Influence of Pressure Holding Time on Ovalbumin Solution Behavior via Small‐Angle Neutron Scattering and Diffusing Wave Spectroscopy

ABSTRACT Protein–protein interactions (PPIs) were characterized as a function of salt concentration and applied hydrostatic pressure for hen egg ovalbumin solutions. In situ data were collected using small‐angle neutron scattering (SANS) at various concentrations of ammonium sulfate. The nondestructive nature of SANS allows for extended pressure holding times and the investigation of the reversibility of effects on PPIs. An empirical scaling developed previously is shown to capture the dependence of the reduced osmotic second virial coefficient on an effective pressure, combining osmotic and hydrostatic contributions. A comparison to small‐angle X‐ray scattering data for ovalbumin indicates enhanced net attraction at all conditions investigated with longer pressure holding times. Pressure effects on PPIs measured by SANS are shown not to be fully reversible in the presence of salt. Pressure‐triggered aggregation was detected in the hours after depressurization at moderate salt concentrations, with slow recovery of pressure‐induced attraction at high salt concentrations. Consistency is demonstrated between predicted solution viscosities and experimental observations from viscometry and in situ high‐pressure diffusing wave spectroscopy. Furthermore, both the strength of ovalbumin PPIs and the relative solution viscosity display Barus‐like scaling with effective pressure, exhibiting distinct pressure‐viscosity coefficients from those of water.