Multicomponent Rayleigh scattering from guanidine hydrochloride solutions

We present results of Brillouin light scattering studies of lysozyme and guanidine hydrochloride solutions in the temperature range 290–350 K. The Brillouin spectra of 6 M guanidine hydrochloride have been found to contain an additional component in Rayleigh scattering that manifests itself as a broad quasi‐elastic scattering line centered at the unshifted frequency and described by a Lorentz function (i.e. a Debye relaxor with relaxation time τ 1  ~ 25 ps at room temperature). The temperature dependence of τ 1 is described by the Arrhenius law with activation energy E a  = 0.11 ± 0.01 eV and prefactor τ 0 = 0.33 ± 0.03 ps. The Brillouin spectra of lysozyme denatured by 6 M guanidine hydrochloride exhibit a more complicated structure of the additional contribution into Rayleigh scattering, which is fitted best of all by a sum of two Lorentzians centered at the unshifted frequency (with relaxation times τ 1  ~ 19 ps and τ 2  ~ 180 ps at 339 K). Possible origins of the quasi‐elastic scattering are discussed. Copyright © 2012 John Wiley & Sons, Ltd.