Circular dichroism studies of helical oligopeptides: Can 310 and α‐helical conformations be chiroptically distinguished?
- 1 October 1983
- journal article
- research article
- Published by Wiley in International Journal of Peptide and Protein Research
- Vol. 22 (4) , 464-468
- https://doi.org/10.1111/j.1399-3011.1983.tb02116.x
Abstract
Circular dichroism [CD] studies of 7 helical oligopeptides containing .alpha.-aminoisobutyric acid (Aib) in methanol and trifluoroethanol (TFE) solutions are reported. Peptides ranging from 10-21 residues in length were examined. In all cases distinct negative CD bands characteristic of helical peptides are obtained at .apprx. 220 and 205 nm corresponding to the N-.pi.* and .pi.-.pi.* transitions, respectivley. The ratio R = [.theta.]n-.pi.*/[.theta.].pi.-.pi.* is < 1.0 for all peptides studied. Crystal structure and NMR results for a 10 residue 310 helical peptide and literature values for an .alpha.-helical 11-residue peptide show that both helical conformations yield R values of .apprx. 0.8 in alcoholic solvents. The CD data are considered in the light of 1H NMR studies on these oligopeptides. The 310 and .alpha.-helical conformations probably cannot be distinguished by CD methods.Keywords
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