Volume 179, 2015

On the question of two-step nucleation in protein crystallization

Abstract

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. The results suggest that increasing the salt concentration near the transition zone pseudo-c** enhances the energy barrier for both MIPs and crystal nucleation, leading to slow growth. The structural evolution of the MIP and its effect on subsequent nucleation is discussed based on the growth kinetics. The observed kinetics can be well described, using a rate-equation model based on a clear physical two-step picture. This real-time study not only provides evidence for a two-step nucleation process for protein crystallization, but also elucidates the role and the structural signature of the MIPs in the nonclassical process of protein crystallization.

Associated articles

Supplementary files

Article information

Article type
Paper
Submitted
18 Nov 2014
Accepted
07 Jan 2015
First published
12 Jan 2015
This article is Open Access
Creative Commons BY license

Faraday Discuss., 2015,179, 41-58

Author version available

On the question of two-step nucleation in protein crystallization

A. Sauter, F. Roosen-Runge, F. Zhang, G. Lotze, A. Feoktystov, R. M. J. Jacobs and F. Schreiber, Faraday Discuss., 2015, 179, 41 DOI: 10.1039/C4FD00225C

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements