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201.
202.
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
203.
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
204.
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
205.
Various secondary and tertiary instabilities in plane channel flow are explored via time-dependent numerical simulations using the incompressible Navier-Stokes equations. Comparisons are made between transitional flows at Reynolds numbers 1500, 5000, and 8000. The lambda vortex, detached shear layer, and inverted vortex regions are identified and the origin of the latter is explained. The laminar breakdown of the Re=1500 flow is computed with high resolution and the nature of its ensuing hairpin eddies is clarified by numerical particle paths. The potential of center-mode rather than wall-mode transitions is proposed and the resulting flow structure is described. 相似文献
206.
The complex velocity field of an oscillating Couette flow is measured with a Laser-Doppler velocimeter. Different evaluation methods are used for the determination of material functions such as relaxation times and the dynamic complex viscosity. 相似文献
207.
208.
The antioxidant activity of a novel artificial glutathione peroxidase-like enzyme, selenium-containing glutathione 5-transferase
from Lucilia cuprina (seleno-LuGST1-1), was studied by using a ferrous sulfate/ascorbate-induced mitochondrial damage model system. Swelling of
mitochondria, lipid peroxidation, and cytochrome-c oxidase activity were selected to evaluate the preservation of mitochondrial integrity in this system. Seleno-LuGST1-1 could
effectively protect the mitochondria against oxidative damage in a dose-dependent manner and exhibited both higher catalytic
activity and greater antioxidant ability than the classic mimic, 2-phenyl-1,2-benziososelenazol-3(2H)-one (Ebselen). This
novel artificial biocatalyst therefore may have great protential for pharmacologic application in the treatment of reactive
oxygen species-related diseases. 相似文献
209.
D. Y. Zang E. Rio D. Langevin B. Wei B. P. Binks 《The European physical journal. E, Soft matter》2010,31(2):125-134
We have investigated the rheological behaviour of silica nanoparticle layers at the air-water interface. Both compressed and
deposited layers have been studied in Langmuir troughs and with a bicone rheometer. The compressed layers are more homogeneous
and rigid, and the elastic response to continuous, step and oscillatory compression are similar, provided the compression
is fast enough and relaxation is prevented. The deposited layers are less rigid and more viscoelastic. Their shear moduli
deduced from the oscillatory uniaxial compression are much smaller than those deduced from pure shear deformation suggesting
that the effective shear rate is smaller than expected in the compression measurements. 相似文献
210.
Qinmin Guo Zhihui Qin Cunding Liu Kan Zang Yinghui Yu Gengyu Cao 《Surface science》2010,604(19-20):1820-1824
Bias-dependent features of the insulating NaCl layer grown on Cu(001) have been investigated by scanning tunneling microscopy/spectroscopy (STM/STS). The apparent layer thickness of the NaCl film is variable at bias voltages ranging from 2.8 to 3.2 V as well as from 4.0 to 5.0 V, and the Moiré pattern induced by NaCl–Cu lattice mismatch also shows bias dependence. The z–V (dz/dV–V) curves and dI/dV mapping measurements reveal that the resonant tunneling between the image potential states (IPSs) on Cu(001) and the Fermi level of the STM tip leads to drastic variations of these features. 相似文献