Defects in associating systems: example of actin.

A statistical mechanical model is given for linear associating systems that contain defects, using the double-stranded actin polymer as an example. We treat the system as a one-dimensional lattice that can desorb monomers (giving defects) using grand partition function techniques. The main difference from a standard adsorption problem is that the monomer units are also responsible for the structural integrity of the lattice (polymer) and if too many desorb the polymer will be broken. We use literature data to estimate the density of defects in the actin polymer.     

Maximum-entropy determination of self-association distribution functions; daunorubicin and ATP.

In the present paper we show how one can use the perturbation of some molecular optical property (for example circular dichroism or chemical shift) as a function of concentration to construct cluster distribution functions describing the self-association of molecules in solution. The optical data are first converted into data giving the variation of the average extent of clustering as a function of the total concentration and then, using straightforward thermodynamics, a set of moments of the cluster distribution function can be obtained. Utilizing the maximum-entropy method, the moments are then used to calculate approximate distribution functions, where the more moments that are used the better the approximation obtained. Given the probability distribution for clusters of different sizes one can then calculate the equilibrium constant for each stage of association. Thus one converts average degree of association into equilibrium constants without having to use any specific model. By this method one can clearly tell whether the equilibrium constants remain constant, increase, or decrease with the number of molecules in a cluster. We apply the method to literature data for two systems, namely daunorubicin, which has a strong tendency to cluster in solution, and Mg(ATP)(2-) which forms weaker clusters. We find that the successive equilibrium constants for adding a monomer to a cluster are approximately constant for daunorubicin but clearly decrease as a function of increasing cluster size for Mg(ATP)(2-).     

Photoaffinity labeling of the Ah receptor

A series of halodibenzo-p-dioxins with the photolabile aryl azide functional group were synthesized and screened as potential photoaffinity labels for the Ah receptor, and 2-azido-3-iodo-7,8-dibromodibenzo-p-dioxin was selected for radiosynthesis with 125I (specific activity 2176 Ci/mmol, equilibrium dissociation constant, KD = 0.76 nM). Following incubation of this 125I-labeled photoaffinity ligand with the protamine sulfate-precipitated fraction of C57BL/6J mouse liver cytosol, and irradiation with long wavelength ultraviolet light, the radiolabeled macromolecules were precipitated with acetone and analyzed by denaturing gel electrophoresis and autoradiography. Among the labeled products, two peptides with apparent molecular masses of 95,000 and 70,000 daltons had the following properties: 1) they were selectively labeled at low ligand concentrations; 2) they were labeled in approximately a 1:1 ratio; 3) co-incubation with receptor agonists inhibited the photoaffinity labeling of both peptides to a similar extent, and structure activity relationship for inhibition of labeling by these agonists corresponded to that for their binding affinity to the Ah receptor; 4) upon nondenaturing chromatographic separation of photoaffinity labeled cytosol on high performance liquid chromatography size exclusion and anion exchange columns, the 95- and 70-kDa peptides coelute; 5) the migration of these peptides upon denaturing electrophoresis is the same in the presence or absence of a thiol reducing agent; and 6) proteolysis of the 95- and 70-kDa peptides produces a similar pattern of cleavage peptides. The simplest structure of the Ah receptor in mouse liver cytosol, appears to be a dimer composed of two noncovalently linked subunits of apparent molecular masses of 95 and 70 kDa, which have homologous structure and similar ligand binding sites, but other possibilities are discussed.     

眼小叶蝉属和东半球眼小叶蝉族评述：（头喙亚目,叶蝉科,小叶蝉亚科）

本文首先根据眼小叶蝉族Alebrini讨论翅的命名,接着是眼小叶蝉属Alebra Fieb.和东半球眼小叶蝉族各属的评论。Homa elongata Kato移入属AsialebraDwor.,Shaddai distanti Dwor.是S.typicus Dist.的异名。描述了6个新种,即Sobralacapreola,S.clara,Orientalebra drawidana,Afralebra melichari,A.youngi,A.paolii. 本文引言部分讨论小叶蝉亚科Typhlocybinae翅的形态学,正文为分类部分。 在描述内部构造以及端节、头、和胸部背面时,使用习惯术语。 新种模式标本系列保存于下列博物馆中;正模的保管者在有关描述中最先提到: SMTD——德国得累斯顿,国家动物学博物馆。 BMNH——英国伦敦,英国自然历史博物馆。 USNM——美国华盛顿,美国国家博物馆。 MM——捷克斯洛伐克Brno,Moravian博物馆。     

Shape-Related Toxicity of Titanium Dioxide Nanofibres

Titanium dioxide (TiO₂) nanofibres are a novel fibrous nanomaterial with increasing applications in a variety of fields. While the biological effects of TiO₂ nanoparticles have been extensively studied, the toxicological characterization of TiO₂ nanofibres is far from being complete. In this study, we evaluated the toxicity of commercially available anatase TiO₂ nanofibres using TiO₂ nanoparticles (NP) and crocidolite asbestos as non-fibrous or fibrous benchmark materials. The evaluated endpoints were cell viability, haemolysis, macrophage activation, trans-epithelial electrical resistance (an indicator of the epithelial barrier competence), ROS production and oxidative stress as well as the morphology of exposed cells. The results showed that TiO₂ nanofibres caused a cell-specific, dose-dependent decrease of cell viability, with larger effects on alveolar epithelial cells than on macrophages. The observed effects were comparable to those of crocidolite, while TiO₂ NP did not decrease cell viability. TiO₂ nanofibres were also found endowed with a marked haemolytic activity, at levels significantly higher than those observed with TiO₂ nanoparticles or crocidolite. Moreover, TiO₂ nanofibres and crocidolite, but not TiO₂ nanoparticles, caused a significant decrease of the trans-epithelial electrical resistance of airway cell monolayers. SEM images demonstrated that the interaction with nanofibres and crocidolite caused cell shape perturbation with the longest fibres incompletely or not phagocytosed. The expression of several pro-inflammatory markers, such as NO production and the induction of Nos2 and Ptgs2, was significantly increased by TiO₂ nanofibres, as well as by TiO₂ nanoparticles and crocidolite. This study indicates that TiO₂ nanofibres had significant toxic effects and, for most endpoints with the exception of pro-inflammatory changes, are more bio-active than TiO₂ nanoparticles, showing the relevance of shape in determining the toxicity of nanomaterials. Given that several toxic effects of TiO₂ nanofibres appear comparable to those observed with crocidolite, the possibility that they exert length dependent toxicity in vivo seems worthy of further investigation.     

Using Genotyping-By-Sequencing (GBS) for Genomic Discovery in Cultivated Oat

Advances in next-generation sequencing offer high-throughput and cost-effective genotyping alternatives, including genotyping-by-sequencing (GBS). Results have shown that this methodology is efficient for genotyping a variety of species, including those with complex genomes. To assess the utility of GBS in cultivated hexaploid oat (Avena sativa L.), seven bi-parental mapping populations and diverse inbred lines from breeding programs around the world were studied. We examined technical factors that influence GBS SNP calls, established a workflow that combines two bioinformatics pipelines for GBS SNP calling, and provided a nomenclature for oat GBS loci. The high-throughput GBS system enabled us to place 45,117 loci on an oat consensus map, thus establishing a positional reference for further genomic studies. Using the diversity lines, we estimated that a minimum density of one marker per 2 to 2.8 cM would be required for genome-wide association studies (GWAS), and GBS markers met this density requirement in most chromosome regions. We also demonstrated the utility of GBS in additional diagnostic applications related to oat breeding. We conclude that GBS is a powerful and useful approach, which will have many additional applications in oat breeding and genomic studies.     

A whole-genome shotgun approach for assembling and anchoring the hexaploid bread wheat genome

Polyploid species have long been thought to be recalcitrant to whole-genome assembly. By combining high-throughput sequencing, recent developments in parallel computing, and genetic mapping, we derive, de novo, a sequence assembly representing 9.1 Gbp of the highly repetitive 16 Gbp genome of hexaploid wheat, Triticum aestivum, and assign 7.1 Gb of this assembly to chromosomal locations. The genome representation and accuracy of our assembly is comparable or even exceeds that of a chromosome-by-chromosome shotgun assembly. Our assembly and mapping strategy uses only short read sequencing technology and is applicable to any species where it is possible to construct a mapping population.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-015-0582-8) contains supplementary material, which is available to authorized users.     

Submergence of black ash logs to control emerald ash borer and preserve wood for American Indian basketmaking

相似文献   

Environmental symbiont acquisition may not be the solution to warming seas for reef-building corals

Background

Coral reefs worldwide are in decline. Much of the mortality can be attributed to coral bleaching (loss of the coral''s intracellular photosynthetic algal symbiont) associated with global warming. How corals will respond to increasing oceanic temperatures has been an area of extensive study and debate. Recovery after a bleaching event is dependent on regaining symbionts, but the source of repopulating symbionts is poorly understood. Possibilities include recovery from the proliferation of endogenous symbionts or recovery by uptake of exogenous stress-tolerant symbionts.

Methodology/Principal Findings

To test one of these possibilities, the ability of corals to acquire exogenous symbionts, bleached colonies of Porites divaricata were exposed to symbiont types not normally found within this coral and symbiont acquisition was monitored. After three weeks exposure to exogenous symbionts, these novel symbionts were detected in some of the recovering corals, providing the first experimental evidence that scleractinian corals are capable of temporarily acquiring symbionts from the water column after bleaching. However, the acquisition was transient, indicating that the new symbioses were unstable. Only those symbiont types present before bleaching were stable upon recovery, demonstrating that recovery was from the resident in situ symbiont populations.

Conclusions/Significance

These findings suggest that some corals do not have the ability to adjust to climate warming by acquiring and maintaining exogenous, more stress-tolerant symbionts. This has serious ramifications for the success of coral reefs and surrounding ecosystems and suggests that unless actions are taken to reverse it, climate change will lead to decreases in biodiversity and a loss of coral reefs.     

Dose-dependent effects of DDAVP on memory in healthy young adult males: a preliminary study

Although several studies have demonstrated the efficacy of the vasopressin analog DDAVP in enhancing human memory, no previous study has reported the dose-response relationship of DDAVP to memory in healthy young adults. The present study was undertaken to explore the dose-response curve for DDAVP on recall of implicational sentences. Five doses of DDAVP (0, 5, 15, 30, and 60 micrograms) were administered intranasally to healthy young adult male volunteers. Results demonstrated a facilitation in cued recall after treatment with the 60-micrograms dose and a general impairment in recall after treatment with the 15-micrograms dose. These effects were independent of subject's weight, vocabulary ability, and concentration of salivary cortisol.