title: Measurement of the second osmotic virial coefficient for protein solutions exhibiting monomer-dimer equilibrium.
abstract: The second osmotic virial coefficient (B) is a measure of solution nonideality that is useful for predicting conditions favorable for protein crystallization and for inhibition of aggregation. Static light scattering is the technique most commonly used to determine B values, typically using protein concentrations less than 5 mg/mL. During static light scattering experiments at low protein concentrations, frequently the protein is assumed to exist either as a single nonassociating species or as a combination of assembly states independent of protein concentration. In the work described here, we examined the limit for ignoring weak reversible dimerization (Kd > or =1 mM) by comparing B values calculated with and without accounting for self-association. Light scattering effects for equilibrium dimer systems with Kd <20 mM and Kd <1 mM will significantly affect apparent B values measured for 20 and 150-kDa proteins, respectively. To interpret correctly light scattering data for monomer-dimer equilibrium systems, we use an expanded coefficient model to account for separate monomer-monomer (B(22)), monomer-dimer (B(23)), and dimer-dimer (B(33)) interactions.
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309-0424, USA.
authors.forename: John R
authors.initials: JR
authors.lastname: Alford
authors.forename: Brent S
authors.initials: BS
authors.lastname: Kendrick
authors.forename: John F
authors.initials: JF
authors.lastname: Carpenter
authors.forename: Theodore W
authors.initials: TW
authors.lastname: Randolph
mesh_terms: D019281:Dimerization; D006801:Humans; D053590:Interleukin 1 Receptor Antagonist Protein / Q000737:chemistry / Q000378:metabolism; D009994:Osmolar Concentration; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D011506:Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D012996:Solutions
chemical_list: C507763:IL1RN protein, human; D053590:Interleukin 1 Receptor Antagonist Protein; D011506:Proteins; D012996:Solutions