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Just published: Electron Crystallography

Model for connexon structure taken from Electron Crystallography.

The Transactions of the 1992 ACA Symposium on Electron Crystallography, edited by D. Dorset, describes analyses of specimens difficult to crystallize for single crystal X-ray data collection. These include: mesomorphic compounds (S. W. Hui, Buffalo and I. G. Voigt-Martin, Mainz), small organic molecules and linear polymers (J. R. Fryer, Glasgow and D. L. Dorset, Buffalo), and inorganic materials (H. F. Fan, Beijing; S. Hovmoller, Stockholm; and K. H. Downing, Berkeley). Other chapters address solving structures via packing analysis (R. P. Scaringe, Rochester), high-resolution studies of bacteriorhodopsin (K. H. Downing, Berkeley), methods for resolution enhancement (C. J. Gilmore, Glasgow) and, high-resolution work on Pho E porin (B. K. Jap, Berkeley). C. A. Mannella (Albany) described the study of an outer membrane porin; G. Sosinsky (Waltham) described work on the gap junction connexon; and A. Engel (Basel) described preparing two-dimensional crystals of integral membrane proteins. Finally, a paper on the type of specimen stages needed for data collection from such samples was given by J. N. Turner (Albany).

In his overview of the IUCr summer school in Beijing (IUCr Newsletter, Vol. 2, No. 1), John Cowley mentions that "an unresolved question was why the kinematical theory-based analysis of crystal structures should be so successful when the dynamical diffraction effects are so pervasive in electron diffraction". This problem occupies a central focus in the research described in the papers above. Most researchers in the field believe implicitly that the multiple beam dynamical scattering theory developed by Cowley and others is the most rigorous description of the scattering of electrons from crystals of any kind. The results reported in this volume are possible only after efforts are taken experimentally to minimize such multiple scattering perturbations to the observed data. Nevertheless, there are certain instances when phase-determining methods seem to be unusually "robust" in the face of these perturbations. Thus, more attention has to be paid as to why this may be so, in order that even more reliable methodologies for structure analysis can be developed.

Doug Dorset
Buffalo, NY, USA