Peptide models for β-turns.
A circular dichroism study
Article first published online: 12 JAN 2009
© 1984 Munksgaard International Publishers Ltd.
International Journal of Peptide and Protein Research
Volume 23, Issue 4, pages 411–419, April 1984
How to Cite
Crisma, M., Fasman, G.D., Balaram, H. and Balaram, P. (1984), Peptide models for β-turns. International Journal of Peptide and Protein Research, 23: 411–419. doi: 10.1111/j.1399-3011.1984.tb02739.x
- Issue published online: 12 JAN 2009
- Article first published online: 12 JAN 2009
- Received 16 May, accepted for publication 23 July 1983
- α-aminoisobutyryl peptides;
- circular dichroism;
- peptide conformation;
- proline peptides;
The circular dichroism spectra of four β-turn model peptides, Z-Aib-Pro-Aib-Pro-OMe (1), Piv-Pro-Aib-NHMe (2), Piv-Pro-D-Ala-NHMe (3) and Piv-Pro-Val-NHMe (4) have been examined under a wide range of solvent conditions, using methanol, hexafluoroisopropanol and cyclohexane. Type I and Type II β-turns have been observed for peptides 1 and 2 respectively, in the solid state, while the Pro-D-Ala sequence adopts a Type II β-turn in a related peptide crystal structure. A class C spectrum is observed for 1 in various solvents, suggesting a variant of a Type I (III) structure. The Type II β-turn is characterized by a CD spectrum having two positive CD bands at ˜ 230 nm and ˜ 202 nm, a feature observed in Piv-Pro-D-Ala-NHMe in cyclohexane and methanol and for Piv-Pro-Aib-NHMe in methanol. Peptide 2 exhibits solvent dependent CD spectra, which may be rationalized by considering Type II, III and V reverse turn structures. Piv-Pro-Val-NHMe adopts non-β-turn structures in polar solvents, but exhibits a class B spectrum in cyclohexane suggesting a population of Type I β-turns.