Crystal structural information

The Cambridge Structural Database (CSD) contains crystal structure information... 

X-Ray Crystallography The crystal structure information on the heavier group 14 elements centered anions available in the scientific literature at the present time is vast. Therefore, in this section we will deal only with the most... 

The third current approach is synthesis of peptide chains as models for the helical peptaibol (Section 8.2) and gramicidin (Section 8.3) ion channels. Considerable work has been carried out in the former area, involving synthesis of Aib-containing small peptides, in order to obtain conformational data applicable to the more complex oligopeptide antibiotics. By working with such fragments it has been possible to obtain valuable X-ray crystal structure information on the helical conformation of ala-methin 246), emerimicin 247), suzukacillin 248), and other members of the peptaibol series. 

P450 2C9 crystal structure information also served in docking and molecule dynamics operations to simulate the simultaneous binding of a heteroactivator and a substrate [ 17]. N SAID substrates were thereby positioned nearer to the heme than the heteroactivator. For the latter, limited conformational freedom was discovered because of the reduced active-site volume. The presence of an activator shortened the substrate-heme iron distances leading to an increase in the number of catalytic... 

In this last paragraph, only the essential crystal structure information is given for a couple of stoichiometries that are frequently found in several families of inter-metallic compounds. 

The crystal structure information is periodic in the image and thus is concentrated at discrete diffraction spots in the FT. The amplitude and phase part of the FT around one such diffraction spot is shown in Fig. 4. The lattice in the FT is refined using all spots and the exact position of each reflection is predicted from the refined lattice. Integrated amplitudes and phases for all reflections are extracted from the numerical data around the expected center of the diffraction spots ... 

DIAMOND — Visual Crystal Structure Information System (2001) CRYSTAL IMPACT, Postfach 1251, D-53002 Bonn, Germany. 

During the last five years, a powerful new method of getting crystal structural information from powder diffraction patterns has become widely used. Known variously as the Rietveld method, profile refinement1, or, more descriptively, whole-pattern-fitting structure refinement, the method was first introduced by Rietveld (X, 2) for use with neutron powder diffraction patterns. It has now been successfully used with neutron data to determine crystal structural details of more than 200 different materials in polycrystalline powder form. Later modified to work with x-ray powder patterns (3, X) the method has now been used for the refinement of more than 30 crystal structures, in 15 space groups, from x-ray powder data. Neutron applications have been reviewed by Cheetham and Taylor (5) and those for x-ray by Young (6). 

Aconitase was the first protein to be identified as containing a catalytic iron-sulfur cluster [24-26]. It was also readily established that the redox properties of the [4Fe-4S](2+ 1+) cluster do not play a role of significance in biological functioning the 1 + oxidation state has some 30% of the activity of the 2+ state [25], Since then several other enzymes have been identified or proposed to be nonredox iron-sulfur catalysts. They are listed in Table 2. It appears that all are involved in stereospecific hydration reactions. However, these proteins are considerably less well characterized than aconitase. In particular, no crystal structural information is available yet. Therefore, later we summarize structural and mechanistic information on aconitase, noting that many of the basic principles are expected to be relevant to the other enzymes of Table 2. 

The calcium channel p subunit is the only calcium channel subunit for which there is crystal structure information. The core of this subunit is homologous to membrane-associated guanylate kinases (MAGUKs), with conserved, interacting SH3 and guanylate kinase (GK) domains (Takahashi et al. 2004). Residues in the... 

Pennington, W. T. DIAMOND Visual Crystal Structure Information System. J. Appl Cryst, 1999, 32, 1029. 

Following a short review of early studies of the valence band of tetrahedral oxyanions of types X04" some recent results of this field are discussed. High resolution XPS measurements of the valence band of phosphorus and sulphur oxyanions made possible a rigorous test of various theoretical models. For DV-Xa cluster MO calculations, experimentally determined crystal structure information were used to set up realistic model clusters. In the case of the S04 cluster, the results of several model calculations ab initio, DV-Xa, hybrid models) are presented. From the comparison of these results a better understanding of the role of the contributions from different effects to the MO one-electron energies can be obtained. 

Theoretical cluster model MO calculations were used for the interpretation of these spectra. The DV-Xa method combined with realistic cluster approach (in which the model clusters were set up using available crystal structure information from diffraction experiments) proved to be a powerful tool to interpret the structural changes in the valence band spectrum due to the changes in the superstructure of the consisting PO4 tetrahedra. We found noticeable differences in the calculated spectra when the cluster geometry was changed, especially in the case of the hydrous and anhydrous pyrophosphate and similarly for the ring and spiral forms of the tetra-metaphosphate. 

The first crystal structure information on a blue copper protein, for poplar plastocyanin in the Cu(II) state, was published in 1978 (2, 3). Since then, the Cu(I) state and related apo and Hg(II) substituted forms (5, 6), the green algal plastocyanin from Enteromorpha prolifera [Cu(II)] (7), azurin from Alcaligenes denitrificans [Cu(II) and Cu(D] (8, 9), azurin from Pseudomonas aeruginosa [Cu(II)] (10, 11), as well as pseudoazurin from Alcaligenes faecalis S-6 (12), and the cucumber basic protein, both in the Cu(II) state, have been published (13), making this one of the best-documented class of proteins. In addition, information as to three-dimensional structure in solution has been obtained from two-dimensional NMR studies on French bean and Scenedesmus obliquus plastocyanins (14,15). This review is concerned in the main with the active site chemistry. Other recent reviews are listed (16-20). 

Crystal structure information (4) for poplar plastocyanin in the Cud) state at low pH has indicated the existence of two conformers. The... 

Since first data concerning structures of uranyl compounds with CV(U(V1)) = 5 appeared in 1999, it is of great interest to include these structures into the analysis of the characteristics of the U(V1) VD polyhedra. Initial crystal structure information was extracted from the known stmcture databases [2, 3] and analyzed using the TOPOS software [16]. Stmctures were included into consideration under conditions that crystallographic agreement index (7 i) is less than 0.10 and that there is no disorder in the U or O sites in the UO polyhedra. In total, 908 compounds were considered that contained 1465 crystallographically independent U(V1) atoms. From these atoms, 15, 306, 906, and 238 have coordination numbers of 5, 6, 7, and 8, respectively. 

Values of cone angles have been revised on the basis of analysis of crystal structure information in the Cambridge Structural Database. For a review of these results and other... 

Whole pattern methods which rely on the comparison of wide range diffraction data with a calculated pattern formed from the summation of individual phase components that have either been (i) measured from pure phase samples or (ii) calculated from crystal structure information. 

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