2,325 research outputs found
Probing the Viscoelastic Properties of Aqueous Protein Solutions using Molecular Dynamics Simulations
We performed molecular dynamics simulations to investigate the viscoelastic
properties of aqueous protein solutions containing an antifreeze protein, a
toxin protein, and bovine serum albumin. These simulations covered a
temperature range from 280 K to 340 K. Our findings demonstrate that lower
temperatures are associated with higher viscosity as well as a lower bulk
modulus and speed of sound for all the systems studied. Furthermore, we observe
an increase in the bulk modulus and speed of sound as the temperature increases
up to a weak maximum while the viscosity decreases. Moreover, we analyzed the
influence of protein concentration on the viscoelastic properties of the
antifreeze protein solution. We observed a consistent increase in the bulk
modulus, speed of sound, and viscosity as the protein concentration increased.
Remarkably, our molecular dynamics simulations results closely resemble the
trends observed in Brillouin scattering experiments on aqueous protein
solutions. The similarity thus validates the use of simulations in studying the
viscoelastic properties of protein water solutions. Ultimately, this work
provides motivation for the integration of computer simulations with
experimental data and holds potential for advancing our understanding of both
simple and complex systems.Comment: 7 pages, and 7 figure
Concentration Dependence of Elastic and Viscoelastic Properties of Aqueous Solutions of Ficoll and Bovine Serum Albumin by Brillouin Light Scattering Spectroscopy
The cellular environment is crowded with macromolecules of different shapes
and sizes. The effect of this macromolecular crowding has been studied in a
variety of synthetic crowding environments: two popular examples are the
compact colloid-like Ficoll macromolecule, and the globular protein bovine
serum albumin (BSA). Recent studies have indicated a significant component of
bound or surface-associated water in these crowders reduces the available free
volume. In this work, Brillouin light scattering experiments were performed on
aqueous solutions of Ficoll 70 and Ficoll 400 with concentrations ranging from
1 wt% to 35 wt% and BSA with concentrations of 1 wt% to 27 wt%. From the
dependence of spectral peak parameters on polymer concentration, we determined
fundamental solution properties: hypersound velocity, adiabatic bulk modulus
and compressibility, apparent viscosity, and hypersound attenuation. Existing
theory that ignores intermolecular interactions can only capture the observed
linear trends in the frequency shift up to a threshold concentration, beyond
which a quadratic term accounting for intermolecular interactions is necessary.
This likely indicates a transition from the dilute to semi-dilute regime. In
the Ficoll solutions (but not BSA) we see evidence for a central mode, with a
characteristic relaxation time of 20 ps, that we attribute to exchange of the
bound water.Comment: 10 pages, 4 figures, 4 table
Caregiving can be costly : a qualitative study of barriers and facilitators to conducting kangaroo mother care in a US tertiary hospital neonatal intensive care unit
Preterm birth is a leading cause of morbidity and mortality in children under five and often requires a newborn to have an extended stay in a neonatal intensive care unit (NICU). Maternal engagement, such as visiting the NICU to provide kangaroo mother care (KMC), can improve outcomes for preterm infants but requires significant investment of time and resources. This study sought to understand barriers and facilitators to provision of KMC in the NICU.; We conducted semi-structured in-depth interviews with mothers of preterm infants (N = 20) at a large academic medical center in Massachusetts. A series of open-ended interview questions were designed to elicit all aspects of mothers' experiences and to understand how these experiences influence provision of KMC. All interviews were recorded and transcribed verbatim. We conducted an inductive thematic analysis to identify themes in the data with a focus on the barriers and facilitators of KMC provision in the NICU.; Findings show that engaging in KMC is heavily influenced by the mental, emotional, and physical effects of preterm birth on the birth mother, such as stress around preterm birth and difficulty recovering from birth. These challenges are compounded by structural barriers such as costly accommodations, unreliable transportation, lack of child care, and inadequate maternity leave policies that limit the frequency and duration of KMC and parental ability to provide care.; A complex array of mental, emotional, physical, and structural factors determine a mother's ability to visit the NICU and provide kangaroo mother care. Providing social supports, such as improved maternity leave policies and reliable hospital access through child care, accommodation, and transportation services, may address the structural barriers that inhibit KMC, reduce burdensome costs, and improve the health of mothers and their preterm infants
Evidence for diversifying selection of genetic regions of encoding putative collagen-like host-adhesive fibers in Pasteuria penetrans
© FEMS 2018. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.Pasteuria spp. belong to a group of genetically diverse endospore-forming bacteria (phylum: Firmicutes) that are known to parasitize plant-parasitic nematodes and water fleas (Daphnia spp.). Collagen-like fibres form the nap on the surface of endospores and the genes encoding these sequences have been hypothesised to be involved in the adhesion of the endospores of Pasteuria spp. to their hosts. We report a group of 17 unique collagen-like genes putatively encoded by Pasteuria penetrans (strain: Res148) that formed five different phylogenetic clusters and suggest that collagen-like proteins are an important source of genetic diversity in animal pathogenic Firmicutes including Pasteuria. Additionally, and unexpectedly, we identified a putative collagen-like sequence which had a very different sequence structure to the other collagen-like proteins but was similar to the protein sequences in Megaviruses that are involved in host-parasite interactions. We, therefore, suggest that these diverse endospore surface proteins in Pasteuria are involved in biological functions, such as cellular adhesion; however, they are not of monophyletic origin and were possibly obtained de novo by mutation or possibly through selection acting upon several historic horizontal gene transfer events.Peer reviewedFinal Published versio
Association between essential tremor and blood lead concentration
Lead is a ubiquitous toxicant that causes tremor and cerebellar damage. Essential tremor (ET) is a highly prevalent neurologic disease associated with cerebellar involvement. Although environmental toxicants may play a role in ET etiology and their identification is a critical step in disease prevention, these toxicants have received little attention. Our objective was to test the hypothesis that ET is associated with lead exposure. Therefore, blood lead (BPb) concentrations were measured and a lifetime occupational history was assessed in ET patients and in controls. We frequency matched 100 ET patients and 143 controls on age, sex, and ethnicity. BPb concentrations were analyzed using graphite furnace atomic absorption spectrophotometry. A lifetime occupational history was reviewed by an industrial hygienist. BPb concentrations were higher in ET patients than in controls (mean ± SD, 3.3 ± 2.4 and 2.6 ± 1.6 µg/dL, respectively; median, 2.7 and 2.3 µg/dL; p = 0.038). In a logistic regression model, BPb concentration was associated with diagnosis [control vs. ET patient, odds ratio (OR) per unit increase = 1.21; 95% confidence interval (CI), 1.05-1.39; p = 0.007]. BPb concentration was associated with diagnosis (OR per unit increase = 1.19; 95% CI, 1.03-1.37; p = 0.02) after adjusting for potential confounders. Prevalence of lifetime occupational lead exposure was similar in ET patients and controls. We report an association between BPb concentration and ET. Determining whether this association is due to increased exposure to lead or a difference in lead kinetics in ET patients requires further investigation
The Close Binary Fraction as a Function of Stellar Parameters in APOGEE:A Strong Anti-Correlation With α Abundances
We use observations from the APOGEE survey to explore the relationship
between stellar parameters and multiplicity. We combine high-resolution repeat
spectroscopy for 41,363 dwarf and subgiant stars with abundance measurements
from the APOGEE pipeline and distances and stellar parameters derived using
\textit{Gaia} DR2 parallaxes from \cite{Sanders2018} to identify and
characterise stellar multiples with periods below 30 years, corresponding to
\drvm 3 \kms, where \drvm\ is the maximum APOGEE-detected shift in the
radial velocities. Chemical composition is responsible for most of the
variation in the close binary fraction in our sample, with stellar parameters
like mass and age playing a secondary role. In addition to the previously
identified strong anti-correlation between the close binary fraction and \feh\,
we find that high abundances of elements also suppress multiplicity at
most values of \feh\ sampled by APOGEE. The anti-correlation between
abundances and multiplicity is substantially steeper than that observed for Fe,
suggesting C, O, and Si in the form of dust and ices dominate the opacity of
primordial protostellar disks and their propensity for fragmentation via
gravitational stability. Near \feh{} = 0 dex, the bias-corrected close binary
fraction ( au) decreases from 100 per cent at \alh{} = 0.2
dex to 15 per cent near \alh{} = 0.08 dex, with a suggestive turn-up
to 20 per cent near \alh{} = 0.2. We conclude that the relationship
between stellar multiplicity and chemical composition for sun-like dwarf stars
in the field of the Milky Way is complex, and that this complexity should be
accounted for in future studies of interacting binaries.Comment: 15 pages, 10 figures, plus appendices; accepted to MNRA
Observation of two new baryon resonances
Two structures are observed close to the kinematic threshold in the mass spectrum in a sample of proton-proton collision data, corresponding
to an integrated luminosity of 3.0 fb recorded by the LHCb experiment.
In the quark model, two baryonic resonances with quark content are
expected in this mass region: the spin-parity and
states, denoted and .
Interpreting the structures as these resonances, we measure the mass
differences and the width of the heavier state to be
MeV,
MeV,
MeV, where the first and second
uncertainties are statistical and systematic, respectively. The width of the
lighter state is consistent with zero, and we place an upper limit of
MeV at 95% confidence level. Relative
production rates of these states are also reported.Comment: 17 pages, 2 figure
Observation of resonances consistent with pentaquark states in decays
Observations of exotic structures in the channel, that we refer to
as pentaquark-charmonium states, in decays are
presented. The data sample corresponds to an integrated luminosity of 3/fb
acquired with the LHCb detector from 7 and 8 TeV pp collisions. An amplitude
analysis is performed on the three-body final-state that reproduces the
two-body mass and angular distributions. To obtain a satisfactory fit of the
structures seen in the mass spectrum, it is necessary to include two
Breit-Wigner amplitudes that each describe a resonant state. The significance
of each of these resonances is more than 9 standard deviations. One has a mass
of MeV and a width of MeV, while the second
is narrower, with a mass of MeV and a width of MeV. The preferred assignments are of opposite parity, with one
state having spin 3/2 and the other 5/2.Comment: 48 pages, 18 figures including the supplementary material, v2 after
referee's comments, now 19 figure
Search for hidden-sector bosons in decays
A search is presented for hidden-sector bosons, , produced in the decay
, with and
. The search is performed using -collision data
corresponding to 3.0 fb collected with the LHCb detector. No significant
signal is observed in the accessible mass range
MeV, and upper limits are placed on the branching fraction product
as
a function of the mass and lifetime of the boson. These limits are of
the order of for lifetimes less than 100 ps over most of the
range, and place the most stringent constraints to date on many
theories that predict the existence of additional low-mass bosons.Comment: All figures and tables, along with supplementary material, are
available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-036.htm
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