613 research outputs found
A model for the conformational activation of the structurally quiescent metalloprotease ADAMTS13 by Von Willebrand factor
Blood loss is prevented by the multi-domain glycoprotein von Willebrand factor (VWF), which binds exposed collagen at damaged vessels and captures platelets. VWF is regulated by the metalloprotease ADAMTS13, which, in turn, is conformationally activated by VWF. To delineate the structural requirements for VWF-mediated conformational activation of ADAMTS13, we performed binding and functional studies with a panel of truncated ADAMTS13 variants. We demonstrate that both the isolated CUB1 and CUB2 domains in ADAMTS13 bind to the spacer domain exosite of a truncated ADAMTS13 variant, MDTCS (KD of 135 ± 10.1 nM and 86.9 ± 9.0 nM, respectively). However, only the CUB1 domain inhibited proteolytic activity of MDTCS. Moreover, ADAMTS13âCUB2, unlike ADAMTS13âCUB1-2, exhibited activity similar to wild-type ADAMTS13 and could be activated by VWF D4-CK. The CUB2 domain is therefore not essential for maintaining the inactive conformation of ADAMTS13. Both CUB domains could bind to the VWF D4-CK domain fragment (KD of 53.7± 2.1 nM and 84.3 ± 2.0 nM, respectively). However, deletion of both CUB domains did not prevent VWF D4-CK binding, suggesting that competition for CUB-domain binding to the spacer domain is not the dominant mechanism behind the conformational activation. ADAMTS13âTSP8-CUB2 could no longer bind to VWF D4-CK, and deletion of TSP8 abrogated ADAMTS13 conformational activation. These findings support an ADAMTS13-activation model in which VWF D4-CK engages the TSP8-CUB2 domains, inducing the conformational change that disrupts the CUB1-spacer domain interaction and thereby activates ADAMTS13
Fitting the incidence data from the city of Campinas, Brazil, based on dengue transmission modellings considering time-dependent entomological parameters
FAPESP - FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULOFour time-dependent dengue transmission models are considered in order to fit the incidence data from the City of Campinas, Brazil, recorded from October 1st 1995 to September 30th 2012. The entomological parameters are allowed to depend on temperature and precipitation, while the carrying capacity and the hatching of eggs depend only on precipitation. The whole period of incidence of dengue is split into four periods, due to the fact that the model is formulated considering the circulation of only one serotype. Dengue transmission parameters from human to mosquito and mosquito to human are fitted for each one of the periods. The time varying partial and overall effective reproduction numbers are obtained to explain the incidence of dengue provided by the models.Four time-dependent dengue transmission models are considered in order to fit the incidence data from the City of Campinas, Brazil, recorded from October 1st 1995 to September 30th 2012. The entomological parameters are allowed to depend on temperature and precipitation, while the carrying capacity and the hatching of eggs depend only on precipitation. The whole period of incidence of dengue is split into four periods, due to the fact that the model is formulated considering the circulation of only one serotype. Dengue transmission parameters from human to mosquito and mosquito to human are fitted for each one of the periods. The time varying partial and overall effective reproduction numbers are obtained to explain the incidence of dengue provided by the models113FAPESP - FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULOFAPESP - FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULO2009/15098-
Ground-based aerosol characterization during the South American Biomass Burning Analysis (SAMBBA) field experiment
This paper investigates the physical and chemical
characteristics of aerosols at ground level at a site
heavily impacted by biomass burning. The site is located
near Porto Velho, RondĂŽnia, in the southwestern part of the
Brazilian Amazon rainforest, and was selected for the deployment
of a large suite of instruments, among them an
Aerosol Chemical Speciation Monitor. Our measurements
were made during the South American Biomass Burning
Analysis (SAMBBA) field experiment, which consisted of
a combination of aircraft and ground-based measurements
over Brazil, aimed to investigate the impacts of biomass
burning emissions on climate, air quality, and numerical
weather prediction over South America. The campaign took
place during the dry season and the transition to the wet season
in September/October 2012.
During most of the campaign, the site was impacted by
regional biomass burning pollution (average CO mixing ratio
of 0.6 ppm), occasionally superimposed by intense (up
to 2 ppm of CO), freshly emitted biomass burning plumes.
Aerosol number concentrations ranged from ⌠1000 cmâ3
to
peaks of up to 35 000 cmâ3
(during biomass burning (BB)
events, corresponding to an average submicron mass mean
concentrations of 13.7 ”g mâ3
and peak concentrations close
to 100 ”g mâ3
. Organic aerosol strongly dominated the submicron
non-refractory composition, with an average concentration
of 11.4 ”g mâ3
. The inorganic species, NH4, SO4,
NO3, and Cl, were observed, on average, at concentrations
of 0.44, 0.34, 0.19, and 0.01 ”g mâ3
, respectively. Equivalent
black carbon (BCe) ranged from 0.2 to 5.5 ”g mâ3
,
with an average concentration of 1.3 ”g mâ3
. During BB
peaks, organics accounted for over 90 % of total mass (submicron
non-refractory plus BCe), among the highest values
described in the literature.
We examined the ageing of biomass burning organic
aerosol (BBOA) using the changes in the H : C and O : C
ratios, and found that throughout most of the aerosol processing
(O : C âŒ= 0.25 to O : C âŒ= 0.6), no remarkable change
is observed in the H : C ratio (⌠1.35). Such a result contrasts
strongly with previous observations of chemical ageing
of both urban and Amazonian biogenic aerosols. At higher
levels of processing (O : C > 0.6), the H : C ratio changes
with a H : C/O : C slope of â0.5, possibly due to the development
of a combination of BB (H : C/O : C slope =
0) and biogenic (H : C/O : C slope = â1) organic aerosol
(OA). An analysis of the 1OA/1CO mass ratios yields
very little enhancement in the OA loading with atmospheric
processing, consistent with previous observations. These
results indicate that negligible secondary organic aerosol
(SOA) formation occurs throughout the observed BB plume
Published by Copernicus Publications on behalf of the European Geosciences Union.
12070 J. Brito et al.: Ground-based aerosol characterization during SAMBBA
processing, or that SOA formation is almost entirely balanced
by OA volatilization.
Positive matrix factorization (PMF) of the organic aerosol
spectra resulted in three factors: fresh BBOA, aged BBOA,
and low-volatility oxygenated organic aerosol (LV-OOA).
Analysis of the diurnal patterns and correlation with external
markers indicates that during the first part of the campaign,
OA concentrations are impacted by local fire plumes
with some chemical processing occurring in the near-surface
layer. During the second part of the campaign, long-range
transport of BB plumes above the surface layer, as well as
potential SOAs formed aloft, dominates OA concentrations
at our ground-based sampling site.
This manuscript describes the first ground-based deployment
of the aerosol mass spectrometry at a site heavily impacted
by biomass burning in the Amazon region, allowing
a deeper understanding of aerosol life cycle in this important
ecosystem.This work was supported by the Foundation
for Research Support of the State of SĂŁo Paulo (FAPESP,
projects 2012/14437-9 and 2013/05014-0), CNPq project 475735-
2012-9, INCT Amazonia, and Natural Environment Research
Council (NERC) project NE/J010073/1. We thank A. Ribeiro,
A. L. Loureiro, F. Morais, F. Jorge, and S. Morais for technical and
logistics support. We thank the National Institute of Meteorology
for providing valuable meteorological data. We gratefully acknowledge
S. Hacon, J. Silva, and W. Bastos for support in the successful
operation of the sampling site
MLH1 deficiency leads to deregulated mitochondrial metabolism
The DNA mismatch repair (MMR) pathway is responsible for the repair of baseâbase mismatches and insertion/deletion loops that arise during DNA replication. MMR deficiency is currently estimated to be present in 15â17% of colorectal cancer cases and 30% of endometrial cancers. MLH1 is one of the key proteins involved in the MMR pathway. Inhibition of a number of mitochondrial genes, including POLG and PINK1 can induce synthetic lethality in MLH1-deficient cells. Here we demonstrate for the first time that loss of MLH1 is associated with a deregulated mitochondrial metabolism, with reduced basal oxygen consumption rate and reduced spare respiratory capacity. Furthermore, MLH1-deficient cells display a significant reduction in activity of the respiratory chain Complex I. As a functional consequence of this perturbed mitochondrial metabolism, MLH1-deficient cells have a reduced anti-oxidant response and show increased sensitivity to reactive oxidative species (ROS)-inducing drugs. Taken together, our results provide evidence for an intrinsic mitochondrial dysfunction in MLH1-deficient cells and a requirement for MLH1 in the regulation of mitochondrial function
Assessing the utility of geospatial technologies to investigate environmental change within lake systems
Over 50% of the world's population live within 3. km of rivers and lakes highlighting the on-going importance of freshwater resources to human health and societal well-being. Whilst covering c. 3.5% of the Earth's non-glaciated land mass, trends in the environmental quality of the world's standing waters (natural lakes and reservoirs) are poorly understood, at least in comparison with rivers, and so evaluation of their current condition and sensitivity to change are global priorities. Here it is argued that a geospatial approach harnessing existing global datasets, along with new generation remote sensing products, offers the basis to characterise trajectories of change in lake properties e.g., water quality, physical structure, hydrological regime and ecological behaviour. This approach furthermore provides the evidence base to understand the relative importance of climatic forcing and/or changing catchment processes, e.g. land cover and soil moisture data, which coupled with climate data provide the basis to model regional water balance and runoff estimates over time. Using examples derived primarily from the Danube Basin but also other parts of the World, we demonstrate the power of the approach and its utility to assess the sensitivity of lake systems to environmental change, and hence better manage these key resources in the future
MLH1 deficiency leads to deregulated mitochondrial metabolism
The DNA mismatch repair (MMR) pathway is responsible for the repair of base\u2013base mismatches and insertion/deletion loops that arise during DNA replication. MMR deficiency is currently estimated to be present in 15\u201317% of colorectal cancer cases and 30% of endometrial cancers. MLH1 is one of the key proteins involved in the MMR pathway. Inhibition of a number of mitochondrial genes, including POLG and PINK1 can induce synthetic lethality in MLH1-deficient cells. Here we demonstrate for the first time that loss of MLH1 is associated with a deregulated mitochondrial metabolism, with reduced basal oxygen consumption rate and reduced spare respiratory capacity. Furthermore, MLH1-deficient cells display a significant reduction in activity of the respiratory chain Complex I. As a functional consequence of this perturbed mitochondrial metabolism, MLH1-deficient cells have a reduced anti-oxidant response and show increased sensitivity to reactive oxidative species (ROS)-inducing drugs. Taken together, our results provide evidence for an intrinsic mitochondrial dysfunction in MLH1-deficient cells and a requirement for MLH1 in the regulation of mitochondrial function
Strong interface-induced spin-orbit coupling in graphene on WS2
Interfacial interactions allow the electronic properties of graphene to be
modified, as recently demonstrated by the appearance of satellite Dirac cones
in the band structure of graphene on hexagonal boron nitride (hBN) substrates.
Ongoing research strives to explore interfacial interactions in a broader class
of materials in order to engineer targeted electronic properties. Here we show
that at an interface with a tungsten disulfide (WS2) substrate, the strength of
the spin-orbit interaction (SOI) in graphene is very strongly enhanced. The
induced SOI leads to a pronounced low-temperature weak anti-localization (WAL)
effect, from which we determine the spin-relaxation time. We find that
spin-relaxation time in graphene is two-to-three orders of magnitude smaller on
WS2 than on SiO2 or hBN, and that it is comparable to the intervalley
scattering time. To interpret our findings we have performed first-principle
electronic structure calculations, which both confirm that carriers in
graphene-on-WS2 experience a strong SOI and allow us to extract a
spin-dependent low-energy effective Hamiltonian. Our analysis further shows
that the use of WS2 substrates opens a possible new route to access topological
states of matter in graphene-based systems.Comment: Originally submitted version in compliance with editorial guidelines.
Final version with expanded discussion of the relation between theory and
experiments to be published in Nature Communication
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