University of Rostock
The University of Rostock is a public university located in Rostock, Mecklenburg-Vorpommern, Germany. Founded in 1419, it is the third-oldest university in Germany, it is the oldest and largest university in continental northern Europe and the Baltic Sea area, 8th oldest in Central Europe. It was the 5th university established in the Holy Roman Empire; the university has been associated with five Nobel laureates. Famous alumni include Nobel laureates: Albrecht Kossel, Karl von Frisch, Otto Stern, it is a member of the European University Association. The language of instruction is German, but English for postgraduate studies, it was founded in 1419 by confirmation of Pope Martin V and thus is one of the oldest universities in Northern Europe. In Germany, there are only five universities that were founded before, while only Heidelberg and Leipzig operated continuously since then: Heidelberg, Erfurt, Würzburg and Leipzig; that makes Rostock University the third oldest German university in continuous operation.
Throughout the 15th century, the University of Rostock had about 400 to 500 students each year, a large number at that time. Rostock was among the largest universities in Germany at the time and many of its students came from the Low Countries, Scandinavia or other states bordering the Baltic Sea. In the course of political struggles and pressure from the church, the university moved to Greifswald in 1437 and remained there until 1443. From 1487 to 1488 teaching took place in Lübeck. A few years the city of Rostock, its university became Protestant in 1542. Humanism and Lutheranism were defining characteristics of the university. After the Thirty Years' War, the University of Rostock played only a regional role; when the "ownership" of the university moved from the city to the state in 1827, things changed for the better. The end of the 19th century saw generous building activity in Rostock's alma mater and the university soon regained its old reputation amongst German universities. On the occasion of the 500th anniversary of the university, Albert Einstein and Max Planck received honorary doctorates on 12 November 1919.
This made the University of Rostock the world's first institute of higher learning to award this honour to Einstein. The doctorate was not revoked despite such orders by the Nazis; the reason for this remains unknown. David Katz, Hans Moral and others lost their posts in 1933; the end of the Second World War in 1945 brought many changes. The university, now finding itself in the Soviet Zone of Germany, was re-opened on 24 February 1946; the Faculty of Law was closed in 1951, a Faculty of Agriculture was introduced in 1950 and in 1951 saw the opening of a Department of Shipbuilding. The University of Rostock was the first traditional university in Germany to open a technical faculty. In 1952, the Faculty of Aviation was opened, but relocated to Dresden. In 1976 the university was renamed Wilhelm-Pieck-Universität after Wilhelm Pieck, the first president of the German Democratic Republic; the renaming was annulled after the German reunification. The regional economy has improved as over 800 companies launched from the university since 1991.
External funding for research increased between 2005 and 2010 by 83% and is above 47 million Euros per year. Over 500 million Euros has been invested in the university infrastructure since 1991, which will reach 750 million Euros by 2015; the number of young people from the West Germany and international students who choose University of Rostock as a study location, are increasing every year. International Students from 99 different countries have been studied at University of Rostock. In 2007, the University of Rostock gathered its research capacities into three profile lines: Life, Light & Matter, Maritime Systems, Aging of Individuals and Society. In 2010 a fourth was called Knowledge-Culture-Transformation. Life, Light & Matter develops new concepts for future technologies based on atomic and molecular processes in connection with laser optics and life sciences. Maritime Systems unites oceanographers, humanities scholars and social scientists and lawyers. Aging of Individuals and Society has as its target a self-determined lifestyle in old age.
Knowledge-Culture-Transformation deals with media and the representation of knowledge, transformation of knowledge and interculturalism as well as knowledge and power. Like many continental European universities, the University of Rostock is divided into academic faculties; those can be sub-divided into academic chairs. It is divided into the following nine faculties: The Rostock University Library consists of 3 divisional libraries and several specialized libraries provides scientific literature and information for research and study; the university statistics shows about 3 million physical volumes recorded in the catalogue. It provides access to specialized databases; the library possesses large special collections of culturally historical and scientifically historical old books. In the Patents and Standards Centre, all DIN norms and regulations as well as the VDI guidelines are provided. Moreover, the library contains the university archive and the art treasure collection; the Rostock Student Services provides accommodation for newly arrived i
Edwin B. Hart
Edwin Bret Hart was an American biochemist long associated with the University of Wisconsin-Madison. A native of Ohio, Hart studied physiological chemistry in Germany under Albrecht Kossel at the University of Marburg and University of Heidelberg. Upon his return to the United States, he worked at the New York State Agricultural Experiment Station in Geneva, New York, at the University of Michigan before being hired in 1906 by Stephen M. Babcock of the University of Wisconsin to conduct what came to be known as the "single-grain experiment" that would run from May 1907 to 1911; this experiment entailed a long-term feeding plan using a chemically balanced diet of carbohydrates and protein instead of single-plant rations as done in Babcock's earlier experiments of 1881 and 1901. Hart directed the experiment, Babcock provided ideas, George C. Humphrey oversaw the welfare of the cattle during the experiment. Elmer Verner McCollum, an organic chemist from Connecticut, was hired by Hart to analyze the grain rations and the cow feces.
The experiment called for four groups of four heifer calves each, of which three groups were raised and two pregnancies were carried through. The first group ate only wheat, the second group ate only bran, the third group ate only corn, the last group ate a mixture of the three. In 1908, it was shown that the corn-fed animals were the most healthy of the group while the wheat-fed groups were the least healthy. All four groups bred during that year, with the corn-fed calves being the healthiest while the wheat and mixed-fed calves were stillborn or died. Similar results were found in 1909. In 1910, the corn-fed cows had their diets switched to wheat and the non-corn-fed cows were fed wheat; this produced unhealthy calves for the corn-fed cows, while the remaining cows produced healthy calves. When the 1909 formulas were reintroduced to the respective cows in 1911, the same gestation results in 1909 occurred again in 1911; these results were published in 1911. Similar results had been determined in the Dutch East Indies in 1901, in Poland in 1910, in England in 1906.
Hart went on during his career to determine in 1917, working with Harry Steenbock, that a possible cause of goitre was iodine deficiency. In 1939, Hart and his associates developed a process that stabilized iodine in table salt, which proved inexpensive and effective in dealing with goiter, he determined that copper facilitates iron assimilation into the body, leading to a possible therapeutic agent to fight anemia, although its use has never been implemented in medical practice. Hart retired in 1944 and died in 1953; the Institute of Food Technologists would rename the Stephen M. Babcock Award the Babcock-Hart Award in honor of both men's work in improving public health through better nutrition. Petition from Madison, Wisconsin to National Park Service for University of Wisconsin–Madison Dairy Barn to be named a National Landmark. Pp.21-25. IFT Babcock-Hart Award winners Career path of Albrecht Kossel University of Wisconsin–Madison plaque commemorating Hart and Harry Steenbock on their iodine-goiter discovery Wisconsin Alumni Research Foundation contribution National Academy of Sciences Biographical Memoir
Rostock is a city in the north German state Mecklenburg-Vorpommern. Rostock is on the Warnow river. Rostock is the largest city in Mecklenburg-Vorpommern, as well as its only regiopolis. Rostock is home to one of the oldest universities in the world, the University of Rostock, founded in 1419; the city territory of Rostock stretches for about 20 km along the Warnow to the Baltic Sea. The largest built-up area of Rostock is on the western side of the river; the eastern part of its territory is dominated by the forested Rostock Heath. In the 11th century Polabian Slavs founded; the Danish king Valdemar I set the town on fire in 1161. Afterwards the place was settled by German traders. There were three separate cities: Altstadt around the Alter Markt, which had St. Petri, Mittelstadt around the Neuer Markt, with St. Marien and Neustadt around the Hopfenmarkt, with St. Jakobi. In 1218, Rostock was granted Lübeck law city rights by prince of Mecklenburg. During the first partition of Mecklenburg following the death of Henry Borwin II of Mecklenburg in 1226, Rostock became the seat of the Lordship of Rostock, which survived for a century.
In 1251, the city became a member of the Hanseatic League. In the 14th century it was a powerful seaport town with 12,000 inhabitants and the largest city in Mecklenburg. Ships for cruising the Baltic Sea were constructed in Rostock; the independent fishing village of Warnemünde at the Baltic Sea became a part of Rostock in 1323, to secure the city's access to the sea. In 1419, the University of Rostock was founded, the oldest university in continental northern Europe and the Baltic Sea area. At the end of the 15th century, the dukes of Mecklenburg succeeded in enforcing their rule over the town of Rostock, which had until been only nominally subject to their rule and independent, they took advantage of a riot known as a failed uprising of the impoverished population. Subsequent quarrels with the dukes and persistent plundering led to a loss of the city's economic and political power. In 1565 there were further clashes with Schwerin. Among other things, the nobility introduced a beer excise. John Albert I advanced on the city with 500 horsemen, after Rostock had refused to take the formal oath of allegiance, had the city wall razed in order to have a fortress built.
The conflict did not end until the first Rostock Inheritance Agreement of 21 September 1573, in which the state princes were guaranteed hereditary rule over the city for centuries and recognizing them as the supreme judicial authority. The citizens razed the fortress the following spring. From 1575 to 1577 the city walls were rebuilt, as was the Lagebusch tower and the Stein Gate, in the Dutch Renaissance style; the inscription sit intra te concordia et publica felicitas, can still be read on the gate, refers directly to the conflict with the Duke. In 1584 the Second Rostock Inheritance Agreement was enforced, which resulted in a further loss of former city tax privileges. At the same time, these inheritance contracts put paid to Rostock's ambition of achieving imperial immediacy, as Lübeck had done in 1226; the strategic location of Rostock provoked the envy of its rivals. Danes and Swedes occupied the city twice, first during the Thirty Years' War and again from 1700 to 1721. In the early 19th century, the French, under Napoleon, occupied the town for about a decade until 1813.
In nearby Lübeck-Ratekau, Gebhard Leberecht von Blücher, born in Rostock and, one of few generals to fight on after defeat at the Battle of Jena, surrendered to the French in 1806. This was only after furious street fighting in the Battle of Lübeck, in which he led some of the cavalry charges himself. By the time of the surrender, the exhausted Prussians had neither ammunition. In the first half of the 19th century, Rostock regained much of its economic importance, due at first to the wheat trade from the 1850s, to industry its shipyards; the first propeller-driven steamers in Germany were constructed here. The city grew in area and population, with new quarters developing in the south and west of the ancient borders of the city. Two notable developments were added to house the increasing population at around 1900: Steintor-Vorstadt in the south, stretching from the old city wall to the facilities of the new Lloydbahnhof, was designed as a living quarter, it consisted of large single houses, once inhabited by wealthy citizens.
Kröpeliner-Tor-Vorstadt in the west, was designed to house the working population as well as to provide smaller and larger industrial facilities, such as the Mahn & Ohlerich's Brewery. The main shipyard, was nearby at the shore of the river. In the 20th century, important aircraft manufacturing facilities were situated in the city, such as the Arado Flugzeugwerke in Warnemünde and the Heinkel Works with facilities at various places, including their secondary Heinkel-Süd facility in Schwechat, Austria, as the original Heinkel firm's Rostock facilities had been renamed Heinkel-
Heinrich Anton de Bary
Heinrich Anton de Bary was a German surgeon, botanist and mycologist. He is considered a founding father of plant pathology as well as the founder of modern mycology, his extensive and careful studies of the life history of fungi and contribution to the understanding of algae and higher plants were landmarks of biology. Born in Frankfurt, Anton de Bary was one of ten children born to physician August Theodor de Bary and Emilie Meyer de Bary, his father encouraged him to join the excursions of the active group of naturalists who collected specimens in the nearby countryside. De Bary’s youthful interest in plants and in examination of fungi and algae were inspired by George Fresenius, a physician, who taught botany at Senckenberg Institute. Fresenius was an expert on thallophytes. In 1848, de Bary graduated from a Gymnasium at Frankfurt, began to study medicine at Heidelberg, continued at Marburg. In 1850, he went to Berlin to continue pursuing his study of medicine, continued to explore and develop his interest in plant science.
He received his degree in medicine at Berlin in 1853, but his dissertation title was "De plantarum generatione sexuali", a botanical subject. The same year, he published a book on the fungi that caused smuts in plants. After the graduation, de Bary practiced medicine in Frankfurt, but only for a short period of time, he was drawn back to botany and became Privatdozent in botany at the University of Tübingen, where he worked as an assistant to Hugo von Mohl for a while. In 1855, he succeeded the position of the well-known botanist Karl Wilhelm von Nägeli at Freiburg, where he established the most advanced botanical laboratory at the time and directed many students. De Bary married Antonie Einert in 1861. In 1867, de Bary moved to the University of Halle to succeed the position of Professor Diederich Franz Leonhard von Schlechtendal, with Hugo von Mohl, co-founded the pioneer botanical journal Botanische Zeitung. De Bary became its coeditor and sole editor; as an editor of and contributor to the journal, he exercised great influence upon the development of botany.
After the Franco-Prussian War, de Bary was appointed professor of botany at the University of Strasbourg, founder of the Jardin botanique de l'Université de Strasbourg, elected as the inaugural rector of the reorganized university. He conducted much research in the university botanical institute, attracted many students from Europe and America, made a large contribution to the development of botany. De Bary was devoted to the study of the life history of fungi. At that time, various fungi were still considered to arise through spontaneous generation, he proved that pathogenic fungi were not the products of cell contents of the affected plants and did not arise from the secretion of the sick cells. In de Bary's time, potato late blight had caused economic loss, he studied the pathogen Phytophthora elucidated its life cycle. The origin of plant diseases was not known at that time. Much as Miles Joseph Berkeley had insisted in 1841 that the oomycete found in potato blight was the cause of the disease, de Bary declared that the rust and smut fungi were the causes of the pathological changes in diseased plants.
He concluded that Ustilaginales were parasites. De Bary spent much time studying the morphology of fungi and noticed that certain forms, classified as separate species were successive stages of development of the same organism. De Bary studied the developmental history of Myxomycetes, thought it was necessary to reclassify the lower animals, he first coined the term Mycetozoa to include slime molds. In his work on Myxomycetes, he pointed out that at one stage of their life cycle, they were little more than formless, motile masses of the substance that Félix Dujardin had called sarcode; this is the fundamental basis of the protoplasmic theory of life. De Bary was the first to demonstrate sexuality in fungi. In 1858, he had observed conjugation in the alga Spirogyra, in 1861, he described sexual reproduction in the fungus Peronospora sp, he saw the necessity of observing the whole life cycle of pathogens and attempted to follow it in the living host plants. De Bary published his first work on fungi in 1861, spent more than 15 years studying Peronosporeae Phytophthora infestans and Cystopus, parasites of potato.
In his published work in 1863 entitled "Recherches sur le developpement de quelques champignons parasites", he reported having inoculated spores of P. infestans on healthy potato leaves and observed the penetration of the leaf and the subsequent growth of the mycelium that affected the tissue, the formation of conidia, the appearance of the characteristic black spots of the potato blight. He did similar experiments on potato stalks and tubers, he watched conidia in the soil and their infection of the tubers, observing that mycelium could survive the cold winter in the tubers. From all these studies, he concluded, he did a thorough investigation on Puccinia graminis, the pathogen of rust of wheat and other grains. He noticed that P. graminis produced reddish summer spores called "urediospores", dark winter spores called "teleutospores". He inoculated sporidia from the winter spores of the wheat rust on the leaves of the "common barberry"; the sporidia germinated and led to the form
The cell is the basic structural and biological unit of all known living organisms. A cell is the smallest unit of life. Cells are called the "building blocks of life"; the study of cells is called cellular biology. Cells consist of cytoplasm enclosed within a membrane, which contains many biomolecules such as proteins and nucleic acids. Organisms can be classified as multicellular; the number of cells in plants and animals varies from species to species, it has been estimated that humans contain somewhere around 40 trillion cells. Most plant and animal cells are visible only under a microscope, with dimensions between 1 and 100 micrometres. Cells were discovered by Robert Hooke in 1665, who named them for their resemblance to cells inhabited by Christian monks in a monastery. Cell theory, first developed in 1839 by Matthias Jakob Schleiden and Theodor Schwann, states that all organisms are composed of one or more cells, that cells are the fundamental unit of structure and function in all living organisms, that all cells come from pre-existing cells.
Cells emerged on Earth at least 3.5 billion years ago. Cells are of two types: eukaryotic, which contain a nucleus, prokaryotic, which do not. Prokaryotes are single-celled organisms, while eukaryotes can be either single-celled or multicellular. Prokaryotes include two of the three domains of life. Prokaryotic cells were the first form of life on Earth, characterised by having vital biological processes including cell signaling, they are simpler and smaller than eukaryotic cells, lack membrane-bound organelles such as a nucleus. The DNA of a prokaryotic cell consists of a single chromosome, in direct contact with the cytoplasm; the nuclear region in the cytoplasm is called the nucleoid. Most prokaryotes are the smallest of all organisms ranging from 0.5 to 2.0 µm in diameter. A prokaryotic cell has three architectural regions: Enclosing the cell is the cell envelope – consisting of a plasma membrane covered by a cell wall which, for some bacteria, may be further covered by a third layer called a capsule.
Though most prokaryotes have both a cell membrane and a cell wall, there are exceptions such as Mycoplasma and Thermoplasma which only possess the cell membrane layer. The envelope gives rigidity to the cell and separates the interior of the cell from its environment, serving as a protective filter; the cell wall consists of peptidoglycan in bacteria, acts as an additional barrier against exterior forces. It prevents the cell from expanding and bursting from osmotic pressure due to a hypotonic environment; some eukaryotic cells have a cell wall. Inside the cell is the cytoplasmic region that contains the genome and various sorts of inclusions; the genetic material is found in the cytoplasm. Prokaryotes can carry extrachromosomal DNA elements called plasmids, which are circular. Linear bacterial plasmids have been identified in several species of spirochete bacteria, including members of the genus Borrelia notably Borrelia burgdorferi, which causes Lyme disease. Though not forming a nucleus, the DNA is condensed in a nucleoid.
Plasmids encode additional genes, such as antibiotic resistance genes. On the outside and pili project from the cell's surface; these are structures made of proteins that facilitate communication between cells. Plants, fungi, slime moulds and algae are all eukaryotic; these cells are about fifteen times wider than a typical prokaryote and can be as much as a thousand times greater in volume. The main distinguishing feature of eukaryotes as compared to prokaryotes is compartmentalization: the presence of membrane-bound organelles in which specific activities take place. Most important among these is a cell nucleus, an organelle that houses the cell's DNA; this nucleus gives the eukaryote its name, which means "true kernel". Other differences include: The plasma membrane resembles that of prokaryotes in function, with minor differences in the setup. Cell walls may not be present; the eukaryotic DNA is organized in one or more linear molecules, called chromosomes, which are associated with histone proteins.
All chromosomal DNA is stored in the cell nucleus, separated from the cytoplasm by a membrane. Some eukaryotic organelles such as mitochondria contain some DNA. Many eukaryotic cells are ciliated with primary cilia. Primary cilia play important roles in chemosensation and thermosensation. Cilia may thus be "viewed as a sensory cellular antennae that coordinates a large number of cellular signaling pathways, sometimes coupling the signaling to ciliary motility or alternatively to cell division and differentiation." Motile eukaryotes can move using motile flagella. Motile cells are absent in flowering plants. Eukaryotic flagella are more complex than those of prokaryotes. All cells, whether prokaryotic or eukaryotic, have a membrane that envelops the cell, regulates what moves in and out, maintains the electric potential of the cell. Inside the membrane, the cytoplasm takes up most of the cell's volume. All cells possess DNA, the hereditary material of genes, RNA, containing the information necessary to build various proteins such as enzymes, the cell's primary machinery.
There are other kinds of biomolecules in cells. This article lists these primary cellular components briefly
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
Nucleobases known as nitrogenous bases or simply bases, are nitrogen-containing biological compounds that form nucleosides, which in turn are components of nucleotides, with all of these monomers constituting the basic building blocks of nucleic acids. The ability of nucleobases to form base pairs and to stack one upon another leads directly to long-chain helical structures such as ribonucleic acid and deoxyribonucleic acid. Five nucleobases—adenine, guanine and uracil —are called primary or canonical, they function as the fundamental units of the genetic code, with the bases A, G, C, T being found in DNA while A, G, C, U are found in RNA. Thymine and uracil are identical excepting. Adenine and guanine have a fused-ring skeletal structure derived of purine, hence they are called purine bases; the simple-ring structure of cytosine and thymine is derived of pyrimidine, so those three bases are called the pyrimidine bases. Each of the base pairs in a typical double-helix DNA comprises a purine and a pyrimidine: either an A paired with a T or a C paired with a G.
These purine-pyrimidine pairs, which are called base complements, connect the two strands of the helix and are compared to the rungs of a ladder. The pairing of purines and pyrimidines may result, in part, from dimensional constraints, as this combination enables a geometry of constant width for the DNA spiral helix; the A-T and C-G pairings function to form double or triple hydrogen bonds between the amine and carbonyl groups on the complementary bases. In August 2011, a report based on NASA studies of meteorites suggested that nucleobases such as adenine, xanthine, purine, 2,6-diaminopurine, 6,8-diaminopurine may have formed in outer space as well as on earth; the origin of the term base reflects these compounds' chemical properties in acid-base reactions, but those properties are not important for understanding most of the biological functions of nucleobases. At the sides of nucleic acid structure, phosphate molecules successively connect the two sugar-rings of two adjacent nucleotide monomers, thereby creating a long chain biomolecule.
These chain-joins of phosphates with sugars create the "backbone" strands for a single- or double helix biomolecule. In the double helix of DNA, the two strands are oriented chemically in opposite directions, which permits base pairing by providing complementarity between the two bases, and, essential for replication of or transcription of the encoded information found in DNA. DNA and RNA contain other bases that have been modified after the nucleic acid chain has been formed. In DNA, the most common modified base is 5-methylcytosine. In RNA, there are many modified bases, including those contained in the nucleosides pseudouridine, inosine, 7-methylguanosine. Hypoxanthine and xanthine are two of the many bases created through mutagen presence, both of them through deamination. Hypoxanthine is produced from adenine, xanthine from guanine, uracil results from deamination of cytosine; these are examples of modified guanosine. These are examples of modified thymine or uridine. A vast number of nucleobase analogues exist.
The most common applications are used as fluorescent probes, either directly or indirectly, such as aminoallyl nucleotide, which are used to label cRNA or cDNA in microarrays. Several groups are working on alternative "extra" base pairs to extend the genetic code, such as isoguanine and isocytosine or the fluorescent 2-amino-6-purine and pyrrole-2-carbaldehyde. In medicine, several nucleoside analogues are used as antiviral agents; the viral polymerase incorporates these compounds with non-canonical bases. These compounds are activated in the cells by being converted into nucleotides. At least one set of new base pairs has been announced as of May 2014. Nucleoside Nucleotide Nucleic acid notation Nucleic acid sequence Base pairing in DNA Double Helix