Stereoselectivity in the interaction between an oligodeoxynucleotide and dipeptides in the presence of the copper(II) ion

A self-complementary decadeoxynucleotide (5'd (CTGGATCCAG)(2)) was synthesized for the purposes of this study. The systems formed by this decadeoxynucleotide and the dipeptides of the diastereoisomeric pairs Ala-Ala, Ala-Trp and Leu-Phe both with and without copper(II) were investigated by CD spectroscopy. The ternary systems were also submitted to an e.s.r. investigation. The formation of ternary copper(II) complexes was ascertained. In these complexes, the influence exerted on the B-DNA type conformation of the double strand as observed by CD spectroscopy strongly suggests intramolecular ligand-ligand interactions which have not been previously described for this type of systems, The discussion centers on how the type and disposition of the dipeptide sidechains influences the type of interaction in the different complexes, as inferred by the experimental results obtained.