Three-way data analysis applied to multispectroscopic monitoring of protein folding

Multivariate curve resolution-alternating least squares (MCR-ALS) is proposed as a threeway analysis method to deal with multispectroscopic monitoring of protein folding. MCRALS provides the concentration profiles associated with the different protein conformations occurring during the process and their related spectra. The concentration profiles describe the folding mechanism and the spectra provide the structural information of the conformations involved. Analysis either of the protein folding process monitored with different techniques (i.e. a row-wise augmented data matrix) or of several experiments done in different conditions using the same technique (i.e. a column-wise augmented matrix) or both possibilities at the same time (i.e. a row- and column-wise augmented matrix), can be performed. Thermal unfolding and refolding of alpha-lactalbumin, monitored using far- and near-UV circular dichroism, fluorescence and UV spectrometry, is shown as example. Information related to changes in the tertiary and the secondary structure of the protein, to the presence of intermediates along the protein folding process and to the reversibility of the thermal process can be obtained.