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121.
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125.
Triplet state sublevel spectroscopy using optical detection of magnetic resonance (ODMR) in zero magnetic field can be successfully
employed to study (i) the environment of tryptophan (Trp) residues in a protein by observing the position and structure of
phosphorescence spectra, zero field ODMR transitions and triplet state sublevel kinetics, (ii) the energy transfer among Trp
residues, and (iii) whether any cysteine (Cys) residue is within van der Waals distance of any Trp residue by studying the
complex of the protein with methylmercury(II) iodide (CH3HgI) which binds to Cys residues. These studies are particularly important where crystal structure study is not possible.
Study of the S1 state often gives ambiguous results since fluorescence is always broad and shows multi-exponential decay. Our results on
bacteriophage lysozyme T4 which contains three Trp residues at positions 126, 138 and 158 are presented. Measurements were
facilitated by the use of a mutated enzyme containing one or two Trp-Tyr substitutions. The results indicate that (i) Trp
126 and 158 are solvent exposed, whereas Trp 138 is buried in a hydrophobic environment, (ii)S ↔S non-radiative energy transfer takes place predominantly from Trp 126 to Trp 158, and (iii) only Trp-158 undergoes a heavy
atom perturbation, which affects selectively the z-sublevel (z is an out-of-plane axis of the indole plane) as a result of
CH3HgI binding to nearby Cys 97. We suggest that the Hg atom is located on the z-axis of Trp 158 in the complex. This interpretation
is based on our investigations on the effect of orientation of heavy atom perturbers in some naphthalene-crown ether metal
ion complexes. 相似文献
126.
We provide a nonexistence theorem of harmonic morphisms between hyperbolic spaces which are proper and C
2-smooth to the boundary. 相似文献
127.
The slanted low electrode matrix is designed and fabricated on one tilting 4.5° (1 1 1) silicon wafer to reduce the actuating voltage of 8×8 micro-electromechanical systems (MEMS) optical switch matrix. Due to compact size of the upper electrode chip and (1 1 1) silicon anisotropic etching in KOH solution, photomask is designed which is to fabricate the slanted low electrode matrix that can be matched with the upper electrode chip and every slanted low electrode has enough space for actuating cantilever. The experimental results show that all of the applied voltages for the full range of actuating micromirrors of 8×8 MEMS optical switch matrix are in the range of 67.2±0.5 V. It is demonstrated that the fabricated slanted low electrode matrix has good consistency and every slanted low electrode can be precisely aligned with one-to-one corresponding upper electrodes. 相似文献
128.
Study of transient photoconductivity of GaN epilayer grown by metalorganic chemical vapor deposition 总被引:1,自引:0,他引:1
Z.Z. Chen B. Shen X.Y. Zhang R. Zhang P. Chen Y.G. Zhou L. Zang R.L. Jiang Z.C. Huang Y.D. Zheng Z.S. Wu X.T. Sun F. Chen 《Applied Physics A: Materials Science & Processing》1998,67(5):567-570
Received: 24 March 1998/Accepted: 10 July 1998 相似文献
129.
Israel Zang 《Mathematical Programming》1978,15(1):36-52
The gradient path of a real valued differentiable function is given by the solution of a system of differential equations. For a quadratic function the above equations are linear, resulting in a closed form solution. A quasi-Newton type algorithm for minimizing ann-dimensional differentiable function is presented. Each stage of the algorithm consists of a search along an arc corresponding to some local quadratic approximation of the function being minimized. The algorithm uses a matrix approximating the Hessian in order to represent the arc. This matrix is updated each stage and is stored in its Cholesky product form. This simplifies the representation of the arc and the updating process. Quadratic termination properties of the algorithm are discussed as well as its global convergence for a general continuously differentiable function. Numerical experiments indicating the efficiency of the algorithm are presented. 相似文献
130.
119Sn Mossbauer spectra for surface layers of thin film Sb doped SnO were obtained by CEMS method, the emissive internal conversion
electrons were detected by multi-wire chamber. In practice the gas-sensing response of these films for H2, CO depended on Sb concentration of doping (X%) and the annealling processes. It was found that the CEMS parameters of samples-(IS),
(QS) and its distribution (HW), reach minima when x=1%, just in agreement with the gas-sensing responsive sensitivity reaching
maximum. And then it is helpful for the study of the gas-sensitive mechanism. 相似文献