A crystal structure

WebLab Viewer gives a very-high-quality display suitable for publication and presentation. Molecules can be displayed as lines, sticks, ball and stick, CPK, and polyhedrons. In addition, different atoms within the same structure may be displayed in different ways. Text can be added to the display as well as labeling parts of the structure in a variety of ways. The user has control over colors, radii, and display quality. The program can also replicate a unit cell to display a crystal structure. Several types of molecular surfaces can be displayed. 

Polymers are a little more complicated. The drop in modulus (like the increase in creep rate) is caused by the increased ease with which molecules can slip past each other. In metals, which have a crystal structure, this reflects the increasing number of vacancies and the increased rate at which atoms jump into them. In polymers, which are amorphous, it reflects the increase in free volume which gives an increase in the rate of reptation. Then the shift factor is given, not by eqn. (23.11) but by... 

Goldman, A., Ollis, D.L., Steitz, T.A. Crystal structure of muconate lactonizing enzyme at 3 A resolution. 

Bode, W., et al. Refined 1.2 A crystal structure of the complex formed between subtilisin Carlsberg and the inhibitor eglin c. Molecular structure of eglin and its detailed interaction with subtilisin. EMBO f. 5 813-818, 1986. 

Bode, W., et al. The refined 1.9 A crystal structure of human a-thrombin interaction with D-Phe-Pro-Arg chloromethylketone and significance of the Tyr-Pro-Pro-Trp insertion segment. EMBO ]. 8 3467-3475,... 

Noel, J.R, Hamm, H.E., Sigler, P.B. The 2.2 A crystal structure of transducin-a complexed with GTPyS. Nature 366 654-663, 1993. 

Sondek, J., et al. GTPase mechanism of G proteins from the 1.7 A crystal structure of transducin a.GDP.AlF4 . Nature 372 276-279, 1994. 

Fremont, D.H., Matsumura, M., 5tura, E.A., Peterson, P.A., Wilson, I.A. Crystal structures of two viral peptides in complex with murine MHC class I H2-K . Science 257 919-927, 1992. 

The compound K0 3NbF3 has an average niobium valency of 2.7 and forms a crystal structure that is referred to as hexagonal tungsten bronze [239]. 

Thermal properties and decomposition mechanisms depend on the crystal structure type. Compounds with a crystal structure that includes shared octahedrons decompose forming tantalum- or niobium-containing gaseous components, while island-type compounds release light atoms and molecules into the gaseous phase. 

If structural information of the protein target is available, e.g., a crystal structure, in silico screening of huge virtual compound libraries can be conducted by the use of docking simulations. Based on identified primary hits, structural variations of the ligand can be evaluated by computational modeling of the ligand-protein complex. 

Methyl m-tolyl (8), ethyl m-tolyl, methyl n-butyl and methyl n-propyl sulfoxides were obtained in 100% e.e. This method was less successful when applied to methyl phenyl sulfoxide (5% e.e.) or to methyl isobutyl and methyl ethyl sulfoxides (25% e.e.). No complexes were formed between methyl o-tolyl, methyl p-tolyl, methyl 2-butyl and methyl isopropyl sulfoxides so these compounds could not be resolved using 7. A crystal structure of the 1 1 complex formed between 7 and 8 revealed that the partners were linked by OH—OS hydrogen bonds in endless zig-zag chains23. More recently, 2-chloroethyl m-tolyl sulfoxide (9) has been resolved using 724. 

Although a number of solid compounds of plutonium were synthesized by ultramicrochemical techniques during our first year and a half at the Metallurgical Laboratory, it was not until November, 1943 that a positive identification of a crystal structure was made. W. H. Zachariasen joined the project in the fall of 1943 and very soon began to make definitive identifi-... 

As the density of a gas increases, free rotation of the molecules is gradually transformed into rotational diffusion of the molecular orientation. After unfreezing , rotational motion in molecular crystals also transforms into rotational diffusion. Although a phenomenological description of rotational diffusion with the Debye theory [1] is universal, the gas-like and solid-like mechanisms are different in essence. In a dense gas the change of molecular orientation results from a sequence of short free rotations interrupted by collisions [2], In contrast, reorientation in solids results from jumps between various directions defined by a crystal structure, and in these orientational sites libration occurs during intervals between jumps. We consider these mechanisms to be competing models of molecular rotation in liquids. The only way to discriminate between them is to compare the theory with experiment, which is mainly spectroscopic. 

Ziegler-Natta catalyst A stereospecific catalyst for polymerization reactions, consisting of titanium tetrachloride and triethylaluminum. zinc-blende structure A crystal structure in which the cations occupy half the tetrahedral holes in a nearly close packed cubic lattice of anions also known as sphalerite structure. 

The correct structure of this compound, which was predicted by Wolfrom et al.,w was subsequently confirmed by X-ray crystallography.19 Nevertheless, this mistaken identification has been quoted in the literature as late20 as 1990. A crystal structure of a-D-Fru/-l,2 2,3 -p-D-Fru/(6) has also been published.21... 

In spite of the alteration due to deacetylation, chitosan from crab tendon possesses a crystal structure showing an orthorhombic unit cell with dimensions a = 0.828, b = 0.862 and c = 1.043 nm (fiber axis). The unit cell comprises four glucosamine units two chains pass through the unit cell with an antiparallel packing arrangement. The main hydrogen bonds are 03 05 (intramolecular) and N2 06 (intermolecular) [82]. This material has also found medical uses (below). 

A crystal-structure determination on [Ni(PhCH2CS2)2] showed evidence of a Ni-Ni bond (Ni—Ni distance, 256 pm) in a bridging, acetate-cage, binuclear complex (363). Each nickel atom is 5-coordinate and is in a tetragonally distorted, square-pyramid spectroscopic evidence for a Ni-Ni bond has been obtained (364). The polarized crystal spectra showed more bands than predicted for a mononuclear, diamagnetic, square-planar nickel(Il), and the spectra are indicative of substantial overlap of the d-orbitals between the two nickel atoms. The bis(dithiobenzation)nickeKII) complex was found to exhibit unusual spectrochemical behavior (365). 

The molecular mechanism of the enantioselective protonation reaction by antibody 14D9 was revealed by a crystal structure analysis [19[. A catalytic carboxyl group AspH 101 was found at the bottom of the catalytic pocket and found to be necessary for catalysis by mutagenesis to Asn or Ala. The mechanism or protonation involves an overall syn addition of water to the enol ether in a chiral binding pocket ensuring complete enantioselectivity (Figure 3.4). 

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