Two-dimensional Raman and Raman optical activity correlation analysis of the α-helix-to-disordered transition in poly(L-glutamic acid)

Lorna Ashton, Laurence D. Barron, Lutz Hecht, Jason Hyde, Ewan W. Blanch

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Rich and complex Raman scattering and Raman optical activity (ROA) spectra have been measured monitoring the pH induced α-helix-to-disordered conformational transition in poly(l-glutamic acid). Two-dimensional (2D) correlation techniques have been applied to facilitate a comprehensive analysis of these two complementary spectral sets. Synchronous contour plots have identified band assignments of α-helical and disordered conformations, and have revealed bands characteristic of changes in the protonation state of the polypeptide. Asynchronous plots, on the other hand, have probed the relative sequential orders of intensity changes indicating a decrease in intensity of α-helical bands in the backbone skeletal stretch region, followed by a subsequent decrease in intensity in the extended amide III and amide I regions, underlying the appearance of disordered structure, including poly(l-proline) II (PPII) helix. The application of a 2D correlation 'moving' window has also disclosed two distinct phases during helix unfolding in the α-helix-to- disordered transition, occurring at ∼pH 4.9 and ∼pH 5.2, possibly a result of the difference in helical stability between the end and central regions of the α-helix. This paper demonstrates the potential value of combining 2D Raman, 2D ROA and moving window correlation techniques for the detailed investigation of complex and subtle changes of secondary structure during the unfolding mechanisms of polypeptides and proteins. © The Royal Society of Chemistry.
    Original languageEnglish
    Pages (from-to)468-479
    Number of pages11
    JournalAnalyst
    Volume132
    Issue number5
    DOIs
    Publication statusPublished - 2007

    Fingerprint

    Dive into the research topics of 'Two-dimensional Raman and Raman optical activity correlation analysis of the α-helix-to-disordered transition in poly(L-glutamic acid)'. Together they form a unique fingerprint.

    Cite this