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Direct Observation of Adsorption Sites of Protein Impurities and Their Effects on Step Advancement of Protein Crystals†.

Authors :
Alexander E. S. Van Driessche
Gen Sazaki
Guoliang Dai
Fermín Otálora
Jose A. Gavira
Takuro Matsui
Izumi Yoshizaki
Katsuo Tsukamoto
Kazuo Nakajima
Source :
Crystal Growth & Design. Jul2009, Vol. 9 Issue 7, p3062-3071. 10p.
Publication Year :
2009

Abstract

We measured noninvasively step velocities of elementary two-dimensional (2D) islands on {110} faces of tetragonal lysozyme crystals, under various supersaturations, by laser confocal microscopy combined with differential interference contrast microscopy. We studied the correlation between the effects of protein impurities on the growth of elementary steps and their adsorption sites on a crystal surface, using three kinds of proteins: fluorescent-labeled lysozyme (F-lysozyme), covalently bonded dimers of lysozyme (dimer), and a 18 kDa polypeptide (18 kDa). These three protein impurities suppressed the advancement of the steps. However, they exhibited different supersaturation dependencies of the suppression of the step velocities. To clarify the cause of this difference, we observed in situ the adsorption sites of individual molecules of F-lysozyme and fluorescent-labeled dimer (F-dimer) on the crystal surface by single-molecule visualization. We found that F-lysozyme adsorbed preferentially on steps (i.e., kinks), whereas F-dimer adsorbed randomly on terraces. Taking into account the different adsorption sites of F-lysozyme and F-dimer, we could successfully explain the different effects of the impurities on the step velocities. These observations strongly suggest that 18 kDa also adsorbs randomly on terraces. Seikagaku lysozyme exhibited a complex effect that could not alone be explained by the two major impurities (dimer and 18 kDa) present in Seikagaku lysozyme, indicating that trace amounts of other impurities significantly affect the step advancement. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
15287483
Volume :
9
Issue :
7
Database :
Academic Search Index
Journal :
Crystal Growth & Design
Publication Type :
Academic Journal
Accession number :
43360567
Full Text :
https://doi.org/10.1021/cg8006684