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251.
Heterocapsa circularisquama RNA virus(HcRNAV) is the first single-stranded RNA virus to be characterized that infects dinoflagellates.The ability of HcRNAV coat protein(HcRNAV CP) to self-assemble into virus-like particles(VLPs) in vitro suggested that heterologous expression was possible,and that the VLPs might be ideal nanocontainers for the targeted delivery of genes and chemicals.In this paper,we report the expression of a codon-optimized HcRNAV 109 CP gene in Pichia pastoris and the production of self-assembled HcRNAV VLPs using large-scale fermentation.The HcRNAV 109 CP gene was synthesized according to the codon preference of P.pastoris and cloned into a pPICZA vector.The recombinant plasmid pPICZA-CPsyns was transformed into P.pastoris by electroporation.The resulting yeast colonies were screened by PCR and analyzed for protein expression by SDS polyacrylamide gel electrophoresis.After large-scale fermentation,the yield of HcRNAV CPsyns reached approximately 2.5 g L 1 within 4 d.The HcRNAV VLPs were purified using PEG precipitation followed by cesium chloride density gradient ultracentrifugation,and were subsequently analyzed using UV spectrophotometry and transmission electron microscopy.Fluorescence dye-labeled myoglobin was loaded into the cages of the HcRNAV VLPs and the encapsulation was confirmed by fluorescence spectroscopy.The results point to the possible utilization in pharmacology or nanotechnology of HcRNAV VLPs produced by P.pastoris fermentation. 相似文献
252.
Hydrogen is a promising energy carrier that can potentially facilitate a transition from
fossil fuels to sustainable energy sources without producing harmful by-products. Prior to realizing
a hydrogen economy, however, viable hydrogen storage materials must be developed. Physical
adsorption in porous solids provides an opportunity for hydrogen storage under low-stringency
conditions. Physically adsorbed hydrogen molecules are weakly bound to a surface and, hence, are
easily released. Among the various surface candidates, porous carbons appear to provide efficient
hydrogen storage, with the advantages that porous carbon is relatively low-cost to produce and is
easily prepared. In this review, we summarize the preparation methods, pore characteristics, and
hydrogen storage capacities of representative nanoporous carbons, including activated carbons,
zeolite-templated carbon, and carbide-derived carbon. We focus particularly on a series of
nanoporous carbons developed recently: metal–organic framework-derived carbons, which exhibit
promising properties for use in hydrogen storage applications. 相似文献
253.
Recently, a new type of Radio Frequency IDentification (RFID) system with mobile readers is introduced. In such a system, it is more desirable for mobile readers to identify tags without a back-end server, and thus it is frequently referred as a serverless mobile RFID system. In this paper, we formalize a serverless mobile RFID system model and propose a new encryption-based system that preserves the privacy of both tags and readers in the model. In addition, we define a new adversary model for the system model and show the security of the proposed system. Throughout comparisons between ours and the other alternatives, we show that our proposed system provides a stronger reader privacy and robustness against a reader forgery attack than the competitors. 相似文献
254.
Herpes simplex virus 2 (HSV-2) infection causes significant morbidity and is an important cofactor for the transmission of HIV infection. A microbicide to prevent sexual transmission of HSV-2 would contribute substantially to controlling the spread of HIV and other infections. Because RNA interference (RNAi) provides effective antiviral defence in plants and other organisms, several studies have focused on harnessing RNAi to inhibit viral infection. Here we show that vaginal instillation of small interfering RNAs (siRNAs) targeting HSV-2 protects mice from lethal infection. siRNAs mixed with lipid are efficiently taken up by epithelial and lamina propria cells and silence gene expression in the mouse vagina and ectocervix for at least nine days. Intravaginal application of siRNAs targeting the HSV-2 UL27 and UL29 genes (which encode an envelope glycoprotein and a DNA binding protein, respectively) was well tolerated, did not induce interferon-responsive genes or cause inflammation, and protected mice when administered before and/or after lethal HSV-2 challenge. These results suggest that siRNAs are attractive candidates for the active component of a microbicide designed to prevent viral infection or transmission. 相似文献
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257.
A phosphatase complex that dephosphorylates gammaH2AX regulates DNA damage checkpoint recovery 总被引:1,自引:0,他引:1
Keogh MC Kim JA Downey M Fillingham J Chowdhury D Harrison JC Onishi M Datta N Galicia S Emili A Lieberman J Shen X Buratowski S Haber JE Durocher D Greenblatt JF Krogan NJ 《Nature》2006,439(7075):497-501
One of the earliest marks of a double-strand break (DSB) in eukaryotes is serine phosphorylation of the histone variant H2AX at the carboxy-terminal SQE motif to create gammaH2AX-containing nucleosomes. Budding-yeast histone H2A is phosphorylated in a similar manner by the checkpoint kinases Tel1 and Mec1 (ref. 2; orthologous to mammalian ATM and ATR, respectively) over a 50-kilobase region surrounding the DSB. This modification is important for recruiting numerous DSB-recognition and repair factors to the break site, including DNA damage checkpoint proteins, chromatin remodellers and cohesins. Multiple mechanisms for eliminating gammaH2AX as DNA repair completes are possible, including removal by histone exchange followed potentially by degradation, or, alternatively, dephosphorylation. Here we describe a three-protein complex (HTP-C, for histone H2A phosphatase complex) containing the phosphatase Pph3 that regulates the phosphorylation status of gammaH2AX in vivo and efficiently dephosphorylates gammaH2AX in vitro. gammaH2AX is lost from chromatin surrounding a DSB independently of the HTP-C, indicating that the phosphatase targets gammaH2AX after its displacement from DNA. The dephosphorylation of gammaH2AX by the HTP-C is necessary for efficient recovery from the DNA damage checkpoint. 相似文献
258.
Zody MC Garber M Sharpe T Young SK Rowen L O'Neill K Whittaker CA Kamal M Chang JL Cuomo CA Dewar K FitzGerald MG Kodira CD Madan A Qin S Yang X Abbasi N Abouelleil A Arachchi HM Baradarani L Birditt B Bloom S Bloom T Borowsky ML Burke J Butler J Cook A DeArellano K DeCaprio D Dorris L Dors M Eichler EE Engels R Fahey J Fleetwood P Friedman C Gearin G Hall JL Hensley G Johnson E Jones C Kamat A Kaur A Locke DP Madan A Munson G Jaffe DB Lui A Macdonald P Mauceli E Naylor JW Nesbitt R Nicol R 《Nature》2006,440(7084):671-675
Here we present a finished sequence of human chromosome 15, together with a high-quality gene catalogue. As chromosome 15 is one of seven human chromosomes with a high rate of segmental duplication, we have carried out a detailed analysis of the duplication structure of the chromosome. Segmental duplications in chromosome 15 are largely clustered in two regions, on proximal and distal 15q; the proximal region is notable because recombination among the segmental duplications can result in deletions causing Prader-Willi and Angelman syndromes. Sequence analysis shows that the proximal and distal regions of 15q share extensive ancient similarity. Using a simple approach, we have been able to reconstruct many of the events by which the current duplication structure arose. We find that most of the intrachromosomal duplications seem to share a common ancestry. Finally, we demonstrate that some remaining gaps in the genome sequence are probably due to structural polymorphisms between haplotypes; this may explain a significant fraction of the gaps remaining in the human genome. 相似文献
259.
Environmental and genetic aberrations lead to neural tube closure defects (NTDs) in 1 out of every 1,000 births. Mouse and frog models for these birth defects have indicated that Van Gogh-like 2 (Vangl2, also known as Strabismus) and other components of planar cell polarity (PCP) signalling might control neurulation by promoting the convergence of neural progenitors to the midline. Here we show a novel role for PCP signalling during neurulation in zebrafish. We demonstrate that non-canonical Wnt/PCP signalling polarizes neural progenitors along the anteroposterior axis. This polarity is transiently lost during cell division in the neural keel but is re-established as daughter cells reintegrate into the neuroepithelium. Loss of zebrafish Vangl2 (in trilobite mutants) abolishes the polarization of neural keel cells, disrupts re-intercalation of daughter cells into the neuroepithelium, and results in ectopic neural progenitor accumulations and NTDs. Remarkably, blocking cell division leads to rescue of trilobite neural tube morphogenesis despite persistent defects in convergence and extension. These results reveal a function for PCP signalling in coupling cell division and morphogenesis at neurulation and indicate a previously unrecognized mechanism that might underlie NTDs. 相似文献
260.
The sensing of reactive oxygen species is essential for cellular responses to oxidative stress. The sensing of peroxides is typically mediated by redox-active cysteines in sensors such as the bacterial OxyR, OhrR, and Hsp33 proteins. Bacillus subtilis PerR is the prototype for a widespread family of metal-dependent peroxide sensors that regulate inducible peroxide-defence genes. Here we show that PerR senses peroxides by metal-catalysed oxidation. PerR contains two metal-binding sites: a structural Zn2+ site and a regulatory divalent metal ion site that preferentially binds Fe2+ or Mn2+ (ref. 5). Protein oxidation, catalysed by a bound ferrous ion, leads to the rapid and direct incorporation of one oxygen atom into histidine 37 (H37) or H91, two of the residues that coordinate the bound Fe2+. This mechanism accounts for the ability of PerR to sense low levels of hydrogen peroxide in vivo. The reduction of hydrogen peroxide by metal ions to generate highly reactive hydroxyl radicals underlies the genotoxic effects of peroxides, and has been shown to contribute to enzyme inactivation, but has not previously been shown to provide a regulatory mechanism for peroxide sensing. 相似文献