3,606 research outputs found
Ionization behavior of the histidine residue in the catalytic triad of serine proteases
α-Lytic protease is a homologue of the mammalian serine proteases such as trypsin, chymotrypsin, and elastase, and its single histidine residue belongs to the Asp-His-Ser catalytic triad. This single histidine residue has been selectively enriched in the C-2 carbon with 13C. Magnetic resonance studies of the chemical shift and coupling constant (1Jch) behavior of this nucleus as a function of pH suggest that the imidazole ring is neutral above pH 5 and therefore that the group which is known to ionize with pKa near 6.7 must be the aspartic acid residue.
Implications of these new pKa assignments for the catalytic mechanism of serine proteases are discussed and include the absence of any need to separate charge during catalysis. The histidine residue plays two roles. (a) It insulates the aspartic acid from an aqueous environment and accordingly raises its pKa. (b) It serves as a bidentate base to accept a proton from the serine at one of its nitrogens and concertedly transfer a proton from its other nitrogen to the buried carboxylate anion during formation of the tetrahedral intermediate
Application of digital control to a magnetic model suspension and balance model
The feasibility of using a digital computer for performing the automatic control functions for a magnetic suspension and balance system (MSBS) for use with wind tunnel models was investigated. Modeling was done using both a prototype MSBS and a one dimensional magnetic balance. A microcomputer using the Intel 8080 microprocessor is described and results are given using this microprocessor to control the one dimensional balance. Hybrid simulations for one degree of freedom of the MSBS were also performed and are reported. It is concluded that use of a digital computer to control the MSBS is eminently feasible and should extend both the accuracy and utility of the system
Apollo experiment S-217 IR/radar study of Apollo data
An experiment using Earth based remote sensing radar, infrared eclipse, and color difference data to deduce surface properties not visible in Apollo photography is reported. The Earth based data provided information on the small scale (centimeter sized) blockiness and on the surface chemical composition (titanium and iron contents) of the lunar surface. These deduced surface properties complemented the new Apollo photography, leading to refined geologic interpretations of the lunar surface
Digital logic optimization using selection operators
According to the invention, a digital design method for manipulating a digital circuit netlist is disclosed. In one step, a first netlist is loaded. The first netlist is comprised of first basic cells that are comprised of first kernel cells. The first netlist is manipulated to create a second netlist. The second netlist is comprised of second basic cells that are comprised of second kernel cells. A percentage of the first and second kernel cells are selection circuits. There is less chip area consumed in the second basic cells than in the first basic cells. The second netlist is stored. In various embodiments, the percentage could be 2% or more, 5% or more, 10% or more, 20% or more, 30% or more, or 40% or more
Digital circuits using universal logic gates
According to the invention, a digital circuit design embodied in at least one of a structural netlist, a behavioral netlist, a hardware description language netlist, a full-custom ASIC, a semi-custom ASIC, an IP core, an integrated circuit, a hybrid of chips, one or more masks, a FPGA, and a circuit card assembly is disclosed. The digital circuit design includes first and second sub-circuits. The first sub-circuits comprise a first percentage of the digital circuit design and the second sub-circuits comprise a second percentage of the digital circuit design. Each of the second sub-circuits is substantially comprised of one or more kernel circuits. The kernel circuits are comprised of selection circuits. The second percentage is at least 5%. In various embodiments, the second percentage could be at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 95%
Emergence of classicality in small number entangled systems
We show the transition from a fully quantized interaction to a semiclassical
one in entangled small number quantum systems using the quantum trajectories
approach. In particular, we simulate the microwave Ramsey zones used in Rydberg
atom interferometry, filling in the gap between the strongly entangling Jaynes
Cummings evolution and the semiclassical rotation of the atomic internal
states. We also correlate the information flowing with leaking photons to the
entanglement generation between cavity field and flying atom and detail the
roles played by the strong dissipation and the external driving force in
preserving atomic coherence through the interaction.Comment: 4 pages, 6 figure
Analyzing Powers and Spin Correlation Coefficients for p+d Elastic Scattering at 135 and 200 MeV
The proton and deuteron analyzing powers and 10 of the possible 12 spin
correlation coefficients have been measured for p+d elastic scattering at
proton bombarding energies of 135 and 200 MeV. The results are compared with
Faddeev calculations using two different NN potentials. The qualitative
features of the extensive data set on the spin dependence in p+d elastic
scattering over a wide range of angles presented here are remarkably well
explained by two-nucleon force predictions without inclusion of a three-nucleon
force. The remaining discrepancies are, in general, not alleviated when
theoretical three-nucleon forces are included in the calculations.Comment: 43 pages, 12 figures, accepted for publication by Phys. Rev.
Early (Days 1–4) post-treatment serum hCG level changes predict single-dose methotrexate treatment success in tubal ectopic pregnancy
Acknowledgements S.C.M. was supported by the South-East Scotland Academic Foundation Programme. Medical Research Council (MRC) Centre grants to the Centre for Reproductive Health (CRH) (G1002033 and MR/N022556/1) are also gratefully acknowledged. Funding This project was supported by funding from the Efficacy and Mechanism Evaluation programme, a Medical Research Council and National Institute for Health Research partnership (grant reference number 14/150/03).Peer reviewedPublisher PD
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