Vibrational Raman Optical Activity Characterization of Poly(L-proline) II Helix in Alanine Oligopeptides

Iain H. McColl, Ewan W. Blanch, Lutz Hecht, Neville R. Kallenbach, Laurence D. Barron

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    A vibrational Raman optical activity (ROA) study of a series of alanine peptides in aqueous solution is presented. The seven-alanine peptide Acetyl-OOAAAAAAAOO-Amide (OAO), recently shown by NMR and UVCD to adopt a predominantly poly(l-proline II) (PPII) helical conformation in aqueous solution, gave an ROA spectrum very similar to that of disordered poly(l-glutamic acid) which has long been considered to adopt the PPII conformation, both being dominated by a strong positive extended amide III ROA band at ∼1319 cm-1 together with weak positive amide I ROA intensity at ∼1675 cm-1. A series of alanine peptides Ala2-Ala6 studied in their cationic states in aqueous solution at low pH displayed ROA spectra which steadily evolved toward that of OAO with increasing chain length. As well as confirming that alanine peptides can support the PPII conformation in aqueous solution, our results also confirm the previous ROA band assignments for PPII structure, thereby reinforcing the foundation for ongoing ROA studies of unfolded and partially folded proteins. Copyright © 2003 American Chemical Society.
    Original languageEnglish
    Pages (from-to)5076-5077
    Number of pages1
    JournalJournal of the American Chemical Society
    Issue number16
    Publication statusPublished - 28 Apr 2004


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