Raman amide bands of type-II β-turns in cyclo-(VPGVG)3 and poly-(VPGVG), and implications for protein secondary-structure analysis
✍ Scribed by George J. Thomas Jr.; Betty Prescott; Dan W. Urry
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1987
- Tongue
- English
- Weight
- 855 KB
- Volume
- 26
- Category
- Article
- ISSN
- 0006-3525
No coin nor oath required. For personal study only.
✦ Synopsis
The cyclopentadecapeptide, c(VPGVG),, a model structure for protein type-I1 8-turns [W. J. Cook et al. (1980) J. Am. Chem. SOC. 102, 5502-55051, has been investigated by laser Raman spectroscopy. Data obtained from both normal and deuterated crystals identify amide I, 111, 1', and 111' bands characteristic of the B(1I)turn. The structurally related polypentapeptide poly(WGVG) in normal and deuterated f o m has also been investigated, and exhibits the same Raman amide bands as c(VPGVG),. The coacervate of poly(VPGVG), obtained by heating the solution to 40°C, likewise exhibits a Raman spectrum very similar to that of the C(VPGVG)~ crystal. Raman spectra thus indicate closely similar secondary structures for crystalline c(VPGVG), and aqueous poly(VPGVG), and provide an empirical basis for interpreting the conformation sensitive amide bands of globular proteins in terms of B(1I)turn structures that may be present. An important conclusion from the present findings is that the amide I Raman profile of a protein may not be su5cient in general to distinguish turns from helix and sheet secondary structures, since the major amide I peaks of the /3(II)turn at 1676 and 1652 ax-' overlap, respectively, with amide I profiles generated by 8-sheet and a-helix conformations.