This title appears in the Scientific Report : 2017 
Effective Interactions and Colloidal Stability of Bovine γ-Globulin in Solution
Da Vela, Stefano
Roosen-Runge, Felix / Skoda, Maximilian W. A. / Jacobs, Robert M. J. / Seydel, Tilo / Frielinghaus, Henrich / Sztucki, Michael / Schweins, Ralf / Zhang, Fajun (Corresponding author) / Schreiber, Frank
Neutronenstreuung; JCNS-1
JCNS-FRM-II; JCNS-FRM-II
The @journal of physical chemistry / B, 121 (2017) 23, S. 5759–5769
Washington, DC Soc. 2017
10.1021/acs.jpcb.7b03510
28520443
Journal Article
Jülich Centre for Neutron Research (JCNS)
FRM II / MLZ
Soft Condensed Matter > 0
Biology > 1
Health and Life > 0
Please use the identifier: http://dx.doi.org/10.1021/acs.jpcb.7b03510 in citations.


Interactions and phase behavior of serum albumin and γ-globulin are of fundamental interest in biophysical and pharmaceutical research, as these are the most abundant proteins in blood plasma. In this work, we report the characterization of the oligomeric state of bovine γ-globulin, the effective protein-protein interactions and the colloidal stability in aqueous solution as a function of protein concentration and ionic strength. Classical biochemical techniques, such as size exclusion chromatography (SEC) and gel electrophoresis together with small angle X-ray and neutron scattering (SAXS/SANS) were employed for this study. The results show that bovine γ-globulin solutions are dominated by monomer and idiotype anti-idiotype dimer. Despite the flexibility and highly non-spherical shape of the protein, a simple model with a disk-type form factor and a structure factor of a square-well potential provide a valid description of the scattering data. The overall interactions are attractive and the strength decreases with increasing protein concentration, or adding buffer or salts. For higher protein volume fraction (> 7%), the model leads to a strong particle-particle correlation which does not appear in the experimental data. This mismatch is most likely due to the smearing effect of the conformation change of proteins in solution. The stability of γ-globulin solutions is highly sensitive to protein concentration, ionic strength and to the type of added salts, such as NaCl, Na2SO4 and NaSCN. For solutions below 50 mg/mL and at low ionic strengths (< 0.1M), protein aggregation is most likely due to subpopulations of IgG molecules with attractive patches of complementary surface charge. This effect is reduced for higher protein concentration due to the self-buffering effects. For high ionic strength (> 1M), typical salting-in and salting-out effects are observed. Results are further discussed in comparison with current studies in the literature on monoclonal antibodies.