29 research outputs found
A simulation study on the measurement of D0-D0bar mixing parameter y at BES-III
We established a method on measuring the \dzdzb mixing parameter for
BESIII experiment at the BEPCII collider. In this method, the doubly
tagged events, with one decays to
CP-eigenstates and the other decays semileptonically, are used to
reconstruct the signals. Since this analysis requires good separation,
a likelihood approach, which combines the , time of flight and the
electromagnetic shower detectors information, is used for particle
identification. We estimate the sensitivity of the measurement of to be
0.007 based on a fully simulated MC sample.Comment: 6 pages, 7 figure
Escherichia coli tRNA<sub>4</sub><sup>Arg</sup>(UCU) induces a constrained conformation of the crucial Ω-loop of arginyl-tRNA synthetase
Previous investigations show that tRNA(Arg)-induced conformational changes of arginyl-tRNA synthetase (ArgRS) Omega-loop region (Escherichia coli (E coli), Ala451-Ala457) may contribute to the productive conformation of the enzyme catalytic core, and E. coli tRNA(2)(Arg)(ICG)-bound and -free conformations of the Omega-loop exchange at an intermediate rate on NMR timescale. Herein, we report that E. coli ArgRS catalyzes tRNA(2)(Arg)(ICG) and tRNA(4)(Arg)(UCU) with similar efficiencies. However, F-19 NMR spectroscopy of 4-fluorotryptophan-labeled E. coli ArgRS reveals that the tRNA(4)(Arg)(UCU)-bound and -free conformations of the Omega-loop region interconvert very slowly and the lifetime of bound conformation is much longer than 0.33ms. Therefore, tRNA(4)(Arg) (UCU) differs from tRNA(2)(Arg)(ICG) in the conformation-exchanging rate of the Omega-loop. Comparative structure model of E. coli ArgRS is presented to rationalize these F-19 NMR data. Our F-19 NMR and catalytic assay results suggest that the tRNA(Arg)-induced conformational changes of Omega-loop little contribute to the productive conformation of ArgRS catalytic core. (C) 2003 Elsevier Inc. All rights reserved