Triple-axis x-ray diffraction analyses of hen egg-white lysozyme crystals

We have used high-resolution triple-axis x-ray diffraction analyses to moni tor the defect structure in tetragonal crystals of hen egg-white lysozyme a s a function of x-ray irradiation time. At long irradiation times we observ ed the expected decrease in peak intensity and increase in the angular exte nt of the peak breadth. In contrast, the initial stages of irradiation show ed relatively complex changes in both the peak breadth and the intensity; i n fact, during the period from 25 to 45 h of irradiation the angular breadt h of the intensity (both the full-width at half-maximum and the full-width at 1% of the maximum intensity) decreased to a minimum value. We have found that the unambiguous analysis of defects at high angular resolution is com plicated by the fact that the diffraction characteristics of protein crysta ls apparently lie at the confluence of the kinematic (ideally imperfect) an d dynamic (ideally perfect) treatments of diffraction.