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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A combined gas chromatographic-mass spectrometric technique is described for the quantification of virazole in serum and urine. Proteins are removed by molecular filtration, lipids by extraction with dichloromethane and interfering endogenous constituents by acidic and basic ion-exchange resins. Virazole is quantified by monitoring the protonated molecular ions of the fully silylated derivatives of virazole (m/e 533) and the arabinose analog (internal standard) obtained by methane chemical ionization. The detection limit is 150 pg (0.6.10(-12) mole) of virazole injected. In serum 10 ng/ml (4.10(-8) mole) can be detected, 25 ng/ml quantified. In urine 0.5 microgram/ml can be quantified without preconcentration. Virazole was detected in serum for at least 96 h at the 70-ng/ml level.
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PMID:Determination of 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide (virazole) in blood and urine by chemical ionization-mass fragmentography. 73 Jul 88

Spalax ehrenbergi mole rats are blind, solitary, territorial, aggressive, subterranean rodents with a yearly breeding season that peaks in December and January. We confirm here an earlier report that estrous females are attracted to substances present in the urine of homospecific as compared to heterospecific adult males. We have also found that nonestrous female mole rats show avoidance behavior to the same homospecific urine. Our objective was to ascertain the nature of the pheromone(s) and gain insight as to its possible role in reproductive isolation and speciation. An active principle, detected in either two- or three-choice behavior tests, was found to be extractable from urine by methylene chloride (CH2Cl2) and mainly found in the neutral lipid fraction. Total lipids were chromatographed by thin layer chromatography on silica gel G60 plates. Most of the activity was found in a zone bounded by Rfs 0.2 and 0.7. Cholesterol, other sterols, and ethyl esters of fatty acids chromatographed in this zone as determined by standards and staining. Ethyl esters of fatty acids were also detected in this fraction by GC/MS analysis. Although a large amount of activity was found in lipids, it only accounted for about 1% of that found in urine. Some activity may have been destroyed or lost during the extraction procedure and some may remain in a lipid insoluble form. Preliminary tests of lipid extracts of various portions of the male urogenital tract revealed pheromonal activity present, particularly in tissues associated with testes, epididymis, prostate, and bladder.
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PMID:Sexual pheromones in lipids and other fractions from urine of the male mole rat, Spalax ehrenbergi. 140 47

The possibility of regulating the retention and selectivity of monoalkyl- and polymethyl-substituted aromatic hydrocarbons in normal-phase high-performance liquid chromatography was investigated by modifying the non-polar (hexane) mobile phase with halide derivatives of hydrocarbons. Dichloromethane, chloroform, carbon tetrachloride and ethyl bromide were employed as modifiers. The decrease in relative retention for small mole fractions of modifier in the eluent increased with decrease in the polarity. The retention mechanism of the aromatic hydrocarbons is discussed. Chromatograms for the group separation of diesel fuel aromatic hydrocarbons are presented.
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PMID:Peculiarities of aromatic hydrocarbon retention in normal-phase high-performance liquid chromatography with eluents containing halide derivatives. 208 83

To assay various secondary amino drugs (sympatomimetic, beta-blocking, antiarrhythmic agents), they were converted to metal (copper or nickel) dithiocarbamate complexes by means of a pre-column derivatization method. The electrochemical properties of the complexes were studied. They were chromatographed on a reversed-phase column (LiChrosorb RP-18) with mixtures of acetate buffer (pH 5.8) and organic solvents (methanol, acetonitrile, ethanol or dichloromethane) as mobile phases. The complexes were detected by amperometry (applied potential of +0.7 V vs. SCE) or by UV spectrophotometry. The procedure has great sensitivity (10(-12) mole for each injected compound) and good selectivity for the more substituted amino drugs.
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PMID:Determination of secondary amino drugs as their metal dithiocarbamate complexes by reversed-phase high-performance liquid chromatography with electrochemical detection. 615 72

The effects of methanol addition and consumption on chloroform degradation rate and product distribution in methanogenic methanol enrichment cultures and in cultures of Methanosarcina barkeri 227 were investigated. Degradation of chloroform with initial concentrations up to 27.3 microM in enrichment cultures and 4.8 microM in pure cultures was stimulated by the addition of methanol. However, methanol consumption was inhibited by as little as 2.5 microM chloroform in enrichment cultures and 0.8 microM chloroform in pure cultures, suggesting that the presence of methanol, not its exact concentration or consumption rate, was the most significant variable affecting chloroform degradation rate. Methanol addition also significantly increased the number of moles of dichloromethane produced per mole of chloroform consumed. In enrichment cultures, the number of moles of dichloromethane produced per mole of chloroform consumed ranged from 0.7 (methanol consumption essentially uninhibited) to 0.35 (methanol consumption significantly inhibited) to less than 0.2 (methanol not added to the culture). In pure cultures, the number of moles of dichloromethane produced per mole of chloroform consumed was 0.47 when methanol was added and 0.24 when no methanol was added. Studies with [14C]chloroform in both enrichment and pure cultures confirmed that methanol metabolism stimulated dichloromethane production compared with CO2 production. The results indicate that while the addition of methanol significantly stimulated chloroform degradation in both methanogenic methanol enrichment cultures and cultures of M. barkeri 227, the prospects for use of methanol as a growth substrate for anaerobic chloroform-degrading systems may be limited unless the increased production of undesirable chloroform degradation products and the inhibition of methanol consumption can be mitigated.
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PMID:Chloroform degradation in methanogenic methanol enrichment cultures and by Methanosarcina barkeri 227. 757 27

In common with a diverse group of low-molecular-weight volatile substrates, dichloromethane (DCM; methylene chloride) is a high-affinity, low-capacity substrate for oxidation by several cytochrome P450 isoenzymes in vivo. DCM oxidation, catalyzed primarily by the 2E1 and 2B1 cytochrome P450 isoforms, yields carbon monoxide (CO) and carbon dioxide. We have studied the characteristics of DCM oxidation in vivo by examining the metabolism of DCM and of both deuterated forms ([2H2]-DCM and [2H]DCM) in female B6C3F1 mice with gas uptake methods. Gas uptake and CO production curves were analyzed by physiologically based pharmacokinetic (PBPK) modeling techniques, permitting differentiation of isotope effects on specific metabolic parameters from those associated with blood flow or diffusion limitations in vivo. A marked isotope effect was observed on the moles of CO produced per mole of DCM oxidized (0.76 +/- 0.06, 0.33 +/- 0.006, and 0.31 +/- 0.07, with DCM, [2H]DCM, and [2H2]DCM, respectively). Based on these ratios, the calculated kH/kD ratio for the rate constant of disproportionation of the putative formyl chloride intermediate was about 7, indicating a significant role of C-H bond breaking in this reaction. Deuterium substitution altered the apparent Km for metabolism; there was 14-fold increase in the apparent Km between DCM and [2H2]DCM (6.5 +/- 0.69 to 97 +/- 3.5 microM) with little effect on Km with [2H]DCM (14.4 +/- 0.015 microM). Vmax was not greatly affected by deuteration (151 +/- 1.2, 116 +/- 0.82, and 149 +/- 2.3 mumol/hr/kg with DCM, [2H]DCM, and [2H2]DCM, respectively). Two kinetic mechanisms are discussed, both of which are consistent with these observations. One, a conventional cytochrome P450 mechanism has a rate-limiting product-release step after the isotopically sensitive step; a second, more like a peroxidase mechanism, has a flux-limiting oxygen activation step followed by a second-order reaction between an activated oxygen-enzyme complex and DCM. Regardless of the correct mechanism, the in vivo kinetic constants for oxidation of DCM are complex and represent more than simple rate-limiting bond-breaking (Vmax) and enzyme-substrate binding (Km). Current PBPK models for metabolism of these volatiles may have to be restructured to account for this unusual kinetic mechanism.
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PMID:Gas uptake studies of deuterium isotope effects on dichloromethane metabolism in female B6C3F1 mice in vivo. 807 49

119Sn NMR spectroscopy was employed for analysis of the interaction and reaction of SnCl4 with the HCl-IBVE adduct [1; CH3CHCl(OiBu)] in the presence of nBu4NCl in CH2Cl2 solution at -78 degreesC, which are model reactions for the living cationic polymerization of isobutyl vinyl ether (IBVE). The addition of 1 to an SnCl4 solution led to upfield shifts of the tin nucleus as the 1/SnCl4 mole ratio (<1) increases, which indicates the formation of SnCl5-, via the interaction between SnCl4 and the chlorine atom in 1. On further addition of 1, the pentacoordinated anion is converted into the hexacoordinated SnCl62-. These tin species are in fast equilibrium among each other, and the 119Sn NMR analyses support the formation of a carbocation [2; CH3CH+(OiBu)] from 1 and the dynamic equilibrium between 1 and 2. More effective chloride-anion donors such as nBu4NCl and Ph3CCl can quantitatively convert SnCl4 into SnCl5-, and then into SnCl62-. Thus under the conditions where living cationic IBVE polymerization proceeds (1 < nBu4NCl/SnCl4 < 2), SnCl4 is fully converted into a weaker Lewis acid, SnCl5-, with the aid of added nBu4NCl. The suppression of the carbocationic species in the living system has thus been found due to the interaction between the added salt and SnCl4.
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PMID:In-Situ Direct Analysis of the Growing Species by 119Sn NMR Spectroscopy: Living Cationic Polymerization of Isobutyl Vinyl Ether with HCl/SnCl4/nBu4NCl1 968 Apr 2

Tetranuclear complexes [Zn(4)(bdmap)(2)(OOCR)(6)] 1 (R = Me) and 2 (R = Et), where Hbdmap = 1,3-bis(dimethylamino)-2-propanol, were prepared from zinc carboxylates and Hbdmap in tetrahydrofuran (THF). The solid-state structures of isomers 1a and 2a consist of two pairs of zinc atoms, each bridged by two mu-1,2 and one mu-1,1 carboxylate ligands. Two pairs are connected by two tridentate bdmap ligands with oxygen acting as a bridging donating atom. The complexes retain the tetranuclear structure in solution and two dynamic processes are observed from variable-temperature (1)H and (13)C NMR spectra. A low-temperature process (LT dynamics) observed already below 200 K is a coalescence of the mu-1,2 and the mu-1,1 resonances to a single resonance. An additional dynamic process (HT dynamics) is observed above 247 K (1) and 263 K (2), leading to a coalescence of two dimethylamino resonances. Both dynamic processes are rationalized by a mechanism involving changes in the carboxylate coordination mode termed as carboxylate shift. The LT dynamics is ascribed to interconversions of a single mu-1,2 and a single mu-1,1 carboxylate ligation by rotations of 60 degrees. The interconversions involve all carboxylate ligands in 1 and 2. The HT dynamics is ascribed to the exchange of the coordinating geometries of two carboxylate-bridged zinc atoms. We propose a mechanism that starts with a cleavage of the Zn-N coordination bond. The resulting coordinatively unsaturated zinc atom acquires an additional oxygen donor atom by carboxylate shift of mu-1,2 carboxylate to mu-1,1 mode. The activation parameters (DeltaH values in kilocalories per mole, DeltaS values in calories per mole per kelvin) were determined by line-shape analysis of VT NMR spectra: for 1 in THF-d(8), DeltaH(LT) = 8.1(3), DeltaS(LT) = -12(2), DeltaH(HT) = 17.9(2), DeltaS(HT) = 14(1); for 1 in CDCl(3), DeltaH(HT) = 13.6(5), DeltaS(HT) = 3(3); for 1 in CD(2)Cl(2), DeltaH(HT) = 9.9(3), DeltaS(HT) = -8(2); for 2 in THF-d(8), DeltaH(LT) = 11(1), DeltaS(LT) = -5(3), DeltaH(HT) = 19.6(5), DeltaS(HT) = 18(3). Polymeric [Zn(4)(bdmap)(2)(OOCMe)(6)](n) 1-catena crystallizes from a dichloromethane solution of 1. In 1-catena, the zinc atoms are linked into a chain through mu-1,2 and mu-1,1 acetate alternated by mu-1,2 acetate and bdmap.
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PMID:Variable-temperature nuclear magnetic resonance spectroscopy allows direct observation of carboxylate shift in zinc carboxylate complexes. 1194 33

Mercaptopropionic acid (MPA) capped Au-Ag alloy nanoparticles consisting of various mole fractions of gold and silver have been synthesized in aqueous medium using a citrate reduction method. UV-visible spectra confirm the formation of alloy phases and transmission electron microscopy (TEM) reveals a rather uniform distribution of several nanometer-sized particles. The particles could easily be phase-transferred into organic solvents, isolated, and redispersed in a variety of solvents such as benzene, chloroform, and dichloromethane. The phase transfer from aqueous medium to an organic solvent does not alter the particle size and distribution. It is also recognized that the surfactant, alkaline MPA, should be aged for about 3 days in order to observe the formation of silver and silver-rich phases of alloy nanoparticles. The reason for this observation is discussed in terms of the competitive interaction between the Na+ and -COOH/-SH groups and subsequent reduction of metal ions.
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PMID:Phase transfer of Au-Ag alloy nanoparticles from aqueous medium to an organic solvent: effect of aging of surfactant on the formation of Ag-rich alloy compositions. 1531 45

Elemental I(2) and Br(2) cleanly react with the 3:3 Pt(ii) metallamacrocycle of 3,3,3',3'-tetra(n-butyl)-1,1'-terephthaloylbis(thiourea)(cis-[Pt(II)(3)(L(p)(1)-S,O)(3)]3), in chloroform at room temperature, to yield oxidative addition products; (195)Pt NMR studies reveal that a stepwise oxidative addition readily occurs to each of the Pt(ii) centres in the metallamacrocycle to yield the mixed valence species cis-[Pt(II)(2)Pt(IV)I(2)(L(p)(1)-S,O)(3)] and cis-[Pt(II)Pt(IV)(2)I(4)(L(p)(1)-S,O)(3)], and the fully oxidised cis-[Pt(IV)(3)I(6)(L(p)(1)-S,O)(3)] in solution, depending on the mole ratio I(2):3. Similar results are obtained on treatment of solutions of 3 with elemental Br(2). Treatment of the corresponding 2:2 Pt(ii) complex of 3,3,3',3'-tetraethyl-1,1'-isophthaloylbis(thiourea)(cis-[Pt(II)(2)(L(m)(1)-S,O)(2)]4) with iodine, results in facile oxidative addition to yield cis-[Pt(IV)(2)(L(m)(1)-S,O)(2)I(4)], with a trans-Pt(iv)-iodo arrangement. Molecules in the crystal structure of 5 have their trans-Pt(iv)-iodo axes essentially aligned, with very close intermolecular iodide contacts (3.775(1)A), resulting in chains of weakly bound metallamacrocycles in the solid. An alternative electrolytic synthesis method, using a simple two-compartment glass cell containing 4 and a chosen halide salt in dichloromethane, led to the formation of cis-[Pt(IV)(2)(L(m)(1)-S,O)(2)Br(4)] 6 and cis-[Pt(IV)(2)(L(m)(1)-S,O)(2)Cl(4)] 7, completing characterization of a series of first-reported trans-Pt(iv)-X (X=I, Br, Cl) metallamacrocyclic complexes.
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PMID:First metallamacrocyclic complexes of Pt(iv) with 3,3,3',3'-tetraalkyl-1,1'-phenylenedicarbonylbis(thioureas): synthesis by direct or electrolytic oxidative addition of I(2), Br(2) and Cl(2). 1609 81


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