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

Abstract We synthesized by solution methods a water‐soluble, terminally blocked heptapeptide based on five markedly helicogenic, C α ‐tetrasubstituted α‐amino acids C α ‐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. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004