title: Estimating hydration changes upon biomolecular reactions from osmotic stress, high pressure, and preferential hydration experiments.
abstract: How do we estimate, from thermodynamic measurements, the number of water molecules adsorbed or released from biomolecules as a result of a biochemical process such as binding and allosteric effects? Volumetric and osmotic stress analyses are established methods for estimating water numbers; however, these techniques often yield conflicting results. In contrast, Kirkwood-Buff theory offers a novel way to calculate excess hydration number from volumetric data, provides a quantitative condition to gauge the accuracy of osmotic stress analysis, and clarifies the relationship between osmotic and volumetric analyses. I have applied Kirkwood-Buff theory to calculate water numbers for two processes: (i) the allosteric transition of hemoglobin and (ii) the binding of camphor to cytochrome P450. I show that osmotic stress analysis may overestimate hydration number changes for these processes.
authors.affiliation: York Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5YW, United Kingdom. shimizu@ysbl.york.ac.uk
authors.forename: Seishi
authors.initials: S
authors.lastname: Shimizu
mesh_terms: D002164:Camphor / Q000737:chemistry; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry; D006454:Hemoglobins / Q000737:chemistry*; D009997:Osmotic Pressure; D011312:Pressure; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D006454:Hemoglobins; D014867:Water; D002164:Camphor; D003577:Cytochrome P-450 Enzyme System