Cysteine chemical structure

Fig. 2.5.9 COSY spectra acquired at 600 MHz with an eight-coil probe along with the chemical structures of the compounds used. Each sample was a 10 mM solution in D20 loaded into the coil via the attached Teflon tubes, with the samples being (A) sucrose, (B) galactose, (C) arginine, (D) chloroquine, (E) cysteine, (F) caffeine, (G) fructose and (H)...

Figure 5.22 Chemical structures of tryptophan and cysteine as subunits of a protein chain...

Twenty amino acids are commonly found in proteins, (a) Draw the chemical structures of alanine, glycine, phenylalanine, and cysteine (see Table 19.4). 

There are currently four racemic PPIs available on the market omeprazole, lansoprazole, pantoprazole, and rabeprazole. (More recently, enantiomerically pure versions have also been studied and developed, e.g., S-omeprazole, marketed by AstraZeneca as esomeprazole see Chapter II-2.) Proton pump inhibitors share the same core structure, the substituted pyridylmethyl-sulfmyl-benzimidazole, but differ in terms of substituents on this core structure. The absolute requirements of the core structure for the activity of PPIs was not understood until it became clear that the active PPIs are derived from inactive prodrugs the prodrugs are transformed, in the acid-secreting parietal cells, by a unique cascade of chemical structural transformations leading to the active principle, a cyclic sulfenamide species. Inhibition of acid secretion in turn is then achieved by formation of covalent disulfide bonds with key cysteines of the (H+/K+)-ATPase. 

The trace element selenium plays an essential role in the activity of some bacterial and eukaryotic antioxidant enzymes (34). Selenium is incorporated into proteins in the form of the so-called twenty-first amino acid selenocysteine, which is encoded by a UGA stop codon. Although the chemical structure of selenocysteine differs from cysteine only by the replacement of the sulfur atom with selenium, the lower pKa of selenocysteine (5.2) allows for ionization of selenocysteine at physiological pH (35). To read through the UGA stop codon selectively, selenocysteine insertion requires a variety of proteins and RNA stmctures. 

Substances related to MSG and purine 5 -ribonucleotides include peptides, amino acids (e.g. cysteine, homocysteine, cysteine S-sulfonic acid, aspartic acid, a-amino adipic acid, a-methyl glutamic acid, tricholomic acid, ibotenic acid), pyrrolidone carboxylic acid, 3-methyl thiopropyl amine, and others [2, 10], They are of less commercial interest than MSG, IMP, and GMP. Chemical structures of some of these substances are depicted in Fig. 3.53. Relative umami effects of some are shown in Tab. 3.49. Tricholomic acid and ibotenic acid have been found in the mushrooms Tricholoma muscarium and Amanita stroboliformis, respectively. 

Fig. 10.6 Chemical structures of the brhverdin IXa (BV), phycocyanobrhn (PCB) and phytochro-mobdin (Pd>B) chromophores shown in the ZsZsZa configuration. Each chromophore forms (at C3) a thioether linkage to a cysteine residue of the protein. Reproduced from Strambi A, Durbeej B (2011) Initial excited-state relaxation of the bdin chromophores of phytochromes a computational study, Photochem Photobiol Sci 10 569-579, with permission of the Royal Society of Chemistry (RSC) on behalf of the European Society for Photobiology, the European Photochemistry Association, and RSC...

Fig. 7 a-g Chemical structures of biohybrid homopolymer amphiphiles. a L-Cysteine-grafted polybutadiene, b Glycosylated polybutadiene, c Glycosylated poly(2-oxazoline). d V,V-l)ialkyl chitosan. e Amphiphilic poly(L-lysine). f PEGylated poly(Z-L-lysine). g Lipid-lysine dendron... 

Using an animal model of ischemia and reperfusion injury, A. M. Lefer etal. (1993) recently showed that sydnonimine C87-3754 infusion, initiated 10 min prior to reperfusion, attenuated myocardial necrosis, prevented neutrophil adherence to the endothelium, and reduced the neutrophil release of damaging superoxide radicals. These effects appear to be related to pharmacological NO donation, since a non-NO compound with a similar chemical structure had no effect in this animal model. Antineutrophil and myocardial protective actions of an experimental NO donor (SPM-5185, a cysteine-containing mononitrate that releases NO) have also been shown in a dog model of myocardial infarction (D. J. Lefer et al., 1993), and in vitro studies have shown that NO donors inhibit activation of human polymorphonuclear leukocytes (Moilanen et al., 1993). 

The penicillins (pen-uh-SILL-ins) are a class of antibiotic compounds derived from the molds Penicillium notatum and Penicillium chryAogenum. The class contains a number of compounds with the same basic bicyclic structure to which are attached different side chains. That basic structure consists of two amino acids, cysteine and valine, joined to each other to make a bicyclic ( two-ring ) compound. The different forms of penicillin are distinguished from each other by adding a single capital letter to their names. Thus penicillin F, penicillin G, penicillin K, penicillin N, penicillin 0, penicillin S, penicillin V, and penicillin X. A number of other antibiotics, including ampicillin, amoxicillin, and methicil-lin, have similar chemical structures. 

Peptide hormones are produced by the endocrine glands (pituitary, thyroid, pineal, adrenal, and pancreas) or by various organs such as the kidney, stomach, intestine, placenta, or liver (Table 3.4). Peptide hormones can have complex, convoluted structures with hundreds of amino acids. Figure 3.2 illustrates the chemical structure of human insulin and its three-dimensional shape. Insulin is made of two amino acid sequences. The A-Chain has 21-amino acids, and the B-Chain has 30-amino acids. The chains are linked together through the sulfur atoms of cysteine (Cys). Peptide hormones are generally different for every species, but they may have similarities [11]. Human insulin is identical to pig insulin, except that the last amino acid of the B-Chain for the pig is alanine (Ala) instead of threonine (Thr) (lUPAC and lUBMB) [9] and [11]. 

Fales and Pisano (1964) have discussed the gas chromatography of amines, alkaloids, and amino acids. Pollock and Kawauchi (1968) have resolved derivatives of serine, hydroxyproline, tyrosine, and cysteine, as well as racemic aspartic acid and tryptophan. VandenHeuvel and Horning (1964) have listed derivatives of steroids that can be separated. VandenHeuvel et al. (1960) first described the separation of bile acid methyl esters and Sjovall (1964) has extended the methods to bile acids. Gas liquid chromatography (GLC) is useful in the analysis of pesticides, herbicides, and pharmaceuticals (Burchfield and Storrs, 1962). Analysis of alkaloids, steroids, and mixtures of anesthetics and expired air are other examples of the application of this very useful technique. Beroza (1970) has discussed the use of gas chromatography for the determination of the chemical structure of organic compounds at the microgram level. 

The folding of a protein explained in the Introduction to this chapter creates an intertwined chemical structure. Ponnuswamy et al. (2012) fabricated knotted molecules, similar to protein structure, which took advantage of hydrophobic interactions. The molecular structure was comprised of three hydrophobic naphthalene diimides held together with alanine linkers and anchored at both ends with cysteine amino acid. 

Figure 4.2 Self-assembling peptide amphiphiles (PA) used for biomimetic mineralization of HA/PA nanocomposite, (a) Chemical structure of the PA, comprising 5 regions (1) a hydrophobic alkyl tail (2) four cysteine residues that can form disulfide bonds to polymerize the self-assembled structure (3) a flexible linker region of three glycine residues (4) a single phosphorylated serine residue that was able to interact strongly with calcium ions and help direct mineralization of HA (5) the cell adhesion ligand ROD. (b) Molecular model of one single PA molecule, (c) Schematic showing the self-assembly of PA molecules into a cylindrical micelle.

The thermal generation of flavor is a very essential process for the "taste" of many different foodstuffs, e.g. cocoa, coffee, bread, meat. The resulting aromas are formed through non-enzymatic reactions mainly with carbohydrates, lipids, amino acids (proteins), and vitamins under the influence of heat. Thiamin (vitamin B ) and the amino acids, cysteine and methionine, belong to those food constituents which act as flavor precursors in thermal reactions. The role of thiamin as a potent flavor precursor is related to its chemical structure which consists of a thiazole as well as a pyrimidine moiety. The thermal degradation of this heterocyclic constituent leads to very reactive intermediates which are able to react directly to highly odoriferous flavor compounds or with degradation products of amino acids or carbohydrates. 

We may divide the sulfur compounds into primary and conjugated, the primary compounds forming a part of more complex chemical structures in the latter. The major primary sulfur compounds that have an established role in the normal biochemical processes of the vertebrate range in variety from the simple inorganic compounds, sulfate, thiosulfate, and thiocyanate, to the amino acids, cysteine, cystine, methionine,... 

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