title: beta-structures of alternating polypeptides and their possible role in chemical evolution.
abstract: The tendency of copolypeptides with alternating hydrophilic and hydrophobic residues to form water soluble beta-structures in presence of salt, already described for poly(Val-Lys) (Brack and Orgel, 1975), was generalized to optically pure poly(Lys-Leu-Lys-Leu) and poly(Leu-Glu-Leu- G lu). Substitution of about 10% of L-lysyl residues by their enantiomers did not prevent the coli to beta transition but had nervertheless a sensitive effect on the beta-structures. Disruption of the alternation by insertion of extra glycyl or L-prolyl residues as in poly(Gly-Lys-Leu-Lys-Leu) and poly(Pro-Lys-Leu-Lys-Leu) decreased dramatically the tendency to form beta-structures. However, by using strong interaction ions such as perchlorate ions or by lengthening the alternating sequences as in the semi-random copoly(Gly-Lys-Leu-Lys-Leu1, Lys-Leu-Lys-Leu1) and copoly(Pro-Lys-Leu-Lys-Leu1, Lys-Leu-Lys-Leu1) it was possible to obtain soluble beta-structures which showed differences in the CD spectra. The binding properties of the beta-surface are examined.
mesh_terms: D002942:Circular Dichroism; D005998:Glycine; D007930:Leucine; D008239:Lysine; D010455:Peptides; D011392:Proline; D011487:Protein Conformation; D012995:Solubility; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
chemical_list: D010455:Peptides; D011392:Proline; D007930:Leucine; D008239:Lysine; D005998:Glycine