engleski

A combined electrophoretic and light scattering approach to elucidate the molecular origin of reverse Hofmeister series effects

We have carried out a systematic study of specific ion effects on lysozyme solutions using static light scattering to characterize protein-protein interactions (in terms of the osmotic second virial coefficient, B22) and electrophoretic light scattering to approximate the diffuse layer potential of lysozyme. Lysozyme has long been used as a model system for specific ion effects in part because its solubility behavior follows the reverse Hofmeister series, where chaotropes rather than kosmotropes are more effective salting-out agents [1]. A key question we address is how chaotropic anion binding alters protein-protein interactions (and protein solubility) as computational work indicates ion binding mainly alter electrical double layer forces between proteins [2, 3]. To check this hypothesis, B22 and electrophoretic mobilities for lysozyme have been measured as a function of pH and salt concentration with different anions spanning the range of the Hofmeister series. We found that under low ionic strength conditions, the measured zeta-potential does not always correlate with the trends in protein-protein interaction measurements. In particular, with increasing ionic strength, chaotropic anions such as thiocyanate are more effective at inducing protein-protein attraction than is the kosmotropic anion sulfate, although the zeta potential remains less positive in sulfate solutions over all ionic strength. The results demonstrate that chaotropic anion binding to proteins induces shortranged attractive forces between proteins of non-electrostatic origin, rather than changing electrical double layer forces.

Electrophoresis, light scattering, Hofmeister series, lysozyme

nije evidentirano