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Biomedical subjects

Claire Wilson

Publications and source records attributed to Claire Wilson.

85 records · Page 5Linked to original sources
PubMed2003

A zinc-lithium complex of 4,7-bis(2-aminoethyl)-1,4,7-triazacyclononane-1-acetate.

The asymmetric unit of ([4,7-bis(2-aminoethyl)-1,4,7-triazacyclononan-1-yl]acetato)zinc(II) triaqua(mu-[4,7-bis(2-aminoethyl)-1,4,7-triazacyclononan-1-yl]acetato)lithium(I)zinc(II) chloride diperchlorate, [Zn(C(12)H(26)N(5)O(2))][LiZn(C(12)H(26)N(5)O(2))(H(2)O)(3)]Cl(ClO(4))(2), obtained from the reaction between the lithium salt of 4,7-bis(2-aminoethyl)-1,4,7-triazacyclononane-1-acetate and Zn(ClO(4))(2), contains two Zn(II) complexes in which each Zn(II) ion is six-coordinated by five N-atom donors and one O-atom donor from the ligand. One carboxylate O-atom donor is not involved in coordination to a Zn(II) atom, but coordinates to an Li+ ion, the tetrahedral geometry of Li+ being completed by three water molecules. The two complexes are linked via a hydrogen bond between a primary amine N-H group and the carboxylate-O atom not involved in coordination to a metal.

Journal Article↗
PubMed2003

Synthesis of the carbocyclic core of the cornexistins by ring-closing metathesis.

An advanced intermediate in the synthesis of the phytotoxins cornexistin and hydroxycornexistin has been synthesized. Sequential palladium-mediated sp(2)-sp(3) fragment coupling and ring-closing diene metathesis have been used to construct the nine-membered carbocyclic core found in the natural products. [reaction--see text]

Biological Factors↗
PubMed2002

Lithium niobium disulfide, Li0.63NbS2.

Lithium niobium disulfide, Li(0.63)NbS(2), has been prepared by a metathesis reaction between physically separated solid reactants, i.e. separated reactant metathesis (SRM). Single-crystal data were collected at reduced temperature [150 (2) K], yielding a refined Li content of y = 0.63 (6). The Li content in the crystalline samples was also determined analytically by flame photometry. The compound crystallizes in hexagonal space group P6(3)/mmc (No. 194), with Li(+) ions situated in octahedral sites between NbS(2) layers.

Journal Article↗
PubMed2002

Structural isomerism in CuSCN coordination polymers.

CuSCN reacts with the angular ligand 2,4-bis(4-pyridyl)-1,3,5-triazine (dpt) to afford rare examples of coordination polymer structural isomers including a non-centrosymmetric three-dimensional framework with Cd(SO4) topology constructed from tetrahedral metal cations.

Journal Article↗
PubMed2002

Constructing terbium co-ordination polymers of 4,4'-bipyridine-N,N'-dioxide by means of diffusion solvent mixtures.

Five different co-ordination polymers of terbium(III) and the bidentate ligand 4,4'-bipyridine-N,N'-dioxide (L), [Tb(L)(CH(3)OH)(NO(3))(3)](infinity) (1), ([Tb(L)(1.5)(NO(3))(3)].CH(2)Cl(2))(infinity) (2), ([Tb(L)(1.5)(NO(3))(3)].CH(3)OH.0.8H(2)O)(infinity) (3), ([Tb(L)(1.5)(NO(3))(3)].0.4C(2)Cl(4).0.8CH(3)OH)(infinity) (4), and [Tb(L)(2)(NO(3))(3)](infinity) (5) have been synthesised by the use of different "diffusion solvent mixtures", and structurally characterised by X-ray crystallography. Compound 1, with a Tb:L stoichiometry of 1:1, adopts a zig-zag chain structure, which forms three-fold interpenetrating diamondoid frameworks through interchain hydrogen bonding between co-ordinated methanol and a nitrate group on an adjacent chain. Polymers 2, 3, and 4 all have a Tb:L stoichiometry of 1:1.5, but adopt different topologies. For 2, a ladder arrangement is found and large channels which accommodate solvent CH(2)Cl(2) molecules are formed by superposition of the ladders. For 3 and 4 4.8(2) net structures are observed. The superposition of the 4.8(2) nets in 3 and 4, by disposing adjacent layers such that every octagon is positioned below a tetragon from the neighbouring layer, allows the formation of two kinds of channel, with that inside the tetragons accommodating methanol molecules. The other kind of channel, between tetragons, accommodates water molecules in the case of 3 and tetrachloroethylene molecules in the case of 4. Compound 5, with a Tb:L stoichiometry of 1:2, has a linear polymeric structure with one bridging and one terminal ligand, and forms (6,3) plane nets by means of intermolecular electrostatic interactions between N-oxide moieties. X-ray powder diffraction studies show that upon desolvation, compound 2 maintains its original ladder framework.

Journal Article↗
PubMed2002

Using multimodal ligands to influence network topology in silver(I) coordination polymers.

A range of Ag(I) one- and two-dimensional coordination frameworks has been prepared and structurally characterized by using the multimodal ligand 3,6-di-pyrazin-2-yl-(1,2,4,5)-tetrazine, which offers both monodentate and chelating binding sites. It is demonstrated that multimodal ligands can be used to prepare coordination frameworks with novel and unusual topologies and to influence the precise geometrical arrangement of both ligands and metal centers within such supramolecular arrays.

Binding Sites↗
PubMed2002

4-Methoxyphenylphosphonic acid: reactivity of Lawesson's reagent.

The title compound, C(7)H(9)O(4)P, obtained as a by-product of the reaction between Lawesson's reagent, (I), and CH(3)I, can be recognized as the final product of the S/O interchange reaction at the P atom of (I). Hydrogen bonds of type P-O-H.O=P link molecules into helical chains and form ten-membered hydrogen-bonded rings with the graph-set notation R(3)(2)(10). Weaker intermolecular contacts between P-O and a phenyl H atom link the chains into a three-dimensional lattice. The parent benzenephosphonic acid [Weakley (1976). Acta Cryst. B32, 2889-2890] does not adopt an analogous structure, but its arsenic analogue [Shimada (1960). Bull. Chem. Soc. Jpn, 33, 301-304] does and can be regarded as isostructural. We rationalize these three structures in terms of their significant intermolecular interactions.

Journal Article↗
PubMed2002

The short form 36 (SF36) in a specialist tinnitus clinic.

Tinnitus is an extremely common condition which is known to have an effect on quality of life. This study reports the health profile of tinnitus sufferers who attend a specialist tinnitus clinic. This cross-sectional study uses the self-report questionnaire SF36. Two hundred consecutive new patients completed the questionnaire as part of their assessment in a specialist tinnitus clinic in Wales. In all eight scales of the SF36 the mean scores were below that of the general population. Compared to a reference population patients referred to a specialist tinnitus clinic show a reduction in their age/sex-adjusted health profile which is comparable to that of people reporting low back pain. The findings also lend weight to the suggestion that tinnitus sufferers may have a general response bias.

Adult↗
PubMed1998

Multitemperature Resonance-Diffraction and Structural Study of the Mixed-Valence Complex [Fe(3)O(OOCC(CH(3))(3))(6)(C(5)H(5)N)(3)].

The Fe-O and Fe-N bond lengths at two iron sites of the mixed-valence complex [Fe(3)O(OOCC(CH(3))(3))(6)(C(5)H(5)N)(3)] show a pronounced temperature dependence; the bonds from two of the Fe atoms to the central oxygen atoms vary by more than 0.10 Å on cooling to 10 K whereas the bond from the third iron atom is essentially invariant. The variation is such that the longest Fe-O bonds at ambient temperature are the shorter ones at 10 K, with the crossover occurring at about 90 K. The bonds to the axial pyridine ligand show the opposite dependence. The variation is attributed to an equilibrium between different configurations, which interconvert through vibronic coupling, a process that involves electron transfer between the metal atoms. The position of the absorption edge for each of the iron atoms has been determined by resonance-diffraction experiments at the Fe K edge, performed at four different temperatures. At each temperature, the order of the absorption edges corresponds to that of the experimentally determined bond lengths. The crossover near 90 K is confirmed by the resonance experiments. The absorption-edge positions are related to the formal oxidation state by calibration with reference complexes of known oxidation state. The experiments demonstrate the close relation between the changes in coordination geometry and the oxidation states of the iron atoms.

Journal Article↗
PubMedDate not supplied

Exploring phase-transfer catalysis with molecular dynamics and 3D/4D quantitative structure-selectivity relationships.

Quantitative Structure-Selectivity Relationships (QSSR) are developed for a library of 40 phase-transfer asymmetric catalysts, based around quaternary ammonium salts, using Comparative Molecular Field Analysis (CoMFA) and closely related variants. Due to the flexibility of these catalysts, we use molecular dynamics (MD) with an implicit Generalized Born solvent model to explore their conformational space. Comparison with crystal data indicates that relevant conformations are obtained and that, furthermore, the correct biphenyl twist conformation is predicted, as illustrated by the superiority of the resulting model (leave-one-out q(2) = 0.78) compared to a random choice of low-energy conformations for each catalyst (average q(2) = 0.22). We extend this model by incorporating the MD trajectory directly into a 4D QSSR and by Boltzmann-weighting the contribution of selected minimized conformations, which we refer to as '3.5D' QSSR. The latter method improves on the predictive ability of the 3D QSSR (leave-one-out q(2) = 0.83), as confirmed by repeated training/test splits.

Catalysis↗