Conformational Analysis of Peptides in Oriented Polyoxyethylene by Infrared Dichroism

R. T. Ingwall, C. Gilon, M. Goodman*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

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 languageEnglish
Pages (from-to)4356-4362
Number of pages7
JournalJournal of the American Chemical Society
Volume97
Issue number15
DOIs
StatePublished - 1 Jul 1975

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