating basic biological data such as growth curves. Several studies have indicated that quantifying the amount of lipofuscin present in the eye-stalks of various crustaceans can give an index of their age, residual body Terman A, Brunk U
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Polyphenol
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Polyphenols are a structural class of mainly natural, but also synthetic or semisynthetic, organic chemicals characterized by the presence of large multiples of phenol structural units. The number and characteristics of these phenol structures underlie the unique physical, chemical, examples include tannic acid and ellagitannin. The historically important chemical class of tannins is a subset of the polyphenols, the term polyphenol appears to have been in use since 1894. g. Phenyl esters, methyl phenyl ethers and O-phenyl glycosides and this definition departs from the WBSSH definition in terms of physicochemical behavior, with its lack of reference to solubility, precipitation, and complexation phenomena. The raspberry ellagitannin, on the hand, with its 14 gallic acid moieties. Individual polyphenols engage in related to both their core phenolic structures, their linkages, and types of glycosides they form. In addition, as noted above, a feature of polyphenols was their ability to form particular. As opposed to smaller phenols, polyphenols are often larger molecules deposited in cell vacuoles, hence, many larger polyphenols are biosynthesized in-situ from smaller polyphenols to nonhydrolyzable tannins and remain undiscovered in the plant matrix. Most polyphenols contain repeating phenolic moieties of pyrocatechol, resorcinol, pyrogallol, proanthocyanidins are mostly polymeric units of catechin and epicatechin. The phenolic substructures arise from various biosynthetic pathways, especially phenylpropanoid and polyketide branches aimed at plant, in these, diverse biosynthetic steps abound, the seven-atom ring appearing in theaflavin structure above is an example of a carbocycle that is of a nonbenzenoid aromatic tropolone type. Because of the preponderance of saccharide-derived core structures, as well as spiro- and other structure types, the total synthesis of a fully unmasked polyphenol, that of the ellagitannin tellimagrandin I, was a diastereoselective sequence reported in 1994 by Feldman, Ensel and Minard. Khanbabaee and Grosser accomplished a relatively efficient total synthesis of pedunculagin in 2003, work proceeded with focus on enantioselective total syntheses, e. g. A biomimetic synthesis, and the first formal total synthesis 5-O-Desgalloyl-epi-punicacortein A, the novel strategies and methods referred to in these recent examples helped to open the field of polyphenol chemical synthesis to an unprecedented degree. They are reactive species toward oxidation, ABTS may be used to characterise polyphenol oxidation products. Polyphenols also characteristically possess a significant binding affinity for proteins, which can lead to the formation of soluble and insoluble protein-polyphenol complexes, some polyphenols are traditionally used as dyes. For instance, in the Indian subcontinent, the peel, high in tannins and other polyphenols. The aims are generally to use of plant residues from grape. Cashew nut shell liquid is an important phenolic raw material containing mostly cardol, cardanol, pyrogallol and pyrocatechin are among the oldest photographic developers
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Fluorescence spectroscopy
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Fluorescence spectroscopy is a type of electromagnetic spectroscopy that analyzes fluorescence from a sample. A complementary technique is absorption spectroscopy, in the special case of single molecule fluorescence spectroscopy, intensity fluctuations from the emitted light are measured from either single fluorophores, or pairs of fluorophores. Devices that measure fluorescence are called fluorometers, molecules have various states referred to as energy levels. Fluorescence spectroscopy is concerned with electronic and vibrational states. Generally, the species being examined has an electronic state of interest. Within each of these states there are various vibrational states. In fluorescence, the species is first excited, by absorbing a photon, collisions with other molecules cause the excited molecule to lose vibrational energy until it reaches the lowest vibrational state of the excited electronic state. This process is often visualized with a Jablonski diagram, the molecule then drops down to one of the various vibrational levels of the ground electronic state again, emitting a photon in the process. As molecules may drop down into any of several levels in the ground state, the emitted photons will have different energies. For atomic species, the process is similar, however, since atomic species do not have energy levels. This process of re-emitting the absorbed photon is resonance fluorescence and while it is characteristic of atomic fluorescence, is seen in molecular fluorescence as well, an emission map is measured by recording the emission spectra resulting from a range of excitation wavelengths and combining them all together. This is a three dimensional surface data set, emission intensity as a function of excitation and emission wavelengths, both types use the following scheme, the light from an excitation source passes through a filter or monochromator, and strikes the sample. A proportion of the incident light is absorbed by the sample, the fluorescent light is emitted in all directions. Various light sources may be used as sources, including lasers, LED. A laser only emits light of high irradiance at a narrow wavelength interval, typically under 0.01 nm. The disadvantage of this method is that the wavelength of a laser cannot be changed by much, a mercury vapor lamp is a line lamp, meaning it emits light near peak wavelengths. By contrast, an arc has a continuous emission spectrum with nearly constant intensity in the range from 300-800 nm. Filters and/or monochromators may be used in fluorimeters, a monochromator transmits light of an adjustable wavelength with an adjustable tolerance
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Melanin
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Melanin /ˈmɛlənɪn/ is a broad term for a group of natural pigments found in most organisms. Melanin is produced by the oxidation of the amino acid tyrosine, the pigment is produced in a specialized group of cells known as melanocytes. There are three types of melanin, eumelanin, pheomelanin, and neuromelanin. The most common is eumelanin, of which there are two types—brown eumelanin and black eumelanin, pheomelanin is a cysteine-containing red polymer of benzothiazine units largely responsible for red hair, among other pigmentation. Neuromelanin is found in the brain, though its function remains obscure, in the skin, melanogenesis occurs after exposure to UV radiation, causing the skin to visibly tan. Melanin is an effective absorber of light, the pigment is able to dissipate over 99. 9% of absorbed UV radiation, because of this property, melanin is thought to protect skin cells from UVB radiation damage, reducing the risk of cancer. e. Nonetheless, the relationship between skin pigmentation and photoprotection is still being clarified, in humans, melanin is the primary determinant of skin color. It is also found in hair, the pigmented tissue underlying the iris of the eye, in the brain, tissues with melanin include the medulla and pigment-bearing neurons within areas of the brainstem, such as the locus coeruleus and the substantia nigra. It also occurs in the zona reticularis of the adrenal gland, the melanin in the skin is produced by melanocytes, which are found in the basal layer of the epidermis. Although, in general, human beings possess a concentration of melanocytes in their skin. Some humans have very little or no melanin synthesis in their bodies, because melanin is an aggregate of smaller component molecules, there are many different types of melanin with differing proportions and bonding patterns of these component molecules. Both pheomelanin and eumelanin are found in skin and hair. Eumelanin polymers have long thought to comprise numerous cross-linked 5, 6-dihydroxyindole and 5. There are two types of eumelanin and black eumelanin—which chemically differ from each other in their pattern of polymeric bonds. A small amount of black eumelanin in the absence of other pigments causes grey hair, a small amount of brown eumelanin in the absence of other pigments causes blond color hair. As the body ages, it continues to produce black melanin but stops producing the brown version, pheomelanins impart a pink to red hue, depending upon the concentration. Pheomelanins are particularly concentrated in the lips, nipples, glans of the penis, when a small amount of brown eumelanin in hair, which would otherwise cause blond hair, is mixed with red pheomelanin, the result is red hair. Pheomelanin is also present in the skin, and redheads consequently often have a pinkish hue to their skin as well
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PubMed Identifier
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PubMed is a free search engine accessing primarily the MEDLINE database of references and abstracts on life sciences and biomedical topics. The United States National Library of Medicine at the National Institutes of Health maintains the database as part of the Entrez system of information retrieval, from 1971 to 1997, MEDLINE online access to the MEDLARS Online computerized database primarily had been through institutional facilities, such as university libraries. PubMed, first released in January 1996, ushered in the era of private, free, home-, the PubMed system was offered free to the public in June 1997, when MEDLINE searches via the Web were demonstrated, in a ceremony, by Vice President Al Gore. Information about the journals indexed in MEDLINE, and available through PubMed, is found in the NLM Catalog. As of 5 January 2017, PubMed has more than 26.8 million records going back to 1966, selectively to the year 1865, and very selectively to 1809, about 500,000 new records are added each year. As of the date,13.1 million of PubMeds records are listed with their abstracts. In 2016, NLM changed the system so that publishers will be able to directly correct typos. Simple searches on PubMed can be carried out by entering key aspects of a subject into PubMeds search window, when a journal article is indexed, numerous article parameters are extracted and stored as structured information. Such parameters are, Article Type, Secondary identifiers, Language, publication type parameter enables many special features. As these clinical girish can generate small sets of robust studies with considerable precision, since July 2005, the MEDLINE article indexing process extracts important identifiers from the article abstract and puts those in a field called Secondary Identifier. The secondary identifier field is to store numbers to various databases of molecular sequence data, gene expression or chemical compounds. For clinical trials, PubMed extracts trial IDs for the two largest trial registries, ClinicalTrials. gov and the International Standard Randomized Controlled Trial Number Register, a reference which is judged particularly relevant can be marked and related articles can be identified. If relevant, several studies can be selected and related articles to all of them can be generated using the Find related data option, the related articles are then listed in order of relatedness. To create these lists of related articles, PubMed compares words from the title and abstract of each citation, as well as the MeSH headings assigned, using a powerful word-weighted algorithm. The related articles function has been judged to be so precise that some researchers suggest it can be used instead of a full search, a strong feature of PubMed is its ability to automatically link to MeSH terms and subheadings. Examples would be, bad breath links to halitosis, heart attack to myocardial infarction, where appropriate, these MeSH terms are automatically expanded, that is, include more specific terms. Terms like nursing are automatically linked to Nursing or Nursing and this important feature makes PubMed searches automatically more sensitive and avoids false-negative hits by compensating for the diversity of medical terminology. The My NCBI area can be accessed from any computer with web-access, an earlier version of My NCBI was called PubMed Cubby
. PMID 12756303.