Cationic oligopeptides with the repeating sequence L-lysyl-L-alanyl-L-alanine: conformational and thermal stability study using optical spectroscopic methods

✍ Scribed by Vladimír Setnička; Jan Hlaváček; Marie Urbanová

• Book ID: 105359789
• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 194 KB
• Volume: 15
• Category: Article
• ISSN: 1075-2617
• DOI: 10.1002/psc.1154

✦ Synopsis

Abstract

The infrared (IR), vibrational circular dichroism (VCD), and electronic circular dichroism (ECD) spectra of short cationic sequential peptides (L‐Lys‐L‐Ala‐L‐Ala)~n~ (n = 1, 2, and 3) were measured over a range of temperatures (20–90 °C) in aqueous solution at near‐neutral pH values in order to investigate their solution conformations and thermally induced conformational changes. VCD spectra of all three oligopeptides measured in the amide I′ region indicate the presence of extended helical polyproline II (PPII)‐like conformation at room temperature. UV‐ECD spectra confirmed this conclusion. Thus, the oligopeptides adopt a PPII‐like conformation, independent of the length of the peptide chain. However, the optimized dihedral angles ϕ and ψ are within the range −82 to −107° and 143–154°, respectively, and differ from the canonical PPII values. At elevated temperatures, the observed intensity and bandshape variations in the VCD and ECD spectra show that the PPII‐like conformation of the Lys‐Ala‐Ala sequence is still preferred, being in equilibrium with an unordered conformer at near‐neutral pH values within the range of temperatures from 20 to 90 °C. This finding was obtained from analysis of the temperature‐dependent spectra using the singular value decomposition method. The study presents KAA‐containing oligopeptides as conformationally stable models of biologically important cationic peptides and proteins. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd.