Isolation and photo-oxidation of lysozyme fragments.
Reduction of the four disulfide bonds and further carboxymethylation of lysozyme followed by its reaction with CNBr brings about L-I, (aa 1-12) and L-II-III (aa 13-129) peptides. When breaking the polypeptidic chain by CNBr action and freeing the peptides formed through S-S bonds reduction and carboxymethylation three peptides are obtained corresponding to L-I (aa 1-12), L-II (aa 13-105) and L-III (aa 106-129). L-II-III, L-III and L-II peptides were separately subjected to photo-oxidation in presence of riboflavin, in 0.05 M phosphate buffer, pH 7.0. The kinetic analysis of Trp photo-oxidation in L-II-III peptides shows that these residues keep, to a great extent, the degree of exposition they had in native lysozyme. L-II peptide also presents Trp residues with a different degree of exposition. Presence of Tyr photo-oxidation in L-II and L-II-III peptides - what does not take place in native lysozyme - suggests a relationship between photo-oxidation selectivity and the degree of exposition of certain amino acid residues in spatial configuration.
D000596:Amino Acids / Q000032:analysis; D005591:Chemical Fractionation; D002850:Chromatography, Gel; D008027:Light; D009113:Muramidase / Q000302:isolation & purification / Q000528:radiation effects*; D010084:Oxidation-Reduction / Q000528:radiation effects; D010446:Peptide Fragments / Q000302:isolation & purification / Q000528:radiation effects
D000596:Amino Acids; D010446:Peptide Fragments; D009113:Muramidase