798 research outputs found
ESR of spin-labeled bacteriophage M13 coat protein in mixed phospholipid bilayers.
Bacteriophage M13 major coat protein was spin-labeled with a nitroxide derivative of iodoacetamide, preferentially at the single methionine that is located in the hydrophobic region of the protein. The spin-labeled protein was incorporated at different lipid-to-protein ratios in phospholipid bilayers composed of dimyristoylphosphatidylglycerol (DMPG), dimyristoylphosphatidylcholine (DMPC), or the 1:1 molar mixture of these lipids. Both conventional and saturation transfer (ST) ESR studies were performed to investigate the rotational motions of the protein over a large dynamic range. The conventional ESR spectra indicate that the mobility of the spin labelled protein in the lipid gel phase decreases in the order: DMPG > DMPC/DMPG (1:1) > DMPC. In the liquid crystalline phase, the largest mobility is found in DMPC/DMPG (1:1, mol/mol) mixtures, but the mobility is still greater in DMPG than in DMPC. The results are interpreted in terms of different degrees of protein aggregation in the different lipids. Segmental motion with rotational correlation times on the order of tens of nanoseconds, motional anisotropy, and spectral overlap complicate the analysis of the STESR spectra. An estimate of the size of the protein aggregates is found to be in the region of 85 monomer units. Removing the polar tails from the protein by proteolytic digestion results in an enhanced aggregation in the gel phase. In the liquid crystalline phase, the segmental wobbling mobility of the protein is increased relative to the native protein, whereas the overall rotational diffusion is not changed greatly
Using the Fermilab Proton Source for a Muon to Electron Conversion Experiment
The Fermilab proton source is capable of providing 8 GeV protons for both the
future long-baseline neutrino program (NuMI), and for a new program of low
energy muon experiments. In particular, if the 8 GeV protons are rebunched and
then slowly extracted into an external beamline, the resulting proton beam
would be suitable for a muon-to-electron conversion experiment designed to
improve on the existing sensitivity by three orders of magnitude. We describe a
scheme for the required beam manipulations. The scheme uses the Accumulator for
momentum stacking, and the Debuncher for bunching and slow extraction. This
would permit simultaneous operation of the muon program with the future NuMI
program, delivering 10^20 protons per year at 8 GeV for the muon program at the
cost of a modest (~10%) reduction in the protons available to the neutrino
program.Comment: 18 pages, 7 figure
Clinical pearls for the monitoring and treatment of antipsychotic induced metabolic syndrome
Antipsychotic medications increase the risk of metabolic syndrome, which then increases the risk of atherosclerotic cardiovascular disease and premature death. Routinely monitoring for signs of metabolic syndrome in patients taking antipsychotics allows for early detection and intervention. Psychiatric pharmacists can improve patient care through metabolic syndrome monitoring and recommendation of appropriate interventions. Monitoring for the metabolic adverse effects of antipsychotics, management of weight gain, and management of lipids and blood pressure are explored through 2 patient cases
Anisotropic spin freezing in the S=1/2 zigzag ladder compound SrCuO2
Using magnetic neutron scattering we characterize an unusual low temperature
phase in orthorhombic SrCuO2. The material contains zigzag spin ladders formed
by pairs of S=1/2 chains (J=180 meV) coupled through a weak frustrated
interaction |J'|<0.1J. At T<Tc1=5.0(4)K an elastic peak develops in a gapless
magnetic excitation spectrum indicating spin freezing on a time scale larger
than 200 picoseconds. While the frozen state has long range commensurate
antiferromagnetic order along the chains with the correlation length exceeding
200 lattice periods along the c-axis and a substantial correlation length of
60(25) spacings along the a-axis perpendicular to the zigzag plane, only 2
lattice units are correlated along the b-axis which is the direction of the
frustrated interactions. The frozen magnetic moment of each Cu ion is very
small, 0.033(7) Bohr magneton even at T=0.35K, and has unusual temperature
dependence with a cusp at Tc2=1.5K reminiscent of a phase transition. We argue
that slow dynamics of stripe-like cooperative magnetic defects in tetragonal
a-c planes yield this anisotropic frozen state.Comment: 4 pages, LaTeX, submitted to PR
Analysis of the low-energy electron-recoil spectrum of the CDMS experiment
We report on the analysis of the low-energy electron-recoil spectrum from the
CDMS II experiment using data with an exposure of 443.2 kg-days. The analysis
provides details on the observed counting rate and possible background sources
in the energy range of 2 - 8.5 keV. We find no significant excess in the
counting rate above background, and compare this observation to the recent DAMA
results. In the framework of a conversion of a dark matter particle into
electromagnetic energy, our 90% confidence level upper limit of 0.246
events/kg/day at 3.15 keV is lower than the total rate above background
observed by DAMA by 8.9. In absence of any specific particle physics
model to provide the scaling in cross section between NaI and Ge, we assume a
Z^2 scaling. With this assumption the observed rate in DAMA differs from the
upper limit in CDMS by 6.8. Under the conservative assumption that the
modulation amplitude is 6% of the total rate we obtain upper limits on the
modulation amplitude a factor of ~2 less than observed by DAMA, constraining
some possible interpretations of this modulation.Comment: 4 pages, 3 figure
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