A SOFT-MODELING APPROACH TO INTERPRET THERMODYNAMIC AND CONFORMATIONAL TRANSITIONS OF POLYNUCLEOTIDES

Multivariate outputs from the experimental monitoring of biochemical p rocesses are usually difficult to interpret applying methods based on a priori chemical models. Curve resolution methods are model-free proc edures, generally known as soft-modeling methods, which obtain the con centration profiles and instrumental responses of each individual spec ies involved in a multivariate monitored process without making any ki nd of external assumption. Of the curve resolution methods available, the alternating least squares (ALS) is proposed here because of its ab ility to operate on one or on several matrices. Furthermore, ALS allow s the introduction of information related to the internal data structu re and to the general features of the concentration profiles and instr umental responses through the input of suitable constraints in the ite rative resolution procedure. The ALS potential is tested on several da ta sets coming from the multivariate spectrometric monitoring of polyu ridylic (polyU), polycytidylic (polyC), and polyadenylic (polyA) proto nation equilibria in dioxane/water 30% (v/v). Information concerning t he evolution of the concentration profiles and the spectra of each ind ividual species involved in the acid-base equilibria, the presence and pattern of polyelectrolyte effects, and the presence of conformationa l transitions associated or not with the proton uptake process is pres ented.