Conformational studies of alanine‐rich peptide using CD and FTIR spectroscopy

Abstract The circular dichroism (CD) and Fourier transform infrared (FTIR) methods were applied to the conformational studies of alanine‐rich peptide Ac‐K‐[A] 11 ‐KGGY‐NH 2 (where K is lysine, A is alanine, G is glycine and Y is tyrozyne) in water, methanol (MeOH) and trifluoroethanol (TFE). The analysis of CD‐spectra of the peptide in water at different concentrations revealed that the secondary structure content depends on the peptide concentration and pH of the solution. The increase of the peptide concentration causes a decrease of α‐helix content and, simultaneously, an increase of β‐sheet structure, while the unordered structure is the predominant one. Additional elements are discovered in MeOH and TFE but α‐helix and β‐turns predominate. Moreover, in these solutions the percentage content of the secondary structure does not depend on the temperature. FTIR measurements, carried out at higher peptide concentration (about one order of magnitude) than these CD measurements mentioned above, revealed that in water solution the solid state β‐sheet, and aggregated structures, dominate. However, in TFE the most abundant are α‐helix and β‐turns structures. The thioflavine T assay showed the tendency of the studied peptide for aggregate. Copyright © 2007 European Peptide Society and John Wiley & Sons, Ltd.