Vibrational analysis of peptides, polypeptides, and proteins. XVIII. Conformational sensitivity of the α-helix spectrum: αI- and αII-Poly(L-alanine)

✍ Scribed by Anil M. Dwivedi; S. Krimm

• Publisher: Wiley (John Wiley & Sons)
• Year: 1984
• Tongue: English
• Weight: 940 KB
• Volume: 23
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360230509

✦ Synopsis

Abstract

The α~II~‐helix (ϕ = −70.47°, ψ = −35.75°) is a structure having the same n and h as the (standard) α~I~‐helix (ϕ = −57.37°, ψ = −47.49°). Its conformational angles are commonly found in proteins. Using an improved α‐helix force field, we have compared the vibrational frequencies of these two structures. Despite the small conformational differences, there are significant predicted differences in frequencies, particularly in the amide A, amide I, and amide II bands, and in the conformation‐sensitive region below 900 cm^−1^. This analysis indicates that α~II~‐helices are likely to be present in bacteriorhodopsin [Krimm, S. & Dwivedi, A. M. (1982) Science 216, 407–408].