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991.
K.B. Eisenthal N.J. Turro E.V. Sitzmann I.R. Gould G. Hefferon J. Langan Y. Cha 《Tetrahedron》1985,41(8):1543-1554
A combination of picosecond and nanosecond laser spectroscopy measurements, chemical quenching experiments and triplet sensitization experiments has allowed the determination of the rapid singlet to triplet and slower triplet to singlet intersystem crossing rates for diphenylmethylene in fluid solution at room temperature. It is shown that under the conditions of the kinetic measurements, singlet and triplet diphenylmethylene (1DPM and 3DPM, respectively) are in rapid equilibrium relative to reactions, so that knowledge of the values of kST and kTS allows determination of the equilibrium constant and change in free energy for the 1DPM 〈 3DPM process. The absolute reactivity of 1DPM toward a series of alcohols has been determined and is discussed in terms of other current investigations of carbene reactivity. 相似文献
992.
In the present study, we examined the effects of methotrexate (MTX) on the development of autoimmune kidney disease in three kinds of autoimmune prone mice, NZB/NZW F1 (BWF1) mice, MRL/Mp-lpr/lpr (MRL/lpr) mice and NZW/BXSB F1 (WBF1) mice. The results showed that MTX delayed the appearance of proteinuria and prolonged survival of both BWF1 and MRL/lpr mice and inhibited the elevation of blood urea nitrogen (BUN) levels which accompanies the development of lupus nephritis. However, MTX treatment did not affect these in WBF1 mice. Furthermore, MTX could not suppress immunoglobulin G (IgG) class anti-deoxyribonucleic acid (DNA) and anti-trinitrophenol (TNP) antibody production in any variety of mice. These suggest that the therapeutic effect of MTX on BWF1 and MRL/lpr mice does not result in the suppression of IgG autoantibody production. 相似文献
993.
Mohamed Shaaban Marwa Y. Issa Mohamed A. Ghani Abdelaaty Hamed Ahmed B. Abdelwahab 《Natural product research》2019,33(1):24-33
During our continual searching programme for novel bioactive metabolites from Sarcophyton trocheliophorum, collected from Red Sea, we describe herein the isolation and structural elucidation of further two new pyrane-based cembranoid diterpenes: 9-hydroxy-7,8-dehydro-sarcotrocheliol (1) and 8,9-expoy-sarcotrocheliol acetate (2), along with the well-known sarcotrocheliol acetate (3), (+)-sarcophine (4), (+)-sarcophytoxide (5) and (-)-sarcophytoxide (6). The chemical structures of compounds 1 and 2 were determined on the basis of 1D and 2D NMR (1H, 13C, 1H–1H COSY, HMQC, HMBC and NOE), mass spectra (ESI and HR-ESIMS) and by comparison with related structures. The antimicrobial activities of the reported compounds 1–6 were investigated. According to the molecular docking study of compounds 1–6 using 3D structure of α,β tubulin in complex with taxol (PDB code 1JFF) and epothilone A (PDB code 1TVK), sarcophine (4) displayed the highest affinity towards both crystal structures, followed by 5 and 6, meanwhile pyrane-based cembranoid diterpenes (1–3) showed less affinity. 相似文献
994.
Ana?C.?F.?RibeiroEmail author Victor?M.?M.?Lobo Artur?J.?M.?Valente Eduarda?F.?G.?Azevedo M.??da?G.?Miguel H.?D.?Burrows 《Colloid and polymer science》2004,283(3):277-283
Differential mutual diffusion coefficients of n-alkyltrimethylammonium bromides [CH3(CH2)n–1N(CH3)3Br, CnTAB] (n=10, 12, 14, 16) have been measured in aqueous solutions at 298.15 K using a conductimetric cell and an automatic apparatus to follow diffusion. The cell is based on an open-ended capillary, and the technique follows the diffusion process by measuring the resistance of a solution inside the capillaries at various times. The electrical conductances of those solutions have also been measured to calculate the critical micellar concentration (cmc). Thermodynamic analysis of the data suggests that the free ion concentration decreases at concentrations above the cmc, in agreement with theoretical predictions. The obtained values of the micellization parameters were used to model the mutual diffusion coefficients of CnTAB aqueous solutions. 相似文献
995.
Characterization of amiodarone metabolites and impurities using liquid chromatography/atmospheric pressure chemical ionization mass spectrometry 总被引:1,自引:0,他引:1
Myung SW Chang YJ Min HK Kim DH Kim M Kang TK Yoo EA Sohn YT Yim YH 《Rapid communications in mass spectrometry : RCM》2000,14(21):2046-2054
Using the high performance liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry (HPLC/APCI-MS/MS) technique, together with established trends from the literature, the structures of metabolites and impurities of amiodarone, an anti-arrhythmic drug, have been assigned. By comparing analyses of products of incubation with rat liver microsomes with controls in which glucose 6-phosphate dehydrogenase was omitted, metabolites could be distinguished from impurities. Structures for the two proposed metabolites and four impurities are proposed. 相似文献
996.
A fluorescent-labeled oligopeptide (DACM-CLRRASLK-fluorescein), containing a consensus amino acid sequence (RRXSL) of cyclic AMP (cAMP) dependent protein kinase A (PKA) substrate-proteins, was designed. The fluorescent peptide was a good substrate of PKA, and the phosphorylation of its serin residue caused an intensive change in fluorescent intensity. We expect that the peptide will be useful as a fluorescent indicator for monitoring PKA activity in living cells. 相似文献
997.
Shah BH Siddiqui A Qureshi KA Khan M Rafi S Ujan VA Yakoob MY Yaqub Y Rasheed H Saeed SA 《Experimental & molecular medicine》1999,31(1):42-46
Our previous studies have shown that subthreshold concentrations of two platelet agonists exert synergistic effects on platelet aggregation. Here we studied the mechanism of synergistic interaction of 5-hydroxytryptamine (5-HT) and epinephrine mediated platelet aggregation. We show that 5-HT had no or little effect on aggregation but it did potentiate the aggregation response of epinephrine. The synergistic interaction of 5-HT (1-5 microM) and epinephrine (0.5-2 microM) was inhibited by alpha2-adrenoceptor blocker (yohimbine; IC50= 0.4 microM), calcium channel blockers (verapamil and diltiazem with IC50 of 10 and 48 mM, respectively), PLC inhibitor (U73122; IC50=6 microM) and nitric oxide (NO) donor, SNAP (IC50=1.6 microM)). The data suggest that synergistic effects of platelet agonists are receptor-mediated and occur through multiple signalling pathways including the activation PLC/Ca2+ signalling cascades. 相似文献
998.
M.G.?CarvalhoEmail author J.M.R.C.A.?Santos A.A.?Martins M.M.?Figueiredo 《Cellulose (London, England)》2005,12(4):371-383
In this work attention has been focused on the effects of papermaking beating, web forming and sizing operations on the physical/chemical
surface properties of bleached Eucalyptus globulus kraft fibres. Inverse gas chromatography (IGC) was used to determine the dispersive component of surface tension (γsd) as well as the acidic/basic character (according to the Lewis concept) of the solid surfaces (pulp fibres and pulp handsheets).
The results have shown that the main effect of beating is to increase the fibre's Lewis acidic character. Web forming caused
a strong decrease in γsd and significant increments in the adhesion works of both acidic and basic probes, lowering the ratio between the two. Nevertheless,
the surface of handsheets still exhibited a dominant acidic character. The sizing operation did not change the dispersive
component of the surface tension significantly but decreased the difference between the adhesion works of the acidic and basic
probes, rendering the handsheet surface less Lewis acidic and more Lewis basic. Thus, although internal sizing is expected
to strongly influence liquid spreading at the paper surface and liquid penetration of the fibre's network, it is concluded
that beating and web forming lead to important changes in the surface energetic properties of the Eucalyptus globulus kraft fibres. 相似文献
999.
Our new trigonometrically fitted predictor–corrector (P–C) schemes presented here are based on the well known Adams–Bashforth–Moulton methods: the predictor is based on the fifth order Adams–Bashforth scheme and the corrector on the sixth order Adams–Moulton scheme. We tested the efficiency of our newly developed schemes against well known methods, with excellent results. The numerical experiments showed that at least one of our schemes is noticeably more efficient compared to other methods, some of which are specially designed for this type of problem. It is also worth mentioning that this is the first time that sixth algebraic order trigonometrically fitted Adams–Bashforth–Moulton P–C schemes are used to efficiently solve the radial Schrödinger equation.Active Member of the European Academy of Sciences and Arts 相似文献
1000.
C. Cismaş I. Grosu G. Plé E. Condamine Y. Ramondenc L. Toupet I. Silaghi-Dumitrescu G. Nemeş A. Terec L. Muntean 《Structural chemistry》2005,16(4):369-377
The synthesis and stereochemistry of some new bis(1,3-oxathian-2-yl) derivatives are reported. The conformational behavior of these compounds and the orientation of their substituents are deduced from the NMR spectra, from the X-ray crystal structures of two compounds and from the ab-initio level calculations. The epimerization of diastereoisomers and the chair ⇌ 22,5-twist equilibria were studied by variable temperature NMR. 相似文献