IMPROVEMENT OF THE METHOD FOR MODIFICATION OF ARGININE RESIDUES IN PROTEINS WITH MALONIC ALDEHYDE

A procedure for selective and quantitative conversion of arginine residues in proteins to N.delta.-(2-pyrimidinyl)ornithine developed. The procedure is based on the King''s method consisting of treatment of the protein with malonic dialdehyde. To avoid side reactions the excess reagent is removed by introducing guanidine hydrochloride into the reaction mixture after the reaction is complete. The method was used to investigate the primary protein structure of RNase A. All the peptides expected were isolated from the tryptic hydrolysate of the modified RNase and their amino acid composition and partial amino acid sequence were determined. No products of non-specific cleavage of the polypeptide chain were observed.