Au and NiO nanocrystals doped into porous sol-gel SiO(2) films and the effect on optical CO detection.

Thin-film composites comprised of NiO and NiO/Au nanoparticles in a porous SiO(2) matrix have been prepared using the sol-gel technique. When at elevated temperatures (200 °C< T<350 °C) and exposed to carbon monoxide, the films undergo reversible changes in optical transmittance at wavelengths in the visible-near IR region. For NiO composite films heated at 330 °C and exposed to 1% CO in air, there is an increase in transmittance which approaches 2-4% over most of the visible range. For NiO/Au composite films the transmittance increase exhibits a wavelength dependence, with a maximum change which is close to 6% at λ≈630 nm and which is close to zero in the Au plasmon resonance range (λ≈550 nm).

alpha-Nucleosides in biological systems. Crystal structure and conformation of alpha-cytidine.

The structure of alpha-cytidine, C9H13N3O5, monoclinic with space group C2 and cell parameters a = 20.064 (3) A, b = 7.100 (1) A, c = 7.860 (2) A, beta = 104.60 (2) degrees, Z = 4, was determined by X-ray diffraction using a combination of direct methods, Patterson and difference Fourier techniques and refined by block-diagonal least-squares to a final R of 0.033 for 1002 reflections measured on a diffractometer. The glycosidic torsional angle, chiCN = -28.4 degrees, is in the anti region; the sugar pucker is C(2')exo-C(3')endo in a nearly pure 32H twist; and the conformation of C(4')-C(5') is gauche-gauche. The molecules are bound by hydrogen bonds in the lattice with little likelihood of base-stacking interactions. The molecular features of the compound are compared and contrasted with those of its naturally occurring beta-anomer, and some biological implications of this structure, and alpha-nucleosides in general, are discussed.

Molecular structures of cytidine-5'-diphosphate and cytidine-5'-diphospho-choline, and their role in intermidiary metabolism.

The nucleotide coenzyme cytidine-5'-diphospho-choline is highly folded. The CMP-5' parts of the molecules in the crystal structure are strongly linked by metal ligation and hydrogen bonds leaving the phosphoryl-choline residues relatively free. Cytidine-5'-diphosphoric acid exists as a zwitterion with N31 protonated. The P-O bond lengths from the anhydride bridging oxygen in the pyrophosphate are significantly different.

Dopamine receptor blockade and the neuroleptics, a crystallographic study.

The X-ray structures of 12 drugs of the tricyclic class having varying pharmacological profiles have been examined in detail in an attempt to rationalize the known structure-activity relations of neuroleptic drugs with respect to their ability to block dopamine receptors in the brain. Further evidence is presented in support of the theory that the neuroleptics are able to block dopamine receptors because of a conformational complementarity between certain portions of these drugs and dopamine.

A crystallographic and theoretical study of the conformation of DOET and its significance for the hallucinogenic amphetamines.

The crystal and molecular structure of 2, 5-dimethoxy-4-ethyl-alpha-methyl-phenylethylamine (DOET) has been determined by X-ray crystallography and the conformation of the side chain has been examined theoretically by the use of a potential energy calculation. There is no indication in the solid state of any intra or inter-molecular hydrogen bonding. The isopropylamine side chain is staggered to the plane of the benzene ring. The alpha-methyl group is fully extended (antiplanar) whereas the amino group is orientated back towards the ring (synclinal). The potential energy calculations show the existence of 6 minima, one of which corresponds to the crystal position. The calculations also show that the energy differences between the various minima of the side chain are very small. The relationship of these data to the conformations of the hallucinogens, mescaline and 2, 4, 5,-trimethoxyamphetamine is discussed.