The interaction specificity of peptides with DNA. Evidence for peptide beta-sheet-DNA binding

Proton magnetic resonance studies (1H NMR) of the interaction of oligopeptide amides of defined sequence (and containing the amino acid, phenylalanine) with salmon sperm DNA are reported. The extent of upfield chemical shifts, deltasigma, and signal line broadening of the aromatic protons (in the presence of excess DNA) are found to depend on the primary sequence and stereochemistry of alpha carbons of the amino acids in the oligopeptide amides. The results obtained with 21 different di-, tri-, tetra-, penta- and hexapeptide amides are found to be consistent with a model whereby the peptide assumes a slightly modified single-stranded beta-sheet structure which is wrapped around the nucleic acid helix in a manner similar to that described by M. H. F. Wilkins (1956), Cold Spring Harbor Symp. Quant. Biol. 21, 75).