A search for specific chemical methods for fission of peptide-bonds. Experiments involving reduction of C-terminal residues

Abstract

Lithium aluminium hydride and lithium Dorohydride were compared as reducing reagents for the C-terminal residues of benzoylated peptide esters. The latter reagent gave satisfactory results provided that the reaction was carried out at 0[degree]. Attempts to devise a stepwise degradation of peptides by means of the N, 0-acyl migration reaction on the reduced peptide derivatives were unsuccessful. A new method for the preparation of the dimitrophenol derivatives of amino alcohols is described. This was used for the quantitative isolation of amino alcohols from hydrolysates of proteins and peptides after reduction. The value of lithium borohy-dride as a reagent for the determination of the C-terminal residues of large peptides and proteins was critically assessed. Owing to the low solubility of these substances in organic solvents, it was necessary to use more vigorous conditions than those required for reduction of simple peptides. Reductive cleavage of peptide bonds then took place simultaneously with the reduction of C-terminal residues. Correct identification of C-terminal residues with this reagent is therefore not possible under the conditions at present available.