Two dynamical crossovers in protein hydration water revealed by the NMR spin-spin relaxation time

Hydration water is essential in determining the optimal conditions for the development of the biological activity of biological systems. Indeed the physical properties of hydration water are responsible for and determine the region of biological stability of proteins. By means of Nuclear Magnetic Resonance, we probe some thermodynamical properties of the first hydration shell of lysozyme from 200K to 360 K. In particular, we study the thermal behavior of the nuclear magnetization and of the apparent spin-spin relaxation time (T∗2). We find the existence of two thermal borders with two corresponding evident crossovers at low and high temperatures signaling the thresholds of the native state of lysozyme and therefore of its functionality

On the signaling effect of reward-based crowdfunding: (When) do later stage venture capitalists rely more on the crowd than their peers?

Venture capitalists (VCs) make only a small number of investments and are more likely to invest in ventures where other VCs have invested previously. As such, valuable opportunities may be forgone if they are not funded by VCs in the first place. We demonstrate how crowdfunding (CF) can remedy this concern. Using a sample of new technology-based ventures, we reveal that ventures initially funded through reward-based CF can be even more likely than those initially backed by VCs in attracting follow-up funds from VCs. This happens when ventures originally funded via reward-based CF complement the certification they derive from CF with patents and a founding team with a track record of success. In those cases, VCs rely on the crowd more than their peers. Overall, the results suggest that signal complementarity can at least equalize the effectiveness of an a priori inferior and an a priori superior signal

New insight into hydration and aging mechanisms of paper by the line shape analysis of proton NMR spectra

The action of water within biological systems is strictly linked either with their physical chemical properties and with their functions. Cellulose is one of the most studied biopolymers due to its biological importance and its wide use in manufactured products. Among them, paper is mainly constituted by an almost equimolar ratio of cellulose and water. Therefore the study of the behavior of water within pristine and aged paper samples can help to shed light on the degradation mechanisms that irremediably act over time and spoil paper. In this work we present Nuclear Magnetic Resonance (NMR) experiments on modern paper samples made of pure cellulose not aged and artificially aged as well as on ancient paper samples made in 1413 in Perpignan (France). The line shape parameters of the proton NMR spectra were studied as a function of the hydration content. Results indicate that water in aged samples is progressively involved in the hydration of the byproducts of cellulose degradation. This enhances the degradation process itself through the progressive consumption of the cellulose amorphous regions

The time dependence dynamics of hydration water changes upon crossing T∗

We carry out a Nuclear Magnetic Resonance (NMR) spectroscopy study on the dynamics of lysozyme hydration water. We consider a hydration level corresponding to a single water monolayer. We investigate the thermodynamical region from 295K to 355 K, at temperatures below and above the “magic” temperature T∗ ≈ 320 K. In particular, we focus our attention on hydration water mean-square displacement (MSD) as a function of the diffusion time at different temperatures. Our results suggest the occurrence of a smooth anomalous diffusion from a sub-diffusive state (T < T ∗) to a super-diffusive one (T > T∗). These conclusions confirm the importance of the temperature T∗ as the border for water behavior

The local order of supercooled water in solution with LiCl studied by NMR proton chemical shift

We study by means of Nuclear Magnetic Resonance (NMR) spectroscopy the local order of water molecules in solution with lithium chloride at eutectic concentration. In particular, by measuring the proton chemical shift as a function of the temperature in the interval 203K < T < 320K, we observe a net change at about 235 K. We ascribe this result to the increase of the hydrogen bond interaction that on decreasing the temperature favors the formation of the network that characterizes the low density liquid phase of water. Furthermore, the Gaussian deconvolution of the NMR peak allows the investigation of the mutual difference between the chemical shift of water solvating lithium and chlorine individually. The thermal behavior of this quantity confirms previous results about the role of the temperature in the solvation mechanisms down to about 225 K. This temperature coincides with that of the so-called Widom line for water supporting the liquid-liquid transition hypothesis

Neutron Tomography at INES: First experimental results

A neutron tomography apparatus has been designed and installed at the Italian neutron experimental station (INES) at ISIS (UK). The instrument has a double aim: an additional opportunity for the INES users and a “bench test” for an instrument component that will be proposed for installation on some of the new neutron scattering instruments of Target Station 2 (TS2) of ISIS. Here, we present the first experimental results achieved with this apparatus

A systematic review of studies with a representative sample of refugees and asylum seekers living in the community for participation in mental health research.

BACKGROUND: The aim was to review the literature to identify the most effective methods for creating a representative sample of refugee and asylum seeker groups living in the community to participate in health and mental health survey research. METHODS: A systematic search of academic and grey literature was conducted for relevant literature with 'hidden' groups published between January 1995 and January 2016. The main search used Medline, PsycINFO, EMBASE, CINAHL and SCOPUS electronic databases. Hidden groups were defined as refugees, asylum seekers, stateless persons or hard/difficult to reach populations. A supplementary grey literature search was conducted. Identified articles were rated according to a created graded system of 'level of evidence for a community representative sample' based on key study factors that indicated possible sources of selection bias. Articles were included if they were assessed as having medium or higher evidence for a representative sample. All full-text papers that met the eligibility criteria were examined in detail and relevant data extracted. RESULTS: The searches identified a total of 20 publications for inclusion: 16 peer-reviewed publications and four highly relevant reports. Seventeen studies had sampled refugee and asylum seekers and three other hidden groups. The main search identified 12 (60.0%) and the grey search identified another eight (40.0%) articles. All 20 described sampling techniques for accessing hidden groups for participation in health-related research. Key design considerations were: an a priori aim to recruit a representative sample; a reliable sampling frame; recording of response rates; implementation of long recruitment periods; using multiple non-probability sampling methods; and, if possible, including a probability sampling component. Online social networking sites were used by one study. Engagement with the refugee and asylum seeker group was universally endorsed in the literature as necessary and a variety of additional efforts to do this were reported. CONCLUSIONS: The strategies for increasing the likelihood of a representative sample of this hidden group were identified and will assist researchers when doing future research with refugee groups. These findings encourage more rigorous reporting of future studies so that the representativeness of samples of these groups in research can be more readily assessed

The neutron irradiation module at the European Spallation Source ESS

The neutron Irradiation Module at the European Spallation Source will make use of the high intensity fast neutron spectrum to study the behaviour of the materials used in the facility, set within the ESS research and development program for the target station. By studying how these materials are affected by radiation, estimates of the material degradation in irrradiated bespoke samples will allow to optimise of the design and lifetime of regularly replaced target components. The general design and a set of results from the neutronics calculations, aimed at estimating proton and neutron flux distributions, displacement damage, heat deposition and activation for the radiological hazard analysis of the Irradiation Module, set within the Italian contributions to the ESS construction phase, are reported. © Published under licence by IOP Publishing Ltd

The Evolution of Reduced Microbial Killing

Bacteria engage in a never-ending arms race in which they compete for limited resources and niche space. The outcome of this intense interaction is the evolution of a powerful arsenal of biological weapons. Perhaps the most studied of these are colicins, plasmid-based toxins produced by and active against Escherichia coli. The present study was designed to explore the molecular responses of a colicin-producing strain during serial transfer evolution. What evolutionary changes occur when colicins are produced with no target present? Can killing ability be maintained in the absence of a target? To address these, and other, questions, colicinogenic strains and a noncolicinogenic ancestor were evolved for 253 generations. Samples were taken throughout the experiment and tested for killing ability. By the 38th transfer, a decreased killing ability and an increase in fitness were observed in the colicin-producing strains. Surprisingly, DNA sequence determination of the colicin plasmids revealed no changes in plasmid sequences. However, a set of chromosomally encoded loci experienced changes in gene expression that were positively associated with the reduction in killing. The most significant expression changes were observed in DNA repair genes (which were downregulated in the evolved strains), Mg ion uptake genes (which were upregulated), and late prophage genes (which were upregulated). These results indicate a fine-tuned response to the evolutionary pressures of colicin production, with far more genes involved than had been anticipated

Repeated, Selection-Driven Genome Reduction of Accessory Genes in Experimental Populations

Genome reduction has been observed in many bacterial lineages that have adapted to specialized environments. The extreme genome degradation seen for obligate pathogens and symbionts appears to be dominated by genetic drift. In contrast, for free-living organisms with reduced genomes, the dominant force is proposed to be direct selection for smaller, streamlined genomes. Most variation in gene content for these free-living species is of “accessory” genes, which are commonly gained as large chromosomal islands that are adaptive for specialized traits such as pathogenicity. It is generally unclear, however, whether the process of accessory gene loss is largely driven by drift or selection. Here we demonstrate that selection for gene loss, and not a shortened genome, per se, drove massive, rapid reduction of accessory genes. In just 1,500 generations of experimental evolution, 80% of populations of Methylobacterium extorquens AM1 experienced nearly parallel deletions removing up to 10% of the genome from a megaplasmid present in this strain. The absence of these deletion events in a mutation accumulation experiment suggested that selection, rather than drift, has dominated the process. Reconstructing these deletions confirmed that they were beneficial in their selective regimes, but led to decreased performance in alternative environments. These results indicate that selection can be crucial in eliminating unnecessary genes during the early stages of adaptation to a specialized environment