Influence of osmolytes on densities, solubilities, osmotic pressures and reaction kinetics in high-pressure biological systems

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This project studies the influence of osmolytes on the thermodynamic properties of high-pressure biomolecule solutions. Properties of interest are density, osmotic coefficients/osmotic pressures, and solubilities as well as activity coefficients of biomolecules in aqueous solutions.These thermodynamic properties at high pressure will be predicted using the thermodynamic model PC-SAFT (Perturbed-Chain Statistical Associating Fluid Theory) which will be parametrized only using experimental data of densities (measured at pressures up to 500 bar) and osmotic coefficients of biomolecules solutions in the absence and presence of osmolytes. Measured densities at pressures up to 500 bar will be used as reference for density measurements in SP2 and in turn, the latter will be used to validate the densities predicted here for pressures up to 5,000 bar. The PC-SAFT predictions will also be validated via high-pressure solubility data taken from the literature.The so-validated predictions of thermodynamic properties will very well contribute to the overall aims the DFG Research Unit: the investigation and understanding of pressure effects in biological systems and the combined effects of pressure and osmolytes on thermodynamic properties and reaction kinetics.PC-SAFT predictions will allow for reliable predictions of densities and osmotic pressures as function of osmolyte concentration and of hydrostatic pressure. This information will serve for validation of the force fields developed in project SP 7 for molecular dynamic simulations in biomolecule/osmolyte solutions.Using PC-SAFT predictions it will moreover be possible to differentiate the effects of high pressure and osmolytes on thermodynamic properties of biological solutions. Moreover, urea will be investigated as non-osmolyte to further understand the specific effects of osmolytes under high pressure.For the first time, PC-SAFT predicted reactant activity coefficients at high pressure in the absence or presence of osmolytes will be used to model the reaction kinetics of a biological reaction performed at high pressure. This will allow differentiating the effect of pressure/osmolytes on the enzyme (investigated in SP 9) from that on the reactants activity coefficients (which are so far usually neglected). This will open up completely new insights into the influence of pressure/osmolytes on reaction kinetics.