2DCOS and MCR-ALS as a combined tool of analysis of β-lactoglobulin CD spectra

Abstract

Since the biological activity of a protein depends on its conformation, therefore a full characterization of a protein involves an understanding of its three-dimensional structure. Any technique involved in determination of a protein structure is aimed at a detailed characterization of measured signal in context of the most common conformational motifs. From among different spectroscopic techniques employed to study a protein structure in solution and processes involved in protein unfolding far-UV circular dichroism spectroscopy is most commonly used. Although CD could give reasonable estimates of the secondary structure content of a protein, raw CD spectra are difficult to interpret due to a strong overlapping of broad bands having significantly different ellipticity that moreover are of opposite sign. For improving resolution of the feature-less CD spectra some resolution-enhancement techniques should be applied. Such methods are generally used for interpretation of the FTIR spectra of protein, but are scarcely applied to the CD spectra. Here, the analysis of the far-UV CD spectra of β-lactoglobulin (BLG) measured as a function of temperature and concentration of trifluoroethanol (TFE) has been performed by the two-dimensional correlation spectroscopy (2DCOS) and multivariate curve resolution-alternating least-squares (MCR-ALS) techniques. On this example a comparison of results obtained by means of the two methods are carried out.