X-ray crystallography applications

Li, X., Volkov, A. V., Szalewicz, K., and Coppens, P. (2006]. Interaction energies between glycopeptide antibiotics and substrates in complexes determined by x-ray crystallography Application of a theoretical databank of aspherical atoms and a symmetry-adapted perturbation theory-based set of interatomic potentials, Acta Crystallogr. D62, pp. 639-bA7, doi 10.1107/S0907444906013072. 

Thus in the presence of an excess of NH4+, which suppresses this forward reaction, and counteranions such as NOa" and C104, which have little tendency to coordinate, complexes such as [Hg(NH3)4] +, [Hg(L-L)2] + and even [Hg(L-L)3] + (L-L = en, bipy, phen) can be prepared. But, in the absence of such precautions, amino, or imino-compounds are likely to be formed, often together. Because of this variety of simultaneous reactions and their dependence on the precise conditions, many reactions between Hg and amines, although first performed by alchemists in the Middle Ages, remained obscure until the application of X-ray crystallography and, still more recently, spectroscopic techniques such as nmr, infrared and Raman. 

On the whole, the four main changes from the previous review (76AFICS1) have been (1) the standard application of high-level theoretical methods, (2) the massive use of X-ray crystallography, (3) the introduc-... 

The potential application of self-assembled scaffolds offering exact positioning of biological macromolecules within micron- to milimeter-size DNA- or protein-made crystals for structural analysis by x-ray crystallography was also suggested [5,50]. 

This chapter consists of four main sections. The first provides an overall description of the process of contemporary protein structure determination by X-ray crystallography and summarizes the current computational requirements. This is followed by a summary and examples of the use of structure-based methods in drug discovery. The third section reviews the key developments in computer hardware and computational methods that have supported the development and application of X-ray crystallography over the past forty or so years. The final section outlines the areas in which improved... 

In the case of being successful in calculating multiple conformations by using time- or ensemble-averaged MD restraints the solved molecular structures are presented as 3D models and can be deposited in an electronic structure database (17). Finally, it is recommended to provide an accurate explanation of the procedures used for the structure elucidation because the application of different methods (NMR, DG, MD, SA, Monte-Carlo calculations. X-ray crystallography) may result in varying conformational models which do not implicitly display the real state of a molecule. This aspect should be always kept in mind when dealing with structure determination methods. 

The elucidation of the structure of the phthalocyanines followed some pioneering research into the chemistry of the system by Linstead of Imperial College, University of London. The structure that we now recognise was first proposed from the results of analysis of a number of metal phthalocyanines, which provided the molecular formulae, and from an investigation of the products from degradation studies. Finally, Robertson confirmed the structure as a result of one of the classical applications of single crystal X-ray crystallography. 

The zinc complexes of bis(2-pyridylmethyl)amine have been studied by X-ray crystallography and 13C NMR. The structures of [ZnL2](C104)2 and [ZnL2]Cl2-6II20 have been determined and 13C NMR demonstrated to be applicable to distinguishing the isomers.109... 

X-ray, neutron, and electron diffraction techniques are used to determine crystal structures and can thus be used for molecular structure determinations. Because of its high resolution and applicability to small and often weakly diffracting samples, x-ray crystallography and powder diffraction are by far the methods of choice for most structure determinations on crystalline compounds,... 

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