Persan is a red French wine grape variety, grown in the Savoie region. While the name hints at a Persian origins for the grape, it is most native to the Rhône-Alpes region with the name "Persan" being a corruption of the synonym "Princens", the name of a small hamlet by Saint-Jean-de-Maurienne in Savoie, noted since the 17th century for the quality of its vineyards; the exact origins of Persan is unknown. The name of the grape lends itself to the theory that it originated in the Middle East and worked its way west via Cyprus. One legend has it that Prince Louis of Savoy had the vine brought to France from Cyprus where he reigned as king in the 15th century. Another theory that Master of Wine Jancis Robinson puts forth is that the name Persan is a corruption of Princens which combined two words from the local dialect meaning prin and cens. Records indicate in the 17th century there was a vineyard located in the small hamlet of Princens by Saint-Jean-de-Maurienne east of Grenoble, regarded and could have been home to the "Princens" grape that late became known as Persan.
The earliest mention of the name Persan itself occurred in 1846 when Albin Gras secretary of the Statistical Society of Isère and a board member for the Agricultural Society of Grenoble noted plantings of the variety in the Isère department. Gras said that the grape was known as Etraire on the right bank of the Isère and as Persan on the left bank. Persan is known as an early mid-ripening vine that produces small bunches of tiny berries, it can be vigorous and needs to be pruned in order to maintain reasonable yields. The vines seems to thrive well on stony, calcareous soils with the main viticultural hazard being a susceptibility to powdery and downy mildew. In the 19th century, Persan was planted throughout the Savoie region and Isère region until the phylloxera epidemic at the end of that century reduced its numbers, it is still found in the Savoie region today where it is a permitted variety in the appellation d'Origine Contrôlée wines of the Vin de Savoie AOC as well as the Vin de Pays d'Allobrogie zone but plantings were down to just 22 acres in 2012.
There have been some efforts to revive the variety with Michel Grisard of Domaine Prieuré St-Christophe in Fréterive increasing his planting to make a varietal style of the grape. Grisard, along with other local Savoie producers such as Domaine de Méjane and Domaine Saint-Germain have been spearheading a local movement to have Persan replanted in the esteemed Princens vineyard of Saint-Jean-de-Maurienne. Across the border from Savoie in Switzerland, more than 1500 vines of Persan were planted in a vineyard outside Geneva that should be in full production by the 2016 vintage. In 2001, DNA testing confirmed that the local Bécuet grape growing in the Susa Valley of Piedmont around Pinerolo was, in fact, the Persan grape of Savoie. Today it is blended with the local grape variety Avanà to make a wine known as Ramiè; some varietal examples of Bécuet are made in the province of Turin in the communes of Gravere and Giaglione. Due to the similarities in synonyms it was long thought that Persan was the same grape as Étraire de la Dui, found in the Savoie wine region.
In 1902, L. Rougier, an ampelographer writing for Pierre Viala and Victor Vermorel's catalog of grape varieties, determined that the two were separate varieties with Étraire de la Dui being an offspring of Persan. Over a 100 years DNA testing conducted by Swiss geneticist José Vouillamoz "strongly suggested" that there was, indeed, a parent-offspring link between Persan and Étraire de la Dui but in what direction is not yet known. Other varieties that Persan has been confused with over the years include Mondeuse noire and Pinot noir. In 1876, French viticulturist Jules Guyot speculated that Persan may have been a local mutation of the Burgundian Pinot noir that developed in Savoie. However, DNA testing has dismissed that theory. Persan was used to crossed with Peloursin to create the red grape variety Joubertin. Over the years Persan has been known under a variety of synonyms including Aguyzelle, Aguzelle, Bâtarde, Bâtarde longue, Becouet, Becuette, Berla'd Crava Cita, Berla Cita, Berlo Citto, Bucuet, Cul de Poule, Étraire, Étrière, Étris, Moirans, Persan Noir, Petit Becquet, Posse de Chèvre, Pousse de Chèvre, Pressan, Prinsan, Rives, Sérine, Sérinne pointue, Siranèze pointue and Siranne pointue
Nicotinamide adenine dinucleotide
Nicotinamide adenine dinucleotide is a cofactor found in all living cells. The compound is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains 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 cofactor is, found in two forms in cells: NAD+ is an oxidizing agent – it accepts electrons from other molecules and becomes reduced. This reaction forms NADH, which can be used as a reducing agent to donate electrons; these electron transfer reactions are the main function of NAD. However, it is used in other cellular processes, most notably a substrate of enzymes that add or remove chemical groups from proteins, in posttranslational modifications; because of the importance of these functions, the enzymes 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 niacin. Similar compounds are released by reactions that break down the structure of NAD; these preformed components pass through a salvage pathway that recycles them back into the active form. Some NAD is converted into the coenzyme nicotinamide adenine dinucleotide phosphate; the chemistry of NADP is similar to that of NAD, but it has different role, being predominantly a cofactor in anabolic metabolism. NAD+ is written with a superscript plus sign because of the formal charge on one of its nitrogen atoms. NADH, on the other hand, is a doubly charged anion because of its two bridging phosphate groups. Nicotinamide adenine dinucleotide, like all dinucleotides, consists of two nucleosides joined by a pair of bridging phosphate groups; the nucleosides each contain a ribose ring, one with adenine attached to the first carbon atom and the other with nicotinamide at this position.
The nicotinamide moiety can be attached in two orientations to this anomeric carbon atom. Because of these two possible structures, the compound exists as two diastereomers, it is the β-nicotinamide diastereomer of NAD+, found in organisms. These nucleotides are joined together by a bridge of two phosphate groups through the 5' carbons. In metabolism, the compound donates electrons in redox reactions; such reactions involve the removal of two hydrogen atoms from the reactant, in the form of a hydride ion, a proton. The proton is released into solution, while the reductant RH2 is oxidized and NAD+ reduced to NADH by transfer of the hydride to the nicotinamide ring. RH2 + NAD+ → NADH + H+ + R; 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+; this means the coenzyme can continuously cycle between the NAD+ and NADH forms without being consumed. In appearance, all forms of this coenzyme are white amorphous powders that are hygroscopic and water-soluble.
The solids are stable. Solutions of NAD+ are colorless and stable for about a week at 4 °C and neutral pH, but decompose in acids or alkalis. Upon decomposition, they form products. Both NAD+ and NADH absorb ultraviolet light because of the adenine. For example, peak absorption of NAD+ is at a wavelength of 259 nanometers, with an extinction coefficient of 16,900 M−1cm−1. NADH absorbs at higher wavelengths, with a second peak in UV absorption at 339 nm with an extinction coefficient of 6,220 M−1cm−1; this difference in the ultraviolet absorption spectra between the oxidized and reduced forms of the coenzymes at higher wavelengths makes it simple to measure the conversion of one to another in enzyme assays – by measuring the amount of UV absorption at 340 nm using a spectrophotometer. NAD+ and NADH differ in their fluorescence. NADH in solution has an emission peak at 460 nm and a fluorescence lifetime of 0.4 nanoseconds, while the oxidized form of the coenzyme does not fluoresce. The properties of the fluorescence signal changes when NADH binds to proteins, so these changes can be used to measure dissociation constants, which are useful in the study of enzyme kinetics.
These changes in fluorescence are used to measure changes in the redox state of living cells, through fluorescence microscopy. In rat liver, the total amount of NAD+ and NADH is 1 μmole per gram of wet weight, about 10 times the concentration of NADP+ and NADPH in the same cells; the actual concentration of NAD+ in cell cytosol is harder to measure, with recent estimates in animal cells ranging around 0.3 mM, 1.0 to 2.0 mM in yeast. However, more than 80% of NADH fluorescence in mitochondria is from bound form, so the concentration in solution is much lower. Data for other compartments in the cell are limited, although in the mitochondrion the concentration of NAD+ is similar to that in the cytosol; this NAD+ is carried into the mitochondrion by a specific membrane transport protein, since the coenzyme cannot diffuse across membranes. The balance between the oxidized and reduced forms of nicotinam
A hydroxy or hydroxyl group is the entity with the formula OH. It contains oxygen bonded to hydrogen. In organic chemistry and carboxylic acids contain hydroxy groups; the anion, called hydroxide, consists of a hydroxyl group. According to IUPAC rules, the term hydroxyl refers to the radical OH only, while the functional group −OH is called hydroxy group. Water, carboxylic acids, many other hydroxy-containing compounds can be deprotonated readily; this behavior is rationalized by the disparate electronegativities of hydrogen. Hydroxy-containing compounds engage in hydrogen bonding, which causes them to stick together, leading to higher boiling and melting points than found for compounds that lack this functional group. Organic compounds, which are poorly soluble in water, become water-soluble when they contain two or more hydroxy groups, as illustrated by sugars and amino acid; the hydroxy group is pervasive in biochemistry. Many inorganic compounds contain hydroxy groups, including sulfuric acid, the chemical compound produced on the largest scale industrially.
Hydroxy groups participate in the dehydration reactions that link simple biological molecules into long chains. The joining of a fatty acid to glycerol to form a triacylglycerol removes the −OH from the carboxy end of the fatty acid; the joining of two aldehyde sugars to form a disaccharide removes the −OH from the carboxy group at the aldehyde end of one sugar. The creation of a peptide bond to link two amino acids to make a protein removes the −OH from the carboxy group of one amino acid. Hydroxyl radicals are reactive and undergo chemical reactions that make them short-lived; when biological systems are exposed to hydroxyl radicals, they can cause damage to cells, including those in humans, where they can react with DNA, proteins. In 2009, India's Chandrayaan-1 satellite, NASA's Cassini spacecraft and the Deep Impact probe have each detected the presence of water by evidence of hydroxyl fragments on the Moon; as reported by Richard Kerr, "A spectrometer detected an infrared absorption at a wavelength of 3.0 micrometers that only water or hydroxyl—a hydrogen and an oxygen bound together—could have created."
NASA reported in 2009 that the LCROSS probe revealed an ultraviolet emission spectrum consistent with hydroxyl presence. The Venus Express orbiter sent back Venus science data from April 2006 until December 2014. Results from Venus Express include the detection of hydroxyl in the atmosphere. Hydronium Ion Oxide Reece, Jane. "Unit 1, Chapter 4 &5." In Campbell Biology. Berge, Susan. San Francisco: Pearson Benjamin Cummings. ISBN 978-0-321-55823-7
The Jmol applet, among other abilities, offers an alternative to the Chime plug-in, no longer under active development. While Jmol has many features that Chime lacks, it does not claim to reproduce all Chime functions, most notably, the Sculpt mode. Chime requires plug-in installation and Internet Explorer 6.0 or Firefox 2.0 on Microsoft Windows, or Netscape Communicator 4.8 on Mac OS 9. Jmol operates on a wide variety of platforms. For example, Jmol is functional in Mozilla Firefox, Internet Explorer, Google Chrome, Safari. Chemistry Development Kit Comparison of software for molecular mechanics modeling Jmol extension for MediaWiki List of molecular graphics systems Molecular graphics Molecule editor Proteopedia PyMOL SAMSON Official website Wiki with listings of websites and moodles Willighagen, Egon. "Fast and Scriptable Molecular Graphics in Web Browsers without Java3D". Doi:10.1038/npre.2007.50.1
Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed of fibroin and is produced by certain insect larvae to form cocoons; the best-known silk is obtained from the cocoons of the larvae of the mulberry silkworm Bombyx mori reared in captivity. The shimmering appearance of silk is due to the triangular prism-like structure of the silk fibre, which allows silk cloth to refract incoming light at different angles, thus producing different colors. Silk is produced by several insects. There has been some research into other types of silk. Silk is produced by the larvae of insects undergoing complete metamorphosis, but some insects, such as webspinners and raspy crickets, produce silk throughout their lives. Silk production occurs in Hymenoptera, mayflies, leafhoppers, lacewings, fleas and midges. Other types of arthropods produce most notably various arachnids, such as spiders; the word silk comes from Old English: sioloc, from Ancient Greek: σηρικός, translit.
Sērikós, "silken" from an Asian source — compare Mandarin sī "silk", Manchurian sirghe, Mongolian sirkek. Several kinds of wild silk, which are produced by caterpillars other than the mulberry silkworm, have been known and used in China, South Asia, Europe since ancient times. However, the scale of production was always far smaller than for cultivated silks. There are several reasons for this: first, they differ from the domesticated varieties in colour and texture and are therefore less uniform. Thus, the only way to obtain silk suitable for spinning into textiles in areas where commercial silks are not cultivated was by tedious and labor-intensive carding. Commercial silks originate from reared silkworm pupae, which are bred to produce a white-colored silk thread with no mineral on the surface; the pupae are killed by either dipping them in boiling water before the adult moths emerge or by piercing them with a needle. These factors all contribute to the ability of the whole cocoon to be unravelled as one continuous thread, permitting a much stronger cloth to be woven from the silk.
Wild silks tend to be more difficult to dye than silk from the cultivated silkworm. A technique known as demineralizing allows the mineral layer around the cocoon of wild silk moths to be removed, leaving only variability in color as a barrier to creating a commercial silk industry based on wild silks in the parts of the world where wild silk moths thrive, such as in Africa and South America. Silk was first developed in ancient China; the earliest example of silk has been found in tombs at the neolithic site Jiahu in Henan, dates back 8,500 years. Silk fabric from 3630 BC was used as wrapping for the body of a child from a Yangshao culture site in Qingtaicun at Xingyang, Henan. Legend gives credit for developing silk to Leizu. Silks were reserved for the Emperors of China for their own use and gifts to others, but spread through Chinese culture and trade both geographically and and to many regions of Asia; because of its texture and lustre, silk became a popular luxury fabric in the many areas accessible to Chinese merchants.
Silk was in great demand, became a staple of pre-industrial international trade. In July 2007, archaeologists discovered intricately woven and dyed silk textiles in a tomb in Jiangxi province, dated to the Eastern Zhou Dynasty 2,500 years ago. Although historians have suspected a long history of a formative textile industry in ancient China, this find of silk textiles employing "complicated techniques" of weaving and dyeing provides direct evidence for silks dating before the Mawangdui-discovery and other silks dating to the Han Dynasty. Silk is described in a chapter of the Fan Shengzhi shu from the Western Han. There is a surviving calendar for silk production in an Eastern Han document; the two other known works on silk from the Han period are lost. The first evidence of the long distance silk trade is the finding of silk in the hair of an Egyptian mummy of the 21st dynasty, c.1070 BC. The silk trade reached as far as the Indian subcontinent, the Middle East and North Africa; this trade was so extensive that the major set of trade routes between Europe and Asia came to be known as the Silk Road.
The Emperors of China strove to keep knowledge of sericulture secret to maintain the Chinese monopoly. Nonetheless sericulture reached Korea with technological aid from China around 200 BC, the ancient Kingdom of Khotan by AD 50, India by AD 140. In the ancient era, silk from China was the most lucrative and sought-after luxury item traded across the Eurasian continent, many civilizations, such as the ancient Persians, benefited economically from trade. Chinese silk making process Silk has a long history in India, it is known as Resham in eastern and north India, Pattu in southern parts of India. Recent archaeological discoveries in Harappa and Chanhu-daro suggest that sericulture, employing wild silk threads from native silkworm species, existed in South Asia during the time of the Indus Valley Civilization dating between 2450 BC and 2000 BC, while "hard and fast evidence" for silk production in China dates back to around 2570 BC. Shelagh Vainker, a s
Nuclear magnetic resonance spectroscopy
Nuclear magnetic resonance spectroscopy, most known as NMR spectroscopy or magnetic resonance spectroscopy, is a spectroscopic technique to observe local magnetic fields around atomic nuclei. The sample is placed in a magnetic field and the NMR signal is produced by excitation of the nuclei sample with radio waves into nuclear magnetic resonance, detected with sensitive radio receivers; the intramolecular magnetic field around an atom in a molecule changes the resonance frequency, thus giving access to details of the electronic structure of a molecule and its individual functional groups. As the fields are unique or characteristic to individual compounds, in modern organic chemistry practice, NMR spectroscopy is the definitive method to identify monomolecular organic compounds. Biochemists use NMR to identify proteins and other complex molecules. Besides identification, NMR spectroscopy provides detailed information about the structure, reaction state, chemical environment of molecules; the most common types of NMR are proton and carbon-13 NMR spectroscopy, but it is applicable to any kind of sample that contains nuclei possessing spin.
NMR spectra are unique, well-resolved, analytically tractable and highly predictable for small molecules. Different functional groups are distinguishable, identical functional groups with differing neighboring substituents still give distinguishable signals. NMR has replaced traditional wet chemistry tests such as color reagents or typical chromatography for identification. A disadvantage is that a large amount, 2–50 mg, of a purified substance is required, although it may be recovered through a workup. Preferably, the sample should be dissolved in a solvent, because NMR analysis of solids requires a dedicated magic angle spinning machine and may not give well-resolved spectra; the timescale of NMR is long, thus it is not suitable for observing fast phenomena, producing only an averaged spectrum. Although large amounts of impurities do show on an NMR spectrum, better methods exist for detecting impurities, as NMR is inherently not sensitive - though at higher frequencies, sensitivity is higher.
Correlation spectroscopy is a development of ordinary NMR. In two-dimensional NMR, the emission is centered around a single frequency, correlated resonances are observed; this allows identifying the neighboring substituents of the observed functional group, allowing unambiguous identification of the resonances. There are more complex 3D and 4D methods and a variety of methods designed to suppress or amplify particular types of resonances. In nuclear Overhauser effect spectroscopy, the relaxation of the resonances is observed; as NOE depends on the proximity of the nuclei, quantifying the NOE for each nucleus allows for construction of a three-dimensional model of the molecule. NMR spectrometers are expensive. Modern NMR spectrometers have a strong and expensive liquid helium-cooled superconducting magnet, because resolution directly depends on magnetic field strength. Less expensive machines using permanent magnets and lower resolution are available, which still give sufficient performance for certain application such as reaction monitoring and quick checking of samples.
There are benchtop nuclear magnetic resonance spectrometers. NMR can be observed than a millitesla. Low-resolution NMR produces broader peaks which can overlap one another causing issues in resolving complex structures; the use of higher strength magnetic fields result in clear resolution of the peaks and is the standard in industry. The Purcell group at Harvard University and the Bloch group at Stanford University independently developed NMR spectroscopy in the late 1940s and early 1950s. Edward Mills Purcell and Felix Bloch shared the 1952 Nobel Prize in Physics for their discoveries; when placed in a magnetic field, NMR active nuclei absorb electromagnetic radiation at a frequency characteristic of the isotope. The resonant frequency, energy of the radiation absorbed, the intensity of the signal are proportional to the strength of the magnetic field. For example, in a 21 Tesla magnetic field, hydrogen atoms resonate at 900 MHz, it is common to refer to a 21 T magnet as a 900 MHz magnet since hydrogen is the most common nucleus detected, however different nuclei will resonate at different frequencies at this field strength in proportion to their nuclear magnetic moments.
An NMR spectrometer consists of a spinning sample-holder inside a strong magnet, a radio-frequency emitter and a receiver with a probe that goes inside the magnet to surround the sample, optionally gradient coils for diffusion measurements, electronics to control the system. Spinning the sample is necessary to average out diffusional motion, however some experiments call for a stationary sample when solution movement is an important variable. For instance, measurements of diffusion constants are done using a stationary sample with spinning off, flow cells can be used for online analysis of process flows; the vast majority of molecules in a solution are solvent molecules, most regular solvents are hydrocarbons and so contain NMR-active protons. In order to avoid detecting only signals from solvent hydrogen atoms, deuterated solvents are used where 99+% of the protons are replaced with deuterium; the most used deuterated solvent is deuterochloroform, although other solvents may be used depending on the solubility of a sample.
Deuterium oxide and deuterated DMSO (DMSO-d
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 amino acid are carbon, hydrogen and nitrogen, although other elements are found in the side chains of certain amino acids. About 500 occurring amino acids are known and can be classified in many ways, they can be classified according to the core structural functional groups' locations as alpha-, beta-, gamma- or delta- amino acids. In the form of proteins, amino acid residues form the second-largest component of human muscles and other tissues. Beyond their role as residues in proteins, amino acids participate in a number of processes such as neurotransmitter transport and biosynthesis. In biochemistry, amino acids having both the amine and the carboxylic acid groups attached to the first carbon atom have particular importance, they are known as α-amino acids. 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, in some antibiotics. 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, pyrrolysine. Pyrrolysine and selenocysteine are encoded via variant codons. N-formylmethionine is considered as a form of methionine rather than as a separate proteinogenic amino acid. Codon–tRNA combinations not found in nature can be used to "expand" the genetic code and form novel proteins known as alloproteins incorporating non-proteinogenic amino acids. Many important proteinogenic and non-proteinogenic amino acids have biological functions. For example, in the human brain and gamma-amino-butyric acid are the main excitatory and inhibitory neurotransmitters. Hydroxyproline, a major component of the connective tissue collagen, is synthesised from proline. Glycine is a biosynthetic precursor to porphyrins used in red blood cells.
Carnitine is used in lipid transport. Nine proteinogenic amino acids are called "essential" for humans because they cannot be produced from other compounds by the human body and so must be taken in as food. Others may be conditionally essential for medical conditions. Essential amino acids may differ between species; because of their biological significance, amino acids are important in nutrition and are used in nutritional supplements, fertilizers and food technology. Industrial uses include the production of drugs, biodegradable plastics, chiral catalysts; 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, subsequently named asparagine, the first amino acid to be discovered. Cystine was discovered in 1810, although its monomer, remained undiscovered until 1884. Glycine and leucine were discovered in 1820; the last of the 20 common amino acids to be discovered was threonine in 1935 by William Cumming Rose, who determined the essential amino acids and established the minimum daily requirements of all amino acids for optimal growth.
The unity of the chemical category was recognized by Wurtz in 1865, but he gave no particular name to it. Usage of the term "amino acid" in the English language is from 1898, while the German term, Aminosäure, was used earlier. Proteins were found to yield amino acids after enzymatic acid hydrolysis. In 1902, Emil Fischer and Franz Hofmeister independently proposed that proteins are formed from many amino acids, whereby bonds are formed between the amino group of one amino acid with the carboxyl group of another, resulting in a linear structure that Fischer termed "peptide". 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 carboxyl group is called the α–carbon. Amino acids containing an amino group bonded directly to the alpha carbon are referred to as alpha amino acids; these include amino acids such as proline which contain secondary amines, which used to be referred to as "imino acids". The alpha amino acids are the most common form found in nature, but only when occurring in the L-isomer.
The alpha carbon is a chiral carbon atom, with the exception of glycine which has two indistinguishable hydrogen atoms on the alpha carbon. Therefore, all alpha amino acids but glycine can exist in either of two enantiomers, called L or D amino acids, which are mirror images of each other. While L-amino acids represent all of the amino acids found in proteins during translation in the ribosome, D-amin