The complete chirospectroscopic signature of the peptide 310-helix in aqueous solution

We synthesized by solution methods a water-soluble, terminally blocked heptapeptide based on five markedly helicogenic, C-alpha-tetrasubstituted alpha-amino acids C-alpha-methyl-L-norvalines and two strongly hydrophilic 2-amino-3-[1-(1,4,7-triazacyclononane)]-L-propanoic acid residues at positions 2 and 5. A Fourier transform infrared absorption and NMR analysis in deuterated chloroform and aqueous solutions of the heptapeptide and two side-chain protected synthetic precursors confirmed our working hypothesis that all oligomers are folded in the 3(10)-helical conformation. Based on these findings, we exploited this heptapeptide as a chiral reference compound for detailed electronic CD, vibrational CD, and Raman optical activity characterizations of the 3(10)-helix in aqueous solution. (C) 2004 Wiley Periodicals, Inc.