issue contents

ISSN: 2053-2733

March 2011 issue

Highlighted illustration

Cover illustration: Polar mode GM6 (left) and antiferrodistortive mode M3-1q (right) present in the monoclinic structure of SrAl2O4, together with a graph of maximal subgroups showing their isotropy subgroups. The amplitude of mode GM6 is much larger, and ab initio calculations confirm its soft character, while distortion M3-1q is a hard mode frozen as an induced secondary distortion [Perez-Mato et al. (2010). Acta Cryst. A66, 558-590]. The mode figures were drawn using FullProf Studio [Rodriguez-Carvajal (1993). Physica B, 192, 55-69].

research papers

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A complete set of structure factors has been extracted from hundreds of thousands of femtosecond X-ray diffraction patterns from randomly oriented Photosystem I membrane protein nanocrystals, using the Monte Carlo method of intensity integration. The data, collected at the Linac Coherent Light Source, are compared with conventional single-crystal data collected at a synchrotron source, and the quality of each data set was found to be similar.

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The existing pseudoatom databases (ELMAM, Invariom, UBDB and ELMAM2) enable structure refinement and estimation of electrostatic properties to be performed with the use of aspherical scattering factors computed from the transferable aspherical atom model (TAAM). Root-mean-square deviations and correlation coefficients from the reference theoretical and experimental models were used as a quantitative measure of the quality of the structural and electrostatic properties obtained from the individual databases.

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Interference fringes are measured from the lateral surface of a plane-parallel Si crystal by changing the distance between the incident point of the X-rays and the crystal edge. The measured fringes are well reproduced by a calculation based on the dynamical theory of diffraction with the visibility taken into account and are attributed to interference fringes between the beams in two different multiple Bragg–Laue modes.

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Multipole models of the electron density in a hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) crystal were obtained at 20, 120 and 298 K followed by topological analysis. The necessity of anharmonic model refinements for RDX is demonstrated, and the results are compared with refinements for 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX). The reliability of anisotropic atomic displacement parameters for H atoms is discussed.

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The investigation of rhinoviruses is applied to the Picornaviridae family. The fingerprint diagrams, based on contact binding points between neighbouring molecules periodically packed in the crystal, are extended to antigenic and receptor binding sites.
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