Abstract
A new procedure for the determination of infrared dichroic spectra of oligo- and polypeptides is described. The peptide is incorporated in a polyoxyethylene film and partially oriented by uniaxial stretching. The infrared characteristics of the polyoxyethylene support allow measurement of the dichroic spectra of amide N-H stretching bands between 3500 and 3000 cm-1, of amide I and II bands between 1700 and 1500 cm-1, and of far-infrared bands below 800 cm-1. Dichroic spectra of both high molecular weight polypeptides and oligopeptides, whose low molecular weight had hindered their orientation, can be conveniently determined in polyoxyethylene. Procedures for measuring the kinetics of N-H to N-D isotopic exchange reactions of molecules oriented in polyoxyethylene are also described. The infrared dichroic spectra of gramicidin S and of several synthetic oligo- and polypeptides are presented. Gramicidin S exhibits a “cross-β” dichroic spectrum which could arise from extensive association of the β-sheet conformation of Hodgkin-Oughton and Schwyzer into ribbon-like aggregates. Polypeptides were found to be oriented in the α-helical, β-sheet, and “cross-β” conformation in polyoxyethylene films.
Original language | English |
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Pages (from-to) | 4356-4362 |
Number of pages | 7 |
Journal | Journal of the American Chemical Society |
Volume | 97 |
Issue number | 15 |
DOIs | |
State | Published - 1 Jul 1975 |