4,601 research outputs found
Altering the stability of the Cdc8 overlap region modulates the ability of this tropomyosin to bind cooperatively to actin and regulate myosin.
Tropomyosin (Tm) is an evolutionarily conserved ?-helical coiled-coil protein, dimers of which form end-to-end polymers capable of associating with and stabilising actin-filaments and regulate myosin function. The fission yeast, Schizosaccharomyces pombe, possesses a single essential Tm, Cdc8, which can be acetylated on its amino terminal methionine to increase its affinity for actin and enhance its ability to regulate myosin function. We have designed and generated a number of novel Cdc8 mutant proteins with amino terminal substitutions to explore how stability of the Cdc8-polymer overlap region affects the regulatory function of this Tm. By correlating the stability of each protein, its propensity to form stable polymers, its ability to associate with actin and to regulate myosin, we have shown the stability of the amino terminal of the Cdc8 ?-helix is crucial for Tm function. In addition we have identified a novel Cdc8 mutant with increased amino-terminal stability, dimers of which are capable of forming Tm-polymers significantly longer than the wild-type protein. This protein had a reduced affinity for actin with respect to wild type, and was unable to regulate actomyosin interactions. The data presented here are consistent with acetylation providing a mechanism for modulating the formation and stability of Cdc8 polymers within the fission yeast cell. The data also provide evidence for a mechanism in which Tm dimers form end-to-end polymers on the actin-filament, consistent with a cooperative model for Tm binding to actin
Punctuated Equilibrium in Software Evolution
The approach based on paradigm of self-organized criticality proposed for
experimental investigation and theoretical modelling of software evolution. The
dynamics of modifications studied for three free, open source programs Mozilla,
Free-BSD and Emacs using the data from version control systems. Scaling laws
typical for the self-organization criticality found. The model of software
evolution presenting the natural selection principle is proposed. The results
of numerical and analytical investigation of the model are presented. They are
in a good agreement with the data collected for the real-world software.Comment: 4 pages, LaTeX, 2 Postscript figure
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FABRIC: A National-Scale Programmable Experimental Network Infrastructure
FABRIC is a unique national research infrastructure to enable cutting-edge and exploratory research at-scale in networking, cybersecurity, distributed computing and storage systems, machine learning, and science applications. It is an everywhere-programmable nationwide instrument comprised of novel extensible network elements equipped with large amounts of compute and storage, interconnected by high speed, dedicated optical links. It will connect a number of specialized testbeds for cloud research (NSF Cloud testbeds CloudLab and Chameleon), for research beyond 5G technologies (Platforms for Advanced Wireless Research or PAWR), as well as production high-performance computing facilities and science instruments to create a rich fabric for a wide variety of experimental activities
Accounting for decarbonisation and reducing capital at risk in the S&P500
This document is the Accepted Manuscript version of the following article: Colin Haslam, Nick Tsitsianis, Glen Lehman, Tord Andersson, and John Malamatenios, ‘Accounting for decarbonisation and reducing capital at risk in the S&P500’, Accounting Forum, Vol. 42 91): 119-129, March 2018. Under embargo until 7 August 2019. The final, definitive version is available online at doi: https://doi.org/10.1016/j.accfor.2018.01.004.This article accounts for carbon emissions in the S&P 500 and explores the extent to which capital is at risk from decarbonising value chains. At a global level it is proving difficult to decouple carbon emissions from GDP growth. Top-down legal and regulatory arrangements envisaged by the Kyoto Protocol are practically redundant given inconsistent political commitment to mitigating global climate change and promoting sustainability. The United Nations Environment Programme (UNEP) and European Commission (EC) are promoting the role of financial markets and financial institutions as drivers of behavioural change mobilising capital allocations to decarbonise corporate activity.Peer reviewe
The Wild Turkey in South Dakota
This bulletin provides an extensive look at the wild turkey in South Dakota
Surface Rearrangement and Evaporation Kinetics of Supported Gold Nanoparticle Catalysts
Heterogeneous catalysts consisting of supported metallic nanoparticles
typically derive exceptional catalytic activity from their large proportion of
under-coordinated surface sites which promote adsorption of reactant molecules.
Simultaneously, these high energy surface configurations are unstable, leading
to nanoparticle growth or degradation, and eventually a loss of catalytic
activity. Surface morphology of catalytic nanoparticles is paramount to
catalytic activity, selectivity, as well as degradation rates, however, it is
well-known that harsh reaction conditions can cause the surface structure to
change. Still, limited research has focused on understanding the link between
nanoparticle surface facets and degradation rates or mechanisms. Here, we study
a model Au supported catalyst system over a range of temperatures using a
combination of \textit{in situ} Transmission Electron Microscopy, kinetic Monte
Carlo simulations, and density functional theory calculations to establish an
atomistic picture of how variations in surface structures and atomic
coordination environments lead to shifting evolution mechanisms as a function
of temperature. By combining experimental results, which yield direct
observation of dynamic shape changes and particle evaporation rates, with
computational techniques, which enable understanding the fundamental
thermodynamics and kinetics of nanoparticle evolution, we illustrate a two-step
evolution mechanism in which mobile adatoms form through desorption from
low-coordination facets and subsequently evaporate off the particle surface. By
understanding the role of temperature in the competition between surface
diffusion and evaporation, we are able to show how individual atomic movements
lead to particle-scale morphological changes, and rationalize why evaporation
rates vary between particles in a system of nearly identical nanoparticles
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