Lysine continued reactions

In Fig. 23, the role of moisture in bimolecular reactions is classified by Hageman into three cases. The increases in reaction rate are attributed to a change in state of the water associated with the solid as reflected by a lower effective viscosity. In Case I, there is a continual increase in reaction rate with increasing water content above the monolayer. When all the reactant has been solubilized and further water dilutes the medium. Case II results. If the dilution is extensive, or if water is a product inhibitor of decomposition, a rate reduction can be observed (Case III). Case III behavior is an example of the effect of moisture on the progress of the Malliard reaction for the glucose-containing formulations of a-A-acetyl-L-lysine, poly-L-lysine, insulin, casein, and plasma proteins. " The fact that there can be a maximum degradation rate at a humidity other than 100% RH is observed in other situations as well. 

To an aliquot of 10-20 mg PL/mL in 0.1 MNaHC03, aliquots of 10% by volume of mixed anhydride of DTPA (50 mg/mL) are added with continuous stirring. For optimal substitution with DTPA, five additions of the anhydride are applied. With each addition of DTPA anhydride, the pH of the reaction is monitored with pH paper, and the pH is maintained above 7.0 without precipitation of the modified polylysine. It appears that when substantial number of lysine residues have been covalently linked with DTPA, the polymers tend to form precipitates, probably because of polymerization by ionic interaction. Lowering the pH iesolublized the precipitate. 

Protein Modification. Acylation was performed at room temperature by adding dropwise the anhydride to the protein solution (2 mg/ml). To reach the maximum level of modification, three equivalents of anhydride per lysine were needed. The pH was kept at 9 during the reaction by a controlled and continuous addition of 0.5 M NaOH using an automated pH-stat titration device. The reaction was considered to be complete when the pH of the reaction medium remained constant. To remove salts and excess reagents, the protein solution was dialyzed exhaustively against water and then lyophilized. 

With the exception of lysine, the process of trityl group removal from the side-chains of these amino acids is an equilibrium. Consequently, in order to push the equilibrium in the desired direction, a cation scavenger such as triisopropylsilane (TIS) or 1,2-ethanedithiol (EDT) is added to the cleavage mixture, or the reaction is conducted in a continuous-flow manner. With the latter approach, the progress of the reaction can be monitored at 400-500 nm and by following the decrease in optical density with time of the reaction effluent. 

For better control of fermentation and to reduce production costs, complex media components are avoided and mostly refined carbon sources are used for the industrial production of L-lysine. Sucrose can be obtained from cane or beet molasses, and glucose is provided in hydrolysates of corn, cassava, or wheat starch [30, 83]. Ammonia, as nitrogen source, can be added pure or as salts [32]. Further media components are vitamins, in particular biotin, as well as salts and trace elements. Amino acids for auxotrophic production strains can be provided by peptones, corn steep liquors, or soybean meal hydrolysates [30]. Preferably, media are sterilized continuously, whereas carbon sources and nitrogen sources are typically sterilized separately to avoid Maillard-type reactions [32]. Sterility is important for processes with the mesophilic and neutrophilic C. glutamicum with bacilli as main contamination risk [84], while phage infection is hardly a problem. 

The work described here is part of a continuing project aimed at investigating the formation of non-volatile compounds, both colorless and colored, in Maillard model systems (P, 10). The focus of this report is the effect of time of heating and subsequent storage on the profile of reaction products formed from an aqueous xylose-lysine hydrochloride model system. 

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