Internal charge transfer in proteins to the Schiff bases of their lysine side chains.

Stereochemical investigations carried out with the aid of molecular models show that the Schiff bases formed between methylglyoxal and the primary amino groups of the lysine side chains of proteins can bend back in such a way to the N atoms of the peptide groups that a charge transfer can occur between these groups and the oxygen atoms of the Schiff bases. Ab initio molecular orbital calculations support this finding.