CONFORMATIONAL VARIETY OF POLYANIONIC PEPTIDES AT LOW-SALT CONCENTRATIONS

Sequential oligo-and polypeptides based on glutamic acid and leucine r esidues have been synthesized. In pure water, they exhibit a random co il conformation. Addition of very small amounts of divalent metallic c ations induces the formation of ordered structure in the peptides whic h remain in solution. Higher salt concentrations precipitate the pepti des. Polypeptides with alternating glutamic acid and leucine residues undergo a coil to beta-sheet transition in the presence of Ca2+, Ba2Mn2+, Co2+, Zn2+ and Hg2+. Addition of Cu2+ or Fe3+ induces the format ion of an alpha-helix. Solid amorphous CdS generates water soluble bet a-sheets, as well. Sequential poly(Leu-Glu-Glu-Leu) adopts an alpha-he lix in the presence of divalent cations. The sequence-dependent confor mational diversity was extended to poly(Asp-Leu) and poly(Leu-Asp-Asp- Leu).