Changes of pH during Biomacromolecule Crystallization by Vapor Diffusion using Ammonium Sulfate as the Precipitant

Published on Apr 1, 1989in Journal of Applied Crystallography2.867
· DOI :10.1107/S0021889888013433
Vincent Mikol7
Estimated H-index: 7
Jean-Luc Rodeau16
Estimated H-index: 16
Richard Giegé56
Estimated H-index: 56
Possible pH variations during crystallization of biological macromolecules by the vapor diffusion method have not been taken into account in most experiments so far reported. The present study demonstrates that when ammonium sulfate is used as the precipitant, pH changes occur due to ammonia transfer following ammonium/ammonia equilibrium. The pH in a crystallization droplet is shown to be controlled by that of the reservoir. The theory of the effect is given and the consequences of pH variations during crystallization are discussed in terms of reproducibility of experiments. An application, the crystallization of concanavalin A induced by pH variation, is presented.
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