X-ray crystallographic structures

Although experimental studies of DNA and RNA structure have revealed the significant structural diversity of oligonucleotides, there are limitations to these approaches. X-ray crystallographic structures are limited to relatively small DNA duplexes, and the crystal lattice can impact the three-dimensional conformation [4]. NMR-based structural studies allow for the determination of structures in solution however, the limited amount of nuclear overhauser effect (NOE) data between nonadjacent stacked basepairs makes the determination of the overall structure of DNA difficult [5]. In addition, nanotechnology-based experiments, such as the use of optical tweezers and atomic force microscopy [6], have revealed that the forces required to distort DNA are relatively small, consistent with the structural heterogeneity observed in both DNA and RNA. 

Hogle, J.M., Maeda, A., Harrison, S.C. Structure and assembly of turnip crinkle virus. I. X-ray crystallographic structure analysis at 3.2 A resolution. /. Mol. Biol. 

X-Ray crystallographic structure of a Ti2(dibenzyltartamide)2(OiPr)4 species has been obtained. 

An interesting mass spectral study of 17 mono- and dflialogenoquinoxahnes, some bearing methyl groups, has been reported the X-ray crystallographic structure of hexachloroquinoxaline has been measured. ... 

Carbocations are intermediates in several kinds of reactions. The more stable ones have been prepared in solution and in some cases even as solid salts, and X-ray crystallographic structures have been obtained in some cases. An isolable dioxa-stabilized pentadienylium ion was isolated and its structure was determined by h, C NMR, mass spectrometry (MS), and IR. A P-fluoro substituted 4-methoxy-phenethyl cation has been observed directly by laser flash photolysis. In solution, the carbocation may be free (this is more likely in polar solvents, in which it is solvated) or it may exist as an ion pair, which means that it is closely associated with a negative ion, called a counterion or gegenion. Ion pairs are more likely in nonpolar solvents. 

Figure 17.3 Anatomy of a redox enzyme representation of the X-ray crystallographic structure of Trametes versicolor laccase III (PDB file IKYA) [Bertrand et al., 2002]. The protein is represented in green lines and the Cu atoms are shown as gold spheres. Sugar moieties attached to the surface of the protein are shown in red. A molecule of 2,5-xyhdine that co-crystallized with the protein (shown in stick form in elemental colors) is thought to occupy the broad-specificity hydrophobic binding pocket where organic substrates ate oxidized by the enzyme. Electrons from substrate oxidation are passed to the mononuclear blue Cu center and then to the trinuclear Cu active site where O2 is reduced to H2O. (See color insert.)...

Figure 17.8 Catal3ftic zinc center of horse liver alcohol dehydrogenase revealed from an X-ray crystallographic structure (PDB file 20HX) [Al-Karadaghi et al., 1994]. The bound NADH cofactor, a molecule of the inhibitor dimethylsulfoxide (DMSO), and the amino acid residues that coordinate the Zn are shown as sticks shaded according to the elements, and the Zn center is shown as a gray sphere, while the protein is shown in thin gray lines.

X-ray crystallographic structure of the Norwalk virus capsid. Science 286, 287-290. 

The H and 13C NMR data for the three metal derivatives were similar. An X-ray crystallographic structure for the gallium derivative (Fig. 6) indicated a shortened Ga—C (carbene) distance of 1.935(6) A, whereas the Ga—C(Me) distances had normal single bond values, 1.994(8) and 1.988(8) A. Thus, the structure may be visualized as being composed of the two canonical forms... 

The X-ray crystal structures of the interesting phosphonium azoniaspiroylides 7 and 8 have been published <1995TL7859, 1997T7557>. The structures were originally deduced from the 111 and 13C spectroscopy data, in particular the chemical shifts of the protons and carbons adjacent to the quaternary nitrogen atom, but were confirmed by the X-ray crystallographic structures. 

Confirmation that the polymerizations proceed via metallacyclic intermediates was obtained by studying the ROMP of functionalized 7-oxanorbornadienes. These polymerize slower than their norbornene analogs, allowing NMR identification of the metallacyclobutane resonances and subsequent monitoring of ring opening to the first insertion product. In addition, the X-ray crystallographic structure of complex (212) has been reported.533... 

X-ray crystallographic structure of a complex between a synthetic protease of human immunodeficiency virus 1 and a substrate based hydroxyethyl-amine inhibitor, Proc. Natl. Acad. Sci. 87 8805 (1990). 

The X-ray crystallographic structure from the mouse protein Zif268 and a consensus DNA-binding site has been determined at 2.1-A resolution, as reported by the authors of reference 27. In this complex, the zinc fingers bind in the major groove of B-DNA and wrap part way around the double helix. Each zinc-finger... 

X-ray crystallographic structures of the enzyme nitrogenase first became available in 1992 with refinements of the structures continuing to the present time. As of this... 

X-ray crystallographic structures of myoglobin and hemoglobin were first completed in 19662 and 19753, respectively. Since then, many other X-ray crystallographic studies of deoxy- and oxy- as well as met-myoglobin and hemoglobin have been carried out.22,24 Additionally, researchers have studied the carbon monoxide bound moieties MbCO and HbCO as well as MbNO. Site-directed mutagenesis of residues near the active sites of Mb and Hb have yielded... 

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