title: High concentration formulations of recombinant human interleukin-1 receptor antagonist: I. Physical characterization.
abstract: At relatively high protein concentrations (i.e., up to 100 mg/mL), recombinant human interleukin-1 receptor antagonist (rhIL-1ra) was found to exist in a monomer-dimer equilibrium controlled by solution ionic strength. Sedimentation equilibrium at 25 degrees C was used to measure the increase in the dimer dissociation constant (K(d)) as a function of ionic strength. K(d) increased from 2.0 to 12.6 mM as the solution ionic strength was increased from 0.011 to 0.184 molal. These K(d) values were used with both static light scattering and membrane osmometry data collected over a protein concentration range of 1-100 mg/mL to determine second osmotic virial coefficients. Expanding the second osmotic virial coefficient model to account for separate monomer-monomer (B(22)), monomer-dimer (B(23)), and dimer-dimer (B(33)) interactions reveals net monomer-dimer interactions are attractive, whereas the others are repulsive. Lastly, isothermal titration calorimetry dilution experiments showed that rhIL-1ra dimerization is enthalpically driven (DeltaH(dimerization) << 0), which is consistent with intermolecular cation-pi interactions previously proposed as the monomer-monomer contact sites in dimers.
authors.affiliation: Department of Chemical and Biological Engineering, Center for Pharmaceutical Biotechnology, ECCH 111, University of Colorado, Boulder, Colorado 80309-0424, USA.
authors.forename: John R
authors.initials: JR
authors.lastname: Alford
authors.forename: Stanley C
authors.initials: SC
authors.lastname: Kwok
authors.forename: Jennifer N
authors.initials: JN
authors.lastname: Roberts
authors.forename: Deborah S
authors.initials: DS
authors.lastname: Wuttke
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: D002151:Calorimetry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D053590:Interleukin 1 Receptor Antagonist Protein / Q000032:analysis* / Q000737:chemistry; D008027:Light; D019906:Nuclear Magnetic Resonance, Biomolecular; D009994:Osmolar Concentration; D011994:Recombinant Proteins / Q000032:analysis / Q000737:chemistry; D012542:Scattering, Radiation
chemical_list: D053590:Interleukin 1 Receptor Antagonist Protein; D011994:Recombinant Proteins