Collect. Czech. Chem. Commun. 1985, 50, 228-244

Conformation of branched polypeptides based on poly(L-lysine): The effect of terminal amino acids in the branches

Hana Votavováa, Ferenc Hudeczb, Judit Kajtárb, Jaroslav Šponara, Karel Bláhaa and Mária Szekerkeb

a Institute of Organic Chemistry and Biochemistry, Czechoslovak Academy of Sciences, 166 10 Prague 6, Czechoslovakia
b Research Group for Peptide Chemistry, Hungarian Academy of Sciences, Budapest, Hungary


CD Spectra of branched polypeptides based on poly(L-lysine) and containing three DL-alanine residues and one to three other L- or D-amino acid residues in the branches were measured in water, water-methanol and water-trifluoroethanol mixtures. In aqueous solutions dependence of the CD spectra on pH and ionic strength was studied. The effect of branch elongation was followed mainly with compounds containing glutamic acid. One terminal D-amino acid residue and also an extension by two L- or D-amino acid residues does not hinder the α-helix formation in the backbone but affects the conditions of its formation. In polypeptides with three L- or D-amino acids additional α-helical segments in the branches are assumed to be formed. For branches with L-amino acids the CD curves express additively the contributions of both helical components, in the case of D-amino acids the increasing population of the ordered structure in branches is manifested by compensation of dichroic contribution of the L-amino acid backbone leading even to enantiomorphous curves.