Circular Dichroism of Oriented Helical Polypeptides: the Alpha-Helix
- 15 October 1972
- journal article
- research article
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 57 (8) , 3469-3477
- https://doi.org/10.1063/1.1678780
Abstract
The oriented circular dichroism spectrum of an alpha‐helical polypeptide in solution is reported between 190 and 250 nm. The linear dichroism, absorption, and unoriented circular dichroism are obtained for the same solvent‐polymer system. The four curves are resolved into a single set of bands consistent with the conclusions of exciton theory. It is shown that (1) the rotatory bands of the helix predicted by Moffitt are allowed only for light propagating perpendicular to the helix axis, (2) the additional rotatory strength predicted theoretically by Moffitt, Fitts, and Kirkwood is detectable and is allowed only for light propagating parallel to the helix axis. However, the Moffitt‐Fitts‐Kirkwood band has only the intensity predicted by strong‐coupling exciton theory.
Keywords
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