Rigorous analysis of static light scattering measurements on buffered protein solutions.

Attention is drawn to the thermodynamic invalidity of the current practice of analyzing static light scattering measurements on globular proteins in terms of theory for a single solute because of its disregard of the need to consider small species such as buffer components as additional cosolutes rather than as part of the solvent. This practice continues despite its demonstrated inadequacy in studies of sucrose-supplemented protein solutions, where the aberrant behavior was recognized to be a consequence of physical protein interaction with the small cosolute. Failure to take into account the consequences of small cosolute effects renders extremely difficult any attempt to obtain a rigorous thermodynamic characterization of protein interactions by this empirical technique.