Lymphotactin: how a protein can adopt two folds

Metamorphic proteins like Lymphotactin are a notable exception of the empirical principle that structured natural proteins possess a unique three dimensional structure. In particular, the human chemokine lymphotactin protein (Ltn) exists in two distinct conformations (one monomeric and one dimeric) under physiological conditions. In this work we use a Ca Go-model to show how this very peculiar behavior can be reproduced. From the study of the thermodynamics and of the kinetics we characterize the interconversion mechanism. In particular, this takes place through the docking of the two chains living in a third monomeric, partially unfolded, state which shows a residual structure involving a set of local contacts common to the two native conformations. The main feature of two-fold proteins appears to be the sharing of a common set of local contacts between the two distinct folds as confirmed by the study of two designed two-fold proteins. Metamorphic proteins may be more common than expected.Comment: 14 pages, 4 figure

Pumping charge with ac magnetic fluxes and the dynamical breakdown of Onsager symmetry

We study the transport properties of setups with one and two mesoscopic rings threaded by ac magnetic fluxes of the form \Phi(t)=\Phi^{dc} + \Phi^{ac} cos(\Omega_0 t + \delta) and connected to two different particle reservoirs. We analyze the conditions to generate a pumped dc current in the adiabatic regime. We also study the symmetry properties of the induced dc current as a function of the static component of the flux, \Phi^{dc}, with and without a dc bias voltage applied at the reservoirs. We analyze, in particular, the validity of the Onsager-Casimir relations for different configurations of the setups.Comment: 12 pages, 9 figures, accepted in PRB. Added refences, corrected typos, we now discuss in the conclusion the possibility of an experimental realization of our findings, we now show the main quantities in terms of universal constant

Analysing Regional Sustainability Through a Systemic Approach: The Lombardy Case Study

The intrinsic complexity of the sustainability concept challenges research towards more sophisticated ways to model and assess the dimensions underlying it. However, currently adopted modelling techniques and indicators frameworks are not able to give an integrated assessment through the different components of sustainability, providing incomplete visuals of the reality that they aim to catch. This paper tries to assess how the INSURE methodology can provide a contribution in the analysis of sustainability through indicator frameworks, describing its application to the Lombardy region (Italy). Developed on the course of a 6th European Framework Program – financed project to measure sustainability in the European regions, the methodology provides two distinct sustainability representations, based on a quantitative “top-down” System Dynamics model and on a qualitative “bottom-up” System Thinking approach. The models are then linked to a hierarchical indicator framework setting policy priorities. The overall objective is thus to create a set of regional indicators, adapting the models of regional sustainability to different policy agendas. The purpose of the paper is twofold: defining a new approach to sustainability appraisal, and assessing how the Region is holistically behaving towards sustainable development. Starting from a basis analysis of the main shortcomings highlighted by the use of most adopted methodologies, the paper will verify the contribution given by the INSURE methodology to research in the fields of modelling and indicators approaches, providing insights over methodological adjustments and the results obtained from the application to Lombardy. The conclusions will show how the methodology has tried to overcome identified constraints in current models, like the strong dependence on existing datasets of the obtained representations, the under-coverage of “immaterial factors” role and the scarce integration between sustainability dimensions.ustainable Development, Regional Economics, Econometric and Input Output Models, Development Planning and Policy, Regional Analyses

The role of biomass in the renewable energy system

Europe is striving for zero carbon electricity production by 2050 in order to avoid dangerous climate change. To meet this target a large variety of options is being explored. Biomass is such an option and should be given serious consideration. In this paper the potential role of biomass in a NW-European electricity mix is analyzed. The situation in NW-Europe is unique since it is a region which is a fore runner in renewable technology promotion but also an area with little sun, almost no potential for hydro and a lot of wind. This will result in a substantial need for non-intermittent low-carbon options such as biomass. The benefits and issues related to biomass are discussed in detail from both an environmental and an economic perspective. The former will focus on the life cycle of a biomass pellet supply chain, from the growth of the trees down to the burning of the pellets on site. The latter will provide detailed insights on the levelized cost of electricity for biomass and the role of biomass as a grid stabilizer in high intermittent scenarios. During the discussion, biomass will be compared to other competing electricity technologies to have a full understanding of its advantages and drawbacks. We find that biomass can play a very important role in the future low carbon electricity mix, the main bottleneck being the supply of large amounts of sustainably produced feedstock