Stimuli-responsive formation of helical polypeptide rod assemblies

Abstract

Two association states of helical polypeptide rods that mimic protein structures, the head-to-head association and side-b γ-side association, were studied. Helix-helix association of α-helical polypeptides was induced by external stimuli of alkaline metal ions. An α-helical polypeptide having a terminal benzo-15-crown-5 was synthesized. Head-to-head type interconnection of the polypeptides was regulated by sodium or potassium ions. Assembly structures of helical polypeptide rods and their functions were controlled by external photostimuli. A photoresponsive amphiphilic sequential polypeptide composed of two amphiphilic α-helical copoly peptides, poly [( γ-methyl- l-glutamate) -co- ( l-glutamic acid)], joined by an azobenzene, was synthesized. In an aqueous solution, the polypeptides formed a micelle with a side-b γ-side association, and the photoinduced structural changes of the polypeptide resulted in disaggregation of the micelle. In a lipid bilayer membrane, the polypeptides formed a transmembrane bundle with a side-by-side association, and the photoinduced structural changes of the polypeptide resulted in destabilization of the bundle. Photoinduced reversible structural changes of the polypeptide in the bilayer membrane could regulate transmembrane ion transport.