Amino acids, literature reviews

The last comprehensive review of the chemistry of oxazolones covered the literature through 1954. Most of the studies up to that time stemmed from either interest in the role of azlactones as precursors of a-amino acids and peptides or the monumental studies on penicillin, which, for a time, was thought to possess an oxazolone ring, rather than the correct jS-lactam moiety. 

Proteins have been hydrolyzed by treatment with sulfuric acid, hydrochloric acid, barium hydroxide, proteolytic enzymes, and other hydrolytic reagents, but no condition has been found which avoids some destruction or incomplete liberation of tryptophan, cystine, and some other amino acids. The early work on this problem has been reviewed by Mitchell and Hamilton (194). The literature and their own excellent experiments on the hydrolysis problem in relation to the liberation and destruction of tryptophan have been presented recently by Spies and Chambers (269). 

A recent review of the literature on the amino acid structure of DAT stated that uptake of dopamine is dependent on multiple functional groups of amino acids within DAT.26 The authors... 

This series in heterocyclic chemistry is being introduced to collectively make available critically and comprehensively reviewed literature scattered in various journals as papers and review articles. All sorts of heterocyclic compounds originating from synthesis, natural products, marine products, insects, etc. will be covered. Several heterocyclic compounds play a significant role in maintaining life. Blood constituent hemoglobin and purines as well as pyrimidines, are constituents of nucleic acid (DNA and RNA) are also heterocyclic compounds. Several amino acids, carbohydrates, vitamins, alkaloids, antibiotics, etc. are also heterocyclic compounds that are essential for life. Heterocyclic compounds are widely used in clinical practice as drugs, but all applications of heterocyclic medicines can not be discussed in detail. In addition to such applications, heterocyclic compounds also find several applications in the plastics industry, in photography as sensitizers and developers, and in dye industry as dyes, etc. 

Numerous applications of chiral separations using CDs can be found in the literature. Some examples, either reviewing chiral separations in CE or presenting the separation of several compounds, can be found in References 97,101,107,121-124. Several studies related to the chiral separation of amino-acid derivatives by CE and micellar electrokinetic capillary chromatography with different types of CDs have also been reported 102,103,114,125-128... 

Chiral ligand-exchange chromatography (CLEC) ° separates enantiomers by the formation of diastereomeric metal complexes. In a first instance the technique was mainly used for the separation of amino acids. Impressive results of the first separations gave rise to intensive investigation in the field and numerous publications appeared in the literature, which have been reviewed. 

According to the report by Bell et al. there are about 800 nonprotein amino acids known to date in the literature. It is not practical to cite all the primary literature of the reported nonprotein amino acids. To the best of our knowledge, we have tried to cite the most relevant references and the recent review papers available. In most cases, further references for the primary literature can be obtained from these reviews. We apologize to the reader for any missed compounds and citations that might be relevant to the material. 

Cytochrome c folding and electron transfer are related topics. An improperly folded protein—engendered through amino acid mutation for instance— will exhibit diminished or nonexistent electron transfer. More reports will be forthcoming from many research groups on the topics of protein folding and electron transfer between proteins. The reader should consult the literature for updates on these related hot topics. The reader is referred to the 2006 Chemical Reviews article from the Bertini group (reference 101), which exhaustively surveys the cytochrome c field. 

This review covers the recent literature (2002-2007) in which either multienzyme systems or, alternatively, true chemoenzymatic processes (i.e. those in which an enzyme is combined with a chemical catalysts/reagent in a key step) are employed for the synthesis of chiral amino acids and amines. Not included are those papers in which the term chemoenzymatic refers to the fact that the substrate for the biotransformation has simply been prepared via chemical synthesis. 

An excellent review of the problems of the enantioselective heterocatalytic hydrogenation of prochiral double bonds, covering the literature up to 1970, has been compiled by Izumi57). Raney nickel catalysts modified with chiral amino acids or dipeptides gave only very moderate enantiomeric excesses of between 0 and 10% in the hydrogenation of olefins, carbonyl compounds or oximes 57). Only Raney nickel modified with (S)-tyrosine furnished a higher enantiomeric excess in the products58). 

The biological properties of phosphorus amino acid analogues (and their derivatives) depend upon their stereochemistry. Consequently, numerous methods for obtaining these compounds in stereochemically pure form have been developed. Two excellent review articles summarize the work performed prior to 1993. 3,4 Resolution of racemates continues to be a useful approach for obtaining optically pure aminoalkylphosphonic and -phosphinic acid derivatives (vide infra), but most of the newer literature describes asymmetric syntheses of these compounds.15-17 Two methods for resolution and one for asymmetric synthesis are described (vide infra) they have been selected since they are relatively easy to perform, work with a variety of side chains, can be carried out on a reasonable scale with readily available starting materials, and produce products of high stereopurity. However, just as in traditional amino acid chemistry, each side chain introduces its own complications, and in many cases, especially for more complex analogues, other methods may be preferred. 

Since no single internal standard can possibly mimic the chemistry of all the amino acids (for overall profile), the choice of internal standard has been based primarily on two criteria. The first is chemical stability. The internal standard must not be labile under the conditions employed. The second is that the internal standard must offer chromatographic resolution. This is not easy, since the overall profile produces a chromatogram that is already very cluttered. A review of the literature reveals that three internal standards are the overwhelming popular choices norleucine, norvaline, and a-amino-n-butanoic acid (AABA). It should be noted that norleucine and norva-line are very hydrophobic amino acids, whereas AABA is relatively hydrophilic. How these standards might behave during sample preparation steps (e.g., filtration) as a function of their hy-drophobicity should be taken into consideration. 

The element Se—not really a metal—is known to play a key role in enzymes such as the well-known glutathione peroxidase, formate dehydrogenase, glycine reductase, and the previously mentioned hydrogenases (Chapter 9). The unusual amino acid selenocysteine has a unique codon on the DNA (TGA/UGA), but selenation of serine also appears to be possible [16]. A brief review on Selenium can be found in the literature [17],... 

The literature of metabolism in proteinoids and proteinoid microspheres is reviewed and criticized from a biochemical and experimental point of view. Closely related literature is also reviewed in order to understand the function of proteinoids and proteinoid microspheres. Proteinoids or proteinoid microspheres have many activities. Esterolysis, decarboxylation, animation, deamination, and oxido-reduction are catabolic enzyme activities. The formation of ATP, peptides or oligonucleotides is synthetic enzyme activities. Additional activities are hormonal and inhibitory. Selective formation of peptides is an activity of nucleoproteinoid microspheres these are a model for ribosomes. Mechanisms of peptide and oligonucleotide syntheses from amino acids and nucleotide triphosphate by proteinoid microspheres are tentatively proposed as an integrative consequence of reviewing the literature. 

Despite the relatively large number of enantioselective receptors of cations and neutral species, reports on the effective chiral recognition of anions are still rare. However, there are a number of reports in the literature describing the recognition of carboxylic acids, and amino acids in particular, performed in aqueous solution at a pH where the carboxylic group has to be at least partly ionized. These reports are also included in this review. 

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