1,721,003 research outputs found
Amino acid sequence around the pyridoxal 5'-phosphate binding sites of 6-phosphogluconate dehydrogenase.
No full text6-Phosphogluconate dehydrogenase (6-phospho-D-gluconate: NADP+ 2-oxidoreductase(decarboxylating), EC 1.1.1.44) from Candida utilis is inhibited by reaction with pyridoxal 5'-phosphate. The aldehydic group of this compound forms a Schiff base with the epsilon-amino group of a lysine residue: reduction of this enamine with tritiated borohydride can label this amino acid. Two tryptic peptides, TS2 and TS3, have been isolated from the labelled protein and found to have the following amino acid sequences: TS2: Ile-Leu-Asx-Glx-Ala-Gly-Gly-Lys(P-Pxy)-Gly-Glx-Thr-Lys TS3: Thr-Val-Ser-Lys(P-Pxy)-Val-Asp-His-Phe-Ile-(Glx,Asx,Glx)-Ala-Lys where Lys(P-Pxy) indicates the modified lysine residue. The similarities between the amino acid sequences around the pyridoxal phosphate binding lysines of 38 peptides, obtained from enzymes which have pyridoxal phosphate as cofactor or inhibitor, are discussed and a prediction is made on the presence of reverse turns in these peptides
Il periodato come reagente specifico per il sito di attacco del fosfato in alcune proteine enzimatiche
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Properties of a diacetyl (acetoin) reductase from Bacillus stearothermophilus
No full textThe cells of Bacillus stearothermophilus contain an NADH-dependent diacetyl (acetoin) reductase. The enzyme was easily purified to homogeinity, partially cahracterized, and found to be composed of two subunits with thw same molecular weight. In the presence of NADH, it catalyses the stereospecific reduction of diacetyl first to 3S-acetoin and then to 2S,3S-butanediol; in the presence of NAD+, it catalyses the oxidation of 2S,3S- and meso-butanediol, respectively, to 3S-acetoin and 3R-acetoin, but is unable to oxidise these compounds to diacetyl
Damage evolution in sandwich components at different extreme temperatures
No full textComposites' structures are subjected to various environmental conditions during their service life. However, only a few papers are focalized on analysing damage history after impact at shallow temperatures and among them, even less concern sandwich components. Futhermore, since the effect of any degradation phenomena may not be visible to the naked eye, the evolution of the damage is followed with non-destructive techniquest. In this paper, the damage suffered by sandwich structure composites was evaluated by three NDT techniques: Ultrasound, Lock-in Thermography and speckle interferometry. Sandwich structures investigated consist of carbon fibre reinforced face sheets surrounding a PVC core. Indentation and penetration tests (U = 7.5J, 10.5 J and 12 J) were carried out at room temperature and −55°C, +70°C. After tests, damage extension and propagation has been evaluated in terms of indentation depth and delamination by NDT. The results provided useful information about the influence of extreme temperature on both impact properties and damage evolution in the system investigated
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