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Study of speciation in biological systems containing macromolecular ligands: application of new chemometric methods

Five different research groups with experience in different specialities, two from INTAS member countries (Austria and Spain) and four from different geographical regions of Russia (St. Petersburg, Ekaterinburg, and Ivanovo) were working together to investigate the interactions in solution between ions and biomolecules in different types of liquid systems.

Several methodological approaches have been developed and applied for the study of solution chemistry of nucleic acids and polynucleotides. These methodologies include on one side the adaptation of traditional data acquisition espectrometric techniques providing multivariate data (spectrometric UV, CD and fluorescence multiwavelength titrations, melting multiwavelength experiments, multiwavelength Job's method and others) and on the other side, the development and application of new data treatment chemometric methods, specially the development and application of the multivariate curve resolution alternating least squares method for the modelling of chemical processes and interactions in solution. pH and temperature dependent acid-base, metal complexation and conformational equilibria of different synthetic and natural polynucleotides and nucleic acids are studied in different solvent media. Investigation of interactions between nucleic acids and possible intercalators using recently developed methodologies has been recently initiated.

New ab initio ion-molecular potentials have been obtained for alkali metal cations and for halide anions in water - formamide mixtures. Molecular dynamics computer simulations have been performed for Na+/Cl- water-formamide mixtures over the whole concentration range of the mixed solvent. The use of a new ab initio ion-molecular potential gave a realistic microscopic picture of the intermolecular motions and ionic shell structure. The ionic preferential solvation phenomena manifest themselves in the reduction of the average number of H-bonds of the solvation shell molecules compared to bulk solvent molecules. The mobility of the Na+ cation depends strongly on the immediate environment of the ion, whereas for Cl- mainly solvation shell - bulk processes control the dynamics of ion movement. Specific cation solvent shell formation leads to a drastic change of the ion microdynamics in the mixture compared to pure solvents. A possibility of extension of the molecular theory of limiting ionic mobility to mixed solvents was tested and could not be confirmed by the simulation.

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