title: Specific-ion effects on the aggregation mechanisms and protein-protein interactions for anti-streptavidin immunoglobulin gamma-1.
abstract: Non-native protein aggregation is common in the biopharmaceutical industry and potentially jeopardizes product shelf life, therapeutic efficacy, and patient safety. The present article focuses on the relationship(s) among protein-protein interactions, aggregate growth mechanisms, aggregate morphologies, and specific-ion effects for an anti-streptavidin (AS) immunoglobulin gamma 1 (IgG1). Aggregation mechanisms of AS-IgG1 were determined as a function of pH and NaCl concentration with sodium acetate buffer and compared to previous work with sodium citrate. Aggregate size and shape were determined using a combination of laser light scattering and small-angle neutron or X-ray scattering. Protein-protein interactions were quantified in terms of the protein-protein Kirkwood-Buff integral (G22) determined from static light scattering and in terms of the protein effective charge (Zeff) measured using electrophoretic light scattering. Changing from citrate to acetate resulted in significantly different protein-protein interactions as a function of pH for low NaCl concentrations when the protein displayed positive Zeff. Overall, the results suggest that electrostatic repulsions between proteins were lessened because of preferential accumulation of citrate anions, compared to acetate anions, at the protein surface. The predominant aggregation mechanisms correlated well with G22, indicating that ion-specific effects beyond traditional mean-field descriptions of electrostatic protein-protein interactions are important for predicting qualitative shifts in protein aggregation state diagrams. Interestingly, while solution conditions dictated which mechanisms predominated, aggregate average molecular weight and size displayed a common scaling behavior across both citrate- and acetate-based systems.
authors.affiliation: †Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware 19716, United States.
authors.forename: Gregory V
authors.initials: GV
authors.lastname: Barnett
authors.affiliation: ‡Drug Product Development, Amgen Inc., Seattle, Washington 98119, United States.
authors.forename: Vladimir I
authors.initials: VI
authors.lastname: Razinkov
authors.affiliation: ‡Drug Product Development, Amgen Inc., Seattle, Washington 98119, United States.
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Kerwin
authors.affiliation: §Department of Molecular, Cellular, and Medical Biosciences, University of New Hampshire, Durham, New Hampshire 03824, United States.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Laue
authors.affiliation: ∥National Institutes of Standards and Technology Center for Neutron Research, Gaithersburg, Maryland 20899, United States.
authors.forename: Andrea H
authors.initials: AH
authors.lastname: Woodka
authors.affiliation: ∥National Institutes of Standards and Technology Center for Neutron Research, Gaithersburg, Maryland 20899, United States.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Butler
authors.affiliation: †Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware 19716, United States.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Perevozchikova
authors.affiliation: †Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware 19716, United States.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Roberts
mesh_terms: D002951:Citrates / Q000737:chemistry; D003102:Colloids / Q000737:chemistry; D057446:Hydrodynamics; D006863:Hydrogen-Ion Concentration; D007074:Immunoglobulin G / Q000737:chemistry*; D007477:Ions / Q000737:chemistry*; D008970:Molecular Weight; D066329:Protein Aggregates; D012542:Scattering, Radiation; D019346:Sodium Acetate / Q000737:chemistry; D012965:Sodium Chloride / Q000737:chemistry; D000077559:Sodium Citrate; D012996:Solutions; D055672:Static Electricity; D019809:Streptavidin / Q000276:immunology*; D013499:Surface Properties
chemical_list: D002951:Citrates; D003102:Colloids; D007074:Immunoglobulin G; D007477:Ions; D066329:Protein Aggregates; D012996:Solutions; D000077559:Sodium Citrate; D012965:Sodium Chloride; D019346:Sodium Acetate; D019809:Streptavidin