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Entatic State
In bioinorganic chemistry, an entatic state is "a state of an atom or group which, due to its binding in a protein, has its geometric or electronic condition adapted for function." The term was coined by Bert Vallee and R. J. P. Williams, following work on the catalytic activity of carbonic anhydrase. These states are thought to enhance the chemistry of metal ions in biological catalysis. An example of an entatic state is the copper center in plastocyanin, a redox enzyme. In this protein, the copper shuttles between oxidized and reduced states, Cu2+ and Cu+, respectively. Each oxidation state prefers a distinct coordination geometry The coordination geometry of an atom is the geometrical pattern defined by the atoms around the central atom. The term is commonly applied in the field of inorganic chemistry, where diverse structures are observed. The coordination geometry depen ...: whereas copper(II) is normally square planar and prefers hard bases such as oxygen and nitrogen lig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bioinorganic Chemistry
Bioinorganic chemistry is a field that examines the role of metals in biology. Bioinorganic chemistry includes the study of both natural phenomena such as the behavior of metalloproteins as well as artificially introduced metals, including those that are non-essential, in medicine and toxicology. Many biological processes such as respiration depend upon molecules that fall within the realm of inorganic chemistry. The discipline also includes the study of inorganic models or mimics that imitate the behaviour of metalloproteins. As a mix of biochemistry and inorganic chemistry, bioinorganic chemistry is important in elucidating the implications of electron-transfer proteins, substrate bindings and activation, atom and group transfer chemistry as well as metal properties in biological chemistry. The successful development of truly interdisciplinary work is necessary to advance bioinorganic chemistry. Composition of living organisms About 99% of mammals' mass are the elements carb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bert L
Bert or BERT may refer to: Persons, characters, or animals known as Bert *Bert (name), commonly an abbreviated forename and sometimes a surname *Bert, a character in the poem "Bert the Wombat" by The Wiggles; from their 1992 album ''Here Comes a Song'' *Bert (Sesame Street), fictional character on the TV series ''Sesame Street'' *Bert (horse), foaled 1934 * Bert (Mary Poppins), a Cockney chimney sweep in the book series & Disney film ''Mary Poppins'' * Iron Bert (one half of the two yellow diesels 'Arry and Bert), also in ''Thomas and Friends'' Places *Berd, Armenia, also known as Bert * Bert, Allier, a commune in the French of Allier (pronounced \bɛʁ\) *Bert, West Virginia Electronics and computing *Bit error rate test, a testing method for digital communication circuits *Bit error rate tester, a test equipment used for testing the bit error rate of digital communication circuits *HP Bert, a CPU in certain Hewlett-Packard programmable calculators *BERT (language model) (Bidir ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Robert Williams (English Chemist)
Robert Joseph Paton Williams (25 February 1926 – 21 March 2015) was an English chemist, an Emeritus Fellow at Wadham College, Oxford and an Emeritus Professor at the University of Oxford. Education and early life Robert Joseph Paton Williams was born on 25 February 1926 in Wallasey to Ernest Ivor Williams, a customs and excise officer at Liverpool, and Alice Williams (née Roberts), a milliner; he was the second of four children. Williams failed to gain a scholarship to Wallasey Grammar School, having missed six months’ schooling with diphtheria, but his parents paid for him to attend. He went on to gain a place and be awarded a Postmastership to read chemistry at Merton College, Oxford in 1944. For his final undergraduate research year he worked with analytical chemist Harry Irving. This enabled him to establish an order of the relative stabilities of metal–organic complexes along the latter half of the transition series manganese through zinc. From these findings he ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plastocyanin
Plastocyanin is a copper-containing protein that mediates electron-transfer. It is found in a variety of plants, where it participates in photosynthesis. The protein is a prototype of the blue copper proteins, a family of intensely blue-colored metalloproteins. Specifically, it falls into the group of small type I blue copper proteins called "cupredoxins". Function In photosynthesis, plastocyanin functions as an electron transfer agent between cytochrome f of the cytochrome ''b''6''f'' complex from photosystem II and P700+ from photosystem I. Cytochrome ''b''6''f'' complex and P700+ are both membrane-bound proteins with exposed residues on the lumen-side of the thylakoid membrane of chloroplasts. Cytochrome f acts as an electron donor while P700+ accepts electrons from reduced plastocyanin. Structure The copper site in plastocyanin, with the four amino acids that bind the metal labelled. Plastocyanin was the first of the blue copper proteins to be characterised by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coordination Geometry
The coordination geometry of an atom is the geometrical pattern defined by the atoms around the central atom. The term is commonly applied in the field of inorganic chemistry, where diverse structures are observed. The coordination geometry depends on the number, not the type, of ligands bonded to the metal centre as well as their locations. The number of atoms bonded is the coordination number. The geometrical pattern can be described as a polyhedron where the vertices of the polyhedron are the centres of the coordinating atoms in the ligands. The coordination preference of a metal often varies with its oxidation state. The number of coordination bonds (coordination number) can vary from two in as high as 20 in . One of the most common coordination geometries is octahedral, where six ligands are coordinated to the metal in a symmetrical distribution, leading to the formation of an octahedron if lines were drawn between the ligands. Other common coordination geometries are tet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HSAB
HSAB is an acronym for "hard and soft (Lewis) acids and bases". HSAB is widely used in chemistry for explaining the stability of compounds, reaction mechanisms and pathways. It assigns the terms 'hard' or 'soft', and 'acid' or 'base' to chemical species. 'Hard' applies to species which are small, have high charge states (the charge criterion applies mainly to acids, to a lesser extent to bases), and are weakly polarizable. 'Soft' applies to species which are big, have low charge states and are strongly polarizable. The theory is used in contexts where a qualitative, rather than quantitative, description would help in understanding the predominant factors which drive chemical properties and reactions. This is especially so in transition metal chemistry, where numerous experiments have been done to determine the relative ordering of ligands and transition metal ions in terms of their hardness and softness. HSAB theory is also useful in predicting the products of metathesis react ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reorganization Energy
In theoretical chemistry, Marcus theory is a theory originally developed by Rudolph A. Marcus, starting in 1956, to explain the rates of electron transfer reactions – the rate at which an electron can move or jump from one chemical species (called the electron donor) to another (called the electron acceptor). It was originally formulated to address outer sphere electron transfer reactions, in which the two chemical species only change in their charge with an electron jumping (e.g. the oxidation of an ion like Fe2+/Fe3+), but do not undergo large structural changes. It was extended to include inner sphere electron transfer contributions, in which a change of distances or geometry in the solvation or coordination shells of the two chemical species is taken into account (the Fe-O distances in Fe(H2O)2+ and Fe(H2O)3+ are different).Hush, N.S. Trans. Faraday Soc. 1961, 57,557 For electron transfer reactions without making or breaking bonds Marcus theory takes the place of Eyring ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
