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101.
We obtain upper Gaussian estimates of transition probabilities of inhomogeneous random walks on the positive quadrant. Among the most important steps in our proof are comparison arguments based on discrete variants of the Harnack principle and large deviations estimates. 相似文献
102.
103.
Thermal and dielectric loss properties of Na3PO4-Pb3(PO4BiPO4 (Na2O-PbO-Bi2O3-P2O5) phosphate glasses, have been studied by the differential scanning calorimetry (DSC) and electrical factor loss (tgδ) measurements. Experiments have been carried out from ambient temperature to 500°C and show a strong influence of sodium ions on Tg and tgδ. 相似文献
104.
Mostafa?Kabine M'hammed?Sa?d?El Kebbaj Assia?Hafiani Norbert?Latruffe Mustapha?Cherkaoui-MalkiEmail author 《BMC biochemistry》2003,4(1):11
Background
Jerboa (Jaculus orientalis) is a deep hibernating rodent native to subdesert highlands. During hibernation, a high level of ketone bodies i.e. acetoacetate (AcAc) and D-3-hydroxybutyrate (BOH) are produced in liver, which are used in brain as energetic fuel. These compounds are bioconverted by mitochondrial D-3-hydroxybutyrate dehydrogenase (BDH) E.C. 1.1.1.30. Here we report, the function and the expression of BDH in terms of catalytic activities, kinetic parameters, levels of protein and mRNA in both tissues i.e brain and liver, in relation to the hibernating process.Results
We found that: 1/ In euthemic jerboa the specific activity in liver is 2.4- and 6.4- fold higher than in brain, respectively for AcAc reduction and for BOH oxidation. The same differences were found in the hibernation state. 2/ In euthermic jerboa, the Michaelis constants, KM BOH and KM NAD+ are different in liver and in brain while KM AcAc, KM NADH and the dissociation constants, KD NAD+and KD NADH are similar. 3/ During prehibernating state, as compared to euthermic state, the liver BDH activity is reduced by half, while kinetic constants are strongly increased except KD NAD+. 4/ During hibernating state, BDH activity is significantly enhanced, moreover, kinetic constants (KM and KD) are strongly modified as compared to the euthermic state; i.e. KD NAD+ in liver and KM AcAc in brain decrease 5 and 3 times respectively, while KD NADH in brain strongly increases up to 5.6 fold. 5/ Both protein content and mRNA level of BDH remain unchanged during the cold adaptation process.Conclusions
These results cumulatively explained and are consistent with the existence of two BDH enzymatic forms in the liver and the brain. The apoenzyme would be subjected to differential conformational folding depending on the hibernation state. This regulation could be a result of either post-translational modifications and/or a modification of the mitochondrial membrane state, taking into account that BDH activity is phospholipid-dependent.105.
Jean Lévy Mustapha Soufyane Catherine Mirand Michèle Döéde Maindreville Daniel Royer 《Tetrahedron: Asymmetry》1997,8(24):1-4133
(−)-Tabersonine 4 was submitted to quaternization and Emde degradation to yield the 3,4-seco derivative 5, which was hydrolyzed and decarboxylated to the diastereomeric indolenines 8 and 9. Oxidative rearrangement of 8 and 9 yielded the two diastereomeric seco-rhazinilams (−)-10 and (+)-11, differing in the atropomeric conformations of their biarylic system. The results are discussed in the realm of oxidation and rearrangements in the aspidosperma series of indole alkaloids. 相似文献
106.
A new family of multifunctional polyethers was synthesized with acceptable yields by condensation of isosorbide with aliphatic and aromatic dihalides in solid-liquid heterogeneous medium (solid KOH in DMSO). Molecular weights evaluated by GPC are rather low (polydispersed oligomers with n = 2–9). On the other hand, polycondensation with aliphatic or aromatic acid dichlorides in mass or in solution allowed the elaboration of polyethers with appreciable weights (4000–8000) in good yields. 相似文献
107.
108.
Richard Brugidou Jean Pierre Bazureau Jack Hamelin Zohra Dahmani Mustapha Rahmouni 《Heteroatom Chemistry》1999,10(6):446-454
A range of various amines 2(a–i) was tested in transamination reactions using ethyl 2‐(1H‐benzimidazol‐2‐yl)‐3‐dimethylamino‐acrylate 1a. The (E)‐s‐cis/trans conformation of some representative products 4 was analyzed by 1H and 13C NMR spectra. The C‐2/C‐3 bond of the compounds 3(a–i) is strongly polarized by a push‐pull effect. In the same manner, reactions of ethyl 2‐(benzoxazol‐2‐yl)‐3‐dimethylamino‐acrylate 1c with 1,4‐diaminobenzene 2i, ethylenediamine 2i, and 1,5‐diaminomaphthalene 2k have been investigated and gave directly the corresponding symmetric bis‐acrylates 4(a–c) in good yields. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 446–454, 1999 相似文献
109.
We present new results on the behaviour of single chains in homo-and copolymer blends which are beyond the rendom phase approximation (RPA). The radius of gyration of a chain in the blend was found to depend strongly on the interactions as well as the effective diffusion constant of a single chain in the blend or copolymer melt. Note that these results cannot be obtained in the original formulation of the RPA. They are based on the effective Hamiltonian of the chain in the medium. In the equation found for the self diffusion constant of a single chain, Ds, the second term is directly the value of the effective potential at zero wave vector. Thus the measurement of Ds would detect the screened potential at q = 0. Experimental verification of these results is in progress. 相似文献
110.