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991.
Franz-Joachim Kaiser Niels Bassler Oliver Jäkel 《Radiation and environmental biophysics》2010,49(3):365-371
Modern radiotherapy facilities for cancer treatment such as the Heavy Ion Therapy Center (HIT) in Heidelberg, Germany, allow
for sub-millimeter precision in dose deposition. For measurement of such dose distributions and characterization of the particle
beams, detectors with high spatial resolution are necessary. Here, a detector based on the commercially available COTS photodiode
(BPW-34) is presented. When applied in hadronic beams of protons and carbon ions, the detector reproduces dose distribution
well, but its response decreases rapidly by radiation damage. However, for MeV photon beams, the detector exhibits a similar
behavior as found in diode detectors usually applied in radiotherapy. 相似文献
992.
Brian E. Oliver 《Dialectical Anthropology》2010,34(4):447-451
While America has increasingly become known for having a higher rate of persons in prison or under correctional supervision than any other country in the world; over the last two decades, new laws have begun emerging in America, placing restrictions on former offenders long after their correctional supervision has ended. These laws directly impact the lives of millions of ex-offenders who are no longer under correctional supervision, placing restrictions on where they may live, work and travel. The following essay, by a former offender who discharged parole in December 2000, highlights the punitive and destructive nature of these laws. 相似文献
993.
Yacine Hemar Li Jiang Cheng Christine M. Oliver Luz Sanguansri Maryann Augustin 《Food biophysics》2010,5(2):120-127
The suitability of water-in-oil-in-water multiple emulsions to encapsulate resveratrol was assessed. Multiple emulsions were
prepared by emulsifying a primary emulsion (40 wt.%) in water containing 0.5 wt.% sodium caseinate and 0.1 M NaCl. Four primary
emulsions of canola oil (20 wt.%) stabilized by 8 wt.% polyglycerol polyricinoleate were chosen. The dispersed phase of the
primary emulsions contained 0.1 M NaCl and either water, 20 wt.% ethanol in water, 2.5 wt.% whey protein isolate (WPI) in
water, or 2.5 wt.% WPI and 5 wt.% gelatine in water. Resveratrol was incorporated into these primary emulsions at 0.25 wt.%
to give a final 0.02 wt.% resveratrol in the multiple emulsions. Slight increase in particle size with storage at 23 °C for
up to 2 weeks was observed. Further, less than 10% of the total encapsulated resveratrol is released to the external, continuous,
aqueous phase. This work demonstrates the potential of multiple emulsions to encapsulate resveratrol for food applications. 相似文献
994.
Oliver Q. Whaley David G. Beresford-Jones William Milliken Alfonso Orellana Anna Smyk Joaquín Leguía 《Kew Bulletin》2010,65(4):613-641
The dry forest of the Peruvian south coast has undergone an almost total process of deforestation. Populations here have increased
exponentially through immigration supplying labour to urban coastal development, and demonstrably unsustainable agro-industrial
expansion for export markets. Society has become dislocated from local traditions of environmental and resource management
whilst still retaining a wealth of Andean agricultural expertise. Indigenous communities still hold on to vestiges of traditional
knowledge. Relicts of natural vegetation, traditional agriculture and agrobiodiversity continue to sustain ecosystem services.
Moreover, offer livelihood options and resources for restoration. These aspects reflect a long cultural trajectory, including
famous extinct cultures such as Nasca, that evolved within an ever-changing riparian and agricultural landscape influenced
by external forces and which incorporated important processes of plant domestication and adaptation to climatic oscillation. 相似文献
995.
Requirements for Construction of a Functional Hybrid Complex of Photosystem I and [NiFe]-Hydrogenase
Alexander Schwarze Marta J. Kopczak Matthias R?gner Oliver Lenz 《Applied and environmental microbiology》2010,76(8):2641-2651
The development of cellular systems in which the enzyme hydrogenase is efficiently coupled to the oxygenic photosynthesis apparatus represents an attractive avenue to produce H2 sustainably from light and water. Here we describe the molecular design of the individual components required for the direct coupling of the O2-tolerant membrane-bound hydrogenase (MBH) from Ralstonia eutropha H16 to the acceptor site of photosystem I (PS I) from Synechocystis sp. PCC 6803. By genetic engineering, the peripheral subunit PsaE of PS I was fused to the MBH, and the resulting hybrid protein was purified from R. eutropha to apparent homogeneity via two independent affinity chromatographical steps. The catalytically active MBH-PsaE (MBHPsaE) hybrid protein could be isolated only from the cytoplasmic fraction. This was surprising, since the MBH is a substrate of the twin-arginine translocation system and was expected to reside in the periplasm. We conclude that the attachment of the additional PsaE domain to the small, electron-transferring subunit of the MBH completely abolished the export competence of the protein. Activity measurements revealed that the H2 production capacity of the purified MBHPsaE fusion protein was very similar to that of wild-type MBH. In order to analyze the specific interaction of MBHPsaE with PS I, His-tagged PS I lacking the PsaE subunit was purified via Ni-nitrilotriacetic acid affinity and subsequent hydrophobic interaction chromatography. Formation of PS I-hydrogenase supercomplexes was demonstrated by blue native gel electrophoresis. The results indicate a vital prerequisite for the quantitative analysis of the MBHPsaE-PS I complex formation and its light-driven H2 production capacity by means of spectroelectrochemistry.Molecular hydrogen (H2) is often discussed as an alternative source of energy (13, 22, 26, 41). It is a highly energetic, renewable, and zero-carbon dioxide emission fuel; however, it is produced mainly from fossil resources. One intriguing possibility for sustainable H2 production is the development of cellular systems in which the light-driven oxygenic photosynthesis is efficiently coupled to hydrogen production by hydrogenase (1, 21, 36).During the process of oxygenic photosynthesis, photosystem II (PS II), a thylakoid membrane (TM)-embedded multiprotein complex, utilizes solar energy to oxidize water into dioxygen (O2), protons, and electrons. The electrons released by PS II are further conducted through an electron transport chain consisting of plastoquinones, the cytochrome b6f complex, and either plastocyanin or cytochrome c6 to the chlorophyll (Chl) dimer P700 in photosystem I (PS I) (20, 48). During light-induced charge separation in PS I, P700 is oxidized, leading to the reduction of the adjacent cofactor A0 (Chl a). From there, the electrons are transmitted to the phylloquinone A1 and subsequently to the Fe4S4 clusters FX, FA, and FB (9) that are located at the acceptor site of PS I. The acceptor site is composed of the PsaC subunit, which harbors the iron-sulfur clusters FA and FB, and the two additional cofactor-free extrinsic subunits PsaD and PsaE. In the final step, the electrons are transferred from FB to the ferredoxin (PetF), which has a midpoint potential of −412 mV (see Fig. Fig.1B)1B) (8, 9).Open in a separate windowFIG. 1.Models of the hydrogenase and photosystem I complexes used in this study. (A) Membrane-bound hydrogenase (MBHwt) of Ralstonia eutropha H16. (B) Wild-type photosystem I (PS I) from Synechocystis sp. PCC 6803. (C) MBHstop protein lacking the C-terminal anchor domain of HoxK. (D) MBHPsaE and PS IΔPsaE.Hydrogenases of the NiFe and FeFe types catalyze the reversible cleavage of H2 into protons and electrons (18, 63). For most hydrogenases, this reaction is highly sensitive to O2 and leads to the reversible or even irreversible inactivation of the enzyme (49, 66, 67). A prominent exception is the oxygen-tolerant membrane-bound [NiFe]-hydrogenase (MBH) from Ralstonia eutropha H16, which catalyzes H2 conversion in the presence of O2 (42, 65). The MBH consists of large subunit HoxG (67 kDa), harboring the NiFe active site, and small subunit HoxK (35 kDa), bearing three FeS clusters (Fig. (Fig.1)1) (32). Both cofactor-containing subunits are completely assembled within the cytoplasm and become subsequently translocated through the cytoplasmic membrane by the twin-arginine translocation (Tat) system. This transport is guided by a specific Tat signal peptide that is located at the N terminus of small subunit HoxK (53). The MBH is then connected to the membrane via the hydrophobic C-terminal “anchor” domain of HoxK, which provides the electronic connection to the diheme cytochrome b, HoxZ (5, 57). All structural, accessory, and regulatory genes for the synthesis of active MBH are arranged in a large, megaplasmid-borne operon (7, 11, 14, 29, 33, 38, 58).The concept of light-driven hydrogen production has been investigated in numerous studies (for reviews, see references 3, 21, and 23), including one involving direct electron transfer from PS I to the free form of hydrogenase in vitro (45). In a preliminary attempt, the MBH from R. eutropha was recently directly fused to PsaE (creating MBHPsaE) (28). The fusion protein was partially purified and subjected to in vitro reconstitution with PS I lacking PsaE (PS IΔPsaE) (54) for light-driven hydrogen production. This concept was based on the previous observation that PS I lacking the peripheral subunit PsaE is fully reconstituted in vitro simply by the addition of independently purified PsaE protein (12).In the present communication, we describe a novel purification procedure for R. eutropha MBHPsaE that yields homogeneous, functionally active MBHPsaE. Additionally, a new method for efficient and fast purification of Synechocystis sp. PCC 6803 (hereafter referred to as Synechocystis) His-tagged PS I was established. Finally, the pure proteins MBHPsaE and PS IΔPsaE were successfully subjected to in vitro reconstitution. 相似文献
996.
997.
Kitti Mueangtoom Roman Kittl Oliver Mann Dietmar Haltrich Roland Ludwig Dr. 《Biotechnology journal》2010,5(8):857-870
In a screening of saprotrophic, ectomycorrhizal and plant pathogen ascomycetes a frequent occurrence of laccase was observed. Lamprospora wrightii, the best producing organism, was chosen to elucidate the properties of a laccase from a moss-associated, saprotrophic ascomycete. The expression of laccase by this bryophilic fungus could be increased by the addition of tomato juice or copper sulfate to the medium. The obtained volumetric activity after optimization was 420 U/mL in either shaking flask or bioreactor-based cultivations. The purified laccase has a molecular mass of 68 kDa and an isoelectric point of 3.4. Although of ascomycete origin, its catalytic properties are similar to typical basidiomycte laccases, and an excellent activity and stability was observed at low pH, which makes it suitable for bioremediation in acidic environments. As an example, the decolorization reactions of azo-, anthraquinone-, trimethylmethane- and indigoid dyes at pH 3.0 and 5.0 were investigated. All ten selected dyes were decolorized, five of them very efficiently. Depending on the dye, the decolorization was found to be a combination of two reactions, degradation of the chromophore and formation of polymerized products, which contributed to the overall process in a dye-specific pattern. 相似文献
998.
Clara Salaheddin Yoshimitsu Takakura Masako Tsunashima Barbara Stranzinger Oliver Spadiut Montarop Yamabhai Clemens K Peterbauer Dietmar Haltrich 《Microbial cell factories》2010,9(1):57
Background
The flavin-dependent enzyme pyranose 2-oxidase (P2Ox) has gained increased attention during the last years because of a number of attractive applications for this enzyme. P2Ox is a unique biocatalyst with high potential for biotransformations of carbohydrates and in synthetic carbohydrate chemistry. Recently, it was shown that P2Ox is useful as bioelement in biofuel cells, replacing glucose oxidase (GOx), which traditionally is used in these applications. P2Ox offers several advantages over GOx for this application, e.g., its much broader substrate specificity. Because of this renewed interest in P2Ox, knowledge on novel pyranose oxidases isolated from organisms other than white-rot fungi, which represent the traditional source of this enzyme, is of importance, as these novel enzymes might differ in their biochemical and physical properties. 相似文献999.
1000.
Jeffrey A. Anderson Li-Hua Ping Oliver Dibben Cassandra B. Jabara Leslie Arney Laura Kincer Yuyang Tang Marcia Hobbs Irving Hoffman Peter Kazembe Corbin D. Jones Persephone Borrow Susan Fiscus Myron S. Cohen Ronald Swanstrom and the Center for HIV/AIDS Vaccine Immunology 《PLoS pathogens》2010,6(8)
HIV-1 is present in anatomical compartments and bodily fluids. Most transmissions occur through sexual acts, making virus in semen the proximal source in male donors. We find three distinct relationships in comparing viral RNA populations between blood and semen in men with chronic HIV-1 infection, and we propose that the viral populations in semen arise by multiple mechanisms including: direct import of virus, oligoclonal amplification within the seminal tract, or compartmentalization. In addition, we find significant enrichment of six out of nineteen cytokines and chemokines in semen of both HIV-infected and uninfected men, and another seven further enriched in infected individuals. The enrichment of cytokines involved in innate immunity in the seminal tract, complemented with chemokines in infected men, creates an environment conducive to T cell activation and viral replication. These studies define different relationships between virus in blood and semen that can significantly alter the composition of the viral population at the source that is most proximal to the transmitted virus. 相似文献