title: Standard state and thermodynamic self-consistency.
abstract: It is pointed out that even though the standard state for solutions is a fictitious state, it nonetheless should be thermodynamically self-consistent. Using a volumetric constraint, it is shown that the biochemical standard state concentration of 1M is too high for macromolecules like proteins and nucleic acids that it violates volumetric self-consistency. Also, at 1 M standard state, the mole fraction of these macromolecular solutes is not the commonly held value of 1/55.5, but rather a meaningless negative number. Thus, the ideal mixing entropy (also called cratic entropy) cannot be meaningfully calculated for macromolecules at such a standard state. The relevance of this conclusion to the interpretation of standard bimolecular binding entropy is discussed.
authors.affiliation: Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, Salt Lake City, Utah 84112, USA. yby1@utah.edu
authors.forename: Y B
authors.initials: YB
authors.lastname: Yu
mesh_terms: D002626:Chemistry, Pharmaceutical / Q000379:methods* / Q000592:standards*; D019277:Entropy; D008956:Models, Chemical; D012015:Reference Standards; D012996:Solutions / Q000592:standards; D012997:Solvents / Q000592:standards; D013816:Thermodynamics
chemical_list: D012996:Solutions; D012997:Solvents