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Sample records for resonance energy transfer-based

  1. Resonant energy transfer based biosensor for detection of multivalent proteins.

    SciTech Connect

    Song, X.; Swanson, Basil I.

    2001-01-01

    We have developed a new fluorescence-based biosensor for sensitive detection of species involved in a multivslent interaction. The biosensor system utilizes specific interactions between proteins and cell surface receptors, which trigger a receptor aggregation process. Distance-dependent fluorescence self-quenching and resonant energy transfer mechanisms were coupled with a multivalent interaction to probe the receptor aggregation process, providing a sensitive and specific signal transduction method for such a binding event. The fluorescence change induced by the aggregation process can be monitored by different instrument platforms, e.g. fluorimetry and flow cytometry. In this article, a sensitive detection of pentavalent cholera toxin which recognizes ganglioside GM1 has been demonstrated through the resonant energy transfer scheme, which can achieve a double color change simultaneously. A detection sensitivity as high as 10 pM has been achieved within a few minutes (c.a. 5 minutes). The simultaneous double color change (an increase of acceptor fluorescence and a decrease of donor fluorescence intensity) of two similar fluorescent probes provides particularly high detection reliability owing to the fact that they act as each other's internal reference. Any external perturbation such as environmental temperature change causes no significant change in signal generation. Besides the application for biological sensing, the method also provides a useful tool for investigation of kinetics and thermodynamics of a multivalent interaction. Keywords: Biosensor, Fluorescence resonant energy transfer, Multivalent interaction, Cholera Toxin, Ganglioside GM1, Signal Transduction

  2. Resonance Energy Transfer-Based Approaches to Study GPCRs.

    PubMed

    Ayoub, Mohammed Akli

    2016-01-01

    Since their discovery, G protein-coupled receptors (GPCRs) constitute one of the most studied proteins leading to important discoveries and perspectives in terms of their biology and implication in physiology and pathophysiology. This is mostly linked to the remarkable advances in the development and application of the biophysical resonance energy transfer (RET)-based approaches, including bioluminescence and fluorescence resonance energy transfer (BRET and FRET, respectively). Indeed, BRET and FRET have been extensively applied to study different aspects of GPCR functioning such as their activation and regulation either statically or dynamically, in real-time and intact cells. Consequently, our view on GPCRs has considerably changed opening new challenges for the study of GPCRs in their native tissues in the aim to get more knowledge on how these receptors control the biological responses. Moreover, the technological aspect of this field of research promises further developments for robust and reliable new RET-based assays that may be compatible with high-throughput screening as well as drug discovery programs.

  3. Fluorescence resonance energy transfer-based stoichiometry in living cells.

    PubMed Central

    Hoppe, Adam; Christensen, Kenneth; Swanson, Joel A

    2002-01-01

    Imaging of fluorescence resonance energy transfer (FRET) between fluorescently labeled molecules can measure the timing and location of intermolecular interactions inside living cells. Present microscopic methods measure FRET in arbitrary units, and cannot discriminate FRET efficiency and the fractions of donor and acceptor in complex. Here we describe a stoichiometric method that uses three microscopic fluorescence images to measure FRET efficiency, the relative concentrations of donor and acceptor, and the fractions of donor and acceptor in complex in living cells. FRET stoichiometry derives from the concept that specific donor-acceptor complexes will give rise to a characteristic FRET efficiency, which, if measured, can allow stoichiometric discrimination of interacting components. A first equation determines FRET efficiency and the fraction of acceptor molecules in complex with donor. A second equation determines the fraction of donor molecules in complex by estimating the donor fluorescence lost due to energy transfer. This eliminates the need for acceptor photobleaching to determine total donor concentrations and allows for repeated measurements from the same cell. A third equation obtains the ratio of total acceptor to total donor molecules. The theory and method were confirmed by microscopic measurements of fluorescence from cyan fluorescent protein (CFP), citrine, and linked CFP-Citrine fusion protein, in solutions and inside cells. Together, the methods derived from these equations allow sensitive, rapid, and repeatable detection of donor-, acceptor-, and donor-acceptor complex stoichiometry at each pixel in an image. By accurately imaging molecular interactions, FRET stoichiometry opens new areas for quantitative study of intracellular molecular networks. PMID:12496132

  4. Quantum dot-DNA bioconjugates for fluorescence-resonance-energy-transfer-based biosensing

    NASA Astrophysics Data System (ADS)

    Medintz, Igor L.; Berti, Lorenzo; Pons, Thomas; Mattoussi, Hedi

    2007-02-01

    Semiconductor quantum dots (QDs) have unique photophysical properties which make them excellent fluorescence resonance energy transfer donors. However, lack of facile methods for conjugating biomolecules such as DNA, proteins and peptides to QDs have limited their applications. In this report, we describe a general procedure for the preparation of a synthetic peptide that can be covalently attached to DNA segments and used to facilitate the self-assembly of the modified DNA onto water soluble QDs. To characterize this conjugation strategy, dye-labeled DNA is first reacted with the synthetic peptide and the resulting peptide-DNA then self-assembled onto QDs. QD attachment is verified by monitoring resonance energy transfer efficiency from the QD donor to the dye-labeled DNA acceptor. QD-DNA bioconjugates assembled using this method may find applications as molecular beacons and hybridization probes.

  5. Revealing Nucleic Acid Mutations Using Förster Resonance Energy Transfer-Based Probes.

    PubMed

    Junager, Nina P L; Kongsted, Jacob; Astakhova, Kira

    2016-01-01

    Nucleic acid mutations are of tremendous importance in modern clinical work, biotechnology and in fundamental studies of nucleic acids. Therefore, rapid, cost-effective and reliable detection of mutations is an object of extensive research. Today, Förster resonance energy transfer (FRET) probes are among the most often used tools for the detection of nucleic acids and in particular, for the detection of mutations. However, multiple parameters must be taken into account in order to create efficient FRET probes that are sensitive to nucleic acid mutations. In this review; we focus on the design principles for such probes and available computational methods that allow for their rational design. Applications of advanced, rationally designed FRET probes range from new insights into cellular heterogeneity to gaining new knowledge of nucleic acid structures directly in living cells. PMID:27472344

  6. Revealing Nucleic Acid Mutations Using Förster Resonance Energy Transfer-Based Probes

    PubMed Central

    Junager, Nina P. L.; Kongsted, Jacob; Astakhova, Kira

    2016-01-01

    Nucleic acid mutations are of tremendous importance in modern clinical work, biotechnology and in fundamental studies of nucleic acids. Therefore, rapid, cost-effective and reliable detection of mutations is an object of extensive research. Today, Förster resonance energy transfer (FRET) probes are among the most often used tools for the detection of nucleic acids and in particular, for the detection of mutations. However, multiple parameters must be taken into account in order to create efficient FRET probes that are sensitive to nucleic acid mutations. In this review; we focus on the design principles for such probes and available computational methods that allow for their rational design. Applications of advanced, rationally designed FRET probes range from new insights into cellular heterogeneity to gaining new knowledge of nucleic acid structures directly in living cells. PMID:27472344

  7. Development of time resolved fluorescence resonance energy transfer-based assay for FXR antagonist discovery.

    PubMed

    Yu, Donna D; Lin, Wenwei; Chen, Taosheng; Forman, Barry M

    2013-07-15

    FXR (farnesoid X receptor, NRIH4), a nuclear receptor, plays a major role in the control of cholesterol metabolism. FXR ligands have been investigated in preclinical studies for targeted therapy against metabolic diseases, but have shown limitations. Therefore, there is a need for new agonist or antagonist ligands of FXR, both for potential clinical applications, as well as to further elucidate its biological functions. Here we describe the use of the X-ray crystal structure of FXR complexed with the potent small molecule agonist GW4064 to design and synthesize a novel fluorescent, high-affinity probe (DY246) for time resolved fluorescence resonance energy transfer (TR-FRET) assays. We then used the TR-FRET assay for high throughput screening of a library of over 5000 bioactive compounds. From this library, we identified 13 compounds that act as putative FXR transcriptional antagonists.

  8. Fluorescent resonance energy transfer based detection of biological contaminants through hybrid quantum dot-quencher interactions.

    PubMed

    Ramadurai, D; Norton, E; Hale, J; Garland, J W; Stephenson, L D; Stroscio, M A; Sivananthan, S; Kumar, A

    2008-06-01

    A nanoscale sensor employing fluorescent resonance energy transfer interactions between fluorescent quantum dots (QDs) and organic quencher molecules can be used for the multiplexed detection of biological antigens in solution. Detection occurs when the antigens to be detected displace quencher-labelled inactivated (or dead) antigens of the same type attached to QD-antibody complexes through equilibrium reactions. This unquenches the QDs, allowing detection to take place through the observation of photoluminescence in solution or through the fluorescence imaging of unquenched QD complexes trapped on filter surfaces. Multiplexing can be accomplished by using several different sizes of QDs, with each size QD labelled with an antibody for a different antigen, providing the ability to detect several types of antigens or biological contaminants simultaneously in near real-time with high specificity and sensitivity.

  9. Revealing Nucleic Acid Mutations Using Förster Resonance Energy Transfer-Based Probes.

    PubMed

    Junager, Nina P L; Kongsted, Jacob; Astakhova, Kira

    2016-01-01

    Nucleic acid mutations are of tremendous importance in modern clinical work, biotechnology and in fundamental studies of nucleic acids. Therefore, rapid, cost-effective and reliable detection of mutations is an object of extensive research. Today, Förster resonance energy transfer (FRET) probes are among the most often used tools for the detection of nucleic acids and in particular, for the detection of mutations. However, multiple parameters must be taken into account in order to create efficient FRET probes that are sensitive to nucleic acid mutations. In this review; we focus on the design principles for such probes and available computational methods that allow for their rational design. Applications of advanced, rationally designed FRET probes range from new insights into cellular heterogeneity to gaining new knowledge of nucleic acid structures directly in living cells.

  10. Hybrid aptamer-antibody linked fluorescence resonance energy transfer based detection of trinitrotoluene.

    PubMed

    Sabherwal, Priyanka; Shorie, Munish; Pathania, Preeti; Chaudhary, Shilpa; Bhasin, K K; Bhalla, Vijayender; Suri, C Raman

    2014-08-01

    Combining synthetic macromolecules and biomolecular recognition units are promising in developing novel diagnostic and analysis techniques for detecting environmental and/or clinically important substances. Fluorescence resonance energy transfer (FRET) apta-immunosensor for explosive detection is reported using 2,4,6-trinitrotoluene (TNT) specific aptamer and antibodies tagged with respective FRET pair dyes in a sandwich immunoassay format. FITC-labeled aptamer was used as a binder molecule in the newly developed apta-immunoassay format where the recognition element was specific anti-TNT antibody labeled with rhodamine isothiocyanate. The newly developed sensing platform showed excellent sensitivity with a detection limit of the order of 0.4 nM presenting a promising candidate for routine screening of TNT in samples.

  11. Visualization of small GTPase activity with fluorescence resonance energy transfer-based biosensors.

    PubMed

    Aoki, Kazuhiro; Matsuda, Michiyuki

    2009-01-01

    Small GTPases act as molecular switches that regulate a variety of cellular functions, such as proliferation, cell movement and vesicle trafficking. Genetically encoded biosensors based on the principle of fluorescence resonance energy transfer (FRET) can visualize a spatio-temporal activity of small GTPases in living cells, thereby helping us to understand the role of small GTPases intuitively and vividly. Here we describe protocols of live cell imaging with the FRET biosensors. There are several types of FRET biosensors; this protocol focuses on intramolecular or unimolecular FRET biosensors of small GTPases that are made up of donor and acceptor fluorescence proteins, a small GTPase, its binding partner, and, if necessary, a subcellular localization signal. These FRET biosensors uncover the spatio-temporal activity of the small GTPases in living cells, which could not be obtained by conventional biochemical methods. Preparation of FRET biosensors and cell culture takes 6 d. Imaging and processing take 3-4 d to complete.

  12. Upconversion luminescence resonance energy transfer-based aptasensor for the sensitive detection of oxytetracycline.

    PubMed

    Zhang, Hui; Fang, Congcong; Wu, Shijia; Duan, Nuo; Wang, Zhouping

    2015-11-15

    In this work, a biosensor based on luminescence resonance energy transfer (LRET) from NaYF4:Yb,Tm upconversion nanoparticles (UCNPs) to SYBR Green I has been developed. The aptamers are covalently linked to UCNPs and hybridized with their complementary strands. The subsequent addition of SYBR Green allows SYBR Green I to insert into the formed double-stranded DNA (dsDNA) duplex and brings the energy donor and acceptor into close proximity, leading to the fluorescence of UCNPs transferred to SYBR Green I. When excited at 980 nm, the UCNPs emit luminescence at 477 nm, and this energy is transferred to SYBR Green I, which emits luminescence at 530 nm. In the presence of oxytetracycline (OTC), the aptamers prefer to bind to its corresponding analyte and dehybridize with the complementary DNA. This dehybridization leads to the liberation of SYBR Green I, which distances SYBR Green I from the UCNPs and recovers the UCNPs' luminescence. Under optimal conditions, a linear calibration is obtained between the ratio of I530 to I477 nm (I530/I477) and the OTC concentration, which ranges from 0.1 to 10 ng/ml with a limit of detection (LOD) of 0.054 ng/ml. PMID:26302361

  13. Upconversion luminescence resonance energy transfer-based aptasensor for the sensitive detection of oxytetracycline.

    PubMed

    Zhang, Hui; Fang, Congcong; Wu, Shijia; Duan, Nuo; Wang, Zhouping

    2015-11-15

    In this work, a biosensor based on luminescence resonance energy transfer (LRET) from NaYF4:Yb,Tm upconversion nanoparticles (UCNPs) to SYBR Green I has been developed. The aptamers are covalently linked to UCNPs and hybridized with their complementary strands. The subsequent addition of SYBR Green allows SYBR Green I to insert into the formed double-stranded DNA (dsDNA) duplex and brings the energy donor and acceptor into close proximity, leading to the fluorescence of UCNPs transferred to SYBR Green I. When excited at 980 nm, the UCNPs emit luminescence at 477 nm, and this energy is transferred to SYBR Green I, which emits luminescence at 530 nm. In the presence of oxytetracycline (OTC), the aptamers prefer to bind to its corresponding analyte and dehybridize with the complementary DNA. This dehybridization leads to the liberation of SYBR Green I, which distances SYBR Green I from the UCNPs and recovers the UCNPs' luminescence. Under optimal conditions, a linear calibration is obtained between the ratio of I530 to I477 nm (I530/I477) and the OTC concentration, which ranges from 0.1 to 10 ng/ml with a limit of detection (LOD) of 0.054 ng/ml.

  14. Upconversion fluorescence resonance energy transfer based biosensor for ultrasensitive detection of matrix metalloproteinase-2 in blood.

    PubMed

    Wang, Yuhui; Shen, Pei; Li, Chunya; Wang, Yanying; Liu, Zhihong

    2012-02-01

    Matrix metalloproteinase-2 (MMP-2) is a very important biomarker in blood. Presently, sensitive and selective determination of MMP-2 directly in blood samples is still a challenging job because of the high complexity of the sample matrix. In this work, we reported a new homogeneous biosensor for MMP-2 based on fluorescence resonance energy transfer (FRET) from upconversion phosphors (UCPs) to carbon nanoparticles (CNPs). A polypeptide chain (NH(2)-GHHYYGPLGVRGC-COOH) comprising both the specific MMP-2 substrate domain (PLGVR) and a π-rich motif (HHYY) was designed and linked to the surface of UCPs at the C terminus. The FRET process was initiated by the π-π interaction between the peptide and CNPs, which thus quenched the fluorescence of the donor. Upon the cleavage of the substrate by the protease at the amide bond between Gly and Val, the donor was separated from the acceptor while the π-rich motif stayed on the acceptor. As a result, the fluorescence of the donor was restored. The fluorescence recovery was found to be proportional to the concentration of MMP-2 within the range from 10-500 pg/mL in an aqueous solution. The quantification limit of this sensor was at least 1 order of magnitude lower than that of other reported assays for MMP-2. The sensor was used to determine the MMP-2 level directly in human plasma and whole blood samples with satisfactory results obtained. Owing to the hypersensitivity of the method, clinical samples of only less than 1 μL were needed for accurate quantification, which can be meaningful in MMP-2-related clinical and bioanalytical applications.

  15. Assessing Gonadotropin Receptor Function by Resonance Energy Transfer-Based Assays

    PubMed Central

    Ayoub, Mohammed Akli; Landomiel, Flavie; Gallay, Nathalie; Jégot, Gwenhael; Poupon, Anne; Crépieux, Pascale; Reiter, Eric

    2015-01-01

    Gonadotropin receptors belong to the super family of G protein-coupled receptors and mediate the physiological effects of follicle-stimulating hormone (FSHR) and luteinizing hormone (LHR). Their central role in the control of reproductive function has made them the focus of intensive studies. Upon binding to their cognate hormone, they trigger complex signaling and trafficking mechanisms that are tightly regulated in concentration, time, and space. Classical cellular assays often fail to capture all these dynamics. Here, we describe the use of various bioluminescence and fluorescence resonance energy transfer (BRET and FRET) assays to investigate the activation and regulation of FSHR and LHR in real-time, in living cells (i.e., transiently expressed in human embryonic kidney 293 cells). Indeed, the dynamics of hormone-mediated heterotrimeric G protein activation, cyclic adenosine-monophosphate (cAMP) production, calcium release, β-arrestin 2 recruitment, and receptor internalization/recycling was assessed. Kinetics and dose–response analyses confirmed the expected pharmacological and signaling properties of hFSHR and hLHR but revealed interesting characteristics when considering the two major pathways (cAMP and β-arrestin 2) of the two receptors assessed by BRET. Indeed, the EC50 values were in picomolar range for cAMP production while nanomolar range was observed for β-arrestin 2 recruitment as well as receptor internalization. Interestingly, the predicted receptor occupancy indicates that the maximal G protein activation and cAMP response occur at <10% of receptor occupancy whereas >90% of activated receptors is required to achieve full β-arrestin 2 recruitment and subsequent receptor internalization. The rapid receptor internalization was also followed by a recycling phase. Collectively, our data reveal that β-arrestin-mediated desensitization, internalization, and the subsequent fast recycling of receptors at the plasma membrane may provide a mechanistic

  16. Förster resonance energy transfer-based sensor targeting endoplasmic reticulum reveals highly oxidative environment

    PubMed Central

    Kolossov, Vladimir L; Leslie, Matthew T; Chatterjee, Abhishek; Sheehan, Bridget M; Kenis, Paul J A; Gaskins, H Rex

    2012-01-01

    The glutathione thiol/disulfide couple is the major redox buffer in the endoplasmic reticulum (ER); however, mechanisms by which it contributes to the tightly regulated redox environment of this intracellular organelle are poorly understood. The recent development of genetically encoded, ratiometric, single green fluorescent protein-based redox-sensitive (roGFP) sensors adjusted for more oxidative environments enables non-invasive measurement of the ER redox environment in living cells. In turn, Förster resonance energy transfer (FRET) sensors based on two fluorophore probes represent an alternative strategy for ratiometric signal acquisition. In previous work, we described the FRET-based redox sensor CY-RL7 with a relatively high midpoint redox potential of −143 mV, which is required for monitoring glutathione potentials in the comparatively high oxidative environment of the ER. Here, the efficacy of the CY-RL7 probe was ascertained in the cytosol and ER of live cells with fluorescence microscopy and flow cytometry. The sensor was found to be fully reduced at steady state in the cytosol and became fully oxidized in response to treatment with 1-chloro-2,4-dinitrobenzene, a depletor of reduced glutathione (GSH). In contrast, the probe was strongly oxidized (88%) upon expression in the ER of cultured cells. We also examined the responsiveness of the ER sensor to perturbations in cellular glutathione homeostasis. We observed that the reductive level of the FRET sensor was increased two-fold to about 28% in cells pretreated with N-acetylcysteine, a substrate for GSH synthesis. Finally, we evaluated the responsiveness of CY-RL7 and roGFP1-iL to various perturbations of cellular glutathione homeostasis to address the divergence in the specificity of these two probes. Together, the present data generated with genetically encoded green fluorescent protein (GFP)-based glutathione probes highlight the complexity of the ER redox environment and indicate that the ER

  17. Novel fluorescence resonance energy transfer-based reporter reveals differential calcineurin activation in neonatal and adult cardiomyocytes.

    PubMed

    Bazzazi, Hojjat; Sang, Lingjie; Dick, Ivy E; Joshi-Mukherjee, Rosy; Yang, Wanjun; Yue, David T

    2015-09-01

    Novel fluorescence resonance energy transfer-based genetically encoded reporters of calcineurin are constructed by fusing the two subunits of calcineurin with P2A-based linkers retaining the expected native conformation of calcineurin. Calcineurin reporters display robust responses to calcium transients in HEK293 cells. The sensor responses are correlated with NFATc1 translocation dynamics in HEK293 cells. The sensors are uniformly distributed in neonatal myocytes and respond efficiently to single electrically evoked calcium transients and show cumulative activation at frequencies of 0.5 and 1 Hz. In adult myocytes, the calcineurin sensors appear to be localized to the cardiac z-lines, and respond to cumulative calcium transients at frequencies of 0.5 and 1 Hz. The phosphatase calcineurin is a central component of many calcium signalling pathways, relaying calcium signals from the plasma membrane to the nucleus. It has critical functions in a multitude of systems, including immune, cardiac and neuronal. Given the widespread importance of calcineurin in both normal and pathological conditions, new tools that elucidate the spatiotemporal dynamics of calcineurin activity would be invaluable. Here we develop two separate genetically encoded fluorescence resonance energy transfer (FRET)-based sensors of calcineurin activation, DuoCaN and UniCaN. Both sensors showcase a large dynamic range and rapid response kinetics, differing primarily in the linker structure between the FRET pairs. Both sensors were calibrated in HEK293 cells and their responses correlated well with NFAT translocation to the nucleus, validating the biological relevance of the sensor readout. The sensors were subsequently expressed in neonatal rat ventricular myocytes and acutely isolated adult guinea pig ventricular myocytes. Both sensors demonstrated robust responses in myocytes and revealed kinetic differences in calcineurin activation during changes in pacing rate for neonatal versus adult myocytes

  18. Novel fluorescence resonance energy transfer-based reporter reveals differential calcineurin activation in neonatal and adult cardiomyocytes.

    PubMed

    Bazzazi, Hojjat; Sang, Lingjie; Dick, Ivy E; Joshi-Mukherjee, Rosy; Yang, Wanjun; Yue, David T

    2015-09-01

    Novel fluorescence resonance energy transfer-based genetically encoded reporters of calcineurin are constructed by fusing the two subunits of calcineurin with P2A-based linkers retaining the expected native conformation of calcineurin. Calcineurin reporters display robust responses to calcium transients in HEK293 cells. The sensor responses are correlated with NFATc1 translocation dynamics in HEK293 cells. The sensors are uniformly distributed in neonatal myocytes and respond efficiently to single electrically evoked calcium transients and show cumulative activation at frequencies of 0.5 and 1 Hz. In adult myocytes, the calcineurin sensors appear to be localized to the cardiac z-lines, and respond to cumulative calcium transients at frequencies of 0.5 and 1 Hz. The phosphatase calcineurin is a central component of many calcium signalling pathways, relaying calcium signals from the plasma membrane to the nucleus. It has critical functions in a multitude of systems, including immune, cardiac and neuronal. Given the widespread importance of calcineurin in both normal and pathological conditions, new tools that elucidate the spatiotemporal dynamics of calcineurin activity would be invaluable. Here we develop two separate genetically encoded fluorescence resonance energy transfer (FRET)-based sensors of calcineurin activation, DuoCaN and UniCaN. Both sensors showcase a large dynamic range and rapid response kinetics, differing primarily in the linker structure between the FRET pairs. Both sensors were calibrated in HEK293 cells and their responses correlated well with NFAT translocation to the nucleus, validating the biological relevance of the sensor readout. The sensors were subsequently expressed in neonatal rat ventricular myocytes and acutely isolated adult guinea pig ventricular myocytes. Both sensors demonstrated robust responses in myocytes and revealed kinetic differences in calcineurin activation during changes in pacing rate for neonatal versus adult myocytes

  19. Advantages of substituting bioluminescence for fluorescence in a resonance energy transfer-based periplasmic binding protein biosensor.

    PubMed

    Dacres, Helen; Michie, Michelle; Anderson, Alisha; Trowell, Stephen C

    2013-03-15

    A genetically encoded maltose biosensor was constructed, comprising maltose binding protein (MBP) flanked by a green fluorescent protein (GFP(2)) at the N-terminus and a Renilla luciferase variant (RLuc2) at the C-terminus. This Bioluminescence resonance energy transfer(2) (BRET(2)) system showed a 30% increase in the BRET ratio upon maltose binding, compared with a 10% increase with an equivalent fluorescence resonance energy transfer (FRET) biosensor. BRET(2) provides a better matched Förster distance to the known separation of the N and C termini of MBP than FRET. The sensor responded to maltose and maltotriose and the response was completely abolished by introduction of a single point mutation in the BRET(2) tagged MBP protein. The half maximal effective concentration (EC(50)) was 0.37 μM for maltose and the response was linear over almost three log units ranging from 10nM to 3.16 μM maltose for the BRET(2) system compared to an EC(50) of 2.3 μM and a linear response ranging from 0.3 μM to 21.1 μM for the equivalent FRET-based biosensor. The biosensor's estimate of maltose in beer matched that of a commercial enzyme-linked assay but was quicker and more precise, demonstrating its applicability to real-world samples. A similar BRET(2)-based transduction scheme approach would likely be applicable to other binding proteins that have a "venus-fly-trap" mechanism.

  20. Visualization of ATP levels inside single living cells with fluorescence resonance energy transfer-based genetically encoded indicators.

    PubMed

    Imamura, Hiromi; Nhat, Kim P Huynh; Togawa, Hiroko; Saito, Kenta; Iino, Ryota; Kato-Yamada, Yasuyuki; Nagai, Takeharu; Noji, Hiroyuki

    2009-09-15

    Adenosine 5'-triphosphate (ATP) is the major energy currency of cells and is involved in many cellular processes. However, there is no method for real-time monitoring of ATP levels inside individual living cells. To visualize ATP levels, we generated a series of fluorescence resonance energy transfer (FRET)-based indicators for ATP that were composed of the epsilon subunit of the bacterial F(o)F(1)-ATP synthase sandwiched by the cyan- and yellow-fluorescent proteins. The indicators, named ATeams, had apparent dissociation constants for ATP ranging from 7.4 muM to 3.3 mM. By targeting ATeams to different subcellular compartments, we unexpectedly found that ATP levels in the mitochondrial matrix of HeLa cells are significantly lower than those of cytoplasm and nucleus. We also succeeded in measuring changes in the ATP level inside single HeLa cells after treatment with inhibitors of glycolysis and/or oxidative phosphorylation, revealing that glycolysis is the major ATP-generating pathway of the cells grown in glucose-rich medium. This was also confirmed by an experiment using oligomycin A, an inhibitor of F(o)F(1)-ATP synthase. In addition, it was demonstrated that HeLa cells change ATP-generating pathway in response to changes of nutrition in the environment.

  1. Fluorescence Resonance Energy Transfer-Based Intracellular Assay for the Conformation of Hepatitis C Virus Drug Target NS5A

    PubMed Central

    Bhattacharya, Dipankar; Ansari, Israrul H.; Mehle, Andrew

    2012-01-01

    Nonstructural protein 5A (NS5A) is essential for hepatitis C virus (HCV) replication and assembly and is a critical drug target. Biochemical data suggest large parts of NS5A are unfolded as an isolated protein, but little is known about its folded state in the cell. We used fluorescence resonance energy transfer (FRET) to probe whether or not different regions of NS5A are in close proximity within the cell. Twenty-three separate reporter constructs were created by inserting one or more fluorophores into different positions throughout the three domains of NS5A. FRET efficiency was maximal when donor and acceptor fluorophores were positioned next to each other but also could be observed when the two fluorophores flanked NS5A domain 1 or domain 3. Informatic and biochemical analysis suggests that large portions of the carboxy terminus of NS5A are in an unfolded and disordered state. Quercetin, a natural product known to disrupt NS5A function in cells, specifically disrupted a conformationally specific domain 3 FRET signal. Intermolecular FRET indicated that the NS5A amino termini, but not other regions, are in close proximity in multimeric complexes. Overall, this assay provides a new window on the intracellular conformation(s) of NS5A and how the conformation changes in response to cellular and viral components of the replication and assembly complex as well as antiviral drugs. PMID:22623794

  2. Continuous Monitoring of Specific mRNA Expression Responses with a Fluorescence Resonance Energy Transfer-Based DNA Nano-tweezer Technique That Does Not Require Gene Recombination.

    PubMed

    Shigeto, Hajime; Nakatsuka, Keisuke; Ikeda, Takeshi; Hirota, Ryuichi; Kuroda, Akio; Funabashi, Hisakage

    2016-08-16

    This letter discusses the feasibility of continuously monitoring specific mRNA expression responses in a living cell with a probe structured as a fluorescence resonance energy transfer (FRET)-based DNA nano-tweezer (DNA-NT). The FRET-based DNA-NT, self-assembled from three single-stranded DNAs, alters its structure from an open state to a closed state in recognition of a target mRNA, resulting in the closing of the distal relation of previously modified FRET-paired fluorescent dyes and generating a FRET signal. The expressions of glucose transporters (GLUT) 1 and 4 in a mouse hepato-carcinoma (Hepa 1-6 cells) were selected as the target model. Live-cell imaging analysis of Hepa 1-6 cells with both FRET-based DNA-NTs indicated that the behaviors of the FRET signals integrated in each individual cell were similar to those measured with the conventional mass analysis technique of semiquantitative real-time (RT) polymerase chain reaction (PCR). From these results, it is concluded that continuous monitoring of gene expression response without gene recombination is feasible with a FRET-based DNA-NT, even in a single cell manner. PMID:27458920

  3. Noninvasive Evaluation of Heavy Metal Uptake and Storage in Micoralgae Using a Fluorescence Resonance Energy Transfer-Based Heavy Metal Biosensor1[C][W][OPEN

    PubMed Central

    Rajamani, Sathish; Torres, Moacir; Falcao, Vanessa; Ewalt Gray, Jaime; Coury, Daniel A.; Colepicolo, Pio; Sayre, Richard

    2014-01-01

    We have developed a fluorescence resonance energy transfer (FRET)-based heavy metal biosensor for the quantification of bioavailable free heavy metals in the cytoplasm of the microalga Chlamydomonas reinhardtii. The biosensor is composed of an end-to-end fusion of cyan fluorescent protein (CFP), chicken metallothionein II (MT-II), and yellow fluorescent protein (YFP). In vitro measurements of YFP/CFP fluorescence emission ratios indicated that the addition of metals to the purified biosensor enhanced FRET between CFP and YFP, consistent with heavy metal-induced folding of MT-II. A maximum YFP/CFP FRET ratio of 2.8 was observed in the presence of saturating concentrations of heavy metals. The sensitivity of the biosensor was greatest for Hg2+ followed by Cd2+ ≈ Pb2+ > Zn2+ > Cu2+. The heavy metal biosensor was unresponsive to metals that do not bind to MT-II (Na+ and Mg2+). When expressed in C. reinhardtii, we observed a differential metal-dependent response to saturating external concentrations (1.6 mm) of heavy metals (Pb2+ > Cd2+) that was unlike that observed for the isolated biosensor (in vitro). Significantly, analysis of metal uptake kinetics indicated that equilibration of the cytoplasm with externally applied heavy metals occurred within seconds. Our results also indicated that algae have substantial buffering capacity for free heavy metals in their cytosol, even at high external metal concentrations. PMID:24368336

  4. Selective ligand activity at Nur/retinoid X receptor complexes revealed by dimer-specific bioluminescence resonance energy transfer-based sensors.

    PubMed

    Giner, Xavier C; Cotnoir-White, David; Mader, Sylvie; Lévesque, Daniel

    2015-10-01

    Retinoid X receptors (RXRs) play a role as master regulators because of their capacity to form heterodimers with other nuclear receptors (NRs). Accordingly, retinoid signaling is involved in multiple biologic processes, including development, cell differentiation, metabolism, and cell death. However, the role and function of RXRs in different heterodimer complexes remain unidentified, mainly because most RXR drugs (called rexinoids) are not selective of specific heterodimer complexes. The lack of selectivity strongly limits the use of rexinoids for specific therapeutic approaches. To better characterize rexinoids at specific NR complexes, we have developed and optimized luciferase (Luc) protein complementation(PCA)-based bioluminescence resonance energy transfer (BRET) assays that can directly measure recruitment of a coactivator (CoA) motif fused to yellow fluorescent protein (YFP) by specific NR dimers. To validate the assays, we compared rexinoid modulation of CoA recruitment by the RXR homodimer and by the heterodimers Nur77/RXR and Nurr1/RXR. Results revealed that some rexinoids display selective CoA recruitment activities with homo- or heterodimer complexes. In particular, SR11237 (BMS649) has stronger potency for recruitment of CoA motif and transcriptional activity with the heterodimer Nur77/RXR than other complexes. This technology should be useful in identifying new compounds with specificity for individual dimeric species formed by NRs.

  5. Poly(A)-targeting molecular beacons: fluorescence resonance energy transfer-based in vitro quantitation and time-dependent imaging in live cells.

    PubMed

    Kim, Min Young; Kim, Jisu; Hah, Sang Soo

    2012-10-15

    Quantitation of poly(A)-RNA, time-dependent visualization of intracellular poly(A)(+)-RNA localization in living mammalian cells, and time-resolved intracellular binding dynamics of molecular beacons at the single-molecule level using a fluorescence resonance energy transfer (FRET)-based molecular beacon are described. FRET-based molecular beacons were designed as poly(A)-targeting probes to be oligonucleotides that contained Cy5 and Cy3 fluorescent dyes at the strand ends and a poly(A)-targeting sequence inside the strand. Our ratiometric analysis using poly(A)-targeting probes allowed for highly specific and wide-ranging detection (from 1.25nM to 0.5μM) of poly(A)-RNA, as well as for determination of K(d) values, and revealed a distribution of the probe itself and localization of the target RNA sequence in cells. Furthermore, time-dependent FRET-mediated fluorescence changes at the single-molecule level caused by the folding-induced gradual conformation changes in live cells were observed.

  6. Fluorescence Resonance Energy Transfer-based Biosensor Composed of Nitrogen-doped Carbon Dots and Gold Nanoparticles for the Highly Sensitive Detection of Organophosphorus Pesticides.

    PubMed

    Gong, Nian Chun; Li, Yan Le; Jiang, Xi; Zheng, Xiao Fang; Wang, Ya Ya; Huan, Shuang Yan

    2016-01-01

    The present article reports a novel biosensor for organophosphorus pesticides based on fluorescence resonance energy transfer (FRET) between nitrogen-doped carbon dots (NC-dots) and gold nanoparticles (AuNPs). The effective NC-dots/AuNPs assembly through the Au-N interaction results in good fluorescence quenching. Active acetylcholinesterase (AChE) catalyzes the hydrolysis of acetylthiocholine into -SH containing thiocholine to replace the NC-dots and trigger the aggregation of AuNPs. In the presence of paraoxon, the activity of AChE is inhibited, and thus preventing the generation of thiocholine, causing fewer NC-dots to be replaced. As a consequence, the fluorescence intensity gradually decreases with increasing amount of paraoxon. This biosensor does not require any complex synthesis or modification, and the results show a wide detection range of from 10(-4) to 10(-9) g/L with a detection limit of 1.0 × 10(-9) g/L (3.6 × 10(-12) mol/L). Two linear response regions have been reported with a turning point at about 10(-6) g/L and three different factors that would influence the response behavior. These phenomena discussed in detail so as to explain the special response mechanism. PMID:27682399

  7. Noninvasive evaluation of heavy metal uptake and storage in micoralgae using a fluorescence resonance energy transfer-based heavy metal biosensor.

    PubMed

    Rajamani, Sathish; Torres, Moacir; Falcao, Vanessa; Ewalt Gray, Jaime; Coury, Daniel A; Colepicolo, Pio; Sayre, Richard

    2014-02-01

    We have developed a fluorescence resonance energy transfer (FRET)-based heavy metal biosensor for the quantification of bioavailable free heavy metals in the cytoplasm of the microalga Chlamydomonas reinhardtii. The biosensor is composed of an end-to-end fusion of cyan fluorescent protein (CFP), chicken metallothionein II (MT-II), and yellow fluorescent protein (YFP). In vitro measurements of YFP/CFP fluorescence emission ratios indicated that the addition of metals to the purified biosensor enhanced FRET between CFP and YFP, consistent with heavy metal-induced folding of MT-II. A maximum YFP/CFP FRET ratio of 2.8 was observed in the presence of saturating concentrations of heavy metals. The sensitivity of the biosensor was greatest for Hg2+ followed by Cd2+≈Pb2+>Zn2+>Cu2+. The heavy metal biosensor was unresponsive to metals that do not bind to MT-II (Na+ and Mg2+). When expressed in C. reinhardtii, we observed a differential metal-dependent response to saturating external concentrations (1.6 mm) of heavy metals (Pb2+>Cd2+) that was unlike that observed for the isolated biosensor (in vitro). Significantly, analysis of metal uptake kinetics indicated that equilibration of the cytoplasm with externally applied heavy metals occurred within seconds. Our results also indicated that algae have substantial buffering capacity for free heavy metals in their cytosol, even at high external metal concentrations.

  8. Energy Transfer Based Nanocomposite Scintillator for Radiation Detection

    NASA Astrophysics Data System (ADS)

    Aslam, Soha; Sahi, Sunil; Chen, Wei; Ma, Lun; Kenarangui, Rasool

    2014-09-01

    Scintillators are the materials that emit light upon irradiation with high energy radiation like X-ray or gamma-ray. Inorganic single crystal and organic (plastic and liquid) are the two most used scintillator types. Both of these scintillator kinds have advantages and disadvantages. Inorganic single crystals are expensive and difficult to grow in desire shape and size. Also, single crystal scintillator such as NaI and CsI are very hygroscopic. On the other hand, organic scintillators have low density which limits their applications in gamma spectroscopy. Due to high quantum yield and size dependent emission, nanoparticles have attracted interested in various field of research. Here, we have studies the nanoparticles for radiation detection. We have synthesized nanoparticles of Cerium fluoride (CeF3), Zinc Oxide (ZnO), Cadmium Telluride (CdTe), Copper complex and Zinc sulfide (ZnS). We have used Fluorescence Resonance Energy Transfer (FRET) principle to enhance the luminescence properties of nanocomposite scintillator. Nanocomposites scintillators are structurally characterized with X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). Optical properties are studied using Photoluminescence, UV-Visible and X-ray. Enhancements in the luminescence are observed under UV and X-ray excitation. Preliminary studies shows nanocomposite scintillators are promising for radiation detection. Scintillators are the materials that emit light upon irradiation with high energy radiation like X-ray or gamma-ray. Inorganic single crystal and organic (plastic and liquid) are the two most used scintillator types. Both of these scintillator kinds have advantages and disadvantages. Inorganic single crystals are expensive and difficult to grow in desire shape and size. Also, single crystal scintillator such as NaI and CsI are very hygroscopic. On the other hand, organic scintillators have low density which limits their applications in gamma spectroscopy. Due to high quantum

  9. Fluorescence Resonance Energy Transfer Based on Interaction of PII and PipX Proteins Provides a Robust and Specific Biosensor for 2-Oxoglutarate, a Central Metabolite and a Signaling Molecule.

    PubMed

    Chen, Hai-Lin; Bernard, Christophe S; Hubert, Pierre; My, Laetitia; Zhang, Cheng-Cai

    2013-12-26

    2-Oxoglutarate is a central metabolite and a signalling molecule in both prokaryotes and eukaryotes. The cellular levels of 2-oxoglutarate vary rapidly in response to environmental changes, but an easy and reliable approach is lacking for the measurement of 2-oxoglutarate. Here we report a biosensor of 2-oxoglutarate based on the 2-oxoglutarate-dependent dissociation of the PII-PipX protein complex from cyanobacteria. Fusions of PII and PipX to either CFP or YFP could form a complex and their interaction could be detected by FRET (Fluorescence Resonance Energy Transfer). Mutations in PII or PipX that affect their interaction strongly decrease the FRET signal. Furthermore, the FRET signal is negatively affected, in a specific and concentration-dependent manner, by the presence of 2-oxoglutarate. This 2-oxoglutarate biosensor responds specifically and rapidly to a large range of 2-oxoglutarate levels, and is highly robust under different conditions, including in bacterial cell extracts. We further used this biosensor to study the interaction between PII and its effectors, and our data indicate that excess in Mg(2+) ions is a key factor for PII to respond efficiently to an increase in 2-oxoglutarate levels. This study paves the way for probing the dynamics of 2-oxoglutarate in various organisms and provides a valuable tool for the understanding of the molecular mechanism in metabolic regulation. PMID:24373496

  10. Wireless power transfer based on magnetic quadrupole coupling in dielectric resonators

    NASA Astrophysics Data System (ADS)

    Song, Mingzhao; Iorsh, Ivan; Kapitanova, Polina; Nenasheva, Elizaveta; Belov, Pavel

    2016-01-01

    We numerically investigate a magnetic resonant wireless power transfer system based on high refractive index dielectric resonators. We propose to operate at magnetic quadrupole mode of the resonators to enlarge the efficiency due to minimization of ohmic and radiation losses. Numerical estimation predicts the 80% efficiency of the wireless power transfer (WPT) system operating at quadrupole mode at 300 MHz. Moreover, the system operating at magnetic quadrupole mode is capable of transferring power with 70% efficiency when the receiver rotates 90°. We verify the simulated results by experimental investigation of the WPT system based on microwave ceramic resonators (ɛ = 80 and tanδ = 10-4).

  11. Magnetic resonance energy and topological resonance energy.

    PubMed

    Aihara, Jun-Ichi

    2016-04-28

    Ring-current diamagnetism of a polycyclic π-system is closely associated with thermodynamic stability due to the individual circuits. Magnetic resonance energy (MRE), derived from the ring-current diamagnetic susceptibility, was explored in conjunction with graph-theoretically defined topological resonance energy (TRE). For many aromatic molecules, MRE is highly correlative with TRE with a correlation coefficient of 0.996. For all π-systems studied, MRE has the same sign as TRE. The only trouble with MRE may be that some antiaromatic and non-alternant species exhibit unusually large MRE-to-TRE ratios. This kind of difficulty can in principle be overcome by prior geometry-optimisation or by changing spin multiplicity. Apart from the semi-empirical resonance-theory resonance energy, MRE is considered as the first aromatic stabilisation energy (ASE) defined without referring to any hypothetical polyene reference.

  12. Luminescence resonance energy transfer

    SciTech Connect

    Selvin, P.R.; Rana, T.M.; Hearst, J.E. Lawrence Berkeley Lab., CA )

    1994-06-29

    Fluorescence resonance energy transfer (FRET), in which a fluorescent donor molecule transfers energy via a nonradiative dipole-dipole interaction to an acceptor molecule (which is usually a fluorescent molecule), is a standard spectroscopic technique for measuring distances in the 10-70 Angstrom range. We have used a luminescent europium chelate as donor and an organic dye, CY-5, as acceptor. This luminescence resonance energy transfer (LRET) has several advantages over the more conventional FRET. The distance at which 50% of the energy is transferred (R[sub 0]) is large, 70 [angstrom]; the donor lifetime is single exponential and long (0.63 ms in H[sub 2]O; 2.5 ms in D[sub 2]O), making lifetime measurements facile and highly accurate; the orientation dependence (k[sup 2]) of energy transfer is minimized by the donor's multiple electronic transitions and long lifetime, limiting uncertainty in the measured distance due to orientation effects to [+-]12% in the worst case; the sensitized emission of the acceptor can be measured with little or no interfering background, yielding a >50-fold improvement in signal to background over standard donor-acceptor pairs and enabling distances several times R[sub 0] to be measured. 13 refs., 4 figs.

  13. A fluorescence energy transfer-based mechanical stress sensor for specific proteins in situ.

    PubMed

    Meng, Fanjie; Suchyna, Thomas M; Sachs, Frederick

    2008-06-01

    To measure mechanical stress in real time, we designed a fluorescence resonance energy transfer (FRET) cassette, denoted stFRET, which could be inserted into structural protein hosts. The probe was composed of a green fluorescence protein pair, Cerulean and Venus, linked with a stable alpha-helix. We measured the FRET efficiency of the free cassette protein as a function of the length of the linker, the angles of the fluorophores, temperature and urea denaturation, and protease treatment. The linking helix was stable to 80 degrees C, unfolded in 8 m urea, and rapidly digested by proteases, but in all cases the fluorophores were unaffected. We modified the alpha-helix linker by adding and subtracting residues to vary the angles and distance between the donor and acceptor, and assuming that the cassette was a rigid body, we calculated its geometry. We tested the strain sensitivity of stFRET by linking both ends to a rubber sheet subjected to equibiaxial stretch. FRET decreased proportionally to the substrate strain. The naked cassette expressed well in human embryonic kidney-293 cells and, surprisingly, was concentrated in the nucleus. However, when the cassette was located into host proteins such alpha-actinin, nonerythrocyte spectrin and filamin A, the labeled hosts expressed well and distributed normally in cell lines such as 3T3, where they were stressed at the leading edge of migrating cells and relaxed at the trailing edge. When collagen-19 was labeled near its middle with stFRET, it expressed well in Caenorhabditis elegans, distributing similarly to hosts labeled with a terminal green fluorescent protein, and the worms behaved normally. PMID:18479457

  14. Energy saver prototype accelerating resonator

    SciTech Connect

    Kerns, Q.; May, M.; Miller, H.W.; Reid, J.; Turkot, F.; Webber, R.; Wildman, D.

    1981-06-01

    A fixed frequency rf accelerating resonator has been built and tested for the Fermilab Energy Saver. The design parameters and prototype resonator test results are given. The resonator features a high permeability nickel alloy resistor which damps unwanted modes and corona rolls designed with the aid of the computer code SUPERFISH. In bench measurements, the prototype resonator has achieved peak accelerating voltages of 500 kV for a 1% duty cycle and cw operation at 360 kV. 4 refs.

  15. Exciton energy transfer-based quantum dot fluorescence sensing array: "chemical noses" for discrimination of different nucleobases.

    PubMed

    Liu, Jianbo; Li, Gui; Yang, Xiaohai; Wang, Kemin; Li, Li; Liu, Wei; Shi, Xing; Guo, Yali

    2015-01-20

    A novel exciton energy transfer-based fluorescence sensing array for the discrimination of different nucleobases was developed through target nucleobase-triggered self-assembly of quantum dots (QDs). Four QD nanoprobes with different ligand receptors, including mercaptoethylamine, N-acetyl-l-cysteine, 2-dimethyl-aminethanethiol, and thioglycolic acid, were created to detect and identify nucleobase targets. These QDs served as both selective recognition scaffolds and signal transduction elements for a biomolecule target. The extent of particle assembly, induced by the analyte-triggered self-assembly of QDs, led to an exciton energy transfer effect between interparticles that gave a readily detectable fluorescence quenching and distinct fluorescence response patterns. These patterns are characteristic for each nucleobase and can be quantitatively differentiated by linear discriminate analysis. Furthermore, a fingerprint-based barcode was established to conveniently discriminate the nucleobases. This pattern sensing was successfully used to identify nucleobase samples at unknown concentrations and five rare bases. In this "chemical noses" strategy, the robust characteristics of QD nanoprobes, coupled with the diversity of surface functionality that can be readily obtained using nanoparticles, provides a simple and label-free biosensing approach that shows great promise for biomedical applications. PMID:25495103

  16. Singlet oxygen triplet energy transfer-based imaging technology for mapping protein-protein proximity in intact cells.

    PubMed

    To, Tsz-Leung; Fadul, Michael J; Shu, Xiaokun

    2014-01-01

    Many cellular processes are carried out by large protein complexes that can span several tens of nanometres. Whereas forster resonance energy transfer has a detection range of <10 nm, here we report the theoretical development and experimental demonstration of a new fluorescence-imaging technology with a detection range of up to several tens of nanometres: singlet oxygen triplet energy transfer. We demonstrate that our method confirms the topology of a large protein complex in intact cells, which spans from the endoplasmic reticulum to the outer mitochondrial membrane and the matrix. This new method is thus suited for mapping protein proximity in large protein complexes.

  17. Singlet oxygen Triplet Energy Transfer based imaging technology for mapping protein-protein proximity in intact cells

    PubMed Central

    To, Tsz-Leung; Fadul, Michael J.; Shu, Xiaokun

    2014-01-01

    Many cellular processes are carried out by large protein complexes that can span several tens of nanometers. Whereas Forster resonance energy transfer has a detection range of <10 nm, here we report the theoretical development and experimental demonstration of a new fluorescence imaging technology with a detection range of up to several tens of nanometers: singlet oxygen triplet energy transfer. We demonstrate that our method confirms the topology of a large protein complex in intact cells, which spans from the endoplasmic reticulum to the outer mitochondrial membrane and the matrix. This new method is thus suited for mapping protein proximity in large protein complexes. PMID:24905026

  18. Energy transfer based emission analysis of (Tb³⁺, Sm³⁺): lithium zinc phosphate glasses.

    PubMed

    Reddy, C Parthasaradhi; Naresh, V; Ramaraghavulu, R; Rudramadevi, B H; Reddy, K T Ramakrishna; Buddhudu, S

    2015-06-01

    The present paper reports on the results pertaining to photoluminescence properties of Tb(3+), Sm(3+) and energy transfer from Tb(3+) to Sm(3+) ions in lithium zinc phosphate (LZP) glass matrix prepared by melt quenching method. Besides photoluminescence studies thermal stability for the LZP glass is also evaluated from TG-DTA measurement. Tb(3+) doped glasses have exhibited a prominent green emission at 547 nm assigned to (5)D4→(7)F5 transitions on exciting at λ(exci)=377 nm. The quenching phenomenon in Tb(3+) emission on varying its concentration has been discussed from cross-relaxations. Sm(3+) incorporated glasses have shown strong orange emission at 603 nm assigned to (4)G5/2→(6)H7/2 transition upon exciting with λ(exci)=404 nm. The possibility of energy transfer process taking place between these two ions is understood from the significant spectral overlap of Sm(3+) absorption and Tb(3+) emission. Migration of excitation energy from Tb(3+) ions to Sm(3+) ions at λ(exci)=375 nm is evaluated from the emission spectra of (0.5 mol.% Tb(3+)+(0.5-2.0 mol.%) Sm(3+)) co-doped glasses. The emission intensity of Sm(3+) has enhanced while Tb(3+) emission intensity decreased with an increase in Sm(3+) concentration suggesting the occurrence of energy transfer through cross-relaxations from Tb(3+) ((5)D4) to Sm(3+) ((4)G5/2). The mechanism behind energy transfer process has been further explained from energy level diagram, decay profiles and confirmed by calculating energy transfer parameters (energy transfer efficiency (η) and energy transfer probability (P)) of co-doped glasses. The dipole-dipole interaction is found to be more responsible for energy transfer Tb(3+) ((5)D4) to Sm(3+) ((4)G5/2) ions in LZP glass matrix.

  19. Engineering interfacial photo-induced charge transfer based on nanobamboo array architecture for efficient solar-to-chemical energy conversion.

    PubMed

    Wang, Xiaotian; Liow, Chihao; Bisht, Ankit; Liu, Xinfeng; Sum, Tze Chien; Chen, Xiaodong; Li, Shuzhou

    2015-04-01

    Engineering interfacial photo-induced charge transfer for highly synergistic photocatalysis is successfully realized based on nanobamboo array architecture. Programmable assemblies of various components and heterogeneous interfaces, and, in turn, engineering of the energy band structure along the charge transport pathways, play a critical role in generating excellent synergistic effects of multiple components for promoting photocatalytic efficiency. PMID:25704499

  20. Engineering interfacial photo-induced charge transfer based on nanobamboo array architecture for efficient solar-to-chemical energy conversion.

    PubMed

    Wang, Xiaotian; Liow, Chihao; Bisht, Ankit; Liu, Xinfeng; Sum, Tze Chien; Chen, Xiaodong; Li, Shuzhou

    2015-04-01

    Engineering interfacial photo-induced charge transfer for highly synergistic photocatalysis is successfully realized based on nanobamboo array architecture. Programmable assemblies of various components and heterogeneous interfaces, and, in turn, engineering of the energy band structure along the charge transport pathways, play a critical role in generating excellent synergistic effects of multiple components for promoting photocatalytic efficiency.

  1. Energy transfer based photoluminescence properties of (Sm3+ + Eu3+):PEO + PVP polymer films for Red luminescent display device applications

    NASA Astrophysics Data System (ADS)

    Naveen Kumar, K.; Vijayalakshmi, L.; Ratnakaram, Y. C.

    2015-07-01

    Eu3+:PEO + PVP, Sm3+:PEO + PVP and co-doped Sm3+ + Eu3+:PEO + PVP polymer films have successfully been synthesized by solution casting method. For these polymer films, their XRD, FTIR and RAMAN spectral profiles were studied systematically. Both absorption and photoluminescence spectra have been assessed by evaluating their optical properties. The Sm3+:PEO + PVP and Eu3+:PEO + PVP polymer film has displayed a reddish-orange and red emissions at 596 nm and 619 nm respectively under an UV lamp. A reddish-orange emission was found for Sm3+:PEO + PVP polymer film at 596 nm (4G5/2 → 6H7/2) and its lifetime has also been evaluated suitably. Red emission at 619 nm (4G5/2 → 6H7/2) of Eu3+ has been identified for Eu3+:PEO + PVP polymer film and its lifetime are also evaluated. The photoluminescence efficiency of Eu3+ ion has been enhanced due to the addition of Sm3+ by means of an energy transfer process. The energy transfer mechanism, from Sm3+ to Eu3+ has been clearly established. At 0.1 wt% concentration of Sm3+ ions (sensitizer), the photoluminescence efficiency of the Eu3+ ion (activator) has been significantly enhanced in co-doped sample through energy transfer from Sm3+ to Eu3+ in the polymer matrix. The energy transfer process has been analyzed using lifetime decay dynamics. From the obtained results, these polymer materials could be proposed as potential Red luminescent optical materials.

  2. Internal resonance for nonlinear vibration energy harvesting

    NASA Astrophysics Data System (ADS)

    Cao, D. X.; Leadenham, S.; Erturk, A.

    2015-11-01

    The transformation of waste vibration energy into low-power electricity has been heavily researched over the last decade to enable self-sustained wireless electronic components. Monostable and bistable nonlinear oscillators have been explored by several research groups in an effort to enhance the frequency bandwidth of operation. Linear two-degree-of-freedom (2-DOF) configurations as well as the combination of a nonlinear single-DOF harvester with a linear oscillator to constitute a nonlinear 2-DOF harvester have also been explored to develop broadband energy harvesters. In the present work, the concept of nonlinear internal resonance in a continuous frame structure is explored for broadband energy harvesting. The L-shaped beam-mass structure with quadratic nonlinearity was formerly studied in the nonlinear dynamics literature to demonstrate modal energy exchange and the saturation phenomenon when carefully tuned for two-to-one internal resonance. In the current effort, piezoelectric coupling and an electrical load are introduced, and electromechanical equations of the L-shaped energy harvester are employed to explore primary resonance behaviors around the first and the second linear natural frequencies for bandwidth enhancement. Simulations using approximate analytical frequency response equations as well as numerical solutions reveal significant bandwidth enhancement as compared to a typical linear 2-DOF counterpart. Vibration and voltage responses are explored, and the effects of various system parameters on the overall dynamics of the internal resonance-based energy harvesting system are reported.

  3. Theory of coherent resonance energy transfer

    SciTech Connect

    Jang, Seogjoo; Cheng, Y.-C.; Reichman, David R.; Eaves, Joel D.

    2008-09-14

    A theory of coherent resonance energy transfer is developed combining the polaron transformation and a time-local quantum master equation formulation, which is valid for arbitrary spectral densities including common modes. The theory contains inhomogeneous terms accounting for nonequilibrium initial preparation effects and elucidates how quantum coherence and nonequilibrium effects manifest themselves in the coherent energy transfer dynamics beyond the weak resonance coupling limit of the Foerster and Dexter (FD) theory. Numerical tests show that quantum coherence can cause significant changes in steady state donor/acceptor populations from those predicted by the FD theory and illustrate delicate cooperation of nonequilibrium and quantum coherence effects on the transient population dynamics.

  4. Energy localization in weakly dissipative resonant chains

    NASA Astrophysics Data System (ADS)

    Kovaleva, Agnessa

    2016-08-01

    Localization of energy in oscillator arrays has been of interest for a number of years, with special attention paid to the role of nonlinearity and discreteness in the formation of localized structures. This work examines a different type of energy localization arising due to the presence of dissipation in nonlinear resonance arrays. As a basic model, we consider a Klein-Gordon chain of finite length subjected to a harmonic excitation applied at an edge of the chain. It is shown that weak dissipation may be a key factor preventing the emergence of resonance in the entire chain, even if its nondissipative analog is entirely captured into resonance. The resulting process in the dissipative oscillator array represents large-amplitude resonant oscillations in a part of the chain adjacent to the actuator and small-amplitude oscillations in the distant part of the chain. The conditions of the emergence of resonance as well as the conditions of energy localization are derived. An agreement between the obtained analytical results and numerical simulations is demonstrated.

  5. Energy localization in weakly dissipative resonant chains.

    PubMed

    Kovaleva, Agnessa

    2016-08-01

    Localization of energy in oscillator arrays has been of interest for a number of years, with special attention paid to the role of nonlinearity and discreteness in the formation of localized structures. This work examines a different type of energy localization arising due to the presence of dissipation in nonlinear resonance arrays. As a basic model, we consider a Klein-Gordon chain of finite length subjected to a harmonic excitation applied at an edge of the chain. It is shown that weak dissipation may be a key factor preventing the emergence of resonance in the entire chain, even if its nondissipative analog is entirely captured into resonance. The resulting process in the dissipative oscillator array represents large-amplitude resonant oscillations in a part of the chain adjacent to the actuator and small-amplitude oscillations in the distant part of the chain. The conditions of the emergence of resonance as well as the conditions of energy localization are derived. An agreement between the obtained analytical results and numerical simulations is demonstrated. PMID:27627299

  6. Subwavelength resonant antennas enhancing electromagnetic energy harvesting

    NASA Astrophysics Data System (ADS)

    Oumbe Tekam, Gabin; Ginis, Vincent; Seetharamdoo, Divitha; Danckaert, Jan

    2016-04-01

    In this work, an electromagnetic energy harvester operating at microwave frequencies is designed based on a cut- wire metasurface. This metamaterial is known to contain a quasistatic electric dipole resonator leading to a strong resonant electric response when illuminated by electromagnetic fields.1 Starting from an equivalent electrical circuit, we analytically design the parameters of the system to tune the resonance frequency of the harvester at the desired frequency band. Subsequently, we compare these results with numerical simulations, which have been obtained using finite elements numerical simulations. Finally, we optimize the design by investigating the best arrangement for energy harvesting by coupling in parallel and in series many single layers of cut-wire metasurfaces. We also discuss the implementation of different geometries and sizes of the cut-wire metasurface for achieving different center frequencies and bandwidths.

  7. Classical approach to multichromophoric resonance energy transfer.

    PubMed

    Duque, Sebastián; Brumer, Paul; Pachón, Leonardo A

    2015-09-11

    A classical formulation of the quantum multichromophoric theory of resonance energy transfer is developed on the basis of classical electrodynamics. The theory allows for the identification of a variety of processes of different order in the interactions that contribute to the energy transfer in molecular aggregates with intracoupling in donors and acceptor chromophores. Enhanced rates in multichromophoric resonance energy transfer are shown to be well described by this theory. Specifically, in a coupling configuration between N_{A} acceptors and N_{D} donors, the theory correctly predicts an enhancement of the energy transfer rate dependent on the total number of donor-acceptor pairs. As an example, the theory, applied to the transfer rate in light harvesting II, gives results in excellent agreement with experiment. Finally, it is explicitly shown that as long as linear response theory holds, the classical multichromophoric theory formally coincides with the quantum formulation.

  8. Classical approach to multichromophoric resonance energy transfer.

    PubMed

    Duque, Sebastián; Brumer, Paul; Pachón, Leonardo A

    2015-09-11

    A classical formulation of the quantum multichromophoric theory of resonance energy transfer is developed on the basis of classical electrodynamics. The theory allows for the identification of a variety of processes of different order in the interactions that contribute to the energy transfer in molecular aggregates with intracoupling in donors and acceptor chromophores. Enhanced rates in multichromophoric resonance energy transfer are shown to be well described by this theory. Specifically, in a coupling configuration between N_{A} acceptors and N_{D} donors, the theory correctly predicts an enhancement of the energy transfer rate dependent on the total number of donor-acceptor pairs. As an example, the theory, applied to the transfer rate in light harvesting II, gives results in excellent agreement with experiment. Finally, it is explicitly shown that as long as linear response theory holds, the classical multichromophoric theory formally coincides with the quantum formulation. PMID:26406811

  9. Resonance energy transfer: Dye to metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Wari, M. N.; Pujar, G. H.; Inamdar, S. R.

    2015-06-01

    In the present study, surface energy transfer (SET) from Coumarin 540A (C540 A) to Gold nanoparticle (Au) is demonstrated. The observed results show pronounced effect on the photoluminescence intensity and shortening of the lifetime of Coumarin 540A upon interaction with the spherical gold nanoparticle, also there are measured effects on radiative rate of the dye. Experimental results are analyzed with fluorescence resonance energy transfer (FRET) and SET theories. The results obtained from distance-dependent quenching provide experimental evidence that the efficiency curve slope and distance of quenching is best modeled by surface energy transfer process.

  10. Resonance energy transfer: Dye to metal nanoparticles

    SciTech Connect

    Wari, M. N.; Pujar, G. H.; Inamdar, S. R.

    2015-06-24

    In the present study, surface energy transfer (SET) from Coumarin 540A (C540 A) to Gold nanoparticle (Au) is demonstrated. The observed results show pronounced effect on the photoluminescence intensity and shortening of the lifetime of Coumarin 540A upon interaction with the spherical gold nanoparticle, also there are measured effects on radiative rate of the dye. Experimental results are analyzed with fluorescence resonance energy transfer (FRET) and SET theories. The results obtained from distance-dependent quenching provide experimental evidence that the efficiency curve slope and distance of quenching is best modeled by surface energy transfer process.

  11. Resonant vibrational energy transfer in ice Ih

    SciTech Connect

    Shi, L.; Li, F.; Skinner, J. L.

    2014-06-28

    Fascinating anisotropy decay experiments have recently been performed on H{sub 2}O ice Ih by Timmer and Bakker [R. L. A. Timmer, and H. J. Bakker, J. Phys. Chem. A 114, 4148 (2010)]. The very fast decay (on the order of 100 fs) is indicative of resonant energy transfer between OH stretches on different molecules. Isotope dilution experiments with deuterium show a dramatic dependence on the hydrogen mole fraction, which confirms the energy transfer picture. Timmer and Bakker have interpreted the experiments with a Förster incoherent hopping model, finding that energy transfer within the first solvation shell dominates the relaxation process. We have developed a microscopic theory of vibrational spectroscopy of water and ice, and herein we use this theory to calculate the anisotropy decay in ice as a function of hydrogen mole fraction. We obtain very good agreement with experiment. Interpretation of our results shows that four nearest-neighbor acceptors dominate the energy transfer, and that while the incoherent hopping picture is qualitatively correct, vibrational energy transport is partially coherent on the relevant timescale.

  12. Magnetic Resonance Studies of Energy Storage Materials

    NASA Astrophysics Data System (ADS)

    Vazquez Reina, Rafael

    In today's society there is high demand to have access to energy for portable devices in different forms. Capacitors with high performance in small package to achieve high charge/discharge rates, and batteries with their ability to store electricity and make energy mobile are part of this demand. The types of internal dielectric material strongly affect the characteristics of a capacitor, and its applications. In a battery, the choice of the electrolyte plays an important role in the Solid Electrolyte Interphase (SEI) formation, and the cathode material for high output voltage. Electron Paramagnetic Resonance (EPR) and Nuclear Magnetic Resonance (NMR) spectroscopy are research techniques that exploit the magnetic properties of the electron and certain atomic nuclei to determine physical and chemical properties of the atoms or molecules in which they are contained. Both EPR and NMR spectroscopy technique can yield meaningful structural and dynamic information. Three different projects are discussed in this dissertation. First, High energy density capacitors where EPR measurements described herein provide an insight into structural and chemical differences in the dielectric material of a capacitor. Next, as the second project, Electrolyte solutions where an oxygen-17 NMR study has been employed to assess the degree of preferential solvation of Li+ ions in binary mixtures of EC (ethylene carbonate) and DMC (dimethyl carbonate) containing LiPF6 (lithium hexafluo-rophosphate) which may be ultimately related to the SEI formation mechanism. The third project was to study Bismuth fluoride as cathode material for rechargeable batteries. The objective was to study 19F and 7Li MAS NMR of some nanocomposite cathode materials as a conversion reaction occurring during lithiation and delithation of the BiF3/C nanocomposite.

  13. Fermi energy instability in resonant tunneling

    NASA Astrophysics Data System (ADS)

    Claro, Francisco; Inkoferer, Jutta; Obermeir, Gustav

    2001-03-01

    In resonant tunneling two different instabilities may arise induced by the electron-electron interaction, depending on whether the conduction channel is at the emitter Fermi energy, or at the bottom of the emitter Fermi sea. The latter leads to a well understood multistable regime in the device characteristics. The former was found in the past for the case when a magnetic field is present in the direction of the current flow*. We shall show that the external field is not required, and that actually the instability can take place in the presence of zero, one and two dimensional quantum wells. Supported in part by FONDECYT 1990425 and Catedra Presidencial en Ciencias *P.Orellana, E.Anda and F.Claro, Phys.Rev.Lett. 79, 1118 (1997)

  14. Energy harvesting with coupled magnetostrictive resonators

    NASA Astrophysics Data System (ADS)

    Naik, Suketu; Phipps, Alex; In, Visarath; Cavaroc, Peyton; Matus-Vargas, Antonio; Palacios, Antonio; Gonzalez-Hernandez, H. G.

    2014-03-01

    We report the investigation of an energy harvesting system composed of coupled resonators with the magnetostrictive material Galfenol (FeGa). A coupled system of meso-scale (1-10 cm) cantilever beams for harvesting vibration energy is described for powering and aiding the performance of low-power wireless sensor nodes. Galfenol is chosen in this work for its durability, compared to the brittleness often encountered with piezoelectric materials, and high magnetomechanical coupling. A lumped model, which captures both the mechanical and electrical behavior of the individual transducers, is first developed. The values of the lumped element parameters are then derived empirically from fabricated beams in order to compare the model to experimental measurements. The governing equations of the coupled system lead to a system of differential equations with all-to-all coupling between transducers. An analysis of the system equations reveals different patterns of collective oscillations. Among the many different patterns, a synchronous state appears to yield the maximum energy that can be harvested by the system. Experiments on coupled system shows that the coupled system exhibits synchronization and an increment in the output power. Discussion of the required power converters is also included.

  15. Ratio-metric sensor to detect riboflavin via fluorescence resonance energy transfer with ultrahigh sensitivity

    NASA Astrophysics Data System (ADS)

    Wang, Jilong; Su, Siheng; Wei, Junhua; Bahgi, Roya; Hope-Weeks, Louisa; Qiu, Jingjing; Wang, Shiren

    2015-08-01

    In this paper, a novel fluorescence resonance energy transfer (FRET) ration-metric fluorescent probe based on heteroatom N, S doped carbon dots (N, S-CDs) was developed to determine riboflavin in aqueous solutions. The ratio of two emission intensities at different wavelengths is applied to determine the concentration of riboflavin (RF). This method is more effective in reducing the background interference and fluctuation of diverse conditions. Therefore, this probe obtains high sensitivity with a low limit of detection (LOD) of 1.9 nM (0.7 ng/ml) which is in the highest level of all riboflavin detection approaches and higher than single wavelength intensity detection (1.9 μM). In addition, this sensor has a high selectivity of detecting riboflavin in deionized water (pH=7) with other biochemical like amino acids. Moreover, riboflavin in aqueous solution is very sensitive to sunlight and can be degraded to lumiflavin, which is toxic. Because the N, S doped carbon dots cannot serve as an energy donor for N, S doped carbon dots and lumiflavin system, this system makes it easy to determine whether the riboflavin is degraded or not, which is first to be reported. This platform may provide possibilities to build a new and facile fluorescence resonance energy transfer based sensor to detect analytes and metamorphous analytes in aqueous solution.

  16. Effect of energy and momentum conservation on fluid resonances for resonant magnetic perturbations in a tokamak

    SciTech Connect

    Leitner, Peter; Heyn, Martin F.; Kernbichler, Winfried; Ivanov, Ivan B.; Kasilov, Sergei V.

    2014-06-15

    In this paper, the impact of momentum and energy conservation of the collision operator in the kinetic description for Resonant Magnetic Perturbations (RMPs) in a tokamak is studied. The particle conserving differential collision operator of Ornstein-Uhlenbeck type is supplemented with integral parts such that energy and momentum are conserved. The application to RMP penetration in a tokamak shows that energy conservation in the electron collision operator is important for the quantitative description of plasma shielding effects at the resonant surface. On the other hand, momentum conservation in the ion collision operator does not significantly change the results.

  17. Energy transfer based photoluminescence properties of co-doped (Er3+ + Pr3+): PEO + PVP blended polymer composites for photonic applications

    NASA Astrophysics Data System (ADS)

    Naveen Kumar, K.; Kang, Misook; Bhaskar Kumar, G.; Ratnakaram, Y. C.

    2016-04-01

    Er3+, Pr3+ singly doped and co-doped PEO + PVP polymer composites have been synthesized by conventional solution casting method. The structural analysis has been carried out for all these polymer composites from XRD analysis. Raman spectral studies confirm the ion-polymer interactions and polymer complex formation. Thermal properties of pure polymer film has also been clearly elucidated by TG/DTA profiles. Well defined optical absorption bands pertaining to Er3+ and Pr3+ are observed in the absorption spectral profile and these bands are assigned with corresponding electronic transitions. The polymer films containing singly doped Er3+ and Pr3+ ions have displayed green and red emissions at 510 nm (2H11/2 → 4I15/2) and 688 nm (3P0 → 3F3) respectively under UV excitation source. Comparing the emission spectra of singly Er3+ and co-doped Er3+ + Pr3+: PEO + PVP polymer films, a significant red emission pertaining to Pr3+ions is remarkably enhanced in co-doped polymer system. This could be ascribed to possible energy transfer from Er3+ to Pr3+ in co-doped polymer system. The energy transfer mechanism is clearly demonstrated using their emission performances, overlapped spectral profiles and also life time decay dynamics. Thus, it could be suggested that Er3+: PEO + PVP, Pr3+: PEO + PVP and (Er3+ + Pr3+): PEO + PVP blended polymer films are potential materials for several photonic applications.

  18. Ag nanoclusters could efficiently quench the photoresponse of CdS quantum dots for novel energy transfer-based photoelectrochemical bioanalysis.

    PubMed

    Zhang, Ling; Sun, Yue; Liang, Yan-Yu; He, Jian-Ping; Zhao, Wei-Wei; Xu, Jing-Juan; Chen, Hong-Yuan

    2016-11-15

    Herein the influence of ultrasmall Ag nanoclusters (Ag NCs) against CdS quantum dots (QDs) in a photoelectrochemical (PEC) nanosystem was exploited for the first time, based on which a novel PEC bioanalysis was successfully developed via the efficient quenching effect of Ag NCs against the CdS QDs. In a model system, DNA assay was achieved by using molecular beacon (MB) probes anchored on a CdS QDs modified electrode, and the MB probes contain two segments that can hybridize with both target DNA sequence and the label of DNA encapsulated Ag NCs. After the MB probe was unfolded by the target DNA sequence, the labels of oligonucleotide encapsulated Ag NCs would be brought in close proximity to the CdS QDs electrode surface, and efficient photocurrent quenching of QDs could be resulted from an energy transfer process that originated from NCs. Thus, by monitoring the attenuation in the photocurrent signal, an elegant and sensitive PEC DNA bioanalysis could be accomplished. The developed biosensor displayed a linear range from 1.0pM to 10nM and the detection limit was experimentally found to be of 0.3pM. This work presents a feasible signaling principle that could act as a common basis for general PEC bioanalysis development. PMID:27315518

  19. Ag nanoclusters could efficiently quench the photoresponse of CdS quantum dots for novel energy transfer-based photoelectrochemical bioanalysis.

    PubMed

    Zhang, Ling; Sun, Yue; Liang, Yan-Yu; He, Jian-Ping; Zhao, Wei-Wei; Xu, Jing-Juan; Chen, Hong-Yuan

    2016-11-15

    Herein the influence of ultrasmall Ag nanoclusters (Ag NCs) against CdS quantum dots (QDs) in a photoelectrochemical (PEC) nanosystem was exploited for the first time, based on which a novel PEC bioanalysis was successfully developed via the efficient quenching effect of Ag NCs against the CdS QDs. In a model system, DNA assay was achieved by using molecular beacon (MB) probes anchored on a CdS QDs modified electrode, and the MB probes contain two segments that can hybridize with both target DNA sequence and the label of DNA encapsulated Ag NCs. After the MB probe was unfolded by the target DNA sequence, the labels of oligonucleotide encapsulated Ag NCs would be brought in close proximity to the CdS QDs electrode surface, and efficient photocurrent quenching of QDs could be resulted from an energy transfer process that originated from NCs. Thus, by monitoring the attenuation in the photocurrent signal, an elegant and sensitive PEC DNA bioanalysis could be accomplished. The developed biosensor displayed a linear range from 1.0pM to 10nM and the detection limit was experimentally found to be of 0.3pM. This work presents a feasible signaling principle that could act as a common basis for general PEC bioanalysis development.

  20. DNA chips with conjugated polyelectrolytes in resonance energy transfer mode.

    PubMed

    Wigenius, Jens A; Magnusson, Karin; Björk, Per; Andersson, Olof; Inganäs, Olle

    2010-03-01

    We show how to use well-defined conjugated polyelectrolytes (CPEs) combined with surface energy patterning to fabricate DNA chips utilizing fluorescence signal amplification. Cholesterol-modified DNA strands in complex with a CPE are adsorbed to a surface energy pattern, formed by printing with soft elastomer stamps. Hybridization of the surface bound DNA strands with a short complementary strand from solution is monitored using both fluorescence microscopy and imaging surface plasmon resonance. The CPEs act as antennas, enhancing resonance energy transfer to the dye-labeled DNA when complementary hybridization of the double strand occurs.

  1. Cluster structure of a low-energy resonance in tetraneutron

    SciTech Connect

    Lashko, Yu. A. Filippov, G. F.

    2008-02-15

    We theoretically investigate the possibility for a tetraneutron to exist as a low-energy resonance state. We explore a microscopic model based on the assumption that the tetraneutron can be treated as a compound system, where {sup 3}n + n and {sup 2}n + {sup 2}n coupled cluster configurations coexist. The influence of the Pauli principle on the kinetic energy of the relative motion of the neutron clusters is shown to result in their attraction. The strength of such attraction is high enough to ensure the existence of a low-energy resonance in the tetraneutron, provided that the oscillator length is large enough.

  2. On the resonance energy of the strange dibaryon

    SciTech Connect

    Yoichi Ikeda, Hiroyuki Kamano, Toru Sato

    2010-03-01

    The three-body resonance energies of the strange dibaryon are studied with the View the MathML source coupled-channels Faddeev equations. Our resonance energies are compared with those of an effective potential approach (EPA), where a coupling to the πYN channel is simulated by an effective View the MathML source potential, and the spectator momentum in the πYN Green function is neglected. About a 30% reduction of the binding energies due to neglecting the spectator momentum in the πYN Green's function is observed.

  3. High Q diamond hemispherical resonators: fabrication and energy loss mechanisms

    NASA Astrophysics Data System (ADS)

    Bernstein, Jonathan J.; Bancu, Mirela G.; Bauer, Joseph M.; Cook, Eugene H.; Kumar, Parshant; Newton, Eric; Nyinjee, Tenzin; Perlin, Gayatri E.; Ricker, Joseph A.; Teynor, William A.; Weinberg, Marc S.

    2015-08-01

    We have fabricated polycrystalline diamond hemispheres by hot-filament CVD (HFCVD) in spherical cavities wet-etched into a high temperature glass substrate CTE matched to silicon. Hemispherical resonators 1.4 mm in diameter have a Q of up to 143 000 in the fundamental wineglass mode, for a ringdown time of 2.4 s. Without trimming, resonators have the two degenerate wineglass modes frequency matched as close as 2 Hz, or 0.013% of the resonant frequency (~16 kHz). Laser trimming was used to match resonant modes on hemispheres to 0.3 Hz. Experimental and FEA energy loss studies on cantilevers and hemispheres examine various energy loss mechanisms, showing that surface related losses are dominant. Diamond cantilevers with a Q of 400 000 and a ringdown time of 15.4 s were measured, showing the potential of polycrystalline diamond films for high Q resonators. These resonators show great promise for use as hemispherical resonant gyroscopes (HRGs) on a chip.

  4. Off-resonance energy absorption in a linear Paul trap due to mass selective resonant quenching.

    PubMed

    Sivarajah, I; Goodman, D S; Wells, J E; Narducci, F A; Smith, W W

    2013-11-01

    Linear Paul traps (LPT) are used in many experimental studies such as mass spectrometry, atom-ion collisions, and ion-molecule reactions. Mass selective resonant quenching (MSRQ) is implemented in LPT either to identify a charged particle's mass or to remove unwanted ions from a controlled experimental environment. In the latter case, MSRQ can introduce undesired heating to co-trapped ions of different mass, whose secular motion is off resonance with the quenching ac field, which we call off-resonance energy absorption (OREA). We present simulations and experimental evidence that show that the OREA increases exponentially with the number of ions loaded into the trap and with the amplitude of the off-resonance external ac field. PMID:24289382

  5. How resonance assists hydrogen bonding interactions: an energy decomposition analysis.

    PubMed

    Beck, John Frederick; Mo, Yirong

    2007-01-15

    Block-localized wave function (BLW) method, which is a variant of the ab initio valence bond (VB) theory, was employed to explore the nature of resonance-assisted hydrogen bonds (RAHBs) and to investigate the mechanism of synergistic interplay between pi delocalization and hydrogen-bonding interactions. We examined the dimers of formic acid, formamide, 4-pyrimidinone, 2-pyridinone, 2-hydroxpyridine, and 2-hydroxycyclopenta-2,4-dien-1-one. In addition, we studied the interactions in beta-diketone enols with a simplified model, namely the hydrogen bonds of 3-hydroxypropenal with both ethenol and formaldehyde. The intermolecular interaction energies, either with or without the involvement of pi resonance, were decomposed into the Hitler-London energy (DeltaEHL), polarization energy (DeltaEpol), charge transfer energy (DeltaECT), and electron correlation energy (DeltaEcor) terms. This allows for the examination of the character of hydrogen bonds and the impact of pi conjugation on hydrogen bonding interactions. Although it has been proposed that resonance-assisted hydrogen bonds are accompanied with an increasing of covalency character, our analyses showed that the enhanced interactions mostly originate from the classical dipole-dipole (i.e., electrostatic) attraction, as resonance redistributes the electron density and increases the dipole moments in monomers. The covalency of hydrogen bonds, however, changes very little. This disputes the belief that RAHB is primarily covalent in nature. Accordingly, we recommend the term "resonance-assisted binding (RAB)" instead of "resonance-assisted hydrogen bonding (RHAB)" to highlight the electrostatic, which is a long-range effect, rather than the electron transfer nature of the enhanced stabilization in RAHBs. PMID:17143867

  6. Opto-fluidic ring resonator lasers based on highly efficient resonant energy transfer.

    PubMed

    Shopova, Siyka I; Cupps, Jay M; Zhang, Po; Henderson, Edward P; Lacey, Scott; Fan, Xudong

    2007-10-01

    We demonstrate an opto-fluidic ring resonator dye laser using highly efficient energy transfer. The active lasing material consists of a donor and acceptor mixture and flows in a fused silica capillary whose circular cross section forms a ring resonator and supports the whispering gallery modes (WGMs) of high Q-factors (>107). The excited states are created in the donor and transferred to the acceptor through the fluorescence resonant energy transfer (FRET), whose emission is coupled into the WGM. Due to the high energy transfer efficiency and high Q-factors, the acceptor exhibits a lasing threshold as low as 0.3 muJ/mm2. We further analyze the energy transfer mechanisms and find that non-radiative Förster transfer is the dominant effect to support the acceptor lasing. FRET lasers using cascade energy transfer and using quantum dots (QDs) as the donor are also presented. Our study will not only lead to development of novel microfluidic lasers with low lasing thresholds and excitation/emission flexibility, but also open an avenue for future laser intra-cavity bio/chemical sensing.

  7. Plasmon resonance energy transfer and plexcitonic solar cell.

    PubMed

    Nan, Fan; Ding, Si-Jing; Ma, Liang; Cheng, Zi-Qiang; Zhong, Yu-Ting; Zhang, Ya-Fang; Qiu, Yun-Hang; Li, Xiaoguang; Zhou, Li; Wang, Qu-Quan

    2016-08-11

    Plasmon-mediated energy transfer is highly desirable in photo-electronic nanodevices, but the direct injection efficiency of "hot electrons" in plasmonic photo-detectors and plasmon-sensitized solar cells (plasmon-SSCs) is poor. On another front, Fano resonance induced by strong plasmon-exciton coupling provides an efficient channel of coherent energy transfer from metallic plasmons to molecular excitons, and organic dye molecules have a much better injection efficiency in exciton-SSCs than "hot electrons". Here, we investigate enhanced light-harvesting of chlorophyll-a molecules strongly coupled to Au nanostructured films via Fano resonance. The enhanced local field and plasmon resonance energy transfer are experimentally revealed by monitoring the ultrafast dynamical processes of the plexcitons and the photocurrent flows of the assembled plexciton-SSCs. By tuning the Fano factor and anti-resonance wavelengths, we find that the local field is largely enhanced and the efficiency of plexciton-SSCs consisting of ultrathin TiO2 films is significantly improved. Most strikingly, the output power of the plexciton-SSCs is much larger than the sum of those of the individual plasmon- and exciton-SSCs. Our observations provide a practical approach to monitor energy and electron transfer in plasmon-exciton hybrids at a strong coupling regime and also offer a new strategy to design photovoltaic nanodevices. PMID:27481652

  8. Plasmon resonance energy transfer and plexcitonic solar cell.

    PubMed

    Nan, Fan; Ding, Si-Jing; Ma, Liang; Cheng, Zi-Qiang; Zhong, Yu-Ting; Zhang, Ya-Fang; Qiu, Yun-Hang; Li, Xiaoguang; Zhou, Li; Wang, Qu-Quan

    2016-08-11

    Plasmon-mediated energy transfer is highly desirable in photo-electronic nanodevices, but the direct injection efficiency of "hot electrons" in plasmonic photo-detectors and plasmon-sensitized solar cells (plasmon-SSCs) is poor. On another front, Fano resonance induced by strong plasmon-exciton coupling provides an efficient channel of coherent energy transfer from metallic plasmons to molecular excitons, and organic dye molecules have a much better injection efficiency in exciton-SSCs than "hot electrons". Here, we investigate enhanced light-harvesting of chlorophyll-a molecules strongly coupled to Au nanostructured films via Fano resonance. The enhanced local field and plasmon resonance energy transfer are experimentally revealed by monitoring the ultrafast dynamical processes of the plexcitons and the photocurrent flows of the assembled plexciton-SSCs. By tuning the Fano factor and anti-resonance wavelengths, we find that the local field is largely enhanced and the efficiency of plexciton-SSCs consisting of ultrathin TiO2 films is significantly improved. Most strikingly, the output power of the plexciton-SSCs is much larger than the sum of those of the individual plasmon- and exciton-SSCs. Our observations provide a practical approach to monitor energy and electron transfer in plasmon-exciton hybrids at a strong coupling regime and also offer a new strategy to design photovoltaic nanodevices.

  9. Power management circuit for resonant energy harvesters

    NASA Astrophysics Data System (ADS)

    Jirku, Tomas; Steinbauer, Miloslav; Kluge, Martin

    2009-05-01

    This paper deals with the design of the power management circuit for the vibration generator developed in the frame of the European WISE project and its testing in the connection with the generator and the dynamic load simulating the real load. This generator is used as an autonomous energy source for wireless sensor applications. It can be used for example in the aeronautic, automotive and many other applications. The generator output power analysis was based on the vibration spectrum measured on the helicopter engine, provided by the consortium EADS, EUROCOPTER, DASSAULT AVIATION - 6.RP -WIreless SEnsing (WISE) project. This spectrum shows very unstable vibration levels. It was done the statistical analysis of these vibration levels and it was shown that there is a need of the power management circuit, which can provide a stable output voltage for the supplied circuit and if there is a need it can store an immediately unusable generated energy. The generator can't be used as the only energy source for the sensor circuit, because there are not any vibrations when for example a motor is stopped. In these periods and in the time of low vibration levels the circuit must be supplied from battery. The power management circuit described in this paper fulfills these requirements. It has two power inputs - the battery and the generator. It can switch between them at certain defined generator output levels by the threshold detector. Also when there is too much of the generated power, it can store the extra energy in the storage for the later usage. The storage device is the advanced capacitor. The advanced capacitor is a device containing three capacitors. These capacitors are connected (and charged) sequentially so the increasing capacity is provided. The developed power management was tested in the connection with the real vibration generator raised by stable vibration levels and the dynamic load simulating the real sensor in the main operation stages - sampling and data

  10. Enhancement of particle-wave energy exchange by resonance sweeping

    SciTech Connect

    Berk, H.L.; Breizman, B.N.

    1996-01-01

    When the resonance condition of the particle-wave interaction is varied adiabatically, the particles trapped in a wave are found to form phase space holes or clumps that enhance the particle-wave energy exchange. This mechanism can cause increased saturation levels of instabilities and even allow the free energy associated with instability to be tapped in a system in which background dissipation suppresses linear instability.

  11. Enhancement of particle-wave energy exchange by resonance sweeping

    SciTech Connect

    Berk, H.L.; Breizman, B.N.

    1995-10-01

    It is shown that as the resonance condition of the particle-wave interaction is varied adiabatically, that the particles trapped in the wave will form phase space holes or clumps that can enhance the particle-wave energy exchange. This mechanism can cause much larger saturation levels of instabilities, and even allow the free energy associated with instability, to be tapped in a system that is linearly stable due to background dissipation.

  12. The Role of Resonant Vibrations in Electronic Energy Transfer

    PubMed Central

    Somsen, Oscar J. G.; Novoderezhkin, Vladimir I.; Mančal, Tomáš; van Grondelle, Rienk

    2016-01-01

    Abstract Nuclear vibrations play a prominent role in the spectroscopy and dynamics of electronic systems. As recent experimental and theoretical studies suggest, this may be even more so when vibrational frequencies are resonant with transitions between the electronic states. Herein, a vibronic multilevel Redfield model is reported for excitonically coupled electronic two‐level systems with a few explicitly included vibrational modes and interacting with a phonon bath. With numerical simulations the effects of the quantized vibrations on the dynamics of energy transfer and coherence in a model dimer are illustrated. The resonance between the vibrational frequency and energy gap between the sites leads to a large delocalization of vibronic states, which then results in faster energy transfer and longer‐lived mixed coherences. PMID:26910485

  13. Resonance versus aerodynamics for energy savings in agile natural flyers

    NASA Astrophysics Data System (ADS)

    Kok, Jia M.; Chahl, Javaan

    2014-03-01

    Insects are the most diverse natural flyers in nature, being able to hover and perform agile manoeuvres. Dragon- flies in particular are aggressive flyers, attaining accelerations of up to 4g. Flight in all insects requires demanding aerodynamic and inertial loads be overcome. It has been proposed that resonance is a primary mechanism for reducing energy costs associated with flapping flight, by storing energy in an elastic thorax and releasing it on the following half-stroke. Certainly in insect flight motors dominated by inertial loads, such a mechanism would be extremely beneficial. However in highly manoeuvrable, aerodynamically dominated flyers, such as the dragonfly, the use of elastic storage members requires further investigation. We show that employing resonant mechanisms in a real world configuration produces minimal energy savings that are further reduced by 50 to 133% across the operational flapping frequency band of the dragonfly. Using a simple harmonic oscillator analysis to represent the dynamics of a dragonfly, we further demonstrate a reduction in manoeuvring limits of ˜1.5 times for a system employing elastic mechanisms. This is in contrast to the potential power reductions of √2/2 from regulating aerodynamics via active wing articulation. Aerodynamic means of energy storage provides flexibility between an energy efficient hover state and a manoeuvrable state capable of large accelerations. We conclude that active wing articulation is preferable to resonance for aerodynamically dominated natural flyers.

  14. Paths to Förster's resonance energy transfer (FRET) theory

    NASA Astrophysics Data System (ADS)

    Masters, B. R.

    2014-02-01

    Theodor Förster (1910-1974) developed a phenomenological theory of nonradiative resonance energy transfer which proved to be transformative in the fields of chemistry, biochemistry, and biology. This paper explores the experimental and the theoretical antecedents of Förster's theory of resonance energy transfer (FRET). Early studies of sensitized fluorescence, fluorescence depolarization, and photosynthesis demonstrated the phenomena of long-range energy transfer. At the same time physicists developed theoretical models which contained common physical mechanisms and parameters: oscillating dipoles as models for the atoms or molecules, dipole-dipole coupling for the interaction, and a distance R0 that is optimal for resonance energy transfer. Early theories predicted R0 that was too large as compared to experiments. Finally, in 1946 Förster developed a classical theory and in 1948 he developed a quantum mechanical theory; both theories predicted an inverse sixth power dependence of the rate of energy transfer and a R0 that agreed with experiments. This paper attempts to determine why Förster succeeded when the other theoreticians failed to develop the correct theory. The putative roles of interdisciplinary education and collaborative research are discussed. Furthermore, I explore the role of science journals and their specific audiences in the popularization of FRET to a broad interdisciplinary community.

  15. Bond resonance energy and verification of the isolated pentagon rule

    SciTech Connect

    Aihara, Jun Ichi

    1995-04-12

    The isolated pentagon rule (IPR) states that fullerenes with isolated pentagons are kinetically much more stable than their fused pentagon counterparts. This rule can be verified in terms of a graph-theoretically defined bond resonance energy. In general, a {pi} bond shared by two pentagons has a large negative bond resonance energy, thus contributing significantly to the increase in kinetic instability or chemical reactivity of the molecule. The existence of such highly antiaromatic local structures sharply distinguishes IPR-violating fullerenes from isolated-pentagon isomers. {pi}bonds shared by two pentagons are shared by many antiaromatic conjugated circuits but not by relatively small aromatic conjugated circuits. 39 refs., 3 figs., 5 tabs.

  16. Gravity resonance spectroscopy constrains dark energy and dark matter scenarios.

    PubMed

    Jenke, T; Cronenberg, G; Burgdörfer, J; Chizhova, L A; Geltenbort, P; Ivanov, A N; Lauer, T; Lins, T; Rotter, S; Saul, H; Schmidt, U; Abele, H

    2014-04-18

    We report on precision resonance spectroscopy measurements of quantum states of ultracold neutrons confined above the surface of a horizontal mirror by the gravity potential of Earth. Resonant transitions between several of the lowest quantum states are observed for the first time. These measurements demonstrate that Newton's inverse square law of gravity is understood at micron distances on an energy scale of 10-14  eV. At this level of precision, we are able to provide constraints on any possible gravitylike interaction. In particular, a dark energy chameleon field is excluded for values of the coupling constant β>5.8×108 at 95% confidence level (C.L.), and an attractive (repulsive) dark matter axionlike spin-mass coupling is excluded for the coupling strength gsgp>3.7×10-16 (5.3×10-16) at a Yukawa length of λ=20  μm (95% C.L.).

  17. Helmholtz Resonator for Lead Zirconate Titanate Acoustic Energy Harvester

    NASA Astrophysics Data System (ADS)

    Matsuda, Tomohiro; Tomii, Kazuki; Hagiwara, Saori; Miyake, Shuntaro; Hasegawa, Yuichi; Sato, Takamitsu; Kaneko, Yuta; Nishioka, Yasushiro

    2013-12-01

    Acoustic energy harvesters that function in environments where sound pressure is extremely high (~150 dB), such as in engine rooms of aircrafts, are expected to be capable of powering wireless health monitoring systems. This paper presents the power generation performances of a lead-zirconate-titanate (PZT) acoustic energy harvester with a vibrating PZT diaphragm. The diaphragm had a diameter of 2 mm, consisting of Al(0.1 μm)/PZT(1 μm)/Pt(0.1 μm)/Ti(0.1 μm)/SiO2(1.5 μm). The harvester generated a power of 1.7×10-13 W under a sound pressure level of 110 dB at the first resonance frequency of 6.28 kHz. It was found that the generated power was increased to 6.8×10-13 W using a sound-collecting Helmholtz resonator cone with the height of 60 mm. The cone provided a Helmholtz resonance at 5.8 kHz, and the generated power increased from 3.4×10-14 W to 1.4×10-13 W at this frequency. The cone was also effective in increasing the bandwidth of the energy harvester.

  18. Fluorescence resonant energy transfer in the optical near field

    SciTech Connect

    Colas des Francs, Gerard; Girard, Christian; Martin, Olivier J.F.

    2003-05-01

    We develop a versatile theoretical framework for the study of fluorescence resonant energy transfer (FRET, or Foerster transfer) in complex environments, under arbitrary illumination, including optical near fields. By combining the field-susceptibility formalism with the optical Bloch equations method, we derive general equations for the computation of the energy transfer between pairs of donor-acceptor molecules excited by optical near fields and placed in a complex geometry. This approach allows accounting for both the variations of the molecular population rates and the influence of the environment. Several examples illustrate the ability of the technique to analyze recent FRET experiments performed in the optical near field.

  19. Excitation-energy dependence of the giant dipole resonance width

    NASA Astrophysics Data System (ADS)

    Enders, G.; Berg, F. D.; Hagel, K.; Kühn, W.; Metag, V.; Novotny, R.; Pfeiffer, M.; Schwalb, O.; Charity, R. J.; Gobbi, A.; Freifelder, R.; Henning, W.; Hildenbrand, K. D.; Holzmann, R.; Mayer, R. S.; Simon, R. S.; Wessels, J. P.; Casini, G.; Olmi, A.; Stefanini, A. A.

    1992-07-01

    High-energy γ rays have been measured in coincidence with heavy fragents in deeply inelastic reactions of 136Xe+48Ti at 18.5 MeV/nucleon. The giant dipole resonance (GDR) strength function is deduced from an analysis of the photon spectra within the statistical model. The GDR width Γ is studied as a function of the fragment excitation energy E*. A saturation at about Γ=10 MeV is observed for E*/A>=1.0 MeV/nucleon.

  20. Effect of internal resistance of a Helmholtz resonator on acoustic energy reduction in enclosures.

    PubMed

    Yu, Ganghua; Li, Deyu; Cheng, Li

    2008-12-01

    The effect of internal resistance of a Helmholtz resonator on acoustic energy reduction in an enclosure and the multimodal coupling-based Helmholtz resonator design are investigated. Using the analytical solution of a resonator-enclosure interaction model, an energy reduction index is defined in a frequency band to optimize the resonator resistance. The dual process of energy dissipation and radiation of the resonator is quantified. Optimal resistance of the resonator and its physical effect on the resonator-enclosure interaction are numerically evaluated and categorized in terms of frequency bandwidths. Predictions on the resonator performance are confirmed by experiments. Comparisons with existing models based on different optimization criteria are also performed. It is shown that the proposed model serves as an effective design tool to determine the internal resistance of the resonator in order to achieve sound reduction in the frequency band enclosing acoustic resonances.

  1. Acoustic energy harvesting using an electromechanical Helmholtz resonator.

    PubMed

    Liu, Fei; Phipps, Alex; Horowitz, Stephen; Ngo, Khai; Cattafesta, Louis; Nishida, Toshikazu; Sheplak, Mark

    2008-04-01

    This paper presents the development of an acoustic energy harvester using an electromechanical Helmholtz resonator (EMHR). The EMHR consists of an orifice, cavity, and a piezoelectric diaphragm. Acoustic energy is converted to mechanical energy when sound incident on the orifice generates an oscillatory pressure in the cavity, which in turns causes the vibration of the diaphragm. The conversion of acoustic energy to electrical energy is achieved via piezoelectric transduction in the diaphragm of the EMHR. Moreover, the diaphragm is coupled with energy reclamation circuitry to increase the efficiency of the energy conversion. Lumped element modeling of the EMHR is used to provide physical insight into the coupled energy domain dynamics governing the energy reclamation process. The feasibility of acoustic energy reclamation using an EMHR is demonstrated in a plane wave tube for two power converter topologies. The first is comprised of only a rectifier, and the second uses a rectifier connected to a flyback converter to improve load matching. Experimental results indicate that approximately 30 mW of output power is harvested for an incident sound pressure level of 160 dB with a flyback converter. Such power level is sufficient to power a variety of low power electronic devices. PMID:18397006

  2. Lessons for Energy Resonance HFGW Detector Designs from Mass Resonance and Interferometric LFGW Detectors

    NASA Astrophysics Data System (ADS)

    Stephenson, Gary V.

    2009-03-01

    Many design and operations challenges have been met and surmounted by four decades of work on low frequency gravitational wave (LFGW) detection schemes such as mass-resonance bars, mass resonance spheres, and interferometers. This design and operations experience could be leveraged to benefit a new class of high frequency gravitational wave (HFGW) energy resonance detectors now in the early planning and design phases. Detection strategy lessons include the characterization of possible GW signal sources, the characterization of what constitutes a detection event, the role of various sources of 'Q' in effective signal amplification and filtering, and the sources of noise and how they can be reduced. Theoretical limits to sensitivity will also be summarized, including the quantum back action limit and how it may be avoided using quantum non-demolition, including the possibilities of squeezed states and even quantum coherence. Modeling, simulation, and processing lessons will also be reviewed, including the use of multiple detectors, delay histograms, statistical filtering, and the pitfalls of non-linear signal processing. Finally, technical management strategies will be reviewed, including collaboration options and data pooling decision strategies.

  3. Complementary split ring resonator arrays for electromagnetic energy harvesting

    NASA Astrophysics Data System (ADS)

    Alavikia, Babak; Almoneef, Thamer S.; Ramahi, Omar M.

    2015-07-01

    This work demonstrates the viability of Ground-backed Complementary Split-Ring Resonator (G-CSRR) arrays with significant power conversion efficiency and bandwidth enhancement in comparison to the technology used in current electromagnetic energy harvesting systems. Through numerical full-wave analysis, we demonstrated correlation between either the resonance frequency or the input impedance of G-CSRR cells with the periodicity of the array. A comparative study of power harvesting efficiency through numerical analysis and laboratory measurement was presented where an array of G-CSRRs is compared to an array of microstrip patch antennas. We demonstrated that a G-CSRR array yields power conversion efficiency of 92%, which represents a significant improvement in comparison to the single G-CSRR reported in our earlier work.

  4. Resonant Electromagnetic Interaction in Low Energy Nuclear Reactions

    NASA Astrophysics Data System (ADS)

    Chubb, Scott

    2008-03-01

    Basic ideas about how resonant electromagnetic interaction (EMI) can take place in finite solids are reviewed. These ideas not only provide a basis for conventional, electron energy band theory (which explains charge and heat transport in solids), but they also explain how through finite size effects, it is possible to create many of the kinds of effects envisioned by Giuliano Preparata. The underlying formalism predicts that the orientation of the external fields in the SPAWAR protocolootnotetextKrivit, Steven B., New Energy Times, 2007, issue 21, item 10. http://newenergytimes.com/news/2007/NET21.htm^,ootnotetextSzpak, S.; Mosier-Boss, P.A.; Gordon, F.E. Further evidence of nuclear reactions in the Pd lattice: emission of charged particles. Naturwissenschaften 94,511(2007)..has direct bearing on the emission of high-energy particles. Resonant EMI also implies that nano-scale solids, of a particular size, provide an optimal environment for initiating Low Energy Nuclear Reactions (LENR) in the PdD system.

  5. Global stabilization of high-energy resonance for a nonlinear wideband electromagnetic vibration energy harvester

    NASA Astrophysics Data System (ADS)

    Masuda, Arata; Sato, Takeru

    2016-04-01

    This paper presents an experimental verification of a wideband nonlinear vibration energy harvester which has a globally stabilized high-energy resonating response. For the conventional linear vibration energy harvester, the maximum performance of the power generation and its bandwidth are in a relation of trade-off. The resonance frequency band can be expanded by introducing a Duffing-type nonlinear resonator in order to enable the harvester to generate larger electric power in a wider frequency range. However, since such nonlinear resonators often have multiple stable steady-state solutions in the resonance band, it is difficult for the nonlinear harvester to maintain the high performance of the power generation constantly. The principle of self-excitation and entrainment has been utilized to provide the global stability to the highest-energy solution by destabilizing other unexpected lower-energy solutions by introducing a switching circuit of the load resistance between positive and the negative values depending on the response amplitude of the oscillator. In this study, an experimental verification of this concept are carried out. An experimental prototype harvester is designed and fabricated and the performance of the proposed harvester is experimentally verified. It has been shown that the numerical and experimental results agreed very well, and the highest-energy solutions above the threshold value were successfully stabilized globally.

  6. Detecting Plasmon Resonance Energy Transfer with Differential Interference Contrast Microscopy

    SciTech Connect

    Augspurger, Ashley E.; Stender, Anthony S.; Han, Rui; Fang, Ning

    2013-12-30

    Gold nanoparticles are ideal probes for studying intracellular environments and energy transfer mechanisms due to their plasmonic properties. Plasmon resonance energy transfer (PRET) relies on a plasmonic nanoparticle to donate energy to a nearby resonant acceptor molecule, a process which can be observed due to the plasmonic quenching of the donor nanoparticle. In this study, a gold nanosphere was used as the plasmonic donor, while the metalloprotein cytochrome c was used as the acceptor molecule. Differential interference contrast (DIC) microscopy allows for simultaneous monitoring of complex environments and noble metal nanoparticles in real time. Using DIC and specially designed microfluidic channels, we were able to monitor PRET at the single gold particle level and observe the reversibility of PRET upon the introduction of phosphate-buffered saline to the channel. In an additional experiment, single gold particles were internalized by HeLa cells and were subsequently observed undergoing PRET as the cell hosts underwent morphological changes brought about by ethanol-induced apoptosis.

  7. Monitoring integrin activation by fluorescence resonance energy transfer.

    PubMed

    Lefort, Craig T; Hyun, Young-Min; Kim, Minsoo

    2012-01-01

    Aberrant integrin activation is associated with several immune pathologies. In leukocyte adhesion deficiency (LAD), the absence or inability of β(2) integrins to undergo affinity upregulation contributes to recurrent infectious episodes and impaired wound healing, while excessive integrin activity leads to an exaggerated inflammatory response with associated tissue damage. Therefore, integrin activation is an attractive target for immunotherapies, and monitoring the effect of agents on integrin activation is necessary during preclinical drug development. The activation of integrins involves the structural rearrangement of both the extracellular and cytoplasmic domains. Here, we describe methods for monitoring integrin conformational activation using fluorescence resonance energy transfer (FRET).

  8. Radio-frequency energy quantification in magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Alon, Leeor

    Mapping of radio frequency (RF) energy deposition has been challenging for 50+ years, especially, when scanning patients in the magnetic resonance imaging (MRI) environment. As result, electromagnetic simulation software is often used for estimating the specific absorption rate (SAR), the rate of RF energy deposition in tissue. The thesis work presents challenges associated with aligning information provided by electromagnetic simulation and MRI experiments. As result of the limitations of simulations, experimental methods for the quantification of SAR were established. A system for quantification of the total RF energy deposition was developed for parallel transmit MRI (a system that uses multiple antennas to excite and image the body). The system is capable of monitoring and predicting channel-by-channel RF energy deposition, whole body SAR and capable of tracking potential hardware failures that occur in the transmit chain and may cause the deposition of excessive energy into patients. Similarly, we demonstrated that local RF power deposition can be mapped and predicted for parallel transmit systems based on a series of MRI temperature mapping acquisitions. Resulting from the work, we developed tools for optimal reconstruction temperature maps from MRI acquisitions. The tools developed for temperature mapping paved the way for utilizing MRI as a diagnostic tool for evaluation of RF/microwave emitting device safety. Quantification of the RF energy was demonstrated for both MRI compatible and non-MRI-compatible devices (such as cell phones), while having the advantage of being noninvasive, of providing millimeter resolution and high accuracy.

  9. Firefly Luciferase-Based Sequential Bioluminescence Resonance Energy Transfer (BRET)-Fluorescence Resonance Energy Transfer (FRET) Protease Assays.

    PubMed

    Branchini, Bruce

    2016-01-01

    We describe here the preparation of ratiometric luminescent probes that contain two well-separated emission peaks produced by a sequential bioluminescence resonance energy transfer (BRET)-fluorescence resonance energy transfer (FRET) process. The probes are single soluble fusion proteins consisting of a thermostable firefly luciferase variant that catalyzes yellow-green (560 nm maximum) bioluminescence and a red fluorescent protein covalently labeled with a near-Infrared fluorescent dye. The two proteins are connected by a decapeptide containing a protease recognition site specific for factor Xa, thrombin, or caspase 3. The rates of protease cleavage of the fusion protein substrates were monitored by recording emission spectra and plotting the change in peak ratios over time. Detection limits of 0.41 nM for caspase 3, 1.0 nM for thrombin, and 58 nM for factor Xa were realized with a scanning fluorometer. This method successfully employs an efficient sequential BRET-FRET energy transfer process based on firefly luciferase bioluminescence to assay physiologically important protease activities and should be generally applicable to the measurement of any endoprotease lacking accessible cysteine residues. PMID:27424898

  10. Firefly Luciferase-Based Sequential Bioluminescence Resonance Energy Transfer (BRET)-Fluorescence Resonance Energy Transfer (FRET) Protease Assays.

    PubMed

    Branchini, Bruce

    2016-01-01

    We describe here the preparation of ratiometric luminescent probes that contain two well-separated emission peaks produced by a sequential bioluminescence resonance energy transfer (BRET)-fluorescence resonance energy transfer (FRET) process. The probes are single soluble fusion proteins consisting of a thermostable firefly luciferase variant that catalyzes yellow-green (560 nm maximum) bioluminescence and a red fluorescent protein covalently labeled with a near-Infrared fluorescent dye. The two proteins are connected by a decapeptide containing a protease recognition site specific for factor Xa, thrombin, or caspase 3. The rates of protease cleavage of the fusion protein substrates were monitored by recording emission spectra and plotting the change in peak ratios over time. Detection limits of 0.41 nM for caspase 3, 1.0 nM for thrombin, and 58 nM for factor Xa were realized with a scanning fluorometer. This method successfully employs an efficient sequential BRET-FRET energy transfer process based on firefly luciferase bioluminescence to assay physiologically important protease activities and should be generally applicable to the measurement of any endoprotease lacking accessible cysteine residues.

  11. Non-resonant energy harvesting via an adaptive bistable potential

    NASA Astrophysics Data System (ADS)

    Haji Hosseinloo, Ashkan; Turitsyn, Konstantin

    2016-01-01

    Narrow bandwidth and easy detuning, inefficiency in broadband and non-stationary excitations, and difficulties in matching a linear harvester’s resonance frequency to low-frequency excitations at small scales, have convinced researchers to investigate nonlinear, and in particular bistable, energy harvesters in recent years. However, bistable harvesters suffer from co-existing low and high energy orbits, and sensitivity to initial conditions, and have recently been proven inefficient when subjected to many real-world random and non-stationary excitations. Here, we propose a novel non-resonant buy-low-sell-high strategy that can significantly improve the harvester’s effectiveness at low frequencies in a much more robust fashion. This strategy could be realized by a passive adaptive bistable system. Simulation results confirm the high effectiveness of the adaptive bistable system following a buy-low-sell-high logic when subjected to harmonic and random non-stationary walking excitations compared to its conventional bistable and linear counterparts.

  12. Resonance energy transfer in DNA duplexes labeled with localized dyes.

    PubMed

    Cunningham, Paul D; Khachatrian, Ani; Buckhout-White, Susan; Deschamps, Jeffrey R; Goldman, Ellen R; Medintz, Igor L; Melinger, Joseph S

    2014-12-18

    The growing maturity of DNA-based architectures has raised considerable interest in applying them to create photoactive light harvesting and sensing devices. Toward optimizing efficiency in such structures, resonant energy transfer was systematically examined in a series of dye-labeled DNA duplexes where donor-acceptor separation was incrementally changed from 0 to 16 base pairs. Cyanine dyes were localized on the DNA using double phosphoramidite attachment chemistry. Steady state spectroscopy, single-pair fluorescence, time-resolved fluorescence, and ultrafast two-color pump-probe methods were utilized to examine the energy transfer processes. Energy transfer rates were found to be more sensitive to the distance between the Cy3 donor and Cy5 acceptor dye molecules than efficiency measurements. Picosecond energy transfer and near-unity efficiencies were observed for the closest separations. Comparison between our measurements and the predictions of Förster theory based on structural modeling of the dye-labeled DNA duplex suggest that the double phosphoramidite linkage leads to a distribution of intercalated and nonintercalated dye orientations. Deviations from the predictions of Förster theory point to a failure of the point dipole approximation for separations of less than 10 base pairs. Interactions between the dyes that alter their optical properties and violate the weak-coupling assumption of Förster theory were observed for separations of less than four base pairs, suggesting the removal of nucleobases causes DNA deformation and leads to enhanced dye-dye interaction. PMID:25397906

  13. Calibration of fluorescence resonance energy transfer in microscopy

    DOEpatents

    Youvan, Dougalas C.; Silva, Christopher M.; Bylina, Edward J.; Coleman, William J.; Dilworth, Michael R.; Yang, Mary M.

    2003-12-09

    Imaging hardware, software, calibrants, and methods are provided to visualize and quantitate the amount of Fluorescence Resonance Energy Transfer (FRET) occurring between donor and acceptor molecules in epifluorescence microscopy. The MicroFRET system compensates for overlap among donor, acceptor, and FRET spectra using well characterized fluorescent beads as standards in conjunction with radiometrically calibrated image processing techniques. The MicroFRET system also provides precisely machined epifluorescence cubes to maintain proper image registration as the sample is illuminated at the donor and acceptor excitation wavelengths. Algorithms are described that pseudocolor the image to display pixels exhibiting radiometrically-corrected fluorescence emission from the donor (blue), the acceptor (green) and FRET (red). The method is demonstrated on samples exhibiting FRET between genetically engineered derivatives of the Green Fluorescent Protein (GFP) bound to the surface of Ni chelating beads by histidine-tags.

  14. Application of fluorescence resonance energy transfer in protein studies

    PubMed Central

    Ma, Linlin; Yang, Fan; Zheng, Jie

    2014-01-01

    Since the physical process of fluorescence resonance energy transfer (FRET) was elucidated more than six decades ago, this peculiar fluorescence phenomenon has turned into a powerful tool for biomedical research due to its compatibility in scale with biological molecules as well as rapid developments in novel fluorophores and optical detection techniques. A wide variety of FRET approaches have been devised, each with its own advantages and drawbacks. Especially in the last decade or so, we are witnessing a flourish of FRET applications in biological investigations, many of which exemplify clever experimental design and rigorous analysis. Here we review the current stage of FRET methods development with the main focus on its applications in protein studies in biological systems, by summarizing the basic components of FRET techniques, most established quantification methods, as well as potential pitfalls, illustrated by example applications. PMID:25368432

  15. Bremsstrahlung from nuclear scattering at low energy near a resonance

    NASA Astrophysics Data System (ADS)

    Trail, C. C.; Lesser, P. M. S.; Liou, M. K.

    1984-04-01

    A program to contribute to the general understanding of nuclear reactions by determining as many of the off-shell properties of the proton-nucleus interaction as possible through the study of the proton-nucleus bremsstrahlung process is discussed. The limits of validity of a model independent analysis of these reactions in the neighborhood of a resonance or a breakup threshold are sought. The differences between this analysis and the data is utilized to elucidate those off-shell constraints which any valid proton-nucleus model interaction must satisfy. The bremsstrahlung process provides a method for determining the off-shell properties of the proton-nucleus potential, and the Brooklyn College program offers a unique opportunity to measure these crucial aspects of the low energy proton-nucleus interaction.

  16. Calibration of fluorescence resonance energy transfer in microscopy

    DOEpatents

    Youvan, Douglas C.; Silva, Christopher M.; Bylina, Edward J.; Coleman, William J.; Dilworth, Michael R.; Yang, Mary M.

    2002-09-24

    Imaging hardware, software, calibrants, and methods are provided to visualize and quantitate the amount of Fluorescence Resonance Energy Transfer (FRET) occurring between donor and acceptor molecules in epifluorescence microscopy. The MicroFRET system compensates for overlap among donor, acceptor, and FRET spectra using well characterized fluorescent beads as standards in conjunction with radiometrically calibrated image processing techniques. The MicroFRET system also provides precisely machined epifluorescence cubes to maintain proper image registration as the sample is illuminated at the donor and acceptor excitation wavelengths. Algorithms are described that pseudocolor the image to display pixels exhibiting radiometrically-corrected fluorescence emission from the donor (blue), the acceptor (green) and FRET (red). The method is demonstrated on samples exhibiting FRET between genetically engineered derivatives of the Green Fluorescent Protein (GFP) bound to the surface of Ni chelating beads by histidine-tags.

  17. Resonance energy transfer: The unified theory via vector spherical harmonics

    NASA Astrophysics Data System (ADS)

    Grinter, Roger; Jones, Garth A.

    2016-08-01

    In this work, we derive the well-established expression for the quantum amplitude associated with the resonance energy transfer (RET) process between a pair of molecules that are beyond wavefunction overlap. The novelty of this work is that the field of the mediating photon is described in terms of a spherical wave rather than a plane wave. The angular components of the field are constructed in terms of vector spherical harmonics while Hankel functions are used to define the radial component. This approach alleviates the problem of having to select physically correct solution from non-physical solutions, which seems to be inherent in plane wave derivations. The spherical coordinate system allows one to easily decompose the photon's fields into longitudinal and transverse components and offers a natural way to analyse near-, intermediate-, and far-zone RET within the context of the relative orientation of the transition dipole moments for the two molecules.

  18. Damping subsynchronous resonance using superconducting magnetic energy storage unit

    SciTech Connect

    Wang, L.; Lee, S.M.; Huang, C.L. . Dept. of Electrical Engineering)

    1994-12-01

    A novel damping scheme using superconducting magnetic energy storage (SMES) unit is proposed in this paper to damp subsynchronous resonance (SSR) of the IEEE Second Benchmark Model, system-1 which is a widely employed standard model for computer simulation of SSR. The studied system contains a turbine-generator set connected to an infinite bus through two parallel transmission lines, one of which is series-capacitor compensated. In order to stabilize all SSR modes, simultaneous active and reactive power modulation and a proportional-integral-derivative (PID) damping controller designed by modal control theory are proposed for the SMES unit. Frequency-domain approach based on eigenvalue analysis and time-domain approach based on nonlinear-model simulations are performed to validate the effectiveness of the damping method. It can be concluded from the simulation results that the proposed damping scheme can effectively suppress SSR of the studied system.

  19. Resonance energy transfer: The unified theory via vector spherical harmonics.

    PubMed

    Grinter, Roger; Jones, Garth A

    2016-08-21

    In this work, we derive the well-established expression for the quantum amplitude associated with the resonance energy transfer (RET) process between a pair of molecules that are beyond wavefunction overlap. The novelty of this work is that the field of the mediating photon is described in terms of a spherical wave rather than a plane wave. The angular components of the field are constructed in terms of vector spherical harmonics while Hankel functions are used to define the radial component. This approach alleviates the problem of having to select physically correct solution from non-physical solutions, which seems to be inherent in plane wave derivations. The spherical coordinate system allows one to easily decompose the photon's fields into longitudinal and transverse components and offers a natural way to analyse near-, intermediate-, and far-zone RET within the context of the relative orientation of the transition dipole moments for the two molecules. PMID:27544087

  20. Non-Resonant Response Using Statistical Energy Analysis

    NASA Astrophysics Data System (ADS)

    RENJI, K.; NAIR, P. S.; NARAYANAN, S.

    2001-03-01

    When excited acoustically, the response of a panel consists of resonant and non-resonant waves. The non-resonant response is negligible for limp panels. However, it can become significant in the case of thin light structural panels. SEA modelling does not predict the non-resonant response of the structure. This paper discusses the above limitation of SEA and presents a modified SEA formulation by which the non-resonant response can also be estimated. The resonant and the non-resonant contributions to the response are assumed to be arising out of two separate subsystems. In the present formulation, modelling for non-resonant response is similar to the conventional SEA modelling for resonant response but uses different expressions for the coupling loss factors. The classical problem of two reverberant rooms separated by a panel is considered as an example. It is shown that by using this procedure the non-resonant response of the structure can be estimated. Also, the non-resonant sound transmission is obtained exactly. Results of a numerical example are presented to compare the conventional and the modified SEA modelling results.

  1. A fluorescence resonance energy transfer activation sensor for Arf6.

    PubMed

    Hall, Brian; McLean, Mark A; Davis, Kathryn; Casanova, James E; Sligar, Steven G; Schwartz, Martin A

    2008-03-15

    The involvement of the small GTPase Arf6 in Rac activation, cell migration, and cancer invasiveness suggests that it is activated in a spatially and temporally regulated manner. Small GTPase activation has been imaged in cells using probes in which the GTPase and a fragment of a downstream effector protein are fused to fluorescent reporter proteins that constitute a fluorescence resonance energy transfer (FRET) donor/acceptor pair. Unlike other Ras family GTPases, the N terminus of Arf6 is critical for membrane targeting and, thus, cannot be modified by fusion to a fluorescent protein. We found that the previously described C-terminal green fluorescent protein (GFP) derivative also shows diminished membrane targeting. Therefore, we inserted a fluorescent protein into an inert loop within the Arf6 sequence. This fusion showed normal membrane targeting, nucleotide-dependent interaction with the downstream effector GGA3, and normal regulation by a GTPase-activating protein (GAP) and a guanine nucleotide exchange factor (GEF). Using the recently developed CyPET/YPET fluorescent proteins as a FRET pair, we found that Arf6-CyPET underwent efficient energy transfer when bound to YPET-GGA3 effector domain in intact cells. The addition of platelet-derived growth factor (PDGF) to fibroblasts triggered a rapid and transient increase in FRET, indicative of Arf6 activation. These reagents should be useful for investigations of Arf6 activation and function.

  2. Fluorescence resonance energy transfer studies on anthrax lethal toxin.

    PubMed

    Croney, John C; Cunningham, Kristina M; Collier, R John; Jameson, David M

    2003-08-28

    Anthrax lethal toxin is a binary bacterial toxin consisting of two proteins, protective antigen (PA) and lethal factor (LF), that self-assemble on receptor-bearing eukaryotic cells to form toxic, non-covalent complexes. PA(63), a proteolytically activated form of PA, spontaneously oligomerizes to form ring-shaped heptamers that bind LF and translocate it into the cell. Site-directed mutagenesis was used to substitute cysteine for each of three residues (N209, E614 and E733) at various levels on the lateral face of the PA(63) heptamer and for one residue (E126) on LF(N), the 30 kDa N-terminal PA binding domain of LF. Cysteine residues in PA were labeled with IAEDANS and that in LF(N) was labeled with Alexa 488 maleimide. The mutagenesis and labeling did not significantly affect function. Time-resolved fluorescence methods were used to study fluorescence resonance energy transfer (FRET) between the AEDANS and Alexa 488 probes after the complex assembled in solution. The results clearly indicate energy transfer between AEDANS labeled at residue N209C on PA and the Alexa 488-labeled LF(N), whereas transfer from residue E614C on PA was slight, and none was observed from residue E733C. These results support a model in which LF(N) binds near the top of the ring-shaped (PA(63))(7) heptamer.

  3. Calculation of resonance energy transfer in crowded biological membranes.

    PubMed

    Zimet, D B; Thevenin, B J; Verkman, A S; Shohet, S B; Abney, J R

    1995-04-01

    Analytical and numerical models were developed to describe fluorescence resonance energy transfer (RET) in crowded biological membranes. It was assumed that fluorescent donors were linked to membrane proteins and that acceptors were linked to membrane lipids. No restrictions were placed on the location of the donor within the protein or the partitioning of acceptors between the two leaflets of the bilayer; however, acceptors were excluded from the area occupied by proteins. Analytical equations were derived that give the average quantum yield of a donor at low protein concentrations. Monte Carlo simulations were used to generate protein and lipid distributions that were linked numerically with RET equations to determine the average quantum yield and the distribution of donor fluorescence lifetimes at high protein concentrations, up to 50% area fraction. The Monte Carlo results show such crowding always reduces the quantum yield, probably because crowding increases acceptor concentrations near donor-bearing proteins; the magnitude of the reduction increases monotonically with protein concentration. The Monte Carlo results also show that the distribution of fluorescence lifetimes can differ markedly, even for systems possessing the same average lifetime. The dependence of energy transfer on acceptor concentration, protein radius, donor position within the protein, and the fraction of acceptors in each leaflet was also examined. The model and results are directly applicable to the analysis of RET data obtained from biological membranes; their application should result in a more complete and accurate determination of the structures of membrane components. PMID:7787045

  4. Rotational piezoelectric wind energy harvesting using impact-induced resonance

    NASA Astrophysics Data System (ADS)

    Yang, Ying; Shen, Qinlong; Jin, Jiamei; Wang, Yiping; Qian, Wangjie; Yuan, Dewang

    2014-08-01

    To improve the output power of a rotational piezoelectric wind energy harvester, impact-induced resonance is proposed to enable effective excitation of the piezoelectric cantilevers' vibration modes and obtain optimum deformation, which enhances the mechanical/electrical energy transformation. The impact force is introduced by forming a piezoelectric bimorph cantilever polygon that is fixed at the circumference of the rotating fan's internal surface. Elastic balls are placed inside the polygon. When wind rotates the device, the balls strike the piezoelectric cantilevers, and thus electricity is generated by the piezoelectric effect. The impact point is carefully chosen to use the first bending mode as much as possible, and thus maximize the harvesting efficiency. The design enables each bimorph to be struck in a similar area and every bimorph is struck in that area at different moments. As a result, a relatively stable output frequency can be obtained. The output frequency can also be changed by choosing different bimorph dimensions, which will also make the device simpler and the costs lower. A prototype piezoelectric energy harvester consisting of twelve piezoelectric cantilevers was constructed. The piezoelectric cantilevers were made from phosphor bronze, the lead zirconium titanate (PZT)-based bimorph cantilever had dimensions of 47 mm × 20 mm × 0.5 mm, and the elastic balls were made from steel with a diameter of 10 mm. The optimal DC output power was 613 μW across the 20 kΩ resistor at a rotation speed of 200 r/min with an inscribed circle diameter of 31 mm.

  5. Review of pyroelectric thermal energy harvesting and new MEMs based resonant energy conversion techniques

    SciTech Connect

    Hunter, Scott Robert; Lavrik, Nickolay V; Mostafa, Salwa; Rajic, Slobodan; Datskos, Panos G

    2012-01-01

    Harvesting electrical energy from thermal energy sources using pyroelectric conversion techniques has been under investigation for over 50 years, but it has not received the attention that thermoelectric energy harvesting techniques have during this time period. This lack of interest stems from early studies which found that the energy conversion efficiencies achievable using pyroelectric materials were several times less than those potentially achievable with thermoelectrics. More recent modeling and experimental studies have shown that pyroelectric techniques can be cost competitive with thermoelectrics and, using new temperature cycling techniques, has the potential to be several times as efficient as thermoelectrics under comparable operating conditions. This paper will review the recent history in this field and describe the techniques that are being developed to increase the opportunities for pyroelectric energy harvesting. The development of a new thermal energy harvester concept, based on temperature cycled pyroelectric thermal-to-electrical energy conversion, are also outlined. The approach uses a resonantly driven, pyroelectric capacitive bimorph cantilever structure that can be used to rapidly cycle the temperature in the energy harvester. The device has been modeled using a finite element multi-physics based method, where the effect of the structure material properties and system parameters on the frequency and magnitude of temperature cycling, and the efficiency of energy recycling using the proposed structure, have been modeled. Results show that thermal contact conductance and heat source temperature differences play key roles in dominating the cantilever resonant frequency and efficiency of the energy conversion technique. This paper outlines the modeling, fabrication and testing of cantilever and pyroelectric structures and single element devices that demonstrate the potential of this technology for the development of high efficiency thermal

  6. Concentric Förster resonance energy transfer imaging.

    PubMed

    Wu, Miao; Algar, W Russ

    2015-08-18

    Concentric Förster resonance energy transfer (cFRET) configurations based on semiconductor quantum dots (QDs) are promising probes for biological sensing because they offer multiplexing capability in a single vector with robust ratiometric detection by exploiting a network of FRET pathways. To expand the scope and utility of cFRET probes, it is necessary to develop and validate cFRET imaging methodology. In this technical note, we present such a methodology using a protease-sensitive cFRET configuration that comprises a green-emitting QD, Alexa Fluor 555 (A555), and Alexa Fluor 647 (A647). Photoluminescence (PL) images were acquired with three filter-based emission channels to permit measurement of A555/QD and A647/QD PL ratios. With reference to calibration samples, these PL ratios were used to calculate quantitative progress curves for proteolytic activity in regions of interest in the acquired images. Importantly, the imaging methodology reproduces quantitative results obtained with a monochromator-based fluorescence plate reader. Spatiotemporal resolution is demonstrated by tracking the activity of two prototypical proteases, trypsin and chymotrypsin, as they diffuse down the length of a capillary. This methodology is expected to enable the future use of cFRET probes for cellular sensing and other imaging assays. PMID:26214686

  7. Theory of coherent resonance energy transfer for coherent initial condition.

    PubMed

    Jang, Seogjoo

    2009-10-28

    A theory of coherent resonance energy transfer [Jang et al., J. Chem. Phys. 129, 101104 (2008)] is extended for coherent initial condition. For the situation where the initial excitation is an arbitrary linear combination of donor and acceptor excitations, a second order time local quantum master equation combined with polaron transformation is derived. Inhomogeneous terms in the resulting equation have contributions not only from initial donor and acceptor populations but also from their coherence terms. Numerical tests are performed for general super Ohmic spectral density where the bath degrees of freedom coupled to donor and acceptor can be correlated with each other. Calculation results demonstrate sensitivity of early nonstationary population dynamics on the relative sign of initial donor and acceptor excitation states. It is shown that contribution of inhomogeneous terms is more significant for coherent initial condition than for localized one. The overall model calculations provide details of the interplay between quantum coherence and nonequilibrium/non-Markovian effects in the time dependent donor population dynamics.

  8. Fluorescence resonance energy transfer in the studies of guanine quadruplexes.

    PubMed

    Juskowiak, Bernard; Takenaka, Shigeori

    2006-01-01

    A guanine (G)-quadruplex DNA motif has recently emerged as a biologically important structure that is believed to interfere with telomere maintenance by telomerase. G-quadruplexes exhibit four-stranded structures containing one or more nucleic acid strands with central channel able to accommodate metal cations. Coordination of certain metal cations stabilizes G-quadruplex as with some promising small organic molecules that promote the formation and/or stabilization of G-quadruplex. Among many techniques employed to explore properties of G-quadruplexes, the fluorescence resonance energy transfer (FRET) technique has been recognized as a powerful tool to study G-quadruplex formation. This review summarizes the current developments in the uses of FRET technique for the fundamental structural investigations and its practical applications. Applications include FRET-based selection of efficient quadruplex-binding ligands, design of a nanomolecular machine, and a molecular aptamer beacon for protein recognition. We also describe a technique for detection of potassium ions in aqueous solution with the use of quadruplex-based sensor (potassium-sensing oligonucleotide).

  9. Fluorescence Resonance Energy Transfer Studies of DNA Polymerase β

    PubMed Central

    Towle-Weicksel, Jamie B.; Dalal, Shibani; Sohl, Christal D.; Doublié, Sylvie; Anderson, Karen S.; Sweasy, Joann B.

    2014-01-01

    During DNA repair, DNA polymerase β (Pol β) is a highly dynamic enzyme that is able to select the correct nucleotide opposite a templating base from a pool of four different deoxynucleoside triphosphates (dNTPs). To gain insight into nucleotide selection, we use a fluorescence resonance energy transfer (FRET)-based system to monitor movement of the Pol β fingers domain during catalysis in the presence of either correct or incorrect dNTPs. By labeling the fingers domain with ((((2-iodoacetyl)amino)ethyl)amino)naphthalene-1-sulfonic acid (IAEDANS) and the DNA substrate with Dabcyl, we are able to observe rapid fingers closing in the presence of correct dNTPs as the IAEDANS comes into contact with a Dabcyl-labeled, one-base gapped DNA. Our findings show that not only do the fingers close after binding to the correct dNTP, but that there is a second conformational change associated with a non-covalent step not previously reported for Pol β. Further analyses suggest that this conformational change corresponds to the binding of the catalytic metal into the polymerase active site. FRET studies with incorrect dNTP result in no changes in fluorescence, indicating that the fingers do not close in the presence of incorrect dNTP. Together, our results show that nucleotide selection initially occurs in an open fingers conformation and that the catalytic pathways of correct and incorrect dNTPs differ from each other. Overall, this study provides new insight into the mechanism of substrate choice by a polymerase that plays a critical role in maintaining genome stability. PMID:24764311

  10. Continuous Energy, Multi-Dimensional Transport Calculations for Problem Dependent Resonance Self-Shielding

    SciTech Connect

    T. Downar

    2009-03-31

    The overall objective of the work here has been to eliminate the approximations used in current resonance treatments by developing continuous energy multi-dimensional transport calculations for problem dependent self-shielding calculations. The work here builds on the existing resonance treatment capabilities in the ORNL SCALE code system.

  11. Characteristics of vibration energy harvesting using giant magnetostrictive cantilevers with resonant tuning

    NASA Astrophysics Data System (ADS)

    Mori, Kotaro; Horibe, Tadashi; Ishikawa, Shigekazu; Shindo, Yasuhide; Narita, Fumio

    2015-12-01

    This work deals with the dynamic bending and energy harvesting characteristics of giant magnetostrictive cantilevers with resonant tuning both numerically and experimentally. The giant magnetostrictive cantilever is fabricated using a thin Terfenol-D layer, SUS layer, movable proof mass, etc, and, is designed to automatically adjust its own resonant frequency to match the external vibration frequency in real time. Three-dimensional finite element analysis was conducted, and the resonant frequency, induced voltage and stress in the magnetostrictive cantilevers were predicted. The resonant frequency and induced voltage were also measured, and comparison was made between simulation and experiment. The time-varying behavior and self-tuning ability are discussed in detail.

  12. Broadband performance of a piezoelectric energy harvester based on the internal resonance of buckled beam

    NASA Astrophysics Data System (ADS)

    Xiong, Liuyang; Tang, Lihua; Ding, Hu; Chen, Liqun; Mace, Brian

    2016-04-01

    Nonlinear internal resonance mechanism is exploited in piezoelectric vibration energy harvesting (PVEH) for the purpose of broadening the resonance band. Conventional linear energy harvester has narrow operating bandwidth. In this research, a buckled piezoelectric beam structure with preload under transverse excitation is investigated to demonstrate the superiority of internal resonance. The condition for 2:1 internal resonance could be established by truncating the continuum beam with geometrical nonlinearity. Integro-partial-differential equations are derived for governing transverse motion measured from a stable equilibrium position. At specific initial axial compressive force, two modes are coupled through the internal resonance interaction. For weak nonlinear perturbations, multiple scales method is used to explore the amplitude-frequency responses of the buckled beam system under primary resonance with 2:1 internal resonance. Numerical examples demonstrate that the resonance bandwidth is broadened thanks to the coexistence of softening and hardening nonlinear characteristics. Moreover, validity of the approximate analytical method is demonstrated by comparing with simulation. Furthermore, the optimal resistance is discussed with a pure resistive load. This research on the internal resonance of buckled beam provides a basis for structure design and optimization in broadband PVEH.

  13. Energy harvesting by dynamic unstability and internal resonance for piezoelectric beam

    SciTech Connect

    Lan, Chunbo; Qin, Weiyang Deng, Wangzheng

    2015-08-31

    We investigated the energy harvesting of a vertical beam with tip mass under vertical excitations. We applied dynamic unstability and internal resonance to improve the efficiency of harvesting. The experiments of harmonic excitation were carried out. Results show that for the beam there exist internal resonances in the dynamically unstable and the buckling bistable cases. The dynamic unstability is a determinant for strong internal resonance or mode coupling, which can be used to create a large output from piezoelectric patches. Then, the experiments of stochastic excitation were carried out. Results prove that the internal resonance or mode coupling can transfer the excitation energy to the low order modes, mainly the first and the second one. This can bring about a large output voltage. For a stochastic excitation, it is proved that there is an optimal weight of tip mass for realizing internal resonance and producing large outputs.

  14. The Evaluation of Empirical Resonance Energies as Reaction Enthalpies with Particular Reference to Benzene.

    ERIC Educational Resources Information Center

    George, Philip; And Others

    1984-01-01

    Discusses the nature of experimental resonance energy, explaining how its magnitude depends upon choice of reference molecules from which bond energies are derived. Also explains how it can be evaluated more simply, without recourse to bond energies, as enthalpy change for a reaction predetermined by choice of reference molecules. (JN)

  15. Biomolecular interactions probed by fluorescence resonance energy transfer

    NASA Astrophysics Data System (ADS)

    Lange, Daniela Charlotte

    2000-09-01

    This thesis describes how a physical phenomenon, Fluorescence Resonance Energy Transfer (FRET), can be exploited for the study of interactions between biomolecules. The physical basis of this phenomenon is discussed and it is described how some of its characteristics can be exploited in measurement. A recently introduced method, photobleaching FRET microscopy, was implemented and its image analysis refined to suit our biological context. Further, a new technique is proposed, which combines FRET with confocal laser scanning microscopy to optimize resolution and to allow for 3D-studies in living cells. The first part of this thesis presents the application of FRET to the study of oligomerization of G-protein coupled receptors (GPCRs), which was performed at the Fraser Laboratories at McGill University in Montreal. It is demonstrated how FRET microscopy allowed us to circumvent problems of traditional biochemical approaches and provided the first direct evidence for GPCR oligomerization in intact cells. We found that somatostatin receptors (SSTRs) functionally interact by forming oligomers with their own kind, with different SSTR isoforms, and even with distantly related GPCRs, such as dopamine receptors, the latter of which is breaking with the dogma that GPCRs would only pair up with their own kind. The high sensitivity of the FRET technique allowed us to characterize these interactions under more physiological conditions, which lead to the observation that oligomerization is induced by receptor agonist. We further studied the differential effects of agonists and antagonists on receptor oligomerization, leading to a model for the molecular mechanism underlying agonist/antagonist function and receptor activation. The second part was carried out at the Neurobiology Laboratory of the VA Medical Center in Newington, CT. The objective was to further our understanding of Niemann- Pick type C disease, which is characterized by a defect in intracellular cholesterol

  16. Direct observation of resonant scattering phase shifts and their energy dependence.

    PubMed

    Gensemer, Stephen D; Martin-Wells, Ross B; Bennett, Aaron W; Gibble, Kurt

    2012-12-28

    We scan the collision energy of two clouds of cesium atoms between 12 and 50  μK in an atomic fountain clock. By directly detecting the difference of s-wave scattering phase shifts, we observe a rapid variation of a scattering phase shift through a series of Feshbach resonances. At the energies we use, resonances that overlap at threshold become resolved. Our statistical phase uncertainty of 8 mrad can be improved in future precision measurements of Feshbach resonances to accurately determine the Cs-Cs interactions, which may provide stringent limits on the time variation of fundamental constants.

  17. The role of the partner atom and resonant excitation energy in ICD in rare gas dimers

    NASA Astrophysics Data System (ADS)

    O'Keeffe, Patrick; Ripani, Enrico; Bolognesi, Paola; Coreno, Marcello; Avaldi, Lorenzo; Devetta, Michele; Callegari, Carlo; Di Praia, Michele; Prince, Kevin; Richter, Robert; Alagial, Michele; Kivimäkil, Antti

    2014-04-01

    We show experimental evidence for Interatomic Coulombic Decay (ICD) in mixed rare gas dimers following resonant Auger decay. A velocity map imaging apparatus together with a cooled supersonic beam containing Ar2, ArNe and ArKr dimers was used to record electron VMI images in coincidence with two mass selected ions following excitation on five resonances converging to the Ar+ 2p-11/2 and 2p-13/2 thresholds using the synchrotron radiation. The results show that the kinetic energy distribution of the ICD electrons observed in coincidence with the ions from Coulomb explosion of the dimers depends on the partner ion and resonant photon energy.

  18. Cryogenic resonant microwave compressors with energy extraction through "warm" interference switches

    NASA Astrophysics Data System (ADS)

    Artemenko, S. N.; Samoilenko, G. M.; Shlapakovski, A. S.; Yushkov, Yu. G.

    2016-01-01

    A method of switching cryogenic resonant microwave compressors from the energy accumulation mode to the energy release mode is proposed and analyzed. The switching process is based on the resonant transfer of the microwave energy from a cryogenic storage cavity to a room temperature commutation cavity. The transfer can be realized using a cascade interference microwave switch weakly coupled to the storage cavity and consisting of two H-plane waveguide tees connected in series. The tees are made of a normally conducting material, located outside the cryostat, and contain commuting units in shorted side arms. The length of the cascade input arm (from the storage cavity to the first tee) is non-resonant, while the space between the storage cavity and the second tee is resonant. The weak coupling of the storage cavity to the cascade and the non-resonant length of its input arm allow one to minimize losses during the energy accumulation phase. When the commuting unit in the first tee is ignited, the tee opens, and the non-resonant volume of the cascade input arm is transformed into the volume of the resonant commutation cavity. The microwave energy is then transferred in a resonant way from the storage cavity to the commutation cavity, and when the transfer is complete, the commuting unit in the second tee is ignited to extract the energy into a load. It is shown analytically that, at a certain value of the coupling (the cryogenic storage cavity to the normally conducting cascade of tees) and length of the cascade input arm, the power gain in the storage cavity can be kept high. It is also shown that the energy accumulated in the storage cavity can be effectively transferred to the commutation cavity and from the commutation cavity to the load.

  19. Energy transfer based photoluminescence spectra of co-doped (Dy3+ + Sm3+): Li2O-LiF-B2O3-ZnO glasses for orange emission

    NASA Astrophysics Data System (ADS)

    Vijayalakshmi, L.; Naveen Kumar, K.; Vijayalakshmi, R. P.

    2016-07-01

    The present paper brings out the results concerning the preparation and optical properties of Sm3+ and Dy3+ each ion separately in different concentrations (0.3, 0.5, 1.0 and 1.5 mol.%) and also together doped (x mol.% Dy3+ + 1.5 mol.% Sm3+): Li2O-LiF-B2O3-ZnO (where x = 0.5, 1.0 and 1.5 mol.%) glasses by a melt quenching method. Structural and thermal properties have been extensively studied for those glasses by XRD and TG/DTA. The compositional analysis has been carried out from FTIR spectral profile. Optical absorption spectral studies were also carried out. Sm3+: LBZ glasses have displayed an intense orange emission at 603 nm (4G5/2 → 6H7/2) with an excitation wavelength at 403 nm and Dy3+: LBZ glasses have shown two emissions located at 485 nm (4F9/2 → 6H15/2; blue) and 574 nm (4F9/2 → 6H13/2; yellow) with an excitation wavelength at 385 nm. Remarkably, it has been identified that the significant increase in the reddish orange emission of Sm3+ ions and diminished yellow emission pertaining to Dy3+ ions in the co-doped LBZ glass system under the excitation of 385 nm which relates to Dy3+ ions. This could be due energy transfer from Dy3+ to Sm3+. The non-radiative energy transfer from Dy3+ to Sm3+ is explained in terms of their emission spectra, donor lifetime, energy level diagram and energy transfer characteristic factors. These significantly enhanced orange emission exhibited glasses could be suggested as potential optical glasses for orange luminescence photonic devices.

  20. Topology of the Adiabatic Potential Energy Surfaces for theResonance States of the Water Anion

    SciTech Connect

    Haxton, Daniel J.; Rescigno, Thomas N.; McCurdy, C. William

    2005-04-15

    The potential energy surfaces corresponding to the long-lived fixed-nuclei electron scattering resonances of H{sub 2}O relevant to the dissociative electron attachment process are examined using a combination of ab initio scattering and bound-state calculations. These surfaces have a rich topology, characterized by three main features: a conical intersection between the {sup 2}A{sub 1} and {sup 2}B{sub 2} Feshbach resonance states; charge-transfer behavior in the OH ({sup 2}{Pi}) + H{sup -} asymptote of the {sup 2}B{sub 1} and {sup 2}A{sub 1} resonances; and an inherent double-valuedness of the surface for the {sup 2}B{sub 2} state the C{sub 2v} geometry, arising from a branch-point degeneracy with a {sup 2}B{sub 2} shape resonance. In total, eight individual seams of degeneracy among these resonances are located.

  1. Multi-directional energy harvesting by piezoelectric cantilever-pendulum with internal resonance

    SciTech Connect

    Xu, J.; Tang, J.

    2015-11-23

    This letter reports a piezoelectric cantilever-pendulum design for multi-directional energy harvesting. A pendulum is attached to the tip of a piezoelectric cantilever-type energy harvester. This design aims at taking advantage of the nonlinear coupling between the pendulum motion in 3-dimensional space and the beam bending vibration at resonances. Experimental studies indicate that, under properly chosen parameters, 1:2 internal resonance can be induced, which enables the multi-directional energy harvesting with a single cantilever. The advantages of the design with respect to traditional piezoelectric cantilever are examined.

  2. Enhanced acoustoelectric coupling in acoustic energy harvester using dual Helmholtz resonators.

    PubMed

    Peng, Xiao; Wen, Yumei; Li, Ping; Yang, Aichao; Bai, Xiaoling

    2013-10-01

    In this paper, enhanced acoustoelectric transduction in an acoustic energy harvester using dual Helmholtz resonators has been reported. The harvester uses a pair of cavities mechanically coupled with a compliant perforated plate to enhance the acoustic coupling between the cavity and the plate. The experimental results show that the volume optimization of the second cavity can significantly increase the generated electric voltage up to 400% and raise the output power to 16 times as large as that of a harvester using a single Helmholtz resonator at resonant frequencies primarily related to the plate.

  3. Calculation of the quasi-energies and resonances behavior of the hydrogen Lyman-alpha problem

    NASA Technical Reports Server (NTRS)

    Ruyten, Wilhelmus M.

    1992-01-01

    Recently, Bakshi and Kalman presented numerical results for the quasi-energies of the n = 2 multiplet in the hydrogen Lyman-alpha transition for a plasma in which both strong static and oscillating electric fields are present. Recent work on related magnetic and optical resonance problems provides a simplified mathematical treatment, as well as greater insight into the complex resonance behavior of this interaction.

  4. Quantum mechanical resonance calculations using an energy selected basis in hyperspherical coordinates

    NASA Astrophysics Data System (ADS)

    Montgomery, Jason

    2007-12-01

    Scattering resonances play a key role in many chemical processes, including unimolecular and bimolecular reactions and photodissociation. A significant theoretical emphasis over the past several decades has been placed on accurate resonance calculations for polyatomic systems. In spite of such efforts, a quantum treatment of molecular systems which exhibit a high density of states and strong coordinate coupling near dissociation remains a formidable task. The research described herein employs improved quantum mechanical methods to calculate a representation of nuclear motion, both bound and unbound, which is used subsequently to calculate accurate resonance energies and lifetimes for two triatomic systems: the neon trimer and ozone. Specifically, theory and results are given regarding the construction of an optimal, L2 eigenbasis using techniques such as the discrete variable representation, the energy selected basis (ESB) method, and iterative diagonalization methods. A new energy selection method is also developed and implemented for the neon trimer. Subsequent resonance calculations are described which make use of the artificial boundary inhomogeneity (ABI) method, adapted to work with the above mentioned ESB and hyperspherical coordinates. The ABI method is used to calculate a set of linearly independent wavefunctions (LIWs) at a given energy for the representation of the scattering wavefunction. Resonance parameters are obtained by imposing scattering boundary conditions on a linear combination of LIWs and solving for the S-matrix, S, its energy derivative, dS/dE, and the Smith lifetime matrix, Q. When available, comparisons are made with previously reported calculations.

  5. On square-wave-driven stochastic resonance for energy harvesting in a bistable system

    NASA Astrophysics Data System (ADS)

    Su, Dongxu; Zheng, Rencheng; Nakano, Kimihiko; Cartmell, Matthew P.

    2014-11-01

    Stochastic resonance is a physical phenomenon through which the throughput of energy within an oscillator excited by a stochastic source can be boosted by adding a small modulating excitation. This study investigates the feasibility of implementing square-wave-driven stochastic resonance to enhance energy harvesting. The motivating hypothesis was that such stochastic resonance can be efficiently realized in a bistable mechanism. However, the condition for the occurrence of stochastic resonance is conventionally defined by the Kramers rate. This definition is inadequate because of the necessity and difficulty in estimating white noise density. A bistable mechanism has been designed using an explicit analytical model which implies a new approach for achieving stochastic resonance in the paper. Experimental tests confirm that the addition of a small-scale force to the bistable system excited by a random signal apparently leads to a corresponding amplification of the response that we now term square-wave-driven stochastic resonance. The study therefore indicates that this approach may be a promising way to improve the performance of an energy harvester under certain forms of random excitation.

  6. On square-wave-driven stochastic resonance for energy harvesting in a bistable system

    SciTech Connect

    Su, Dongxu; Zheng, Rencheng; Nakano, Kimihiko; Cartmell, Matthew P

    2014-11-15

    Stochastic resonance is a physical phenomenon through which the throughput of energy within an oscillator excited by a stochastic source can be boosted by adding a small modulating excitation. This study investigates the feasibility of implementing square-wave-driven stochastic resonance to enhance energy harvesting. The motivating hypothesis was that such stochastic resonance can be efficiently realized in a bistable mechanism. However, the condition for the occurrence of stochastic resonance is conventionally defined by the Kramers rate. This definition is inadequate because of the necessity and difficulty in estimating white noise density. A bistable mechanism has been designed using an explicit analytical model which implies a new approach for achieving stochastic resonance in the paper. Experimental tests confirm that the addition of a small-scale force to the bistable system excited by a random signal apparently leads to a corresponding amplification of the response that we now term square-wave-driven stochastic resonance. The study therefore indicates that this approach may be a promising way to improve the performance of an energy harvester under certain forms of random excitation.

  7. Nucleon resonances and pion-nucleon interaction in nuclear matter above the [Delta] resonance energy

    SciTech Connect

    Arima, M. ); Masutani, K. ); Seki, R. Department of Physics, California State University, Northridge, California 91330 )

    1995-01-01

    We investigate the [pi]-nucleon interaction in nuclear matter around [radical][ital s] =1.5 GeV by examining dynamical modifications of [ital N][sup *] resonances microscopically. The pion production through the [pi][Delta] channel is suppressed appreciably in nuclear matter because the pion produced is strongly distorted through a [Delta] formation with a neighboring nucleon. This effect makes the width of [ital N](1520) smaller and the mass larger in nuclear medium than in free space, and the [pi][ital N] [ital D][sub 13]-wave amplitude loses much of its inelasticity. A similar situation arises with [ital N](1535) and the [pi][ital N] [ital S][sub 11]-wave amplitude because the [eta][ital N] channel is suppressed by Pauli blocking of the nucleus that accompanies [eta]. The total widths of [ital N][sup *] in nuclear medium, however, could be larger than in free space because of their spreading potentials.

  8. The Properties and Origins of Resonant Patterns in the Energy Spectra of the Inner Electron Belt

    NASA Astrophysics Data System (ADS)

    Ukhorskiy, A. Y.; Sitnov, M. I.; Mitchell, D. G.; Takahashi, K.; Lanzerotti, L. J.

    2013-12-01

    The Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) on the Van Allen Probes mission provides electron and ion measurements from ~20 keV to ~10 MeV. High temporal and energy resolution electron measurements at RBSPICE show that energy spectra of the inner belt electrons exhibit regular resonance patterns which are more pronounced during intervals of increased geomagnetic activity. While these modulations were previously inferred from electron precipitation measurements on the low orbiting spacecraft, RBSPICE provides important insights into their properties at the equator where these patterns are formed. The modulations are observed over the entire inner belt and approximately follow 1/L energy dependence. This suggests that the modulation patterns are produced in the process of drift-resonant interaction of radiation belt electrons with large-scale fluctuations in the geomagnetic field. In this paper we describe properties of the resonant patterns and discuss their generation mechanisms.

  9. Bearing fault identification by higher order energy operator fusion: A non-resonance based approach

    NASA Astrophysics Data System (ADS)

    Faghidi, H.; Liang, M.

    2016-10-01

    We report a non-resonance based approach to bearing fault detection. This is achieved by a higher order energy operator fusion (HOEO_F) method. In this method, multiple higher order energy operators are fused to form a single simple transform to process the bearing signal obscured by noise and vibration interferences. The fusion is guided by entropy minimization. Unlike the popular high frequency resonance technique, this method does not require the information of resonance excited by the bearing fault. The effects of the HOEO_F method on signal-to-noise ratio (SNR) and signal-to-interference ratio (SIR) are illustrated in this paper. The performance of the proposed method in handling noise and interferences has been examined using both simulated and experimental data. The results indicate that the HOEO_F method outperforms both the envelope method and the original energy operator method.

  10. A new Skyrme energy density functional for a better description of spin-isospin resonances

    NASA Astrophysics Data System (ADS)

    Roca-Maza, X.; Colò, G.; Cao, Li-Gang; Sagawa, H.

    2015-10-01

    A correct determination of the isospin and spin-isospin properties of the nuclear effective interaction should lead to an accurate description of the Gamow-Teller resonance (GT), the Spin Dipole Resonance (SDR), the Giant Dipole Resonance (GDR) or the Antianalog Giant Dipole Resonance (AGDR), among others. A new Skyrme energy density functional named SAMi is introduced with the aim of going a step forward in setting the bases for a more precise description of spin-isospin resonances [1, 2]. In addition, we will discuss some new features of our analysis on the AGDR in 208Pb [3] as compared with available experimental data on this resonance [4, 5, 6], and on the GDR [7]. Such study, guided by a simple yet physical pocket formula, has been developed by employing the so called SAMi-J family of systematically varied interactions. This set of interactions is compatible with experimental data for values of the symmetry energy at saturation J and slope parameter L falling in the ranges 31-33 MeV and 75-95 MeV, respectively.

  11. A new Skyrme energy density functional for a better description of spin-isospin resonances

    SciTech Connect

    Roca-Maza, X.; Colò, G.; Cao, Li-Gang; Sagawa, H.

    2015-10-15

    A correct determination of the isospin and spin-isospin properties of the nuclear effective interaction should lead to an accurate description of the Gamow-Teller resonance (GT), the Spin Dipole Resonance (SDR), the Giant Dipole Resonance (GDR) or the Antianalog Giant Dipole Resonance (AGDR), among others. A new Skyrme energy density functional named SAMi is introduced with the aim of going a step forward in setting the bases for a more precise description of spin-isospin resonances [1, 2]. In addition, we will discuss some new features of our analysis on the AGDR in {sup 208}Pb [3] as compared with available experimental data on this resonance [4, 5, 6], and on the GDR [7]. Such study, guided by a simple yet physical pocket formula, has been developed by employing the so called SAMi-J family of systematically varied interactions. This set of interactions is compatible with experimental data for values of the symmetry energy at saturation J and slope parameter L falling in the ranges 31−33 MeV and 75−95 MeV, respectively.

  12. Brightening gold nanoparticles: new sensing approach based on plasmon resonance energy transfer.

    PubMed

    Shi, Lei; Jing, Chao; Gu, Zhen; Long, Yi-Tao

    2015-05-11

    Scattering recovered plasmonic resonance energy transfer (SR-PRET) was reported by blocking the plasmon resonance energy transfer (PRET) from gold nanoparticle (GNP) to the adsorbed molecules (RdBS). Due to the selective cleavage of the Si-O bond by F- ions, the quenching is switched off causing an increase in the brightness of the GNPs,detected using dark-field microscopy (DFM) were brightened. This method was successfully applied to the determination of fluoride ions in water. The SR-PRET provides a potential approach for a vitro/vivo sensing with high sensitivity and selectivity.

  13. Brightening Gold Nanoparticles: New Sensing Approach Based on Plasmon Resonance Energy Transfer

    PubMed Central

    Shi, Lei; Jing, Chao; Gu, Zhen; Long, Yi-Tao

    2015-01-01

    Scattering recovered plasmonic resonance energy transfer (SR-PRET) was reported by blocking the plasmon resonance energy transfer (PRET) from gold nanoparticle (GNP) to the adsorbed molecules (RdBS). Due to the selective cleavage of the Si-O bond by F− ions, the quenching is switched off causing an increase in the brightness of the GNPs,detected using dark-field microscopy (DFM) were brightened. This method was successfully applied to the determination of fluoride ions in water. The SR-PRET provides a potential approach for a vitro/vivo sensing with high sensitivity and selectivity. PMID:25959016

  14. Nonradiative resonance energy transfer between semiconductor quantum dots

    SciTech Connect

    Samosvat, D. M. Chikalova-Luzina, O. P.; Zegrya, G. G.

    2015-07-15

    A microscopic analysis of the mechanisms of nonradiative energy transfer in a system of two semiconductor QDs caused by Coulomb interaction of donor and acceptor electrons is performed. The energy transfer rate is calculated for QDs based on III–V compounds using the Kane model. Conditions are analyzed under which energy transfer from a donor to an acceptor is possible. The mixing in of the p states of the valence band to the s states of the conduction band is found to give rise to additional contributions to the matrix element of energy transfer. It is shown that these additional contributions play a considerable role in the energy transfer process at distances between QDs close to contact distances or much greater. The influence of the exchange interaction on the energy transfer mechanism is analyzed, and it is shown that this interaction should be taken into account for a quantitative description of the energy transfer when QDs are separated by a distance close to the contact distance.

  15. Nonradiative resonance energy transfer between semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Samosvat, D. M.; Chikalova-Luzina, O. P.; Zegrya, G. G.

    2015-07-01

    A microscopic analysis of the mechanisms of nonradiative energy transfer in a system of two semiconductor QDs caused by Coulomb interaction of donor and acceptor electrons is performed. The energy transfer rate is calculated for QDs based on III-V compounds using the Kane model. Conditions are analyzed under which energy transfer from a donor to an acceptor is possible. The mixing in of the p states of the valence band to the s states of the conduction band is found to give rise to additional contributions to the matrix element of energy transfer. It is shown that these additional contributions play a considerable role in the energy transfer process at distances between QDs close to contact distances or much greater. The influence of the exchange interaction on the energy transfer mechanism is analyzed, and it is shown that this interaction should be taken into account for a quantitative description of the energy transfer when QDs are separated by a distance close to the contact distance.

  16. Resonant gate driver with efficient gate energy recovery and switching loss reduction

    NASA Astrophysics Data System (ADS)

    Kim, I.-G.; Kwak, S.-S.

    2016-04-01

    This article describes a novel resonant gate driver for charging the gate capacitor of power metal-oxide semiconductor field-effect-transistors (MOSFETs) that operate at a high switching frequency in power converters. The proposed resonant gate driver is designed with three small MOSFETs to build up the inductor current in addition to an inductor for temporary energy storage. The proposed resonant gate driver recovers the CV2 gate loss, which is the largest loss dissipated in the gate resistance in conventional gate drivers. In addition, the switching loss is reduced at the instants of turn on and turn off in the power MOSFETs of power converters by using the proposed gate driver. Mathematical analyses of the total loss appearing in the gate driver circuit and the switching loss reduction in the power switch of power converters are discussed. Finally, the proposed resonant gate driver is verified with experimental results at a switching frequency of 1 MHz.

  17. Measuring distances within unfolded biopolymers using fluorescence resonance energy transfer: The effect of polymer chain dynamics on the observed fluorescence resonance energy transfer efficiency

    PubMed Central

    Makarov, Dmitrii E.; Plaxco, Kevin W.

    2009-01-01

    Recent years have seen a number of investigations in which distances within unfolded proteins, polypeptides, and other biopolymers are probed via fluorescence resonance energy transfer, a method that relies on the strong distance dependence of energy transfer between a pair of dyes attached to the molecule of interest. In order to interpret the results of such experiments it is commonly assumed that intramolecular diffusion is negligible during the excited state lifetime. Here we explore the conditions under which this “frozen chain” approximation fails, leading to significantly underestimated donor-acceptor distances, and describe a means of correcting for polymer dynamics in order to estimate these distances more accurately. PMID:19725638

  18. Piezoelectric cantilever-pendulum for multi-directional energy harvesting with internal resonance

    NASA Astrophysics Data System (ADS)

    Xu, J.; Tang, J.

    2015-04-01

    Piezoelectric transducers are widely employed in vibration-based energy harvesting schemes. Simple piezoelectric cantilever for energy harvesting is uni-directional and has bandwidth limitation. In this research we explore utilizing internal resonances to harvest vibratory energy due to excitations from an arbitrary direction with the usage of a single piezoelectric cantilever. Specifically, it is identified that by attaching a pendulum to the piezoelectric cantilever, 1:2 internal resonances can be induced based on the nonlinear coupling. The nonlinear effect induces modal energy exchange between beam bending motion and pendulum motions in 3-dimensional space, which ultimately yield multidirectional energy harvesting by a single cantilever. Systematic analysis and experimental investigation are carried out to demonstrate this new concept.

  19. Intense energy transfer and superharmonic resonance in a system of two coupled oscillators.

    PubMed

    Kovaleva, Agnessa; Manevitch, Leonid; Manevitch, Elina

    2010-05-01

    The paper presents the analytic study of energy exchange in a system of coupled nonlinear oscillators subject to superharmonic resonance. The attention is given to complete irreversible energy transfer that occurs in a system with definite initial conditions corresponding to a so-called limiting phase trajectory (LPT). We show that the energy imparted in the system is partitioned among the principal and superharmonic modes but energy exchange can be due to superharmonic oscillations. Using the LPT concept, we construct approximate analytic solutions describing intense irreversible energy transfer in a harmonically excited Duffing oscillator and a system of two nonlinearly coupled oscillators. Numerical simulations confirm the accuracy of the analytic approximations. PMID:20866315

  20. Dual-Functional Energy-Harvesting and Vibration Control: Electromagnetic Resonant Shunt Series Tuned Mass Dampers.

    PubMed

    Zuo, Lei; Cui, Wen

    2013-10-01

    This paper proposes a novel retrofittable approach for dual-functional energy-harvesting and robust vibration control by integrating the tuned mass damper (TMD) and electromagnetic shunted resonant damping. The viscous dissipative element between the TMD and primary system is replaced by an electromagnetic transducer shunted with a resonant RLC circuit. An efficient gradient based numeric method is presented for the parameter optimization in the control framework for vibration suppression and energy harvesting. A case study is performed based on the Taipei 101 TMD. It is found that by tuning the TMD resonance and circuit resonance close to that of the primary structure, the electromagnetic resonant-shunt TMD achieves the enhanced effectiveness and robustness of double-mass series TMDs, without suffering from the significantly amplified motion stroke. It is also observed that the parameters and performances optimized for vibration suppression are close to those optimized for energy harvesting, and the performance is not sensitive to the resistance of the charging circuit or electrical load.

  1. Dual-Functional Energy-Harvesting and Vibration Control: Electromagnetic Resonant Shunt Series Tuned Mass Dampers.

    PubMed

    Zuo, Lei; Cui, Wen

    2013-10-01

    This paper proposes a novel retrofittable approach for dual-functional energy-harvesting and robust vibration control by integrating the tuned mass damper (TMD) and electromagnetic shunted resonant damping. The viscous dissipative element between the TMD and primary system is replaced by an electromagnetic transducer shunted with a resonant RLC circuit. An efficient gradient based numeric method is presented for the parameter optimization in the control framework for vibration suppression and energy harvesting. A case study is performed based on the Taipei 101 TMD. It is found that by tuning the TMD resonance and circuit resonance close to that of the primary structure, the electromagnetic resonant-shunt TMD achieves the enhanced effectiveness and robustness of double-mass series TMDs, without suffering from the significantly amplified motion stroke. It is also observed that the parameters and performances optimized for vibration suppression are close to those optimized for energy harvesting, and the performance is not sensitive to the resistance of the charging circuit or electrical load. PMID:23918165

  2. A small-form-factor piezoelectric vibration energy harvester using a resonant frequency-down conversion

    SciTech Connect

    Sun, Kyung Ho; Kim, Young-Cheol; Kim, Jae Eun

    2014-10-15

    While environmental vibrations are usually in the range of a few hundred Hertz, small-form-factor piezoelectric vibration energy harvesters will have higher resonant frequencies due to the structural size effect. To address this issue, we propose a resonant frequency-down conversion based on the theory of dynamic vibration absorber for the design of a small-form-factor piezoelectric vibration energy harvester. The proposed energy harvester consists of two frequency-tuned elastic components for lowering the first resonant frequency of an integrated system but is so configured that an energy harvesting beam component is inverted with respect to the other supporting beam component for a small form factor. Furthermore, in order to change the unwanted modal characteristic of small separation of resonant frequencies, as is the case with an inverted configuration, a proof mass on the supporting beam component is slightly shifted toward a second proof mass on the tip of the energy harvesting beam component. The proposed small-form-factor design capability was experimentally verified using a fabricated prototype with an occupation volume of 20 × 39 × 6.9 mm{sup 3}, which was designed for a target frequency of as low as 100 Hz.

  3. Efficient Structure Resonance Energy Transfer from Microwaves to Confined Acoustic Vibrations in Viruses.

    PubMed

    Yang, Szu-Chi; Lin, Huan-Chun; Liu, Tzu-Ming; Lu, Jen-Tang; Hung, Wan-Ting; Huang, Yu-Ru; Tsai, Yi-Chun; Kao, Chuan-Liang; Chen, Shih-Yuan; Sun, Chi-Kuang

    2015-12-09

    Virus is known to resonate in the confined-acoustic dipolar mode with microwave of the same frequency. However this effect was not considered in previous virus-microwave interaction studies and microwave-based virus epidemic prevention. Here we show that this structure-resonant energy transfer effect from microwaves to virus can be efficient enough so that airborne virus was inactivated with reasonable microwave power density safe for the open public. We demonstrate this effect by measuring the residual viral infectivity of influenza A virus after illuminating microwaves with different frequencies and powers. We also established a theoretical model to estimate the microwaves power threshold for virus inactivation and good agreement with experiments was obtained. Such structure-resonant energy transfer induced inactivation is mainly through physically fracturing the virus structure, which was confirmed by real-time reverse transcription polymerase chain reaction. These results provide a pathway toward establishing a new epidemic prevention strategy in open public for airborne virus.

  4. Efficient Structure Resonance Energy Transfer from Microwaves to Confined Acoustic Vibrations in Viruses

    NASA Astrophysics Data System (ADS)

    Yang, Szu-Chi; Lin, Huan-Chun; Liu, Tzu-Ming; Lu, Jen-Tang; Hung, Wan-Ting; Huang, Yu-Ru; Tsai, Yi-Chun; Kao, Chuan-Liang; Chen, Shih-Yuan; Sun, Chi-Kuang

    2015-12-01

    Virus is known to resonate in the confined-acoustic dipolar mode with microwave of the same frequency. However this effect was not considered in previous virus-microwave interaction studies and microwave-based virus epidemic prevention. Here we show that this structure-resonant energy transfer effect from microwaves to virus can be efficient enough so that airborne virus was inactivated with reasonable microwave power density safe for the open public. We demonstrate this effect by measuring the residual viral infectivity of influenza A virus after illuminating microwaves with different frequencies and powers. We also established a theoretical model to estimate the microwaves power threshold for virus inactivation and good agreement with experiments was obtained. Such structure-resonant energy transfer induced inactivation is mainly through physically fracturing the virus structure, which was confirmed by real-time reverse transcription polymerase chain reaction. These results provide a pathway toward establishing a new epidemic prevention strategy in open public for airborne virus.

  5. DEVELOPMENT OF A REAL-TIME FLUORESCENCE RESONANCE ENERGY TRANSFER (FRET) PCR TO DETECT ARCOBACTER SPECIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A real-time PCR targeting the gyrase A subunit gene outside the quinolone resistance-determining region has been developed to detect Arcobacter species. The species identification was made by probe hybridization and melting curve analysis, using the Fluorescence Resonance Energy Transfer technology...

  6. Evaluation of Silicon Neutron Resonance Parameters in the Energy Range Thermal to 1800 keV

    SciTech Connect

    Derrien, H.

    2002-09-30

    The evaluation of the neutron cross sections of the three stable isotopes of silicon in the energy range thermal to 20 MeV was performed by Hetrick et al. for ENDF/B-VI (Evaluated Nuclear Data File). Resonance parameters were obtained in the energy range thermal to 1500 keV from a SAMMY analysis of the Oak Ridge National Laboratory experimental neutron transmission data. A new measurement of the capture cross section of natural silicon in the energy range 1 to 700 keV has recently been performed at the Oak Ridge Electron Linear Accelerator. Results of this measurement were used in a SAMMY reevaluation of the resonance parameters, allowing determination of the capture width of a large number of resonances. The experimental data base is described; properties of the resonance parameters are given. For the first time the direct neutron capture component has been taken into account from the calculation by Rauscher et al. in the energy range from thermal to 1 MeV. Results of benchmark calculations are also given. The new evaluation is available in the ENDF/B-VI format.

  7. Stark resonances of the Yukawa potential: Energies and widths, crossings and avoided crossings

    SciTech Connect

    Pawlak, Mariusz; Bylicki, Miroslaw

    2011-02-15

    The resonance energy spectrum of a system interacting with the Yukawa potential and embedded in an external homogeneous and static electric field is investigated. The positions and widths of levels have been computed by using the complex coordinate rotation method. Interesting avoided-crossing and crossing effects appear.

  8. DEVELOPMENT OF A REAL-TIME FLUORESCENCE RESONANCE ENERGY TRANSFER PCR TO DETECT ARCOBACTER SPECIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A real-time PCR targeting the gyrase A subunit gene outside the quinolone resistance-determining region has been developed to detect Arcobacter species. The species identification was made by probe hybridization and melting curve analysis, using Fluorescence Resonance Energy Transfer technology. D...

  9. The impact of covariance information on criticality safety calculations in the resolved resonance energy range.

    SciTech Connect

    Naberejnev, D. G.; Palmiotti, G.; Yang, W. S.

    2004-06-11

    Resonance data play a significant role in the calculations of systems considered for criticality safety applications. K{sub eff}, the major parameter of interest in such a type of calculations, can be heavily dependent both on the quality of the resonance data as well as on the accuracy achieved in the processing of these data. If reasonable uncertainty values are available, in conjunction with their correlation in energy and among type of resonance parameters, one can exploit existing methodologies, based on perturbation theory, in order to evaluate their impact on the integral parameter of interest, i.e., K{sub eff} in our case, in practical applications. In this way, one could be able to judge if the uncertainty on specific quantities, e.g., covariances on resonance data, have a significant impact and, therefore, deserve a careful evaluation. This report, first, will recall the basic principles that lie behind an uncertainty evaluation and review the current situation in the field of covariance data. Then an attempt is made for defining a methodology that allows calculating covariances values for resolved resonance parameters. Finally, practical applications, of interest for criticality safety calculations, illustrate the impact of different assumptions on correlations among resolved resonance parameters.

  10. High-energy tail distributions and resonant wave particle interaction

    NASA Technical Reports Server (NTRS)

    Leubner, M. P.

    1983-01-01

    High-energy tail distributions (k distributions) are used as an alternative to a bi-Lorentzian distribution to study the influence of energetic protons on the right- and left-hand cyclotron modes in a hot two-temperature plasma. Although the parameters are chosen to be in a range appropriate to solar wind or magnetospheric configurations, the results apply not only to specific space plasmas. The presence of energetic particles significantly alters the behavior of the electromagnetic ion cyclotron modes, leading to a wide range of unstable frequencies and increased growth rates. From the strongly enhanced growth rates it can be concluded that high-energy tail distributions should not show major temperature anisotropies, which is consistent with observations.

  11. Resonant scattering and charm showers in ultrahigh-energy neutrino interactions

    NASA Technical Reports Server (NTRS)

    Wilczek, F.

    1985-01-01

    Electron antineutrinos with energy of about 7 x 10 to the 6th GeV have much-enhanced cross sections due to W-boson production off electrons. Possible signals due to cosmic-ray sources are estimated. Higher-energy antineutrinos can efficiently produce a W accompanied by radiation. Another possibility, which could lead to shadowing at modest depths, is resonant production of a charged Higgs particle. The importance of muon production by charm showers in rock is pointed out.

  12. ''Magic'' Energies for Detecting Light Elements with Resonant Alpha Particle Backscattering

    SciTech Connect

    Wetteland, C.J.; Maggiore, C.J.; Tesmer, J.R.; He, X-M.; Lee, D-H.

    1998-11-04

    Resonant backscattering is widely used to improve the detection limit of the light elements such as B, C, N and O. One disadvantage, however, is that several incident energies are normally needed if the sample contains a number of the light elements. There are ''magic'' energies at which several light elements can be detected simultaneously with suitable sensitivities. When these energies are used along with the elastic recoil detection of hydrogen, multiple elements can be detected without changing the beam energy, and the analysis time is greatly reduced. These reactions along with examples will be discussed.

  13. Solid state nuclear magnetic resonance investigations of advanced energy materials

    NASA Astrophysics Data System (ADS)

    Bennett, George D.

    In order to better understand the physical electrochemical changes that take place in lithium ion batteries and asymmetric hybrid supercapacitors solid state nuclear magnetic resonance (NMR) spectroscopy has been useful to probe and identify changes on the atomic and molecular level. NMR is used to characterize the local environment and investigate the dynamical properties of materials used in electrochemical storage devices (ESD). NMR investigations was used to better understand the chemical composition of the solid electrolyte interphase which form on the negative and positive electrodes of lithium batteries as well as identify the breakdown products that occur in the operation of the asymmetric hybrid supercapacitors. The use of nano-structured particles in the development of new materials causes changes in the electrical, structural and other material properties. NMR was used to investigate the affects of fluorinated and non fluorinated single wall nanotubes (SWNT). In this thesis three experiments were performed using solid state NMR samples to better characterize them. The electrochemical reactions of a lithium ion battery determine its operational profile. Numerous means have been employed to enhance battery cycle life and operating temperature range. One primary means is the choice and makeup of the electrolyte. This study focuses on the characteristics of the solid electrolyte interphase (SEI) that is formed on the electrodes surface during the charge discharge cycle. The electrolyte in this study was altered with several additives in order to determine the influence of the additives on SEI formation as well as the intercalation and de-intercalation of lithium ions in the electrodes. 7Li NMR studies where used to characterize the SEI and its composition. Solid state NMR studies of the carbon enriched acetonitrile electrolyte in a nonaqueous asymmetric hybrid supercapacitor were performed. Magic angle spinning (MAS) coupled with cross polarization NMR

  14. A Wireless Magnetic Resonance Energy Transfer System for Micro Implantable Medical Sensors

    PubMed Central

    Li, Xiuhan; Zhang, Hanru; Peng, Fei; Li, Yang; Yang, Tianyang; Wang, Bo; Fang, Dongming

    2012-01-01

    Based on the magnetic resonance coupling principle, in this paper a wireless energy transfer system is designed and implemented for the power supply of micro-implantable medical sensors. The entire system is composed of the in vitro part, including the energy transmitting circuit and resonant transmitter coils, and in vivo part, including the micro resonant receiver coils and signal shaping chip which includes the rectifier module and LDO voltage regulator module. Transmitter and receiver coils are wound by Litz wire, and the diameter of the receiver coils is just 1.9 cm. The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system. When the distance between the transmitter coils and the receiver coils is 1.5 cm, the transfer efficiency is 85% at the frequency of 742 kHz. The power transfer efficiency can be optimized by adding magnetic enhanced resonators. The receiving voltage signal is converted to a stable output voltage of 3.3 V and a current of 10 mA at the distance of 2 cm. In addition, the output current varies with changes in the distance. The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm3. PMID:23112600

  15. Performance optimization of total momentum filtering double-resonance energy selective electron heat pump

    NASA Astrophysics Data System (ADS)

    Ding, Ze-Min; Chen, Lin-Gen; Ge, Yan-Lin; Sun, Feng-Rui

    2016-04-01

    A theoretical model for energy selective electron (ESE) heat pumps operating with two-dimensional electron reservoirs is established in this study. In this model, a double-resonance energy filter operating with a total momentum filtering mechanism is considered for the transmission of electrons. The optimal thermodynamic performance of the ESE heat pump devices is also investigated. Numerical calculations show that the heating load of the device with two resonances is larger, whereas the coefficient of performance (COP) is lower than the ESE heat pump when considering a single-resonance filter. The performance characteristics of the ESE heat pumps in the total momentum filtering condition are generally superior to those with a conventional filtering mechanism. In particular, the performance characteristics of the ESE heat pumps considering a conventional filtering mechanism are vastly different from those of a device with total momentum filtering, which is induced by extra electron momentum in addition to the horizontal direction. Parameters such as resonance width and energy spacing are found to be associated with the performance of the electron system.

  16. Broadening the Frequency Bandwidth of Piezoelectric Energy Harvesters Using Coupled Linear Resonators

    NASA Astrophysics Data System (ADS)

    Sadeqi, Soheil

    The desire to reduce power consumption of current integrated circuits has led design engineers to focus on harvesting energy from free ambient sources such as vibrations. The energy harvested this way can eliminate the need for battery replacement, particularly, in low-energy remote sensing and wireless devices. Currently, most vibration-based energy harvesters are designed as linear resonators, therefore, they have a narrow resonance frequency. The optimal performance of such harvesters is achieved only when their resonance frequency is matched with the ambient excitation. In practice, however, a slight shift of the excitation frequency will cause a dramatic reduction in their performance. In the majority of cases, the ambient vibrations are totally random with their energy distributed over a wide frequency spectrum. Thus, developing techniques to extend the bandwidth of vibration-based energy harvesters has become an important field of research in energy harvesting systems. This thesis first reviews the broadband vibration-based energy harvesting techniques currently known in some detail with regard to their merits and applicability under different circumstances. After that, the design, fabrication, modeling and characterization of three new piezoelectric-based energy harvesting mechanism, built typically for rotary motion applications, is discussed. A step-by-step procedure is followed in order to broaden the bandwidth of such energy harvesters by introducing a coupled spring-mass system attached to a PZT beam undergoing rotary motion. It is shown that the new strategies can indeed give rise to a wide-band frequency response making it possible to fine-tune their dynamical response. The numerical results are shown to be in good agreement with the experimental data as far as the frequency response is concerned.

  17. Broadband vibration energy harvesting by application of stochastic resonance from rotational environments

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Zheng, R.; Kaizuka, T.; Su, D.; Nakano, K.; Cartmell, M. P.

    2015-11-01

    A model for energy harvesting from a rotating automotive tyre is suggested in which the principle of stochastic resonance is advantageously exploited. A bistable response characteristic is obtained by recourse a small harvester comprising a magnetically repellant configuration in which an instrumented cantilever beam can flip between two physical response states when suitably excited by the rotation of a car wheel into which it is fitted. The rotation of the wheel creates a periodic modulation which enables stochastic resonance to take place and as a consequence of this for energy to be harvested from road noise transmitted through the tyre. An optimised mathematical model of the system is presented based on a series of experimental tests and it is shown that a ten-fold increase in harvested energy over a comparable monostable case is feasible. The suggested application for this harvester is to provide electrical power for a tyre pressure monitoring system.

  18. Resonance Energy of an Arene Hydrocarbon from Heat of Combustion Measurements

    PubMed Central

    Kolesnichenko, Vladimir L.

    2015-01-01

    A simple experimental method for determination of the resonance energy by measuring the energies of combustion for two isomeric compounds, aromatic 1-tert-butyl-3,5-dimethylbenzene and nonaromatic trans,trans,cis-1,5,9-cyclododecatriene is proposed. Both compounds not only have the same molecular formula, but also contain the same number of sp2 and sp3 carbon atoms. After converting the obtained values into the gas phase heats of combustion and subtracting one value from another, the resulting mean resonance energy of 184 kJ/mol was obtained. The proposed method can be offered as an experiment for an undergraduate physical chemistry lab curriculum. PMID:26997668

  19. Energy harvesting from coherent resonance of horizontal vibration of beam excited by vertical base motion

    SciTech Connect

    Lan, C. B.; Qin, W. Y.

    2014-09-15

    This letter investigates the energy harvesting from the horizontal coherent resonance of a vertical cantilever beam subjected to the vertical base excitation. The potential energy of the system has two symmetric potential wells. So, under vertical excitation, the system can jump between two potential wells, which will lead to the large vibration in horizontal direction. Two piezoelectric patches are pasted to harvest the energy. From experiment, it is found that the vertical excitation can make the beam turn to be bistable. The system can transform vertical vibration into horizontal vibration of low frequency when excited by harmonic motion. The horizontal coherence resonance can be observed when excited by a vertical white noise. The corresponding output voltages of piezoelectric films reach high values.

  20. Resonant energy transfer between Eu luminescent sites and their local geometry in GaN

    SciTech Connect

    Timmerman, Dolf; Wakamatsu, Ryuta; Tanaka, Kazuteru; Lee, Dong-gun; Koizumi, Atsushi; Fujiwara, Yasufumi

    2015-10-12

    Eu-doped GaN is a solid state material with promising features for quantum manipulation. In this study, we investigate the population dynamics of Eu in ions in this system by resonant excitation. From differences in the emission related to transitions between the {sup 5}D{sub 0} and {sup 7}F{sub 2} manifold in the Eu ions, we can distinguish different luminescence sites and observe that a resonant energy transfer takes place between two of these sites which are in proximity of each other. The time constants related to this energy transfer are on the order of 100 μs. By using different substrates, the energy transfer efficiency could be strongly altered, and it is demonstrated that the coupling between ions has an out-of-plane character. Based on these results, a microscopic model of this combined center is presented.

  1. Zero-energy resonances of hydrogen diatom isotopologs: tuning quasiresonant transitions in vibration space.

    PubMed

    Yang, Benhui; Forrey, R C; Stancil, P C; Fonseca dos Santos, S; Balakrishnan, N

    2012-12-01

    Highly efficient and specific energy transfer mechanisms that involve rotation-rotation, vibration-vibration, and vibration-rotation exchange in diatomic molecules are examined theoretically in ultracold H(2), D(2), and HD self-collisions as a function of initial vibrational level v. The three quasiresonant mechanisms are found to operate for all vibrational levels and yield complex scattering lengths which vary smoothly with v. Exceptions to this trend occur at select high values of v where the scattering lengths are modulated by orders of magnitude corresponding to the location of an s-wave zero-energy resonance in "vibration space." The quasiresonant mechanisms, which are not very sensitive to the details of the interaction potential, generally control the final distribution of molecular states for any given initial distribution. The zero-energy resonances are more sensitive to the potential and may be used to vibrationally "tune" the interaction strength, similar to methods which vary applied external fields.

  2. Experimental characterization of cantilever-type piezoelectric generator operating at resonance for vibration energy harvesting

    NASA Astrophysics Data System (ADS)

    Montanini, Roberto; Quattrocchi, Antonino

    2016-06-01

    A cantilever-type resonant piezoelectric generator (RPG) has been designed by gluing a PZT patch working in d31 mode onto a glass fibre reinforced composite cantilever beam with a discrete mass applied on its free end. The electrical and dynamic behaviour of the RPG prototype has been investigated by carrying out laboratory tests aimed to assess the effect of definite design parameters, specifically the electric resistance load and the excitation frequency. Results showed that an optimum resistance load exists, at which power generation is maximized. Moreover, it has been showed that power generation is strongly influenced by the vibration frequency highlighting that, at resonance, output power can be increased by more than one order of magnitude. Possible applications include inertial resonant harvester for energy recovery from vibrating machines, sea waves or wind flux and self-powering of wireless sensor nodes.

  3. Anomalies in the theory of viscous energy losses due to shear in rotational MEMS resonators.

    SciTech Connect

    Walsh, Timothy Francis; Klody, Kelly Anne; Jenkins, Mark W.; Dohner, Jeffrey Lynn

    2003-12-01

    In this paper, the effect of viscous wave motion on a micro rotational resonator is discussed. This work shows the inadequacy of developing theory to represent energy losses due to shear motion in air. Existing theory predicts Newtonian losses with little slip at the interface. Nevertheless, experiments showed less effect due to Newtonian losses and elevated levels of slip for small gaps. Values of damping were much less than expected. Novel closed form solutions for the response of components are presented. The stiffness of the resonator is derived using Castigliano's theorem, and viscous fluid motion above and below the resonator is derived using a wave approach. Analytical results are compared with experimental results to determine the utility of existing theory. It was found that existing macro and molecular theory is inadequate to describes measured responses.

  4. Spectral energy analysis of locally resonant nanophononic metamaterials by molecular simulations

    NASA Astrophysics Data System (ADS)

    Honarvar, Hossein; Hussein, Mahmoud I.

    2016-02-01

    A nanophononic metamaterial is a new type of nanostructured material that features an array, or a forest, of intrinsically distributed resonating substructures. Each substructure exhibits numerous local resonances, each of which may hybridize with the phonon dispersion of the underlying host material, causing significant reductions in the group velocities and consequently a reduction in the lattice thermal conductivity. In this Rapid Communication, molecular dynamics simulations are utilized to investigate both the dynamics and the thermal transport properties of a nanophononic metamaterial configuration consisting of a freely suspended silicon membrane with an array of silicon nanopillars standing on the surface. The simulations yield results consistent with earlier lattice-dynamics-based predictions which showed a reduction in the thermal conductivity due to the presence of the local resonators. Using a spectral energy density approach, in which only simulation data are utilized and no a priori information on the nanostructure resonant phonon modes is provided, we show direct evidence of the existence of resonance hybridizations as an inherent mechanism contributing to the slowing down of thermal transport in the host medium.

  5. Superconducting resonator used as a phase and energy detector for linac setup

    NASA Astrophysics Data System (ADS)

    Lobanov, Nikolai R.

    2016-07-01

    Booster linacs for tandem accelerators and positive ion superconducting injectors have matured into standard features of many accelerator laboratories. Both types of linac are formed as an array of independently-phased resonators operating at room temperature or in a superconducting state. Each accelerating resonator needs to be individually set in phase and amplitude for optimum acceleration efficiency. The modularity of the linac allows the velocity profile along the structure to be tailored to accommodate a wide range charge to mass ratio. The linac setup procedure, described in this paper, utilizes a superconducting resonator operating in a beam bunch phase detection mode. The main objective was to derive the full set of phase distributions for quick and efficient tuning of the entire accelerator. The phase detector was operated in overcoupling mode in order to minimize de-tuning effects of microphonic background. A mathematical expression was derived to set a limit on resonator maximum accelerating field during the crossover search to enable extracting unambiguous beam phase data. A set of equations was obtained to calculate the values of beam phase advance and energy gain produced by accelerating resonators. An extensive range of linac setting up configurations was conducted to validate experimental procedures and analytical models. The main application of a superconducting phase detector is for fast tuning for beams of ultralow intensities, in particular in the straight section of linac facilities.

  6. Three New Low-Energy Resonances in the ^{22}Ne(p,γ)^{23}Na Reaction.

    PubMed

    Cavanna, F; Depalo, R; Aliotta, M; Anders, M; Bemmerer, D; Best, A; Boeltzig, A; Broggini, C; Bruno, C G; Caciolli, A; Corvisiero, P; Davinson, T; di Leva, A; Elekes, Z; Ferraro, F; Formicola, A; Fülöp, Zs; Gervino, G; Guglielmetti, A; Gustavino, C; Gyürky, Gy; Imbriani, G; Junker, M; Menegazzo, R; Mossa, V; Pantaleo, F R; Prati, P; Scott, D A; Somorjai, E; Straniero, O; Strieder, F; Szücs, T; Takács, M P; Trezzi, D

    2015-12-18

    The ^{22}Ne(p,γ)^{23}Na reaction takes part in the neon-sodium cycle of hydrogen burning. This cycle affects the synthesis of the elements between ^{20}Ne and ^{27}Al in asymptotic giant branch stars and novae. The ^{22}Ne(p,γ)^{23}Na reaction rate is very uncertain because of a large number of unobserved resonances lying in the Gamow window. At proton energies below 400 keV, only upper limits exist in the literature for the resonance strengths. Previous reaction rate evaluations differ by large factors. In the present work, the first direct observations of the ^{22}Ne(p,γ)^{23}Na resonances at 156.2, 189.5, and 259.7 keV are reported. Their resonance strengths are derived with 2%-7% uncertainty. In addition, upper limits for three other resonances are greatly reduced. Data are taken using a windowless ^{22}Ne gas target and high-purity germanium detectors at the Laboratory for Underground Nuclear Astrophysics in the Gran Sasso laboratory of the National Institute for Nuclear Physics, Italy, taking advantage of the ultralow background observed deep underground. The new reaction rate is a factor of 20 higher than the recent evaluation at a temperature of 0.1 GK, relevant to nucleosynthesis in asymptotic giant branch stars. PMID:26722918

  7. Low-frequency two-dimensional resonators for vibrational micro energy harvesting

    NASA Astrophysics Data System (ADS)

    Bartsch, U.; Gaspar, J.; Paul, O.

    2010-03-01

    The fabrication, characterization and theoretical analysis of a novel two-dimensional silicon resonator with threefold rotational symmetry are described. The resonator consists of a 4 mm wide disk-shaped seismic mass having the full-wafer thickness of 525 µm and suspended by a system of concentric circular springs. The device is structured using two-sided deep reactive-ion etching of silicon. With its current spring thickness and height, the device has two closely spaced resonance frequencies at 370.5 and 373.9 Hz and a quality factor of 1800 at ambient pressure. The spring height and thus the resonance frequency of the device are easily tuned by simple adjustment of a single etch duration in the entire fabrication process. The dynamic response of the structure is modeled under the two assumptions that silicon is elastically (i) isotropic and (ii) anisotropic. In comparison with the isotropic model, the elastic anisotropy leads to a predicted mode splitting by 6.2 Hz, with oscillation directions aligned with the cubic crystal axes. Even small geometrical imperfections are found to significantly rotate the eigenmodes and to further modulate their frequency splitting. Experimental and numerical results corroborate these conclusions. Overall the present resonator design has the potential for a higher energy harvesting efficiency than a combination of two separate one-dimensional oscillators.

  8. Three New Low-Energy Resonances in the ^{22}Ne(p,γ)^{23}Na Reaction.

    PubMed

    Cavanna, F; Depalo, R; Aliotta, M; Anders, M; Bemmerer, D; Best, A; Boeltzig, A; Broggini, C; Bruno, C G; Caciolli, A; Corvisiero, P; Davinson, T; di Leva, A; Elekes, Z; Ferraro, F; Formicola, A; Fülöp, Zs; Gervino, G; Guglielmetti, A; Gustavino, C; Gyürky, Gy; Imbriani, G; Junker, M; Menegazzo, R; Mossa, V; Pantaleo, F R; Prati, P; Scott, D A; Somorjai, E; Straniero, O; Strieder, F; Szücs, T; Takács, M P; Trezzi, D

    2015-12-18

    The ^{22}Ne(p,γ)^{23}Na reaction takes part in the neon-sodium cycle of hydrogen burning. This cycle affects the synthesis of the elements between ^{20}Ne and ^{27}Al in asymptotic giant branch stars and novae. The ^{22}Ne(p,γ)^{23}Na reaction rate is very uncertain because of a large number of unobserved resonances lying in the Gamow window. At proton energies below 400 keV, only upper limits exist in the literature for the resonance strengths. Previous reaction rate evaluations differ by large factors. In the present work, the first direct observations of the ^{22}Ne(p,γ)^{23}Na resonances at 156.2, 189.5, and 259.7 keV are reported. Their resonance strengths are derived with 2%-7% uncertainty. In addition, upper limits for three other resonances are greatly reduced. Data are taken using a windowless ^{22}Ne gas target and high-purity germanium detectors at the Laboratory for Underground Nuclear Astrophysics in the Gran Sasso laboratory of the National Institute for Nuclear Physics, Italy, taking advantage of the ultralow background observed deep underground. The new reaction rate is a factor of 20 higher than the recent evaluation at a temperature of 0.1 GK, relevant to nucleosynthesis in asymptotic giant branch stars.

  9. English to Sanskrit Machine Translation Using Transfer Based approach

    NASA Astrophysics Data System (ADS)

    Pathak, Ganesh R.; Godse, Sachin P.

    2010-11-01

    Translation is one of the needs of global society for communicating thoughts and ideas of one country with other country. Translation is the process of interpretation of text meaning and subsequent production of equivalent text, also called as communicating same meaning (message) in another language. In this paper we gave detail information on how to convert source language text in to target language text using Transfer Based Approach for machine translation. Here we implemented English to Sanskrit machine translator using transfer based approach. English is global language used for business and communication but large amount of population in India is not using and understand the English. Sanskrit is ancient language of India most of the languages in India are derived from Sanskrit. Sanskrit can be act as an intermediate language for multilingual translation.

  10. Continuous energy, multi-dimensional discrete ordinates transport calculations for problem dependent resonance treatment

    NASA Astrophysics Data System (ADS)

    Zhong, Zhaopeng

    In the past twenty 20 years considerable progress has been made in developing new methods for solving the multi-dimensional transport problem. However the effort devoted to the resonance self-shielding calculation has lagged, and much less progress has been made in enhancing resonance-shielding techniques for generating problem-dependent multi-group cross sections (XS) for the multi-dimensional transport calculations. In several applications, the error introduced by self-shielding methods exceeds that due to uncertainties in the basic nuclear data, and often they can be the limiting factor on the accuracy of the final results. This work is to improve the accuracy of the resonance self-shielding calculation by developing continuous energy multi-dimensional transport calculations for problem dependent self-shielding calculations. A new method has been developed, it can calculate the continuous-energy neutron fluxes for the whole two-dimensional domain, which can be utilized as weighting function to process the self-shielded multi-group cross sections for reactor analysis and criticality calculations, and during this process, the two-dimensional heterogeneous effect in the resonance self-shielding calculation can be fully included. A new code, GEMINEWTRN (Group and Energy-Pointwise Methodology Implemented in NEWT for Resonance Neutronics) has been developed in the developing version of SCALE [1], it combines the energy pointwise (PW) capability of the CENTRM [2] with the two-dimensional discrete ordinates transport capability of lattice physics code NEWT [14]. Considering the large number of energy points in the resonance region (typically more than 30,000), the computational burden and memory requirement for GEMINEWTRN is tremendously large, some efforts have been performed to improve the computational efficiency, parallel computation has been implemented into GEMINEWTRN, which can save the computation and memory requirement a lot; some energy points reducing

  11. Electron energy distribution function by using probe method in electron cyclotron resonance multicharged ion source

    SciTech Connect

    Kumakura, Sho Kurisu, Yosuke; Kimura, Daiju; Yano, Keisuke; Imai, Youta; Sato, Fuminobu; Kato, Yushi; Iida, Toshiyuki

    2014-02-15

    We are constructing a tandem type electron cyclotron resonance (ECR) ion source (ECRIS). High-energy electrons in ECRIS plasma affect electron energy distribution and generate multicharged ion. In this study, we measure electron energy distribution function (EEDF) of low energy region (≦100 eV) in ECRIS plasma at extremely low pressures (10{sup −3}–10{sup −5} Pa) by using cylindrical Langmuir probe. From the result, it is found that the EEDF correlates with the electron density and the temperature from the conventional probe analysis. In addition, we confirm that the tail of EEDF spreads to high energy region as the pressure rises and that there are electrons with high energy in ECR multicharged ion source plasma. The effective temperature estimated from the experimentally obtained EEDF is larger than the electron temperature obtained from the conventional method.

  12. Electron energy distribution function by using probe method in electron cyclotron resonance multicharged ion source.

    PubMed

    Kumakura, Sho; Kurisu, Yosuke; Kimura, Daiju; Yano, Keisuke; Imai, Youta; Sato, Fuminobu; Kato, Yushi; Iida, Toshiyuki

    2014-02-01

    We are constructing a tandem type electron cyclotron resonance (ECR) ion source (ECRIS). High-energy electrons in ECRIS plasma affect electron energy distribution and generate multicharged ion. In this study, we measure electron energy distribution function (EEDF) of low energy region (≦100 eV) in ECRIS plasma at extremely low pressures (10(-3)-10(-5) Pa) by using cylindrical Langmuir probe. From the result, it is found that the EEDF correlates with the electron density and the temperature from the conventional probe analysis. In addition, we confirm that the tail of EEDF spreads to high energy region as the pressure rises and that there are electrons with high energy in ECR multicharged ion source plasma. The effective temperature estimated from the experimentally obtained EEDF is larger than the electron temperature obtained from the conventional method.

  13. Orbital Feshbach resonances with a small energy gap between open and closed channels

    NASA Astrophysics Data System (ADS)

    Cheng, Yanting; Zhang, Ren; Zhang, Peng

    2016-04-01

    Recently, a new type of Feshbach resonance, i.e., orbital Feshbach resonance (OFR), was proposed for the ultracold alkaline-earth-metal-like atoms and was experimentally observed in the ultracold gases of 173Yb atoms. Unlike most of the magnetic Feshbach resonances of ultracold alkali atoms, when the OFR of 173Yb atoms appears, the energy gap between the thresholds of the open channel (OC) and the closed channel (CC) is much smaller than the characteristic energy of the interatomic interaction, i.e., the van der Waals energy. In this paper we study the OFR in systems with a small CC-OC threshold gap. We show that in these systems the OFR can be induced by the coupling between the OC and either an isolated bound state of the CC or the scattering states of the CC. Moreover, we also show that in each case the two-channel Huang-Yang pesudopotential is always applicable for the approximate calculation of the low-energy scattering amplitude. Our results imply that in the two-channel theoretical calculations for these systems it is appropriate to take into account the contributions from the scattering states of the CC.

  14. Metastable anions of dinitrobenzene: Resonances for electron attachment and kinetic energy release

    SciTech Connect

    Mauracher, A.; Denifl, S.; Edtbauer, A.; Hager, M.; Probst, M.; Scheier, P.; Echt, O.; Maerk, T. D.; Field, T. A.; Graupner, K.

    2010-12-28

    Attachment of free, low-energy electrons to dinitrobenzene (DNB) in the gas phase leads to DNB{sup -} as well as several fragment anions. DNB{sup -}, (DNB-H){sup -}, (DNB-NO){sup -}, (DNB-2NO){sup -}, and (DNB-NO{sub 2}){sup -} are found to undergo metastable (unimolecular) dissociation. A rich pattern of resonances in the yield of these metastable reactions versus electron energy is observed; some resonances are highly isomer-specific. Most metastable reactions are accompanied by large average kinetic energy releases (KER) that range from 0.5 to 1.32 eV, typical of complex rearrangement reactions, but (1,3-DNB-H){sup -} features a resonance with a KER of only 0.06 eV for loss of NO. (1,3-DNB-NO){sup -} offers a rare example of a sequential metastable reaction, namely, loss of NO followed by loss of CO to yield C{sub 5}H{sub 4}O{sup -} with a large KER of 1.32 eV. The G4(MP2) method is applied to compute adiabatic electron affinities and reaction energies for several of the observed metastable channels.

  15. A resonant electromagnetic vibration energy harvester for intelligent wireless sensor systems

    SciTech Connect

    Qiu, Jing Wen, Yumei; Li, Ping; Liu, Xin; Chen, Hengjia; Yang, Jin

    2015-05-07

    Vibration energy harvesting is now receiving more interest as a means for powering intelligent wireless sensor systems. In this paper, a resonant electromagnetic vibration energy harvester (VEH) employing double cantilever to convert low-frequency vibration energy into electrical energy is presented. The VEH is made up of two cantilever beams, a coil, and magnetic circuits. The electric output performances of the proposed electromagnetic VEH have been investigated. With the enhancement of turns number N, the optimum peak power of electromagnetic VEH increases sharply and the resonance frequency deceases gradually. When the vibration acceleration is 0.5 g, we obtain the optimum output voltage and power of 9.04 V and 50.8 mW at frequency of 14.9 Hz, respectively. In a word, the prototype device was successfully developed and the experimental results exhibit a great enhancement in the output power and bandwidth compared with other traditional electromagnetic VEHs. Remarkably, the proposed resonant electromagnetic VEH have great potential for applying in intelligent wireless sensor systems.

  16. Multi-resonant wideband energy harvester based on a folded asymmetric M-shaped cantilever

    SciTech Connect

    Wu, Meng; Mao, Haiyang; Li, Zhigang; Liu, Ruiwen; Ming, Anjie; Ou, Yi; Ou, Wen

    2015-07-15

    This article reports a compact wideband piezoelectric vibration energy harvester consisting of three proof masses and an asymmetric M-shaped cantilever. The M-shaped beam comprises a main beam and two folded and dimension varied auxiliary beams interconnected through the proof mass at the end of the main cantilever. Such an arrangement constitutes a three degree-of-freedom vibrating body, which can tune the resonant frequencies of its first three orders close enough to obtain a utility wide bandwidth. The finite element simulation results and the experimental results are well matched. The operation bandwidth comprises three adjacent voltage peaks on account of the frequency interval shortening mechanism. The result shows that the proposed piezoelectric energy harvester could be efficient and adaptive in practical vibration circumstance based on multiple resonant modes.

  17. Deciphering activation of olfactory receptors using heterologous expression in Saccharomyces cerevisiae and bioluminescence resonance energy transfer.

    PubMed

    Sanz, Guenhaël; Pajot-Augy, Edith

    2013-01-01

    Hetero- and homo-oligomerization of G protein-coupled receptors (GPCRs) has been addressed in the past years using various approaches such as co-immunoprecipitation, fluorescence resonance energy transfer and bioluminescence resonance energy transfer (BRET). Here, we report the methodological details from a previously published study to investigate the relationships between oligomerization and activation states of olfactory receptors (ORs). This methodology combines heterologous expression of ORs in Saccharomyces cerevisiae and BRET assays on membrane fractions, in particular, upon odorant stimulation. We have demonstrated that ORs constitutively homodimerize at the plasma membrane and that high odorant concentrations promote a conformational change of the dimer, which becomes inactive. We proposed a model in which one odorant molecule binding the dimer would induce activation, while two odorant molecules, each binding one protomer of the dimer, would blunt signaling.

  18. Investigating real-time activation of adenosine receptors by bioluminescence resonance energy transfer technique

    NASA Astrophysics Data System (ADS)

    Huang, Yimei; Yang, Hongqin; Zheng, Liqin; Chen, Jiangxu; Wang, Yuhua; Li, Hui; Xie, Shusen

    2013-02-01

    Adenosine receptors play important roles in many physiological and pathological processes, for example regulating myocardial oxygen consumption and the release of neurotransmitters. The activations of adenosine receptors have been studied by some kinds of techniques, such as western blot, immunohistochemistry, etc. However, these techniques cannot reveal the dynamical response of adenosine receptors under stimulation. In this paper, bioluminescence resonance energy transfer technique was introduced to study the real-time activation of adenosine receptors by monitoring the dynamics of cyclic adenosine monophosphate (cAMP) level. The results showed that there were significant differences between adenosine receptors on real-time responses under stimulation. Moreover, the dynamics of cAMP level demonstrated that competition between adenosine receptors existed. Taken together, our study indicates that monitoring the dynamics of cAMP level using bioluminescence resonance energy transfer technique could be one potential approach to investigate the mechanism of competitions between adenosine receptors.

  19. Non-resonant electromechanical energy harvesting using inter-ferroelectric phase transitions

    SciTech Connect

    Pérez Moyet, Richard; Rossetti, George A.; Stace, Joseph; Amin, Ahmed; Finkel, Peter

    2015-10-26

    Non-resonant electromechanical energy harvesting is demonstrated under low frequency excitation (<50 Hz) using [110]{sub C}-poled lead indium niobate-lead magnesium niobate-lead titanate relaxor ferroelectric single crystals with compositions near the morphotropic phase boundary. The efficiency of power generation at the stress-induced phase transition between domain-engineered rhombohedral and orthorhombic ferroelectric states is as much as four times greater than is obtained in the linear piezoelectric regime under identical measurement conditions but during loading below the coercive stress of the phase change. The phase transition mode of electromechanical transduction holds potential for non-resonant energy harvesting from low-frequency vibrations and does not require mechanical frequency up-conversion.

  20. Multi-resonant wideband energy harvester based on a folded asymmetric M-shaped cantilever

    NASA Astrophysics Data System (ADS)

    Wu, Meng; Ou, Yi; Mao, Haiyang; Li, Zhigang; Liu, Ruiwen; Ming, Anjie; Ou, Wen

    2015-07-01

    This article reports a compact wideband piezoelectric vibration energy harvester consisting of three proof masses and an asymmetric M-shaped cantilever. The M-shaped beam comprises a main beam and two folded and dimension varied auxiliary beams interconnected through the proof mass at the end of the main cantilever. Such an arrangement constitutes a three degree-of-freedom vibrating body, which can tune the resonant frequencies of its first three orders close enough to obtain a utility wide bandwidth. The finite element simulation results and the experimental results are well matched. The operation bandwidth comprises three adjacent voltage peaks on account of the frequency interval shortening mechanism. The result shows that the proposed piezoelectric energy harvester could be efficient and adaptive in practical vibration circumstance based on multiple resonant modes.

  1. A Bioluminescence Resonance Energy Transfer (BRET) System: Application to Interacting Circadian Clock Proteins

    NASA Astrophysics Data System (ADS)

    Xu, Yao; Piston, David W.; Hirschie Johnson, Carl

    1999-01-01

    We describe a method for assaying protein interactions that offers some attractive advantages over previous assays. This method, called bioluminescence resonance energy transfer (BRET), uses a bioluminescent luciferase that is genetically fused to one candidate protein, and a green fluorescent protein mutant fused to another protein of interest. Interactions between the two fusion proteins can bring the luciferase and green fluorescent protein close enough for resonance energy transfer to occur, thus changing the color of the bioluminescent emission. By using proteins encoded by circadian (daily) clock genes from cyanobacteria, we use the BRET technique to demonstrate that the clock protein KaiB interacts to form homodimers. BRET should be particularly useful for testing protein interactions within native cells, especially with integral membrane proteins or proteins targeted to specific organelles.

  2. Measuring IL-1β Processing by Bioluminescence Sensors I: Using a Bioluminescence Resonance Energy Transfer Biosensor.

    PubMed

    Compan, Vincent; Pelegrín, Pablo

    2016-01-01

    IL-1β processing is one of the hallmarks of inflammasome activation and drives the initiation of the inflammatory response. For decades, Western blot or ELISA have been extensively used to study this inflammatory event. Here, we describe the use of a bioluminescence resonance energy transfer (BRET) biosensor to monitor IL-1β processing in real time and in living macrophages either using a plate reader or a microscope.

  3. Resonant energy transfer from argon dimers to atomic oxygen in microhollow cathode discharges

    NASA Astrophysics Data System (ADS)

    Moselhy, M.; Stark, R. H.; Schoenbach, K. H.; Kogelschatz, U.

    2001-02-01

    The emission of atomic oxygen lines at 130.2 and 130.5 nm from a microhollow cathode discharge in argon with oxygen added indicates resonant energy transfer from argon dimers to oxygen atoms. The internal efficiency of the vacuum-ultraviolet (VUV) radiation was measured as 0.7% for a discharge in 1100 Torr argon with 0.1% oxygen added. The direct current VUV point source operates at voltages below 300 V and at current levels of milliamperes.

  4. Molding resonant energy transfer by colloidal crystal: Dexter transfer and electroluminescence

    NASA Astrophysics Data System (ADS)

    González-Urbina, Luis; Kolaric, Branko; Libaers, Wim; Clays, Koen

    2010-05-01

    Building photonic crystals by combination of colloidal ordering and metal sputtering we were able to construct a system sensitive to an electrical field. In corresponding crystals we embedded the Dexter pair (Ir(ppy3) and BAlq) and investigated the influence of the band gap on the resonant energy transfer when the system is excited by light and by an electric field respectively. Our investigations extend applications of photonic crystals into the field of electroluminescence and LED technologies.

  5. Ground state potential energy surfaces around selected atoms from resonant inelastic x-ray scattering

    NASA Astrophysics Data System (ADS)

    Schreck, Simon; Pietzsch, Annette; Kennedy, Brian; Såthe, Conny; Miedema, Piter S.; Techert, Simone; Strocov, Vladimir N.; Schmitt, Thorsten; Hennies, Franz; Rubensson, Jan-Erik; Föhlisch, Alexander

    2016-01-01

    Thermally driven chemistry as well as materials’ functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future.

  6. Ground state potential energy surfaces around selected atoms from resonant inelastic x-ray scattering

    PubMed Central

    Schreck, Simon; Pietzsch, Annette; Kennedy, Brian; Såthe, Conny; Miedema, Piter S.; Techert, Simone; Strocov, Vladimir N.; Schmitt, Thorsten; Hennies, Franz; Rubensson, Jan-Erik; Föhlisch, Alexander

    2016-01-01

    Thermally driven chemistry as well as materials’ functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future. PMID:26821751

  7. Ground state potential energy surfaces around selected atoms from resonant inelastic x-ray scattering.

    PubMed

    Schreck, Simon; Pietzsch, Annette; Kennedy, Brian; Såthe, Conny; Miedema, Piter S; Techert, Simone; Strocov, Vladimir N; Schmitt, Thorsten; Hennies, Franz; Rubensson, Jan-Erik; Föhlisch, Alexander

    2016-01-01

    Thermally driven chemistry as well as materials' functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future.

  8. Dynamics of suspended microchannel resonators conveying opposite internal fluid flow: Stability, frequency shift and energy dissipation

    NASA Astrophysics Data System (ADS)

    Zhang, Wen-Ming; Yan, Han; Jiang, Hui-Ming; Hu, Kai-Ming; Peng, Zhi-Ke; Meng, Guang

    2016-04-01

    In this paper, the dynamics of suspended microchannel resonators which convey internal flows with opposite directions are investigated. The fluid-structure interactions between the laminar fluid flow and oscillating cantilever are analyzed by comprehensively considering the effects of velocity profile, flow viscosity and added flowing particle. A new model is developed to characterize the dynamic behavior of suspended microchannel resonators with the fluid-structure interactions. The stability, frequency shift and energy dissipation of suspended microchannel resonators are analyzed and discussed. The results demonstrate that the frequency shifts induced by the added flowing particle which are obtained from the new model have a good agreement with the experimental data. The steady mean flow can cause the frequency shift and influence the stability of the dynamic system. As the flow velocity reaches the critical value, the coupled-mode flutter occurs via a Hamiltonian Hopf bifurcation. The perturbation flow resulted from the vibration of the microcantilever leads to energy dissipation, while the steady flow does not directly cause the damping which increases with the increasing of the flow velocity predicted by the classical model. It can also be found that the steady flow firstly changes the mode shape of the cantilever and consequently affects the energy dissipation.

  9. Energy harvesting using rattleback: Theoretical analysis and simulations of spin resonance

    NASA Astrophysics Data System (ADS)

    Nanda, Aditya; Singla, Puneet; Karami, M. Amin

    2016-05-01

    This paper investigates the spin resonance of a rattleback subjected to base oscillations which is able to transduce vibrations into continuous rotary motion and, therefore, is ideal for applications in Energy harvesting and Vibration sensing. The rattleback is a toy with some curious properties. When placed on a surface with reasonable friction, the rattleback has a preferred direction of spin. If rotated anti to it, longitudinal vibrations are set up and spin direction is reversed. In this paper, the dynamics of a rattleback placed on a sinusoidally vibrating platform are simulated. We can expect base vibrations to excite the pitch motion of the rattleback, which, because of the coupling between pitch and spin motion, should cause the rattleback to spin. Results are presented which show that this indeed is the case-the rattleback has a mono-peak spin resonance with respect to base vibrations. The dynamic response of the rattleback was found to be composed of two principal frequencies that appeared in the pitch and rolling motions. One of the frequencies was found to have a large coupling with the spin of the rattleback. Spin resonance was found to occur when the base oscillatory frequency was twice the value of the coupled frequency. A linearized model is developed which can predict the values of the two frequencies accurately and analytical expressions for the same in terms of the parameters of the rattleback have been derived. The analysis, thus, forms an effective and easy method for obtaining the spin resonant frequency of a given rattleback. Novel ideas for applications utilizing the phenomenon of spin resonance, for example, an energy harvester composed of a magnetized rattleback surrounded by ferromagnetic walls and a small scale vibration sensor comprising an array of several magnetized rattlebacks, are included.

  10. Fluorescence resonance energy transfers measurements on cell surfaces via fluorescence polarization.

    PubMed Central

    Cohen-Kashi, Meir; Moshkov, Sergey; Zurgil, Naomi; Deutsch, Mordechai

    2002-01-01

    A method has been developed for the determination of the efficiency of fluorescence resonance energy transfer efficiency between moieties located on cell surfaces by performing individual cell fluorescence polarization (FP) measurements. The absolute value of energy transfer efficiency (E) is calculated on an individual cell basis. The examination of this methodology was carried out using model experiments on human T lymphocyte cells. The cells were labeled with fluorescein-conjugated Concanavalin A (ConA) as donor, or rhodamine-conjugated ConA as acceptor. The experiments and results clearly indicate that determination of E via FP measurements is possible, efficient, and more convenient than other methods. PMID:12202365

  11. Piezoelectric Wind-Energy-Harvesting Device with Reed and Resonant Cavity

    NASA Astrophysics Data System (ADS)

    Ji, Jun; Kong, Fanrang; He, Liangguo; Guan, Qingchun; Feng, Zhihua

    2010-05-01

    A wind-energy-harvesting device utilizing the principle of a harmonica was created. A reed in a resonant cavity vibrated efficiently with the blowing wind, and a piezoelectric element stuck on the reed generated electricity. The dimensions of the wind inlet were approximately 30×20 mm2. The device was investigated with a wind speed ranging from 2.8 to 10 m/s. An output power of 0.5-4.5 mW was obtained with a matching load of 0.46 MΩ. The energy conversion efficiency of the device could reach up to 2.4%.

  12. Shape resonances, overtones, and electron energy loss spectroscopy of gas phase and physisorbed diatomic molecules

    NASA Astrophysics Data System (ADS)

    Gadzuk, J. W.

    1983-10-01

    Electron energy loss spectra of O2 and N2 physisorbed on metallic substrates showing a series of high overtone losses have recently been reported. In the case of N2, the intense overtone excitation is credited to the formation of a well-known temporary negative ion state with a resonance lifetime ˜10-15 s for gas phase N2-. The principal distinction between the gaseous and physisorbed molecule EELS spectrum is a significant depletion of the overtone intensity which has been attributed to a surface-induced decrease in the resonance lifetime. In the present work, a time dependent quantum mechanical model applicable to vibrational excitation in resonance scattering is outlined which quantitatively accounts for the observed spectra and, in particular, the surface modifications to the gas phase results. The essential feature of the model is one in which the intramolecular dynamics of the intermediate state is characterized by nuclear propagation over a harmonic potential curve spatially displaced from the ground state curve for a time duration equal to the resonance lifetime. The resulting calculated overtone spectra agree well with the experimentally observed ones. The results suggest that the physisorbed N-2 lifetime is about 40% of that of the free molecule.

  13. Two-dimensional resonance frequency tuning approach for vibration-based energy harvesting

    NASA Astrophysics Data System (ADS)

    Dong, Lin; Prasad, M. G.; Fisher, Frank T.

    2016-06-01

    Vibration-based energy harvesting seeks to convert ambient vibrations to electrical energy and is of interest for, among other applications, powering the individual nodes of wireless sensor networks. Generally it is desired to match the resonant frequencies of the device to the ambient vibration source to optimize the energy harvested. This paper presents a two-dimensionally (2D) tunable vibration-based energy harvesting device via the application of magnetic forces in two-dimensional space. These forces are accounted for in the model separately, with the transverse force contributing to the transverse stiffness of the system while the axial force contributes to a change in axial stiffness of the beam. Simulation results from a COMSOL magnetostatic 3D model agree well with the analytical model and are confirmed with a separate experimental study. Furthermore, analysis of the three possible magnetization orientations between the fixed and tuning magnets shows that the transverse parallel magnetization orientation is the most effective with regards to the proposed 2D tuning approach. In all cases the transverse stiffness term is in general significantly larger than the axial stiffness contribution, suggesting that from a tuning perspective it may be possible to use these stiffness contributions for coarse and fine frequency tuning, respectively. This 2D resonant frequency tuning approach extends earlier 1D approaches and may be particularly useful in applications where space constraints impact the available design space of the energy harvester.

  14. Resonant principle for operation of energy recuperator for a magnetized electron beam: A numerical simulation

    NASA Astrophysics Data System (ADS)

    Arzhannikov, A. V.; Astrelin, V. T.; Koidan, V. S.; Sinitsky, S. L.

    2002-04-01

    The problem of energy recuperator for a high current sheet electron beam used to drive a millimeter-waves generator is considered. There are two main obstacles to solving the problem. The first one is the presence of a magnetic field guiding beam electrons. The second obstacle is significant energy and angular spreads of the electrons in the waste beam. To overcome these obstacles, we suggest a novel scheme of a recuperator. The main idea of the proposed scheme is the use of a decelerating electrical field together with a guiding magnetic field that has longitudinal and spatial periodic transverse components. Resonance of a bounce electron motion with the cyclotron motion in this field gives a strong increase in the Larmour radius of electrons with the energy in a narrow interval. The decelerated electrons with the resonance energy fall away from the beam and are absorbed by a collector at a proper potential. It is shown that efficiency of this novel scheme can reach about 80% even if the sheet beam has a broad energy spectrum.

  15. Hunting for dark matter coannihilation by mixing dijet resonances and missing transverse energy

    NASA Astrophysics Data System (ADS)

    Buschmann, Malte; El Hedri, Sonia; Kaminska, Anna; Liu, Jia; de Vries, Maikel; Wang, Xiao-Ping; Yu, Felix; Zurita, José

    2016-09-01

    Simplified models of the dark matter (co)annihilation mechanism predict striking new collider signatures untested by current searches. These models, which were codified in the coannihilation codex, provide the basis for a dark matter (DM) discovery program at the Large Hadron Collider (LHC) driven by the measured DM relic density. In this work, we study an exemplary model featuring s-channel DM coannihilation through a scalar diquark mediator as a representative case study of scenarios with strongly interacting coannihilation partners. We discuss the full phenomenology of the model, ranging from low energy flavor constraints, vacuum stability requirements, and precision Higgs effects to direct detection and indirect detection prospects. Moreover, motivated by the relic density calculation, we find significant portions of parameter space are compatible with current collider constraints and can be probed by future searches, including a proposed analysis for the novel signature of a dijet resonance accompanied by missing transverse energy (MET). Our results show that the 13 TeV LHC with 100 fb-1 luminosity should be sensitive to mediators as heavy as 1 TeV and dark matter in the 400-500 GeV range. The combination of searches for single and paired dijet peaks, non-resonant jets + MET excesses, and our novel resonant dijet + MET signature have strong coverage of the motivated relic density region, reflecting the tight connections between particles determining the dark matter abundance and their experimental signatures at the LHC.

  16. Efficient Structure Resonance Energy Transfer from Microwaves to Confined Acoustic Vibrations in Viruses

    PubMed Central

    Yang, Szu-Chi; Lin, Huan-Chun; Liu, Tzu-Ming; Lu, Jen-Tang; Hung, Wan-Ting; Huang, Yu-Ru; Tsai, Yi-Chun; Kao, Chuan-Liang; Chen, Shih-Yuan; Sun, Chi-Kuang

    2015-01-01

    Virus is known to resonate in the confined-acoustic dipolar mode with microwave of the same frequency. However this effect was not considered in previous virus-microwave interaction studies and microwave-based virus epidemic prevention. Here we show that this structure-resonant energy transfer effect from microwaves to virus can be efficient enough so that airborne virus was inactivated with reasonable microwave power density safe for the open public. We demonstrate this effect by measuring the residual viral infectivity of influenza A virus after illuminating microwaves with different frequencies and powers. We also established a theoretical model to estimate the microwaves power threshold for virus inactivation and good agreement with experiments was obtained. Such structure-resonant energy transfer induced inactivation is mainly through physically fracturing the virus structure, which was confirmed by real-time reverse transcription polymerase chain reaction. These results provide a pathway toward establishing a new epidemic prevention strategy in open public for airborne virus. PMID:26647655

  17. Beyond the Lorentzian Model in Quantum Transport: Energy-Dependent Resonance Broadening in Molecular Junctions

    NASA Astrophysics Data System (ADS)

    Liu, Zhenfei; Neaton, Jeffrey B.

    In quantum transport calculations, transmission functions of molecular junctions, as well as spectral functions of metal-organic interfaces, often feature peaks originating from molecular resonances. These resonance peaks are often assumed to be Lorentzian, with an energy-independent broadening function Γ. However, in the general case, the wide-band-limit breaks down, and the Lorentzian approximation is no longer valid. Here, we develop a new energy-dependent broadening function Γ (E) , based on diagonalization of non-Hermitian matrices within a non-equilbrium Green's function (NEGF) formalism. As defined, Γ (E) can describe resonances of non-Lorentzian nature and can be decomposed into components associated with the left and right leads, respectively; and it is particularly useful in understanding transport properties in terms of molecular orbitals in asymmetric junctions. We compute this quantity via an ab initio NEGF approach based on density functional theory and illustrate its utility with several junctions of experimental relevance, including recent work on rectification in Au-graphite junctions. This work is supported by the DOE, and computational resources are provided by NERSC.

  18. Organic Solar Cells: Understanding the Role of Förster Resonance Energy Transfer

    PubMed Central

    Feron, Krishna; Belcher, Warwick J.; Fell, Christopher J.; Dastoor, Paul C.

    2012-01-01

    Organic solar cells have the potential to become a low-cost sustainable energy source. Understanding the photoconversion mechanism is key to the design of efficient organic solar cells. In this review, we discuss the processes involved in the photo-electron conversion mechanism, which may be subdivided into exciton harvesting, exciton transport, exciton dissociation, charge transport and extraction stages. In particular, we focus on the role of energy transfer as described by Förster resonance energy transfer (FRET) theory in the photoconversion mechanism. FRET plays a major role in exciton transport, harvesting and dissociation. The spectral absorption range of organic solar cells may be extended using sensitizers that efficiently transfer absorbed energy to the photoactive materials. The limitations of Förster theory to accurately calculate energy transfer rates are discussed. Energy transfer is the first step of an efficient two-step exciton dissociation process and may also be used to preferentially transport excitons to the heterointerface, where efficient exciton dissociation may occur. However, FRET also competes with charge transfer at the heterointerface turning it in a potential loss mechanism. An energy cascade comprising both energy transfer and charge transfer may aid in separating charges and is briefly discussed. Considering the extent to which the photo-electron conversion efficiency is governed by energy transfer, optimisation of this process offers the prospect of improved organic photovoltaic performance and thus aids in realising the potential of organic solar cells. PMID:23235328

  19. Organic solar cells: understanding the role of Förster resonance energy transfer.

    PubMed

    Feron, Krishna; Belcher, Warwick J; Fell, Christopher J; Dastoor, Paul C

    2012-12-12

    Organic solar cells have the potential to become a low-cost sustainable energy source. Understanding the photoconversion mechanism is key to the design of efficient organic solar cells. In this review, we discuss the processes involved in the photo-electron conversion mechanism, which may be subdivided into exciton harvesting, exciton transport, exciton dissociation, charge transport and extraction stages. In particular, we focus on the role of energy transfer as described by F¨orster resonance energy transfer (FRET) theory in the photoconversion mechanism. FRET plays a major role in exciton transport, harvesting and dissociation. The spectral absorption range of organic solar cells may be extended using sensitizers that efficiently transfer absorbed energy to the photoactive materials. The limitations of F¨orster theory to accurately calculate energy transfer rates are discussed. Energy transfer is the first step of an efficient two-step exciton dissociation process and may also be used to preferentially transport excitons to the heterointerface, where efficient exciton dissociation may occur. However, FRET also competes with charge transfer at the heterointerface turning it in a potential loss mechanism. An energy cascade comprising both energy transfer and charge transfer may aid in separating charges and is briefly discussed. Considering the extent to which the photo-electron conversion efficiency is governed by energy transfer, optimisation of this process offers the prospect of improved organic photovoltaic performance and thus aids in realising the potential of organic solar cells.

  20. Excitation of the copper resonance lines by low-energy electrons

    NASA Astrophysics Data System (ADS)

    Flynn, Connor; Wei, Zuyi; Stumpf, Bernhard

    1993-08-01

    The optical-excitation-function method has been used in a crossed-atom and electron-beam arrangement to measure the electron-impact cross section of the copper 4 2P-->4 2S resonance lines (324.8, 327.4 nm) from threshold (3.8 eV) to 8 eV. Relative experimental cross-section data are normalized at an energy of 1000 eV with respect to first Born theory that includes the 4 2S-->4 2P resonance transition with an oscillator strength of 0.652 and cascading from the (3d10nd)2D states with n=4,...,10. The measured Cu 4 2S-->4 2P cross section is compared with recent theoretical calculations in close-coupling approximation. Very good agreement is found with the ten-state close-coupling theory of Scheibner and Hazi (private communication).

  1. Parallelization in SCALE continuous-energy resonance module GEMINEWTRN and transport module NEWT

    SciTech Connect

    Zhong, Z.; Downar, T. J.; DeHart, M. D.; Williams, M. L.

    2006-07-01

    A new resonance module, GEMINEWTRN, has been developed in SCALE, it can calculate the continuous-energy neutron flux within the whole two-dimensional geometry, providing us a rigorous solution. However, the new code needs tremendously amount of computation and memory for practical problem. To relieve the computational burden and memory requirement, parallelization has been implemented into GEMINEWTRN, both angular and spatial decomposition have been adopted so that both the computation and the memory requirement on each processor can be saved considerably, and this effort makes the new resonance method much feasible for practical use. Because the two-dimensional geometry capability and SN/ESC solver of GEMINEWTRN come from lattice physics code NEWT, the similar parallel technique has also been implemented into NEWT, which can also save the computation considerably. (authors)

  2. Non-resonant electromagnetic energy harvester for car-key applications

    NASA Astrophysics Data System (ADS)

    Li, X.; Hehn, T.; Thewes, M.; Kuehne, I.; Frey, A.; Scholl, G.; Manoli, Y.

    2013-12-01

    This paper presents a novel non-resonant electromagnetic energy harvester for application in a remote car-key, to extend the lifetime of the battery or even to realize a fully energy autonomous, maintenance-free car-key product. Characteristic for a car-key are low frequency and large amplitude motions during normal daily operation. The basic idea of this non-resonant generator is to use a round flat permanent magnet moving freely in a round flat cavity, which is packaged on both sides by printed circuit boards embedded with multi-layer copper coils. The primary goal of this structure is to easily integrate the energy harvester with the existing electrical circuit module into available commercial car-key designs. The whole size of the energy harvester is comparable to a CR2032 coin battery. To find out the best power-efficient and optimal design, several magnets with different dimensions and magnetizations, and various layouts of copper coils were analysed and built up for prototype testing. Experimental results show that with an axially magnetized NdFeB magnet and copper coils of design variant B a maximum open circuit voltage of 1.1V can be observed.

  3. Efficient Exciton Diffusion and Resonance-Energy Transfer in Multilayered Organic Epitaxial Nanofibers

    PubMed Central

    2015-01-01

    Multilayered epitaxial nanofibers are exemplary model systems for the study of exciton dynamics and lasing in organic materials because of their well-defined morphology, high luminescence efficiencies, and color tunability. We use temperature-dependent continuous wave and picosecond photoluminescence (PL) spectroscopy to quantify exciton diffusion and resonance-energy transfer (RET) processes in multilayered nanofibers consisting of alternating layers of para-hexaphenyl (p6P) and α-sexithiophene (6T) serving as exciton donor and acceptor material, respectively. The high probability for RET processes is confirmed by quantum chemical calculations. The activation energy for exciton diffusion in p6P is determined to be as low as 19 meV, proving p6P epitaxial layers also as a very suitable donor material system. The small activation energy for exciton diffusion of the p6P donor material, the inferred high p6P-to-6T resonance-energy-transfer efficiency, and the observed weak PL temperature dependence of the 6T acceptor material together result in an exceptionally high optical emission performance of this all-organic material system, thus making it well suited, for example, for organic light-emitting devices. PMID:26191119

  4. Temporal Homogenization of Linear ODEs, with Applications to Parametric Super-Resonance and Energy Harvest

    NASA Astrophysics Data System (ADS)

    Tao, Molei; Owhadi, Houman

    2016-04-01

    We consider the temporal homogenization of linear ODEs of the form {dot{x}=Ax+ɛ P(t)x+f(t)}, where P( t) is periodic and {ɛ} is small. Using a 2-scale expansion approach, we obtain the long-time approximation {x(t)≈ exp(At) ( Ω(t)+int_0^t exp(-A τ) f(τ) dτ )}, where {Ω} solves the cell problem {dot{Ω}=ɛ B Ω + ɛ F(t)} with an effective matrix B and an explicitly-known F( t). We provide necessary and sufficient conditions for the accuracy of the approximation (over a O(ɛ^{-1})} time-scale), and show how B can be computed (at a cost independent of {ɛ}). As a direct application, we investigate the possibility of using RLC circuits to harvest the energy contained in small scale oscillations of ambient electromagnetic fields (such as Schumann resonances). Although a RLC circuit parametrically coupled to the field may achieve such energy extraction via parametric resonance, its resistance R needs to be smaller than a threshold κ proportional to the fluctuations of the field, thereby limiting practical applications. We show that if n RLC circuits are appropriately coupled via mutual capacitances or inductances, then energy extraction can be achieved when the resistance of each circuit is smaller than nκ. Hence, if the resistance of each circuit has a non-zero fixed value, energy extraction can be made possible through the coupling of a sufficiently large number n of circuits ({n≈ 1000} for the first mode of Schumann resonances and contemporary values of capacitances, inductances and resistances). The theory is also applied to the control of the oscillation amplitude of a (damped) oscillator.

  5. R-MATRIX RESONANCE ANALYSIS AND STATISTICAL PROPERTIES OF THE RESONANCE PARAMETERS OF 233U IN THE NEUTRON ENERGY RANGE FROM THERMAL TO 600 eV

    SciTech Connect

    Leal, L.C.

    2001-02-27

    The R-matrix resonance analysis of experimental neutron transmission and cross sections of {sup 233}U, with the Reich-Moore Bayesian code SAMMY, was extended up to the neutron energy of 600 eV by taking advantage of new high resolution neutron transmission and fission cross section measurements performed at the Oak Ridge Electron Linear Accelerator (ORELA). The experimental data base is described. In addition to the microscopic data (time-of-flight measurements of transmission and cross sections), some experimental and evaluated integral quantities were included in the data base. Tabulated and graphical comparisons between the experimental data and the SAMMY calculated cross sections are given. The ability of the calculated cross sections to reproduce the effective multiplication factors k{sub eff} for various thermal, intermediate, and fast systems was tested. The statistical properties of the resonance parameters were examined and recommended values of the average s-wave resonance parameters are given.

  6. Resonance energy transfer from dibucaine to acriflavine in polystyrene latex dispersions.

    PubMed

    Li, Yuan; Kuwabara, Hiroe; Gong, Yong-Kuan; Takaki, Yuki; Nakashima, Kenichi

    2003-07-01

    Resonance energy transfer from dibucaine (DC) to acriflavine (AF) has been investigated both in homogeneous aqueous solutions and in polystyrene latex dispersions. The energy transfer reaction is observed by monitoring fluorescence quenching of DC as well as sensitized emission of AF. It is found that the energy transfer from DC to AF is remarkably enhanced on going from the aqueous homogeneous solution to the latex dispersion. This is mainly attributed to the fact that both the donor and acceptor are effectively adsorbed onto the latex particles, as evidenced by the measurement of adsorption isotherms. From the adsorption experiments, it is also elucidated that electrostatic interaction is significant at low DC concentration, while hydrophobic interaction dominates at the higher concentration especially at higher pH.

  7. Ultrafast Studies of Resonance Energy Transfer in Myoglobin: A-Helix and Local Conformational Fluctuations

    NASA Astrophysics Data System (ADS)

    Stevens, Jeffrey A.; Link, Justin J.; Kao, Ya-Ting; Zang, Chen; Guo, Lijun; Zhong, Dongping

    2009-06-01

    Myoglobin (Mb), a heme containing protein, is involved in the storage and release of ligands. We report here our studies of resonance energy transfer in Mb using an intrinsic tryptophan (Trp) and the prosthetic heme as an energy transfer pair. With site-directed mutagenesis, we placed one-at-a-time a single Trp donor into four locations on the A-helix. Utilizing the femtosecond up-conversion method, we examined a series of energy transfer dynamics in Mb. A molecular dynamics (MD) simulation was also used to infer structure and dipole orientation fluctuations for specific Trp. Both methodologies were used to characterize the local dynamic nature of Mb in solution compared to the static crystal structure.

  8. Excitation and photon decay of giant multipole resonances - the role and future of medium-energy heavy ions

    SciTech Connect

    Bertrand, F.E.; Beene, J.R.; Horen, D.J.

    1988-01-01

    Inelastic scattering of medium energy heavy ions provides very large cross sections and peak-to-continuum ratios for excitation of giant resonances. For energies above about 50 MeV/nucleon, giant resonances are excited primarily through Coulomb excitation, which is indifferent to isospin, thus providing a good probe for the study of isovector giant resonances. The extremely large cross sections available from heavy ion excitation permit the study of rare decay modes of the photon decay of giant resonances following excitation by 22 and 84 MeV/nucleon /sup 17/O projectiles. The singles results at 84 MeV/nucleon yield peak cross sections for the isoscalar giant quadrupole resonance and the isovector giant dipole resonance of approximately 0.8 and 3 barns/sr, respectively. Data on the ground state decay of the isoscalar giant quadrupole and isovector giant dipole resonances are presented and compared with calculations. Decays to low-lying excited states are also discussed. Preliminary results from an experiment to isolate the /sup 208/Pb isovector quadrupole resonance using its gamma decay are presented.

  9. Performance Improvement of Polymer Solar Cells by Surface-Energy-Induced Dual Plasmon Resonance.

    PubMed

    Yao, Mengnan; Shen, Ping; Liu, Yan; Chen, Boyuan; Guo, Wenbin; Ruan, Shengping; Shen, Liang

    2016-03-01

    The surface plasmon resonance (SPR) effect of metal nanoparticles (MNPs) is effectively applied on polymer solar cells (PSCs) to improve power conversion efficiency (PCE). However, universality of the reported results mainly focused on utilizing single type of MNPs to enhance light absorption only in specific narrow wavelength range. Herein, a surface-energy-induced dual MNP plasmon resonance by thermally evaporating method was presented to achieve the absorption enhancement in wider range. The differences of surface energy between silver (Ag), gold (Au), and tungsten trioxide (WO3) compared by contact angle images enable Ag and Au prefer to respectively aggregate into isolated islands rather than films at the initial stage of the evaporation process, which was clearly demonstrated in the atomic force microscopy (AFM) measurement. The sum of plasmon-enhanced wavelength range induced by both Ag NPs (350-450 nm) and Au NPs (450-600 nm) almost cover the whole absorption spectra of active layers, which compatibly contribute a significant efficiency improvement from 4.57 ± 0.16 to 6.55 ± 0.12% compared to the one without MNPs. Besides, steady state photoluminescence (PL) measurements provide strong evidence that the SPR induced by the Ag-Au NPs increase the intensity of light absorption. Finally, ultraviolet photoelectron spectroscopy (UPS) reveals that doping Au and Ag causes upper shift of both the work function and valence band of WO3, which is directly related to hole collection ability. We believe the surface-energy-induced dual plasmon resonance enhancement by simple thermally evaporating technique might pave the way toward higher-efficiency PSCs. PMID:26900763

  10. Performance Improvement of Polymer Solar Cells by Surface-Energy-Induced Dual Plasmon Resonance.

    PubMed

    Yao, Mengnan; Shen, Ping; Liu, Yan; Chen, Boyuan; Guo, Wenbin; Ruan, Shengping; Shen, Liang

    2016-03-01

    The surface plasmon resonance (SPR) effect of metal nanoparticles (MNPs) is effectively applied on polymer solar cells (PSCs) to improve power conversion efficiency (PCE). However, universality of the reported results mainly focused on utilizing single type of MNPs to enhance light absorption only in specific narrow wavelength range. Herein, a surface-energy-induced dual MNP plasmon resonance by thermally evaporating method was presented to achieve the absorption enhancement in wider range. The differences of surface energy between silver (Ag), gold (Au), and tungsten trioxide (WO3) compared by contact angle images enable Ag and Au prefer to respectively aggregate into isolated islands rather than films at the initial stage of the evaporation process, which was clearly demonstrated in the atomic force microscopy (AFM) measurement. The sum of plasmon-enhanced wavelength range induced by both Ag NPs (350-450 nm) and Au NPs (450-600 nm) almost cover the whole absorption spectra of active layers, which compatibly contribute a significant efficiency improvement from 4.57 ± 0.16 to 6.55 ± 0.12% compared to the one without MNPs. Besides, steady state photoluminescence (PL) measurements provide strong evidence that the SPR induced by the Ag-Au NPs increase the intensity of light absorption. Finally, ultraviolet photoelectron spectroscopy (UPS) reveals that doping Au and Ag causes upper shift of both the work function and valence band of WO3, which is directly related to hole collection ability. We believe the surface-energy-induced dual plasmon resonance enhancement by simple thermally evaporating technique might pave the way toward higher-efficiency PSCs.

  11. Electromagnetic production of mesons and nucleon resonances at GeV energies

    SciTech Connect

    Lee, T.S.H.; Pichowsky, M.; Sato, T.

    1995-08-01

    A coupled-channels model for investigating the electromagnetic excitation of nucleon resonances (N*) at energies accessible to CEBAF, was developed. Motivated by the existing QCD-based hadron models, we assume that the basic resonant interaction mechanisms of the model Hamiltonian are the absorption and emission of photons and mesons by a bare quark core. The matrix elements of nonresonant interactions are deduced from low-order Feynman diagrams of an effective Lagrangian with chiral symmetry. The standard projection operator technique was applied to obtain a set of unitary scattering equations for describing {pi}N and {gamma}N reactions up to the GeV energy region. By assuming that the nonresonant two-pion continuum can be approximated as a fictitious {sigma}N state, the scattering equations can then be cast into a set of coupled-channels equations involving only two-particle {gamma}N, {pi}N, {eta}N, {rho}N, {pi}{Delta}, {omega}N and {sigma}N channels, which can be solved by well-developed numerical methods. The bare coupling constants and the range parameters of the hadronic form factors are adjusted to reproduce {pi}N scattering phase shifts up to 2-GeV incident pion energy. We then explore the dependence of the {gamma}N {yields} {pi}N and N(e,e{prime}{pi}) observables on the {gamma}N {yields} N* excitation strengths predicted by various QCD-based models of hadrons.

  12. Probing the conformation of the fibronectin III1-2 domain by fluorescence resonance energy transfer.

    PubMed

    Karuri, Nancy W; Lin, Zong; Rye, Hays S; Schwarzbauer, Jean E

    2009-02-01

    Fibronectin (FN) matrix is crucial for cell and tissue functions during embryonic development, wound healing, and oncogenesis. Assembly of FN matrix fibrils requires FN domains that mediate interactions with integrin receptors and with other FN molecules. In addition, regulation of FN matrix assembly depends on the first two FN type III modules, III(1) and III(2), which harbor FN-binding sites. We propose that interactions between these two modules sequester FN-binding sites in soluble FN and that these sites become exposed by FN conformational changes during assembly. To test the idea that III(1-2) has a compact conformation, we constructed CIIIY, a conformational sensor of III(1-2) based on fluorescent resonance energy transfer between cyan and yellow fluorescent proteins conjugated at its N and C termini. We demonstrate energy transfer in CIIIY and show that fluorescent resonance energy transfer was eliminated by proteolysis and by treatment with mild denaturants that disrupted intramolecular interactions between the two modules. We also show that mutations of key charged residues resulted in conformational changes that exposed binding sites for the N-terminal 70-kDa FN fragment. Collectively, these results support a conformation-dependent mechanism for the regulation of FN matrix assembly by III(1-2).

  13. Fluorescence resonance energy transfer induced by conjugation of metalloproteins to nanoparticles

    NASA Astrophysics Data System (ADS)

    Pompa, P. P.; Chiuri, R.; Manna, L.; Pellegrino, T.; del Mercato, L. L.; Parak, W. J.; Calabi, F.; Cingolani, R.; Rinaldi, R.

    2006-01-01

    We show the possibility of realizing a hybrid system composed of a semiconductor nanoparticle (NP) and a metalloprotein, in which the photophysical properties of the two species can be exploited to elicit fluorescence resonance energy transfer mechanisms from the biomolecule to the NP. A specific conjugation process between CdSe/ZnS core/shell water soluble NPs, functionalized with surface exposed thiol groups (-SH), and the apo form of the metalloprotein azurin (Az) has been achieved, resulting in a fixed distance in the donor-acceptor pairs. The increase in the NP fluorescence intensity was found to be dependent on the Az to NP molar ratio.

  14. Methods and kits for nucleic acid analysis using fluorescence resonance energy transfer

    DOEpatents

    Kwok, Pui-Yan; Chen, Xiangning

    1999-01-01

    A method for detecting the presence of a target nucleotide or sequence of nucleotides in a nucleic acid is disclosed. The method is comprised of forming an oligonucleotide labeled with two fluorophores on the nucleic acid target site. The doubly labeled oligonucleotide is formed by addition of a singly labeled dideoxynucleoside triphosphate to a singly labeled polynucleotide or by ligation of two singly labeled polynucleotides. Detection of fluorescence resonance energy transfer upon denaturation indicates the presence of the target. Kits are also provided. The method is particularly applicable to genotyping.

  15. Local Orientational Order in Liquids Revealed by Resonant Vibrational Energy Transfer

    NASA Astrophysics Data System (ADS)

    Panman, M. R.; Shaw, D. J.; Ensing, B.; Woutersen, S.

    2014-11-01

    We demonstrate that local orientational ordering in a liquid can be observed in the decay of the vibrational anisotropy caused by resonant transfer of vibrational excitations between its constituent molecules. We show that the functional form of this decay is determined by the (distribution of) angles between the vibrating bonds of the molecules between which energy transfer occurs, and that the initial drop in the decay reflects the average angle between nearest neighbors. We use this effect to observe the difference in local orientational ordering in the two hydrogen-bonded liquids ethanol and N -methylacetamide.

  16. Förster Resonance Energy Transfer imaging in vivo with approximated Radiative Transfer Equation

    PubMed Central

    Soloviev, Vadim Y.; McGinty, James; Stuckey, Daniel W.; Laine, Romain; Wylezinska-Arridge, Marzena; Wells, Dominic J.; Sardini, Alessandro; Hajnal, Joseph V.; French, Paul M.W.; Arridge, Simon R.

    2012-01-01

    We describe a new light transport model that we have applied to 3-D image reconstruction of in vivo fluorescence lifetime tomography data applied to read out Förster Resonance Energy Transfer in mice. The model is an approximation to the Radiative Transfer Equation and combines light diffusion and rays optics. This approximation is well adopted to wide-field time-gated intensity based data acquisition. Reconstructed image data are presented and compared with results obtained by using the Telegraph Equation approximation. The new approach provides improved recovery of absorption and scattering parameters while returning similar values for the fluorescence parameters. PMID:22193187

  17. Sterile neutrinos, dark matter, and resonant effects in ultra high energy regimes

    NASA Astrophysics Data System (ADS)

    Miranda, O. G.; Moura, C. A.; Parada, A.

    2015-05-01

    Interest in light dark matter candidates has recently increased in the literature; some of these works consider the role of additional neutrinos, either active or sterile. Furthermore, extragalactic neutrinos have been detected with energies higher than have ever been reported before. This opens a new window of opportunities to the study of neutrino properties that were unreachable up to now. We investigate how an interaction potential between neutrinos and dark matter might induce a resonant enhancement in the oscillation probability, an effect that may be tested with future neutrino data.

  18. Multi-Color Single Molecule Fluorescence Resonance Energy Transfer (smFret)

    NASA Astrophysics Data System (ADS)

    Anderson, Trevor; Weninger, Keith

    2008-10-01

    The assembly of multi-protein complexes is a vital part of intracellular biology. High resolution methods for characterizing such multi-protein complexes are required to understand functions of these complexes at the mechanistic level. Single molecule Fluorescence Resonance Energy Transfer is a promising method for both characterizing protein conformations and co-localizing different members of such multi-protein complexes. We present our progress towards developing an instrument for three and four color FRET studies at the single molecule level. This method will be useful for characterizing multi-protien complexes.

  19. Femtosecond study of ultrafast fluorescence resonance energy transfer in a catanionic vesicle

    NASA Astrophysics Data System (ADS)

    Kumar Das, Atanu; Mondal, Tridib; Kumar Sasmal, Dibyendu; Bhattacharyya, Kankan

    2011-08-01

    Ultrafast fluorescence resonance energy transfer (FRET) in a catanionic [sodium dodecyl sulfate (SDS)-dodecyltrimethyl ammonium bromide (DTAB)] vesicle is studied by femtosecond up-conversion. The vesicles (diameter ˜400 nm for SDS-rich and ˜250 nm for DTAB-rich vesicles) are much larger than the SDS and DTAB micelles (diameter ˜4 nm). In both micelle and vesicles, FRET occurs in multiple time scales and the time scales of FRET correspond to a donor-acceptor distance varying between 12 and 36 Å.

  20. Resonant features of energy and particle transport during application of resonant magnetic perturbation fields at TEXTOR and DIII-D

    SciTech Connect

    Schmitz, O.; Evans, T. E.; Fenstermacher, M. E.; Lehnen, M.; Stoschus, H.

    2012-01-01

    In this paper, results of a direct comparison of TEXTOR and DIII-D experiments with resonant magnetic perturbation (RMP) fields are presented. This comparison of resistive L-mode plasmas at TEXTOR with highly conductive H-mode plasmas at DIII-D is useful to identify generic physics mechanisms during application of RMP fields with a strong field line pitch angle alignment in the plasma edge. A reduction in the pedestal electron pressure p(e) with increasing extension of the vacuum modelled stochastic layer and p(e) recovery with decreasing layer width is found caused by a q(95) resonant reduction in the edge (0.8 < Psi(N) < 0.95) electron temperature T-e(q(95)) on both devices. For RMP edge-localized mode (ELM) suppressed H-mode plasmas at DIII-D, the gradients del T-e and nominal values of T-e are reduced in this edge region while increasing in the pedestal (0.95 < Psi(N) < 1.0) with RMP field applied and both are highly dependent on q(95). In contrast, an increase in the central ion temperature with strong steepening of the ion temperature profile at mid-radius is found-again being highly dependent on q(95). However, these resonant thermal transport effects are only seen in high triangularity plasmas revealing a strong shape dependence of the thermal transport. In contrast to the highly q(95) dependent thermal transport features, the reduction of n(e)-known as density pump out-shows a much weaker dependence on q(95). We show the potential to reduce the RMP induced particle pump out by fine tuning of the RMP spectral properties. At low resonant field amplitudes enhanced particle confinement is seen in high-field side limited L-mode discharges on both devices while higher resonant field amplitudes yield particle pumps out.

  1. Energy harvesting using parametric resonant system due to time-varying damping

    NASA Astrophysics Data System (ADS)

    Scapolan, Matteo; Tehrani, Maryam Ghandchi; Bonisoli, Elvio

    2016-10-01

    In this paper, the problem of energy harvesting is considered using an electromechanical oscillator. The energy harvester is modelled as a spring-mass-damper, in which the dissipated energy in the damper can be stored rather than wasted. Previous research provided the optimum damping parameter, to harvest maximum amount of energy, taking into account the stroke limit of the device. However, the amount of the maximum harvested energy is limited to a single frequency in which the device is tuned. Active and semi-active strategies have been suggested, which increases the performance of the harvester. Recently, nonlinear damping in the form of cubic damping has been proposed to extend the dynamic range of the harvester. In this paper, a periodic time-varying damper is introduced, which results in a parametrically excited system. When the frequency of the periodic time-varying damper is twice the excitation frequency, the system internal energy increases proportionally to the energy already stored in the system. Thus, for certain parametric damping values, the system can become unstable. This phenomenon can be exploited for energy harvesting. The transition curves, which separate the stable and unstable dynamics are derived, both analytically using harmonic balance method, and numerically using time simulations. The design of the harvester is such that its response is close to the transition curves of the Floquet diagram, leading to stable but resonant system. The performance of the parametric harvester is compared with the non-parametric one. It is demonstrated that performances and the frequency bandwidth in which the energy can be harvested can be both increased using time-varying damping.

  2. High-Precision Calibration of Electron Beam Energy from the Hefei Light Source Using Spin Resonant Depolarization

    NASA Astrophysics Data System (ADS)

    Lan, Jie-Qin; Xu, Hong-Liang

    2014-12-01

    The electron beam energy at the Hefei Light Source (HLS) in the National Synchrotron Radiation Laboratory is highly precisely calibrated by using the method of spin resonant depolarization for the first time. The spin tune and the beam energy are determined by sweeping the frequency of a radial rf stripline oscillating magnetic field to artificially excite a spin resonance and depolarize the beam. The resonance signal is recognized by observing the sudden change of the Touschek loss counting rate of the beam. The possible systematic errors of the experiment are presented and the accuracy of the calibrated energy is shown to be about 10-4. A series of measurements show that the energy stability of the machine is of the order of 9 × 10-3.

  3. Energy operator demodulating of optimal resonance components for the compound faults diagnosis of gearboxes

    NASA Astrophysics Data System (ADS)

    Zhang, Dingcheng; Yu, Dejie; Zhang, Wenyi

    2015-11-01

    Compound faults diagnosis is a challenge for rotating machinery fault diagnosis. The vibration signals measured from gearboxes are usually complex, non-stationary, and nonlinear. When compound faults occur in a gearbox, weak fault characteristic signals are always submerged by the strong ones. Therefore, it is difficult to detect a weak fault by using the demodulating analysis of vibration signals of gearboxes directly. The key to compound faults diagnosis of gearboxes is to separate different fault characteristic signals from the collected vibration signals. Aiming at that problem, a new method for the compound faults diagnosis of gearboxes is proposed based on the energy operator demodulating of optimal resonance components. In this method, the genetic algorithm is first used to obtain the optimal decomposition parameters. Then the compound faults vibration signals of a gearbox are subject to resonance-based signal sparse decomposition (RSSD) to separate the fault characteristic signals of the gear and the bearing by using the optimal decomposition parameters. Finally, the separated fault characteristic signals are analyzed by energy operator demodulating, and each one’s instantaneous amplitude can be calculated. According to the spectra of instantaneous amplitudes of fault characteristic signals, the faults of the gear and the bearing can be diagnosed, respectively. The performance of the proposed method is validated by using the simulation data and the experiment vibration signals from a gearbox with compound faults.

  4. Design and development of high bioluminescent resonance energy transfer efficiency hybrid-imaging constructs.

    PubMed

    Kumar, Manoj; Kovalski, Letícia; Broyles, David; Hunt, Eric A; Daftarian, Pirouz; Dikici, Emre; Daunert, Sylvia; Deo, Sapna K

    2016-04-01

    Here we describe the design and construction of an imaging construct with high bioluminescent resonance energy transfer (BRET) efficiency that is composed of multiple quantum dots (QDs; λem = 655 nm) self-assembled onto a bioluminescent protein, Renilla luciferase (Rluc). This is facilitated by the streptavidin-biotin interaction, allowing the facile formation of a hybrid-imaging construct (HIC) comprising up to six QDs (acceptor) grafted onto a light-emitting Rluc (donor) core. The resulting assembly of multiple acceptors surrounding a donor permits this construct to exhibit high resonance energy transfer efficiency (∼64.8%). The HIC was characterized using fluorescence excitation anisotropy measurements and high-resolution transmission electron microscopy. To demonstrate the application of our construct, a generation-5 (G5) polyamidoamine dendrimer (PAMAM) nanocarrier was loaded with our HIC for in vitro and in vivo imaging. We envision that this design of multiple acceptors and bioluminescent donor will lead to the development of new BRET-based systems useful in sensing, imaging, and other bioanalytical applications.

  5. Photodisintegration of heavy nuclei in the energy region above the giant dipole resonance

    SciTech Connect

    Ermakov, A. N.; Ishkhanov, B. S.; Kapitonov, I. M.; Makarenko, I. V. Orlin, V. N.

    2010-05-15

    Experimental data on yields of multiparticle photonuclear reactions (involving the emission of up to seven neutrons from the nucleus involved) on {sup 197}Au, {sup 203,205}Tl, and {sup 209}Bi nuclei in the region extending from the giant dipole resonance to an energy of 67.7 MeV are presented. These data are compared with the results of modern theoretical calculations that take into account both the excitation of a giant dipole resonance (GDR) in a nucleus and the photodisintegration of quasideutrons (QD) in it. By and large, experimental data confirm the results of theoretical calculations-that is, only upon taking simultaneously into account both alternative photodisintegration mechanisms (GDR excitation and QD photodisintegration) can one describe these experimental data. The contribution of QD photodisintegration grows with increasing photon energy and neutron multiplicity and becomes dominant for reactions involving the emission of not less than five neutrons from the nucleus being considered. The integrated cross sections for the processes in question were estimated on the basis of simultaneously employing experimental yields of multinucleon photonuclear reactions and the respective cross-section shapes calculated theoretically.

  6. Thermoregulated formation and disintegration of cationic block copolymer vesicles: fluorescence resonance energy transfer study.

    PubMed

    Maiti, Chiranjit; Dey, Debabrata; Mandal, Sarthak; Dhara, Dibakar

    2014-02-27

    Formation and disintegration of self-assembled nanostructures in response to external stimuli are important phenomena that have been widely explored for a variety of biomedical applications. In this contribution, we report the thermally triggered assembly of block copolymer molecules in aqueous solution to form vesicles (polymersomes) and their disassembly on reduction of temperature. A new thermoresponsive diblock copolymer of poly(N-isopropylacrylamide) poly((3-methacrylamidopropyl)trimethylammonium chloride) (PNIPA-b-PMAPTAC) was synthesized by reversible addition-fragmentation chain transfer technique. The solution properties and self-assembling behavior of the block copolymer molecules were studied by turbidimetry, temperature-dependent proton nuclear magnetic resonance, fluorescence spectroscopy, dynamic light scattering, and transmission electron microscopy. Fluorescence resonance energy transfer studies between coumarin-153 (C-153, donor) and rhodamine 6G (R6G, acceptor) have been performed by steady-state and picosecond-resolved fluorescence spectroscopy to probe the structural and dynamic heterogeneity of the vesicles. The occurrence of efficient energy transfer was evident from the shortening of donor lifetime in the presence of the acceptor. The capability of the vesicles to encapsulate both hydrophobic and hydrophilic molecules and release them in response to decrease in temperature makes them potentially useful as drug delivery vehicles. PMID:24490812

  7. Detection of ochratoxin A (OTA) in coffee using chemiluminescence resonance energy transfer (CRET) aptasensor.

    PubMed

    Jo, Eun-Jung; Mun, Hyoyoung; Kim, Su-Ji; Shim, Won-Bo; Kim, Min-Gon

    2016-03-01

    We report a chemiluminescence resonance energy transfer (CRET) aptasensor for the detection of ochratoxin A (OTA) in roasted coffee beans. The aptamer sequences used in this study are 5'-DNAzyme-Linker-OTA aptamer-3'-dabcyl. Dabcyl at the end of the OTA aptamer region plays as a quencher in CRET aptasensor. When hemin and OTA are added, the dabcyl-labeled OTA aptamer approaches to the G-quadruplex-hemin complex by formation of the G-quadruplex-OTA complex. The G-quadruplex-hemin complexes possess horseradish peroxidase (HRP)-like activity, and therefore, the HRP-mimicking DNAzyme (HRPzyme) catalyzes peroxidation in the presence of luminol and H2O2. Resonance energy transfer between luminol (donor) and dabcyl (acceptor) enables quenching of chemiluminescence signals. The signal decreases with increasing the concentration of OTA within the range of 0.1-100ngmL(-1) (limit of detection 0.22ngmL(-1)), and the level of recovery of the respective 1ngmL(-1) and 10ngmL(-1) spiked coffee samples was 71.5% and 93.3%. These results demonstrated the potential of the proposed method for OTA analysis in diverse foods.

  8. Gold nanoparticles-based chemiluminescence resonance energy transfer for ultrasensitive detection of melamine.

    PubMed

    Du, Jianxiu; Wang, Yadi; Zhang, Weimin

    2015-01-01

    A turn-on chemiluminescence resonance energy transfer method was fabricated for the determination of melamine by using bis(2,4,6-trichlorophenyl)oxalate-hydrogen peroxide-fluorescein chemiluminescence reaction as a donor and dispersed gold nanoparticles as an acceptor. The chemiluminescence signal of bis(2,4,6-trichlorophenyl)oxalate-hydrogen peroxide-fluorescein reaction decreased significantly in the presence of dispersed gold nanoparticles because the absorption band of dispersed gold nanoparticles perfectly overlapped with the chemiluminescence spectrum. Melamine could induce the aggregation of gold nanoparticles, leading to a dramatic red-shift of the absorption band of dispersed gold nanoparticles. The absorption band of the aggregated gold nanoparticles does not overlap with the chemiluminescence spectrum of the reaction. In such a case, chemiluminescence resonance energy transfer could not happen and the chemiluminescence signal was restored. The procedure allowed the measurement of 3.2×10(-12)-3.2×10(-7) mol/L melamine with a limit of detection of 3×10(-13) mol/L. The method was applied to the determination of melamine in spiked milk samples; with recoveries within the range 94.1-104.2%.

  9. Förster Resonance Energy Transfer between Quantum Dot Donors and Quantum Dot Acceptors

    PubMed Central

    Chou, Kenny F.; Dennis, Allison M.

    2015-01-01

    Förster (or fluorescence) resonance energy transfer amongst semiconductor quantum dots (QDs) is reviewed, with particular interest in biosensing applications. The unique optical properties of QDs provide certain advantages and also specific challenges with regards to sensor design, compared to other FRET systems. The brightness and photostability of QDs make them attractive for highly sensitive sensing and long-term, repetitive imaging applications, respectively, but the overlapping donor and acceptor excitation signals that arise when QDs serve as both the donor and acceptor lead to high background signals from direct excitation of the acceptor. The fundamentals of FRET within a nominally homogeneous QD population as well as energy transfer between two distinct colors of QDs are discussed. Examples of successful sensors are highlighted, as is cascading FRET, which can be used for solar harvesting. PMID:26057041

  10. Resonance energy transfer in a model system of membranes: application to gel and liquid crystalline phases.

    PubMed

    Loura, L M; Fedorov, A; Prieto, M

    1996-10-01

    Resonance energy transfer between octadecyl rhodamine B (donor) and 1,1',3,3,3',3'-hexamethylindotricarbocyanine (acceptor) was studied in a model system of membranes (large unilamellar vesicles of dipalmitoylphosphatidylcholine), using both steady-state and time-resolved techniques. In the fluid phase (temperature = 50 degrees C) the decay law and the steady-state theoretical curve for energy transfer in two dimensions are verified. In the gel phase (temperature = 25 degrees C) an apparent reduction of dimensionality is observed, which is explained on the basis of probe segregation to the defect lines (grain boundaries). An estimation of the domain size from the model recovered linear probe concentrations is approximately 1750-2000 lipid molecules. In both phases, the existence of a fractal geometry was ruled out. PMID:8889159

  11. Determination of molecular spectroscopic parameters and energy-transfer rates by double-resonance spectroscopy

    NASA Technical Reports Server (NTRS)

    Steinfeld, J. I.; Foy, B.; Hetzler, J.; Flannery, C.; Klaassen, J.; Mizugai, Y.; Coy, S.

    1990-01-01

    The spectroscopy of small to medium-size polyatomic molecules can be extremely complex, especially in higher-lying overtone and combination vibrational levels. The high density of levels also complicates the understanding of inelastic collision processes, which is required to model energy transfer and collision broadening of spectral lines. Both of these problems can be addressed by double-resonance spectroscopy, i.e., time-resolved pump-probe measurements using microwave, infrared, near-infrared, and visible-wavelength sources. Information on excited-state spectroscopy, transition moments, inelastic energy transfer rates and propensity rules, and pressure-broadening parameters may be obtained from such experiments. Examples are given for several species of importance in planetary atmospheres, including ozone, silane, ethane, and ammonia.

  12. Bioanalytical systems based on bioluminescence resonance energy transfer using firefly luciferase.

    PubMed

    Smirnova, Darya V; Ugarova, Natalia N

    2015-01-01

    Bioanalytical systems based on the Bioluminescence Resonance Energy Transfer (BRET) are widely used in fundamental biochemical studies, as well as for screening and analysis of biologically active compounds. The Renilla luciferase is the most often used energy donor in this system despite the fact that it has low bioluminescence quantum yield and demonstrates not so stable luminescence in time as the firefly luciferase. Moreover, the bioluminescence λmax is observed in the green region of the spectrum, which complicates signal recording in tissues during in vivo experiments. The firefly luciferases do not have such drawbacks and show great promise for applications in BRET systems. Different versions of BRET systems based on firefly luciferases and the methods for increasing their efficiency are considered in this review; examples of the use of BRET systems based on the firefly luciferases for highly sensitive determination of proteases and for homogeneous immunoassays are presented. PMID:26377546

  13. Preliminary investigation into the design of thermally responsive Forster resonance energy transfer colloids

    NASA Astrophysics Data System (ADS)

    Bedford, Monte Scott

    While nuclear imaging techniques (Magnetic Resonance Imaging, Computed Tomography, and Positron Emission Tomography) have proven effective for diagnosis and treatment of disease in the human body, fluorescence-enhanced optical imaging offers additional benefits. Fluorescent imaging provides high resolution with real-time response, persistent lifetime (hours to days), cell targeting, and transdermal penetration with minimal physical encumbrance. Malignant cells can be targeted by absorbance of exogenous fluorescent nanoprobe contrast agents. Imaging is improved by fluorescent enhancement, especially by energy transfer between attached dyes. Also for use against cancer are heat-active treatments, such as hyperthermal, photothermal, and chemothermal therapies. Helpful to these treatments is the thermal response from nanoprobes, within human cells, which provide real-time feedback. The present study investigates the design and feasibility of a nanoprobe molecular device, absorbable into malignant human cells, which provides real-time tracking and thermal response, as indicated by enhanced fluorescence by energy transfer. A poly(propargyl acrylate) colloidal suspension was synthesized. The particles were modified with a triblock copolymer, previously shown to be thermally responsive, and an end-attached fluorescent dye. A second dye was modeled for attachment in subsequent work. When two fluorescent dyes are brought within sufficiently close proximity, and excitation light is supplied, energy can be transferred between dyes to give enhanced fluorescence with a large Stokes shift (increase in wavelength between excitation and emission). The dye pair was modeled for overlap of emission and absorbance wavelengths, and energy transfer was demonstrated with 23% efficiency and a 209 nm Stokes shift. The quantum yield of the donor dye was determined at 70%, and the distance for 50% energy transfer was calculated at 2.9 nm, consistent with reports for similar compounds. When

  14. Nanoscale energy-route selector consisting of multiple photo-switchable fluorescence-resonance-energy-transfer structures on DNA

    NASA Astrophysics Data System (ADS)

    Fujii, Ryo; Nishimura, Takahiro; Ogura, Yusuke; Tanida, Jun

    2015-04-01

    We report on a nanoscale energy-route selector consisting of multiple fluorescence resonance energy transfer (FRET) structures switched by external signaling with multiple wavelengths of light. In each FRET structure, a specific activator molecule is incorporated to a FRET pair of a donor and an acceptor to control the activation of the acceptor. Owing to this configuration, the FRET structures are switched independently, and an energy route is selected. Two photo-switchable FRET structures, one consists of Alexa Fluor 568 (donor), Cy5 (acceptor), and Alexa Fluor 405 (activator), and the other consists of Alexa Fluor 568 (donor), Cy5.5 (acceptor), and Cy3 (activator), were constructed using DNA strands modified with fluorescence molecules. Switching rates for the individual FRET structures were measured as 64 and 49 %, respectively. An energy-route selector was then assembled with the FRET structures which share a single donor. Experimental results demonstrate that the energy route can be changed repeatedly by activation control using three wavelengths of light.

  15. Energy calibration issues in nuclear resonant vibrational spectroscopy: observing small spectral shifts and making fast calibrations.

    PubMed

    Wang, Hongxin; Yoda, Yoshitaka; Dong, Weibing; Huang, Songping D

    2013-09-01

    The conventional energy calibration for nuclear resonant vibrational spectroscopy (NRVS) is usually long. Meanwhile, taking NRVS samples out of the cryostat increases the chance of sample damage, which makes it impossible to carry out an energy calibration during one NRVS measurement. In this study, by manipulating the 14.4 keV beam through the main measurement chamber without moving out the NRVS sample, two alternative calibration procedures have been proposed and established: (i) an in situ calibration procedure, which measures the main NRVS sample at stage A and the calibration sample at stage B simultaneously, and calibrates the energies for observing extremely small spectral shifts; for example, the 0.3 meV energy shift between the 100%-(57)Fe-enriched [Fe4S4Cl4](=) and 10%-(57)Fe and 90%-(54)Fe labeled [Fe4S4Cl4](=) has been well resolved; (ii) a quick-switching energy calibration procedure, which reduces each calibration time from 3-4 h to about 30 min. Although the quick-switching calibration is not in situ, it is suitable for normal NRVS measurements.

  16. Investigations and system design for simultaneous energy and data transmission through inductively coupled resonances

    NASA Astrophysics Data System (ADS)

    Schmidt, C.; Lloret Fuentes, E.; Buchholz, M.

    2015-11-01

    Wireless Power Transfer (WPT) with simultaneous data transmission through coupled magnetic resonators is investigated in this paper. The development of this system is dedicated to serve as a basis for applications in the field of Ambient Assisted Living (AAL), for example tracking vital parameters remotely, charge and control sensors and so on. Due to these different scenarios we consider, it is important to have a system which is reliable under the circumstance of changing positioning of the receiving device. State of the art radio systems would be able to handle this. Nevertheless, energy harvesting from far field sources is not sufficient to power the devices additionally on mid-range distances. For this reason, coupled magnetic resonant circuits are proposed as a promising alternative, although suffering from more complex positioning dependency. Based on measurements on a simple prototype system, an equivalent circuit description is used to model the transmission system dependent on different transmission distances and impedance matching conditions. Additionally, the simulation model is used to extract system parameters such as coupling coefficients, coil resistance and self-capacitance, which cannot be calculated in a simple and reliable way. Furthermore, a mathematical channel model based on the schematic model has been built in MATLAB©. It is used to point out the problems occurring in a transmission system with variable transmission distance, especially the change of the passband's centre frequency and its bandwidth. Existing solutions dealing with this distance dependent behaviour, namely the change of the transmission frequency dependent on distance and the addition of losses to the resonators to increase the bandwidth, are considered as not inventive. First, changing the transmission frequency increases the complexity in the data transmission system and would use a disproportional total bandwidth compared to the actually available bandwidth

  17. Resonant features of energy and particle transport during application of resonant magnetic perturbation fields at TEXTOR and DIII-D

    NASA Astrophysics Data System (ADS)

    Schmitz, O.; Evans, T. E.; Fenstermacher, M. E.; Lehnen, M.; Stoschus, H.; Unterberg, E. A.; Coenen, J. W.; Frerichs, H.; Jakubowski, M. W.; Laengner, R.; Lasnier, C. L.; Mordijck, S.; Moyer, R. A.; Osborne, T. H.; Reimerdes, H.; Reiter, D.; Samm, U.; Unterberg, B.; DIII-D, the; TEXTOR Teams

    2012-04-01

    In this paper, results of a direct comparison of TEXTOR and DIII-D experiments with resonant magnetic perturbation (RMP) fields are presented. This comparison of resistive L-mode plasmas at TEXTOR with highly conductive H-mode plasmas at DIII-D is useful to identify generic physics mechanisms during application of RMP fields with a strong field line pitch angle alignment in the plasma edge. A reduction in the pedestal electron pressure pe with increasing extension of the vacuum modelled stochastic layer and pe recovery with decreasing layer width is found caused by a q95 resonant reduction in the edge (0.8 < ΨN < 0.95) electron temperature Te(q95) on both devices. For RMP edge-localized mode (ELM) suppressed H-mode plasmas at DIII-D, the gradients ∇Te and nominal values of Te are reduced in this edge region while increasing in the pedestal (0.95 < ΨN < 1.0) with RMP field applied and both are highly dependent on q95. In contrast, an increase in the central ion temperature with strong steepening of the ion temperature profile at mid-radius is found—again being highly dependent on q95. However, these resonant thermal transport effects are only seen in high triangularity plasmas revealing a strong shape dependence of the thermal transport. In contrast to the highly q95 dependent thermal transport features, the reduction of ne—known as density pump out—shows a much weaker dependence on q95. We show the potential to reduce the RMP induced particle pump out by fine tuning of the RMP spectral properties. At low resonant field amplitudes enhanced particle confinement is seen in high-field side limited L-mode discharges on both devices while higher resonant field amplitudes yield particle pumps out. This is the paper of the IAEA contribution by Schmitz O. et al 2010 Key results from the DIII-D/TEXTOR Collaboration on the Physics of Stochastic Boundaries projected to ELM control at ITER, EXD/P3-30.

  18. Effect of Diffusion on Resonance Energy Transfer Rate Distributions: Implications for Distance Measurements.

    PubMed

    Toptygin, Dmitri; Chin, Alexander F; Hilser, Vincent J

    2015-10-01

    Intrinsically disordered protein regions and many other biopolymers lack the three-dimensional structure that could be determined by X-ray crystallography or NMR, which encourages the application of alternative experimental methods. Time-resolved resonance energy transfer data are often used to measure distances between two fluorophores attached to a flexible biopolymer. This is complicated by the rotational and translational diffusion of the fluorophores and by nonmonoexponential donor decay in the absence of the acceptor. Equation I(DA)(t) = I(D)(t)·F(t) is derived here, which is applicable regardless of whether I(D)(t) is monoexponential. I(D)(t) and I(DA)(t) are the δ-excitation donor emission decays in the absence and in the presence of the acceptor; F(t) contains information about energy transfer, donor-acceptor distance distribution, and diffusion dynamics. It is shown that in the absence of rotational and translational diffusion, F(t) is a continuous distribution of exponentials, whereas in the presence of rotational and translational diffusion, F(t) is a sum of discrete exponentials. For each case it is shown how F(t) is related to the distance distribution. Experimental data obtained with a flexible tetradecapeptide in aqueous solution clearly demonstrate that F(t) is a sum of discrete exponential terms. A partial differential equation describing resonance energy transfer in the presence of both rotational and translational diffusion of the donor and acceptor tethered to the ends of a semiflexible chain is solved in this work using a combination of analytical and numerical methods; the solution is used to fit time-resolved emission of the donor, which makes it possible to determine the model parameters: contour length, persistence length, and the end-to-end translational diffusion coefficient.

  19. Resonance energy transfer between fluorescent BSA protected Au nanoclusters and organic fluorophores.

    PubMed

    Raut, Sangram; Rich, Ryan; Fudala, Rafal; Butler, Susan; Kokate, Rutika; Gryczynski, Zygmunt; Luchowski, Rafal; Gryczynski, Ignacy

    2014-01-01

    Bovine serum albumin (BSA) protected nanoclusters (Au and Ag) represent a group of nanomaterials that holds great promise in biophysical applications due to their unique fluorescence properties and lack of toxicity. These metal nanoclusters have utility in a variety of disciplines including catalysis, biosensing, photonics, imaging and molecular electronics. However, they suffer from several disadvantages such as low fluorescence quantum efficiency (typically near 6%) and broad emission spectrum (540 nm to 800 nm). We describe an approach to enhance the apparent brightness of BSA Au clusters by linking them with a high extinction donor organic dye pacific blue (PB). In this conjugate PB acts as a donor to BSA Au clusters and enhances its brightness by resonance energy transfer (RET). We found that the emission of BSA Au clusters can be enhanced by a magnitude of two-fold by resonance energy transfer (RET) from the high extinction donor PB, and BSA Au clusters can act as an acceptor to nanosecond lifetime organic dyes. By pumping the BSA Au clusters using a high extinction donor, one can increase the effective brightness of less bright fluorophores like BSA Au clusters. Moreover, we prepared another conjugate of BSA Au clusters with the near infrared (NIR) dye Dylight 750 (Dy750), where BSA Au clusters act as a donor to Dy750. We observed that BSA Au clusters can function as a donor, showing 46% transfer efficiency to the NIR dye Dy750 with a long lifetime component in the acceptor decay through RET. Such RET-based probes can be used to prevent the problems of a broad emission spectrum associated with the BSA Au clusters. Moreover, transferring energy from BSA Au clusters to Dy750 will result in a RET probe with a narrow emission spectrum and long lifetime component which can be utilized in imaging applications.

  20. Amorphous carbon nanoparticle used as novel resonance energy transfer acceptor for chemiluminescent immunoassay of transferrin.

    PubMed

    Gao, Hongfei; Wang, Wenwen; Wang, Zhenxing; Han, Jing; Fu, Zhifeng

    2014-03-28

    Amorphous carbon nanoparticles (ACNPs) showing highly efficient quenching of chemiluminescence (CL) were prepared from candle soot with a very simple protocol. The prepared ACNP was employed as the novel energy acceptor for a chemiluminescence resonance energy transfer (CRET)-based immunoassay. In this work, ACNP was linked with transferrin (TRF), and horseradish peroxidase (HRP) was conjugated to TRF antibody (HRP-anti-TRF). The immunoreaction rendered the distance between the ACNP acceptor and the HRP-catalyzed CL emitter to be short enough for CRET occurring. In the presence of TRF, this antigen competed with ACNP-TRF for HRP-anti-TRF, thus led to the decreased occurrence of CRET. A linear range of 20-400 ng mL(-1) and a limit of detection of 20 ng mL(-1) were obtained in this immunoassay. The proposed method was successfully applied for detection of TRF levels in human sera, and the results were in good agreement with ELISA method. Moreover, the ACNPs show higher energy transfer efficiency than other conventional nano-scaled energy acceptors such as graphene oxide in CRET assay. It is anticipated that this approach can be developed for determination of other analytes with low cost, simple manipulation and high specificity. PMID:24636417

  1. Resonant nature of intrinsic defect energy levels in PbTe revealed by infrared photoreflectance spectroscopy

    SciTech Connect

    Zhang, Bingpo; Cai, Chunfeng; Jin, Shuqiang; Ye, Zhenyu; Wu, Huizhen; Qi, Zhen

    2014-07-14

    Step-scan Fourier-transform infrared photoreflectance and modulated photoluminescence spectroscopy were used to characterize the optical transitions of the epitaxial PbTe thin film grown by molecular beam epitaxy on BaF{sub 2} (111) substrate in the vicinity of energy gap of lead telluride at 77 K. It is found that the intrinsic defect energy levels in the electronic structure are of resonant nature. The Te-vacancy energy level is located above the conduction band minimum by 29.1 meV. Another defect (V{sub X}) energy level situated below valance band maximum by 18.1 meV is also revealed. Whether it is associated with the Pb vacancy is still not clear. It might also be related to the misfit dislocations stemming from the lattice mismatch between PbTe and BaF{sub 2} substrate. The experimental results support the theory prediction (N. J. Parada and G. W. Pratt, Jr., Phys. Rev. Lett. 22, 180 (1969), N. J. Parada, Phys. Rev. B 3, 2042 (1971)) and are consistent with the reported Hall experimental results (G. Bauer, H. Burkhard, H. Heinrich, and A. Lopez-Otero, J. Appl. Phys. 47, 1721 (1976)).

  2. Resonant nature of intrinsic defect energy levels in PbTe revealed by infrared photoreflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Bingpo; Cai, Chunfeng; Jin, Shuqiang; Ye, Zhenyu; Wu, Huizhen; Qi, Zhen

    2014-07-01

    Step-scan Fourier-transform infrared photoreflectance and modulated photoluminescence spectroscopy were used to characterize the optical transitions of the epitaxial PbTe thin film grown by molecular beam epitaxy on BaF2 (111) substrate in the vicinity of energy gap of lead telluride at 77 K. It is found that the intrinsic defect energy levels in the electronic structure are of resonant nature. The Te-vacancy energy level is located above the conduction band minimum by 29.1 meV. Another defect (VX) energy level situated below valance band maximum by 18.1 meV is also revealed. Whether it is associated with the Pb vacancy is still not clear. It might also be related to the misfit dislocations stemming from the lattice mismatch between PbTe and BaF2 substrate. The experimental results support the theory prediction (N. J. Parada and G. W. Pratt, Jr., Phys. Rev. Lett. 22, 180 (1969), N. J. Parada, Phys. Rev. B 3, 2042 (1971)) and are consistent with the reported Hall experimental results (G. Bauer, H. Burkhard, H. Heinrich, and A. Lopez-Otero, J. Appl. Phys. 47, 1721 (1976)).

  3. Direct Imaging of Transient Fano Resonances in N2 Using Time-, Energy-, and Angular-Resolved Photoelectron Spectroscopy

    NASA Astrophysics Data System (ADS)

    Eckstein, Martin; Yang, Chung-Hsin; Frassetto, Fabio; Poletto, Luca; Sansone, Giuseppe; Vrakking, Marc J. J.; Kornilov, Oleg

    2016-04-01

    Autoionizing Rydberg states of molecular N2 are studied using time-, energy-, and angular-resolved photoelectron spectroscopy. A femtosecond extreme ultraviolet pulse with a photon energy of 17.5 eV excites the resonance and a subsequent IR pulse ionizes the molecule before the autoionization takes place. The angular-resolved photoelectron spectra depend on pump-probe time delay and allow for the distinguishing of two electronic states contributing to the resonance. The lifetime of one of the contributions is determined to be 14 ±1 fs , while the lifetime of the other appears to be significantly shorter than the time resolution of the experiment. These observations suggest that the Rydberg states in this energy region are influenced by the effect of interference stabilization and merge into a complex resonance.

  4. Imaging of the dissociation dynamics of polyatomic molecules following low-energy electron resonant attachment

    NASA Astrophysics Data System (ADS)

    Belkacem, Ali

    2014-05-01

    There is a very large body of experimental work on dissociative electron attachment to molecules but the majority of that work is focused on the measurement of absolute total cross sections or energetic positions of the resonances. There is scarce information on the dynamics of electron attachment and the subsequent dissociation that often involves highly non-Born-Oppenheimer dynamics, funneling through conical intersections or intricate nuclear motion during the dissociation process. Through COLTRIMS detection techniques we investigate the electron attachment in a fixed-in-frame manner that yields direct information on the symmetries of the neutral and negatively charged resonant states. We will present a study that combines experimental data along with theoretical analysis of dissociative electron attachment to carbon dioxide, methanol and uracil. In these studies we demonstrated that an understanding of anion dissociation dynamics beyond simple one-dimensional models is crucial in interpreting the measured angular distributions. This work is supported by the Chemical Sciences Biosciences and Geosciences Division, Basic Energy Sciences, DOE.

  5. Robust energy transfer mechanism via precession resonance in nonlinear turbulent wave systems

    NASA Astrophysics Data System (ADS)

    Lucas, Dan; Bustamante, Miguel; Quinn, Brenda

    2014-11-01

    The precise mechanisms by which energy is most efficiently transferred in a turbulent system remain an important open question for the fluid mechanics community. In this talk we present a newly discovered resonance which is found to drive transfers across the spectrum of Fourier modes in a nonlinear wave system. Quadratic nonlinearity results in modes interacting in triads and, by considering the ``truly dynamical degrees of freedom'' (amplitudes and triad phases) and the precessional frequencies of the triads, we show transfers are maximal when the precession resonates with the nonlinear temporal frequencies. This can lead to a collective state of synchronised triads with intense cascades at intermediate nonlinearity; we find greatest transfer between the traditional weak and strong turbulence regimes and discover that this new mechanism is dominant here. We present the effect in a hierarchy of models including a full DNS of the Charney-Hasegawa-Mima equation and confirm analytical predictions. Supported by Science Foundation Ireland (SFI) under Grant Number 12/IP/1491.

  6. Nonlinear M-shaped broadband piezoelectric energy harvester for very low base accelerations: primary and secondary resonances

    NASA Astrophysics Data System (ADS)

    Leadenham, S.; Erturk, A.

    2015-05-01

    It has been well demonstrated over the past few years that vibration energy harvesters with intentionally designed nonlinear stiffness components can be used for frequency bandwidth enhancement under harmonic excitation for sufficiently high vibration amplitudes. In order to overcome the need for high excitation intensities that are required to exploit nonlinear dynamic phenomena, we have developed an M-shaped piezoelectric energy harvester configuration that can exhibit a nonlinear frequency response under very low vibration levels. This configuration is made from a continuous bent spring steel with piezoelectric laminates and a proof mass but no magnetic components. Careful design of this nonlinear architecture that minimizes piezoelectric softening further enables the possibility of achieving the jump phenomenon in hardening at few milli-g base acceleration levels. In the present work, such a design is explored for both primary and secondary resonance excitations at different vibration levels and load resistance values. Following the primary resonance excitation case that offers a 660% increase in the half-power bandwidth as compared to the linear system at a root-mean-square excitation level as low as 0.04g, secondary resonance behavior is investigated with a focus on 1:2 and 1:3 superharmonic resonance neighborhoods. A multi-term harmonic balance formulation is employed for a computationally effective yet high-fidelity analysis of this high-quality-factor system with quadratic and cubic nonlinearities. In addition to primary resonance and secondary (superharmonic) resonance cases, multi-harmonic excitation is modeled and experimentally validated.

  7. Resonance Strength Measurement at Astrophysical Energies: The 17O(p,α)14N Reaction Studied via THM

    NASA Astrophysics Data System (ADS)

    Sergi, M. L.; Spitaleri, C.; La Cognata, M.; Lamia, L.; Pizzone, R. G.; Rapisarda, G. G.; Mukhamedzhanov, A.; Irgaziev, B.; Tang, X. D.; Wischer, M.; Mrazek, J.; Kroha, V.

    2016-05-01

    In recent years, the Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of proton-induced reactions on 17O nuclei, overcoming extrapolation procedures and enhancement effects due to electron screening. We will report on the indirect study of the 17O(p,α)14N reaction via the Trojan Horse Method by applying the approach developed for extracting the resonance strength of narrow resonance in the ultralow energy region. The mean value of the strengths obtained in the two measurements was calculated and compared with the direct data available in literature.

  8. Resonance strength measurement at astrophysical energies: The 17O(p,α)14N reaction studied via Trojan Horse Method

    NASA Astrophysics Data System (ADS)

    Sergi, M. L.; Spitaleri, C.; La Cognata, M.; Lamia, L.; Pizzone, R. G.; Rapisarda, G. G.; Mukhamedzhanov, A.; Irgaziev, B.; Tang, X. D.; Wiescher, M.; Mrazek, J.; Kroha, V.

    2015-10-01

    In recent years, the Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of proton-induced reactions on 17O nuclei, overcoming extrapolation procedures and enhancement effects due to electron screening. We will report on the indirect study of the 17O(p,α)14N reaction via the THM by applying the approach developed for extracting the resonance strength of narrow resonance in the ultralow energy region. Two measurements will be described and the experimental THM cross sections will be shown for both experiments.

  9. Time-resolved luminescence resonance energy transfer imaging of protein-protein interactions in living cells.

    PubMed

    Rajapakse, Harsha E; Miller, Lawrence W

    2012-01-01

    Lanthanide-based or luminescence resonance energy transfer (LRET) microscopy can be used to sensitively image interactions between reporter-labeled proteins in living mammalian cells. With LRET, luminescent lanthanide complexes are used as donors, conventional fluorophores are used as acceptors, and donor-sensitized acceptor emission occurs at time scales that reflect the long (~ms) lanthanide emission lifetime. These long-lived signals can be separated from short-lifetime (~ns) sample autofluorescence and directly excited acceptor fluorescence by using pulsed light to excite the specimen and by implementing a short delay (>100 ns) before detection, thereby increasing measurement sensitivity. As practical implementation of time-resolved LRET microscopy requires several potentially unfamiliar experimental techniques, we explicitly describe herein methods to label proteins in living mammalian cells with luminescent terbium complexes, image interactions between terbium-labeled proteins and green fluorescent protein fusions, and quantitatively analyze LRET images. PMID:22289461

  10. Detection of focal adhesion kinase activation at membrane microdomains by fluorescence resonance energy transfer.

    PubMed

    Seong, Jihye; Ouyang, Mingxing; Kim, Taejin; Sun, Jie; Wen, Po-Chao; Lu, Shaoying; Zhuo, Yue; Llewellyn, Nicholas M; Schlaepfer, David D; Guan, Jun-Lin; Chien, Shu; Wang, Yingxiao

    2011-07-26

    Proper subcellular localization of focal adhesion kinase (FAK) is crucial for many cellular processes. It remains, however, unclear how FAK activity is regulated at subcellular compartments. To visualize the FAK activity at different membrane microdomains, we develop a fluorescence resonance energy transfer (FRET)-based FAK biosensor, and target it into or outside of detergent-resistant membrane (DRM) regions at the plasma membrane. Here we show that, on cell adhesion to extracellular matrix proteins or stimulation by platelet-derived growth factor (PDGF), the FRET responses of DRM-targeting FAK biosensor are stronger than that at non-DRM regions, suggesting that FAK activation can occur at DRM microdomains. Further experiments reveal that the PDGF-induced FAK activation is mediated and maintained by Src activity, whereas FAK activation on cell adhesion is independent of, and in fact essential for the Src activation. Therefore, FAK is activated at membrane microdomains with distinct activation mechanisms in response to different physiological stimuli.

  11. Highly efficient Forster resonance energy transfer between CdTe nanocrystals and two different dye molecules

    NASA Astrophysics Data System (ADS)

    Alphandery, Edouard; Walsh, Laura; Rakovich, Yury P.; Bradley, A. L.; Donegan, John F.; Gaponik, Nicolai; Gunko, Yurii K.

    2004-09-01

    We report highly efficient Forster resonance energy transfer between CdTe nanocrystals and two different dyes, Rhodamine B and Oxazine, where the nanocrystals are mixed with the dyes on top of glass substrates. A faster NC decay curve is observed in the samples containing NCs mixed with dyes than in those containing NCs on their own. For the samples containing nanocrystals mixed with Rhodamine B, room temperature PL measurements are presented as a function of the ratio between the amount of acceptors and the amount of donors, CA/CD. This ratio is varied between 0.03 and 5. The strongest enhancement of the acceptor PL intensity relative to that of the donor PL intensity is reached for 0.2

  12. Wideband resonator arrays for electromagnetic energy harvesting and wireless power transfer

    NASA Astrophysics Data System (ADS)

    Alavikia, Babak; Almoneef, Thamer S.; Ramahi, Omar M.

    2015-12-01

    This work demonstrates the viability of wideband Ground-backed Complementary Split-Ring Resonator (WG-CSRR) arrays with significant power conversion efficiency and bandwidth enhancement in comparison to the technology used in current electromagnetic energy harvesting systems. Through numerical full-wave analysis, we demonstrated the correlation between the topology of the WG-CSRR patch and the electric current distribution over the patch at different frequencies. A comparative study of power harvesting efficiency and frequency bandwidth through numerical analysis was presented where an array of WG-CSRRs is compared to an array of G-CSRRs and an array of microstrip patch antennas. A significant improvement in bandwidth is achieved in comparison to the G-CSRR array reported in earlier work.

  13. High Efficiency Forster Resonance Energy Transfer in Solid-State Dye Sensitized Solar Cells

    SciTech Connect

    Mor, Gopal K.; Basham, James; Paulose, Maggie; Kim, Sanghoon; Varghese, Oomman K.; Vaish, Amit; Yoriya, Sorachon; Grimes, Craig A.

    2010-07-14

    Solid-state dye-sensitized solar cells (SS-DSCs) offer the potential to make low cost solar power a reality, however their photoconversion efficiency must first be increased. The dyes used are commonly narrow band with high absorption coefficients, while conventional photovoltaic operation requires proper band edge alignment significantly limiting the dyes and charge transporting materials that can be used in combination. We demonstrate a significant enhancement in the light harvesting and photocurrent generation of SS-DSCs due to Förster resonance energy transfer (FRET). TiO{sub 2} nanotube array films are sensitized with red/near IR absorbing SQ-1 acceptor dye, subsequently intercalated with Spiro-OMeTAD blended with a visible light absorbing DCM-pyran donor dye. The calculated Förster radius is 6.1 nm. The donor molecules contribute a FRET-based maximum IPCE of 25% with a corresponding excitation transfer efficiency of approximately 67.5%.

  14. Evidence for enhanced optical properties through plasmon resonance energy transfer in silver silica nanocomposites

    NASA Astrophysics Data System (ADS)

    Mol, Beena; Joy, Lija K.; Thomas, Hysen; Thomas, Vinoy; Joseph, Cyriac; Narayanan, T. N.; Al-Harthi, Salim; Unnikrishnan, N. V.; Anantharaman, M. R.

    2016-02-01

    Silver nanoparticles were dispersed in the pores of monolithic mesoporous silica prepared by a modified sol-gel method. Structural and microstructural analyses were carried out by Fourier transform infrared spectroscopy and transmission electron microscopy. X-ray photoelectron spectroscopy was employed to determine the chemical states of silver in the silica matrix. Optical absorption studies show the evolution absorption band around 300 nm for silver (Ag) in a silica matrix and it was found to be redshifted to 422 nm on annealing. Photoluminescence studies indicate the presence of various luminescent emitting centers corresponding to silver ions and silver dimers in the SiO2 matrix. The enhancement of absorption and photoluminescence properties is attributed to plasmon resonance energy transfer from Ag nanoparticles to luminescent species in the matrix.

  15. Paper-based upconversion fluorescence resonance energy transfer biosensor for sensitive detection of multiple cancer biomarkers

    PubMed Central

    Xu, Sai; Dong, Biao; Zhou, Donglei; Yin, Ze; Cui, Shaobo; Xu, Wen; Chen, Baojiu; Song, Hongwei

    2016-01-01

    A paper-based upconversion fluorescence resonance energy transfer assay device is proposed for sensitive detection of CEA. The device is fabricated on a normal filter paper with simple nano-printing method. Upconversion nanoparticles tagged with specific antibodies are printed to the test zones on the test paper, followed by the introduction of assay antigen. Upconversion fluorescence measurements are directly conducted on the test zones after the antigen-to-antibody reactions. Furthermore, a multi-channel test paper for simultaneous detection of multiple cancer biomarkers was established by the same method and obtained positive results. The device showed high anti-interfere, stability, reproducible and low detection limit (0.89 ng/mL), moreover it is very easy to fabricate and operate, which is a promising prospect for a clinical point-of-care test. PMID:27001460

  16. Upconversion nanoparticle-based fluorescence resonance energy transfer assay for organophosphorus pesticides.

    PubMed

    Long, Qian; Li, Haitao; Zhang, Youyu; Yao, Shouzhuo

    2015-06-15

    This paper reports a novel nanosensor for organophosphorus pesticides based on the fluorescence resonance energy transfer (FRET) between NaYF4:Yb,Er upconversion nanoparticles (UCNPs) and gold nanoparticles (AuNPs). The detection mechanism is based on the facts that AuNPs quench the fluorescence of UCNPs and organophosphorus pesticides (OPs) inhibit the activity of acetylcholinesterase (AChE) which catalyzes the hydrolysis of acetylthiocholine (ATC) into thiocholine. Under the optimized conditions, the logarithm of the pesticides concentration was proportional to the inhibition efficiency. The detection limits of parathion-methyl, monocrotophos and dimethoate reached 0.67, 23, and 67 ng/L, respectively. Meanwhile, the biosensor shows good sensitivity, stability, and could be successfully applied to detection of OPs in real food samples, suggesting the biosensor has potentially extensive application clinic diagnoses assays.

  17. Rapid caspase-3 activation during apoptosis revealed using fluorescence-resonance energy transfer

    PubMed Central

    Tyas, Lorraine; Brophy, Victoria A.; Pope, Andrew; Rivett, A. Jennifer; Tavaré, Jeremy M.

    2000-01-01

    Caspase-3 is a crucial component of the apoptotic machinery in many cell types. Here, we report the timescale of caspase-3 activation in single living cells undergoing apoptosis. This was achieved by measuring the extent of fluorescence resonance energy transfer within a recombinant substrate containing cyan fluorescent protein (CFP) linked by a short peptide possessing the caspase-3 cleavage sequence, DEVD, to yellow fluorescent protein (YFP; i.e. CFP–DEVD–YFP). We demonstrate that, once initiated, the activation of caspase-3 is a very rapid process, taking 5 min or less to reach completion. Furthermore, this process occurs almost simultaneously with a depolarization of the mitochondrial membrane potential. These events occur just prior to the characteristic morphological changes associated with apoptosis. Our results clearly demonstrate that, once initiated, the commitment of cells to apoptosis is a remarkably rapid event when visualized at the single cell level. PMID:11256610

  18. Tracking polymer diffusion in a wet latex film with fluorescence resonance energy transfer.

    PubMed

    Haley, Jeffrey C; Liu, Yuanqin; Winnik, Mitchell A; Demmer, David; Haslett, Tom; Lau, Willie

    2007-08-01

    We describe an instrument to measure the polymer interdiffusion between donor-labeled and acceptor-labeled latex polymers in a partially wet latex film with fluorescence resonance energy transfer (FRET). It is possible to temporarily arrest the drying process of a wet latex film by sealing the film in an airtight chamber. In our approach, we measure donor fluorescence decays from 0.5 mm diameter spots at various positions across an arrested latex film with time-correlated single photon counting. We interpret the resulting decays with a Monte Carlo simulation of the FRET process and extract information about the extent of polymer diffusion as a function of position on the film. These results enable us to determine the extent of polymer interdiffusion as a function of distance from the wet-dry edge in the latex film. To highlight this device's ability to capture the rapid early stages of latex interdiffusion, we report results from an acrylate copolymer latex.

  19. Biophysical Insights from Temperature-Dependent Single-Molecule Förster Resonance Energy Transfer

    NASA Astrophysics Data System (ADS)

    Holmstrom, Erik D.; Nesbitt, David J.

    2016-05-01

    Single-molecule fluorescence microscopy techniques can be used in combination with micrometer length-scale temperature control and Förster resonance energy transfer (FRET) in order to gain detailed information about fundamental biophysical phenomena. In particular, this combination of techniques has helped foster the development of remarkable quantitative tools for studying both time- and temperature-dependent structural kinetics of biopolymers. Over the past decade, multiple research efforts have successfully incorporated precise spatial and temporal control of temperature into single-molecule FRET (smFRET)-based experiments, which have uncovered critical thermodynamic information on a wide range of biological systems such as conformational dynamics of nucleic acids. This review provides an overview of various temperature-dependent smFRET approaches from our laboratory and others, highlighting efforts in which such methods have been successfully applied to studies of single-molecule nucleic acid folding.

  20. Prolonged irradiation of enhanced cyan fluorescent protein or Cerulean can invalidate Forster resonance energy transfer measurements.

    PubMed

    Hoffmann, Birgit; Zimmer, Thomas; Klöcker, Nikolaj; Kelbauskas, Laimonas; König, Karsten; Benndorf, Klaus; Biskup, Christoph

    2008-01-01

    Since its discovery, green fluorescent protein (GFP) and its variants have proven to be a good and convenient fluorescent label for proteins: GFP and other visible fluorescent proteins (VFPs) can be fused selectively to the protein of interest by simple cloning techniques and develop fluorescence without additional cofactors. Among the steadily growing collection of VFPs, several pairs can be chosen that can serve as donor and acceptor fluorophores in Forster resonance energy transfer (FRET) experiments. Among them, the cyan fluorescent proteins (ECFP/Cerulean) and the enhanced yellow fluorescent protein (EYFP) are most commonly used. We show that ECFP and Cerulean have some disadvantages despite their common use: Upon irradiation with light intensities that are commonly used for intensity- and lifetime-based FRET measurements, both the fluorescence intensity and the fluorescence lifetime of ECFP and Cerulean decrease. This can hamper both intensity- and lifetime-based FRET measurements and emphasizes the need for control measurements to exclude these artifacts. PMID:18601529

  1. The influence of DNA shape fluctuations on fluorescence resonance energy transfer efficiency measurements in nucleosomes

    NASA Astrophysics Data System (ADS)

    Lenz, Lucia; Hoenderdos, Maurice; Prinsen, Peter; Schiessel, Helmut

    2015-02-01

    Fluorescence resonance energy transfer (FRET) measurements allow one to observe site exposure in nucleosomes, i.e. the transient unwrapping of a part of the wrapped DNA from the histone octamer. In such experiments one can typically distinguish between a closed state and an open state but in principle one might hope to detect several states, each corresponding to a certain number of open binding sites. Here we show that even in an ideal FRET setup it would be hard to detect unwrapping states with intermediate levels of FRET efficiencies. As the unwrapped DNA molecule, modelled here as a wormlike chain, has a finite stiffness, shape fluctuations smear out FRET signals completely from such intermediate states.

  2. Near infrared bioluminescence resonance energy transfer from firefly luciferase—quantum dot bionanoconjugates

    NASA Astrophysics Data System (ADS)

    Alam, Rabeka; Karam, Liliana M.; Doane, Tennyson L.; Zylstra, Joshua; Fontaine, Danielle M.; Branchini, Bruce R.; Maye, Mathew M.

    2014-12-01

    The bioluminescence resonance energy transfer (BRET) between firefly luciferase enzymes and semiconductive quantum dots (QDs) with near infrared emission is described. The QD were phase transferred to aqueous buffers using a histidine mediated phase transfer route, and incubated with a hexahistidine tagged, green emitting variant of firefly luciferase from Photinus pyralis (PPyGRTS). The PPyGRTS were bound to the QD interface via the hexahistidine tag, which effectively displaces the histidine layer and binds directly to the QD interfaces, allowing for short donor-acceptor distances (˜5.5 nm). Due to this, high BRET efficiency ratios of ˜5 were obtained. These PPyGRTS-QD bio-nano conjugates were characterized by transmission electron microscopy, thermal gravimetric analysis, Fourier transform infrared spectroscopy and BRET emission studies. The final optimized conjugate was easily observable by night vision imaging, demonstrating the potential of these materials in imaging and signaling/sensing applications.

  3. Exploring the optimal performances of irreversible single resonance energy selective electron refrigerators

    NASA Astrophysics Data System (ADS)

    Zhou, Junle; Chen, Lingen; Ding, Zemin; Sun, Fengrui

    2016-05-01

    Applying finite-time thermodynamics (FTT) and electronic transport theory, the optimal performances of irreversible single resonance energy selective electron (ESE) refrigerator are analyzed. The effects of heat leakage between two electron reservoirs on optimal performances are discussed. The influences of system operating parameters on cooling load, coefficient of performance (COP), figure of merit and ecological function are demonstrated using numerical examples. Comparative performance analyses among different objective functions show that performance characteristics at maximum ecological function and maximum figure of merit are of great practical significance. Combining the two optimization objectives of maximum ecological function and maximum figure of merit together, more specific optimal ranges of cooling load and COP are obtained. The results can provide some advices to the design of practical electronic machine systems.

  4. Generating tunable white light by resonance energy transfer in transparent dye-conjugated metal oxide nanocrystals.

    PubMed

    Wang, Ting; Chirmanov, Vadim; Chiu, Wan Hang M; Radovanovic, Pavle V

    2013-10-01

    We report the design and properties of hybrid white-light-emitting nanophosphors obtained by electronic coupling of defect states in colloidal Ga2O3 nanocrystals emitting in blue-green with selected organic molecules emitting in orange-red. Coupling between the two components is enabled by the nanocrystal's size-dependent resonance energy transfer, allowing the photoluminescence chromaticity to be precisely tuned by changing the nanocrystal size and selecting the complementary organic dye molecule. Using this approach, we demonstrate the generation of pure white light with quantum yield of ~30%, color rendering index up to 95, and color temperature of 5500 K. These results provide a guideline for the design of a new class of hybrid white-light-emitting nanophosphors and other multifunctional nanostructures based on transparent metal oxides.

  5. Note: High-efficiency broadband acoustic energy harvesting using Helmholtz resonator and dual piezoelectric cantilever beams

    SciTech Connect

    Yang, Aichao; Li, Ping Wen, Yumei; Lu, Caijiang; Peng, Xiao; He, Wei; Zhang, Jitao; Wang, Decai; Yang, Feng

    2014-06-15

    A high-efficiency broadband acoustic energy harvester consisting of a compliant-top-plate Helmholtz resonator (HR) and dual piezoelectric cantilever beams is proposed. Due to the high mechanical quality factor of beams and the strong multimode coupling of HR cavity, top plate and beams, the high efficiency in a broad bandwidth is obtained. Experiment exhibits that the proposed harvester at 170–206 Hz has 28–188 times higher efficiency than the conventional harvester using a HR with a piezoelectric composite diaphragm. For input acoustic pressure of 2.0 Pa, the proposed harvester exhibits 0.137–1.43 mW output power corresponding to 0.035–0.36 μW cm{sup −3} volume power density at 170–206 Hz.

  6. Note: High-efficiency broadband acoustic energy harvesting using Helmholtz resonator and dual piezoelectric cantilever beams.

    PubMed

    Yang, Aichao; Li, Ping; Wen, Yumei; Lu, Caijiang; Peng, Xiao; He, Wei; Zhang, Jitao; Wang, Decai; Yang, Feng

    2014-06-01

    A high-efficiency broadband acoustic energy harvester consisting of a compliant-top-plate Helmholtz resonator (HR) and dual piezoelectric cantilever beams is proposed. Due to the high mechanical quality factor of beams and the strong multimode coupling of HR cavity, top plate and beams, the high efficiency in a broad bandwidth is obtained. Experiment exhibits that the proposed harvester at 170-206 Hz has 28-188 times higher efficiency than the conventional harvester using a HR with a piezoelectric composite diaphragm. For input acoustic pressure of 2.0 Pa, the proposed harvester exhibits 0.137-1.43 mW output power corresponding to 0.035-0.36 μW cm(-3) volume power density at 170-206 Hz. PMID:24985867

  7. Detection of β-Amyloid Peptide Dimer in Solution by Fluorescence Resonance Energy Transfer

    NASA Astrophysics Data System (ADS)

    Han, Jun; Mei, Erwen; Kung, Mei-Ping; Kung, Hank; Dai, Hai-Lung

    2006-03-01

    Studies have suggested that there is a connection between ß-amyloid-derived diffusible ligands (ADDLs), small oligomers formed from clustering of peptides with 39-42 amino acid units, and pathogenicity of Alzheimer's disease. It is believed that the soluble ADDL oligomers eventually coagulate and precipitate into fibrils that cause neurotoxicity. Although there have been studies characterizing the fibrils structure and the large coagulate formation kinetics, little experimental information exists for the oligomers in the solution phase. We report here the use of fluorescence resonance energy transfer detected through a confocal microscope under single molecule conditions for the detection of the β-amyloid (1-40) peptide dimer in solution. The structure of the dimer is characterized in terms of the distance of the two N-terminals.

  8. Effect of diffusion on Förster resonance energy transfer in low-viscosity solution

    NASA Astrophysics Data System (ADS)

    Muratsugu, Atsushi; Watanabe, Junji; Kinoshita, Shuichi

    2014-06-01

    The effect of translational diffusion on Förster resonance energy transfer between rhodamine 6G (the donor) and malachite green (the acceptor) was investigated by examining the donor's fluorescence decay profile. Eight straight-chain alkyl alcohols were used, and the temperature of ethanol was changed to vary the viscosity; the decay profiles were analyzed using the theory developed by Gösele. The critical transfer distance obtained from the decay profile is in good agreement with that evaluated using the spectroscopic quantities, and the diffusion coefficients are consistent with the Stokes-Einstein relation. The fluorescence decay profile was described well by Gösele's theory and the effect of diffusion is clearly verified by the temperature/viscosity dependence of the diffusion constant.

  9. Near infrared bioluminescence resonance energy transfer from firefly luciferase--quantum dot bionanoconjugates.

    PubMed

    Alam, Rabeka; Karam, Liliana M; Doane, Tennyson L; Zylstra, Joshua; Fontaine, Danielle M; Branchini, Bruce R; Maye, Mathew M

    2014-12-12

    The bioluminescence resonance energy transfer (BRET) between firefly luciferase enzymes and semiconductive quantum dots (QDs) with near infrared emission is described. The QD were phase transferred to aqueous buffers using a histidine mediated phase transfer route, and incubated with a hexahistidine tagged, green emitting variant of firefly luciferase from Photinus pyralis (PPyGRTS). The PPyGRTS were bound to the QD interface via the hexahistidine tag, which effectively displaces the histidine layer and binds directly to the QD interfaces, allowing for short donor-acceptor distances (∼5.5 nm). Due to this, high BRET efficiency ratios of ∼5 were obtained. These PPyGRTS-QD bio-nano conjugates were characterized by transmission electron microscopy, thermal gravimetric analysis, Fourier transform infrared spectroscopy and BRET emission studies. The final optimized conjugate was easily observable by night vision imaging, demonstrating the potential of these materials in imaging and signaling/sensing applications.

  10. Polaronic quantum master equation theory of inelastic and coherent resonance energy transfer for soft systems.

    PubMed

    Yang, Lei; Devi, Murali; Jang, Seogjoo

    2012-07-14

    This work extends the theory of coherent resonance energy transfer [S. Jang, J. Chem. Phys. 131, 164101 (2009)] by including quantum mechanical inelastic effects due to modulation of donor-acceptor electronic coupling. Within the approach of the second order time local quantum master equation (QME) in the polaron picture and under the assumption that the bath degrees of freedom modulating the electronic coupling are independent of other modes, a general time evolution equation for the reduced system density operator is derived. Detailed expressions for the relaxation operators and inhomogeneous terms of the QME are then derived for three specific models of modulation in distance, axial angle, and dihedral angle, which are all approximated by harmonic oscillators. Numerical tests are conducted for a set of model parameters. Model calculation shows that the torsional modulation can make significant contribution to the relaxation and dephasing mechanisms.

  11. [Fluorescence Resonance Energy Transfer Detection of Cobalt Ions by Silver Triangular Nanoplates and Rhodamine 6G].

    PubMed

    Zhang, Xiu-qing; Peng, Jun; Ling, Jian; Liu, Chao-juan; Cao, Qiu-e; Ding, Zhong-tao

    2015-04-01

    In the present paper, the authors studied fluorescence resonance energy transfer (FRET) phenomenon between silver triangular nanoplates and bovine serum albumin (BSA)/Rhodamine 6G fluorescence complex, and established a fluorescence method for the detection of cobalt ions. We found that when increasing the silver triangular nanoplates added to certain concentrations of fluorescent bovine serum albumin (BSA)/Rhodamine 6G complex, the fluorescence of Rhodamine 6G would be quenched up to 80% due to the FRET between the quencher and donor. However, in the presence of cobalt ions, the disassociation of the fluorescent complex from silver triangular nanoplates occurred and the fluorescence of the Rhodamine 6G recovered. The recovery of fluorescence intensity rate (I/I0) has a good relationship with the cobalt ion concentration (cCO2+) added. Thus, the authors developed a fluorescence method for the detection of cobalt ions based on the FRET of silver triangular nanoplates and Rhodamine 6G.

  12. Fluorescence Resonance Energy Transfer Microscopy for Measuring Chromatin Complex Structure and Dynamics.

    PubMed

    Cherubini, Alessandro; Zippo, Alessio

    2016-01-01

    The Polycomb group (PcG) proteins form regulatory complexes that modify the chromatin structure and silence their target genes. Recent works have found that the composition of Polycomb complexes is highly dynamic. Defining the different protein components of each complex is fundamental for better understanding their biological functions. Fluorescent resonance energy transfer (FRET) is a powerful tool to measure protein-protein interactions, in nanometer order and in their native cellular environment. Here we describe the preparation and execution of a typical FRET experiment using CFP-tagged protein as donor and YFP-tagged protein as acceptor. We further show that FRET can be used in a competition assay to measure binding affinities of different components of the same chromatin complex. PMID:27659982

  13. Imaging protein interactions with bioluminescence resonance energy transfer (BRET) in plant and mammalian cells and tissues

    PubMed Central

    Xu, Xiaodong; Soutto, Mohammed; Xie, Qiguang; Servick, Stein; Subramanian, Chitra; von Arnim, Albrecht G.; Johnson, Carl Hirschie

    2007-01-01

    FRET is a well established method for cellular and subcellular imaging of protein interactions. However, FRET obligatorily necessitates fluorescence excitation with its concomitant problems of photobleaching, autofluorescence, phototoxicity, and undesirable stimulation of photobiological processes. A sister technique, bioluminescence resonance energy transfer (BRET), avoids these problems because it uses enzyme-catalyzed luminescence; however, BRET signals usually have been too dim to image effectively in the past. Using a new generation electron bombardment-charge-coupled device camera coupled to an image splitter, we demonstrate that BRET can be used to image protein interactions in plant and animal cells and in tissues; even subcellular imaging is possible. We have applied this technology to image two different protein interactions: (i) dimerization of the developmental regulator, COP1, in plant seedlings; and (ii) CCAAT/enhancer binding protein α (C/EBPα) in the mammalian nucleus. This advance heralds a host of applications for imaging without fluorescent excitation and its consequent limitations. PMID:17551013

  14. Time-resolved Förster-resonance-energy-transfer DNA assay on an active CMOS microarray

    PubMed Central

    Schwartz, David Eric; Gong, Ping; Shepard, Kenneth L.

    2008-01-01

    We present an active oligonucleotide microarray platform for time-resolved Förster resonance energy transfer (TR-FRET) assays. In these assays, immobilized probe is labeled with a donor fluorophore and analyte target is labeled with a fluorescence quencher. Changes in the fluorescence decay lifetime of the donor are measured to determine the extent of hybridization. In this work, we demonstrate that TR-FRET assays have reduced sensitivity to variances in probe surface density compared with standard fluorescence-based microarray assays. Use of an active array substrate, fabricated in a standard complementary metal-oxide-semiconductor (CMOS) process, provides the additional benefits of reduced system complexity and cost. The array consists of 4096 independent single-photon avalanche diode (SPAD) pixel sites and features on-chip time-to-digital conversion. We demonstrate the functionality of our system by measuring a DNA target concentration series using TR-FRET with semiconductor quantum dot donors. PMID:18515059

  15. Biosensing with Förster Resonance Energy Transfer Coupling between Fluorophores and Nanocarbon Allotropes

    PubMed Central

    Ding, Shaowei; Cargill, Allison A.; Das, Suprem R.; Medintz, Igor L.; Claussen, Jonathan C.

    2015-01-01

    Nanocarbon allotropes (NCAs), including zero-dimensional carbon dots (CDs), one-dimensional carbon nanotubes (CNTs) and two-dimensional graphene, exhibit exceptional material properties, such as unique electrical/thermal conductivity, biocompatibility and high quenching efficiency, that make them well suited for both electrical/electrochemical and optical sensors/biosensors alike. In particular, these material properties have been exploited to significantly enhance the transduction of biorecognition events in fluorescence-based biosensing involving Förster resonant energy transfer (FRET). This review analyzes current advances in sensors and biosensors that utilize graphene, CNTs or CDs as the platform in optical sensors and biosensors. Widely utilized synthesis/fabrication techniques, intrinsic material properties and current research examples of such nanocarbon, FRET-based sensors/biosensors are illustrated. The future outlook and challenges for the research field are also detailed. PMID:26110411

  16. Förster resonance energy transfer rate in any dielectric nanophotonic medium with weak dispersion

    NASA Astrophysics Data System (ADS)

    Wubs, Martijn; Vos, Willem L.

    2016-05-01

    Motivated by the ongoing debate about nanophotonic control of Förster resonance energy transfer (FRET), notably by the local density of optical states (LDOS), we study FRET and spontaneous emission in arbitrary nanophotonic media with weak dispersion and weak absorption in the frequency overlap range of donor and acceptor. This system allows us to obtain the following two new insights. Firstly, we derive that the FRET rate only depends on the static part of the Green function. Hence, the FRET rate is independent of frequency, in contrast to spontaneous-emission rates and LDOS that are strongly frequency dependent in nanophotonic media. Therefore, the position-dependent FRET rate and the LDOS at the donor transition frequency are completely uncorrelated for any nondispersive medium. Secondly, we derive an exact expression for the FRET rate as a frequency integral of the imaginary part of the Green function. This leads to very accurate approximation for the FRET rate that features the LDOS that is integrated over a huge bandwidth ranging from zero frequency to far into the UV. We illustrate these general results for the analytic model system of a pair of ideal dipole emitters—donor and acceptor—in the vicinity of an ideal mirror. We find that the FRET rate is independent of the LDOS at the donor emission frequency. Moreover, we observe that the FRET rate hardly depends on the frequency-integrated LDOS. Nevertheless, the FRET is controlled between inhibition and 4×enhancement at distances close to the mirror, typically a few nm. Finally, we discuss the consequences of our results to applications of Förster resonance energy transfer, for instance in quantum information processing.

  17. A graphitic carbon nitride based fluorescence resonance energy transfer detection of riboflavin.

    PubMed

    Han, Jing; Zou, Hong Yan; Gao, Ming Xuan; Huang, Cheng Zhi

    2016-01-01

    Fluorescence resonance energy transfer (FRET), which occurs between two luminescent chromophores, can greatly improve the selectivity and sensitivity of a fluorescent assay when a ratiometric signaling with the fluorescence enhancement of the acceptor at the expense of the donor is adopted. In this study, a fluorescence ratiometric detection (FRD) of riboflavin (RF) has been made based on FRET, as the strong overlap occurred between the emission spectrum of graphitic carbon nitride (g-C3N4) and absorption spectrum of RF, in which g-C3N4 acts as the energy donor and RF as the energy acceptor. With increasing concentration of RF, the fluorescence intensity of g-C3N4 emission at 444 nm decreased and the fluorescence peak at 523 nm for RF increased regularly, making the fluorescence intensity ratio of 523 nm to 444 nm linearly dependent on the concentration of RF in the range from 0.4 μM to 10 μM, giving a limit of the detection of 170 nM. This method can be used to quantify RF in complex systems such as milk and drink, showing that the novel FRET-based fluorescence ratiometric detection can enable an attractive assay platform for analytes of interest. PMID:26653450

  18. Non-radiative resonance energy transfer in bi-polymer nanoparticles of fluorescent conjugated polymers.

    PubMed

    Ozel, Ilkem Ozge; Ozel, Tuncay; Demir, Hilmi Volkan; Tuncel, Donus

    2010-01-18

    This work demonstrates the comparative studies of non-radiative resonance energy transfer in bi-polymer nanoparticles based on fluorescent conjugated polymers. For this purpose, poly[(9,9-dihexylfluorene) (PF) as a donor (D) and poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) as an acceptor (A) have been utilized, from which four different bi-polymer nanoparticle systems are designed and synthesized. Both, steady-state fluorescence spectra and time-resolved fluorescence measurements indicate varying energy transfer efficiencies from the host polymer PF to the acceptor polymer MEH-PPV depending on the D-A distances and structural properties of the nanoparticles. The first approach involves the preparation of PF and MEH-PPV nanoparticles separately and mixing them at a certain ratio. In the second approach, first PF and MEH-PPV solutions are mixed prior to nanoparticle formation and then nanoparticles are prepared from the mixture. Third and fourth approaches involve the sequential nanoparticle preparation. In the former, nanoparticles are prepared to have PF as a core and MEH-PPV as a shell. The latter is the reverse of the third in which the core is MEH-PPV and the shell is PF. The highest energy transfer efficiency recorded to be 35% is obtained from the last system, in which a PF layer is sequentially formed on MEH-PPV NPs.

  19. Green Stimulated Emission Boosted by Nonradiative Resonant Energy Transfer from Blue Quantum Dots.

    PubMed

    Gao, Yuan; Yu, Guannan; Wang, Yue; Dang, Cuong; Sum, Tze Chien; Sun, Handong; Demir, Hilmi Volkan

    2016-07-21

    Thanks to their tunability and versatility, the colloidal quantum dots (CQDs) made of II-VI semiconductor compound offer the potential to bridge the "green gap" in conventional semiconductors. However, when the CQDs are pumped to much higher initial excitonic states compared to their bandgap, multiexciton interaction is enhanced, leading to a much higher stimulated emission threshold. Here, to circumvent this drawback, for the first time, we show a fully colloidal gain in green enabled by a partially indirect pumping approach assisted by Förster resonance energy transfer process. By introducing the blue CQDs as exciton donors, the lasing threshold of the green CQDs, is reduced dramatically. The blue CQDs thus serve as an energy-transferring buffer medium to reduce excitation energy from pumping photons in a controlled way by injecting photoinduced excitons into green CQDs. Our newly developed colloidal pumping scheme could enable efficient CQD lasers of full visible colors by a single pump source and cascaded exciton transfer. This would potentially pave the way for an efficient multicolor laser for lighting and display applications. PMID:27388758

  20. Characterization of one- and two-photon excitation fluorescence resonance energy transfer microscopy.

    PubMed

    Elangovan, Masilamani; Wallrabe, Horst; Chen, Ye; Day, Richard N; Barroso, Margarida; Periasamy, Ammasi

    2003-01-01

    Advances in molecular biology provide various methods to define the structure and function of the individual proteins that form the component parts of subcellular structures. The ability to see the dynamic behavior of a specific protein inside the living cell became possible through the application of advanced fluorescence resonance energy transfer (FRET) microscope techniques. The fluorophore molecule used for FRET imaging has a characteristic absorption and emission spectrum that should be considered for characterizing the FRET signal. In this article we describe the system development for the image acquisition for one- and two-photon excitation FRET microscopy. We also describe the precision FRET (PFRET) data analysis algorithm that we developed to remove spectral bleed-through and variation in the fluorophore expression level (or concentration) for the donor and acceptor molecules. The acquired images have been processed using a PFRET algorithm to calculate the energy transfer efficiency and the distance between donor and acceptor molecules. We implemented the software correction to study the organization of the apical endosome in epithelial polarized MDCK cells and dimerization of the CAATT/enhancer binding protein alpha (C/EBPalpha). For these proteins, the results revealed that the extent of correction affects the conventionally calculated energy transfer efficiency (E) and the distance (r) between donor and acceptor molecules by 38 and 9%, respectively. PMID:12543072

  1. Resonance energy transfer in self-organized organic/inorganic dendrite structures.

    PubMed

    Melnikau, D; Savateeva, D; Lesnyak, V; Gaponik, N; Fernández, Y Núnez; Vasilevskiy, M I; Costa, M F; Mochalov, K E; Oleinikov, V; Rakovich, Y P

    2013-10-01

    Hybrid materials formed by semiconductor quantum dots and J-aggregates of cyanine dyes provide a unique combination of enhanced absorption in inorganic constituents with large oscillator strength and extremely narrow exciton bands of the organic component. The optical properties of dendrite structures with fractal dimension 1.7-1.8, formed from J-aggregates integrated with CdTe quantum dots (QDs), have been investigated by photoluminescence spectroscopy and fluorescence lifetime imaging microscopy. Our results demonstrate that (i) J-aggregates are coupled to QDs by Förster-type resonant energy transfer and (ii) there are energy fluxes from the periphery to the centre of the structure, where the QD density is higher than in the periphery of the dendrite. Such an anisotropic energy transport can be only observed when dendrites are formed from QDs integrated with J-aggregates. These QD/J-aggregate hybrid systems can have applications in light harvesting systems and optical sensors with extended absorption spectra. PMID:23949098

  2. Green Stimulated Emission Boosted by Nonradiative Resonant Energy Transfer from Blue Quantum Dots.

    PubMed

    Gao, Yuan; Yu, Guannan; Wang, Yue; Dang, Cuong; Sum, Tze Chien; Sun, Handong; Demir, Hilmi Volkan

    2016-07-21

    Thanks to their tunability and versatility, the colloidal quantum dots (CQDs) made of II-VI semiconductor compound offer the potential to bridge the "green gap" in conventional semiconductors. However, when the CQDs are pumped to much higher initial excitonic states compared to their bandgap, multiexciton interaction is enhanced, leading to a much higher stimulated emission threshold. Here, to circumvent this drawback, for the first time, we show a fully colloidal gain in green enabled by a partially indirect pumping approach assisted by Förster resonance energy transfer process. By introducing the blue CQDs as exciton donors, the lasing threshold of the green CQDs, is reduced dramatically. The blue CQDs thus serve as an energy-transferring buffer medium to reduce excitation energy from pumping photons in a controlled way by injecting photoinduced excitons into green CQDs. Our newly developed colloidal pumping scheme could enable efficient CQD lasers of full visible colors by a single pump source and cascaded exciton transfer. This would potentially pave the way for an efficient multicolor laser for lighting and display applications.

  3. Resonance energy transfer in self-organized organic/inorganic dendrite structures

    NASA Astrophysics Data System (ADS)

    Melnikau, D.; Savateeva, D.; Lesnyak, V.; Gaponik, N.; Fernández, Y. Núnez; Vasilevskiy, M. I.; Costa, M. F.; Mochalov, K. E.; Oleinikov, V.; Rakovich, Y. P.

    2013-09-01

    Hybrid materials formed by semiconductor quantum dots and J-aggregates of cyanine dyes provide a unique combination of enhanced absorption in inorganic constituents with large oscillator strength and extremely narrow exciton bands of the organic component. The optical properties of dendrite structures with fractal dimension 1.7-1.8, formed from J-aggregates integrated with CdTe quantum dots (QDs), have been investigated by photoluminescence spectroscopy and fluorescence lifetime imaging microscopy. Our results demonstrate that (i) J-aggregates are coupled to QDs by Förster-type resonant energy transfer and (ii) there are energy fluxes from the periphery to the centre of the structure, where the QD density is higher than in the periphery of the dendrite. Such an anisotropic energy transport can be only observed when dendrites are formed from QDs integrated with J-aggregates. These QD/J-aggregate hybrid systems can have applications in light harvesting systems and optical sensors with extended absorption spectra.

  4. Study on the fluorescence resonance energy transfer between CdS quantum dots and Eosin Y.

    PubMed

    Yan, Zhengyu; Zhang, Zhengwei; Yu, Yan; Chen, Jianqiu

    2015-03-01

    Water-soluble CdS quantum dots (QDs) were prepared using mercaptoacetic acid (TGA) as the stabilizer in an aqueous system. A fluorescence resonance energy transfer (FRET) system was constructed between water-soluble CdS QDs (donor) and Eosin Y (acceptor). Several factors that impacted the fluorescence spectra of the FRET system, such as pH (3.05-10.10), concentration of Eosin Y (2-80 mg/L) and concentration of CdS QDs (2-80 mg/L), were investigated and refined. Donor-to-acceptor ratios, the energy transfer efficiency (E) and the distance (r) between CdS QDs and Eosin Y were obtained. The results showed that a FRET system could be established between water-soluble CdS QDs and Eosin Y at pH 5.0; donor-to-acceptor ratios demonstrated a 1: 8 proportion of complexes; the energy transfer efficiency (E) and the distance (r) between the QDs and Eosin Y were 20.07% and 4.36 nm,respectively.

  5. A graphitic carbon nitride based fluorescence resonance energy transfer detection of riboflavin.

    PubMed

    Han, Jing; Zou, Hong Yan; Gao, Ming Xuan; Huang, Cheng Zhi

    2016-01-01

    Fluorescence resonance energy transfer (FRET), which occurs between two luminescent chromophores, can greatly improve the selectivity and sensitivity of a fluorescent assay when a ratiometric signaling with the fluorescence enhancement of the acceptor at the expense of the donor is adopted. In this study, a fluorescence ratiometric detection (FRD) of riboflavin (RF) has been made based on FRET, as the strong overlap occurred between the emission spectrum of graphitic carbon nitride (g-C3N4) and absorption spectrum of RF, in which g-C3N4 acts as the energy donor and RF as the energy acceptor. With increasing concentration of RF, the fluorescence intensity of g-C3N4 emission at 444 nm decreased and the fluorescence peak at 523 nm for RF increased regularly, making the fluorescence intensity ratio of 523 nm to 444 nm linearly dependent on the concentration of RF in the range from 0.4 μM to 10 μM, giving a limit of the detection of 170 nM. This method can be used to quantify RF in complex systems such as milk and drink, showing that the novel FRET-based fluorescence ratiometric detection can enable an attractive assay platform for analytes of interest.

  6. Low-energy d-d excitations in MnO studied by resonant x-ray fluorescence spectroscopy

    SciTech Connect

    Butorin, S.M.; Guo, J.; Magnuson, M.

    1997-04-01

    Resonant soft X-ray emission spectroscopy has been demonstrated to possess interesting abilities for studies of electronic structure in various systems, such as symmetry probing, alignment and polarization dependence, sensitivity to channel interference, etc. In the present abstract the authors focus on the feasibility of resonant soft X-ray emission to probe low energy excitations by means of resonant electronic X-ray Raman scattering. Resonant X-ray emission can be regarded as an inelastic scattering process where a system in the ground state is transferred to a low excited state via a virtual core excitation. The energy closeness to a core excitation of the exciting radiation enhances the (generally) low probability for inelastic scattering at these wavelengths. Therefore soft X-ray emission spectroscopy (in resonant electronic Raman mode) can be used to study low energy d-d excitations in transition metal systems. The involvement of the intermediate core state allows one to use the selection rules of X-ray emission, and the appearance of the elastically scattered line in the spectra provides the reference to the ground state.

  7. Near-resonant rotational energy transfer in HCl-H2 inelastic collisions.

    PubMed

    Lanza, Mathieu; Kalugina, Yulia; Wiesenfeld, Laurent; Lique, François

    2014-02-14

    We present a new four-dimensional (4D) potential energy surface for the HCl-H2 van der Waals system. Both molecules were treated as rigid rotors. Potential energy surface was obtained from electronic structure calculations using a coupled cluster with single, double, and perturbative triple excitations method. The four atoms were described using the augmented correlation-consistent quadruple zeta basis set and bond functions were placed at mid-distance between the HCl and H2 centers of mass for a better description of the van der Waals interaction. The global minimum is characterized by the well depth of 213.38 cm(-1) corresponding to the T-shape structure with H2 molecule on the H side of the HCl molecule. The dissociation energies D0 are 34.7 cm(-1) and 42.3 cm(-1) for the complex with para- and ortho-H2, respectively. These theoretical results obtained using our new PES are in good agreement with experimental values [D. T. Anderson, M. Schuder, and D. J. Nesbitt, Chem. Phys. 239, 253 (1998)]. Close coupling calculations of the inelastic integral rotational cross sections of HCl in collisions with para-H2 and ortho-H2 were performed at low and intermediate collisional energies. Significant differences exist between para- and ortho-H2 results. The strongest collision-induced rotational HCl transitions are the transitions with Δj = 1 for collisions with both para-H2 and ortho-H2. Rotational relaxation of HCl in collision with para-H2 in the rotationally excited states j = 2 is dominated by near-resonant energy transfer. PMID:24527924

  8. Near-resonant rotational energy transfer in HCl-H2 inelastic collisions

    NASA Astrophysics Data System (ADS)

    Lanza, Mathieu; Kalugina, Yulia; Wiesenfeld, Laurent; Lique, François

    2014-02-01

    We present a new four-dimensional (4D) potential energy surface for the HCl-H2 van der Waals system. Both molecules were treated as rigid rotors. Potential energy surface was obtained from electronic structure calculations using a coupled cluster with single, double, and perturbative triple excitations method. The four atoms were described using the augmented correlation-consistent quadruple zeta basis set and bond functions were placed at mid-distance between the HCl and H2 centers of mass for a better description of the van der Waals interaction. The global minimum is characterized by the well depth of 213.38 cm-1 corresponding to the T-shape structure with H2 molecule on the H side of the HCl molecule. The dissociation energies D0 are 34.7 cm-1 and 42.3 cm-1 for the complex with para- and ortho-H2, respectively. These theoretical results obtained using our new PES are in good agreement with experimental values [D. T. Anderson, M. Schuder, and D. J. Nesbitt, Chem. Phys. 239, 253 (1998)]. Close coupling calculations of the inelastic integral rotational cross sections of HCl in collisions with para-H2 and ortho-H2 were performed at low and intermediate collisional energies. Significant differences exist between para- and ortho-H2 results. The strongest collision-induced rotational HCl transitions are the transitions with Δj = 1 for collisions with both para-H2 and ortho-H2. Rotational relaxation of HCl in collision with para-H2 in the rotationally excited states j = 2 is dominated by near-resonant energy transfer.

  9. Near-resonant rotational energy transfer in HCl–H{sub 2} inelastic collisions

    SciTech Connect

    Lanza, Mathieu; Lique, François; Kalugina, Yulia; Wiesenfeld, Laurent

    2014-02-14

    We present a new four-dimensional (4D) potential energy surface for the HCl–H{sub 2} van der Waals system. Both molecules were treated as rigid rotors. Potential energy surface was obtained from electronic structure calculations using a coupled cluster with single, double, and perturbative triple excitations method. The four atoms were described using the augmented correlation-consistent quadruple zeta basis set and bond functions were placed at mid-distance between the HCl and H{sub 2} centers of mass for a better description of the van der Waals interaction. The global minimum is characterized by the well depth of 213.38 cm{sup −1} corresponding to the T-shape structure with H{sub 2} molecule on the H side of the HCl molecule. The dissociation energies D{sub 0} are 34.7 cm{sup −1} and 42.3 cm{sup −1} for the complex with para- and ortho-H{sub 2}, respectively. These theoretical results obtained using our new PES are in good agreement with experimental values [D. T. Anderson, M. Schuder, and D. J. Nesbitt, Chem. Phys. 239, 253 (1998)]. Close coupling calculations of the inelastic integral rotational cross sections of HCl in collisions with para-H{sub 2} and ortho-H{sub 2} were performed at low and intermediate collisional energies. Significant differences exist between para- and ortho-H{sub 2} results. The strongest collision-induced rotational HCl transitions are the transitions with Δj = 1 for collisions with both para-H{sub 2} and ortho-H{sub 2}. Rotational relaxation of HCl in collision with para-H{sub 2} in the rotationally excited states j = 2 is dominated by near-resonant energy transfer.

  10. 57Co (n,γ) 58Co reaction cross section: Thermal and resonance integral measurements and energy dependence

    NASA Astrophysics Data System (ADS)

    Maidana, Nora L.; Mesa, Joel; Vanin, Vito R.; Castro, Ruy M.; Dias, Mauro S.; Koskinas, Marina F.

    2004-07-01

    The 57Co (n,γ) 58Co thermal and resonance integral cross section were measured as 51 (5) b and 20.0 (19) b , respectively, by irradiating aliquots of 57Co solution sealed inside quartz bottles near the core of the IEA-R1 IPEN research reactor and counting the gamma-ray residual activity. The irradiations were monitored using Au-Al alloy foils, with and without Cd cover. The gamma-ray measurements were performed with a shielded HPGe detector. Westcott formalism was applied for the average neutron flux determination. The cross section energy dependence was evaluated using the multilevel Breit-Wigner expression considering the first two resonances and the statistical model for energies above the second resonance. Maxwellian averaged neutron capture cross section with neutron temperatures between 5 and 100 keV were also evaluated.

  11. {sup 57}Co(n,{gamma}){sup 58}Co reaction cross section: Thermal and resonance integral measurements and energy dependence

    SciTech Connect

    Maidana, Nora L.; Mesa, Joel; Vanin, Vito R.; Castro, Ruy M.; Dias, Mauro S.; Koskinas, Marina F.

    2004-07-01

    The {sup 57}Co(n,{gamma}){sup 58}Co thermal and resonance integral cross section were measured as 51(5) b and 20.0(19) b, respectively, by irradiating aliquots of {sup 57}Co solution sealed inside quartz bottles near the core of the IEA-R1 IPEN research reactor and counting the gamma-ray residual activity. The irradiations were monitored using Au-Al alloy foils, with and without Cd cover. The gamma-ray measurements were performed with a shielded HPGe detector. Westcott formalism was applied for the average neutron flux determination. The cross section energy dependence was evaluated using the multilevel Breit-Wigner expression considering the first two resonances and the statistical model for energies above the second resonance. Maxwellian averaged neutron capture cross section with neutron temperatures between 5 and 100 keV were also evaluated.

  12. Forster Resonance Energy Transfer and Conformational Stability of Proteins: An Advanced Biophysical Module for Physical Chemistry Students

    ERIC Educational Resources Information Center

    Sanchez, Katheryn M.; Schlamadinger, Diana E.; Gable, Jonathan E.; Kim, Judy E.

    2008-01-01

    Protein folding is an exploding area of research in biophysics and physical chemistry. Here, we describe the integration of several techniques, including absorption spectroscopy, fluorescence spectroscopy, and Forster resonance energy transfer (FRET) measurements, to probe important topics in protein folding. Cytochrome c is used as a model…

  13. High-energy resonantly diode-pumped Q-switched Er:YAG laser at 1617 nm

    NASA Astrophysics Data System (ADS)

    Yu, Zhenzhen; Wang, Mingjian; Hou, Xia; Chen, Weibiao

    2016-04-01

    We report high-energy linearly polarized operation of an Er:YAG laser at 1617 nm, resonantly pumped by quasi-continuous-wave 1470-nm laser diodes. A U-shape resonator incorporating two 0.25 at.% Er:YAG rods and an acousto-optic Q-switch was employed. Polarized output with pulse energy of 20.5 mJ and pulse width of 52 ns at a 50 Hz repetition rate was obtained. At the maximum output energy, the output beam quality M 2 was approximately 1.02 and 1.03 in horizontal and vertical directions, respectively. To the best of our knowledge, this polarized pulse energy is the highest ever reported for a directly diode-pumped Q-switched Er:YAG laser operating at 1617 nm.

  14. Twenty-Eight Orders of Parametric Resonance in a Microelectromechanical Device for Multi-band Vibration Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Jia, Yu; Du, Sijun; Seshia, Ashwin A.

    2016-07-01

    This paper contends to be the first to report the experimental observation of up to 28 orders of parametric resonance, which has thus far only been envisioned in the theoretical realm. While theory has long predicted the onset of n orders of parametric resonance, previously reported experimental observations have been limited up to about the first 5 orders. This is due to the rapid narrowing nature of the frequency bandwidth of the higher instability intervals, making practical accessibility increasingly more difficult. Here, the authors have experimentally confirmed up to 28 orders of parametric resonance in a micromachined membrane resonator when electrically undamped. While the implication of this finding spans across the vibration dynamics and transducer application spectrum, the particular significance of this work is to broaden the accumulative operational frequency bandwidth of vibration energy harvesting for enabling self-powered microsystems. Up to 5 orders were recorded when driven at 1.0 g of acceleration across a matched load of 70 kΩ. With a natural frequency of 980 Hz, the fundamental mode direct resonance had a ‑3 dB bandwidth of 55 Hz, in contrast to the 314 Hz for the first order parametric resonance; furthermore, the half power bands of all 5 orders accumulated to 478 Hz.

  15. Twenty-Eight Orders of Parametric Resonance in a Microelectromechanical Device for Multi-band Vibration Energy Harvesting

    PubMed Central

    Jia, Yu; Du, Sijun; Seshia, Ashwin A.

    2016-01-01

    This paper contends to be the first to report the experimental observation of up to 28 orders of parametric resonance, which has thus far only been envisioned in the theoretical realm. While theory has long predicted the onset of n orders of parametric resonance, previously reported experimental observations have been limited up to about the first 5 orders. This is due to the rapid narrowing nature of the frequency bandwidth of the higher instability intervals, making practical accessibility increasingly more difficult. Here, the authors have experimentally confirmed up to 28 orders of parametric resonance in a micromachined membrane resonator when electrically undamped. While the implication of this finding spans across the vibration dynamics and transducer application spectrum, the particular significance of this work is to broaden the accumulative operational frequency bandwidth of vibration energy harvesting for enabling self-powered microsystems. Up to 5 orders were recorded when driven at 1.0 g of acceleration across a matched load of 70 kΩ. With a natural frequency of 980 Hz, the fundamental mode direct resonance had a −3 dB bandwidth of 55 Hz, in contrast to the 314 Hz for the first order parametric resonance; furthermore, the half power bands of all 5 orders accumulated to 478 Hz. PMID:27445205

  16. Radiative resonant energy transfer process in projectile-like ion formed in beam-foil interaction

    NASA Astrophysics Data System (ADS)

    Mishra, Adya P.; Nandi, T.; Jagatap, B. N.

    2013-03-01

    The formation of projectile-like M2555n ion during bombardment of a thin carbon foil by V12+2351 ion beam of energies above the Coulomb barrier is inferred through the observation of unresolved 1s2pP2o3→1sS01 and 1s2pP0o3→1sS01 transitions of He-like Mn at 6.14 keV. From the decay of intensity of this line the measured radiative lifetime of the upper state is found to be 78.7±11.6 ps which is close to the theoretical lifetime of the 1s2pP0o3 state (86.18 ps), but substantially lower than that of 1s2pP2o3 state (147.1 ps). This suggests that the 1s2pP0o3 state is populated more than the 1s2pP2o3 state when He-like Mn exits the carbon foil. This behavior is explained on the basis of radiative resonant energy transfer process in beam-foil excitation as reported recently (Nandi T, et al. J Quant Spectrosc Radiat Transfer 2012;113:783-8).

  17. Resonant Interaction, Approximate Symmetry, and Electromagnetic Interaction (EMI) in Low Energy Nuclear Reactions (LENR)

    NASA Astrophysics Data System (ADS)

    Chubb, Scott

    2007-03-01

    Only recently (talk by P.A. Mosier-Boss et al, in this session) has it become possible to trigger high energy particle emission and Excess Heat, on demand, in LENR involving PdD. Also, most nuclear physicists are bothered by the fact that the dominant reaction appears to be related to the least common deuteron(d) fusion reaction,d+d ->α+γ. A clear consensus about the underlying effect has also been illusive. One reason for this involves confusion about the approximate (SU2) symmetry: The fact that all d-d fusion reactions conserve isospin has been widely assumed to mean the dynamics is driven by the strong force interaction (SFI), NOT EMI. Thus, most nuclear physicists assume: 1. EMI is static; 2. Dominant reactions have smallest changes in incident kinetic energy (T); and (because of 2), d+d ->α+γ is suppressed. But this assumes a stronger form of SU2 symmetry than is present; d+d ->α+γ reactions are suppressed not because of large changes in T but because the interaction potential involves EMI, is dynamic (not static), the SFI is static, and because the two incident deuterons must have approximate Bose Exchange symmetry and vanishing spin. A generalization of this idea involves a resonant form of reaction, similar to the de-excitation of an atom. These and related (broken gauge) symmetry EMI effects on LENR are discussed.

  18. White light generation using Förster resonance energy transfer between 3-hydroxyisoquinoline and Nile Red.

    PubMed

    Joshi, Neeraj K; Polgar, Alexander M; Steer, Ronald P; Paige, Matthew F

    2016-05-11

    Simple composite films consisting of a polymer blended with organic emitters have the potential for broad-band "white" light emission that can be used for general lighting applications. In the present work, a simple mixture of 3-hydroxyisoquinoline (HIQ) with Nile Red (NR) in a polymeric matrix of polyvinyl alcohol (PVA) is used to generate white light through a non-radiative excitation energy transfer (NREET) mechanism. NREET between HIQ and NR doped in PVA films is investigated using a combination of steady state and time resolved fluorescence spectroscopic methods. It is observed that NR has very weak fluorescence in the PVA film upon excitation at 400 nm, but upon mixing NR with HIQ, sensitized emission of NR is observed with decreased emission of HIQ. The behavior of the sensitized emission of NR is consistent with Förster resonance energy transfer (FRET) between the donor HIQ and acceptor NR. By adjusting the relative fractions of HIQ and NR in the films, the extent of FRET could be regulated and the overall film emission color could be manipulated to enable overall "white" (CIE color coordinates 0.34, 0.38) emission. The films showed excellent photostability with 405 nm diode illumination, along with mechanical flexibility, suggesting good potential utility as a down converting element for lighting applications. PMID:26928071

  19. A Protein L -Based Immunodiagnostic Approach Utilizing Time-Resolved Förster Resonance Energy Transfer

    PubMed Central

    Hepojoki, Satu; Nurmi, Visa; Vaheri, Antti; Hedman, Klaus; Vapalahti, Olli; Hepojoki, Jussi

    2014-01-01

    Chelated lanthanides such as europium (Eu) have uniquely long fluorescence emission half-lives permitting their use in time-resolved fluorescence (TRF) assays. In Förster resonance energy transfer (FRET) a donor fluorophore transfers its emission energy to an acceptor fluorophore if in sufficiently close proximity. The use of time-resolved (TR) FRET minimizes the autofluorescence of molecules present in biological samples. In this report, we describe a homogenous immunoassay prototype utilizing TR-FRET for detection of antibodies in solution. The assay is based on labeled protein L, a bacterial protein that binds to immunoglobulin (Ig) light chain, and labeled antigen, which upon association with the same Ig molecule produce a TR-FRET active complex. We show that the approach is functional and can be utilized for both mono- and polyvalent antigens. We also compare the assay performance to that of another homogenous TR-FRET immunoassay reported earlier. This novel assay may have wide utility in infectious disease point-of-care diagnostics. PMID:25181527

  20. Ion-induced folding of the hammerhead ribozyme: a fluorescence resonance energy transfer study.

    PubMed Central

    Bassi, G S; Murchie, A I; Walter, F; Clegg, R M; Lilley, D M

    1997-01-01

    The ion-induced folding transitions of the hammerhead ribozyme have been analysed by fluorescence resonance energy transfer. The hammerhead ribozyme may be regarded as a special example of a three-way RNA junction, the global structure of which has been studied by comparing the distances (as energy transfer efficiencies) between the ends of pairs of labelled arms for the three possible end-to-end vectors as a function of magnesium ion concentration. The data support two sequential ion-dependent transitions, which can be interpreted in the light of the crystal structures of the hammerhead ribozyme. The first transition corresponds to the formation of a coaxial stacking between helices II and III; the data can be fully explained by a model in which the transition is induced by a single magnesium ion which binds with an apparent association constant of 8000-10 000 M-1. The second structural transition corresponds to the formation of the catalytic domain of the ribozyme, induced by a single magnesium ion with an apparent association constant of approximately 1100 M-1. The hammerhead ribozyme provides a well-defined example of ion-dependent folding in RNA. PMID:9405376

  1. Resonant tunneling diodes as energy-selective contacts used in hot-carrier solar cells

    SciTech Connect

    Takeda, Yasuhiko Sugimoto, Noriaki; Ichiki, Akihisa; Kusano, Yuya; Motohiro, Tomoyoshi

    2015-09-28

    Among the four features unique to hot-carrier solar cells (HC-SCs): (i) carrier thermalization time and (ii) carrier equilibration time in the absorber, (iii) energy-selection width and (iv) conductance of the energy-selective contacts (ESCs), requisites of (i)-(iii) for high conversion efficiency have been clarified. We have tackled the remaining issues related to (iv) in the present study. The detailed balance model of HC-SC operation has been improved to involve a finite value of the ESC conductance to find the required values, which in turn has been revealed to be feasible using resonant tunneling diodes (RTDs) consisting of semiconductor quantum dots (QDs) and quantum wells (QWs) by means of a formulation to calculate the conductance of the QD- and QW-RTDs derived using the rigorous solutions of the effective-mass Hamiltonians. Thus, all of the four requisites unique to HC-SCs to achieve high conversion efficiency have been elucidated, and the two requisites related to the ESCs can be fulfilled using the QD- and QW-RTDs.

  2. An upconversion fluorescent resonant energy transfer biosensor for hepatitis B virus (HBV) DNA hybridization detection.

    PubMed

    Zhu, Hao; Lu, Feng; Wu, Xing-Cai; Zhu, Jun-Jie

    2015-11-21

    A novel fluorescent resonant energy transfer (FRET) biosensor was fabricated for the detection of hepatitis B virus (HBV) DNA using poly(ethylenimine) (PEI) modified upconversion nanoparticles (NH2-UCNPs) as energy donor and gold nanoparticles (Au NPs) as acceptor. The PEI modified upconversion nanoparticles were prepared directly with a simple one-pot hydrothermal method, which provides high quality amino-group functionalized UCNPs with uniform morphology and strong upconversion luminescence. Two single-stranded DNA strands, which were partially complementary to each other, were then conjugated with NH2-UCNPs and Au NPs. When DNA conjugated NH2-UCNPs and Au NPs are mixed together, the hybridization between complementary DNA sequences on UCNPs and Au NPs will lead to the quenching of the upconversion luminescence due to the FRET process. Meanwhile, upon the addition of target DNA, Au NPs will leave the surface of the UCNPs and the upconversion luminescence can be restored because of the formation of the more stable double-stranded DNA on the UCNPs. The sensor we fabricated here for target DNA detection shows good sensitivity and high selectivity, which has the potential for clinical applications in the analysis of HBV and other DNA sequences. PMID:26421323

  3. Incident-energy-dependent spectral weight of resonant inelastic x-ray scattering in doped cuprates

    NASA Astrophysics Data System (ADS)

    Tsutsui, Kenji; Tohyama, Takami

    2016-08-01

    We theoretically investigate the incident-photon energy ωi dependence of resonant inelastic x-ray scattering (RIXS) tuned for the Cu L edge in cuprate superconductors by using the exact diagonalization technique for a single-band Hubbard model. Depending on the value of core-hole Coulomb interaction in the intermediate state, RIXS for non-spin-flip channel shows either a ωi-dependent fluorescencelike or ωi-independent Raman-like behavior for hole doping. An analysis of x-ray absorption suggests that the core-hole Coulomb interaction is larger than on-site Coulomb interaction in the Hubbard model, resulting in a fluorescencelike behavior in RIXS consistent with recent RIXS experiments. A shift on the high-energy side of the center of spectral distribution is also predicted for electron-doped systems though spectral weight is small. Main structures in the spin-flip channel exhibit a Raman-like behavior as expected, accompanied with a fluorescencelike behavior with small intensity.

  4. Resonant tunneling diodes as energy-selective contacts used in hot-carrier solar cells

    NASA Astrophysics Data System (ADS)

    Takeda, Yasuhiko; Ichiki, Akihisa; Kusano, Yuya; Sugimoto, Noriaki; Motohiro, Tomoyoshi

    2015-09-01

    Among the four features unique to hot-carrier solar cells (HC-SCs): (i) carrier thermalization time and (ii) carrier equilibration time in the absorber, (iii) energy-selection width and (iv) conductance of the energy-selective contacts (ESCs), requisites of (i)-(iii) for high conversion efficiency have been clarified. We have tackled the remaining issues related to (iv) in the present study. The detailed balance model of HC-SC operation has been improved to involve a finite value of the ESC conductance to find the required values, which in turn has been revealed to be feasible using resonant tunneling diodes (RTDs) consisting of semiconductor quantum dots (QDs) and quantum wells (QWs) by means of a formulation to calculate the conductance of the QD- and QW-RTDs derived using the rigorous solutions of the effective-mass Hamiltonians. Thus, all of the four requisites unique to HC-SCs to achieve high conversion efficiency have been elucidated, and the two requisites related to the ESCs can be fulfilled using the QD- and QW-RTDs.

  5. Fluorescence resonance energy transfer (FRET) imaging of a single living cell using green fluorescent protein

    NASA Astrophysics Data System (ADS)

    Periasamy, Ammasi; Kay, Steve A.; Day, Richard N.

    1997-05-01

    Fluorescence resonance energy transfer (FRET) imaging microscopy is a unique tool to visualize the spatiotemporal dynamics of protein interactions in living cells. Genetic vectors that encode protein fusions with green fluorescent protein (GFP) provide a method for imaging protein localization in living cells. We used FRET to study dimerization of the pituitary-specific transcription factor Pit-1 fused to GFP and BFP. A fusion protein containing GFP separated from BFP by 29 amino acids served as a positive control for FRET. Transcriptional activity of the GFP- and BFP-Pit-1 fusion proteins was demonstrated by their ability to activate the prolactin gene promoter. Using optimized excitation and emission filters, cells expressing the fluorescently-tagged Pit-1 proteins were imaged with a back- thinned, back-illuminated CCD chip that has about 50% quantum efficiency in the blue range. 2D FRET images acquired at the focal plane demonstrated Pit-1 protein associations in the nucleus of living cells. The significance of 2- and 3-D energy transfer imaging from these living cells is discussed.

  6. Development of a bioluminescence resonance energy transfer (BRET) for monitoring estrogen receptor alpha activation

    NASA Astrophysics Data System (ADS)

    Michelini, Elisa; Mirasoli, Mara; Karp, Matti; Virta, Marko; Roda, Aldo

    2004-06-01

    Estrogen receptor (ER) is a ligand-activated transcriptional factor, able to dimerize after activation and to bind specific DNA sequences (estrogen response elements), thus activating gene target transcription. Since ER homo- and hetero-dimerization (giving a-a and a-b isoforms) is a fundamental step for receptor activation, we developed an assay for detecting compounds that induce human ERa homo-dimerization based on bioluminescence resonance energy transfer (BRET). BRET is a non-radiative energy transfer, occurring between a luminescent donor and a fluorescent acceptor, that strictly depends on the closeness between the two proteins and can therefore be used for studying protein-protein interactions. We cloned ERa coding sequence in frame with either a variant of the green fluorescent protein (enhanced yellow fluorescent protein, EYFP) or Renilla luciferase (RLuc). Upon ERa homo-dimerization, BRET process takes place in the presence of the RLuc substrate coelenterazine resulting in EYFP emission at its characteristic wavelength. The ER alpha-Rluc and ER alpha-EYFP fusion proteins were cloned, then the occurrence of BRET in the presence of ER alpha activators was assayed both in vivo, within cells, and in vitro, with purified fusion proteins.

  7. Intramolecular fluorescence resonance energy transfer and living cell imaging of novel pyridyltriphenylamine dye

    NASA Astrophysics Data System (ADS)

    Cao, Duojun; Qian, Ying

    2016-07-01

    A novel pyridyltriphenylamine-rhodamine dye PTRh and a pyridyltriphenylamine derivative PTO were synthesized and characterized by 1H NMR and HRMS-MALDI-TOF. PTRh performed typical fluorescence resonance energy transfer (FRET) signal from pyridyltriphenylamine to rhodamine along with notable color change from green to rose when interacting with Hg2+ in EtOH/H2O. And PTRh as a ratiometric probe for Hg2+ based on FRET could achieve a very low detection limit of 32 nM and energy transfer efficiency of 83.7% in aqueous organic system. On the other hand, spectra properties of PTO in its aggregates, THF/H2O mixed solution and silica nanoparticles (Si-NPs) dispersed in water were investigated. And the results indicated PTO exhibited bright green fluorescence in solid state, and PTO was successfully encapsulated in silica matrix (30-40 nm), emitting bright blue fluorescence with 11.7% quantum yield. Additionally, living cell imaging experiments demonstrated that PTRh could effectively response to intracellular Hg2+ and PTO-doped Si-NPs were well uptaken by MCF-7 breast cancer cells. It could be concluded that the chromophores are promising materials used as biosensors.

  8. Development of homogeneous binding assays based on fluorescence resonance energy transfer between quantum dots and Alexa Fluor fluorophores.

    PubMed

    Nikiforov, Theo T; Beechem, Joseph M

    2006-10-01

    We studied the fluorescence resonance energy transfer (FRET) between quantum dots emitting at 565, 605, and 655 nm as energy donors and Alexa Fluor fluorophores with absorbance maxima at 594, 633, 647, and 680 nm as energy acceptors. As a first step, we prepared covalent conjugates between all three types of quantum dots and each of the Alexa Fluor fluorophores that could act as an energy acceptor. All of these conjugates displayed efficient resonance energy transfer. Then we prepared covalent conjugates of these quantum dots with biotin, fluorescein, and cortisol and established that the binding of these conjugates to suitable Alexa Fluor-labeled antibodies and streptavidin (in the case of biotin) can be efficiently detected by measuring the resonance energy transfer in homogeneous solutions. Finally, based on these observations, competitive binding assays for these three small analytes were developed. The performance of these assays as a function of the degree of labeling of the quantum dots was evaluated. It was found that decreasing the degree of loading of the quantum dots leads to decreases of the limits of detection. The results show the great potential of this FRET system for the development of new homogeneous binding assays.

  9. Resonance energy transfer in a calcium concentration-dependent cameleon protein.

    PubMed Central

    Habuchi, Satoshi; Cotlet, Mircea; Hofkens, Johan; Dirix, Gunter; Michiels, Jan; Vanderleyden, Jos; Subramaniam, Vinod; De Schryver, Frans C

    2002-01-01

    We report investigations of resonance energy transfer in the green fluorescent protein and calmodulin-based fluorescent indicator constructs for Ca(2+) called cameleons using steady-state and time-resolved spectroscopy of the full construct and of the component green fluorescent protein mutants, namely ECFP (donor) and EYFP (acceptor). EYFP displays a complicated photophysical behavior including protonated and deprotonated species involved in an excited-state proton transfer. When EYFP is excited in the absorption band of the protonated species, a fast nonradiative deactivation occurs involving almost 97% of the excited protonated population and leading to a low efficiency of excited-state proton transfer to the deprotonated species. ECFP displays a multiexponential fluorescence decay with a major contributing component of 3.2 ns. The time-resolved fluorescence data obtained upon excitation at 420 nm of Ca(2+)-free and Ca(2+)-bound YC3.1 cameleon constructs point to the existence of different conformations of calmodulin dependent on Ca(2+) binding. Whereas steady-state data show only an increase in the efficiency of energy transfer upon Ca(2+) binding, the time-resolved data demonstrate the existence of three distinct conformations/populations within the investigated sample. Although the mechanism of the interconversion between the different conformations and the extent of interconversion are still unclear, the time-resolved fluorescence data offer an estimation of the rate constants, of the efficiency of the energy transfer, and of the donor-acceptor distances in the Ca(2+)-free and Ca(2+)-bound YC3.1 samples. PMID:12496116

  10. Compact thermally-denatured state of a staphylococcal nuclease mutant from resonance energy transfer measurements.

    PubMed

    Wu, P G; James, E; Brand, L

    1993-12-01

    Thermal denaturation of a staphylococcal nuclease mutant K78C, where lysine 78 is replaced by cysteine, was studied by circular dichroism (CD) and resonance energy transfer. CD spectra suggest that residual structures remain in the denatured state. Steady-state energy transfer from intrinsic tyrosines to a single and intrinsic tryptophan was measured at different temperatures. In the thermally-denatured state of K78C, there is still a substantial degree of energy transfer from tyrosine(s) to tryptophan, indicating residual structures in the denatured state. The cysteine residue in mutant K78C was labeled with a cysteine specific probe IAEDANS. Fluorescence decays of the tryptophan were measured to estimate distance distributions between Trp 140 and IAEDANS at position 78. Measurements were done as a function of temperature from 4 degrees C (native) to 65 degrees C (denatured) both with and without Ca2+ and inhibitor pdTp. Below 30 degrees C, the apparent distance distribution of both the ligand-free nuclease and the enzyme with bound pdTp can be adequately described by a Gaussian model. Above 40 degrees C, where the ligand-free nuclease but not the ternary complex begins to denature, two different populations are required to fit the data both with and without pdTp. One population has a compact structure and the other has an expanded structure. As temperature rises, the population of the expanded structure increases. At the highest temperature, the non-native compact structure is still the major form (60 to 70%). The overall thermally-denatured states of staphylococcal nuclease mutant K78C in the absence and presence of ligands are thus compact and heterogeneous.

  11. Conformational transitions in the calcium adenosinetriphosphatase studied by time-resolved fluorescence resonance energy transfer.

    PubMed

    Birmachu, W; Nisswandt, F L; Thomas, D D

    1989-05-01

    We have used time-resolved fluorescence to study proposed conformational transitions in the Ca-ATPase in skeletal sarcoplasmic reticulum (SR). Resonance energy transfer was used to measure distances between the binding sites of 5-[[2-[(iodoacetyl)amino]ethyl]amino]naphthalene-1-sulfonic acid (IAEDANS) and fluorescein 5-isothiocyanate (FITC) as a function of conditions proposed to affect the enzyme's conformation. When 1.0 +/- 0.15 IAEDANS is bound per Ca-ATPase, most (76 +/- 4%) of the probes have an excited-state lifetime (tau) of 18.6 +/- 0.5 ns, and the remainder have a lifetime of 2.5 +/- 0.9 ns. When FITC is bound to a specific site on each IAEDANS-labeled enzyme, most of the long-lifetime component is quenched into two short-lifetime components, indicating energy transfer that corresponds to two donor-acceptor distances. About one-third of the quenched population has a lifetime tau = 11.1 +/- 2.5 ns, corresponding to a transfer efficiency E = 0.40 +/- 0.07 and a donor-acceptor distance R1 = 52 +/- 3 A. The remaining two-thirds exhibit lifetimes in the range of 1.2-4.2 ns, corresponding to a second distance 31 A less than or equal to R2 less than or equal to 40 A. Addition of Ca2+ (in the micromolar to millimolar range), or vanadate (to produce a phosphoenzyme analogue), had no effect on the donor-acceptor distances. Addition of decavanadate results in the quenching of IAEDANS fluorescence but has no effect on the energy-transfer distance.(ABSTRACT TRUNCATED AT 250 WORDS)

  12. Measurements of plasma bremsstrahlung and plasma energy density produced by electron cyclotron resonance ion source plasmas

    NASA Astrophysics Data System (ADS)

    Noland, Jonathan David

    2011-12-01

    The goal of this dissertation was to gain an understanding on the relative importance of microwave power, neutral pressure, and magnetic field configuration on the behavior of the hot electrons within an Electron Cyclotron Resonance Ion Source (ECRIS) plasma. This was carried out through measurement of plasma bremsstrahlung with both NaI(Tl) (hv > 30 keV) and CdTe (2 keV < hv < 70 keV) x-ray detectors, and through measurement of the plasma energy density with a diamagnetic loop placed around the plasma chamber. We also examined the anisotropy in x-ray power by simultaneously measuring the x-ray spectra in two orthogonal directions: radially and axially, using NaI(Tl) detectors. We have seen that for a 6.4 GHz ECRIS, both the x-ray power produced by confined electrons and the plasma energy density behave logarithmically with microwave power. The x-ray flux created by electrons lost from the plasma, however, does not saturate. Thus, the small increase in plasma density that occurred at high microwave powers (> 150 W on a 6.4 GHz ECRIS) was accompanied by a large increase in total x-ray power. We suggest that the saturation of x-ray power and plasma energy density was due to rf-induced pitch-angle scattering of the electrons. X-ray power and plasma energy density were also shown to saturate with neutral pressure, and to increase nearly linearly as the gradient of the magnetic field in the resonance zone was decreased. All of these findings were in agreement with the theoretical models describing ECRIS plasmas. We have discussed the use of a diamagnetic loop as a means of exploring various plasma time scales on a relative basis. Specifically, we focused much of our attention on studying how changing ion source parameters, such as microwave power and neutral pressure, would effect the rise and decay of the integrated diamagnetic signal, which can be related to plasma energy density. We showed that increasing microwave power lowers the e-fold times at both the leading

  13. Importance of resonance widths in low-energy scattering of weakly bound light-mass nuclei

    NASA Astrophysics Data System (ADS)

    Fraser, P. R.; Massen-Hane, K.; Amos, K.; Bray, I.; Canton, L.; Fossión, R.; Kadyrov, A. S.; Karataglidis, S.; Svenne, J. P.; van der Knijff, D.

    2016-09-01

    What effect do particle-emitting resonances have on the scattering cross section? What physical considerations are necessary when modeling these resonances? These questions are important when theoretically describing scattering experiments with radioactive ion beams which investigate the frontiers of the table of nuclides, far from stability. Herein, a novel method is developed that describes resonant nuclear scattering from which centroids and widths in the compound nucleus are obtained when one of the interacting bodies has particle unstable resonances. The method gives cross sections without unphysical behavior that is found if simple Lorentzian forms are used to describe resonant target states. The resultant cross sections differ significantly from those obtained when the states in the coupled channel calculations are taken to have zero width, and compound-system resonances are better matched to observed values.

  14. Internal movement in myosin subfragment 1 detected by fluorescence resonance energy transfer.

    PubMed

    Xing, J; Cheung, H C

    1995-05-16

    We have determined intersite distances from Cys374 of actin to Cys707 (SH1) and Cys697 (SH2) of myosin subfragment 1 (S1) in actosubfragment 1 (A.S1) by fluorescence resonance energy transfer for rigor complex A.S1 and complexes containing bound ADP and ADP plus orthovanadate (Vi), A.S1.ADP, and A.S1.ADP.Vi. A single energy acceptor (4-dimethylaminophenylazophenyl-4'-maleimide, DABMI) was attached to Cys374, and two different energy donors [(5-(iodoacetamideothyl)aminonaphthalene-1-sulfonic acid (IAEDANS) and 2-(4'-maleimidylanilino)naphthalene-6-sulfonic acid (MIANS)] were each attached to SH1 and SH2 for the distance determination. The two sites SH1 and SH2 of S1 were approximately equidistant (ca. 45 A) from actin Cys374 in rigor A.S1 when MIANS was the energy donor attached to the two thiols. The Cys374-SH1 distance decreased by 7-8 A in the presence of ADP plus Vi, but the distance Cys374-SH2 was essentially unaltered under identical conditions. Slightly different but similar distance results were obtained with AEDANS as energy donor. If the structure of actin monomer in A.S1 is assumed to be rigid [Miki, M. (1991) Biochemistry 30, 10878-10884], the present results indicate that MgADP plus Vi induced a movement of SH1 toward the actin site and that SH2 was insensitive to saturation of the active site pocket of S1 and relatively immobile. These results suggest that during the steady-state hydrolysis of ATP or in the weak-binding state of actomyosin, the short helical segment of S1 heavy chain containing SH1 moves closer to the COOH-terminal end of actin, while the adjacent helical segment containing SH2 remains stationary. The emission spectrum of MIANS attached to SH2 experienced a large red spectral shift (6-10 nm) in the presence of MgADP, MgADP + Vi, MgADP + beryllium fluoride, and ATP. A crude model of S1 based on the C alpha coordinates suggests that SH2 is located in a hydrophobic cage surrounded by three hydrophobic residues. Reorientation of one of

  15. Dyes at Ag colloids: The role of energy transfer processes for surface fluorescence and surface enhanced resonance raman scattering

    NASA Astrophysics Data System (ADS)

    Pettinger, B.; Gerolymatou, A.

    1985-06-01

    The comparison of Raman spectra of a pure water solution with those of an aqueous AG colloid reveals only very weak differences. This indicates, not unexpectedly, a low electromagnetic (EM) enhancement factor ( F ≈ 100) for the Raman scattering of water. Just in opposite to these weak effects, the addition of Ag sol to a {10 -10 M }/{l} rhodamine 6G solution causes the replacement of the former solution fluorescence by a similar intense surface enhanced resonance Raman scattering (SERRS). At higher dye concentrations (up to {10 -8 M }/{l}) it is replaced by both, by SERRS and surface fluorescence. The SERRS cross section is generally higher than 10 -20 cm 2 sr -1 molecule -1 photon -1. This indicates that a model based on a combination of weak EM resonances with molecular resonance Raman effects cannot explain a total enhancement by more than 10 orders of magnitude. An energy-transfer model seems to be more suitable.

  16. High-Q cross-plate phononic crystal resonator for enhanced acoustic wave localization and energy harvesting

    NASA Astrophysics Data System (ADS)

    Yang, Aichao; Li, Ping; Wen, Yumei; Yang, Chao; Wang, Decai; Zhang, Feng; Zhang, Jiajia

    2015-05-01

    A high-Q cross-plate phononic crystal resonator (Cr-PCR) coupled with an electromechanical Helmholtz resonator (EMHR) is proposed to improve acoustic wave localization and energy harvesting. Owing to the strongly directional wave-scattering effect of the cross-plate corners, strong confinement of acoustic waves emerges. Consequently, the proposed Cr-PCR structure exhibits ∼353.5 times higher Q value and ∼6.1 times greater maximum pressure amplification than the phononic crystal resonator (Cy-PCR) (consisting of cylindrical scatterers) of the same size. Furthermore, the harvester using the proposed Cr-PCR and the EMHR has ∼22 times greater maximum output-power volume density than the previous harvester using Cy-PCR and EMHR structures.

  17. Resonantly enhanced multiphoton ionization and zero kinetic energy photoelectron spectroscopy of chrysene: a comparison with tetracene.

    PubMed

    Zhang, Jie; Harthcock, Colin; Kong, Wei

    2012-07-01

    We report the electronic and vibrational spectroscopy of chrysene using resonantly enhanced multiphoton ionization (REMPI) and zero kinetic energy (ZEKE) photoelectron spectroscopy. As an isomer of tetracene, chrysene contains a kink in the middle of the four fused hexagonal rings, which complicates not just the symmetry but, more importantly, the molecular orbitals and hence vibronic transitions. Incidentally, the two nearby electronically excited states of chrysene have the same symmetry, and vibronic coupling introduces no out-of-plane vibrational modes. As a result, the REMPI spectrum of chrysene contains essentially only in-plane ring deformation modes, similar to that of tetracene. However, density functional calculations using gaussian even after the inclusion of vibronic coupling can only duplicate the observed REMPI spectrum in a qualitative sense, and the agreement is considerably worse than our recent work on a few pericondensed polycyclic aromatic hydrocarbons and on tetracene. The ZEKE spectrum of chrysene via the origin band of the intermediate electronic state S(1), however, can be qualitatively reproduced by a straightforward Franck-Condon calculation. The ZEKE spectra from vibrationally excited states of the S(1), on the other hand, demonstrate some degree of mode selectivity: the overall intensity of the ZEKE spectrum can vary by an order of magnitude depending on the vibrational mode of the intermediate state. A scaling factor in the theoretical vibrational frequency for the cation is also needed to compare with the experimental result, unlike tetracene and pentacene.

  18. Quantitative Förster resonance energy transfer analysis for kinetic determinations of SUMO-specific protease.

    PubMed

    Liu, Yan; Song, Yang; Madahar, Vipul; Liao, Jiayu

    2012-03-01

    Förster resonance energy transfer (FRET) technology has been widely used in biological and biomedical research, and it is a very powerful tool for elucidating protein interactions in either dynamic or steady state. SUMOylation (the process of SUMO [small ubiquitin-like modifier] conjugation to substrates) is an important posttranslational protein modification with critical roles in multiple biological processes. Conjugating SUMO to substrates requires an enzymatic cascade. Sentrin/SUMO-specific proteases (SENPs) act as an endopeptidase to process the pre-SUMO or as an isopeptidase to deconjugate SUMO from its substrate. To fully understand the roles of SENPs in the SUMOylation cycle, it is critical to understand their kinetics. Here, we report a novel development of a quantitative FRET-based protease assay for SENP1 kinetic parameter determination. The assay is based on the quantitative analysis of the FRET signal from the total fluorescent signal at acceptor emission wavelength, which consists of three components: donor (CyPet-SUMO1) emission, acceptor (YPet) emission, and FRET signal during the digestion process. Subsequently, we developed novel theoretical and experimental procedures to determine the kinetic parameters, k(cat), K(M), and catalytic efficiency (k(cat)/K(M)) of catalytic domain SENP1 toward pre-SUMO1. Importantly, the general principles of this quantitative FRET-based protease kinetic determination can be applied to other proteases.

  19. Imaging Erg and Jun transcription factor interaction in living cells using fluorescence resonance energy transfer analyses

    SciTech Connect

    Camuzeaux, Barbara; Heliot, Laurent; Coll, Jean . E-mail: martine.duterque@ibl.fr

    2005-07-15

    Physical interactions between transcription factors play important roles in modulating gene expression. Previous in vitro studies have shown a transcriptional synergy between Erg protein, an Ets family member, and Jun/Fos heterodimer, members of the bZip family, which requires direct Erg-Jun protein interactions. Visualization of protein interactions in living cells is a new challenge in biology. For this purpose, we generated fusion proteins of Erg, Fos, and Jun with yellow and cyan fluorescent proteins, YFP and CFP, respectively. After transient expression in HeLa cells, interactions of the resulting fusion proteins were explored by fluorescence resonance energy transfer microscopy (FRET) in fixed and living cells. FRET between YFP-Erg and CFP-Jun was monitored by using photobleaching FRET and fluorescence lifetime imaging microscopy. Both techniques revealed the occurrence of intermolecular FRET between YFP-Erg and CFP-Jun. This is stressed by loss of FRET with an YFP-Erg version carrying a point mutation in its ETS domain. These results provide evidence for the interaction of Erg and Jun proteins in living cells as a critical prerequisite of their transcriptional synergy, but also for the essential role of the Y371 residue, conserved in most Ets proteins, in this interaction.

  20. A silver nanorod resonance rayleigh scattering-energy transfer analytical platform for trace tea polyphenols.

    PubMed

    Liang, Aihui; Wang, Yaohui; Wen, Guiqing; Zhang, Xinghui; Luo, Yanghe; Jiang, Zhiliang

    2016-04-15

    The stable silver nanorod (AgNR) sol in red was prepared by the two-step procedure of NaBH4-H2O2 and citrate heating reduction, and it exhibited a strong resonance Rayleigh scattering (RRS) peak at 346 nm. In pH 3.8 HAc-NaAc buffer solution, tea polyphenols (TP) reacted with ammonium molybdate (AM) to form yellow organic molybdate (OM) as receptor that was closed to the donor of AgNR, the RRS energy transfer (RRS-ET) takes place, owing to the overlapping between the AgNR RRS spectra and OM absorption spectra. When TP concentration increased, the RRS intensity decreased due to the RRS-ET increasing. So, a simple and sensitive AgNR surface plasmon RRS-ET analytical platform was fabricated to detect trace TP in the range of 0.05-0.85 μg/mL, with a detection limit of 0.03 μg/mL TP. The TP in tea samples was analyzed by this RRS-ET analysis platform, with satisfactory results.

  1. Lighting Up Ultraviolet Fluorescence From Chicken Albumen Through Plasmon Resonance Energy Transfer of Gold Nanoparticles

    PubMed Central

    -Tsung Chen, I.; Chang, Po-Hsiang; Chang, Yun-Chorng; Guo, Tzung-Fang

    2013-01-01

    Au nanoparticles (AuNPs), which easily aggregate in organic thin film, are observed to well-disperse in chicken albumen thin films. The incorporated AuNPs is distributed uniformly inside the thin film and is as dense as 650 (particles/μm3). In addition, enhanced ultraviolet (UV) fluorescence centered at 350 nm is observed from the AuNPs-containing chicken albumen thin film. The enhancement is proposed to be originated from the plasmon resonance energy transfer (PRET) from the d-band absorption of AuNPs to the chicken albumen protein. The enhanced fluorescence is further verified by the shorter fluorescence lifetime from the time-resolved fluorescence spectra. These results indicate that d-band transition of AuNPs can be used to interface with other UV-emitting biomolecules. Results in this study demonstrate that AuNPs exhibit future potentials in applications for both the organic thin-film technology and nano-biotechnology. PMID:23514900

  2. Fluorescence resonance energy transfer between quantum dots and graphene oxide for sensing biomolecules.

    PubMed

    Dong, Haifeng; Gao, Wenchao; Yan, Feng; Ji, Hanxu; Ju, Huangxian

    2010-07-01

    This work designed a novel platform for effective sensing of biomolecules by fluorescence resonance energy transfer (FRET) from quantum dots (QDs) to graphene oxide (GO). The QDs were first modified with a molecular beacon (MB) as a probe to recognize the target analyte. The strong interaction between MB and GO led to the fluorescent quenching of QDs. Upon the recognition of the target, the distance between the QDs and GO increased, and the interaction between target-bound MB and GO became weaker, which significantly hindered the FRET and, thus, increased the fluorescence of QDs. The change in fluorescent intensity produced a novel method for detection of the target. The GO-quenching approach could be used for detection of DNA sequences, with advantages such as less labor for synthesis of the MB-based fluorescent probe, high quenching efficiency and sensitivity, and good specificity. By substituting the MB with aptamer, this strategy could be conveniently extended for detection of other biomolecules, which had been demonstrated by the interaction between aptamer and protein. To the best of our knowledge, this is the first application of the FRET between QDs and GO and opens new opportunities for sensitive detection of biorecognition events.

  3. Gold nanoparticles-based fluorescence resonance energy transfer for competitive immunoassay of biomolecules.

    PubMed

    Chen, Jia; Huang, Yong; Zhao, Shulin; Lu, Xin; Tian, Jianniao

    2012-12-21

    A novel platform for competitive immunoassay of biomolecules was designed based on fluorescence resonance energy transfer (FRET) between fluorescein isothiocyanate (FITC) and gold nanoparticles (AuNPs). The antigen was first labeled with FITC, and the FITC labeled antigen was then reacted with AuNPs functionalized with a relative antibody to obtain the nanometer-sized sensor. The FRET between FITC and AuNPs led to the fluorescent quenching of FITC. Upon the recognition of the target antigen, the FICT labeled antigen was released from the AuNPs surface because of competitive immunoreaction, the distance between the FITC and AuNPs increased, and the interaction between FITC and AuNPs became weaker, which significantly hindered the FRET and, thus, increased the fluorescence of FITC. The change in fluorescence intensity produced a novel method for detection of the target. By using immunoglobulin M (IgM) as a model analyte, the competitive immunoassay had a limit of detection of 42 pM. The present method was applied for the determination of IgM in human serum with satisfactory results. The proposed method exhibits several advantages such as high quenching efficiency and sensitivity, and good specificity toward target versus other analogues. Moreover, this strategy could be conveniently extended for the detection of other biomolecules by using the corresponding antigens and respective antibodies.

  4. Measuring protein interactions using Förster resonance energy transfer and fluorescence lifetime imaging microscopy

    PubMed Central

    Day, Richard N.

    2013-01-01

    The method of fluorescence lifetime imaging microscopy (FLIM) is a quantitative approach that can be used to detect Förster Resonance Energy Transfer (FRET). The use of FLIM to measure the FRET that results from the interactions between proteins labeled with fluorescent proteins (FPs) inside living cells provides a non-invasive method for mapping interactomes. Here, the use of the phasor plot method to analyze frequency domain (FD) FLIM measurements is described, and measurements obtained from cells producing the 'FRET standard' fusion proteins are used to validate the FLIM system for FRET measurements. The FLIM FRET approach is then used to measure both homologous and heterologous protein-protein interactions (PPI) involving the CCAAT/enhancer-binding protein alpha (C/EBPα). C/EBPα is a transcription factor that controls cell differentiation, and localizes to heterochromatin where it interacts with the heterochromatin protein 1 alpha (HP1α). The FLIM-FRET method is used to quantify the homologous interactions between the FP-labeled basic leucine zipper (BZip) domain of C/EBPα. Then the heterologous interactions between the C/EBPa BZip domain and HP1a are quantified using the FRET-FLIM method. The results demonstrate that the basic region and leucine zipper (BZip) domain of C/EBPα is sufficient for the interaction with HP1α in regions of heterochromatin. PMID:23806643

  5. In Vivo Fluorescence Resonance Energy Transfer Imaging for Targeted Anti-Cancer Drug Delivery Kinetics

    NASA Astrophysics Data System (ADS)

    Webb, Kevin; Gaind, Vaibhav; Tsai, Hsiaorho; Bentz, Brian; Chelvam, Venkatesh; Low, Philip

    2012-02-01

    We describe an approach for the evaluation of targeted anti-cancer drug delivery in vivo. The method emulates the drug release and activation process through acceptor release from a targeted donor-acceptor pair that exhibits fluorescence resonance energy transfer (FRET). In this case, folate targeting of the cancer cells is used - 40 % of all human cancers, including ovarian, lung, breast, kidney, brain and colon cancer, over-express folate receptors. We demonstrate the reconstruction of the spatially-dependent FRET parameters in a mouse model and in tissue phantoms. The FRET parameterization is incorporated into a source for a diffusion equation model for photon transport in tissue, in a variant of optical diffusion tomography (ODT) called FRET-ODT. In addition to the spatially-dependent tissue parameters in the diffusion model (absorption and diffusion coefficients), the FRET parameters (donor-acceptor distance and yield) are imaged as a function of position. Modulated light measurements are made with various laser excitation positions and a gated camera. More generally, our method provides a new vehicle for studying disease at the molecular level by imaging FRET parameters in deep tissue, and allows the nanometer FRET ruler to be utilized in deep tissue.

  6. Distance distributions of short polypeptides recovered by fluorescence resonance energy transfer in the 10 A domain.

    PubMed

    Sahoo, Harekrushna; Roccatano, Danilo; Zacharias, Martin; Nau, Werner M

    2006-06-28

    Fluorescence resonance energy transfer (FRET) between tryptophan (Trp) as donor and 2,3-diazabicyclo[2.2.2]oct-2-ene (Dbo) as acceptor was studied by steady-state and time-resolved fluorescence spectroscopy. The unique feature of this FRET pair is its exceptionally short Förster radius (10 A), which allows one to recover distance distributions in very short structureless peptides. The technique was applied to Trp-(GlySer)n-Dbo-NH2 peptides with n = 0-10, for which the average probe/quencher distance ranged between 8.7 and 13.7 A experimentally (in propylene glycol, analysis according to wormlike chain model) and 8.6-10.2 A theoretically (for n = 0-6, GROMOS96 molecular dynamics simulations). The larger FRET efficiency in steady-state compared to time-resolved fluorescence experiments was attributed to a static quenching component, suggesting that a small but significant part (ca. 10%) of the conformations are already in van der Waals contact when excitation occurs.

  7. Drug transport mechanism of P-glycoprotein monitored by single molecule fluorescence resonance energy transfer

    NASA Astrophysics Data System (ADS)

    Ernst, S.; Verhalen, B.; Zarrabi, N.; Wilkens, S.; Börsch, M.

    2011-03-01

    In this work we monitor the catalytic mechanism of P-glycoprotein (Pgp) using single-molecule fluorescence resonance energy transfer (FRET). Pgp, a member of the ATP binding cassette family of transport proteins, is found in the plasma membrane of animal cells where it is involved in the ATP hydrolysis driven export of hydrophobic molecules. When expressed in the plasma membrane of cancer cells, the transport activity of Pgp can lead to the failure of chemotherapy by excluding the mostly hydrophobic drugs from the interior of the cell. Despite ongoing effort, the catalytic mechanism by which Pgp couples MgATP binding and hydrolysis to translocation of drug molecules across the lipid bilayer is poorly understood. Using site directed mutagenesis, we have introduced cysteine residues for fluorescence labeling into different regions of the nucleotide binding domains (NBDs) of Pgp. Double-labeled single Pgp molecules showed fluctuating FRET efficiencies during drug stimulated ATP hydrolysis suggesting that the NBDs undergo significant movements during catalysis. Duty cycle-optimized alternating laser excitation (DCO-ALEX) is applied to minimize FRET artifacts and to select the appropriate molecules. The data show that Pgp is a highly dynamic enzyme that appears to fluctuate between at least two major conformations during steady state turnover.

  8. Nanoluciferase signal brightness using furimazine substrates opens bioluminescence resonance energy transfer to widefield microscopy.

    PubMed

    Kim, Jiho; Grailhe, Regis

    2016-08-01

    Fluorescence and bioluminescence resonance energy transfer (FRET, BRET) techniques are powerful tools for studying protein-protein interactions in cellular assays. In contrast to fluorescent proteins, chemiluminescent proteins do not require excitation light, known to trigger autofluorescence, phototoxicity, and photobleaching. Regrettably, low signal intensity of luciferase systems restricts their usage as they require specialized microscopes equipped with ultra low-light imaging cameras. In this study, we report that bioluminescence quantification in living cells using a standard widefield automated microscope dedicated to screening and high content analysis is possible with the newer luciferase systems, Nanoluciferase (Nluc). With such equipment, we showed that robust intramolecular BRET can be measured using a combination of Nluc and yellow fluorescent protein (YFP). Using the human Superoxide Dismutase 1 (SOD1) dimer model, we next validated that intermolecular BRET could be quantified at a single cell level. The enhanced signal brightness of Nluc enabling BRET imaging to widefield microscopy shows strong potential to open up single cell protein-protein interactions studies to a wider audience. © 2016 International Society for Advancement of Cytometry.

  9. Upconversion Nanoparticle-Based Förster Resonance Energy Transfer for Detecting DNA Methylation.

    PubMed

    Kim, Seockjune; Hwang, Sang-Hyun; Im, Su-Gyeong; Lee, Min-Ki; Lee, Chang-Hun; Son, Sang Jun; Oh, Heung-Bum

    2016-01-01

    Aberrant methylation of a crucial CpG island is the main mechanism for the inactivation of CDKN2A in the early stages of carcinogenesis. Therefore, the detection of DNA methylation with high sensitivity and specificity is important, and various detection methods have been developed. Recently, upconversion nanoparticles (UCNPs) have been found to display a high signal-to-noise ratio and no photobleaching, making them useful for diagnostic applications. In this pilot study, we applied UCNPs to the detection of CDKN2A methylation and evaluated the feasibility of this system for use in molecular diagnostics. DNA PCR was performed using biotinylated primers, and the PCR amplicon was then intercalated with SYTOX Orange dye, followed by incubation with streptavidin-conjugated UCNPs. Fluorescence detection of the Förster resonance energy transfer (FRET) of the UCNPs (MS-UC-FRET) was then performed, and the results were compared to those from real-time PCR (RQ-PCR) and pyrosequencing. Detection by MS-UC-FRET was more sensitive than that by either RQ-PCR or pyrosequencing. Our results confirmed the success of our MS-UC-FRET system for detecting DNA methylation and demonstrated the potential application of this system in molecular diagnostics. PMID:27517925

  10. Toward automated denoising of single molecular Förster resonance energy transfer data.

    PubMed

    Lee, Hao-Chih; Lin, Bo-Lin; Chang, Wei-Hau; Tu, I-Ping

    2012-01-01

    A wide-field two-channel fluorescence microscope is a powerful tool as it allows for the study of conformation dynamics of hundreds to thousands of immobilized single molecules by Förster resonance energy transfer (FRET) signals. To date, the data reduction from a movie to a final set containing meaningful single-molecule FRET (smFRET) traces involves human inspection and intervention at several critical steps, greatly hampering the efficiency at the post-imaging stage. To facilitate the data reduction from smFRET movies to smFRET traces and to address the noise-limited issues, we developed a statistical denoising system toward fully automated processing. This data reduction system has embedded several novel approaches. First, as to background subtraction, high-order singular value decomposition (HOSVD) method is employed to extract spatial and temporal features. Second, to register and map the two color channels, the spots representing bleeding through the donor channel to the acceptor channel are used. Finally, correlation analysis and likelihood ratio statistic for the change point detection (CPD) are developed to study the two channels simultaneously, resolve FRET states, and report the dwelling time of each state. The performance of our method has been checked using both simulation and real data.

  11. A homogeneous time-resolved fluorescence resonance energy transfer assay for phosphatidylserine exposure on apoptotic cells.

    PubMed

    Gasser, Jean-Philippe; Hehl, Michaela; Millward, Thomas A

    2009-01-01

    A simple, "mix-and-measure" microplate assay for phosphatidylserine (PtdSer) exposure on the surface of apoptotic cells is described. The assay exploits the fact that annexin V, a protein with high affinity and specificity for PtdSer, forms trimers and higher order oligomers on binding to membranes containing PtdSer. The transition from soluble monomer to cell-bound oligomer is detected using time-resolved fluorescence resonance energy transfer from europium chelate-labeled annexin V to Cy5-labeled annexin V. PtdSer detection is achieved by a single addition of a reagent mix containing labeled annexins and calcium ions directly to cell cultures in a 96-well plate, followed by a brief incubation before fluorescence measurement. The assay can be used to quantify PtdSer exposure on both suspension cells and adherent cells in situ. This method is simpler and faster than existing annexin V binding assays based on flow cytometry or microscopy, and it yields precise data with Z' values of 0.6-0.7. PMID:18835236

  12. Rubredoxin mutant A51C unfolding dynamics: a Förster Resonance Energy Transfer study.

    PubMed

    Santos, Andrea; Duarte, Américo G; Fedorov, Alexander; Martinho, José M G; Moura, Isabel

    2010-05-01

    The unfolding dynamics of the rubredoxin mutant A51C (RdA51C) from Desulfovibrio vulgaris (DvRd) was studied on the temperature range from 25 degrees C to 90 degrees C and by incubation at 90 degrees C. By Förster Resonance Energy Transfer (FRET) the donor (D; Trp37) to acceptor (A; 1,5-IAEDANS) distance distribution was probed at several temperatures between 25 degrees C and 90 degrees C, and incubation times at 90 degrees C. From 25 degrees C to 50 degrees C the half-width distributions values (hw) are small and the presence of a discrete D-A distance was considered. At temperatures higher than 60 degrees C broader hw values were observed reflecting the existence of a distance distribution. The protein denaturation was only achieved by heating the solution for 2h at 90 degrees C, as probed by the increase of the D-A mean distance. From Trp fluorescence it was shown that its vicinity was maintained until approximately 70 degrees C, being the protein hydrodynamic radius invariant until 50 degrees C. However, at approximately 70 degrees C a change in the partial unfolding kinetics indicates the disruption of specific H-bonds occurring in the hydrophobic core. The red shift of 13nm, observed on the Trp37 emission, confirms the exposition of Trp to solvent after protein incubation at 90 degrees C for 2.5h.

  13. Förster resonance energy transfer as a probe of membrane protein folding

    PubMed Central

    Kang, Guipeun; López-Peña, Ignacio; Oklejas, Vanessa; Gary, Cyril S.; Cao, Weihan; Kim, Judy E.

    2011-01-01

    The folding reaction of a β-barrel membrane protein, Outer Membrane Protein A (OmpA), is probed with Förster resonance energy transfer (FRET) experiments. Four mutants of OmpA were generated in which the donor fluorophore, tryptophan, and acceptor molecule, 1,5-IAEDANS, are placed in various locations on the protein to report the evolution of distances across the bilayer and across the protein pore during a folding event. Analysis of the FRET efficiencies reveals three timescales for tertiary structure changes associated with insertion and folding into a synthetic bilayer. A narrow pore forms during the initial stage of insertion, followed by bilayer traversal. Finally, a long-time component is attributed to equilibration and relaxation, and may involve global changes such as pore expansion and strand extension. These results augment the existing models that describe concerted insertion and folding events, and highlight the ability of FRET to provide insight into the complex mechanisms of membrane protein folding. PMID:21925139

  14. Single-molecule-sensitive fluorescence resonance energy transfer in freely-diffusing attoliter droplets

    SciTech Connect

    Rahmanseresht, Sheema; Ramos, Kieran P.; Gamari, Ben D.; Goldner, Lori S.; Milas, Peker

    2015-05-11

    Fluorescence resonance energy transfer (FRET) from individual, dye-labeled RNA molecules confined in freely-diffusing attoliter-volume aqueous droplets is carefully compared to FRET from unconfined RNA in solution. The use of freely-diffusing droplets is a remarkably simple and high-throughput technique that facilitates a substantial increase in signal-to-noise for single-molecular-pair FRET measurements. We show that there can be dramatic differences between FRET in solution and in droplets, which we attribute primarily to an altered pH in the confining environment. We also demonstrate that a sufficient concentration of a non-ionic surfactant mitigates this effect and restores FRET to its neutral-pH solution value. At low surfactant levels, even accounting for pH, we observe differences between the distribution of FRET values in solution and in droplets which remain unexplained. Our results will facilitate the use of nanoemulsion droplets as attoliter volume reactors for use in biophysical and biochemical assays, and also in applications such as protein crystallization or nanoparticle synthesis, where careful attention to the pH of the confined phase is required.

  15. Analysis of Arrestin Recruitment to Chemokine Receptors by Bioluminescence Resonance Energy Transfer.

    PubMed

    Bonneterre, J; Montpas, N; Boularan, C; Galés, C; Heveker, N

    2016-01-01

    Chemokine receptors recruit the multifunctional scaffolding protein beta arrestin in response to binding of their chemokine ligands. Given that arrestin recruitment represents a signaling axis that is in part independent from G-protein signaling, it has become a hallmark of G protein-coupled receptor functional selectivity. Therefore, quantification of arrestin recruitment has become a requirement for the delineation of chemokine and drug candidate activity along different signaling axes. Bioluminescence resonance energy transfer (BRET) techniques provide methodology for such quantification that can reveal differences between nonredundant chemokines binding the same receptor, and that can be upscaled for high-throughput testing. We here provide protocols for the careful setup of BRET-based arrestin recruitment assays, and examples for the application of such systems in dose-response or time-course experiments. Suggestions are given for troubleshooting, optimizing test systems, and the interpretation of results obtained with BRET-based assays, which indeed yield an intricate blend of quantitative and qualitative information.

  16. Photonic effects on the Förster resonance energy transfer efficiency

    NASA Astrophysics Data System (ADS)

    Rabouw, Freddy T.; den Hartog, Stephan A.; Senden, Tim; Meijerink, Andries

    2014-04-01

    Förster resonance energy transfer (ET) between luminescent species is applied in bio-imaging, lighting and photovoltaics, and has an important role in photosynthesis. However, the fundamental question of whether ET rates and efficiencies can be tuned by the photonic environment remains under debate. Here we show that ET rates are independent of the photonic environment, using the model system of LaPO4 nanocrystals co-doped with Ce3+ donors and Tb3+ acceptors. Although the radiative emission rate of the Ce3+ excited state increases with the refractive index of the solvent in which the nanocrystals are dispersed, the Ce3+-to-Tb3+ ET rate does not. We demonstrate that, as a result, lower refractive index solvents enable higher ET efficiencies leading to higher Tb3+ emission intensities. Furthermore, an analytical model for ET in (nano)crystalline host materials is presented, able to predict the dependence of ET efficiencies on the photonic environment and the concentration of acceptor ions.

  17. Fluorescent proteins as biosensors by quenching resonance energy transfer from endogenous tryptophan: detection of nitroaromatic explosives.

    PubMed

    Gingras, Alexa; Sarette, Joseph; Shawler, Evan; Lee, Taeyoung; Freund, Steve; Holwitt, Eric; Hicks, Barry W

    2013-10-15

    Ensuring domestic safety from terrorist attack is a daunting challenge because of the wide array of chemical agents that must be screened. A panel of purified fluorescent protein isoforms (FPs) was screened for the ability to detect various explosives, explosive simulants, and toxic agents. In addition to their commonly used visible excitation wavelengths, essentially all FPs can be excited by UV light at 280 nm. Ultraviolet illumination excites electrons in endogenous tryptophan (W) residues, which then relax by Förster Resonance Energy Transfer (FRET) to the chromophore of the FP, and thus the FPs emit with their typical visible spectra. Taking advantage of the fact that tryptophan excitation can be quenched by numerous agents, including nitroaromatics like TNT and nitramines like RDX, it is demonstrated that quenching of visible fluorescence from UV illumination of FPs can be used as the basis for detecting these explosives and explosive degradation products. This work provides the foundation for production of an array of genetically-modified FPs for in vitro biosensors capable of rapid, simultaneous, sensitive and selective detection of a wide range of explosive or toxic agents.

  18. Judgment of pure fermented soy sauce by fluorescence resonance energy transfer of OPA-tryptophan adduct.

    PubMed

    Gao, You-Syuan; Hsieh, Bo-Chuan; Cheng, Tzong-Jih; Chen, Richie L C

    2015-07-01

    Tryptophan was detected with a flow-injection manifold after reacting with mM order of fluorogenic o-phthalaldehyde (OPA)/thiol reagent (pH 10.0) in the carrier stream (0.63 mL/min). Based on the intra-molecular fluorescence resonance energy transfer of OPA-tryptophan adduct, the difference in fluorescence intensity obtained at 280 and 300 nm excitation was used to detect tryptophan content with satisfactory precision (CV<6.5% for concentration higher than 0.5 μM), linearity (0.1-10 μM, R(2)=0.9893) and sensitivity (≈10 nM). Since tryptophan will decompose during manufacturing non-fermented soy sauce by acid-hydrolysis procedure, the method was used to discriminate pure fermented soy sauces, adulterated soy sauces and chemical soy sauces in less than 5 min. The ratio of tryptophan to total amino acid content served as the index for the judgment, and the results were validated by capillary electrophoresis.

  19. Spectroscopic features of dual fluorescence/luminescence resonance energy-transfer molecular beacons.

    PubMed

    Tsourkas, Andrew; Behlke, Mark A; Xu, Yangqing; Bao, Gang

    2003-08-01

    Molecular beacons have the potential to become a powerful tool in gene detection and quantification in living cells. Here we report a novel dual molecular beacons approach to reduce false-positive signals in detecting target nucleic acids in homogeneous assays. A pair of molecular beacons, each containing a fluorescence quencher and a reporter fluorophore, one with a donor and a second with an acceptor fluorophore, hybridize to adjacent regions on the same target resulting in fluorescence resonance energy transfer (FRET). The detection of a FRET signal leads to a substantially increased signal-to-background ratio compared with that seen in single molecular beacon assays and enables discrimination between fluorescence due to specific probe/target hybridization and a variety of possible false-positive events. Further, when a lanthanide chelate is used as a donor in a dual-probe assay, extremely high signal-to-background ratios can be achieved owing to the long lifetime and sharp emission peaks of the donor and the time-gated detection of acceptor fluorescence emission. These new approaches allow for the ultrasensitive detection of target molecules in a way that could be readily applied to real-time imaging of gene expression in living cells.

  20. Upconversion Nanoparticle-Based Förster Resonance Energy Transfer for Detecting DNA Methylation

    PubMed Central

    Kim, Seockjune; Hwang, Sang-Hyun; Im, Su-Gyeong; Lee, Min-Ki; Lee, Chang-Hun; Son, Sang Jun; Oh, Heung-Bum

    2016-01-01

    Aberrant methylation of a crucial CpG island is the main mechanism for the inactivation of CDKN2A in the early stages of carcinogenesis. Therefore, the detection of DNA methylation with high sensitivity and specificity is important, and various detection methods have been developed. Recently, upconversion nanoparticles (UCNPs) have been found to display a high signal-to-noise ratio and no photobleaching, making them useful for diagnostic applications. In this pilot study, we applied UCNPs to the detection of CDKN2A methylation and evaluated the feasibility of this system for use in molecular diagnostics. DNA PCR was performed using biotinylated primers, and the PCR amplicon was then intercalated with SYTOX Orange dye, followed by incubation with streptavidin-conjugated UCNPs. Fluorescence detection of the Förster resonance energy transfer (FRET) of the UCNPs (MS-UC-FRET) was then performed, and the results were compared to those from real-time PCR (RQ-PCR) and pyrosequencing. Detection by MS-UC-FRET was more sensitive than that by either RQ-PCR or pyrosequencing. Our results confirmed the success of our MS-UC-FRET system for detecting DNA methylation and demonstrated the potential application of this system in molecular diagnostics. PMID:27517925

  1. Determination of GLUT1 Oligomerization Parameters using Bioluminescent Förster Resonance Energy Transfer

    PubMed Central

    Looyenga, Brendan; VanOpstall, Calvin; Lee, Zion; Bell, Jed; Lodge, Evans; Wrobel, Katherine; Arnoys, Eric; Louters, Larry

    2016-01-01

    The facilitated glucose transporter GLUT1 (SLC2A1) is an important mediator of glucose homeostasis in humans. Though it is found in most cell types to some extent, the level of GLUT1 expression across different cell types can vary dramatically. Prior studies in erythrocytes—which express particularly high levels of GLUT1—have suggested that GLUT1 is able to form tetrameric complexes with enhanced transport activity. Whether dynamic aggregation of GLUT1 also occurs in cell types with more modest expression of GLUT1, however, is unclear. To address this question, we developed a genetically encoded bioluminescent Förster resonance energy transfer (BRET) assay using the luminescent donor Nanoluciferase and fluorescent acceptor mCherry. By tethering these proteins to the N-terminus of GLUT1 and performing saturation BRET analysis, we were able to demonstrate the formation of multimeric complexes in live cells. Parallel use of flow cytometry and immunoblotting further enabled us to estimate the density of GLUT1 proteins required for spontaneous oligomerization. These data provide new insights into the physiological relevance of GLUT1 multimerization as well as a new variant of BRET assay that is useful for measuring the interactions among other cell membrane proteins in live cells. PMID:27357903

  2. Thrombin detection in murine plasma using engineered fluorescence resonance energy transfer aptadimers

    NASA Astrophysics Data System (ADS)

    Trapaidze, Ana; Brut, Marie; Mazères, Serge; Estève, Daniel; Gué, Anne-Marie; Bancaud, Aurélien

    2015-12-01

    Biodetection strategies, in which two sides of one target protein are targeted simultaneously, have been shown to increase specificity, selectivity, and affinity, and it has been suggested that they constitute excellent candidates for protein sensing in complex media. In this study we propose a method to engineer the sequence of a DNA construct dedicated to reversible thrombin detection. This construct, called Fluorescence Resonance Energy Transfer (FRET) aptadimer, is assembled with two aptamers, which target different epitopes of thrombin, interconnected with a DNA linker that contains a FRET couple and a reversible double helix stem. In the absence of target, the stem is stable maintaining a FRET couple in close proximity, and fluorescence is unquenched upon thrombin addition due to the dehybridization of the stem. We define design rules for the conception of FRET aptadimers, and develop a software to optimize their functionality. One engineered FRET aptadimer sequence is subsequently characterized experimentally by temperature scanning fluorimetry, demonstrating the relevance of our technology for thrombin sensing in bulk and diluted murine plasma.

  3. Förster resonance energy transfer as a tool to study photoreceptor biology.

    PubMed

    Hovan, Stephanie C; Howell, Scott; Park, Paul S-H

    2010-01-01

    Vision is initiated in photoreceptor cells of the retina by a set of biochemical events called phototransduction. These events occur via coordinated dynamic processes that include changes in secondary messenger concentrations, conformational changes and post-translational modifications of signaling proteins, and protein-protein interactions between signaling partners. A complete description of the orchestration of these dynamic processes is still unavailable. Described in this work is the first step in the development of tools combining fluorescent protein technology, Förster resonance energy transfer (FRET), and transgenic animals that have the potential to reveal important molecular insights about the dynamic processes occurring in photoreceptor cells. We characterize the fluorescent proteins SCFP3A and SYFP2 for use as a donor-acceptor pair in FRET assays, which will facilitate the visualization of dynamic processes in living cells. We also demonstrate the targeted expression of these fluorescent proteins to the rod photoreceptor cells of Xenopus laevis, and describe a general method for detecting FRET in these cells. The general approaches described here can address numerous types of questions related to phototransduction and photoreceptor biology by providing a platform to visualize dynamic processes in molecular detail within a native context.

  4. Förster resonance energy transfer as a tool to study photoreceptor biology

    NASA Astrophysics Data System (ADS)

    Hovan, Stephanie C.; Howell, Scott; Park, Paul S.-H.

    2010-11-01

    Vision is initiated in photoreceptor cells of the retina by a set of biochemical events called phototransduction. These events occur via coordinated dynamic processes that include changes in secondary messenger concentrations, conformational changes and post-translational modifications of signaling proteins, and protein-protein interactions between signaling partners. A complete description of the orchestration of these dynamic processes is still unavailable. Described in this work is the first step in the development of tools combining fluorescent protein technology, Förster resonance energy transfer (FRET), and transgenic animals that have the potential to reveal important molecular insights about the dynamic processes occurring in photoreceptor cells. We characterize the fluorescent proteins SCFP3A and SYFP2 for use as a donor-acceptor pair in FRET assays, which will facilitate the visualization of dynamic processes in living cells. We also demonstrate the targeted expression of these fluorescent proteins to the rod photoreceptor cells of Xenopus laevis, and describe a general method for detecting FRET in these cells. The general approaches described here can address numerous types of questions related to phototransduction and photoreceptor biology by providing a platform to visualize dynamic processes in molecular detail within a native context.

  5. Temperature- and energy-dependent phase shifts of resonant multiple-beam X-ray diffraction in germanium crystals.

    PubMed

    Liao, Po-Yu; Liu, Wen-Chung; Cheng, Chih-Hao; Chiu, Yi-Hua; Kung, Ying-Yu; Chang, Shih-Lin

    2015-07-01

    This paper reports temperature- and energy-dependent phase shifts of resonant multiple-beam X-ray diffraction in germanium crystals, involving forbidden (002) and weak (222) reflections. Phase determination based on multiple-beam diffraction is employed to estimate phase shifts from (002)-based {(002)(375)(373̅)} four-beam cases and (222)-based { (222)(5̅33̅)} three-beam cases in the vicinity of the Ge K edge for temperatures from 20 K up to 300 K. The forbidden/weak reflections enhance the sensitivity of measuring phases at resonance. At room temperature, the resonance triplet phases reach a maximum of 8° for the four-beam cases and -19° for the three-beam cases. It is found that the peak intensities and triplet phases obtained from the (002) four-beam diffraction are related to thermal motion induced anisotropy and anomalous dispersion, while the (222) three-beam diffraction depends on the aspherical covalent electron distribution and anomalous dispersion. However, the electron-phonon interaction usually affects the forbidden reflections with increasing temperatures and seems to have less effect on the resonance triplet phase shifts measured from the (002) four-beam diffraction. The resonance triplet phase shifts of the (222) three-beam diffraction versus temperature are also small. PMID:26131901

  6. Magnetic resonance temperature imaging-based quantification of blood flow-related energy losses.

    PubMed

    Dillon, Christopher; Roemer, Robert; Payne, Allison

    2015-07-01

    This study presents a new approach for evaluating bioheat transfer equation (BHTE) models used in treatment planning, control and evaluation of all thermal therapies. First, 3D magnetic resonance temperature imaging (MRTI) data are used to quantify blood flow-related energy losses, including the effects of perfusion and convection. Second, this information is used to calculate parameters of a BHTE model: in this paper the widely used Pennes BHTE. As a self-consistency check, the BHTE parameters are utilized to predict the temperatures from which they were initially derived. The approach is evaluated with finite-difference simulations and implemented experimentally with focused ultrasound heating of an ex vivo porcine kidney perfused at 0, 20 and 40 ml/min (n = 4 each). The simulation results demonstrate accurate quantification of blood flow-related energy losses, except in regions of sharp blood flow discontinuities, where the transitions are spatially smoothed. The smoothed transitions propagate into estimates of the Pennes perfusion parameter but have limited effect on the accuracy of temperature predictions using these estimates. Longer acquisition time periods mitigate the effects of MRTI noise, but worsen the effect of flow discontinuities. For the no-flow kidney experiments the estimates of a uniform, constant Pennes perfusion parameter are approximately zero, and at 20 and 40 ml/min the average estimates increase with flow rate to 3.0 and 4.2 kg/m(3) /s, respectively. When Pennes perfusion parameter values are allowed to vary spatially, but remain temporally constant, BHTE temperature predictions are more accurate than when using spatially uniform, constant Pennes perfusion values, with reductions in RMSE values of up to 79%. Locations with large estimated perfusion values correspond to high flow regions of the kidney observed in T1 -weighted MR images. This novel, MRTI-based technique holds promise for improving understanding of thermal therapy biophysics

  7. Chemiluminescent detection of cell apoptosis enzyme by gold nanoparticle-based resonance energy transfer assay.

    PubMed

    Huang, Xiangyi; Liang, Yiran; Ruan, Lingao; Ren, Jicun

    2014-09-01

    We report a new chemiluminescence resonance energy transfer (CRET) technique, using gold nanoparticles (AuNPs) as efficient energy acceptor, for homogeneous measurement of cell apoptosis enzyme with high sensitivity. In the design of the CRET system, we chose the highly sensitive chemiluminescence (CL) reaction between luminol and hydrogen peroxide catalysed by horseradish peroxidase (HRP) because the CL spectrum of luminol (λ max 425 nm) partially overlaps the visible absorption bands of AuNPs. In this system, the peptide substrate (DEVD) of caspase 3 was linked to the AuNP surface by Au-S linkage. HRP was attached to the AuNP surface by means of a bridge formed by the streptavidin-biotin reaction. CRET occurred as a result of formation of AuNP-peptide-biotin-streptavidin-HRP complexes. The CL of luminol was significantly reduced, because of the quenching effect of AuNPs. The quenched CL was recovered after cleavage of DEVD by caspase 3, an enzyme involved in the apoptotic process. Experimental conditions were systematically investigated. Under the optimum conditions the increase of the CL signal was linearly dependent on caspase 3 concentration within the concentration range 25 pmol L(-1) to 800 pmol L(-1) and the detection limit of caspase 3 was as low as 20 pmol L(-1), one order of magnitude lower than for FRET sensors based on graphene oxides. Our method was successfully used to detect drug-induced apoptosis of cells. This approach is expected to be extended to other assays, i.e., using other enzymes, analytes, CL substances, and even other nanoparticles (e.g., quantum dots and graphene). PMID:24481623

  8. Quantification of Förster resonance energy transfer by monitoring sensitized emission in living plant cells

    PubMed Central

    Müller, Sara M.; Galliardt, Helena; Schneider, Jessica; Barisas, B. George; Seidel, Thorsten

    2013-01-01

    Förster resonance energy transfer (FRET) describes excitation energy exchange between two adjacent molecules typically in distances ranging from 2 to 10 nm. The process depends on dipole-dipole coupling of the molecules and its probability of occurrence cannot be proven directly. Mostly, fluorescence is employed for quantification as it represents a concurring process of relaxation of the excited singlet state S1 so that the probability of fluorescence decreases as the probability of FRET increases. This reflects closer proximity of the molecules or an orientation of donor and acceptor transition dipoles that facilitates FRET. Monitoring sensitized emission by 3-Filter-FRET allows for fast image acquisition and is suitable for quantifying FRET in dynamic systems such as living cells. In recent years, several calibration protocols were established to overcome to previous difficulties in measuring FRET-efficiencies. Thus, we can now obtain by 3-filter FRET FRET-efficiencies that are comparable to results from sophisticated fluorescence lifetime measurements. With the discovery of fluorescent proteins and their improvement toward spectral variants and usability in plant cells, the tool box for in vivo FRET-analyses in plant cells was provided and FRET became applicable for the in vivo detection of protein-protein interactions and for monitoring conformational dynamics. The latter opened the door toward a multitude of FRET-sensors such as the widely applied Ca2+-sensor Cameleon. Recently, FRET-couples of two fluorescent proteins were supplemented by additional fluorescent proteins toward FRET-cascades in order to monitor more complex arrangements. Novel FRET-couples involving switchable fluorescent proteins promise to increase the utility of FRET through combination with photoactivation-based super-resolution microscopy. PMID:24194740

  9. Tomographic imaging of flourescence resonance energy transfer in highly light scattering media

    NASA Astrophysics Data System (ADS)

    Soloviev, Vadim Y.; McGinty, James; Tahir, Khadija B.; Laine, Romain; Stuckey, Daniel W.; Mohan, P. Surya; Hajnal, Joseph V.; Sardini, Alessandro; French, Paul M. W.; Arridge, Simon R.

    2010-02-01

    Three-dimensional localization of protein conformation changes in turbid media using Förster Resonance Energy Transfer (FRET) was investigated by tomographic fluorescence lifetime imaging (FLIM). FRET occurs when a donor fluorophore, initially in its electronic excited state, transfers energy to an acceptor fluorophore in close proximity through non-radiative dipole-dipole coupling. An acceptor effectively behaves as a quencher of the donor's fluorescence. The quenching process is accompanied by a reduction in the quantum yield and lifetime of the donor fluorophore. Therefore, FRET can be localized by imaging changes in the quantum yield and the fluorescence lifetime of the donor fluorophore. Extending FRET to diffuse optical tomography has potentially important applications such as in vivo studies in small animal. We show that FRET can be localized by reconstructing the quantum yield and lifetime distribution from time-resolved non-invasive boundary measurements of fluorescence and transmitted excitation radiation. Image reconstruction was obtained by an inverse scattering algorithm. Thus we report, to the best of our knowledge, the first tomographic FLIM-FRET imaging in turbid media. The approach is demonstrated by imaging a highly scattering cylindrical phantom concealing two thin wells containing cytosol preparations of HEK293 cells expressing TN-L15, a cytosolic genetically-encoded calcium FRET sensor. A 10mM calcium chloride solution was added to one of the wells to induce a protein conformation change upon binding to TN-L15, resulting in FRET and a corresponding decrease in the donor fluorescence lifetime. The resulting fluorescence lifetime distribution, the quantum efficiency, absorption and scattering coefficients were reconstructed.

  10. General Bioluminescence Resonance Energy Transfer Homogeneous Immunoassay for Small Molecules Based on Quantum Dots.

    PubMed

    Yu, Xuezhi; Wen, Kai; Wang, Zhanhui; Zhang, Xiya; Li, Chenglong; Zhang, Suxia; Shen, Jianzhong

    2016-04-01

    Here, we describe a general bioluminescence resonance energy transfer (BRET) homogeneous immunoassay based on quantum dots (QDs) as the acceptor and Renilla luciferase (Rluc) as the donor (QD-BRET) for the determination of small molecules. The ratio of the donor-acceptor that could produce energy transfer varied in the presence of different concentrations of free enrofloxacin (ENR), an important small molecule in food safety. The calculated Förster distance (R0) was 7.86 nm. Under optimized conditions, the half-maximal inhibitory concentration (IC50) for ENR was less than 1 ng/mL and the linear range covered 4 orders of magnitude (0.023 to 25.60 ng/mL). The cross-reactivities (CRs) of seven representative fluoroquinolones (FQs) were similar to the data obtained by an enzyme-linked immunosorbent assay (ELISA). The average intra- and interassay recoveries from spiked milk of were 79.8-118.0%, and the relative standard deviations (RSDs) were less than 10%, meeting the requirement of residue detection, which was a satisfactory result. Furthermore, we compared the influence of different luciferase substrates on the performance of the assay. Considering sensitivity and stability, coelenterazine-h was the most appropriate substrate. The results from this study will enable better-informed decisions on the choice of Rluc substrate for QD-BRET systems. For the future, the QD-BRET immunosensor could easily be extended to other small molecules and thus represents a versatile strategy in food safety, the environment, clinical diagnosis, and other fields.

  11. Electro-mechanical energy conversion system having a permanent magnet machine with stator, resonant transfer link and energy converter controls

    DOEpatents

    Skeist, S. Merrill; Baker, Richard H.

    2006-01-10

    An electro-mechanical energy conversion system coupled between an energy source and an energy load comprising an energy converter device including a permanent magnet induction machine coupled between the energy source and the energy load to convert the energy from the energy source and to transfer the converted energy to the energy load and an energy transfer multiplexer to control the flow of power or energy through the permanent magnetic induction machine.

  12. Ion beam extraction from electron cyclotron resonance ion sources and the subsequent low energy beam transport

    NASA Astrophysics Data System (ADS)

    Winklehner, Daniel

    Electron Cyclotron Resonance Ion Sources (ECRIS) are capable of delivering high currents of Highly Charged Ions (HCIs) to heavy ion accelerators (e.g.: to the future FRIB). The use of a sextupole magnet for confinement of the plasma inside the source imposes a unique triangular structure on the beam. This, together with the multitude of ion species that are extracted at the same time and the high axial magnetic field at the plasma aperture, resulting from additional confining solenoids, make the simulation and design of ECRIS extraction systems particularly challenging. The first objective of this thesis was to refine and test a semi-empirical simulation model of the formation and extraction of HCIs from ECR ion sources as well as their transport through the subsequent Low Energy Beam Transport (LEBT) system. To this end, a set of utility functions was written to simplify performing the simulations. In the LEBT system, another interesting, yet so far unanswered, question arises: The influence of space-charge effects on the beam and the level of space-charge compensation in the ECRIS beam line. This interesting topic quickly became the second main objective of the thesis. A Retarding Field Analyzer (RFA) was built and systematic measurements of the neutralization level in ECRIS LEBT systems were done for the first time as part of this thesis (this intensity and pressure regime was previously not well explored). The measured neutralization levels for typical ECRIS beams were found to be between 0% and 50% and agreed reasonably well with a simple formula developed by Gabovich et al. for highly neutralized proton and H- beams after it was re-derived and extended in this thesis for low neutralization and multiple species. Preliminary tests of the refined and integrated simulation model for the ECR ion sources VENUS and SuSI and their respective low energy beam transport systems include comparisons of measured beam currents, cross sections and emittances with the

  13. Conjunction of standing wave and resonance in asymmetric nanowires: a mechanism for thermal rectification and remote energy accumulation.

    PubMed

    Liu, Yue-Yang; Zhou, Wu-Xing; Chen, Ke-Qiu

    2015-12-02

    As an important way to control and manage heat transport, thermal rectification has become an elementary issue in the field of phononics and plays a key role in the designing of thermal devices. Here we investigate systematically the standing wave and the accompanying resonance process in asymmetric nanowires to understand the standing wave itself and its great effect on thermal rectification. Results show that the standing wave is sensitive to both the structural and thermal properties of the material, and its great effect on enhancing the thermal rectification is realized not only by the energy-localization nature of the standing wave, but also by the resonance-caused large amplitude and high energy of the standing wave.

  14. Conjunction of standing wave and resonance in asymmetric nanowires: a mechanism for thermal rectification and remote energy accumulation

    PubMed Central

    Liu, Yue-Yang; Zhou, Wu-Xing; Chen, Ke-Qiu

    2015-01-01

    As an important way to control and manage heat transport, thermal rectification has become an elementary issue in the field of phononics and plays a key role in the designing of thermal devices. Here we investigate systematically the standing wave and the accompanying resonance process in asymmetric nanowires to understand the standing wave itself and its great effect on thermal rectification. Results show that the standing wave is sensitive to both the structural and thermal properties of the material, and its great effect on enhancing the thermal rectification is realized not only by the energy-localization nature of the standing wave, but also by the resonance-caused large amplitude and high energy of the standing wave. PMID:26628291

  15. A revised set of values of single-bond radii derived from the observed interatomic distances in metals by correction for bond number and resonance energy

    PubMed Central

    Pauling, Linus; Kamb, Barclay

    1986-01-01

    An earlier discussion [Pauling, L. (1947) J. Am. Chem. Soc. 69, 542] of observed bond lengths in elemental metals with correction for bond number and resonance energy led to a set of single-bond metallic radii with values usually somewhat less than the corresponding values obtained from molecules and complex ions. A theory of resonating covalent bonds has now been developed that permits calculation of the number of resonance structures per atom and of the effective resonance energy per bond. With this refined method of correcting the observed bond lengths for the effect of resonance energy, a new set of single-bond covalent radii, in better agreement with values from molecules and complex ions, has been constructed. PMID:16593698

  16. Localization of the hinge region of the Ca(2+)-ATPase of sarcoplasmic reticulum using resonance energy transfer.

    PubMed

    Baker, K J; East, J M; Lee, A G

    1994-06-01

    The Ca(2+)-ATPase of skeletal muscle sarcoplasmic reticulum can be labelled at Cys-670 and Cys-674 with 5-[[2-[(iodoacetyl) amino]ethyl]amino]naphthalene-1-sulphonic acid (IAEDANS). Resonance energy transfer has been used to measure the distance between Cys-670/Cys-674 and Glu-439 labelled with 5-(bromomethyl)fluorescein as 40 A. The height of Cys-670/Cys-674 above the phospholipid/water interface has been measured by resonance energy transfer between IAEDANS-labelled ATPase and fluorescein-labelled phosphatidylethanolamine as 54 A. This locates the hinge region of the ATPase close to the mouth of the pore observed in the cytoplasmic region of the ATPase in electron micrographs. No significant changes in these distances can be detected by resonance energy transfer on binding Ca2+ or vanadate. The height of the IAEDANS label above the phospholipid/water interface is the same for bilayers of dimyristoleoylphosphatidylcholine and dioleoylphosphatidylcholine. Conformation changes on the Ca(2+)-ATPase appear to be localised to small regions of the ATPase.

  17. Mode- and Direction-Dependent Mechanical Energy Dissipation in Single-Crystal Resonators due to Anharmonic Phonon-Phonon Scattering

    NASA Astrophysics Data System (ADS)

    Iyer, Srikanth S.; Candler, Robert N.

    2016-03-01

    In this work, we determine the intrinsic mechanical energy dissipation limit for single-crystal resonators due to anharmonic phonon-phonon scattering in the Akhiezer (Ω τ ≪1 ) regime. The energy loss is derived using perturbation theory and the linearized Boltzmann transport equation for phonons, and includes the direction- and polarization-dependent mode-Grüneisen parameters in order to capture the strain-induced anharmonicity among phonon branches. This expression reveals the fundamental differences among the internal friction limits for different types of bulk-mode elastic waves. For cubic crystals, 2D-extensional modes have increased dissipation compared to width-extensional modes because the biaxial deformation opposes the natural Poisson contraction of the solid. Additionally, we show that shear-mode vibrations, which preserve volume, have significantly reduced energy loss because dissipative phonon-phonon scattering is restricted to pure-shear phonon branches, indicating that Lamé- or wineglass-mode resonators will have the highest upper limit on mechanical efficiency. Finally, we employ key simplifications to evaluate the quality factor limits for common mode shapes in single-crystal silicon devices, explicitly including the correct effective elastic storage moduli for different vibration modes and crystal orientations. Our expression satisfies the pressing need for a reliable analytical model that can predict the phonon-phonon dissipation limits for modern resonant microelectromechanical systems, where precise manufacturing techniques and accurate finite-element methods can be used to select particular vibrational mode shapes and crystal orientations.

  18. Real-time detection of cellular death receptor-4 activation by fluorescence resonance energy transfer.

    PubMed

    Dereli-Korkut, Zeynep; Gandhok, Harmeet; Zeng, Ling Ge; Waqas, Sidra; Jiang, Xuejun; Wang, Sihong

    2013-05-01

    Targeted therapy involving the activation of death receptors DR4 and/or DR5 by its ligand, TRAIL, can selectively induce apoptosis in certain tumor cells. In order to profile the dynamic activation or trimerization of TRAIL-DR4 in live cells in real-time, the development of an apoptosis reporter cell line is essential. Fluorescence resonance energy transfer (FRET) technology via a FRET pair, cyan fluorescence protein (CFP) and yellow fluorescence protein (YFP), was used in this study. DR4-CFP and DR4-YFP were stably expressed in human lung cancer PC9 cells. Flow cytometer sorting and limited dilution coupled with fluorescence microscopy were used to select a monoclonal reporter cell line with high and compatible expression levels of DR4-CFP and DR4-YFP. FRET experiments were conducted and FRET efficiencies were monitored according to the Siegel's YFP photobleaching FRET protocol. Upon TRAIL induction a significant increase in FRET efficiencies from 5% to 9% demonstrated the ability of the DR4-CFP/YFP reporter cell line in monitoring the dynamic activation of TRAIL pathways. 3D reconstructed confocal images of DR4-CFP/YFP reporter cells exhibited a colocalized expression of DR4-CFP and DR4-YFP mainly on cell membranes. FRET results obtained during this study complements the use of epi-fluorescence microscopy for FRET analysis. The real-time FRET analysis allows the dynamic profiling of the activation of TRAIL pathways by using the time-lapse fluorescence microscopy. Therefore, DR4-CFP/YFP PC9 reporter cells along with FRET technology can be used as a tool for anti-cancer drug screening to identify compounds that are capable of activating TRAIL pathways.

  19. Coexisting conformations of fibronectin in cell culture imaged using fluorescence resonance energy transfer

    PubMed Central

    Baneyx, Gretchen; Baugh, Loren; Vogel, Viola

    2001-01-01

    Fluorescence resonance energy transfer (FRET) between fluorophores attached to single proteins provides a tool to study the conformation of proteins in solution and in cell culture. As a protein unfolds, nanometer-scale increases in distance between donor and acceptor fluorophores cause decreases in FRET. Here we demonstrate the application of FRET to imaging coexisting conformations of fibronectin (Fn) in cell culture. Fn is a flexible 440-kDa extracellular matrix protein, with functional sites that are regulated by unfolding events. Fn was labeled with multiple donor and acceptor fluorophores such that intramolecular FRET could be used to distinguish a range of Fn conformations. The sensitivity of FRET to unfolding was tested by progressively denaturing labeled Fn using guanidium chloride. To investigate Fn conformation changes during cell binding and matrix assembly, we added labeled Fn to the culture medium of NIH 3T3 fibroblasts. Coexisting conformations of Fn were visualized using fluorescence microscopy, and spectra from specific features were measured with an attached spectrometer. Using FRET as an indicator of Fn conformation, Fn diffusely bound to cells was in a compact state, whereas Fn in matrix fibrils was highly extended. Matrix fibrils exhibited a range of FRET that suggested some degree of unfolding of Fn's globular modules. Fn in cell-associated clusters that preceded fibril formation appeared more extended than diffuse cell-bound Fn but less extended than fibrillar Fn, suggesting that Fn undergoes extension after cell binding and before polymerization. FRET thus provides an approach to gain insight into the integrin-mediated pathway of Fn fibrillogenesis. PMID:11717404

  20. Fluorescence resonance energy transfer biosensor between upconverting nanoparticles and palladium nanoparticles for ultrasensitive CEA detection.

    PubMed

    Li, Hui; Shi, Liang; Sun, De-En; Li, Peiwu; Liu, Zhihong

    2016-12-15

    An ultrasensitive biosensor for carcinoembryonic antigen (CEA) was constructed based on fluorescence resonance energy transfer (FRET) between upconverting nanoparticles (UCPs) and palladium nanoparticles (PdNPs). PdNPs was synthesized by the addition of a solution of Na2PdCl4 into a mixture of N2H4·H2O as the reducing agent and 11-mercaptoundecanoic acid (MUDA) as the stabilizer. The CEA aptamer (5'-NH2-ATACCAGCTTATTCAATT-3') was conjugated to hexanedioic acid (HDA) modified UCPs (HDA-UCPs) through an EDC-NHS coupling protocol. The coordination interaction between nitrogen functional groups of the CEA aptamer and PdNPs brought UCPs and PdNPs in close proximity, which resulted in the fluorescence quenching of UCPs to an extent of 85%. And the non-specific fluorescence quenching caused by PdNPs towards HDA-UCPs was negligible. After the introduction of CEA into the UCPs-CEA aptamer-PdNPs fluorescence quenching system, the CEA aptamer preferentially combined with CEA accompanied by the conformational change which weakened the coordination interaction between the CEA aptamer and PdNPs. So fluorescence recovery of UCPs was observed and a linear relationship between the fluorescence recovery of UCPs and the concentration of CEA was obtained in the range from 2pg/mL to 100pg/mL in the aqueous buffer with the detection limit of 0.8pg/mL. The ultrasensitive detection of CEA was also realized in diluted human serum with a linear range from 4pg/mL to 100pg/mL and a detection limit of 1.7pg/mL. This biosensor makes the most of the high quenching ability of PdNPs towards UCPs with negligible non-specific fluorescence quenching and has broad application prospects in biochemistry. PMID:27476061

  1. Concatenation of cyan and yellow fluorescent proteins for efficient resonance energy transfer.

    PubMed

    Shimozono, Satoshi; Hosoi, Haruko; Mizuno, Hideaki; Fukano, Takashi; Tahara, Tahei; Miyawaki, Atsushi

    2006-05-23

    Highly efficient fluorescence resonance energy transfer between cyan(CFP) and yellow fluorescent proteins (YFP), the cyan- and yellow-emitting variants of the Aequorea green fluorescent protein, respectively, was achieved by tightly concatenating the two proteins. After the C-terminus of CFP and the N-terminus of YFP were truncated by 11 and 5 amino acids, respectively, the proteins were fused through a leucine-glutamate dipeptide. The resulting chimeric protein, which we called Cy11.5, exhibited a simple emission spectrum that peaked at 527 nm when the protein was excited at 436 nm. The time-resolved emission of Cy11.5 was measured using a streak camera. After excitation of Cy11.5 with a 400 nm ultrashort pulse, a fast decay of the CFP emission and a concomitant rise of the YFP emission were observed with a lifetime of 66 ps. By contrast, the emission from CFP alone showed a decay component with a lifetime of 2.9 ns. We concluded that in fully folded Cy11.5 molecules, intramolecular FRET occurred with an efficiency of 98%. Importantly, most Cy11.5 molecules were properly folded, and the protein was highly resistant to all of the tested proteases. In living cells, therefore, Cy11.5 behaved as a single fluorescent protein with a broad excitation spectrum. Moreover, Cy11.5 was used as an optical highlighter after photobleaching of YFP. When HeLa cells expressing Cy11.5 were irradiated at 514.5 nm, a 10-fold increase in the 475 nm fluorescence intensity was observed. These features make Cy11.5 useful as an optical highlighter and a new-colored fluorescent protein for multicolor imaging.

  2. Fluid-fluid membrane microheterogeneity: a fluorescence resonance energy transfer study.

    PubMed Central

    Loura, L M; Fedorov, A; Prieto, M

    2001-01-01

    Large unilamellar vesicles of dimyristoylphosphatidylcholine/cholesterol mixtures were studied using fluorescence techniques (steady-state fluorescence intensity and anisotropy, fluorescence lifetime, and fluorescence resonance energy transfer (FRET)). Three compositions (cholesterol mole fraction 0.15, 0.20, and 0.25) and two temperatures (30 and 40 degrees C) inside the coexistence range of liquid-ordered (l(o)) and liquid-disordered (l(d)) phases were investigated. Two common membrane probes, N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-dimyristoylphosphatidylethanolamine (NBD-DMPE) and N-(lissamine(TM)-rhodamine B)-dimyristoylphosphatidylethanolamine (Rh-DMPE), which form a FRET pair, were used. The l(o)/l(d) partition coefficients of the probes were determined by individual photophysical measurements and global analysis of time-resolved FRET decays. Although the acceptor, Rh-DMPE, prefers the l(d) phase, the opposite is observed for the donor, NBD-DMPE. Accordingly, FRET efficiency decreases as a consequence of phase separation. Comparing the independent measurements of partition coefficient, it was possible to detect very small domains (<20 nm) of l(o) in the cholesterol-poor end of the phase coexistence range. In contrast, domains of l(d) in the cholesterol-rich end of the coexistence range have comparatively large size. These observations are probably related to different processes of phase separation, nucleation being preferred in formation of l(o) phase from initially pure l(d), and domain growth being faster in formation of l(d) phase from initially pure l(o). PMID:11159445

  3. Mapping of adherens junction components using microscopic resonance energy transfer imaging.

    PubMed

    Kam, Z; Volberg, T; Geiger, B

    1995-03-01

    Quantitative microscopic imaging of resonance energy transfer (RET) was applied for immunological high resolution proximity mapping of several cytoskeletal components of cell adhesions. To conduct this analysis, a microscopic system was developed, consisting of a highly stable field illuminator, computer-controlled filter wheels for rapid multiple-color imaging and a sensitive, high resolution CCD camera, enabling quantitative data recording and processing. Using this system, we have investigated the spatial inter-relationships and organization of four adhesion-associated proteins, namely vinculin, talin, alpha-actinin and actin. Cultured chick lens cells were double labeled for each of the junctional molecules, using fluorescein- and rhodamine-conjugated antibodies or phalloidin. RET images were acquired with fluorescein excitation and rhodamine emission filter setting, corrected for fluorescein and rhodamine fluorescence, and normalized to the fluorescein image. The results pointed to high local densities of vinculin, talin and F-actin in focal adhesions, manifested by mean RET values of 15%, 12% and 10%, respectively. On the other hand, relatively low values (less than 1%) were observed following double immunofluorescence labeling of the same cells for alpha-actinin. Double indirect labeling for pairs of these four proteins (using fluorophore-conjugated antibodies or phalloidin) resulted in RET values of 5% or lower, except for the pair alpha-actinin and actin, which yielded significantly higher values (13-15%). These results suggest that despite their overlapping staining patterns, at the level of resolution of the light microscope, the plaque proteins vinculin and talin are not homogeneously interspersed at the molecular level but form segregated clusters. alpha-Actinin, on the other hand, does not appear to form such clusters but, rather, closely interacts with actin. We discuss here the conceptual and applicative aspects of RET measurements and the

  4. Fluorescent Resonance Energy Transfer: A Tool for Probing Molecular Cell-Biomaterial Interactions in Three Dimensions

    PubMed Central

    Huebsch, Nathaniel D.; Mooney, David J.

    2007-01-01

    The current paradigm in designing biomaterials is to optimize material chemical and physical parameters based on correlations between these parameters and downstream biological responses, whether in vitro or in vivo. Extensive developments in molecular design of biomaterials have facilitated identification of several biophysical and biochemical variables (e.g. adhesion peptide density, substrate elastic modulus) as being critical to cell response. However, these empirical observations do not indicate whether different parameters elicit cell responses by modulating redundant variables of the cell-material interface (e.g. number of cell-material bonds, cell-matrix mechanics). Recently, a molecular fluorescence technique, Fluorescence Resonance Energy Transfer (FRET) has been applied to quantitatively analyze parameters of the cell-material interface for both two and three-dimensional adhesion substrates. Tools based on FRET have been utilized to quantify several parameters of the cell-material interface relevant to cell response, including molecular changes in matrix proteins induced by interactions both with surfaces and cells, the number of bonds between integrins and their adhesion ligands, and changes in the crosslink density of hydrogel synthetic extracellular matrix analogs. As such techniques allow both dynamic and 3D analyses they will be useful to quantitatively relate downstream cellular responses (e.g. gene expression) to the composition of this interface. Such understanding will allow bioengineers to fully exploit the potential of biomaterials engineered on the molecular scale, by optimizing material chemical and physical properties to a measurable set of interfacial parameters known to elicit a predictable response in a specific cell population. This will facilitate the rational design of complex, multi-functional biomaterials used as model systems for studying diseases or for clinical applications. PMID:17270268

  5. Refolding of triosephosphate isomerase in low-water media investigated by fluorescence resonance energy transfer.

    PubMed

    Sepúlveda-Becerra, M A; Ferreira, S T; Strasser, R J; Garzón-Rodríguez, W; Beltrán, C; Gómez-Puyou, A; Darszon, A

    1996-12-10

    The refolding and reassociation of rabbit muscle triosephosphate isomerase (TPI) monomers unfolded with guanidine hydrochloride (GdnHCl) was studied in aqueous media and in reverse micelles (RM) formed with hexadecyltrimethylammonium bromide and n-octane/hexanol. Fluorescence resonance energy transfer (FRET) studies were carried out using TPI labeled at Cys-217 with 5-((2-((iodoacetyl)-amino)ethyl)amino)naphthalene-1-sulfonic acid (1,5-IAEDANS) and TPI labeled at one of the free amino groups with fluorescein 5'-isothiocyanate (FITC). Efficient FRET between monomers of AEDANS-TPI and FITC-TPI in aqueous media was detected 2-3 min after denaturant dilution and remained constant for hours. The distance between AEDANS and FITC in a labeled, renatured hetero-TPI dimer calculated from FRET results was 48 A, in reasonable agreement with estimates based on the crystal structure of TPI. In RM, recovery of enzyme activity during renaturation correlates with the appearance of a high-intrinsic fluorescence intermediate believed to be a partially folded monomer (Fernández-Velasco et al., 1995). Nevertheless, when AEDANS- and FITC-labeled monomers were mixed in RM, FRET occurred as soon as GdnHCl was diluted (FRET efficiency = 0.36), preceding the changes in TPI intrinsic fluorescence and reactivation. Thereafter, the efficiency of FRET increased during the next hour up to approximately 0.50, where it remained after 24 h, when 80% of the enzyme activity was recovered. The high initial FRET seen in RM could indicate the formation of an inactive dimer within the first minutes after denaturant dilution. The further increase in FRET observed over the next hour could reflect conformational rearrangements of the protein and transition from the inactive to the active dimer.

  6. Aggregation-induced emission: a simple strategy to improve chemiluminescence resonance energy transfer.

    PubMed

    Zhang, Lijuan; He, Nan; Lu, Chao

    2015-01-20

    The emergence of aggregation-induced emission (AIE) has opened up a new avenue for scientists. There is a great demand for the development of a new generation chemiluminescence resonance energy transfer (CRET) acceptors with AIE characteristics due to the aggregation-caused chemiluminescence (CL) quenching effect commonly observed in the conventional fluorophore CL acceptors at high concentrations. However, the systematical studies involving in AIE-amplified CL are still scarce. Herein, it is the first report that the gold nanocluster aggregates (a type of well-defined AIE molecules) are used to study their influence on the bis(2,4,6-trichlorophenyl) oxalate (TCPO)-H2O2 CL reaction. Interestingly, the AIE molecules in the diluted solution are unable to boost the CL signal of the TCPO-H2O2 system, but their aggregates display a strongly enhanced CL emission compared to their counterparts of fluorophore molecules, thanks to the unique AIE effect of gold nanoclusters. In comparison to rhodamine B with the aid of an imidazole catalyst, the detection limit of the gold nanocluster aggregate-amplified CL probe for H2O2 (S/N = 3) is low in the absence of any catalyst. Finally, the other two typical AIE molecules, Au(I)-thiolate complexes and 9,10-bis[4-(3-sulfonatopropoxyl)-styryl]anthracene (BSPSA), are investigated to verify the generality of the AIE molecule-amplified CL emissions. These results demonstrate effective access to highly fluorescent AIE molecules with practical applications in avoiding the aggregation-induced CL quenching at high concentrations, which can be expected to provide a novel and sensitive platform for the CL amplified detection.

  7. Low energy excitations in iridates studied with Resonant Inelastic X-ray Scattering

    NASA Astrophysics Data System (ADS)

    Liu, Xuerong

    2013-03-01

    In the iridium oxides, the strong spin-orbit coupling (SOC) of the 5d iridium electrons entangles the orbital and spin degrees of freedom, providing opportunities for exotic magnetic states with highly anisotropic exchange interactions. At the same time, the spatially extended 5d electrons are expected to have much stronger hybridization with the oxygen 2p orbitals, comparing with that in 3d transition element compounds. Both factors make crystal symmetry and local environment crucial in determining the electronic and magnetic properties of the iridates. We present here our resonant inelastic X-ray scattering (RIXS) studies of a number of octahedrally coordinated iridates with special structures, exploring these effects. In particular, for the 1-D spin 1/2 chain compound, Sr3CuIrO6, the wavefunction of the hole in the t2g manifold was reconstructed based on the RIXS spectra. Our results show that it is significantly modified from the isotropic shape expected for Jeff = 1 / 2 states in the strong SOC limit, due to the distortion of the oxygen octahedral cage. This distortion is comparable to, or smaller than, that present in most iridates and thus this work emphasizes the importance of local symmetry for the iridate families. Further, the magnetic excitations of this material were also measured. A large gap of ~30 meV, was found, comparable to the magnetic dispersion bandwidth. This is in contrast to the gapless dispersion expected for linear chain with isotropic Heisenberg exchange interaction. We also studied Na4Ir3O8 which has a hyperkagome lattice, and is a candidate quantum spin liquid. Here, a low energy continuum is observed below the d-d excitations. Optical conductivity measurements performed on the same sample and polarization dependence of the RIXS signal suggest that these excitations are magnetic in origin, agreeing with the spin-liquid state prediction. The work at Brookhaven was supported by the U.S. Department of Energy, Division of Materials Science

  8. FAST TRACK COMMUNICATION: Different patterns of high-energy and low-energy electrons in an atmospheric-pressure microplasma generated by a hairpin resonator

    NASA Astrophysics Data System (ADS)

    Tian, Wei; Zhu, Xi-Ming; Pu, Yi-Kang

    2010-02-01

    A newly developed device, a hairpin resonator, is used to generate an atmospheric-pressure microplasma with a 1.8 GHz power supply in argon. The two-dimensional distributions of emission lines in such a microplasma are obtained by a spatially resolved optical system. For the first time, it is found that the distributions of high-energy and low-energy electrons have different patterns. The density distribution of the high-energy electrons (with energy higher than that of argon 2p levels) is obtained from the line intensity, while the density of the low-energy ones (approximately equal to the total electron density) is deduced from the emission line ratios. The difference in distribution between the two groups of electrons is related to the different energy-loss characteristic lengths.

  9. Recent Advances in Nanoparticle-Based Förster Resonance Energy Transfer for Biosensing, Molecular Imaging and Drug Release Profiling

    PubMed Central

    Chen, Nai-Tzu; Cheng, Shih-Hsun; Liu, Ching-Ping; Souris, Jeffrey S.; Chen, Chen-Tu; Mou, Chung-Yuan; Lo, Leu-Wei

    2012-01-01

    Förster resonance energy transfer (FRET) may be regarded as a “smart” technology in the design of fluorescence probes for biological sensing and imaging. Recently, a variety of nanoparticles that include quantum dots, gold nanoparticles, polymer, mesoporous silica nanoparticles and upconversion nanoparticles have been employed to modulate FRET. Researchers have developed a number of “visible” and “activatable” FRET probes sensitive to specific changes in the biological environment that are especially attractive from the biomedical point of view. This article reviews recent progress in bringing these nanoparticle-modulated energy transfer schemes to fruition for applications in biosensing, molecular imaging and drug delivery. PMID:23443121

  10. Inorganic-Organic Hybrid Luminescent Binary Probe for DNA Detection Based on Spin-Forbidden Resonance Energy Transfer

    PubMed Central

    Marti, Angel A.; Puckett, Cindy A.; Dyer, Joanne; Stevens, Nathan; Jockusch, Steffen; Ju, Jingyue; Barton, Jacqueline K.; Turro, Nicholas J.

    2009-01-01

    We describe the design of new fluorescent binary probe sensors for DNA detection based on spin-forbidden resonance energy transfer (SF-RET). Binary probes consist of a donor and acceptor fluorophores that are attached to two different oligonucleotides and serve as resonance energy transfer (RET) donor-acceptor pair when hybridized to adjacent sites of a target sequence. In the absence of target, excitation of the donor results in fluorescence only from the donor, but when the probes hybridize to target, the fluorophores are brought into close proximity favoring RET, yielding fluorescence mainly from the acceptor fluorophore. These new binary probes use the metal complex Ru(bpy′)(DIP)22+ as the energy donor and an organic fluorophore (Cy5) as the energy acceptor. Energy transfer from the MLCT state of the Ru complex to singlet Cy5 is spin forbidden and produces a delayed fluorescence of Cy5. This paper demonstrate that fluorescence delay of Cy5 can be used to time resolve the emission of the probe from the intense fluorescence background of a model system for cellular background; this provides the reported system to overcome intense autofluorescence, an important and general advantage over “classical” spin-allowed steady-state probes. PMID:17592843

  11. Resonant energy transfer between patterned InGaN/GaN quantum wells and CdSe/ZnS quantum dots.

    PubMed

    Xu, Xingsheng; Wang, Huayong

    2016-01-01

    We explore an easy method for preparation of a hybrid device of a photonic crystal InGaN/GaN quantum well (QW) and colloidal quantum dots using conventional photolithography. It is demonstrated from electroluminescence spectra that Förster resonance energy transfer takes place efficiently between the photonic crystal InGaN/GaN QW and CdSe/ZnS colloidal quantum dots. From the photoluminescence decay of the InGaN/GaN QW, the largest Förster resonance energy transfer efficiency between the photonic crystal GaN quantum well and colloidal quantum dots is measured as 88% and the corresponding Förster-resonance-energy-transfer fraction reached 42%. An easy approach is explored to realize a highly efficient electrically driven colloidal quantum dot device using the Förster-resonance-energy-transfer mechanism.

  12. A Finite Element Model Of Self-Resonating Bimorph Microcantilever For Fast Temperature Cycling In A Pyroelectric Energy Harvester

    SciTech Connect

    Mostafa, Salwa; Lavrik, Nickolay V; Bannuru, Thirumalesh; Rajic, Slobodan; Islam, Syed K; Datskos, Panos G; Hunter, Scott Robert

    2011-01-01

    A self resonating bimorph cantilever structure for fast temperature cycling in a pyroelectric energy harvester has been modeled using a finite element method. The effect of constituting material properties and system parameters on the frequency and magnitude of temperature cycling and the efficiency of energy recycling using the proposed structure has been investigated. Results show that thermal contact conductance and heat source temperature play a key role in dominating the cycling frequency and efficiency of energy recycling. An optimal solution for the most efficient energy scavenging process has been sought by studying the performance trend with different variable parameters such as thermal contact conductance, heat source temperature, device aspect ratio and constituent materials of varying thermal conductivity and expansion coefficients.

  13. New odd-parity high-lying energy levels of the europium atom by resonance ionization spectroscopy

    NASA Astrophysics Data System (ADS)

    Nakhate, S. G.; Razvi, M. A. N.; Bhale, G. L.; Ahmad, S. A.

    1996-04-01

    Odd-parity energy levels of the neutral europium atom (Eu I) have been investigated by employing both single-colour and two-colour stepwise laser excitation using the technique of resonance ionization spectroscopy in a heat-pipe thermionic diode system. Fifty-two new odd-parity energy levels of Eu I have been found in the energy region 40 575 - 43 410 0953-4075/29/8/009/img1. The J values for most of these new energy levels have been assigned unambiguously. In addition to this, 19 odd levels which were reported earlier, in the region of our present study, have also been investigated; the assignments of J values to nine of these levels have been confirmed and four levels, which had no unique J assignments, have been assigned definite J values.

  14. ELECTROSPRAY IONIZATION (ESI) FRAGMENTATIONS AND DIMETHYLDIOXIRANE REACTIVITIES OF THREE DIVERSE LACTAMS HAVING FULL, HALF, AND ZERO RESONANCE ENERGIES

    PubMed Central

    Morgan, Kathleen M.; Ashline, David J.; Morgan, Jessica P.; Greenberg, Arthur

    2014-01-01

    Three lactams having respectively ~20 kcal/mol, ~10 kcal/mol, and 0 kcal/mol of resonance energy have been subjected to electrospray ionization mass spectrometry (ESI/MS) as well as to attempted reaction with dimethyldioxirane (DMDO). The ESI/MS for all three lactams are consistent with fragmentation from the N-protonated, rather than the O-protonated tautomer. Each exhibits a unique fragmentation pathway. DFT calculations are employed to provide insights concerning these pathways. N-Ethyl-2-pyrrolidinone and 1-azabicyclo[3.3.1]nonan-2-one, the full- and half-resonance lactams, are unreactive with DMDO. The “Kirby lactam” (3,5,7-trimethyl-1-azaadamantan-2-one), has zero resonance energy and reacts rapidly with DMDO to generate a mixture of reaction products. The structure assigned to one of these is the 2,2-dihydroxy-N-oxide, thought to be stabilized by intramolecular hydrogen bonding and buttressing by the methyl substituents. A reasonable pathway to this derivative might involve formation of an extremely labile N-oxide, in a purely formal sense an example of the hithertounknown amide N-oxides, followed by hydration with traces of moisture. PMID:24313276

  15. On the possibility of ephedrine detection: time-resolved fluorescence resonance energy transfer (FRET)-based approach.

    PubMed

    Varriale, Antonio; Marzullo, Vincenzo Manuel; Di Giovanni, Stefano; Scala, Andrea; Capo, Alessandro; Majoli, Adelia; Pennacchio, Angela; Staiano, Maria; D'Auria, Sabato

    2016-09-01

    Ephedrine is one of the main precursor compounds used in the illegal production of amphetamines and related drugs. Actually, conventional analytical methods such as high-performance liquid chromatography (HPLC), capillary electrophoresis (CE), and gas chromatography-mass spectrometry (GC-MS) are used for the detection of ephedrine; sadly, these methods require qualified personnel and are time-consuming and expensive. In order to overcome these problems, in recent years, different methods have been developed based on the surface plasmon resonance (SPR) and electrochemical method. In this work, we present a simple, rapid, and effective method to detect the presence of ephedrine in solution, based on competitive fluorescence resonance energy transfer (FRET) assay. The antibody anti-ephedrine and ephedrine derivative were produced and labeled respectively, with two different fluorescent probes (donor and acceptor). The change in FRET signal intensity between donor and acceptor ephedrine compounds gives the possibility of detecting ephedrine traces of at least 0.81 ± 0.04 ppm (LOD). Graphical abstract A new Time-resolved Fluorescence Resonance Energy Transfer (FRET) assay for ephedrine detection. PMID:27395357

  16. Exciton Recombination, Energy-, and Charge Transfer in Single- and Multilayer Quantum-Dot Films on Silver Plasmonic Resonators

    PubMed Central

    Shin, Taeho; Cho, Kyung-Sang; Yun, Dong-Jin; Kim, Jinwoo; Li, Xiang-Shu; Moon, Eui-Seong; Baik, Chan-Wook; Il Kim, Sun; Kim, Miyoung; Choi, Jun Hee; Park, Gyeong-Su; Shin, Jai-Kwang; Hwang, Sungwoo; Jung, Tae-Sung

    2016-01-01

    We examine exciton recombination, energy-, and charge transfer in multilayer CdS/ZnS quantum dots (QDs) on silver plasmonic resonators using photoluminescence (PL) and excitation spectroscopy along with kinetic modeling and simulations. The exciton dynamics including all the processes are strongly affected by the separation distance between QDs and silver resonators, excitation wavelength, and QD film thickness. For a direct contact or very small distance, interfacial charge transfer and tunneling dominate over intrinsic radiative recombination and exciton energy transfer to surface plasmons (SPs), resulting in PL suppression. With increasing distance, however, tunneling diminishes dramatically, while long-range exciton-SP coupling takes place much faster (>6.5 ns) than intrinsic recombination (~200 ns) causing considerable PL enhancement. The exciton-SP coupling strength shows a strong dependence on excitation wavelengths, suggesting the state-specific dynamics of excitons and the down-conversion of surface plasmons involved. The overlayers as well as the bottom monolayer of QD multilayers exhibit significant PL enhancement mainly through long-range exciton-SP coupling. The overall emission behaviors from single- and multilayer QD films on silver resonators are described quantitatively by a photophysical kinetic model and simulations. The present experimental and simulation results provide important and useful design rules for QD-based light harvesting applications using the exciton-surface plasmon coupling. PMID:27184469

  17. Analytical continuation in coupling constant method; application to the calculation of resonance energies and widths for organic molecules: Glycine, alanine and valine and dimer of formic acid

    NASA Astrophysics Data System (ADS)

    Papp, P.; Matejčík, Š.; Mach, P.; Urban, J.; Paidarová, I.; Horáček, J.

    2013-06-01

    The method of analytic continuation in the coupling constant (ACCC) in combination with use of the statistical Padé approximation is applied to the determination of resonance energy and width of some amino acids and formic acid dimer. Standard quantum chemistry codes provide accurate data which can be used for analytic continuation in the coupling constant to obtain the resonance energy and width of organic molecules with a good accuracy. The obtained results are compared with the existing experimental ones.

  18. Characterization and inhibition of norovirus proteases of genogroups I and II using a fluorescence resonance energy transfer assay

    SciTech Connect

    Chang, Kyeong-Ok; Takahashi, Daisuke; Prakash, Om; Kim, Yunjeong

    2012-02-20

    Noroviruses are the major cause of food- or water-borne gastroenteritis outbreaks in humans. The norovirus protease that cleaves a large viral polyprotein to nonstructural proteins is essential for virus replication and an attractive target for antiviral drug development. Noroviruses show high genetic diversity with at least five genogroups, GI-GV, of which GI and GII are responsible for the majority of norovirus infections in humans. We cloned and expressed proteases of Norwalk virus (GI) and MD145 virus (GII) and characterized the enzymatic activities with fluorescence resonance energy transfer substrates. We demonstrated that the GI and GII proteases cleaved the substrates derived from the naturally occurring cleavage site in the open reading frame (ORF) 1 of G1 norovirus with similar efficiency, and that enzymatic activity of both proteases was inhibited by commercial protease inhibitors including chymostatin. The interaction of chymostatin to Norwalk virus protease was validated by nuclear magnetic resonance (NMR) spectroscopy.

  19. On the role of electron energy distribution function in double frequency heating of electron cyclotron resonance ion source plasmas

    SciTech Connect

    Schachter, L. Dobrescu, S.; Stiebing, K. E.

    2014-02-15

    Double frequency heating (DFH) is a tool to improve the output of highly charged ions particularly from modern electron cyclotron resonance ion source installations with very high RF-frequencies. In order to gain information on the DFH-mechanism and on the role of the lower injected frequency we have carried out a series of dedicated experiments where we have put emphasis on the creation of a discrete resonance surface also for this lower frequency. Our well-established method of inserting an emissive MD (metal-dielectric) liner into the plasma chamber of the source is used in these experiments as a tool of investigation. In this way, the electron temperature and density for both ECR zones is increased in a controlled manner, allowing conclusions on the role of the change of the electron-energy-distribution function with and without DFH.

  20. Energy correlations of photon pairs generated by a silicon microring resonator probed by Stimulated Four Wave Mixing

    PubMed Central

    Grassani, Davide; Simbula, Angelica; Pirotta, Stefano; Galli, Matteo; Menotti, Matteo; Harris, Nicholas C.; Baehr-Jones, Tom; Hochberg, Michael; Galland, Christophe; Liscidini, Marco; Bajoni, Daniele

    2016-01-01

    Compact silicon integrated devices, such as micro-ring resonators, have recently been demonstrated as efficient sources of quantum correlated photon pairs. The mass production of integrated devices demands the implementation of fast and reliable techniques to monitor the device performances. In the case of time-energy correlations, this is particularly challenging, as it requires high spectral resolution that is not currently achievable in coincidence measurements. Here we reconstruct the joint spectral density of photons pairs generated by spontaneous four-wave mixing in a silicon ring resonator by studying the corresponding stimulated process, namely stimulated four wave mixing. We show that this approach, featuring high spectral resolution and short measurement times, allows one to discriminate between nearly-uncorrelated and highly-correlated photon pairs. PMID:27032688

  1. Energy correlations of photon pairs generated by a silicon microring resonator probed by Stimulated Four Wave Mixing.

    PubMed

    Grassani, Davide; Simbula, Angelica; Pirotta, Stefano; Galli, Matteo; Menotti, Matteo; Harris, Nicholas C; Baehr-Jones, Tom; Hochberg, Michael; Galland, Christophe; Liscidini, Marco; Bajoni, Daniele

    2016-01-01

    Compact silicon integrated devices, such as micro-ring resonators, have recently been demonstrated as efficient sources of quantum correlated photon pairs. The mass production of integrated devices demands the implementation of fast and reliable techniques to monitor the device performances. In the case of time-energy correlations, this is particularly challenging, as it requires high spectral resolution that is not currently achievable in coincidence measurements. Here we reconstruct the joint spectral density of photons pairs generated by spontaneous four-wave mixing in a silicon ring resonator by studying the corresponding stimulated process, namely stimulated four wave mixing. We show that this approach, featuring high spectral resolution and short measurement times, allows one to discriminate between nearly-uncorrelated and highly-correlated photon pairs. PMID:27032688

  2. Energy correlations of photon pairs generated by a silicon microring resonator probed by Stimulated Four Wave Mixing

    NASA Astrophysics Data System (ADS)

    Grassani, Davide; Simbula, Angelica; Pirotta, Stefano; Galli, Matteo; Menotti, Matteo; Harris, Nicholas C.; Baehr-Jones, Tom; Hochberg, Michael; Galland, Christophe; Liscidini, Marco; Bajoni, Daniele

    2016-04-01

    Compact silicon integrated devices, such as micro-ring resonators, have recently been demonstrated as efficient sources of quantum correlated photon pairs. The mass production of integrated devices demands the implementation of fast and reliable techniques to monitor the device performances. In the case of time-energy correlations, this is particularly challenging, as it requires high spectral resolution that is not currently achievable in coincidence measurements. Here we reconstruct the joint spectral density of photons pairs generated by spontaneous four-wave mixing in a silicon ring resonator by studying the corresponding stimulated process, namely stimulated four wave mixing. We show that this approach, featuring high spectral resolution and short measurement times, allows one to discriminate between nearly-uncorrelated and highly-correlated photon pairs.

  3. On the role of electron energy distribution function in double frequency heating of electron cyclotron resonance ion source plasmas.

    PubMed

    Schachter, L; Stiebing, K E; Dobrescu, S

    2014-02-01

    Double frequency heating (DFH) is a tool to improve the output of highly charged ions particularly from modern electron cyclotron resonance ion source installations with very high RF-frequencies. In order to gain information on the DFH-mechanism and on the role of the lower injected frequency we have carried out a series of dedicated experiments where we have put emphasis on the creation of a discrete resonance surface also for this lower frequency. Our well-established method of inserting an emissive MD (metal-dielectric) liner into the plasma chamber of the source is used in these experiments as a tool of investigation. In this way, the electron temperature and density for both ECR zones is increased in a controlled manner, allowing conclusions on the role of the change of the electron-energy-distribution function with and without DFH.

  4. Förster resonance energy transfer structural kinetic studies of cardiac thin filament deactivation.

    PubMed

    Xing, Jun; Jayasundar, Jayant J; Ouyang, Yexin; Dong, Wen-Ji

    2009-06-12

    Cardiac thin filament deactivation is initiated by Ca2+ dissociation from troponin C (cTnC), followed by multiple structural changes of thin filament proteins. These structural transitions are the molecular basis underlying the thin filament regulation of cardiac relaxation, but the detailed mechanism remains elusive. In this study Förster resonance energy transfer (FRET) was used to investigate the dynamics and kinetics of the Ca2+-induced conformational changes of the cardiac thin filaments, specifically the closing of the cTnC N-domain, the cTnC-cTnI (troponin I) interaction, and the cTnI-actin interaction. The cTnC N-domain conformational change was examined by monitoring FRET between a donor (AEDANS) attached to one cysteine residue and an acceptor (DDPM) attached the other cysteine of the mutant cTnC(L13C/N51C). The cTnC-cTnI interaction was investigated by monitoring the distance changes from residue 89 of cTnC to residues 151 and 167 of cTnI, respectively. The cTnI-actin interaction was investigated by monitoring the distance changes from residues 151 and 167 of cTnI to residue 374 of actin. FRET Ca2+ titrations and stopped-flow kinetic measurements show that different thin filament structural transitions have different Ca2+ sensitivities and Ca2+ dissociation-induced kinetics. The observed structural transitions involving the regulatory region and the mobile domain of cTnI occurred at fast kinetic rates, whereas the kinetics of the structural transitions involving the cTnI inhibitory region was slow. Our results suggest that the thin filament deactivation upon Ca2+ dissociation is a two-step process. One step involves rapid binding of the mobile domain of cTnI to actin, which is kinetically coupled with the conformational change of the N-domain of cTnC and the dissociation of the regulatory region of cTnI from cTnC. The other step involves switching the inhibitory region of cTnI from interacting with cTnC to interacting with actin. The latter processes

  5. Förster Resonance Energy Transfer Structural Kinetic Studies of Cardiac Thin Filament Deactivation*

    PubMed Central

    Xing, Jun; Jayasundar, Jayant J.; Ouyang, Yexin; Dong, Wen-Ji

    2009-01-01

    Cardiac thin filament deactivation is initiated by Ca2+ dissociation from troponin C (cTnC), followed by multiple structural changes of thin filament proteins. These structural transitions are the molecular basis underlying the thin filament regulation of cardiac relaxation, but the detailed mechanism remains elusive. In this study Förster resonance energy transfer (FRET) was used to investigate the dynamics and kinetics of the Ca2+-induced conformational changes of the cardiac thin filaments, specifically the closing of the cTnC N-domain, the cTnC-cTnI (troponin I) interaction, and the cTnI-actin interaction. The cTnC N-domain conformational change was examined by monitoring FRET between a donor (AEDANS) attached to one cysteine residue and an acceptor (DDPM) attached the other cysteine of the mutant cTnC(L13C/N51C). The cTnC-cTnI interaction was investigated by monitoring the distance changes from residue 89 of cTnC to residues 151 and 167 of cTnI, respectively. The cTnI-actin interaction was investigated by monitoring the distance changes from residues 151 and 167 of cTnI to residue 374 of actin. FRET Ca2+ titrations and stopped-flow kinetic measurements show that different thin filament structural transitions have different Ca2+ sensitivities and Ca2+ dissociation-induced kinetics. The observed structural transitions involving the regulatory region and the mobile domain of cTnI occurred at fast kinetic rates, whereas the kinetics of the structural transitions involving the cTnI inhibitory region was slow. Our results suggest that the thin filament deactivation upon Ca2+ dissociation is a two-step process. One step involves rapid binding of the mobile domain of cTnI to actin, which is kinetically coupled with the conformational change of the N-domain of cTnC and the dissociation of the regulatory region of cTnI from cTnC. The other step involves switching the inhibitory region of cTnI from interacting with cTnC to interacting with actin. The latter processes

  6. Lanthanide-containing polycations for monitoring polyplex dynamics via lanthanide resonance energy transfer.

    PubMed

    Kelkar, Sneha S; Xue, Lian; Turner, S Richard; Reineke, Theresa M

    2014-05-12

    Theranostic nanomaterials have emerged in the past decade that combine therapeutic delivery and diagnostic imaging into one package. Such materials offer the opportunity to aid diagnosis, track therapeutic biodistribution, and monitor drug release. We have developed a series of nucleic acid delivery polymers containing oligoethylene amines that are able to be protonated at physiological pH (for binding/compacting pDNA) and a lanthanide-chelating domain, which imparts diagnostic functionality. Diamine monomers (containing between 3 and 6 Boc-protected ethyleneamines) were prepared via a multistep procedure involving the selective protection and deprotection of primary and secondary amines. The polymer structures were then synthesized by step-growth polymerization of the oligoethylene diamines with a bisanhydride of diethylenetriamine pentaacetic acid (DTPA-BA), yielding degrees of polymerization between 18 and 24. Chelation of the polymers with gadolinium and terbium was performed to offer MRI contrast agent and luminescence properties, respectively. All of the polymer chelates were found to house approximately one water coordination site, as calculated by the Horrock's equation and possess longitudinal relaxivities (r1, on a per Gd basis) at least twice that of Magnevist, a clinical contrast agent. All the structures formed polyplexes with pDNA with highly positive zeta potentials and hydrodynamic diameters around 50-80 nm. Lanthanide resonance energy transfer (LRET) was used to monitor polyplex association and dissociation. Polyplexes were formed using the donor-acceptor pair comprising of terbium-chelated polymer with five ethyleneamines within the repeat unit (6c-Tb) and tetramethyl rhodamine (TMR)-labeled pDNA. Association/dissociation in the presence of heparin and NaCl was monitored. The effect of amine number along the polymer backbone on transfection efficiency and cytotoxicity was also investigated. None of the polymers revealed cytotoxic effects with

  7. Reexamination of the Energy Levels of 15F by 14O + 1H ElasticResonance Scattering with BEARS

    SciTech Connect

    Guo, F.Q.; Powell, J.; Lee, D.W.; Leitner, D.; McMahan, M.A.; Moltz, D.M.; O'Neil, J.P.; Perajarvi, K.; Phair, L.; Ramsey, C.A.; Xu,X.J.; Cerny, Joseph

    2005-05-30

    The energy levels of 15F have been measured by the p(14O,p)14O reaction. The 120 MeV 14O radioactive ion beam was produced by the BEARS coupled cyclotron system at an intensity averaging 1x104 particles/second on target. Energy calibration was obtained using resonances from the p(14N,p)14N reaction. The two lowest resonances in 15F were fitted with an R-matrix calculation. The fit to the ground state had Jp = 1/2+ at 1.23+-0.05 MeV (width 0.5-0.84 MeV), and the first excited state was Jp=5/2+ at 2.81+-0.02 MeV (width 0.30+-0.06 MeV), both relative to the mass-energy of the proton and 14O. The 15F ground state energy supports the disappearance of the Z=8 proton magic number for odd Z, Tz=-3/2 nuclei.

  8. Resonance energy-transfer studies of the conformational change on the adsorption of oligonucleotides to a silica interface.

    PubMed

    Scholes, Colin A; Millar, David P; Gee, Michelle L; Smith, Trevor A

    2011-05-19

    Time-resolved evanescent wave-induced fluorescence studies have been carried out on a series of fluorescently labeled oligonucleotide sequences adsorbed to a silica surface from solution. The fluorescence decay profiles of a fluorescent energy donor group undergoing resonance energy transfer to a nonemissive energy-acceptor molecule have been analyzed in terms of a distribution of donor-acceptor distances to reveal the conformational changes that occur in these oligonucleotides upon adsorption. Evanescent wave-induced time-resolved Förster resonance energy-transfer (EW-TRFRET) measurements indicate that at a high electrolyte concentration, there is localized separation of the oligonucleotide strands, and the helical structure adopts an "unraveled" conformation as a result of adsorption. This is attributed to the flexibility within the oligonucleotide at high electrolyte concentration allowing multiple segments of the oligonucleotide to have direct surface interaction. In contrast, the EW-TRFRET measurements at a lower electrolyte concentration reveal that the oligonucleotide retains its helical conformation in a localized extended state. This behavior implies that the rigidity of the oligonucleotide at this electrolyte concentration restricts direct interaction with the silica to a few segments, which correspondingly introduces kinks in the double helix conformation and results in significant oligonucleotide segmental extension into solution.

  9. The inhibition of fluorescence resonance energy transfer between multicolor quantum dots for rapid and sensitive detection of Staphylococcus aureus

    NASA Astrophysics Data System (ADS)

    Wang, Beibei; Wang, Qi; Ma, Meihu; Cai, Zhaoxia

    2015-01-01

    In this paper, we constructed the fluorescence resonance energy transfer (FRET) system between two multi-color quantum dots (QDs) of two sizes for rapid and sensitive detection of Staphylococcus aureus. In this system, green-emitting QDs conjugated with rabbit anti-S. aureus antibodies were used as energy donors while orange-emitting QDs conjugated with goat-anti-rabbit IgG were used as energy acceptors to form FRET system. Pre-binding of Staphylococcus aureus (S. aureus) on the donor occupied the binding sites and thus blocked resonance energy transfer between two colors QDs, leading to the quenching fluorescence of the acceptor. The fluorescence of acceptor has a linear calibration graph with the concentrations of S. aureus from 52 to 2.6 × 105 CFU mL-1. The low detection limit was 10 CFU/mL. It was worth mentioning that the detection method of S. aureus had been applied to the analysis of apple juice and milk samples, which could potentially be developed into a sensor in the further study.

  10. Depolarization after resonance energy transfer (DARET): a sensitive fluorescence-based assay for botulinum neurotoxin protease activity.

    PubMed

    Gilmore, Marcella A; Williams, Dudley; Okawa, Yumiko; Holguin, Bret; James, Nicholas G; Ross, Justin A; Roger Aoki, K; Jameson, David M; Steward, Lance E

    2011-06-01

    The DARET (depolarization after resonance energy transfer) assay is a coupled Förster resonance energy transfer (FRET)-fluorescence polarization assay for botulinum neurotoxin type A or E (BoNT/A or BoNT/E) proteolytic activity that relies on a fully recombinant substrate. The substrate consists of blue fluorescent protein (BFP) and green fluorescent protein (GFP) flanking SNAP-25 (synaptosome-associated protein of 25 kDa) residues 134-206. In this assay, the substrate is excited with polarized light at 387 nm, which primarily excites the BFP, whereas emission from the GFP is monitored at 509 nm. Energy transfer from the BFP to the GFP in the intact substrate results in a substantial depolarization of the GFP emission. The energy transfer is eliminated when the fluorescent domains separate on cleavage by the endopeptidase, and emission from the directly excited GFP product fragment is then highly polarized, resulting in an overall increase in polarization. This increase in polarization can be monitored to assay the proteolytic activity of BoNT/A and BoNT/E in real time. It allows determination of the turnover rate of the substrate and the kinetic constants (V(max) and k(cat)) based on the concentration of cleaved substrate determined directly from the measurements using the additivity properties of polarization. The assay is amenable to high-throughput applications.

  11. Repetitive resonant railgun power supply

    DOEpatents

    Honig, E.M.; Nunnally, W.C.

    1985-06-19

    A repetitive resonant railgun power supply provides energy for repetitively propelling projectiles from a pair of parallel rails. The supply comprises an energy storage capacitor, a storage inductor to form a resonant circuit with the energy storage capacitor and a magnetic switch to transfer energy between the resonant circuit and the pair of parallel rails for the propelling of projectiles.

  12. Repetitive resonant railgun power supply

    DOEpatents

    Honig, Emanuel M.; Nunnally, William C.

    1988-01-01

    A repetitive resonant railgun power supply provides energy for repetitively propelling projectiles from a pair of parallel rails. The supply comprises an energy storage capacitor, a storage inductor to form a resonant circuit with the energy storage capacitor and a magnetic switch to transfer energy between the resonant circuit and the pair of parallel rails for the propelling of projectiles.

  13. Direct measurement of several resonance strengths and energies in 34S(α , γ) 38 Ar within the T = 2 . 2 GK Gamow window with DRAGON

    NASA Astrophysics Data System (ADS)

    Connolly, D.; O'Malley, P.; Akers, C.; Chen, A. A.; Christian, G.; Davids, B.; Erikson, L. E.; Fallis, J.; Fulton, B. R.; Greife, U.; Hager, Ulrike; Hutcheon, D. A.; Ilyushkin, S.; Laird, A. M.; Mahl, A.; Ruiz, C.

    2015-10-01

    Radiative α capture on 34S can impact nucleosynthesis in several astrophysical environments, including oxygen burning, explosive oxygen burning (Type II supernovae), and Type Ia supernovae. However, there exist discrepancies in the literature for the resonance strengths of two strong resonances within the Gamow window for oxygen burning temperatures (E0 +/- Δ / 2 = 3183 +/- 897 keV at T = 2 . 2 GK). Previous measurements suffered from systematic uncertainties inherent in the experimental technique. Furthermore, there are several states in 38Ar in the energy range of interest for which no 34S + α resonance strength/energy measurements have been performed. This measurement was performed in inverse kinematics at the DRAGON recoil separator at TRIUMF in BC, Canada. DRAGON's experimental technique allows direct measurement of quantities such as stopping power and resonance energy, alleviating the need for external inputs and reducing uncertainty. This talk will discuss DRAGON's experimental technique, analysis methods and results.

  14. New generation polyphase resonant converter-modulators for the Korean atomic energy research institute

    SciTech Connect

    Reass, William A; Baca, David M; Gribble, Robert F

    2009-01-01

    This paper will present operational data and performance parameters of the newest generation polyphase resonant high voltage converter modulator (HVCM) as developed and delivered to the KAERI 100 MeV ''PEFP'' accelerator [1]. The KAERI design realizes improvements from the SNS and SLAC designs [2]. To improve the IGBT switching performance at 20 kHz for the KAERI system, the HVCM utilizes the typical zero-voltage-switching (ZVS) at turn on and as well as artificial zero-current-switching (ZCS) at turn-off. The new technique of artificial ZCS technique should result in a 6 fold reduction of IGBT switching losses (3). This improves the HCVM conversion efficiency to better than 95% at full average power, which is 500 kW for the KAERI two klystron 105 kV, 50 A application. The artificial ZCS is accomplished by placing a resonant RLC circuit across the input busswork to the resonant boost transformer. This secondary resonant circuit provides a damped ''kick-back'' to assist in IGBT commutation. As the transformer input busswork is extremely low inductance (< 10 nH), the single RLC network acts like it is across each of the four IGBT collector-emitter terminals of the H-bridge switching network. We will review these topological improvements and the overall system as delivered to the KAERI accelerator and provide details of the operational results.

  15. Estimation of the electron density and radiative energy losses in a calcium plasma source based on an electron cyclotron resonance discharge

    SciTech Connect

    Potanin, E. P. Ustinov, A. L.

    2013-06-15

    The parameters of a calcium plasma source based on an electron cyclotron resonance (ECR) discharge were calculated. The analysis was performed as applied to an ion cyclotron resonance system designed for separation of calcium isotopes. The plasma electrons in the source were heated by gyrotron microwave radiation in the zone of the inhomogeneous magnetic field. It was assumed that, in such a combined trap, the energy of the extraordinary microwave propagating from the high-field side was initially transferred to a small group of resonance electrons. As a result, two electron components with different transverse temperatures-the hot resonance component and the cold nonresonance component-were created in the plasma. The longitudinal temperatures of both components were assumed to be equal. The entire discharge space was divided into a narrow ECR zone, where resonance electrons acquired transverse energy, and the region of the discharge itself, where the gas was ionized. The transverse energy of resonance electrons was calculated by solving the equations for electron motion in an inhomogeneous magnetic field. Using the law of energy conservation and the balance condition for the number of hot electrons entering the discharge zone and cooled due to ionization and elastic collisions, the density of hot electrons was estimated and the dependence of the longitudinal temperature T{sub e Parallel-To} of the main (cold) electron component on the energy fraction {beta} lost for radiation was obtained.

  16. Higher lying resonances in low-energy electron scattering with carbon monoxide*

    NASA Astrophysics Data System (ADS)

    Dora, Amar; Tennyson, Jonathan; Chakrabarti, Kalyan

    2016-10-01

    R-matrix calculations on electron collisions with CO are reported whose aim is to identify any higher-lying resonances above the well-reported and lowest 2Π resonance at about 1.6 eV. Extensive tests with respect to basis sets, target models and scattering models are performed. The final results are reported for the larger cc-pVTZ basis set using a 50 state close-coupling (CC) calculation. The Breit-Wigner eigenphase sum and the time-delay methods are used to detect and fit any resonances. Both these methods find a very narrow 2Σ+ symmetry Feshbach-type resonance very close to the target excitation threshold of the b 3Σ+ state which lies at 12.9 eV in the calculations. This resonance is seen in the CC calculation using cc-pVTZ basis set while a CC calculation using the cc-pVDZ basis set does not produce this feature. The electronic structure of CO- is analysed in the asymptotic region; 45 molecular states are found to correlate with states dissociating to an anion and an atom. Electronic structure calculations are used to study the behaviour of these states at large internuclear separation. Quantitative results for the total, elastic and electronic excitation cross sections are also presented. The significance of these results for models of the observed dissociative electron attachment of CO in the 10 eV region is discussed. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limão-Vieira, Gustavo García, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrović.

  17. Magnetic Resonance Measurement of Turbulent Kinetic Energy for the Estimation of Irreversible Pressure Loss in Aortic Stenosis

    PubMed Central

    Dyverfeldt, Petter; Hope, Michael D.; Tseng, Elaine E.; Saloner, David

    2013-01-01

    OBJECTIVES The authors sought to measure the turbulent kinetic energy (TKE) in the ascending aorta of patients with aortic stenosis and to assess its relationship to irreversible pressure loss. BACKGROUND Irreversible pressure loss caused by energy dissipation in post-stenotic flow is an important determinant of the hemodynamic significance of aortic stenosis. The simplified Bernoulli equation used to estimate pressure gradients often misclassifies the ventricular overload caused by aortic stenosis. The current gold standard for estimation of irreversible pressure loss is catheterization, but this method is rarely used due to its invasiveness. Post-stenotic pressure loss is largely caused by dissipation of turbulent kinetic energy into heat. Recent developments in magnetic resonance flow imaging permit noninvasive estimation of TKE. METHODS The study was approved by the local ethics review board and all subjects gave written informed consent. Three-dimensional cine magnetic resonance flow imaging was used to measure TKE in 18 subjects (4 normal volunteers, 14 patients with aortic stenosis with and without dilation). For each subject, the peak total TKE in the ascending aorta was compared with a pressure loss index. The pressure loss index was based on a previously validated theory relating pressure loss to measures obtainable by echocardiography. RESULTS The total TKE did not appear to be related to global flow patterns visualized based on magnetic resonance–measured velocity fields. The TKE was significantly higher in patients with aortic stenosis than in normal volunteers (p < 0.001). The peak total TKE in the ascending aorta was strongly correlated to index pressure loss (R2 = 0.91). CONCLUSIONS Peak total TKE in the ascending aorta correlated strongly with irreversible pressure loss estimated by a well-established method. Direct measurement of TKE by magnetic resonance flow imaging may, with further validation, be used to estimate irreversible pressure loss

  18. New concepts in molecular and energy transport within carbon nanotubes: thermopower waves and stochastically resonant ion channels

    NASA Astrophysics Data System (ADS)

    Strano, Michael

    2012-02-01

    Our laboratory has been interested in how carbon nanotubes can be utilized to illustrate new concepts in molecular and energy transfer. In the first example, we predict and demonstrate the concept of thermopower waves for energy generation [1]. Coupling an exothermic chemical reaction with a thermally conductive CNT creates a self-propagating reactive wave driven along its length. We realize such waves in MWNT and show that they produce concomitant electrical pulses of high specific power >7 kW/kg. Such waves of high power density may find uses as unique energy sources. In the second system, we fabricate and study SWNT ion channels for the first time [2] and show that the longest, highest aspect ratio, and smallest diameter synthetic nanopore examined to date, a 500 μm SWNT, demonstrates oscillations in electro-osmotic current at specific ranges of electric field, that are the signatures of coherence resonance, yielding self-generated rhythmic and frequency locked transport. The observed oscillations in the current occur due to a coupling between stochastic pore blocking and a diffusion limitation that develops at the pore mouth during proton transport. [4pt] [1] Choi W, Hong S, Abrahamson JT, Han JH, Song C, Nair N, Baik S, Strano MS: Chemically driven carbon-nanotube-guided thermopower waves. NATURE MATERIALS, 9 (2010) 423-429.[0pt] [2] Lee, CY, Choi W, Han, JH, Strano MS: Coherence Resonance in a Single-Walled Carbon Nanotube Ion Channel. SCIENCE, 239

  19. Non-resonant elastic scattering of low-energy photons by atomic sodium confined in quantum plasmas

    SciTech Connect

    Ghosh, Avijit Ray, Debasis

    2015-03-15

    The non-resonant elastic scattering of low-energy photons by the bound valence electron in the ground state 3s of atomic sodium confined in quantum plasmas is investigated theoretically. The incident photon energy is assumed to be much smaller than the 3s-3p excitation energy. The alkali atom sodium is first formulated as an effective one-electron problem in which the attractive interaction between the valence electron and the atomic ion core is simulated by a spherically symmetric model potential. The Shukla-Eliasson oscillatory exponential cosine screened-Coulomb potential model is then used to mimic the effective two-body (valence-core) interaction within quantum plasmas. Non-relativistic calculations performed within the electric dipole approximation indicate that the non-resonant elastic photon scattering cross-section undergoes a dramatic growth by several orders of magnitude as the quantum wave number increases. A qualitative explanation of this phenomenon is presented. In the absence of the oscillatory cosine screening term, a similar growth is observed at larger values of the quantum wave number. Our computed relevant atomic data are in very good agreement with the experimental as well as the previous theoretical data for the zero-screening (free atom) case, and with the very limited, accurate theoretical results available for the case of exponential screened-Coulomb two-body interaction, without the cosine screening term.

  20. Probing the Conformation of the Fibronectin III1–2 Domain by Fluorescence Resonance Energy Transfer*S⃞

    PubMed Central

    Karuri, Nancy W.; Lin, Zong; Rye, Hays S.; Schwarzbauer, Jean E.

    2009-01-01

    Fibronectin (FN) matrix is crucial for cell and tissue functions during embryonic development, wound healing, and oncogenesis. Assembly of FN matrix fibrils requires FN domains that mediate interactions with integrin receptors and with other FN molecules. In addition, regulation of FN matrix assembly depends on the first two FN type III modules, III1 and III2, which harbor FN-binding sites. We propose that interactions between these two modules sequester FN-binding sites in soluble FN and that these sites become exposed by FN conformational changes during assembly. To test the idea that III1–2 has a compact conformation, we constructed CIIIY, a conformational sensor of III1–2 based on fluorescent resonance energy transfer between cyan and yellow fluorescent proteins conjugated at its N and C termini. We demonstrate energy transfer in CIIIY and show that fluorescent resonance energy transfer was eliminated by proteolysis and by treatment with mild denaturants that disrupted intramolecular interactions between the two modules. We also show that mutations of key charged residues resulted in conformational changes that exposed binding sites for the N-terminal 70-kDa FN fragment. Collectively, these results support a conformation-dependent mechanism for the regulation of FN matrix assembly by III1–2. PMID:19064996

  1. Low-energy MOS depletion modulators in silicon-on-insulator micro-donut resonators coupled to bus waveguides.

    PubMed

    Soref, Richard; Guo, Junpeng; Sun, Greg

    2011-09-12

    Electrical, optical and electro-optical simulations are presented for a waveguided, resonant, bus-coupled, p-doped Si micro-donut MOS depletion modulator operating at the 1.55 μm wavelength. To minimize the switching voltage and energy, a high-K dielectric film of HfO₂ or ZrO₂ is chosen as the gate dielectric, while a narrow ring-shaped layer of p-doped poly-silicon is selected for the gate electrode, rather than metal, to minimize plasmonic loss loading of the fundamental TE mode. In a 6-μm-diam high-Q resonator, an infrared intensity extinction ratio of 6 dB is predicted for a modulation voltage of 2 V and a switching energy of 4 fJ/bit. A speed-of-response around 1 ps is anticipated. For a modulator scaled to operate at 1.3 μm, the estimated switching energy is 2.5 fJ/bit.

  2. Rapid vibrational and rotational energy-transfer rates in heated carbon dioxide collisions by double-resonance laser spectroscopy

    SciTech Connect

    Thomason, M.D.

    1982-07-01

    Rates for resonant vibrational and rotational energy transfer from the 001 state by CO/sub 2/ + CO/sub 2/ collisions have been measured. All data were obtained by double resonance spectroscopy with CO/sub 2/ lasers in a 2.5 meter absorption cell at 700/sup 0/K. Results for rotation transfer include pumped-level relaxation and the response of other 001 levels with ..delta..J up to 18. These data are compared to four relevant collision models via a 35-level rate equation analysis. Sequence-band (002 ..-->.. 101) and hot-band (011 ..-->.. 110) lasting have been used to observe resonant nu/sub 3/-transfer relaxation involving 001 + 001 reversible 002 + 000, 001 + 100 reversible 101 + 000, and 001 + 010 reversible 011 + 000. A multilevel rate analysis has been utilized to determine the rate coefficients for 001 going to the 002, the 101, and the 011 levels. Part of the hot-band data has been interpreted as due to 110 + 000 reversible 100 + 010, and the associated rate constant has been estimated. The results of the study are compared to the theory and to other experiments.

  3. Ionization potentials, electron affinities, resonance excitation energies, oscillator strengths, and ionic radii of element Uus (Z = 117) and astatine.

    PubMed

    Chang, Zhiwei; Li, Jiguang; Dong, Chenzhong

    2010-12-30

    Multiconfiguration Dirac-Fock (MCDF) method was employed to calculate the first five ionization potentials, electron affinities, resonance excitation energies, oscillator strengths, and radii for the element Uus and its homologue At. Main valence correlation effects were taken into account. The Breit interaction and QED effects were also estimated. The uncertainties of calculated IPs, EAs, and IR for Uus and At were reduced through an extrapolation procedure. The good consistency with available experimental and other theoretical values demonstrates the validity of the present results. These theoretical data therefore can be used to predict some unknown physicochemical properties of element Uus, Astatine, and their compounds. PMID:21141866

  4. Binomial distribution-based quantitative measurement of multiple-acceptors fluorescence resonance energy transfer by partially photobleaching acceptor

    NASA Astrophysics Data System (ADS)

    Zhang, Lili; Yu, Huaina; Zhang, Jianwei; Chen, Tongsheng

    2014-06-01

    We report that binomial distribution depending on acceptor photobleaching degree can be used to characterize the proportions of various kinds of FRET (Fluorescence Resonance Energy Transfer) constructs resulted from partial acceptor photobleaching of multiple-acceptors FRET system. On this basis, we set up a rigorous quantitation theory for multiple-acceptors FRET construct named as Mb-PbFRET which is not affected by the imaging conditions and fluorophore properties. We experimentally validate Mb-PbFRET with FRET constructs consisted of one donor and two or three acceptors inside living cells on confocal and wide-field microscopes.

  5. A high quantum efficiency preserving approach to ligand exchange on lead sulfide quantum dots and interdot resonant energy transfer.

    PubMed

    Lingley, Zachary; Lu, Siyuan; Madhukar, Anupam

    2011-07-13

    We present a new approach to ligand exchange on lead sulfide (PbS) quantum dots (QDs) in which the QDs are reacted with preformed Pb cation-ligand exchange units designed to promote reactions that replace surface Pb and oleate groups on the as-grown QDs. This process introduces negligible surface defects as the high quantum efficiency (∼55%) of the as-grown QDs is maintained. Infrared spectroscopy and electron microscopy are used to confirm the replacement of ligands and time-resolved photoluminescence to demonstrate the expected inverse sixth power dependence of the nonradiative resonant energy transfer rate on inter-QD spacing.

  6. Ionization potentials, electron affinities, resonance excitation energies, oscillator strengths, and ionic radii of element Uus (Z = 117) and astatine.

    PubMed

    Chang, Zhiwei; Li, Jiguang; Dong, Chenzhong

    2010-12-30

    Multiconfiguration Dirac-Fock (MCDF) method was employed to calculate the first five ionization potentials, electron affinities, resonance excitation energies, oscillator strengths, and radii for the element Uus and its homologue At. Main valence correlation effects were taken into account. The Breit interaction and QED effects were also estimated. The uncertainties of calculated IPs, EAs, and IR for Uus and At were reduced through an extrapolation procedure. The good consistency with available experimental and other theoretical values demonstrates the validity of the present results. These theoretical data therefore can be used to predict some unknown physicochemical properties of element Uus, Astatine, and their compounds.

  7. Probing the Ion Binding Site in a DNA Holliday Junction Using Förster Resonance Energy Transfer (FRET)

    PubMed Central

    Litke, Jacob L.; Li, Yan; Nocka, Laura M.; Mukerji, Ishita

    2016-01-01

    Holliday Junctions are critical DNA intermediates central to double strand break repair and homologous recombination. The junctions can adopt two general forms: open and stacked-X, which are induced by protein or ion binding. In this work, fluorescence spectroscopy, metal ion luminescence and thermodynamic measurements are used to elucidate the ion binding site and the mechanism of junction conformational change. Förster resonance energy transfer measurements of end-labeled junctions monitored junction conformation and ion binding affinity, and reported higher affinities for multi-valent ions. Thermodynamic measurements provided evidence for two classes of binding sites. The higher affinity ion-binding interaction is an enthalpy driven process with an apparent stoichiometry of 2.1 ± 0.2. As revealed by Eu3+ luminescence, this binding class is homogeneous, and results in slight dehydration of the ion with one direct coordination site to the junction. Luminescence resonance energy transfer experiments confirmed the presence of two ions and indicated they are 6–7 Å apart. These findings are in good agreement with previous molecular dynamics simulations, which identified two symmetrical regions of high ion density in the center of stacked junctions. These results support a model in which site-specific binding of two ions in close proximity is required for folding of DNA Holliday junctions into the stacked-X conformation. PMID:26978349

  8. A reduced graphene oxide-based fluorescence resonance energy transfer sensor for highly sensitive detection of matrix metalloproteinase 2.

    PubMed

    Xi, Gaina; Wang, Xiaoping; Chen, Tongsheng

    2016-01-01

    A novel fluorescence nanoprobe (reduced nano-graphene oxide [nrGO]/fluorescein isothiocyanate-labeled peptide [Pep-FITC]) for ultrasensitive detection of matrix metalloproteinase 2 (MMP2) has been developed by engineering the Pep-FITC comprising the specific MMP2 substrate domain (PLGVR) onto the surface of nrGO particles through non-covalent linkage. The nrGO was obtained by water bathing nano-graphene oxide under 90°C for 4 hours. After mixing the nrGO and Pep-FITC for 30 seconds, the fluorescence from Pep-FITC was almost completely quenched due to the fluorescence resonance energy transfer between fluorescein isothiocyanate (FITC) and nrGO. Upon cleavage of the amide bond between Leu and Gly in the Pep-FITC by protease-MMP2, the FITC bound to nrGO was separated from nrGO surface, disrupting the fluorescence resonance energy transfer process and resulting in fluorescence recovery of FITC. Under optimal conditions, the fluorescence recovery of nrGO/Pep-FITC was found to be directly proportional to the concentration of MMP2 within 0.02-0.1 nM. The detection limit of the nrGO/Pep-FITC was determined to be 3 pM, which is approximately tenfold lower than that of the unreduced carboxylated nano-graphene oxide/Pep-FITC probe.

  9. Probing the Ion Binding Site in a DNA Holliday Junction Using Förster Resonance Energy Transfer (FRET).

    PubMed

    Litke, Jacob L; Li, Yan; Nocka, Laura M; Mukerji, Ishita

    2016-01-01

    Holliday Junctions are critical DNA intermediates central to double strand break repair and homologous recombination. The junctions can adopt two general forms: open and stacked-X, which are induced by protein or ion binding. In this work, fluorescence spectroscopy, metal ion luminescence and thermodynamic measurements are used to elucidate the ion binding site and the mechanism of junction conformational change. Förster resonance energy transfer measurements of end-labeled junctions monitored junction conformation and ion binding affinity, and reported higher affinities for multi-valent ions. Thermodynamic measurements provided evidence for two classes of binding sites. The higher affinity ion-binding interaction is an enthalpy driven process with an apparent stoichiometry of 2.1 ± 0.2. As revealed by Eu(3+) luminescence, this binding class is homogeneous, and results in slight dehydration of the ion with one direct coordination site to the junction. Luminescence resonance energy transfer experiments confirmed the presence of two ions and indicated they are 6-7 Å apart. These findings are in good agreement with previous molecular dynamics simulations, which identified two symmetrical regions of high ion density in the center of stacked junctions. These results support a model in which site-specific binding of two ions in close proximity is required for folding of DNA Holliday junctions into the stacked-X conformation. PMID:26978349

  10. Intrinsic Tryptophan Fluorescence in the Detection and Analysis of Proteins: A Focus on Förster Resonance Energy Transfer Techniques

    PubMed Central

    Ghisaidoobe, Amar B. T.; Chung, Sang J.

    2014-01-01

    Förster resonance energy transfer (FRET) occurs when the distance between a donor fluorophore and an acceptor is within 10 nm, and its application often necessitates fluorescent labeling of biological targets. However, covalent modification of biomolecules can inadvertently give rise to conformational and/or functional changes. This review describes the application of intrinsic protein fluorescence, predominantly derived from tryptophan (λEX ∼ 280 nm, λEM ∼ 350 nm), in protein-related research and mainly focuses on label-free FRET techniques. In terms of wavelength and intensity, tryptophan fluorescence is strongly influenced by its (or the protein’s) local environment, which, in addition to fluorescence quenching, has been applied to study protein conformational changes. Intrinsic Förster resonance energy transfer (iFRET), a recently developed technique, utilizes the intrinsic fluorescence of tryptophan in conjunction with target-specific fluorescent probes as FRET donors and acceptors, respectively, for real time detection of native proteins. PMID:25490136

  11. A reduced graphene oxide-based fluorescence resonance energy transfer sensor for highly sensitive detection of matrix metalloproteinase 2

    PubMed Central

    Xi, Gaina; Wang, Xiaoping; Chen, Tongsheng

    2016-01-01

    A novel fluorescence nanoprobe (reduced nano-graphene oxide [nrGO]/fluorescein isothiocyanate-labeled peptide [Pep-FITC]) for ultrasensitive detection of matrix metalloproteinase 2 (MMP2) has been developed by engineering the Pep-FITC comprising the specific MMP2 substrate domain (PLGVR) onto the surface of nrGO particles through non-covalent linkage. The nrGO was obtained by water bathing nano-graphene oxide under 90°C for 4 hours. After mixing the nrGO and Pep-FITC for 30 seconds, the fluorescence from Pep-FITC was almost completely quenched due to the fluorescence resonance energy transfer between fluorescein isothiocyanate (FITC) and nrGO. Upon cleavage of the amide bond between Leu and Gly in the Pep-FITC by protease-MMP2, the FITC bound to nrGO was separated from nrGO surface, disrupting the fluorescence resonance energy transfer process and resulting in fluorescence recovery of FITC. Under optimal conditions, the fluorescence recovery of nrGO/Pep-FITC was found to be directly proportional to the concentration of MMP2 within 0.02–0.1 nM. The detection limit of the nrGO/Pep-FITC was determined to be 3 pM, which is approximately tenfold lower than that of the unreduced carboxylated nano-graphene oxide/Pep-FITC probe. PMID:27143876

  12. Two-color resonantly enhanced multiphoton ionization and zero-kinetic-energy photoelectron spectroscopy of jet-cooled indan

    NASA Astrophysics Data System (ADS)

    He, Yonggang; Kong, Wei

    2005-06-01

    We report studies of supersonically cooled indan using two-color resonantly enhanced multiphoton ionization and two-color zero-kinetic-energy photoelectron spectroscopy. With the aid of ab initio and density-functional calculations, vibrational modes of the first electronically excited state of the neutral species and those of the cation have been assigned, and the adiabatic ionization energy has been determined to be 68458±5cm-1. Similar to the ground state and the first electronically excited state of the neutral molecule, the ground state of the cation is also proven to be nonplanar, with an estimated barrier of 213cm-1 and a puckering angle of 15.0°. These conclusions will be discussed in comparison with a previous study of an indan derivative 1,3-benzodioxole.

  13. Optical bar code recognition of methyl salicylate (MES) for environmental monitoring using fluorescence resonance energy transfer (FRET) on thin films

    NASA Astrophysics Data System (ADS)

    Smith, Clint; Tatineni, Balaji; Anderson, John; Tepper, Gary

    2006-10-01

    Fluorescence resonance energy transfer (FRET) is a process in which energy is transferred nonradiatively from one fluorophore (the donor) in an excited electron state to another, the chromophore (the acceptor). FRET is distinctive in its ability to reveal the presence of specific recognition of select targets such as the nerve agent stimulant Methyl Salicylate (MES) upon spectroscopic excitation. We introduce a surface imprinted and non-imprinted thin film that underwent AC-Electrospray ionization for donor-acceptor pair(s) bound to InGaP quantum dots and mesoporous silicate nanoparticles. The donor-acceptor pair used in this investigation included MES (donor) and 6-(fluorescein-5-(and-6)- carboxamido) hexanoic acid, succinimidyl ester bound to InGaP quantum dots (acceptor). MES was then investigated as a donor to various acceptor fluorophore: InGaP: mesoporous silicate nanoparticle layers.

  14. Red-Green-Blue Trichromophoric Nanoparticles with Dual Fluorescence Resonance Energy Transfer: Highly Sensitive Fluorogenic Response Toward Polyanions.

    PubMed

    Xu, Jinjia; Takai, Atsuro; Takeuchi, Masayuki

    2016-09-01

    A red-green-blue (RGB) trichromophoric fluorescent organic nanoparticle exhibiting multi-colour emission was constructed; the blue-emitting cationic oligofluorene nanoparticle acted as an energy-donor scaffold to undergo fluorescence resonance energy transfer (FRET) to a red-emitting dye embedded in the nanoparticle (interior FRET) and to a green-emitting dye adsorbed on the surface through electrostatic interactions (exterior FRET). Each FRET event occurs independently and is free from sequential FRET, thus the resultant dual-FRET system exhibits multi-colour emission, including white, in aqueous solution and film state. A characteristic white-emissive nanoparticle showed visible responses upon perturbation of the exterior FRET efficiency by acceptor displacement, leading to highly sensitive responses toward polyanions in a ratiometric manner. Specifically, our system exhibits high sensitivity toward heparin with an extremely low detection limit.

  15. Systematics of the 4f energies in a series of rare-earth organic complexes determined by resonant photoemission

    NASA Astrophysics Data System (ADS)

    Thompson, J.; Arima, V.; Zou, Y.; Fink, R.; Umbach, E.; Cingolani, R.; Blyth, R. I. R.

    2004-10-01

    We report a photoemission study of the systematics of the 4f electronic structure of a family of rare-earth organic compounds. Resonant photoemission has been used to determine the binding energies of the 4fN-1 ground states, relative to those of the ligand orbitals, of a number of rare-earth tris-8-hydroxyquinolines ( REQ3 ’s). Using an empirical model these results have been extrapolated to the full series (Ce-Lu) of REQ3 ’s. It is found that in all cases, with the possible exception of Ce, the energy of the 4fN-1 ground state is less than that of the highest occupied molecular orbital, and therefore individual holes on lanthanide sites will not be stable.

  16. Red-Green-Blue Trichromophoric Nanoparticles with Dual Fluorescence Resonance Energy Transfer: Highly Sensitive Fluorogenic Response Toward Polyanions.

    PubMed

    Xu, Jinjia; Takai, Atsuro; Takeuchi, Masayuki

    2016-09-01

    A red-green-blue (RGB) trichromophoric fluorescent organic nanoparticle exhibiting multi-colour emission was constructed; the blue-emitting cationic oligofluorene nanoparticle acted as an energy-donor scaffold to undergo fluorescence resonance energy transfer (FRET) to a red-emitting dye embedded in the nanoparticle (interior FRET) and to a green-emitting dye adsorbed on the surface through electrostatic interactions (exterior FRET). Each FRET event occurs independently and is free from sequential FRET, thus the resultant dual-FRET system exhibits multi-colour emission, including white, in aqueous solution and film state. A characteristic white-emissive nanoparticle showed visible responses upon perturbation of the exterior FRET efficiency by acceptor displacement, leading to highly sensitive responses toward polyanions in a ratiometric manner. Specifically, our system exhibits high sensitivity toward heparin with an extremely low detection limit. PMID:27487175

  17. Detection of electron energy distribution function anisotropy in a magnetized electron cyclotron resonance plasma by using a directional Langmuir probe

    SciTech Connect

    Shikama, T. Hasuo, M.; Kitaoka, H.

    2014-07-15

    Anisotropy in the electron energy distribution function (EEDF) in an electron cyclotron resonance plasma with magnetized electrons and weakly magnetized ions is experimentally investigated using a directional Langmuir probe. Under an assumption of independent EEDFs in the directions parallel and perpendicular to the magnetic field, the directional variation of the EEDF is evaluated. In the measured EEDFs, a significantly large population density of electrons with energies larger than 30 eV is found in one of the cross-field directions depending on the magnetic field direction. With the aid of an electron trajectory calculation, it is suggested that the observed anisotropic electrons originate from the EEDF anisotropy and the cross-field electron drift.

  18. Resonances and resonance widths

    SciTech Connect

    Collins, T.

    1986-05-01

    Two-dimensional betatron resonances are much more important than their simple one-dimensional counterparts and exhibit a strong dependence on the betatron phase advance per cell. A practical definition of ''width'' is expanded upon in order to display these relations in tables. A primarily pedagogical introduction is given to explain the tables, and also to encourage a wider capability for deriving resonance behavior and wider use of ''designer'' resonances.

  19. Electronic resonance with anticorrelated pigment vibrations drives photosynthetic energy transfer outside the adiabatic framework

    PubMed Central

    Tiwari, Vivek; Peters, William K.; Jonas, David M.

    2013-01-01

    The delocalized, anticorrelated component of pigment vibrations can drive nonadiabatic electronic energy transfer in photosynthetic light-harvesting antennas. In femtosecond experiments, this energy transfer mechanism leads to excitation of delocalized, anticorrelated vibrational wavepackets on the ground electronic state that exhibit not only 2D spectroscopic signatures attributed to electronic coherence and oscillatory quantum energy transport but also a cross-peak asymmetry not previously explained by theory. A number of antennas have electronic energy gaps matching a pigment vibrational frequency with a small vibrational coordinate change on electronic excitation. Such photosynthetic energy transfer steps resemble molecular internal conversion through a nested intermolecular funnel. PMID:23267114

  20. Communication: Energy-dependent resonance broadening in symmetric and asymmetric molecular junctions from an ab initio non-equilibrium Green's function approach

    SciTech Connect

    Liu, Zhen-Fei; Neaton, Jeffrey B.

    2014-10-07

    The electronic structure of organic-inorganic interfaces often features resonances originating from discrete molecular orbitals coupled to continuum lead states. An example is molecular junction, individual molecules bridging electrodes, where the shape and peak energy of such resonances dictate junction conductance, thermopower, I-V characteristics, and related transport properties. In molecular junctions where off-resonance coherent tunneling dominates transport, resonance peaks in the transmission function are often assumed to be Lorentzian functions with an energy-independent broadening parameter Γ. Here we define a new energy-dependent resonance broadening function, Γ(E), based on diagonalization of non-Hermitian matrices, which can describe resonances of a more complex, non-Lorentzian nature and can be decomposed into components associated with the left and right leads, respectively. We compute this quantity via an ab initio non-equilibrium Green's function (NEGF) approach based on density functional theory (DFT) for both symmetric and asymmetric molecular junctions, and show that our definition of Γ(E), when combined with Breit-Wigner formula, reproduces the transmission calculated from DFT-NEGF. Through a series of examples, we illustrate how this approach can shed new light on experiments and understanding of junction transport properties in terms of molecular orbitals.

  1. Communication: Energy-dependent resonance broadening in symmetric and asymmetric molecular junctions from an ab initio non-equilibrium Green's function approach

    NASA Astrophysics Data System (ADS)

    Liu, Zhen-Fei; Neaton, Jeffrey B.

    2014-10-01

    The electronic structure of organic-inorganic interfaces often features resonances originating from discrete molecular orbitals coupled to continuum lead states. An example is molecular junction, individual molecules bridging electrodes, where the shape and peak energy of such resonances dictate junction conductance, thermopower, I-V characteristics, and related transport properties. In molecular junctions where off-resonance coherent tunneling dominates transport, resonance peaks in the transmission function are often assumed to be Lorentzian functions with an energy-independent broadening parameter Γ. Here we define a new energy-dependent resonance broadening function, Γ(E), based on diagonalization of non-Hermitian matrices, which can describe resonances of a more complex, non-Lorentzian nature and can be decomposed into components associated with the left and right leads, respectively. We compute this quantity via an ab initio non-equilibrium Green's function (NEGF) approach based on density functional theory (DFT) for both symmetric and asymmetric molecular junctions, and show that our definition of Γ(E), when combined with Breit-Wigner formula, reproduces the transmission calculated from DFT-NEGF. Through a series of examples, we illustrate how this approach can shed new light on experiments and understanding of junction transport properties in terms of molecular orbitals.

  2. Vibrational Levels and Resonances on a New Potential Energy Surface for the Ground Electronic State of Ozone

    NASA Astrophysics Data System (ADS)

    Ndengue, Steve Alexandre; Dawes, Richard; Wang, Xiao-Gang; Carrington, Tucker

    2014-06-01

    The isotopic ratios for ozone observed in laboratory and atmospheric measurements, known as the ozone isotopic anomaly,[1,2] have been an open question in physical and atmospheric chemistry for the past 30 years. The biggest limitation in achieving agreement between theory and experiment has been the availability of a satisfactory[3-5] ground state potential energy surface (PES). The presence of a spurious reef feature in the asymptotic region of most PESs has been associated with large discrepancies between calculated and observed rates of formation especially at low temperature. We recently proposed a new global potential energy surface for ozone[6,7] possessing 4 features that make it suitable for kinetics and dynamics studies: excellent equilibrium parameters, good agreement with experimental vibrational levels, accurate dissociation energy and a transition region with accurate topography (without the reef artifact). This PES has been used recently to simulate the temperature dependent exchange reaction (16O+16O2) with a quantum statistical model[6,7], and, for the first time, a negative temperature dependence which agrees with experiments was obtained, indicating the good quality of this global surface. A quantum description of the ozone exchange and recombination reaction requires knowledge of the resonances but also the rovibrational levels just below the dissociation. We present results of global 3-well vibrational-state calculations up to the dissociation threshold and (J = 0) resonances up to 1000 wn beyond. The calculations were done using a large DVR basis ( 24 million functions) with a symmetry-adapted Lanczos algorithm as well as MCTDH. Results indicate the presence of localized bound states at energies close to the dissociation threshold beyond which some long-lived resonances follow, contrasted with a few delocalized bound states with density at large values of the stretching coordinates. References: 1- K. Mauersberger et al., Adv. At. Mol. Opt

  3. A framework to analyze the stochastic harmonics and resonance of wind energy grid interconnection

    DOE PAGESBeta

    Cho, Youngho; Lee, Choongman; Hur, Kyeon; Kang, Yong Cheol; Muljadi, Eduard; Park, Sang -Ho; Choy, Young -Do; Yoon, Gi -Gab

    2016-08-31

    This study addresses a modeling and analysis methodology for investigating the stochastic harmonics and resonance concerns of wind power plants (WPPs). Wideband harmonics from modern wind turbines are observed to be stochastic, associated with real power production, and they may adversely interact with the grid impedance and cause unexpected harmonic resonance if not comprehensively addressed in the planning and commissioning of the WPPs. These issues should become more critical as wind penetration levels increase. We thus propose a planning study framework comprising the following functional steps: First, the best-fitted probability density functions (PDFs) of the harmonic components of interest inmore » the frequency domain are determined. In operations planning, maximum likelihood estimations followed by a chi-square test are used once field measurements or manufacturers' data are available. Second, harmonic currents from the WPP are represented by randomly-generating harmonic components based on their PDFs (frequency spectrum) and then synthesized for time-domain simulations via inverse Fourier transform. Finally, we conduct a comprehensive assessment by including the impacts of feeder configurations, harmonic filters, and the variability of parameters. We demonstrate the efficacy of the proposed study approach for a 100-MW offshore WPP consisting of 20 units of 5-MW full-converter turbines, a realistic benchmark system adapted from a WPP under development in Korea, and discuss lessons learned through this research.« less

  4. Solid-state effects on thermal-neutron cross sections and on low-energy resonances

    SciTech Connect

    Harvey, J.A.; Mook, H.A.; Hill, N.W.; Shahal, O.

    1982-01-01

    The neutron total cross sections of several single crystals (Si, Cu, sapphire), several polycrystalline samples (Cu, Fe, Be, C, Bi, Ta), and a fine-powder copper sample have been measured from 0.002 to 5 eV. The Cu powder and polycrystalline Fe, Be and C data exhibit the expected abrupt changes in cross section. The cross section of the single crystal of Si is smooth with only small broad fluctuations. The data on two single Cu crystals, the sapphire crystal, cast Bi, and rolled samples of Ta and Cu have many narrow peaks approx. 10/sup -3/ eV wide. High resolution (0.3%) transmission measurements were made on the 1.057-eV resonance in /sup 240/Pu and the 0.433-eV resonance in /sup 180/Ta, both at room and low temperatures to study the effects of crystal binding. Although the changes in Doppler broadening with temperature were apparent, no asymmetries due to a recoilless contribution were observed.

  5. Resonances and threshold effects in low-energy electron collisions with methyl halides

    SciTech Connect

    Gallup, Gordon A.; Fabrikant, Ilya I.

    2007-03-15

    Cross sections for elastic and inelastic electron collisions with CH{sub 3}X (X=Cl,Br,I) molecules are calculated. For the lowest partial wave, the resonance R-matrix theory, and for the higher partial waves, the theory of scattering by dipolar plus polarization potential, are used. It is shown that the rotationally elastic scattering amplitude for a polar molecule in the fixed-nuclei approximation is logarithmically divergent for the forward direction, and a closure formula is derived to speed up the convergence at small angles. In treating the nuclear motion, only C-X stretch vibrations are taken into account. The dipole moment as a function of the C-X distance is modeled by a function incorporating the experimental value of the molecular dipole moments at the equilibrium distance and the derivatives of the dipole moments extracted from the experimental data on infrared intensities. This is supplemented by ab initio calculations of the dipole moment function for CH{sub 3}Br using the multiconfigurational valence bond method. The results for scattering cross sections show pronounced features caused by vibrational Feshbach resonances and threshold cusps. The features are most noticeable at the v=6, 7, and 8 thresholds in CH{sub 3}Cl, at the v=3 and 4 thresholds in CH{sub 3}Br, and at the v=1 threshold in CH{sub 3}I.

  6. The Concept of Resonance

    ERIC Educational Resources Information Center

    Truhlar, Donald G.

    2007-01-01

    A general example of a delocalization system associated with a higher energy than the localized one, which suggests that it is wrong to consider delocalization as equivalent to resonance stabilization, is presented. The meaning of resonance energy as it appears in valence bond theory is described as the lowering of the calculated ground-state…

  7. The energy scaling in a side-pumped ultra-low-magnification unstable resonator by employing a compact master oscillator power amplifier

    NASA Astrophysics Data System (ADS)

    Cho, C. Y.; Huang, Y. P.; Su, K. W.

    2016-10-01

    The energy scaling for a diode-side-pumped passively Q-switched Nd:YAG laser in an ultra-low-magnification unstable convex-concave resonator is investigated. Theoretical analysis and experimental results indicate the fact that the energy scaling is restricted by the increasing of side-pumping sources inside the resonator because of the significant pump-to-mode size mismatching. It is verified that employing the master oscillation power amplifier can effectively enlarge the output pulse energy and improve the beam quality. Up to 60-mJ pulse energy with 17-MW peak power is obtained at a pump energy of 520 mJ. A 1573-nm eye-safe laser emission with pulse energy up to 25 mJ is further attended via the extracavity optical parametric oscillator.

  8. Determination of effective resonance energy for the 193Ir(n,γ)194Ir reaction by the cadmium ratio method

    NASA Astrophysics Data System (ADS)

    Budak, Mustafa Guray; Karadag, Mustafa; Yücel, Haluk

    2016-04-01

    In this work, the effective resonance energy, Ebarr -value for the 193Ir(n,γ)194Ir reaction was measured using cadmium ratio method. A dual monitor (197Au-98Mo), which has convenient resonance properties, was employed for characterization of the irradiation sites. Then analytical grade iridium oxide samples diluted with CaCO3 to lower neutron self-shielding effect stacked in small cylindrical Teflon boxes were irradiated once with a 1 mm thick Cd cylindrical box placed in a thermalized neutron field of an 241Am-Be neutron source then without it. The activities produced in samples during 193Ir(n,γ)194Ir reaction were measured using a p-type HPGe detector γ-ray spectrometer with a 44.8% relative efficiency. The correction factors for thermal, epithermal neutron self-shielding (Gth, Gepi), true coincidence summing (Fcoi) and gamma-ray self-absorption (Fs) effects were determined with appropriate approaches and programs. Thus, the experimental Ebarr -value was determined to be 2.65 ± 0.61 eV for 193Ir target nuclide. The recent data for Q0 and FCd values for Ebarr determination were based on k0-NAA online database. The present experimental Ebarr value was calculated and compared with more recent values for Q0 and FCd for 193Ir. Additionally, the Ebarr -values was theoretically calculated from the up-to-date resonance data obtained from ENDF/B VII library using two different approaches. Since there is no experimentally determined Ebarr -value for the 193Ir isotope, the results are compared with the calculated ones given in the literature.

  9. Förster resonance energy transfer, absorption and emission spectra in multichromophoric systems. III. Exact stochastic path integral evaluation

    SciTech Connect

    Moix, Jeremy M.; Ma, Jian; Cao, Jianshu

    2015-03-07

    A numerically exact path integral treatment of the absorption and emission spectra of open quantum systems is presented that requires only the straightforward solution of a stochastic differential equation. The approach converges rapidly enabling the calculation of spectra of large excitonic systems across the complete range of system parameters and for arbitrary bath spectral densities. With the numerically exact absorption and emission operators, one can also immediately compute energy transfer rates using the multi-chromophoric Förster resonant energy transfer formalism. Benchmark calculations on the emission spectra of two level systems are presented demonstrating the efficacy of the stochastic approach. This is followed by calculations of the energy transfer rates between two weakly coupled dimer systems as a function of temperature and system-bath coupling strength. It is shown that the recently developed hybrid cumulant expansion (see Paper II) is the only perturbative method capable of generating uniformly reliable energy transfer rates and emission spectra across a broad range of system parameters.

  10. Observation of ultrahigh-energy electrons by resonance absorption of high-power microwaves in a pulsed plasma.

    PubMed

    Rajyaguru, C; Fuji, T; Ito, H; Yugami, N; Nishida, Y

    2001-07-01

    The interaction of high power microwave with collisionless unmagnetized plasma is studied. Investigation on the generation of superthermal electrons near the critical layer, by the resonance absorption phenomenon, is extended to very high microwave power levels (eta=E(2)(0)/4 pi n(e)kT(e) approximately 0.3). Here E0, n(e), and T(e) are the vacuum electric field, electron density, and electron temperature, respectively. Successive generation of electron bunches having maximum energy of about 2 keV, due to nonlinear wave breaking, is observed. The electron energy epsilon scales as a function of the incident microwave power P, according to epsilon proportional to P0.5 up to 250 kW. The two-dimensional spatial distribution of high energy electrons reveals that they are generated near the critical layer. However, the lower energy component is again produced in the subcritical density region indicating the possibility of other electron heating mechanisms. PMID:11461406

  11. Proposal of a New Method for Measuring Förster Resonance Energy Transfer (FRET) Rapidly, Quantitatively and Non-Destructively

    PubMed Central

    Helm, Paul Johannes

    2012-01-01

    The process of radiationless energy transfer from a chromophore in an excited electronic state (the “donor”) to another chromophore (an “acceptor”), in which the energy released by the donor effects an electronic transition, is known as “Förster Resonance Energy Transfer” (FRET). The rate of energy transfer is dependent on the sixth power of the distance between donor and acceptor. Determining FRET efficiencies is tantamount to measuring distances between molecules. A new method is proposed for determining FRET efficiencies rapidly, quantitatively, and non-destructively on ensembles containing donor acceptor pairs: at wavelengths suitable for mutually exclusive excitations of donors and acceptors, two laser beams are intensity-modulated in rectangular patterns at duty cycle ½ and frequencies f1 and f2 by electro-optic modulators. In an ensemble exposed to these laser beams, the donor excitation is modulated at f1, and the acceptor excitation, and therefore the degree of saturation of the excited electronic state of the acceptors, is modulated at f2. Since the ensemble contains donor acceptor pairs engaged in FRET, the released donor fluorescence is modulated not only at f1 but also at the beat frequency Δf: = |f1 − f2|. The depth of the latter modulation, detectable via a lock-in amplifier, quantitatively indicates the FRET efficiency. PMID:23202903

  12. Additional correction for energy transfer efficiency calculation in filter-based Förster resonance energy transfer microscopy for more accurate results

    NASA Astrophysics Data System (ADS)

    Sun, Yuansheng; Periasamy, Ammasi

    2010-03-01

    Förster resonance energy transfer (FRET) microscopy is commonly used to monitor protein interactions with filter-based imaging systems, which require spectral bleedthrough (or cross talk) correction to accurately measure energy transfer efficiency (E). The double-label (donor+acceptor) specimen is excited with the donor wavelength, the acceptor emission provided the uncorrected FRET signal and the donor emission (the donor channel) represents the quenched donor (qD), the basis for the E calculation. Our results indicate this is not the most accurate determination of the quenched donor signal as it fails to consider the donor spectral bleedthrough (DSBT) signals in the qD for the E calculation, which our new model addresses, leading to a more accurate E result. This refinement improves E comparisons made with lifetime and spectral FRET imaging microscopy as shown here using several genetic (FRET standard) constructs, where cerulean and venus fluorescent proteins are tethered by different amino acid linkers.

  13. Understanding double-resonant Raman scattering in chiral carbon nanotubes: Diameter and energy dependence of the D mode

    NASA Astrophysics Data System (ADS)

    Herziger, Felix; Vierck, Asmus; Laudenbach, Jan; Maultzsch, Janina

    2015-12-01

    We present a theoretical model to describe the double-resonant scattering process in arbitrary carbon nanotubes (CNTs). We use this approach to investigate the defect-induced D mode in CNTs and unravel the dependence of the D -mode frequency on the CNT diameter and on the energy of the resonant optical transition. Our approach is based on the symmetry of the hexagonal lattice and geometric considerations; hence the method is independent of the exact model that is chosen to describe the electronic band structure or the phonon dispersion. We finally clarify the diameter dependence of this Raman mode that has been under discussion in the past and demonstrate that, depending on the experimental conditions, in general two different dependencies can be measured. We also prove that CNTs with an arbitrary chiral index can exhibit a D mode in their Raman spectrum, in contrast to previous symmetry-based arguments. Furthermore, we give a direct quantification of the curvature-induced phonon frequency corrections of the D mode in CNTs with respect to graphite.

  14. Resonance strength measurement at astrophysical energies: The {sup 17}O(p,α){sup 14}N reaction studied via Trojan Horse Method

    SciTech Connect

    Sergi, M. L. La Cognata, M.; Pizzone, R. G.; Spitaleri, C.; Lamia, L.; Rapisarda, G. G.; Mukhamedzhanov, A.; Irgaziev, B.; Tang, X. D.; Wiescher, M.; Mrazek, J.; Kroha, V.

    2015-10-15

    In recent years, the Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of proton-induced reactions on {sup 17}O nuclei, overcoming extrapolation procedures and enhancement effects due to electron screening. We will report on the indirect study of the {sup 17}O(p,α){sup 14}N reaction via the THM by applying the approach developed for extracting the resonance strength of narrow resonance in the ultralow energy region. Two measurements will be described and the experimental THM cross sections will be shown for both experiments.

  15. Chemiluminescence Resonance Energy Transfer Competitive Immunoassay Employing Hapten-Functionalized Quantum Dots for the Detection of Sulfamethazine.

    PubMed

    Ma, Mingfang; Wen, Kai; Beier, Ross C; Eremin, Sergei A; Li, Chenglong; Zhang, Suxia; Shen, Jianzhong; Wang, Zhanhui

    2016-07-20

    We describe a new strategy for using chemiluminescence resonance energy transfer (CRET) by employing hapten-functionalized quantum dots (QDs) in a competitive immunoassay for detection of sulfamethazine (SMZ). Core/multishell QDs were synthesized and modified with phospholipid-PEG. The modified QDs were functionalized with the hapten 4-(4-aminophenyl-sulfonamido)butanoic acid. The CRET-based immunoassay exhibited a limit of detection for SMZ of 9 pg mL(-1), which is >4 orders of magnitude better than a homogeneous fluorescence polarization immunoassay and is 2 orders of magnitude better than a heterogeneous enzyme-linked immunosorbent assay. This strategy represents a simple, reliable, and universal approach for detection of chemical contaminants.

  16. [Determination of Trace Boron Based on Gold Nanorod Plasmonic Resonance Rayleigh Scattering Energy Transfer to the Coordinate].

    PubMed

    Ye, Ling-ling; Li, Ting-sheng; Luo, Yang-he; Wen, Gui-qing; Liang, Ai-hui; Jiang, Zhi-liang

    2015-05-01

    B is a necessary trace element for human and animals, but the excess intake of B caused poison. Thus, it is very important to determination of B in foods and water. The target of this study is development of a new, sensitive and selective resonance Rayleigh scattering energy transfer (RRS-ET) for the determination of B. The combination of energy transfer with resonance Rayleigh scattering (RRS) has developed a new technology called RRS-ET, which can realize selective and sensitive detection of boric acid. The gold nanorods in diameter of 12 nm and length of 37 nm were prepared by the seed growth procedure. In pH 5. 6 NH4 Ac-HAc buffer solution and in the presence of azomethine-H (AMH), the gold nanorod particles exhibited a strong resonance Rayleigh scattering (RRS) peak at 404 nm. In the presence of boric acid, it reacts with AMH to form AMH-boric acid (AMH-B) complexes. When the complexe as a receptor close to the gold nanorod as a donor, the resonance Rayleigh scattering energy transfer (RRS-ET) take placed that resulted in the Rayleigh scattering signal quenching. With the increase of the concentration of boric acid, the formed complexes increased, the scattering light energy of gold nanorod transfer to the complexes increased, resulting in the Rayleigh scattering intensity linearly reduced at 404 nrn. The decreased RRS intensity responds linearly to the concentration of boron over 10~750 ng . mL-1 B, with a regress equation of ΔI404 nm =3. 53c+24 and a detection of 5 ng mL-1 B. The influence of coexistence substances on the RRS-ET determination of 2. 3 X 10(-7) mol . L-1 B was considered in details. Results showed that this new RRS-ET method is of high selectivity, that is, 4 X 10(-4) mol . L-1 Mn2+, Cd2+, Zn2+, Bi+, Na+, Al3+, glucose, Hg2+, IO3-, F-, SO(2-)3, SiO3-, NO3-, CIO4-, H2O2, mannitol, glycerol, and ethylene glycol, 4X 10(-5) mol . L-1 L-tyrosine, and 2 X 10(-4) mol . L-1 L-glutamic acid do not interfere with the determination. Based on this, a new

  17. Homeotropic alignment and Förster resonance energy transfer: The way to a brighter luminescent solar concentrator

    SciTech Connect

    Tummeltshammer, Clemens; Taylor, Alaric; Kenyon, Anthony J.; Papakonstantinou, Ioannis

    2014-11-07

    We investigate homeotropically aligned fluorophores and Förster resonance energy transfer (FRET) for luminescent solar concentrators using Monte-Carlo ray tracing. The homeotropic alignment strongly improves the trapping efficiency, while FRET circumvents the low absorption at homeotropic alignment by separating the absorption and emission processes. We predict that this design doped with two organic dye molecules can yield a 82.9% optical efficiency improvement compared to a single, arbitrarily oriented dye molecule. We also show that quantum dots are prime candidates for absorption/donor fluorophores due to their wide absorption band. The potentially strong re-absorption and low quantum yield of quantum dots is not a hindrance for this design.

  18. DNAzyme-based biosensor for Cu(2+) ion by combining hybridization chain reaction with fluorescence resonance energy transfer technique.

    PubMed

    Chen, Ying; Chen, Ling; Ou, Yidian; Wang, Zhenhua; Fu, Fengfu; Guo, Liangqia

    2016-08-01

    A novel signal amplification strategy based on Cu(2+)-dependent DNAzyme was developed for sensing Cu(2+) ion by combining hybridization chain reaction (HCR) with fluorescence resonance energy transfer (FRET) technique. In the presence of Cu(2+) ion, the substrate strands of Cu(2+)-dependent DNAzyme immobilized on magnetic beads were specifically cleaved and released. The released strands initiated the HCR process of hairpin H1 and H2 labeled with FAM as the donor and TAMRA as the acceptor, respectively. Long nicked dsDNA structures were self-assembled to bring the donor and the acceptor in close proximity, resulting in a FRET process. The relative ratio of fluorescent intensities of the acceptor and donor was used to quantitatively detect Cu(2+) ion with a limit of detection of 0.5nmolL(-1). This proposed biosensor was applied to detect Cu(2+) ion in tap water with satisfactory results.

  19. Resonant vortex-core reversal in magnetic nano-spheres as robust mechanism of efficient energy absorption and emission

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Koog; Yoo, Myoung-Woo; Lee, Jehyun; Lee, Jae-Hyeok; Kim, Min-Kwan

    2016-08-01

    We report on novel vortex-core reversal dynamics in nano-spheres of single-vortex spin configuration as revealed by micromagnetic simulations combined with analytical derivations. When the frequency of an AC magnetic field is tuned to the frequency of the vortex-core precession around the direction of a given static field, oscillatory vortex-core reversals occur, and additionally, the frequency is found to change with both the strength of the applied AC field and the particle size. Such resonant vortex-core reversals in nano-spheres may provide a new and efficient means of energy absorption by, and emission from, magnetic nanoparticles, which system can be effectively implemented in bio-applications such as magnetic hyperthermia.

  20. Resonant vortex-core reversal in magnetic nano-spheres as robust mechanism of efficient energy absorption and emission

    PubMed Central

    Kim, Sang-Koog; Yoo, Myoung-Woo; Lee, Jehyun; Lee, Jae-Hyeok; Kim, Min-Kwan

    2016-01-01

    We report on novel vortex-core reversal dynamics in nano-spheres of single-vortex spin configuration as revealed by micromagnetic simulations combined with analytical derivations. When the frequency of an AC magnetic field is tuned to the frequency of the vortex-core precession around the direction of a given static field, oscillatory vortex-core reversals occur, and additionally, the frequency is found to change with both the strength of the applied AC field and the particle size. Such resonant vortex-core reversals in nano-spheres may provide a new and efficient means of energy absorption by, and emission from, magnetic nanoparticles, which system can be effectively implemented in bio-applications such as magnetic hyperthermia. PMID:27531408

  1. Observations of a free-energy source for intense electrostatic waves. [in upper atmosphere near upper hybrid resonance frequency

    NASA Technical Reports Server (NTRS)

    Kurth, W. S.; Frank, L. A.; Gurnett, D. A.; Burek, B. G.; Ashour-Abdalla, M.

    1980-01-01

    Significant progress has been made in understanding intense electrostatic waves near the upper hybrid resonance frequency in terms of the theory of multiharmonic cyclotron emission using a classical loss-cone distribution function as a model. Recent observations by Hawkeye 1 and GEOS 1 have verified the existence of loss-cone distributions in association with the intense electrostatic wave events, however, other observations by Hawkeye and ISEE have indicated that loss cones are not always observable during the wave events, and in fact other forms of free energy may also be responsible for the instability. Now, for the first time, a positively sloped feature in the perpendicular distribution function has been uniquely identified with intense electrostatic wave activity. Correspondingly, we suggest that the theory is flexible under substantial modifications of the model distribution function.

  2. Homeotropic alignment and Förster resonance energy transfer: The way to a brighter luminescent solar concentrator

    NASA Astrophysics Data System (ADS)

    Tummeltshammer, Clemens; Taylor, Alaric; Kenyon, Anthony J.; Papakonstantinou, Ioannis

    2014-11-01

    We investigate homeotropically aligned fluorophores and Förster resonance energy transfer (FRET) for luminescent solar concentrators using Monte-Carlo ray tracing. The homeotropic alignment strongly improves the trapping efficiency, while FRET circumvents the low absorption at homeotropic alignment by separating the absorption and emission processes. We predict that this design doped with two organic dye molecules can yield a 82.9% optical efficiency improvement compared to a single, arbitrarily oriented dye molecule. We also show that quantum dots are prime candidates for absorption/donor fluorophores due to their wide absorption band. The potentially strong re-absorption and low quantum yield of quantum dots is not a hindrance for this design.

  3. Förster resonance energy transfer microscopy and spectroscopy for localizing protein-protein interactions in living cells

    PubMed Central

    Sun, Yuansheng; Rombola, Christina; Jyothikumar, Vinod; Periasamy, Ammasi

    2014-01-01

    The fundamental theory of Förster resonance energy transfer (FRET) was established in the 1940's. Its great power was only realized in the past 20 years after different techniques were developed and applied to biological experiments. This success was made possible by the availability of suitable fluorescent probes, advanced optics, detectors, microscopy instrumentation and analytical tools. Combined with state-of-the-art microscopy and spectroscopy, FRET imaging allows scientists to study a variety of phenomena that produce changes in molecular proximity, thereby leading to many significant findings in the life sciences. In this review, we outline various FRET imaging techniques and their strengths and limitations; we also provide a biological model to demonstrate how to investigate protein-protein interactions in living cells using both intensity- and fluorescence lifetime-based FRET microscopy methods. PMID:23813736

  4. Vibrational analysis of HOCl up to 98{percent} of the dissociation energy with a Fermi resonance Hamiltonian

    SciTech Connect

    Jost, R.; Joyeux, M.; Skokov, S.; Bowman, J.

    1999-10-01

    We have analyzed the vibrational energies and wave functions of HOCl obtained from previous {ital ab initio} calculations [J. Chem. Phys. {bold 109}, 2662 (1998); {bold 109}, 10273 (1998)]. Up to approximately 13&hthinsp;000 cm{sup {minus}1}, the normal modes are nearly decoupled, so that the analysis is straightforward with a Dunham model. In contrast, above 13&hthinsp;000 cm{sup {minus}1} the Dunham model is no longer valid for the levels with no quanta in the OH stretch (v{sub 1}=0). In addition to v{sub 1}, these levels can only be assigned a so-called polyad quantum number P=2v{sub 2}+v{sub 3}, where 2 and 3 denote, respectively, the bending and OCl stretching normal modes. In contrast, the levels with v{sub 1}{ge}2 remain assignable with three v{sub i} quantum numbers up to the dissociation (D{sub 0}=19&hthinsp;290&hthinsp;cm{sup {minus}1}). The interaction between the bending and the OCl stretch ({omega}{sub 2}{congruent}2{omega}{sub 3}) is well described with a simple, fitted Fermi resonance Hamiltonian. The energies and wave functions of this model Hamiltonian are compared with those obtained from {ital ab initio} calculations, which in turn enables the assignment of many additional {ital ab initio} vibrational levels. Globally, among the 809 bound levels calculated below dissociation, 790 have been assigned, the lowest unassigned level, No. 736, being located at 18&hthinsp;885 cm{sup {minus}1} above the (0,0,0) ground level, that is, at about 98{percent} of D{sub 0}. In addition, 84 {open_quotes}resonances{close_quotes} located above D{sub 0} have also been assigned. Our best Fermi resonance Hamiltonian has 29 parameters fitted with 725 {ital ab initio} levels, the rms deviation being of 5.3 cm{sup {minus}1}. This set of 725 fitted levels includes the full set of levels up to No. 702 at 18&hthinsp;650 cm{sup {minus}1}. The {ital ab initio} levels, which are assigned but not included in the fit, are reasonably predicted by the model Hamiltonian, but with a

  5. Investigation of Förster Resonance Energy Transfer (FRET) and Competition of Fluorescent Dyes on DNA Microparticles

    PubMed Central

    Kim, Jieun; Lee, Jae Sung; Lee, Jong Bum

    2015-01-01

    Fluorescent labeling is widely used to investigate the structural stability and changes to DNA nano- and microstructures. Despite this, the conventional method for observing DNA structures has several limitations in terms of cost-efficiency. This paper introduces a DNA spherical particle stained with DNA intercalating dyes (SYBR Green and SYTOX Orange) as tracers and reports the interaction between multiple dyes. The interference between the dyes was analyzed in terms of Förster resonance energy transfer (FRET) and competition. The changes in the fluorescence intensity by FRET were uniform, regardless of the sequence. The competition effect could occur when several dyes were added simultaneously. These properties are expected to help in the design of multicolor tracers in bioimaging and environmental applications. PMID:25856674

  6. Time-resolved fluorescence resonance energy transfer as a versatile tool in the development of homogeneous cellular kinase assays.

    PubMed

    Saville, Lisa; Spais, Chrysanthe; Mason, Jennifer L; Albom, Mark S; Murthy, Seetha; Meyer, Sheryl L; Ator, Mark A; Angeles, Thelma S; Husten, Jean

    2012-12-01

    Homogeneous cellular assays can streamline product detection in the drug discovery process. One commercially available assay employing time-resolved fluorescence resonance energy transfer (TR-FRET) that detects phosphorylated products was used to evaluate inhibitors of the receptor tyrosine kinase AXL in a cell line expressing an AXL-green fluorescent protein fusion protein. This TR-FRET assay was modified to evaluate the phosphorylation state of the AXL family member MER in a cell line expressing MER with a V5 tag by adding a fluorescein-labeled anti-V5 antibody. This homogeneous cellular assay was further modified to evaluate the nonreceptor tyrosine kinase focal adhesion kinase (FAK) in cell lines that expressed an untagged kinase by the inclusion of a commercially available anti-FAK antibody conjugated with an acceptor dye. The methods described here can be further adapted for TR-FRET detection of other cellular kinase activities.

  7. Single-pair fluorescence resonance energy transfer of nucleosomes in free diffusion: optimizing stability and resolution of subpopulations.

    PubMed

    Gansen, Alexander; Hauger, Florian; Tóth, Katalin; Langowski, Jörg

    2007-09-15

    We applied fluorescence detection methods on the single-molecule level to study structural variations and dynamic processes occurring within nucleosomes. Four fluorescent nucleosome constructs were made by attaching donor and acceptor fluorophores to different positions of two nucleosome positioning sequences and reconstituting nucleosomes by salt dialysis. The photochemical and biochemical stability of nucleosomes under single-molecule conditions was optimized by adding inert protein and free radical capturing additives, allowing us to define the best experimental conditions for single-molecule spectroscopy on highly diluted solutions of nucleosome complexes. We could demonstrate for the first time the resolution of conformational subpopulations of nucleosomes by single-pair fluorescence resonance energy transfer in a freely diffusing system and could show the effect of thermally induced nucleosome repositioning.

  8. Chemiluminescence Resonance Energy Transfer Competitive Immunoassay Employing Hapten-Functionalized Quantum Dots for the Detection of Sulfamethazine.

    PubMed

    Ma, Mingfang; Wen, Kai; Beier, Ross C; Eremin, Sergei A; Li, Chenglong; Zhang, Suxia; Shen, Jianzhong; Wang, Zhanhui

    2016-07-20

    We describe a new strategy for using chemiluminescence resonance energy transfer (CRET) by employing hapten-functionalized quantum dots (QDs) in a competitive immunoassay for detection of sulfamethazine (SMZ). Core/multishell QDs were synthesized and modified with phospholipid-PEG. The modified QDs were functionalized with the hapten 4-(4-aminophenyl-sulfonamido)butanoic acid. The CRET-based immunoassay exhibited a limit of detection for SMZ of 9 pg mL(-1), which is >4 orders of magnitude better than a homogeneous fluorescence polarization immunoassay and is 2 orders of magnitude better than a heterogeneous enzyme-linked immunosorbent assay. This strategy represents a simple, reliable, and universal approach for detection of chemical contaminants. PMID:27362827

  9. Fluorescence resonance energy transfer microscopy as demonstrated by measuring the activation of the serine/threonine kinase Akt

    PubMed Central

    Broussard, Joshua A; Rappaz, Benjamin; Webb, Donna J; Brown, Claire M

    2013-01-01

    This protocol describes procedures for performing fluorescence resonance energy transfer (FRET) microscopy analysis by three different methods: acceptor photobleaching, sensitized emission and spectral imaging. We also discuss anisotropy and fluorescence lifetime imaging microscopy–based FRET techniques. By using the specific example of the FRET probe Akind (Akt indicator), which is a version of Akt modified such that FRET occurs when the probe is activated by phosphorylation, indicating Akt activation. The protocol provides a detailed step-by-step description of sample preparation, image acquisition and analysis, including control samples, image corrections and the generation of quantitative FRET/CFP ratio images for both sensitized emission and spectral imaging. The sample preparation takes 2 d, equipment setup takes 2–3 h and image acquisition and analysis take 6–8 h. PMID:23306460

  10. Electrochemiluminescence resonance energy transfer between graphene quantum dots and graphene oxide for sensitive protein kinase activity and inhibitor sensing.

    PubMed

    Liang, Ru-Ping; Qiu, Wei-Bin; Zhao, Hui-Fang; Xiang, Cai-Yun; Qiu, Jian-Ding

    2016-01-21

    Herein, a novel electrochemiluminescence resonance energy transfer (ECL-RET) biosensor using graphene quantum dots (GQDs) as donor and graphene oxide (GO) as acceptor for monitoring the activity of protein kinase was presented for the first time. Anti-phosphoserine antibody conjugated graphene oxide (Ab-GO) nonocomposite could be captured onto the phosphorylated peptide/GQDs modified electrode surface through antibody-antigen interaction in the presence of casein kinase II (CK2) and adenosine 5'-triphosphate (ATP), resulting in ECL from the GQDs quenching by closely contacting GO. This ECL quenching degree was positively correlated with CK2 activity. Therefore, on the basis of ECL-RET between GQDs and GO, the activity of protein kinase can be detected sensitively. This biosensor can also be used for quantitative analysis CK2 activity in serum samples and qualitative screening kinase inhibition, indicating the potential application of the developed method in biochemical fundamental research and clinical diagnosis. PMID:26724763

  11. Electrochemiluminescence resonance energy transfer between graphene quantum dots and graphene oxide for sensitive protein kinase activity and inhibitor sensing.

    PubMed

    Liang, Ru-Ping; Qiu, Wei-Bin; Zhao, Hui-Fang; Xiang, Cai-Yun; Qiu, Jian-Ding

    2016-01-21

    Herein, a novel electrochemiluminescence resonance energy transfer (ECL-RET) biosensor using graphene quantum dots (GQDs) as donor and graphene oxide (GO) as acceptor for monitoring the activity of protein kinase was presented for the first time. Anti-phosphoserine antibody conjugated graphene oxide (Ab-GO) nonocomposite could be captured onto the phosphorylated peptide/GQDs modified electrode surface through antibody-antigen interaction in the presence of casein kinase II (CK2) and adenosine 5'-triphosphate (ATP), resulting in ECL from the GQDs quenching by closely contacting GO. This ECL quenching degree was positively correlated with CK2 activity. Therefore, on the basis of ECL-RET between GQDs and GO, the activity of protein kinase can be detected sensitively. This biosensor can also be used for quantitative analysis CK2 activity in serum samples and qualitative screening kinase inhibition, indicating the potential application of the developed method in biochemical fundamental research and clinical diagnosis.

  12. Simple Model for Gold Nano Particles Concentration Dependence of Resonance Energy Transfer Intensity

    NASA Astrophysics Data System (ADS)

    Hoa, N. M.; Ha, C. V.; Nga, D. T.; Lan, N. T.; Nhung, T. H.; Viet, N. A.

    2016-06-01

    Gold nano particles (GNPs) concentration dependence of the energy transfer occurs between the fluorophores and GNPs is investigated. In the case of theses pairs, GNPs can enhance or quench the fluorescence of fluorophores depending upon the relative magnitudes of two energy transfer mechanisms: i) the plasmonic field enhancement at the fluorophores emission frequencies (plasmon coupled fluorescence enhancement) and ii) the localized plasmon coupled Forster energy transfer from fluorescent particles to gold particles, which quenches the fluorescence. The competition of these mechanisms is depending on the spectral overlap of fluorophores and GNPs, their relative concentration, excitation wavelength. Simple two branches surface plasmon polariton model for GNPs concentration dependence of the energy transfer is proposed. The experimental data and theoretical results confirm our findings.

  13. Forster resonance energy transfer in the system of human serum albumin-xanthene dyes

    NASA Astrophysics Data System (ADS)

    Kochubey, V. I.; Pravdin, A. B.; Melnikov, A. G.; Konstantinova, I.; Alonova, I. V.

    2016-04-01

    The processes of interaction of fluorescent probes: eosin and erythrosine with human serum albumin (HSA) were studied by the methods of absorption and fluorescence spectroscopy. Extinction coefficients of probes were determined. Critical transfer radius and the energy transfer efficiency were defined by fluorescence quenching of HSA. Analysis of the excitation spectra of HSA revealed that the energy transfer process is carried out mainly between tryptophanyl and probes.

  14. Enhanced Plasmonic Resonance Energy Transfer in Mesoporous Silica-Encased Gold Nanorod for Two-Photon-Activated Photodynamic Therapy

    PubMed Central

    Chen, Nai-Tzu; Tang, Kuo-Chun; Chung, Ming-Fang; Cheng, Shih-Hsun; Huang, Ching-Mao; Chu, Chia-Hui; Chou, Pi-Tai; Souris, Jeffrey S.; Chen, Chin-Tu; Mou, Chung-Yuan; Lo, Leu-Wei

    2014-01-01

    The unique optical properties of gold nanorods (GNRs) have recently drawn considerable interest from those working in in vivo biomolecular sensing and bioimaging. Especially appealing in these applications is the plasmon-enhanced photoluminescence of GNRs induced by two-photon excitation at infrared wavelengths, owing to the significant penetration depth of infrared light in tissue. Unfortunately, many studies have also shown that often the intensity of pulsed coherent irradiation of GNRs needed results in irreversible deformation of GNRs, greatly reducing their two-photon luminescence (TPL) emission intensity. In this work we report the design, synthesis, and evaluation of mesoporous silica-encased gold nanorods (MS-GNRs) that incorporate photosensitizers (PSs) for two-photon-activated photodynamic therapy (TPA-PDT). The PSs, doped into the nano-channels of the mesoporous silica shell, can be efficiently excited via intra-particle plasmonic resonance energy transfer from the encased two-photon excited gold nanorod and further generates cytotoxic singlet oxygen for cancer eradication. In addition, due to the mechanical support provided by encapsulating mesoporous silica matrix against thermal deformation, the two-photon luminescence stability of GNRs was significantly improved; after 100 seconds of 800 nm repetitive laser pulse with the 30 times higher than average power for imaging acquisition, MS-GNR luminescence intensity exhibited ~260% better resistance to deformation than that of the uncoated gold nanorods. These results strongly suggest that MS-GNRs with embedded PSs might provide a promising photodynamic therapy for the treatment of deeply situated cancers via plasmonic resonance energy transfer. PMID:24955141

  15. Enhanced plasmonic resonance energy transfer in mesoporous silica-encased gold nanorod for two-photon-activated photodynamic therapy.

    PubMed

    Chen, Nai-Tzu; Tang, Kuo-Chun; Chung, Ming-Fang; Cheng, Shih-Hsun; Huang, Ching-Mao; Chu, Chia-Hui; Chou, Pi-Tai; Souris, Jeffrey S; Chen, Chin-Tu; Mou, Chung-Yuan; Lo, Leu-Wei

    2014-01-01

    The unique optical properties of gold nanorods (GNRs) have recently drawn considerable interest from those working in in vivo biomolecular sensing and bioimaging. Especially appealing in these applications is the plasmon-enhanced photoluminescence of GNRs induced by two-photon excitation at infrared wavelengths, owing to the significant penetration depth of infrared light in tissue. Unfortunately, many studies have also shown that often the intensity of pulsed coherent irradiation of GNRs needed results in irreversible deformation of GNRs, greatly reducing their two-photon luminescence (TPL) emission intensity. In this work we report the design, synthesis, and evaluation of mesoporous silica-encased gold nanorods (MS-GNRs) that incorporate photosensitizers (PSs) for two-photon-activated photodynamic therapy (TPA-PDT). The PSs, doped into the nano-channels of the mesoporous silica shell, can be efficiently excited via intra-particle plasmonic resonance energy transfer from the encased two-photon excited gold nanorod and further generates cytotoxic singlet oxygen for cancer eradication. In addition, due to the mechanical support provided by encapsulating mesoporous silica matrix against thermal deformation, the two-photon luminescence stability of GNRs was significantly improved; after 100 seconds of 800 nm repetitive laser pulse with the 30 times higher than average power for imaging acquisition, MS-GNR luminescence intensity exhibited ~260% better resistance to deformation than that of the uncoated gold nanorods. These results strongly suggest that MS-GNRs with embedded PSs might provide a promising photodynamic therapy for the treatment of deeply situated cancers via plasmonic resonance energy transfer. PMID:24955141

  16. Fluorescence resonance energy transfer between points on tropomyosin and actin in skeletal muscle thin filaments: does tropomyosin move?

    PubMed

    Miki, M; Miura, T; Sano, K; Kimura, H; Kondo, H; Ishida, H; Maéda, Y

    1998-06-01

    Fluorescence resonance energy transfer (FRET) spectroscopy has been used to determine spatial relationships between residues on tropomyosin and actin in reconstituted muscle thin filament, and to detect a positional change of tropomyosin relative to actin on the thin filament in the presence and absence of Ca2+ ions. In addition to Cys-190 which is a single cysteine residue in rabbit skeletal muscle alpha-tropomyosin, a new site, Cys-87 which is a unique cysteine residue in a mutant alpha-tropomyosin, was labeled with a resonance energy donor molecule, 5-(2-iodoacetylaminoethyl)aminonaphthalene 1-sulfonic acid (IAEDANS). On the other hand, Gln-41, Lys-61, Cys-374, and the ATP-binding site of actin were selectively labeled with acceptor probes: fluorescein cadaverine, fluorescein 5-isothiocyanate, 4-dimethyl-aminophenylazophenyl 4'-maleimide, and TNP-ATP (or TNP-ADP), respectively. The distances between probes attached to position 87 of the mutant tropomyosin and Gln-41, Lys-61, Cys-374, or the nucleotide-binding site of actin on the reconstituted thin filament in the presence of Ca2+ ion were measured to be 43.2, 49.7, 45.4, and 35.2 A, respectively, and the distance between probes attached to position 190 of tropomyosin and Gln-41 or the nucleotide-binding site of actin were 51.6 and 43.1 A, respectively. The transfer efficiencies between these donor and acceptor molecules were large, so that the efficiency should be very sensitive to changes in distance between probes attached to tropomyosin and actin. However, the transfer efficiency did not change appreciably upon removal of Ca2+ ions, suggesting that tropomyosin does not change its position on the reconstituted thin filament in response to a change in Ca2+ ion concentration. The present results do not support the notion of tropomyosin movement on skeletal muscle thin filaments as proposed in the steric blocking theory.

  17. Electric dipole response of nuclei studied by proton inelastic scattering: neutron thickness, symmetry energy, and pygmy dipole resonance

    NASA Astrophysics Data System (ADS)

    Tamii, Atsushi; RCNP E282/E316/E326/E350/E376/E377 Collaboration

    2014-09-01

    Electric dipole (E1) responses of heavy nuclei have been studied by high-resolution measurement of proton inelastic scattering at forward angles including zero degrees. Here the proton scattering at 300 MeV is used as an electromagnetic probe to extract precisely the distribution of E1 reduced transition probability B(E1). The measurement has been done on various stable nuclei such as 208Pb, 120Sn, 90Zr, 154Sm, and 96Mo. The dipole polarizability and pygmy dipole resonance (PDR) strength has been extracted. Those quantities are considered to have strong correlations to the neutron skin thickness and the first order density dependence of the symmetry energy of the nuclear equation of state. We will present the experimental methods and highlights of the results as well as the preliminary ones of recent analyses. Electric dipole (E1) responses of heavy nuclei have been studied by high-resolution measurement of proton inelastic scattering at forward angles including zero degrees. Here the proton scattering at 300 MeV is used as an electromagnetic probe to extract precisely the distribution of E1 reduced transition probability B(E1). The measurement has been done on various stable nuclei such as 208Pb, 120Sn, 90Zr, 154Sm, and 96Mo. The dipole polarizability and pygmy dipole resonance (PDR) strength has been extracted. Those quantities are considered to have strong correlations to the neutron skin thickness and the first order density dependence of the symmetry energy of the nuclear equation of state. We will present the experimental methods and highlights of the results as well as the preliminary ones of recent analyses. JSPS No. 25105509.

  18. The function of the milk-clotting enzymes bovine and camel chymosin studied by a fluorescence resonance energy transfer assay.

    PubMed

    Jensen, Jesper Langholm; Jacobsen, Jonas; Moss, Marcia L; Rasmussen, Fred; Qvist, Karsten Bruun; Larsen, Sine; van den Brink, Johannes M

    2015-05-01

    Enzymatic coagulation of bovine milk can be divided in 2 steps: an enzymatic step, in which the Phe105-Met106 bond of the milk protein bovine κ-casein is cleaved, and an aggregation step. The aspartic peptidases bovine and camel chymosin (EC 3.4.23.4) are typically used to catalyze the enzymatic step. The most commonly used method to study chymosin activity is the relative milk-clotting activity test that measures the end point of the enzymatic and aggregation step. This method showed that camel chymosin has a 2-fold higher milk-clotting activity toward bovine milk than bovine chymosin. To enable a study of the enzymatic step independent of the aggregation step, a fluorescence resonance energy transfer assay has been developed using a peptide substrate derived from the 98-108 sequence of bovine κ-casein. This assay and Michaelis-Menten kinetics were employed to determine the enzymatic activity of camel and bovine chymosin under milk clotting-like conditions (pH 6.65, ionic strength 80 mM). The results obtained show that the catalytic efficiency of camel chymosin is 3-fold higher than bovine chymosin. The substrate affinity and catalytic activity of bovine and camel chymosin increase at lower pH (6.00 and 5.50). The glycosylation of bovine and camel chymosin did not affect binding of the fluorescence resonance energy transfer substrate, but doubly glycosylated camel chymosin seems to have slightly higher catalytic efficiency. In the characterization of the enzymes, the developed assay is easier and faster to use than the traditionally used relative milk-clotting activity test method.

  19. Measurement of the high energy component of the x-ray spectra in the VENUS electron cyclotron resonance ion source.

    PubMed

    Leitner, D; Benitez, J Y; Lyneis, C M; Todd, D S; Ropponen, T; Ropponen, J; Koivisto, H; Gammino, S

    2008-03-01

    High performance electron cyclotron resonance (ECR) ion sources, such as VENUS (Versatile ECR for NUclear Science), produce large amounts of x-rays. By studying their energy spectra, conclusions can be drawn about the electron heating process and the electron confinement. In addition, the bremsstrahlung from the plasma chamber is partly absorbed by the cold mass of the superconducting magnet, adding an extra heat load to the cryostat. Germanium or NaI detectors are generally used for x-ray measurements. Due to the high x-ray flux from the source, the experimental setup to measure bremsstrahlung spectra from ECR ion sources is somewhat different from that for the traditional nuclear physics measurements these detectors are generally used for. In particular, the collimation and background shielding can be problematic. In this paper, we will discuss the experimental setup for such a measurement, the energy calibration and background reduction, the shielding of the detector, and collimation of the x-ray flux. We will present x-ray energy spectra and cryostat heating rates depending on various ion source parameters, such as confinement fields, minimum B-field, rf power, and heating frequency. PMID:18377002

  20. BRET: NanoLuc-Based Bioluminescence Resonance Energy Transfer Platform to Monitor Protein-Protein Interactions in Live Cells.

    PubMed

    Mo, Xiu-Lei; Fu, Haian

    2016-01-01

    Bioluminescence resonance energy transfer (BRET) is a prominent biophysical technology for monitoring molecular interactions, and has been widely used to study protein-protein interactions (PPI) in live cells. This technology requires proteins of interest to be associated with an energy donor (i.e., luciferase) and an acceptor (e.g., fluorescent protein) molecule. Upon interaction of the proteins of interest, the donor and acceptor will be brought into close proximity and energy transfer of chemical reaction-induced luminescence to its corresponding acceptor will result in an increased emission at an acceptor-defined wavelength, generating the BRET signal. We leverage the advantages of the superior optical properties of the NanoLuc(®) luciferase (NLuc) as a BRET donor coupled with Venus, a yellow fluorescent protein, as acceptor. We term this NLuc-based BRET platform "BRET(n)". BRET(n) has been demonstrated to have significantly improved assay performance, compared to previous BRET technologies, in terms of sensitivity and scalability. This chapter describes a step-by-step practical protocol for developing a BRET(n) assay in a multi-well plate format to detect PPIs in live mammalian cells. PMID:27317001

  1. A New Polymer Nanoprobe Based on Chemiluminescence Resonance Energy Transfer for Ultrasensitive Imaging of Intrinsic Superoxide Anion in Mice.

    PubMed

    Li, Ping; Liu, Lu; Xiao, Haibin; Zhang, Wei; Wang, Lulin; Tang, Bo

    2016-03-01

    Despite significant developments in optical imaging of superoxide anion (O2(•-)) as the preliminary reactive oxygen species, novel visualizing strategies that offer ultrahigh sensitivity are still imperative. This is mainly because intrinsic concentrations of O2(•-) are extremely low in living systems. Herein, we present the rational design and construction of a new polymer nanoprobe PCLA-O2(•-) for detecting O2(•-) based on chemiluminescence (CL) resonance energy transfer without an external excitation source. Structurally, PCLA-O2(•-) contains two moieties linked covalently, namely imidazopyrazinone that is capable of CL triggered by O2(•-) as the energy donor and conjugated polymers with light-amplifying property as the energy acceptor. Experiment results demonstrate that PCLA-O2(•-) exhibits ultrahigh sensitivity at the picomole level, dramatically prolonged luminescence time, specificity, and excellent biocompatibility. Without exogenous stimulation, this probe for the first time in situ visualizes O2(•-) level differences between normal and tumor tissues of mice. These exceptional features ensure that PCLA-O2(•-) as a self-luminescing probe is an alternative in vivo imaging approach for ultralow level O2(•-). PMID:26908223

  2. BRET: NanoLuc-Based Bioluminescence Resonance Energy Transfer Platform to Monitor Protein-Protein Interactions in Live Cells.

    PubMed

    Mo, Xiu-Lei; Fu, Haian

    2016-01-01

    Bioluminescence resonance energy transfer (BRET) is a prominent biophysical technology for monitoring molecular interactions, and has been widely used to study protein-protein interactions (PPI) in live cells. This technology requires proteins of interest to be associated with an energy donor (i.e., luciferase) and an acceptor (e.g., fluorescent protein) molecule. Upon interaction of the proteins of interest, the donor and acceptor will be brought into close proximity and energy transfer of chemical reaction-induced luminescence to its corresponding acceptor will result in an increased emission at an acceptor-defined wavelength, generating the BRET signal. We leverage the advantages of the superior optical properties of the NanoLuc(®) luciferase (NLuc) as a BRET donor coupled with Venus, a yellow fluorescent protein, as acceptor. We term this NLuc-based BRET platform "BRET(n)". BRET(n) has been demonstrated to have significantly improved assay performance, compared to previous BRET technologies, in terms of sensitivity and scalability. This chapter describes a step-by-step practical protocol for developing a BRET(n) assay in a multi-well plate format to detect PPIs in live mammalian cells.

  3. Low-energy physical properties of high- Tc superconducting Cu oxides: A comparison between the resonating valence bond and experiments

    NASA Astrophysics Data System (ADS)

    Yang, Kai-Yu; Shih, C. T.; Chou, C. P.; Huang, S. M.; Lee, T. K.; Xiang, T.; Zhang, F. C.

    2006-06-01

    In a recent review by Anderson and co-workers, it was pointed out that an early resonating valence bond (RVB) theory is able to explain a number of unusual properties of high-temperature superconducting (SC) Cu oxides. Here we extend previous calculations to study more systematically the low-energy physical properties of the plain vanilla d -wave RVB state, and to compare the results with the available experiments. We use a renormalized mean-field theory combined with variational Monte Carlo and power Lanczos methods to study the RVB state of an extended t-J model in a square lattice with parameters suitable for the hole-doped Cu oxides. The physical observable quantities we study include the specific heat, the linear residual thermal conductivity, the in-plane magnetic penetration depth, the quasiparticle energy at the antinode (π,0) , the superconducting energy gap, the quasiparticle spectra, and the Drude weights. The traits of nodes (including kF , the Fermi velocity vF , and the velocity along Fermi surface v2 ), and the SC order parameter are studied. Comparisons of the theory and the experiments in cuprates show an overall qualitative agreement, especially on their doping dependences.

  4. A novel upconversion, fluorescence resonance energy transfer biosensor (FRET) for sensitive detection of lead ions in human serum.

    PubMed

    Xu, Sai; Xu, Shihan; Zhu, Yongsheng; Xu, Wen; Zhou, Pingwei; Zhou, Chunyang; Dong, Biao; Song, Hongwei

    2014-11-01

    There has been great progress in the development of fluorescence biosensors based on quantum dots (QDs) for the detection of lead ions. However, most methods are detecting lead ions in aqueous solution rather than in human serum due to the influence of protein autofluorescence in serum excited by visible light. Thus, we developed a novel fluorescence resonance energy transfer (FRET) biosensor by choosing the upconversion NaYF4:Yb(3+)/Tm(3+) nanoparticles as the energy donor and the CdTe QDs as the energy acceptor for lead ion detection. It is the first near infrared (NIR)-excited fluorescent probe for determination of lead ions in serum that is capable of overcoming self-luminescence from serum excitation with visible light. The sensor also shows high selectivity, a low detection limit (80 nm) and good linear Stern-Volmer characteristics (R = 0.996), both in the buffer and serum. This biosensor has great potential for versatile applications in lead ion detection in biological and analytical fields. PMID:25184968

  5. Synthesis and systematic evaluation of dark resonance energy transfer (DRET)-based library and its application in cell imaging.

    PubMed

    Su, Dongdong; Teoh, Chai Lean; Kang, Nam-Young; Yu, Xiaotong; Sahu, Srikanta; Chang, Young-Tae

    2015-03-01

    In this paper, we report a new strategy for constructing a dye library with large Stokes shifts. By coupling a dark donor with BODIPY acceptors of tunable high quantum yield, a novel dark resonance energy transfer (DRET)-based library, named BNM, has been synthesized. Upon excitation of the dark donor (BDN) at 490 nm, the absorbed energy is transferred to the acceptor (BDM) with high efficiency, which was tunable in a broad range from 557 nm to 716 nm, with a high quantum yield of up to 0.8. It is noteworthy to mention that the majority of the non-radiative energy loss of the donor was converted into the acceptor's fluorescence output with a minimum leak of donor emission. Fluorescence imaging tested in live cells showed that the BNM compounds are cell-permeable and can also be employed for live-cell imaging. This is a new library which can be excited through a dark donor allowing for strong fluorescence emission in a wide range of wavelengths. Thus, the BNM library is well suited for high-throughput screening or multiplex experiments in biological applications by using a single laser excitation source.

  6. Measurement of the high energy component of the x-ray spectra in the VENUS electron cyclotron resonance ion source

    SciTech Connect

    Leitner, D.; Benitez, J. Y.; Lyneis, C. M.; Todd, D. S.; Ropponen, T.; Ropponen, J.; Koivisto, H.; Gammino, S.

    2008-03-15

    High performance electron cyclotron resonance (ECR) ion sources, such as VENUS (Versatile ECR for NUclear Science), produce large amounts of x-rays. By studying their energy spectra, conclusions can be drawn about the electron heating process and the electron confinement. In addition, the bremsstrahlung from the plasma chamber is partly absorbed by the cold mass of the superconducting magnet, adding an extra heat load to the cryostat. Germanium or NaI detectors are generally used for x-ray measurements. Due to the high x-ray flux from the source, the experimental setup to measure bremsstrahlung spectra from ECR ion sources is somewhat different from that for the traditional nuclear physics measurements these detectors are generally used for. In particular, the collimation and background shielding can be problematic. In this paper, we will discuss the experimental setup for such a measurement, the energy calibration and background reduction, the shielding of the detector, and collimation of the x-ray flux. We will present x-ray energy spectra and cryostat heating rates depending on various ion source parameters, such as confinement fields, minimum B-field, rf power, and heating frequency.

  7. Probing Bioluminescence Resonance Energy Transfer in Quantum Rod-Luciferase Nanoconjugates.

    PubMed

    Alam, Rabeka; Karam, Liliana M; Doane, Tennyson L; Coopersmith, Kaitlin; Fontaine, Danielle M; Branchini, Bruce R; Maye, Mathew M

    2016-02-23

    We describe the necessary design criteria to create highly efficient energy transfer conjugates containing luciferase enzymes derived from Photinus pyralis (Ppy) and semiconductor quantum rods (QRs) with rod-in-rod (r/r) microstructure. By fine-tuning the synthetic conditions, CdSe/CdS r/r-QRs were prepared with two different emission colors and three different aspect ratios (l/w) each. These were hybridized with blue, green, and red emitting Ppy, leading to a number of new BRET nanoconjugates. Measurements of the emission BRET ratio (BR) indicate that the resulting energy transfer is highly dependent on QR energy accepting properties, which include absorption, quantum yield, and optical anisotropy, as well as its morphological and topological properties, such as aspect ratio and defect concentration. The highest BR was found using r/r-QRs with lower l/w that were conjugated with red Ppy, which may be activating one of the anisotropic CdSe core energy levels. The role QR surface defects play on Ppy binding, and energy transfer was studied by growth of gold nanoparticles at the defects, which indicated that each QR set has different sites. The Ppy binding at those sites is suggested by the observed BRET red-shift as a function of Ppy-to-QR loading (L), where the lowest L results in highest efficiency and furthest shift. PMID:26760436

  8. Energy-Based Adaptive Focusing: Optimal Ultrasonic Focusing Using Magnetic Resonance Guidance

    NASA Astrophysics Data System (ADS)

    Larrat, B.; Pernot, M.; Montaldo, G.; Fink, M.; Tanter, M.

    2010-03-01

    Adaptive focusing of ultrasonic waves is performed under the guidance of a Magnetic Resonance (MR) system. The technique is based on the maximization of the ultrasonic wave intensity at a target point. The wave intensity is indirectly estimated from the local tissue motion induced at the chosen focus by the acoustic radiation force of the ultrasonic beam. A motion sensitive MR sequence is used to measure the resulting local tissue displacements. Based on the transmission of a set of spatially coded ultrasonic waves, a non iterative inversion process is used to estimate the phase aberrations induced by the propagation medium and to maximize the acoustical intensity at the target. Both programmable and physical aberrating layers introducing strong distortions (up to 2π radians) are recovered within acceptable errors (<0.8 rad). This non invasive technique is shown to accurately correct the phase aberrations in a phantom gel with negligible heat deposition and limited acquisition time. These refocusing performances demonstrate a major potential in the field of MR-Guided Ultrasound Therapy in particular for transcranial brain HIFU.

  9. Fluorescence resonance energy transfer between green fluorescent protein and doxorubicin enabled by DNA nanotechnology.

    PubMed

    Heger, Zbynek; Kominkova, Marketa; Cernei, Natalia; Krejcova, Ludmila; Kopel, Pavel; Zitka, Ondrej; Adam, Vojtech; Kizek, Rene

    2014-12-01

    DNA nanotechnology is a rapidly growing research area, where DNA may be used for wide range of applications such as construction of nanodevices serving for large scale of diverse purposes. Likewise a panel of various purified fluorescent proteins is investigated for their ability to emit their typical fluorescence spectra under influence of particular excitation. Hence these proteins may form ideal donor molecules for assembly of fluorescence resonance emission transfer (FRET) constructions. To extend the application possibilities of fluorescent proteins, while using DNA nanotechnology, we developed nanoconstruction comprising green fluorescent protein (GFP) bound onto surface of surface active nanomaghemite and functionalized with gold nanoparticles. We took advantage of natural affinity between gold and thiol moieties, which were modified to bind DNA fragment. Finally we enclosed doxorubicin into fullerene cages. Doxorubicin intercalated in DNA fragment bound on the particles and thus we were able to connect these parts together. Because GFP behaved as a donor and doxorubicin as an acceptor using excitation wavelength for GFP (395 nm) in emission wavelength of doxorubicin (590 nm) FRET was observed. This nanoconstruction may serve as a double-labeled transporter of doxorubicin guided by force of external magnetic force owing to the presence of nanomaghemite. Further nanomaghemite offers the possibility of using this technology for thermotherapy.

  10. ALINET: neural net automatic alignment of high-energy laser resonator optical elements

    NASA Astrophysics Data System (ADS)

    Hart, George A.; Bailey, Adam W.; Palumbo, Louis J.; Kuperstein, Michael

    1993-10-01

    A novel neural net approach has successfully solved the time consuming practical problem of aligning the many optical elements used in the resonator of high power chemical lasers. Moreover, because the neural net can achieve optimal performance in only 2 - 4 steps, as compared with 50 for other techniques, the important ability to effect real time control is gained. This represents a significant experimental breakthrough because of the difficulty previously associated with this alignment process. Use of either near or far field image information produces excellent performance. The method is very robust in the presence of noise. For cases where the initial misalignment falls outside the regime encompassed by the training set, a hybrid approach utilizing an advanced conventional method can bring the optical system within the capture range of the neural net. This reported use of a neural net to rapidly convert imagery information into high precision control information is of broad applicability to optical, acoustic, or electromagnetic alignment, positioning, and control problems.

  11. Blinking fluorescence of single donor-acceptor pairs: important role of "dark'' states in resonance energy transfer via singlet levels.

    PubMed

    Osad'ko, I S; Shchukina, A L

    2012-06-01

    The influence of triplet levels on Förster resonance energy transfer via singlet levels in donor-acceptor (D-A) pairs is studied. Four types of D-A pair are considered: (i) two-level donor and two-level acceptor, (ii) three-level donor and two-level acceptor, (iii) two-level donor and three-level acceptor, and (iv) three-level donor and three-level acceptor. If singlet-triplet transitions in a three-level acceptor molecule are ineffective, the energy transfer efficiency E=I_{A}/(I_{A}+I_{D}), where I_{D} and I_{A} are the average intensities of donor and acceptor fluorescence, can be described by the simple theoretical equation E(F)=FT_{D}/(1+FT_{D}). Here F is the rate of energy transfer, and T_{D} is the donor fluorescence lifetime. In accordance with the last equation, 100% of the donor electronic energy can be transferred to an acceptor molecule at FT_{D}≫1. However, if singlet-triplet transitions in a three-level acceptor molecule are effective, the energy transfer efficiency is described by another theoretical equation, E(F)=F[over ¯](F)T_{D}/[1+F[over ¯](F)T_{D}]. Here F[over ¯](F) is a function of F depending on singlet-triplet transitions in both donor and acceptor molecules. Expressions for the functions F[over ¯](F) are derived. In this case the energy transfer efficiency will be far from 100% even at FT_{D}≫1. The character of the intensity fluctuations of donor and acceptor fluorescence indicates which of the two equations for E(F) should be used to find the value of the rate F. Therefore, random time instants of photon emission in both donor and acceptor fluorescence are calculated by the Monte Carlo method for all four types of D-A pair. Theoretical expressions for start-stop correlators (waiting time distributions) in donor and acceptor fluorescence are derived. The probabilities w_{N}^{D}(t) and w_{N}^{A}(t) of finding N photons of donor and acceptor fluorescence in the time interval t are calculated for various values of the energy

  12. Nanoparticles based on quantum dots and a luminol derivative: implications for in vivo imaging of hydrogen peroxide by chemiluminescence resonance energy transfer.

    PubMed

    Lee, Eun Sook; Deepagan, V G; You, Dong Gil; Jeon, Jueun; Yi, Gi-Ra; Lee, Jung Young; Lee, Doo Sung; Suh, Yung Doug; Park, Jae Hyung

    2016-03-18

    Overproduction of hydrogen peroxide is involved in the pathogenesis of inflammatory diseases such as cancer and arthritis. To image hydrogen peroxide via chemiluminescence resonance energy transfer in the near-infrared wavelength range, we prepared quantum dots functionalized with a luminol derivative. PMID:26857551

  13. Novel molecular recognition via fluorescent resonance energy transfer using a biotin-PEG/polyamine stabilized CdS quantum dot.

    PubMed

    Nagasaki, Yukio; Ishii, Takehiko; Sunaga, Yuka; Watanabe, Yousuke; Otsuka, Hidenori; Kataoka, Kazunori

    2004-07-20

    A novel functionally PEGylated quantum dot (QD) was prepared by a coprecipitation method in the presence of the biotin-PEG/polyamine block copolymer. When CdCl2 and Na2S were mixed in aqueous media in the presence of the biotin-PEG-b-poly(2-(N,N-dimethylamino)ethyl methacrylate) [biotin-PEG/PAMA], a CdS QD with a size of ca. 5 nm was prepared. The polyamine segment was anchored on the surface of the formed CdS nanoparticle, whereas the PEG segment was tethered on the surface to form a hydrophilic palisade, thus improving the dispersion stability in aqueous media even under a high salt concentration condition. An effective fluorescent resonance energy transfer (FRET) was observed by the specific interaction of the biotin-PEG/PAMA stabilized CdS QD with TexasRed-labeled streptavidin of the physiological ionic strength of 0.15 M. The extent of the energy transfer was in proportion to the concentration of the TexasRed-streptavidin. This FRET system using the PEGylated CdS QD coupled with fluorescent-labeled protein can be utilized as a highly sensitive bioanalytical system.

  14. Förster resonance energy transfer and protein-induced fluorescence enhancement as synergetic multi-scale molecular rulers

    PubMed Central

    Ploetz, Evelyn; Lerner, Eitan; Husada, Florence; Roelfs, Martin; Chung, SangYoon; Hohlbein, Johannes; Weiss, Shimon; Cordes, Thorben

    2016-01-01

    Advanced microscopy methods allow obtaining information on (dynamic) conformational changes in biomolecules via measuring a single molecular distance in the structure. It is, however, extremely challenging to capture the full depth of a three-dimensional biochemical state, binding-related structural changes or conformational cross-talk in multi-protein complexes using one-dimensional assays. In this paper we address this fundamental problem by extending the standard molecular ruler based on Förster resonance energy transfer (FRET) into a two-dimensional assay via its combination with protein-induced fluorescence enhancement (PIFE). We show that donor brightness (via PIFE) and energy transfer efficiency (via FRET) can simultaneously report on e.g., the conformational state of double stranded DNA (dsDNA) following its interaction with unlabelled proteins (BamHI, EcoRV, and T7 DNA polymerase gp5/trx). The PIFE-FRET assay uses established labelling protocols and single molecule fluorescence detection schemes (alternating-laser excitation, ALEX). Besides quantitative studies of PIFE and FRET ruler characteristics, we outline possible applications of ALEX-based PIFE-FRET for single-molecule studies with diffusing and immobilized molecules. Finally, we study transcription initiation and scrunching of E. coli RNA-polymerase with PIFE-FRET and provide direct evidence for the physical presence and vicinity of the polymerase that causes structural changes and scrunching of the transcriptional DNA bubble. PMID:27641327

  15. Förster resonance energy transfer between pyrene and bovine serum albumin: Effect of the hydrophobic pockets of cyclodextrins

    NASA Astrophysics Data System (ADS)

    Maity, Arnab; Mukherjee, Puspal; Das, Tarasankar; Ghosh, Prasun; Purkayastha, Pradipta

    The phenomenon of Förster resonance energy transfer (FRET) between pyrene and bovine serum albumin (BSA) protein in presence of cyclodextrins (CDs) is explored in the present work. CDs provide hydrophobic environment and thus the aromatic molecules get encapsulated in them depending on the relative size and space. In this work we revealed that along with pyrene monomer, the side chains of amino acids in BSA can get trapped partly in the hydrophobic cavities of CDs if space permits. While being encapsulated by β-CD as pyrene monomer, it can interact with the BSA tryptophan moiety exposed toward the aqueous environment to form a dimer through π-π interaction. This, in turn, affects the energy transfer process by reducing the efficiency. On the other hand, pyrene excimer gets encapsulated in a γ-CD molecule due to availability of enough space. The excimer shows a new band at a higher wavelength. This further reduces FRET efficiency due to scarcity of acceptor for the tryptophan moieties in BSA.

  16. Exciton transport in organic semiconductors: Förster resonance energy transfer compared with a simple random walk

    NASA Astrophysics Data System (ADS)

    Feron, K.; Zhou, X.; Belcher, W. J.; Dastoor, P. C.

    2012-02-01

    Förster resonance energy transfer theory (FRET) and a simple random walk (RW) are both implemented in a dynamic Monte Carlo simulation with the aim of determining the exciton diffusion length from photoluminescence (PL) measurements. The calculated diffusion lengths obtained from both models are shown to be the same. As such, given that the computational time of a random walk is typically 2-3 orders of magnitude smaller than the FRET approach, this work shows that the RW methodology can be a preferable model for the determination of diffusion lengths. We also show that the RW approach may also be implemented in Monte Carlo simulations that describe organic solar cells. Despite the fact that (compared with FRET) RW does not account for non-nearest neighbor hopping or energy relaxation, we show that the resulting overestimation of the simulated current will not exceed 2% for typical OPV parameters. In addition, by taking advantage of the gain in speed we are able to investigate the impact of the exciton diffusion length on the optimal interface distance and show that materials with longer exciton diffusion lengths are less sensitive to variations in the morphology of the active layer of an organic solar cell.

  17. Förster resonance energy transfer and protein-induced fluorescence enhancement as synergetic multi-scale molecular rulers

    NASA Astrophysics Data System (ADS)

    Ploetz, Evelyn; Lerner, Eitan; Husada, Florence; Roelfs, Martin; Chung, Sangyoon; Hohlbein, Johannes; Weiss, Shimon; Cordes, Thorben

    2016-09-01

    Advanced microscopy methods allow obtaining information on (dynamic) conformational changes in biomolecules via measuring a single molecular distance in the structure. It is, however, extremely challenging to capture the full depth of a three-dimensional biochemical state, binding-related structural changes or conformational cross-talk in multi-protein complexes using one-dimensional assays. In this paper we address this fundamental problem by extending the standard molecular ruler based on Förster resonance energy transfer (FRET) into a two-dimensional assay via its combination with protein-induced fluorescence enhancement (PIFE). We show that donor brightness (via PIFE) and energy transfer efficiency (via FRET) can simultaneously report on e.g., the conformational state of double stranded DNA (dsDNA) following its interaction with unlabelled proteins (BamHI, EcoRV, and T7 DNA polymerase gp5/trx). The PIFE-FRET assay uses established labelling protocols and single molecule fluorescence detection schemes (alternating-laser excitation, ALEX). Besides quantitative studies of PIFE and FRET ruler characteristics, we outline possible applications of ALEX-based PIFE-FRET for single-molecule studies with diffusing and immobilized molecules. Finally, we study transcription initiation and scrunching of E. coli RNA-polymerase with PIFE-FRET and provide direct evidence for the physical presence and vicinity of the polymerase that causes structural changes and scrunching of the transcriptional DNA bubble.

  18. The simultaneous measurement of energy and linear polarization of the scattered radiation in resonant inelastic soft x-ray scattering

    SciTech Connect

    Braicovich, L. Minola, M.; Dellea, G.; Ghiringhelli, G.; Le Tacon, M.; Moretti Sala, M.; Morawe, C.; Peffen, J.-Ch.; Yakhou, F.; Brookes, N. B.; Supruangnet, R.

    2014-11-15

    Resonant Inelastic X-ray Scattering (RIXS) in the soft x-ray range is an element-specific energy-loss spectroscopy used to probe the electronic and magnetic excitations in strongly correlated solids. In the recent years, RIXS has been progressing very quickly in terms of energy resolution and understanding of the experimental results, but the interpretation of spectra could further improve, sometimes decisively, from a full knowledge of the polarization of incident and scattered photons. Here we present the first implementation, in a high resolution soft-RIXS spectrometer used to analyze the scattered radiation, of a device allowing the measurement of the degree of linear polarization. The system, based on a graded W/B{sub 4}C multilayer mirror installed in proximity of the CCD detector, has been installed on the AXES spectrometer at the ESRF (European Synchrotron Radiation Facility); it has been fully characterized and it has been used for a demonstration experiment at the Cu L{sub 3} edge on a high-T{sub c} superconducting cuprate. The loss in efficiency suffered by the spectrometer equipped with this test facility was a factor 17.5. We propose also a more advanced version, suitable for a routine use on the next generation of RIXS spectrometers and with an overall efficiency up to 10%.

  19. Molecular dynamics study of chemically engineered green fluorescent protein mutants: comparison of intramolecular fluorescence resonance energy transfer rate.

    PubMed

    Mitchell, Felicity L; Frank, Filipp; Marks, Gabriel E; Suzuki, Miho; Douglas, Kenneth T; Bryce, Richard A

    2009-04-01

    Because of its unusual spectroscopic properties, green fluorescent protein (GFP) has become a useful tool in molecular genetics, biochemistry and cell biology. Here, we computationally characterize the behavior of two GFP constructs, designed as bioprobes for enzymatic triggering using intramolecular fluorescence resonance energy transfer (FRET). These constructs differ in the location of an intramolecular FRET partner, an attached chemical chromophore (either near an N-terminal or C-terminal site). We apply the temperature replica exchange molecular dynamics method to the two flexible constructs in conjunction with a generalized Born implicit solvent model. The calculated rate of FRET was derived from the interchromophore distance, R, and orientational factor, kappa(2). In agreement with experiment, the construct with the C-terminally attached dye was predicted to have higher energy transfer rate than observed for the N-terminal construct. The molecular basis for this observation is discussed. In addition, we find that the orientational factor, kappa(2), deviates from the commonly assumed value, the implications of which are also considered.

  20. Förster resonance energy transfer and protein-induced fluorescence enhancement as synergetic multi-scale molecular rulers.

    PubMed

    Ploetz, Evelyn; Lerner, Eitan; Husada, Florence; Roelfs, Martin; Chung, SangYoon; Hohlbein, Johannes; Weiss, Shimon; Cordes, Thorben

    2016-01-01

    Advanced microscopy methods allow obtaining information on (dynamic) conformational changes in biomolecules via measuring a single molecular distance in the structure. It is, however, extremely challenging to capture the full depth of a three-dimensional biochemical state, binding-related structural changes or conformational cross-talk in multi-protein complexes using one-dimensional assays. In this paper we address this fundamental problem by extending the standard molecular ruler based on Förster resonance energy transfer (FRET) into a two-dimensional assay via its combination with protein-induced fluorescence enhancement (PIFE). We show that donor brightness (via PIFE) and energy transfer efficiency (via FRET) can simultaneously report on e.g., the conformational state of double stranded DNA (dsDNA) following its interaction with unlabelled proteins (BamHI, EcoRV, and T7 DNA polymerase gp5/trx). The PIFE-FRET assay uses established labelling protocols and single molecule fluorescence detection schemes (alternating-laser excitation, ALEX). Besides quantitative studies of PIFE and FRET ruler characteristics, we outline possible applications of ALEX-based PIFE-FRET for single-molecule studies with diffusing and immobilized molecules. Finally, we study transcription initiation and scrunching of E. coli RNA-polymerase with PIFE-FRET and provide direct evidence for the physical presence and vicinity of the polymerase that causes structural changes and scrunching of the transcriptional DNA bubble. PMID:27641327

  1. Compartment syndrome: A quantitative study of high-energy phosphorus compounds using sup 31 P-magnetic resonance spectroscopy

    SciTech Connect

    Heppenstall, R.B.; Sapega, A.A.; Izant, T.; Fallon, R.; Shenton, D.; Park, Y.S.; Chance, B. )

    1989-08-01

    The purpose of this study was to quantitate the intracellular high-energy phosphate compounds during 6 hours of tissue ischemia in the anterior tibial compartment of beagles subjected to an induced traumatized compartment syndrome. The goal of this work was to provide clinicians with objective criteria to augment clinical judgment regarding surgical intervention in the impending compartment syndrome. A beagle model was utilized in which the Delta pressure (difference between the mean arterial pressure and compartment pressure) could be controlled. The model, in conjunction with {sup 31}P-magnetic resonance spectroscopy (MRS), allowed a measure of high-energy phosphate compounds and pH in the compartment at various Delta pressures. The extent of ischemic metabolic insult in the compartment was then quantitated. Our data suggest the following: (1) lower Delta pressures result in a proportionally greater drop in the intracellular phosphocreatine ratio and pH; (2) at lower Delta pressures, there is proportionally greater decline in the percentage recovery post-fasciotomy; (3) blood pressure is extremely important and periods of hypotension may result in increased muscle damage at lower compartment pressures.

  2. Simulation of coherent energy transfer in an alpha-helical peptide by Fermi resonance.

    PubMed Central

    Clarke, D L; Collins, M A

    1992-01-01

    A mechanism by which NH stretching quanta are coherently transported along a chain of hydrogen bonded peptide groups is demonstrated by classical simulation of a section of the alpha-helical peptide poly(L-alanine). Vibrational motion takes place on a complex energy surface constructed from earlier ab initio and empirical surfaces. A speculative hypothesis of the biological role of this mechanism is presented, and the critical parameters governing the dynamics are identified and discussed. Images FIGURE 1 PMID:1547322

  3. Resonance behaviour of whole-body averaged specific energy absorption rate (SAR) in the female voxel model, NAOMI

    NASA Astrophysics Data System (ADS)

    Dimbylow, Peter

    2005-09-01

    Finite-difference time-domain (FDTD) calculations have been performed of the whole-body averaged specific energy absorption rate (SAR) in a female voxel model, NAOMI, under isolated and grounded conditions from 10 MHz to 3 GHz. The 2 mm resolution voxel model, NAOMI, was scaled to a height of 1.63 m and a mass of 60 kg, the dimensions of the ICRP reference adult female. Comparison was made with SAR values from a reference male voxel model, NORMAN. A broad SAR resonance in the NAOMI values was found around 900 MHz and a resulting enhancement, up to 25%, over the values for the male voxel model, NORMAN. This latter result confirmed previously reported higher values in a female model. The effect of differences in anatomy was investigated by comparing values for 10-, 5- and 1-year-old phantoms rescaled to the ICRP reference values of height and mass which are the same for both sexes. The broad resonance in the NAOMI child values around 1 GHz is still a strong feature. A comparison has been made with ICNIRP guidelines. The ICNIRP occupational reference level provides a conservative estimate of the whole-body averaged SAR restriction. The linear scaling of the adult phantom using different factors in longitudinal and transverse directions, in order to match the ICRP stature and weight, does not exactly reproduce the anatomy of children. However, for public exposure the calculations with scaled child models indicate that the ICNIRP reference level may not provide a conservative estimate of the whole-body averaged SAR restriction, above 1.2 GHz for scaled 5- and 1-year-old female models, although any underestimate is by less than 20%.

  4. Repulsive magnetic levitation-based ocean wave energy harvester with variable resonance: Modeling, simulation and experiment

    NASA Astrophysics Data System (ADS)

    Masoumi, Masoud; Wang, Ya

    2016-10-01

    This paper investigates a magnetic levitation characteristic used in a vibration based energy harvester, called repulsive magnetic scavenger (RMS). The RMS is capable of harvesting ocean wave energy with a unique repelling permanent magnet array, which provides a stronger and more uniform magnetic field, compared to its attracting magnetic counterparts. The levitating magnets are stacked together around a threaded rod so that the same pole is facing each other. Two fixed magnets placed with one at each end of the RMS provides a collocated harvesting and braking mechanism in the face of high amplitude vibrations. Magnets in the levitated magnet stack are separated by pole pieces which are made of metals to intensify the magnetic field strength. The effect of the thickness and the use of different materials with different permeability for pole pieces is also studied to obtain an optimal energy harvesting efficiency. Moreover, the procedure to find the restoring force applied to the levitating magnet stack is demonstrated. Then, the Duffing vibration equation of the harvester is solved and the frequency response function is calculated for various force amplitudes and electrical damping so as to investigate the effect of these parameters on the response of the system. Furthermore, the effect of the maximum displacement of the moving magnet stack on the natural frequency of the device is studied. And finally, Faraday's law is employed to estimate the output voltage and power of the system under the specified input excitation force. Experiments show that the output emf voltage of the manufactured prototype reaches up to 42 V for an excitation force with the frequency of 9 Hz and the maximum amplitude of 3.4 g.

  5. Effect of compartmentalization of donor and acceptor on the ultrafast resonance energy transfer from DAPI to silver nanoclusters

    NASA Astrophysics Data System (ADS)

    Prajapati, Roopali; Chatterjee, Surajit; Kannaujiya, Krishna K.; Mukherjee, Tushar Kanti

    2016-06-01

    The mechanism and dynamics of excitation energy transfer (EET) from photo-excited 4',6-diamidino-2-phenylindole (DAPI) to silver nanoclusters (Ag NCs) and its subsequent modulation in the presence of cationic polymer poly(diallyldimethylammonium chloride) (PDADMAC) and Calf Thymus DNA (CT-DNA) have been demonstrated using steady-state fluorescence and femtosecond fluorescence upconversion techniques. The synthesized Ag NCs were characterized using FTIR, mass spectrometry, XPS, HRTEM, DLS, UV-Vis and PL spectroscopy. Mass spectrometric analysis reveals the formation of ultrasmall Ag4 NCs with a small amount of Ag5 NCs. UV-Vis and PL spectra reveal distinct molecular-like optoelectronic behaviour of these ultrasmall Ag NCs. The dihydrolipoic acid-capped Ag NCs strongly quench the fluorescence of DAPI with concomitant increase in its photoluminescence (PL) intensity at 675 nm. This steady-state fluorescence quenching proceeds with a significant shortening of the fluorescence lifetime of DAPI in the presence of Ag NCs, signifying the nonradiative Förster resonance energy transfer (FRET) from DAPI to Ag NCs. Various energy transfer parameters have been estimated from FRET theory. The present FRET pair shows a characteristic Förster distance of 2.45 nm and can be utilized as a reporter of short-range distances in various FRET based applications. Moreover, this nonradiative FRET is completely suppressed in the presence of both 0.2 wt% PDADMAC and CT-DNA. Our results reveal selective compartmentalization of Ag NCs and DAPI in the presence of 0.2 wt% PDADMAC and CT-DNA, respectively. This selective compartmentalization of donor and acceptor and the subsequent modification of the FRET process may find application in various sensing, photovoltaic, and light harvesting applications.The mechanism and dynamics of excitation energy transfer (EET) from photo-excited 4',6-diamidino-2-phenylindole (DAPI) to silver nanoclusters (Ag NCs) and its subsequent modulation in the presence

  6. Pressure and kinetic energy transport across the cavity mouth in resonating cavities.

    PubMed

    Bailey, Peter Roger; Abbá, Antonella; Tordella, Daniela

    2013-01-01

    Basic properties of the incompressible fluid motion in a rectangular cavity located along one wall of a plane channel are considered. For Mach numbers of the order of 1×10(-3) and using the incompressible formulation, we look for observable properties that can be associated with acoustic emission, which is normally observed in this kind of flow beyond a critical value of Reynolds number. The focus is put on the energy dynamics, in particular on the accumulation of energy in the cavity which takes place in the form of pressure and kinetic energy. By increasing the external forcing, we observe that the pressure flow into the cavity increases very rapidly, then peaks. However, the flow of kinetic energy, which is many orders of magnitude lower than that of the pressure, slowly but continuously grows. This leads to the pressure-kinetic energy flows ratio reaching an asymptotic state around the value 1000 for the channel bulk speed Reynolds number. It is interesting to note that beyond this threshold when the channel flow is highly unsteady-a sort of coarse turbulent flow-a sequence of high and low pressure spots is seen to depart from the downward cavity step in the statistically averaged field. The set of spots forms a steady spatial structure, a sort of damped standing wave stretching along the spanwise direction. The line joining the centers of the spots has an inclination similar to the normal to the fronts of density or pressure waves, which are observed to propagate from the downstream cavity edge in compressible cavity flows (at Mach numbers of 1×10(2) to 1×10(3), larger than those considered here). The wavelength of the standing wave is of the order of 1/8 the cavity depth and observed at the channel bulk Reynolds number, Re~2900. In this condition, the measure of the maximum pressure differences in the cavity field shows values of the order of 1×10(-1) Pa. We interpret the presence of this sort of wave as the fingerprint of the noise emission spots which

  7. Pressure and kinetic energy transport across the cavity mouth in resonating cavities.

    PubMed

    Bailey, Peter Roger; Abbá, Antonella; Tordella, Daniela

    2013-01-01

    Basic properties of the incompressible fluid motion in a rectangular cavity located along one wall of a plane channel are considered. For Mach numbers of the order of 1×10(-3) and using the incompressible formulation, we look for observable properties that can be associated with acoustic emission, which is normally observed in this kind of flow beyond a critical value of Reynolds number. The focus is put on the energy dynamics, in particular on the accumulation of energy in the cavity which takes place in the form of pressure and kinetic energy. By increasing the external forcing, we observe that the pressure flow into the cavity increases very rapidly, then peaks. However, the flow of kinetic energy, which is many orders of magnitude lower than that of the pressure, slowly but continuously grows. This leads to the pressure-kinetic energy flows ratio reaching an asymptotic state around the value 1000 for the channel bulk speed Reynolds number. It is interesting to note that beyond this threshold when the channel flow is highly unsteady-a sort of coarse turbulent flow-a sequence of high and low pressure spots is seen to depart from the downward cavity step in the statistically averaged field. The set of spots forms a steady spatial structure, a sort of damped standing wave stretching along the spanwise direction. The line joining the centers of the spots has an inclination similar to the normal to the fronts of density or pressure waves, which are observed to propagate from the downstream cavity edge in compressible cavity flows (at Mach numbers of 1×10(2) to 1×10(3), larger than those considered here). The wavelength of the standing wave is of the order of 1/8 the cavity depth and observed at the channel bulk Reynolds number, Re~2900. In this condition, the measure of the maximum pressure differences in the cavity field shows values of the order of 1×10(-1) Pa. We interpret the presence of this sort of wave as the fingerprint of the noise emission spots which

  8. Highly-efficient Förster Resonance Energy Transfer in hybrid organic/inorganic semiconductor nanostructures

    NASA Astrophysics Data System (ADS)

    Savateeva, Diana; Melnikau, Dzmitry; Rakovich, Yury P.

    2012-04-01

    Highly luminescent semiconductor nanocrystals or quantum dots (QDs) possess a number of interesting and important properties that are tunable thanks to their size-dependent discrete electronic spectra. In this work we studied the optical properties of a novel type of hybrid structures that combine CdTe QDs with organic dye molecules (Pseudocyanine iodide) in a J-aggregate state. Due to the excitonic nature of electronic excitations, J-aggregates have the narrowest absorption and luminescence bands among organic materials, large oscillator strengths and giant third-order nonlinear susceptibility. In developed structures optical energy harvested by the quantum dots as artificial antennas then transferred to J-aggregates to enhance the photostability and efficiency of the carriers recombination. To fabricate CdTe/J-aggregates hybrid nanostructures we have used an approach based on electrostatic interaction between the positively charged dye and CdTe QDs capped with thioglycolic acid and, thus, carrying a negative charge. In order to develop an efficient hybrid material operating in the FRET regime, we carefully selected the PL colors (diameters) of the QD to be optically coupled with absorption of J-aggregates. We took advantage of extremely thin ligand shell (~0.5 nm) of CdTe QDs, which insures high efficiency of energy transfer. Formed QD/J-aggregate FRET system shows the broadband absorption in the visible and the ultraviolet part of the spectrum typical of QDs, along with the narrow emission linewidths characteristic of J-band emitters (~15 nm full width at half-maximum). We use absorption and photoluminescence spectroscopy and photoluminescence lifetime studies to conclude that efficiency of energy transfer is 95%. Also we report on development of active whispering-gallery microcavities integrated with with hybrid QDs/J-aggregate shell. Results of micro-PL spectroscopy and PL lifetime imaging confirm strong quenching of QDs emission and multifold shortening of

  9. Ion-Switchable Quantum Dot Förster Resonance Energy Transfer Rates in Ratiometric Potassium Sensors.

    PubMed

    Ruckh, Timothy T; Skipwith, Christopher G; Chang, Wendi; Senko, Alexander W; Bulovic, Vladimir; Anikeeva, Polina O; Clark, Heather A

    2016-04-26

    The tools for optically imaging cellular potassium concentrations in real-time are currently limited to a small set of molecular indicator dyes. Quantum dot-based nanosensors are more photostable and tunable than organic indicators, but previous designs have fallen short in size, sensitivity, and selectivity. Here, we introduce a small, sensitive, and selective nanosensor for potassium measurements. A dynamic quencher modulates the fluorescence emitted by two different quantum dot species to produce a ratiometric signal. We characterized the potassium-modulated sensor properties and investigated the photonic interactions within the sensors. The quencher's protonation changes in response to potassium, which modulates its Förster radiative energy transfer rate and the corresponding interaction radii with each quantum dot species. The nanosensors respond to changes in potassium concentrations typical of the cellular environment and thus provide a promising tool for imaging potassium fluxes during biological events.

  10. Compact denatured state of a staphylococcal nuclease mutant by guanidinium as determined by resonance energy transfer.

    PubMed

    James, E; Wu, P G; Stites, W; Brand, L

    1992-10-27

    The protein from a mutant clone of staphylococcal nuclease with a cysteine substituting for a lysine at position 78 was prepared and labeled with a cysteine-specific fluorescent probe 5-[[2-[(iodoacetyl)-amino]ethyl]amino]naphthalene-1-sulfonic acid (IAEDANS). Time-resolved nonradiative energy-transfer studies were done using the single tryptophan at position 140 as the energy donor and the IAEDANS as the receptor. Changes in distance and distance distributions were observed as a function of increasing guanidinium (GuHCl) concentration (0-2 M) and in the presence or absence of Ca2+ and inhibitor 2'-deoxythymidine 3',5'-diphosphate (pdTp). In the native state, both the ternary complex and the noncomplexed protein are best fit with one population having an average donor-acceptor distance of approximately 23 A and an "apparent" full width at half-maximum (fwhm) of distance distribution of approximately 18 A. Besides the contribution of linker arm of the acceptor, it appears that there are some conformational heterogeneties either due to the disordering of the tryptophan region or due to the whole protein in the native state. During GuHCl unfolding, the average distance remains relatively constant up to GuHCl concentrations where both the ternary complex and the ligand-free protein are denatured (1-1.3 M). The compact denatured states persist up to 2 M GuHCl. At 2 M GuHCl, the heterogeneity of the denatured state in the ternary complex is much larger than that of the ligand-free nuclease. The results show that the denatured states of staphylococcal nuclease mutant K78C by GuHCl are compact and these compact denatured states are likely due to residual structures or incompletely disrupted hydrophobic cores under these conditions.

  11. Phenomena of nonlinear oscillation and special resonance of a dielectric elastomer minimum energy structure rotary joint

    NASA Astrophysics Data System (ADS)

    Zhao, Jianwen; Niu, Junyang; McCoul, David; Ren, Zhi; Pei, Qibing

    2015-03-01

    The dielectric elastomer minimum energy structure can realize large angular deformations by a small voltage-induced strain of the dielectric elastomer, so it is a suitable candidate to make a rotary joint for a soft robot. Driven with an alternating electric field, the joint deformation vibrational frequency follows the input voltage frequency. However, the authors find that if the rotational inertia increases such that the inertial torque makes the frame deform over a negative angle, then the joint motion will become complicated and the vibrational mode will alter with the change of voltage frequency. The vibration with the largest amplitude does not occur while the voltage frequency is equal to natural response frequency of the joint. Rather, the vibrational amplitude will be quite large over a range of other frequencies at which the vibrational frequency is half of the voltage frequency. This phenomenon was analyzed by a comparison of the timing sequences between voltage and joint vibration. This vibrational mode with the largest amplitude can be applied to the generation lift in a flapping wing actuated by dielectric elastomers.

  12. 3D Atomic Arrangement at Functional Interfaces Inside Nanoparticles by Resonant High-Energy X-ray Diffraction.

    PubMed

    Petkov, Valeri; Prasai, Binay; Shastri, Sarvjit; Chen, Tsan-Yao

    2015-10-21

    With current science and technology moving rapidly into smaller scales, nanometer-sized materials, often referred to as NPs, are produced in increasing numbers and explored for numerous useful applications. Evidence is mounting, however, that useful properties of NPs can be improved further and even new NP functionality achieved by not only controlling the NP size and shape but also interfacing chemically or structurally distinct entities into single, so-called "composite" NPs. A typical example is core-shell NPs wherein the synergy of distinct atoms at the core\\shell interface endows the NPs with otherwise unachievable functionality. However, though advantageous, the concept of functional interfaces inside NPs is still pursued largely by trial-and-error. That is because it is difficut to assess the interfaces precisely at the atomic level using traditional experimental techniques and, hence, difficult to take control of. Using the core\\shell interface in less than 10 nm in size Ru core-Pt shells NPs as an example, we demonstrate that precise knowledge of the 3D atomic arrangement at functional interfaces inside NPs can be obtained by resonant high-energy X-ray diffraction (XRD) coupled to element-specific atomic pair distribution function (PDF) analysis. On the basis of the unique structure knowledge obtained, we scrutinize the still-debatable influence of core\\shell interface on the catalytic functionality of Ru core-Pt shell NPs, thus evidencing the usefulness of this nontraditional technique for practical applications.

  13. A Quantitative Theoretical Framework For Protein-Induced Fluorescence Enhancement-Förster-Type Resonance Energy Transfer (PIFE-FRET).

    PubMed

    Lerner, Eitan; Ploetz, Evelyn; Hohlbein, Johannes; Cordes, Thorben; Weiss, Shimon

    2016-07-01

    Single-molecule, protein-induced fluorescence enhancement (PIFE) serves as a molecular ruler at molecular distances inaccessible to other spectroscopic rulers such as Förster-type resonance energy transfer (FRET) or photoinduced electron transfer. In order to provide two simultaneous measurements of two distances on different molecular length scales for the analysis of macromolecular complexes, we and others recently combined measurements of PIFE and FRET (PIFE-FRET) on the single molecule level. PIFE relies on steric hindrance of the fluorophore Cy3, which is covalently attached to a biomolecule of interest, to rotate out of an excited-state trans isomer to the cis isomer through a 90° intermediate. In this work, we provide a theoretical framework that accounts for relevant photophysical and kinetic parameters of PIFE-FRET, show how this framework allows the extraction of the fold-decrease in isomerization mobility from experimental data, and show how these results provide information on changes in the accessible volume of Cy3. The utility of this model is then demonstrated for experimental results on PIFE-FRET measurement of different protein-DNA interactions. The proposed model and extracted parameters could serve as a benchmark to allow quantitative comparison of PIFE effects in different biological systems.

  14. Analyzing conformational dynamics of single P-glycoprotein transporters by Förster resonance energy transfer using hidden Markov models

    PubMed Central

    Zarrabi, Nawid; Ernst, Stefan; Verhalen, Brandy; Wilkens, Stephan; Börsch, Michael

    2013-01-01

    Single-molecule Förster resonance energy (smFRET) transfer has become a powerful tool for observing conformational dynamics of biological macromolecules. Analyzing smFRET time trajectories allows to identify the state transitions occuring on reaction pathways of molecular machines. Previously, we have developed a smFRET approach to monitor movements of the two nucleotide binding domains (NBDs) of P-glycoprotein (Pgp) during ATP hydrolysis driven drug transport in solution. One limitation of this initial work was that single-molecule photon bursts were analyzed by visual inspection with manual assignment of individual FRET levels. Here a fully automated analysis of Pgp smFRET data using hidden Markov models (HMM) for transitions up to 9 conformational states is applied. We propose new estimators for HMMs to integrate the information of fluctuating intensities in confocal smFRET measurements of freely diffusing lipid bilayer bound membrane proteins in solution. HMM analysis strongly supports that under conditions of steady state turnover, conformational states with short NBD distances and short dwell times are more populated compared to conditions without nucleotide or transport substrate present. PMID:23891547

  15. Highly sensitive determination of antimony in food by resonance Rayleigh scattering-energy transfer between grapheme oxide and I3(.).

    PubMed

    Wen, Guiqing; Zhang, Xinghui; Li, Yuan; Luo, Yanghe; Liang, Aihui; Jiang, Zhiliang

    2017-01-01

    Sb(III) was reduced to SbH3 gas and introduced to the I3(-)-grapheme oxide (GO) or I3(-)-silver nanorod (AgNR)-Victoria blue B (VBB) solutions. Resonance Rayleigh scattering energy transfer (RRS-ET) occurred between the donor GO and the acceptor I3(-) due to the overlap between the absorption peak of I3(-) and RRS peak of GO. When I3(-) was reduced by SbH3, RRS-ET weakened and the RRS intensity enhanced. The increased RRS intensity was linear to Sb concentration in the range of 2.1-376.6μg/L. In the I3(-)-AgNR-VBB solution, I3(-) combined with VBB to form VBB-I3 and there was a weak surface-enhanced Raman scattering (SERS) effect. When SbH3 reduced I3(-), the SERS intensity increased due to the release of SERS active VBB. The enhanced SERS intensity was linear for Sb concentration in the range of 8.4-292.9μg/L. The RRS-ET method was applied for determination of Sb in food with satisfactory results. PMID:27507443

  16. A Fluorescence Resonance Energy Transfer Assay For Monitoring α- Synclein Aggregation in a Caenorhabditis Elegans Model For Parkinson's Disease.

    PubMed

    Nagarajan, Archana; Bodhicharla, Rakesh; Winter, Jody; Anbalagan, Charumathi; Morgan, Kevin; Searle, Mark; Nazir, Aamir; Adenle, Ademola; Fineberg, April; Brady, Declan; Vere, Kelly; Richens, Jo; O'Shea, Paul; Bell, David; de-Pomerai, David

    2015-01-01

    The aggregation of α-synuclein (Syn or S) to form insoluble fibrils is important in the pathogenesis of Parkinson's disease, but key risk factors remain ill-defined. We have developed Fluorescence Resonance Energy Transfer (FRET)-based assays for α-synuclein aggregation, using Green Fluorescent Protein variants Cerulean (C) or Venus (V), fused to each other (CV, VC) or to human synuclein (SC, SV etc). Bacterially expressed proteins were purified to homogeneity, and C-terminal fusions SC and SV largely retained their ability to aggregate in vitro. FRET signals from mixtures of SC and SV were used to monitor aggregation. These fusion genes were linked to the C. elegans unc-54 myosin promoter to generate integrated transgenic strains. Increased FRET signals, indicative of S aggregation, were observed following treatment of unc-54::SC + unc-54::SV double transgenic worms with low concentrations of mercury or chlorpyrifos, or with RNAi against hsp-70 and hip-1. Opposite changes in Yellow Fluorescent Protein (YFP) fluorescence in an unc-54::SV strain (NL5901) are likely to reflect FRET from Yellow Fluorescent Protein to aggregates of Syn fusion protein. This could provide the basis for a high throughput screening assay, which could be used for studying the effects of toxic chemicals and environmental pollutants on the aggregation of proteins such as Syn in vivo. PMID:26295817

  17. Microsecond protein folding events revealed by time-resolved fluorescence resonance energy transfer in a microfluidic mixer.

    PubMed

    Jiang, Liguo; Zeng, Yan; Sun, Qiqi; Sun, Yueru; Guo, Zhihong; Qu, Jianan Y; Yao, Shuhuai

    2015-06-01

    We demonstrate the combination of the time-resolved fluorescence resonance energy transfer (tr-FRET) measurement and the ultrarapid hydrodynamic focusing microfluidic mixer. The combined technique is capable of probing the intermolecular distance change with temporal resolution at microsecond level and structural resolution at Angstrom level, and the use of two-photon excitation enables a broader exploration of FRET with spectrum from near-ultraviolet to visible wavelength. As a proof of principle, we used the coupled microfluidic laminar flow and time-resolved two-photon excitation microscopy to investigate the early folding states of Cytochrome c (cyt c) by monitoring the distance between the tryptophan (Trp-59)-heme donor-acceptor (D-A) pair. The transformation of folding states of cyt c in the early 500 μs of refolding was revealed on the microsecond time scale. For the first time, we clearly resolved the early transient state of cyt c, which is populated within the dead time of the mixer (<10 μs) and has a characteristic Trp-59-heme distance of ∼31 Å. We believe this tool can find more applications in studying the early stages of biological processes with FRET as the probe.

  18. G protein-coupled receptor signaling analysis using homogenous time-resolved Förster resonance energy transfer (HTRF®) technology.

    PubMed

    Nørskov-Lauritsen, Lenea; Thomsen, Alex Rojas Bie; Bräuner-Osborne, Hans

    2014-01-01

    Studying multidimensional signaling of G protein-coupled receptors (GPCRs) in search of new and better treatments requires flexible, reliable and sensitive assays in high throughput screening (HTS) formats. Today, more than half of the detection techniques used in HTS are based on fluorescence, because of the high sensitivity and rich signal, but quenching, optical interferences and light scattering are serious drawbacks. In the 1990s the HTRF® (Cisbio Bioassays, Codolet, France) technology based on Förster resonance energy transfer (FRET) in a time-resolved homogeneous format was developed. This improved technology diminished the traditional drawbacks. The optimized protocol described here based on HTRF® technology was used to study the activation and signaling pathways of the calcium-sensing receptor, CaSR, a GPCR responsible for maintaining calcium homeostasis. Stimulation of the CaSR by agonists activated several pathways, which were detected by measuring accumulation of the second messengers D-myo-inositol 1-phosphate (IP1) and cyclic adenosine 3',5'-monophosphate (cAMP), and by measuring the phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/2). Here we show how an optimized HTRF® platform with numerous advantages compared to previous assays provides a substantial and robust mode of investigating GPCR signaling. It is furthermore discussed how these assays can be optimized and miniaturized to meet HTS requirements and for screening compound libraries.

  19. [Study of TGF-β/Smad3 signal pathway using the technology of flurorescence resonance energy transfer].

    PubMed

    Cao, Weiwei; Liu, Wei; Wang, Weishan; Chen, Zhao; He, Renhao; He, Jianwei

    2014-10-01

    The transforming growth factor-β1 (TGF-β1)/Smad3 signal pathway is related to mutiple physiological and pathological generation mechanism of human being. Up to date, however, the spacial and time information on the phosphorylated Smad3 is still unclear. In this study, the process of Smad3 phosphorylation was observed under the physiological state in the living cells. Firstly, the ECFP-Smad3-Citrine (Smad3 biosensor) fusion protein expression vector was constructed and identified. Then the Smad3 biosensor was transfected into 293T cells. The transfection efficiency and the expressions of fusion proteins were observed in 24 hours. Thirdly, Smad3 biosensor flurorescence resonance energy transfer (FRET) was observed with the inversion fluorescence microscope and measured by the MetaFlour FRET 4. 6 software. Smad3 biosensor transfection efficiency was nearly 40% and the fusion protein was seen under the fluorescence microscope. The FRET ratio of Smad3 biosensor in living 293T cells was decreased after 10 minutes incubation with the ligand of TGF-β1. The period of decreasing CFP and enhancing Citrine signals was about 300 seconds. With the technology of FRET, the TGF-β1/Smad3 signal pathway could be real time monitored dynamically under the physiological condition in living cells.

  20. Homomultimerization of the Coxsackievirus 2B Protein in Living Cells Visualized by Fluorescence Resonance Energy Transfer Microscopy

    PubMed Central

    van Kuppeveld, Frank J. M.; Melchers, Willem J. G.; Willems, Peter H. G. M.; Gadella, Jr., Theodorus W. J.

    2002-01-01

    The 2B protein of enteroviruses is the viral membrane-active protein that is responsible for the modifications in host cell membrane permeability that take place in enterovirus-infected cells. The 2B protein shows structural similarities to the group of lytic polypeptides, polypeptides that permeate membranes either by forming multimeric membrane-integral pores or, alternatively, by lying parallel to the lipid bilayer and disturbing the curvature and symmetry of the membrane. Our aim is to gain more insight into the molecular architecture of the 2B protein in vivo. In this study, the possible existence of multimers of the coxsackie B3 virus 2B protein in single living cells was explored by fluorescence resonance energy transfer (FRET) microscopy. FRET between fusion proteins 2B-ECFP and 2B-EYFP (enhanced cyan and yellow fluorescent variants of green fluorescent protein) was monitored by using spectral imaging microscopy (SPIM) and fluorescence lifetime imaging microscopy (FLIM). Both techniques revealed the occurrence of intermolecular FRET between 2B-ECFP and 2B-EYFP, providing evidence for the formation of protein 2B homomultimers. Putative models for the mode of action of the membrane-active 2B protein and the formation of membrane-integral pores by 2B multimers are discussed. PMID:12186926