The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
J. Zeman - One of the best experts on this subject based on the ideXlab platform.
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Discrete states of conduction electrons bound to magnetoAcceptors in quantum wells
Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2003Co-Authors: S. Bonifacie, Andre Raymond, Ym Meziani, Sandrine Juillaguet, Christophe Chaubet, W. Zawadzki, V. Thierry-mieg, J. ZemanAbstract:Discrete states of conduction electrons bound to ionized Acceptors are observed in intraband magneto-optical experiments on Be-doped GaAs/Ga0.67Al0.33As quantum wells. The electrons are bound to Acceptors by a joint effect of the quantum well and an external magnetic field. The observed transition energies are successfully described using states of single magnetoAcceptors. The energies show evidence for oscillatory screening of Acceptor potentials. Also, two disorder modes of the cyclotron resonance related to Acceptor potential fluctuations are observed at higher filling factors.
Alice Telesnitsky - One of the best experts on this subject based on the ideXlab platform.
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Effects of Identity Minimization on Moloney Murine Leukemia Virus Template Recognition and Frequent Tertiary Template-Directed Insertions during Nonhomologous Recombination
Journal of Virology, 2007Co-Authors: Nisha K. Duggal, Steven R. King, Alice TelesnitskyAbstract:Homology requirements for Moloney murine leukemia virus recombination were addressed in this study by monitoring titer defects observed when Acceptor/donor template identity lengths were systematically reduced. Recombination Acceptors with at least 16 contiguous bases of donor template identity were recognized as efficiently as longer Acceptors. In contrast, a sharp 1-log titer drop was observed for an Acceptor of only 15 bases long, with an additional 1-log titer decline for an 8-base Acceptor and further decreases for shorter Acceptors. Eighty-three independent nonhomologous recombination products were sequenced to examine recombination template selection in the absence of significant sequence identity. These replication products contained a total of 152 nonhomologous crossover junctions. Forced copy choice models predict that forced nonhomologous recombination should result in DNA synthesis to the donor template9s 5′ end, followed by microidentity-guided Acceptor template selection. However, only a single product displayed this structure. The majority of examined nonhomologous recombination products contained junction-associated sequence insertions. Most insertions resulted from the use of one or more tertiary templates, recognizable as discontiguous portions of viral or host RNA or minus-strand DNA. The donor/Acceptor template microidentity evident at most crossovers reconfirmed the remarkable capability of the reverse transcription machinery to recognize short regions of sequence identity. These results demonstrate that recruitment of discontiguous host or viral sequences is a common way for retroviruses to resolve nonhomologous recombination junctions and provide experimental support for the role of splinting templates in the generation of retroviral insertions.
M. Gavand - One of the best experts on this subject based on the ideXlab platform.
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Hydrogen diffusion and Acceptor passivation in p‐type GaAs
Journal of Applied Physics, 1993Co-Authors: R. Rahbi, Jacques Chevallier, B. Pajot, A. Marbeuf, R. C. Logan, M. GavandAbstract:Deuterium diffusion profiles in GaAs doped with different Acceptors of group II (Mg,Zn,Cd) or group IV (C,Ge) have similar characteristics even though the neutralization of Acceptors measured at 300 K is not always efficient. Conductivity and Hall measurements have been used to study the electrical characteristics of hydrogenated p‐type GaAs epilayers. The temperature dependence of the free‐carrier concentration and hole mobility before and after hydrogenation shows that the neutralization of Acceptors by atomic hydrogen leads to the elimination of the shallow Acceptor states. Infrared‐absorption lines associated with hydrogen‐Acceptor complexes are observed for all Acceptors except magnesium. It is established that the microscopic structure of hydrogen‐Acceptor complexes depends on the Acceptor site in the lattice.
Chung S. Yang - One of the best experts on this subject based on the ideXlab platform.
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Subunit functional studies of NAD(P)H:quinone oxidoreductase with a heterodimer approach
Proceedings of the National Academy of Sciences of the United States of America, 1995Co-Authors: Anthony Y. H. Lu, Chung S. YangAbstract:NAD(P)H:quinone oxidoreductase (NQOR; EC 1.6.99.2) is a homodimeric enzyme which catalyzes the reduction of quinones, azo dyes, and other electron Acceptors by NADPH or NADH. To pursue subunit functional studies, we expressed a wild-type/mutant heterodimer of NQOR in Escherichia coli. The wild-type subunit of the heterodimer was tagged with polyhistidine and the other subunit contained a His-194-->Ala mutation (H194A), a change known to dramatically increase the Km for NADPH. This approach enabled us to efficiently purify the heterodimer (H194A/HNQOR) from the homodimers by stepwise elution with imidazole from a nickel nitrilotriacetate column under nondenaturing conditions. The composition of the purified heterodimer was confirmed by SDS and nondenaturing polyacrylamide gel electrophoresis and immunoblot analysis. The enzyme kinetics of the purified heterodimer were studied with two two-electron Acceptors, 2,6-dichloroindophenol and menadione, and a four-electron Acceptor, methyl red, as the substrates. With two-electron Acceptors, the Km(NADPH) and Km(NADH) values of the heterodimer H194A/HNQOR were virtually identical to those of the wild-type homodimer, but the kcat-(NADPH) and kcat(NADH) values were only about 50% those of the wild-type homodimer. With the four-electron Acceptor, the Km and kcat values of H194A/HNQOR for NADPH and NADH were similar to those of the low-efficiency mutant homodimer. These results suggest that the subunits of NQOR function independently with two-electron Acceptors, but dependently with a four-electron Acceptor. This heterodimer approach may have general applications for studying the functional and structural relationships of subunits in dimeric or oligomeric proteins.
Yilmaz Aksu - One of the best experts on this subject based on the ideXlab platform.
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Lithium related deep and shallow Acceptors in Li-doped ZnO nanocrystals
Journal of Applied Physics, 2010Co-Authors: Christian Rauch, Wolfgang Gehlhoff, Markus R. Wagner, Enno Malguth, Gordon Callsen, Ronny Kirste, B. Salameh, Axel Hoffmann, Sebastian Polarz, Yilmaz AksuAbstract:We study the existence of Li-related shallow and deep Acceptor levels in Li-doped ZnO nanocrystals using electron paramagnetic resonance (EPR) and photoluminescence (PL) spectroscopy. ZnO nanocrystals with adjustable Li concentrations between 0% and 12% have been prepared using organometallic precursors and show a significant lowering of the Fermi energy upon doping. The deep Li Acceptor with an Acceptor energy of 800 meV could be identified in both EPR and PL measurements and is responsible for the yellow luminescence at 2.2 eV. Additionally, a shallow Acceptor state at 150 meV above the valence band maximum is made responsible for the observed donor-Acceptor pair and free electron-Acceptor transitions at 3.235 and 3.301 eV, possibly stemming from the formation of Li-related defect complexes acting as Acceptors.
