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11.
Protein tyrosine nitration is a post-translational modification that occurs under conditions of oxidative stress and may play a role in the pathogenesis of diseases such as asthma. Through their ability to generate reactive oxygen species in macrophages and epithelial cells, particulate pollutants, such as diesel exhaust particles (DEPs), may lead to a worsening of the asthmatic condition. In this study, we looked for evidence of oxidative modification of proteins in RAW 264.7 cell line treated with DEP chemicals. We show that the induction of oxidative stress is accompanied by 53 newly expressed proteins which are suppressed by a thiol antioxidant, N-acetylcysteine. These include antioxidant enzymes, pro-inflammatory components, and products of intermediary metabolism. In addition, inducible nitric oxide synthase (iNOS) was identified as a biologically relevant oxidative stress protein that is induced concurrent with increased NO production and protein tyrosine-nitration in DEP-exposed RAW 264.7 cells. Utilizing two-dimensional gel electrophoresis, anti-nitrotyrosine immunoblotting, and mass spectrometry led to the identification of an additional ten nitrotyrosine modified proteins, including oxidative stress proteins involved in intermediary metabolism (e.g., GAPDH and enolase), antioxidant defense (e.g., MnSOD) and inhibition of proteosomal activity (e.g., Hsp 90alpha). These oxidative proteins may serve as markers for oxidative stress generation in vivo. 相似文献
12.
Carette M Zerega Y March RE Perrier P Andre J 《Rapid communications in mass spectrometry : RCM》2000,14(11):979-986
The coupling of a Rydberg electron capture ion source with a Nermag R10-10H quadrupole mass filter is described. Details are given of the addition to this instrument of a creation cell for atoms excited in Rydberg states. Within the Nermag ion source, such atoms allow attachment of electrons of well-defined thermal energy. SF(6) was used for optimization of the main experimental parameters (gas pressures and voltages applied to the electrodes). The procedure by which Rydberg electron attachment was confirmed is described. A polychlorobiphenyl compound was used to illustrate the performance of this ionization technique. Ion formation was observed in the absence of fragmentation. 相似文献
13.
A. Bouchy J. C. Andre F. Baros M. Bouchy-Noirel 《Reaction Kinetics and Catalysis Letters》1989,39(1):199-205
Starting from a uniform distribution and knowing the space dependent rate constant, it is possible to express the fluorescence quenching effect. In the case of long distance energy transfer (Forster), we show that the introduction of radial distribution functions and of non-uniform repartition of quenchers has only small effects on the kinetics of such reactions.
. (Forster) , .相似文献
14.
Andre Rosowsky Ronald A. Forsch Richard G. Moran 《Journal of heterocyclic chemistry》1996,33(4):1355-1361
Nα-[4-[[(4-Aminopteridin-6-yl)methyl]amino]benzoyl]-L-ornithine (dAPA-Orn) was synthesized, and its ability to inhibit folylpolyglutamate synthetase from mouse liver was compared with that of the corresponding 2,4-diamino analogue APA-Orn. Also compared were the inhibitory activities of the deaza analogues 5-deazaAPA-Orn, 8-deazaAPA-Orn, and 5,8-dideazaAPA-Orn, as well as those of Nα-pteroyl-L-ornithine (PteOrn) and its deaza analogues 5-deazaPteOrn and 5,8-dideazaPteOrn. The inhibition constant Ki of dAPA-Orn was 7-fold greater than that of APA-Orn, indicating that the 2-amino group plays a role in binding to the active site. The binding affinity of the 2,4-diamino compounds increased in the order 5-deazaAPA < APA-Orn <5,8-dideazaAPA-Orn < 8-deazaAPA-Orn, and that of the 2-amino-4(3H)-oxo compounds increased in the order 5-deazaPteOrn < PteOrn < 5,8-dideazaPteOrn. The most potent inhibitor of both groups was 8-deazaAPA-Orn, with a Ki of 0.018 μM, coresponding to an 8-fold and 15-fold increase in affinity relative to APA-Orn and 5-deazaAPA-Orn, respectively. The results suggest (a) that the binding of Orn-containing folylpolyglutamate synthetase inhibitors is affected to a greater degree by replacement of N8 by a carbon atom than it is by the corresponding change at N5, (b) that the effect of carbon for nitrogen replacement is greater in the 2,4-diamino derivatives than in the 2-amino-4(3H)-oxo compounds, and (c) that the 2,4-diamines are the better inhibitors. Comparison of the Ki values of the Orn-containing inhibitors with the Km values of the corresponding glutamate-containing substrates revealed that Km/Ki ratio can vary as much as 100-fold depending on the nature of the heterocyclic moiety, suggesting that caution should be exercised in using Km values of known substrates to predict Ki values of putative inhibitors. 相似文献
15.
[reaction: see text] A regiospecific and convergent route the lipophilic antifolate piritrexim (PTX) is described in which a key step is a Pd(0)-catalyzed cross-coupling reaction between 2-amino-3-cyano-4-methyl-5-bromopyridine and 2,5-dimethoxybenzylzinc chloride to form 2-amino-4-methyl-5-(2,5-dimethoxybenzyl)nicotinonitrile. To complete the synthesis, the amino group is replaced by a more reactive bromine atom via nonaqueous diazotization with tert-butyl nitrite, and the resultant bromo nitrile is cyclized with guanidine. 相似文献
16.
J. M. Andre J. Delhalle J. G. Fripiat G. Leroy 《International journal of quantum chemistry》1971,5(1):67-84
The LCAO form of the Hartree–Fock method is discussed in its application to crystals. General formulae are given for obtaining Fourier coefficient of electronic density (in direct space) as well as of the band structure (in momentum space). Finally, it is shown that in its LCAO form, Slater–Hartree–Fock equations are very simple and that this method is of interest for numerical applications. Special integrals occurring in this formalism are evaluated for a Gaussian basis in the last part of this paper. 相似文献
17.
Thomas Andre´s Wolcan Ezequiel Fe´liz Mario R. Capparelli Alberto L. 《Transition Metal Chemistry》1997,22(6):541-544
The kinetics of the complexation of NiII by pteroylglutamic acid have been studied in the 545 ∘C range, the ionic strength
(0.6 M) being regulated with KNO3, in the 5.5–7.0pH range, using the stopped-flow method. Under the experimental conditions
two processes were observed. The faster process was detected in the millisecond range and is associated with the reaction
between NiII and the ligand. The slower is observed within a few seconds. Complementary equilibrium studies were made at 25
∘C. The results are consistent with the formation of a 1:1 complex between the reactants, and a mechanism is proposed to account
for the observed behaviour. Equilibrium constants for the NiII plus pteroylglutamic acid system, as well as activation parameters,
are reported.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
18.
Galan MC Venot AP Glushka J Imberty A Boons GJ 《Journal of the American Chemical Society》2002,124(21):5964-5973
It is demonstrated that conformationally restricted oligosaccharides can act as acceptors for glycosyltransferases. Correlation of the conformational properties of N-acetyl lactosamine (Galbeta(1-4)GlcNAc, LacNAc) and several preorganized derivatives with the corresponding apparent kinetic parameters of rat liver alpha-(2,6)-sialyltransferase-catalyzed sialylations revealed that this enzyme recognizes LacNAc in a low energy conformation. Furthermore, small variations in the conformational properties of the acceptors resulted in large differences in catalytic efficiency. Collectively, our data suggest that preorganization of acceptors in conformations that are favorable for recognition by a transferase may improve catalytic efficiencies. 相似文献
19.
20.
Andre Julg Et Francis Marinelli 《International journal of quantum chemistry》1976,10(6):1037-1047
The introduction of symmetry-adapted hybrid atomic orbitals on the metallic atoms allows us to divide the crystal into elementary cells which contain 8 valence electrons each. These cells are described by linear combinations of the halogen valence shell s and p orbitals and the hybrid orbitals of the nearest metallic atoms which point to the halogen. The electronic delocalization of the halogen ions is very weak (?0.02) for: LiF, NaF, KF, LiCl, NaCI, and KCI. The cell energy in the crystal is obtained by using a first-order perturbative treatment. In agreement with experiment, the f.c.c. type is found more stable than the b.c.c. or the blende type. 相似文献