CRYSTALLIZATION OF BIOLOGICAL MACROMOLECULES UNDER AN EXTERNAL ELECTRIC FIELD

M. Taleb¹, C. Didierjean¹, C. Jelsch¹, J. P. Mangeot¹, B. Capelle² & A. Aubry¹

¹ Groupe Biocristallographie, Laboratoire de Cristallographie et Modélisation des Matériaux Minéraux et Biologiques,UPRESA CNRS 7036, B. P. 239, 54506 Vandoeuvre-les-Nancy, France.
Email : didier@lcm3b.u-nancy.fr

² Laboratoire de Minéralogie et Cristallographie, UMR CNRS 7590, case 115, 4 place Jussieu, 75252 Paris, France.

Keywords : Crystallogenesis, Macromolecules Electric Field.

Proteins and peptides are polymers of amino acids containing dipoles and ionic groups suscesptible to be influenced by an external electric field. In order to obtain crystals, these molecules are dissolved in a ëmother liquorí containing some salts and precipitant agents at define pH values. The net charge of the biological molecule depends on the pH value of the solution and it is possible to obtain migration of these molecules in the solvent when an electric field is applied. It this way , it could be possible to create some supersaturated aeras leading to crystals.

In order to verify experimentally these possibilities, we crystalllized very pure lysozyme at pH 4.5 with sodium chloride as crystallizing agent. Experiments were carried out with and without the superposition of an electric field. The mosaicity was measured at LURE, for both kind of crystals, by direct recording of Bragg reflection profiles with a quasi-planar X-ray wave (Fourme et al., 1995). The statistical results showed a better homogeneity of the crystal quality when an electric field is applied during the crystallization. In order to improve this study, we have built a new experimental device. This new system gives very interesting results which can be correlated with theorical calculations. In one hand, fewer crystals were found in drops under an external electric field, in the other hand these crystals were always located on the surface of the drop, near the cathode side. Details of the new experimental device and of results will be presented.

Fourme R., Ducruix A., Ries-Kautt M. and Capelle B., 1995, J. Synchrotron Rad. , 2, 136