Effective Use of Gel-Tube Method

Confocal Science Inc.* MolLogics Inc.** Japan Aerospace Exploration Agency***
â—‹Hiroaki Tanaka* Mari Yamanaka* Koji Inaka** Masaru Sato*** Sachiko Takahashi* Shigeru Sugiyama** Satoshi Sano*** Moritoshi Motohara*** Tomoyuki Kobahashi*** Tetsuo Tanaka***

Gel-Tube [1] is a simplified method for a protein crystallization using counter-diffusion technique, based on gel-acupuncture method [2]. In the Gel-Tube method, a gel in a silicon tube, through which protein and precipitant solution diffuse each other from the opposite direction, is attached to the end of a capillary. The crystallization can be controlled not only by the concentrations of protein and crystallization solution but also the length and the diameter of the gel-tube. We have applied this method for microgravity experiment since 2004, yielding high quality crystals with high probability and high reproducibility.
If the vapor-diffusion method is preliminarily used, an optimized crystallization condition can be estimated. In some cases, crystals of higher quality grew in the Gel-Tube method not only in microgravity but also in ground-based experiment. Post-diffusion of ligand slowly to the crystal in the capillary makes this method suitable for making protein-ligand complex.
Using 1-dimensional (1-D) simulation [1], the diffusion process inside the capillary can be estimated, so that the crystallization condition can be optimized in a short time and the Gel-Tube method can work more effectively. We will show the 1-D simulation of various kinds of precipitant and new method for controlling diffusion in a capillary.

[1] Tanaka, H. et al., J. Synchrotron Rad., 11, 45-48, 2004
[2] Garcia-Ruiz, J.M. and Moreno, A., Acta Cryst., D50, 484-490, 1994