Analysis of dislocation images in X-ray topography of protein crystals: tetragonal hen egg-white lysozyme crystals

Abstract

Dislocation images in X-ray topography of protein crystals such as tetragonal hen egg-white lysozyme crystals were analyzed. Not only extinction but also double contrast of dislocation images are clearly observed on the X-ray topographs. It should be noted that the observed image widths of the dislocation contrasts are much less than those calculated on the basis of the kinematical theory in X-ray topography, which has been successfully applied for inorganic crystals and organic crystals of small molecules so far. Moreover, in tetragonal HEW lysozyme crystals, the rocking curve widths of the perfect crystal related to the kinematical theory are less than the measured ones by two orders of magnitude. This discrepancy is consistent with that in the image width of the dislocation contrast. From this correlation, it is suggested that the larger rocking curve width, or higher mosaicity, is mainly responsible for the observed image width in the grown crystals.

Acknowledgements

The synchrotron radiation experiments were carried out at Photon Factory (PF) under the auspices of the PF Program Advisory Committee of the High Energy Accelerator Research Organization (KEK) (Proposal Nos. 2003G022, 2004G173 and 2005G015) and at SPring-8 with approval of the Japan Synchrotron Radiation Research Institute (Proposal Nos. 2004A0034-ND3c-np and 2005A0405-ND3c-np). M.T. and K.K. acknowledge the financial support of Yokohama City University.