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Sample records for recombinant luminescent bacterial

  1. A suite of recombinant luminescent bacterial strains for the quantification of bioavailable heavy metals and toxicity testing

    PubMed Central

    2009-01-01

    Background Recombinant whole-cell sensors have already proven useful in the assessment of the bioavailability of environmental pollutants like heavy metals and organic compounds. In this work 19 recombinant bacterial strains representing various Gram-positive (Staphylococcus aureus and Bacillus subtilis) and Gram-negative (Escherichia coli, Pseudomonas fluorescens) bacteria were constructed to express the luminescence encoding genes luxCDABE (from Photorhabdus luminescens) as a response to bioavailable heavy metals ("lights-on" metal sensors containing metal-response elements, 13 strains) or in a constitutive manner ("lights-off" constructs, 6 strains). Results The bioluminescence of all 13 "lights-on" metal sensor strains was expressed as a function of the sub-toxic metal concentrations enabling the quantitative determination of metals bioavailable for these strains. Five sensor strains, constructed for detecting copper and mercury, proved to be target metal specific, whereas eight other sensor strains were simultaneously induced by Cd2+, Hg2+, Zn2+and Pb2+. The lowest limits of determination of the "lights-on" sensor strains for the metals tested in this study were (μg l-1): 0.002 of CH3HgCl, 0.03 of HgCl2, 1.8 of CdCl2, 33 of Pb(NO3)2, 1626 of ZnSO4, 24 of CuSO4 and 340 of AgNO3. In general, the sensitivity of the "lights-on" sensor strains was mostly dependent on the metal-response element used while the selection of host bacterium played a relatively minor role. In contrast, toxicity of metals to the "lights-off" strains was only dependent on the bacterial host so that Gram-positive strains were remarkably more sensitive than Gram-negative ones. Conclusion The constructed battery of 19 recombinant luminescent bacterial strains exhibits several novel aspects as it contains i) metal sensor strains with similar metal-response elements in different host bacteria; ii) metal sensor strains with metal-response elements in different copies and iii) a "lights

  2. Bacterial Recombineering: Genome Engineering via Phage-Based Homologous Recombination.

    PubMed

    Pines, Gur; Freed, Emily F; Winkler, James D; Gill, Ryan T

    2015-11-20

    The ability to specifically modify bacterial genomes in a precise and efficient manner is highly desired in various fields, ranging from molecular genetics to metabolic engineering and synthetic biology. Much has changed from the initial realization that phage-derived genes may be employed for such tasks to today, where recombineering enables complex genetic edits within a genome or a population. Here, we review the major developments leading to recombineering becoming the method of choice for in situ bacterial genome editing while highlighting the various applications of recombineering in pushing the boundaries of synthetic biology. We also present the current understanding of the mechanism of recombineering. Finally, we discuss in detail issues surrounding recombineering efficiency and future directions for recombineering-based genome editing. PMID:25856528

  3. Application of internal standard method in recombinant luminescent bacteria test.

    PubMed

    Wang, Yong-Zhi; Li, Dan; He, Miao

    2015-09-01

    Mercury and its organic compounds have been of severe concern worldwide due to their damage to the ecosystem and human health. The development of effective and affordable technology to monitor and signal the presence of bioavailable mercury is an urgent need. The Mer gene is a mercury-responsive resistant gene, and a mercury-sensing recombinant luminescent bacterium using the Mer gene was constructed in this study. The mer operon from marine Pseudomonas putida strain SP1 was amplified and fused with prompterless luxCDABE in the pUCD615 plasmid within Escherichia coli cells, resulting in pTHE30-E. coli. The recombinant strain showed high sensitivity and specificity. The detection limit of Hg(2+) was 5nmol/L, and distinct luminescence could be detected in 30min. Cd(2+), Cu(2+), Zn(2+), Ca(2+), Pb(2+), Mg(2+), Mn(2+), and Al(3+) did not interfere with the detection over a range of 10(-5)-1mM. Application of recombinant luminescent bacteria testing in environmental samples has been a controversial issue: especially for metal-sensing recombinant strains, false negatives caused by high cytotoxicity are one of the most important issues when applying recombinant luminescent bacteria in biomonitoring of heavy metals. In this study, by establishing an internal standard approach, the false negative problem was overcome; furthermore, the method can also help to estimate the suspected mercury concentration, which ensures high detection sensitivity of bioavailable Hg(2+). PMID:26354701

  4. Bacterial genome remodeling through bacteriophage recombination.

    PubMed

    Menouni, Rachid; Hutinet, Geoffrey; Petit, Marie-Agnès; Ansaldi, Mireille

    2015-01-01

    Bacteriophages co-exist and co-evolve with their hosts in natural environments. Virulent phages lyse infected cells through lytic cycles, whereas temperate phages often remain dormant and can undergo lysogenic or lytic cycles. In their lysogenic state, prophages are actually part of the host genome and replicate passively in rhythm with host division. However, prophages are far from being passive residents: they can modify or bring new properties to their host. In this review, we focus on two important phage-encoded recombination mechanisms, i.e. site-specific recombination and homologous recombination, and how they remodel bacterial genomes. PMID:25790500

  5. [Homologous recombination among bacterial genomes: the measurement and identification].

    PubMed

    Xianwei, Yang; Ruifu, Yang; Yujun, Cui

    2016-02-01

    Homologous recombination is one of important sources in shaping the bacterial population diversity, which disrupts the clonal relationship among different lineages through horizontal transferring of DNA-segments. As consequence of blurring the vertical inheritance signals, the homologous recombination raises difficulties in phylogenetic analysis and reconstruction of population structure. Here we discuss the impacts of homologous recombination in inferring phylogenetic relationship among bacterial isolates, and summarize the tools and models separately used in recombination measurement and identification. We also highlight the merits and drawbacks of various approaches, aiming to assist in the practical application for the analysis of homologous recombination in bacterial evolution research. PMID:26907777

  6. Surface Bacterial-Spore Assay Using Tb3+/DPA Luminescence

    NASA Technical Reports Server (NTRS)

    Ponce, Adrian

    2007-01-01

    Equipment and a method for rapidly assaying solid surfaces for contamination by bacterial spores are undergoing development. The method would yield a total (nonviable plus viable) spore count of a surface within minutes and a viable-spore count in about one hour. In this method, spores would be collected from a surface by use of a transparent polymeric tape coated on one side with a polymeric adhesive that would be permeated with one or more reagent(s) for detection of spores by use of visible luminescence. The sticky side of the tape would be pressed against a surface to be assayed, then the tape with captured spores would be placed in a reader that illuminates the sample with ultraviolet light and counts the green luminescence spots under a microscope to quantify the number of bacterial spores per unit area. The visible luminescence spots seen through the microscope would be counted to determine the concentration of spores on the surface. This method is based on the chemical and physical principles of methods described in several prior NASA Tech Briefs articles, including Live/Dead Spore Assay Using DPA-Triggered Tb Luminescence (NPO-30444), Vol. 27, No. 3 (March 2003), page 7a. To recapitulate: The basic idea is to exploit the observations that (1) dipicolinic acid (DPA) is present naturally only in bacterial spores; and (2) when bound to Tb3+ ions, DPA triggers intense green luminescence of the ions under ultraviolet excitation; (3) DPA can be released from the viable spores by using L-alanine to make them germinate; and (4) by autoclaving, microwaving, or sonicating the sample, one can cause all the spores (non-viable as well as viable) to release their DPA. One candidate material for use as the adhesive in the present method is polydimethysiloxane (PDMS). In one variant of the method for obtaining counts of all (viable and nonviable) spores the PDMS would be doped with TbCl3. After collection of a sample, the spores immobilized on the sticky tape surface

  7. Evidence that the variable fluorescence in Chlorella is recombination luminescence.

    PubMed

    Mauzerall, D C

    1985-08-28

    The fluorescence lifetime of oxygen-forming photosynthetic systems as a function of closed traps has been studied by several groups using light and poisons (usually 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU)) to fix the closed trap state during the experiment. These measurements have now been carried out using light alone, by means of pump and probe laser pulses and a very efficient fast photomultiplier-digitizing system. It is found that the absolute amplitude of fast fluorescence (mean tau, approx. 0.3 ns) remains constant until over half the traps are filled. The amplitude of the slow fluorescence (tau approximately equal to 1.2 ns) increases with pump energy, and its response is best fit with a lag or finite rise-time of approx. 200 ps. This novel result is consistent with the hypothesis that the slow component of the fluorescence is actually recombination luminescence in the trap. Thus, the full trapping time, i.e., the time to form the P+I- state from an excitation in the O2 photosystem, is relatively slow. PMID:3896315

  8. A novel BOD sensor based on bacterial luminescence

    SciTech Connect

    Hyun, Changkee; Tamiya, Eiichi; Takeuchi, Toshifumi; Karube, Isao ); Inoue, Noriuki )

    1993-05-01

    A reagent-type BOD sensor with a new principle employing a luminous bacterium, Photobacterium phosphoreum, was developed. The increased intensity of luminescence resulting from the cellular assimilation of organic compounds in wastewater was detected by a photodiode. The BOD response of the bacterial reagent could be obtained within 15 min with [plus minus] 7% error. The temperature condition for optimal BOD response was 18 to 25 C at pH 7 to 8, indicating that it is possible to measure BOD at room temperature without having to stabilize the temperature of the measuring system. For practical use, two procedures for long-term preservation of the bacterial reagent, vacuum drying method and freezing method, are suggested. The metabolic characteristics of employed luminous bacteria were investigated by comparing the BOD values for several pure organic substrates estimated by the BOD sensor with conventional 5-day BOD values. In comparison with the 5-day BOD measurement for some wastewater samples, BOD values estimated by the sensor showed comparatively good agreement with those measured by the 5-day method.

  9. [Cashmere goat bacterial artificial chromosome recombination and cell transfection system].

    PubMed

    Huang, Tian; Cao, Zhongyang; Yang, Yaohui; Cao, Gengsheng

    2016-03-01

    The Cashmere goat is mainly used to produce cashmere, which is very popular for its delicate fiber, luscious softness and natural excellent warm property. Keratin associated protein (KAP) and bone morphogenetic protein (BMP) of the Cashmere goat play an important role in the proliferation and development of cashmere fiber follicle cells. Bacterial artificial chromosome containing kap6.3, kap8.1 and bmp4 genes were used to increase the production and quality of Cashmere. First, we constructed bacterial artificial chromosomes by homology recombination. Then Tol2 transposon was inserted into bacterial artificial chromosomes that were then transfected into Cashmere goat fibroblasts by Amaxa Nucleofector technology according to the manufacture's instructions. We successfully constructed the BAC-Tol2 vectors containing target genes. Each vector contained egfp report gene with UBC promoter, Neomycin resistant gene for cell screening and two loxp elements for resistance removing after transfected into cells. The bacterial artificial chromosome-Tol2 vectors showed a high efficiency of transfection that can reach 1% to 6% with a highest efficiency of 10%. We also obtained Cashmere goat fibroblasts integrated exogenous genes (kap6.3, kap8.1 and bmp4) preparing for the clone of Cashmere goat in the future. Our research demonstrates that the insertion of Tol2 transposons into bacterial artificial chromosomes improves the transfection efficiency and accuracy of bacterial artificial chromosome error-free recombination. PMID:27349114

  10. Bioavailability of Cd, Zn and Hg in Soil to Nine Recombinant Luminescent Metal Sensor Bacteria

    PubMed Central

    Bondarenko, Olesja; Rõlova, Taisia; Kahru, Anne; Ivask, Angela

    2008-01-01

    A set of nine recombinant heavy metal-specific luminescent bacterial sensors belonging to Gram-negative (Escherichia and Pseudomonas) and Gram-positive (Staphylococcus and Bacillus) genera and containing various types of recombinant metal-response genetic elements was characterized for heavy metal bioavailability studies. All nine strains were induced by Hg and Cd and five strains also by Zn. As a lowest limit, the sensors were detecting 0.03 μg·L-1 of Hg, 2 μg·L-1 of Cd and 400 μg·L-1 of Zn. Limit of determination of the sensors depended mostly on metal-response element, whereas the toxicity of those metals towards the sensor bacteria was mostly dependent on the type of the host bacterium, with Gram-positive strains being more sensitive than Gram-negative ones. The set of sensors was used to evaluate bioavailability of Hg, Cd and Zn in spiked soils. The bioavailable fraction of Cd and Zn in soil suspension assay (2.6 – 5.1% and 0.32 – 0.61%, of the total Cd and Zn, respectively) was almost comparable for all the sensors, whereas the bioavailability of Hg was about 10-fold higher for Gram-negative sensor cells (30.5% of total Hg), compared to Gram-positive ones (3.2% of the total Hg). For Zn, the bioavailable fraction in soil-water suspensions and respective extracts was comparable (0.37 versus 0.33% of the total Zn). However, in the case of Cd, for all the sensors used and for Hg concerning only Gram-negative sensor strains, the bioavailable fraction in soil-water suspensions exceeded the water-extracted fraction about 14-fold, indicating that upon direct contact, an additional fraction of Cd and Hg was mobilized by those sensor bacteria. Thus, for robust bioavailability studies of heavy metals in soils any type of genetic metal-response elements could be used for the construction of the sensor strains. However, Gram-positive and Gram-negative senor strains should be used in parallel as the bioavailability of heavy metals to those bacterial groups may be

  11. Recombination luminescence in irradiated silicon - Effects of thermal annealing and lithium impurity.

    NASA Technical Reports Server (NTRS)

    Johnson, E. S.; Compton, W. D.

    1971-01-01

    Use of luminescence in irradiated silicon to determine the thermal stability of the defects responsible for the recombination. It is found that the defect responsible for the zero-phonon line at 0.97 eV has an annealing behavior similar to that of the divacancy and that the zero-phonon line at 0.79 eV anneals in a manner similar to the G-15 or K-center. Annealing at temperatures up to 500 C generates other defects whose luminescence is distinct from that seen previously. Addition of lithium to the material produces defects with new characteristic luminescence. Of particular importance is a defect with a level at E sub g -1.045 eV.

  12. Recombination luminescence from electron-irradiated Li-diffused Si

    NASA Technical Reports Server (NTRS)

    Johnson, E. S.; Compton, W. D.; Noonan, J. R.; Streetman, B. G.

    1973-01-01

    Lithium doping has a dramatic effect on the low-temperature photoluminescence of electron-irradiated Si. In oxigen-lean Si with Li doping, a new irradiation-dependent luminescence band between 0.75 and 1.05 eV is observed, which is dominated by a zero-phonon peak at 1.045 eV. This band is believed to be due to radiative transitions involving a Li-modified divacancy. This band is present also in oxygen-rich, Li-diffused Si and is accompanied by bands previously related to the Si-G15(K) center and the divacancy. The intensities of the Li-modified divacancy and Si-G15(K) center bands are relatively weak in the oxygen-rich material, apparently due to the formation of lithium-oxygen complexes which reduce the concentration of unassociated interstitial Li and O.

  13. Genetic manipulation of poxviruses using bacterial artificial chromosome recombineering.

    PubMed

    Cottingham, Matthew G

    2012-01-01

    Traditional methods for genetic manipulation of poxviruses rely on low-frequency natural recombination in virus-infected cells. Although these powerful systems represent the technical foundation of current knowledge and applications of poxviruses, they require long (≥ 500 bp) flanking sequences for homologous recombination, an efficient viral selection method, and burdensome, time-consuming plaque purification. The beginning of the twenty-first century has seen the application of bacterial artificial chromosome (BAC) technology to poxviruses as an alternative method for their genetic manipulation, following the invention of a long-sought-after method for deriving a BAC clone of vaccinia virus (VAC-BAC) by Arban Domi and Bernard Moss. The key advantages of the BAC system are the ease and versatility of performing genetic manipulation using bacteriophage λ Red recombination (recombineering), which requires only ∼50 bp homology arms that can be easily created by PCR, and which allows seamless mutations lacking any marker gene without having to perform transient-dominant selection. On the other hand, there are disadvantages, including the significant setup time, the risk of contamination of the cloned genome with bacterial insertion sequences, and the nontrivial issue of removal of the BAC cassette from derived viruses. These must be carefully weighed to decide whether the use of BACs will be advantageous for a particular application, making pox-BAC systems likely to complement, rather than supplant, traditional methods in most laboratories. PMID:22688760

  14. Fluorescence-PCR Assays and Isolation of Luminescent Bacterial Clones Using an Automated Plate Reader

    ERIC Educational Resources Information Center

    Crowley, Thomas E.

    2011-01-01

    The genes responsible for luminescence in various species of the marine microorganism "Photobacterium", have been used for many years as a tool by researchers and instructors. In particular, the "lux" operon of "Photobacterium fischeri" has been used by many instructors to teach recombinant DNA techniques. Two methods using an automated plate…

  15. Method bacterial endospore quantification using lanthanide dipicolinate luminescence

    NASA Technical Reports Server (NTRS)

    Ponce, Adrian (Inventor); Venkateswaran, Kasthuri J. (Inventor); Kirby, James Patrick (Inventor)

    2007-01-01

    A lanthanide is combined with a medium to be tested for endospores. The dipicolinic acid released from the endospores binds the lanthanides, which have distinctive emission (i.e., luminescence) spectra, and are detected using photoluminescence. The concentration of spores is determined by preparing a calibration curve generated from photoluminescence spectra of lanthanide complex mixed with spores of a known concentration. A lanthanide complex is used as the analysis reagent, and is comprised of lanthanide ions bound to multidentate ligands that increase the dipicolinic acid binding constant through a cooperative binding effect with respect to lanthanide chloride. The resulting combined effect of increasing the binding constant and eliminating coordinated water and multiple equilibria increase the sensitivity of the endospore assay by an estimated three to four orders of magnitude over prior art of endospore detection based on lanthanide luminescence.

  16. Donor-acceptor pair recombination luminescence from monoclinic Cu2SnS3 thin film

    NASA Astrophysics Data System (ADS)

    Aihara, Naoya; Tanaka, Kunihiko; Uchiki, Hisao; Kanai, Ayaka; Araki, Hideaki

    2015-07-01

    The defect levels in Cu2SnS3 (CTS) were investigated using photoluminescence (PL) spectroscopy. A CTS thin film was prepared on a soda-lime glass/molybdenum substrate by thermal co-evaporation and sulfurization. The crystal structure was determined to be monoclinic, and the compositional ratios of Cu/Sn and S/Metal were determined to be 1.8 and 1.2, respectively. The photon energy of the PL spectra observed from the CTS thin film was lower than that previously reported. All fitted PL peaks were associated with defect related luminescence. The PL peaks observed at 0.843 and 0.867 eV were assigned to donor-acceptor pair recombination luminescence, the thermal activation energies of which were determined to be 22.9 and 24.8 meV, respectively.

  17. Live/Dead Bacterial Spore Assay Using DPA-Triggered Tb Luminescence

    NASA Technical Reports Server (NTRS)

    Ponce, Adrian

    2003-01-01

    A method of measuring the fraction of bacterial spores in a sample that remain viable exploits DPA-triggered luminescence of Tb(3+) and is based partly on the same principles as those described earlier. Unlike prior methods for performing such live/dead assays of bacterial spores, this method does not involve counting colonies formed by cultivation (which can take days), or counting of spores under a microscope, and works whether or not bacterial spores are attached to other small particles (i.e., dust), and can be implemented on a time scale of about 20 minutes.

  18. Species Specific Bacterial Spore Detection Using Lateral-Flow Immunoassay with DPA-Triggered Tb Luminescence

    NASA Technical Reports Server (NTRS)

    Ponce, Adrian

    2003-01-01

    A method of detecting bacterial spores incorporates (1) A method of lateral-flow immunoassay in combination with (2) A method based on the luminescence of Tb3+ ions to which molecules of dipicolinic acid (DPA) released from the spores have become bound. The present combination of lateral-flow immunoassay and DPA-triggered Tb luminescence was developed as a superior alternative to a prior lateral-flow immunoassay method in which detection involves the visual observation and/or measurement of red light scattered from colloidal gold nanoparticles. The advantage of the present combination method is that it affords both (1) High selectivity for spores of the species of bacteria that one seeks to detect (a characteristic of lateral-flow immunoassay in general) and (2) Detection sensitivity much greater (by virtue of the use of DPA-triggered Tb luminescence instead of gold nanoparticles) than that of the prior lateral-flow immunoassay method

  19. A new, sensitive marine microalgal recombinant biosensor using luminescence monitoring for toxicity testing of antifouling biocides.

    PubMed

    Sanchez-Ferandin, Sophie; Leroy, Fanny; Bouget, François-Yves; Joux, Fabien

    2013-01-01

    In this study, we propose the use of the marine green alga Ostreococcus tauri, the smallest free-living eukaryotic cell known to date, as a new luminescent biosensor for toxicity testing in the environment. Diuron and Irgarol 1051, two antifouling biocides commonly encountered in coastal waters, were chosen to test this new biosensor along with two degradation products of diuron. The effects of various concentrations of the antifoulants on four genetic constructs of O. tauri (based on genes involved in photosynthesis, cell cycle, and circadian clock) were compared using 96-well culture microplates and a luminometer to automatically measure luminescence over 3 days. This was compared to growth inhibition of O. tauri wild type under the same conditions. Luminescence appeared to be more sensitive than growth inhibition as an indicator of toxicity. Cyclin-dependent kinase (CDKA), a protein involved in the cell cycle, fused to luciferase (CDKA-Luc) was found to be the most sensitive of the biosensors, allowing an accurate determination of the 50% effective concentration (EC(50)) after only 2 days (diuron, 5.65 ± 0.44 μg/liter; Irgarol 1015, 0.76 ± 0.10 μg/liter). The effects of the antifoulants on the CDKA-Luc biosensor were then compared to growth inhibition in natural marine phytoplankton. The effective concentrations of diuron and Irgarol 1051 were found to be similar, indicating that this biosensor would be suitable as a reliable ecotoxicological test. The advantage of this biosensor over cell growth inhibition testing is that the process can be easily automated and could provide a high-throughput laboratory approach to perform short-term toxicity tests. The ability to genetically transform and culture recombinant O. tauri gives it huge potential for screening many other toxic compounds. PMID:23144143

  20. Bacterial recombination promotes the evolution of multi-drug-resistance in functionally diverse populations

    PubMed Central

    Perron, Gabriel G.; Lee, Alexander E. G.; Wang, Yun; Huang, Wei E.; Barraclough, Timothy G.

    2012-01-01

    Bacterial recombination is believed to be a major factor explaining the prevalence of multi-drug-resistance (MDR) among pathogenic bacteria. Despite extensive evidence for exchange of resistance genes from retrospective sequence analyses, experimental evidence for the evolutionary benefits of bacterial recombination is scarce. We compared the evolution of MDR between populations of Acinetobacter baylyi in which we manipulated both the recombination rate and the initial diversity of strains with resistance to single drugs. In populations lacking recombination, the initial presence of multiple strains resistant to different antibiotics inhibits the evolution of MDR. However, in populations with recombination, the inhibitory effect of standing diversity is alleviated and MDR evolves rapidly. Moreover, only the presence of DNA harbouring resistance genes promotes the evolution of resistance, ruling out other proposed benefits for recombination. Together, these results provide direct evidence for the fitness benefits of bacterial recombination and show that this occurs by mitigation of functional interference between genotypes resistant to single antibiotics. Although analogous to previously described mechanisms of clonal interference among alternative beneficial mutations, our results actually highlight a different mechanism by which interactions among co-occurring strains determine the benefits of recombination for bacterial evolution. PMID:22048956

  1. Development of luminescent pH sensor films for monitoring bacterial growth through tissue

    PubMed Central

    Wang, Fenglin; Raval, Yash; Chen, Hongyu; Tzeng, Tzuen-Rong J.; DesJardins, John D.

    2014-01-01

    Although implanted medical devices (IMDs) offer many benefits, they are susceptible to bacterial colonization and infections. Such infections are difficult to treat because bacteria could form biofilms on the implant surface, which reduce antibiotics penetration and generate local dormant regions with low pH and low oxygen. In addition, these infections are hard to detect early because biofilms are often localized on the surface. Herein, an optical sensor film is developed to detect local acidosis on an implanted surface. The film contains both upconverting particles (UCPs) that serve as a light source and a pH indicator that alters the luminescence spectrum. When irradiated with 980 nm light, the UCPs produce deeply penetrating red light emission, while generating negligible autofluorescence in the tissue. The basic form of the pH indicator absorbs more of upconversion luminescence at 661 nm than at 671 nm and consequently the spectral ratio indicates pH. Implanting this pH sensor film beneath 6-7 mm of porcine tissue does not substantially affect the calibration curve because the peaks are closely spaced. Furthermore, growth of Staphylococcus epidermidis on the sensor surface causes a local pH decrease that can be detected non-invasively through the tissue. PMID:23832869

  2. Effect of concentrating and exposing the bioluminescent bacteria to the non-luminescent allo-bacterial extracellular products on their luminescence.

    PubMed

    Ravindran, J; Geetha Priya, G; Kannapiran, E

    2011-01-01

    Bioluminescence is a biochemical process occurring in many organisms. Bacterial bioluminescence has been investigated extensively that lead to many applications of such knowledge. Quorum sensing in the bioluminescent bacteria is a chemical signal process to recognize the strength of its own population to start luminescence in harmony. There is a mechanism in these bacteria to also recognize inter-species strength. When there is a higher number of these bacteria, the possibility and frequency of cell-cell physical contact will be high. In this study, the physical proximity was artificially enhanced between cells and the effect on luminescence in the concentrated cells in the normal culture medium and in the presence of other non-bacterial cell-free supernatants was investigated. The role of such physical contact in the quorum sensing in the bioluminescence is not known. Increase in the luminescence of V. fischeri when concentrated shows that the presence of physical proximity facilitates the quorum sensing for their bioluminescence. PMID:20017129

  3. Donor-acceptor pair recombination luminescence from monoclinic Cu{sub 2}SnS{sub 3} thin film

    SciTech Connect

    Aihara, Naoya; Tanaka, Kunihiko Uchiki, Hisao; Kanai, Ayaka; Araki, Hideaki

    2015-07-20

    The defect levels in Cu{sub 2}SnS{sub 3} (CTS) were investigated using photoluminescence (PL) spectroscopy. A CTS thin film was prepared on a soda-lime glass/molybdenum substrate by thermal co-evaporation and sulfurization. The crystal structure was determined to be monoclinic, and the compositional ratios of Cu/Sn and S/Metal were determined to be 1.8 and 1.2, respectively. The photon energy of the PL spectra observed from the CTS thin film was lower than that previously reported. All fitted PL peaks were associated with defect related luminescence. The PL peaks observed at 0.843 and 0.867 eV were assigned to donor-acceptor pair recombination luminescence, the thermal activation energies of which were determined to be 22.9 and 24.8 meV, respectively.

  4. The Effect of Pre-irradiation Defects on the Recombination Luminescence in Activated Crystals K2SO4

    NASA Astrophysics Data System (ADS)

    Koketai, Temirgaly; Tagayeva, Batima; Tussupbekova, Ainura; Mussenova, Elmira

    The recombinational luminescence of crystals of K2SO4-Mn2+ and K2SO4-Ni2+ is studied in the article. It is established that impurity ions form the radiation induced centers. The cause of changes of the distribution of lightsum on TSL peaks of a matrix is established. It is proposed that it is related to pre-radiation defeсts in crystals. It is established from this effect that ions of Mn2+ and Ni2+ selectively replace cations in a crystal lattice of potassium sulfate.

  5. Bacterial expression and purification of recombinant bovine Fab fragments.

    PubMed

    O'Brien, Philippa M; Maxwell, Gavin; Campo, M Saveria

    2002-02-01

    We have previously described a recombinant phagemid expression vector, pComBov, designed for the production of native sequence bovine monoclonal antibodies (mAb) generated by antibody phage display. Bovine mAb Fab fragments isolated from libraries constructed using pComBov in Escherichia coli strain XL1-Blue, which is routinely used for antibodies expressed on the surface of phage, were expressed at very low yields. Therefore, a study was undertaken to determine optimal growth conditions for maximal expression of bovine Fab fragments in E. coli. By varying the E. coli strain, and the temperature and length of the culture growth, we were able to substantially increase the yield of soluble Fab fragments. A high yield of Fab fragments was found in the culture growth medium, which enabled us to devise a rapid and simple single-step method for the purification of native (nondenatured) Fabs based on immobilized metal affinity chromatography against a six-histidine amino acid carboxyl-terminal extension of the heavy-chain constant region. Using these methods we were able to express and purify antigen-specific bovine Fab fragments from E. coli. PMID:11812221

  6. Essential bacterial helicases that counteract the toxicity of recombination proteins.

    PubMed

    Petit, Marie-Agnès; Ehrlich, Dusko

    2002-06-17

    PcrA, Rep and UvrD are three closely related bacterial helicases with a DExx signature. PcrA is encoded by Gram-positive bacteria and is essential for cell growth. Rep and UvrD are encoded by Gram-negative bacteria, and mutants lacking both helicases are also not viable. To understand the non-viability of the helicase mutants, we characterized spontaneous extragenic suppressors of a Bacillus subtilis pcrA null mutation. Here we report that one of these suppressors maps in recF and that previously isolated mutations in B.subtilis recF, recL, recO and recR, which belong to the same complementation group, all suppress the lethality of a pcrA mutation. Similarly, recF, recO or recR mutations suppress the lethality of the Escherichia coli rep uvrD double mutant. We conclude that RecFOR proteins are toxic in cells devoid of PcrA in Gram-positive bacteria, or Rep and UvrD in Gram-negative bacteria, and propose that the RecFOR proteins interfere with an essential cellular process, possibly replication, when DExx helicases PcrA, or Rep and UvrD are absent. PMID:12065426

  7. ClonalFrameML: Efficient Inference of Recombination in Whole Bacterial Genomes

    PubMed Central

    Didelot, Xavier; Wilson, Daniel J.

    2015-01-01

    Recombination is an important evolutionary force in bacteria, but it remains challenging to reconstruct the imports that occurred in the ancestry of a genomic sample. Here we present ClonalFrameML, which uses maximum likelihood inference to simultaneously detect recombination in bacterial genomes and account for it in phylogenetic reconstruction. ClonalFrameML can analyse hundreds of genomes in a matter of hours, and we demonstrate its usefulness on simulated and real datasets. We find evidence for recombination hotspots associated with mobile elements in Clostridium difficile ST6 and a previously undescribed 310kb chromosomal replacement in Staphylococcus aureus ST582. ClonalFrameML is freely available at http://clonalframeml.googlecode.com/. PMID:25675341

  8. Recombination luminescence in irradiated silicon-effects of uniaxial stress and temperature variations.

    NASA Technical Reports Server (NTRS)

    Jones, C. E.; Compton, W. D.

    1971-01-01

    Demonstration that luminescence in irradiated silicon consists of a spectral group between 0.80 and 1.0 eV which seems to be independent of impurities, while a lower energy group between 0.60 and 0.80 eV is seen only in pulled crystals. The small halfwidth and temperature dependence of the sharp zero-phonon lines observed in these spectra indicate that the luminescence arises from a bound-to-bound transition. A model is proposed for the transition mechanism. Stress data taken on the 0.79-eV zero-phonon line in pulled crystals can be fit by either a tetragonal 100 (in brackets) defect symmetry or by conduction-band splitting effects. It is suggested that the 0.79-eV zero-phonon line and the 0.60- to 0.80-eV spectral group arise from the EPR G-15 center. Stress data on a zero-phonon line at 0.97 eV associated with the 0.80- to 1.0-eV spectral group can be explained by a trigonal 111 (in brackets) defect. The divacancy is tentatively suggested as responsible for this luminescence spectra.

  9. Three R's of bacterial evolution: how replication, repair, and recombination frame the origin of species.

    PubMed

    Brown, E W; LeClerc, J E; Kotewicz, M L; Cebula, T A

    2001-01-01

    The genetic diversity of bacteria results not only from errors in DNA replication and repair but from horizontal exchange and recombination of DNA sequences from similar and disparate species as well. New individuals carrying adaptive changes are thus being spawned constantly among the population at large. When new selection pressures appear, these are the individuals that survive, at the expense of the general population, to forge new populations. Depending on the severity and uniqueness of the selection pressure, this could lead to new speciation. It is becoming more and more evident that, as nucleotide sequences of numerous loci from many bacterial strains continue to amass, horizontal transfer has played a key role in configuring the Escherichia coli chromosome. Here, we examine views, both old and new, for the role of recombination in the evolution of bacterial chromosomes. We present novel phylogenetic evidence for horizontal transfer of three genes involved in DNA replication and repair (mutS, uvrD, and polA). These data reveal a prominent role for horizontal transfer in the evolution of genes known to play a key role in the fidelity of DNA replication and, thus, ultimate survival of the organism. Our data underscore that recombination plays both a diversifying and a homogenizing role in defining the structure of the E. coli genome. PMID:11746762

  10. Rapid phylogenetic analysis of large samples of recombinant bacterial whole genome sequences using Gubbins.

    PubMed

    Croucher, Nicholas J; Page, Andrew J; Connor, Thomas R; Delaney, Aidan J; Keane, Jacqueline A; Bentley, Stephen D; Parkhill, Julian; Harris, Simon R

    2015-02-18

    The emergence of new sequencing technologies has facilitated the use of bacterial whole genome alignments for evolutionary studies and outbreak analyses. These datasets, of increasing size, often include examples of multiple different mechanisms of horizontal sequence transfer resulting in substantial alterations to prokaryotic chromosomes. The impact of these processes demands rapid and flexible approaches able to account for recombination when reconstructing isolates' recent diversification. Gubbins is an iterative algorithm that uses spatial scanning statistics to identify loci containing elevated densities of base substitutions suggestive of horizontal sequence transfer while concurrently constructing a maximum likelihood phylogeny based on the putative point mutations outside these regions of high sequence diversity. Simulations demonstrate the algorithm generates highly accurate reconstructions under realistically parameterized models of bacterial evolution, and achieves convergence in only a few hours on alignments of hundreds of bacterial genome sequences. Gubbins is appropriate for reconstructing the recent evolutionary history of a variety of haploid genotype alignments, as it makes no assumptions about the underlying mechanism of recombination. The software is freely available for download at github.com/sanger-pathogens/Gubbins, implemented in Python and C and supported on Linux and Mac OS X. PMID:25414349

  11. Rapid phylogenetic analysis of large samples of recombinant bacterial whole genome sequences using Gubbins

    PubMed Central

    Croucher, Nicholas J.; Page, Andrew J.; Connor, Thomas R.; Delaney, Aidan J.; Keane, Jacqueline A.; Bentley, Stephen D.; Parkhill, Julian; Harris, Simon R.

    2015-01-01

    The emergence of new sequencing technologies has facilitated the use of bacterial whole genome alignments for evolutionary studies and outbreak analyses. These datasets, of increasing size, often include examples of multiple different mechanisms of horizontal sequence transfer resulting in substantial alterations to prokaryotic chromosomes. The impact of these processes demands rapid and flexible approaches able to account for recombination when reconstructing isolates’ recent diversification. Gubbins is an iterative algorithm that uses spatial scanning statistics to identify loci containing elevated densities of base substitutions suggestive of horizontal sequence transfer while concurrently constructing a maximum likelihood phylogeny based on the putative point mutations outside these regions of high sequence diversity. Simulations demonstrate the algorithm generates highly accurate reconstructions under realistically parameterized models of bacterial evolution, and achieves convergence in only a few hours on alignments of hundreds of bacterial genome sequences. Gubbins is appropriate for reconstructing the recent evolutionary history of a variety of haploid genotype alignments, as it makes no assumptions about the underlying mechanism of recombination. The software is freely available for download at github.com/sanger-pathogens/Gubbins, implemented in Python and C and supported on Linux and Mac OS X. PMID:25414349

  12. [Dual promoters enhance heterologous enzyme production from bacterial phage based recombinant Bacillus subtilis].

    PubMed

    Liu, Gang; Zhang, Yan; Xing, Miao

    2006-03-01

    The effect of dual promoters on recombinant protein production from bacterial phage based Bacillus subtilis expression system was investigated. Alpha amylase (from Bacillus amyloliquefaciens) and penicillin acylase (from Bacillus megaterium) were selected as the indicating enzymes. Both the promoterless genes and the promoter-bearing genes were isolated through PCR amplification with properly designed primers, and were inserted into plasmid pSG703 that contains the lacZ-cat expression cartridge. The lysogenic B. subtilis (phi105 MU331) was transformed with the resultant recombinant plasmids, and the heterologous genes were thereby integrated into the chromosommal DNA of B. subtilis via homologous recombination. The transformants were designated as B. subtilis AMY1, B. subtilis AMY2, B. subtilis PA1, and B. subtilis PA2, respectively. In the recombinant B. subtilis strains, the inserted sequences were located down stream of a strong phage promoter that could be activated by thermal induction. In B. subtilis AMY1 and B. subtilis PA1, transcription of the heterologous genes was only initiated by the phage promoter after heat shock, whereas in B. subtilis AMY2 and B. subtilis PA2, transcription of the heterologous genes was initiated by dual promoters, the phage promoter and the native promoter. The application of dual promoters increased the productivity of both enzymes, with 133% enhancement for alpha-amylase production and 113% enhancement for penicillin acylase production. PMID:16607942

  13. Functional Expression of Recombinant Human Stefin A in Mammalian and Bacterial Cells

    PubMed Central

    Calkins, Catharine C.; Dosescu, Julie; Day, Nancy A.; Ren, Wei-Ping; Fridman, Rafael; Sloane, Bonnie F.; Moin, Kamiar

    2007-01-01

    Recombinant human cysteine protease inhibitor, stefin A, was expressed in both E. coli and BSC-1 monkey kidney cells utilizing pET and recombinant Vaccinia virus systems, respectively. The expressed protein was purified and analyzed by SDS-PAGE and western blot analysis utilizing a polyclonal antibody against rat cystatin α. In both cases the purified protein appeared as a single band corresponding to the molecular weight of stefin A (~10 kDa). Viability of the expressed stefin A was determined by the inhibition of the plant cysteine protease, papain. Recombinant human stefin A expressed in both E. coli and BSC-1 cells was shown to almost completely inhibit papain. The expression of a fully functional recombinant human stefin A in the bacterial system provides a highly efficient tool for the production of large quantities of the protein. This can be an important tool in kinetic studies as well as in production of antibodies for other analytical studies (immunoblot, immunohistochemical studies, etc.). Expression in the mammalian cells on the other hand, can provide a significant research tool to study the functional roles of stefin A in the mammalian systems such as the regulation of cysteine proteases. PMID:17208452

  14. Identification and characterization of a bacterial hyaluronidase and its production in recombinant form.

    PubMed

    Messina, Luciano; Gavira, Jose A; Pernagallo, Salvatore; Unciti-Broceta, Juan D; Sanchez Martin, Rosario M; Diaz-Mochon, Juan J; Vaccaro, Susanna; Conejero-Muriel, Mayte; Pineda-Molina, Estela; Caruso, Salvatore; Musumeci, Luca; Di Pasquale, Roberta; Pontillo, Angela; Sincinelli, Francesca; Pavan, Mauro; Secchieri, Cynthia

    2016-07-01

    Hyaluronidases (Hyals) are broadly used in medical applications to facilitate the dispersion and/or absorption of fluids or medications. This study reports the isolation, cloning, and industrial-scale recombinant production, purification and full characterization, including X-ray structure determination at 1.45 Å, of an extracellular Hyal from the nonpathogenic bacterium Streptomyces koganeiensis. The recombinant S. koganeiensis Hyal (rHyal_Sk) has a novel bacterial catalytic domain with high enzymatic activity, compared with commercially available Hyals, and is more thermostable and presents higher proteolytic resistance, with activity over a broad pH range. Moreover, rHyal_Sk exhibits remarkable substrate specificity for hyaluronic acid (HA) and poses no risk of animal cross-infection. PMID:27311405

  15. Room temperature electrocompetent bacterial cells improve DNA transformation and recombineering efficiency

    PubMed Central

    Tu, Qiang; Yin, Jia; Fu, Jun; Herrmann, Jennifer; Li, Yuezhong; Yin, Yulong; Stewart, A. Francis; Müller, Rolf; Zhang, Youming

    2016-01-01

    Bacterial competent cells are essential for cloning, construction of DNA libraries, and mutagenesis in every molecular biology laboratory. Among various transformation methods, electroporation is found to own the best transformation efficiency. Previous electroporation methods are based on washing and electroporating the bacterial cells in ice-cold condition that make them fragile and prone to death. Here we present simple temperature shift based methods that improve DNA transformation and recombineering efficiency in E. coli and several other gram-negative bacteria thereby economizing time and cost. Increased transformation efficiency of large DNA molecules is a significant advantage that might facilitate the cloning of large fragments from genomic DNA preparations and metagenomics samples. PMID:27095488

  16. Room temperature electrocompetent bacterial cells improve DNA transformation and recombineering efficiency.

    PubMed

    Tu, Qiang; Yin, Jia; Fu, Jun; Herrmann, Jennifer; Li, Yuezhong; Yin, Yulong; Stewart, A Francis; Müller, Rolf; Zhang, Youming

    2016-01-01

    Bacterial competent cells are essential for cloning, construction of DNA libraries, and mutagenesis in every molecular biology laboratory. Among various transformation methods, electroporation is found to own the best transformation efficiency. Previous electroporation methods are based on washing and electroporating the bacterial cells in ice-cold condition that make them fragile and prone to death. Here we present simple temperature shift based methods that improve DNA transformation and recombineering efficiency in E. coli and several other gram-negative bacteria thereby economizing time and cost. Increased transformation efficiency of large DNA molecules is a significant advantage that might facilitate the cloning of large fragments from genomic DNA preparations and metagenomics samples. PMID:27095488

  17. Dual Colorimetric and Luminescent Assay for Dipicolinate, a Biomarker of Bacterial Spores

    PubMed Central

    Clear, Kasey J.; Stroud, Sarah

    2013-01-01

    A binary mixture of Tb3+ and pyrocatechol violet (PV) forms a 1:1 Tb3+/PV complex that can be used in a dye displacement assay. Addition of dipicolinate (DPA) to the Tb3+/DPA complex simultaneously produces a PV color change from blue to yellow and luminescence emission from the newly formed Tb3+/DPA complex. PMID:24106737

  18. Genome-wide survey of codons under diversifying selection in a highly recombining bacterial species, Helicobacter pylori

    PubMed Central

    Yahara, Koji; Furuta, Yoshikazu; Morimoto, Shinpei; Kikutake, Chie; Komukai, Sho; Matelska, Dorota; Dunin-Horkawicz, Stanisław; Bujnicki, Janusz M.; Uchiyama, Ikuo; Kobayashi, Ichizo

    2016-01-01

    Selection has been a central issue in biology in eukaryotes as well as prokaryotes. Inference of selection in recombining bacterial species, compared with clonal ones, has been a challenge. It is not known how codons under diversifying selection are distributed along the chromosome or among functional categories or how frequently such codons are subject to mutual homologous recombination. Here, we explored these questions by analysing genes present in >90% among 29 genomes of Helicobacter pylori, one of the bacterial species with the highest mutation and recombination rates. By a method for recombining sequences, we identified codons under diversifying selection (dN/dS > 1), which were widely distributed and accounted for ∼0.2% of all the codons of the genome. The codons were enriched in genes of host interaction/cell surface and genome maintenance (DNA replication, recombination, repair, and restriction modification system). The encoded amino acid residues were sometimes found adjacent to critical catalytic/binding residues in protein structures. Furthermore, by estimating the intensity of homologous recombination at a single nucleotide level, we found that these codons appear to be more frequently subject to recombination. We expect that the present study provides a new approach to population genomics of selection in recombining prokaryotes. PMID:26961370

  19. Incorporation of a lambda phage recombination system and EGFP detection to simplify mutagenesis of Herpes simplex virus bacterial artificial chromosomes

    PubMed Central

    Schmeisser, Falko; Weir, Jerry P

    2007-01-01

    Background Targeted mutagenesis of the herpesvirus genomes has been facilitated by the use of bacterial artificial chromosome (BAC) technology. Such modified genomes have potential uses in understanding viral pathogenesis, gene identification and characterization, and the development of new viral vectors and vaccines. We have previously described the construction of a herpes simplex virus 2 (HSV-2) BAC and the use of an allele replacement strategy to construct HSV-2 recombinants. While the BAC mutagenesis procedure is a powerful method to generate HSV-2 recombinants, particularly in the absence of selective marker in eukaryotic culture, the mutagenesis procedure is still difficult and cumbersome. Results Here we describe the incorporation of a phage lambda recombination system into an allele replacement vector. This strategy enables any DNA fragment containing the phage attL recombination sites to be efficiently inserted into the attR sites of the allele replacement vector using phage lambda clonase. We also describe how the incorporation of EGFP into the allele replacement vector can facilitate the selection of the desired cross-over recombinant BACs when the allele replacement reaction is a viral gene deletion. Finally, we incorporate the lambda phage recombination sites directly into an HSV-2 BAC vector for direct recombination of gene cassettes using the phage lambda clonase-driven recombination reaction. Conclusion Together, these improvements to the techniques of HSV BAC mutagenesis will facilitate the construction of recombinant herpes simplex viruses and viral vectors. PMID:17501993

  20. Novel osmotically induced antifungal chitinases and bacterial expression of an active recombinant isoform.

    PubMed Central

    Yun, D J; D'Urzo, M P; Abad, L; Takeda, S; Salzman, R; Chen, Z; Lee, H; Hasegawa, P M; Bressan, R A

    1996-01-01

    NaCl (428 mM)-adapted tobacco (Nicotiana tabacum L. var Wisconsin 38) cells accumulate and secrete several antifungal chitinases. The predominant protein secreted to the culture medium was a 29-kD peptide that, based on internal amino acid sequence, was determined to be a class II acidic chitinase with similarity to PR-Q. The four predominant chitinases (T1, T2, T3, and T4) that accumulated intracellularly in 428 mM NaCl-adapted cells were purified. Based on N-terminal sequence analyses, two of these were identified as class I chitinase isoforms, one similar to the N. tomentosiformis (H. Shinshi, J.M. Neuhaus, J. Ryals, F. Meins [1990] Plant Mol Biol 14:357-368) protein (T1) and the other homologous to the N. sylvestris (Y. Fukuda, M. Ohme, H. Shinshi [1991] Plant Mol Biol 16:1-10) protein (T2). The other two proteins (T3 and T4) were determined to be novel chitinases that have sequence similarity with class I chitinases, but each lacks a chitin-binding domain. All four chitinases inhibited Fusarium oxysporum f. sp. lycopersici and Trichoderma longibrachiatum hyphal growth in vitro, although the isoforms containing a chitin-binding domain were somewhat more active. Conditions were established for the successful expression of soluble and active bacterial recombinant T2. Expression of soluble recombinant T2 was achieved when isopropyl beta-D-thiogalactopyranoside induction occurred at 18 degrees C but not at 25 or 37 degrees C. The purified recombinant protein exhibited antifungal activity comparable to a class I chitinase purified from NaCl-adapted tobacco cells. PMID:8756502

  1. BACTERIAL METABOLISM OF NAPTHALENE: CONSTRUCTION AND USE OF RECOMBINANT BACTERIA TO STUDY THE RING CLEAVAGE OF 1,2-DIIHYDROXYNAPTHALENE

    EPA Science Inventory

    The reactions involved in the bacterial metabolism of napthalene to salicylate have been reinvestigated by using recombinant bacteria carrying genes cloned form plasmid NAH7. hen intact cells of Pseudomonas aeruginosa PAO1 carrying DNA fragments encoding the first three enzymes o...

  2. Genetic recombination of bacterial plasmid DNA: effect of RecF pathway mutations on plasmid recombination in Escherichia coli.

    PubMed Central

    Kolodner, R; Fishel, R A; Howard, M

    1985-01-01

    Tn5 insertion mutations in the recN gene, and in what appears to be a new RecF pathway gene designated recO and mapping at approximately 55.4 min on the standard genetic map, were isolated by screening Tn5 insertion mutations that cotransduced with tyrA. The recO1504::Tn5 mutation decreased the frequency of recombination during Hfr-mediated crosses and increased the susceptibility to killing by UV irradiation and mitomycin C when present in a recB recC sbcB background, but only increased the sensitivity to killing by UV irradiation when present in an otherwise Rec+ background. The effects of these and other RecF pathway mutations on plasmid recombination were tested. Mutations in the recJ, recO, and ssb genes, when present in otherwise Rec+ E. coli strains, decreased the frequency of plasmid recombination, whereas the lexA3, recAo281, recN, and ruv mutations had no effect on plasmid recombination. Tn5 insertion mutations in the lexA gene increased the frequency of plasmid recombination. These data indicate that plasmid recombination events in wild-type Escherichia coli strains are catalyzed by a recombination pathway that is related to the RecF recombination pathway and that some component of this pathway besides the recA gene product is regulated by the lexA gene product. PMID:2993230

  3. High yield soluble bacterial expression and streamlined purification of recombinant human interferon α-2a.

    PubMed

    Bis, Regina L; Stauffer, Tara M; Singh, Surinder M; Lavoie, Thomas B; Mallela, Krishna M G

    2014-07-01

    Interferon α-2a (IFNA2) is a member of the Type I interferon cytokine family, known for its antiviral and anti-proliferative functions. The role of this family in the innate immune response makes it an attractive candidate for the treatment of many viral and chronic immune-compromised diseases. Recombinant IFNA2 is clinically used to modulate hairy cell leukemia as well as hepatitis c. Historically, IFNA2 has been purified from human leukocytes as well as bacterial expression systems. In most cases, bacterial expression of IFNA2 resulted in inclusion body formation, or required numerous purification steps that decreased the protein yield. Here, we describe an expression and purification scheme for IFNA2 using a pET-SUMO bacterial expression system and a single purification step. Using the SUMO protein as the fusion tag achieved high soluble protein expression. The SUMO tag was cleaved with the Ulp1 protease leaving no additional amino acids on the fusion terminus following cleavage. Mass spectrometry, circular dichroism, 2D heteronuclear NMR, and analytical ultracentrifugation confirmed the amino acid sequence identity, secondary and tertiary protein structures, and the solution behavior of the purified IFNA2. The purified protein also had antiviral and anti-proliferative activities comparable to the WHO International Standard, NIBSC 95/650, and the IFNA2 standard available from PBL Assay Science. Combining the expression and purification protocols developed here to produce IFNA2 on a laboratory scale with the commercial fermenter technology commonly used in pharmaceutical industry may further enhance IFNA2 yields, which will promote the development of interferon-based protein drugs to treat various disorders. PMID:24794500

  4. Use of Bacterial Artificial Chromosomes in Baculovirus Research and Recombinant Protein Expression: Current Trends and Future Perspectives

    PubMed Central

    Roy, Polly; Noad, Rob

    2012-01-01

    The baculovirus expression system is one of the most successful and widely used eukaryotic protein expression methods. This short review will summarise the role of bacterial artificial chromosomes (BACS) as an enabling technology for the modification of the virus genome. For many years baculovirus genomes have been maintained in E. coli as bacterial artificial chromosomes, and foreign genes have been inserted using a transposition-based system. However, with recent advances in molecular biology techniques, particularly targeting reverse engineering of the baculovirus genome by recombineering, new frontiers in protein expression are being addressed. In particular, BACs have facilitated the propagation of disabled virus genomes that allow high throughput protein expression. Furthermore, improvement in the selection of recombinant viral genomes inserted into BACS has enabled the expression of multiprotein complexes by iterative recombineering of the baculovirus genome. PMID:23762754

  5. Carrier recombination spatial transfer by reduced potential barrier causes blue/red switchable luminescence in C8 carbon quantum dots/organic hybrid light-emitting devices

    NASA Astrophysics Data System (ADS)

    Chen, Xifang; Yan, Ruolin; Zhang, Wenxia; Fan, Jiyang

    2016-04-01

    The underlying mechanism behind the blue/red color-switchable luminescence in the C8 carbon quantum dots (CQDs)/organic hybrid light-emitting devices (LEDs) is investigated. The study shows that the increasing bias alters the energy-level spatial distribution and reduces the carrier potential barrier at the CQDs/organic layer interface, resulting in transition of the carrier transport mechanism from quantum tunneling to direct injection. This causes spatial shift of carrier recombination from the organic layer to the CQDs layer with resultant transition of electroluminescence from blue to red. By contrast, the pure CQDs-based LED exhibits green-red electroluminescence stemming from recombination of injected carriers in the CQDs.

  6. Exploitation of bacterial N-linked glycosylation to develop a novel recombinant glycoconjugate vaccine against Francisella tularensis

    PubMed Central

    Cuccui, Jon; Thomas, Rebecca M.; Moule, Madeleine G.; D'Elia, Riccardo V.; Laws, Thomas R.; Mills, Dominic C.; Williamson, Diane; Atkins, Timothy P.; Prior, Joann L.; Wren, Brendan W.

    2013-01-01

    Glycoconjugate-based vaccines have proved to be effective at producing long-lasting protection against numerous pathogens. Here, we describe the application of bacterial protein glycan coupling technology (PGCT) to generate a novel recombinant glycoconjugate vaccine. We demonstrate the conjugation of the Francisella tularensis O-antigen to the Pseudomonas aeruginosa carrier protein exotoxin A using the Campylobacter jejuni PglB oligosaccharyltransferase. The resultant recombinant F. tularensis glycoconjugate vaccine is expressed in Escherichia coli where yields of 3 mg l−1 of culture were routinely produced in a single-step purification process. Vaccination of BALB/c mice with the purified glycoconjugate boosted IgG levels and significantly increased the time to death upon subsequent challenge with F. tularensis subsp. holarctica. PGCT allows different polysaccharide and protein combinations to be produced recombinantly and could be easily applicable for the production of diverse glycoconjugate vaccines. PMID:23697804

  7. Exploitation of bacterial N-linked glycosylation to develop a novel recombinant glycoconjugate vaccine against Francisella tularensis.

    PubMed

    Cuccui, Jon; Thomas, Rebecca M; Moule, Madeleine G; D'Elia, Riccardo V; Laws, Thomas R; Mills, Dominic C; Williamson, Diane; Atkins, Timothy P; Prior, Joann L; Wren, Brendan W

    2013-05-01

    Glycoconjugate-based vaccines have proved to be effective at producing long-lasting protection against numerous pathogens. Here, we describe the application of bacterial protein glycan coupling technology (PGCT) to generate a novel recombinant glycoconjugate vaccine. We demonstrate the conjugation of the Francisella tularensis O-antigen to the Pseudomonas aeruginosa carrier protein exotoxin A using the Campylobacter jejuni PglB oligosaccharyltransferase. The resultant recombinant F. tularensis glycoconjugate vaccine is expressed in Escherichia coli where yields of 3 mg l(-1) of culture were routinely produced in a single-step purification process. Vaccination of BALB/c mice with the purified glycoconjugate boosted IgG levels and significantly increased the time to death upon subsequent challenge with F. tularensis subsp. holarctica. PGCT allows different polysaccharide and protein combinations to be produced recombinantly and could be easily applicable for the production of diverse glycoconjugate vaccines. PMID:23697804

  8. Recombination luminescence and trap levels in undoped and Al-doped ZnO thin films on quartz and GaSe (0 0 0 1) substrates

    SciTech Connect

    Evtodiev, I.; Caraman, I.; Leontie, L.; Rusu, D.-I.; Dafinei, A.; Nedeff, V.; Lazar, G.

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer ZnO films on GaSe create electron trapping states and PL recombination levels. Black-Right-Pointing-Pointer Zn and Al diffusion in GaSe produces low-energy widening of its PL emission. Black-Right-Pointing-Pointer ZnO:Al films on GaSe lamellas are suitable for gas-discharge lamp applications. -- Abstract: Photoluminescence spectra of ZnO and ZnO:Al (1.00, 2.00 and 5.00 at.%) films on GaSe (0 0 0 1) lamellas and amorphous quartz substrates, obtained by annealing, at 700 K, of undoped and Al-doped metal films, are investigated. For all samples, the nonequilibrium charge carriers recombine by radiative band-to-band transitions with energy of 3.27 eV, via recombination levels created by the monoionized oxygen atoms, forming the impurity band laying in the region 2.00 - 2.70 eV. Al doping induces an additional recombination level at 1.13 eV above the top of the valence band of ZnO films on GaSe substrates. As a result of thermal diffusion of Zn and Al into the GaSe interface layer from ZnO:Al/GaSe heterojunction, electron trap levels located at 0.22 eV and 0.26 eV below the conduction band edge of GaSe, as well as a deep recombination level, responsible for the luminescent emission in the region 1.10 - 1.40 eV, are created.

  9. A versatile bacterial expression vector designed for single-step cloning of multiple DNA fragments using homologous recombination.

    PubMed

    Holmberg, Mats A; Gowda, Naveen Kumar Chandappa; Andréasson, Claes

    2014-06-01

    Production of recombinant proteins is the starting point for biochemical and biophysical analyses and requires methodology to efficiently proceed from gene sequence to purified protein. While optimized strategies for the efficient cloning of single-gene fragments for bacterial expression is available, efficient multiple DNA fragment cloning still presents a challenge. To facilitate this step, we have developed an efficient cloning strategy based on yeast homologous recombination cloning (YHRC) into the new pET-based bacterial expression vector pSUMO-YHRC. The vector supports cloning for untagged expression as well as fusions to His6-SUMO or His6 tags. We demonstrate that YHRC from single PCR products of 6 independent genes into the vector results in virtually no background. Importantly, in a quantitative assay for functional expression we find that single-step YHRC of 7 DNA fragments can be performed with very high cloning efficiencies. The method and reagents described in this paper significantly simplifies the construction of expression plasmids from multiple DNA fragments, including complex gene fusions, chimeric genes and polycistronic constructs. PMID:24631626

  10. Recombinant Immunotoxins Containing Truncated Bacterial Toxins for the Treatment of Hematologic Malignancies

    PubMed Central

    Kreitman, Robert J.

    2009-01-01

    Immunotoxins are molecules that contain a protein toxin and a ligand that is either an antibody or a growth factor. The ligand binds to a target cell antigen, and the target cell internalizes the immunotoxin, allowing the toxin to migrate to the cytoplasm where it can kill the cell. In the case of recombinant immunotoxins, the ligand and toxin are encoded in DNA that is then expressed in bacteria, and the purified immunotoxin contains the ligand and toxin fused together. Among the most active recombinant immunotoxins clinically tested are those that are targeted to hematologic malignancies. One agent, containing human interleukin-2 and truncated diphtheria toxin (denileukin diftitox), has been approved for use in cutaneous T-cell lymphoma, and has shown activity in other hematologic malignancies, including leukemias and lymphomas. Diphtheria toxin has also been targeted by other ligands, including granulocyte-macrophage colony-stimulating factor and interleukin-3, to target myelogenous leukemia cells. Single-chain antibodies containing variable heavy and light antibody domains have been fused to truncated Pseudomonas exotoxin to target lymphomas and lymphocytic leukemias. Recombinant immunotoxins anti-Tac(Fv)-PE38 (LMB-2), targeting CD25, and RFB4(dsFv)-PE38 (BL22, CAT-3888), targeting CD22, have each been tested in patients. Major responses have been observed after failure of standard chemotherapy. The most successful application of recombinant immunotoxins today is in hairy cell leukemia, where BL22 has induced complete remissions in most patients who were previously treated with optimal chemotherapy. PMID:19344187

  11. Weakly Deleterious Mutations and Low Rates of Recombination Limit the Impact of Natural Selection on Bacterial Genomes

    SciTech Connect

    Price, Morgan N.; Arkin, Adam P.

    2015-12-15

    Free-living bacteria are usually thought to have large effective population sizes, and so tiny selective differences can drive their evolution. However, because recombination is infrequent, “background selection” against slightly deleterious alleles should reduce the effective population size (Ne) by orders of magnitude. For example, for a well-mixed population with 1012 individuals and a typical level of homologous recombination (r/m= 3, i.e., nucleotide changes due to recombination [r] occur at 3 times the mutation rate [m]), we predict that Ne is<107. An argument for high Ne values for bacteria has been the high genetic diversity within many bacterial “species,” but this diversity may be due to population structure: diversity across subpopulations can be far higher than diversity within a subpopulation, which makes it difficult to estimate Ne correctly. Given an estimate ofNe, standard population genetics models imply that selection should be sufficient to drive evolution if Ne ×s is >1, where s is the selection coefficient. We found that this remains approximately correct if background selection is occurring or when population structure is present. Overall, we predict that even for free-living bacteria with enormous populations, natural selection is only a significant force ifs is above 10-7 or so. Because bacteria form huge populations with trillions of individuals, the simplest theoretical prediction is that the better allele at a site would predominate even if its advantage was just 10-9 per generation. In other words, virtually every nucleotide would be at the local optimum in most individuals. A more

  12. Weakly Deleterious Mutations and Low Rates of Recombination Limit the Impact of Natural Selection on Bacterial Genomes

    DOE PAGESBeta

    Price, Morgan N.; Arkin, Adam P.

    2015-12-15

    Free-living bacteria are usually thought to have large effective population sizes, and so tiny selective differences can drive their evolution. However, because recombination is infrequent, “background selection” against slightly deleterious alleles should reduce the effective population size (Ne) by orders of magnitude. For example, for a well-mixed population with 1012 individuals and a typical level of homologous recombination (r/m= 3, i.e., nucleotide changes due to recombination [r] occur at 3 times the mutation rate [m]), we predict that Ne is<107. An argument for high Ne values for bacteria has been the high genetic diversity within many bacterial “species,” but thismore » diversity may be due to population structure: diversity across subpopulations can be far higher than diversity within a subpopulation, which makes it difficult to estimate Ne correctly. Given an estimate ofNe, standard population genetics models imply that selection should be sufficient to drive evolution if Ne ×s is >1, where s is the selection coefficient. We found that this remains approximately correct if background selection is occurring or when population structure is present. Overall, we predict that even for free-living bacteria with enormous populations, natural selection is only a significant force ifs is above 10-7 or so. Because bacteria form huge populations with trillions of individuals, the simplest theoretical prediction is that the better allele at a site would predominate even if its advantage was just 10-9 per generation. In other words, virtually every nucleotide would be at the local optimum in most individuals. A more sophisticated theory considers that bacterial genomes have millions of sites each and selection events on these many sites could interfere with each other, so that only larger effects would be important. However, bacteria can exchange genetic material, and in principle, this exchange could eliminate the interference between the evolution of

  13. EFFECTS OF BACTERIAL LIGNIN PEROXIDASE ON ORGANIC CARBON MINERALIZATION IN SOIL, USING RECOMBINANT STREPTOMYCES STRAINS

    EPA Science Inventory

    Purified lignin peroxidase was added to sterile and nonsterile silt loam soil to study the effects of bacterial lignin peroxidase ALip-P3 of Streptomyces viridosporus T7A on the rate of organic carbon turnover in soil. ignin peroxidase ALip-P3 appears to affect the short-term tur...

  14. Origins and Recombination of the Bacterial-Sized Multichromosomal Mitochondrial Genome of Cucumber[C][W

    PubMed Central

    Alverson, Andrew J; Rice, Danny W; Dickinson, Stephanie; Barry, Kerrie; Palmer, Jeffrey D

    2011-01-01

    Members of the flowering plant family Cucurbitaceae harbor the largest known mitochondrial genomes. Here, we report the 1685-kb mitochondrial genome of cucumber (Cucumis sativus). We help solve a 30-year mystery about the origins of its large size by showing that it mainly reflects the proliferation of dispersed repeats, expansions of existing introns, and the acquisition of sequences from diverse sources, including the cucumber nuclear and chloroplast genomes, viruses, and bacteria. The cucumber genome has a novel structure for plant mitochondria, mapping as three entirely or largely autonomous circular chromosomes (lengths 1556, 84, and 45 kb) that vary in relative abundance over a twofold range. These properties suggest that the three chromosomes replicate independently of one another. The two smaller chromosomes are devoid of known functional genes but nonetheless contain diagnostic mitochondrial features. Paired-end sequencing conflicts reveal differences in recombination dynamics among chromosomes, for which an explanatory model is developed, as well as a large pool of low-frequency genome conformations, many of which may result from asymmetric recombination across intermediate-sized and sometimes highly divergent repeats. These findings highlight the promise of genome sequencing for elucidating the recombinational dynamics of plant mitochondrial genomes. PMID:21742987

  15. Optimization of Recombinant Expression of Synthetic Bacterial Phytase in Pichia pastoris Using Response Surface Methodology

    PubMed Central

    Akbarzadeh, Ali; Dehnavi, Ehsan; Aghaeepoor, Mojtaba; Amani, Jafar

    2015-01-01

    Background: Escherichia coli phytase is an acidic histidine phytase with great specific activity. Pichia pastoris is a powerful system for the heterologous expression of active and soluble proteins which can express recombinant proteins in high cell density fermenter without loss of product yield and efficiently secrete heterologous proteins into the media. Recombinant protein expression is influenced by expression conditions such as temperature, concentration of inducer, and pH. By optimization, the yield of expressed proteins can be increase. Response surface methodology (RSM) has been widely used for the optimization and studying of different parameters in biotechnological processes. Objectives: In this study, the expression of synthetic appA gene in P. pastoris was greatly improved by adjusting the expression condition. Materials and Methods: The appA gene with 410 amino acids was synthesized by P. pastoris codon preference and cloned in expression vector pPinkα-HC, under the control of AOX1 promoter, and it was transformed into P. pastoris GS115 by electroporation. Recombinant phytase was expressed in buffered methanol-complex medium (BMMY) and the expression was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and enzymatic assay. To achieve the highest level of expression, methanol concentration, pH and temperature were optimized via RSM. Finally, the optimum pH and temperature for recombinant phytase activity was determined. Results: Escherichia coli phytase was expressed in P. pastoris under different cultivation conditions (post-induction temperature, methanol concentration, and post-induction pH). The optimized conditions by RSM using face centered central composite design were 1% (v/v) methanol, pH = 5.8, and 24.5°C. Under the optimized conditions, appA was successfully expressed in P. pastoris and the maximum phytase activity was 237.2 U/mL after 72 hours of expression. Conclusions: By optimization of recombinant

  16. Characterization of a synthetic bacterial self-destruction device for programmed cell death and for recombinant proteins release

    PubMed Central

    2011-01-01

    Background Bacterial cell lysis is a widely studied mechanism that can be achieved through the intracellular expression of phage native lytic proteins. This mechanism can be exploited for programmed cell death and for gentle cell disruption to release recombinant proteins when in vivo secretion is not feasible. Several genetic parts for cell lysis have been developed and their quantitative characterization is an essential step to enable the engineering of synthetic lytic systems with predictable behavior. Results Here, a BioBrick™ lysis device present in the Registry of Standard Biological Parts has been quantitatively characterized. Its activity has been measured in E. coli by assembling the device under the control of a well characterized N-3-oxohexanoyl-L-homoserine lactone (HSL) -inducible promoter and the transfer function, lysis dynamics, protein release capability and genotypic and phenotypic stability of the device have been evaluated. Finally, its modularity was tested by assembling the device to a different inducible promoter, which can be triggered by heat induction. Conclusions The studied device is suitable for recombinant protein release as 96% of the total amount of the intracellular proteins was successfully released into the medium. Furthermore, it has been shown that the device can be assembled to different input devices to trigger cell lysis in response to a user-defined signal. For this reason, this lysis device can be a useful tool for the rational design and construction of complex synthetic biological systems composed by biological parts with known and well characterized function. Conversely, the onset of mutants makes this device unsuitable for the programmed cell death of a bacterial population. PMID:21645422

  17. Production of recombinant proteins and metabolites in yeasts: when are these systems better than bacterial production systems?

    PubMed

    Porro, Danilo; Gasser, Brigitte; Fossati, Tiziana; Maurer, Michael; Branduardi, Paola; Sauer, Michael; Mattanovich, Diethard

    2011-02-01

    Recombinant DNA (rDNA) technologies allow the production of a wide range of peptides, proteins and metabolites from naturally non-producing cells. Since human insulin was the first heterologous compound produced in a laboratory in 1977, rDNA technology has become one of the most important technologies developed in the 20th century. Recombinant protein and metabolites production is a multi-billion dollar market. The development of a new product begins with the choice of the cell factory. The final application of the compound dictates the main criteria that should be taken into consideration: (1) quality, (2) quantity, (3) yield and (4) space time yield of the desired product. Quantity and quality are the most predominant requirements that must be considered for the commercial production of a protein. Quantity and yield are the requirements for the production of a metabolite. Finally, space time yield is crucial for any production process. It therefore becomes clear why the perfect host does not exist yet, and why-despite important advances in rDNA applications in higher eukaryotic cells-microbial biodiversity continues to represent a potential source of attractive cell factories. In this review, we compare the advantages and limitations of the principal yeast and bacterial workhorse systems. PMID:21125266

  18. Production of a recombinant vaccine candidate against Burkholderia pseudomallei exploiting the bacterial N-glycosylation machinery.

    PubMed

    Garcia-Quintanilla, Fatima; Iwashkiw, Jeremy A; Price, Nancy L; Stratilo, Chad; Feldman, Mario F

    2014-01-01

    Vaccines developing immune responses toward surface carbohydrates conjugated to proteins are effective in preventing infection and death by bacterial pathogens. Traditional production of these vaccines utilizes complex synthetic chemistry to acquire and conjugate the glycan to a protein. However, glycoproteins produced by bacterial protein glycosylation systems are significantly easier to produce, and could possible be used as vaccine candidates. In this work, we functionally expressed the Burkholderia pseudomallei O polysaccharide (OPS II), the Campylobacter jejuni oligosaccharyltransferase (OTase), and a suitable glycoprotein (AcrA) in a designer E. coli strain with a higher efficiency for production of glycoconjugates. We were able to produce and purify the OPS II-AcrA glycoconjugate, and MS analysis confirmed correct glycan was produced and attached. We observed the attachment of the O-acetylated deoxyhexose directly to the acceptor protein, which expands the range of substrates utilized by the OTase PglB. Injection of the glycoprotein into mice generated an IgG immune response against B. pseudomallei, and this response was partially protective against an intranasal challenge. Our experiments show that bacterial engineered glycoconjugates can be utilized as vaccine candidates against B. pseudomallei. Additionally, our new E. coli strain SDB1 is more efficient in glycoprotein production, and could have additional applications in the future. PMID:25120536

  19. Production of a recombinant vaccine candidate against Burkholderia pseudomallei exploiting the bacterial N-glycosylation machinery

    PubMed Central

    Garcia-Quintanilla, Fatima; Iwashkiw, Jeremy A.; Price, Nancy L.; Stratilo, Chad; Feldman, Mario F.

    2014-01-01

    Vaccines developing immune responses toward surface carbohydrates conjugated to proteins are effective in preventing infection and death by bacterial pathogens. Traditional production of these vaccines utilizes complex synthetic chemistry to acquire and conjugate the glycan to a protein. However, glycoproteins produced by bacterial protein glycosylation systems are significantly easier to produce, and could possible be used as vaccine candidates. In this work, we functionally expressed the Burkholderia pseudomallei O polysaccharide (OPS II), the Campylobacter jejuni oligosaccharyltransferase (OTase), and a suitable glycoprotein (AcrA) in a designer E. coli strain with a higher efficiency for production of glycoconjugates. We were able to produce and purify the OPS II-AcrA glycoconjugate, and MS analysis confirmed correct glycan was produced and attached. We observed the attachment of the O-acetylated deoxyhexose directly to the acceptor protein, which expands the range of substrates utilized by the OTase PglB. Injection of the glycoprotein into mice generated an IgG immune response against B. pseudomallei, and this response was partially protective against an intranasal challenge. Our experiments show that bacterial engineered glycoconjugates can be utilized as vaccine candidates against B. pseudomallei. Additionally, our new E. coli strain SDB1 is more efficient in glycoprotein production, and could have additional applications in the future. PMID:25120536

  20. Lederberg on bacterial recombination, Haldane, and cold war genetics: an interview.

    PubMed

    Sarkar, Sahotra

    2014-01-01

    Joshua Lederberg (1925-2008), was one of the pioneers of molecular genetics perhaps best known for his discovery of genetic recombination in bacteria which earned him a Nobel Prize in 1958 (shared with George Beadle and Edward Tatum). Lederberg's interests were broad including the origin of life, exobiology (a term that he coined) and emerging diseases and artificial intelligence in his, later years. This article contains the transcription of an interview in excerpts, docu- menting the interactions between Lederberg and fellow biologist J.B.S. Haldane wlich lasted from 1946 until Haldane's death in Kolkata (then Calcutta) in 1964. PMID:25515361

  1. Construction of a recombinant bacterial plasmid containing DNA sequences for a mouse embryonic globin chain.

    PubMed

    Fantoni, A; Bozzoni, I; Ullu, E; Farace, M G

    1979-08-10

    Messenger RNAs for mouse embryonic globins were purified from yolk sac derived eyrthroid cells in mouse fetuses. Double stranded DNAs complementary to these messengers were synthesized and blunt end ligated to a EcoRI digested and DNA polymerase I repaired pBR322 plasmid. Of the ampicillin resistant transformants, one contained a plasmid with globin-specific cDNA. The inserted sequence is about 350 base pairs long. It contains one restriction site for EcoRI and one restriction site for HinfI about 170 and 80 base pairs from one end. The insert is not cleaved by HindIII, HindII, BamHI, PstI, SalI, AvaI, TaqI, HpaII, BglI. A mixture of purified messengers coding for alpha chains and for x, y and z embryonic chains was incubated with the recombinant plasmid and the hybridized messenger was translated in a mRNA depleted reticulocyte lysate protein synthesizing system. The product of translation was identified as a z chain by carboxymethylcellulose cromatography. The recombinant plasmid is named "pBR322-egz" after embryonic globin z. PMID:493112

  2. Construction of a recombinant bacterial plasmid containing DNA sequences for a mouse embryonic globin chain.

    PubMed Central

    Fantoni, A; Bozzoni, I; Ullu, E; Farace, M G

    1979-01-01

    Messenger RNAs for mouse embryonic globins were purified from yolk sac derived eyrthroid cells in mouse fetuses. Double stranded DNAs complementary to these messengers were synthesized and blunt end ligated to a EcoRI digested and DNA polymerase I repaired pBR322 plasmid. Of the ampicillin resistant transformants, one contained a plasmid with globin-specific cDNA. The inserted sequence is about 350 base pairs long. It contains one restriction site for EcoRI and one restriction site for HinfI about 170 and 80 base pairs from one end. The insert is not cleaved by HindIII, HindII, BamHI, PstI, SalI, AvaI, TaqI, HpaII, BglI. A mixture of purified messengers coding for alpha chains and for x, y and z embryonic chains was incubated with the recombinant plasmid and the hybridized messenger was translated in a mRNA depleted reticulocyte lysate protein synthesizing system. The product of translation was identified as a z chain by carboxymethylcellulose cromatography. The recombinant plasmid is named "pBR322-egz" after embryonic globin z. Images PMID:493112

  3. Recombinant expression and purification of "virus-like" bacterial encapsulin protein cages.

    PubMed

    Rurup, W Frederik; Cornelissen, Jeroen J L M; Koay, Melissa S T

    2015-01-01

    Ultracentrifugation, particularly the use of sucrose or cesium chloride density gradients, is a highly reliable and efficient technique for the purification of virus-like particles and protein cages. Since virus-like particles and protein cages have a unique size compared to cellular macromolecules and organelles, the rate of migration can be used as a tool for purification. Here we describe a detailed protocol for the purification of recently discovered virus-like assemblies called bacterial encapsulins from Thermotoga maritima and Brevibacterium linens. PMID:25358773

  4. Multilocus sequence analysis of xanthomonads causing bacterial spot of tomato and pepper plants reveals strains generated by recombination among species and recent global spread of Xanthomonas gardneri.

    PubMed

    Timilsina, Sujan; Jibrin, Mustafa O; Potnis, Neha; Minsavage, Gerald V; Kebede, Misrak; Schwartz, Allison; Bart, Rebecca; Staskawicz, Brian; Boyer, Claudine; Vallad, Gary E; Pruvost, Olivier; Jones, Jeffrey B; Goss, Erica M

    2015-02-01

    Four Xanthomonas species are known to cause bacterial spot of tomato and pepper, but the global distribution and genetic diversity of these species are not well understood. A collection of bacterial spot-causing strains from the Americas, Africa, Southeast Asia, and New Zealand were characterized for genetic diversity and phylogenetic relationships using multilocus sequence analysis of six housekeeping genes. By examining strains from different continents, we found unexpected phylogeographic patterns, including the global distribution of a single multilocus haplotype of X. gardneri, possible regional differentiation in X. vesicatoria, and high species diversity on tomato in Africa. In addition, we found evidence of multiple recombination events between X. euvesicatoria and X. perforans. Our results indicate that there have been shifts in the species composition of bacterial spot pathogen populations due to the global spread of dominant genotypes and that recombination between species has generated genetic diversity in these populations. PMID:25527544

  5. Expression and biochemical characterisation of recombinant AceA, a bacterial alpha-mannosyltransferase.

    PubMed

    Geremia, R A; Roux, M; Ferreiro, D U; Dauphin-Dubois, R; Lellouch, A C; Ielpi, L

    1999-07-01

    Biosynthesis of repeat-unit polysaccharides and N-linked glycans proceeds by sequential transfer of sugars from the appropriate sugar donor to an activated lipid carrier. The transfer of each sugar is catalysed by a specific glycosyltransferase. The molecular basis of the specificity of sugar addition is not yet well understood, mainly because of the difficulty of isolating these proteins. In this study, the aceA gene product expressed by Acetobacter xylinum, which is involved in the biosynthesis of the exopolysaccharide acetan, was overproduced in Escherichia coli and its function was characterised. The aceA ORF was subcloned into the expression vector pET29 in frame with the S.tag epitope. The recombinant protein was identified, and culture conditions were optimised for production of the soluble protein. The results of test reactions showed that AceA is able to transfer one alpha-mannose residue from GDP-mannose to cellobiose-P-P-lipid to produce alpha-mannose-cellobiose-P-P-lipid. AceA was not able to use free cellobiose as a substrate, indicating that the pyrophosphate-lipid moiety is needed for enzymatic activity. PMID:10485283

  6. Construction of the recombinant broad-host-range plasmids providing their bacterial hosts arsenic resistance and arsenite oxidation ability.

    PubMed

    Drewniak, Lukasz; Ciezkowska, Martyna; Radlinska, Monika; Sklodowska, Aleksandra

    2015-02-20

    The plasmid pSinA of Sinorhizobium sp. M14 was used as a source of functional phenotypic modules, encoding proteins involved in arsenite oxidation and arsenic resistance, to obtain recombinant broad-host-range plasmids providing their bacterial hosts arsenic resistance and arsenite oxidative ability. An arsenite oxidation module was cloned into pBBR1MCS-2 vector yielding plasmid vector pAIO1, while an arsenic resistance module was cloned into pCM62 vector yielding plasmid pARS1. Both plasmid constructs were introduced (separately and together) into the cells of phylogenetically distant (representing Alpha-, Beta-, and Gammaproteobacteria) and physiologically diversified (unable to oxidize arsenite and susceptible/resistant to arsenite and arsenate) bacteria. Functional analysis of the modified strains showed that: (i) the plasmid pARS1 can be used for the construction of strains with an increased resistance to arsenite [up to 20mM of As(III), (ii) the presence of the plasmid pAIO1 in bacteria previously unable to oxidize As(III) to As(V), contributes to the acquisition of arsenite oxidation abilities by these cells, (iii) the highest arsenite utilization rate are observed in the culture of strains harbouring both the plasmids pAIO1 and pARS1, (iv) the strains harbouring the plasmid pAIO1 were able to grow on arsenic-contaminated mine waters (∼ 3.0 mg As L(-1)) without any supplementation. PMID:25617684

  7. In vitro bactericidal activity of recombinant human beta-defensin-3 against pathogenic bacterial strains in human tooth root canal.

    PubMed

    Song, Wei; Shi, Yong; Xiao, Mingzhen; Lu, Hong; Qu, Tiejun; Li, Ping; Wu, Gang; Tian, Yu

    2009-03-01

    Human beta-defensin-3 (HBD3), an endogenous antimicrobial peptide, has strong broad-spectrum antimicrobial activity. This study aimed to obtain recombinant HBD3 (rHBD3) and to test the hypothesis that the antimicrobial characteristics of HBD3 may offer an advantage over conventional medicine in reducing intracanal bacteria. Genetic engineering was used to obtain active rHBD3 and analysis revealed that it exhibited a broad spectrum of antibacterial activity at low micromolar concentrations against not only Staphylococcus aureus and Escherichia coli but also against some critical pathogenic microbes in infected root canals, including Fusobacterium nucleatum, Prevotella melaninogenica, Peptostreptococcus anaerobius, Streptococcus mutans, Actinomyces naeslundii, Enterococcus faecalis and Candida albicans. In an in vitro antibacterial experiment, rHBD3 significantly eliminated pathogenic bacteria in root canals. The ratio of bacterial death was up to 98%. We conclude that HBD3 has the potential to eliminate bacteria effectively and rapidly in the local microenvironment of the root canal system and that it may contribute to successful endodontic treatment. PMID:18775647

  8. Telomerase repeat amplification protocol (TRAP) activity upon recombinant expression and purification of human telomerase in a bacterial system.

    PubMed

    Hansen, Debra T; Thiyagarajan, Thirumagal; Larson, Amy C; Hansen, Jeffrey L

    2016-07-01

    Telomerase biogenesis is a highly regulated process that solves the DNA end-replication problem. Recombinant expression has so far been accomplished only within a eukaryotic background. Towards structural and functional analyses, we developed bacterial expression of human telomerase. Positive activity by the telomerase repeat amplification protocol (TRAP) was identified in cell extracts of Escherichia coli expressing a sequence-optimized hTERT gene, the full-length hTR RNA with a self-splicing hepatitis delta virus ribozyme, and the human heat shock complex of Hsp90, Hsp70, p60/Hop, Hsp40, and p23. The Hsp90 inhibitor geldanamycin did not affect post-assembly TRAP activity. By various purification methods, TRAP activity was also obtained upon expression of only hTERT and hTR. hTERT was confirmed by tandem mass spectrometry in a ∼120 kDa SDS-PAGE fragment from a TRAP-positive purification fraction. TRAP activity was also supported by hTR constructs lacking the box H/ACA small nucleolar RNA domain. End-point TRAP indicated expression levels within 3-fold of that from HeLa carcinoma cells, which is several orders of magnitude below detection by the direct assay. These results represent the first report of TRAP activity from a bacterium and provide a facile system for the investigation of assembly factors and anti-cancer therapeutics independently of a eukaryotic setting. PMID:26965413

  9. λ Recombination and Recombineering.

    PubMed

    Murphy, Kenan C

    2016-05-01

    The bacteriophage λ Red homologous recombination system has been studied over the past 50 years as a model system to define the mechanistic details of how organisms exchange DNA segments that share extended regions of homology. The λ Red system proved useful as a system to study because recombinants could be easily generated by co-infection of genetically marked phages. What emerged from these studies was the recognition that replication of phage DNA was required for substantial Red-promoted recombination in vivo, and the critical role that double-stranded DNA ends play in allowing the Red proteins access to the phage DNA chromosomes. In the past 16 years, however, the λ Red recombination system has gained a new notoriety. When expressed independently of other λ functions, the Red system is able to promote recombination of linear DNA containing limited regions of homology (∼50 bp) with the Escherichia coli chromosome, a process known as recombineering. This review explains how the Red system works during a phage infection, and how it is utilized to make chromosomal modifications of E. coli with such efficiency that it changed the nature and number of genetic manipulations possible, leading to advances in bacterial genomics, metabolic engineering, and eukaryotic genetics. PMID:27223821

  10. Expression screening of bacterial libraries of recombinant alpha-1 proteinase inhibitor variants for candidates with thrombin inhibitory capacity.

    PubMed

    Bhakta, Varsha; Gierczak, Richard F; Sheffield, William P

    2013-12-01

    Exhaustive mutagenesis studies of the reactive centre loop (RCL), a key structural component of proteins belonging to the serpin superfamily of protease inhibitors, are complicated by the size of the RCL, serpin conformational complexity, and, for most serpins, the lack of a serpin-dependent phenotype of expressing cells. Here, we describe a thrombin capture assay that distinguished thrombin-inhibitory recombinant human alpha-1 proteinase inhibitor (API M358R) from non-inhibitory API variants in Escherichia coli lysates prepared from either single clones or pools. Binding of API proteins in the lysates to thrombin immobilized on microtiter plate wells was quantified via colour generated by a peroxidase-coupled anti-API antibody. Bacterial expression plasmids encoding inhibitory API M358R were mixed 1:99 with plasmids encoding non-inhibitory API T345R/M358R and the resulting library screened in pools of 10. All above-background signals arising from pools or subsequently re-probed single clones were linked to the presence of plasmids encoding API M358R. Screening of a portion of another expression library encoding hypervariable API with all possibilities at codons 352-358 also yielded only novel, thrombin-inhibitory variants. Probing a smaller library expressing all possible codons at Ala347 yielded the wild type, 6 different functional variants, one partially active variant, and two variants with no thrombin-inhibitory activity. API antigen levels varied considerably less among Ala347 variants than activity levels, and comparison of rate constants of inhibition of purified API variants to their corresponding thrombin capture assay lysate values was used to establish the sensitivity and specificity of the assay. The results indicate that the approach is sufficiently robust to correctly identify functional versus non-functional candidates in API expression libraries, and could be of value in systematically probing structure/function relationships not only in the API

  11. Removal of bacterial suspension water occupying the intercellular space of detached leaves after agroinfiltration improves the yield of recombinant hemagglutinin in a Nicotiana benthamiana transient gene expression system.

    PubMed

    Fujiuchi, Naomichi; Matsuda, Ryo; Matoba, Nobuyuki; Fujiwara, Kazuhiro

    2016-04-01

    The use of detached leaves instead of whole plants provides an alternative means for recombinant protein production based on Agrobacterium tumefaciens-mediated transient gene overexpression. However, the process for high-level protein production in detached leaves has not yet been established. In this study, we focused on leaf handling and maintenance conditions immediately after infiltration with Agrobacterium suspension (agroinfiltration) to improve recombinant protein expression in detached Nicotiana benthamiana leaves. We demonstrated that the residual water of bacterial suspension in detached leaves had significant impact on the yield of recombinant influenza hemagglutinin (HA). Immediately after agroinfiltration, detached leaves were stored in a dehumidified chamber to allow bacterial suspension water occupying intercellular space to be removed by transpiration. We varied the duration of this water removal treatment from 0.7 to 4.4 h, which resulted in leaf fresh weights ranging from 0.94 to 1.28 g g(-1) relative to weights measured just before agroinfiltration. We used these relative fresh weights (RFWs) as an indicator of the amount of residual water. The detached leaves were then incubated in humidified chambers for 6 days. We found that the presence of residual water significantly decreased HA yield, with a clear inverse correlation observed between HA yield and RFW. We next compared HA yields in detached leaves with those obtained from intact leaves by whole-plant expression performed at the same time. The maximum HA yield obtained from a detached leaf with a RFW of approximately 1.0, namely, 800 μg gFW(-1), was comparable to the mean HA yield of 846 μg gFW(-1) generated in intact leaves. Our results indicate the necessity of removing bacterial suspension water from agroinfiltrated detached leaves in transient overexpression systems and point to a critical factor enabling the detached-leaf system as a viable recombinant protein factory. PMID

  12. Type III Restriction Is Alleviated by Bacteriophage (RecE) Homologous Recombination Function but Enhanced by Bacterial (RecBCD) Function

    PubMed Central

    Handa, Naofumi; Kobayashi, Ichizo

    2005-01-01

    Previous works have demonstrated that DNA breaks generated by restriction enzymes stimulate, and are repaired by, homologous recombination with an intact, homologous DNA region through the function of lambdoid bacteriophages lambda and Rac. In the present work, we examined the effect of bacteriophage functions, expressed in bacterial cells, on restriction of an infecting tester phage in a simple plaque formation assay. The efficiency of plaque formation on an Escherichia coli host carrying EcoRI, a type II restriction system, is not increased by the presence of Rac prophage—presumably because, under the single-infection conditions of the plaque assay, a broken phage DNA cannot find a homologue with which to recombine. To our surprise, however, we found that the efficiency of plaque formation in the presence of a type III restriction system, EcoP1 or EcoP15, is increased by the bacteriophage-mediated homologous recombination functions recE and recT of Rac prophage. This type III restriction alleviation does not depend on lar on Rac, unlike type I restriction alleviation. On the other hand, bacterial RecBCD-homologous recombination function enhances type III restriction. These results led us to hypothesize that the action of type III restriction enzymes takes place on replicated or replicating DNA in vivo and leaves daughter DNAs with breaks at nonallelic sites, that bacteriophage-mediated homologous recombination reconstitutes an intact DNA from them, and that RecBCD exonuclease blocks this repair by degradation from the restriction breaks. PMID:16237019

  13. Recombinant bacterial amylopullulanases

    PubMed Central

    Nisha, M; Satyanarayana, T

    2013-01-01

    Pullulanases are endo-acting enzymes capable of hydrolyzing α-1, 6-glycosidic linkages in starch, pullulan, amylopectin, and related oligosaccharides, while amylopullulanases are bifunctional enzymes with an active site capable of cleaving both α-1, 4 and α-1, 6 linkages in starch, amylose and other oligosaccharides, and α-1, 6 linkages in pullulan. The amylopullulanases are classified in GH13 and GH57 family enzymes based on the architecture of catalytic domain and number of conserved sequences. The enzymes with two active sites, one for the hydrolysis of α-1, 4- glycosidic bond and the other for α-1, 6-glycosidic bond, are called α-amylase-pullulanases, while amylopullulanases have only one active site for cleaving both α-1, 4- and α-1, 6-glycosidic bonds. The amylopullulanases produced by bacteria find applications in the starch and baking industries as a catalyst for one step starch liquefaction-saccharification for making various sugar syrups, as antistaling agent in bread and as a detergent additive. PMID:23645215

  14. The RecRO pathway of DNA recombinational repair in Helicobacter pylori and its role in bacterial survival in the host

    PubMed Central

    Wang, Ge; Lo, Leja F.; Maier, Robert J.

    2011-01-01

    Two pathways for DNA recombination, AddAB (RecBCD-like) and RecRO, were identified in Helicobacter pylori, a pathogenic bacterium that colonizes human stomachs resulting in a series of gastric diseases. In this study, we examined the physiological roles of H. pylori RecRO pathway in DNA recombinational repair. We characterized H. pylori single mutants in recR and in recO, genes in the putative gap repair recombination pathway, and an addA recO double mutant that is thus deficient in both pathways that initiate DNA recombinational repair. The recR or recO single mutants showed the same level of sensitivity to mitomycin C as the parent strain, suggesting that the RecRO pathway is not responsible for the repair of DNA double strand breaks. However, H. pylori recR and recO mutants are highly sensitive to oxidative stress and separately to acid stress, two major stress conditions that H. pylori encounters in its physiological niche. The complementation of the recR mutant restored the sensitivity to oxidative and acid stress to the wild type level. By measuring DNA transformation frequencies, the recR and recO single mutants were shown to have no effect on inter-genomic recombination, whereas the addA recO double mutant had a greatly (~12-fold) reduced transformation frequency. On the other hand, the RecRO pathway was shown to play a significant role in intra-genomic recombination with direct repeat sequences. Whereas the recA strain had a deletion frequency 35-fold lower than that of background level, inactivation of recR resulted in a 4-fold decrease in deletion frequency. In a mouse infection model, the three mutant strains displayed a greatly reduced ability to colonize the host stomachs. The geometric means of colonization number for the wild type, recR, recO, and addA recO strains were 6 × 105, 1.6 × 104, 1.4 × 104 and 4 × 103 CFU/g stomach, respectively. H. pylori RecRO-mediated DNA recombinational repair (intra-genomic recombination) is thus involved in

  15. The Bacteroides mobilizable transposon Tn4555 integrates by a site-specific recombination mechanism similar to that of the gram-positive bacterial element Tn916.

    PubMed Central

    Tribble, G D; Parker, A C; Smith, C J

    1997-01-01

    The Bacteroides mobilizable transposon Tn4555 is a 12.2-kb molecule that encodes resistance to cefoxitin. Conjugal transposition is hypothesized to occur via a circular intermediate and is stimulated by coresident tetracycline resistance elements and low levels of tetracycline. In this work, the ends of the transposon were identified and found to consist of 12-bp imperfect inverted repeats, with an extra base at one end. In the circular form, the ends were separated by a 6-bp "coupling sequence" which was associated with either the left or the right transposon terminus when the transposon was inserted into the chromosome. Tn4555 does not duplicate its target site upon insertion. Using a conjugation-based transposition assay, we showed that the coupling sequence originated from 6 bases of genomic DNA flanking either side of the transposon prior to excision. Tn4555 preferentially transposed into a 589-bp genomic locus containing a 207-bp direct repeat. Integration occurred before or after the repeated sequence, with one integration site between the two repeats. These observations are consistent with a transposition model based on site-specific recombination. In the bacteriophage lambda model for site-specific recombination, the bacteriophage recombines with the Escherichia coli chromosome via a 7-bp "crossover" region. We propose that the coupling sequence of Tn4555 is analogous in function to the crossover region of lambda but that unlike the situation in lambda, recombination occurs between regions of nonhomologous DNA. This ability to recombine into divergent target sites is also a feature of the gram-positive bacterial transposon Tn916. PMID:9098073

  16. Population genetics and phylogenetic inference in bacterial molecular systematics: the roles of migration and recombination in Bradyrhizobium species cohesion and delineation.

    PubMed

    Vinuesa, Pablo; Silva, Claudia; Werner, Dietrich; Martínez-Romero, Esperanza

    2005-01-01

    A combination of population genetics and phylogenetic inference methods was used to delineate Bradyrhizobium species and to uncover the evolutionary forces acting at the population-species interface of this bacterial genus. Maximum-likelihood gene trees for atpD, glnII, recA, and nifH loci were estimated for diverse strains from all but one of the named Bradyrhizobium species, and three unnamed "genospecies," including photosynthetic isolates. Topological congruence and split decomposition analyses of the three housekeeping loci are consistent with a model of frequent homologous recombination within but not across lineages, whereas strong evidence was found for the consistent lateral gene transfer across lineages of the symbiotic (auxiliary) nifH locus, which grouped strains according to their hosts and not by their species assignation. A well resolved Bayesian species phylogeny was estimated from partially congruent glnII+recA sequences, which is highly consistent with the actual taxonomic scheme of the genus. Population-level analyses of isolates from endemic Canarian genistoid legumes based on REP-PCR genomic fingerprints, allozyme and DNA polymorphism analyses revealed a non-clonal and slightly epidemic population structure for B. canariense isolates of Canarian and Moroccan origin, uncovered recombination and migration as significant evolutionary forces providing the species with internal cohesiveness, and demonstrated its significant genetic differentiation from B. japonicum, its sister species, despite their sympatry and partially overlapped ecological niches. This finding provides strong evidence for the existence of well delineated species in the bacterial world. The results and approaches used herein are discussed in the context of bacterial species concepts and the evolutionary ecology of (brady)rhizobia. PMID:15579380

  17. The Role of Trap-assisted Recombination in Luminescent Properties of Organometal Halide CH3NH3PbBr3 Perovskite Films and Quantum Dots.

    PubMed

    Zhang, Zhen-Yu; Wang, Hai-Yu; Zhang, Yan-Xia; Hao, Ya-Wei; Sun, Chun; Zhang, Yu; Gao, Bing-Rong; Chen, Qi-Dai; Sun, Hong-Bo

    2016-01-01

    Hybrid metal halide perovskites have been paid enormous attentions in photophysics research, whose excellent performances were attributed to their intriguing charge carriers proprieties. However, it still remains far from satisfaction in the comprehensive understanding of perovskite charge-transport properities, especially about trap-assisted recombination process. In this Letter, through time-resolved transient absorption (TA) and photoluminescence (PL) measurements, we provided a relative comprehensive investigation on the charge carriers recombination dynamics of CH3NH3PbBr3 (MAPbBr3) perovskite films and quantum dots (QDs), especially about trap-assisted recombination. It was found that the integral recombination mode of MAPbBr3 films was highly sensitive to the density distribution of generated charge carriers and trap states. Additional, Trap effects would be gradually weakened with elevated carrier densities. Furthermore, the trap-assisted recombination can be removed from MAPbBr3 QDs through its own surface passivation mechanism and this specialty may render the QDs as a new material in illuminating research. This work provides deeper physical insights into the dynamics processes of MAPbBr3 materials and paves a way toward more light-harvesting applications in future. PMID:27249792

  18. The Role of Trap-assisted Recombination in Luminescent Properties of Organometal Halide CH3NH3PbBr3 Perovskite Films and Quantum Dots

    PubMed Central

    Zhang, Zhen-Yu; Wang, Hai-Yu; Zhang, Yan-Xia; Hao, Ya-Wei; Sun, Chun; Zhang, Yu; Gao, Bing-Rong; Chen, Qi-Dai; Sun, Hong-Bo

    2016-01-01

    Hybrid metal halide perovskites have been paid enormous attentions in photophysics research, whose excellent performances were attributed to their intriguing charge carriers proprieties. However, it still remains far from satisfaction in the comprehensive understanding of perovskite charge-transport properities, especially about trap-assisted recombination process. In this Letter, through time-resolved transient absorption (TA) and photoluminescence (PL) measurements, we provided a relative comprehensive investigation on the charge carriers recombination dynamics of CH3NH3PbBr3 (MAPbBr3) perovskite films and quantum dots (QDs), especially about trap-assisted recombination. It was found that the integral recombination mode of MAPbBr3 films was highly sensitive to the density distribution of generated charge carriers and trap states. Additional, Trap effects would be gradually weakened with elevated carrier densities. Furthermore, the trap-assisted recombination can be removed from MAPbBr3 QDs through its own surface passivation mechanism and this specialty may render the QDs as a new material in illuminating research. This work provides deeper physical insights into the dynamics processes of MAPbBr3 materials and paves a way toward more light-harvesting applications in future. PMID:27249792

  19. The Role of Trap-assisted Recombination in Luminescent Properties of Organometal Halide CH3NH3PbBr3 Perovskite Films and Quantum Dots

    NASA Astrophysics Data System (ADS)

    Zhang, Zhen-Yu; Wang, Hai-Yu; Zhang, Yan-Xia; Hao, Ya-Wei; Sun, Chun; Zhang, Yu; Gao, Bing-Rong; Chen, Qi-Dai; Sun, Hong-Bo

    2016-06-01

    Hybrid metal halide perovskites have been paid enormous attentions in photophysics research, whose excellent performances were attributed to their intriguing charge carriers proprieties. However, it still remains far from satisfaction in the comprehensive understanding of perovskite charge-transport properities, especially about trap-assisted recombination process. In this Letter, through time-resolved transient absorption (TA) and photoluminescence (PL) measurements, we provided a relative comprehensive investigation on the charge carriers recombination dynamics of CH3NH3PbBr3 (MAPbBr3) perovskite films and quantum dots (QDs), especially about trap-assisted recombination. It was found that the integral recombination mode of MAPbBr3 films was highly sensitive to the density distribution of generated charge carriers and trap states. Additional, Trap effects would be gradually weakened with elevated carrier densities. Furthermore, the trap-assisted recombination can be removed from MAPbBr3 QDs through its own surface passivation mechanism and this specialty may render the QDs as a new material in illuminating research. This work provides deeper physical insights into the dynamics processes of MAPbBr3 materials and paves a way toward more light-harvesting applications in future.

  20. Effect of radiation-sensitive mutations and mutagens/carcinogens on bacterial recombination and mutagenesis. Progress report

    SciTech Connect

    Not Available

    1982-01-01

    Progress is reported in the following research areas: (1) mutagen assay using Escherichia coli was investigated; (2) a recombination assay has been developed with use of an E. coli partial diploid; (3) the Ames test has been expanded to include Salmonella strains with excision repair capability; and (4) the expanded Ames test was used to test the mutagenicity of various antineoplastic drugs. (ACR)

  1. Profiling of the reactive oxygen species-related ecotoxicity of CuO, ZnO, TiO2, silver and fullerene nanoparticles using a set of recombinant luminescent Escherichia coli strains: differentiating the impact of particles and solubilised metals.

    PubMed

    Ivask, A; Bondarenko, O; Jepihhina, N; Kahru, A

    2010-09-01

    We propose a novel combination of high-throughput luminescent bacterial tests for the evaluation of the reactive oxygen species (ROS)-generating potential of engineered nanoparticles (eNPs) and the role of solubilised metal ions in this process. The set of tests consists of differently engineered recombinant Escherichia coli strains: (1) a new sensor strain, which bioluminescence is induced by superoxide anions; (2) six recombinant E. coli strains (superoxide dismutase (sod) single, double and triple mutants and a respective wild-type strain), transformed with luxCDABE genes responding to toxic compounds by decreasing their luminescence; and (3) three strains in which bioluminescence is specifically induced by bioavailable metals (Cu, Zn and Ag). The applicability of this battery of tests in profiling oxidative potential of eNPs was evaluated on nTiO(2), nCuO, nZnO and nAg (25, 30, 70 and <100 nm, respectively) NPs and fullerenes. As controls for the size or solubility, the bulk formulations (bTiO(2), bCuO and bZnO) and soluble salts (ZnSO(4), CuSO(4) and AgNO(3)) were also analysed. Bacterial toxicity tests showed that nCuO was four-fold more toxic, and nAg was 15-fold more toxic to triple sod mutant than to wild type (2-h EC(50) values were 8.1 and 2.0 mg Cu l(-1), respectively, and 46 and 3.1 mg Ag l(-1), respectively). Formation of ROS by nCuO and nAg was proved by superoxide anion-inducible strain. The metal sensor bacteria showed that the ROS formation by CuO NPs was caused by solubilised Cu ions, but in case of nAg, particles also had an effect. nZnO was remarkably more toxic to sod triple mutant than to wild type strain (2-h EC(50) were 4.5 and 54 mg Zn l(-1), respectively). Fullerenes inhibited the bioluminescence of sod triple mutant at 3,882 mg l(-1) but had no effect on the wild-type strain even at 20,800 mg l(-1). Nano and bTiO(2) showed some effect on viability of bacteria only at high concentrations (>4,000 mg l(-1)) although nTiO(2) (but not bTiO(2

  2. Design of a Comprehensive Biochemistry and Molecular Biology Experiment: Phase Variation Caused by Recombinational Regulation of Bacterial Gene Expression

    ERIC Educational Resources Information Center

    Sheng, Xiumei; Xu, Shungao; Lu, Renyun; Isaac, Dadzie; Zhang, Xueyi; Zhang, Haifang; Wang, Huifang; Qiao, Zheng; Huang, Xinxiang

    2014-01-01

    Scientific experiments are indispensable parts of Biochemistry and Molecular Biology. In this study, a comprehensive Biochemistry and Molecular Biology experiment about "Salmonella enterica" serovar Typhi Flagellar phase variation has been designed. It consisted of three parts, namely, inducement of bacterial Flagellar phase variation,…

  3. Vaccination with Brucella abortus recombinant in vivo-induced antigens reduces bacterial load and promotes clearance in a mouse model for infection.

    PubMed

    Lowry, Jake E; Isaak, Dale D; Leonhardt, Jack A; Vernati, Giulia; Pate, Jessie C; Andrews, Gerard P

    2011-01-01

    Current vaccines used for the prevention of brucellosis are ineffective in inducing protective immunity in animals that are chronically infected with Brucella abortus, such as elk. Using a gene discovery approach, in vivo-induced antigen technology (IVIAT) on B. abortus, we previously identified ten loci that encode products up-regulated during infection in elk and consequently may play a role in virulence. In our present study, five of the loci (D15, 0187, VirJ, Mdh, AfuA) were selected for further characterization and compared with three additional antigens with virulence potential (Hia, PrpA, MltA). All eight genes were PCR-amplified from B. abortus and cloned into E. coli. The recombinant products were then expressed, purified, adjuvanted, and delivered subcutaneously to BALB/c mice. After primary immunization and two boosts, mice were challenged i.p. with 5 x 10⁴ CFU of B. abortus strain 19. Spleens from challenged animals were harvested and bacterial loads determined by colony count at various time points. While vaccination with four of the eight individual proteins appeared to have some effect on clearance kinetics, mice vaccinated with recombinant Mdh displayed the most significant reduction in bacterial colonization. Furthermore, mice immunized with Mdh maintained higher levels of IFN-γ in spleens compared to other treatment groups. Collectively, our in vivo data gathered from the S19 murine colonization model suggest that vaccination with at least three of the IVIAT antigens conferred an enhanced ability of the host to respond to infection, reinforcing the utility of this methodology for the identification of potential vaccine candidates against brucellosis. Mechanisms for immunity to one protein, Mdh, require further in vitro exploration and evaluation against wild-type B. abortus challenge in mice, as well as other hosts. Additional studies are being undertaken to clarify the role of Mdh and other IVI antigens in B. abortus virulence and induction of

  4. High-yield bacterial expression and structural characterization of recombinant human insulin-like growth factor binding protein-2

    PubMed Central

    Swain, Monalisa; Slomiany, Mark G.; Rosenzweig, Steven A.; Atreya, Hanudatta S.

    2010-01-01

    The diverse biological activities of the insulin-like growth factors (IGF-1 and IGF-2) are mediated by the IGF-1 receptor (IGF-IR). These actions are modulated by a family of six IGF-binding proteins (IGFBP-1–6; 22–31 kDa) that via high affinity binding to the IGFs (KD ~ 300–700 pM) both protect the IGFs in the circulation and attenuate IGF action by blocking their receptor access. In recent years, IGFBPs have been implicated in a variety of cancers. However, the structural basis of their interaction with IGFs and/or other proteins is not completely understood. A critical challenge in the structural characterization of full-length IGFBPs has been the difficulty in expressing these proteins at levels suitable for NMR/X-ray crystallography analysis. Here we describe the high-yield expression of full-length recombinant human IGFBP-2 (rhIGFBP-2) in E. coli. Using a single step purification protocol, rhIGFBP-2 was obtained with >95% purity and structurally characterized using NMR spectroscopy. The protein was found to exist as a monomer at the high concentrations required for structural studies and to exist in a single conformation exhibiting a unique intra-molecular disulfide-bonding pattern. The protein retained full biologic activity. This study represents the first high-yield expression of wild-type recombinant human IGFBP-2 in E. coli and first structural characterization of a full-length IGFBP. PMID:20541521

  5. Cattle Immunized with a Recombinant Subunit Vaccine Formulation Exhibits a Trend towards Protection against Histophilus somni Bacterial Challenge

    PubMed Central

    Madampage, Claudia Avis; Wilson, Don; Townsend, Hugh; Crockford, Gordon; Rawlyk, Neil; Dent, Donna; Evans, Brock; Van Donkersgoed, Joyce; Dorin, Craig; Potter, Andrew

    2016-01-01

    Histophilosis, a mucosal and septicemic infection of cattle is caused by the Gram negative pathogen Histophilus somni (H. somni). As existing vaccines against H. somni infection have shown to be of limited efficacy, we used a reverse vaccinology approach to identify new vaccine candidates. Three groups (B, C, D) of cattle were immunized with subunit vaccines and a control group (group A) was vaccinated with adjuvant alone. All four groups were challenged with H. somni. The results demonstrate that there was no significant difference in clinical signs, joint lesions, weight change or rectal temperature between any of the vaccinated groups (B,C,D) vs the control group A. However, the trend to protection was greatest for group C vaccinates. The group C vaccine was a pool of six recombinant proteins. Serum antibody responses determined using ELISA showed significantly higher titers for group C, with P values ranging from < 0.0148 to < 0.0002, than group A. Even though serum antibody titers in group B (5 out of 6 antigens) and group D were significantly higher compared to group A, they exerted less of a trend towards protection. In conclusion, the vaccine used in group C exhibits a trend towards protective immunity in cattle and would be a good candidate for further analysis to determine which proteins were responsible for the trend towards protection. PMID:27501390

  6. Cattle Immunized with a Recombinant Subunit Vaccine Formulation Exhibits a Trend towards Protection against Histophilus somni Bacterial Challenge.

    PubMed

    Madampage, Claudia Avis; Wilson, Don; Townsend, Hugh; Crockford, Gordon; Rawlyk, Neil; Dent, Donna; Evans, Brock; Van Donkersgoed, Joyce; Dorin, Craig; Potter, Andrew

    2016-01-01

    Histophilosis, a mucosal and septicemic infection of cattle is caused by the Gram negative pathogen Histophilus somni (H. somni). As existing vaccines against H. somni infection have shown to be of limited efficacy, we used a reverse vaccinology approach to identify new vaccine candidates. Three groups (B, C, D) of cattle were immunized with subunit vaccines and a control group (group A) was vaccinated with adjuvant alone. All four groups were challenged with H. somni. The results demonstrate that there was no significant difference in clinical signs, joint lesions, weight change or rectal temperature between any of the vaccinated groups (B,C,D) vs the control group A. However, the trend to protection was greatest for group C vaccinates. The group C vaccine was a pool of six recombinant proteins. Serum antibody responses determined using ELISA showed significantly higher titers for group C, with P values ranging from < 0.0148 to < 0.0002, than group A. Even though serum antibody titers in group B (5 out of 6 antigens) and group D were significantly higher compared to group A, they exerted less of a trend towards protection. In conclusion, the vaccine used in group C exhibits a trend towards protective immunity in cattle and would be a good candidate for further analysis to determine which proteins were responsible for the trend towards protection. PMID:27501390

  7. High-level soluble expression of a bacterial N-acyl-d-glucosamine 2-epimerase in recombinant Escherichia coli.

    PubMed

    Klermund, Ludwig; Riederer, Amelie; Groher, Anna; Castiglione, Kathrin

    2015-07-01

    N-Acyl-d-glucosamine 2-epimerase (AGE) is an important enzyme for the biocatalytic synthesis of N-acetylneuraminic acid (Neu5Ac). Due to the wide range of biological applications of Neu5Ac and its derivatives, there has been great interest in its large-scale synthesis. Thus, suitable strategies for achieving high-level production of soluble AGE are needed. Several AGEs from various organisms have been recombinantly expressed in Escherichia coli. However, the soluble expression level was consistently low with an excessive formation of inclusion bodies. In this study, the effects of different solubility-enhancement tags, expression temperatures, chaperones and host strains on the soluble expression of the AGE from the freshwater cyanobacterium Anabaena variabilis ATCC 29413 (AvaAGE) were examined. The optimum combination of tag, expression temperature, co-expression of chaperones and host strain (His6-tag, 37°C, GroEL/GroES, E. coli BL21(DE3)) led to a 264-fold improvement of the volumetric epimerase activity, a measure of the soluble expression, compared to the starting conditions (His6-maltose-binding protein-tag, 20°C, without chaperones, E. coli BL21(DE3)). A maximum yield of 22.5mg isolated AvaAGE per liter shake flask culture was obtained. PMID:25804337

  8. The protein environment of the bacteriopheophytin anion modulates charge separation and charge recombination in bacterial reaction centers.

    PubMed

    Pan, Jie; Saer, Rafael G; Lin, Su; Guo, Zhi; Beatty, J Thomas; Woodbury, Neal W

    2013-06-20

    The kinetics and pathway of electron transfer has been explored in a series of reaction center mutants from Rhodobacter sphaeroides, in which the leucine residue at M214 near the bacteriopheophytin cofactor in the A-branch has been replaced with methionine, cysteine, alanine, and glycine. These amino acids have substantially different volumes, both from each other and, except for methionine, from the native leucine. Though the mutation site of M214 is close to the bacteriopheophytin cofactor, which is involved in the electron transfer, none of the mutations alter the cofactor composition of the reaction center and the primary charge separation reaction is essentially undisturbed. However, the kinetics of electron transfer from HA(-) → QA becomes both slower and substantially heterogeneous in three of the four mutants. The decreased HA(-) → QA electron transfer rate allows charge recombination between P(+) and HA(-) to compete with the forward reaction, resulting in a drop in the overall yield of charge separation. Both the yield change and the variation in kinetics correlate well with the volume of the mutant amino acid side chains. Analysis of the kinetics suggests that the introduction of a smaller side chain at M214 results in greater protein structural heterogeneity and dynamics on multiple time scales, resulting in perturbation of the electronic environment and its evolution in the vicinity of the early charge-separated radical pair, P(+)HA(-), and the subsequent acceptor QA, affecting both the extent and time scale of dielectric relaxation. It appears that the reaction center has been optimized not only in terms of its static structure-function relationships, but also finely tuned to favor particular reaction pathways on particular time scales by adjusting protein dynamics. PMID:23688348

  9. Measuring Carrier Lifetime in GaAs by Luminescence

    NASA Technical Reports Server (NTRS)

    Von Roos, O.

    1986-01-01

    Luminescence proposed as nondestructive technique for measuring Shockley-Read-Hall (SRH) recombination lifetime GaAs. Sample irradiated, and luminescence escapes through surface. Measurement requires no mechanical or electrical contact with sample. No ohmic contacts or p/n junctions needed. Sample not scrapped after tested.

  10. White luminescence from silica glass containing red/green/blue luminescent nanocrystalline silicon particles

    SciTech Connect

    Sato, Keisuke; Kishimoto, Naoki; Hirakuri, Kenji

    2007-11-15

    Silica glasses containing blue/green/red luminescent nanocrystalline silicon (nc-Si) particles that consist of monolayer and/or three-layer structures were fabricated by a radio-frequency sputtering technique and postannealing treatment. These silica glasses showed very broad luminescence spectra with a peak at 460 nm (blue light), 550 nm (green light), and 800 nm (red light). When these samples were irradiated by using a xenon lamp with an optical bandpass filter of 313 nm, the luminescence colors from these silica glasses were a white light. The white luminescence of the sample with the three-layer structure exhibited the high luminance value of 1.5 cd/m{sup 2}. This value was ascribed to the adjustment of sizes and densities of blue/green/red luminescent nc-Si particles, and the lowering of densities of P{sub b} centers (nonradiative recombination centers) at the nc-Si particle/silica glass interface layer.

  11. Quantitative analysis of time-resolved infrared stimulated luminescence in feldspars

    NASA Astrophysics Data System (ADS)

    Pagonis, Vasilis; Ankjærgaard, Christina; Jain, Mayank; Chithambo, Makaiko L.

    2016-09-01

    Time-resolved infrared-stimulated luminescence (TR-IRSL) from feldspar samples is of importance in the field of luminescence dating, since it provides information on the luminescence mechanism in these materials. In this paper we present new analytical equations which can be used to analyze TR-IRSL signals, both during and after short infrared stimulation pulses. The equations are developed using a recently proposed kinetic model, which describes localized electronic recombination via tunneling between trapped electrons and recombination centers in luminescent materials. Recombination is assumed to take place from the excited state of the trapped electron to the nearest-neighbor center within a random distribution of luminescence recombination centers. Different possibilities are examined within the model, depending on the relative importance of electron de-excitation and recombination. The equations are applied to experimental TR-IRSL data of natural feldspars, and good agreement is found between experimental and modeling results.

  12. Cleavage of a Recombinant Human Immunoglobulin A2 (IgA2)-IgA1 Hybrid Antibody by Certain Bacterial IgA1 Proteases

    PubMed Central

    Senior, Bernard W.; Dunlop, James I.; Batten, Margaret R.; Kilian, Mogens; Woof, Jenny M.

    2000-01-01

    To understand more about the factors influencing the cleavage of immunoglobulin A1 (IgA1) by microbial IgA1 proteases, a recombinant human IgA2/IgA1 hybrid molecule was generated. In the hybrid, termed IgA2/A1 half hinge, a seven-amino-acid sequence corresponding to one half of the duplicated sequence making up the IgA1 hinge was incorporated into the equivalent site in IgA2. Insertion of the IgA1 half hinge into IgA2 did not affect antigen binding capacity or the functional activity of the hybrid molecule, as judged by its ability to bind to IgA Fcα receptors and trigger respiratory bursts in neutrophils. Although the IgA2/A1 hybrid contained only half of the IgA1 hinge, it was found to be cleaved by a variety of different bacterial IgA1 proteases, including representatives of those that cleave IgA1 in the different duplicated halves of the hinge, namely, those of Prevotella melaninogenica, Streptococcus pneumoniae, S. sanguis, Neisseria meningitidis types 1 and 2, N. gonorrhoeae types 1 and 2, and Haemophilus influenzae type 2. Thus, for these enzymes the recognition site for IgA1 cleavage is contained within half of the IgA1 hinge region; additional distal elements, if required, are provided by either an IgA1 or an IgA2 framework. In contrast, the IgA2/A1 hybrid appeared to be resistant to cleavage with S. oralis and some H. influenzae type 1 IgA1 proteases, suggesting these enzymes require additional determinants for efficient substrate recognition. PMID:10639405

  13. Cleavage of a recombinant human immunoglobulin A2 (IgA2)-IgA1 hybrid antibody by certain bacterial IgA1 proteases.

    PubMed

    Senior, B W; Dunlop, J I; Batten, M R; Kilian, M; Woof, J M

    2000-02-01

    To understand more about the factors influencing the cleavage of immunoglobulin A1 (IgA1) by microbial IgA1 proteases, a recombinant human IgA2/IgA1 hybrid molecule was generated. In the hybrid, termed IgA2/A1 half hinge, a seven-amino-acid sequence corresponding to one half of the duplicated sequence making up the IgA1 hinge was incorporated into the equivalent site in IgA2. Insertion of the IgA1 half hinge into IgA2 did not affect antigen binding capacity or the functional activity of the hybrid molecule, as judged by its ability to bind to IgA Fcalpha receptors and trigger respiratory bursts in neutrophils. Although the IgA2/A1 hybrid contained only half of the IgA1 hinge, it was found to be cleaved by a variety of different bacterial IgA1 proteases, including representatives of those that cleave IgA1 in the different duplicated halves of the hinge, namely, those of Prevotella melaninogenica, Streptococcus pneumoniae, S. sanguis, Neisseria meningitidis types 1 and 2, N. gonorrhoeae types 1 and 2, and Haemophilus influenzae type 2. Thus, for these enzymes the recognition site for IgA1 cleavage is contained within half of the IgA1 hinge region; additional distal elements, if required, are provided by either an IgA1 or an IgA2 framework. In contrast, the IgA2/A1 hybrid appeared to be resistant to cleavage with S. oralis and some H. influenzae type 1 IgA1 proteases, suggesting these enzymes require additional determinants for efficient substrate recognition. PMID:10639405

  14. Recombinant thermoactive phosphoenolpyruvate carboxylase (PEPC) from Thermosynechococcus elongatus and its coupling with mesophilic/thermophilic bacterial carbonic anhydrases (CAs) for the conversion of CO2 to oxaloacetate.

    PubMed

    Del Prete, Sonia; De Luca, Viviana; Capasso, Clemente; Supuran, Claudiu T; Carginale, Vincenzo

    2016-01-15

    With the continuous increase of atmospheric CO2 in the last decades, efficient methods for carbon capture, sequestration, and utilization are urgently required. The possibility of converting CO2 into useful chemicals could be a good strategy to both decreasing the CO2 concentration and for achieving an efficient exploitation of this cheap carbon source. Recently, several single- and multi-enzyme systems for the catalytic conversion of CO2 mainly to bicarbonate have been implemented. In order to design and construct a catalytic system for the conversion of CO2 to organic molecules, we implemented an in vitro multienzyme system using mesophilic and thermophilic enzymes. The system, in fact, was constituted by a recombinant phosphoenolpyruvate carboxylase (PEPC) from the thermophilic cyanobacterium Thermosynechococcus elongatus, in combination with mesophilic/thermophilic bacterial carbonic anhydrases (CAs), for converting CO2 into oxaloacetate, a compound of potential utility in industrial processes. The catalytic procedure is in two steps: the conversion of CO2 into bicarbonate by CA, followed by the carboxylation of phosphoenolpyruvate with bicarbonate, catalyzed by PEPC, with formation of oxaloacetate (OAA). All tested CAs, belonging to α-, β-, and γ-CA classes, were able to increase OAA production compared to procedures when only PEPC was used. Interestingly, the efficiency of the CAs tested in OAA production was in good agreement with the kinetic parameters for the CO2 hydration reaction of these enzymes. This PEPC also revealed to be thermoactive and thermostable, and when coupled with the extremely thermostable CA from Sulphurhydrogenibium azorense (SazCA) the production of OAA was achieved even if the two enzymes were exposed to temperatures up to 60 °C, suggesting a possible role of the two coupled enzymes in biotechnological processes. PMID:26712095

  15. A luminescent nisin biosensor

    NASA Astrophysics Data System (ADS)

    Immonen, Nina; Karp, Matti

    2006-02-01

    Nisin is a lantibiotic, an antibacterial peptide produced by certain Lactococcus lactis strains that kills or inhibits the growth of other bacteria. Nisin is widely used as a food preservative, and its long-time use suggests that it can be generally regarded as safe. We have developed a method for determining the amount of nisin in food samples that is based on luminescent biosensor bacteria. Bacterial luciferase operon luxABCDE was inserted into plasmid pNZ8048, and the construct was transformed by electroporation into Lc. lactis strain NZ9800, whose ability to produce nisin has been erased by deletion of the gene nisA. The operon luxABCDE has been modified to be functional in gram-positive bacteria to confer a bioluminescent phenotype without the requirement of adding an exogenous substrate. In the plasmid pNZ8048, the operon was placed under control of the nisin-inducible nisA promoter. The chromosomal nisRK genes of Lc. lactis NZ9800 allow it to sense nisin in the environment and relay this signal via signal transduction proteins NisK and NisR to initiate transcription from nisA promoter. In the case of our sensor bacteria, this leads to production of luciferase and, thus, luminescence that can be directly measured from living bacteria. Luminescence can be detected as early as within minutes of induction. The nisin assay described here provides a detection limit in the sub-picogram level per ml, and a linear area between 1 - 1000 pg/ml. The sensitivity of this assay exceeds the performance of all previously published methods.

  16. The recombination of genetic material

    SciTech Connect

    Low, K.B.

    1988-01-01

    Genetic recombination is the major mechanism by which new arrangements of genetic elements are produced in all living organisms, from the simplest bacterial viruses to humans. This volume presents an overview of the types of recombination found in prokaryotes and eukaryotes.

  17. Oligonucleotide recombination in bacteria

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Today, there are more than 1,500 completed or draft bacterial genome sequences available for public access. To functionally analyze these genomes and to test the hypotheses that are generated from the sequence information we require new and generically useful tools. Recombineering (genetic engineer...

  18. Hot-exciton luminescence in ZnTe/MnTe quantum wells

    NASA Astrophysics Data System (ADS)

    Pelekanos, N.; Ding, J.; Fu, Q.; Nurmikko, A. V.; Durbin, S. M.; Kobayashi, M.; Gunshor, R. L.

    1991-04-01

    Hot-exciton luminescence phenomena are investigated in a ZnTe/MnTe single-quantum-well structure where tunneling through thin MnTe barriers suppresses the formation of thermalized luminescence. The longitudinal-optical-phonon-modulated recombination spectra are excitonic in nature and show strong resonance enhancement at energies that lie within localized states below the n=1 exciton.

  19. Synchrotron and laser excitation of luminescence in PbWO4:Tb crystals at different temperatures

    NASA Astrophysics Data System (ADS)

    Novosad, S. S.; Kostyk, L. V.; Novosad, I. S.

    2011-09-01

    The effect of temperature on the spectral luminescence characteristics of PbWO4:Tb3+ crystals with synchrotron and laser excitation is studied. If PbWO4:Tb3+ is excited by synchrotron radiation with λ = 88 nm at 300 K, a faint recombination luminescence of the impurity terbium is observed against the matrix luminescence. When the temperature is reduced to 8 K, the luminescence intensity of PbWO4:Tb3+ increases by roughly an order of magnitude and the characteristic luminescence of the unactivated crystal is observed. Excitation of PbWO4:Tb3+ by a nitrogen laser at 300 K leads to the appearance of emission from Tb3+ ions. At 90 K, a faint matrix luminescence is observed in addition to the activator emission. The formation of the luminescence excitation spectra for wavelengths of 60-320 nm is analyzed and the nature of the emission bands is discussed.

  20. Construction and bacterial expression of a recombinant single-chain antibody fragment against Wuchereria bancrofti SXP-1 antigen for the diagnosis of lymphatic filariasis.

    PubMed

    Kamatchi, R; Charumathi, J; Ravishankaran, R; Kaliraj, P; Meenakshisundaram, S

    2016-01-01

    Global programmes to eliminate lymphatic filariasis (GPELF) require mapping, monitoring and evaluation using filarial antigen diagnostic kits. To meet this objective, a functional single-chain fragment variable (ScFv) specific for filarial Wuchereria bancrofti SXP-1 (Wb-SXP-1) antigen was constructed for the diagnosis of active filarial infection, an alternative to the production of complete antibodies using hybridomas. The variable heavy chain (VH) and the variable light chain (kappa) (Vκ) genes were amplified from the mouse hybridoma cell line and were linked together with a flexible linker by overlap extension polymerase chain reaction (PCR). The ScFv construct (Vκ-Linker-VH) was expressed as a fusion protein with N-terminal His tag in Escherichia coli and purified using immobilized metal affinity chromatography (IMAC) without the addition of reducing agents. Immunoblotting and sandwich enzyme-linked immunosorbent assay (ELISA) were used to analyse the antigen binding affinity of purified ScFv. The purified ScFv was found to recognize recombinant and native Wb-SXP-1 antigen in microfilariae (Mf)-positive patient sera. The affinity of ScFv was comparable with that of the monoclonal antibody. The development of recombinant ScFv to replace monoclonal antibody for detection of filarial antigen was achieved. The recombinant ScFv was purified, on-column refolded and its detection ability validated using field samples. PMID:26693887

  1. Direct charge recombination from D +Q AQ B- to DQ AQ B in bacterial reaction centers from Rhodobacter sphaeroides containing low potential quinone in the Q A site

    NASA Astrophysics Data System (ADS)

    Labahn, A.; Bruce, J. M.; Okamura, M. Y.; Feher, G.

    1995-08-01

    In native RCs from Rb. sphaeroides the recombination D +Q AQ B- → DQ AQ B proceeds via an indirect path involving the intermediate state D +Q A-Q B. To observe the direct recombination rate, kBD, the energy difference between the D +Q A-Q B and D +Q AQ B- states has to be increased. This had been accomplished in mutant RCs (DN(L213)) by lowering the energy of the D +Q AQ B- state [A. Labahn, M.L. Paddock, P.H. McPherson, M.Y. Okamura and G. Feher, J. Phys. Chem. 98 (1994) 3417] or, as presented in this work, by arising the energy of the D +Q A-Q B state through substitution of Q 10 by the low potential quinones: (2,3,5-trimethyl-1,4-naphthoquinone, 2,3,6,7-tetramethyl-1,4-naphthoquinone, 2-chloro-9,10-anthraquinone) while retaining the native Q 10 in the Q B site. The recombination rates kBD in these hybrid RCs were fitted with the Marcus theory giving a reorganization energy, λBD = 1.1 ± 0.1 eV and an electronic matrix element V( r) = (1.2 ± 0.5) × 10 -8 eV. The larger value of λBD compared to λAD (1.1 versus 0.6 eV) is consistent with the more polar environment of Q B- and is believed to be the main contributor to the large observed ratio of kAD/ kBD ≈ 100.

  2. Time-resolved measurements of Cooper-pair radiative recombination in InAs quantum dots

    SciTech Connect

    Mou, S. S.; Nakajima, H.; Kumano, H.; Suemune, I.; Irie, H.; Asano, Y.; Akahane, K.; Sasaki, M.; Murayama, A.

    2015-08-21

    We studied InAs quantum dots (QDs) where electron Cooper pairs penetrate from an adjacent niobium (Nb) superconductor with the proximity effect. With time-resolved luminescence measurements at the wavelength around 1550 nm, we observed luminescence enhancement and reduction of luminescence decay time constants at temperature below the superconducting critical temperature (T{sub C}) of Nb. On the basis of these measurements, we propose a method to determine the contribution of Cooper-pair recombination in InAs QDs. We show that the luminescence enhancement measured below T{sub C} is well explained with our theory including Cooper-pair recombination.

  3. Production by Tobacco Transplastomic Plants of Recombinant Fungal and Bacterial Cell-Wall Degrading Enzymes to Be Used for Cellulosic Biomass Saccharification

    PubMed Central

    Leelavathi, Sadhu; Doria, Enrico; Reddy, Vanga Siva; Cella, Rino

    2015-01-01

    Biofuels from renewable plant biomass are gaining momentum due to climate change related to atmospheric CO2 increase. However, the production cost of enzymes required for cellulosic biomass saccharification is a major limiting step in this process. Low-cost production of large amounts of recombinant enzymes by transgenic plants was proposed as an alternative to the conventional microbial based fermentation. A number of studies have shown that chloroplast-based gene expression offers several advantages over nuclear transformation due to efficient transcription and translation systems and high copy number of the transgene. In this study, we expressed in tobacco chloroplasts microbial genes encoding five cellulases and a polygalacturonase. Leaf extracts containing the recombinant enzymes showed the ability to degrade various cell-wall components under different conditions, singly and in combinations. In addition, our group also tested a previously described thermostable xylanase in combination with a cellulase and a polygalacturonase to study the cumulative effect on the depolymerization of a complex plant substrate. Our results demonstrate the feasibility of using transplastomic tobacco leaf extracts to convert cell-wall polysaccharides into reducing sugars, fulfilling a major prerequisite of large scale availability of a variety of cell-wall degrading enzymes for biofuel industry. PMID:26137472

  4. Effect of ionic strength on intra-protein electron transfer reactions: The case study of charge recombination within the bacterial reaction center.

    PubMed

    Giustini, Mauro; Parente, Matteo; Mallardi, Antonia; Palazzo, Gerardo

    2016-09-01

    It is a common believe that intra-protein electron transfer (ET) involving reactants and products that are overall electroneutral are not influenced by the ions of the surrounding solution. The results presented here show an electrostatic coupling between the ionic atmosphere surrounding a membrane protein (the reaction center (RC) from the photosynthetic bacterium Rhodobacter sphaeroides) and two very different intra-protein ET processes taking place within it. Specifically we have studied the effect of salt concentration on: i) the kinetics of the charge recombination between the reduced primary quinone acceptor QA(-) and the primary photoxidized donor P(+); ii) the thermodynamic equilibrium (QA(-)↔QB(-)) for the ET between QA(-) and the secondary quinone acceptor QB. A distinctive point of this investigation is that reactants and products are overall electroneutral. The protein electrostatics has been described adopting the lowest level of complexity sufficient to grasp the experimental phenomenology and the impact of salt on the relative free energy level of reactants and products has been evaluated according to suitable thermodynamic cycles. The ionic strength effect was found to be independent on the ion nature for P(+)QA(-) charge recombination where the leading electrostatic term was the dipole moment. In the case of the QA(-)↔QB(-) equilibrium, the relative stability of QA(-) and QB(-) was found to depend on the salt concentration in a fashion that is different for chaotropic and kosmotropic ions. In such a case both dipole moment and quadrupole moments of the RC must be considered. PMID:27297026

  5. Production by Tobacco Transplastomic Plants of Recombinant Fungal and Bacterial Cell-Wall Degrading Enzymes to Be Used for Cellulosic Biomass Saccharification.

    PubMed

    Longoni, Paolo; Leelavathi, Sadhu; Doria, Enrico; Reddy, Vanga Siva; Cella, Rino

    2015-01-01

    Biofuels from renewable plant biomass are gaining momentum due to climate change related to atmospheric CO2 increase. However, the production cost of enzymes required for cellulosic biomass saccharification is a major limiting step in this process. Low-cost production of large amounts of recombinant enzymes by transgenic plants was proposed as an alternative to the conventional microbial based fermentation. A number of studies have shown that chloroplast-based gene expression offers several advantages over nuclear transformation due to efficient transcription and translation systems and high copy number of the transgene. In this study, we expressed in tobacco chloroplasts microbial genes encoding five cellulases and a polygalacturonase. Leaf extracts containing the recombinant enzymes showed the ability to degrade various cell-wall components under different conditions, singly and in combinations. In addition, our group also tested a previously described thermostable xylanase in combination with a cellulase and a polygalacturonase to study the cumulative effect on the depolymerization of a complex plant substrate. Our results demonstrate the feasibility of using transplastomic tobacco leaf extracts to convert cell-wall polysaccharides into reducing sugars, fulfilling a major prerequisite of large scale availability of a variety of cell-wall degrading enzymes for biofuel industry. PMID:26137472

  6. Oligonucleotide recombination enabled site-specific mutagenesis in bacteria

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Recombineering refers to a strategy for engineering DNA sequences using a specialized mode of homologous recombination. This technology can be used for rapidly constructing precise changes in bacterial genome sequences in vivo. Oligo recombination is one type of recombineering that uses ssDNA olig...

  7. Luminescent properties of semiconductor photoelectrodes

    NASA Astrophysics Data System (ADS)

    Ellis, A. B.; Karas, B. R.

    1980-08-01

    The use of luminescent, n-type 5-1000-ppm CdS:Te and 10 ppm-CdS:Ag polycrystalline photoelectrodes as probes of recombination in photo-electrochemical cells is reported. Except for intensity, the emission spectra (lambda sub max, 600-700 nm) are insensitive to the presence of S2-/Sn2- electrolyte and to the excitation wavelengths and electrode potentials employed. With ultraband gap irradiation (lambda less than or = 500 nm) and aqueous S2-/Sn2- or Te2-/(Te2)2- electrolytes, optical energy is converted to electricity at 0.1-5% efficiency and to luminescence at 0.01-1.0% efficiency; the effects of surface preparation and grain boundaries in determining efficiency and discussed. Increasingly negative bias applied to CdS:Te and CdS:Ag photoanodes increases emission intensity by 15-100% while the photocurrent simultaneously declines to zero. Band gap edge 514.5-nm excitation yields smaller photocurrents and larger but much less potential dependent emission intensity. These results are consistent with the band bending model presently used to described photoelectrochemical phenomena.

  8. Increase in Bacterial Colony Formation from a Permafrost Ice Wedge Dosed with a Tomitella biformata Recombinant Resuscitation-Promoting Factor Protein.

    PubMed

    Puspita, Indun Dewi; Kitagawa, Wataru; Kamagata, Yoichi; Tanaka, Michiko; Nakatsu, Cindy H

    2015-01-01

    Resuscitation-promoting factor (Rpf) is a protein that has been found in a number of different Actinobacteria species and has been shown to promote the growth of active cells and resuscitate dormant (non-dividing) cells. We previously reported the biological activity of an Rpf protein in Tomitella biformata AHU 1821(T), an Actinobacteria isolated from a permafrost ice wedge. This protein is excreted outside the cell; however, few studies have investigated its contribution in environmental samples to the growth or resuscitation of bacteria other than the original host. Therefore, the aim of the present study was to determine whether Rpf from T. biformata impacted the cultivation of other bacteria from the permafrost ice wedge from which it was originally isolated. All experiments used recombinant Rpf proteins produced using a Rhodococcus erythropolis expression system. Dilutions of melted surface sterilized ice wedge samples mixed with different doses of the purified recombinant Rpf (rRpf) protein indicated that the highest concentration tested, 1250 pM, had a significantly (p <0.05) higher number of CFUs on agar plates after 8 d, approximately 14-fold higher than that on control plates without rRpf. 16S rRNA gene sequences revealed that all the colonies on plates were mainly related to Brevibacterium antiquum strain VKM Ac-2118 (AY243344), with 98-99% sequence identity. This species is also a member of the phylum Actinobacteria and was originally isolated from Siberian permafrost sediments. The results of the present study demonstrated that rRpf not only promoted the growth of T. biformata from which it was isolated, but also enhanced colony formation by another Actinobacteria in an environmental sample. PMID:25843055

  9. Comparison of mammalian and bacterial expression library screening to detect recombinant alpha-1 proteinase inhibitor variants with enhanced thrombin inhibitory capacity.

    PubMed

    Gierczak, Richard F; Bhakta, Varsha; Xie, Michael; Sheffield, William P

    2015-08-20

    Serpins are a widely distributed family of serine proteases. A key determinant of their specificity is the reactive centre loop (RCL), a surface motif of ∼20 amino acids in length. Expression libraries of variant serpins could be rapidly probed with proteases to develop novel inhibitors if optimal systems were available. The serpin variant alpha-1 proteinase inhibitor M358R (API M358R) inhibits the coagulation protease thrombin, but at sub-maximal rates compared to other serpins. Here we compared two approaches to isolate functional API variants from serpin expression libraries, using the same small library of API randomized at residue 358 (M358X): flow cytometry of transfected HEK 293 cells expressing membrane-displayed API; and a thrombin capture assay (TCA) performed on pools of bacterial lysates expressing soluble API. No enrichment for specific P1 residues was observed when the RCL codons of the 1% of sorted transfected 293 cells with the highest fluorescent thrombin-binding signals were subcloned and sequenced. In contrast, screening of 16 pools of bacterial API-expressing transformants led to the facile identification of API M358R and M358K as functional variants. Kinetic characterization showed that API M358R inhibited thrombin 17-fold more rapidly than API M358K. Reducing the incubation time with immobilized thrombin improved the sensitivity of TCA to detect supra-active API M358R variants and was used to screen a hypervariable library of API variants expressing 16 different amino acids at residues 352-357. The most active variant isolated, with TLSATP substituted for FLEAI, inhibited thrombin 2.9-fold more rapidly than API M358R. Our results indicate that flow cytometric approaches used in protein engineering of antibodies are not appropriate for serpins, and highlight the utility of the optimized TCA for serpin protein engineering. PMID:26043905

  10. In vivo excitation of nanoparticles using luminescent bacteria

    PubMed Central

    Dragavon, Joe; Blazquez, Samantha; Rekiki, Abdessalem; Samson, Chelsea; Theodorou, Ioanna; Rogers, Kelly L.; Tournebize, Régis; Shorte, Spencer L.

    2012-01-01

    The lux operon derived from Photorhabdus luminescens incorporated into bacterial genomes, elicits the production of biological chemiluminescence typically centered on 490 nm. The light-producing bacteria are widely used for in vivo bioluminescence imaging. However, in living samples, a common difficulty is the presence of blue-green absorbers such as hemoglobin. Here we report a characterization of fluorescence by unbound excitation from luminescence, a phenomenon that exploits radiating luminescence to excite nearby fluorophores by epifluorescence. We show that photons from bioluminescent bacteria radiate over mesoscopic distances and induce a red-shifted fluorescent emission from appropriate fluorophores in a manner distinct from bioluminescence resonance energy transfer. Our results characterizing fluorescence by unbound excitation from luminescence, both in vitro and in vivo, demonstrate how the resulting blue-to-red wavelength shift is both necessary and sufficient to yield contrast enhancement revealing mesoscopic proximity of luminescent and fluorescent probes in the context of living biological tissues. PMID:22615349

  11. Attempts at validating a recombinant Flavobacterium psychrophilum gliding motility protein N as a vaccine candidate in rainbow trout, Oncorhynchus mykiss (Walbaum) against bacterial cold-water disease.

    PubMed

    Plant, Karen P; LaPatra, Scott E; Call, Douglas R; Cain, Kenneth D

    2014-09-01

    The Flavobacterium psychrophilum gliding motility N (GldN) protein was investigated to determine its ability to elicit antibody responses and provide protective immunity in rainbow trout Oncorhynchus mykiss (Walbaum). GldN was PCR-amplified, cloned into pET102/D-TOPO, and expressed in Escherichia coli. Bacteria expressing recombinant GldN (rGldN) were formalin-inactivated and injected intraperitoneally (i.p.) into rainbow trout with Freund's complete adjuvant (FCA) in four separate studies that used two different immunization protocols followed by challenge evaluations. Fish injected with E. coli only in FCA served as the control. Antibody responses to F. psychrophilum whole-cell lysates measured by ELISA were low in all four studies. Protection against F. psychrophilum challenge was observed in the first study, but not in the three following studies. The discrepancies in results obtained in the later studies are unclear but may relate to formalin treatment of the antigen preparations. Overall, it appeared that rGldN delivered i.p. as a crude formalin-killed preparation is not a consistent vaccine candidate, and more work is required. Additionally, this study illustrates the importance of conducting multiple in vivo evaluations on potential vaccine(s) before any conclusions are drawn. PMID:25053267

  12. Sensitivity of detection of bacteria with fluorescent and luminescent phenotypes using different instruments

    NASA Astrophysics Data System (ADS)

    Brovko, Lubov Y.; Griffiths, Mansel W.

    2000-04-01

    The problem of bacterial enumeration in different samples is of great importance in many fields of research. Construction of recombinant fluorescent and luminescent bacteria that can be easily detected by nondestructive instrumental methods proves us with an opportunity to monitor bacteria in a wide variety of clinical, environmental and food samples in real time. Three different labels were employed: Green Fluorescent Protein (GFP), Bacterial luciferase (BL) and Firefly Luciferase (FFL). Both plasmid and chromosomal transformants of different strains of E. coli, P. putida and S. enteritidis were used. For the detection of the in vivo GFP the Shimadzu RF 540 spectrofluorimeter, Labsystems FL- 500 plate fluorimeter and Night Owl LB 98 CCD-camera from EG and G Berthold supplied with excitation light source and proper spectral filters both in macroscopic and microscopic mode were used. For the detection of in vivo luminescence of BL and FFL, tube luminometer BG-P from GEM Biomedical Inc., luminometric plate reader from BioOrbit, BIQ Bioview CCD camera from Cambridge Imaging Ltd and Night Owl LB 98 CCD camera both in macroscopic and microscopic mode were used. The expression levels of the labels, their stability, stability of the signal and detection limits of tagged bacteria were investigated. The detection limits for GFP tagged bacteria were 5 X 104 - 6 X 106, for BL tagged bacteria 5 X 102 - 2 X 105, and for FFL tagged bacteria - 4 X 103 - 106 CFU/ml, depending on the instrument used. Single bacteria could be detected with the help of the Night Owl in the microscopic mode.

  13. Study of Luminescence Characteristics of Trivalent Terbium in Silicate Glass

    NASA Technical Reports Server (NTRS)

    West, Mike S.; Armagan, Guzin; Winfree, William P.

    1995-01-01

    An important use of silicate glasses doped with terbium oxide (Tb2O3) is their use as fiber optic sensors for high-resolution imaging applications requiring the detection of x-rays (e.g. tomography and radiography). The x-ray radiation is absorbed by the glass, producing electron-hole pairs (excitons). The excitons migrate through the glass matrix and then recombine, emitting characteristic Tb(3+) luminescence in the optical wavelength region. This emission is due to forbidden transitions of 4f electrons and therefore has a long decay time. Long decay time is undesirable when imaging transient events since it results in blurring in time of the images. It has been reported elsewhere that in crystals Tb(3+) ions can act both as luminescence centers and as fluorescence traps. These traps can capture excitons and delay their recombination. This delayed fluorescence is seen as a long lived, secondary component to the luminescence decay curve, or afterglow. Such a secondary decay component to the luminescence decay of Tb(3+) has been observed before in soda glass following pulsed optical excitation. In order to determine the conditions under which afterglow occurs, an understanding of the material's luminescent properties is required.

  14. Stored luminescence computed tomography.

    PubMed

    Cong, Wenxiang; Wang, Chao; Wang, Ge

    2014-09-01

    Phosphor nanoparticles made of doped semiconductors and pre-excited by x-ray radiation were recently reported for their luminescence emission in the range of 650-770 nm upon near-infrared (NIR) light stimulation. These nanophosphors can be functionalized as optical probes for molecular imaging. In this paper, we present stored luminescence computed tomography to reconstruct a nanophosphor distribution in an object. The propagation of x rays in a biological object allows significantly better localization and deeper penetration. Moreover, the nanophosphors, which are pre-excited with collimated x-ray beams or focused x-ray waves, can be successively stimulated for stored luminescence emissions by variable NIR stimulation patterns. The sequentially detected luminescence signals provide more information of a nanophosphor spatial distribution for more accurate image reconstruction and higher image resolution. A realistic numerical study is performed to demonstrate the feasibility and merits of the proposed approach. PMID:25321362

  15. Advanced synchronous luminescence system

    DOEpatents

    Vo-Dinh, Tuan

    1997-01-01

    A method and apparatus for determining the condition of tissue or otherwise making chemical identifications includes exposing the sample to a light source, and using a synchronous luminescence system to produce a spectrum that can be analyzed for tissue condition.

  16. Structured luminescence conversion layer

    DOEpatents

    Berben, Dirk; Antoniadis, Homer; Jermann, Frank; Krummacher, Benjamin Claus; Von Malm, Norwin; Zachau, Martin

    2012-12-11

    An apparatus device such as a light source is disclosed which has an OLED device and a structured luminescence conversion layer deposited on the substrate or transparent electrode of said OLED device and on the exterior of said OLED device. The structured luminescence conversion layer contains regions such as color-changing and non-color-changing regions with particular shapes arranged in a particular pattern.

  17. Pickled luminescent silicon nanostructures

    NASA Astrophysics Data System (ADS)

    Boukherroub, R.; Morin, S.; Wayner, D. D. M.; Lockwood, D. J.

    2001-05-01

    In freshly prepared porous Si, the newly exposed silicon-nanostructure surface is protected with a monolayer of hydrogen, which is very reactive and oxidizes in air leading to a loss of luminescence intensity and a degradation of the electronic properties. We report a surface passivation approach based on organic modification that stabilizes the luminescence. This novel 'pickling' process not only augments the desired optoelectronic properties, but also is adaptable to further chemical modification for integration into chemical and biophysical sensors.

  18. Genetic Recombination

    ERIC Educational Resources Information Center

    Whitehouse, H. L. K.

    1973-01-01

    Discusses the mechanisms of genetic recombination with particular emphasis on the study of the fungus Sordaria brevicollis. The study of recombination is facilitated by the use of mutants of this fungus in which the color of the ascospores is affected. (JR)

  19. Oligo Recombination in Gram Negative Bacteria

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Homologous recombination is important for bacterial survival because it simultaneously provides genomic stability as well as genomic plasticity. Of the mechanistic pathways for homologous recombination, those mediated by RecA are the most thoroughly characterized and are understood to be structural...

  20. Oligonucleotide recombination in gram negative bacteria

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report describes several key aspects of a novel form of RecA-independent homologous recombination. We found that synthetic single stranded DNA oligonucleotides (oligos) introduced into bacteria by transformation can site-specifically recombine with bacterial chromosomes in the absence of any a...

  1. The persistent luminescence and up conversion photostimulated luminescence properties of nondoped Mg2SnO4 material

    NASA Astrophysics Data System (ADS)

    Zhang, Jiachi; Yu, Minghui; Qin, Qingsong; Zhou, Hongliang; Zhou, Meijiao; Xu, Xuhui; Wang, Yuhua

    2010-12-01

    The nondoped Mg2SnO4 material with inverse spinel structure was synthesized by solid state reaction. This phosphor showed a broad green emission band covering 470-550 nm under 291 nm excitation, which was due to the recombination of F centers with holes. Stimulated by 980 nm infrared laser, the green photostimulated luminescence was first observed in a nondoped oxide. After ultraviolet irradiation, the green persistent luminescence of Mg2SnO4 could be seen in darkness for about 5 h. The decay curves revealed that the long persistent luminescence was governed by tunneling mechanism and it proved the presence of different trap clusters in Mg2SnO4. These trap clusters (such as [SnMg••-Oi″], [SnMg••-2e'], and [SnMg••-e″]) induced the trap levels with different depths in band gap and corresponded to the three components (at 110, 168, and 213 °C) of the thermoluminescence glow curve of Mg2SnO4. These trap levels with different depths were proved to be not independent. It revealed that the shallow traps (110 °C) and part of the deep traps (168 and 213 °C) were involved in the persistent luminescence. Meanwhile, all the shallow and deep traps were responsible for the photostimulated luminescence. Accordingly, the photoluminescence, persistent, and photostimulated luminescence mechanisms of the nondoped Mg2SnO4 material were first proposed.

  2. Wireless Luminescence Integrated Sensors (WLIS)

    SciTech Connect

    Simpson, M.L.; Sayler, G.S.

    2003-11-10

    The goal of this project was the development of a family of wireless, single-chip, luminescence-sensing devices to solve a number of difficult distributed measurement problems in areas ranging from environmental monitoring and assessment to high-throughput screening of combinatorial chemistry libraries. These wireless luminescence integrated sensors (WLIS) consist of a microluminometer, wireless data transmitter, and RF power input circuit all realized in a standard integrated circuit (IC) process with genetically engineered, whole-cell, bioluminescent bioreporters encapsulated and deposited on the IC. The end product is a family of compact, low-power, rugged, low-cost sensors. As part of this program they developed an integrated photodiode/signal-processing scheme with an rms noise level of 175 electrons/second for a 13-minute integration time, and a quantum efficiency of 66% at the 490-nm bioluminescent wavelength. this performance provided a detection limit of < 1000 photons/second. Although sol-gel has previously been used to encapsulate yeast cells, the reaction conditions necessary for polymerization (primarily low pH) have beforehand proven too harsh for bacterial cell immobilizations. Utilizing sonication methods, they have were able to initiate polymerization under pH conditions conductive to cell survival. both a toluene bioreporter (Pseudomonas putida TVA8) and a naphthalene bioreporter (Pseudomonas fluorescens HK44) were successfully encapsulated in sol-gel and shown to produce a fairly significant bioluminescent response. In addition to the previously developed naphthalene- and toluene-sensitive bioreporters, they developed a yeast-based xenoestrogen reporter. This technology has been licensed by Micro Systems Technologies, a startup company in Dayton, Ohio for applications in environmental containments monitoring, and for detecting weapons of mass destruction (i.e. homeland security).

  3. Bacteriophage recombination systems and biotechnical applications.

    PubMed

    Nafissi, Nafiseh; Slavcev, Roderick

    2014-04-01

    Bacteriophage recombination systems have been widely used in biotechnology for modifying prokaryotic species, for creating transgenic animals and plants, and more recently, for human cell gene manipulation. In contrast to homologous recombination, which benefits from the endogenous recombination machinery of the cell, site-specific recombination requires an exogenous source of recombinase in mammalian cells. The mechanism of bacteriophage evolution and their coexistence with bacterial cells has become a point of interest ever since bacterial viruses' life cycles were first explored. Phage recombinases have already been exploited as valuable genetic tools and new phage enzymes, and their potential application to genetic engineering and genome manipulation, vectorology, and generation of new transgene delivery vectors, and cell therapy are attractive areas of research that continue to be investigated. The significance and role of phage recombination systems in biotechnology is reviewed in this paper, with specific focus on homologous and site-specific recombination conferred by the coli phages, λ, and N15, the integrase from the Streptomyces phage, ΦC31, the recombination system of phage P1, and the recently characterized recombination functions of Yersinia phage, PY54. Key steps of the molecular mechanisms involving phage recombination functions and their application to molecular engineering, our novel exploitations of the PY54-derived recombination system, and its application to the development of new DNA vectors are discussed. PMID:24442504

  4. Lunar luminescence measurements

    NASA Technical Reports Server (NTRS)

    Morgan, T. H.

    1983-01-01

    Spectra of lunar sites obtained in June 1983 have been analyzed for residual luminescence using the spectral line depth technique. The results or three sites each at three wavelengths are presented. The sites observed were Mare Crisium, Kepler, and Aristarchus. In each case, the value quoted was based not only on the strong Fraunhofer line in the spectral range covered but also on from 11 to 21 weaker lines within 80 A of the strongest feature. These data do not support previous observations. The values given do not indicate a greatly reddened spectrum, and the luminescence spectrum of the mare site is not significantly different from the two young crater sites. These observations cannot be adequately explained by thermal luminescence, theories of direct excitation are also unable to explain the strength of the flux.

  5. Luminescent nanocrystal stress gauge

    PubMed Central

    Choi, Charina L.; Koski, Kristie J.; Olson, Andrew C. K.; Alivisatos, A. Paul

    2010-01-01

    Microscale mechanical forces can determine important outcomes ranging from the site of material fracture to stem cell fate. However, local stresses in a vast majority of systems cannot be measured due to the limitations of current techniques. In this work, we present the design and implementation of the CdSe-CdS core-shell tetrapod nanocrystal, a local stress sensor with bright luminescence readout. We calibrate the tetrapod luminescence response to stress and use the luminescence signal to report the spatial distribution of local stresses in single polyester fibers under uniaxial strain. The bright stress-dependent emission of the tetrapod, its nanoscale size, and its colloidal nature provide a unique tool that may be incorporated into a variety of micromechanical systems including materials and biological samples to quantify local stresses with high spatial resolution. PMID:21098301

  6. [Comparative Sensitivity of the Luminescent Photobacterium phosphoreum, Escherichia coli, and Bacillus subtilis Strains to Toxic Effects of Carbon-Based Nanomaterials and Metal Nanoparticles].

    PubMed

    Deryabina, D G; Efremova, L V; Karimov, I F; Manukhov, I V; Gnuchikh, E Yu; Miroshnikov, S A

    2016-01-01

    A comparative analysis of the four commercially available and laboratory luminescent sensor strains to the toxic effect of 10 carbon-based nanomatherials (CBNs) and 10 metal nanoparticles (MNPs) was carried out in this study. The bioluminescence inhibition assays with marine Photobacterium phosphoreum and recombinant Escherichia coli strains were varied in minimal toxic concentrations and EC50 values but led to well correlated biotoxicity evaluation for the most active compounds were ranked as Cu > (MgO, CuO) > (fullerenol, graphene oxide). The novel sensor strain Bacillus subtilis EG 168-1 exhibited the highest sensitivity to CBNs and MNPs that increased significantly number of toxic compounds causing the bacterial bioluminescence inhibition effect. PMID:27476206

  7. Cosmological Recombination

    NASA Astrophysics Data System (ADS)

    Wong, Wan Yan

    2008-11-01

    In this thesis we focus on studying the physics of cosmological recombination and how the details of recombination affect the Cosmic Microwave Background (CMB) anisotropies. We present a detailed calculation of the spectral line distortions on the CMB spectrum arising from the Lyman-alpha and the lowest two-photon transitions in the recombination of hydrogen (H), and the corresponding lines from helium (He). The peak of these distortions mainly comes from the Lyman-alpha transition and occurs at about 170 microns, which is the Wien part of the CMB. The major theoretical limitation for extracting cosmological parameters from the CMB sky lies in the precision with which we can calculate the cosmological recombination process. With this motivation, we perform a multi-level calculation of the recombination of H and He with the addition of the spin-forbidden transition for neutral helium (He I), plus the higher order two-photon transitions for H and among singlet states of He I. We find that the inclusion of the spin-forbidden transition results in more than a percent change in the ionization fraction, while the other transitions give much smaller effects. Last we modify RECFAST by introducing one more parameter to reproduce recent numerical results for the speed-up of helium recombination. Together with the existing hydrogen `fudge factor', we vary these two parameters to account for the remaining dominant uncertainties in cosmological recombination. By using a Markov Chain Monte Carlo method with Planck forecast data, we find that we need to determine the parameters to better than 10% for He I and 1% for H, in order to obtain negligible effects on the cosmological parameters.

  8. Quantum chemical modelling of ``green'' luminescence in ABO perovskites

    NASA Astrophysics Data System (ADS)

    Eglitis, R. I.; Kotomin, E. A.; Borstel, G.

    2002-06-01

    The origin of the intrinsic excitonic (``green'') luminescence in ABO3 perovskites remains a hot topic over the last quarter of a century. We suggest as a theoretical interpretation for the ``green'' luminescence in these crystals, the recombination of electron and hole polarons forming a charge transfer vibronic exciton. In order to check quantitatively the proposed model, we performed quantum chemical calculations using the Intermediate Neglect of Differential Overlap (INDO) method combined with the periodic defect model. The luminescence energies calculated for four perovskite crystals are found to be in good agreement with experimental data.

  9. A broadly applicable function for describing luminescence dose response

    SciTech Connect

    Burbidge, C. I.

    2015-07-28

    The basic form of luminescence dose response is investigated, with the aim of developing a single function to account for the appearance of linear, superlinear, sublinear, and supralinear behaviors and variations in saturation signal level and rate. A function is assembled based on the assumption of first order behavior in different major factors contributing to measured luminescence-dosimetric signals. Different versions of the function are developed for standardized and non-dose-normalized responses. Data generated using a two trap two recombination center model and experimental data for natural quartz are analyzed to compare results obtained using different signals, measurement protocols, pretreatment conditions, and radiation qualities. The function well describes a range of dose dependent behavior, including sublinear, superlinear, supralinear, and non-monotonic responses and relative response to α and β radiation, based on change in relative recombination and trapping probability affecting signals sourced from a single electron trap.

  10. A broadly applicable function for describing luminescence dose response

    NASA Astrophysics Data System (ADS)

    Burbidge, C. I.

    2015-07-01

    The basic form of luminescence dose response is investigated, with the aim of developing a single function to account for the appearance of linear, superlinear, sublinear, and supralinear behaviors and variations in saturation signal level and rate. A function is assembled based on the assumption of first order behavior in different major factors contributing to measured luminescence-dosimetric signals. Different versions of the function are developed for standardized and non-dose-normalized responses. Data generated using a two trap two recombination center model and experimental data for natural quartz are analyzed to compare results obtained using different signals, measurement protocols, pretreatment conditions, and radiation qualities. The function well describes a range of dose dependent behavior, including sublinear, superlinear, supralinear, and non-monotonic responses and relative response to α and β radiation, based on change in relative recombination and trapping probability affecting signals sourced from a single electron trap.

  11. Advanced synchronous luminescence system

    DOEpatents

    Vo-Dinh, T.

    1997-02-04

    A method and apparatus are disclosed for determining the condition of tissue or otherwise making chemical identifications includes exposing the sample to a light source, and using a synchronous luminescence system to produce a spectrum that can be analyzed for tissue condition. 14 figs.

  12. CCD Luminescence Camera

    NASA Technical Reports Server (NTRS)

    Janesick, James R.; Elliott, Tom

    1987-01-01

    New diagnostic tool used to understand performance and failures of microelectronic devices. Microscope integrated to low-noise charge-coupled-device (CCD) camera to produce new instrument for analyzing performance and failures of microelectronics devices that emit infrared light during operation. CCD camera also used to indentify very clearly parts that have failed where luminescence typically found.

  13. Recombinant bacterial amylopullulanases: developments and perspectives.

    PubMed

    Nisha, M; Satyanarayana, T

    2013-01-01

    Pullulanases are endo-acting enzymes capable of hydrolyzing α-1, 6-glycosidic linkages in starch, pullulan, amylopectin, and related oligosaccharides, while amylopullulanases are bifunctional enzymes with an active site capable of cleaving both α-1, 4 and α-1, 6 linkages in starch, amylose and other oligosaccharides, and α-1, 6 linkages in pullulan. The amylopullulanases are classified in GH13 and GH57 family enzymes based on the architecture of catalytic domain and number of conserved sequences. The enzymes with two active sites, one for the hydrolysis of α-1, 4- glycosidic bond and the other for α-1, 6-glycosidic bond, are called α-amylase-pullulanases, while amylopullulanases have only one active site for cleaving both α-1, 4- and α-1, 6-glycosidic bonds. The amylopullulanases produced by bacteria find applications in the starch and baking industries as a catalyst for one step starch liquefaction-saccharification for making various sugar syrups, as antistaling agent in bread and as a detergent additive. PMID:23645215

  14. Temperature influence on luminescent coupling efficiency in concentrator MJ SCs

    SciTech Connect

    Shvarts, Maxim Emelyanov, Viktor; Mintairov, Mikhail; Evstropov, Valery; Timoshina, Nailya

    2015-09-28

    In the work, presented are the results of investigation of temperature dependencies of the luminescent coupling effectiveness in lattice-matched (LM) GaInP/GaAs/Ge and metamorphic (MM) GaInP/GaInAs/Ge solar cells. The “ordinary” luminescent coupling effectiveness rise has been observed with temperature decrease for GaAs-Ge, GaInP-GaInAs and GaInAs-Ge pairs of subcells, and its limiting values have been defined. A “reverse” behavior of the luminescent coupling effectiveness for the GaInP-GaAs pair has been found, determined emittance potential drop of wideband GaInP p-n junction. It is shown that the established “unusual” behavior of the LC efficiency may be determined by the presence of thermalized centers of non-radiative recombination of charge carriers for the GaInP subcell in GaInP/GaAs/Ge LM structure. Estimation of characteristic parameters for the nonradiative recombination processes in wideband GaInP p-n junction has been carried out, and values for the energy of the nonradiative center thermalization (E{sub nrad2} =79.42meV) and for the activation energy of nonradiative band-to-band recombination (E{sub A}=33.4meV) have been obtained.

  15. A long persistent phosphor based on recombination centers originating from Zn imperfections.

    PubMed

    Li, Yang; Du, Xi; Sharafudeen, Kaniyarakkal; Liao, Chenxing; Qiu, Jianrong

    2014-04-01

    The recombination luminescence from Zn imperfections has been extensively investigated; however, there have been few reports on the long persistent luminescence of Zn imperfections as emitting centers. Here, we observed a long persistent luminescence in blue-white visible region from 6 ZnO:3 GeO2:Al2O3 phosphor with Zn imperfections as emitting centers. Persistent luminescence could be observed beyond 2h with naked eyes. The properties of traps were also elaborated by the measurements of thermo-luminescence spectra and photo-stimulated luminescence decay curves. Furthermore, a long persistent phosphor with warm white color was developed by doping Cr(3+) into 6 ZnO:3 GeO2:Al2O3 phosphor. PMID:24388995

  16. Spectrum Recombination.

    ERIC Educational Resources Information Center

    Greenslade, Thomas B., Jr.

    1984-01-01

    Describes several methods of executing lecture demonstrations involving the recombination of the spectrum. Groups the techniques into two general classes: bringing selected portions of the spectrum together using lenses or mirrors and blurring the colors by rapid movement or foreshortening. (JM)

  17. Interactions between bicarbonate, potassium, and magnesium, and sulfur-dependent induction of luminescence in Vibrio fischeri.

    PubMed

    Tabei, Yosuke; Era, Mariko; Ogawa, Akane; Morita, Hiroshi

    2012-06-01

    In spite of its central importance in research efforts, the relationship between seawater compounds and bacterial luminescence has not previously been investigated in detail. Thus, in this study, we investigated the effect of cations (Na(+) , K(+) , NH(4) (+) , Mg(2+) , and Ca(2+) ) and anions (Cl(-) , HCO(3) (-) , CO(3) (2-) , and NO(3) (-) ) on the induction of both inorganic (sulfate, sulfite, and thiosulfate) and organic (L-cysteine and L-cystine) sulfur-dependent luminescence in Vibrio fischeri. We found that HCO(3) (-) (bicarbonate) and CO(3) (2-) (carbonate), in the form of various compounds, had a stimulatory effect on sulfur-dependent luminescence. The luminescence induced by bicarbonate was further promoted by the addition of magnesium. Potassium also increased sulfur-dependent luminescence when sulfate or thiosulfate was supplied as the sole sulfur source, but not when sulfite, L-cysteine, or L-cystine was supplied. The positive effect of potassium was accelerated by the addition of magnesium and/or calcium. Furthermore, the additional supply of magnesium improved the induction of sulfite- or L-cysteine-dependent luminescence, but not the l-cystine-dependent type. These results suggest that sulfur-dependent luminescence of V. fischeri under nutrient-starved conditions is mainly controlled by bicarbonate, carbonate, and potassium. In addition, our results indicate that an additional supply of magnesium is effective for increasing V. fischeri luminescence. PMID:21953119

  18. Quantitative luminescence imaging system

    DOEpatents

    Erwin, D.N.; Kiel, J.L.; Batishko, C.R.; Stahl, K.A.

    1990-08-14

    The QLIS images and quantifies low-level chemiluminescent reactions in an electromagnetic field. It is capable of real time nonperturbing measurement and simultaneous recording of many biochemical and chemical reactions such as luminescent immunoassays or enzyme assays. The system comprises image transfer optics, a low-light level digitizing camera with image intensifying microchannel plates, an image process or, and a control computer. The image transfer optics may be a fiber image guide with a bend, or a microscope, to take the light outside of the RF field. Output of the camera is transformed into a localized rate of cumulative digitalized data or enhanced video display or hard-copy images. The system may be used as a luminescent microdosimetry device for radiofrequency or microwave radiation, as a thermal dosimeter, or in the dosimetry of ultra-sound (sonoluminescence) or ionizing radiation. It provides a near-real-time system capable of measuring the extremely low light levels from luminescent reactions in electromagnetic fields in the areas of chemiluminescence assays and thermal microdosimetry, and is capable of near-real-time imaging of the sample to allow spatial distribution analysis of the reaction. It can be used to instrument three distinctly different irradiation configurations, comprising (1) RF waveguide irradiation of a small Petri-dish-shaped sample cell, (2) RF irradiation of samples in a microscope for the microscopic imaging and measurement, and (3) RF irradiation of small to human body-sized samples in an anechoic chamber. 22 figs.

  19. Quantitative luminescence imaging system

    DOEpatents

    Erwin, David N.; Kiel, Johnathan L.; Batishko, Charles R.; Stahl, Kurt A.

    1990-01-01

    The QLIS images and quantifies low-level chemiluminescent reactions in an electromagnetic field. It is capable of real time nonperturbing measurement and simultaneous recording of many biochemical and chemical reactions such as luminescent immunoassays or enzyme assays. The system comprises image transfer optics, a low-light level digitizing camera with image intensifying microchannel plates, an image process or, and a control computer. The image transfer optics may be a fiber image guide with a bend, or a microscope, to take the light outside of the RF field. Output of the camera is transformed into a localized rate of cumulative digitalized data or enhanced video display or hard-copy images. The system may be used as a luminescent microdosimetry device for radiofrequency or microwave radiation, as a thermal dosimeter, or in the dosimetry of ultra-sound (sonoluminescence) or ionizing radiation. It provides a near-real-time system capable of measuring the extremely low light levels from luminescent reactions in electromagnetic fields in the areas of chemiluminescence assays and thermal microdosimetry, and is capable of near-real-time imaging of the sample to allow spatial distribution analysis of the reaction. It can be used to instrument three distinctly different irradiation configurations, comprising (1) RF waveguide irradiation of a small Petri-dish-shaped sample cell, (2) RF irradiation of samples in a microscope for the microscopie imaging and measurement, and (3) RF irradiation of small to human body-sized samples in an anechoic chamber.

  20. An Overview of Genetic Mechanisms in the Bacterial Cell.

    ERIC Educational Resources Information Center

    Metcalfe, Judith; Baumberg, Simon

    1988-01-01

    Outlines the genetic elements found in the bacterial cell which play a role in recombining DNA sequences. Provides a core structure to which the mechanisms occurring in and between bacterial cells can be related. Discusses the practicalities of recombinant DNA techniques. (Author/CW)

  1. An Introduction to Luminescence in Inorganic Solids.

    ERIC Educational Resources Information Center

    DeLuca, John A.

    1980-01-01

    Introduces luminescence by characterizing phosphors, describing phosphor phenomena, presenting a configurational coordinate model of characteristic luminescence, and describing some commercial applications of phosphors. (CS)

  2. Fibre-optic biosensor based on luminescence and immobilized enzymes: microdetermination of sorbitol, ethanol and oxaloacetate.

    PubMed

    Gautier, S M; Blum, L J; Coulet, P R

    1990-01-01

    We have investigated highly selective and ultrasensitive biosensors based on luminescent enzyme systems linked to optical transducers. A fibre-optic sensor with immobilized enzymes was designed; the solid-phase bioreagent was maintained in close contact contact with the tip of a glass fibre bundle connected to the photomultiplier tube of a luminometer. A bacterial luminescence fibre-optic sensor was used for the microdetermination of NADH. Various NAD(P)-dependent enzymes, sorbitol dehydrogenase, alcohol dehydrogenase and malate dehydrogenase, were co-immobilized on preactivated polyamide membranes with the bacterial system and used for the microdetermination of sorbitol, ethanol and oxaloacetate at the nanomolar level with a good precision. PMID:2316395

  3. Luminescence properties of lustre decorated majolica

    NASA Astrophysics Data System (ADS)

    Galli, A.; Martini, M.; Sibilia, E.; Padeletti, G.; Fermo, P.

    Luminescence measurements have been performed on several Italian Renaissance ceramic shards produced in central Italy, as well as on some others from Hispano-Moresque and Fatimid periods. The aim of this study was the characterisation of the raw materials used to manufacture lustre decorated majolica. At first, the thermoluminescence (TL) dating of all ceramic bodies was performed, because the shards lacked sure chronological attribution, having been provided by private collectors, or found during emergency restoration works or archaeological surveys. To characterise the defects and the recombination centers of the different components of the ceramics (ceramic body, glaze, glaze, and lustre), radioluminescence (RL) measurements have been performed on samples representative of each historical period. The dating results are reported, as well as the preliminary RL results.

  4. The nature of unusual luminescence in natural calcite, CaCO3

    SciTech Connect

    Gaft, M.; Nagli, L.; Panczer, G.; Waychunas, G.; Porat, N.

    2008-11-01

    The unusual luminescence of particular varieties of natural pink calcite (CaCO{sub 3}) samples was studied by laser-induced time-resolved luminescence spectroscopy at different temperatures. The luminescence is characterized by intense blue emission under short-wave UV lamp excitation with an extremely long decay time, accompanied by pink-orange luminescence under long wave UV excitation. Our investigation included optical absorption, natural thermostimulated luminescence (NTL) and Laser-Induced Breakdown Spectroscopy (LIBS) studies. Two luminescence centers were detected: a narrow violet band, with {lambda}{sub max} = 412 nm, {Delta} = 45 nm, two decay components of {tau}{sub 1} = 5 ns and {tau}{sub 2} = 7.2 ms, accompanied by very long afterglow, and an orange emission band with {lambda}{sub max} = 595 nm, {Delta} = 90 nm and {tau} = 5 ns. Both luminescence centers are thermally unstable with the blue emission disappearing after heating at 500 C, and the orange emission disappearing after heating at different temperatures starting from 230 C, although sometimes it is stable up to 500 C in different samples. Both centers have spectral-kinetic properties very unusual for mineral luminescence, which in combination with extremely low impurity concentrations, prevent their identification with specific impurity related emission. The most likely explanation of these observations may be the presence of radiation-induced luminescence centers. The long violet afterglow is evidently connected with trapped charge carrier liberation, with their subsequent migration through the valence band and ultimate recombination with a radiation-induced center responsible for the unusual violet luminescence.

  5. Recombinant bacteria for mosquito control.

    PubMed

    Federici, B A; Park, H-W; Bideshi, D K; Wirth, M C; Johnson, J J

    2003-11-01

    Bacterial insecticides have been used for the control of nuisance and vector mosquitoes for more than two decades. Nevertheless, due primarily to their high cost and often only moderate efficacy, these insecticides remain of limited use in tropical countries where mosquito-borne diseases are prevalent. Recently, however, recombinant DNA techniques have been used to improve bacterial insecticide efficacy by markedly increasing the synthesis of mosquitocidal proteins and by enabling new endotoxin combinations from different bacteria to be produced within single strains. These new strains combine mosquitocidal Cry and Cyt proteins of Bacillus thuringiensis with the binary toxin of Bacillus sphaericus, improving efficacy against Culex species by 10-fold and greatly reducing the potential for resistance through the presence of Cyt1A. Moreover, although intensive use of B. sphaericus against Culex populations in the field can result in high levels of resistance, most of this can be suppressed by combining this bacterial species with Cyt1A; the latter enables the binary toxin of this species to enter midgut epithelial cells via the microvillar membrane in the absence of a midgut receptor. The availability of these novel strains and newly discovered mosquitocidal proteins, such as the Mtx toxins of B. sphaericus, offers the potential for constructing a range of recombinant bacterial insecticides for more effective control of the mosquito vectors of filariasis, Dengue fever and malaria. PMID:14506223

  6. Self-trapped exciton and core-valence luminescence in BaF{sub 2} nanoparticles

    SciTech Connect

    Vistovskyy, V. V. Zhyshkovych, A. V.; Chornodolskyy, Ya. M.; Voloshinovskii, A. S.; Myagkota, O. S.; Gloskovskii, A.; Gektin, A. V.; Vasil'ev, A. N.; Rodnyi, P. A.

    2013-11-21

    The influence of the BaF{sub 2} nanoparticle size on the intensity of the self-trapped exciton luminescence and the radiative core-valence transitions is studied by the luminescence spectroscopy methods using synchrotron radiation. The decrease of the self-trapped exciton emission intensity at energies of exciting photons in the range of optical exciton creation (hν ≤ E{sub g}) is less sensitive to the reduction of the nanoparticle sizes than in the case of band-to-band excitation, where excitons are formed by the recombination way. The intensity of the core-valence luminescence shows considerably weaker dependence on the nanoparticle sizes in comparison with the intensity of self-trapped exciton luminescence. The revealed regularities are explained by considering the relationship between nanoparticle size and photoelectron or photohole thermalization length as well as the size of electronic excitations.

  7. Boron clusters in luminescent materials.

    PubMed

    Mukherjee, Sanjoy; Thilagar, Pakkirisamy

    2016-01-21

    In recent times, luminescent materials with tunable emission properties have found applications in almost all aspects of modern material sciences. Any discussion on the recent developments in luminescent materials would be incomplete if one does not account for the versatile photophysical features of boron containing compounds. Apart from triarylboranes and tetra-coordinate borate dyes, luminescent materials consisting of boron clusters have also found immense interest in recent times. Recent studies have unveiled the opportunities hidden within boranes, carboranes and metalloboranes, etc. as active constituents of luminescent materials. From simple illustrations of luminescence, to advanced applications in LASERs, OLEDs and bioimaging, etc., the unique features of such compounds and their promising versatility have already been established. In this review, recent revelations about the excellent photophysical properties of such materials are discussed. PMID:26574714

  8. New strategies for genetic engineering Pseudomonas syringae using recombination

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Here we report that DNA oligonucleotides (oligos) introduced directly into bacteria by electroporation can recombine with the bacterial chromosome. This phenomenon was identified in Pseudomonas syringae and we subsequently found that Escherichia coli, Salmonella typhimurium and Shigella flexneri are...

  9. Luminescent macrocyclic lanthanide complexes

    DOEpatents

    Raymond, Kenneth N; Corneillie, Todd M; Xu, Jide

    2014-05-20

    The present invention provides a novel class of macrocyclic compounds as well as complexes formed between a metal (e.g., lanthanide) ion and the compounds of the invention. Preferred complexes exhibit high stability as well as high quantum yields of lanthanide ion luminescence in aqueous media without the need for secondary activating agents. Preferred compounds incorporate hydroxy-isophthalamide moieties within their macrocyclic structure and are characterized by surprisingly low, non-specific binding to a variety of polypeptides such as antibodies and proteins as well as high kinetic stability. These characteristics distinguish them from known, open-structured ligands.

  10. Luminescent macrocyclic lanthanide complexes

    DOEpatents

    Raymond, Kenneth N.; Corneillie, Todd M.; Xu, Jide

    2012-05-08

    The present invention provides a novel class of macrocyclic compounds as well as complexes formed between a metal (e.g., lanthanide) ion and the compounds of the invention. Preferred complexes exhibit high stability as well as high quantum yields of lanthanide ion luminescence in aqueous media without the need for secondary activating agents. Preferred compounds incorporate hydroxy-isophthalamide moieties within their macrocyclic structure and are characterized by surprisingly low, non-specific binding to a variety of polypeptides such as antibodies and proteins as well as high kinetic stability. These characteristics distinguish them from known, open-structured ligands.

  11. Colloidal luminescent silicon nanorods.

    PubMed

    Lu, Xiaotang; Hessel, Colin M; Yu, Yixuan; Bogart, Timothy D; Korgel, Brian A

    2013-07-10

    Silicon nanorods are grown by trisilane decomposition in hot squalane in the presence of tin (Sn) nanocrystals and dodecylamine. Sn induces solution-liquid-solid nanorod growth with dodecylamine serving as a stabilizing ligand. As-prepared nanorods do not luminesce, but etching with hydrofluoric acid to remove residual surface oxide followed by thermal hydrosilylation with 1-octadecene induces bright photoluminescence with quantum yields of 4-5%. X-ray photoelectron spectroscopy shows that the ligands prevent surface oxidation for months when stored in air. PMID:23731184

  12. Method and apparatus for detecting and quantifying bacterial spores on a surface

    NASA Technical Reports Server (NTRS)

    Ponce, Adrian (Inventor)

    2009-01-01

    A method and an apparatus for detecting and quantifying bacterial spores on a surface. In accordance with the method: a matrix including lanthanide ions is provided on the surface containing the bacterial spores; functionalized aromatic molecules are released from the bacterial spores on the surface; a complex of the lanthanide ion and the aromatic molecule is formed on the surface; the complex of the lanthanide ion and the aromatic molecule is excited to generate a characteristic luminescence of the complex on the surface; and the bacterial spores exhibiting the luminescence of the complex on the surface are detected and quantified.

  13. Enhanced radiation detectors using luminescent materials

    DOEpatents

    Vardeny, Zeev V.; Jeglinski, Stefan A.; Lane, Paul A.

    2001-01-01

    A radiation detecting device comprising a radiation sensing element, and a layer of luminescent material to expand the range of wavelengths over which the sensing element can efficiently detect radiation. The luminescent material being selected to absorb radiation at selected wavelengths, causing the luminescent material to luminesce, and the luminescent radiation being detected by the sensing element. Radiation sensing elements include photodiodes (singly and in arrays), CCD arrays, IR detectors and photomultiplier tubes. Luminescent materials include polymers, oligomers, copolymers and porphyrines, Luminescent layers include thin films, thicker layers, and liquid polymers.

  14. Bacterial Sialidase

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Data shows that elevated sialidase in bacterial vaginosis patients correlates to premature births in women. Bacterial sialidase also plays a significant role in the unusual colonization of Pseudomonas aeruginosa in cystic fibrosis patients. Crystals of Salmonella sialidase have been reproduced and are used for studying the inhibitor-enzyme complexes. These inhibitors may also be used to inhibit a trans-sialidase of Trypanosome cruzi, a very similar enzyme to bacterial sialidase, therefore preventing T. cruzi infection, the causitive agent of Chagas' disease. The Center for Macromolecular Crystallography suggests that inhibitors of bacterial sialidases can be used as prophylactic drugs to prevent bacterial infections in these critical cases.

  15. Temperature lags of luminescence measurements in a commercial luminescence reader

    NASA Astrophysics Data System (ADS)

    Kitis, George; Kiyak, Nafiye G.; Polymeris, George S.

    2015-09-01

    The temperature recorded in thermoluminescence and optically stimulated luminescence equipments is not the temperature of the sample but that of the heating element on which the thermocouple is attached. Depending upon the rate of heating, a temperature difference appears between the samples and the heating element, termed as temperature lag, which could have serious effects on the curve shapes and trapping parameters. In the present work the temperature lag effect is studied in a newly developed luminescence equipment measuring both thermoluminescence and optically stimulated luminescence. It is found that the temperature lag could be large for heating rates above 2 K/s and it is strongly dependent upon the sample holder. A simple approximation method is proposed in order to both predict as well as correct for temperature lag effects in luminescence measurements.

  16. Luminescent screen composition and apparatus

    NASA Technical Reports Server (NTRS)

    Hilborn, E. H.

    1970-01-01

    Ultraviolet light projects photographically produced images on a screen composed of a mixture of linear and nonlinear phosphors whose spectral emissions are different. This allows the display of polychromatic luminescent images, which gives better discrimination of the objects being viewed.

  17. Lattice defects and recombination processes in non-linear crystals LiB3O5

    NASA Astrophysics Data System (ADS)

    Ogorodnikov, I. N.; Kruzhalov, A. V.; Porotnikov, A. V.; Yakovlev, Yu. V.

    The paper presents the results of a study of kinetics of the recombination processes in crystals LiB3O5 (LBO) obtained by the use of time-resolved luminescence and optical absorption spectroscopy. It was revealed that the observed peculiarities of the recombination processes in LBO are due to a participation of the trapped electron (B2+) and hole (O-) centres. In the framework of a model of the competing trapped hole centres the time dependence of both transient optical absorption and luminescence as well as their temperature dependencies was interpreted.

  18. Extrinsic optical recombination in pentacene single crystals: Evidence of gap states

    NASA Astrophysics Data System (ADS)

    He, Rui; Chi, X.; Pinczuk, Aron; Lang, D. V.; Ramirez, A. P.

    2005-11-01

    Two luminescence bands observed in pentacene single crystals with different degrees of purity are identified as due to extrinsic optical emissions. A band at 1.49 eV remains in the crystal with the highest purity. Its redshift of about 0.3 eV from the free exciton optical recombination suggests that the extrinsic transitions could involve gap states recently discovered in pentacene transistors. Absence of resonance Raman scattering when photon energies overlap the extrinsic recombination suggests that the gap states are likely due to impurities. The temperature dependence of luminescence intensities is interpreted by activated decay of excitons to radiative and nonradiative states.

  19. An infrared and luminescence study of tritiated amorphous silicon

    SciTech Connect

    Sidhu, L.S.; Kosteski, T.; Kherani, N.P.; Gaspari, F.; Zukotynski, S.; Shmayda, W.

    1997-07-01

    Tritium has been incorporated into amorphous silicon. Infrared spectroscopy shows new infrared vibration modes due to silicon-tritium (Si-T) bonds in the amorphous silicon network. Si-T vibration frequencies are related to Si-H vibration frequencies by simple mass relationships. Inelastic collisions of {beta} particles, produced as a result of tritium decay, with the amorphous silicon network results in the generation of electron-hole pairs. Radiative recombination of these carriers is observed. Dangling bonds associated with the tritium decay reduce luminescence efficiency.

  20. Photoactivation of luminescence in CdS nanocrystals

    PubMed Central

    Smyntyna, Valentyn; Skobeeva, Valentyna; Malushin, Nikolay

    2014-01-01

    Summary This paper presents the results of the research on the luminescence of cadmium sulfide nanocrystals (NCs) synthesized by colloid chemistry in a gelatinous matrix. The photostimulation of the short-wavelength emission band with λmax = 480 nm has been detected. It is shown that the determining factor of the photostimulation effect is the adsorption of the water molecules on the surface of NC. The observed effect is explained by the recombination mechanism that is responsible for the short-wavelength emission band. PMID:24778959

  1. Enhancement of Luminescence of Colloidal Ag2S Quantum Dots by Thionine Molecules

    NASA Astrophysics Data System (ADS)

    Ovchinnikov, O. V.; Grevtseva, I. G.; Kondratenko, T. S.; Smirnov, M. S.; Evtukhova, A. V.

    2016-07-01

    Enhancement of IR luminescence (1205 nm) of colloidal Ag2S quantum dots (QDs) with an average size of 2.5 ± 0.3 nm was detected upon excitation in the absorption band of thionine dye molecules (530-610 nm). It is found that the observed effect occurs during a hybrid association of Ag2S QDs with monomers of the cationic thionine (Th + ) molecule. It is concluded that the photosensitization of IR luminescence of colloidal Ag2S QDs is realized due to a resonance nonradiative transfer of electronic excitation energy directly to the centers of radiative recombination from the excited Th + molecules.

  2. Interfering with Bacterial Quorum Sensing

    PubMed Central

    Reuter, Kerstin; Steinbach, Anke; Helms, Volkhard

    2016-01-01

    Quorum sensing (QS) describes the exchange of chemical signals in bacterial populations to adjust the bacterial phenotypes according to the density of bacterial cells. This serves to express phenotypes that are advantageous for the group and ensure bacterial survival. To do so, bacterial cells synthesize autoinducer (AI) molecules, release them to the environment, and take them up. Thereby, the AI concentration reflects the cell density. When the AI concentration exceeds a critical threshold in the cells, the AI may activate the expression of virulence-associated genes or of luminescent proteins. It has been argued that targeting the QS system puts less selective pressure on these pathogens and should avoid the development of resistant bacteria. Therefore, the molecular components of QS systems have been suggested as promising targets for developing new anti-infective compounds. Here, we review the QS systems of selected gram-negative and gram-positive bacteria, namely, Vibrio fischeri, Pseudomonas aeruginosa, and Staphylococcus aureus, and discuss various antivirulence strategies based on blocking different components of the QS machinery. PMID:26819549

  3. Interfering with Bacterial Quorum Sensing.

    PubMed

    Reuter, Kerstin; Steinbach, Anke; Helms, Volkhard

    2016-01-01

    Quorum sensing (QS) describes the exchange of chemical signals in bacterial populations to adjust the bacterial phenotypes according to the density of bacterial cells. This serves to express phenotypes that are advantageous for the group and ensure bacterial survival. To do so, bacterial cells synthesize autoinducer (AI) molecules, release them to the environment, and take them up. Thereby, the AI concentration reflects the cell density. When the AI concentration exceeds a critical threshold in the cells, the AI may activate the expression of virulence-associated genes or of luminescent proteins. It has been argued that targeting the QS system puts less selective pressure on these pathogens and should avoid the development of resistant bacteria. Therefore, the molecular components of QS systems have been suggested as promising targets for developing new anti-infective compounds. Here, we review the QS systems of selected gram-negative and gram-positive bacteria, namely, Vibrio fischeri, Pseudomonas aeruginosa, and Staphylococcus aureus, and discuss various antivirulence strategies based on blocking different components of the QS machinery. PMID:26819549

  4. A Novel Universal Detection Agent for Time-Gated Luminescence Bioimaging

    PubMed Central

    Sayyadi, Nima; Care, Andrew; Connally, Russell E.; Try, Andrew C.; Bergquist, Peter L.; Sunna, Anwar

    2016-01-01

    Luminescent lanthanide chelates have been used to label antibodies in time-gated luminescence (TGL) bioimaging. However, it is a challenging task to label directly an antibody with lanthanide-binding ligands and achieve control of the target ligand/protein ratios whilst ensuring that affinity and avidity of the antibody remain uncompromised. We report the development of a new indirect detection reagent to label antibodies with detectable luminescence that circumvents this problem by labelling available lysine residues in the linker portion of the recombinant fusion protein Linker-Protein G (LPG). Succinimide-activated lanthanide chelating ligands were attached to lysine residues in LPG and Protein G (without Linker) and the resulting Luminescence-Activating (LA-) conjugates were compared for total incorporation and conjugation efficiency. A higher and more efficient incorporation of ligands at three different molar ratios was observed for LPG and this effect was attributed to the presence of eight readily available lysine residues in the linker region of LPG. These Luminescence-Activating (LA-) complexes were subsequently shown to impart luminescence (upon formation of europium(III) complexes) to cell-specific antibodies within seconds and without the need for any complicated bioconjugation procedures. The potential of this technology was demonstrated by direct labelling of Giardia cysts and Cryptosporidium oocysts in TGL bioimaging. PMID:27282464

  5. A Novel Universal Detection Agent for Time-Gated Luminescence Bioimaging.

    PubMed

    Sayyadi, Nima; Care, Andrew; Connally, Russell E; Try, Andrew C; Bergquist, Peter L; Sunna, Anwar

    2016-01-01

    Luminescent lanthanide chelates have been used to label antibodies in time-gated luminescence (TGL) bioimaging. However, it is a challenging task to label directly an antibody with lanthanide-binding ligands and achieve control of the target ligand/protein ratios whilst ensuring that affinity and avidity of the antibody remain uncompromised. We report the development of a new indirect detection reagent to label antibodies with detectable luminescence that circumvents this problem by labelling available lysine residues in the linker portion of the recombinant fusion protein Linker-Protein G (LPG). Succinimide-activated lanthanide chelating ligands were attached to lysine residues in LPG and Protein G (without Linker) and the resulting Luminescence-Activating (LA-) conjugates were compared for total incorporation and conjugation efficiency. A higher and more efficient incorporation of ligands at three different molar ratios was observed for LPG and this effect was attributed to the presence of eight readily available lysine residues in the linker region of LPG. These Luminescence-Activating (LA-) complexes were subsequently shown to impart luminescence (upon formation of europium(III) complexes) to cell-specific antibodies within seconds and without the need for any complicated bioconjugation procedures. The potential of this technology was demonstrated by direct labelling of Giardia cysts and Cryptosporidium oocysts in TGL bioimaging. PMID:27282464

  6. Bacterial Proteasomes

    PubMed Central

    Jastrab, Jordan B.; Darwin, K. Heran

    2015-01-01

    Interest in bacterial proteasomes was sparked by the discovery that proteasomal degradation is required for the pathogenesis of Mycobacterium tuberculosis, one of the world's deadliest pathogens. Although bacterial proteasomes are structurally similar to their eukaryotic and archaeal homologs, there are key differences in their mechanisms of assembly, activation, and substrate targeting for degradation. In this article, we compare and contrast bacterial proteasomes with their archaeal and eukaryotic counterparts, and we discuss recent advances in our understanding of how bacterial proteasomes function to influence microbial physiology. PMID:26488274

  7. Turning on the Light: Lessons from Luminescence

    ERIC Educational Resources Information Center

    O'Hara, Patricia B.; Engelson, Carol; St. Peter, Wayne

    2005-01-01

    Some of the processes by which light is emitted without a simultaneous change in temperature are discussed and is classified as luminescence or cold light. Luminescent processes include triboluminescence, fluorescence, phosphorescence, chemiluminescence, and bioluminescence.

  8. Utilizing Nanofabrication to Construct Strong, Luminescent Materials

    SciTech Connect

    Chen, Wei; Huang, Gang; Lu, Hong B.; McCready, David E.; Joly, Alan G.; Bovin, Jan-Olov

    2006-05-28

    Luminescent materials have been utilized widely in applications from lighting to sensing. The new development of technologies based on luminescence properties requires the materials to have high luminescence efficiency and mechanical strength. In this article, we report the fabrication of luminescent materials possessing high mechanical strength by nanofabrication with polyvinyl alcohol used as a stabilizer or coupling agent. X-ray diffraction and high resolution transmission microscope observations reveal that the nanocomposite sample contains ZnS and ZnO nanoparticles as well as kozoite and sodium nitrate. The mechanical strength and hardness of these nanocomposite materials are higher than polycarbonate and some carbon nanotube reinforced nanocomposites. Strong luminescence is observed in the new nanocomposites and the luminescence intensity does not degrade following up to 30 minutes of X-ray irradiation. Our results indicate that nanofabrication may provide a good method to improve the mechanical strength of luminescent materials for some applications in which high strength luminescent materials are needed.

  9. Applications of luminescent systems to infectious disease methodology

    NASA Technical Reports Server (NTRS)

    Picciolo, G. L.; Chappelle, E. W.; Deming, J. W.; Mcgarry, M. A.; Nibley, D. A.; Okrend, H.; Thomas, R. R.

    1976-01-01

    The characterization of a clinical sample by a simple, fast, accurate, automatable analytical measurement is important in the management of infectious disease. Luminescence assays offer methods rich with options for these measurements. The instrumentation is common to each assay, and the investment is reasonable. Three general procedures were developed to varying degrees of completeness which measure bacterial levels by measuring their ATP, FMN and iron porphyrins. Bacteriuria detection and antibiograms can be determined within half a day. The characterization of the sample for its soluble ATP, FMN or prophyrins was also performed.

  10. Method and apparatus for detecting and quantifying bacterial spores on a surface

    NASA Technical Reports Server (NTRS)

    Ponce, Adrian (Inventor)

    2009-01-01

    A method and an apparatus for detecting and quantifying bacterial spores on a surface. In accordance with the method: bacterial spores are transferred from a place of origin to a test surface, the test surface comprises lanthanide ions. Aromatic molecules are released from the bacterial spores; a complex of the lanthanide ions and aromatic molecules is formed on the test surface, the complex is excited to generate a characteristic luminescence on the test surface; the luminescence on the test surface is detected and quantified.

  11. Luminescence study of homeopathic remedies

    NASA Astrophysics Data System (ADS)

    Lobyshev, Valentin I.; Tomkevitch, Marie

    2001-06-01

    It was shown in our recent papers that distilled water possesses intrinsic luminescence at wavelength of about 400 nm with excitation wavelength 300 nm, which is very sensitive to small amount of dissolved substances. This phenomena was chosen to study homeopathic remedies. Pronounced difference in the intensity of luminescence between several commercial preparations with the same potency and one preparation with various potencies was obtained. Long scale evolution of the spectra was registered and final result was dependent on preparation and its potency. Systematic study of homeopathic preparations of halit (natural sodium chloride) from 1 to 30 decimal dilution was done. A stepwise dilution with mechanical agitation between the dilution steps, the so-called potentisation, was produced specially by homeopathic company Weleda. Luminescence intensity against concentration (potency) of halit is non monotonous function with several maxima, the main maximum is located at 13-14-th dilution. Evolution of the spectra was registered during several months. The analogous potentisation treatment of water without additional substances results also in changes of the luminescence spectra, depending on the number of potentisation. The obtained differences of luminescence spectra at ultra high dilutions and potentisation show that the collective properties of water are really changed in homeopathic preparations.

  12. Method of measuring luminescence of a material

    DOEpatents

    Miller, Steven D.

    2015-12-15

    A method of measuring luminescence of a material is disclosed. The method includes applying a light source to excite an exposed material. The method also includes amplifying an emission signal of the material. The method further includes measuring a luminescent emission at a fixed time window of about 10 picoseconds to about 10 nanoseconds. The luminescence may be radio photoluminescence (RPL) or optically stimulated luminescence (OSL).

  13. Turn-On Luminescent Probes for the Real-Time Monitoring of Endogenous Hydroxyl Radicals in Living Cells.

    PubMed

    Zhou, Wenjuan; Cao, Yuqing; Sui, Dandan; Lu, Chao

    2016-03-18

    The utilization of semiconductor quantum dots (QDs) as optical labels for biosensing and biorecognition has made substantial progress. However, the development of a suitable QD-based luminescent probe that is capable of detecting individual reactive oxygen species (ROS) represents a great challenge, mainly because the fluorescence of QDs is quenched by a wide variety of ROS. To overcome this limitation, a novel QD-based turn-on luminescent probe for the specific detection of (.) OH has been designed, and its application in monitoring the endogenous release of (.) OH species in living cells is demonstrated. Metal citrate complexes on the surfaces of the QDs can act as electron donors, injecting electrons into the LUMO of the QDs, while (.) OH can inject holes into the HOMO of the QDs. Accordingly, electron-hole pairs are produced, which could emit strong luminescence by electron-hole recombination. Importantly, this luminescent probe does not respond to other ROS. PMID:26918802

  14. Specificity of aequorin luminescence to calcium

    NASA Technical Reports Server (NTRS)

    Shimomura, O.; Johnson, F. H.

    1975-01-01

    The presence of Pb(++), Co(++), Cu(++), and Cd(++), each of which possesses a certain luminescence-triggering activity of aequorin, potentially interferes with the specificity of the aequorin luminescence response to Ca(++). Interference by the above cations can be eliminated, without influencing the sensitivity of the luminescence of aequorin to Ca(++), by adding 1 mM of sodium diethyldithiocarbamate.

  15. Bias-dependence of luminescent coupling efficiency in multijunction solar cells.

    PubMed

    Jia, Jieyang; Miao, Yu; Kang, Yangsen; Huo, Yijie; Mazouchi, Mojgan; Chen, Yusi; Zhao, Li; Deng, Huiyang; Supaniratisai, Pakapol; AlQahtani, Sara H; Harris, James S

    2015-04-01

    In this work, we demonstrate an improved method to simulate the characteristics of multijunction solar cell by introducing a bias-dependent luminescent coupling efficiency. The standard two-diode equivalent-circuit model with constant luminescent coupling efficiency has limited accuracy because it does not include the recombination current from photogenerated carriers. Therefore, we propose an alternative analytical method with bias-dependent luminescent coupling efficiency to model multijunction cell behavior. We show that there is a noticeable difference in the J-V characteristics and cell performance generated by simulations with a constant vs. bias-dependent coupling efficiency. The results indicate that introducing a bias-dependent coupling efficiency produces more accurate modeling of multijunction cell behavior under real operating conditions. PMID:25968788

  16. Defect luminescence in films containing Ge and GeO{sub 2} nanocrystals

    SciTech Connect

    Zacharias, M.; Atherton, S.J.; Fauchet, P.M.

    1997-07-01

    Amorphous SiO{sub x} alloys containing Ge or GeO{sub 2} nanocrystals are produced by dc-magnetron sputtering and controlled crystallization. The samples are investigated by Raman scattering, transmission electron microscopy, photoluminescence and excitation spectroscopy. Under UV excitation, both types of films luminesce around 3.1 eV, with identical PL line shapes and subnanosecond PL dynamics. The strongest PL intensity is found for the films containing FeO{sub 2} crystals and for the largest nanocrystals. These results are a clear indication that although the blue luminescence is without a doubt correlated with the formation of Ge (or GeO{sub 2}) nanocrystals, it is not produced by the radiative recombination of excitons confined in the nanocrystals. Possible mechanisms for the luminescence are discussed, including defects at the nanocrystal/matric interface or in the matrix itself.

  17. Surface Chemically Switchable Ultraviolet Luminescence from Interfacial Two-Dimensional Electron Gas.

    PubMed

    Islam, Mohammad A; Saldana-Greco, Diomedes; Gu, Zongquan; Wang, Fenggong; Breckenfeld, Eric; Lei, Qingyu; Xu, Ruijuan; Hawley, Christopher J; Xi, X X; Martin, Lane W; Rappe, Andrew M; Spanier, Jonathan E

    2016-01-13

    We report intense, narrow line-width, surface chemisorption-activated and reversible ultraviolet (UV) photoluminescence from radiative recombination of the two-dimensional electron gas (2DEG) with photoexcited holes at LaAlO3/SrTiO3. The switchable luminescence arises from an electron transfer-driven modification of the electronic structure via H-chemisorption onto the AlO2-terminated surface of LaAlO3, at least 2 nm away from the interface. The control of the onset of emission and its intensity are functionalities that go beyond the luminescence of compound semiconductor quantum wells. Connections between reversible chemisorption, fast electron transfer, and quantum-well luminescence suggest a new model for surface chemically reconfigurable solid-state UV optoelectronics and molecular sensing. PMID:26675987

  18. Unraveling the luminescence signatures of chemical defects in polyethylene.

    PubMed

    Chen, Lihua; Tran, Huan Doan; Wang, Chenchen; Ramprasad, Rampi

    2015-09-28

    Chemical defects in polyethylene (PE) can deleteriously downgrade its electrical properties and performance. Although these defects usually leave spectroscopic signatures in terms of characteristic luminescence peaks, it is nontrivial to make unambiguous assignments of the peaks to specific defect types. In this work, we go beyond traditional density functional theory calculations to determine intra-defect state transition and charge recombination process derived emission and absorption energies in PE. By calculating the total energy differences of the neutral defect at excited and ground states, the emission energies from intra-defect state transition are obtained, reasonably explaining the photoluminescence peaks in PE. In order to study the luminescence emitted in charge recombination processes, we characterize PE defect levels in terms of thermodynamic and optical charge transition levels that involve total energy calculations of neutral and charged defects. Calculations are performed at several levels of theory including those involving (semi)local and hybrid electron exchange-correlation functionals, and many-body perturbation theory. With these critical elements, the emission energies are computed and further used to clarify and confirm the origins of the observed electroluminescence and thermoluminescence peaks. PMID:26429041

  19. Unraveling the luminescence signatures of chemical defects in polyethylene

    SciTech Connect

    Chen, Lihua; Tran, Huan Doan; Wang, Chenchen; Ramprasad, Rampi

    2015-09-28

    Chemical defects in polyethylene (PE) can deleteriously downgrade its electrical properties and performance. Although these defects usually leave spectroscopic signatures in terms of characteristic luminescence peaks, it is nontrivial to make unambiguous assignments of the peaks to specific defect types. In this work, we go beyond traditional density functional theory calculations to determine intra-defect state transition and charge recombination process derived emission and absorption energies in PE. By calculating the total energy differences of the neutral defect at excited and ground states, the emission energies from intra-defect state transition are obtained, reasonably explaining the photoluminescence peaks in PE. In order to study the luminescence emitted in charge recombination processes, we characterize PE defect levels in terms of thermodynamic and optical charge transition levels that involve total energy calculations of neutral and charged defects. Calculations are performed at several levels of theory including those involving (semi)local and hybrid electron exchange-correlation functionals, and many-body perturbation theory. With these critical elements, the emission energies are computed and further used to clarify and confirm the origins of the observed electroluminescence and thermoluminescence peaks.

  20. A luminescent nanocrystal stress gauge

    SciTech Connect

    Choi, Charina; Koski, Kristie; Olson, Andrew; Alivisatos, Paul

    2010-10-25

    Microscale mechanical forces can determine important outcomes ranging from the site of material fracture to stem cell fate. However, local stresses in a vast majority of systems cannot be measured due to the limitations of current techniques. In this work, we present the design and implementation of the CdSe/CdS core/shell tetrapod nanocrystal, a local stress sensor with bright luminescence readout. We calibrate the tetrapod luminescence response to stress, and use the luminescence signal to report the spatial distribution of local stresses in single polyester fibers under uniaxial strain. The bright stress-dependent emission of the tetrapod, its nanoscale size, and its colloidal nature provide a unique tool that may be incorporated into a variety of micromechanical systems including materials and biological samples to quantify local stresses with high spatial resolution.

  1. Quantitative Luminescence Imaging System

    SciTech Connect

    Batishko, C.R.; Stahl, K.A.; Fecht, B.A.

    1992-12-31

    The goal of the MEASUREMENT OF CHEMILUMINESCENCE project is to develop and deliver a suite of imaging radiometric instruments for measuring spatial distributions of chemiluminescence. Envisioned deliverables include instruments working at the microscopic, macroscopic, and life-sized scales. Both laboratory and field portable instruments are envisioned. The project also includes development of phantoms as enclosures for the diazoluminomelanin (DALM) chemiluminescent chemistry. A suite of either phantoms in a variety of typical poses, or phantoms that could be adjusted to a variety of poses, is envisioned. These are to include small mammals (rats), mid-sized mammals (monkeys), and human body parts. A complete human phantom that can be posed is a long-term goal of the development. Taken together, the chemistry and instrumentation provide a means for imaging rf dosimetry based on chemiluminescence induced by the heat resulting from rf energy absorption. The first delivered instrument, the Quantitative Luminescence Imaging System (QLIS), resulted in a patent, and an R&D Magazine 1991 R&D 100 award, recognizing it as one of the 100 most significant technological developments of 1991. The current status of the project is that three systems have been delivered, several related studies have been conducted, two preliminary human hand phantoms have been delivered, system upgrades have been implemented, and calibrations have been maintained. Current development includes sensitivity improvements to the microscope-based system; extension of the large-scale (potentially life-sized targets) system to field portable applications; extension of the 2-D large-scale system to 3-D measurement; imminent delivery of a more refined human hand phantom and a rat phantom; rf, thermal and imaging subsystem integration; and continued calibration and upgrade support.

  2. Luminescent lanthanide coordination polymers

    SciTech Connect

    Ma, L.; Evans, O.R.; Foxman, B.M.; Lin, W.

    1999-12-13

    One-dimensional lanthanide coordination polymers with the formula Ln(isonicotinate){sub 3}(H{sub 2}O){sub 2} (Ln = Ce, Pr, Nd, Sm, Eu, Tb; 1a-f) were synthesized by treating nitrate or perchlorate salts of Ln(III) with 4-pyridinecarboxaldehyde under hydro(solvo)thermal conditions. Single-crystal and powder X-ray diffraction studies indicate that these lanthanide coordination polymers adopt two different structures. While Ce(III), Pr(III), and Nd(III) complexes adopt a chain structure with alternating Ln-(carboxylate){sub 2}-Ln and Ln-(carboxylate){sub 4}-Ln linkages, Sm(III), Eu(III), and Tb(III) complexes have a doubly carboxylate-bridged infinite-chain structure with one chelating carboxylate group on each metal center. In both structures, the lanthanide centers also bind to two water molecules to yield an eight-coordinate, square antiprismatic geometry. The pyridine nitrogen atoms of the isonicotinate groups do not coordinate to the metal centers in these lanthanide(III) complexes; instead, they direct the formation of Ln(III) coordination polymers via hydrogen bonding with coordinated water molecules. Photoluminescence measurements show that Tb(isonicotinate){sub 3}(H{sub 2}O){sub 2} is highly emissive at room temperature with a quantum yield of {approximately}90%. These results indicate that highly luminescent lanthanide coordination polymers can be assembled using a combination of coordination and hydrogen bonds. Crystal data for 1a: monoclinic space group P2{sub 1}/c, a = 9.712(2) {angstrom}, b = 19.833(4) {angstrom}, c = 11.616(2) {angstrom}, {beta} = 111.89(3){degree}, Z = 4. Crystal data for 1f: monoclinic space group C2/c, a = 20.253(4) {angstrom}, b = 11.584(2) {angstrom}, c = 9.839(2) {angstrom}, {beta} = 115.64(3){degree}, Z = 8.

  3. Rapid screening for soil ecotoxicity with a battery of luminescent bacteria tests.

    PubMed

    Heinlaan, Margit; Kahru, Anne; Kasemets, Kaja; Kurvet, Imbi; Waterlot, Cristophe; Sepp, Kalev; Dubourguier, Henri-Charles; Douay, Francis

    2007-03-01

    A bacterial test battery, involving i) Microtox, an aquatic test, ii) the Flash assay, a soil-suspension test (with Vibrio fischeri as the test organism), and iii) the Metal Detector assay, a semi-specific aquatic test for heavy metals (with recombinant luminescent Escherichia coli), was used in a combined toxicological and chemical hazard assessment of Estonian soils sampled from a former Soviet military airfield (13 samples) and from traffic-influenced roadsides (5 samples). The soils showed slightly elevated levels of total petroleum hydrocarbons (TPH), but not of heavy metals. In most of the samples, the levels of TPH did not exceed the Estonian permitted limit values set for residential areas. Toxicity testing was performed on both fresh and dried soils, after aqueous extraction for 1 hour and 24 hours. The toxicity results obtained with the Microtox test did not significantly differ in all of the sample treatment schemes; however, it appeared that the drying and sieving of the soils increased the bioavailability of toxicants, probably due to an enlarged reactive soil surface area. According to chemical analysis of the soils and the data from the Microtox test and the Metal Detector assay (performed on aqueous elutriates of the soils), these soils would not be considered to be hazardous. In contrast, the Flash assay performed on soil-water suspensions of dried soils, showed that most of the soils were toxic and thus probably contained undetermined particle-bound bioavailable toxicants. The photobacterial toxicity test (the Flash assay) can be recommended for the rapid screening of soils, as it is sensitive, cheap and inexpensive, and provides valuable information on particle-bound bioavailable toxicants, useful for complementing a chemical analysis and for assessing the risks originating from polluted soils. PMID:17411358

  4. Tunable Luminescence of Silicon Nanoparticles

    NASA Astrophysics Data System (ADS)

    Vladimirov, A.; Korovin, S.; Surkov, A.; Kelm, E.; Pustovoy, V.

    2010-10-01

    The luminescent properties of silicon nanoparticles were studied. The particles were prepared by laser pyrolysis of silane in a gas flow reactor. Initially non-luminescent particles were treated by the chemical etching in mixture of fluoric and nitric acids. The high and stable photoluminescence from etched particles was observed. With increasing etching time, the PL peak shifted to blue region. With decreasing of the excitation wavelength from 660 nm to 365 nm, the PL peak shifted from 820 nm to 660 nm. This allows us to use the silicon based particles for wavelength selected excitation in some practical application.

  5. Bacterial Keratitis

    MedlinePlus

    ... very quickly, and if left untreated, can cause blindness. The bacteria usually responsible for this type of ... to intense ultraviolet radiation exposure, e.g. snow blindness or welder's arc eye). Next Bacterial Keratitis Symptoms ...

  6. Recombinant protein production technology

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Recombinant protein production is an important technology for antibody production, biochemical activity study, and structural determination during the post-genomic era. Limiting factors in recombinant protein production include low-level protein expression, protein precipitation, and loss of protein...

  7. Effect of ultrasonic treatment on photoelectric and luminescent properties of ZnSe crystals

    SciTech Connect

    Zobov, E. M. Zobov, M. E.; Gabibov, F. S.; Kamilov, I. K.; Manyakhin, F. I.; Naimi, E. K.

    2008-03-15

    The results of the effect of ultrasonic treatment of ZnSe crystals on the structure of the energy spectrum of electronic states of centers with deep levels forming photoelectric and luminescent properties of this compound are presented. It is for the first time proved experimentally that the climb of edge dislocations under the effect of ultrasound leads to regrouping and generation of defects forming deep levels, which manifest themselves in phenomena of photosensitivity and radiative recombination.

  8. Therapeutic Recombinant Monoclonal Antibodies

    ERIC Educational Resources Information Center

    Bakhtiar, Ray

    2012-01-01

    During the last two decades, the rapid growth of biotechnology-derived techniques has led to a myriad of therapeutic recombinant monoclonal antibodies with significant clinical benefits. Recombinant monoclonal antibodies can be obtained from a number of natural sources such as animal cell cultures using recombinant DNA engineering. In contrast to…

  9. Radiation-induced luminescence in magnesium aluminate spinel crystals and ceramics

    NASA Astrophysics Data System (ADS)

    Gritsyna, V. T.; Kazarinov, Yu. G.; Kobyakov, V. A.; Reimanis, I. E.

    2006-09-01

    Radioluminescence (RL) and thermoluminescence (TL) in spinel crystals and ceramics were investigated to elucidate the radiation-induced electronic processes in single crystals grown by Verneuil and Czochralski methods as well as transparent and translucent ceramics. Both RL and TL spectra demonstrate a UV-band related to electron-hole recombination luminescence at intrinsic defects; green and red luminescence are identified with emission of Mn 2+- and Cr 3+-ions, respectively. The kinetics of growth of different RL luminescence bands depending on dose at the prolonged X-irradiation shows the competitive character of charge and energy transfer between defects and impurity ions. The dependence of RL intensity on the temperature of the sample was measured in the range of 300-750 K and compared with TL for different emission bands. The variety of maxima in the temperature dependence of RL and in the glow curves of TL measured for different luminescence bands in spinels of different origins and crystalline forms is used to show that charge carrier traps and luminescence centers are not isolated defects but are complexes of defects and impurities. The formation, structure and properties of these complexes depend on the processing conditions.

  10. Luminescence evolution from alumina ceramic surface before flashover under direct and alternating current voltage in vacuum

    NASA Astrophysics Data System (ADS)

    Su, Guo-Qiang; Wang, Yi-Bo; Song, Bai-Peng; Mu, Hai-Bao; Zhang, Guan-Jun; Li, Feng; Wang, Meng

    2016-06-01

    The luminescence evolution phenomena from alumina ceramic surface in vacuum under high voltage of direct and alternating current are reported, with the voltage covering a large range from far below to close to the flashover voltage. Its time resolved and spatial distributed behaviors are examined by a photon counting system and an electron-multiplying charge-coupled device (EMCCD) together with a digital camera, respectively. The luminescence before flashover exhibits two stages as voltage increasing, i.e., under a relative low voltage (Stage A), the luminescence is ascribed to radiative recombination of hetero-charges injected into the sample surface layer by Schottky effect; under a higher voltage (Stage B), a stable secondary electron emission process, resulting from the Fowler-Nordheim emission at the cathode triple junction (CTJ), is responsible for the luminescence. Spectrum analysis implies that inner secondary electrons within the surface layer of alumina generated during the SSEE process also participate in the luminescence of Stage B. A comprehensive interpretation of the flashover process is formulated, which might promote a better understanding of flashover issue in vacuum.

  11. Origin of green luminescence in hydrothermally grown ZnO single crystals

    SciTech Connect

    Čížek, J. Hruška, P.; Melikhova, O.; Procházka, I.; Valenta, J.; Novotný, M.; Bulíř, J.

    2015-06-22

    Combining photoluminescence and positron annihilation studies of hydrothermally grown ZnO crystals with stoichiometry varied by controlled annealing enabled us to clarify the origin of green luminescence. It was found that green luminescence in ZnO has multiple origins and consists of a band at 2.3(1) eV due to recombination of electrons of the conduction band by zinc vacancy acceptors coupled with hydrogen and a band at 2.47(2) eV related to oxygen vacancies. The as-grown ZnO crystals contain zinc vacancies associated with hydrogen and exhibit a green luminescence at 2.3(1) eV. Annealing in Zn vapor removed zinc vacancies and introduced oxygen vacancies. This led to disappearance of the green luminescence band at 2.3(1) eV and appearance of a green emission at higher energy of 2.47(2) eV. Moreover, the color of the crystal was changed from colorless to dark red. In contrast, annealing of the as-grown crystal in Cd vapor did not remove zinc vacancies and did not cause any significant change of green luminescence nor change in coloration.

  12. Luminescence dynamics of bound exciton of hydrogen doped ZnO nanowires

    DOE PAGESBeta

    Yoo, Jinkyoung; Yi, Gyu -Chul; Chon, Bonghwan; Joo, Taiha; Wang, Zhehui

    2016-04-11

    In this study, all-optical camera, converting X-rays into visible photons, is a promising strategy for high-performance X-ray imaging detector requiring high detection efficiency and ultrafast detector response time. Zinc oxide is a suitable material for all-optical camera due to its fast radiative recombination lifetime in sub-nanosecond regime and its radiation hardness. ZnO nanostructures have been considered as proper building blocks for ultrafast detectors with spatial resolution in sub-micrometer scale. To achieve remarkable enhancement of luminescence efficiency n-type doping in ZnO has been employed. However, luminescence dynamics of doped ZnO nanostructures have not been thoroughly investigated whereas undoped ZnO nanostructures havemore » been employed to study their luminescence dynamics. Here we report a study of luminescence dynamics of hydrogen doped ZnO nanowires obtained by hydrogen plasma treatment. Hydrogen doping in ZnO nanowires gives rise to significant increase in the near-band-edge emission of ZnO and decrease in averaged photoluminescence lifetime from 300 to 140 ps at 10 K. The effects of hydrogen doping on the luminescent characteristics of ZnO nanowires were changed by hydrogen doping process variables.« less

  13. Recombineering homologous recombination constructs in Drosophila.

    PubMed

    Carreira-Rosario, Arnaldo; Scoggin, Shane; Shalaby, Nevine A; Williams, Nathan David; Hiesinger, P Robin; Buszczak, Michael

    2013-01-01

    The continued development of techniques for fast, large-scale manipulation of endogenous gene loci will broaden the use of Drosophila melanogaster as a genetic model organism for human-disease related research. Recent years have seen technical advancements like homologous recombination and recombineering. However, generating unequivocal null mutations or tagging endogenous proteins remains a substantial effort for most genes. Here, we describe and demonstrate techniques for using recombineering-based cloning methods to generate vectors that can be used to target and manipulate endogenous loci in vivo. Specifically, we have established a combination of three technologies: (1) BAC transgenesis/recombineering, (2) ends-out homologous recombination and (3) Gateway technology to provide a robust, efficient and flexible method for manipulating endogenous genomic loci. In this protocol, we provide step-by-step details about how to (1) design individual vectors, (2) how to clone large fragments of genomic DNA into the homologous recombination vector using gap repair, and (3) how to replace or tag genes of interest within these vectors using a second round of recombineering. Finally, we will also provide a protocol for how to mobilize these cassettes in vivo to generate a knockout, or a tagged gene via knock-in. These methods can easily be adopted for multiple targets in parallel and provide a means for manipulating the Drosophila genome in a timely and efficient manner. PMID:23893070

  14. Plasmon enhancement of luminescence upconversion.

    PubMed

    Park, Wounjhang; Lu, Dawei; Ahn, Sungmo

    2015-05-21

    Frequency conversion has always been an important topic in optics. Nonlinear optics has traditionally focused on frequency conversion based on nonlinear susceptibility but with the recent development of upconversion nanomaterials, luminescence upconversion has begun to receive renewed attention. While upconversion nanomaterials open doors to a wide range of new opportunities, they remain too inefficient for most applications. Incorporating plasmonic nanostructures provides a promising pathway to highly efficient upconversion. Naturally, a plethora of theoretical and experimental studies have been published in recent years, reporting enhancements up to several hundred. It is however difficult to make meaningful comparisons since the plasmonic fields are highly sensitive to the local geometry and excitation condition. Also, many luminescence upconversion processes involve multiple steps via different physical mechanisms and the overall output is often determined by a delicate interplay among them. This review is aimed at offering a comprehensive framework for plasmon enhanced luminescence upconversion. We first present quantum electrodynamics descriptions for all the processes involved in luminescence upconversion, which include absorption, emission, energy transfer and nonradiative transitions. We then present a bird's eye view of published works on plasmon enhanced upconversion, followed by more detailed discussion on comparable classes of nanostructures, the effects of spacer layers and local heating, and the dynamics of the plasmon enhanced upconversion process. Plasmon enhanced upconversion is a challenging and exciting field from the fundamental scientific perspective and also from technological standpoints. It offers an excellent system to study how optical processes are affected by the local photonic environment. This type of research is particularly timely as the plasmonics is placing heavier emphasis on nonlinearity. At the same time, efficient upconversion

  15. Differential Requirements of Singleplex and Multiplex Recombineering of Large DNA Constructs

    PubMed Central

    Reddy, Thimma R.; Kelsall, Emma J.; Fevat, Léna M. S.; Munson, Sarah E.; Cowley, Shaun M.

    2015-01-01

    Recombineering is an in vivo genetic engineering technique involving homologous recombination mediated by phage recombination proteins. The use of recombineering methodology is not limited by size and sequence constraints and therefore has enabled the streamlined construction of bacterial strains and multi-component plasmids. Recombineering applications commonly utilize singleplex strategies and the parameters are extensively tested. However, singleplex recombineering is not suitable for the modification of several loci in genome recoding and strain engineering exercises, which requires a multiplex recombineering design. Defining the main parameters affecting multiplex efficiency especially the insertion of multiple large genes is necessary to enable efficient large-scale modification of the genome. Here, we have tested different recombineering operational parameters of the lambda phage Red recombination system and compared singleplex and multiplex recombineering of large gene sized DNA cassettes. We have found that optimal multiplex recombination required long homology lengths in excess of 120 bp. However, efficient multiplexing was possible with only 60 bp of homology. Multiplex recombination was more limited by lower amounts of DNA than singleplex recombineering and was greatly enhanced by use of phosphorothioate protection of DNA. Exploring the mechanism of multiplexing revealed that efficient recombination required co-selection of an antibiotic marker and the presence of all three Red proteins. Building on these results, we substantially increased multiplex efficiency using an ExoVII deletion strain. Our findings elucidate key differences between singleplex and multiplex recombineering and provide important clues for further improving multiplex recombination efficiency. PMID:25954970

  16. Photoionization and Recombination

    NASA Technical Reports Server (NTRS)

    Nahar, Sultana N.

    2000-01-01

    Theoretically self-consistent calculations for photoionization and (e + ion) recombination are described. The same eigenfunction expansion for the ion is employed in coupled channel calculations for both processes, thus ensuring consistency between cross sections and rates. The theoretical treatment of (e + ion) recombination subsumes both the non-resonant recombination ("radiative recombination"), and the resonant recombination ("di-electronic recombination") processes in a unified scheme. In addition to the total, unified recombination rates, level-specific recombination rates and photoionization cross sections are obtained for a large number of atomic levels. Both relativistic Breit-Pauli, and non-relativistic LS coupling, calculations are carried out in the close coupling approximation using the R-matrix method. Although the calculations are computationally intensive, they yield nearly all photoionization and recombination parameters needed for astrophysical photoionization models with higher precision than hitherto possible, estimated at about 10-20% from comparison with experimentally available data (including experimentally derived DR rates). Results are electronically available for over 40 atoms and ions. Photoionization and recombination of He-, and Li-like C and Fe are described for X-ray modeling. The unified method yields total and complete (e+ion) recombination rate coefficients, that can not otherwise be obtained theoretically or experimentally.

  17. Bacterial ghosts as multifunctional vaccine particles.

    PubMed

    Szostak, M P; Mader, H; Truppe, M; Kamal, M; Eko, F O; Huter, V; Marchart, J; Jechlinger, W; Haidinger, W; Brand, E; Denner, E; Resch, S; Dehlin, E; Katinger, A; Kuen, B; Haslberger, A; Hensel, A; Lubitz, W

    1997-02-01

    Expression of cloned PhiX174 gene E in Gram-negative bacteria results in lysis of the bacteria by formation of an E-specific transmembrane tunnel structure built through the cell envelope complex. Bacterial ghosts have been produced from a variety of bacteria including Escherichia coli. Salmonella typhimurium, Salmonella enteritidis, Vibrio cholerae, Klebsiella pneumoniae, Actinobacillus pleuropneumoniae, Haemophilus influenzae, Pasteurella haemolytica, Pasteurella multocida, and Helicobacter pylori. Such ghosts are used as non-living candidate vaccines and represent an alternative to heat or chemically inactivated bacteria. In recombinant ghosts, foreign proteins can be inserted into the inner membrane prior to E-mediated lysis via specific N-, or C-, or N- and C-terminal anchor sequences. The export of proteins into the periplasmic space or the expression of recombinant S-layer proteins vastly extents the capacity of ghosts or recombinant ghosts as carriers of foreign epitopes or proteins. Oral, aerogenic or parenteral applications of (recombinant) ghosts in experimental animals induced specific humoral and cellular immune responses against bacterial and target components including protective mucosal immunity. The most relevant advantage of ghosts and recombinant bacterial ghosts as immunogens is that no inactivation procedures that denature relevant immunogenic determinants are employed in the production of ghosts used as vaccines or as carriers of relevant antigens. The inserted target antigens into the inner membrane or into S-layer proteins are not limited in size. PMID:9382740

  18. Biodiversity among luminescent symbionts from squid of the genera Uroteuthis, Loliolus and Euprymna (Mollusca: Cephalopoda).

    PubMed

    Guerrero-Ferreira, R C; Nishiguchi, M K

    2007-10-01

    Luminescent bacteria in the family Vibrionaceae (Bacteria: γ-Proteobacteria) are commonly found in complex, bilobed light organs of sepiolid and loliginid squids. Although morphology of these organs in both families of squid is similar, the species of bacteria that inhabit each host has yet to be verified. We utilized sequences of 16S ribosomal RNA, luciferase α-subunit (luxA) and the glyceraldehyde-3-phosphate dehydrogenase (gapA) genes to determine phylogenetic relationships between 63 strains of Vibrio bacteria, which included representatives from different environments as well as unidentified luminescent isolates from loliginid and sepiolid squid from Thailand. A combined phylogenetic analysis was used including biochemical data such as carbon use, growth and luminescence. Results demonstrated that certain symbiotic Thai isolates found in the same geographic area were included in a clade containing bacterial species phenotypically suitable to colonize light organs. Moreover, multiple strains isolated from a single squid host were identified as more than one bacteria species in our phylogeny. This research presents evidence of species of luminescent bacteria that have not been previously described as symbiotic strains colonizing light organs of Indo-West Pacific loliginid and sepiolid squids, and supports the hypothesis of a non-species-specific association between certain sepiolid and loliginid squids and marine luminescent bacteria. PMID:22707847

  19. Bacterial Immunity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A variety of bacterial agents reside in and around the environment that can cause illness and death in a poultry flock. Many cause disseminated disease while others exert more local effects such as the respiratory or gastrointestinal tract. The host, for our current purposes the laying hen, has de...

  20. Specific features of the luminescence and conductivity of zinc selenide on exposure to X-ray and optical excitation

    SciTech Connect

    Degoda, V. Ya. Sofienko, A. O.

    2010-05-15

    The set of experimental data on the X-ray-excited luminescence and X-ray induced conductivity of ZnSe are compared to the data on the photoluminescence and photoconductivity. It is experimentally established that the current-voltage characteristics and the kinetics of phosphorescence and current relaxation depend on the type of excitation. It is found that the external electric field influences the intensity and shape of bands in the luminescence spectra. It is shown that the character of excitation defines the kinetics of recombination, charge carrier trapping, and conductivity in wide-gap semiconductors.

  1. Dating sediments using luminescence signals

    SciTech Connect

    Wintle, A. )

    1993-05-01

    Before siting a nuclear power station or a nuclear waste repository, it is necessary to establish that the area has been free of earthquake activity for a sufficient period of time. Evidence of past earthquake activity is often provided by faults in surface sediments. Age limits for fault formation can be set by obtaining the depositional ages of the sediment unit in which the fault was formed and the overlying sediment. A useful technique would be one that dating could be applied to the mineral grains that make up the sediments and that would give the time that has passed since the grains were blown or washed into position. Luminescence dating techniques, of which the most well known is thermo-luminescence (TL), provide such information. This approach has been successful in dating movement on the Wasatch Fault in Utah. A combination of TL and radiocarbon dates indicated that three faulting events had occurred within the past 5000 years. 2 refs., 1 fig.

  2. Material for a luminescent solar concentrator

    DOEpatents

    Andrews, L.J.

    1984-01-01

    A material for use in a luminescent solar concentrator, formed by ceramitizing the luminescent ion Cr/sup 3 +/ with a transparent ceramic glass containing mullite. The resultant material has tiny Cr/sup 3 +/-bearing crystallites dispersed uniformly through an amorphous glass. The invention combines the high luminescent efficiency of Cr/sup 3 +/ in the crystalline phase with the practical and economical advantages of glass technology.

  3. Apparatus for reducing solvent luminescence background emissions

    DOEpatents

    Affleck, R.L.; Ambrose, W.P.; Demas, J.N.; Goodwin, P.M.; Johnson, M.E.; Keller, R.A.; Petty, J.T.; Schecker, J.A.; Wu, M.

    1998-11-10

    The detectability of luminescent molecules in solution is enhanced by reducing the background luminescence due to impurity species also present in the solution. A light source that illuminates the solution acts to photolyze the impurities so that the impurities do not luminesce in the fluorescence band of the molecule of interest. Molecules of interest may be carried through the photolysis region in the solution or may be introduced into the solution after the photolysis region. 6 figs.

  4. Apparatus for reducing solvent luminescence background emissions

    DOEpatents

    Affleck, Rhett L.; Ambrose, W. Patrick; Demas, James N.; Goodwin, Peter M.; Johnson, Mitchell E.; Keller, Richard A.; Petty, Jeffrey T.; Schecker, Jay A.; Wu, Ming

    1998-01-01

    The detectability of luminescent molecules in solution is enhanced by reducing the background luminescence due to impurity species also present in the solution. A light source that illuminates the solution acts to photolyze the impurities so that the impurities do not luminesce in the fluorescence band of the molecule of interest. Molecules of interest may be carried through the photolysis region in the solution or may be introduced into the solution after the photolysis region.

  5. Photon Luminescence of the Moon

    NASA Technical Reports Server (NTRS)

    Wilson, T.L.; Lee, K.T.

    2009-01-01

    Luminescence is typically described as light emitted by objects at low temperatures, induced by chemical reactions, electrical energy, atomic interactions, or acoustical and mechanical stress. An example is photoluminescence created when photons (electromagnetic radiation) strike a substance and are absorbed, resulting in the emission of a resonant fluorescent or phosphorescent albedo. In planetary science, there exists X-ray fluorescence induced by sunlight absorbed by a regolith a property used to measure some of the chemical composition of the Moon s surface during the Apollo program. However, there exists an equally important phenomenon in planetary science which will be designated here as photon luminescence. It is not conventional photoluminescence because the incoming radiation that strikes the planetary surface is not photons but rather cosmic rays (CRs). Nevertheless, the result is the same: the generation of a photon albedo. In particular, Galactic CRs (GCRs) and solar energetic particles (SEPs) both induce a photon albedo that radiates from the surface of the Moon. Other particle albedos are generated as well, most of which are hazardous (e.g. neutrons). The photon luminescence or albedo of the lunar surface induced by GCRs and SEPs will be derived here, demonstrating that the Moon literally glows in the dark (when there is no sunlight or Earthshine). This extends earlier work on the same subject [1-4]. A side-by-side comparison of these two albedos and related mitigation measures will also be discussed.

  6. Luminescent detection of hydrazine and hydrazine derivatives

    DOEpatents

    Swager, Timothy M.; Thomas, III, Samuel W.

    2012-04-17

    The present invention generally relates to methods for modulating the optical properties of a luminescent polymer via interaction with a species (e.g., an analyte). In some cases, the present invention provides methods for determination of an analyte by monitoring a change in an optical signal of a luminescent polymer upon exposure to an analyte. Methods of the present invention may be useful for the vapor phase detection of analytes such as explosives and toxins. The present invention also provides methods for increasing the luminescence intensity of a polymer, such as a polymer that has been photobleached, by exposing the luminescent polymer to a species such as a reducing agent.

  7. Luminescence properties of a Fibonacci photonic quasicrystal.

    PubMed

    Passias, V; Valappil, N V; Shi, Z; Deych, L; Lisyansky, A A; Menon, V M

    2009-04-13

    An active one-dimensional Fibonacci photonic quasi-crystal is realized via spin coating. Luminescence properties of an organic dye embedded in the quasi-crystal are studied experimentally and compared to theoretical simulations. The luminescence occurs via the pseudo-bandedge mode and follows the dispersion properties of the Fibonacci crystal. Time resolved luminescence measurement of the active structure shows faster spontaneous emission rate, indicating the effect of the large photon densities available at the bandedge due to the presence of critically localized states. The experimental results are in good agreement with the theoretical calculations for steady-state luminescence spectra. PMID:19365490

  8. Resonance-shifting luminescent solar concentrators

    SciTech Connect

    Giebink, Noel Christopher; Wiederrecht, Gary P; Wasielewski, Michael R

    2014-09-23

    An optical system and method to overcome luminescent solar concentrator inefficiencies by resonance-shifting, in which sharply directed emission from a bi-layer cavity into a glass substrate returns to interact with the cavity off-resonance at each subsequent reflection, significantly reducing reabsorption loss en route to the edges. In one embodiment, the system comprises a luminescent solar concentrator comprising a transparent substrate, a luminescent film having a variable thickness; and a low refractive index layer disposed between the transparent substrate and the luminescent film.

  9. Recombination of cluster ions

    NASA Technical Reports Server (NTRS)

    Johnsen, Rainer

    1993-01-01

    Some of our recent work on molecular band emissions from recombination of molecular dimer ions (N4(+) and CO(+) CO) is discussed. Much of the experimental work was done by Y. S. Cao; the results on N4(+) recombination have been published. A brief progress report is given on our ongoing measurements of neutral products of recombination using the flowing-afterglow Langmuir-probe technique in conjunction with laser-induced fluorescence.

  10. Recombination in electron coolers

    NASA Astrophysics Data System (ADS)

    Wolf, A.; Gwinner, G.; Linkemann, J.; Saghiri, A. A.; Schmitt, M.; Schwalm, D.; Grieser, M.; Beutelspacher, M.; Bartsch, T.; Brandau, C.; Hoffknecht, A.; Müller, A.; Schippers, S.; Uwira, O.; Savin, D. W.

    2000-02-01

    An introduction to electron-ion recombination processes is given and recent measurements are described as examples, focusing on low collision energies. Discussed in particular are fine-structure-mediated dielectronic recombination of fluorine-like ions, the moderate recombination enhancement by factors of typically 1.5-4 found for most ion species at relative electron-ion energies below about 10 meV, and the much larger enhancement occurring for specific highly charged ions of complex electronic structure, apparently caused by low-energy dielectronic recombination resonances. Recent experiments revealing dielectronic resonances with very large natural width are also described.

  11. Theoretical study of time-resolved luminescence in semiconductors. III. Trap states in the band gap

    SciTech Connect

    Maiberg, Matthias Hölscher, Torsten; Zahedi-Azad, Setareh; Scheer, Roland

    2015-09-14

    In the third part of this series, we study the influence of trap states in the band gap of semiconductors on the time-resolved luminescence decay (TRL) after a pulsed excitation. The results based on simulations with Synopsys TCAD{sup ®} and analytical approximations are given for p-doped Cu(In,Ga)Se{sub 2} as a working example. We show that a single trap can be mostly described by two parameters which are assigned to minority carrier capture and emission. We analyze their influence on the luminescence decay and study the difference between a single trap and an energetic Gaussian trap distribution. It is found that trap states artificially increase the TRL decay and obscure the recombination dynamics. Thus, there is a demand for experimental methods which can reveal the recombination of minority carriers in a TRL experiment without trapping effect. In this regard, a variation of the device temperature, the excitation frequency, the injection level, as well as a bias illumination may be promising approaches. We study these methods, discuss advantages and disadvantages, and show experimental TRL for prove of concept. At the end, we validate our approach of simulating only band-to-band radiative recombination although photoluminescence spectra often exhibit free-to-bound radiative recombination of charge carriers.

  12. Studying bacterial quorum-sensing at the single cell level

    NASA Astrophysics Data System (ADS)

    Delfino Perez, Pablo; Pelakh, Leslie; Young, Jonathan; Johnson, Elaine; Hagen, Stephen

    2010-03-01

    Like many bacterial species, Vibrio fischeri can detect its own population density through a quorum sensing (QS) mechanism. The bacterium releases a signal molecule (AI, autoinducer), which accumulates at high population density and triggers a genetic switch. In V.fischeri this leads to bioluminescence. Little is known about how stochastic gene expression affects QS at the level of single cells. We are imaging the luminescence of individual V.fischeri cells in a flow chamber and directly measuring the intercell variability in AI activation of the QS circuit. Our single-cell luminescence experiments allow us to track cells over time and characterize variations in their response to AI levels. We find heterogeneous response to the external signal: at a given AI concentration some cells may be strongly luminescent while others are virtually dark. The analysis of noise in the individual cell response can eventually lead to a better understanding of how cells use QS to gather information about their environment.

  13. Infrared negative luminescent devices and higher operating temperature detectors

    NASA Astrophysics Data System (ADS)

    Nash, Geoff R.; Gordon, Neil T.; Hall, David J.; Little, J. Chris; Masterton, G.; Hails, J. E.; Giess, J.; Haworth, L.; Emeny, Martin T.; Ashley, Tim

    2004-02-01

    Infrared LEDs and negative luminescent devices, where less light is emitted than in equilibrium, have been attracting an increasing amount of interest recently. They have a variety of applications, including as a ‘source" of IR radiation for gas sensing; radiation shielding for and non-uniformity correction of high sensitivity starring infrared detectors; and dynamic infrared scene projection. Similarly, IR detectors are used in arrays for thermal imaging and, discretely, in applications such as gas sensing. Multi-layer heterostructure epitaxy enables the growth of both types of device using designs in which the electronic processes can be precisely controlled and techniques such as carrier exclusion and extraction can be implemented. This enables detectors to be made which offer good performance at higher than normal operating temperatures, and efficient negative luminescent devices to be made which simulate a range of effective temperatures whilst operating uncooled. In both cases, however, additional performance benefits can be achieved by integrating optical concentrators around the diodes to reduce the volume of semiconductor material, and so minimise the thermally activated generation-recombination processes which compete with radiative mechanisms. The integrated concentrators are in the form of Winston cones, which can be formed using an iterative dry etch process involving methane/hydrogen and oxygen. We will present results on negative luminescence in the mid and long IR wavebands, from devices made from indium antimonide and mercury cadmium telluride, where the aim is sizes greater than 1cm x 1cm. We will also discuss progress on, and the potential for, operating temperature and/or sensitivity improvement of detectors, where very higher performance imaging is anticipated from systems which require no mechanical cooling.

  14. Infrared negative luminescent devices and higher operating temperature detectors

    NASA Astrophysics Data System (ADS)

    Nash, G. R.; Gordon, N. T.; Hall, D. J.; Ashby, M. K.; Little, J. C.; Masterton, G.; Hails, J. E.; Giess, J.; Haworth, L.; Emeny, M. T.; Ashley, T.

    2004-01-01

    Infrared LEDs and negative luminescent devices, where less light is emitted than in equilibrium, have been attracting an increasing amount of interest recently. They have a variety of applications, including as a ‘source’ of IR radiation for gas sensing; radiation shielding for, and non-uniformity correction of, high sensitivity staring infrared detectors; and dynamic infrared scene projection. Similarly, infrared (IR) detectors are used in arrays for thermal imaging and, discretely, in applications such as gas sensing. Multi-layer heterostructure epitaxy enables the growth of both types of device using designs in which the electronic processes can be precisely controlled and techniques such as carrier exclusion and extraction can be implemented. This enables detectors to be made which offer good performance at higher than normal operating temperatures, and efficient negative luminescent devices to be made which simulate a range of effective temperatures whilst operating uncooled. In both cases, however, additional performance benefits can be achieved by integrating optical concentrators around the diodes to reduce the volume of semiconductor material, and so minimise the thermally activated generation-recombination processes which compete with radiative mechanisms. The integrated concentrators are in the form of Winston cones, which can be formed using an iterative dry etch process involving methane/hydrogen and oxygen. We present results on negative luminescence in the mid- and long-IR wavebands, from devices made from indium antimonide and mercury cadmium telluride, where the aim is sizes greater than 1 cm×1 cm. We also discuss progress on, and the potential for, operating temperature and/or sensitivity improvement of detectors, where very high-performance imaging is anticipated from systems which require no mechanical cooling.

  15. Infrared Negative Luminescent Devices and Higher Operating Temperature Detectors

    NASA Astrophysics Data System (ADS)

    Ashley, Tim

    2003-03-01

    Infrared LEDs and negative luminescent devices, where less light is emitted than in equilibrium, have been attracting an increasing amount of interest recently. They have a variety of applications, including as a source' of IR radiation for gas sensing; radiation shielding for and non-uniformity correction of high sensitivity starring infrared detectors; and dynamic infrared scene projection. Similarly, IR detectors are used in arrays for thermal imaging and, discretely, in applications such as gas sensing. Multi-layer heterostructure epitaxy enables the growth of both types of device using designs in which the electronic processes can be precisely controlled and techniques such as carrier exclusion and extraction can be implemented. This enables detectors to be made which offer good performance at higher than normal operating temperatures, and efficient negative luminescent devices to be made which simulate a range of effective temperatures whilst operating uncooled. In both cases, however, additional performance benefits can be achieved by integrating optical concentrators around the diodes to reduce the volume of semiconductor material, and so minimise the thermally activated generation-recombination processes which compete with radiative mechanisms. The integrated concentrators are in the form of Winston cones, which can be formed using an iterative dry etch process involving methane/hydrogen and oxygen. We will present results on negative luminescence in the mid and long IR wavebands, from devices made from indium antimonide and mercury cadmium telluride, where the aim is sizes greater than 1cm x 1cm. We will also discuss progress on, and the potential for, operating temperature and/or sensitivity improvement of detectors, where very high performance imaging is anticipated from systems which require no mechanical cooling.

  16. The origin of white luminescence from silicon oxycarbide thin films

    SciTech Connect

    Nikas, V.; Gallis, S. Huang, M.; Kaloyeros, A. E.; Nguyen, A. P. D.; Stesmans, A.; Afanas'ev, V. V.

    2014-02-10

    Silicon oxycarbide (SiC{sub x}O{sub y}) is a promising material for achieving strong room-temperature white luminescence. The present work investigated the mechanisms for light emission in the visible/ultraviolet range (1.5–4.0 eV) from chemical vapor deposited amorphous SiC{sub x}O{sub y} thin films, using a combination of optical characterizations and electron paramagnetic resonance (EPR) measurements. Photoluminescence (PL) and EPR studies of samples, with and without post-deposition passivation in an oxygen and forming gas (H{sub 2} 5 at. % and N{sub 2} 95 at. %) ambient, ruled out typical structural defects in oxides, e.g., Si-related neutral oxygen vacancies or non-bridging oxygen hole centers, as the dominant mechanism for white luminescence from SiC{sub x}O{sub y}. The observed intense white luminescence (red, green, and blue emission) is believed to arise from the generation of photo-carriers by optical absorption through C-Si-O related electronic transitions, and the recombination of such carriers between bands and/or at band tail states. This assertion is based on the realization that the PL intensity dramatically increased at an excitation energy coinciding with the E{sub 04} band gaps of the material, as well as by the observed correlation between the Si-O-C bond density and the PL intensity. An additional mechanism for the existence of a blue component of the white emission is also discussed.

  17. [Bacterial vaginosis].

    PubMed

    Romero Herrero, Daniel; Andreu Domingo, Antonia

    2016-07-01

    Bacterial vaginosis (BV) is the main cause of vaginal dysbacteriosis in the women during the reproductive age. It is an entity in which many studies have focused for years and which is still open for discussion topics. This is due to the diversity of microorganisms that cause it and therefore, its difficult treatment. Bacterial vaginosis is probably the result of vaginal colonization by complex bacterial communities, many of them non-cultivable and with interdependent metabolism where anaerobic populations most likely play an important role in its pathogenesis. The main symptoms are an increase of vaginal discharge and the unpleasant smell of it. It can lead to serious consequences for women, such as an increased risk of contracting sexually transmitted infections including human immunodeficiency virus and upper genital tract and pregnancy complications. Gram stain is the gold standard for microbiological diagnosis of BV, but can also be diagnosed using the Amsel clinical criteria. It should not be considered a sexually transmitted disease but it is highly related to sex. Recurrence is the main problem of medical treatment. Apart from BV, there are other dysbacteriosis less characterized like aerobic vaginitis of which further studies are coming slowly but are achieving more attention and consensus among specialists. PMID:27474242

  18. An improved recombineering approach by adding RecA to lambda Red recombination.

    PubMed

    Wang, Junping; Sarov, Mihail; Rientjes, Jeanette; Fu, Jun; Hollak, Heike; Kranz, Harald; Xie, Wei; Stewart, A Francis; Zhang, Youming

    2006-01-01

    Recombineering is the use of homologous recombination in Escherichia coli for DNA engineering. Of several approaches, use of the lambda phage Red operon is emerging as the most reliable and flexible. The Red operon includes three components: Redalpha, a 5' to 3' exonuclease, Redbeta, an annealing protein, and Redgamma, an inhibitor of the major E. coli exonuclease and recombination complex, RecBCD. Most E. coli cloning hosts are recA deficient to eliminate recombination and therefore enhance the stability of cloned DNAs. However, loss of RecA also impairs general cellular integrity. Here we report that transient RecA co-expression enhances the total number of successful recombinations in bacterial artificial chromosomes (BACs), mostly because the E. coli host is more able to survive the stresses of DNA transformation procedures. We combined this practical improvement with the advantages of a temperature-sensitive version of the low copy pSC101 plasmid to develop a protocol that is convenient and more efficient than any recombineering procedure, for use of either double- or single-stranded DNA, published to date. PMID:16382181

  19. Stacking fault related luminescence in GaN nanorods.

    PubMed

    Forsberg, M; Serban, A; Poenaru, I; Hsiao, C-L; Junaid, M; Birch, J; Pozina, G

    2015-09-01

    Optical and structural properties are presented for GaN nanorods (NRs) grown in the [0001] direction on Si(111) substrates by direct-current reactive magnetron sputter epitaxy. Transmission electron microscopy (TEM) reveals clusters of dense stacking faults (SFs) regularly distributed along the c-axis. A strong emission line at ∼3.42 eV associated with the basal-plane SFs has been observed in luminescence spectra. The optical signature of SFs is stable up to room temperatures with the activation energy of ∼20 meV. Temperature-dependent time-resolved photoluminescence properties suggest that the recombination mechanism of the 3.42 eV emission can be understood in terms of multiple quantum wells self-organized along the growth axis of NRs. PMID:26267041

  20. Luminescence stability of porous Si terminated by hydrophilic organic molecules

    NASA Astrophysics Data System (ADS)

    Matsumoto, Kimihisa; Kamiguchi, Masao; Kamiya, Kazuhide; Nomura, Takashi; Suzuki, Shinya

    2016-02-01

    The effects of the surface termination of a porous Si surface by propionic acid and by undecylenic acid on their hydrophilicity and luminescence stability were studied. In the measurements of the contact angle of water droplets on porous Si films, the hydrophilicity of porous Si is improved by the surface termination each types of organic molecule. The PL intensity of as-prepared porous Si decreased with increasing aging time in ambient air. As PL quenching involves PL blue shift and increasing Si-O bonds density, nonradiative recombination centers are formed in the surface oxide. After the hydrosilylation process of propionic acid and undecylenic acid, PL intensity decreased and became 30% that of as-prepared porous Si film. However, the PL intensity was stable and exceeded that of the as-prepared film after 1000 min of aging in the ambient air. The PL stabilities are contributed to the termination by organic molecules that inhibits surface oxidation.

  1. EBIC and luminescence studies of defects in solar cells.

    PubMed

    Breitenstein, O; Bauer, J; Kittler, M; Arguirov, T; Seifert, W

    2008-01-01

    Electron beam-induced current (EBIC) can be used to detect electronic irregularities in solar cells, such as shunts and precipitates, and to perform physical characterization of defects by, e.g. measuring the temperature dependence of their recombination activity. Recently also luminescence methods such as electroluminescence (EL) and photoluminescence (PL) have been shown to provide useful information on crystal defects in solar cells. In this contribution it will be shown that the combined application of EBIC, EL and PL may deliver useful information on the presence and on the physical properties of crystal defects in silicon solar cells. Also pre-breakdown sites in multicrystalline cells can be investigated by reverse-bias EL and by microplasma-type EBIC, in comparison with lock-in thermography investigations. PMID:18561253

  2. Genetic recombination. [Escherichia coli

    SciTech Connect

    Stahl, F.W.

    1987-02-01

    The molecular pathways of gene recombination are explored and compared in studies of the model organisms, Escherichia coli and phase lambda. In the discussion of data from these studies it seems that recombination varies with the genetic idiosyncrasies of the organism and may also vary within a single organism.

  3. Simple fiber optic coupled luminescence cryostat

    NASA Astrophysics Data System (ADS)

    Meyer, G. D.; Ortiz, T. P.; Costello, A. L.; Brozik, J. A.; Kenney, J. W.

    2002-12-01

    An easy to fabricate, easy to operate, miniature liquid helium insert cryostat has been designed for variable low-temperature luminescence investigations in the 2.7-77 K region with minimal liquid helium consumption. The cryostat, which can be used inside of a standard liquid helium storage Dewar, is optically coupled both to the luminescence spectrophotometer and to the chosen luminescence excitation source (laser or conventional) by a single 1 mm fused silica fiber optic cable. This extremely simple and compact optical system is designed to give highly reproducible luminescence excitation and collection efficiencies for quantitative luminescence intensity studies. Temperature control in the cryostat is achieved through the dynamic balance of up to three distinct heating/cooling processes: raising or lowering the cryostat with respect to the liquid helium level in the Dewar, heating the cryostat with a small resistance heater, or pumping on the cryostat for sub-4.2 K temperatures. The cryostat can operate effectively throughout the 2.7-77 K range in liquid helium storage Dewars containing less than a liter of liquid helium. The wide range of spectroscopic experiments that this novel optical cryostat design can support is illustrated by a temperature-dependent zero field splitting luminescence lifetime study of Ru(bpy)3Cl2, a temperature-dependent relative luminescence intensity (quantum yield) study of Ru(bpy)3Cl2, and a temperature-dependent luminescence vibronic fine structure study of Ti(Cp)2(NCS)2.

  4. Spectral Characterization of a Novel Luminescent Organogel

    ERIC Educational Resources Information Center

    Waguespack, Yan; White, Shawn R.

    2007-01-01

    The spectroscopic-based luminescence experiments were designed to expose the students to various concepts of single-triplet excited states, electron spin, vibrational relaxation, fluorescence-phosphorescence lifetimes and quenching. The students were able to learn about luminescence spectra of the gel and have the experience of synthesizing a…

  5. Photoluminescence of Sm doped porous silicon—evidence for light emission through luminescence centers in SiO2 layers

    NASA Astrophysics Data System (ADS)

    Lin, J.; Zhang, L. Z.; Huang, Y. M.; Zhang, B. R.; Qin, G. G.

    1994-06-01

    After oxidation promoted by gamma-ray irradiation, in the photoluminescence (PL) spectra of Sm doped porous silicon (PS), there are three sharp peaks, superimposed on a broad band, with wavelengths near to those of the Sm doped SiO2 [R. Morimo, T. Mizushima, and H. Okumura, J. Electrochem. Soc. 137, 2340 (1990)]. The experimental results indicate that Sm-related luminescence centers can be created within the oxide of porous silicon, and only in porous silicon with high porosity can the Sm-related luminescence be found in the SiO2 layer. This experimental result can be explained by the fact that the excitation of electron-hole pairs occurs in nanoscale silicon, and the recombination occurs at the Sm-related luminescence centers in SiO2 layers covering nanoscale silicon.

  6. Bacterial chromosome organization and segregation.

    PubMed

    Badrinarayanan, Anjana; Le, Tung B K; Laub, Michael T

    2015-01-01

    If fully stretched out, a typical bacterial chromosome would be nearly 1 mm long, approximately 1,000 times the length of a cell. Not only must cells massively compact their genetic material, but they must also organize their DNA in a manner that is compatible with a range of cellular processes, including DNA replication, DNA repair, homologous recombination, and horizontal gene transfer. Recent work, driven in part by technological advances, has begun to reveal the general principles of chromosome organization in bacteria. Here, drawing on studies of many different organisms, we review the emerging picture of how bacterial chromosomes are structured at multiple length scales, highlighting the functions of various DNA-binding proteins and the impact of physical forces. Additionally, we discuss the spatial dynamics of chromosomes, particularly during their segregation to daughter cells. Although there has been tremendous progress, we also highlight gaps that remain in understanding chromosome organization and segregation. PMID:26566111

  7. Luminescence enhancement of Mn doped ZnS nanocrystals passivated with zinc hydroxide

    NASA Astrophysics Data System (ADS)

    Jiang, Daixun; Cao, Lixin; Su, Ge; Qu, Hua; Sun, Dake

    2007-10-01

    Mn-doped ZnS nanocrystals prepared by solvothermal method have been successfully coated with different thicknesses of Zn(OH) 2 shells through precipitation reaction. The impact of Zn(OH) 2 shells on luminescent properties of the ZnS:Mn nanocrystals was investigated. X-ray diffraction (XRD) measurements showed that the ZnS:Mn nanocrystals have cubic zinc blende structure. The morphology of nanocrystals is spherical shape measured by transmission electron microscopy (TEM). ZnS:Mn/Zn(OH) 2 core/shell nanocrystals exhibited much improved luminescent properties than those of unpassivated ZnS:Mn nanocrystals. The luminescence enhancement was observed with the Zn(OH) 2 shell thickening by photoluminescence (PL) spectra at room temperature and the luminescence lifetime of transition from 4T 1 to 6A 1 of Mn 2+ ions was also prolonged. This result was led by the effective, robust passivation of ZnS surface states by the Zn(OH) 2 shells, which consequently suppressed nonradiative recombination transitions.

  8. Using luciferase to image bacterial infections in mice.

    PubMed

    Chang, Mi Hee; Cirillo, Suat L G; Cirillo, Jeffrey D

    2011-01-01

    infections in real time. After luciferin injection, images are acquired using the IVIS Imaging System. During imaging, mice are anesthetized with isoflurane using an XGI-8 Gas Anethesia System. Images can be analyzed to localize and quantify the signal source, which represents the bacterial infection site(s) and number, respectively. After imaging, CFU determination is carried out on homogenized tissue to confirm the presence of bacteria. Several doses of bacteria are used to correlate bacterial numbers with luminescence. Imaging can be applied to study of pathogenesis and evaluation of the efficacy of antibacterial compounds and vaccines. PMID:21372790

  9. Luminescent gold nanoparticles for bioimaging

    NASA Astrophysics Data System (ADS)

    Zhou, Chen

    Inorganic nanoparticles (NPs) with tunable and diverse material properties hold great potential as contrast agents for better disease management. Over the past decades, luminescent gold nanoparticles (AuNPs) with intrinsic emissions ranging from the visible to the near infrared have been synthesized and emerge as a new class of fluorophores for bioimaging. This dissertation aims to fundamentally understand the structure-property relationships in luminescent AuNPs and apply them as contrast agents to address some critical challenges in bioimaging at both the in vitro and in vivo level. In Chapter 2, we described the synthesized ~20 nm polycrystalline AuNPs (pAuNPs), which successfully integrated and enhanced plasmonic and fluorescence properties into a single AuNP through the grain size effect. The combination of these properties in one NP enabled AuNPs to serve as a multimodal contrast agent for in vitro optical microscopic imaging, making it possible to develop correlative microscopic imaging techniques. In Chapters 3-5, we proposed a feasible approach to optimize the in vivo kinetics and clearance profile of nanoprobes for multimodality in vivo bioimaging applications by using straightforward surface chemistry with luminescent AuNPs as a model. Luminescent glutathione-coated AuNPs of ~2 nm were synthesized. Investigation of the biodistribution showed that these glutathione-coated AuNPs (GS-AuNPs) exhibit stealthiness to the reticuloendothelial system (RES) organs and efficient renal clearance, with only 3.7+/-1.9% and 0.3+/-0.1% accumulating in the liver and spleen, and over 65% of the injection dose cleared out via the urine within the first 72 hours. In addition, ~2.5 nm NIR-emitting radioactive glutathione-coated [198Au]AuNPs (GS-[198Au]AuNPs) were synthesized for further evaluation of the pharmacokinetic profile of GS-AuNPs and potential multimodal imaging. The results showed that the GS-[198Au]AuNPs behave like small-molecule contrast agents in

  10. Development of luminescent bacteria as tracers for geological reservoir characterization

    SciTech Connect

    King, J.W.

    1991-10-01

    Bioluminescent cultures were acquired and tested for use as biological tracers for reservoir characterization by small independent oil companies. Initially these bacterial cultures were fastidious to work with, but when we finally determined their critical growth parameters simple test variations were developed that could be routinely accomplished. The intensity of their luminescence is easily distinguished by the human eye and requires no sophisticated technical knowledge or instrumentation. Cultures were received from culture banks and collected from marine environments. In our laboratory they were screened using the criteria of optimum growth and luminescence. Three stock cultures proved to grow profusely even when variations were made in nutrient additions, salts, and temperature. These three selected cultures were not inhibited when introduced to formations and formation waters and were not overgrown by other bacteria. Cultures isolated from the Gulf of Mexico were overgrown by indigenous bacteria and therefore, they were eliminated from further screening and adaption. Experiments were performed according to three major task descriptions: 1. Establish growth and luminescencing limitations of selected bacteria in various media, varying salt concentration and temperature. 2. Adapt cultures to formation waters. 3. Determine transport limitations of bioluminescent bacteria through representative reservoir cores. 19 refs., 5 figs., 7 tabs.

  11. [Luminescence characteristics of PVK doped with Ir(ppy)3].

    PubMed

    Yang, Shao-Peng; Zhang, Xue-Feng; Zhao, Su-Ling; Xu, Zheng; Zhang, Fu-Jun; Yang, Ya-Ru; Li, Qing; Pang, Xue-Xia

    2008-03-01

    With the increasing development of organic light emitting devices (OLED), interest in the mechanisms of charge carrier photogeneration, separation, transport and recombination continues to grow. Electromodulation of photoluminescence has been used as an efficient probe to investigate the evolution of primary excitation in all electric field. This method can provide useful information on carrier photogeneration, the formation and dissociation of excitons, energy transfer, and exciton recombination in the presence of electric field. The operation of OLED brings electrons and holes from opposite electrodes and generates singlet and triplet excitons. However, triplet excitons are wasted because a radiative transition from triplets is spin-forbidden. Spin statistics predicts that singlet-to-triplet ratio is 1 : 3 in organic semiconductors. One way to harvest light from triplet excitons is to use phosphorescent materials. These materials incorporate a heavy metal atom to mix singlet and triplet states by the strong spin-orbit coupling. As a result, a spin forbidden transition may occur allowing an enhanced triplet emission. Among phosphorescent materials, Ir(ppy)3 has attracted much attention because of its short triplet lifetime to minimize the triplet-triplet annihilation. High quantum efficiencies have been obtained by doping organic molecules and in polymers with Ir(ppy)3. In the present paper, the photoluminescence and electroluminescence spectra of Ir(ppy)3 doped PVK film are measured at room temperature. The device structure is ITO/PEDOT : PSS/PVK Ir(ppy)3/BCP/Alq3/Al. The results show that the luminescence capabilities of devices are different when the concentration of Ir(ppy)3 is different. When the concentration of Ir(ppy)3 is suitable, the luminescence of PVK is lower but that of Ir(ppy)3 is stronger relatively, indicating that the energy transfer from the host materials to the guest materials is sufficient. It is concluded that the device with 5% of Ir(ppy)3

  12. Bacterial Games

    NASA Astrophysics Data System (ADS)

    Frey, Erwin; Reichenbach, Tobias

    Microbial laboratory communities have become model systems for studying the complex interplay between nonlinear dynamics of evolutionary selection forces, stochastic fluctuations arising from the probabilistic nature of interactions, and spatial organization. Major research goals are to identify and understand mechanisms that ensure viability of microbial colonies by allowing for species diversity, cooperative behavior and other kinds of "social" behavior. A synthesis of evolutionary game theory, nonlinear dynamics, and the theory of stochastic processes provides the mathematical tools and conceptual framework for a deeper understanding of these ecological systems. We give an introduction to the modern formulation of these theories and illustrate their effectiveness, focusing on selected examples of microbial systems. Intrinsic fluctuations, stemming from the discreteness of individuals, are ubiquitous, and can have important impact on the stability of ecosystems. In the absence of speciation, extinction of species is unavoidable, may, however, take very long times. We provide a general concept for defining survival and extinction on ecological time scales. Spatial degrees of freedom come with a certain mobility of individuals. When the latter is sufficiently high, bacterial community structures can be understood through mapping individual-based models, in a continuum approach, onto stochastic partial differential equations. These allow progress using methods of nonlinear dynamics such as bifurcation analysis and invariant manifolds. We conclude with a perspective on the current challenges in quantifying bacterial pattern formation, and how this might have an impact on fundamental research in nonequilibrium physics .

  13. The Landscape of Realized Homologous Recombination in Pathogenic Bacteria

    PubMed Central

    Yahara, Koji; Didelot, Xavier; Jolley, Keith A.; Kobayashi, Ichizo; Maiden, Martin C.J.; Sheppard, Samuel K.; Falush, Daniel

    2016-01-01

    Recombination enhances the adaptive potential of organisms by allowing genetic variants to be tested on multiple genomic backgrounds. Its distribution in the genome can provide insight into the evolutionary forces that underlie traits, such as the emergence of pathogenicity. Here, we examined landscapes of realized homologous recombination of 500 genomes from ten bacterial species and found all species have “hot” regions with elevated rates relative to the genome average. We examined the size, gene content, and chromosomal features associated with these regions and the correlations between closely related species. The recombination landscape is variable and evolves rapidly. For example in Salmonella, only short regions of around 1 kb in length are hot whereas in the closely related species Escherichia coli, some hot regions exceed 100 kb, spanning many genes. Only Streptococcus pyogenes shows evidence for the positive correlation between GC content and recombination that has been reported for several eukaryotes. Genes with function related to the cell surface/membrane are often found in recombination hot regions but E. coli is the only species where genes annotated as “virulence associated” are consistently hotter. There is also evidence that some genes with “housekeeping” functions tend to be overrepresented in cold regions. For example, ribosomal proteins showed low recombination in all of the species. Among specific genes, transferrin-binding proteins are recombination hot in all three of the species in which they were found, and are subject to interspecies recombination. PMID:26516092

  14. Functional silk: colored and luminescent.

    PubMed

    Tansil, Natalia C; Koh, Leng Duei; Han, Ming-Yong

    2012-03-15

    Silkworm silk is among the most widely used natural fibers for textile and biomedical applications due to its extraordinary mechanical properties and superior biocompatibility. A number of physical and chemical processes have also been developed to reconstruct silk into various forms or to artificially produce silk-like materials. In addition to the direct use and the delicate replication of silk's natural structure and properties, there is a growing interest to introduce more new functionalities into silk while maintaining its advantageous intrinsic properties. In this review we assess various methods and their merits to produce functional silk, specifically those with color and luminescence, through post-processing steps as well as biological approaches. There is a highlight on intrinsically colored and luminescent silk produced directly from silkworms for a wide range of applications, and a discussion on the suitable molecular properties for being incorporated effectively into silk while it is being produced in the silk gland. With these understanding, a new generation of silk containing various functional materials (e.g., drugs, antibiotics and stimuli-sensitive dyes) would be produced for novel applications such as cancer therapy with controlled release feature, wound dressing with monitoring/sensing feature, tissue engineering scaffolds with antibacterial, anticoagulant or anti-inflammatory feature, and many others. PMID:22302383

  15. Recombinant protein blends: silk beyond natural design.

    PubMed

    Dinjaski, Nina; Kaplan, David L

    2016-06-01

    Recombinant DNA technology and new material concepts are shaping future directions in biomaterial science for the design and production of the next-generation biomaterial platforms. Aside from conventionally used synthetic polymers, numerous natural biopolymers (e.g., silk, elastin, collagen, gelatin, alginate, cellulose, keratin, chitin, polyhydroxyalkanoates) have been investigated for properties and manipulation via bioengineering. Genetic engineering provides a path to increase structural and functional complexity of these biopolymers, and thereby expand the catalog of available biomaterials beyond that which exists in nature. In addition, the integration of experimental approaches with computational modeling to analyze sequence-structure-function relationships is starting to have an impact in the field by establishing predictive frameworks for determining material properties. Herein, we review advances in recombinant DNA-mediated protein production and functionalization approaches, with a focus on hybrids or combinations of proteins; recombinant protein blends or 'recombinamers'. We highlight the potential biomedical applications of fibrous protein recombinamers, such as Silk-Elastin Like Polypeptides (SELPs) and Silk-Bacterial Collagens (SBCs). We also discuss the possibility for the rationale design of fibrous proteins to build smart, stimuli-responsive biomaterials for diverse applications. We underline current limitations with production systems for these proteins and discuss the main trends in systems/synthetic biology that may improve recombinant fibrous protein design and production. PMID:26686863

  16. Recombinant laccase: I. Enzyme cloning and characterization.

    PubMed

    Nicolini, Claudio; Bruzzese, Debora; Cambria, Maria Teresa; Bragazzi, Nicola Luigi; Pechkova, Eugenia

    2013-03-01

    We obtained structural and functional characterization of a recombinant Laccase from Rigidoporus lignosus (formerly Rigidoporus microporus), a white-rot basidiomycete, by means of circular dichroism (CD) spectra, cyclic voltammetry (CV) and biochemical assays. Here we report the optimization of expression and purification procedures of a recombinant Laccase expressed in supercompetent Escherichia coli cells. We amplified the coding sequence of Laccase using PCR from cDNA and cloned into a bacterial expression system. The resulting expression plasmid, pET-28b, was under a strong T7/Lac promoter induced by IPTG (isopropyl-β-d-thiogalactoipyranoside). We obtained purification by fast protein liquid chromatography (FPLC) method. We recorded the variation of the current of a solution containing purified Laccase with increasing Syringaldazine (SGZ) concentration using a potentiometer as proof of principle, showing its compatibility with the development of a new enzymatic biosensor for medical purposes, as described in Part II. PMID:22991171

  17. Recombineering BAC transgenes for protein tagging.

    PubMed

    Ciotta, Giovanni; Hofemeister, Helmut; Maresca, Marcello; Fu, Jun; Sarov, Mihail; Anastassiadis, Konstantinos; Stewart, A Francis

    2011-02-01

    Protein tagging offers many advantages for proteomic and regulomic research, particularly due to the use of generic and highly sensitive methods that can be applied with reasonable throughput. Ideally, protein tagging is equivalent to having a high affinity antibody for every chosen protein. However, these advantages are compromised if the tagged protein is overexpressed, which is usually the case from cDNA expression vectors. BAC (bacterial artificial chromosome) transgenes present a way to express a chosen protein at physiological levels with all regulatory elements in their native configurations, including cell cycle, alternative splicing and microRNA regulation. Recombineering has become the method of choice for modifying large constructs like BACs. Here, we present a method for protein tagging by recombineering BACs, transfecting cells and evaluating tagged protein expression. PMID:20868752

  18. Bacterial Hydrodynamics

    NASA Astrophysics Data System (ADS)

    Lauga, Eric

    2016-01-01

    Bacteria predate plants and animals by billions of years. Today, they are the world's smallest cells, yet they represent the bulk of the world's biomass and the main reservoir of nutrients for higher organisms. Most bacteria can move on their own, and the majority of motile bacteria are able to swim in viscous fluids using slender helical appendages called flagella. Low-Reynolds number hydrodynamics is at the heart of the ability of flagella to generate propulsion at the micrometer scale. In fact, fluid dynamic forces impact many aspects of bacteriology, ranging from the ability of cells to reorient and search their surroundings to their interactions within mechanically and chemically complex environments. Using hydrodynamics as an organizing framework, I review the biomechanics of bacterial motility and look ahead to future challenges.

  19. [Recombinant antibodies against bioweapons].

    PubMed

    Thullier, Philippe; Pelat, Thibaut; Vidal, Dominique

    2009-12-01

    The threat posed by bioweapons (BW) could lead to the re-emergence of such deadly diseases as plague or smallpox, now eradicated from industrialized countries. The development of recombinant antibodies allows tackling this risk because these recombinant molecules are generally well tolerated in human medicine, may be utilized for prophylaxis and treatment, and because antibodies neutralize many BW. Recombinant antibodies neutralizing the lethal toxin of anthrax, botulinum toxins and the smallpox virus have in particular been isolated recently, with different technologies. Our approach, which uses phage-displayed immune libraries built from non-human primates (M. fascicularis) to obtain recombinant antibodies, which may later be super-humanized (germlinized), has allowed us to obtain such BWs-neutralizing antibodies. PMID:20035695

  20. Experimental setup for camera-based measurements of electrically and optically stimulated luminescence of silicon solar cells and wafers.

    PubMed

    Hinken, David; Schinke, Carsten; Herlufsen, Sandra; Schmidt, Arne; Bothe, Karsten; Brendel, Rolf

    2011-03-01

    We report in detail on the luminescence imaging setup developed within the last years in our laboratory. In this setup, the luminescence emission of silicon solar cells or silicon wafers is analyzed quantitatively. Charge carriers are excited electrically (electroluminescence) using a power supply for carrier injection or optically (photoluminescence) using a laser as illumination source. The luminescence emission arising from the radiative recombination of the stimulated charge carriers is measured spatially resolved using a camera. We give details of the various components including cameras, optical filters for electro- and photo-luminescence, the semiconductor laser and the four-quadrant power supply. We compare a silicon charged-coupled device (CCD) camera with a back-illuminated silicon CCD camera comprising an electron multiplier gain and a complementary metal oxide semiconductor indium gallium arsenide camera. For the detection of the luminescence emission of silicon we analyze the dominant noise sources along with the signal-to-noise ratio of all three cameras at different operation conditions. PMID:21456750

  1. Bioluminescent microassay of various metabolites using bacterial luciferase co-immobilized with multienzyme systems.

    PubMed

    Ugarova, N N; Lebedeva, O V; Frumkina, I G

    1988-09-01

    Co-immobilization methods have been developed for a bienzymatic system of luminescent Beneckea harveyi bacteria with formate dehydrogenase, glucose-6-phosphate dehydrogenase, and phosphoglucomutase. Bioluminescent assays have been devised for NADH, NAD, FMN, glucose 6-phosphate, and glucose 1-phosphate using the co-immobilized enzyme preparation. The lowest detection limits were in the picomole range with the bacterial extract and in the femtomole range with the partially purified enzymes, bacterial luciferase, and NADH:FMN oxidoreductase. PMID:3263818

  2. Detection of Bacterial Spores with Lanthanide-Macrocycle Binary Complexes

    PubMed Central

    Cable, Morgan L.; Kirby, James P.; Levine, Dana J.; Manary, Micah J.; Gray, Harry B.; Ponce, Adrian

    2009-01-01

    The detection of bacterial spores via dipicolinate-triggered lanthanide luminescence has been improved in terms of detection limit, stability, and susceptibility to interferents by use of lanthanide-macrocycle binary complexes. Specifically, we compared the effectiveness of Sm, Eu, Tb and Dy complexes with the macrocycle 1,4,7,10-tetraazacyclododecane-1,7-diacetate (DO2A) to the corresponding lanthanide aquo ions. The Ln(DO2A)+ binary complexes bind dipicolinic acid (DPA), a major constituent of bacterial spores, with greater affinity and demonstrate significant improvement in bacterial spore detection. Of the four luminescent lanthanides studied, the terbium complex exhibits the greatest dipicolinate binding affinity (100-fold greater than Tb3+ alone, and 10-fold greater than other Ln(DO2A)+ complexes) and highest quantum yield. Moreover, the inclusion of DO2A extends the pH range over which Tb-DPA coordination is stable, reduces the interference of calcium ions nearly 5-fold, and mitigates phosphate interference 1000-fold compared to free terbium alone. In addition, detection of Bacillus atrophaeus bacterial spores was improved by the use of Tb(DO2A)+, yielding a 3-fold increase in the signal-to-noise ratio over Tb3+. Out of the eight cases investigated, the Tb(DO2A)+ binary complex is best for the detection of bacterial spores. PMID:19537757

  3. Activated recombinant adenovirus proteinases

    DOEpatents

    Anderson, C.W.; Mangel, W.F.

    1999-08-10

    This application describes methods and expression constructs for producing activatable recombinant adenovirus proteinases. Purified activatable recombinant adenovirus proteinases and methods of purification are described. Activated adenovirus proteinases and methods for obtaining activated adenovirus proteinases are further included. Isolated peptide cofactors of adenovirus proteinase activity, methods of purifying and identifying peptide cofactors are also described. Antibodies immunoreactive with adenovirus proteinases, immunospecific antibodies, and methods for preparing them are also described. Other related methods and materials are also described. 29 figs.

  4. Activated recombinant adenovirus proteinases

    DOEpatents

    Anderson, Carl W.; Mangel, Walter F.

    1999-08-10

    This application describes methods and expression constructs for producing activatable recombinant adenovirus proteinases. Purified activatable recombinant adenovirus proteinases and methods of purification are described. Activated adenovirus proteinases and methods for obtaining activated adenovirus proteinases are further included. Isolated peptide cofactors of adenovirus proteinase activity, methods of purifying and identifying said peptide cofactors are also described. Antibodies immunoreactive with adenovirus proteinases, immunospecific antibodies, and methods for preparing them are also described. Other related methods and materials are also described.

  5. Organization of the bacterial chromosome.

    PubMed Central

    Krawiec, S; Riley, M

    1990-01-01

    Recent progress in studies on the bacterial chromosome is summarized. Although the greatest amount of information comes from studies on Escherichia coli, reports on studies of many other bacteria are also included. A compilation of the sizes of chromosomal DNAs as determined by pulsed-field electrophoresis is given, as well as a discussion of factors that affect gene dosage, including redundancy of chromosomes on the one hand and inactivation of chromosomes on the other hand. The distinction between a large plasmid and a second chromosome is discussed. Recent information on repeated sequences and chromosomal rearrangements is presented. The growing understanding of limitations on the rearrangements that can be tolerated by bacteria and those that cannot is summarized, and the sensitive region flanking the terminator loci is described. Sources and types of genetic variation in bacteria are listed, from simple single nucleotide mutations to intragenic and intergenic recombinations. A model depicting the dynamics of the evolution and genetic activity of the bacterial chromosome is described which entails acquisition by recombination of clonal segments within the chromosome. The model is consistent with the existence of only a few genetic types of E. coli worldwide. Finally, there is a summary of recent reports on lateral genetic exchange across great taxonomic distances, yet another source of genetic variation and innovation. PMID:2087223

  6. Mechanochromic luminescence of copper iodide clusters.

    PubMed

    Benito, Quentin; Maurin, Isabelle; Cheisson, Thibaut; Nocton, Gregory; Fargues, Alexandre; Garcia, Alain; Martineau, Charlotte; Gacoin, Thierry; Boilot, Jean-Pierre; Perruchas, Sandrine

    2015-04-01

    Luminescent mechanochromic materials are particularly appealing for the development of stimuli-responsive materials. Establishing the mechanism responsible for the mechanochromism is always an issue owing to the difficulty in characterizing the ground phase. Herein, the study of real crystalline polymorphs of a mechanochromic and thermochromic luminescent copper iodide cluster permits us to clearly establish the mechanism involved. The local disruption of the crystal packing induces changes in the cluster geometry and in particular the modification of the cuprophilic interactions, which consequently modify the emissive states. This study constitutes a step further toward the understanding of the mechanism involved in the mechanochromic luminescent properties of multimetallic coordination complexes. PMID:25755012

  7. Luminescence-induced photorefractive spatial solitons

    NASA Astrophysics Data System (ADS)

    Fazio, E.; Alonzo, M.; Devaux, F.; Toncelli, A.; Argiolas, N.; Bazzan, M.; Sada, C.; Chauvet, M.

    2010-03-01

    We report the observation of spatial confinement of a pump beam into a photorefractive solitonic channel induced by luminescence [luminescence induced spatial soliton (LISS)]. Trapped beams have been obtained in erbium doped lithium niobate crystals at concentrations as high as 0.7 mol % of erbium. By pumping at 980 nm, erbium ions emit photons at 550 nm by two-step absorption, wavelength which can be absorbed by lithium niobate and originates the photorefractive effect. The luminescence at 550 nm generates at the same time the solitonic channel and the background illumination reaching a steady-state soliton regime.

  8. Spectrometer for cluster ion beam induced luminescence

    SciTech Connect

    Ryuto, H. Sakata, A.; Takeuchi, M.; Takaoka, G. H.; Musumeci, F.

    2015-02-15

    A spectrometer to detect the ultra-weak luminescence originated by the collision of cluster ions on the surfaces of solid materials was constructed. This spectrometer consists of 11 photomultipliers with band-pass interference filters that can detect the luminescence within the wavelength ranging from 300 to 700 nm and of a photomultiplier without filter. The calibration of the detection system was performed using the photons emitted from a strontium aluminate fluorescent tape and from a high temperature tungsten filament. Preliminary measurements show the ability of this spectrometer to detect the cluster ion beam induced luminescence.

  9. Persistent luminescence in Ba{sub 5}(PO{sub 4}){sub 3}Cl:Eu{sup 2+},R{sup 3+} (R = Y, La, Ce, Gd, Tb and Lu)

    SciTech Connect

    Ju, Guifang; Hu, Yihua Chen, Li; Wang, Xiaojuan; Mu, Zhongfei

    2013-07-15

    Graphical abstract: - Highlights: • The persistent luminescence in Ba{sub 5}(PO{sub 4}){sub 3}Cl:Eu{sup 2+},R{sup 3+} was reported. • The influences of auxiliary codopants was discussed. • The concentration quenching of persistent luminescence was discussed. - Abstract: We investigated the persistent luminescence in europium-doped barium chloroapatite upon codoping with auxiliary rare earth ions. Luminescence properties of the phosphors, including photoluminescence, luminescence decay, and thermoluminescence are systematically studied. We formulated a model of persistent luminescence on the basis of the experimental results. In our model, some Eu{sup 2+} ions are oxidized to Eu{sup 3+} under short UV excitation, and the released electrons are trapped at the positive defect. The persistent luminescence arises from the recombination of these trapped electrons with the photo-ionized Eu{sup 3+} ions. The influence of auxiliary codopants was discussed in terms of ionic potential and ionic radius. Eventually, the concentration quenching of persistent luminescence was reported and discussed.

  10. Cell probing by delayed luminescence

    NASA Astrophysics Data System (ADS)

    Musumeci, Francesco; Ballerini, Monica; Baroni, Giuliana; Costato, Michele; Ferraro, Lorenzo; Milani, Marziale; Scordino, Agata; Triglia, Antonio

    1999-05-01

    Delayed luminescence (D.L.) is a measure that provides important information on biological systems fields, structures and activities, by counting impinging and emitted photons. Many recent experimental works have shown the existence of a close connection, sometimes analytically expressed between the biological state of the system and D.L. parameters. Our investigations aim to show that D.L. is a workable analytical technique covering a large number of disciplinary fields, from agriculture to pollution control and from medical diagnostics to food quality control. The authors have conducted systematic research about D.L. from unicellular alga Acetabularia acetabulum to Saccharomyces cerevisiae yeast cultures and about more complex systems such as Soya seed (Glycine max, L.) and its dependence on sample preparation, history, intracellular signaling, metabolism and pollutant presence. We will discuss the most relevant results together with theoretical considerations on the basic interaction at work between biological systems and electromagnetic fields.

  11. MICROFLUIDIC MODULES FOR ISOLATION OF RECOMBINANT CYTOKINE FROM BACTERIAL LYSATES

    SciTech Connect

    Retterer, Scott T; Doktycz, Mitchel John

    2014-01-01

    The portability and personalization of health-care diagnostics and treatments benefits from advancements and applications of micro and nanotechnology. Modularization and miniaturization of standardized biochemical processes and tests facilitates the advancement and customization of analyte detection and diagnosis on-chip. The goal of our work here is to develop modular platforms for on-chip biochemical processing of synthesized biologics for a range of on-demand applications. Our report focuses on the initial development, characterization and application of microfluidic size exclusion/gel filtration and ion exchange protein concentration modules for cytokine isolation from spiked cell extracts.

  12. Designed coiled coils promote folding of a recombinant bacterial collagen.

    PubMed

    Yoshizumi, Ayumi; Fletcher, Jordan M; Yu, Zhuoxin; Persikov, Anton V; Bartlett, Gail J; Boyle, Aimee L; Vincent, Thomas L; Woolfson, Derek N; Brodsky, Barbara

    2011-05-20

    Collagen triple helices fold slowly and inefficiently, often requiring adjacent globular domains to assist this process. In the Streptococcus pyogenes collagen-like protein Scl2, a V domain predicted to be largely α-helical, occurs N-terminal to the collagen triple helix (CL). Here, we replace this natural trimerization domain with a de novo designed, hyperstable, parallel, three-stranded, α-helical coiled coil (CC), either at the N terminus (CC-CL) or the C terminus (CL-CC) of the collagen domain. CD spectra of the constructs are consistent with additivity of independently and fully folded CC and CL domains, and the proteins retain their distinctive thermal stabilities, CL at ∼37 °C and CC at >90 °C. Heating the hybrid proteins to 50 °C unfolds CL, leaving CC intact, and upon cooling, the rate of CL refolding is somewhat faster for CL-CC than for CC-CL. A construct with coiled coils on both ends, CC-CL-CC, retains the ∼37 °C thermal stability for CL but shows less triple helix at low temperature and less denaturation at 50 °C. Most strikingly however, in CC-CL-CC, the CL refolds slower than in either CC-CL or CL-CC by almost two orders of magnitude. We propose that a single CC promotes folding of the CL domain via nucleation and in-register growth from one end, whereas initiation and growth from both ends in CC-CL-CC results in mismatched registers that frustrate folding. Bioinformatics analysis of natural collagens lends support to this because, where present, there is generally only one coiled-coil domain close to the triple helix, and it is nearly always N-terminal to the collagen repeat. PMID:21454493

  13. Calibration beads containing luminescent lanthanide ion complexes

    EPA Science Inventory

    The reliability of lanthanide luminescence measurements, by both flow cytometry and digital microscopy, will be enhanced by the availability of narrow-band emitting lanthanide calibration beads. These beads can also be used to characterize spectrographic instruments, including mi...

  14. Towards Luminescence Dating Of Mosaic Glass

    NASA Astrophysics Data System (ADS)

    Galli, A.; Martini, M.; Sibila, E.; Villa, I.

    The possibility of dating archaeological glass by means of luminescent techniques has been investigated in recent years, despite the difficulties of this application, mainly linked to the amorphous structure of the material. We focused in particular on mosaic glass, after the encouraging results obtained on byzantine and medieval samples. Further studies were devoted to the comprehension of the luminescent mechanisms in silica glasses, and to the investigation of the relationships between luminescence, colouring or opacifier ions and crystalline phase of the vitreous matrix. The results of a study on the dosimetric characteristics of thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) of a few medieval blue-green mosaic glasses from the San Lorenzo church (Milan) are presented, and the experimental protocols established to identify their suitability for dating are discussed.

  15. Orbital surveys of solar stimulated luminescence

    NASA Astrophysics Data System (ADS)

    Hemphill, W. R.; Theisen, A. F.; Tyson, R. M.; Granata, J. S.

    The Fraunhofer line discriminator (FLD) is an electro-optical device for imaging natural and manmade materials which have been stimulated to luminesce by the sun. An airborne FLD has been used to detect geochemically stressed vegetation, drought-stressed agricultural crops, industrial and residential pollution effluents, marine oil seeps, phosphate rock, uranium-bearing sandstone, and bioluminescent ocean plankton. Three-dimensional perspective plots of excitation and emission spectra, measured with a laboratory spectrometer, graphically depict similarities and differences in luminescence properties between sample materials. The laboratory data also include luminescence intensities at six Fraunhofer lines in the visible and near-infrared regions of the electromagnetic spectrum. Both the airborne and laboratory data suggest the feasibility of delineating and monitoring at least some of these luminescing materials from orbital altitude, such as a test flight aboard the Space Shuttle using an improved third-generation FLD.

  16. Bacterial vaginosis.

    PubMed Central

    Spiegel, C A

    1991-01-01

    Bacterial vaginosis (BV) is the most common of the vaginitides affecting women of reproductive age. It appears to be due to an alteration in the vaginal ecology by which Lactobacillus spp., the predominant organisms in the healthy vagina, are replaced by a mixed flora including Prevotella bivia, Prevotella disiens, Porphyromonas spp., Mobiluncus spp., and Peptostreptococcus spp. All of these organisms except Mobiluncus spp. are also members of the endogenous vaginal flora. While evidence from treatment trials does not support the notion that BV is sexually transmitted, recent studies have shown an increased risk associated with multiple sexual partners. It has also been suggested that the pathogenesis of BV may be similar to that of urinary tract infections, with the rectum serving as a reservoir for some BV-associated flora. The organisms associated with BV have also been recognized as agents of female upper genital tract infection, including pelvic inflammatory disease, and the syndrome BV has been associated with adverse outcome of pregnancy, including premature rupture of membranes, chorioamnionitis, and fetal loss; postpartum endometritis; cuff cellulitis; and urinary tract infections. The mechanisms by which the BV-associated flora causes the signs of BV are not well understood, but a role for H2O2-producing Lactobacillus spp. in protecting against colonization by catalase-negative anaerobic bacteria has been recognized. These and other aspects of BV are reviewed. PMID:1747864

  17. Calibration beads containing luminescent lanthanide ion complexes

    NASA Astrophysics Data System (ADS)

    Leif, Robert C.; Jin, Dayong; Piper, James; Vallarino, Lidia M.; Williams, John W.; Yang, Sean; Zucker, Robert M.

    2008-02-01

    The reliability of lanthanide luminescence measurements, by both flow cytometry and digital microscopy, will be enhanced by the availability of narrow-band emitting lanthanide calibration beads. These beads can also be used to characterize spectrographic instruments, including microscopes. Methods: 0.5, 3, and 5 micron (µm) beads containing a luminescent europium-complex were manufactured and the luminescence distribution of the 5 µm beads was measured with a time-delayed luminescence flow cytometer and a timedelayed digital microscope. The distribution of the luminescence intensity from the europium-complex in individual beads was determined on optical sections by confocal microscopy. The emission spectra of the beads under UV excitation were determined with a PARISS® spectrophotometer. The kinetics of the luminescence bleaching caused by UV irradiation were measured under LED excitation with a fluorescence microscope. Results: The kinetics of UV bleaching were very similar for the 0.5, 3, and 5 µm beads. Emission peaks were found at 592, 616, and 685 nanometers (nm). The width of the principal peak at half-maximum (616 nm) was 9.9 nm. The luminescence lifetimes in water and in air were 340 and 460 microseconds (µs), respectively. The distribution of the europium- complex in the beads was homogeneous. Conclusions: The 5 µm beads can be used for spectral calibration of microscopes equipped with a spectrograph, as test particles for time-delayed luminescence flow cytometers, and possibly as labels for macromolecules and cells.

  18. Luminescence conversion of blue light emitting diodes

    NASA Astrophysics Data System (ADS)

    Schlotter, P.; Schmidt, R.; Schneider, J.

    Using blue-emitting GaN/6HSiC chips as primary light sources, we have fabricated green, yellow, red and white emitting LEDs. The generation of mixed colors, as turquoise and magenta is also demonstrated. The underlying physical principle is that of luminescence down-conversion (Stokes shift), as typical for organic luminescent dye molecules. A white emitting LED, using an inorganic converter, Y3Al5O12:Ce3+( ), has also been realized.

  19. Regulation of Meiotic Recombination

    SciTech Connect

    Gregory p. Copenhaver

    2011-11-09

    Meiotic recombination results in the heritable rearrangement of DNA, primarily through reciprocal exchange between homologous chromosome or gene conversion. In plants these events are critical for ensuring proper chromosome segregation, facilitating DNA repair and providing a basis for genetic diversity. Understanding this fundamental biological mechanism will directly facilitate trait mapping, conventional plant breeding, and development of genetic engineering techniques that will help support the responsible production and conversion of renewable resources for fuels, chemicals, and the conservation of energy (1-3). Substantial progress has been made in understanding the basal recombination machinery, much of which is conserved in organisms as diverse as yeast, plants and mammals (4, 5). Significantly less is known about the factors that regulate how often and where that basal machinery acts on higher eukaryotic chromosomes. One important mechanism for regulating the frequency and distribution of meiotic recombination is crossover interference - or the ability of one recombination event to influence nearby events. The MUS81 gene is thought to play an important role in regulating the influence of interference on crossing over. The immediate goals of this project are to use reverse genetics to identify mutants in two putative MUS81 homologs in the model plant Arabidopsis thaliana, characterize those mutants and initiate a novel forward genetic screen for additional regulators of meiotic recombination. The long-term goal of the project is to understand how meiotic recombination is regulated in higher eukaryotes with an emphasis on the molecular basis of crossover interference. The ability to monitor recombination in all four meiotic products (tetrad analysis) has been a powerful tool in the arsenal of yeast geneticists. Previously, the qrt mutant of Arabidopsis, which causes the four pollen products of male meiosis to remain attached, was developed as a facile system

  20. Isolation, purification, and study of properties of recombinant hepsin from Escherichia coli.

    PubMed

    Raevskaya, A A; Kuznetsova, E M; Savvateeva, M V; Severin, S E

    2010-07-01

    A recombinant hepsin-producing strain of Escherichia coli was obtained and the conditions for hepsin expression in a bacterial system were optimized. To study the physicochemical properties of the enzyme, a procedure for purification of active recombinant hepsin using metal-chelate affinity chromatography and ion-exchange chromatography was developed. The interaction of recombinant hepsin with various peptide substrates is characterized. The dose-dependent inhibition of the recombinant hepsin enzyme activity by anthralin in vitro and an increase in the hepsin enzymatic activity in the presence of resveratrol were revealed. PMID:20673210

  1. Surface pressure field mapping using luminescent coatings

    NASA Technical Reports Server (NTRS)

    Mclachlan, B. G.; Kavandi, J. L.; Callis, J. B.; Gouterman, M.; Green, E.; Khalil, G.; Burns, D.

    1993-01-01

    In recent experiments we demonstrated the feasibility of using the oxygen dependence of luminescent molecules for surface pressure measurement in aerodynamic testing. This technique is based on the observation that for many luminescent molecules the light emitted increases as the oxygen partial pressure, and thus the air pressure, the molecules see decreases. In practice the surface to be observed is coated with an oxygen permeable polymer containing a luminescent molecule and illuminated with ultraviolet radiation. The airflow induced surface pressure field is seen as a luminescence intensity distribution which can be measured using quantitative video techniques. Computer processing converts the video data into a map of the surface pressure field. The experiments consisted of evaluating a trial luminescent coating in measuring the static surface pressure field over a two-dimensional NACA-0012 section model airfoil for Mach numbers ranging from 0.3 and 0.66. Comparison of the luminescent coating derived pressures were made to those obtained from conventional pressure taps. The method along with the experiment and its results will be described.

  2. Infectious delivery of alphaherpesvirus bacterial artificial chromosomes.

    PubMed

    Tobler, Kurt; Fraefel, Cornel

    2015-01-01

    Bacterial artificial chromosomes (BACs) can accommodate and stably propagate the genomes of large DNA viruses in E. coli. As DNA virus genomes are often per se infectious upon transfection into mammalian cells, their cloning in BACs and easy modification by homologous recombination in bacteria has become an important strategy to investigate the functions of individual virus genes. This chapter describes a strategy to clone the genomes of viruses of the Alphaherpesvirinae subfamily within the family of the Herpesviridae, which is a group of large DNA viruses that can establish both lytic and latent infections in most animal species including humans. The cloning strategy includes the following steps: (1) Construction of a transfer plasmid that contains the BAC backbone with selection and screening markers, and targeting sequences which support homologous recombination between the transfer plasmid and the alphaherpesvirus genome. (2) Introduction of the transfer plasmid sequences into the alphaherpesvirus genome via homologous recombination in mammalian cells. (3) Isolation of recombinant virus genomes containing the BAC backbone sequences from infected mammalian cells and electroporation into E. coli. (4) Preparation of infectious BAC DNA from bacterial cultures and transfection into mammalian cells. (5) Isolation and characterization of progeny virus. PMID:25239748

  3. Bacterial tyrosinases.

    PubMed

    Claus, Harald; Decker, Heinz

    2006-01-01

    Tyrosinases are nearly ubiquitously distributed in all domains of life. They are essential for pigmentation and are important factors in wound healing and primary immune response. Their active site is characterized by a pair of antiferromagnetically coupled copper ions, CuA and CuB, which are coordinated by six histidine residues. Such a "type 3 copper centre" is the common feature of tyrosinases, catecholoxidases and haemocycanins. It is also one of several other copper types found in the multi-copper oxidases (ascorbate oxidase, laccase). The copper pair of tyrosinases binds one molecule of atmospheric oxygen to catalyse two different kinds of enzymatic reactions: (1) the ortho-hydroxylation of monophenols (cresolase activity) and (2) the oxidation of o-diphenols to o-diquinones (catecholase activity). The best-known function is the formation of melanins from L-tyrosine via L-dihydroxyphenylalanine (L-dopa). The complicated hydroxylation mechanism at the active centre is still not completely understood, because nothing is known about their tertiary structure. One main reason for this deficit is that hitherto tyrosinases from eukaryotic sources could not be isolated in sufficient quantities and purities for detailed structural studies. This is not the case for prokaryotic tyrosinases from different Streptomyces species, having been intensively characterized genetically and spectroscopically for decades. The Streptomyces tyrosinases are non-modified monomeric proteins with a low molecular mass of ca. 30kDa. They are secreted to the surrounding medium, where they are involved in extracellular melanin production. In the species Streptomyces, the tyrosinase gene is part of the melC operon. Next to the tyrosinase gene (melC2), this operon contains an additional ORF called melC1, which is essential for the correct expression of the enzyme. This review summarizes the present knowledge of bacterial tyrosinases, which are promising models in order to get more insights in

  4. Bacterial Protein N-Glycosylation: New Perspectives and Applications*

    PubMed Central

    Nothaft, Harald; Szymanski, Christine M.

    2013-01-01

    Protein glycosylation is widespread throughout all three domains of life. Bacterial protein N-glycosylation and its application to engineering recombinant glycoproteins continue to be actively studied. Here, we focus on advances made in the last 2 years, including the characterization of novel bacterial N-glycosylation pathways, examination of pathway enzymes and evolution, biological roles of protein modification in the native host, and exploitation of the N-glycosylation pathways to create novel vaccines and diagnostics. PMID:23329827

  5. Meiotic recombination mechanisms.

    PubMed

    Grelon, Mathilde

    2016-01-01

    Meiosis is a specialized cell division at the origin of the haploid cells that eventually develop into the gametes. It therefore lies at the heart of Mendelian heredity. Recombination and redistribution of the homologous chromosomes arising during meiosis constitute an important source of genetic diversity, conferring to meiosis a particularly important place in the evolution and the diversification of the species. Our understanding of the molecular mechanisms governing meiotic recombination has considerably progressed these last decades, benefiting from complementary approaches led on various model species. An overview of these mechanisms will be provided as well as a discussion on the implications of these recent discoveries. PMID:27180110

  6. Investigation of InGaN/GaN laser degradation based on luminescence properties

    NASA Astrophysics Data System (ADS)

    Wen, Pengyan; Zhang, Shuming; Liu, Jianping; Li, Deyao; Zhang, Liqun; Sun, Qian; Tian, Aiqin; Zhou, Kun; Zhou, Taofei; Yang, Hui

    2016-06-01

    Degradation of InGaN/GaN laser diode (LD) is investigated based on the luminescence properties. Gradual degradation of the LD is presented with the threshold current increase and the slope efficiency decrease. The cathodoluminescence and photoluminescence characterizations of the LD show a dislocation independent degradation of the active region under the ridge. Detailed studies on the temperature-dependent micro-photoluminescence and the electroluminescence indicate that the degradation of the LD is attributed to the generation of non-radiative recombination centers in the local multiple quantum well regions with lower indium content. The activation energy of the non-radiative recombination centers is about 10.2 meV.

  7. Recombinant renewable polyclonal antibodies

    PubMed Central

    Ferrara, Fortunato; D’Angelo, Sara; Gaiotto, Tiziano; Naranjo, Leslie; Tian, Hongzhao; Gräslund, Susanne; Dobrovetsky, Elena; Hraber, Peter; Lund-Johansen, Fridtjof; Saragozza, Silvia; Sblattero, Daniele; Kiss, Csaba; Bradbury, Andrew RM

    2015-01-01

    Only a small fraction of the antibodies in a traditional polyclonal antibody mixture recognize the target of interest, frequently resulting in undesirable polyreactivity. Here, we show that high-quality recombinant polyclonals, in which hundreds of different antibodies are all directed toward a target of interest, can be easily generated in vitro by combining phage and yeast display. We show that, unlike traditional polyclonals, which are limited resources, recombinant polyclonal antibodies can be amplified over one hundred million-fold without losing representation or functionality. Our protocol was tested on 9 different targets to demonstrate how the strategy allows the selective amplification of antibodies directed toward desirable target specific epitopes, such as those found in one protein but not a closely related one, and the elimination of antibodies recognizing common epitopes, without significant loss of diversity. These recombinant renewable polyclonal antibodies are usable in different assays, and can be generated in high throughput. This approach could potentially be used to develop highly specific recombinant renewable antibodies against all human gene products. PMID:25530082

  8. Recombinant DNA for Teachers.

    ERIC Educational Resources Information Center

    Duvall, James G., III

    1992-01-01

    A science teacher describes his experience at a workshop to learn to teach the Cold Spring Harbor DNA Science Laboratory Protocols. These protocols lead students through processes for taking E. coli cells and transforming them into a new antibiotic resistant strain. The workshop featured discussions of the role of DNA recombinant technology in…

  9. Recombineering Pseudomonas syringae

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Here we report the identification of functions that promote genomic recombination of linear DNA introduced into Pseudomonas cells by electroporation. The genes encoding these functions were identified in Pseudomonas syringae pv. syringae B728a based on similarity to the lambda Red Exo/Beta and RecE...

  10. The Contribution of Genetic Recombination to CRISPR Array Evolution

    PubMed Central

    Kupczok, Anne; Landan, Giddy; Dagan, Tal

    2015-01-01

    CRISPR (clustered regularly interspaced short palindromic repeats) is a microbial immune system against foreign DNA. Recognition sequences (spacers) encoded within the CRISPR array mediate the immune reaction in a sequence-specific manner. The known mechanisms for the evolution of CRISPR arrays include spacer acquisition from foreign DNA elements at the time of invasion and array erosion through spacer deletion. Here, we consider the contribution of genetic recombination between homologous CRISPR arrays to the evolution of spacer repertoire. Acquisition of spacers from exogenic arrays via recombination may confer the recipient with immunity against unencountered antagonists. For this purpose, we develop a novel method for the detection of recombination in CRISPR arrays by modeling the spacer order in arrays from multiple strains from the same species. Because the evolutionary signal of spacer recombination may be similar to that of pervasive spacer deletions or independent spacer acquisition, our method entails a robustness analysis of the recombination inference by a statistical comparison to resampled and perturbed data sets. We analyze CRISPR data sets from four bacterial species: two Gammaproteobacteria species harboring CRISPR type I and two Streptococcus species harboring CRISPR type II loci. We find that CRISPR array evolution in Escherichia coli and Streptococcus agalactiae can be explained solely by vertical inheritance and differential spacer deletion. In Pseudomonas aeruginosa, we find an excess of single spacers potentially incorporated into the CRISPR locus during independent acquisition events. In Streptococcus thermophilus, evidence for spacer acquisition by recombination is present in 5 out of 70 strains. Genetic recombination has been proposed to accelerate adaptation by combining beneficial mutations that arose in independent lineages. However, for most species under study, we find that CRISPR evolution is shaped mainly by spacer acquisition and

  11. Bacterial differentiation.

    PubMed

    Shapiro, L; Agabian-Keshishian, N; Bendis, I

    1971-09-01

    technique can be used to select for mutants blocked in the various stages of morphogenesis. 3) Temperature-sensitive mutants of Caulobacter that are restricted in macromolecular synthesis and development at elevated temperatures have been isolated. 4) Genetic exchange in the Calflobacter genus has been demonstrated and is now being defined. Two questions related to control processes can now readily be approached experimentally. (i) Is the temporal progression of events occurring during bacterial differentiation controlled by regulator gene products? (ii) Is the differentiation cycle like a biosynthetic pathway where one event must follow another? The availability of temperature-sensitive mutants blocked at various stages of development permits access to both questions. An interesting feature of the differentiation cycle is that the polar organelle may represent a special segregated unit which is operative in the control of the differentiation process. Perhaps the sequential morphogenic changes exhibited by Caulobacter are dependent on the initial synthesis of this organelle. Because the ultimate expression of cell changes are dependent on selective protein synthesis, specific messenger RNA production-either from DNA present in an organelle or from the chromosome-may prove to be a controlling factor in cell differentiation. We have begun studies with RNA polymerase purified from Caulobacter crescentus to determine whether cell factors or alterations in the enzyme structure serve to change the specificity of transcription during the cell cycle. Control of sequential cell changes at the level of transcription has long been postulated and has recently been substantiated in the case of Bacillus sporulation (6). The Caulobacter bacteria now present another system in which direct analysis of these control mechanisms is feasible. PMID:5572165

  12. Defects and Luminescence in Lithium FLUORIDE:MAGNESIUM, Titanium

    NASA Astrophysics Data System (ADS)

    He, Shulin Sam

    This research investigated the characteristics of the defect centers produced by ionizing radiation in LiF:Mg,Ti and the mechanism of the luminescence associated with the defect centers. Experimental methods used in this work include the measurement of the optical absorption of the defect centers (produced by gamma ray irradiation) under thermal annealing treatment and optical bleaching treatment, the photoluminescence (after irradiation with gamma rays and/or neutrons) and the thermoluminescence (after irradiation with gamma rays and/or beta particles) related to the defect centers. It has been concluded that both Mg^{+2} ions and Ti^{+4} ions act as electron traps in LiF. Upon ionizing irradiation, a Mg ^{+2} ion can trap two electrons to form a Mg^{0} center absorbing at 3.25 eV in LiF and one electron to form a Mg^{+} center which absorbs at 3.5 eV, and a Mg^{+} center in a vacancy complex environment absorbs at 4.0 eV, in contrast to the Z center model and the Mg ^{+2}{rm V}_{ rm c}^{-} pair/trimer model. The absorption band near 5.5 eV in LiF:Mg,Ti produced by ionizing radiation at room temperature is attributed to Ti^{+3} ions (formed by Ti^{+4} ion's trapping of one electron) related charge transfer absorption. It could also be a result of the optical absorption of Z _3 centers and/or Mg^{+2 }{rm V}_{rm c} ^{-} dimers, trimers produced by thermal annealing and optical bleaching following irradiation. The mechanism of the luminescence spectra associated with these defect centers upon either optical excitation or thermal stimulation is concluded to be due to an electron-hole recombination process with the perturbation of vacancies and/or impurities. During the electron-hole recombination process, electrons originate from all electron traps (F center and its aggregates, Mg^{+2} ion and Ti^{+4} ion related defect centers) while hole centers are only V_3 centers if irradiated at room temperature, and include both V_{rm K} centers and V_3 center if irradiated at

  13. Defect luminescence in oxides nanocrystals grown by laser assisted techniques

    NASA Astrophysics Data System (ADS)

    Rodrigues, J.; Soares, M. R. N.; Santos, N. F.; Holz, T.; Ben Sedrine, N.; Nico, C.; Fernandes, A. J. S.; Neves, A. J.; Costa, F. M.; Monteiro, T.

    2015-06-01

    Wide band gap oxides, such as ZnO, SnO2 and ZrO2, are functional materials with a wide range of applications in several important technological areas such as those including lighting, transparent electronics, sensors, catalysis and biolabeling. Recently, doping and co-doping of oxides with lanthanides have attracted a strong interest for lighting purposes, especially among them nanophosphors for bioassays. Tailoring the crystalline materials physical properties for such applications often requires a well-controlled incorporation of dopants in the material lattice and a comprehensive understanding of their role in the oxides matrices. These undoped or intentionally doped oxides have band gap energies exceeding 3.3 eV at room temperature and are known to exhibit optically active centers that span from the ultraviolet to the near infrared region. Typically, by using photon energy excitation above the materials band gap, high quality undoped materials display narrow emission lines near the band edge due to free and bound-exciton recombination, as well as shallow donor-acceptor recombination pairs. Additionally, broad emission bands are often observed in these wide band gap hosts, hampering some of the desired physical properties for further applications. Recognizing and understanding the role of the dopant-related defects when deliberately introduced in the oxide hosts, as well as their influence on the samples luminescence properties, constitutes a matter of exploitation by the scientific community worldwide. In this work, we investigate the luminescence properties of undoped and lanthanide doped oxide materials grown by laser assisted techniques. Laser assisted flow deposition (LAFD) and pulse laser ablation in liquids (PLAL) were used for the growth of ZnO, SnO2 and yttria stabilized ZrO2 (YSZ) micro and nanocrystals with different morphologies, respectively. Regarding the YSZ host, trivalent lanthanide ions were optically activated by in-situ doping and co

  14. Characterization of Luminescent Minerals in CM2 Chondrite (Jbilet Winselwan)

    NASA Astrophysics Data System (ADS)

    Kiku, Y. K.; Ohgo, S. O.; Nishido, H. N.

    2014-09-01

    We have characterized luminescent minerals of forsterite, diopside and spinel in the CM2 chondrite (Jbilet Winselwan) using SEM-CL and to discuss the formation of the luminescent minerals under aqueous conditions.

  15. Order and disorder around Cr(3+) in chromium doped persistent luminescent AB2O4 spinels.

    PubMed

    Basavaraju, Neelima; Priolkar, Kaustubh R; Gourier, Didier; Bessière, Aurélie; Viana, Bruno

    2015-04-28

    The X-ray absorption near edge structure (XANES) spectroscopy technique is used to better understand the charging and decharging processes of the persistent luminescence in the Cr(3+)doped AB2O4 spinels (A = Zn, Mg and B = Ga and Al) with low photon energy excitation by visible light. Cr K edge XANES spectra have been simulated for different near neighbour environments around the Cr(3+) recombination centres and compared with the experimental curve. In the Cr(3+):ZnGa2O4 compound, the Cr(3+) local structure corresponds mostly to that of a normal spinel (∼70%), while the rest comprises of a distorted octahedral environment arising from cationic site inversion and a contribution from chromium clustering. This local structure is considerably different in Cr(3+):MgGa2O4 and Cr(3+):ZnAl2O4, where, for both cases, chromium clustering represents the main contribution. The strong correlation between the intensity of persistent luminescence and the percentage of Cr in clusters leads us to infer that the presence of Cr clusters is responsible for the decrease of the intensity of the visible light induced persistent luminescence in the Cr(3+) doped AB2O4 spinels. PMID:25825209

  16. Genomic homologous recombination in planta.

    PubMed Central

    Gal, S; Pisan, B; Hohn, T; Grimsley, N; Hohn, B

    1991-01-01

    A system for monitoring intrachromosomal homologous recombination in whole plants is described. A multimer of cauliflower mosaic virus (CaMV) sequences, arranged such that CaMV could only be produced by recombination, was integrated into Brassica napus nuclear DNA. This set-up allowed scoring of recombination events by the appearance of viral symptoms. The repeated homologous regions were derived from two different strains of CaMV so that different recombinant viruses (i.e. different recombination events) could be distinguished. In most of the transgenic plants, a single major virus species was detected. About half of the transgenic plants contained viruses of the same type, suggesting a hotspot for recombination. The remainder of the plants contained viruses with cross-over sites distributed throughout the rest of the homologous sequence. Sequence analysis of two recombinant molecules suggest that mismatch repair is linked to the recombination process. Images PMID:2026150

  17. Monitoring Temperatures of Tires Using Luminescent Materials

    NASA Technical Reports Server (NTRS)

    Bencic, Timothy J

    2006-01-01

    A method of noncontact, optical monitoring of the surface temperature of a tire has been devised to enable the use of local temperature rise as an indication of potential or impending failures. The method involves the use of temperature-sensitive paint (or filler): Temperature-sensitive luminescent dye molecules or other luminescent particles are incorporated into a thin, flexible material coating the tire surface of interest. (Alternatively, in principle, the luminescent material could be incorporated directly into the tire rubber, though this approach has not yet been tested.) The coated surface is illuminated with shorter-wavelength light to excite longer-wavelength luminescence, which is observed by use of a charge-coupled-device camera or a photodetector (see Figure 1). If temporally constant illumination is used, then the temperature can be deduced from the known temperature dependence of the intensity response of the luminescence. If pulsed illumination is used, then the temperature can be deduced from the known temperature dependence of the time or frequency response of the luminescence. If sinusoidally varying illumination is used, then the temperature can be deduced from the known temperature dependence of the phase response of the luminescence. Unlike a prior method of monitoring the temperature at a fixed spot on a tire by use of a thermocouple, this method is not restricted to one spot and can, therefore, yield information on the spatial distribution of temperature: in particular, it enables the discovery of newly forming hot spots where damage may be starting. Also unlike in the thermocouple method, the measurements in this method are not vulnerable to breakage of wires in repeated flexing of the tire. Moreover, unlike in another method in which infrared radiation is monitored as an indication of surface temperature, the luminescence measurements in this method are not significantly affected by changes in infrared emissivity. This method has been

  18. Recombinant medaka (Oryzias melastigmus) pro-hepcidin: Multifunctional characterization.

    PubMed

    Cai, Ling; Cai, Jing-Jing; Liu, Hai-Peng; Fan, Dan-Qing; Peng, Hui; Wang, Ke-Jian

    2012-02-01

    Recently, two hepcidin variant genes (Om-hep1 and Om-hep2) were identified in a model fish marine medaka and both were highly induced in vivo with bacterial challenge, suggesting that the medaka hepcidin may have a similar function to other reported teleostean hepcidins. In the present study, the antibacterial, antiviral and antitumor activities of Om-hep1 were determined using its synthetic and recombinant pro-peptides. The recombinant pro-hepcidin1 was expressed in Escherichia coli and an effective method to produce recombinant Pro-Omhep1 was developed in order to obtain a right folded structure. The results showed that both the synthetic mature peptide and recombinant pro-peptide had similar antibacterial activity against Gram-positive and negative bacteria. In particular, both the synthetic mature Om-hep1 and recombinant Pro-Omhep1 inhibited the viral replication of white spot syndrome virus in the hematopoietic tissue cells of the crayfish Cherax quadricarinatus. Om-hep1 also presented antitumor activity on the cultured human hepatocellular carcinoma cells. In addition, the antimicrobial mechanism of Om-hep1 was measured and it was found that Om-hep1 was likely to be non-membranolytic. The recombinant Pro-Omhep1 performed better biological activity compared to the synthetic mature Om-hep1. This study suggested that Om-hep1 was likely to be an important multifunction protein involved in various resistance actions in the marine medaka immune system. PMID:22051539

  19. Singlet-Triplet Splittings in the Luminescent Excited States of Colloidal Cu(+):CdSe, Cu(+):InP, and CuInS2 Nanocrystals: Charge-Transfer Configurations and Self-Trapped Excitons.

    PubMed

    Knowles, Kathryn E; Nelson, Heidi D; Kilburn, Troy B; Gamelin, Daniel R

    2015-10-14

    The electronic and magnetic properties of the luminescent excited states of colloidal Cu(+):CdSe, Cu(+):InP, and CuInS2 nanocrystals were investigated using variable-temperature photoluminescence (PL) and magnetic circularly polarized luminescence (MCPL) spectroscopies. The nanocrystal electronic structures were also investigated by absorption and magnetic circular dichroism (MCD) spectroscopies. By every spectroscopic measure, the luminescent excited states of all three materials are essentially indistinguishable. All three materials show very similar broad PL line widths and large Stokes shifts. All three materials also show similar temperature dependence of their PL lifetimes and MCPL polarization ratios. Analysis shows that this temperature dependence reflects Boltzmann population distributions between luminescent singlet and triplet excited states with average singlet-triplet splittings of ∼1 meV in each material. These similarities lead to the conclusion that the PL mechanism in CuInS2 NCs is fundamentally different from that of bulk CuInS2 and instead is the same as that in Cu(+)-doped NCs, which are known to luminesce via charge-transfer recombination of conduction-band electrons with copper-localized holes. The luminescence of CuInS2 nanocrystals is explained well by invoking exciton self-trapping, in which delocalized photogenerated holes contract in response to strong vibronic coupling at lattice copper sites to form a luminescent excited state that is essentially identical to that of the Cu(+)-doped semiconductor nanocrystals. PMID:26389577

  20. Integrated Detector for Ballistic Electron Emission Luminescence

    NASA Astrophysics Data System (ADS)

    Huang, Biqin; Xu, Jing; Appelbaum, Ian

    2008-03-01

    Ballistic electron emission luminescence (BEEL) uses injected hot electrons to induce interband transitions and light emission in semiconductor collectors. Local hot electron injection and rastering from a scanning tunneling probe can therefore potentially provide a means to image buried luminescent layers. However, a sensitive photon detector is required to compensate for low external efficiency. We have directly integrated a Si photodetector to a GaAs/AlGaAs BEEL structure by UHV thin-film metal wafer bonding. This room-temperature technique overcomes index mismatch and numerical aperture problems associated with far-field detection. We expect this method will make BEEL microscopy generally applicable to the study of buried luminescent layers in light emitting devices based on arbitrary material systems. THis work is funded by US DOE.

  1. Luminescence of europium (III) complexes for visualization

    NASA Astrophysics Data System (ADS)

    Kolontaeva, Olga A.; Pozharov, Mikhail V.; Korolovich, Vladimir F.; Khokhlova, Anastasia R.; Kirdyanova, Anna N.; Burmistrova, Natalia A.; Zakharova, Tamara V.; Goryacheva, Irina Y.

    2016-04-01

    With the purpose to develop bright non-toxic luminescent label for theranostic application we have studied complexation of lanthanide dipicolinates (2,6-pyridinedicarboxylates) by sodium alginate and effect of thermal exposure of synthesized micro-capsules on their luminescent properties. Synthesized micro-capsules are stable in acidic medium but dissolve at pH ~ 4 due to transformation of cationic europium dipicolinate complex to anionic. Luminescence studies have shown that emission spectra of europium(III)-alginate complexes (both chloride and dipicolinate) contain two intensive bands characteristic to Eu3+ ion (5D0 --> 7F1 (590 nm) and 5D0 --> 7F1 (612 nm)). We have also found that at 160ºC europium(III)- alginate micro-capsules decompose to black, soot-like substance, therefore, their thermal treatment must be performed in closed environment (i.e., sealed ampoules).

  2. Mechanically induced luminescence changes in molecular assemblies.

    PubMed

    Sagara, Yoshimitsu; Kato, Takashi

    2009-11-01

    Altering the shape and properties of a material through external factors such as heat, light, pressure, pH, electric or magnetic fields, or the introduction of a guest molecule, is an attractive prospect. In this Perspective, piezochromic luminescent materials - which change the colour of their luminescence in response to mechanical stimuli - are described. Such piezochromism has been observed for a few molecular materials that contain luminescent cores in liquid-crystalline and crystalline solid states, as well as for polymeric materials doped with dyes. These changes in photoluminescent colour can be activated by various types of mechanical pressure such as shearing, grinding or elongation, which can trigger different mechanisms of producing the colour. Such stimuli-responsive materials have potential for various applications, including sensors, memory and displays. PMID:21378953

  3. ZnO Luminescence and scintillation studied via photoexcitation, X-ray excitation, and gamma-induced positron spectroscopy.

    PubMed

    Ji, J; Colosimo, A M; Anwand, W; Boatner, L A; Wagner, A; Stepanov, P S; Trinh, T T; Liedke, M O; Krause-Rehberg, R; Cowan, T E; Selim, F A

    2016-01-01

    The luminescence and scintillation properties of ZnO single crystals were studied by photoluminescence and X-ray-induced luminescence (XRIL) techniques. XRIL allowed a direct comparison to be made between the near-band emission (NBE) and trap emissions providing insight into the carrier recombination efficiency in the ZnO crystals. It also provided bulk luminescence measurements that were not affected by surface states. The origin of a green emission, the dominant trap emission in ZnO, was then investigated by gamma-induced positron spectroscopy (GIPS) - a unique defect spectroscopy method that enables positron lifetime measurements to be made for a sample without contributions from positron annihilation in the source materials. The measurements showed a single positron decay curve with a 175 ps lifetime component that was attributed to Zn vacancies passivated by hydrogen. Both oxygen vacancies and hydrogen-decorated Zn vacancies were suggested to contribute to the green emission. By combining scintillation measurements with XRIL, the fast scintillation in ZnO crystals was found to be strongly correlated with the ratio between the defect luminescence and NBE. This study reports the first application of GIPS to semiconductors, and it reveals the great benefits of the XRIL technique for the study of emission and scintillation properties of materials. PMID:27550235

  4. ZnO Luminescence and scintillation studied via photoexcitation, X-ray excitation, and gamma-induced positron spectroscopy

    PubMed Central

    Ji, J.; Colosimo, A. M.; Anwand, W.; Boatner, L. A.; Wagner, A.; Stepanov, P. S.; Trinh, T. T.; Liedke, M. O.; Krause-Rehberg, R.; Cowan, T. E.; Selim, F. A.

    2016-01-01

    The luminescence and scintillation properties of ZnO single crystals were studied by photoluminescence and X-ray-induced luminescence (XRIL) techniques. XRIL allowed a direct comparison to be made between the near-band emission (NBE) and trap emissions providing insight into the carrier recombination efficiency in the ZnO crystals. It also provided bulk luminescence measurements that were not affected by surface states. The origin of a green emission, the dominant trap emission in ZnO, was then investigated by gamma-induced positron spectroscopy (GIPS) - a unique defect spectroscopy method that enables positron lifetime measurements to be made for a sample without contributions from positron annihilation in the source materials. The measurements showed a single positron decay curve with a 175 ps lifetime component that was attributed to Zn vacancies passivated by hydrogen. Both oxygen vacancies and hydrogen-decorated Zn vacancies were suggested to contribute to the green emission. By combining scintillation measurements with XRIL, the fast scintillation in ZnO crystals was found to be strongly correlated with the ratio between the defect luminescence and NBE. This study reports the first application of GIPS to semiconductors, and it reveals the great benefits of the XRIL technique for the study of emission and scintillation properties of materials. PMID:27550235

  5. Recombinant vaccines against leptospirosis.

    PubMed

    Dellagostin, Odir A; Grassmann, André A; Hartwig, Daiane D; Félix, Samuel R; da Silva, Éverton F; McBride, Alan J A

    2011-11-01

    Leptospirosis is an important neglected infectious disease that occurs in urban environments, as well as in rural regions worldwide. Rodents, the principal reservoir hosts of pathogenic Leptospira spp., and other infected animals shed the bacteria in their urine. During occupational or even recreational activities, humans that come into direct contact with infected animals or with a contaminated environment, particularly water, are at risk of infection. Prevention of urban leptospirosis is largely dependent on sanitation measures that are often difficult to implement, especially in developing countries. Vaccination with inactivated whole-cell preparations (bacterins) has limited efficacy due to the wide antigenic variation of the pathogen. Intensive efforts towards developing improved recombinant vaccines are ongoing. During the last decade, many reports on the evaluation of recombinant vaccines have been published. Partial success has been obtained with some surface-exposed protein antigens. The combination of protective antigens and new adjuvants or delivery systems may result in the much-needed effective vaccine. PMID:22048111

  6. Recombinant influenza vaccines.

    PubMed

    Sedova, E S; Shcherbinin, D N; Migunov, A I; Smirnov, Iu A; Logunov, D Iu; Shmarov, M M; Tsybalova, L M; Naroditskiĭ, B S; Kiselev, O I; Gintsburg, A L

    2012-10-01

    This review covers the problems encountered in the construction and production of new recombinant influenza vaccines. New approaches to the development of influenza vaccines are investigated; they include reverse genetics methods, production of virus-like particles, and DNA- and viral vector-based vaccines. Such approaches as the delivery of foreign genes by DNA- and viral vector-based vaccines can preserve the native structure of antigens. Adenoviral vectors are a promising gene-delivery platform for a variety of genetic vaccines. Adenoviruses can efficiently penetrate the human organism through mucosal epithelium, thus providing long-term antigen persistence and induction of the innate immune response. This review provides an overview of the practicability of the production of new recombinant influenza cross-protective vaccines on the basis of adenoviral vectors expressing hemagglutinin genes of different influenza strains. PMID:23346377

  7. Site directed recombination

    DOEpatents

    Jurka, Jerzy W.

    1997-01-01

    Enhanced homologous recombination is obtained by employing a consensus sequence which has been found to be associated with integration of repeat sequences, such as Alu and ID. The consensus sequence or sequence having a single transition mutation determines one site of a double break which allows for high efficiency of integration at the site. By introducing single or double stranded DNA having the consensus sequence flanking region joined to a sequence of interest, one can reproducibly direct integration of the sequence of interest at one or a limited number of sites. In this way, specific sites can be identified and homologous recombination achieved at the site by employing a second flanking sequence associated with a sequence proximal to the 3'-nick.

  8. Spectral luminescence analysis of amniotic fluid

    NASA Astrophysics Data System (ADS)

    Slobozhanina, Ekaterina I.; Kozlova, Nataly M.; Kasko, Leonid P.; Mamontova, Marina V.; Chernitsky, Eugene A.

    1997-12-01

    It is shown that the amniotic fluid has intensive ultra-violet luminescence caused by proteins. Along with it amniotic fluid radiated in the field of 380 - 650 nm with maxima at 430 - 450 nm and 520 - 560 nm. The first peak of luminescence ((lambda) exc equals 350 nm; (lambda) em equals 430 - 440 nm) is caused (most probably) by the presence in amniotic fluid of some hormones, NADH2 and NADPH2. A more long-wave component ((lambda) exc equals 460 nm; (lambda) em equals 520 - 560 nm) is most likely connected with the presence in amniotic fluid pigments (bilirubin connected with protein and other). It is shown that intensity and maximum of ultra-violet luminescence spectra of amniotic fluid in normality and at pathology are identical. However both emission spectra and excitation spectra of long-wave ((lambda) greater than 450 nm) luminescence of amniotic fluid from pregnant women with such prenatal abnormal developments of a fetus as anencephaly and spina bifida are too long-wave region in comparison with the norm. Results of research testify that spectral luminescent analysis of amniotic fluid can be used for screening of malformations of the neural tube. It is very difficult for a practical obstetrician to reveal pregnant women with a high risk of congenital malformations of the fetus. Apart from ultrasonic examination, cytogenetic examination of amniotic fluid and defumination of concentrations of alpha-fetoprotein and acetylcholin-esterases in the amniotic fluid and blood plasma are the most widely used diagnostic approaches. However, biochemical and cytogenetic diagnostic methods are time-consuming. In the present work spectral luminescence properties of the amniotic fluid are investigated to determine spectral parameters that can be used to reveal pregnant women with a high risk of congenital malformations of their offsprings.

  9. Directional sideward emission from luminescent plasmonic nanostructures.

    PubMed

    de Boer, Dick K G; Verschuuren, Marc A; Guo, Ke; Koenderink, A Femius; Rivas, Jaime Gómez; Rodriguez, Said Rahimzadeh-Kalaleh

    2016-01-25

    Periodic arrays of metallic nanoparticles can be used to enhance the emission of light in certain directions. We fabricated hexagonal arrays of aluminium nanoparticles combined with thin layers of luminescent material and optimized period (275 nm) and thickness (1500 nm) to obtain sideward directional emission into glass for a wavelength band around 620 nm. The key physics is that the luminescent layer acts as a waveguide, from which light is emitted at preferential angles using diffractive effects. This phenomenon has applications in the field of solid-state lighting, where there is a desire for small, bright and directional sources. PMID:26832590

  10. Simultaneous Luminescence Pressure and Temperature Mapping

    NASA Technical Reports Server (NTRS)

    Buck, Gregory M. (Inventor)

    1998-01-01

    A simultaneous luminescence pressure and temperature mapping system is developed including improved dye application techniques for surface temperature and pressure measurements from 5 torr to 1000 torr with possible upgrade to from 0.5 torr to several atmospheres with improved camera resolution. Adsorbed perylene dye on slip-cast silica is pressure (oxygen) sensitive and reusable to relatively high temperatures (-150 C). Adsorbed luminescence has an approximately linear color shift with temperature, which can be used for independent temperature mapping and brightness pressure calibration with temperature.

  11. Simultaneous Luminescence Pressure and Temperature Mapping System

    NASA Technical Reports Server (NTRS)

    Buck, Gregory M. (Inventor)

    1995-01-01

    A simultaneous luminescence pressure and temperature mapping system is developed including improved dye application techniques for surface temperature and pressure measurements from 5 torr to 1000 torr with possible upgrade to from 0.5 torr to several atmospheres with improved camera resolution. Adsorbed perylene dye on slip-cast silica is pressure (oxygen) sensitive and reusable to relatively high temperatures (approximately 150 C). Adsorbed luminescence has an approximately linear color shift with temperature, which can be used for independent temperature mapping and brightness pressure calibration with temperature.

  12. Luminescence of apollo 11 lunar samples.

    PubMed

    Greenman, N N; Gross, H G

    1970-01-30

    Luminescence measurements were made of four lunar rocks, two terrestrial rocks (granite and gabbro), and one terrestrial mineral (willemite) by comparing the spectral curves with the curve of a barium sulfate standard. Efficiencies with 3000 angstrom excitation were < 6 x 10(-5) for the lunar samples, < 8 x 10(-5) for gabbro of very similar composition to the lunar samples, approximately 10(-4) for granite, and approximately 2 X 10(-2) for willemite. If these are typical values for other ultraviolet excitation wavelengths, the Apollo 11 site appears to contribute little to the observed lunar luminescence. PMID:17781561

  13. The recombination epoch revisited

    NASA Technical Reports Server (NTRS)

    Krolik, Julian H.

    1989-01-01

    Previous studies of cosmological recombination have shown that this process produces as a by-product a highly superthermal population of Ly-alpha photons which retard completion of recombination. Cosmological redshifting was thought to determine the frequency distribution of the photons, while two-photon decay of hydrogen's 2s state was thought to control their numbers. It is shown here that frequency diffusion due to photon scattering dominate the cosmological redshift in the frequency range near line center which fixes the ratio of ground state to excited state population, while incoherent scattering into the far-red damping wing effectively destroys Ly-alpha photons as a rate which is competitive with two-photon decay. The former effect tends to hold back recombination, while the latter tends to accelerate it; the net results depends on cosmological parameters, particularly the combination Omega(b) h/sq rt (2q0), where Omega(b) is the fraction of the critical density provided by baryons.

  14. A recombineering-based gene tagging system for Arabidopsis.

    PubMed

    Alonso, Jose M; Stepanova, Anna N

    2015-01-01

    Many of the experimental approaches aimed at studying gene function heavily rely on the ability to make precise modifications in the gene's DNA sequence. Homologous recombination (HR)-based strategies provide a convenient way to create such types of modifications. HR-based DNA sequence manipulations can be enormously facilitated by expressing in E. coli a small set of bacteriophage proteins that make the exchange of DNA between a linear donor and the target DNA molecules extremely efficient. These in vivo recombineering techniques have been incorporated as essential components of the molecular toolbox in many model organisms. In this chapter, we describe the experimental procedures involved in recombineering-based tagging of an Arabidopsis gene contained in a plant transformation-ready bacterial artificial chromosome (TAC). PMID:25239749

  15. Optimized readout system for cooled optically stimulated luminescence

    NASA Astrophysics Data System (ADS)

    Miller, S. D.; Eschbach, P. A.

    1990-09-01

    Cooled Optically Stimulated Luminescence (COSL) in CaF2:Mn is an ionizing radiation dosimetry method recently developed at the Pacific Northwest Laboratory (PNL). In this method CaF2:Mn crystals irradiated by gamma radiation at room temperature are cooled to liquid nitrogen temperature (77 K), stimulated by ultraviolet laser light at 326 nm, and allowed to warm to room temperature. Light emission proportional to the gamma exposure occurs as the TLD warms from liquid nitrogen temperature to room temperature. The new method is an example of a highly sensitive phototransfer technique which could form the basis for future radiation dosimetry applications. Measurements to date have shown high potential for measuring gamma exposures in the range of 10 microR. The high sensitivity of the COSL technique is due in part to the larger quantum efficiency of radiative recombination at low temperatures and to the complete absence of the incandescent background associated with conventional thermoluminescent readout methods. Along with the potential for a system which is more sensitive than thermoluminescent readers, multiple COSL readouts can be performed with minimal reduction in the COSL intensity. The multiple readout capability can serve as a possible permanent dosimetry record, thus allowing the reanalysis of a questionable reading. In an attempt to optimize the sensitivity of the COSL method, a new readout system is being developed.

  16. Characterizations and luminescence properties of annealed porous silicon films

    NASA Astrophysics Data System (ADS)

    Songyan, Chen; Kashkarov, P. K.; Timoshenko, V. Yu; Baolin, Liu; Bingxi, Jiang

    2003-01-01

    Porous silicon (PS) samples were prepared by common electrochemical etching in HF-based electrolytes. Significantly increased current density (150 mA/cm 2) during anodization led to the accumulation of oxygen on the internal surface of the pores in the PS. Annealing of the samples was achieved in plasma of hydrogen for 15-30 min. During annealing at higher temperature (420-450°C) for 15 min or at lower temperature (250°C) for a longer time (30 min), the hydride coverage of the internal surface of the pores was replaced by a high-quality suboxide partially oxidized hydride layer or suboxide layer, as was shown by the evolution of infra-red absorption spectra due to annealing. Efficient violet and blue emissions were observed in these samples, which could be the result of the recombination of non-equilibrium carriers via an impurity center in the suboxide layer. In the sample that has a suboxide partially oxidized hydride layer, the luminescence mechanism needs a further investigation.

  17. A stable live bacterial vaccine.

    PubMed

    Kunda, Nitesh K; Wafula, Denis; Tram, Meilinn; Wu, Terry H; Muttil, Pavan

    2016-06-01

    Formulating vaccines into a dry form enhances its thermal stability. This is critical to prevent administering damaged and ineffective vaccines, and to reduce its final cost. A number of vaccines in the market as well as those being evaluated in the clinical setting are in a dry solid state; yet none of these vaccines have achieved long-term stability at high temperatures. We used spray-drying to formulate a recombinant live attenuated Listeria monocytogenes (Lm; expressing Francisella tularensis immune protective antigen pathogenicity island protein IglC) bacterial vaccine into a thermostable dry powder using various sugars and an amino acid. Lm powder vaccine showed minimal loss in viability when stored for more than a year at ambient room temperature (∼23°C) or for 180days at 40°C. High temperature viability was achieved by maintaining an inert atmosphere in the storage container and removing oxygen free radicals that damage bacterial membranes. Further, in vitro antigenicity was confirmed by infecting a dendritic cell line with cultures derived from spray dried Lm and detection of an intracellularly expressed protective antigen. A combination of stabilizing excipients, a cost effective one-step drying process, and appropriate storage conditions could provide a viable option for producing, storing and transporting heat-sensitive vaccines, especially in regions of the world that require them the most. PMID:27020530

  18. Fabrication of luminescent porous silicon with stain etches and evidence that luminescence originates in amorphous layers

    NASA Technical Reports Server (NTRS)

    Fathauer, R. W.; George, T.; Ksendzov, A.; Lin, T. L.; Pike, W. T.; Vasquez, R. P.; Wu, Z.-C.

    1992-01-01

    Simple immersion of Si in stain etches of HF:HNO3:H2O or NaNO2 in aqueous HF was used to produce films exhibiting luminescence in the visible similar to that of anodically-etched porous Si. All of the luminescent samples consist of amorphous porous Si in at least the near surface region. No evidence was found for small crystalline regions within these amorphous layers.

  19. A direct evidence of allocating yellow luminescence band in undoped GaN by two-wavelength excited photoluminescence

    SciTech Connect

    Julkarnain, M. E-mail: jnain.apee@ru.ac.bd; Fukuda, T.; Kamata, N.; Arakawa, Y.

    2015-11-23

    The behavior of below-gap luminescence of undoped GaN grown by MOCVD has been studied by the scheme of two-wavelength-excited photoluminescence. The emission intensity of shallow donor to valence band transition (I{sub OX}) increased while intensities of donor-acceptor pair transition and the Yellow Luminescence band (YLB) decreased after the irradiation of a below-gap excitation source of 1.17 eV. The conventional energy schemes and recombination models have been considered to explain our experimental result but only one model in which YLB is the transition of a shallow donor to a deep state placed at ∼1 eV above the valence band maximum satisfies our result. The defect related parameters that give a qualitative insight in the samples have been evaluated by systematically solving the rate equations and fitting the result with the experiment.

  20. Effect of irradiation on the luminescence properties of low-dimensional SiGe/Si(001) heterostructures

    SciTech Connect

    Novikov, A. V. Yablonskiy, A. N.; Platonov, V. V.; Obolenskiy, S. V.; Lobanov, D. N.; Krasilnik, Z. F.

    2010-03-15

    This study is concerned with the effect of irradiation on the luminescence properties of low-dimensional Si/Ge heterostructures with different degrees of spatial localization of charge carriers. It is shown that the radiation stability of Si/Ge heterostructures is improved with increasing efficiency of localization of charge carriers in the structures. The spatial localization of charge carriers in the SiGe nanostructures decreases the probability of nonradiative recombination of charge carriers at radiation defects produced in the Si matrix. It is demonstrated that, among the structures explored in the study, the highest radiation stability of luminescence properties is inherent in the multilayered structures containing self-assembled Ge(Si) nanoislands, in which the most efficient spatial localization of charge carriers is attained. In this case, the localization is three- and two-dimensional, correspondingly, for holes in the islands and for electrons in the Si layers that separate neighboring layers containing the islands.

  1. Enhancing and quenching luminescence with gold nanoparticle films: the influence of substrate on the luminescent properties

    NASA Astrophysics Data System (ADS)

    José Guidelli, Eder; Ramos, Ana Paula; Baffa, Oswaldo

    2016-01-01

    Gold nanoparticle (AuNP) films were sputtered over glass and aluminum substrates to enhance optically stimulated luminescence (OSL), a luminescent technique employed for radiation detection, from x-ray irradiated NaCl nanocrystals. The AuNP films deposited over glass led to enhanced-OSL emission, whereas the AuNP films deposited on aluminum substrates quenched the OSL emission. The enhanced-OSL intensity is proportional to the optical density of the film's plasmon resonance band at the stimulation wavelength. For the case of the AuNP/aluminum films, the luminescence quenching diminishes, and OSL intensity partially recovers upon increasing the distance between the AuNPs and the aluminum substrates, and between the luminescent nanocrystals and the AuNP films. These results suggest that plasmonic interactions between the emitter nanocrystals, the localized surface plasmons (LSP) of the AuNPs, and the substrate are responsible for the OSL enhancement and quenching. In this sense, the substrate dictates whether LSP relaxation occurs by radiative or non-radiative transisitions, leading to enhanced or quenched OSL, respectively. Therefore, besides showing that AuNP films can enhance and/or tune the sensitivity of luminescent radiation detectors, and demonstrating OSL as a new technique to investigate mechanisms of plasmon-enhanced luminescence, these results bring insights on how substrates strongly modify the optical properties of AuNP films.

  2. Enhancing and quenching luminescence with gold nanoparticle films: the influence of substrate on the luminescent properties.

    PubMed

    Guidelli, Eder José; Ramos, Ana Paula; Baffa, Oswaldo

    2016-01-01

    Gold nanoparticle (AuNP) films were sputtered over glass and aluminum substrates to enhance optically stimulated luminescence (OSL), a luminescent technique employed for radiation detection, from x-ray irradiated NaCl nanocrystals. The AuNP films deposited over glass led to enhanced-OSL emission, whereas the AuNP films deposited on aluminum substrates quenched the OSL emission. The enhanced-OSL intensity is proportional to the optical density of the film's plasmon resonance band at the stimulation wavelength. For the case of the AuNP/aluminum films, the luminescence quenching diminishes, and OSL intensity partially recovers upon increasing the distance between the AuNPs and the aluminum substrates, and between the luminescent nanocrystals and the AuNP films. These results suggest that plasmonic interactions between the emitter nanocrystals, the localized surface plasmons (LSP) of the AuNPs, and the substrate are responsible for the OSL enhancement and quenching. In this sense, the substrate dictates whether LSP relaxation occurs by radiative or non-radiative transisitions, leading to enhanced or quenched OSL, respectively. Therefore, besides showing that AuNP films can enhance and/or tune the sensitivity of luminescent radiation detectors, and demonstrating OSL as a new technique to investigate mechanisms of plasmon-enhanced luminescence, these results bring insights on how substrates strongly modify the optical properties of AuNP films. PMID:26606392

  3. Modeling Light Propagation in Luminescent Media

    NASA Astrophysics Data System (ADS)

    Sahin, Derya

    This study presents physical, computational and analytical modeling approaches for light propagation in luminescent random media. Two different approaches are used, namely (i) a statistical approach: Monte-Carlo simulations for photon transport and (ii) a deterministic approach: radiative transport theory. Both approaches account accurately for the multiple absorption and reemission of light at different wavelengths and for anisotropic luminescence. The deterministic approach is a generalization of radiative transport theory for solving inelastic scattering problems in random media. We use the radiative transport theory to study light propagation in luminescent media. Based on this theory, we also study the optically thick medium. Using perturbation methods, a corrected diffusion approximation with asymptotically accurate boundary conditions and a boundary layer solution are derived. The accuracy and the efficacy of this approach is verified for a plane-parallel slab problem. In particular, we apply these two approaches (MC and radiative transport theory) to model light propagation in semiconductor-based luminescent solar concentrators (LSCs). The computational results for both approaches are compared with each other and found to agree. The results of this dissertation present practical and reliable techniques to use for solving forward/inverse inelastic scattering problems arising in various research areas such as optics, biomedical engineering, nuclear engineering, solar science and material science.

  4. Dehydration-induced luminescence in clay minerals

    NASA Technical Reports Server (NTRS)

    Coyne, L. M.; Lahav, N.; Lawless, J. G.

    1981-01-01

    Reports of triboluminescent phenomena in organic crystalline materials prompted a search for related processes in clay minerals. The reported extensive mechanical distortion produced on freezing and drying of montmorillonite was particularly interesting because of studies of condensation reactions in a wet/dry cycled reaction sequence. The discovery of an unusual luminescent process in several clay minerals is reported and its characteristics are described.

  5. Derivative luminescence spectra in lanthanide analysis

    SciTech Connect

    Bel'tyukova, S.V.; Poluektov, N.S.; Tochidlovskaya, T.L.; Kucher, A.A.

    1987-06-01

    This communication presents the results of derivative spectroscopic study of luminescence of complex compounds of europium and terbium. Solutions of complexes of europium with ethylenediaminetetraacetate, thenoyltrifluoroacetone, dibenzoylmethane, salicylate and 1,10-phenanthroline, and of terbium with phenyl ester of salicyclic acid and nalidixic acid were investigated.

  6. The mensuration of delayed luminescence on ginseng

    NASA Astrophysics Data System (ADS)

    Xiang, Fenghua; Bai, Hua; Tang, Guoqing

    2008-12-01

    In this paper, the delayed luminescence of ginseng produced from two different areas was determined with the self built bioluminescence detecting system. And the attenuation curve of bioluminescence of the experimental samples were studied, before and after the samples extracted by 58% alcohol. We primarily gave out the parameters describing emitting characteristic. Using the method of optic induced bioluminescence, we also determined the weak luminescence emitting from the ginseng tuber, and find the intensity and decay time having obvious difference from skin and core, with these data we can distinguish the producing area and feature of the ginseng. In the experiment, the light-induce luminescence of the sample was menstruated, which has been infused by water and 58% alcohol; the difference between two kinds of samples which were infused and not infused has been delivered. In order to investigate the effect of excitation-light spectrum component to delayed luminescence of ginseng, a light filter witch allow a wavelength scope of 225nm~420nm pass through was installed between the light source and sample, keeping other work condition unchanged, the bioluminescence was also determined. For investigating the effect of extracting to emitting, the absorption spectrum of above samples ware studied, and the time-sequence of absorption spectrum was obtained. Based on the data obtained from our experiment, we analyzed the radiation mechanism of ginseng slice and tuber.

  7. Dielectronic recombination theory

    SciTech Connect

    LaGattuta, K.J.

    1991-12-31

    A theory now in wide use for the calculation of dielectronic recombination cross sections ({sigma}{sup DR}) and rate coefficients ({alpha}{sup DR}) was one introduced originally by Feshbach for nuclear physics applications, and then later adapted for atomic scattering problems by Hahn. In the following, we briefly review this theory in a very general form, which allows one to account for the effects of overlapping and interacting resonances, as well as continuum-continuum coupling. An extension of our notation will then also allow for the inclusion of the effects of direct radiative recombination, along with a treatment of the interference between radiative and dielectronic recombination. Other approaches to the calculation of {sigma}{sup DR} have been described by Fano and by Seaton. We will not consider those theories here. Calculations of {alpha}{sup DR} have progressed considerably over the last 25 years, since the early work of Burgess. Advances in the reliability of theoretical predictions have also been promoted recently b a variety of direct laboratory measurements of {sigma}{sup DR}. While the measurements of {sigma}{sup DR} for {delta}n {ne} 0 excitations have tended to agree very well with calculations, the case of {delta}n = 0 has been much problematic. However, by invoking a mechanism originally proposed by Jacobs, which takes into account the effect of stray electric fields on high Rydberg states (HRS) participating in the DR process, new calculations have improved the agreement between theory and experiment for these cases. Nevertheless, certain discrepancies still remain.

  8. Recombinant Collagenlike Proteins

    NASA Technical Reports Server (NTRS)

    Fertala, Andzej

    2007-01-01

    A group of collagenlike recombinant proteins containing high densities of biologically active sites has been invented. The method used to express these proteins is similar to a method of expressing recombinant procollagens and collagens described in U. S. Patent 5,593,859, "Synthesis of human procollagens and collagens in recombinant DNA systems." Customized collagenous proteins are needed for biomedical applications. In particular, fibrillar collagens are attractive for production of matrices needed for tissue engineering and drug delivery. Prior to this invention, there was no way of producing customized collagenous proteins for these and other applications. Heretofore, collagenous proteins have been produced by use of such biological systems as yeasts, bacteria, and transgenic animals and plants. These products are normal collagens that can also be extracted from such sources as tendons, bones, and hides. These products cannot be made to consist only of biologically active, specific amino acid sequences that may be needed for specific applications. Prior to this invention, it had been established that fibrillar collagens consist of domains that are responsible for such processes as interaction with cells, binding of growth factors, and interaction with a number of structural proteins present in the extracellular matrix. A normal collagen consists of a sequence of domains that can be represented by a corresponding sequence of labels, e.g., D1D2D3D4. A collagenlike protein of the present invention contains regions of collagen II that contain multiples of a single domain (e.g., D1D1D1D1 or D4D4D4D4) chosen for its specific biological activity. By virtue of the multiplicity of the chosen domain, the density of sites having that specific biological activity is greater than it is in a normal collagen. A collagenlike protein according to this invention can thus be made to have properties that are necessary for tissue engineering.

  9. Did the universe recombine?

    NASA Technical Reports Server (NTRS)

    Bartlett, James G.; Stebbins, Albert

    1991-01-01

    The Zel'dovich-Sunyaev model-independent arguments for the existence of a neutral hydrogen phase is reviewed in light of new limits on the Compton y parameter from COBE. It is concluded that with baryon densities compatible with standard cosmological nucleosynthesis, the universe could have remained fully ionized throughout its history without producing a detectable spectral distortion. It is argued that it is unlikely that spectral observations of the cosmic microwave background will ever require the universe to have recombined for flat cosmologies.

  10. Quenching methods for background reduction in luminescence-based probe-target binding assays

    DOEpatents

    Cai, Hong; Goodwin, Peter M; Keller, Richard A.; Nolan, Rhiannon L.

    2007-04-10

    Background luminescence is reduced from a solution containing unbound luminescent probes, each having a first molecule that attaches to a target molecule and having an attached luminescent moiety, and luminescent probe/target adducts. Quenching capture reagent molecules are formed that are capable of forming an adduct with the unbound luminescent probes and having an attached quencher material effective to quench luminescence of the luminescent moiety. The quencher material of the capture reagent molecules is added to a solution of the luminescent probe/target adducts and binds in a proximity to the luminescent moiety of the unbound luminescent probes to quench luminescence from the luminescent moiety when the luminescent moiety is exposed to exciting illumination. The quencher capture reagent does not bind to probe molecules that are bound to target molecules and the probe/target adduct emission is not quenched.

  11. Paper-based biodetection using luminescent nanoparticles.

    PubMed

    Ju, Qiang; Noor, M Omair; Krull, Ulrich J

    2016-05-10

    Point-of-care and in-field technologies for rapid, sensitive and selective detection of molecular biomarkers have attracted much interest. Rugged bioassay technology capable of fast detection of markers for pathogens and genetic diseases would in particular impact the quality of health care in the developing world, but would also make possible more extensive screening in developed countries to tackle problems such as those associated with water and food quality, and tracking of infectious organisms in hospitals and clinics. Literature trends indicate an increasing interest in the use of nanomaterials, and in particular luminescent nanoparticles, for assay development. These materials may offer attributes for development of assays and sensors that could achieve improvements in analytical figures of merit, and provide practical advantages in sensitivity and stability. There is opportunity for cost-efficiency and technical simplicity by implementation of luminescent nanomaterials as the basis for transduction technology, when combined with the use of paper substrates, and the ubiquitous availability of cell phone cameras and associated infrastructure for optical detection and transmission of results. Luminescent nanoparticles have been described for a broad range of bioanalytical targets including small molecules, oligonucleotides, peptides, proteins, saccharides and whole cells (e.g., cancer diagnostics). The luminescent nanomaterials that are described herein for paper-based bioassays include metal nanoparticles, quantum dots and lanthanide-doped nanocrystals. These nanomaterials often have broad and strong absorption and narrow emission bands that improve opportunity for multiplexed analysis, and can be designed to provide emission at wavelengths that are efficiently processed by conventional digital cameras. Luminescent nanoparticles can be embedded in paper substrates that are designed to direct fluid flow, and the resulting combination of technologies can offer

  12. The uncultured luminous symbiont of Anomalops katoptron (Beryciformes: Anomalopidae) represents a new bacterial genus.

    PubMed

    Hendry, Tory A; Dunlap, Paul V

    2011-12-01

    Flashlight fishes (Beryciformes: Anomalopidae) harbor luminous symbiotic bacteria in subocular light organs and use the bacterial light for predator avoidance, feeding, and communication. Despite many attempts anomalopid symbionts have not been brought into laboratory culture, which has restricted progress in understanding their phylogenetic relationships with other luminous bacteria, identification of the genes of their luminescence system, as well as the nature of their symbiotic interactions with their fish hosts. To begin addressing these issues, we used culture-independent analysis of the bacteria symbiotic with the anomalopid fish, Anomalops katoptron, to characterize the phylogeny of the bacteria and to identify the genes of their luminescence system including those involved in the regulation of luminescence. Analysis of the 16S rRNA, atpA, gapA, gyrB, pyrH, recA, rpoA, and topA genes resolved the A. katoptron symbionts as a clade nested within and deeply divergent from other members of Vibrionaceae. The bacterial luminescence (lux) genes were identified as a contiguous set (luxCDABEG), as found for the lux operons of other luminous bacteria. Phylogenetic analysis based on the lux genes confirmed the housekeeping gene phylogenetic placement. Furthermore, genes flanking the lux operon in the A. katoptron symbionts differed from those flanking lux operons of other genera of luminous bacteria. We therefore propose the candidate name Candidatus Photodesmus (Greek: photo = light, desmus = servant) katoptron for the species of bacteria symbiotic with A. katoptron. Results of a preliminary genomic analysis for genes regulating luminescence in other bacteria identified only a Vibrio harveyi-type luxR gene. These results suggest that expression of the luminescence system might be continuous in P. katoptron. PMID:21864694

  13. Identification of genes and gene products necessary for bacterial bioluminescence.

    PubMed

    Engebrecht, J; Silverman, M

    1984-07-01

    Expression of luminescence in Escherichia coli was recently achieved by cloning genes from the marine bacterium Vibrio fischeri. One DNA fragment on a hybrid plasmid encoded regulatory functions and enzymatic activities necessary for light production. We report the results of a genetic analysis to identify the luminescence genes (lux) that reside on this recombinant plasmid. lux gene mutations were generated by hydroxylamine treatment, and these mutations were ordered on a linear map by complementation in trans with a series of polar transposon insertions on other plasmids. lux genes were defined by complementation of lux gene defects on pairs of plasmids in trans in E. coli. Hybrid plasmids were also used to direct the synthesis of polypeptides in the E. coli minicell system. Seven lux genes and the corresponding gene products were identified from the complementation analysis and the minicell programing experiments. These genes, in the order of their position on a linear map, and the apparent molecular weights of the gene products are luxR (27,000), luxI (25,000), luxC (53,000), luxD (33,000), luxA (40,000), luxB (38,000), and luxE (42,000). From the luminescence phenotypes of E. coli containing mutant plasmids, functions were assigned to these genes: luxA, luxB, luxC, luxD, and luxE encode enzymes for light production and luxR and luxI encode regulatory functions. PMID:6377310

  14. CRISPR-Cas9-assisted recombineering in Lactobacillus reuteri.

    PubMed

    Oh, Jee-Hwan; van Pijkeren, Jan-Peter

    2014-01-01

    Clustered regularly interspaced palindromic repeats (CRISPRs) and the CRISPR-associated (Cas) nuclease protect bacteria and archeae from foreign DNA by site-specific cleavage of incoming DNA. Type-II CRISPR-Cas systems, such as the Streptococcus pyogenes CRISPR-Cas9 system, can be adapted such that Cas9 can be guided to a user-defined site in the chromosome to introduce double-stranded breaks. Here we have developed and optimized CRISPR-Cas9 function in the lactic acid bacterium Lactobacillus reuteri ATCC PTA 6475. We established proof-of-concept showing that CRISPR-Cas9 selection combined with single-stranded DNA (ssDNA) recombineering is a realistic approach to identify at high efficiencies edited cells in a lactic acid bacterium. We show for three independent targets that subtle changes in the bacterial genome can be recovered at efficiencies ranging from 90 to 100%. By combining CRISPR-Cas9 and recombineering, we successfully applied codon saturation mutagenesis in the L. reuteri chromosome. Also, CRISPR-Cas9 selection is critical to identify low-efficiency events such as oligonucleotide-mediated chromosome deletions. This also means that CRISPR-Cas9 selection will allow identification of recombinant cells in bacteria with low recombineering efficiencies, eliminating the need for ssDNA recombineering optimization procedures. We envision that CRISPR-Cas genome editing has the potential to change the landscape of genome editing in lactic acid bacteria, and other Gram-positive bacteria. PMID:25074379

  15. Novel Heterotypic Rox Sites for Combinatorial Dre Recombination Strategies

    PubMed Central

    Chuang, Katherine; Nguyen, Eileen; Sergeev, Yuri; Badea, Tudor C.

    2015-01-01

    Site-specific recombinases (SSRs) such as Cre are widely used in gene targeting and genetic approaches for cell labeling and manipulation. They mediate DNA strand exchange between two DNA molecules at dedicated recognition sites. Precise understanding of the Cre recombination mechanism, including the role of individual base pairs in its loxP target site, guided the generation of mutant lox sites that specifically recombine with themselves but not with the wild type loxP. This has led to the development of a variety of combinatorial Cre-dependent genetic strategies, such as multicolor reporters, irreversible inversions, or recombination-mediated cassette exchange. Dre, a Cre-related phage integrase that recognizes roxP sites, does not cross-react with the Cre-loxP system, but has similar recombination efficiency. We have previously described intersectional genetic strategies combining Dre and Cre. We now report a mutagenesis screen aimed at identifying roxP base pairs critical for self-recognition. We describe several rox variant sites that are incompatible with roxP, but are able to efficiently recombine with themselves in either purified systems or bacterial and eukaryotic tissue culture systems. These newly identified rox sites are not recognized by Cre, thus enabling potential combinatorial strategies involving Cre, Dre, and target loci including multiple loxP and roxP variants. PMID:26715092

  16. Recombination shapes the structure of an environmental Vibrio cholerae population.

    PubMed

    Keymer, Daniel P; Boehm, Alexandria B

    2011-01-01

    Vibrio cholerae consists of pathogenic strains that cause sporadic gastrointestinal illness or epidemic cholera disease and nonpathogenic strains that grow and persist in coastal aquatic ecosystems. Previous studies of disease-causing strains have shown V. cholerae to be a primarily clonal bacterial species, but isolates analyzed have been strongly biased toward pathogenic genotypes, while representing only a small sample of the vast diversity in environmental strains. In this study, we characterized homologous recombination and structure among 152 environmental V. cholerae isolates and 13 other putative Vibrio isolates from coastal waters and sediments in central California, as well as four clinical V. cholerae isolates, using multilocus sequence analysis of seven housekeeping genes. Recombinant regions were identified by at least three detection methods in 72% of our V. cholerae isolates. Despite frequent recombination, significant linkage disequilibrium was still detected among the V. cholerae sequence types. Incongruent but nonrandom associations were observed for maximum likelihood topologies from the individual loci. Overall, our estimated recombination rate in V. cholerae of 6.5 times the mutation rate is similar to those of other sexual bacteria and appears frequently enough to restrict selection from purging much of the neutral intraspecies diversity. These data suggest that frequent recombination among V. cholerae may hinder the identification of ecotypes in this bacterioplankton population. PMID:21075874

  17. Chemiluminescence enzyme immunoassay using ProteinA-bacterial magnetite complex

    NASA Astrophysics Data System (ADS)

    Matsunaga, Tadashi; Sato, Rika; Kamiya, Shinji; Tanaka, Tsuyosi; Takeyama, Haruko

    1999-04-01

    Bacterial magnetic particles (BMPs) which have ProteinA expressed on their surface were constructed using magA which is a key gene in BMP biosynthesis in the magnetic bacterium Magnetospirillum sp. AMB-1. Homogenous chemiluminescence enzyme immunoassay using antibody bound ProteinA-BMP complexes was developed for detection of human IgG. A good correlation between the luminescence yield and the concentration of human IgG was obtained in the range of 1-10 3 ng/ml.

  18. Biofilms, bacterial signaling, and their ties to marine biology.

    PubMed

    Pasmore, Mark; Costerton, J William

    2003-07-01

    Much of what is know about quorum sensing has come from the study of marine biology. The original description of the phenomenon was based on the study of marine bacteria and the luminescent pathway. More recently, aquatic organisms have been found to inhibit bacterial fouling of surfaces by blocking signaling pathways in the bacteria. These signaling effects have, over the last 5 years, been linked to biofilms. However, this correlation is not as straight forward as originally believed. Here, a brief overview of quorum sensing, and background on biofilms is provided, followed by a discussion of more recent work looking at the effects that environment may have on signal expression. PMID:12884126

  19. Expression of Recombinant Antibodies

    PubMed Central

    Frenzel, André; Hust, Michael; Schirrmann, Thomas

    2013-01-01

    Recombinant antibodies are highly specific detection probes in research, diagnostics, and have emerged over the last two decades as the fastest growing class of therapeutic proteins. Antibody generation has been dramatically accelerated by in vitro selection systems, particularly phage display. An increasing variety of recombinant production systems have been developed, ranging from Gram-negative and positive bacteria, yeasts and filamentous fungi, insect cell lines, mammalian cells to transgenic plants and animals. Currently, almost all therapeutic antibodies are still produced in mammalian cell lines in order to reduce the risk of immunogenicity due to altered, non-human glycosylation patterns. However, recent developments of glycosylation-engineered yeast, insect cell lines, and transgenic plants are promising to obtain antibodies with “human-like” post-translational modifications. Furthermore, smaller antibody fragments including bispecific antibodies without any glycosylation are successfully produced in bacteria and have advanced to clinical testing. The first therapeutic antibody products from a non-mammalian source can be expected in coming next years. In this review, we focus on current antibody production systems including their usability for different applications. PMID:23908655

  20. Recombinant factor VIIa.

    PubMed

    Aitken, Michael G

    2004-01-01

    Human coagulation factor (F) VII is a single chain protease that circulates in the blood as a weakly active zymogen at concentrations of approximately 10 nmol/L. When converted to the active 2 chain form (FVIIa), it is a powerful initiator of haemostasis. Recombinant factor VIIa (rFVIIa, eptacog alfa, NovoSeven) is a genetically engineered product that was first introduced in 1988 for the treatment of patients with haemophilia A and B with high inhibitory antibody titres to factors VIII and IX. Recent reports in the form of case studies and series, and early trial data, have suggested a role for rFVIIa across a diverse range of indications including bleeding associated with trauma, surgery, thrombocytopaenia, liver disease and oral anticoagulant toxicity. This review describes the physiology of the coagulation pathway and in particular the role of recombinant factor VIIa. It will also focus on the emerging role of rFVIIa in both trauma and non-trauma bleeding and its potential use in the ED. PMID:15537408

  1. Lipopolysaccharide induced conversion of recombinant prion protein

    PubMed Central

    Saleem, Fozia; Bjorndahl, Trent C; Ladner, Carol L; Perez-Pineiro, Rolando; Ametaj, Burim N; Wishart, David S

    2014-01-01

    The conformational conversion of the cellular prion protein (PrPC) to the β-rich infectious isoform PrPSc is considered a critical and central feature in prion pathology. Although PrPSc is the critical component of the infectious agent, as proposed in the “protein-only” prion hypothesis, cellular components have been identified as important cofactors in triggering and enhancing the conversion of PrPC to proteinase K resistant PrPSc. A number of in vitro systems using various chemical and/or physical agents such as guanidine hydrochloride, urea, SDS, high temperature, and low pH, have been developed that cause PrPC conversion, their amplification, and amyloid fibril formation often under non-physiological conditions. In our ongoing efforts to look for endogenous and exogenous chemical mediators that might initiate, influence, or result in the natural conversion of PrPC to PrPSc, we discovered that lipopolysaccharide (LPS), a component of gram-negative bacterial membranes interacts with recombinant prion proteins and induces conversion to an isoform richer in β sheet at near physiological conditions as long as the LPS concentration remains above the critical micelle concentration (CMC). More significant was the LPS mediated conversion that was observed even at sub-molar ratios of LPS to recombinant ShPrP (90–232). PMID:24819168

  2. The lambda red proteins promote efficient recombination between diverged sequences: implications for bacteriophage genome mosaicism.

    PubMed

    Martinsohn, Jann T; Radman, Miroslav; Petit, Marie-Agnès

    2008-05-01

    Genome mosaicism in temperate bacterial viruses (bacteriophages) is so great that it obscures their phylogeny at the genome level. However, the precise molecular processes underlying this mosaicism are unknown. Illegitimate recombination has been proposed, but homeologous recombination could also be at play. To test this, we have measured the efficiency of homeologous recombination between diverged oxa gene pairs inserted into lambda. High yields of recombinants between 22% diverged genes have been obtained when the virus Red Gam pathway was active, and 100 fold less when the host Escherichia coli RecABCD pathway was active. The recombination editing proteins, MutS and UvrD, showed only marginal effects on lambda recombination. Thus, escape from host editing contributes to the high proficiency of virus recombination. Moreover, our bioinformatics study suggests that homeologous recombination between similar lambdoid viruses has created part of their mosaicism. We therefore propose that the remarkable propensity of the lambda-encoded Red and Gam proteins to recombine diverged DNA is effectively contributing to mosaicism, and more generally, that a correlation may exist between virus genome mosaicism and the presence of Red/Gam-like systems. PMID:18451987

  3. Ad 2.0: a novel recombineering platform for high-throughput generation of tailored adenoviruses.

    PubMed

    Mück-Häusl, Martin; Solanki, Manish; Zhang, Wenli; Ruzsics, Zsolt; Ehrhardt, Anja

    2015-04-30

    Recombinant adenoviruses containing a double-stranded DNA genome of 26-45 kb were broadly explored in basic virology, for vaccination purposes, for treatment of tumors based on oncolytic virotherapy, or simply as a tool for efficient gene transfer. However, the majority of recombinant adenoviral vectors (AdVs) is based on a small fraction of adenovirus types and their genetic modification. Recombineering techniques provide powerful tools for arbitrary engineering of recombinant DNA. Here, we adopted a seamless recombineering technology for high-throughput and arbitrary genetic engineering of recombinant adenoviral DNA molecules. Our cloning platform which also includes a novel recombination pipeline is based on bacterial artificial chromosomes (BACs). It enables generation of novel recombinant adenoviruses from different sources and switching between commonly used early generation AdVs and the last generation high-capacity AdVs lacking all viral coding sequences making them attractive candidates for clinical use. In combination with a novel recombination pipeline allowing cloning of AdVs containing large and complex transgenes and the possibility to generate arbitrary chimeric capsid-modified adenoviruses, these techniques allow generation of tailored AdVs with distinct features. Our technologies will pave the way toward broader applications of AdVs in molecular medicine including gene therapy and vaccination studies. PMID:25609697

  4. Vaxvec: The first web-based recombinant vaccine vector database and its data analysis.

    PubMed

    Deng, Shunzhou; Martin, Carly; Patil, Rasika; Zhu, Felix; Zhao, Bin; Xiang, Zuoshuang; He, Yongqun

    2015-11-27

    A recombinant vector vaccine uses an attenuated virus, bacterium, or parasite as the carrier to express a heterologous antigen(s). Many recombinant vaccine vectors and related vaccines have been developed and extensively investigated. To compare and better understand recombinant vectors and vaccines, we have generated Vaxvec (http://www.violinet.org/vaxvec), the first web-based database that stores various recombinant vaccine vectors and those experimentally verified vaccines that use these vectors. Vaxvec has now included 59 vaccine vectors that have been used in 196 recombinant vector vaccines against 66 pathogens and cancers. These vectors are classified to 41 viral vectors, 15 bacterial vectors, 1 parasitic vector, and 1 fungal vector. The most commonly used viral vaccine vectors are double-stranded DNA viruses, including herpesviruses, adenoviruses, and poxviruses. For example, Vaxvec includes 63 poxvirus-based recombinant vaccines for over 20 pathogens and cancers. Vaxvec collects 30 recombinant vector influenza vaccines that use 17 recombinant vectors and were experimentally tested in 7 animal models. In addition, over 60 protective antigens used in recombinant vector vaccines are annotated and analyzed. User-friendly web-interfaces are available for querying various data in Vaxvec. To support data exchange, the information of vaccine vectors, vaccines, and related information is stored in the Vaccine Ontology (VO). Vaxvec is a timely and vital source of vaccine vector database and facilitates efficient vaccine vector research and development. PMID:26403370

  5. Unraveling recombination rate evolution using ancestral recombination maps

    PubMed Central

    Munch, Kasper; Schierup, Mikkel H; Mailund, Thomas

    2014-01-01

    Recombination maps of ancestral species can be constructed from comparative analyses of genomes from closely related species, exemplified by a recently published map of the human-chimpanzee ancestor. Such maps resolve differences in recombination rate between species into changes along individual branches in the speciation tree, and allow identification of associated changes in the genomic sequences. We describe how coalescent hidden Markov models are able to call individual recombination events in ancestral species through inference of incomplete lineage sorting along a genomic alignment. In the great apes, speciation events are sufficiently close in time that a map can be inferred for the ancestral species at each internal branch - allowing evolution of recombination rate to be tracked over evolutionary time scales from speciation event to speciation event. We see this approach as a way of characterizing the evolution of recombination rate and the genomic properties that influence it. PMID:25043668

  6. Recombinant phage probes for Listeria monocytogenes

    NASA Astrophysics Data System (ADS)

    Carnazza, S.; Gioffrè, G.; Felici, F.; Guglielmino, S.

    2007-10-01

    Monitoring of food and environmental samples for biological threats, such as Listeria monocytogenes, requires probes that specifically bind biological agents and ensure their immediate and efficient detection. There is a need for robust and inexpensive affinity probes as an alternative to antibodies. These probes may be recruited from random peptide libraries displayed on filamentous phage. In this study, we selected from two phage peptide libraries phage clones displaying peptides capable of specific and strong binding to the L. monocytogenes cell surface. The ability of isolated phage clones to interact specifically with L. monocytogenes was demonstrated using enzyme-linked immunosorbent assay (ELISA) and confirmed by co-precipitation assay. We also assessed the sensitivity of phage-bacteria binding by PCR on phage-captured Listeria cells, which could be detected at a concentration of 104 cells ml-1. In addition, as proof-of-concept, we tested the possibility of immobilizing the affinity-selected phages to a putative biosensor surface. The quality of phage deposition was monitored by ELISA and fluorescent microscopy. Phage-bacterial binding was confirmed by high power optical phase contrast microscopy. Overall, the results of this work validate the concept of affinity-selected recombinant filamentous phages as probes for detecting and monitoring bacterial agents under any conditions that warrant their recognition, including in food products.

  7. Algebraic theory of recombination spaces.

    PubMed

    Stadler, P F; Wagner, G P

    1997-01-01

    A new mathematical representation is proposed for the configuration space structure induced by recombination, which we call "P-structure." It consists of a mapping of pairs of objects to the power set of all objects in the search space. The mapping assigns to each pair of parental "genotypes" the set of all recombinant genotypes obtainable from the parental ones. It is shown that this construction allows a Fourier decomposition of fitness landscapes into a superposition of "elementary landscapes." This decomposition is analogous to the Fourier decomposition of fitness landscapes on mutation spaces. The elementary landscapes are obtained as eigenfunctions of a Laplacian operator defined for P-structures. For binary string recombination, the elementary landscapes are exactly the p-spin functions (Walsh functions), that is, the same as the elementary landscapes of the string point mutation spaces (i.e., the hypercube). This supports the notion of a strong homomorphism between string mutation and recombination spaces. However, the effective nearest neighbor correlations on these elementary landscapes differ between mutation and recombination and among different recombination operators. On average, the nearest neighbor correlation is higher for one-point recombination than for uniform recombination. For one-point recombination, the correlations are higher for elementary landscapes with fewer interacting sites as well as for sites that have closer linkage, confirming the qualitative predictions of the Schema Theorem. We conclude that the algebraic approach to fitness landscape analysis can be extended to recombination spaces and provides an effective way to analyze the relative hardness of a landscape for a given recombination operator. PMID:10021760

  8. Recombinant Human Erythropoietin

    PubMed Central

    Bartels, Claudia; Späte, Kira; Krampe, Henning

    2008-01-01

    Treatment of multiple sclerosis (MS) is still unsatisfactory and essentially non-existing for the progressive course of the disease. Recombinant human erythropoietin (EPO) may be a promising neuroprotective/neuroregenerative treatment of MS. In the nervous system, EPO acts anti-apoptotic, antioxidative, anti-inflammatory, neurotrophic and plasticity-modulating. Beneficial effects have been shown in animal models of various neurological and psychiatric diseases, including different models of experimental autoimmune encephalomyelitis. EPO is also effective in human brain disease, as shown in double-blind placebo-controlled clinical studies on ischemic stroke and chronic schizophrenia. An exploratory study on chronic progressive MS yielded lasting improvement in motor and cognitive performance upon high-dose long-term EPO treatment. PMID:21180577

  9. Recombinant glucose uptake system

    DOEpatents

    Ingrahm, Lonnie O.; Snoep, Jacob L.; Arfman, Nico

    1997-01-01

    Recombinant organisms are disclosed that contain a pathway for glucose uptake other than the pathway normally utilized by the host cell. In particular, the host cell is one in which glucose transport into the cell normally is coupled to PEP production. This host cell is transformed so that it uses an alternative pathway for glucose transport that is not coupled to PEP production. In a preferred embodiment, the host cell is a bacterium other than Z. mobilis that has been transformed to contain the glf and glk genes of Z. mobilis. By uncoupling glucose transport into the cell from PEP utilization, more PEP is produced for synthesis of products of commercial importance from a given quantity of biomass supplied to the host cells.

  10. Facial bacterial infections: folliculitis.

    PubMed

    Laureano, Ana Cristina; Schwartz, Robert A; Cohen, Philip J

    2014-01-01

    Facial bacterial infections are most commonly caused by infections of the hair follicles. Wherever pilosebaceous units are found folliculitis can occur, with the most frequent bacterial culprit being Staphylococcus aureus. We review different origins of facial folliculitis, distinguishing bacterial forms from other infectious and non-infectious mimickers. We distinguish folliculitis from pseudofolliculitis and perifolliculitis. Clinical features, etiology, pathology, and management options are also discussed. PMID:25441463

  11. NOTE ON THE EXCITATION AND INHIBITION OF LUMINESCENCE IN BEROE.

    PubMed

    Heymans, C; Moore, A R

    1925-01-20

    1. The ions of Ca and K condition general luminescence, and are therefore necessary to the conduction of the impulse. 2. In van't Hoff's solution from which Mg is omitted, Beroe shows hyperirritability with respect to luminescence. This is the result of the action of Ca and K ions unantagonized by Mg. 3. The luminescent material spread on filter paper does not show luminescence in sea water, NaCl, MgCl(2), or saccharose solutions isotonic with sea water. In solutions of CaCl(2), SrCl(2), BaCl(2), KCl, and K(2)SO(4) the indicator paper glows with a bright luminescence. 4. In dark adapted Beroe, luminescence is inhibited by a certain quantity of light. This quantity has an average value of 57,285 meter-candle-minutes, which is twelve times the value given by Mnemiopsis. PMID:19872141

  12. Spatial distribution of defect luminescence in GaN nanowires.

    PubMed

    Li, Qiming; Wang, George T

    2010-05-12

    The spatial distribution of defect-related and band-edge luminescence from GaN nanowires grown by metal-organic chemical vapor deposition was studied by spatially resolved cathodoluminescence imaging and spectroscopy. A surface layer exhibiting strong yellow luminescence (YL) near 566 nm in the nanowires was revealed, compared to weak YL in the bulk. In contrast, other defect-related luminescence near 428 nm (blue luminescence) and 734 nm (red luminescence), in addition to band-edge luminescence (BEL) at 366 nm, were observed in the bulk of the nanowires but were largely absent at the surface. As the nanowire width approaches a critical dimension, the surface YL layer completely quenches the BEL. The surface YL is attributed to the diffusion and piling up of mobile point defects, likely isolated gallium vacancies, at the surface during growth. PMID:20392110

  13. Demonstrating Bacterial Flagella.

    ERIC Educational Resources Information Center

    Porter, John R.; And Others

    1992-01-01

    Describes an effective laboratory method for demonstrating bacterial flagella that utilizes the Proteus mirabilis organism and a special harvesting technique. Includes safety considerations for the laboratory exercise. (MDH)

  14. Neutron dosimetry using optically stimulated luminescence

    NASA Astrophysics Data System (ADS)

    Miller, S. D.; Eschbach, P. A.

    1991-06-01

    The addition of thermoluminescent (TL) materials within hydrogenous matrices to detect neutron induced proton recoils for radiation dosimetry is a well known concept. Previous attempts to implement this technique have met with limited success, primarily due to the high temperatures required for TL readout and the low melting temperatures of hydrogen-rich plastics. Research in recent years PNL has produced a new Optically Stimulated Luminescence (OSL) technique known as the Cooled Optically Stimulated Luminescence (COSL) that offers, for the first time, the capability of performing extremely sensitive radiation dosimetry at low temperatures. In addition to its extreme sensitivity, the COSL technique offers multiple readout capability, limited fading in a one year period, and the capability of analyzing single grains within a hydrogenous matrix.

  15. Tunable lifetime multiplexing using luminescent nanocrystals

    NASA Astrophysics Data System (ADS)

    Lu, Yiqing; Zhao, Jiangbo; Zhang, Run; Liu, Yujia; Liu, Deming; Goldys, Ewa M.; Yang, Xusan; Xi, Peng; Sunna, Anwar; Lu, Jie; Shi, Yu; Leif, Robert C.; Huo, Yujing; Shen, Jian; Piper, James A.; Robinson, J. Paul; Jin, Dayong

    2014-01-01

    Optical multiplexing plays an important role in applications such as optical data storage, document security, molecular probes and bead assays for personalized medicine. Conventional fluorescent colour coding is limited by spectral overlap and background interference, restricting the number of distinguishable identities. Here, we show that tunable luminescent lifetimes τ in the microsecond region can be exploited to code individual upconversion nanocrystals. In a single colour band, one can generate more than ten nanocrystal populations with distinct lifetimes ranging from 25.6 µs to 662.4 µs and decode their well-separated lifetime identities, which are independent of both colour and intensity. Such `τ-dots' potentially suit multichannel bioimaging, high-throughput cytometry quantification, high-density data storage, as well as security codes to combat counterfeiting. This demonstration extends the optical multiplexing capability by adding the temporal dimension of luminescent signals, opening new opportunities in the life sciences, medicine and data security.

  16. Neutron dosimetry using optically stimulated luminescence

    SciTech Connect

    Miller, S.D.; Eschbach, P.A.

    1991-06-01

    The addition of thermoluminescent (TL) materials within hydrogenous matrices to detect neutron-induced proton recoils for radiation dosimetry is a well-known concept. Previous attempts to implement this technique have met with limited success, primarily due to the high temperatures required for TL readout and the low melting temperatures of hydrogen-rich plastics. Research in recent years at Pacific Northwest laboratories (PNL) has produced a new Optically Stimulated Luminescence (OSL) technique known as the Cooled Optically Stimulated Luminescence (COSL) that offers, for the first time, the capability of performing extremely sensitive radiation dosimetry at low temperatures. In addition to its extreme sensitivity, the COSL technique offers multiple readout capability, limited fading in a one-year period, and the capability of analyzing single grains within a hydrogenous matrix. 4 refs., 10 figs.

  17. Luminescent lanthanide chelates and methods of use

    DOEpatents

    Selvin, Paul R.; Hearst, John

    1997-01-01

    The invention provides lanthanide chelates capable of intense luminescence. The celates comprise a lanthanide chelator covalently joined to a coumarin-like or quinolone-like sensitizer. Exemplary sensitzers include 2- or 4-quinolones, 2- or 4-coumarins, or derivatives thereof e.g. carbostyril 124 (7-amino-4-methyl-2-quinolone), coumarin 120 (7-amino-4-methyl-2-coumarin), coumarin 124 (7-amino-4-(trifluoromethyl)-2-coumarin), aminomethyltrimethylpsoralen, etc. The chelates form high affinity complexes with lanthanides, such as terbium or europium, through chelator groups, such as DTPA. The chelates may be coupled to a wide variety of compounds to create specific labels, probes, diagnostic and/or therapeutic reagents, etc. The chelates find particular use in resonance energy transfer between chelate-lanthanide complexes and another luminescent agent, often a fluorescent non-metal based resonance energy acceptor. The methods provide useful information about the structure, conformation, relative location and/or interactions of macromolecules.

  18. A luminescent and biocompatible photoCORM.

    PubMed

    Pierri, Agustin E; Pallaoro, Alessia; Wu, Guang; Ford, Peter C

    2012-11-01

    The water-soluble rhenium(I) complex fac-[Re(bpy)(CO)(3)(thp)](+) (1) [CF(3)SO(3)(-) salt; bpy = 2,2'-bipyridine, thp = tris(hydroxymethyl)phosphine] is both strongly luminescent and photoactive toward carbon monoxide release. It is stable in aerated aqueous media, is incorporated into cells from the human prostatic carcinoma cell line PPC-1, and shows no apparent cytotoxicity. Furthermore, the solvated Re(I) photoproduct of CO release (2) is also luminescent, a feature that allows one to track the transformation of 1 to 2 inside such cells using confocal fluorescence microscopy. In this context, 1 is a very promising candidate as a photoactivated CO releasing moiety (photoCORM) with potential therapeutic applications. PMID:23077984

  19. Dual analyte detection using tandem flash luminescence.

    PubMed

    Adamczyk, Maciej; Moore, Jeffrey A; Shreder, Kevin

    2002-02-11

    A heterogeneous, dual analyte-binding assay which makes use of the flash luminescence from both aequorin and an acridinium-9-carboxamide label is presented. The signal generating species were triggered both differentially and sequentially using Ca(2+) followed by basic peroxide. Both signals were resolved readily using a single photomultiplier tube without the need for multiwavelength detection. To demonstrate the tandem luminescence concept in a model assay system, dose-response curves for two analytes, biotinylated BSA and myoglobin, were generated using a competitive binding format. Because of the relatively short assay time and the well-resolved signals, this format will be useful in the development of dual analyte high-throughput assays. PMID:11814805

  20. Luminescence properties of silicon-cellulose nanocomposite

    PubMed Central

    2012-01-01

    We have characterized the structure and luminescence properties for two-component material composed of nanocrystalline cellulose and nanocrystalline (less to 100 nm) silicon powder. An efficient and stable photoluminescence of nanocomposite, resistant to the influence of gas-phase oxidants, has been found. The obtained material has electret-like properties and demonstrates the possibility of multiple-recharging in an electric field near 5·103 V/cm at temperatures ranging from −70°C to 100°C. The presence of the electric field, as well as ozone or low-temperature plasma treatment, does not change the luminescence spectrum due to quantum size properties of silicon nanoparticles. We believe that these particles may appear in two states: both embedded in a cellulose matrix and in the form of mechanical mixture. PMID:22849811

  1. Luminescence properties of silicon-cellulose nanocomposite

    NASA Astrophysics Data System (ADS)

    Pikulev, Vitaly; Loginova, Svetlana; Gurtov, Valery

    2012-07-01

    We have characterized the structure and luminescence properties for two-component material composed of nanocrystalline cellulose and nanocrystalline (less to 100 nm) silicon powder. An efficient and stable photoluminescence of nanocomposite, resistant to the influence of gas-phase oxidants, has been found. The obtained material has electret-like properties and demonstrates the possibility of multiple-recharging in an electric field near 5·103 V/cm at temperatures ranging from -70°C to 100°C. The presence of the electric field, as well as ozone or low-temperature plasma treatment, does not change the luminescence spectrum due to quantum size properties of silicon nanoparticles. We believe that these particles may appear in two states: both embedded in a cellulose matrix and in the form of mechanical mixture.

  2. Method and apparatus for reducing solvent luminescence background emissions

    DOEpatents

    Affleck, Rhett L.; Ambrose, W. Patrick; Demas, James N.; Goodwin, Peter M.; Johnson, Mitchell E.; Keller, Richard A.; Petty, Jeffrey T.; Schecker, Jay A.; Wu, Ming

    1998-01-01

    The detectability of luminescent molecules in solution is enhanced by reducing the background luminescence due to impurity species also present in the solution. A light source that illuminates the solution acts to photolyze the impurities so that the impurities do not luminesce in the fluorescence band of the molecule of interest. Molecules of interest may be carried through the photolysis region in the solution or may be introduced into the solution after the photolysis region.

  3. Method and apparatus for reducing solvent luminescence background emissions

    DOEpatents

    Affleck, R.L.; Ambrose, W.P.; Demas, J.N.; Goodwin, P.M.; Johnson, M.E.; Keller, R.A.; Petty, J.T.; Schecker, J.A.; Wu, M.

    1998-10-27

    The detectability of luminescent molecules in solution is enhanced by reducing the background luminescence due to impurity species also present in the solution. A light source that illuminates the solution acts to photolyze the impurities so that the impurities do not luminesce in the fluorescence band of the molecule of interest. Molecules of interest may be carried through the photolysis region in the solution or may be introduced into the solution after the photolysis region. 6 figs.

  4. On the potential for molecular imaging with Cerenkov luminescence

    PubMed Central

    Lewis, Matthew A.; Kodibagkar, Vikram D.; Öz, Orhan K.; Mason, Ralph P.

    2011-01-01

    Recent observation of optical luminescence due to beta decay from suitable radiotracers has led to the possible development of new preclinical optical imaging methods. The generation of photons that can be detected using instrumentation optimized for bioluminescence imaging has been putatively associated with the Cerenkov effect. We describe the simultaneous utilization of fluorescence reporters to convert the Cerenkov luminescence to longer wavelengths for better tissue penetration and also for modulating the luminescence spectrum for potential molecular imaging strategies. PMID:21124555

  5. Luminescence of erbium ions in tellurite glasses

    SciTech Connect

    Savikin, Alexander P.; Grishin, Igor A.; Sharkov, Valery V.; Budruev, Andrei V.

    2013-11-15

    Optical characteristics of new generation of tellurite glasses having high stability against crystallization have been studied. As the initial reagents for the glasses synthesis on the base of tellurium oxide (TeO{sub 2}) there were used such oxides as WO{sub 3}, MoO{sub 3}, La{sub 2}O{sub 3}, Li{sub 2}CO{sub 3}, ZnO—Bi{sub 2}O{sub 2}CO{sub 3} and active components such as high purity Er{sub 2}O{sub 3}, Yb{sub 2}O{sub 3}, ErF{sub 3} and YbF{sub 3}. Intensities of luminescence at 1.53 µm of the erbium ions were determined after excitation at 975 nm. Experimental data obtained have shown the possibility to use the studied glasses doped by Er{sup 3+} and Yb{sup 3+} as active elements for fiber and integrated optics. - Graphical abstract: In contrast to the case of ZBLAN glass the TeO{sub 2}–WO{sub 3} (Er{sup 3+}) glass has bright intensity of luminescence at 1.53 µm for erbium ions that should be caused by excitation at 975 nm. Experimental data obtained have shown the possibility to use the studied glasses doped by Er{sup 3+} and Yb{sup 3+} as active elements for fiber and integrated optics. Display Omitted - Highlights: • We examined changes in growth of luminescence in doubly-doped tellurite glasses. • We found that luminescence grows in two orders by using Er{sup 3+} and Yb{sup 3+} at 1.53 μm. • We see possibility to use those glasses as active elements for integrated optics.

  6. Coalescent Simulation of Intracodon Recombination

    PubMed Central

    Arenas, Miguel; Posada, David

    2010-01-01

    The coalescent with recombination is a very useful tool in molecular population genetics. Under this framework, genealogies often represent the evolution of the substitution unit, and because of this, the few coalescent algorithms implemented for the simulation of coding sequences force recombination to occur only between codons. However, it is clear that recombination is expected to occur most often within codons. Here we have developed an algorithm that can evolve coding sequences under an ancestral recombination graph that represents the genealogies at each nucleotide site, thereby allowing for intracodon recombination. The algorithm is a modification of Hudson's coalescent in which, in addition to keeping track of events occurring in the ancestral material that reaches the sample, we need to keep track of events occurring in ancestral material that does not reach the sample but that is produced by intracodon recombination. We are able to show that at typical substitution rates the number of nonsynonymous changes induced by intracodon recombination is small and that intracodon recombination does not generally result in inflated estimates of the overall nonsynonymous/synonymous substitution ratio (ω). On the other hand, recombination can bias the estimation of ω at particular codons, resulting in apparent rate variation among sites and in the spurious identification of positively selected sites. Importantly, in this case, allowing for variable synonymous rates across sites greatly reduces the false-positive rate and recovers statistical power. Finally, coalescent simulations with intracodon recombination could be used to better represent the evolution of nuclear coding genes or fast-evolving pathogens such as HIV-1.We have implemented this algorithm in a computer program called NetRecodon, freely available at http://darwin.uvigo.es. PMID:19933876

  7. Luminescent Platinum Compounds: From Molecules to OLEDs

    NASA Astrophysics Data System (ADS)

    Murphy, Lisa; Williams, J. A. Gareth

    Around 30 years ago, much of the research into platinum coordination chemistry was being driven either by research into one-dimensional, electrically conducting molecular materials exploiting the stacking interactions of planar complexes, or by the unprecedented success of cis-Pt(NH3)2Cl2 (cisplatin) as an anticancer agent. At that time, a number of simple platinum(II) compounds were known to be photoluminescent at low temperature or in the solid state, but almost none in fluid solution at room temperature. Since that time, several families of complexes have been discovered that are brightly luminescent, and a number of investigations have shed light on the factors that govern the luminescence efficiencies of Pt(II) complexes. Over the past decade, such studies have been spurred on by the potential application of triplet-emitting metal complexes as phosphors in organic light-emitting devices (OLEDs), where their ability to trap otherwise wasted triplet states can lead to large gains in efficiency. In this contribution, we take a chemist's perspective of the field, overviewing in the first instance the factors that need to be taken into account in the rational design of highly luminescent platinum(II) complexes, and the background to their use in OLEDs. We then consider in more detail the properties of some individual classes, highlighting work from the past 3 years, and including selected examples of their utility in OLEDs and other applications.

  8. Tuning luminescence and reducing reabsorption of CdSe quantum disks for luminescent solar concentrators

    NASA Astrophysics Data System (ADS)

    Lin, Huichuan; Xie, Peng; Liu, Yong; Zhou, Xiang; Li, Baojun

    2015-08-01

    Cadmium selenide (CdSe) quantum disks (QDs) have been synthesized for application in luminescent solar concentrators (LSCs). Luminescence tuning and reabsorption reduction of the QDs were achieved by controlling their size using a hot injection method. The overlap of the absorption and photoluminescence spectra of the as-prepared CdSe QDs was negligible. The as-prepared CdSe QDs were incorporated into polymethylmethacrylate without aggregation and luminescence quenching. The obtained highly transparent composites with non-affecting light-emitting properties were used as LSCs. The placement of a CdSe QDs doped LSC prototype (10 × 1 × 0.1 cm) on a Si-cell resulted in a 201% increase in the electrical power output of the Si-cell compared with that of the bare Si-cell.

  9. Dislocation luminescence in GaN single crystals under nanoindentation

    NASA Astrophysics Data System (ADS)

    Huang, Jun; Xu, Ke; Fan, Ying Min; Wang, Jian Feng; Zhang, Ji Cai; Ren, Guo Qiang

    2014-12-01

    This work presents an experimental study on the dislocation luminescence in GaN by nanoindentation, cathodoluminescence, and Raman. The dislocation luminescence peaking at 3.12 eV exhibits a series of special properties in the cathodoluminescence measurements, and it completely disappears after annealing at 500°C. Raman spectroscopy shows evidence for existence of vacancies in the indented region. A comprehensive investigation encompassing cathodoluminescence, Raman, and annealing experiments allow the assignment of dislocation luminescence to conduction-band-acceptor transition involving Ga vacancies. The nanoscale plasticity of GaN can be better understood by considering the dislocation luminescence mechanism.

  10. Recombination Does Not Hinder Formation or Detection of Ecological Species of Synechococcus Inhabiting a Hot Spring Cyanobacterial Mat

    PubMed Central

    Melendrez, Melanie C.; Becraft, Eric D.; Wood, Jason M.; Olsen, Millie T.; Bryant, Donald A.; Heidelberg, John F.; Rusch, Douglas B.; Cohan, Frederick M.; Ward, David M.

    2016-01-01

    Recent studies of bacterial speciation have claimed to support the biological species concept—that reduced recombination is required for bacterial populations to diverge into species. This conclusion has been reached from the discovery that ecologically distinct clades show lower rates of recombination than that which occurs among closest relatives. However, these previous studies did not attempt to determine whether the more-rapidly recombining close relatives within the clades studied may also have diversified ecologically, without benefit of sexual isolation. Here we have measured the impact of recombination on ecological diversification within and between two ecologically distinct clades (A and B') of Synechococcus in a hot spring microbial mat in Yellowstone National Park, using a cultivation-free, multi-locus approach. Bacterial artificial chromosome (BAC) libraries were constructed from mat samples collected at 60°C and 65°C. Analysis of multiple linked loci near Synechococcus 16S rRNA genes showed little evidence of recombination between the A and B' lineages, but a record of recombination was apparent within each lineage. Recombination and mutation rates within each lineage were of similar magnitude, but recombination had a somewhat greater impact on sequence diversity than mutation, as also seen in many other bacteria and archaea. Despite recombination within the A and B' lineages, there was evidence of ecological diversification within each lineage. The algorithm Ecotype Simulation identified sequence clusters consistent with ecologically distinct populations (ecotypes), and several hypothesized ecotypes were distinct in their habitat associations and in their adaptations to different microenvironments. We conclude that sexual isolation is more likely to follow ecological divergence than to precede it. Thus, an ecology-based model of speciation appears more appropriate than the biological species concept for bacterial and archaeal diversification

  11. Recombination Does Not Hinder Formation or Detection of Ecological Species of Synechococcus Inhabiting a Hot Spring Cyanobacterial Mat.

    PubMed

    Melendrez, Melanie C; Becraft, Eric D; Wood, Jason M; Olsen, Millie T; Bryant, Donald A; Heidelberg, John F; Rusch, Douglas B; Cohan, Frederick M; Ward, David M

    2015-01-01

    Recent studies of bacterial speciation have claimed to support the biological species concept-that reduced recombination is required for bacterial populations to diverge into species. This conclusion has been reached from the discovery that ecologically distinct clades show lower rates of recombination than that which occurs among closest relatives. However, these previous studies did not attempt to determine whether the more-rapidly recombining close relatives within the clades studied may also have diversified ecologically, without benefit of sexual isolation. Here we have measured the impact of recombination on ecological diversification within and between two ecologically distinct clades (A and B') of Synechococcus in a hot spring microbial mat in Yellowstone National Park, using a cultivation-free, multi-locus approach. Bacterial artificial chromosome (BAC) libraries were constructed from mat samples collected at 60°C and 65°C. Analysis of multiple linked loci near Synechococcus 16S rRNA genes showed little evidence of recombination between the A and B' lineages, but a record of recombination was apparent within each lineage. Recombination and mutation rates within each lineage were of similar magnitude, but recombination had a somewhat greater impact on sequence diversity than mutation, as also seen in many other bacteria and archaea. Despite recombination within the A and B' lineages, there was evidence of ecological diversification within each lineage. The algorithm Ecotype Simulation identified sequence clusters consistent with ecologically distinct populations (ecotypes), and several hypothesized ecotypes were distinct in their habitat associations and in their adaptations to different microenvironments. We conclude that sexual isolation is more likely to follow ecological divergence than to precede it. Thus, an ecology-based model of speciation appears more appropriate than the biological species concept for bacterial and archaeal diversification. PMID

  12. Recombinant Collagen Engineered to Bind to Discoidin Domain Receptor Functions as a Receptor Inhibitor*

    PubMed Central

    An, Bo; Abbonante, Vittorio; Xu, Huifang; Gavriilidou, Despoina; Yoshizumi, Ayumi; Bihan, Dominique; Farndale, Richard W.; Kaplan, David L.; Balduini, Alessandra; Leitinger, Birgit; Brodsky, Barbara

    2016-01-01

    A bacterial collagen-like protein Scl2 has been developed as a recombinant collagen model system to host human collagen ligand-binding sequences, with the goal of generating biomaterials with selective collagen bioactivities. Defined binding sites in human collagen for integrins, fibronectin, heparin, and MMP-1 have been introduced into the triple-helical domain of the bacterial collagen and led to the expected biological activities. The modular insertion of activities is extended here to the discoidin domain receptors (DDRs), which are collagen-activated receptor tyrosine kinases. Insertion of the DDR-binding sequence from human collagen III into bacterial collagen led to specific receptor binding. However, even at the highest testable concentrations, the construct was unable to stimulate DDR autophosphorylation. The recombinant collagen expressed in Escherichia coli does not contain hydroxyproline (Hyp), and complementary synthetic peptide studies showed that replacement of Hyp by Pro at the critical Gly-Val-Met-Gly-Phe-Hyp position decreased the DDR-binding affinity and consequently required a higher concentration for the induction of receptor activation. The ability of the recombinant bacterial collagen to bind the DDRs without inducing kinase activation suggested it could interfere with the interactions between animal collagen and the DDRs, and such an inhibitory role was confirmed in vitro and with a cell migration assay. This study illustrates that recombinant collagen can complement synthetic peptides in investigating structure-activity relationships, and this system has the potential for the introduction or inhibition of specific biological activities. PMID:26702058

  13. Recombinant Collagen Engineered to Bind to Discoidin Domain Receptor Functions as a Receptor Inhibitor.

    PubMed

    An, Bo; Abbonante, Vittorio; Xu, Huifang; Gavriilidou, Despoina; Yoshizumi, Ayumi; Bihan, Dominique; Farndale, Richard W; Kaplan, David L; Balduini, Alessandra; Leitinger, Birgit; Brodsky, Barbara

    2016-02-26

    A bacterial collagen-like protein Scl2 has been developed as a recombinant collagen model system to host human collagen ligand-binding sequences, with the goal of generating biomaterials with selective collagen bioactivities. Defined binding sites in human collagen for integrins, fibronectin, heparin, and MMP-1 have been introduced into the triple-helical domain of the bacterial collagen and led to the expected biological activities. The modular insertion of activities is extended here to the discoidin domain receptors (DDRs), which are collagen-activated receptor tyrosine kinases. Insertion of the DDR-binding sequence from human collagen III into bacterial collagen led to specific receptor binding. However, even at the highest testable concentrations, the construct was unable to stimulate DDR autophosphorylation. The recombinant collagen expressed in Escherichia coli does not contain hydroxyproline (Hyp), and complementary synthetic peptide studies showed that replacement of Hyp by Pro at the critical Gly-Val-Met-Gly-Phe-Hyp position decreased the DDR-binding affinity and consequently required a higher concentration for the induction of receptor activation. The ability of the recombinant bacterial collagen to bind the DDRs without inducing kinase activation suggested it could interfere with the interactions between animal collagen and the DDRs, and such an inhibitory role was confirmed in vitro and with a cell migration assay. This study illustrates that recombinant collagen can complement synthetic peptides in investigating structure-activity relationships, and this system has the potential for the introduction or inhibition of specific biological activities. PMID:26702058

  14. Protective efficacy of a recombinant BAC clone of Marek's disease virus containing REV-LTR

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Insertion of reticuloendotheliosis virus (REV) long-terminal repeat (LTR) into a bacterial artificial chromosome (BAC) clone of a very virulent strain of Marek’s disease (MD) virus (MDV), Md5 (Kim et al, 2011) rendered the resultant recombinant virus termed rMd5 REV-LTR BAC fully attenuated at passa...

  15. recA-independent recombination between repeated IS50 elements is not caused by an IS50-encoded function.

    PubMed Central

    Phadnis, S H; Berg, D E

    1985-01-01

    Certain pBR322-related plasmids containing direct repeats of the insertion element IS50 appear to be unstable in recA Escherichia coli because smaller recombinant derivatives accumulate rapidly in plasmid DNA populations. We show here that (i) this instability is plasmid specific, but not IS50 specific; (ii) it is due to a detrimental effect exerted by these plasmids on bacterial growth; and (iii) the growth impairment is alleviated in cells harboring the smaller recombinant plasmids. Although a recent report had concluded that accumulation of recombinants reflected an IS50-specific recombination function, when correction is made for the relative growth rates of cells containing the parental and recombinant plasmids the evidence for such a recombination function disappears. Images PMID:2982795

  16. The bacterial ghost platform system

    PubMed Central

    Langemann, Timo; Koller, Verena Juliana; Muhammad, Abbas; Kudela, Pavol; Mayr, Ulrike Beate

    2010-01-01

    The Bacterial Ghost (BG) platform technology is an innovative system for vaccine, drug or active substance delivery and for technical applications in white biotechnology. BGs are cell envelopes derived from Gram-negative bacteria. BGs are devoid of all cytoplasmic content but have a preserved cellular morphology including all cell surface structures. Using BGs as delivery vehicles for subunit or DNA-vaccines the particle structure and surface properties of BGs are targeting the carrier itself to primary antigen-presenting cells. Furthermore, BGs exhibit intrinsic adjuvant properties and trigger an enhanced humoral and cellular immune response to the target antigen. Multiple antigens of the native BG envelope and recombinant protein or DNA antigens can be combined in a single type of BG. Antigens can be presented on the inner or outer membrane of the BG as well as in the periplasm that is sealed during BG formation. Drugs or supplements can also be loaded to the internal lumen or periplasmic space of the carrier. BGs are produced by batch fermentation with subsequent product recovery and purification via tangential flow filtration. For safety reasons all residual bacterial DNA is inactivated during the BG production process by the use of staphylococcal nuclease A and/or the treatment with β-propiolactone. After purification BGs can be stored long-term at ambient room temperature as lyophilized product. The production cycle from the inoculation of the pre-culture to the purified BG concentrate ready for lyophilization does not take longer than a day and thus meets modern criteria of rapid vaccine production rather than keeping large stocks of vaccines. The broad spectrum of possible applications in combination with the comparably low production costs make the BG platform technology a safe and sophisticated product for the targeted delivery of vaccines and active agents as well as carrier of immobilized enzymes for applications in white biotechnology. PMID:21326832

  17. Vimentin in Bacterial Infections

    PubMed Central

    Mak, Tim N.; Brüggemann, Holger

    2016-01-01

    Despite well-studied bacterial strategies to target actin to subvert the host cell cytoskeleton, thus promoting bacterial survival, replication, and dissemination, relatively little is known about the bacterial interaction with other components of the host cell cytoskeleton, including intermediate filaments (IFs). IFs have not only roles in maintaining the structural integrity of the cell, but they are also involved in many cellular processes including cell adhesion, immune signaling, and autophagy, processes that are important in the context of bacterial infections. Here, we summarize the knowledge about the role of IFs in bacterial infections, focusing on the type III IF protein vimentin. Recent studies have revealed the involvement of vimentin in host cell defenses, acting as ligand for several pattern recognition receptors of the innate immune system. Two main aspects of bacteria-vimentin interactions are presented in this review: the role of vimentin in pathogen-binding on the cell surface and subsequent bacterial invasion and the interaction of cytosolic vimentin and intracellular pathogens with regards to innate immune signaling. Mechanistic insight is presented involving distinct bacterial virulence factors that target vimentin to subvert its function in order to change the host cell fate in the course of a bacterial infection. PMID:27096872

  18. Bacterial Ion Channels.

    PubMed

    Compton, Emma L R; Mindell, Joseph A

    2010-09-01

    Bacterial ion channels were known, but only in special cases, such as outer membrane porins in Escherichia coli and bacterial toxins that form pores in their target (bacterial or mammalian) membranes. The exhaustive coverage provided by a decade of bacterial genome sequencing has revealed that ion channels are actually widespread in bacteria, with homologs of a broad range of mammalian channel proteins coded throughout the bacterial and archaeal kingdoms. This review discusses four groups of bacterial channels: porins, mechano-sensitive (MS) channels, channel-forming toxins, and bacterial homologs of mammalian channels. The outer membrane (OM) of gram-negative bacteria blocks access of essential nutrients; to survive, the cell needs to provide a mechanism for nutrients to penetrate the OM. Porin channels provide this access by forming large, nonspecific aqueous pores in the OM that allow ions and vital nutrients to cross it and enter the periplasm. MS channels act as emergency release valves, allowing solutes to rapidly exit the cytoplasm and to dissipate the large osmotic disparity between the internal and external environments. MS channels are remarkable in that they do this by responding to forces exerted by the membrane itself. Some bacteria produce toxic proteins that form pores in trans, attacking and killing other organisms by virtue of their pore formation. The review focuses on those bacterial toxins that kill other bacteria, specifically the class of proteins called colicins. Colicins reveal the dangers of channel formation in the plasma membrane, since they kill their targets with exactly that approach. PMID:26443789

  19. Vimentin in Bacterial Infections.

    PubMed

    Mak, Tim N; Brüggemann, Holger

    2016-01-01

    Despite well-studied bacterial strategies to target actin to subvert the host cell cytoskeleton, thus promoting bacterial survival, replication, and dissemination, relatively little is known about the bacterial interaction with other components of the host cell cytoskeleton, including intermediate filaments (IFs). IFs have not only roles in maintaining the structural integrity of the cell, but they are also involved in many cellular processes including cell adhesion, immune signaling, and autophagy, processes that are important in the context of bacterial infections. Here, we summarize the knowledge about the role of IFs in bacterial infections, focusing on the type III IF protein vimentin. Recent studies have revealed the involvement of vimentin in host cell defenses, acting as ligand for several pattern recognition receptors of the innate immune system. Two main aspects of bacteria-vimentin interactions are presented in this review: the role of vimentin in pathogen-binding on the cell surface and subsequent bacterial invasion and the interaction of cytosolic vimentin and intracellular pathogens with regards to innate immune signaling. Mechanistic insight is presented involving distinct bacterial virulence factors that target vimentin to subvert its function in order to change the host cell fate in the course of a bacterial infection. PMID:27096872

  20. Fungal and Bacterial Diseases.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fungal and bacterial diseases are important constraints to production. Recognition of diseases and information on their biology is important in disease management. This chapter is aimed at providing diagnostic information on fungal and bacterial diseases of sugar beet and their biology, epidemiolo...

  1. Synthesizing a Cellulase like Chimeric Protein by Recombinant Molecular Biology Techniques

    PubMed Central

    Banerjee, Hirendra Nath; Krauss, Christopher; Smith, Valerie; Mahaffey, Kelly; Boston, Ava

    2016-01-01

    In order to meet the Renewable Fuels Standard demands for 30 billion gallons of biofuels by the end of 2020, new technologies for generation of cellulosic ethanol must be exploited. Breaking down cellulose by cellulase enzyme is very important for this purpose but this is not thermostable and degrades at higher temperatures in bioreactors. Towards creation of a more ecologically friendly method of rendering bioethanol from cellulosic waste, we attempted to produce recombinant higher temperature resistant cellulases for use in bioreactors. The project involved molecular cloning of genes for cellulose-degrading enzymes based on bacterial source, expressing the recombinant proteins in E. coli and optimizing enzymatic activity. We were able to generate in vitro bacterial expression systems to produce recombinant His-tag purified protein which showed cellulase like activity. PMID:27468362

  2. Bacterial expression of human kynurenine 3-monooxygenase: solubility, activity, purification.

    PubMed

    Wilson, K; Mole, D J; Binnie, M; Homer, N Z M; Zheng, X; Yard, B A; Iredale, J P; Auer, M; Webster, S P

    2014-03-01

    Kynurenine 3-monooxygenase (KMO) is an enzyme central to the kynurenine pathway of tryptophan metabolism. KMO has been implicated as a therapeutic target in several disease states, including Huntington's disease. Recombinant human KMO protein production is challenging due to the presence of transmembrane domains, which localise KMO to the outer mitochondrial membrane and render KMO insoluble in many in vitro expression systems. Efficient bacterial expression of human KMO would accelerate drug development of KMO inhibitors but until now this has not been achieved. Here we report the first successful bacterial (Escherichia coli) expression of active FLAG™-tagged human KMO enzyme expressed in the soluble fraction and progress towards its purification. PMID:24316190

  3. Delayed recombination and standard rulers

    SciTech Connect

    De Bernardis, Francesco; Melchiorri, Alessandro; Bean, Rachel; Galli, Silvia; Silk, Joseph I.; Verde, Licia

    2009-02-15

    Measurements of baryonic acoustic oscillations (BAOs) in galaxy surveys have been recognized as a powerful tool for constraining dark energy. However, this method relies on the knowledge of the size of the acoustic horizon at recombination derived from cosmic microwave background (CMB) anisotropy measurements. This estimate is typically derived assuming a standard recombination scheme; additional radiation sources can delay recombination altering the cosmic ionization history and the cosmological inferences drawn from CMB and BAO data. In this paper we quantify the effect of delayed recombination on the determination of dark energy parameters from future BAO surveys such as the Baryon Oscillation Spectroscopic Survey and the Wide-Field Multi-Object Spectrograph. We find the impact to be small but still not negligible. In particular, if recombination is nonstandard (to a level still allowed by CMB data), but this is ignored, future surveys may incorrectly suggest the presence of a redshift-dependent dark energy component. On the other hand, in the case of delayed recombination, adding to the analysis one extra parameter describing deviations from standard recombination does not significantly degrade the error bars on dark energy parameters and yields unbiased estimates. This is due to the CMB-BAO complementarity.

  4. Oligonucleotide recombination in corynebacteria without the expression of exogenous recombinases.

    PubMed

    Krylov, Alexander A; Kolontaevsky, Egor E; Mashko, Sergey V

    2014-10-01

    Brevibacterium lactofermentum and Corynebacterium glutamicum are important biotechnology species of the genus Corynebacterium. The single-strand DNA annealing protein (SSAP)-independent oligonucleotide-mediated recombination procedure was successfully applied to the commonly used wild-type strains B. lactofermentum AJ1511 and C. glutamicum ATCC13032. When the rpsL gene was used as a target, the optimized protocol yielded up to (1.4±0.3)×10(3) and (6.7±1.3)×10(3) streptomycin-resistant colonies per 10(8) viable cells for the corresponding strains. We tested the influence of several parameters that are known to enhance the efficiency of oligonucleotide-mediated recombination in other bacterial species. Among them, increasing the concentration of oligonucleotides and targeting the lagging strand of the chromosome have proven to have positive effects on both of the tested species. No difference in the efficiency of recombination was observed between the oligonucleotides phosphorothiorated at the 5' ends and the unmodified oligonucleotides or between the oligonucleotides with four mutated nucleotides and those with one mutated nucleotide. The described approach demonstrates that during the adaptation of the recombineering technique, testing SSAP-independent oligonucleotide-mediated recombination could be a good starting point. Such testing could decrease the probability of an incorrect interpretation of the effect of exogenous protein factors (such as SSAP and/or corresponding exonucleases) due to non-optimal experimental conditions. In addition, SSAP-independent recombination itself could be useful in combination with suitable selection/enrichment methods. PMID:25087479

  5. Sensitive, Rapid Detection of Bacterial Spores

    NASA Technical Reports Server (NTRS)

    Kern, Roger G.; Venkateswaran, Kasthuri; Chen, Fei; Pickett, Molly; Matsuyama, Asahi

    2009-01-01

    A method of sensitive detection of bacterial spores within delays of no more than a few hours has been developed to provide an alternative to a prior three-day NASA standard culture-based assay. A capability for relatively rapid detection of bacterial spores would be beneficial for many endeavors, a few examples being agriculture, medicine, public health, defense against biowarfare, water supply, sanitation, hygiene, and the food-packaging and medical-equipment industries. The method involves the use of a commercial rapid microbial detection system (RMDS) that utilizes a combination of membrane filtration, adenosine triphosphate (ATP) bioluminescence chemistry, and analysis of luminescence images detected by a charge-coupled-device camera. This RMDS has been demonstrated to be highly sensitive in enumerating microbes (it can detect as little as one colony-forming unit per sample) and has been found to yield data in excellent correlation with those of culture-based methods. What makes the present method necessary is that the specific RMDS and the original protocols for its use are not designed for discriminating between bacterial spores and other microbes. In this method, a heat-shock procedure is added prior to an incubation procedure that is specified in the original RMDS protocols. In this heat-shock procedure (which was also described in a prior NASA Tech Briefs article on enumerating sporeforming bacteria), a sample is exposed to a temperature of 80 C for 15 minutes. Spores can survive the heat shock, but nonspore- forming bacteria and spore-forming bacteria that are not in spore form cannot survive. Therefore, any colonies that grow during incubation after the heat shock are deemed to have originated as spores.

  6. The morphology, microstructure, and luminescent properties of CdS/CdTe films

    SciTech Connect

    Al-Jassim, M.M.; Dhere, R.G.; Jones, K.M.; Hasoon, F.S.; Sheldon, P.

    1998-09-01

    This paper is concerned with the characterization of CdS/CdTe polycrystalline thin films for solar cells. The morphology, microstructure, and luminescent properties are studied by a powerful array of characterization techniques. The presence of pinholes in 100-nm thick CdS is observed. The microstructure of CdS and CdTe films is shown to be heavily faulted polycrystalline. The effect of deposition temperature on the grain size and the microstructure is investigated. The interdiffusion of sulfur and tellurium at the CdS/CdTe interface is studied for the first time by a nanoprobe technique. Considerable amount of sulfur is detected in CdTe in the vicinity of the interface of samples deposited at 625 C. The recombination behavior of grain boundaries and intragrain defects is investigated in as-deposited and heat-treated samples.

  7. Luminescence and electrical properties of single ZnO/MgO core/shell nanowires

    SciTech Connect

    Grinblat, Gustavo; Comedi, David; Bern, Francis; Barzola-Quiquia, José; Esquinazi, Pablo; Tirado, Mónica

    2014-03-10

    To neutralise the influence of the surface of ZnO nanowires for photonics and optoelectronic applications, we have covered them with insulating MgO film and individually contacted them for electrical characterisation. We show that such a metal-insulator-semiconductor-type nanodevice exhibits a high diode ideality factor of 3.4 below 1 V. MgO shell passivates ZnO surface states and provides confining barriers to electrons and holes within the ZnO core, favouring excitonic ultraviolet radiative recombination, while suppressing defect-related luminescence in the visible and improving electrical conductivity. The results indicate the potential use of ZnO/MgO nanowires as a convenient building block for nano-optoelectronic devices.

  8. Time resolved photo-luminescent decay characterization of mercury cadmium telluride focal plane arrays

    DOE PAGESBeta

    Soehnel, Grant

    2015-01-20

    The minority carrier lifetime is a measurable material property that is an indication of infrared detector device performance. To study the utility of measuring the carrier lifetime, an experiment has been constructed that can time resolve the photo-luminescent decay of a detector or wafer sample housed inside a liquid nitrogen cooled Dewar. Motorized stages allow the measurement to be scanned over the sample surface, and spatial resolutions as low as 50µm have been demonstrated. A carrier recombination simulation was developed to analyze the experimental data. Results from measurements performed on 4 mercury cadmium telluride focal plane arrays show strong correlationmore » between spatial maps of the lifetime, dark current, and relative response.« less

  9. Time resolved photo-luminescent decay characterization of mercury cadmium telluride focal plane arrays

    SciTech Connect

    Soehnel, Grant

    2015-01-20

    The minority carrier lifetime is a measurable material property that is an indication of infrared detector device performance. To study the utility of measuring the carrier lifetime, an experiment has been constructed that can time resolve the photo-luminescent decay of a detector or wafer sample housed inside a liquid nitrogen cooled Dewar. Motorized stages allow the measurement to be scanned over the sample surface, and spatial resolutions as low as 50µm have been demonstrated. A carrier recombination simulation was developed to analyze the experimental data. Results from measurements performed on 4 mercury cadmium telluride focal plane arrays show strong correlation between spatial maps of the lifetime, dark current, and relative response.

  10. Ag/ZnO hybrid systems studied with scanning tunnelling microscopy-based luminescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Pascua, Leandro; Stavale, Fernando; Nilius, Niklas; Freund, Hans-Joachim

    2016-03-01

    Coupled metal/oxide systems are prepared by depositing and embedding Ag nanoparticles into crystalline ZnO films grown on Au(111) supports. The morphology and optical properties of the compounds are investigated by topographic imaging and luminescence spectroscopy performed in a scanning tunnelling microscope (STM). The luminescence of bare ZnO is governed by the band-recombination and a Zn-vacancy related peak. After Ag deposition, two additional maxima are detected that are assigned to the in-plane and out-of-plane plasmon in Ag nanoparticles and have energies below and slightly above the oxide band-gap, respectively. Upon coating the particles with additional ZnO, the out-of-plane plasmon redshifts and loses intensity, indicating strong coupling to the oxide electronic system, while the in-plane mode broadens but remains detectable. The original situation can be restored by gently heating the sample, which drives the silver back to the surface. However, the optical response of pristine ZnO is not recovered even after silver evaporation at high temperature. Small discrepancies are explained with changes in the ZnO defect landscape, e.g., due to silver incorporation. Our experiments demonstrate how energy-transfer processes can be investigated in well-defined metal/oxide systems by means of STM-based spectroscopic techniques.

  11. Laser-induced generation of micrometer-sized luminescent patterns on rare-earth-doped amorphous films

    SciTech Connect

    Zanatta, A.R.; Ribeiro, C.T.M.

    2004-12-01

    Room-temperature photoluminescence has been achieved from rare-earth-doped amorphous (a-) GeN films. The samples were prepared by the radio-frequency-sputtering method, and light emission from the rare-earth (RE) centers was obtained after irradiating the films with a highly focused laser beam. As a result of this laser annealing procedure, almost circular holes with approximately 1-{mu}m diameter were produced on the surface of the a-GeN films. The area nearby these holes correspond to crystalline Ge and coincide with the regions, where relatively strong RE-related luminescence takes place. These laser-annealed areas can be easily and conveniently managed in order to generate different microscopic luminescent patterns. Depending on the RE ion employed, visible and near-infrared light emission were obtained from the patterns so produced. The development of these micrometer-sized luminescent centers, as well as their probable mechanisms of excitation-recombination, will be presented and discussed. The importance of the current experimental results to future technological applications such as microdevices, for example, will also be outlined.

  12. ZnO Luminescence and scintillation studied via photoexcitation, x-ray excitation, and gamma-induced positron spectroscopy"

    SciTech Connect

    Ji, C; Colosimo, A; Anwand, W; Boatner, Lynn A; Wagner, A; Stepanov, P S; Trinh, t t; Liedke, m o; Krause-Rehberg, R; Cowan, T E; Selim, F. A.

    2016-01-01

    Luminescence and scintillation in ZnO single crystals were measured by photoluminescence and X-ray-induced luminescence (XRIL). XRIL allowed a direct comparison to be made between the near-band emission (NBE) and trap emissions providing insight into the carrier recombination efficiency in the ZnO crystals. The origin of green emission, the dominant trap emission in ZnO, was investigated by gamma-induced positron spectroscopy (GIPS) - a unique defect spectroscopy method that enables positron lifetime measurements to be made for a sample without contributions from positron annihilation in the source materials or the surroundings. The measurements showed the absence of positron traps in the crystals and yielded a bulk positron lifetime value that is in complete agreement with the predicted theoretical value = thereby confirming the advantage of the GIPS method. By combining scintillation measurements with XRIL, the fast scintillation in ZnO crystals was found to be strongly correlated with the ratio between the defect luminescence and NBE.

  13. ZnO Luminescence and scintillation studied via photoexcitation, x-ray excitation, and gamma-induced positron spectroscopy"

    DOE PAGESBeta

    Ji, C; Colosimo, A; Anwand, W; Boatner, Lynn A; Wagner, A; Stepanov, P S; Trinh, t t; Liedke, m o; Krause-Rehberg, R; Cowan, T E; et al

    2016-01-01

    Luminescence and scintillation in ZnO single crystals were measured by photoluminescence and X-ray-induced luminescence (XRIL). XRIL allowed a direct comparison to be made between the near-band emission (NBE) and trap emissions providing insight into the carrier recombination efficiency in the ZnO crystals. The origin of green emission, the dominant trap emission in ZnO, was investigated by gamma-induced positron spectroscopy (GIPS) - a unique defect spectroscopy method that enables positron lifetime measurements to be made for a sample without contributions from positron annihilation in the source materials or the surroundings. The measurements showed the absence of positron traps in the crystalsmore » and yielded a bulk positron lifetime value that is in complete agreement with the predicted theoretical value = thereby confirming the advantage of the GIPS method. By combining scintillation measurements with XRIL, the fast scintillation in ZnO crystals was found to be strongly correlated with the ratio between the defect luminescence and NBE.« less

  14. Phylogeographic variation in recombination rates within a global clone of methicillin-resistant Staphylococcus aureus

    PubMed Central

    2012-01-01

    Background Next-generation sequencing (NGS) is a powerful tool for understanding both patterns of descent over time and space (phylogeography) and the molecular processes underpinning genome divergence in pathogenic bacteria. Here, we describe a synthesis between these perspectives by employing a recently developed Bayesian approach, BRATNextGen, for detecting recombination on an expanded NGS dataset of the globally disseminated methicillin-resistant Staphylococcus aureus (MRSA) clone ST239. Results The data confirm strong geographical clustering at continental, national and city scales and demonstrate that the rate of recombination varies significantly between phylogeographic sub-groups representing independent introductions from Europe. These differences are most striking when mobile non-core genes are included, but remain apparent even when only considering the stable core genome. The monophyletic ST239 sub-group corresponding to isolates from South America shows heightened recombination, the sub-group predominantly from Asia shows an intermediate level, and a very low level of recombination is noted in a third sub-group representing a large collection from Turkey. Conclusions We show that the rapid global dissemination of a single pathogenic bacterial clone results in local variation in measured recombination rates. Possible explanatory variables include the size and time since emergence of each defined sub-population (as determined by the sampling frame), variation in transmission dynamics due to host movement, and changes in the bacterial genome affecting the propensity for recombination. PMID:23270620

  15. No Evidence that Infection Alters Global Recombination Rate in House Mice

    PubMed Central

    Dumont, Beth L.; Devlin, Amy A.; Truempy, Dana M.; Miller, Jennifer C.; Singh, Nadia D.

    2015-01-01

    Recombination rate is a complex trait, with genetic and environmental factors shaping observed patterns of variation. Although recent studies have begun to unravel the genetic basis of recombination rate differences between organisms, less attention has focused on the environmental determinants of crossover rates. Here, we test the effect of one ubiquitous environmental pressure–bacterial infection–on global recombination frequency in mammals. We applied MLH1 mapping to assay global crossover rates in male mice infected with the pathogenic bacterium Borrelia burgdorferi, the causative agent of Lyme Disease, and uninfected control animals. Despite ample statistical power to identify biologically relevant differences between infected and uninfected animals, we find no evidence for a global recombination rate response to bacterial infection. Moreover, broad-scale patterns of crossover distribution, including the number of achiasmate bivalents, are not affected by infection status. Although pathogen exposure can plastically increase recombination in some species, our findings suggest that recombination rates in house mice may be resilient to at least some forms of infection stress. This negative result motivates future experiments with alternative house mouse pathogens to evaluate the generality of this conclusion. PMID:26550833

  16. Lanthanide Luminescence Modulation by Cation-π Interaction in a Bioinspired Scaffold: Selective Detection of Copper(I).

    PubMed

    Isaac, Manon; Denisov, Sergey A; Roux, Amandine; Imbert, Daniel; Jonusauskas, Gediminas; McClenaghan, Nathan D; Sénèque, Olivier

    2015-09-21

    A prototype luminescent turn-on probe for Cu(+) (and Ag(+)) is described, harnessing a selective binding site (log Kass = 9.4 and 7.3 for Cu(+) and Ag(+), respectively) based on the coordinating environment of the bacterial metallo-chaperone CusF, integrated with a terbium-ion-signaling moiety. Cation-π interactions were shown to enhance tryptophan triplet population, which subsequently sensitized, on the microsecond timescale, the long-lived terbium emission, offering a novel approach in bioinspired chemosensor design. PMID:26223738

  17. The insecticidal activity of recombinant garlic lectins towards aphids.

    PubMed

    Fitches, Elaine; Wiles, Duncan; Douglas, Angela E; Hinchliffe, Gareth; Audsley, Neil; Gatehouse, John A

    2008-10-01

    The heterodimeric and homodimeric garlic lectins ASAI and ASAII were produced as recombinant proteins in the yeast Pichia pastoris. The proteins were purified as functional dimeric lectins, but underwent post-translational proteolysis. Recombinant ASAII was a single homogenous polypeptide which had undergone C-terminal processing similar to that occurring in planta. The recombinant ASAI was glycosylated and subject to variable and heterogenous proteolysis. Both lectins showed insecticidal effects when fed to pea aphids (Acyrthosiphon pisum) in artificial diet, ASAII being more toxic than ASAI at the same concentration. Acute toxicity (mortality at < or =48 h exposure; similar timescale to starvation) was only apparent at the highest lectin concentrations tested (2.0 mg ml(-)1), but dose-dependent chronic toxicity (mortality at >3d exposure) was observed over the concentration range 0.125-2.0 mg ml(-1). The recombinant lectins caused mortality in both symbiotic and antibiotic-treated aphids, showing that toxicity is not dependent on the presence of the bacterial symbiont (Buchnera aphidicola), or on interaction with symbiont proteins, such as the previously identified lectin "receptor" symbionin. A pull-down assay coupled with peptide mass fingerprinting identified two abundant membrane-associated aphid gut proteins, alanyl aminopeptidase N and sucrase, as "receptors" for lectin binding. PMID:18707000

  18. Bacterial Cellular Engineering by Genome Editing and Gene Silencing

    PubMed Central

    Nakashima, Nobutaka; Miyazaki, Kentaro

    2014-01-01

    Genome editing is an important technology for bacterial cellular engineering, which is commonly conducted by homologous recombination-based procedures, including gene knockout (disruption), knock-in (insertion), and allelic exchange. In addition, some new recombination-independent approaches have emerged that utilize catalytic RNAs, artificial nucleases, nucleic acid analogs, and peptide nucleic acids. Apart from these methods, which directly modify the genomic structure, an alternative approach is to conditionally modify the gene expression profile at the posttranscriptional level without altering the genomes. This is performed by expressing antisense RNAs to knock down (silence) target mRNAs in vivo. This review describes the features and recent advances on methods used in genomic engineering and silencing technologies that are advantageously used for bacterial cellular engineering. PMID:24552876

  19. Subcloning plus insertion (SPI)--a novel recombineering method for the rapid construction of gene targeting vectors.

    PubMed

    Reddy, Thimma R; Kelsall, Emma J; Fevat, Léna M S; Munson, Sarah E; Cowley, Shaun M

    2015-01-01

    Gene targeting refers to the precise modification of a genetic locus using homologous recombination. The generation of novel cell lines and transgenic mouse models using this method necessitates the construction of a 'targeting' vector, which contains homologous DNA sequences to the target gene, and has for many years been a limiting step in the process. Vector construction can be performed in vivo in Escherichia coli cells using homologous recombination mediated by phage recombinases using a technique termed recombineering. Recombineering is the preferred technique to subclone the long homology sequences (>4 kb) and various targeting elements including selection markers that are required to mediate efficient allelic exchange between a targeting vector and its cognate genomic locus. Typical recombineering protocols follow an iterative scheme of step-wise integration of the targeting elements and require intermediate purification and transformation steps. Here, we present a novel recombineering methodology of vector assembly using a multiplex approach. Plasmid gap repair is performed by the simultaneous capture of genomic sequence from mouse Bacterial Artificial Chromosome libraries and the insertion of dual bacterial and mammalian selection markers. This subcloning plus insertion method is highly efficient and yields a majority of correct recombinants. We present data for the construction of different types of conditional gene knockout, or knock-in, vectors and BAC reporter vectors that have been constructed using this method. SPI vector construction greatly extends the repertoire of the recombineering toolbox and provides a simple, rapid and cost-effective method of constructing these highly complex vectors. PMID:25590226

  20. Recombinant cells that highly express chromosomally-integrated heterologous genes

    DOEpatents

    Ingram, L.O.; Ohta, Kazuyoshi; Wood, B.E.

    1998-10-13

    Recombinant host cells are obtained that comprise (A) a heterologous, polypeptide-encoding polynucleotide segment, stably integrated into a chromosome, which is under transcriptional control of an endogenous promoter and (B) a mutation that effects increased expression of the heterologous segment, resulting in enhanced production by the host cells of each polypeptide encoded by that segment, relative to production of each polypeptide by the host cells in the absence of the mutation. The increased expression thus achieved is retained in the absence of conditions that select for cells displaying such increased expression. When the integrated segment comprises, for example, ethanol-production genes from an efficient ethanol producer like Zymomonas mobilis, recombinant Escherichia coli and other enteric bacterial cells within the present invention are capable of converting a wide range of biomass-derived sugars efficiently to ethanol. 13 figs.

  1. Recombinant cells that highly express chromosomally-integrated heterologous gene

    DOEpatents

    Ingram, Lonnie O.; Ohta, Kazuyoshi; Wood, Brent E.

    2007-03-20

    Recombinant host cells are obtained that comprise (A) a heterologous, polypeptide-encoding polynucleotide segment, stably integrated into a chromosome, which is under transcriptional control of an endogenous promoter and (B) a mutation that effects increased expression of the heterologous segment, resulting in enhanced production by the host cells of each polypeptide encoded by that segment, relative to production of each polypeptide by the host cells in the absence of the mutation. The increased expression thus achieved is retained in the absence of conditions that select for cells displaying such increased expression. When the integrated segment comprises, for example, ethanol-production genes from an efficient ethanol producer like Zymomonas mobilis, recombinant Escherichia coli and other enteric bacterial cells within the present invention are capable of converting a wide range of biomass-derived sugars efficiently to ethanol.

  2. Recombinant cells that highly express chromosomally-integrated heterologous genes

    DOEpatents

    Ingram, Lonnie O.; Ohta, Kazuyoshi; Wood, Brent E.

    1998-01-01

    Recombinant host cells are obtained that comprise (A) a heterologous, polypeptide-encoding polynucleotide segment, stably integrated into a chromosome, which is under transcriptional control of an endogenous promoter and (B) a mutation that effects increased expression of the heterologous segment, resulting in enhanced production by the host cells of each polypeptide encoded by that segment, relative to production of each polypeptide by the host cells in the absence of the mutation. The increased expression thus achieved is retained in the absence of conditions that select for cells displaying such increased expression. When the integrated segment comprises, for example, ethanol-production genes from an efficient ethanol producer like Zymomonas mobilis, recombinant Escherichia coli and other enteric bacterial cells within the present invention are capable of converting a wide range of biomass-derived sugars efficiently to ethanol.

  3. Recombinant cells that highly express chromosomally-integrated heterologous genes

    DOEpatents

    Ingram, Lonnie O.; Ohta, Kazuyoshi; Wood, Brent E.

    2000-08-22

    Recombinant host cells are obtained that comprise (A) a heterologous, polypeptide-encoding polynucleotide segment, stably integrated into a chromosome, which is under transcriptional control of an endogenous promoter and (B) a mutation that effects increased expression of the heterologous segment, resulting in enhanced production by the host cells of each polypeptide encoded by that segment, relative to production of each polypeptide by the host cells in the absence of the mutation. The increased expression thus achieved is retained in the absence of conditions that select for cells displaying such increased expression. When the integrated segment comprises, for example, ethanol-production genes from an efficient ethanol producer like Zymomonas mobilis, recombinant Escherichia coli and other enteric bacterial cells within the present invention are capable of converting a wide range of biomass-derived sugars efficiently to ethanol.

  4. Recombinant baculovirus vectors expressing glutathione-S-transferase fusion proteins.

    PubMed

    Davies, A H; Jowett, J B; Jones, I M

    1993-08-01

    Recombinant baculoviruses are a popular means of producing heterologous protein in eukaryotic cells. Purification of recombinant proteins away from the insect cell background can, however, remain an obstacle for many developments. Recently, prokaryotic fusion protein expression systems have been developed allowing single-step purification of the heterologous protein and specific proteolytic cleavage of the affinity tag moiety from the desired antigen. Here we report the introduction of these attributes to the baculovirus system. "Baculo-GEX" vectors enable baculovirus production of fusion proteins with the above advantages, but in a eukaryotic post-translational processing environment. Glutathione-S-transferase (GST) fusions are stable cytoplasmic proteins in insect cells and may therefore be released by sonication alone, avoiding the solubility problems and detergent requirements of bacterial systems. Thus large amounts of authentic antigen may be purified in a single, non-denaturing step. PMID:7763917

  5. Analysis of the luminescent centers in silicon rich silicon nitride light-emitting capacitors

    NASA Astrophysics Data System (ADS)

    Cabañas-Tay, S. A.; Palacios-Huerta, L.; Luna-López, J. A.; Aceves-Mijares, M.; Alcántara-Iniesta, S.; Pérez-García, S. A.; Morales-Sánchez, A.

    2015-06-01

    An analysis of the luminescent center and its effect on the optical, electrical and electro-optical properties of silicon rich silicon nitride (SRN) films deposited by low pressure chemical vapor deposition is reported. As-deposited SRN films emit a broad photoluminescence (PL) spectrum in the visible range where the maximum peak shifts from ∼490 to ∼590 nm as the silicon excess increases. After thermal annealing, a PL blue-shift is observed and it is ascribed to a compositional-dependent change in the concentration of defect states within the films. A correlation between the PL peak energy with the optical band-gap indicates that the luminescence is related to the band tail carrier recombination in the SRN films. Light emitting capacitors (LECs) based on fluor-doped tin oxide SnO2:F (FTO)/SRN active layer/n-Si substrate emit a broad electroluminescent spectra where the maximum emission peak blue-shifts when the polarity is changed from reverse to forward bias. In the reverse bias, the electroluminescence (EL) is related to the states of valence band tail and Si dangling bonds (K0 centers), while in the forward bias the EL is originated from electronic transitions from the conduction band minimum to K0 centers. A model based on the trap assisted tunneling carrier transport is correlated with the proposed EL radiative recombination process in the FTO/SRN/n-Si structures. A discussion of the differences between the PL and EL spectra is reported. The results open new alternatives toward the development of Si-based light emitters where two different EL spectra can be obtained changing the polarity.

  6. ABC transporters: bacterial exporters.

    PubMed Central

    Fath, M J; Kolter, R

    1993-01-01

    The ABC transporters (also called traffic ATPases) make up a large superfamily of proteins which share a common function and a common ATP-binding domain. ABC transporters are classified into three major groups: bacterial importers (the periplasmic permeases), eukaryotic transporters, and bacterial exporters. We present a comprehensive review of the bacterial ABC exporter group, which currently includes over 40 systems. The bacterial ABC exporter systems are functionally subdivided on the basis of the type of substrate that each translocates. We describe three main groups: protein exporters, peptide exporters, and systems that transport nonprotein substrates. Prototype exporters from each group are described in detail to illustrate our current understanding of this protein family. The prototype systems include the alpha-hemolysin, colicin V, and capsular polysaccharide exporters from Escherichia coli, the protease exporter from Erwinia chrysanthemi, and the glucan exporters from Agrobacterium tumefaciens and Rhizobium meliloti. Phylogenetic analysis of the ATP-binding domains from 29 bacterial ABC exporters indicates that the bacterial ABC exporters can be divided into two primary branches. One branch contains the transport systems where the ATP-binding domain and the membrane-spanning domain are present on the same polypeptide, and the other branch contains the systems where these domains are found on separate polypeptides. Differences in substrate specificity do not correlate with evolutionary relatedness. A complete survey of the known and putative bacterial ABC exporters is included at the end of the review. PMID:8302219

  7. Three Decades of Recombinant DNA.

    ERIC Educational Resources Information Center

    Palmer, Jackie

    1985-01-01

    Discusses highlights in the development of genetic engineering, examining techniques with recombinant DNA, legal and ethical issues, GenBank (a national database of nucleic acid sequences), and other topics. (JN)

  8. Controlled Release from Recombinant Polymers

    PubMed Central

    Price, Robert; Poursaid, Azadeh; Ghandehari, Hamidreza

    2014-01-01

    Recombinant polymers provide a high degree of molecular definition for correlating structure with function in controlled release. The wide array of amino acids available as building blocks for these materials lend many advantages including biorecognition, biodegradability, potential biocompatibility, and control over mechanical properties among other attributes. Genetic engineering and DNA manipulation techniques enable the optimization of structure for precise control over spatial and temporal release. Unlike the majority of chemical synthetic strategies used, recombinant DNA technology has allowed for the production of monodisperse polymers with specifically defined sequences. Several classes of recombinant polymers have been used for controlled drug delivery. These include, but are not limited to, elastin-like, silk-like, and silk-elastinlike proteins, as well as emerging cationic polymers for gene delivery. In this article, progress and prospects of recombinant polymers used in controlled release will be reviewed. PMID:24956486

  9. Recombinant DNA means and method

    SciTech Connect

    Alford, B.L.; Mao, J.I.; Moir, D.T.; Taunton-Rigby, A.; Vovis, G.F.

    1987-05-19

    This patent describes a transformed living cell selected from the group consisting of fungi, yeast and bacteria, and containing genetic material derived from recombinant DNA material and coding for bovine rennin.

  10. Stable recombination hotspots in birds.

    PubMed

    Singhal, Sonal; Leffler, Ellen M; Sannareddy, Keerthi; Turner, Isaac; Venn, Oliver; Hooper, Daniel M; Strand, Alva I; Li, Qiye; Raney, Brian; Balakrishnan, Christopher N; Griffith, Simon C; McVean, Gil; Przeworski, Molly

    2015-11-20

    The DNA-binding protein PRDM9 has a critical role in specifying meiotic recombination hotspots in mice and apes, but it appears to be absent from other vertebrate species, including birds. To study the evolution and determinants of recombination in species lacking the gene that encodes PRDM9, we inferred fine-scale genetic maps from population resequencing data for two bird species: the zebra finch, Taeniopygia guttata, and the long-tailed finch, Poephila acuticauda. We found that both species have recombination hotspots, which are enriched near functional genomic elements. Unlike in mice and apes, most hotspots are shared between the two species, and their conservation seems to extend over tens of millions of years. These observations suggest that in the absence of PRDM9, recombination targets functional features that both enable access to the genome and constrain its evolution. PMID:26586757

  11. Recombination device for storage batteries

    DOEpatents

    Kraft, H.; Ledjeff, K.

    1984-01-01

    A recombination device including a gas-tight enclosure connected to receive the discharge gases from a rechargeable storage battery. Catalytic material for the recombination of hydrogen and oxygen to form water is supported within the enclosure. The enclosure is sealed from the atmosphere by a liquid seal including two vertical chambers interconnected with an inverted U-shaped overflow tube. The first chamber is connected at its upper portion to the enclosure and the second chamber communicates at its upper portion with the atmosphere. If the pressure within the enclosure differs as overpressure or vacuum by more than the liquid level, the liquid is forced into one of the two chambers and the overpressure is vented or the vacuum is relieved. The recombination device also includes means for returning recombined liquid to the battery and for absorbing metal hydrides.

  12. Recombination device for storage batteries

    DOEpatents

    Kraft, Helmut; Ledjeff, Konstantin

    1985-01-01

    A recombination device including a gas-tight enclosure connected to receive he discharge gases from a rechargeable storage battery. Catalytic material for the recombination of hydrogen and oxygen to form water is supported within the enclosure. The enclosure is sealed from the atmosphere by a liquid seal including two vertical chambers interconnected with an inverted U-shaped overflow tube. The first chamber is connected at its upper portion to the enclosure and the second chamber communicates at its upper portion with the atmosphere. If the pressure within the enclosure differs as overpressure or vacuum by more than the liquid level, the liquid is forced into one of the two chambers and the overpressure is vented or the vacuum is relieved. The recombination device also includes means for returning recombined liquid to the battery and for absorbing metal hydrides.

  13. Recombinant soluble adenovirus receptor

    DOEpatents

    Freimuth, Paul I.

    2002-01-01

    Disclosed are isolated polypeptides from human CAR (coxsackievirus and adenovirus receptor) protein which bind adenovirus. Specifically disclosed are amino acid sequences which corresponds to adenovirus binding domain D1 and the entire extracellular domain of human CAR protein comprising D1 and D2. In other aspects, the disclosure relates to nucleic acid sequences encoding these domains as well as expression vectors which encode the domains and bacterial cells containing such vectors. Also disclosed is an isolated fusion protein comprised of the D1 polypeptide sequence fused to a polypeptide sequence which facilitates folding of D1 into a functional, soluble domain when expressed in bacteria. The functional D1 domain finds application for example in a therapeutic method for treating a patient infected with a virus which binds to D1, and also in a method for identifying an antiviral compound which interferes with viral attachment. Also included is a method for specifically targeting a cell for infection by a virus which binds to D1.

  14. Wide-range thermochromic luminescence of organoboronium complexes.

    PubMed

    Chen, Xiaofeng; Zhang, Xuepeng; Zhang, Guoqing

    2015-01-01

    Alkyl-substituted tetra-coordinate organoboronium bisdiketone complexes exhibit dramatic luminescence thermochromism in organic solvents. In glass-forming alcohols, these complexes exhibit a reversible aqua blue to orange-red to greenish yellow luminescence emission colour change upon cooling. PMID:25387801

  15. Luminescent Processes Elucidated by Simple Experiments on ZnS.

    ERIC Educational Resources Information Center

    Schwankner, R.; And Others

    1981-01-01

    Describes some impurity-related optical properties of semiconductors, with special emphasis on the luminescence of zinc sulfide (ZnS). Presents and interprets five experiments using a ZnS screen, ultraviolet lamp, transparent Dewar liquid nitrogen, and a helium/neon gas base. Includes application of luminescence measurements to archaeology. (SK)

  16. Doped luminescent materials and particle discrimination using same

    DOEpatents

    Doty, F. Patrick; Allendorf, Mark D; Feng, Patrick L

    2014-10-07

    Doped luminescent materials are provided for converting excited triplet states to radiative hybrid states. The doped materials may be used to conduct pulse shape discrimination (PSD) using luminescence generated by harvested excited triplet states. The doped materials may also be used to detect particles using spectral shape discrimination (SSD).

  17. Method for altering the luminescence of a semiconductor

    DOEpatents

    Barbour, J. Charles; Dimos, Duane B.

    1999-01-01

    A method is described for altering the luminescence of a light emitting semiconductor (LES) device. In particular, a method is described whereby a silicon LES device can be selectively irradiated with a radiation source effective for altering the intensity of luminescence of the irradiated region.

  18. Electroluminescent apparatus having a structured luminescence conversion layer

    DOEpatents

    Krummacher, Benjamin Claus

    2008-09-02

    An apparatus such as a light source is disclosed which has an OLED device and a structured luminescence conversion layer disposed on the substrate or transparent electrode of said OLED device and on the exterior of said OLED device. The structured luminescence conversion layer contains color-changing and non-color-changing regions arranged in a particular pattern.

  19. Method for altering the luminescence of a semiconductor

    DOEpatents

    Barbour, J.C.; Dimos, D.B.

    1999-01-12

    A method is described for altering the luminescence of a light emitting semiconductor (LES) device. In particular, a method is described whereby a silicon LES device can be selectively irradiated with a radiation source effective for altering the intensity of luminescence of the irradiated region. 4 figs.

  20. Luminescence of perovskite-like niobates and tantalates

    SciTech Connect

    Blasse, G. . Fysisch Lab.); Brixner, L.H. and Co., Wilmington, DE . Central Research and Development Dept.)

    1989-03-01

    The luminescence of perovskite-like niobates and tantalates is compared and discussed in connection with that of titanates. The luminescence properties are strongly related to each other. Electronic delocalization in corner-sharing octahedra is shown to play an important role.

  1. Ultrashort pulse laser microsurgery system with plasma luminescence feedback control

    SciTech Connect

    Kim, B.M.; Feit, M.D.; Rubenchik, A.M.; Gold, D.M.; Darrow, C.B.; Da Silva, L.B.

    1997-11-10

    Plasma luminescence spectroscopy was used for precise ablation of bone tissue during ultrashort pulse laser (USPL) micro-spinal surgery. Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so that only bone tissue can be selectively ablated while preserving the spinal cord.

  2. [Antithrombotic recombinant antibodies].

    PubMed

    Muzard, Julien; Loyau, Stéphane; Ajzenberg, Nadine; Billiald, Philippe; Jandrot-Perrus, Martine

    2006-01-01

    Coronary syndromes, stroke and other ischaemic arterial diseases are the leading cause of death in the world and will probably remain it at least until 2020. Cardiovascular diseases kill 17 million people each year with an expected increase to 20 million in 2020 and 24 million in 2030. The global impact of recurrence and death during the 6 months following an acute coronary syndrome remains at 8-15% in the present state of medical practice. Acute ischaemic syndromes have a common aetiology that is the formation of a platelet-rich clot at the site of severe coronary stenosis and of eroded atherosclerotic plaques. Therapy consists of medical treatments associating thrombolysis, antiplatelet drugs, and the re-opening of the coronary artery by angioplasty. But these treatments do not prevent morbidity and mortality reaching 15% at 6 months. Finally the treatment of stroke is very limited. There is thus a real clinical need to improve existing treatments and to discover new molecules. Platelet activation is a critical step in ischaemic cardiovascular diseases. This is the reason why antiplatelet drugs are most often prescribed in these cases. Currently, only one recombinant antithrombotic antibody is used in therapy. This is a chimeric Fab, c7E3 or abciximab, which inhibits the final phase of platelet aggregation. Abciximab is prescribed in acute coronary syndromes treated by angioplasty. However, treatment by abciximab can induce severe complications, principally, hemorrages and thrombopenia. Other platelet receptors involved in the earlier steps of platelet activation, such as the phases of contact with and of activation by the subendothelium matrix, have been identified as potential targets for the development of antithrombotic antibodies and are described in this revue. PMID:17652972

  3. Genetic recombination in Streptomyces griseus.

    PubMed Central

    Parag, Y

    1978-01-01

    Low-frequency (10(-6)) genetic recombination was observed in a cephamycin-producing strain of Streptomyces griseus. The recombinants were predominantly heteroclones. Heteroclone analysis was performed involving four heteroclones of one cross. In 100 mutants correlation was found between the type of auxotrophy and the level of antibiotic activity. A cross of this strain with a streptomycin-producing strain of S. griesus is described. PMID:415037

  4. [Vaccine application of recombinant herpesviruses].

    PubMed

    Yokoyama, N; Xuan, X; Mikami, T

    2000-04-01

    Recently, genetic engineering using recombinant DNA techniques has been applied to design new viral vaccines in order to reduce some problems which the present viral vaccines have. Up to now, many viruses have been investigated for development of recombinant attenuated vaccines or live viral vectors for delivery of foreign genes coding immunogenic antigens. In this article, we introduced the new vaccine strategy using genetically engineered herpesviruses. PMID:10774221

  5. Combinatorics in Recombinational Population Genomics

    NASA Astrophysics Data System (ADS)

    Parida, Laxmi

    The work that I will discuss is motivated by the need for understanding, and processing, the manifestations of recombination events in chromosome sequences. In this talk, we focus on two related problems. First, we explore the very general problem of reconstructability of pedigree history. How plausible is it to unravel the history of a complete unit (chromosome) of inheritance? The second problem deals with reconstructing the recombinational history of a collection of chromosomes.

  6. Luminescence quenching of conductive Si nanocrystals via “Linkage emission”: Hopping-like propagation of infrared-excited Auger electrons

    SciTech Connect

    Ishii, Masashi; Crowe, Iain F.; Halsall, Matthew P.; Hamilton, Bruce; Knights, Andrew P.; Gwilliam, Russell M.

    2014-08-14

    Phosphorus (P) is an n-type dopant for conductive silicon nanocrystals (Si-nc's), the electrical activation of which may be monitored through a non-radiative Auger recombination process that quenches the Si-nc luminescence. We investigated this quenching mechanism through electrical measurements of Si-nc's. Infrared-excited Auger electron emission as the non-radiative process was directly probed and the dynamics of the process are determined from a frequency response analysis. To explain the dynamics, we propose a model in which Auger electrons with a low kinetic energy establish a local inter-nanocrystal conductance and the repetition of this local conductance results in a constant photocurrent (“linkage emission”). This emission becomes significant by electron filling in the Si-nc's owing to the electrical activation of P, which is consistent with observed luminescence quenching behavior. We found that the IR photo-excited emission is distinct from the thermally induced hopping conduction and show that confined, rather than trapped, charges are the source of the Auger electrons. Thus, the process consumes both confined charges and the recombination energy for Auger emission, which explains the luminescence quenching mechanism of Si-nc:P.

  7. Bacterial challenges in food

    PubMed Central

    Collee, J. G.

    1974-01-01

    Qualitative and quantitative aspects of bacterial challenges that might be encountered in food are discussed with reference to recognized and relatively unrecognized hazards. Mechanisms of pathogenicity are reviewed and the populations at risk are noted. The bacterial content of food as it is served at table merits more study. The challenge of prevention by education is discussed. Indirect bacterial challenges in our food are considered. The real challenge of diagnosis depends upon an awareness of a complex range of conditions; the importance of effective communication with efficient laboratory and epidemiological services is stressed. There is an increasing need for care in the preparation and distribution of food. PMID:4467860

  8. Radiative recombination kinetics in electroluminescent spin cast pristine α-4T

    NASA Astrophysics Data System (ADS)

    Ben Hamed, Zied; Kouki, Fayçal; Bouchriha, Habib; Mejatty, Mohamed

    2016-09-01

    Many experimental studies have established the substantial impact of the sound structure of the organic thin films on optoelectronic device performances. This study is a collection of experimental and theoretical investigation of the radiative recombination kinetics in an organic light emitting diode based on spin cast α-4T. The structural properties of the organic thin films (α-4T) deposited by the spin coating technique are discussed. The electrical characterization of the diode-like samples (ITO/α-4T/Al) have revealed a very low effective mobility of charge carriers in the spin cast α-4Tand the radiative recombination current was extracted. The luminescence-current characterization of the diode-like samples (ITO/α-4T/Al) was investigated and modeled.

  9. Delayed recombination and cosmic parameters

    NASA Astrophysics Data System (ADS)

    Galli, Silvia; Bean, Rachel; Melchiorri, Alessandro; Silk, Joseph

    2008-09-01

    Current cosmological constraints from cosmic microwave background anisotropies are typically derived assuming a standard recombination scheme, however additional resonance and ionizing radiation sources can delay recombination, altering the cosmic ionization history and the cosmological inferences drawn from the cosmic microwave background data. We show that for recent observations of the cosmic microwave background anisotropy, from the Wilkinson microwave anisotropy probe satellite mission (WMAP) 5-year survey and from the arcminute cosmology bolometer array receiver experiment, additional resonance radiation is nearly degenerate with variations in the spectral index, ns, and has a marked effect on uncertainties in constraints on the Hubble constant, age of the universe, curvature and the upper bound on the neutrino mass. When a modified recombination scheme is considered, the redshift of recombination is constrained to z*=1078±11, with uncertainties in the measurement weaker by 1 order of magnitude than those obtained under the assumption of standard recombination while constraints on the shift parameter are shifted by 1σ to R=1.734±0.028. From the WMAP5 data we obtain the following constraints on the resonance and ionization sources parameters: γα<0.39 and γi<0.058 at 95% c.l.. Although delayed recombination limits the precision of parameter estimation from the WMAP satellite, we demonstrate that this should not be the case for future, smaller angular scales measurements, such as those by the Planck satellite mission.

  10. Ethanol production by recombinant hosts

    DOEpatents

    Ingram, Lonnie O.; Beall, David S.; Burchhardt, Gerhard F. H.; Guimaraes, Walter V.; Ohta, Kazuyoshi; Wood, Brent E.; Shanmugam, Keelnatham T.

    1995-01-01

    Novel plasmids comprising genes which code for the alcohol dehydrogenase and pyruvate decarboxylase are described. Also described are recombinant hosts which have been transformed with genes coding for alcohol dehydrogenase and pyruvate. By virtue of their transformation with these genes, the recombinant hosts are capable of producing significant amounts of ethanol as a fermentation product. Also disclosed are methods for increasing the growth of recombinant hosts and methods for reducing the accumulation of undesirable metabolic products in the growth medium of these hosts. Also disclosed are recombinant host capable of producing significant amounts of ethanol as a fermentation product of oligosaccharides and plasmids comprising genes encoding polysaccharases, in addition to the genes described above which code for the alcohol dehydrogenase and pyruvate decarboxylase. Further, methods are described for producing ethanol from oligomeric feedstock using the recombinant hosts described above. Also provided is a method for enhancing the production of functional proteins in a recombinant host comprising overexpressing an adhB gene in the host. Further provided are process designs for fermenting oligosaccharide-containing biomass to ethanol.

  11. Ethanol production by recombinant hosts

    DOEpatents

    Fowler, David E.; Horton, Philip G.; Ben-Bassat, Arie

    1996-01-01

    Novel plasmids comprising genes which code for the alcohol dehydrogenase and pyruvate decarboxylase are described. Also described are recombinant hosts which have been transformed with genes coding for alcohol dehydrogenase and pyruvate. By virtue of their transformation with these genes, the recombinant hosts are capable of producing significant amounts of ethanol as a fermentation product. Also disclosed are methods for increasing the growth of recombinant hosts and methods for reducing the accumulation of undesirable metabolic products in the growth medium of these hosts. Also disclosed are recombinant host capable of producing significant amounts of ethanol as a fermentation product of oligosaccharides and plasmids comprising genes encoding polysaccharases, in addition to the genes described above which code for the alcohol dehydrogenase and pyruvate decarboxylase. Further, methods are described for producing ethanol from oligomeric feedstock using the recombinant hosts described above. Also provided is a method for enhancing the production of functional proteins in a recombinant host comprising overexpressing an adhB gene in the host. Further provided are process designs for fermenting oligosaccharide-containing biomass to ethanol.

  12. Delayed recombination and cosmic parameters

    SciTech Connect

    Galli, Silvia; Melchiorri, Alessandro; Bean, Rachel; Silk, Joseph

    2008-09-15

    Current cosmological constraints from cosmic microwave background anisotropies are typically derived assuming a standard recombination scheme, however additional resonance and ionizing radiation sources can delay recombination, altering the cosmic ionization history and the cosmological inferences drawn from the cosmic microwave background data. We show that for recent observations of the cosmic microwave background anisotropy, from the Wilkinson microwave anisotropy probe satellite mission (WMAP) 5-year survey and from the arcminute cosmology bolometer array receiver experiment, additional resonance radiation is nearly degenerate with variations in the spectral index, n{sub s}, and has a marked effect on uncertainties in constraints on the Hubble constant, age of the universe, curvature and the upper bound on the neutrino mass. When a modified recombination scheme is considered, the redshift of recombination is constrained to z{sub *}=1078{+-}11, with uncertainties in the measurement weaker by 1 order of magnitude than those obtained under the assumption of standard recombination while constraints on the shift parameter are shifted by 1{sigma} to R=1.734{+-}0.028. From the WMAP5 data we obtain the following constraints on the resonance and ionization sources parameters: {epsilon}{sub {alpha}}<0.39 and {epsilon}{sub i}<0.058 at 95% c.l.. Although delayed recombination limits the precision of parameter estimation from the WMAP satellite, we demonstrate that this should not be the case for future, smaller angular scales measurements, such as those by the Planck satellite mission.

  13. Photostimulated luminescence properties of Eu2+ -doped barium aluminate phosphor.

    PubMed

    He, Quanlong; Qiu, Guangyu; Xu, Xuhui; Qiu, Jianbei; Yu, Xue

    2015-03-01

    An intense green photostimulated luminescence in BaAl2 O4 :Eu(2+) phosphor was prepared. The thermoluminescence results indicate that there are at least three types of traps (T1 , T2 , T3 ) with different trap depths in BaAl2 O4 :Eu(2+) phosphor according to the bands located at 327, 361 and 555 K, respectively, which are closely associated with the phosphor's long persistent luminescence and photostimulated luminescence properties. In addition, as a novel optical read-out form, a photostimulated persistent luminescence signal can be repeatedly obtained in BaAl2 O4 :Eu(2+) phosphor. This shows that re-trapping of the electron released from a deep trap plays an important role in photostimulated persistent luminescence. PMID:24954192

  14. Magnetic-luminescent spherical particles synthesized by ultrasonic spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Michel, Norma L.; Flores, Dora L.; Hirata, Gustavo A.

    2015-07-01

    The combination of magnetic and luminescent properties in a single particle system, opens-up a wide range of potential applications in biotechnology and biomedicine. In this work, we performed the synthesis of magnetic-luminescent Gd2O3:Eu3+@Fe2O3 particles by ultrasonic spray pyrolysis performed in a tubular furnace. In order to achieve the composite formation, commercial superparamagnetic Fe3O4 nanoparticles were coated with a luminescent Eu3+-doped Gd2O3 shell in a low-cost one-step process. The spray pyrolysis method yields deagglomerated spherical shape magneto/luminescent particles. The photoluminescence spectra under UV excitation (λExc = 265 nm) of the magnetic Gd2O3:Eu3+@Fe2O3 compound showed the characteristic red emission of Eu3+ (λEm = 612 nm). This magneto/luminescent system will find applications in biomedicine and biotechnology.

  15. Single layer multi-color luminescent display

    NASA Technical Reports Server (NTRS)

    Robertson, James B. (Inventor)

    1991-01-01

    The invention is a multi-color luminescent display comprising an insulator substrate and a single layer of host material which may be a phosphor deposited thereon that hosts one or more differential impurities, therein forming a pattern of selected and distinctly colored phosphors such as blue, green, and red phosphors in a single layer of host material. Transparent electrical conductor means may be provided for subjecting selected portions of the pattern of colored phosphors to an electric field thereby forming a multi-color, single layer electroluminescent display.

  16. Development of novel edible luminescent nanoparticle sensors

    NASA Astrophysics Data System (ADS)

    Jalalian, Sanaz

    This project has developed a novel class of edible hydrocolloid food nanosensors which are doped with luminescent chromophores and investigated whether they can be used to provide information about the local food matrix - temperature, oxygen concentration, and the presence of food-borne pathogens. The luminescence properties of the probes such as phosphorescence and fluorescence provide the sensor sensitivity to the food properties. Hydrocolloid nanoparticles were made from gelatin and starch with diameters ranging from 50 to ˜200 nm and labeled with food grade luminescent probes. The chromophore was covalently and non-covalently attached to the nanoparticle and the photophysical properties of the probe in the food system were studied. Temperature sensors were developed by using the phosphorescence sensitivity of a chromophore to temperature. Experiments with two different probes, namely erythrosine B labeled gelatin nanoparticles and phloxine B labeled gelatin nanoparticles have demonstrated that both probes can be effectively used as temperature sensors in liquid and solid food. The Van't Hoff plots of ln(IDF/IP) versus 1/T vary monotonically over a relatively wide temperature range and thus provide a basis for estimating temperature from measurements of phosphorescence and delayed fluorescence. The tests indicated that the presence of some ingredients such as tannin and anthocyanins in the composition of the food may prohibit the use of gelatin nanoparticle probes due to precipitation of gelatin nanoparticles. The luminescence quenching of the probe by oxygen was used to develop a nanoparticle sensor for oxygen. The results of experiments on liquid and solid food samples indicate that erythrosine B labeled gelatin nanoparticles can be used as a probe to detect the presence or absence of oxygen in some liquid foods. Precise control of oxygen concentration in solutions will pose a challenge as has been observed in this study. The probe did not work as an

  17. Luminescence and photoconductivity in magnesium aluminum spinel

    NASA Astrophysics Data System (ADS)

    Bandyopadhyay, Pradip K.; Summers, G. P.

    1985-02-01

    Ultraviolet-light excitation of thermochemically reduced MgAl2O4 single crystals below room temperature produces a luminescence band with a peak at 2.69 eV. The excitation spectrum of the 2.69-eV band coincides with the broad F-center absorption band at 5.30 eV. The 2.69-eV band is also emitted in uv-stimulated glow peaks which occur at 95 and 265 K. A photoconductivity maximum is observed at 5.39 eV at temperatures above 160 K, but the band is readily bleached by uv light.

  18. Image registration for luminescent paint applications

    NASA Technical Reports Server (NTRS)

    Bell, James H.; Mclachlan, Blair G.

    1993-01-01

    The use of pressure sensitive luminescent paints is a viable technique for the measurement of surface pressure on wind tunnel models. This technique requires data reduction of images obtained under known as well as test conditions and spatial transformation of the images. A general transform which registers images to subpixel accuracy is presented and the general characteristics of transforms for image registration and their derivation are discussed. Image resection and its applications are described. The mapping of pressure data to the three dimensional model surface for small wind tunnel models to a spatial accuracy of 0.5 percent of the model length is demonstrated.

  19. Polyethylene terephthalate thin films; a luminescence study

    NASA Astrophysics Data System (ADS)

    Carmona-Téllez, S.; Alarcón-Flores, G.; Meza-Rocha, A.; Zaleta-Alejandre, E.; Aguilar-Futis, M.; Murrieta S, H.; Falcony, C.

    2015-04-01

    Polyethylene Terephthalate (PET) films doped with Rare Earths (RE3+) have been deposited on glass by spray pyrolysis technique at 240 °C, using recycled PET and (RE3+) chlorides as precursors. Cerium, terbium, dysprosium and europium were used as dopants materials, these dopants normally produce luminescent emissions at 450, 545, 573 and 612 nm respectively; the doped films also have light emissions at blue, green, yellow and red respectively. All RE3+ characteristic emissions were observed at naked eyes. Every deposited films show a high transmission in the visible range (close 80% T), films surfaces are pretty soft and homogeneous. Films thickness is around 3 μm.

  20. Optical Receiver Based On Luminescent Light Trapping

    NASA Technical Reports Server (NTRS)

    Perry, Joseph W.; Cole, Terry; Zewail, Ahmed H.

    1991-01-01

    Experiment demonstrates feasibility of optical-communication receiver based on luminescent light trapping. Light-gathering element plate of transparent material impregnated with laser dye. Light from distant laser transmitter falls on plate and absorbed by dye molecules, which become excited and reradiate. Reradiated light confined within plate by total internal reflection as it propagates toward edge of plate. Light arriving at edge escapes from plate and detected by small, high-speed, high-gain photomultiplier tubes or other photosensitive devices. Simple, inexpensive, and accepts light from almost any angle. Receiver of this configuration supports reception of data at rate of 13 MHz and higher.

  1. Circularly Polarized Luminescence from Simple Organic Molecules.

    PubMed

    Sánchez-Carnerero, Esther M; Agarrabeitia, Antonia R; Moreno, Florencio; Maroto, Beatriz L; Muller, Gilles; Ortiz, María J; de la Moya, Santiago

    2015-09-21

    This article aims to show the identity of "circularly polarized luminescent active simple organic molecules" as a new concept in organic chemistry due to the potential interest of these molecules, as availed by the exponentially growing number of research articles related to them. In particular, it describes and highlights the interest and difficulty in developing chiral simple (small and non-aggregated) organic molecules able to emit left- or right-circularly polarized light efficiently, the efforts realized up to now to reach this challenging objective, and the most significant milestones achieved to date. General guidelines for the preparation of these interesting molecules are also presented. PMID:26136234

  2. Laser-induced luminescence in hybrid nanofilms

    NASA Astrophysics Data System (ADS)

    Saifutyarov, R. R.; Khomyakov, A. V.; Akkuzina, A. A.; Avetisov, R. I.; Petrova, O. B.; Avetisov, I. Kh.; Kravchenko, S. V.

    2015-07-01

    Tris(8-hydroxyquinoline) boron (Bq3) was synthesized by a high-temperature exchange reaction. Bq3 powders containing various polymorphous modifications were synthesized, and their photoluminescent characteristics were analyzed. Films of Alq3/B2O3/Al hybrid materials (HMs) were deposited on glass substrates by vacuum thermal evaporation. It is shown that local heating by a diode laser (785 nm) with an intensity of 150 W/cm2 for one second causes irreversible transformation in the HM film structure. The chromaticity coordinates of the photoluminescence of laser-irradiated regions considerably differ from those of the initial HM film luminescence.

  3. Pervasive recombination and sympatric genome diversification driven by frequency-dependent selection in Borrelia burgdorferi, the Lyme disease bacterium.

    PubMed

    Haven, James; Vargas, Levy C; Mongodin, Emmanuel F; Xue, Vincent; Hernandez, Yozen; Pagan, Pedro; Fraser-Liggett, Claire M; Schutzer, Steven E; Luft, Benjamin J; Casjens, Sherwood R; Qiu, Wei-Gang

    2011-11-01

    How genomic diversity within bacterial populations originates and is maintained in the presence of frequent recombination is a central problem in understanding bacterial evolution. Natural populations of Borrelia burgdorferi, the bacterial agent of Lyme disease, consist of diverse genomic groups co-infecting single individual vertebrate hosts and tick vectors. To understand mechanisms of sympatric genome differentiation in B. burgdorferi, we sequenced and compared 23 genomes representing major genomic groups in North America and Europe. Linkage analysis of >13,500 single-nucleotide polymorphisms revealed pervasive horizontal DNA exchanges. Although three times more frequent than point mutation, recombination is localized and weakly affects genome-wide linkage disequilibrium. We show by computer simulations that, while enhancing population fitness, recombination constrains neutral and adaptive divergence among sympatric genomes through periodic selective sweeps. In contrast, simulations of frequency-dependent selection with recombination produced the observed pattern of a large number of sympatric genomic groups associated with major sequence variations at the selected locus. We conclude that negative frequency-dependent selection targeting a small number of surface-antigen loci (ospC in particular) sufficiently explains the maintenance of sympatric genome diversity in B. burgdorferi without adaptive divergence. We suggest that pervasive recombination makes it less likely for local B. burgdorferi genomic groups to achieve host specialization. B. burgdorferi genomic groups in the northeastern United States are thus best viewed as constituting a single bacterial species, whose generalist nature is a key to its rapid spread and human virulence. PMID:21890743

  4. Immunogenic response to a recombinant pseudorabies virus carrying bp26 gene of Brucella melitensis in mice.

    PubMed

    Yao, Lan; Wu, Chang-Xian; Zheng, Ke; Xu, Xian-Jin; Zhang, Hui; Chen, Chuang-Fu; Liu, Zheng-Fei

    2015-06-01

    Brucellae are facultative intracellular bacterial pathogens of a zoonotic disease called brucellosis. Live attenuated vaccines are utilized for prophylaxis of brucellosis; however, they retain residual virulence to human and/or animals, as well as interfere with diagnosis. In this study, recombinant virus PRV ΔTK/ΔgE/bp26 was screened and purified. One-step growth curve assay showed that the titer of recombinant virus was comparable to the parent strain. Mice experiments showed the recombinant virus elicited high titer of humoral antibodies against Brucella detected by enzyme-linked immunosorbent assay and against PRV by serum neutralization test. The recombinant virus induced high level of Brucella-specific lymphocyte proliferation response and production of interferon gamma. Collectively, these data suggest that the bivalent virus was capable of inducing both humoral and cellular immunity, and had the potential to be a vaccine candidate to prevent Brucella and/or pseudorabies virus infections. PMID:25890577

  5. Bacterial Wound Culture

    MedlinePlus

    ... Home Visit Global Sites Search Help? Bacterial Wound Culture Share this page: Was this page helpful? Also known as: Aerobic Wound Culture; Anaerobic Wound Culture Formal name: Culture, wound Related ...

  6. Bacterial Nail Infection (Paronychia)

    MedlinePlus

    ... in people who work in the health care industry. Chronic paronychia is most common in adult women and those who work in places where their hands are kept moist, such as food handlers. Signs and Symptoms Bacterial nail infection most ...

  7. Small bowel bacterial overgrowth

    MedlinePlus

    Overgrowth - intestinal bacteria; Bacterial overgrowth - intestine ... Unlike the large intestine, the small intestine does not have a high number of bacteria. When there are too many bacteria in the ...

  8. Bacterial surface adaptation

    NASA Astrophysics Data System (ADS)

    Utada, Andrew

    2014-03-01

    Biofilms are structured multi-cellular communities that are fundamental to the biology and ecology of bacteria. Parasitic bacterial biofilms can cause lethal infections and biofouling, but commensal bacterial biofilms, such as those found in the gut, can break down otherwise indigestible plant polysaccharides and allow us to enjoy vegetables. The first step in biofilm formation, adaptation to life on a surface, requires a working knowledge of low Reynolds number fluid physics, and the coordination of biochemical signaling, polysaccharide production, and molecular motility motors. These crucial early stages of biofilm formation are at present poorly understood. By adapting methods from soft matter physics, we dissect bacterial social behavior at the single cell level for several prototypical bacterial species, including Pseudomonas aeruginosa and Vibrio cholerae.

  9. Probing Polytopic Membrane Protein-Substrate Interactions by Luminescence Resonance Energy Transfer.

    PubMed

    Musial-Siwek, Monika; Jaffee, Marcie B; Imperiali, Barbara

    2016-03-23

    Integral membrane proteins play essential roles in all living systems; however, major technical hurdles challenge analyses of this class of proteins. Biophysical approaches that provide structural information to complement and leverage experimentally determined and computationally predicted structures are urgently needed. Herein we present the application of luminescence resonance energy transfer (LRET) for investigating the interactions of the polytopic membrane-bound oligosaccharyl transferases (OTases) with partner substrates. Monomeric OTases, such as the PglBs from Campylobacter jejuni and Campylobacter lari, catalyze transfer of glycans from membrane-associated undecaprenol diphosphate-linked substrates to proteins in the bacterial periplasm. LRET-based distance measurements are enabled by the inclusion of an encoded N-terminal lanthanide-binding tag (LBT), and LRET between the luminescent (LBT)-Tb(3+) donor complex and fluorescently labeled peptide and glycan substrates provides discrete distance measurements across the span of the membrane. LRET-based measurements of detergent-solubilized PglB from C. lari allowed direct comparison with the distances based on the previously reported the C. lari PglB crystal structure, thereby validating the approach in a defined system. Distance measurements between peptide and glycan substrates and the C. jejuni PglB offer new experimental information on substrate binding to the related, but structurally uncharacterized, eukaryotic OTase. PMID:26918528

  10. A Simple Luminescent Adenylate-Cyclase Functional Assay for Evaluation of Bacillus anthracis Edema Factor Activity

    PubMed Central

    Israeli, Ma’ayan; Rotem, Shahar; Elia, Uri; Bar-Haim, Erez; Cohen, Ofer; Chitlaru, Theodor

    2016-01-01

    Edema Factor (EF), the toxic sub-unit of the Bacillus anthracis Edema Toxin (ET) is a calmodulin-dependent adenylate cyclase whose detrimental activity in the infected host results in severe edema. EF is therefore a major virulence factor of B. anthracis. We describe a simple, rapid and reliable functional adenylate-cyclase assay based on inhibition of a luciferase-mediated luminescence reaction. The assay exploits the efficient adenylate cyclase-mediated depletion of adenosine tri-phosphate (ATP), and the strict dependence on ATP of the light-emitting luciferase-catalyzed luciferin-conversion to oxyluciferin, which can be easily visualized. The assay exhibits a robust EF-dose response decrease in luminescence, which may be specifically reverted by anti-EF antibodies. The application of the assay is exemplified in: (a) determining the presence of EF in B. anthracis cultures, or its absence in cultures of EF-defective strains; (b) evaluating the anti-EF humoral response in experimental animals infected/vaccinated with B. anthracis; and (c) rapid discrimination between EF producing and non-producing bacterial colonies. Furthermore, the assay may be amenable with high-throughput screening for EF inhibitory molecules. PMID:27548219

  11. A Simple Luminescent Adenylate-Cyclase Functional Assay for Evaluation of Bacillus anthracis Edema Factor Activity.

    PubMed

    Israeli, Ma'ayan; Rotem, Shahar; Elia, Uri; Bar-Haim, Erez; Cohen, Ofer; Chitlaru, Theodor

    2016-01-01

    Edema Factor (EF), the toxic sub-unit of the Bacillus anthracis Edema Toxin (ET) is a calmodulin-dependent adenylate cyclase whose detrimental activity in the infected host results in severe edema. EF is therefore a major virulence factor of B. anthracis. We describe a simple, rapid and reliable functional adenylate-cyclase assay based on inhibition of a luciferase-mediated luminescence reaction. The assay exploits the efficient adenylate cyclase-mediated depletion of adenosine tri-phosphate (ATP), and the strict dependence on ATP of the light-emitting luciferase-catalyzed luciferin-conversion to oxyluciferin, which can be easily visualized. The assay exhibits a robust EF-dose response decrease in luminescence, which may be specifically reverted by anti-EF antibodies. The application of the assay is exemplified in: (a) determining the presence of EF in B. anthracis cultures, or its absence in cultures of EF-defective strains; (b) evaluating the anti-EF humoral response in experimental animals infected/vaccinated with B. anthracis; and (c) rapid discrimination between EF producing and non-producing bacterial colonies. Furthermore, the assay may be amenable with high-throughput screening for EF inhibitory molecules. PMID:27548219

  12. Deciphering the bacterial glycocode: recent advances in bacterial glycoproteomics

    PubMed Central

    Longwell, Scott A.; Dube, Danielle H.

    2012-01-01

    Bacterial glycoproteins represent an attractive target for new antibacterial treatments, as they are frequently linked to pathogenesis and contain distinctive glycans that are absent in humans. Despite their potential therapeutic importance, many bacterial glycoproteins remain uncharacterized. This review focuses on recent advances in deciphering the bacterial glycocode, including metabolic glycan labeling to discover and characterize bacterial glycoproteins, lectin-based microarrays to monitor bacterial glycoprotein dynamics, crosslinking sugars to assess the roles of bacterial glycoproteins, and harnessing bacterial glycosylation systems for the efficient production of industrially important glycoproteins. PMID:23276734

  13. Bistability and Bacterial Infections

    PubMed Central

    Malka, Roy; Shochat, Eliezer; Rom-Kedar, Vered

    2010-01-01

    Bacterial infections occur when the natural host defenses are overwhelmed by invading bacteria. The main component of the host defense is impaired when neutrophil count or function is too low, putting the host at great risk of developing an acute infection. In people with intact immune systems, neutrophil count increases during bacterial infection. However, there are two important clinical cases in which they remain constant: a) in patients with neutropenic-associated conditions, such as those undergoing chemotherapy at the nadir (the minimum clinically observable neutrophil level); b) in ex vivo examination of the patient's neutrophil bactericidal activity. Here we study bacterial population dynamics under fixed neutrophil levels by mathematical modelling. We show that under reasonable biological assumptions, there are only two possible scenarios: 1) Bacterial behavior is monostable: it always converges to a stable equilibrium of bacterial concentration which only depends, in a gradual manner, on the neutrophil level (and not on the initial bacterial level). We call such a behavior type I dynamics. 2) The bacterial dynamics is bistable for some range of neutrophil levels. We call such a behavior type II dynamics. In the bistable case (type II), one equilibrium corresponds to a healthy state whereas the other corresponds to a fulminant bacterial infection. We demonstrate that published data of in vitro Staphylococcus epidermidis bactericidal experiments are inconsistent with both the type I dynamics and the commonly used linear model and are consistent with type II dynamics. We argue that type II dynamics is a plausible mechanism for the development of a fulminant infection. PMID:20463954

  14. Linearly working low-light-level imaging method for luminescence applications

    NASA Astrophysics Data System (ADS)

    Braeuer, Reinhard; Helma, Hans; Ochs, Rainer

    1994-05-01

    We propose a two-stage linearly working integration method for low light level imaging systems. The influence of integration and background substraction on the signal to noise ratio is discussed in the paper. The introduced linear approach avoids thresholding and creates images with enhanced spatial resolution. After 5 minutes integration time the system reaches a sensitivity of 0.6 Photons/(Pixel X second). The linearity of the system can be checked with a suitable calibration device. We propose an electronic light standard with a pulsed LED, that allows us to cover a wide range of brightness by variation of the pulse frequency. Very low light intensities of luminescence can be produced in a stable and reproducible manner. The system has powerful software functions for bioluminescence applications like bacterial cloning as well as measurement functions for chemiluminescence applications within the DNA or protein blotting. Utilities for documentation, image printing, and data export to spreadsheet or graphics programs are also provided.

  15. A luminescence endotoxin biosensor prepared by the sol-gel method

    NASA Astrophysics Data System (ADS)

    Hreniak, A.; Maruszewski, K.; Rybka, J.; Gamian, A.; Czyżewski, J.

    2004-07-01

    Silicate thin films with terminal amino groups were prepared via the sol-gel technique and selected biological molecules labeled with luminophores were covalently attached to their surfaces. The obtained thin films with covalently bound Concanavalin-A (Con-A) labeled with fluorescein (FITC) were immersed in a buffer and polarized emission spectra were measured. In the next step, the samples were incubated with a lipopolysaccharide (LPS) isolated from Hafnia alvei PCM 1186 bacterial strain and the emission spectra were collected again. The influence of LPS binding to Con-A on the luminescence depolarization has been proven. The system based on the this effect can be employed as an optical sensor for detection of certain types of bacteria.

  16. New cross-linking quinoline- and quinolone-based luminescent lanthanide probes for sensitive labeling

    NASA Astrophysics Data System (ADS)

    Pillai, Shyamala; Wirpsza, Laura; Kozlov, Maxim; Marras, Salvatore A. E.; Krasnoperov, Lev N.; Mustaev, Arkady

    2012-03-01

    New luminescent lanthanide chelates containing thiol-, amine-, and click-reactive groups in antenna-fluorophore moieties were synthesized. The chelates include diethylenetriaminepentaacetic acid (DTPA) coupled to two types of chromophores: 7-amino-4-trifluoromethyl-2(1H) quinolinone, and 7-amino-4-trifluoromethyl-2-alkoxyquinoline. The synthesized compounds were characterized using NMR, light absorption, steady-state and time-resolved fluorescent spectroscopy. Some of the compounds displayed high brightness with Tb3+, Eu3+, and Dy3+. Obtained reactive lanthanide chelates can be easily attached to biological molecules. The probes demonstrated high performance in molecular beaconbased DNA hybridization assays (sub-pico molar detection limit), in bacterial proteome labeling, and in live cell imaging.

  17. Recombination Drives Vertebrate Genome Contraction

    PubMed Central

    Nam, Kiwoong; Ellegren, Hans

    2012-01-01

    Selective and/or neutral processes may govern variation in DNA content and, ultimately, genome size. The observation in several organisms of a negative correlation between recombination rate and intron size could be compatible with a neutral model in which recombination is mutagenic for length changes. We used whole-genome data on small insertions and deletions within transposable elements from chicken and zebra finch to demonstrate clear links between recombination rate and a number of attributes of reduced DNA content. Recombination rate was negatively correlated with the length of introns, transposable elements, and intergenic spacer and with the rate of short insertions. Importantly, it was positively correlated with gene density, the rate of short deletions, the deletion bias, and the net change in sequence length. All these observations point at a pattern of more condensed genome structure in regions of high recombination. Based on the observed rates of small insertions and deletions and assuming that these rates are representative for the whole genome, we estimate that the genome of the most recent common ancestor of birds and lizards has lost nearly 20% of its DNA content up until the present. Expansion of transposable elements can counteract the effect of deletions in an equilibrium mutation model; however, since the activity of transposable elements has been low in the avian lineage, the deletion bias is likely to have had a significant effect on genome size evolution in dinosaurs and birds, contributing to the maintenance of a small genome. We also demonstrate that most of the observed correlations between recombination rate and genome contraction parameters are seen in the human genome, including for segregating indel polymorphisms. Our data are compatible with a neutral model in which recombination drives vertebrate genome size evolution and gives no direct support for a role of natural selection in this process. PMID:22570634

  18. Recombination processes in ionised plasmas

    NASA Astrophysics Data System (ADS)

    Bastin, Robert

    The observational analysis of astrophysical plasmas relies on accurate calculations of the atomic processes involved. The recombination spectra of singly ionised oxygen (O il) and carbon (C il) present excellent tools for investigating regions such as planetary nebulae and H II regions. In this thesis, detailed treatments of the recombination processes of both O II and C II are presented. Using the R-matrix solution to the close coupling equations, I present the results of accurate photoionisation calculations. Bound state energy levels are determined and oscillator strengths calculated for both species. Recombination coefficients were evalu ated for low n and 1, for C II in LS-coupling, and 0 II in intermediate coupling, taking particular care to treat resonances effectively. Sample photoionisation cross-sections are presented for both species, and compared to previous work. A complete radiative-cascade model is treated for both species, in order to determine line emissivities under nebular conditions at a wide range of temperatures and densities. Collisional effects are treated for C II, along with, for the first time, the effects of high temperature dielectronic recombination, allowing the modelling of regions of much higher electron temperature than previous work. The O II calculations were performed under intermediate coupling for the first time, allowing the effects of non-statistical popula tions of the parent ion fine-structure levels and dielectronic recombination onto bound states within this fine-structure to be taken into account in line emissivities. Detailed comparison with previous theoretical work was made for both species. The application of the C II and 0 n recombination spectra to determining tempera ture and densities from the observed spectra of a number of ionised nebulae is considered. The potential for using the new recombination spectra as diagnostic tools to solve some of the key problems in the study of ionised nebulae is demonstrated.

  19. Recombination at the DNA level. Abstracts

    SciTech Connect

    Not Available

    1984-01-01

    Abstracts of papers in the following areas are presented: (1) chromosome mechanics; (2) yeast systems; (3) mammalian homologous recombination; (4) transposons; (5) Mu; (6) plant transposons/T4 recombination; (7) topoisomerase, resolvase, and gyrase; (8) Escherichia coli general recombination; (9) recA; (10) repair; (11) eucaryotic enzymes; (12) integration and excision of bacteriophage; (13) site-specific recombination; and (14) recombination in vitro. (ACR)

  20. Novel luminescent nanoparticles for DNA detection

    NASA Astrophysics Data System (ADS)

    Dong, Ling; Yang, Zhihua; Zhang, Yi; Zhu, Yanyu; Wang, Lun; Wang, Leyu

    2010-05-01

    Highly luminescent LaF 3:Ce 3+/Tb 3+ nanocrystals were successfully prepared and surface functionalized via Layer-by-Layer technology. These as-prepared nanocrystals are highly resistant to photobleaching and pretty dispersible in aqueous solution. Due to the efficient luminescence quenching of the nanocrystals by nucleic acids, a facile fluorescence quenching method was developed for the detection of trace amount of nucleic acids. Under optimal conditions, the fluorescence intensity was proportional to the DNA concentration over the range of 0.60-25.0 μg mL -1 for calf thymus DNA (ct-DNA) and 0.60-30.0 μg mL -1 for herring sperm DNA (hs-DNA), respectively. The corresponding detection limit is 0.21 μg mL -1 for ct-DNA and 0.31 μg mL -1 for hs-DNA, respectively. The results indicated that the reported method is simple and rapid with wide linear range. Also, the recovery and relative standard deviation of this method are reasonable and satisfactory.

  1. Luminescent Quantum Dots as Ultrasensitive Biological Labels

    NASA Astrophysics Data System (ADS)

    Nie, Shuming

    2000-03-01

    Highly luminescent semiconductor quantum dots have been covalently coupled to biological molecules for use in ultrasensitive biological detection. This new class of luminescent labels is considerably brighter and more resistant againt photobleaching in comparison with organic dyes. Quantum dots labeled with the protein transferrin undergo receptor-mediated endocytosis (RME) in cultured HeLa cells, and those dots that were conjugated to immunomolecules recognize specific antibodies or antigens. In addition, we show that DNA functionalized quantum dots can be used to target specific genes by hybridization. We expect that quantum dot bioconjugates will have a broad range of biological applications, such as ligand-receptor interactions, real-time monitoring of molecular trafficking inside living cells, multicolor fluorescence in-situ hybridization (FISH), high-sensitivity detection in miniaturized devices (e.g., DNA chips), and fluorescent tagging of combinatorial chemical libraries. A potential clinical application is the use of quantum dots for ultrasensitive viral RNA detection, in which as low as 100 copies of hepatitis C and HIV viruses per ml blood should be detected.

  2. Quantitative Characterization of Cerenkov Luminescence Imaging

    NASA Astrophysics Data System (ADS)

    Gill, Ruby

    An optical imaging modality for small animal cancer studies using Cerenkov radiation is currently being developed in the Cherry lab at the University of California, Davis. Cerenkov radiation is a well-known phenomenon, in which optical photons are emitted when a charged particle moves faster than the speed of light in a medium. This emerging modality is referred to as Cerenkov Luminescence Imaging. The significance of this work is that it enables imaging on widely available small animal optical imaging systems of radionuclides being developed for therapeutic applications and positron emitting radiotracers developed for diagnostic purposes. A Monte Carlo based simulation was performed to predict the number of photons expected for a given radionuclide decay. The simulations calculated Cerenkov light intensity produced by radionuclides of interest for nuclear imaging and radionuclide therapy treatments. A quantitative understanding of Cerenkov light levels using parameters that are representative of situations encountered in vivo will help guide future applications and possible clinical implementation of Cerenkov luminescence imaging.

  3. Measuring chronic toxicity using luminescent bacteria

    SciTech Connect

    Huynh, H.; Bulich, A.

    1994-12-31

    Bioassays using luminescent bacteria are routinely used to assess the acute toxicity of environmental samples. Two physiological characteristics of these test organisms, a short division cycle and the inducible luciferase pathway, provide functional attributes for measuring chronic toxicity. Freeze-dried luminescent bacteria, following inoculation into appropriate growth medium, initiate a series of reproductive cycles while inducing a complex series of metabolic pathways resulting in production of bioluminescence. Toxic chemicals or samples which inhibit any aspect of this reproductive cycle or induction of light production are detected in low concentrations. The development of this bioassay is based upon a detailed understanding of the growth requirements and biochemistry of this organism and the genetics of luciferase induction. A defined growth medium was developed which supports the necessary cell growth and luciferase induction, yet which does not mask the presence of toxic substances. To perform the assay, the test organisms are inoculated into a series of cuvettes containing growth medium and dilutions of the sample. After 18 hrs incubation at 27 C, control cuvettes show high light levels while sample dilutions containing toxic materials show decreasing light levels. Details of the test protocol and reproducibility are presented. Sensitivity data from this chronic toxicity test are summarized and compared with the Microtox{reg_sign} acute test and the Ceriodaphnia dubia chronic toxicity test method. This test method is about 20 times more sensitive than Microtox and exhibits sensitivity similar to C. dubia for tested metals and organic compounds.

  4. Microscopic x-ray luminescence computed tomography

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Zhu, Dianwen; Zhang, Kun; Li, Changqing

    2015-03-01

    X-ray luminescence computed tomography (XLCT) was emerged as a new hybrid imaging modality, in which the x-rays are used to excite phosphors emitting optical photons to be measured for imaging. In this paper, we reported a microscopic x-ray luminescence computed tomography (microXLCT) with a spatial resolution up to hundreds of micrometers for deep targets. We use a superfine x-ray pencil beam to scan the phosphor targets. The superfine x-ray pencil beam is generated by a small collimator mounted in front of a powerful x-ray tube (93212, Oxford Instrument). A CT detector is used to image the x-ray beam. We have generated an x-ray beam with a diameter of 192 micrometers with a collimator of 100 micrometers in diameter. The emitted optical photons on the top surface of phantom are reflected by a mirror and acquired by an electron multiplier charge-coupled device (EMCCD) camera (C9100-13, Hamamatsu Photonics). The microXLCT imaging system is built inside an x-ray shielding and light tight cabinet. The EMCCD camera is placed in a lead box. All the imaging components are controlled by a VC++ program. The optical photon propagation is modeled with the diffusion equation solved by the finite element method. We have applied different regularization methods including L2 and L1 in the microXLCT reconstruction algorithms. Numerical simulations and phantom experiments are used to validate the microXLCT imaging system.

  5. Synchronized cycles of bacterial lysis for in vivo delivery.

    PubMed

    Din, M Omar; Danino, Tal; Prindle, Arthur; Skalak, Matt; Selimkhanov, Jangir; Allen, Kaitlin; Julio, Ellixis; Atolia, Eta; Tsimring, Lev S; Bhatia, Sangeeta N; Hasty, Jeff

    2016-08-01

    The widespread view of bacteria as strictly pathogenic has given way to an appreciation of the prevalence of some beneficial microbes within the human body. It is perhaps inevitable that some bacteria would evolve to preferentially grow in environments that harbor disease and thus provide a natural platform for the development of engineered therapies. Such therapies could benefit from bacteria that are programmed to limit bacterial growth while continually producing and releasing cytotoxic agents in situ. Here we engineer a clinically relevant bacterium to lyse synchronously ata threshold population density and to release genetically encoded cargo. Following quorum lysis, a small number of surviving bacteria reseed the growing population, thus leading to pulsatile delivery cycles. We used microfluidic devices to characterize the engineered lysis strain and we demonstrate its potential as a drug delivery platform via co-culture with human cancer cells in vitro. Asa proof of principle, we tracked the bacterial population dynamics in ectopic syngeneic colorectal tumours in mice via a luminescent reporter. The lysis strain exhibits pulsatile population dynamics in vivo, with mean bacterial luminescence that remained two orders of magnitude lower than an unmodified strain. Finally, guided by previous findings that certain bacteria can enhance the efficacy of standard therapies, we orally administered the lysis strain alone or in combination with a clinical chemotherapeutic to a syngeneic mouse transplantation model of hepatic colorectal metastases. We found that the combination of both circuit-engineered bacteria and chemotherapy leads to a notable reduction of tumour activity along with a marked survival benefit over either therapy alone.Our approach establishes a methodology for leveraging the tools of synthetic biology to exploit the natural propensity for certain bacteria to colonize disease sites. PMID:27437587

  6. Construction of an infectious clone of canine herpesvirus genome as a bacterial artificial chromosome.

    PubMed

    Arii, Jun; Hushur, Orkash; Kato, Kentaro; Kawaguchi, Yasushi; Tohya, Yukinobu; Akashi, Hiroomi

    2006-04-01

    Canine herpesvirus (CHV) is an attractive candidate not only for use as a recombinant vaccine to protect dogs from a variety of canine pathogens but also as a viral vector for gene therapy in domestic animals. However, developments in this area have been impeded by the complicated techniques used for eukaryotic homologous recombination. To overcome these problems, we used bacterial artificial chromosomes (BACs) to generate infectious BACs. Our findings may be summarized as follows: (i) the CHV genome (pCHV/BAC), in which a BAC flanked by loxP sites was inserted into the thymidine kinase gene, was maintained in Escherichia coli; (ii) transfection of pCHV/BAC into A-72 cells resulted in the production of infectious virus; (iii) the BAC vector sequence was almost perfectly excisable from the genome of the reconstituted virus CHV/BAC by co-infection with CHV/BAC and a recombinant adenovirus that expressed the Cre recombinase; and (iv) a recombinant virus in which the glycoprotein C gene was deleted was generated by lambda recombination followed by Flp recombination, which resulted in a reduction in viral titer compared with that of the wild-type virus. The infectious clone pCHV/BAC is useful for the modification of the CHV genome using bacterial genetics, and CHV/BAC should have multiple applications in the rapid generation of genetically engineered CHV recombinants and the development of CHV vectors for vaccination and gene therapy in domestic animals. PMID:16515874

  7. Transformation of valence states and luminescence of chromium ions in the YAG:Cr, Mg and GGG:Cr, Mg single crystalline films

    NASA Astrophysics Data System (ADS)

    Zakharko, Ya. M.; Luchechko, A. P.; Syvorotka, I. M.; Syvorotka, I. I.; Ubizskii, S. B.; Melnyk, S. S.

    2005-01-01

    Peculiarities of absorption spectra and recombination luminescence of Y3Al5O12 (YAG) and Cd3Ga5O12 (GGG) single crystalline films co-doped with chromium and magnesium have been studied. The change of impurities concentration and annealing of samples in the reducing atmosphere have an influence on absorption in the visible and UV range. Using the results on absorption coefficient measurements in the band of 480 nm and in the absorption bands of Cr3+ ions, it was determined, that near 50% of the chromium ions located in octahedral sites are in the Cr4+ state in films with high chromium concentration. The investigation of thermostimulated luminescence confirms the existence of Cr2+ trap centres in the irradiated films caused by the magnesium dopant.

  8. DNA secondary structures are associated with recombination in major Plasmodium falciparum variable surface antigen gene families

    PubMed Central

    Sander, Adam F.; Lavstsen, Thomas; Rask, Thomas S.; Lisby, Michael; Salanti, Ali; Fordyce, Sarah L.; Jespersen, Jakob S.; Carter, Richard; Deitsch, Kirk W.; Theander, Thor G.; Pedersen, Anders Gorm; Arnot, David E.

    2014-01-01

    Many bacterial, viral and parasitic pathogens undergo antigenic variation to counter host immune defense mechanisms. In Plasmodium falciparum, the most lethal of human malaria parasites, switching of var gene expression results in alternating expression of the adhesion proteins of the Plasmodium falciparum-erythrocyte membrane protein 1 class on the infected erythrocyte surface. Recombination clearly generates var diversity, but the nature and control of the genetic exchanges involved remain unclear. By experimental and bioinformatic identification of recombination events and genome-wide recombination hotspots in var genes, we show that during the parasite’s sexual stages, ectopic recombination between isogenous var paralogs occurs near low folding free energy DNA 50-mers and that these sequences are heavily concentrated at the boundaries of regions encoding individual Plasmodium falciparum-erythrocyte membrane protein 1 structural domains. The recombinogenic potential of these 50-mers is not parasite-specific because these sequences also induce recombination when transferred to the yeast Saccharomyces cerevisiae. Genetic cross data suggest that DNA secondary structures (DSS) act as inducers of recombination during DNA replication in P. falciparum sexual stages, and that these DSS-regulated genetic exchanges generate functional and diverse P. falciparum adhesion antigens. DSS-induced recombination may represent a common mechanism for optimizing the evolvability of virulence gene families in pathogens. PMID:24253306

  9. The production of recombinant dengue virus E protein using Escherichia coli and Pichia pastoris.

    PubMed

    Sugrue, R J; Cui, T; Xu, Q; Fu, J; Chan, Y C

    1997-12-01

    The dengue virus envelope protein was expressed as a GST fusion protein using E. coli and P. pastoris as expression hosts. In E. coli the recombinant E protein is expressed initially as a soluble 81 kDa GST fusion protein. Treatment of the fusion protein with thrombin released a 55 kDa protein, which is the expected size for correctly processed, non-glycosylated recombinant E protein. The antiserum from animals immunised with this recombinant E protein was found to specifically recognise the dengue virus E protein in virus-infected cells, thus demonstrating the immunogenic nature of the recombinant E protein. This expression system allowed production of up to 2 mg of purified recombinant E protein from a 1 1 bacterial culture. In contrast, expression of this GST fusion protein in P. pastoris is associated with extensive proteolytic degradation of the recombinant E protein. However, this proteolytic degradation was not observed in the truncated E protein sequences which were expressed. One of these recombinant fusion proteins, GST E401 was secreted into the culture medium at levels of up to 100 microg/l of growth medium. PMID:9504761

  10. A Gateway recombination herpesvirus cloning system with negative selection that produces vectorless progeny.

    PubMed

    Kunec, Dusan; van Haren, Sandra; Burgess, Shane C; Hanson, Larry A

    2009-01-01

    Crossover recombination based on the lambda phage integration/excision functions enables insertion of a gene of interest into a specific locus by a simple one-step in vitro recombination reaction. Recently, a highly efficient recombination system for targeted mutagenesis, which utilizes lambda phage crossover recombination cloning, has been described for a human herpesvirus 2 bacterial artificial chromosome (BAC). The disadvantages of the system are that it allows only neutral selection (loss of green fluorescent protein) of desired recombinants and that it regenerates herpesvirus progeny containing the BAC sequence inserted in the herpesvirus genome. In this study, the existing channel catfish herpesvirus (CCV) infectious clone (in the form of overlapping fragments) was modified to allow introduction of foreign genes by modified lambda phage crossover recombination cloning. This novel system enables negative and neutral selection and regenerates vectorless herpesvirus progeny. Construction of two CCV mutants expressing lacZ, one from the native CCV ORF5 promoter and the other from the immediate-early cytomegalovirus promoter, demonstrated the efficiency and reliability of this system. This novel cloning system enables rapid incorporation, direct delivery and high-level expression of foreign genes by a herpesvirus. This system has broad utility and could be used to facilitate development of recombinant viruses, viral vectors and better vaccines. PMID:18948138

  11. PROGENITORS OF RECOMBINING SUPERNOVA REMNANTS

    SciTech Connect

    Moriya, Takashi J.

    2012-05-01

    Usual supernova remnants have either ionizing plasma or plasma in collisional ionization equilibrium, i.e., the ionization temperature is lower than or equal to the electron temperature. However, the existence of recombining supernova remnants, i.e., supernova remnants with ionization temperature higher than the electron temperature, has been recently confirmed. One suggested way to have recombining plasma in a supernova remnant is to have a dense circumstellar medium at the time of the supernova explosion. If the circumstellar medium is dense enough, collisional ionization equilibrium can be established in the early stage of the evolution of the supernova remnant and subsequent adiabatic cooling, which occurs after the shock wave gets out of the dense circumstellar medium, makes the electron temperature lower than the ionization temperature. We study the circumstellar medium around several supernova progenitors and show which supernova progenitors can have a circumstellar medium dense enough to establish collisional ionization equilibrium soon after the explosion. We find that the circumstellar medium around red supergiants (especially massive ones) and the circumstellar medium dense enough to make Type IIn supernovae can establish collisional ionization equilibrium soon after the explosion and can evolve to become recombining supernova remnants. Wolf-Rayet stars and white dwarfs have the possibility to be recombining supernova remnants but the fraction is expected to be very small. As the occurrence rate of the explosions of red supergiants is much higher than that of Type IIn supernovae, the major progenitors of recombining supernova remnants are likely to be red supergiants.

  12. Recombinant allergens for specific immunotherapy.

    PubMed

    Cromwell, Oliver; Häfner, Dietrich; Nandy, Andreas

    2011-04-01

    Recombinant DNA technology provides the means for producing allergens that are equivalent to their natural counterparts and also genetically engineered variants with reduced IgE-binding activity. The proteins are produced as chemically defined molecules with consistent structural and immunologic properties. Several hundred allergens have been cloned and expressed as recombinant proteins, and these provide the means for making a very detailed diagnosis of a patient's sensitization profile. Clinical development programs are now in progress to assess the suitability of recombinant allergens for both subcutaneous and sublingual immunotherapy. Recombinant hypoallergenic variants, which are developed with the aim of increasing the doses that can be administered while at the same time reducing the risks for therapy-associated side effects, are also in clinical trials for subcutaneous immunotherapy. Grass and birch pollen preparations have been shown to be clinically effective, and studies with various other allergens are in progress. Personalized or patient-tailored immunotherapy is still a very distant prospect, but the first recombinant products based on single allergens or defined mixtures could reach the market within the next 5 years. PMID:21377719

  13. Luminescent chiral lanthanide(III) complexes as potential molecular probes

    PubMed Central

    Muller, Gilles

    2009-01-01

    This perspective gives an introduction into the design of luminescent lanthanide(III)-containing complexes possessing chiral properties and used to probe biological materials. The first part briefly describes general principles, focusing on the optical aspect (i.e. lanthanide luminescence, sensitization processes) of the most emissive trivalent lanthanide ions, europium and terbium, incorporated into molecular luminescent edifices. This is followed by a short discussion on the importance of chirality in the biological and pharmaceutical fields. The second part is devoted to the assessment of the chiroptical spectroscopic tools available (typically circular dichroism and circularly polarized luminescence) and the strategies used to introduce a chiral feature into luminescent lanthanide(III) complexes (chiral structure resulting from a chiral arrangement of the ligand molecules surrounding the luminescent center or presence of chiral centers in the ligand molecules). Finally, the last part illustrates these fundamental principles with recent selected examples of such chiral luminescent lanthanide-based compounds used as potential probes of biomolecular substrates. PMID:19885510

  14. Luminescence imaging of water during alpha particle irradiation

    NASA Astrophysics Data System (ADS)

    Yamamoto, Seiichi; Komori, Masataka; Koyama, Shuji; Toshito, Toshiyuki

    2016-05-01

    The luminescence imaging of water using the alpha particle irradiation of several MeV energy range is thought to be impossible because this alpha particle energy is far below the Cerenkov-light threshold and the secondary electrons produced in this energy range do not emit Cerenkov-light. Contrary to this consensus, we found that the luminescence imaging of water was possible with 5.5 MeV alpha particle irradiation. We placed a 2 MBq of 241Am alpha source in water, and luminescence images of the source were conducted with a high-sensitivity, cooled charge-coupled device (CCD) camera. We also carried out such imaging of the alpha source in three different conditions to compare the photon productions with that of water, in air, with a plastic scintillator, and an acrylic plate. The luminescence imaging of water was observed from 10 to 20 s acquisition, and the intensity was linearly increased with time. The intensity of the luminescence with the alpha irradiation of water was 0.05% of that with the plastic scintillator, 4% with air, and 15% with the acrylic plate. The resolution of the luminescence image of water was better than 0.25 mm FWHM. Alpha particles of 5.5 MeV energy emit luminescence in water. Although the intensity of the luminescence was smaller than that in air, it was clearly observable. The luminescence of water with alpha particles would be a new method for alpha particle detection and distribution measurements in water.

  15. Luminescence enhancement by energy transfer in melamine-Y2O3:Tb3+ nanohybrids

    NASA Astrophysics Data System (ADS)

    Stagi, Luigi; Chiriu, Daniele; Ardu, Andrea; Cannas, Carla; Carbonaro, Carlo M.; Ricci, Pier Carlo

    2015-09-01

    The phenomenon of luminescence enhancement was studied in melamine-Y2O3:Tb hybrids. Terbium doped Y2O3 mesoporous nanowires were synthesized by hydrothermal method. X-ray diffraction patterns and Raman scattering spectra testified the realization of a cubic crystal phase. Organic-inorganic melamine-Y2O3:Tb3+ hybrid system was successfully obtained by vapour deposition method. Vibration Raman active modes of the organic counterpart were investigated in order to verify the achievement of hybrid system. Photoluminescence excitation and photoluminescence spectra, preformed in the region between 250 and 350 nm, suggest a strong interaction among melamine and Terbium ions. In particular, a remarkable improvement of 5D4→ FJ Rare Earth emission (at about 542 nm) of about 102 fold was observed and attributed to an efficient organic-Tb energy transfer. The energy transfer mechanism was studied by the use of time resolved photoluminescence measurements. The melamine lifetime undergoes to a significant decrease when adsorbed to oxide surfaces and it was connected to a sensitization mechanism. The detailed analysis of time decay profile of Terbium radiative recombination shows a variation of double exponential law toward a single exponential one. Its correlation with surface defects and non-radiative recombination was thus discussed.

  16. Ideal diode equation for organic heterojunctions. II. The role of polaron pair recombination

    SciTech Connect

    Giebink, Noel C; Lassiter, Brian E; Wiederrecht, Gary P; Wasielewski, Michael R; Forrest, Stephen R.

    2010-10-04

    In paper I [N. C. Giebink, G. P. Wiederrecht, M. R. Wasielewski, and S. R. Forrest, Phys. Rev. B 82, 155305 (2010)], we proposed that current transport in a donor-acceptor heterojunction (HJ) depends on the balance of polaron pair (PP) dissociation and recombination. Here, we directly investigate these processes in archetype planar copper phthalocyanine (CuPc)/C{sub 60} and boron subpthalocyanine chloride (SubPc)/C{sub 60} HJs. Using intensity-modulated photocurrent spectroscopy (IMPS) along with emission from interfacial Pc/C{sub 60} exciplex states, we monitor the geminate PP density at the HJ as a function of bias and illumination intensity. We find that the SubPc/C{sub 60} PP density is limited by the dynamics of dissociation, where it increases from short circuit, and peaks at open circuit. In contrast, that of CuPc/C{sub 60} is dominated by faster recombination kinetics and declines monotonically over the same voltage domain. We conclude that the PP recombination rate depends on electric field, and propose a simple expression that qualitatively explains the observed exciplex luminescence and IMPS behavior for these HJs. Our results provide insight into polaron pair recombination, which governs the current-voltage characteristics of organic heterojunctions in the dark and under illumination.

  17. Ideal Diode Equation for Organic Heterojunctions. II. The Role of Polaron Pair Recombination

    SciTech Connect

    Giebink, Noel C; Wiederrecht, Gary P; Wasielewski, Michael R; Forrest, Stephen R.

    2010-10-04

    In paper I [N. C. Giebink, G. P. Wiederrecht, M. R. Wasielewski, and S. R. Forrest, Phys. Rev. B 82, 155305 (2010)], we proposed that current transport in a donor-acceptor heterojunction (HJ) depends on the balance of polaron pair (PP) dissociation and recombination. Here, we directly investigate these processes in archetype planar copper phthalocyanine (CuPc)/C{sub 60} and boron subpthalocyanine chloride (SubPc)/C{sub 60} HJs. Using intensity-modulated photocurrent spectroscopy (IMPS) along with emission from interfacial Pc/C{sub 60} exciplex states, we monitor the geminate PP density at the HJ as a function of bias and illumination intensity. We find that the SubPc/C{sub 60} PP density is limited by the dynamics of dissociation, where it increases from short circuit, and peaks at open circuit. In contrast, that of CuPc/C{sub 60} is dominated by faster recombination kinetics and declines monotonically over the same voltage domain. We conclude that the PP recombination rate depends on electric field, and propose a simple expression that qualitatively explains the observed exciplex luminescence and IMPS behavior for these HJs. Our results provide insight into polaron pair recombination, which governs the current-voltage characteristics of organic heterojunctions in the dark and under illumination.

  18. Stable recombination hotspots in birds

    PubMed Central

    Singhal, Sonal; Leffler, Ellen M.; Sannareddy, Keerthi; Turner, Isaac; Venn, Oliver; Hooper, Daniel M.; Strand, Alva I.; Li, Qiye; Raney, Brian; Balakrishnan, Christopher N.; Griffith, Simon C.; McVean, Gil; Przeworski, Molly

    2016-01-01

    The DNA-binding protein PRDM9 has a critical role in specifying meiotic recombination hotspots in mice and apes, but appears to be absent from other vertebrate species, including birds. To study the evolution and determinants of recombination in species lacking PRDM9, we inferred fine-scale genetic maps from population resequencing data for two bird species, the zebra finch Taeniopygia guttata and the long-tailed finch Poephila acuticauda. We find that both species have hotspots, which are enriched near functional genomic elements. Unlike in mice and apes, the two species share most hotspots, with conservation seemingly extending over tens of millions of years. These observations suggest that in the absence of PRDM9, recombination targets functional features that both enable access to the genome and constrain its evolution. PMID:26586757

  19. Recombinant snake venom prothrombin activators.

    PubMed

    Lövgren, Ann

    2013-01-01

    Three prothrombin activators; ecarin, which was originally isolated from the venom of the saw-scaled viper Echis carinatus, trocarin from the rough-scaled snake Tropidechis carinatus, and oscutarin from the Taipan snake Oxyuranus scutellatus, were expressed in mammalian cells with the purpose to obtain recombinant prothrombin activators that could be used to convert prothrombin to thrombin. We have previously reported that recombinant ecarin can efficiently generate thrombin without the need for additional cofactors, but does not discriminate non-carboxylated prothrombin from biologically active γ-carboxylated prothrombin. Here we report that recombinant trocarin and oscutarin could not efficiently generate thrombin without additional protein co-factors. We confirm that both trocarin and oscutarin are similar to human coagulation Factor X (FX), explaining the need for additional cofactors. Sequencing of a genomic fragment containing 7 out of the 8 exons coding for oscutarin further confirmed the similarity to human FX. PMID:23111318

  20. The Dissociative Recombination of OH(+)

    NASA Technical Reports Server (NTRS)

    Guberman, Steven L.

    1995-01-01

    Theoretical quantum chemical calculations of the cross sections and rates for the dissociative recombination of the upsilon = 0 level of the ground state of OH(+) show that recombination occurs primarily along the 2 (2)Pi diabatic route. The products are 0((1)D) and a hot H atom with 6.1 eV kinetic energy. The coupling to the resonances is very small and the indirect recombination mechanism plays only a minor role. The recommended value for the rate coefficient is (6.3 +/- 0.7) x 10(exp -9)x (T(e)/1300)(exp -0.48) cu.cm/s for 10 less than T(e) less than 1000 K.

  1. Current Drive in Recombining Plasma

    SciTech Connect

    P.F. Schmit and N.J. Fisch

    2012-05-15

    The Langevin equations describing the average collisional dynamics of suprathermal particles in nonstationary plasma remarkably admit an exact analytical solution in the case of recombining plasma. The current density produced by arbitrary particle fluxes is derived including the effect of charge recombination. Since recombination has the effect of lowering the charge density of the plasma, thus reducing the charged particle collisional frequencies, the evolution of the current density can be modified substantially compared to plasma with fixed charge density. The current drive efficiency is derived and optimized for discrete and continuous pulses of current, leading to the discovery of a nonzero "residual" current density that persists indefinitely under certain conditions, a feature not present in stationary plasmas.

  2. Structure and luminescence properties of tellurium(IV) complex compounds

    NASA Astrophysics Data System (ADS)

    Sedakova, T. V.; Mirochnik, A. G.; Karasev, V. E.

    2011-05-01

    Using the tellurium(IV) complex compounds as an example, we study the interrelation between the geometric structure and spectral luminescence properties. We find that, in the series of compounds of Te(IV), which are characterized by the island octahedral coordination of Te(IV) ions, the luminescence intensity depends on the degree of distortion of the Te(IV) coordination polyhedron, the Stokes shift, and the energy of the luminescence transition. We revealed that the considered series of Te(IV) compounds possess reversible thermochromic properties.

  3. Surface pressure measurement by oxygen quenching of luminescence

    NASA Technical Reports Server (NTRS)

    Gouterman, Martin P. (Inventor); Kavandi, Janet L. (Inventor); Gallery, Jean (Inventor); Callis, James B. (Inventor)

    1994-01-01

    Methods and compositions for measuring the pressure of an oxygen-containing gas on an aerodynamic surface, by oxygen-quenching of luminescence of molecular sensors is disclosed. Objects are coated with luminescent films containing a first sensor and at least one of two additional sensors, each of the sensors having luminescences that have different dependencies on temperature and oxygen pressure. Methods and compositions are also provided for improving pressure measurements (qualitative or quantitive) on surfaces coated with a film having one or more types of sensor.

  4. Quantification of the luminescence intensity of natural materials

    NASA Technical Reports Server (NTRS)

    Watson, R. D.; Hessin, T. D.; Hemphill, W. R.

    1973-01-01

    Review of some of the results of an evaluation of the use of an airborne Fraunhofer line discriminator (FLD) for the detection of sun-stimulated luminescence emitted by rhodamine WT dye and some other materials. Rhodamine dye is reported to have been detected by airborne FDL in sea water in concentrations of less than 2 ppb. Experiments with a fluorescence spectrometer in the laboratory indicate that luminescence of some samples of crude and refined petroleum exceeds the luminescence intensity of rhodamine dye in concentrations of 10 ppm.

  5. Luminescence dating of the Wabar meteorite craters, Saudi Arabia

    USGS Publications Warehouse

    Prescott, J.R.; Robertson, G.B.; Shoemaker, C.; Shoemaker, E.M.; Wynn, J.

    2004-01-01

    Luminescence dating has been used to find the age of meteorite impact craters at Wabar (Al Hadida) in Saudi Arabia. The luminescence characteristics of the shocked material were determined. Using a variety of luminescence dating techniques applied to impactite formed by the meteorite, and to the underlying sand, the age is found to be 290 ± 38 years. A comparison is made with two possible historically recorded ages. An impact as young as this has implications for the assessment of hazards from the impact on Earth of small meteorites.

  6. Surface pressure measurement by oxygen quenching of luminescence

    NASA Technical Reports Server (NTRS)

    Gouterman, Martin P. (Inventor); Kavandi, Janet L. (Inventor); Gallery, Jean (Inventor); Callis, James B. (Inventor)

    1993-01-01

    Methods and compositions for measuring the pressure of an oxygen-containing gas on an aerodynamic surface, by oxygen-quenching of luminescence of molecular sensors is disclosed. Objects are coated with luminescent films containing a first sensor and at least one of two additional sensors, each of the sensors having luminescences that have different dependencies on temperature and oxygen pressure. Methods and compositions are also provided for improving pressure measurements (qualitative or quantitive) on surfaces coated with a film having one or more types of sensor.

  7. PEG functionalized luminescent lipid particles for cellular imaging

    NASA Astrophysics Data System (ADS)

    Rana, Suman; Barick, K. C.; Shetake, Neena G.; Verma, Gunjan; Aswal, V. K.; Panicker, Lata; Pandey, B. N.; Hassan, P. A.

    2016-08-01

    We report here the synthesis, characterization and cellular uptake of luminescent micelle-like particles with phospholipid core and non-ionic PEG based surfactant polysorbate 80 shell. The adsorption of polysorbate 80 at the interface of lipid containing microemulsion droplets and its solidification upon removal of solvent leads to anchoring of PEG chain to the lipid particles. Hydrophobic partitioning of luminescent molecules, sodium 3-hydroxynaphthalene-2-carboxylic acid to the phospholipid core offers additional functionality to these particles. Thus, the cooperative assembly of lipid, non-ionic amphiphile and organic luminescent probe leads to the formation of multifunctional biocompatible particles which are useful for simultaneous imaging and therapy.

  8. Proceedings of the third CECRI research conference on luminescence

    SciTech Connect

    Rao, R.P.

    1992-01-01

    This book reports on luminescence phenomena. Some important papers included in this part are theory of multiple trapping rate, radiationless processes, upconversion processes, lyo-and pyroelectric luminescence, photo and laser stimulated luminescence, linear and nonlinear TL effects, deep centers in diamonds, localized states in mixed crystals and fluorescence in polymers. This book also covers a side spectrum of phosphor materials such as alkaline earth sulphides, sulphates, fluorides and borates, zinc and cadmium sulphides, zinc and aluminum oxides, alkali halides, semiconductors, high T{sub c} superconductors, pigments and polymers.

  9. Bacterial start site prediction.

    PubMed

    Hannenhalli, S S; Hayes, W S; Hatzigeorgiou, A G; Fickett, J W

    1999-09-01

    With the growing number of completely sequenced bacterial genes, accurate gene prediction in bacterial genomes remains an important problem. Although the existing tools predict genes in bacterial genomes with high overall accuracy, their ability to pinpoint the translation start site remains unsatisfactory. In this paper, we present a novel approach to bacterial start site prediction that takes into account multiple features of a potential start site, viz., ribosome binding site (RBS) binding energy, distance of the RBS from the start codon, distance from the beginning of the maximal ORF to the start codon, the start codon itself and the coding/non-coding potential around the start site. Mixed integer programing was used to optimize the discriminatory system. The accuracy of this approach is up to 90%, compared to 70%, using the most common tools in fully automated mode (that is, without expert human post-processing of results). The approach is evaluated using Bacillus subtilis, Escherichia coli and Pyrococcus furiosus. These three genomes cover a broad spectrum of bacterial genomes, since B.subtilis is a Gram-positive bacterium, E.coli is a Gram-negative bacterium and P. furiosus is an archaebacterium. A significant problem is generating a set of 'true' start sites for algorithm training, in the absence of experimental work. We found that sequence conservation between P. furiosus and the related Pyrococcus horikoshii clearly delimited the gene start in many cases, providing a sufficient training set. PMID:10446249

  10. Ligand sensitized luminescence of uranyl by benzoic acid in acetonitrile medium: A new luminescent uranyl benzoate specie

    NASA Astrophysics Data System (ADS)

    Kumar, Satendra; Maji, S.; Joseph, M.; Sankaran, K.

    2015-03-01

    Benzoic acid (BA) is shown to sensitize and enhance the luminescence of uranyl ion in acetonitrile medium. Luminescence spectra and especially UV-Vis spectroscopy studies reveal the formation of tri benzoate complex of uranyl i.e. [UO2(C6H5COO)3]- which is highly luminescent. In particular, three sharp bands at 431, 443, 461 nm of absorption spectra provides evidence for tri benzoate specie of uranyl in acetonitrile medium. The luminescence lifetime of uranyl in this complex is 68 μs which is much more compared to the lifetime of uncomplexed uranyl (20 μs) in acetonitrile medium. In contrary to aqueous medium where uranyl benzoate forms 1:1 and 1:2 species, spectroscopic data reveal formation of 1:3 complex in acetonitrile medium. Addition of water to acetonitrile results in decrease of luminescence intensity of this specie and the luminescence features implode at 20% (v/v) of water content. For the first time, to the best of our knowledge, the existence of [UO2(C6H5COO)3]- specie in acetonitrile is reported. Mechanism of luminescence enhancement is discussed.

  11. Ligand sensitized luminescence of uranyl by benzoic acid in acetonitrile medium: a new luminescent uranyl benzoate specie.

    PubMed

    Kumar, Satendra; Maji, S; Joseph, M; Sankaran, K

    2015-03-01

    Benzoic acid (BA) is shown to sensitize and enhance the luminescence of uranyl ion in acetonitrile medium. Luminescence spectra and especially UV-Vis spectroscopy studies reveal the formation of tri benzoate complex of uranyl i.e. [UO2(C6H5COO)3](-) which is highly luminescent. In particular, three sharp bands at 431, 443, 461nm of absorption spectra provides evidence for tri benzoate specie of uranyl in acetonitrile medium. The luminescence lifetime of uranyl in this complex is 68μs which is much more compared to the lifetime of uncomplexed uranyl (20μs) in acetonitrile medium. In contrary to aqueous medium where uranyl benzoate forms 1:1 and 1:2 species, spectroscopic data reveal formation of 1:3 complex in acetonitrile medium. Addition of water to acetonitrile results in decrease of luminescence intensity of this specie and the luminescence features implode at 20% (v/v) of water content. For the first time, to the best of our knowledge, the existence of [UO2(C6H5COO)3](-) specie in acetonitrile is reported. Mechanism of luminescence enhancement is discussed. PMID:25528510

  12. Selenium incorporation using recombinant techniques

    SciTech Connect

    Walden, Helen

    2010-04-01

    An overview of techniques for recombinant incorporation of selenium and subsequent purification and crystallization of the resulting labelled protein. Using selenomethionine to phase macromolecular structures is common practice in structure determination, along with the use of selenocysteine. Selenium is consequently the most commonly used heavy atom for MAD. In addition to the well established recombinant techniques for the incorporation of selenium in prokaryal expression systems, there have been recent advances in selenium labelling in eukaryal expression, which will be discussed. Tips and things to consider for the purification and crystallization of seleno-labelled proteins are also included.

  13. Container Verification Using Optically Stimulated Luminescence

    SciTech Connect

    Tanner, Jennifer E.; Miller, Steven D.; Conrady, Matthew M.; Simmons, Kevin L.; Tinker, Michael R.

    2008-10-01

    Containment verification is a high priority for safeguards containment and surveillance. Nuclear material containers, safeguards equipment cabinets, camera housings, and detector cable conduit are all vulnerable to tampering. Even with a high security seal on a lid or door, custom-built hinges and interfaces, and special colors and types of finishes, the surfaces of enclosures can be tampered with and any penetrations repaired and covered over. With today’s technology, these repairs would not be detected during a simple visual inspection. Several suggested solutions have been to develop complicated networks of wires, fiber-optic cables, lasers or other sensors that line the inside of a container and alarm when the network is disturbed. This results in an active system with real time evidence of tampering but is probably not practical for most safeguards applications. A more practical solution would be to use a passive approach where an additional security feature was added to surfaces which would consist of a special coating or paint applied to the container or enclosure. One type of coating would incorporate optically stimulated luminescent (OSL) material. OSL materials are phosphors that luminesce in proportion to the ionizing radiation dose when stimulated with the appropriate optical wavelengths. The OSL fluoresces at a very specific wavelength when illuminated at another, very specific wavelength. The presence of the pre-irradiated OSL material in the coating is confirmed using a device that interrogates the surface of the enclosure using the appropriate optical wavelength and then reads the resulting luminescence. The presence of the OSL indicates that the integrity of the surface is intact. The coating itself could be transparent which would allow the appearance of the container to remain unchanged or the OSL material could be incorporated into certain paints or epoxies used on various types of containers. The coating could be applied during manufacturing

  14. Preparation of an active recombinant peptide of crustacean androgenic gland hormone.

    PubMed

    Okuno, Atsuro; Hasegawa, Yuriko; Nishiyama, Makoto; Ohira, Tsuyoshi; Ko, Rinkei; Kurihara, Masaaki; Matsumoto, Shogo; Nagasawa, Hiromichi

    2002-03-01

    In crustaceans, male sexual characteristics are induced by a hormone referred to as androgenic gland hormone. We have recently cloned a candidate cDNA in the terrestrial isopod Armadillidium vulgare. In order to prove that this cDNA encodes the hormone, recombinant single-chain precursor molecules consisting of B chain, C peptide and A chain were produced using both baculovirus and bacterial expression systems. Neither recombinant precursors showed activity. Digestion of only the precursor carrying a glycan moiety with lysyl endopeptidase gave a heterodimeric peptide with hormonal activity by removing a part of C peptide. These results indicate that the cDNA encodes the hormone. PMID:11836008

  15. Data on the identity and myristoylation state of recombinant, purified hippocalcin.

    PubMed

    Krishnan, Anuradha; Viviano, Jeffrey; Morozov, Yaroslav; Venkataraman, Venkat

    2016-09-01

    In this data article we report on the purity and post translation modification of bacterially expressed and purified recombinant hippocalcin (HPCA): a member of the neuronal calcium sensor protein family, whose functions are regulated by calcium. MALDI-TOF in source decay (ISD) analysis was used to identify both the myristoylated or non-myristoylated forms of the protein. MALDI-TOF ISD data on the identity of the protein, amino acid sequence and myristoylation efficiency are provided. This data relates to the article "Single-Column Purification of the Tag-free, Recombinant Form of the Neuronal Calcium Sensor Protein, Hippocalcin Expressed in Eschericia coli" [1]. PMID:27284566

  16. Lipoproteins of bacterial pathogens.

    PubMed

    Kovacs-Simon, A; Titball, R W; Michell, S L

    2011-02-01

    Bacterial lipoproteins are a set of membrane proteins with many different functions. Due to this broad-ranging functionality, these proteins have a considerable significance in many phenomena, from cellular physiology through cell division and virulence. Here we give a general overview of lipoprotein biogenesis and highlight examples of the roles of lipoproteins in bacterial disease caused by a selection of medically relevant Gram-negative and Gram-positive pathogens: Mycobacterium tuberculosis, Streptococcus pneumoniae, Borrelia burgdorferi, and Neisseria meningitidis. Lipoproteins have been shown to play key roles in adhesion to host cells, modulation of inflammatory processes, and translocation of virulence factors into host cells. As such, a number of lipoproteins have been shown to be potential vaccines. This review provides a summary of some of the reported roles of lipoproteins and of how this knowledge has been exploited in some cases for the generation of novel countermeasures to bacterial diseases. PMID:20974828

  17. In situ evolutionary rate measurements show ecological success of recently emerged bacterial hybrids.

    PubMed

    Denef, Vincent J; Banfield, Jillian F

    2012-04-27

    Few data are available on how quickly free-living microorganisms evolve. We analyzed biofilms collected from a well-defined acid mine drainage system over 9 years to investigate the processes and determine rates of bacterial evolution directly in the environment. Population metagenomic analyses of the dominant primary producer yielded the nucleotide substitution rate, which we used to show that proliferation of a series of recombinant bacterial strains occurred over the past few decades. The ecological success of hybrid bacterial types highlights the role of evolutionary processes in rapid adaptation within natural microbial communities. PMID:22539719

  18. Classifications and comparisons of multilocus recombination distributions

    PubMed Central

    Karlin, Samuel; Liberman, Uri

    1978-01-01

    Various classifications and representations of multilocus recombination structures are delineated based on generalized notions of linkage values and recombination rates. An important class of recombination distributions (called the count-location chiasma process) is parameterized by a distribution of the number of crossover events and, for each such crossover count, by a conditional distribution of crossover locations. A number of properties of this recombination structure are developed. A multilocus definition of a “natural” recombination range is set forth. Orderings among recombination distributions in the multilocus setting are also discussed. Comparisons are made in terms of complete linkage, free assortment and noninterference schemes serving as standards. PMID:16592601

  19. Bacterial transfer RNAs

    PubMed Central

    Shepherd, Jennifer; Ibba, Michael

    2015-01-01

    Transfer RNA is an essential adapter molecule that is found across all three domains of life. The primary role of transfer RNA resides in its critical involvement in the accurate translation of messenger RNA codons during protein synthesis and, therefore, ultimately in the determination of cellular gene expression. This review aims to bring together the results of intensive investigations into the synthesis, maturation, modification, aminoacylation, editing and recycling of bacterial transfer RNAs. Codon recognition at the ribosome as well as the ever-increasing number of alternative roles for transfer RNA outside of translation will be discussed in the specific context of bacterial cells. PMID:25796611

  20. Biosensing with Luminescent Semiconductor Quantum Dots

    PubMed Central

    Sapsford, Kim E.; Pons, Thomas; Medintz, Igor L.; Mattoussi, Hedi

    2006-01-01

    Luminescent semiconductor nanocrystals or quantum dots (QDs) are a recently developed class of nanomaterial whose unique photophysical properties are helping to create a new generation of robust fluorescent biosensors. QD properties of interest for biosensing include high quantum yields, broad absorption spectra coupled to narrow size-tunable photoluminescent emissions and exceptional resistance to both photobleaching and chemical degradation. In this review, we examine the progress in adapting QDs for several predominantly in vitro biosensing applications including use in immunoassays, as generalized probes, in nucleic acid detection and fluorescence resonance energy transfer (FRET) - based sensing. We also describe several important considerations when working with QDs mainly centered on the choice of material(s) and appropriate strategies for attaching biomolecules to the QDs.

  1. Video luminescent barometry - The induction period

    NASA Technical Reports Server (NTRS)

    Uibel, Rory H.; Khalil, Gamal; Gouterman, Martin; Gallery, Jean; Callis, James B.

    1993-01-01

    Video monitoring of oxygen quenching of the photoluminescence of platinum octaethylporphyrin (PtOEP) in silicone polymer resin may be used to measure pressure distribution over an airfoil. A continuous increase of the luminescence intensity of PtOEP on exposure to the exciting light is known as the induction effect. The effect of several factors on PtOEP photoluminescence and the induction effect was investigated. The experimental apparatus is described and results are presented. It was observed that the relative induction amplitude and induction time increase at higher oxygen pressure and with thicker films. These observations may be explained if the singlet oxygen produced by oxygen quenching is consumed by the polymer and is therefore unavailable for further quenching. Researchers using this method for measuring pressure distribution on airfoil surfaces should be aware of the induction effect and its implications.

  2. Thermal luminescence spectroscopy chemical imaging sensor.

    PubMed

    Carrieri, Arthur H; Buican, Tudor N; Roese, Erik S; Sutter, James; Samuels, Alan C

    2012-10-01

    The authors present a pseudo-active chemical imaging sensor model embodying irradiative transient heating, temperature nonequilibrium thermal luminescence spectroscopy, differential hyperspectral imaging, and artificial neural network technologies integrated together. We elaborate on various optimizations, simulations, and animations of the integrated sensor design and apply it to the terrestrial chemical contamination problem, where the interstitial contaminant compounds of detection interest (analytes) comprise liquid chemical warfare agents, their various derivative condensed phase compounds, and other material of a life-threatening nature. The sensor must measure and process a dynamic pattern of absorptive-emissive middle infrared molecular signature spectra of subject analytes to perform its chemical imaging and standoff detection functions successfully. PMID:23033092

  3. Dispersion and luminescence measurements of optical waveguides

    NASA Astrophysics Data System (ADS)

    Faik, A.; Allen, L.; Eicher, C.; Gagola, A.; Townsend, P. D.; Pitt, C. W.

    1983-05-01

    The results of measurements are presented for the dispersion curves in the visible wavelength range of a variety of optical waveguides which were formed in LiNbO3 and LiTaO3 by the implantation of helium ions. It is found that the radiation damage reduces the refractive index in both materials by about 12 percent throughout the visible region, probably resulting from amorphization of the lattice. Waveguides formed by impurity enhancement of the refractive index were measured in soda lime glass which had been doped by ion exchange of Li, K, Rb, Cs, or Ag; and it was found that in each case the percentage increase in index was wavelength dependent. The Ag ion exchange waveguides were found to have features which could be attributed to colloidal silver metal. The metal colloids give dispersion anomalies as well as a red luminescence which was used to measure the losses in the waveguide.

  4. Mechanically Induced Multicolor Change of Luminescent Materials.

    PubMed

    Ma, Zhiyong; Wang, Zhijian; Teng, Mingjun; Xu, Zejun; Jia, Xinru

    2015-06-22

    Mechanofluorochromic or piezochromic fluorescence chemistry involves the switching and tuning of the luminescent properties of solid-state materials induced by exogenous forces, such as grinding, shearing, compression, tension, and so forth. Up until now, most reported mechanochromic systems, including liquid crystals, organic molecules, organometallic compounds, polymers, and dye-doped polymers, have displayed reversible two-color changes, which arise from either supramolecular or chemical structure transformations. However, fluorescent materials that undergo mechanically induced multicolor changes remain rare; this Minireview is focused on such materials. Topics are categorized according to the different applied forces that are required to induce the multicolor change, including mechanical control of either the supramolecular structures or the chemical structures, and mechanical control of both the supramolecular structures and chemical structures. PMID:25965783

  5. Luminescent solar concentrator improvement by stimulated emission

    NASA Astrophysics Data System (ADS)

    Kaysir, Md Rejvi; Fleming, Simon; MacQueen, Rowan W.; Schmidt, Timothy W.; Argyros, Alexander

    2015-12-01

    Luminescent solar concentrators (LSCs) offer the prospect of reducing the cost of solar energy, and are a promising candidate for building integrated photovoltaic (PV) structures. However, the realization of commercially viable efficiency of LSCs is currently hindered by reabsorption losses. In this work, a method is introduced for reducing reabsorption as well as improving directional emission in LSCs by using stimulated emission. Light from a seed laser (potentially an inexpensive laser diode) passes through the entire length of the LSC panel, modifying the emission spectrum of excited dye molecules such that it is spectrally narrower, at wavelengths that minimize reabsorption, and directed by the seed laser towards a small target PV cell. A mathematical model of such a system is presented which identifies different physical parameters responsible for the power conversion efficiency and gives the net effective output power.

  6. Luminescent solar concentrators utilizing stimulated emission.

    PubMed

    Kaysir, Md Rejvi; Fleming, Simon; MacQueen, Rowan W; Schmidt, Timothy W; Argyros, Alexander

    2016-03-21

    Luminescent solar concentrators (LSCs) are an emerging technology that aims primarily to reduce the cost of solar energy, with great potential for building integrated photovoltaic (PV) structures. However, realizing LSCs with commercially viable efficiency is currently hindered by reabsorption losses. Here, we introduce an approach to reducing reabsorption as well as improving directional emission in LSCs by using stimulated emission. Light from a seed laser (potentially an inexpensive laser diode) passes through the entire area of the LSC panel, modifying the emission spectrum of excited dye molecules such that it is spectrally narrower, at wavelengths that minimize reabsorption to allow net gain in the system, and directed towards a small PV cell. A mathematical model, taking into account thermodynamic considerations, of such a system is presented which identifies key parameters and allows evaluation in terms of net effective output power. PMID:27136870

  7. Luminescence studies of individual quantum dot photocatalysts.

    PubMed

    Amirav, Lilac; Alivisatos, A Paul

    2013-09-01

    Using far-field optical microscopy we report the first measurements of photoluminescence from single nanoparticle photocatalysts. Fluence-dependent luminescence is investigated from metal-semiconductor heterojunction quantum dot catalysts exposed to a variety of environments, ranging from gaseous argon to liquid water containing a selection of hole scavengers. The catalysts each exhibit characteristic nonlinear fluence dependence. From these structurally and environmentally sensitive trends, we disentangle the separate rate-determining steps in each particle across the very wide range of time scales, which follow the initial light absorption process. This information will significantly benefit the design of effective artificial photocatalytic systems for renewable direct solar-to-fuel energy conversion. PMID:23895591

  8. Luminescence upconversion in colloidal double quantum dots.

    PubMed

    Deutsch, Zvicka; Neeman, Lior; Oron, Dan

    2013-09-01

    Luminescence upconversion nanocrystals capable of converting two low-energy photons into a single photon at a higher energy are sought-after for a variety of applications, including bioimaging and photovoltaic light harvesting. Currently available systems, based on rare-earth-doped dielectrics, are limited in both tunability and absorption cross-section. Here we present colloidal double quantum dots as an alternative nanocrystalline upconversion system, combining the stability of an inorganic crystalline structure with the spectral tunability afforded by quantum confinement. By tailoring its composition and morphology, we form a semiconducting nanostructure in which excited electrons are delocalized over the entire structure, but a double potential well is formed for holes. Upconversion occurs by excitation of an electron in the lower energy transition, followed by intraband absorption of the hole, allowing it to cross the barrier to a higher energy state. An overall conversion efficiency of 0.1% per double excitation event is achieved. PMID:23912060

  9. Alternatives to overcoming bacterial resistances: State-of-the-art.

    PubMed

    Rios, Alessandra C; Moutinho, Carla G; Pinto, Flávio C; Del Fiol, Fernando S; Jozala, Angela; Chaud, Marco V; Vila, Marta M D C; Teixeira, José A; Balcão, Victor M

    2016-10-01

    Worldwide, bacterial resistance to chemical antibiotics has reached such a high level that endangers public health. Presently, the adoption of alternative strategies that promote the elimination of resistant microbial strains from the environment is of utmost importance. This review discusses and analyses several (potential) alternative strategies to current chemical antibiotics. Bacteriophage (or phage) therapy, although not new, makes use of strictly lytic phage particles as an alternative, or a complement, in the antimicrobial treatment of bacterial infections. It is being rediscovered as a safe method, because these biological entities devoid of any metabolic machinery do not possess any affinity whatsoever to eukaryotic cells. Lysin therapy is also recognized as an innovative antimicrobial therapeutic option, since the topical administration of preparations containing purified recombinant lysins with amounts in the order of nanograms, in infections caused by Gram-positive bacteria, demonstrated a high therapeutic potential by causing immediate lysis of the target bacterial cells. Additionally, this therapy exhibits the potential to act synergistically when combined with certain chemical antibiotics already available on the market. Another potential alternative antimicrobial therapy is based on the use of antimicrobial peptides (AMPs), amphiphilic polypeptides that cause disruption of the bacterial membrane and can be used in the treatment of bacterial, fungal and viral infections, in the prevention of biofilm formation, and as antitumoral agents. Interestingly, bacteriocins are a common strategy of bacterial defense against other bacterial agents, eliminating the potential opponents of the former and increasing the number of available nutrients in the environment for their own growth. They can be applied in the food industry as biopreservatives and as probiotics, and also in fighting multi-resistant bacterial strains. The use of antibacterial antibodies

  10. Seeding Specificity and Ultrastructural Characteristics of Infectious Recombinant Prions

    PubMed Central

    Piro, Justin R.; Wang, Fei; Walsh, Daniel J.; Rees, Judy R.; Ma, Jiyan; Supattapone, Surachai

    2012-01-01

    Infectious mouse prions can be produced from a mixture of bacterially expressed recombinant prion protein (recPrP), palmitoyloleoylphosphatidylglycerol (POPG), and RNA [Wang, F.; et al. (2010) Science 327, 1132 ]. In contrast, amyloid fibers produced from pure recPrP without POPG or RNA (recPrP fibers) fail to infect wild type mice [Colby, D. W.; et al. (2010) PLoS Pathog. 387, e1000736 ]. We compared the seeding specificity and ultrastructural features of infectious recombinant prions (recPrPSc) with those of recPrP fibers. Our results indicate that PrP fibers are not able to induce the formation of PrPSc molecules from wild type mouse brain homogenate substrate in serial protein misfolding cyclic amplification (sPMCA) reactions. Conversely, recPrPSc molecules did not accelerate the formation of amyloid in vitro, under conditions that produce recPrP fibers spontaneously. Ultrastructurally, recombinant prions appear to be small spherical aggregates rather than elongated fibers, as determined by atomic force and electron microscopy. Taken together, our results show that recPrPSc molecules and PrP fibers have different ultrastructural features and seeding specificities, suggesting that prion infectivity may be propagated by a specific and unique assembly pathway facilitated by cofactors. PMID:21776987

  11. Recombinant Thermus aquaticus RNA Polymerase for Structural Studies

    SciTech Connect

    Juznedelov,K.; Lamour, V.; Patikoglou, G.; Chlenov, M.; Darst, S.; Severinov, K.

    2006-01-01

    Advances in the structural biology of bacterial transcription have come from studies of RNA polymerases (RNAPs) from the thermophilic eubacteria Thermus aquaticus (Taq) and Thermus thermophilus (Tth). These structural studies have been limited by the fact that only endogenous Taq or Tth RNAP, laboriously purified from large quantities of Taq or Tth cell paste and offering few options for genetic modification, is suitable for structural studies. Recombinant systems for the preparation of Taq RNAP by co-overexpression and assembly in the heterologous host, Escherichia coli, have been described, but these did not yield enzyme suitable for crystallographic studies. Here we describe recombinant systems for the preparation of Taq RNAP harboring full or partial deletions of the Taq {beta}' non-conserved domain (NCD), yielding enzyme suitable for crystallographic studies. This opens the way for structural studies of genetically manipulated enzymes, allowing the preparation of more crystallizable enzymes and facilitating detailed structure/function analysis. Characterization of the Taq{beta}'NCD deletion mutants generated in this study showed that the {beta}'NCD is important for the efficient binding of the s subunit, confirming previous hypotheses. Finally, preliminary structural analysis (at 4.1 Angstroms resolution) of one of the recombinant mutants revealed a previously unobserved conformation of the {beta}-flap, further defining the range of conformations accessible to this flexible structural element.

  12. Use of recombinant approaches to construct human cytomegalovirus mutants.

    PubMed

    Dekhtiarenko, Iryna; Cičin-Šain, Luka; Messerle, Martin

    2014-01-01

    To fully understand the function of cytomegalovirus (CMV) genes, it is imperative that they be studied in the context of infection. Therefore, the targeted deletion of individual viral genes and the comparison of loss of function viral mutants to the wild-type virus allow the identification of the relevance and role for a particular gene in the viral replication cycle. Targeted CMV mutagenesis has made huge advances over the past 15 years. The cloning of CMV genomes into (E. coli) as bacterial artificial chromosomes (BAC) allows not only quick and efficient deletion of viral genomic regions, individual genes, or single nucleotide exchanges in the viral genome but also the insertion of heterologous genetic sequences for gain of function approaches. The conceptual advantage of this strategy is that it overcomes the restrictions of recombinant technologies in cell culture systems. Namely, recombination in infected cells occurs only in a few clones, and their selection is not possible if the targeted genes are relevant for virus replication and are not able to compete for growth against the unrecombined viruses. On the other hand, BAC mutagenesis enables the selection for antibiotic resistance in E. coli, allowing a selective growth advantage to the recombined genomes. Here we describe the methods used for the generation of a CMV BAC, targeted mutagenesis of BAC clones, and transfection of human cells with CMV BAC DNA in order to reconstitute the viral infection process. PMID:24639218

  13. Luminescent DNA- and agar-based membranes.

    PubMed

    Leones, R; Fernandes, M; Ferreira, R A S; Cesarino, I; Lima, J F; Carlos, L D; Bermudez, V de Zea; Magon, C J; Donoso, J P; Silva, M M; Pawlicka, A

    2014-09-01

    Luminescent materials containing europium ions are investigated for different optical applications. They can be obtained using bio-macromolecules, which are promising alternatives to synthetic polymers based on the decreasing oil resources. This paper describes studies of the DNA- and Agar-europium triflate luminescent membranes and its potential technological applications are expanded to electroluminescent devices. Polarized optical microscopy demonstrated that the samples are birefringent with submicrometer anisotropy. The X-ray diffraction analysis revealed predominantly amorphous nature of the samples and the atomic force microscopy images showed a roughness of the membranes of 409.0 and 136.1 nm for the samples of DNA10Eu and Agar1.11Eu, respectively. The electron paramagnetic resonance spectra of the DNA(n)Eu membranes with the principal lines at g ≈ 2.0 and g ≈ 4.8 confirmed uniform distribution of rare earth ions in a disordered matrix. Moreover, these strong and narrow resonance lines for the samples of DNA(n)Eu when compared to the Agar(n)Eu suggested a presence of paramagnetic radicals arising from the DNA matrix. The emission spectra suggested that the Eu3+ ions occupy a single local environment in both matrices and the excitation spectra monitored around the Eu emission lines pointed out that the Eu3+ ions in the Agar host were mainly excited via the broad band component rather than by direct intra-4f(6) excitation, whereas the opposite case occurred for the DNA-based sample. PMID:25924317

  14. Optically Stimulated Luminescence Properties Of Natural Schist

    NASA Astrophysics Data System (ADS)

    Stefanaki, E. C.; Afouxenidis, D.; Polymeris, G. S.; Sakalis, A.; Tsirliganis, N. C.; Kitis, G.

    Schist is a common siliciclastic geological material that has been extensively used in buildings as brick, tile and roofing slates. Its use, especially in the Mediterranean sea is widespread through the centuries. There are various examples from the ancient Greece, such as monuments from Knossos, Karthaia, as well as from modern Greece, such as traditional houses, etc. Schist is a metamorphic crystalline rock composed largely of silicon minerals, such as quartz, muscovite mica and feldspars. The type and composition of schists, as well as, the concentration of each mineral depends strongly on the type and the origin of the schist. Its past and modern use makes it a suitable candidate form archaeological dating, as well as, for retrospective dosimetry purposes. In the present work a preliminary characterization of schist is performed in order to investigate if some basic properties required for dating applications can be found in this material. The preliminary study concerns the optical stability, the sensitization and linearity of the Infrared Stimulated Luminescence (IRSL) resulting from feldspars, as well as the post IR Blue Optically Stimulated Luminescence (post - IR Blue OSL) resulting mostly from quartz. The results indicate that both signals are rapidly bleached when the sample is exposed to sunlight. The dose response was found to be linear for radiation doses at least up to 75 Gy for the IRSL signal and at least up to 25 Gy in the case of post - IR Blue OSL. The use of a single aliquot measurement protocol, due to the lack of sensitisation, extends the latter dose response linearity region up to 75 Gy for the post - IR Blue OSL signal of schist. Finally, the application of the double single-aliquot regenerative-dose protocol to schist was investigated, in order to recover,successfully, the equivalent dose in 4 - 11 μm grains of the compound.

  15. Genetically engineered luminescent proteins in biosensing

    NASA Astrophysics Data System (ADS)

    Rowe, Laura; Ensor, Mark; Scott, Daniel; Deo, Sapna; Daunert, Sylvia

    2006-02-01

    Luminescent proteins originally isolated from marine or terrestrial organisms have played a key role in the development of several biosensing systems. These proteins have been used in a variety of applications including, immunoassays, binding assays, cell-based sensing, high throughput screening, optical imaging, etc. Among the luminescent proteins isolated, the bioluminescent protein aequorin has been one of the proteins at the forefront in terms of its use in a vast number of biosensing systems. In our laboratory, we have employed aequorin as a label in the development of highly sensitive assays through chemical and genetic modifications from single step analysis of physiologically important molecules in biological fluids. An important aspect of optimizing these assays for clinical use involves understanding the stability of the various aequorin variants that are available. To this end we have designed several stability studies involving three important aequorin mutants, Mutant S, Mutant 5, and Mutant 53. The cysteine free aequorin, Mutant S, has been the most ubiquitously used aequorin variant in our laboratory because of its increased stability and activity as compared to native aequorin. Mutant 5 and Mutant 53 contain a single cyteine residue at position 5 and 53 in the protein, respectively. Because of the presence of a single cysteine residue, Mutant 5 and Mutant 53 both can be site-specifically conjugated. This site specific conjugation capability gives Mutant 5 and Mutant 53 an advantage over native aequorin when developing assays. Additional studies optimizing the expression, purification, and charging of aequorin Mutant S were also performed. A thorough understanding of the efficient expression, purification, and storage of these aequorin mutants will allow for the more practical utilization of these mutants in the development of future biosensing systems.

  16. Topaz and Kyanite Luminescence Under High Pressure

    NASA Astrophysics Data System (ADS)

    O'Bannon, E. F., III; Williams, Q. C.

    2014-12-01

    The luminescence spectra of Cr3+ in heat-treated topaz Al2SiO4(OH,F)2 and natural kyanite Al2SiO5 were measured from 650 - 800 nm in a hydrostatic environment up to pressures of 15 GPa. The R1 and R2 peaks of topaz shift at average rates of 0.30 nm/GPa and 0.22 nm/GPa, respectively, implying that the deformation of the Cr3+ octahedra increases with pressure. Three peaks are fit under each R line of topaz at both room and high pressure, and these peaks are associated with different Al sites into which the Cr substitutes. The shift of the R lines in topaz under pressure is remarkably linear, which appears to be a general feature of many Cr3+-bearing oxides: the underlying cause of this linearity may lie in anharmonic coupling with lattice vibrations. In this context, we also characterize the frequency shifts of two vibronic peaks within topaz. The R1 and R2 peaks of kyanite shift at 0.37 nm/GPa and 0.88 nm/GPa respectively. Two peaks are fit under R1 and three peaks are fit under R2 of kyanite at both room and high pressure; this result is also consistent with three different Cr3+ sites in this material. The R lines in kyanite are notably optically anisotropic, depending strongly on crystallographic orientation: this is most strongly manifested in the R2 peak. The Cr3+ luminescence in these materials provides a sensitive probe of pressure-dependent shifts in the local geometry of the Al-sites in these materials, which are analyzed in the context of previous single-crystal x-ray diffraction measurements.

  17. Luminescent coupling in planar opto-electronic devices

    NASA Astrophysics Data System (ADS)

    Wilkins, Matthew; Valdivia, Christopher E.; Gabr, Ahmed M.; Masson, Denis; Fafard, Simon; Hinzer, Karin

    2015-10-01

    Effects of luminescent coupling are observed in monolithic 5 V, five-junction GaAs phototransducers. Power conversion efficiency was measured at 61.6% ± 3% under the continuous, monochromatic illumination for which they were designed. Modeling shows that photon recycling can account for up to 350 mV of photovoltage in these devices. Drift-diffusion based simulations including a luminescent coupling term in the continuity equation show a broadening of the internal quantum efficiency curve which agrees well with experimental measurements. Luminescent coupling is shown to expand the spectral bandwidth of the phototransducer by a factor of at least 3.5 for devices with three or more junctions, even in cases where multiple absorption/emission events are required to transfer excess carriers into the limiting junction. We present a detailed description of the novel luminescent coupling modeling technique used to predict these performance enhancements.

  18. Near-Infrared Quantum Cutting Long Persistent Luminescence

    PubMed Central

    Zou, Zehua; Feng, Lin; Cao, Cheng; Zhang, Jiachi; Wang, Yuhua

    2016-01-01

    By combining the unique features of the quantum cutting luminescence and long persistent luminescence, we design a new concept called “near-infrared quantum cutting long persistent luminescence (NQPL)”, which makes it possible for us to obtain highly efficient (>100%) near-infrared long persistent luminescence in theory. Guided by the NQPL concept, we fabricate the first NQPL phosphor Ca2Ga2GeO7:Pr3+,Yb3+. It reveals that both the two-step energy transfer of model (I) and the one-step energy transfer of model (IV) occur in 3P0 levels of Pr3+. Although the actual efficiency is not sufficient for the practical application at this primitive stage, this discovery and the associated materials are still expected to have important implications for several fields such as crystalline Si solar cells and bio-medical imaging. PMID:27143282

  19. Near-Infrared Quantum Cutting Long Persistent Luminescence.

    PubMed

    Zou, Zehua; Feng, Lin; Cao, Cheng; Zhang, Jiachi; Wang, Yuhua

    2016-01-01

    By combining the unique features of the quantum cutting luminescence and long persistent luminescence, we design a new concept called "near-infrared quantum cutting long persistent luminescence (NQPL)", which makes it possible for us to obtain highly efficient (>100%) near-infrared long persistent luminescence in theory. Guided by the NQPL concept, we fabricate the first NQPL phosphor Ca2Ga2GeO7:Pr(3+),Yb(3+). It reveals that both the two-step energy transfer of model (I) and the one-step energy transfer of model (IV) occur in (3)P0 levels of Pr(3+). Although the actual efficiency is not sufficient for the practical application at this primitive stage, this discovery and the associated materials are still expected to have important implications for several fields such as crystalline Si solar cells and bio-medical imaging. PMID:27143282

  20. Luminescent Metal-Containing Polymers for White Light Emission.

    PubMed

    Ho, Cheuk-Lam; Wong, Wai-Yeung

    2016-10-01

    This chapter focuses on the recent developments in luminescent metallopolymers. Synthetic routes to these polymers are briefly described and their applications in polymer white light-emitting diodes are discussed. PMID:27573506