14,364 research outputs found
Cooperative Gating and Spatial Organization of Membrane Proteins through Elastic Interactions
Biological membranes are elastic media in which the presence of a
transmembrane protein leads to local bilayer deformation. The energetics of
deformation allow two membrane proteins in close proximity to influence each
other's equilibrium conformation via their local deformations, and spatially
organize the proteins based on their geometry. We use the mechanosensitive
channel of large conductance (MscL) as a case study to examine the implications
of bilayer-mediated elastic interactions on protein conformational statistics
and clustering. The deformations around MscL cost energy on the order of 10 kT
and extend ~3nm from the protein edge, as such elastic forces induce
cooperative gating and we propose experiments to measure these effects.
Additionally, since elastic interactions are coupled to protein conformation,
we find that conformational changes can severely alter the average separation
between two proteins. This has important implications for how conformational
changes organize membrane proteins into functional groups within membranes.Comment: 12 pages, 6 figures, 63 references, submitted to PLoS Computational
Biolog
Conformal cosmology with a positive effective gravitational constant
The conformal cosmological model presented by Mannheim predicts a negative
value for the effective gravitational constant, G. It also involves a scalar
field, S, which is treated classically. In this paper we point out that a
classical treatment of S is inappropriate, because the Hamiltonian is
non-Hermitean, and the theory must be developed in the way pioneered by Bender
and others. When this is done, we arrive at a Hamiltonian with an energy
spectrum that is bounded below, and also a G that is positive. The resulting
theory closely resembles the conventional cosmology based on Einstein
relativity
Specialist alcohol inpatient treatment admissions and non-specialist hospital admissions for alcohol withdrawal in England: an inverse relationship
© The Author(s) 2020. Medical Council on Alcohol and Oxford University Press. AIMS: We assessed the relationship between specialist and non-specialist admissions for alcohol withdrawal since the introduction of the UK government Health and Social Care Act in 2012. METHODS: Using publicly available national data sets from 2009 to 2019, we compared the number of alcohol withdrawal admissions and estimated costs in specialist and non-specialist treatment settings. RESULTS: A significant negative correlation providing strong evidence of an association was observed between the fall in specialist and rise in non-specialist admissions. Significant cost reductions within specialist services were displaced to non-specialist settings. CONCLUSIONS: The shift in demand from specialist to non-specialist alcohol admissions due to policy changes in England should be reversed by specialist workforce investment to improve outcomes. In the meantime, non-specialist services and staff must be resourced and equipped to meet the complex needs of these service users
Weight bias 2.0: the effect of perceived weight change on performance evaluation and the moderating role of anti-fat bias
Overweight employees are viewed as lazy, slow, inactive, and even incapable. Even if such attributes are false, this perspective can seriously undermine others' evaluation of their work performance. The current study explores a broader phenomenon of weight bias that has an effect on weight change. In a longitudinal study with a time lag of 6 months, we surveyed 226 supervisor-employee dyads. We found supervisor perceptions of employee weight change notably altered their evaluation of the employee performance from Time 1, especially following low vs. high Time-1 performance evaluation. Meanwhile, the moderating effects among different levels of supervisor anti-fat bias functioned as boundary conditions for such performance evaluation alteration. In particular, the interaction between the Time-1 performance evaluation and the impact of supervisor perception of employee weight change on the Time-2 performance evaluation was significant only if supervisors held a stronger anti-fat bias
Thermodynamics of an Exactly Solvable Model for Superconductivity in a Doped Mott Insulator
Computing superconducting properties starting from an exactly solvable model
for a doped Mott insulator stands as a grand challenge. We have recently shown
that this can be done starting from the Hatsugai-Kohmoto (HK) model which can
be understood generally as the minimal model that breaks the non-local symmetry of a Fermi liquid, thereby constituting a new quartic fixed point
for Mott physics [Phillips et al., Nature Physics 16, 1175 (2020); Huang et
al., Nature Physics (2022)]. In the current work, we compute the
thermodynamics, condensation energy, and electronic properties such as the NMR
relaxation rate and ultrasonic attenuation rate. Key differences arise
with the standard BCS analysis from a Fermi liquid: 1) the free energy exhibits
a local minimum at where the pairing gap turns on discontinuously above a
critical value of the repulsive HK interaction, thereby indicating a
first-order transition, 2) a tri-critical point emerges, thereby demarcating
the boundary between the standard second-order superconducting transition and
the novel first-order regime, 3) Mottness changes the sign of the quartic
coefficient in the Landau-Ginzburg free-energy fuctional relative to that in
BCS, 4) as this obtains in the strongly interacting regime, it is Mott physics
that underlies the generic first-order transition, 5) the condensation energy
exceeds that in BCS theory suggesting that multiple Mott bands might be a way
of enhancing superconducting, 6) the heat-capacity jump is non-universal and
increases with the Mott scale, 7) Mottness destroys the Hebel-Slichter peak in
NMR, and 8) Mottness enhances the fall-off of the ultrasonic attenuation at the
pairing temperature . As several of these properties are observed in the
cuprates, our analysis here points a way forward in computing superconducting
properties of strongly correlated electron matter.Comment: accepted in PR
Chronic behavioral and cognitive deficits in a rat survival model of paraoxon toxicity
Organophosphate (OP) compounds, including paraoxon (POX), are similar to nerve agents such as sarin. There is a growing concern that OP agents could be weaponized to cause mass civilian causalities. We have developed a rodent survival model of POX toxicity that is being used to evaluate chronic morbidity and to screen for medical countermeasures against severe OP exposure. It is well known that the survivors of nerve gas and chronic OP exposure exhibit neurobehavioral deficits such as mood changes, depression, and memory impairments. In this study we investigated whether animals surviving severe POX exposure exhibited long-term neurological impairments. POX exposure produced overt signs of cholinergic toxicity. Rats were rescued using an optimized atropine, 2-PAM and diazepam therapy. Surviving rats were studied using established behavioral assays for identifying symptoms of depression and memory impairment 3-months after POX exposure. In the forced swim test, POX rats exhibited increased immobility time indicative of a despair-like state. In the sucrose preference test, POX rats consumed significantly less sucrose water indicating anhedonia-like condition. POX rats also displayed increased anxiety as characterized by significantly lower performance in the open arm of the elevated plus maze. Further, when tested with a novel object recognition paradigm, POX rats exhibited a negative discrimination ratio indicative of impaired recognition memory. The results indicate that this model of survival from severe POX exposure can be employed to study some of the molecular bases for OP-induced chronic behavioral and cognitive comorbidities and develop therapies for their treatment
Analytic models for mechanotransduction: gating a mechanosensitive channel
Analytic estimates for the forces and free energy generated by bilayer
deformation reveal a compelling and intuitive model for MscL channel gating
analogous to the nucleation of a second phase. We argue that the competition
between hydrophobic mismatch and tension results in a surprisingly rich story
which can provide both a quantitative comparison to measurements of opening
tension for MscL when reconstituted in bilayers of different thickness and
qualitative insights into the function of the MscL channel and other
transmembrane proteins
Ascospore release and survival in Sclerotinia sclerotiorum
The release and survival of ascospores of a UK Sclerotinia sclerotiorum isolate were studied. Apothecia placed in a spore clock apparatus with different lighting regimes at 15 °C released ascospores continuously with an increasing rate for the duration of experiments (72–84 h). Spore release was not confined to light or dark periods in alternating regimes and occurred in continuous dark or light. Ascospores were released in both saturated air (90–95% rh) and at 65–75% rh. High temperature and rh were detrimental to ascospore survival but spore viability was maintained for longer periods than previously reported. The significance of these results in relation to disease control is discussed
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