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121.
Communicated by 相似文献
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Communicated by 相似文献
123.
J Wen S W Nelson R B Honzatko H J Fromm J W Petrich 《Photochemistry and photobiology》2001,74(5):679-685
The environment of Trp57, introduced by the mutation of a tyrosine in the dynamic loop of porcine liver fructose-1,6-bisphosphatase (FBPase), was examined using time-resolved fluorescence and directed mutation. The Trp57 enzyme was studied previously by X-ray crystallography and steady-state fluorescence, the latter revealing an unexpected redshift in the wavelength of maximum fluorescence emission for the R-state conformer. The redshift was attributed to the negative charge of Asp127 in contact with the indole side chain of Trp57. Time-resolved fluorescence experiments here reveal an indole side chain less solvent exposed and more rigid in the R-state, than in the T-state of the enzyme, consistent with X-ray crystal structures. Replacement of Asp127 with an asparagine causes a 6 nm blueshift in the wavelength of maximum fluorescence emission for the R-state conformer, with little effect on the emission maximum of the T-state enzyme. The data here support the direct correspondence between X-ray crystal structures of FBPase and conformational states of the enzyme in solution, and provide a clear example of the influence of microenvironment on the fluorescence properties of tryptophan. 相似文献
124.
T. Kühl S. Borneis G. Greten D. Marx R. Neumann S. Schröder R. Grieser I. Hoog G. Huber I. Klaft R. Klein P. Merz V. Balykin M. Bock C. Ellert P. Forck M. Grieser R. Grimm D. Habs H. J. Miesner W. Petrich B. Wanner C. Becker D. Schwalm A. Wolf 《Hyperfine Interactions》1992,74(1-4):277-285
At the TSR cooler ring at Heidelberg, laser studies were carried out using singly charged lithium and beryllium ions. Laser
spectroscopy of relativistic lithium ions (v=0.04c) yielded signals with a narrow linewidth, suitable for an experimental
test of special relativity. A dramatic reduction of the beam temperature, as defined by the longitudinal velocity spread,
was achieved via laser cooling in both cases. At the ion energies available at ESR it will become possible to prepare and
store bare ions up to U92+. Electron cooling was succesfully demonstrated for hydrogen-like Bi82+ ions, where a laser experiment is scheduled to study the ground-state hyperfine splitting. 相似文献
125.
M. Petrich 《Acta Mathematica Hungarica》1969,20(1-2):111-120
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127.
A subgroup H of a regular semigroup S is said to be an associate subgroup of S if for every s ∈ S, there is a unique associate of s in H. An idempotent z of S is said to be medial if czc = c, for every c product of idempotents of S. Blyth and Martins established a structure theorem for semigroups with an associate subgroup whose identity is a medial idempotent, in terms of an idempotent generated semigroup, a group and a single homomorphism. Here, we construct a system of axioms which characterize these semigroups in terms of a unary operation satisfying those axioms. As a generalization of this class of semigroups, we characterize regular semigroups S having a subgroup which is a transversal of a congruence on S. 相似文献
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Mario Petrich 《Results in Mathematics》1990,18(1-2):153-177