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Do protein crystals nucleate within dense liquid clusters?
Author(s) -
Maes Dominique,
Vorontsova Maria A.,
Potenza Marco A. C.,
Sanvito Tiziano,
Sleutel Mike,
Giglio Marzio,
Vekilov Peter G.
Publication year - 2015
Publication title -
acta crystallographica section f
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.572
H-Index - 37
ISSN - 2053-230X
DOI - 10.1107/s2053230x15008997
Subject(s) - nucleation , protein crystallization , chemical physics , lysozyme , dynamic light scattering , crystal (programming language) , cluster (spacecraft) , crystallography , glucose 6 phosphate isomerase , chemistry , scattering , light scattering , materials science , crystallization , nanotechnology , optics , physics , nanoparticle , enzyme , biochemistry , organic chemistry , computer science , programming language
Protein‐dense liquid clusters are regions of high protein concentration that have been observed in solutions of several proteins. The typical cluster size varies from several tens to several hundreds of nanometres and their volume fraction remains below 10 −3 of the solution. According to the two‐step mechanism of nucleation, the protein‐rich clusters serve as locations for and precursors to the nucleation of protein crystals. While the two‐step mechanism explained several unusual features of protein crystal nucleation kinetics, a direct observation of its validity for protein crystals has been lacking. Here, two independent observations of crystal nucleation with the proteins lysozyme and glucose isomerase are discussed. Firstly, the evolutions of the protein‐rich clusters and nucleating crystals were characterized simultaneously by dynamic light scattering (DLS) and confocal depolarized dynamic light scattering (cDDLS), respectively. It is demonstrated that protein crystals appear following a significant delay after cluster formation. The cDDLS correlation functions follow a Gaussian decay, indicative of nondiffusive motion. A possible explanation is that the crystals are contained inside large clusters and are driven by the elasticity of the cluster surface. Secondly, depolarized oblique illumination dark‐field microscopy reveals the evolution from liquid clusters without crystals to newly nucleated crystals contained in the clusters to grown crystals freely diffusing in the solution. Collectively, the observations indicate that the protein‐rich clusters in lysozyme and glucose isomerase solutions are locations for crystal nucleation.