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51.
Mishanina TV Koehn EM Conrad JA Palfey BA Lesley SA Kohen A 《Journal of the American Chemical Society》2012,134(9):4442-4448
Thymidylate is a DNA nucleotide that is essential to all organisms and is synthesized by the enzyme thymidylate synthase (TSase). Several human pathogens rely on an alternative flavin-dependent thymidylate synthase (FDTS), which differs from the human TSase both in structure and molecular mechanism. It has recently been shown that FDTS catalysis does not rely on an enzymatic nucleophile and that the proposed reaction intermediates are not covalently bound to the enzyme during catalysis, an important distinction from the human TSase. Here we report the chemical trapping, isolation, and identification of a derivative of such an intermediate in the FDTS-catalyzed reaction. The chemically modified reaction intermediate is consistent with currently proposed FDTS mechanisms that do not involve an enzymatic nucleophile, and it has never been observed during any other TSase reaction. These findings establish the timing of the methylene transfer during FDTS catalysis. The presented methodology provides an important experimental tool for further studies of FDTS, which may assist efforts directed toward the rational design of inhibitors as leads for future antibiotics. 相似文献
52.
Quantum equations for massless particles of any spin are considered in stationary uncharged axially symmetric spacetimes. It is demonstrated that up to a normalization function, the angular wave function does not depend on the metric and practically is the same as in the Minkowskian case. The radial wave functions satisfy second order nonhomogeneous differential equations with three nonhomogeneous terms, which depend in a unique way on time and space curvatures. In agreement with the principle of equivalence, these terms vanish locally, and the radial equations reduce to the same homogeneous equations as in Minkowski spacetime. 相似文献
53.
Amnon Besser 《Israel Journal of Mathematics》2006,151(1):53-59
We give a short proof of a formula of de Shalit, expressing the cup product of two vector-valued one-forms of the second kind
on a Mumford curve in terms of Coleman integrals and residues. The proof uses the notion of double indices on curves and their
reciprocity laws. 相似文献
54.
Amnon Rapoport 《International Journal of Game Theory》1997,26(1):113-136
“Can we find a pair of extensive form games that give rise to the same strategic form game such that, when played by a reasonable subject population, there is a statistically significant difference in how the games are played?” (Kreps, 1990, p. 112). And if yes, “can we organize these significant differences according to some principles that reflect recognizable differences in the extensive forms?” Both questions are answered positively by reporting results from three different experiments on public goods provision, resource dilemmas, and pure coordination games. 相似文献
55.
Amnon Yekutieli 《Proceedings of the American Mathematical Society》1996,124(12):3613-3618
Let be a scheme of finite type over a field . Denote by the sheaf of Beilinson adeles with values in the algebraic De Rham complex . Then is a flasque resolution. So if is smooth, calculates De Rham cohomology. In this note we rewrite the proof of Deligne-Illusie for the degeneration of the Hodge spectral sequence in terms of adeles. We also give a counterexample to show that the filtration does not induce Hodge decomposition.
56.
Joan Adler Yigal Meir Amnon Aharony A. B. Harris Lior Klein 《Journal of statistical physics》1990,58(3-4):511-538
We discuss recent work on the development and analysis of low-concentration series. For many models, the recent breakthrough in the extremely efficient no- free-end method of series generation facilitates the derivation of 15th-order series for multiple moments in general dimension. The 15th-order series have been obtained for lattice animals, percolation, and the Edwards-Anderson Ising spin glass. In the latter cases multiple moments have been found. From complete graph tables through to 13th order, general dimension 13th-order series have been derived for the resistive susceptibility, the moments of the logarithms of the distribution of currents in resistor networks, and the average transmission coefficient in the quantum percolation problem, 11th-order series have been found for several other systems, including the crossover from animals to percolation, the full resistance distribution, nonlinear resistive susceptibility and current distribution in dilute resistor networks, diffusion on percolation clusters, the dilute Ising model, dilute antiferromagnet in a field, and random field Ising model and self-avoiding walks on percolation clusters. Series for the dilute spin-1/2 quantum Heisenberg ferromagnet are in the process of development. Analysis of these series gives estimates for critical thresholds, amplitude ratios, and critical exponents for all dimensions. Where comparisons are possible, our series results are in good agreement with both-expansion results near the upper critical dimension and with exact results (when available) in low dimensions, and are competitive with other numerical approaches in intermediate realistic dimensions. 相似文献
57.
A new furanoterpene designated dehydrofurodendin and nine scalarane sesterterpenes of which four are new, were isolated from two different species of Madagascan sponges of the genus Lendenfeldia, both of which seem to be yet undescribed. The structure of the compounds was elucidated by interpretation of 1D and 2D NMR data. Dehydrofurodendin was found to be a potent inhibitor of HIV-1 RT. Several of the isolated scalaranes exhibited cyctotoxicity against several human tumor cells. 相似文献
58.
J. D. Brock D. Y. Noh B. R. McClain J. D. Litster R. J. Birgeneau Amnon Aharony P. M. Horn Jason C. Liang 《Zeitschrift für Physik B Condensed Matter》1989,74(2):197-213
In this paper, we report results from synchrotron X-ray scattering studies of thefluid/hexactic/solid phases and phase transitions in both very thick and very thin, freely suspended films of tilted hexatic liquid crystals. Contrary to the thick film case, the higher Fourier coefficients describing the bond orientational order are suppressed in very thin films. This suppression is consistent with a two-dimensional bond orientational order parameter,
6, rather than the three-dimensional bond orientational order parameter found in very thick films. For a film containing twently-three (23) smectic layers we find that
6 is two-dimensional whereas the positional order in the crystallineS
J phase is three-dimensional. We present an analysis of the thick film data in terms of the three-dimensionalXY-model and a new mean field theory model which incorporates explicitly the quasi two-dimensional nature of bulk smectic phases. 相似文献
59.
Simaan S Marks V Gottlieb HE Stanger A Biali SE 《The Journal of organic chemistry》2003,68(2):637-640
Octakis(bromomethyl)naphthalene (4) adopts in the crystal a chiral conformation with a helical central naphthalene core and the bromomethyl groups disposed in an alternate up-down "in" arrangement. According to MM3 calculations, this conformation is less stable than the corresponding all alternated "out" form, while B3LYP/LANL2DZ calculations suggest the opposite stability order. The topomerization barrier (16.0 kcal mol(-1)) is ascribed to an enantiomerization process requiring 180 degrees rotation of all the bromomethyl groups and reversal of the helical sense of the naphthalene core. 相似文献
60.
Amnon Yekutieli 《Advances in Mathematics》2010,225(1):445-45
We introduce the notion of central extension of gerbes on a topological space X. We show that there are obstruction classes to lifting objects and isomorphisms in a central extension. We also discuss pronilpotent gerbes. These results are used in the paper [15] by A. Yekutieli to study twisted deformation quantization on algebraic varieties. 相似文献