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D and amino acids

Amino acids D- and L-amino acid oxidases Hydrogen peroxide Platinum... [Pg.304]

Peptide antibiotics are composed of the peptide chain of amino acids, d and l, covalently linked to other moieties. Most peptides are toxic and are poorly absorbed from the alimentary tract. Peptide antibiotics are difficult to analyze in biological and food samples, as they are similar to matrix components. They can be separated on silica gel, amino silica gel, and silanized silica gel plates. A variety of mobile phases are applied, from a simple one like chloroform-methanol to a multicomponent one like n-butanol-butyl acetate-... [Pg.166]

Another interesting question concerns the origin of chirality ( handedness ) on Earth Why are the alpha-amino acids that compose proteins on Earth all L (not D) in absolute configuration (see the figure on page 379) while glucose and related saccharides are all D (not L) Why are not the amino acids D and the saccharides L A protein molecule com-... [Pg.378]

Amino acids, and phenyl thiohydantoin (PTH) derivatized amino acids D- and... [Pg.575]

The factor 0.5 relates to identically shaped reactant and product potential energy curves. Thus, through perturbation of A /, ionization of amino acids D and E will slow down the forward electron transfer and accelerate the reverse electron transfer. Because of the large distance between Qa and (3b (== 18 A), we neglect the electrostatic interactions between D and E and Qa, but some effect can be expected. [Pg.379]

Glycine-Dependent Aldolases (ThrA) The group of the glycine-dependent aldolases affords the synthesis of (S-hydroxy-a-amino-acids, d- and L-threonine and serine, most of them are known as L-threonine aldolases (ThrA). They catalyzed the addition of glycine 31 to various aldehyde substrates with pyridoxal-5 -phosphate (PLP) as cofactor. The formed products contain two stereogenic centers whose stereochemistry is controlled by the choice of D- or L-threonine and corresponding d- or L-a//o-threo-nine aldolases (Scheme 28.16). [Pg.839]

Derivatization of an amino acid with FDAA produces a diastereomer referred to as 2,4-dinitrophenyl-5-L-alanine amide amino acid or simply DNPA-amino acid. Aqueous solutions (50 vaM) of amino acids (D- and L-isomers) are used as starting materials for synthesis. Solution of each of the amino acid (50 lA, 2.5 /tmol) is placed in separate 2 ml plastic tubes. To each is added 100 ii of 1% acetone solution of FDAA (1 mg, 3.6 /zmol), the molar ratio of FDAA to amino acid is 1.4 1, followed by NaHCOs (1 M, 20 ii, 20 umol). The contents are mixed and heated over a hot plate at 30-40°C for 1 h with frequent mixing. After cooling to room temperature, HCl (2 Af, 10 /u-1, 20 /umol) is added to each reaction mixture. After mixing, the contents are dried in a vacuum desiccator over NaOH pallets. Each residue is then dissolved in DMSO (0.5 ml). A1 1 dilution of these is made (2.5 mM) and 5 /ul sample of each is pooled and analyzed, for example, injected for HPLC. [Pg.388]

Hydrolysis of the azlactone leads to the acylaminooinnamic acid the latter may be be reduced catal3rtlcally (Adams PtOj catalyst 40 lb. p.s.i.) and then hydrolysed by hydrochloric acid to the amino acid. Alternatively, the azlactone (say, of a-benzylaminocinnamic acid) may undergo reduction and cleavage with phosphorus, hydriodic acid and acetic anhydride directly to the a-amino acid (d/ p phenylalanine). [Pg.908]

The amino acids L-leucine, T-phenylalanine, L-tyrosine, and L-tryptophan all taste bitter, whereas their D-enantiomers taste sweet (5) (see Amino ACIDS). D-Penicillamine [52-67-5] a chelating agent used to remove heavy metals from the body, is a relatively nontoxic dmg effective in the treatment of rheumatoid arthritis, but T.-penicillamine [1113-41 -3] produces optic atrophy and subsequent blindness (6). T.-Penicillamine is roughly eight times more mutagenic than its enantiomer. Such enantioselective mutagenicity is likely due to differences in renal metaboHsm (7). (R)-ThaHdomide (3) is a sedative—hypnotic (3)-thaHdomide (4) is a teratogen (8). [Pg.237]

An estimation of the amount of amino acid production and the production methods are shown ia Table 11. About 340,000 t/yr of L-glutamic acid, principally as its monosodium salt, are manufactured ia the world, about 85% ia the Asian area. The demand for DL-methionine and L-lysiae as feed supplements varies considerably depending on such factors as the soybean harvest ia the United States and the anchovy catch ia Pern. Because of the actions of D-amiao acid oxidase and i.-amino acid transamiaase ia the animal body (156), the D-form of methionine is as equally nutritive as the L-form, so that DL-methionine which is iaexpensively produced by chemical synthesis is primarily used as a feed supplement. In the United States the methionine hydroxy analogue is partially used ia place of methionine. The consumption of L-lysiae has iacreased ia recent years. The world consumption tripled from 35,000 t ia 1982 to 100,000 t ia 1987 (214). Current world consumption of L-tryptophan and i.-threonine are several tens to hundreds of tons. The demand for L-phenylalanine as the raw material for the synthesis of aspartame has been increasing markedly. [Pg.291]

William Howard Stein fl 911-1980) was born in New York City and received his Ph.D. in 1938 from the Columbia College of Physicians and Surgeons. He immediately joined the faculty of the Rockefeller Institute, where he remained until his death. In 1972, he shared the Nobel Prize in chemistry for his work with Stanford Moore on developing methods of amino acid analysis and for determining the structure of ribonuclease. [Pg.1030]

I. Ugi, D. Marquarding, R. Urban in Chemistry and Biochemistry of Amino Acids, Peptides and Proteins, B. Weinstein, Ed., p 245, Marcel Dckkcr, New York 1982. [Pg.802]

PTH is the most important regulator of bone remodelling and calcium homeostasis. PTH is an 84-amino acid polypeptide and is secreted by the parathyroid glands in response to reductions in blood levels of ionised calcium. The primary physiological effect of PTH is to increase serum calcium. To this aim, PTH acts on the kidney to decrease urine calcium, increase mine phosphate, and increase the conversion of 25-OH-vitamin D to l,25-(OH)2-vitamin D. PTH acts on bone acutely to increase bone resorption and thus release skeletal calcium into the circulation. However, due to the coupling of bone resorption and bone formation, the longer-term effect of increased PTH secretion is to increase both bone resorption and bone formation. [Pg.279]

Complex formation between palladium(II) and amino acids, peptides and related ligands. L. D. Pettit and M. Bezer, Coord. Chem. Rev., 1985, 61, 97 (90). [Pg.67]

Extensive studies of stereoselective polymerization of epoxides were carried out by Tsuruta et al.21 s. Copolymerization of a racemic mixture of propylene oxide with a diethylzinc-methanol catalyst yielded a crystalline polymer, which was resolved into optically active polymers216 217. Asymmetric selective polymerization of d-propylene oxide from a racemic mixture occurs with asymmetric catalysts such as diethyzinc- (+) bomeol218. This reaction is explained by the asymmetric adsorption of monomers onto the enantiomorphic catalyst site219. Furukawa220 compared the selectivities of asymmetric catalysts composed of diethylzinc amino acid combinations and attributed the selectivity to the bulkiness of the substituents in the amino acid. With propylene sulfide, excellent asymmetric selective polymerization was observed with a catalyst consisting of diethylzinc and a tertiary-butyl substituted a-glycol221,222. ... [Pg.18]

HIV integrase consists of three distinct domains. The N-terminal domain contains a HHCC motif that coordinates a zinc atom that is required for viral cDNA integration. Three highly conserved amino acids (D,D-35-E) are embedded in the core domain, which form the acidic catalytic triad coordinating one or possibly two divalent metals (Mn + or Mg +). The C-terminal domain (residues 213-288) is responsible for unspecific DNA binding and adopts an overall SH3 fold (Chiu and Davies 2004). The enzyme functions as a multimer and to this end all three domains can form homodimers. [Pg.159]

Benzaldehyde dimethyl acetal 121 reacts, for example, with the silylated allylic alcohol 645, in the presence of SnCl2-MeCOCl, via an intermediate analogous to 641, to the 3-methylenetetrahydrofuran 646 and methoxytrimethylsilane 13 a [182], whereas benzaldehyde dimethyl acetal 121 reacts with the silylated homoallylalco-hol 640 in the presence of TMSOTf 20 to afford exclusively the ds 4-vinyltetrahy-drofuran 647 and 13 a [183]. A related cyclization of an a-acetoxy urethane 648 containing an allyltrimethylsilane moiety gives the 3-vinylpyrrohdine 649 in 88% yield and trimethylsilyl acetate 142 [184, 185]. Likewise, methyl 2-formylamido-2-trimethylsilyloxypropionate reacts with allyltrimethylsilane 82 or other allyltri-methylsilanes to give methyl 2-formamido-2-aUyl-propionate and some d -unsatu-rated amino acid esters and HMDSO 7 [186] (Scheme 5.56). [Pg.114]

Lynch DR, Guttmann RP (2002) Excitotoxicity perspectives based on N-methyl-D-aspartate receptor subtypes. J Pharmacol Exp Ther 300(3) 717-723 Magnuson DS, Knudsen BE, Geiger JD, Brownstone RM, Nath A (1995) Human immunodeficiency virus type 1 tat activates non-N-methyl-D-aspartate excitatory amino acid receptors and causes neurotoxicity. Ann Neurol 37(3) 373-380 Mamdouh Z, Chen X, Kerini LM, Maxfield FR, Muller WA (2003) Targeted recycling of PECAM from endothelial surface-connected compartments during diapedesis. Nature 421(6924) 748-753... [Pg.27]

Abraham, D. J., Leo, A. J. Extension of the fragment method to calculate amino acid zwitterion and side chain partition coefficients. Proteins 1987, 2,130-152. [Pg.404]

Hermosin, I., Chicon, R. M., and Cabezudo, M. D. (2003). Free amino acid composition and botanical origin of honey. Food Chem. 83, 263-268. [Pg.128]

Several other organic and inorganic reaction intermediates have been studied using NMR methods. Trahanovsky et al. [12] reported a series of experiments in which they studied unstable molecules, such as benzocyclobutadiene, using flow NMR. Tan and Cocivera [13, 14] studied the reaction of 4-formylpyridine with amino acids, imidazole and D,L-alanylglycine using stopped-flow proton NMR. [Pg.128]

Sasagawa, T. and Teller, D. C., Prediction of peptide retention times in re-versed-pahase HPLC, in CRC Handbook of HPLC for the Separation of Amino Acids, Peptides, and Proteins, Vol. II, Hancock, W. S., Ed., CRC Press, Boca Raton, FL, 1984, 53. [Pg.191]


See other pages where D and amino acids is mentioned: [Pg.108]    [Pg.63]    [Pg.144]    [Pg.562]    [Pg.6541]    [Pg.1541]    [Pg.108]    [Pg.63]    [Pg.144]    [Pg.562]    [Pg.6541]    [Pg.1541]    [Pg.372]    [Pg.68]    [Pg.17]    [Pg.63]    [Pg.21]    [Pg.50]    [Pg.141]    [Pg.157]    [Pg.87]    [Pg.99]    [Pg.99]    [Pg.214]    [Pg.71]    [Pg.701]    [Pg.9]    [Pg.32]    [Pg.77]    [Pg.128]    [Pg.108]   
See also in sourсe #XX -- [ Pg.106 ]




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