A series of diastereomeric dipeptide amides, containing an N-terminal L-lysyl residue and a C-terminal L- or D-amino acid with a derivatized aromatic ring on the side chain, was synthesized to determine the dependence of the chirality of the N-terminal amino acid .alpha.-C and the length of the N-terminal amino acid side chain for intercalation of the aromatic ring. The nature of the complex between the peptide and DNA (i.e., electrostatic, intercalative, or a combination of these) was determined by UV and CD [circular dichroism] studies, viscometric titrations, and 1H NMR studies. The results of these studies reveal distinct differences in the binding site of the aromatic rings of the various peptides. In particular, the .alpha.- and .epsilon.-amino groups of the lysyl residue bind electrostatically to adjacent phosphates on the DNA backbone in a stereospecific manner. As a result of this stereospecificity, the aromatic rings of the peptides with the L-L-designation point toward the DNA helix, while those of the peptides of the L-D designation point away from the helix. This is completely consistent with previously reported work. The results also indicate a great dependence on the length of the side chain for intercalation of the aromatic ring. Specifically, if the side chain is long enough, and flexible enough, the aromatic ring can fully or partially intercalate, regardless of the chirality of the N-terminal amino acid .alpha.-C. However, if the side chain is too short, only partial intercalation is observed for peptides of the L-L designation, and no intercalation is observed for peptides of the L-D designation.