Aspartic acid protein concentration

If the environmental temperature is constant, the racemization process takes place at a uniform rate, which is determined, at any time during the process, by the relative amounts of / and d forms of the amino acid can be measured. As the racemization proceeds and the concentration of the / form amino acid decreases, the rate of racemization gradually slows down. When there is a mixture of 50% of each of the d and / forms, the racemization process stops altogether. The half-life of the racemization of aspartic acid, for example, a common amino acid in proteins, at 20°C is about 20,000 years. This half-life makes it possible to date proteins as old as about 100,000 years. So far, however, the dates obtained with the technique have proved somewhat inconsistent, probably because of the difficulty in verifying whether the temperature of the amino acids has been constant. 

An excellent review on protein hydrolysis for amino acid composition analysis has been published by Eountoulakis and Lahm [190], Hydrolysis can be performed by either chemical (under either acidic or basic conditions) or enzymatic means. The acidic hydrolysis itself can be carried out in a liquid or a gas-phase mode. The conventional acid hydrolysis uses 6M HCl for 20-24 h at 110°C under vacuum [200], In these conditions, asparagine and glutamine are completely hydrolyzed to aspartic acid and glutamic acid, respectively. Tryptophan is completely destroyed (particularly in the presence of high concentrations of carbohydrate), while cysteine and sometimes methionine are partially oxidized. Tyrosine, serine, and threonine are partially destroyed or hydrolyzed and correction factors have to be applied for precise quantification [190,201],... 

Fig. 8. Schematic representation of protein-mediated cell adhesion on biomaterial surfaces. Biomaterial surface properties (such as hydrophilicity/hydrophobicity, topography, energy, and charge) affect subsequent interactions of adsorbed proteins these interactions include but are not limited to adsorbed protein type, concentration, and conformation. Changes in protein-surface interactions may alter accessibility of adhesive domains (such as the peptide sequence arginine-glycine-aspartic acid) to cells (such as osteoblasts, fibroblasts, or endothelial cells) and thus modulate cellular adhesion. (Adapted and redrawn from Schakenraad, 1996.)...

The pH dependence of the raeemization rate of aspartic acid in casein was also investigated. The results are plotted in Figure 3. Raeemization rates are estimated fron the log conversion of the D/L ratios. The pH of the NaCH buffer at 65° was calculated fron the temperature variation of the pK of water (32). The pH values of the borate buffers at 65° were calculated using the temperature data of Bates (33). The solid line represents rates which are first order with respect to hydroxide concentration. This line is a reasonable fit to the data points above pH 10. Further experiments are in progress with other proteins in order to identify the lowest CH concentrations that induce first-order raeemization kinetics. If the critical base concentrations for racemiza-tion correspond with the different responses of the four proteins (see Tables I and III), one may expect k(rac) for Promine-D to become first order at lower CH concentration than casein, while that of wheat gluten should be about the same as for casein. Lactalbumin may have the highest CH concentration tolerance. 

Following two simultaneous cases of accidental human exposure to sulfur mustard, Smith et al. (2008) investigated the concentration of the cysteine-34 adduct to albumin and adducts to glutamic and aspartic acids of plasma proteins. In the case of a more severely exposed patient who required hospitalization, both adducts were detected over a 42 day period, though decreasing by approximately 75% towards... 

The SCM-cysteine content of the SCMKB proteins ranges between that of wool itself and double this value. Compared with wool these proteins contain high concentrations of proline, serine, and threonine, but low concentrations of aspartic acid, glutamic acid, histidine, lysine, and leucine. In general, reverse trends are shown by the amino acid analyses for SCMKA fractions. SCMKB2 and SCM feather rachis are unique in that they contain virtually no histidine or lysine. In this respect they resemble... 

Active transport is often carried out at the expense of ATP hydrolysis. P-type ATPases pump ions against a concentration gradient and become transiently phosphorylated on an aspartic acid residue in the process of transport. P-type ATPases, which include the sarcoplasmic reticulum Ca2+ ATPase and the Na+-K+ ATPase, are integral membrane proteins with conserved structures and catalytic mechanisms. 

Sunflower meal (blended with wheat flour) can be used for human nutrition. Despite their dark color, sunflower protein concentrates are of excellent digestibility. A method was proposed (147) for obtaining sunflower protein concentrates from defatted wholemeal sunflower flour, through extraction of these proteins with a basic solution. The process yields a concentrate of 71% protein (dry basis), rich in glutamic and aspartic acids. The supernatant liquid, rich in potassium and phosphorous, can be used as agricultural fertilizer. 

Factor X is a plasma protein involved in both the intrinsic and extrinsic pathways of blood coagulation. Factor X has a mass of 55kDa and the activated Xa of 40kDa. The normal concentration in plasma is 6-8 pg/ml. Post-translational modifications of the protein involve y-carboxylation of specific glutamic acid residues, 3-hydroxylation of one aspartic acid residue, and N- and 0-linked glycosylation. 

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