Reentrant Phase Behavior in Protein Solutions Induced by Multivalent Salts: Strong Effect of Anions Cl Versus NO.

In this work, the effects of the two anions Cl and NO on the phase behavior of bovine serum albumin (BSA) in solution with trivalent salts are compared systematically. In the presence of trivalent metal salts, negatively charged proteins such as BSA in solution undergo a reentrant condensation (RC) phase behavior, which has been established for several proteins with chlorides of trivalent salts. Here, we show that replacing Cl by NO leads to a marked change in the phase behavior.

Structural Evolution of Metastable Protein Aggregates in the Presence of Trivalent Salt Studied by (V)SANS and SAXS.

We present a study of the structural evolution of protein aggregates formed in solutions of a globular protein, β-lactoglobulin (BLG), in the presence of YCl3. These aggregates are often observed before crystallization starts and they are metastable with respect to the crystalline phase. Here we focus on the characterization of the hierarchical structure of this intermediate phase and its temperature dependent structure evolution using a combination of (very) small angle neutron and X-ray scattering (VSANS, SANS, and SAXS).

On the question of two-step nucleation in protein crystallization.

We report a real-time study on protein crystallization in the presence of multivalent salts using small angle X-ray scattering (SAXS) and optical microscopy, focusing particularly on the nucleation mechanism as well as on the role of the metastable intermediate phase (MIP). Using bovine beta-lactoglobulin as a model system in the presence of the divalent salt CdCl2, we have monitored the early stage of crystallization kinetics which demonstrates a two-step nucleation mechanism: protein aggregates form a MIP, which is followed by the nucleation of crystals within the MIP. Here we focus on characterizing and tuning the structure of the MIP using salt and the related effects on the two-step nucleation kinetics.

Real-time observation of nonclassical protein crystallization kinetics.

We present a real-time study of protein crystallization of bovine β-lactoglobulin in the presence of CdCl(2) using small-angle X-ray scattering and optical microscopy. From observing the crystallization kinetics, we propose the following multistep crystallization mechanism that is consistent with our data. In the first step, an intermediate phase is formed, followed by the nucleation of crystals within the intermediate phase.