Synthesis and highly stable beta-sheet formation of sequential alternating amphiphilic polypeptides

Alternating amphiphilic copolypeptides poly(Glu-Val-Lys-Val) and poly(Glu-Leu-Lys-Leu) were obtained by syntheses and polymerizations of the respective tetrapeptides and conformations were determined by circular dichroism measurements. The polypeptides reveal a very strong tendency to adopt the beta-sheet conformation in aqueous solution even al various pH as well as in the presence of 1 M NaCl, 6 M guanidine hydrochloride or 6 M urea. The beta-sheet structures also show thermal stability and independence of polypeptide concentrations. The high stability of. beta-sheet structures could be responsible for electrostatic interactions in addition to hydrophobic interactions and conventional beta-sheet hydrogen bondings. It is presumed that two polypeptides form monomeric beta-sheet structures by intramolecular interactions. These highly stable beta-sheet forming polypeptides should provide good models for contributing hydrophobic and electrostatic interactions to the beta-sheet structural formation in proteins, constructing de novo designed proteins and peptides involving beta-sheet structures and studying the mechanism of beta-protein folding.