Application of MCR-ALS to reveal intermediate conformations in the thermally induced α-β transition of poly-l-lysine monitored by FT-IR spectroscopy

Mirta R Alcaráz; Andreas Schwaighofer; Héctor Goicoechea; Bernhard Lendl

doi:10.1016/j.saa.2017.05.005

Application of MCR-ALS to reveal intermediate conformations in the thermally induced α-β transition of poly-l-lysine monitored by FT-IR spectroscopy

Spectrochim Acta A Mol Biomol Spectrosc. 2017 Oct 5:185:304-309. doi: 10.1016/j.saa.2017.05.005. Epub 2017 May 5.

Authors

Mirta R Alcaráz¹, Andreas Schwaighofer², Héctor Goicoechea³, Bernhard Lendl⁴

Affiliations

¹ Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9/164-UPA, 1060 Vienna, Austria; Laboratorio de Desarrollo Analítico y Quimiometría, FBCB, Universidad Nacional del Litoral-CONICET, Ciudad Universitaria, 3000 Santa Fe, Argentina.
² Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9/164-UPA, 1060 Vienna, Austria.
³ Laboratorio de Desarrollo Analítico y Quimiometría, FBCB, Universidad Nacional del Litoral-CONICET, Ciudad Universitaria, 3000 Santa Fe, Argentina.
⁴ Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9/164-UPA, 1060 Vienna, Austria. Electronic address: bernhard.lendl@tuwien.ac.at.

PMID: 28599234
DOI: 10.1016/j.saa.2017.05.005

Abstract

Temperature-induced conformational transitions of poly-l-lysine were monitored with Fourier-transform infrared (FT-IR) spectroscopy between 10°C and 70°C. Chemometric analysis of dynamic IR spectra was performed by multivariate curve analysis-alternating least squares (MCR-ALS) of the amide I' and amide II' spectral region. With this approach, the pure spectral and concentration profiles of the conformational transition were obtained. Beside the initial α-helical, the intermediate random coil/extended helices and the final β-sheet structure, an additional intermediate PLL conformation was identified and attributed to a transient β-sheet structure.

Keywords: Conformational analysis; Fourier transform infrared spectroscopy; Multivariate curve analysis–alternating least squares; Poly-l-lysine; Secondary structure.