What is the Entanglement Length in a Polymer Melt ?

We present results of molecular dynamics simulations of very long model polymer chains analyzed by various experimentally relevant techniques. The segment motion of the chains is found to be in very good agreement with the repatation model. We also calculated the plateau-modulus G_N. The predicitions of the entanglement length N_e from G_N and from the mean square displacements of the chains segments disagree by a factor of about 2.2(2), indicating an error in the prefactor in the standard formula for G_N. We show that recent neutron spin echo measurements were carried out for chain lengths which are too small for a correct determination of N_e.Comment: 5 pages, 4 figures, RevTe

Quantifying drivers of supplementary food use by a reintroduced, critically endangered passerine to inform management and habitat restoration

The provision of supplementary food is widely used in the management of endangered species. Typically, food is provided ad libitum and often without a planned exit strategy, which can be costly. The role supplementary food plays within population demography can be challenging to identify and therefore any reduction must be carefully considered to avoid negative impacts. Here we investigate the role supplementary food plays within a reintroduced population of a Critically Endangered passerine species by quantifying its use alongside intrinsic and extrinsic factors. Specifically, we illustrate how the provision of supplementary food could be refined in response to breeding stage and the time of food provisioning and, via habitat restoration, create a long-term exit strategy based on influential plant species. The consumption of supplementary food increases during energetically expensive phases of the breeding cycle, during the morning provision of food and when natural plant resource availability is low. We also show a pattern whereby supplementary food could act as a buffer during periods of low natural resource availability during breeding. Based on these findings short-term management could take a reactive approach; refining supplementary food supply in response to breeding stages of pairs and potentially removing the provision of food in the afternoon. In the long-term key plant species, found to correlate with a decrease in supplementary food consumption, could be incorporated into habitat restoration efforts which could create a continuous natural food supply and contribute to creating a self-sustaining population and a potential exit strategy

Using Qualitative Disease Risk Analysis for Herpetofauna Conservation Translocations Transgressing Ecological and Geographical Barriers

Through the exploration of disease risk analysis methods employed for four different UK herpetofauna translocations, we illustrate how disease hazards can be identified, and how the risk of disease can be analysed. Where ecological or geographical barriers between source and destination sites exist, parasite populations are likely to differ in identity or strain between the two sites, elevating the risk from disease and increasing the number and category of hazards requiring analysis. Simplification of the translocation pathway through the avoidance of these barriers reduces the risk from disease. The disease risk analysis tool is intended to aid conservation practitioners in decision making relating to disease hazards prior to implementation of a translocation

Glassy Dynamics of Protein Folding

A coarse grained model of a random polypeptide chain, with only discrete torsional degrees of freedom and Hookean springs connecting pairs of hydrophobic residues is shown to display stretched exponential relaxation under Metropolis dynamics at low temperatures with the exponent $\beta\simeq 1/4$, in agreement with the best experimental results. The time dependent correlation functions for fluctuations about the native state, computed in the Gaussian approximation for real proteins, have also been found to have the same functional form. Our results indicate that the energy landscape exhibits universal features over a very large range of energies and is relatively independent of the specific dynamics.Comment: RevTeX, 4 pages, multicolumn, including 5 figures; larger computations performed, error bars improve

Cloning of the Canine \u3cem\u3eABCA4\u3c/em\u3e Gene and Evaluation in Canine Cone-Rod Dystrophies and Progressive Retinal Atrophies

PURPOSE: To characterize a novel early onset canine retinal disease, and evaluate the ATP-binding cassette transporter gene ABCA4 as a potential candidate gene in this and other canine retinal degenerations. METHODS: Retinal disease was characterized ophthalmoscopically and electroretinographically in two pit bull terrier dogs and their purpose-bred descendants. All 50 exons of the canine ABCA4 gene were amplified, cloned and sequenced from retinal mRNA of a normal, a carrier and an affected animal, and polymorphisms identified. The latter were used to search for association between ABCA4 and retinal disease both within the study pedigrees and in additional canine breeds segregating retinal degenerations. RESULTS: The disease derived from either founder is distinguished by early, severe, and rapidly progressive loss of cone function accompanied by progressive rod loss that is only relatively slower. Cloning and comparative sequencing of ABCA4 identified six point mutations, none of which were obviously pathogenic. Crossbreeding studies revealed that the diseases in the two founders, although similar, are nonallelic. Pedigree analysis of segregating polymorphisms revealed dissociation between ABCA4 and both retinal phenotypes. CONCLUSIONS: The early, severe cone dysfunction in these diseases distinguish them from other forms of canine Progressive Retinal Atrophy. The development of a research population segregating these diseases presents two large animal models for the heterogenous human diseases termed cone-rod dystrophies. Analysis of the canine ABCA4 homolog gene documented its sequence and identified a set of point mutations that were used to exclude this gene as causal to these canine cone-rod dystrophies

Is there a future for genome-editing technologies in conservation?

In a recent review, Pimm et al. (2015) highlight emerging technologies in protecting biodiversity. While their list is noteworthy, the authors’ exclusion of innovations in genomic research, with the exception of single-species DNA barcoding methods, was surprising given recent advances in genome-editing technology and its potential application to conservation. Taylor & Gemmell (2016) address that deficiency in a subsequent commentary identifying three avenues where emerging genomic technologies have great potential for increasing our ability to conserve biodiversity. Those areas include the use of next-generation sequencing technologies and methods such as RADseq for monitoring genetic diversity, effective population size, and introgression (Andrews et al., 2016); the use of environmental DNA (eDNA) and metabarcoding approaches to map species occurrence and interaction networks (Evans et al., 2016); and the use of genomic data and gene-editing technology to identify and alter regions of the genome that may impact fitness and limit survival in endangered taxa (Taylor & Gemmell, 2016). Here, we extend that the theme with additional discussion on how genome-editing technologies can benefit the conservation of threatened and endangered species

Is there a future for genome-editing technologies in conservation?

In a recent review, Pimm et al. (2015) highlight emerging technologies in protecting biodiversity. While their list is noteworthy, the authors’ exclusion of innovations in genomic research, with the exception of single-species DNA barcoding methods, was surprising given recent advances in genome-editing technology and its potential application to conservation. Taylor & Gemmell (2016) address that deficiency in a subsequent commentary identifying three avenues where emerging genomic technologies have great potential for increasing our ability to conserve biodiversity. Those areas include the use of next-generation sequencing technologies and methods such as RADseq for monitoring genetic diversity, effective population size, and introgression (Andrews et al., 2016); the use of environmental DNA (eDNA) and metabarcoding approaches to map species occurrence and interaction networks (Evans et al., 2016); and the use of genomic data and gene-editing technology to identify and alter regions of the genome that may impact fitness and limit survival in endangered taxa (Taylor & Gemmell, 2016). Here, we extend that the theme with additional discussion on how genome-editing technologies can benefit the conservation of threatened and endangered species

A multidomain hub anchors the chromosome segregation and chemotactic machinery to the bacterial pole

The cell poles constitute key subcellular domains that are often critical for motility, chemotaxis, and chromosome segregation in rod-shaped bacteria. However, in nearly all rods, the processes that underlie the formation, recognition, and perpetuation of the polar domains are largely unknown. Here, in Vibrio cholerae, we identified HubP (hub of the pole), a polar transmembrane protein conserved in all vibrios, that anchors three ParA-like ATPases to the cell poles and, through them, controls polar localization of the chromosome origin, the chemotactic machinery, and the flagellum. In the absence of HubP, oriCI is not targeted to the cell poles, chemotaxis is impaired, and a small but increased fraction of cells produces multiple, rather than single, flagella. Distinct cytoplasmic domains within HubP are required for polar targeting of the three ATPases, while a periplasmic portion of HubP is required for its localization. HubP partially relocalizes from the poles to the mid-cell prior to cell division, thereby enabling perpetuation of the polar domain in future daughter cells. Thus, a single polar hub is instrumental for establishing polar identity and organization