title: Roles of conformational stability and colloidal stability in the aggregation of recombinant human granulocyte colony-stimulating factor.
abstract: We studied the non-native aggregation of recombinant human granulocyte stimulating factor (rhGCSF) in solution conditions where native rhGCSF is both conformationally stable compared to its unfolded state and at concentrations well below its solubility limit. Aggregation of rhGCSF first involves the perturbation of its native structure to form a structurally expanded transition state, followed by assembly process to form an irreversible aggregate. The energy barriers of the two steps are reflected in the experimentally measured values of free energy of unfolding (DeltaG(unf)) and osmotic second virial coefficient (B(22)), respectively. Under solution conditions where rhGCSF conformational stability dominates (i.e., large DeltaG(unf) and negative B(22)), the first step is rate-limiting, and increasing DeltaG(unf) (e.g., by the addition of sucrose) decreases aggregation. In solutions where colloidal stability is high (i.e., large and positive B(22) values) the second step is rate-limiting, and solution conditions (e.g., low pH and low ionic strength) that increase repulsive interactions between protein molecules are effective at reducing aggregation. rhGCSF aggregation is thus controlled by both conformational stability and colloidal stability, and depending on the solution conditions, either could be rate-limiting.
authors.affiliation: Department of Chemical Engineering, Center for Pharmaceutical Biotechnology, University of Colorado, Boulder, Colorado 80309-0242, USA.
authors.forename: Eva Y
authors.initials: EY
authors.lastname: Chi
authors.forename: Sampathkumar
authors.initials: S
authors.lastname: Krishnan
authors.forename: Brent S
authors.initials: BS
authors.lastname: Kendrick
authors.forename: Byeong S
authors.initials: BS
authors.lastname: Chang
authors.forename: John F
authors.initials: JF
authors.lastname: Carpenter
authors.forename: Theodore W
authors.initials: TW
authors.lastname: Randolph
mesh_terms: D003102:Colloids; D019281:Dimerization; D004355:Drug Stability; D016179:Granulocyte Colony-Stimulating Factor / Q000737:chemistry*; D006801:Humans; D011487:Protein Conformation; D011489:Protein Denaturation; D011994:Recombinant Proteins / Q000737:chemistry; D012996:Solutions; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics
chemical_list: D003102:Colloids; D011994:Recombinant Proteins; D012996:Solutions; D016179:Granulocyte Colony-Stimulating Factor