Glucose-Lysozyme Reactions in a Restricted Water Environment

Effect of protein glycation on subsequent volatile formation

“…Small amounts of ethenylpyrazine and pyridinecarbonitrile were detected when the 65 % RH sample but not the 76 % RH sample was heated, a result that may be due to the variability (due, in part, to the use of oncolumn instead of split-splitless injection with the thermal desorber as well as the nonhomogeneity of the samples) of our analytical procedures and/or the small quantities of these two volatiles generated. It is interesting to note that previous and on-going studies (Wu et al, 1991) have shown that only the lysine-1 of lysozyme is glycated during incubation of lysozyme-glucose mixtures at 25 °C at different RH values. It appears, therefore, that the additional volatiles generated at 65% and 76% RH arose from increased numbers of lysine-1 moieties becoming glycated, probably due to the increased mobility of the glucose.…”

“…In addition, the 50 °C incubate gave increased amounts of most of those volatiles formed as a consequence of incubation at 25 °C. Fast atom bombardment mass spectrometry analysis of the chymotryptic peptides of the 50 °C incubate indicated that, in addition to lysine-1, at least three more lysine moieties had been glycated (Wu et al, 1991) and that some polymer formation had occurred. Electrophoresis of the materials separated by gel permeation chromatography indicated that the fraction with a molecular weight approximately the same as that of native lysozyme (monomer fraction) was pure but that the dimer was contaminated with 16% monomer and 20 % trimer.…”

The cognition-enhancing drug tenilsetam is an inhibitor of protein crosslinking by advanced glycosylation

“…Proteins can also form polymers by AGE crosslinking, but, due to steric parameters, with a much slower reaction rate than amino acids (Dominiczak, 1991). Lysozyme is widely used as a standard model protein of in vitro studies of AGE mediated polymerisation (Dyer et al, 1991), its three major glycation sites are lysine 1, 13 and 33 (Wu et al, 1991 Data for this table were generated by densitrometric scanning of the autoradiographs of the polyacrylamide gel shown in Fig. 6.…”

Contribution of coffee proteins to roasted coffee volatiles in a model system

“…Identification of the volatile compounds in the condensate was primarily based on GC‐MS, and information from the GC retention indices of the compounds against the C6‐C25 n‐paraffins were used as references. The structure assignment of the volatile compounds was accomplished by comparing the mass spectra data of individual compounds with authentic compounds available from the National Institute of Standards and Technology, the Central Institute for Nutrition and Food Research TNO, an on‐line computer library in the ITD M/S software program, or previously published literature (Wu et al. , 1990; Umano et al.…”