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531.
Franke A Hessenauer-Ilicheva N Meyer D Stochel G Woggon WD van Eldik R 《Journal of the American Chemical Society》2006,128(41):13611-13624
A new model for the P450 enzyme carrying a SO(3)(-) ligand coordinated to iron(III) (complex 2) reversibly binds NO to yield the nitrosyl adduct. The rate constant for NO binding to 2 in toluene is of the same order of magnitude as that found for the nitrosylation of the native, substrate-bound form of P450(cam) (E.S-P450(cam)). Large and negative activation entropy and activation volume values for the binding of NO to complex 2 support a mechanism that is dominated by bond formation with concomitant iron spin change from S = (5)/(2) to S = 0, as proposed for the reaction between NO and E.S-P450(cam). In contrast, the dissociation of NO from 2(NO) was found to be several orders of magnitude faster than the corresponding reaction for the E.S-P450(cam)/NO system. In a coordinating solvent such as methanol, the alcohol coordinates to iron(III) of 2 at the distal position, generating a six-coordinate, high-spin species 5. The reaction of NO with 5 in methanol was found to be much slower in comparison to the nitrosylation reaction of 2 in toluene. This behavior can be explained in terms of a mechanism in which methanol must be displaced during Fe-NO bond formation. The thermodynamic and kinetic data for NO binding to the new model complexes of P450 (2 and 5) are discussed in reference to earlier results obtained for closely related nitrosylation reactions of cytochrome P450(cam) (in the presence and in the absence of the substrate) and a thiolate-ligated iron(III) model complex. 相似文献
532.
An efficient synthesis of 17-epi-calcitriol 2, an epimer of natural hormone, via 17-epi-cholesterol 5a is described. Synthesis of 5a includes palladium-catalyzed cyclopropanation of the common androstane derivative 7 with an alkyl diazoacetate, reductive fission of the less shielded side of cyclopropane carboxylic acid esters 6, oxidation of the products into acid 11a, and alkylation of ester 11b. Photolysis of 7,8-dedydro-17-epi-25-hydroxycholesterol 19b and consecutive thermal rearrangement gave a mixture of several products that was subjected to ozonolysis to provide, after chromatography, hydroxy ketone 3a. The silyl derivative 3b was coupled with the respective ring A building block. 相似文献
533.
We show that every (continuous) endomorphism of the complex space (s) has a proper closed invariant subspace which is either
of dimension one or of codimension one. We give also a related result for the real space (s).
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
534.
P. Żenczykowski 《Zeitschrift fur Physik C Particles and Fields》1980,5(4):319-323
The recently proposed mechanism of dynamical SU(3) symmetry breaking in linear baryons is applied to the α-γ sector after taking into account two types of α and γ trajectories. The observed splitting pattern of leading strange baryon trajectories is qualitatively explained. The implications of the scheme for ground state baryons are discussed. 相似文献
535.
R. Gebarowski P. Šeba K. Życzkowski J. Zakrzewski 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(3):399-409
Quantum scattering is studied in a system consisting of randomly distributed point scatterers in the strip. The model is continuous
yet exactly solvable. Varying the number of scatterers (the sample length) we investigate a transition between the ballistic
and the localized regimes. By considering the cylinder geometry and introducing the magnetic flux we are able to study time
reversal symmetry breaking in the system. Both macroscopic (conductance) and microscopic (eigenphases distribution, statistics
of S-matrix elements) characteristics of the system are examined.
Received: 28 January 1998 / Revised: 16 June 1998 / Accepted: 6 July 1998 相似文献
536.
537.
It is known that Goertzels algorithm is much less numerically accurate than the Fast Fourier Transform (FFT) (cf. [2]). In order to improve accuracy we propose modifications of both Goertzels and Horners algorithms based on the divide-and-conquer techniques. The proof of the numerical stability of these two modified algorithms is given. The numerical tests in Matlab demonstrate the computational advantages of the proposed modifications. The appendix contains the proof of numerical stability of Goertzels algorithm of polynomial evaluation.
AMS subject classification 65F35, 65G50 相似文献
538.
Z. Janas L. Batist J. Döring M. Gierlik R. Kirchner J. Kurcewicz H. Mahmud C. Mazzocchi A. Płochocki E. Roeckl K. Schmidt P. J. Woods J. Żylicz 《The European Physical Journal A - Hadrons and Nuclei》2005,23(3):401-408
The very neutron-deficient 117Ba nuclei were produced in 58Ni-induced reactions on a 63Cu target and selected for spectroscopic studies by using BaF+ molecules formed in the ion source of the GSI on-line mass separator. The -decay of 117Ba was investigated by means of the total absorption -ray spectrometer and a telescope for -delayed particle detection. In the analysis combining the -delayed -ray and proton data the energy window available for -delayed proton emission, the branching ratios for proton transitions to the 116Xe levels and the -feeding of the -ray and proton-emitting 117Cs states were determined. The -strength function for 117Ba derived from the measured -feeding distribution revealed the existence of a broad resonance structure at 117Cs excitation energy of about 4-5 MeV. The results of the -delayed proton studies and -strength measurements are confronted with theoretical predictions. 相似文献
539.
The elution of the anion exchanger from the membranes of ion-selective electrodes and its influence on the electrode characteristics are studied. The decrease of the exchanger concentration in the PVC membrane depends on the exchanger lipophilicity and the concentration of the counter ion in the external solution. On this basis it is possible to estimate the electrode life time and limit of detection.Dedicated to Professor W. Simon on the occasion of his 60th birthday 相似文献
540.
The equivalence of ergodicity and weak mixing for general infinitely divisible processes is proven. Using this result and [9], simple conditions for ergodicity of infinitely divisible processes are derived. The notion of codifference for infinitely divisible processes is investigated, it plays the crucial role in the proofs but it may be also of independent interest. 相似文献