Association Characteristics of Amphiphilic α-Helices Connected by Flexible Links

Amphiphilic helical peptides interlinked with sequences bearing a flexible mobility were designed and synthesized. The sequences containing glycine and/or cystine were adopted for the linkage parts. The secondary structure of the peptides was investigated by circular dichroism(CD) and the super-secondary structure was estimated. The CD spectra and their pH dependence show that the peptides have almost the same α-helix contents as designed and that the helices associate to be “coiled-coil” at neutral pH. The apparent helix contents increase at low pH and some of helices are subject to denaturation at high pH. The denaturation of α-helix bundles by guanidine hydrochloride is contemplated to be three-state transition. It is proposed that the peptides construct α-helix bundles with both loose and tight contacts between helices. Two kinds of folded structure constructed with 2 or more helices are also suggested.