Helix formation in methylated copolymers of lysine and alanine.
Random copolymers of lysine and alanine, 2:1 and 1:1, were trimethylated on the lysine amino groups to quaternary ammonium groups. Methylated and unmethylated polymers were prepared with Cl- or ClO4- as the counterion. CD spectra were measured for increasing concentration of peptide without added salt, and at constant peptide concentration in increasing NaCl or NaClO4. Unmethylated peptides, as the chloride, form alpha-helix more readily than do the methylated peptides. The opposite occurs with ClO4- as counterion. The helix-promoting effect of methylated lysine residues (ClO4- counterion) is diminished by the presence of alanine, as compared with effects when lysine is the only type of residue. The effect of methylation of proteins on helix formation may depend on the types of anionic groups with which the protein may be involved.
Bello
J
J
Department of Chemistry, Roswell Park Division of the Graduate School, State University of New York, Buffalo 14263.
D000409:Alanine; D008239:Lysine; D008745:Methylation; D008970:Molecular Weight; D009994:Osmolar Concentration; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation
D010455:Peptides; D008239:Lysine; D000409:Alanine