9,084 research outputs found
Electroblotting onto activated glass. High efficiency preparation of proteins from analytical sodium dodecyl sulfate-polyacrylamide gels for direct sequence analysis
We have developed a new method for the isolation of proteins for microsequencing. It consists of electrophoretic transfer (electroblotting) of proteins or their cleavage fragments onto activated glass filter paper sheets immediately after separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The proteins are immobilized on the glass fiber sheets by ionic interactions or by covalent attachment. A wide range of proteins can be prepared in this fashion with no apparent restriction due to solubility, size, charge, or other intrinsic properties of the proteins. As little as 50 ng of the transferred proteins can be detected using Coomassie Blue or fluorescent dye staining procedures and even smaller amounts of radiolabeled proteins by autoradiography. After detection, the protein- containing bands or spots are cut out and inserted directly into a gas- phase sequenator. The piece of glass fiber sheet acts as a support for the protein during the sequencing. Amounts of protein in the 5- to 150- pmol range can be sequenced, and extended runs can be obtained from the blotted samples because of improved stepwise yields and lower backgrounds. The method has been successfully applied to the sequencing of a variety of proteins and peptides isolated from one-dimensional and two-dimensional polyacrylamide gels
The Mr 28,000 gap junction proteins from rat heart and liver are different but related
The sequence of the amino-terminal 32 residues of the rat heart Mr 28,000 gap junction protein presented here allows, for the first time, a sequence comparison of gap junctional proteins from different tissues (heart and liver). Comparison of the rat heart gap junction protein sequence and that available from rat liver reveals 43% sequence identity and conservative changes at an additional 25% of the positions. Both proteins exhibit a hydrophobic domain which could represent a transmembrane span of the junction. This result unequivocally demonstrates the existence of at least two forms of the gap junction protein. As yet, no homology is evident between the gap junctional proteins of either heart or liver and main intrinsic protein from rat eye lens
Temperature dependent nucleation and propagation of domain walls in a sub-100 nm perpendicularly magnetized Co/Ni multilayer
We present a study of the temperature dependence of the switching fields in
Co/Ni-based perpendicularly magnetized spin-valves. While magnetization
reversal of all-perpendicular Co/Ni spin valves at ambient temperatures is
typically marked by a single sharp step change in resistance, low temperature
measurements can reveal a series of resistance steps, consistent with
non-uniform magnetization configurations. We propose a model that consists of
domain nucleation, propagation and annihilation to explain the temperature
dependence of the switching fields. Interestingly, low temperature (<30 K) step
changes in resistance that we associate with domain nucleation, have a bimodal
switching field and resistance step distribution, attributable to two competing
nucleation pathways.Comment: 5 pages, 4 figure
Temperature dependence of the switching field distributions in all-perpendicular spin-valve nanopillars
We present temperature dependent switching measurements of the Co/Ni
multilayered free element of 75 nm diameter spin-valve nanopillars. Angular
dependent hysteresis measurements as well as switching field measurements taken
at low temperature are in agreement with a model of thermal activation over a
perpendicular anisotropy barrier. However, the statistics of switching (mean
switching field and switching variance) from 20 K up to 400 K are in
disagreement with a N\'{e}el-Brown model that assumes a temperature independent
barrier height and anisotropy field. We introduce a modified N\'{e}el-Brown
model thats fit the experimental data in which we take a dependence
to the barrier height and the anisotropy field due to the temperature dependent
magnetization and anisotropy energy.Comment: 5 pages, 4 figure
Olanzapine Attenuates Cue-elicited Craving for Tobacco
Rationale: Recent biological conceptualizations of craving and addiction have implicated mesolimbic dopamine activity as a central feature of the process of addiction. Imaging, and pharmacological studies have supported a role for dopaminergic structures in cue-elicited craving for tobacco.
Objective: If mesolimbic dopamine activity is associated with cue-elicited craving for tobacco, a dopamine antagonist should attenuate cueelicited craving for tobacco. Thus, the aim of the present study was to determine whether an atypical antipsychotic (olanzapine, 5 mg) decreased cue-elicited craving for tobacco.
Method: Participants were randomly assigned to 5 days of pretreatment with olanzapine (5 mg; n=31) or were randomly assigned to 5 days of a matching placebo (n=28). Approximately 8 h after the last dose, participants were exposed to a control cue (pencil) followed by exposure to smoking cues. Participants subsequently smoked either nicotine cigarettes or de-nicotinized cigarettes.
Results: Olanzapine attenuated cue-elicited craving for tobacco but did not moderate the subjective effects of smoking.
Discussion: This study represents one of the first investigations of the effect of atypical antipsychotics on cue-elicited craving for tobacco. The results suggest that medications with similar profiles may reduce cue-elicited craving, which in turn, may partially explain recent observations that atypical antipsychotics may reduce substance use
Bimodal switching field distributions in all-perpendicular spin-valve nanopillars
Switching field measurements of the free layer element of 75 nm diameter
spin-valve nanopillars reveal a bimodal distribution of switching fields at low
temperatures (below 100 K). This result is inconsistent with a model of thermal
activation over a single perpendicular anisotropy barrier. The correlation
between antiparallel to parallel and parallel to antiparallel switching fields
increases to nearly 50% at low temperatures. This reflects random fluctuation
of the shift of the free layer hysteresis loop between two different
magnitudes, which may originate from changes in the dipole field from the
polarizing layer. The magnitude of the loop shift changes by 25% and is
correlated to transitions of the spin-valve into an antiparallel configuration.Comment: 3 pages, 4 figures. Submitted to JAP for 58th MMM Proceeding
Accurate Discretization Of Poroelasticity Without Darcy Stability -- Stokes-Biot Stability Revisited
In this manuscript we focus on the question: what is the correct notion of
Stokes-Biot stability? Stokes-Biot stable discretizations have been introduced,
independently by several authors, as a means of discretizing Biot's equations
of poroelasticity; such schemes retain their stability and convergence
properties, with respect to appropriately defined norms, in the context of a
vanishing storage coefficient and a vanishing hydraulic conductivity. The basic
premise of a Stokes-Biot stable discretization is: one part Stokes stability
and one part mixed Darcy stability. In this manuscript we remark on the
observation that the latter condition can be generalized to a wider class of
discrete spaces. In particular: a parameter-uniform inf-sup condition for a
mixed Darcy sub-problem is not strictly necessary to retain the practical
advantages currently enjoyed by the class of Stokes-Biot stable Euler-Galerkin
discretization schemes.Comment: 25 page
Unstable and Stable Classifications of Scombroid Fishes
Many cladists believe that a classification should strictly reflect a cladistic hypothesis. Consequently, they propose classifications that often differ markedly from existing ones and are potentially unstable due to phylogenetic uncertainty. This is problematic for economically or ecologically important organisms since changing classifications can cause confusion in their management as resources. The classification of the 44 genera of scombroid fishes (the mackerels, tunas, billfishes, and their relatives) illustrates this problem of instability. Previous cladistic analyses and analyses presented in this paper, using different data sets, result in many different cladistic hypotheses. In addition, the inferred cladograms are unstable because of different plausible interpretations of character coding. A slight change in coding of a single character, the presence of splint-like gill rakers, changes cladistic relationships substantially. These many alternative cladistic hypotheses for scombroids can be converted into various cladistic classifications, all of which are substantially different from the classification currently in use. In contrast, a quantitative evolutionary systematic method produces a classification that is unchanged despite variations in the cladistic hypothesis. The evolutionary classification has the advantage of being consistent with the classification currently in use, it summarizes anagenetic information, and it can be considered a new form of cladistic classification since a cladistic hypothesis can-be unequivocally retrieved from an annotated form of the classification
- …