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101.
102.
The silver(I) oxide mediated reactions of the gold(III) dichloride complex [{C6H3(CH2
uCl2] 2a with thiosalicylic or salicylic acid gives the respective complexes [{C6H3(CH2
)-2}] 3a (X=S) or 6b (X=O), containing chelating thiosalicylate or salicylate dianion ligands. X-ray studies show that for the thiosalicylate system, the thiosalicylate sulfur atom is trans to the N,N-dimethylamino group, whereas in the structure of the salicylate complex, it is the carboxylate group that is trans to NMe2. Both complexes show puckered metallacycles in the solid state. Electrospray mass spectrometry (ESMS) shows strong [M+H]+ and [2M+H]+ ions for both the gold-thiosalicylate and -salicylate complexes, and these ions possess a high stability towards cone voltage-induced fragmentation. ESMS was also used to identify a minor impurity, the bis(cyclo-aurated) cationic complex [A
Me2)-2-(OMe)-5}2]+ in the starting dihalide complex 2a and in the product 3a. This complex can be formed by reaction of Me4N[AuCl4] with 2 equivalents of the organomercury precursor [Hg{C6H3(CH2NMe2)-2-(OMe)-5}Cl]. The biological (antitumour, antimicrobial and antiviral) activities are also reported, and these reveal the complexes have moderate to high anti-tumour, antibacterial and antifungal activity. 相似文献
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103.
Joseph T. Repine Douglas S. Johnson Timothy Stuk Michael A. Stier Zhixiang Yang 《Tetrahedron letters》2007,48(46):8189-8191
Processes for the synthesis of fluorinated 1,8-naphthyridinone derivatives including 6,7-difluoro-1,8-naphthyridin-2-one are described. 相似文献
104.
Susan T. Weintraub R. Neal Pinckard Timothy G. Heath Douglas A. Gage 《Journal of the American Society for Mass Spectrometry》1991,2(6):476-482
Direct derivatization of the acyl analogue of platelet-activating factor (acyl-PAF) with heptafluorobutyric anhydride results in replacement of the phosphocholine moiety with a heptafluorobutyryl (HFB) group. Electron capture (EC) mass spectrometric analysis of this compound that makes use of negative ion detection along with subsequent accurate mass measurement and tandem mass spectrometry studies revealed that in addition to expected fragmentation due to losses of elements of HF, ketene, and/or acetic acid, there is a rearrangement reaction between the HFB group and the substituent on carbon-2 of the glycerol backbone. For 2-acetyl isomers, this fragmentation yields a characteristic ion at m/z 237; for 1-acetyl isomers, the analogous ion is observed at [M-135]−, along with a corresponding carboxylate anion. The use of the HFB derivative is invaluable for analysis of PAF homologues and analogues because it provides detailed structural information in combination with the high sensitivity of a gas chromatography combined with EC-mass spectrometry assay. 相似文献
105.
Gillitzer E Willits D Young M Douglas T 《Chemical communications (Cambridge, England)》2002,(20):2390-2391
Here we present generalized methods for chemically modifying the surface of a viral protein cage; this exploits the chemistry of native and engineered surface exposed functional groups for multivalent presentation of ligands. 相似文献
106.
107.
Alex Berlin Neil Gilkes Douglas Kilburn Vera Maximenko Renata Bura Alexander Markov Anton Skomarovsky Alexander Gusakov Arkady Sinitsyn Oleg Okunev Irina Solovieva John N. Saddler 《Applied biochemistry and biotechnology》2006,130(1-3):528-545
Seven cellulase preparations from Penicillium and Trichoderma spp. were evaluated for their ability to hydrolyze the cellulose fraction of hardwoods (yellow poplar and red maple) pretreated by organosolv extraction, as well as model cellulosic substrates such as filter paper. There was no significant correlation among hydrolytic performance on pretreated hardwood, based on glucose release, and filter paper activity. However, performance on pretreated hardwood showed significant correlations to the levels of endogenous β-glucosidase and xylanase activities in the cellulase preparation. Accordingly, differences in performance were reduced or eliminated following supplementation with a crude β-glucosidase preparation containing both activities. These results complement a previous investigation using softwoods pretreated by either organosolv extraction or steam explosion. Cellulase preparations that performed best on hardwood also showed superior performance on the softwood substrates. 相似文献
108.
Cheikhousman R Zude M Bouveresse DJ Léger CL Rutledge DN Birlouez-Aragon I 《Analytical and bioanalytical chemistry》2005,382(6):1438-1443
The potential of fluorescence spectroscopy for characterizing the deterioration of extra virgin olive oil (EVOO) during heating was investigated. Two commercial EVOO were analysed by HPLC to determine changes in EVOO vitamin E and polyphenols as a result of heating at 170°C for 3 h. This thermal oxidation of EVOO caused an exponential decrease in hydroxytyrosol and vitamin E (R2=0.90 and 0.93, respectively) whereas the tyrosol content was relatively stable. At the same time, amounts of preformed hydroperoxides (ROOH), analysed by an indirect colorimetric method, decreased exponentially during the heating process (R2=0.94), as a result of their degradation into secondary peroxidation products. Fluorescence excitation spectra with emission at 330 and 450 nm were recorded to monitor polyphenols and vitamin E evolution and ROOH degradation, respectively. Partial least-squares calibration models were built to predict these indicators of EVOO quality from oil fluorescence spectra. A global approach was then proposed to monitor the heat charge from the overall fluorescence fingerprint. Different data pretreatment methods were tested. This study indicates that fluorescence spectroscopy is a promising, rapid, and cost-effective approach for evaluating the quality of heat-treated EVOO, and is an alternative to time-consuming conventional analyses. In future work, calibration models will be developed using a wide range of EVOO samples. 相似文献
109.
Douglas O. Spry Anita R. Bhala Wayne A. Spitzer Noel D. Jones John K. Swartzendruber 《Tetrahedron letters》1984,25(24):2531-2534
The major product from the thermolysis and photolysis of C(3)-azido cephem 2 is the ring expanded 1,4,6-thiadiazepine azetidinone. 相似文献
110.
Alginate beads containing entrapped DNA were produced using both external and internal calcium sources, and coated with chitosan
or poly-l-lysine membranes. The beads were assayed with DNase nuclease to determine formulation conditions offering the highest level
of DNA protection fromnucleic acid hydrolysis, simulating gastrointestinal exposure. A method was developed to extract and
assay intracapsular DNA through a modified agarose electrophoresis system. Both external and internally gelled beads were
permeable to DNase (Mw=31 kDa), indicated by the absence of DNA after nuclease exposure. At low levels of DNase exposure, coated high guluronic
content alginate beads offered a higher level of DNA protection compared with coated beads with low guluronic alginate. No
apparent correlation was found with chitosan membrane molecular weight and degree of deacetylation; however, increasing poly-l-lysine molecular weight appeared to increase DNase exclusion from beads. At elevated levels of DNase exposure, DNA hydrolysis
was evident within all coated beads with the exception of those coated with the highest molecular weight poly-l-lysine (Mw=197.1 kDa), which provided almost total nuclease protection. Optimal combination then for DNA protection from nucleases is
a high guluronic alginate core, coated with high molecular weight poly-l-lysine. 相似文献