A reduced graphene oxide-based fluorescence resonance energy transfer sensor for highly sensitive detection of matrix metalloproteinase 2.

Science.gov (United States)

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.

Detection of Thrombin Based on Fluorescence Energy Transfer between Semiconducting Polymer Dots and BHQ-Labelled Aptamers

Directory of Open Access Journals (Sweden)

Yizhang Liu

2018-02-01

Full Text Available Carboxyl-functionalized semiconducting polymer dots (Pdots were synthesized as an energy donor by the nanoprecipitation method. A black hole quenching dye (BHQ-labelled thrombin aptamers was used as the energy acceptor, and fluorescence resonance energy transfer between the aptamers and Pdots was used for fluorescence quenching of the Pdots. The addition of thrombin restored the fluorescence intensity. Under the optimized experimental conditions, the fluorescence of the system was restored to the maximum when the concentration of thrombin reached 130 nM, with a linear range of 0–50 nM (R2 = 0.990 and a detection limit of 0.33 nM. This sensor was less disturbed by impurities, showing good specificity and signal response to thrombin, with good application in actual samples. The detection of human serum showed good linearity in the range of 0–30 nM (R2 = 0.997, with a detection limit of 0.56 nM and a recovery rate of 96.2–104.1%, indicating that this fluorescence sensor can be used for the detection of thrombin content in human serum.

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

Science.gov (United States)

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.

Simulation of fluorescence resonance energy transfer experiments: effect of the dyes on protein folding

International Nuclear Information System (INIS)

Allen, Lucy R; Paci, Emanuele

2010-01-01

Fluorescence resonance energy transfer is a powerful technique which is often used to probe the properties of proteins and complex macromolecules. The technique relies on relatively large fluorescent dyes which are engineered into the molecule of interest. In the case of small proteins, these dyes may affect the stability of the protein, and modify the folding kinetics and the folding mechanisms which are being probed. Here we use atomistic simulation to investigate the effect that commonly used fluorescent dyes have on the folding of a four-helix bundle protein. We show that, depending on where the dyes are attached, their effect on the kinetic and thermodynamic properties of the protein may be significant. We find that, while the overall folding mechanism is not affected by the dyes, they can destabilize, or even stabilize, intermediate states.

Cardiac Calcium ATPase Dimerization Measured by Cross-Linking and Fluorescence Energy Transfer.

Science.gov (United States)

Blackwell, Daniel J; Zak, Taylor J; Robia, Seth L

2016-09-20

The cardiac sarco/endoplasmic reticulum calcium ATPase (SERCA) establishes the intracellular calcium gradient across the sarcoplasmic reticulum membrane. It has been proposed that SERCA forms homooligomers that increase the catalytic rate of calcium transport. We investigated SERCA dimerization in rabbit left ventricular myocytes using a photoactivatable cross-linker. Western blotting of cross-linked SERCA revealed higher-molecular-weight species consistent with SERCA oligomerization. Fluorescence resonance energy transfer measurements in cells transiently transfected with fluorescently labeled SERCA2a revealed that SERCA readily forms homodimers. These dimers formed in the absence or presence of the SERCA regulatory partner, phospholamban (PLB) and were unaltered by PLB phosphorylation or changes in calcium or ATP. Fluorescence lifetime data are compatible with a model in which PLB interacts with a SERCA homodimer in a stoichiometry of 1:2. Together, these results suggest that SERCA forms constitutive homodimers in live cells and that dimer formation is not modulated by SERCA conformational poise, PLB binding, or PLB phosphorylation. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Fluorescence resonance energy transfer: A promising tool for investigation of the interaction between 1-anthracene sulphonate and serum albumins

International Nuclear Information System (INIS)

Banerjee, Paltu; Ghosh, Saptaparni; Sarkar, Arindam; Bhattacharya, Subhash Chandra

2011-01-01

This present investigation has revealed that steady state as well as time-resolved fluorescence techniques can serve as highly sensitive monitors for exploring the interaction of fluorescent probe 1-anthracene sulphonate (1-AS) with model transport proteins, bovine serum albumin (BSA) and human serum albumin (HSA).We have focused on fluorescence resonance energy transfer (FRET) between excited tryptophan in transport proteins to 1-AS, for the study of relaxation dynamics of biological molecules.

Fluorescence Resonance Energy Transfer in Polydiacetylene Liposomes

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Li, Xuelian; Matthews, Shelton; Kohli, Punit

2009-01-01

Conjugated polydiacetylene (PDA) possessing stimuli-responsive properties has been intensively investigated for developing efficient sensors. We report here fluorescence resonance energy transfer (FRET) in liposomes synthesized using different molar ratios of dansyl-tagged diacetylene and diacetylene–carboxylic acid monomers. Photopolymerization of diacetylene resulted in cross-linked PDA liposomes. We used steady-state electronic absorption, emission, and fluorescence anisotropy (FA) analysis to characterize the thermal-induced FRET between dansyl fluorophores (donor) and PDA (acceptor). We found that the monomer ratio of acceptor to donor (Rad) and length of linkers (functional part that connects dansyl fluorophores to the diacetylene group in the monomer) strongly affected FRET. For Rad = 10 000, the acceptor emission intensity was amplified by more than 18 times when the liposome solution was heated from 298 to 338 K. A decrease in Rad resulted in diminished acceptor emission amplification. This was primarily attributed to lower FRET efficiency between donors and acceptors and a higher background signal. We also found that the FRET amplification of PDA emissions after heating the solution was much higher when dansyl was linked to diacetylene through longer and flexible linkers than through shorter linkers. We attributed this to insertion of dansyl in the bilayer of the liposomes, which led to an increased dansyl quantum yield and a higher interaction of multiple acceptors with limited available donors. This was not the case for shorter and more rigid linkers where PDA amplification was much smaller. The present studies aim at enhancing our understanding of FRET between fluorophores and PDA-based conjugated liposomes. Furthermore, receptor tagged onto PDA liposomes can interact with ligands present on proteins, enzymes, and cells, which will produce emission sensing signal. Therefore, using the present approach, there exist opportunities for designing FRET

Energy transfer properties and mechanisms

International Nuclear Information System (INIS)

Barker, J.R.

1993-01-01

Since no single experimental technique is the best method for energy transfer experiments, we have used both time-dependent infrared fluorescence (IRF) and time-dependent thermal lensing (TDTL) to study energy transfer in various systems. We are investigating pump-probe techniques employing resonance enhanced multiphoton ionization (REMPI). IRF was used to study benzene, azulene, and toluene. TDTL was used to study CS 2 and SO 2 (data not given for latter). Large molecule energy transfer mechanisms are discussed. 10 figs

Energy transfer in Anabaena variabilis filaments adapted to nitrogen-depleted and nitrogen-enriched conditions studied by time-resolved fluorescence.

Science.gov (United States)

Onishi, Aya; Aikawa, Shimpei; Kondo, Akihiko; Akimoto, Seiji

2017-09-01

Nitrogen is among the most important nutritious elements for photosynthetic organisms such as plants, algae, and cyanobacteria. Therefore, nitrogen depletion severely compromises the growth, development, and photosynthesis of these organisms. To preserve their integrity under nitrogen-depleted conditions, filamentous nitrogen-fixing cyanobacteria reduce atmospheric nitrogen to ammonia, and self-adapt by regulating their light-harvesting and excitation energy-transfer processes. To investigate the changes in the primary processes of photosynthesis, we measured the steady-state absorption and fluorescence spectra and time-resolved fluorescence spectra (TRFS) of whole filaments of the nitrogen-fixing cyanobacterium Anabaena variabilis at 77 K. The filaments were grown in standard and nitrogen-free media for 6 months. The TRFS were measured with a picosecond time-correlated single photon counting system. Despite the phycobilisome degradation, the energy-transfer paths within phycobilisome and from phycobilisome to both photosystems were maintained. However, the energy transfer from photosystem II to photosystem I was suppressed and a specific red chlorophyll band appeared under the nitrogen-depleted condition.

A study of the compartmentalization of core-shell nanoparticles through fluorescence energy transfer of dopants

Energy Technology Data Exchange (ETDEWEB)

Chavez, Jorge L; Jiang Hui; Duran, Randolph S, E-mail: rduran@lsu.edu [Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611 (United States)

2010-02-05

Hybrid organic-inorganic templates and core-shell nanoparticles were used as models to study the communication between fluorescent probes placed inside nanoparticles. The hybrid templates were prepared on the basis of a mixed-surfactant system using octadecyltrimethoxysilane as a reactive amphiphile. The core-shell particles were obtained after coating of the templates with a siloxane shell, using the silanol groups on their surface. Atomic force microscopy imaging showed that the templates were made of a flexible material that flattened significantly after deposition on a substrate and evaporation of the solvent. Pyrene was sequestered by the templates in an aqueous suspension, which placed it in a nonpolar environment, as observed by its fluorescence response. Subsequently, double-doped templates were prepared by sequestering coumarin 153 (C153), with pyrene-doped hybrid templates. The communication between these probes was studied on the basis of their spectral properties, by means of fluorescence resonance energy transfer (FRET). Energy transfer between the dyes with efficiencies up to 55% was observed. Similarly, double-doped core-shell particles prepared on the basis of the hybrid templates were doped with this pair of dyes. Despite the presence of the shell, which was intended to increment the average separation between the probes, interaction of the dyes was observed, although with lower efficiencies. A similar study was performed with C153 and 4-(dicyanomethylene)-2-methyl-6-p-(dimethylamino)styryl-4H-pyran (DCM). FRET studies indicated that the probes were placed in proximity to each other. We confirmed these observations by means of fluorescence lifetime measurements, which showed a decrease in the lifetime of the donor upon addition of the acceptor.

Dimeric fluorescent energy transfer dyes comprising asymmetric cyanine azole-indolenine chromophores

Science.gov (United States)

Glazer, Alexander N.; Benson, Scott C.

1998-01-01

Novel fluorescent heterodimeric DNA-staining energy transfer dyes are provided combining asymmetric cyanine azole-indolenine dyes, which provide for strong DNA affinity, large Stokes shifts and emission in the red region of the spectrum. The dyes find particular application in gel electrophoresis and for labels which may be bound to a variety of compositions in a variety of contexts. Kits and individual compounds are provided, where the kits find use for simultaneous detection of a variety of moieties, particularly using a single narrow wavelength irradiation source. The individual compounds are characterized by high donor quenching and high affinity to dsDNA as a result of optimizing the length of the linking group separating the two chromophores.

Design and fabrication of fluorescence resonance energy transfer-mediated fluorescent polymer nanoparticles for ratiometric sensing of lysosomal pH.

Science.gov (United States)

Chen, Jian; Tang, Ying; Wang, Hong; Zhang, Peisheng; Li, Ya; Jiang, Jianhui

2016-12-15

The design of effective tools capable of sensing lysosome pH is highly desirable for better understanding its biological functions in cellular behaviors and various diseases. Herein, a lysosome-targetable ratiometric fluorescent polymer nanoparticle pH sensor (RFPNS) was synthesized via incorporation of miniemulsion polymerization and surface modification technique. In this system, the donor: 4-ethoxy-9-allyl-1,8-naphthalimide (EANI) and the acceptor: fluorescein isothiocyanate (FITC) were covalently linked to the polymer nanoparticle to construct pH-responsive fluorescence resonance energy transfer (FRET) system. The FITC moieties on the surface of RFPNS underwent structural and spectral transformation as the presence of pH changes, resulting in ratiometric fluorescent sensing of pH. The as-prepared RFPNS displayed favorable water dispersibility, good pH-induced spectral reversibility and so on. Following the living cell uptake, the as-prepared RFPNS with good cell-membrane permeability can mainly stain in the lysosomes; and it can facilitate visualization of the intracellular lysosomal pH changes. This nanosensor platform offers a novel method for future development of ratiometric fluorescent probes for targeting other analytes, like ions, metabolites,and other biomolecules in biosamples. Copyright © 2016 Elsevier Inc. All rights reserved.

Diphenylacrylonitrile-connected BODIPY dyes: fluorescence enhancement based on dark and AIE resonance energy transfer.

Science.gov (United States)

Lin, Liangbin; Lin, Xiaoru; Guo, Hongyu; Yang, Fafu

2017-07-19

This study focuses on the construction of novel diphenylacrylonitrile-connected BODIPY dyes with high fluorescence in both solution and an aggregated state by combining DRET and FRET processes in a single donor-acceptor system. The first BODIPY derivatives with one, two, or three AIE-active diphenylacrylonitrile groups were designed and synthesized in moderate yields. Strong fluorescence emissions were observed in the THF solution under excitation at the absorption wavelength of non-emissive diphenylacrylonitrile chromophores, implying the existence of the DRET process between the dark diphenylacrylonitrile donor and the emissive BODIPY acceptor. In the THF/H 2 O solution, the fluorescence intensity of the novel BODIPY derivatives gradually increased under excitation at the absorption wavelength of diphenylacrylonitrile chromophores, suggesting a FRET process between diphenylacrylonitrile and BODIPY moieties. A greater number of diphenylacrylonitrile units led to higher energy-transfer efficiencies. The pseudo-Stokes shift for both DRET and FRET processes was as large as 190 nm.

Relocation of the disulfonic stilbene sites of AE1 (band 3) on the basis of fluorescence energy transfer measurements.

Science.gov (United States)

Knauf, Philip A; Law, Foon-Yee; Leung, Tze-Wah Vivian; Atherton, Stephen J

2004-09-28

Previous fluorescence resonance energy transfer (FRET) measurements, using BIDS (4-benzamido-4'-isothiocyanostilbene-2,2'-disulfonate) as a label for the disulfonic stilbene site and FM (fluorescein-5-maleimide) as a label for the cytoplasmic SH groups on band 3 (AE1), combined with data showing that the cytoplasmic SH groups lie about 40 A from the cytoplasmic surface of the lipid bilayer, would place the BIDS sites very near the membrane's inner surface, a location that seems to be inconsistent with current models of AE1 structure and mechanism. We reinvestigated the BIDS-FM distance, using laser single photon counting techniques as well as steady-state fluorescence of AE1, in its native membrane environment. Both techniques agree that there is very little energy transfer from BIDS to FM. The mean energy transfer (E), based on three-exponential fits to the fluorescence decay data, is 2.5 +/- 0.7% (SEM, N = 12). Steady-state fluorescence measurements also indicate BIDS to FM. These data indicate that the BIDS sites are probably over 63 A from the cytoplasmic SH groups, placing them near the middle or the external half of the lipid bilayer. This relocation of the BIDS sites fits with other evidence that the disulfonic stilbene sites are located farther toward the external membrane surface than Glu-681, a residue near the inner membrane surface whose modification affects the pH dependence and anion selectivity of band 3. The involvement of two relatively distant parts of the AE1 protein in transport function suggests that the transport mechanism requires coordinated large-scale conformational changes in the band 3 protein.

Effect of membrane microheterogeneity and domain size on fluorescence resonance energy transfer.

Science.gov (United States)

Towles, Kevin B; Brown, Angela C; Wrenn, Steven P; Dan, Nily

2007-07-15

Studies of multicomponent membranes suggest lateral inhomogeneity in the form of membrane domains, but the size of small (nanoscale) domains in situ cannot be determined with current techniques. In this article, we present a model that enables extraction of membrane domain size from time-resolved fluorescence resonance energy transfer (FRET) data. We expand upon a classic approach to the infinite phase separation limit and formulate a model that accounts for the presence of disklike domains of finite dimensions within a two-dimensional infinite planar bilayer. The model was tested against off-lattice Monte Carlo calculations of a model membrane in the liquid-disordered (l(d)) and liquid-ordered (l(o)) coexistence regime. Simulated domain size was varied from 5 to 50 nm, and two fluorophores, preferentially partitioning into opposite phases, were randomly mixed to obtain the simulated time-resolved FRET data. The Monte Carlo data show clear differences in the efficiency of energy transfer as a function of domain size. The model fit of the data yielded good agreement for the domain size, especially in cases where the domain diameter is membrane domains using time-resolved FRET.

Intermolecular energy transfer in binary systems of dye polymers

Science.gov (United States)

Liu, Lin-I.; Barashkov, Nikolay N.; Palsule, Chintamani P.; Gangopadhyay, Shubhra; Borst, Walter L.

2000-10-01

We present results and physical interpretations for the energy transfer mechanisms in two-component dye polymer systems. The data consist of fluorescence emission spectra and decays. Two dyes were embedded in an epoxypolymer base, and only they participated in the energy transfer. Following pulsed laser excitation of the donor dye, energy transfer took place to the accept dye. The possible transfer paths considered here were nonradiative and radiative transfer. The latter involves two steps, emission and absorption of a photon, and therefore is relatively slow, while nonradiative transfer is a fast single step resulting from direct Coulomb interactions. A predominantly nonradiative transfer is desirable for applications, for instance in wavelength shifters in high energy particle detection. We studied the concentration effects of the dyes on the energy transfer and obtained the relative quantum efficiencies of various wavelength shifters from the fluorescence emission spectra. For low acceptor concentrations, radiative transfer was found to dominate, while nonradiative transfer became dominant at increasing dye concentrations. The fluorescence decays were analyzed with a sum-of-exponentials method and with Förster kinetics. The sum of exponential model yielded mean decay times of the dye polymers useful for a general classification. The decay times decreased as desired with increasing acceptor concentration. The samples, in which nonradiative energy transfer dominated, were analyzed with Förster kinetics. As a result, the natural decay times of the donor and acceptor dyes and the critical radii for nonradiative energy transfer were obtained from a global best fit.

CH3 NH3 PbBr3 Perovskite Nanocrystals as Efficient Light-Harvesting Antenna for Fluorescence Resonance Energy Transfer.

Science.gov (United States)

Muthu, Chinnadurai; Vijayan, Anuja; Nair, Vijayakumar C

2017-05-04

Hybrid perovskites have created enormous research interest as a low-cost material for high-performance photovoltaic devices, light-emitting diodes, photodetectors, memory devices and sensors. Perovskite materials in nanocrystal form that display intense luminescence due to the quantum confinement effect were found to be particularly suitable for most of these applications. However, the potential use of perovskite nanocrystals as a light-harvesting antenna for possible applications in artificial photosynthesis systems is not yet explored. In the present work, we study the light-harvesting antenna properties of luminescent methylammonium lead bromide (CH 3 NH 3 PbBr 3 )-based perovskite nanocrystals using fluorescent dyes (rhodamine B, rhodamine 101, and nile red) as energy acceptors. Our studies revealed that CH 3 NH 3 PbBr 3 nanocrystals are an excellent light-harvesting antenna, and efficient fluorescence resonance energy transfer occurs from the nanocrystals to fluorescent dyes. Further, the energy transfer efficiency is found to be highly dependent on the number of anchoring groups and binding ability of the dyes to the surface of the nanocrystals. These observations may have significant implications for perovskite-based light-harvesting devices and their possible use in artificial photosynthesis systems. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Using Carbon Nanotubes for Nanometer-Scale Energy Transfer Microscopy

Science.gov (United States)

Johnston, Jessica; Shafran, Eyal; Mangum, Ben; Mu, Chun; Gerton, Jordan

2009-10-01

We investigate optical energy transfer between fluorophores and carbon nanotubes (CNTs). CNTs are grown on Si-oxide wafers by chemical vapor deposition (CVD), lifted off substrates by atomic force microscope (AFM) tips via Van der Waals forces, then shortened by electrical pulses. The tip-attached CNTs are scanned over fluorescent CdSe-ZnS quantum dots (QDs) with sub-nm precision while recording the fluorescence rate. A novel photon counting technique enables us to produce 3D maps of the QD-CNT coupling, revealing nanoscale lateral and vertical features. All CNTs tested (>50) strongly quenched the QD fluorescence, apparently independent of chirality. In some data, a delay in the recovery of QD fluorescence following CNT-QD contact was observed, suggesting possible charge transfer in this system. In the future, we will perform time-resolved studies to quantify the rate of energy and charge transfer processes and study the possible differences in fluorescence quenching and nanotube-QD energy transfer when comparing single-walled (SW) versus multi-walled (MW) CNTs, attempting to grow substrates consisting primarily of SW or MWCNTs and characterizing the structure of tip-attached CNTs using optical spectroscopy.

Fluorescence lifetime microscopy for monitoring cell adhesion using metal induced energy transfer

Science.gov (United States)

Hwang, Wonsang; Seo, JinWon; Song, Jun ho; Kim, DongEun; Won, YoungJae; Choi, In-Hong; Yoo, Kyung-Hwa; Kim, Dug Young

2018-02-01

A precise control and a reliable monitoring tool for the adhesion properties of a cell are very important in atherosclerosis studies. If endothelial cells in contact with the intracellular membrane are not attached securely, low-density lipoprotein (LDL) particles can enter into the inner membrane. It is therefore necessary to measure conditions under which endothelial cell detachment occurs. When a cell is attached to a metal thin film, the lifetime of a fluorescence probe attached to the membrane of the cell is reduced by the metal-induced energy transfer (MIET). Fluorescence lifetime imaging microscopy (FLIM) is used to monitor the attachment condition of a cell to a metal surface using FRET. However, this requires high numerical aperture (NA) objective lens because axial confocal resolution must be smaller than the cell thickness. This requirement limits the field of view of the measurement specimen. In this study we provides a new method which can measure adhesion properties of endothelial cells even with a low NA objective lens by resolving two lifetime components in FLIM.

Forster resonance energy transfer in the system of human serum albumin-xanthene dyes

Science.gov (United States)

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.

Decay time shortening of fluorescence from donor-acceptor pair proteins using ultrafast time-resolved fluorescence resonance energy transfer spectroscopy

International Nuclear Information System (INIS)

Baba, Motoyoshi; Suzuki, Masayuki; Ganeev, Rashid A.; Kuroda, Hiroto; Ozaki, Tsuneyuki; Hamakubo, Takao; Masuda, Kazuyuki; Hayashi, Masahiro; Sakihama, Toshiko; Kodama, Tatsuhiko; Kozasa, Tohru

2007-01-01

We improved an ultrafast time-resolved fluorescence resonance energy transfer (FRET) spectroscopy system and measured directly the decrease in the fluorescence decay time of the FRET signal, without any entanglement of components in the picosecond time scale from the donor-acceptor protein pairs (such as cameleon protein for calcium ion indicator, and ligand-activated GRIN-Go proteins pair). The drastic decrease in lifetime of the donor protein fluorescence under the FRET condition (e.g. a 47.8% decrease for a GRIN-Go protein pair) proves the deformation dynamics between donor and acceptor fluorescent proteins in an activated state of a mixed donor-acceptor protein pair. This study is the first clear evidence of physical contact of the GRIN-Go proteins pair using time-resolved FRET system. G protein-coupled receptors (GPCRs) are the most important protein family for the recognition of many chemical substances at the cell surface. They are the targets of many drugs. Simultaneously, we were able to observe the time-resolved spectra of luminous proteins at the initial stage under the FRET condition, within 10 ns from excitation. This new FRET system allows us to trace the dynamics of the interaction between proteins at the ligand-induced activated state, molecular structure change and combination or dissociation. It will be a key technology for the development of protein chip technology

A high-throughput direct fluorescence resonance energy transfer-based assay for analyzing apoptotic proteases using flow cytometry and fluorescence lifetime measurements.

Science.gov (United States)

Suzuki, Miho; Sakata, Ichiro; Sakai, Takafumi; Tomioka, Hiroaki; Nishigaki, Koichi; Tramier, Marc; Coppey-Moisan, Maïté

2015-12-15

Cytometry is a versatile and powerful method applicable to different fields, particularly pharmacology and biomedical studies. Based on the data obtained, cytometric studies are classified into high-throughput (HTP) or high-content screening (HCS) groups. However, assays combining the advantages of both are required to facilitate research. In this study, we developed a high-throughput system to profile cellular populations in terms of time- or dose-dependent responses to apoptotic stimulations because apoptotic inducers are potent anticancer drugs. We previously established assay systems involving protease to monitor live cells for apoptosis using tunable fluorescence resonance energy transfer (FRET)-based bioprobes. These assays can be used for microscopic analyses or fluorescence-activated cell sorting. In this study, we developed FRET-based bioprobes to detect the activity of the apoptotic markers caspase-3 and caspase-9 via changes in bioprobe fluorescence lifetimes using a flow cytometer for direct estimation of FRET efficiencies. Different patterns of changes in the fluorescence lifetimes of these markers during apoptosis were observed, indicating a relationship between discrete steps in the apoptosis process. The findings demonstrate the feasibility of evaluating collective cellular dynamics during apoptosis. Copyright © 2015 Elsevier Inc. All rights reserved.

Resonance Energy Transfer Molecular Imaging Application in Biomedicine

Directory of Open Access Journals (Sweden)

NIE Da-hong1,2;TANG Gang-hua1,3

2016-11-01

Full Text Available Resonance energy transfer molecular imaging (RETI can markedly improve signal intensity and tissue penetrating capacity of optical imaging, and have huge potential application in the deep-tissue optical imaging in vivo. Resonance energy transfer (RET is an energy transition from the donor to an acceptor that is in close proximity, including non-radiative resonance energy transfer and radiative resonance energy transfer. RETI is an optical imaging technology that is based on RET. RETI mainly contains fluorescence resonance energy transfer imaging (FRETI, bioluminescence resonance energy transfer imaging (BRETI, chemiluminescence resonance energy transfer imaging (CRETI, and radiative resonance energy transfer imaging (RRETI. RETI is the hot field of molecular imaging research and has been widely used in the fields of biology and medicine. This review mainly focuses on RETI principle and application in biomedicine.

A sensitive and selective fluorescence assay for metallothioneins by exploiting the surface energy transfer between rhodamine 6G and gold nanoparticles

International Nuclear Information System (INIS)

Yan, Yu-Qian; Tang, Xian; Wang, Yong-Sheng; Li, Ming-Hui; Cao, Jin-Xiu; Chen, Si-Han; Zhu, Yu-Feng; Wang, Xiao-Feng; Huang, Yan-Qin

2015-01-01

We report on a sensitive and selective strategy for the determination of metallothioneins (MTs). The assay is based on the suppression of the surface energy transfer that occurs between rhodamine 6G (Rh6G) and gold nanoparticles (AuNPs). If Rh6G is adsorbed onto the surface of AuNPs in water solution of pH 3.0, its fluorescence is quenched due to surface energy transfer. However, on addition of MTs to the Rh6G-AuNPs system, fluorescence is recovered owing to the formation of the MTs-AuNPs complex and the release of Rh6G into the solution. Under optimized conditions, the increase in fluorescence intensity is directly proportional to the concentration of the MTs in the range from 9.68 to 500 ng mL −1 , with a detection limit as low as 2.9 ng mL −1 . The possible mechanism of this assay is discussed. The method was successfully applied to the determination of MTs in (spiked) human urine. (author)

Deciphering the fluorescence resonance energy transfer from denatured transport protein to anthracene 1,5 disulphonate in reverse micellar environment

Science.gov (United States)

Singharoy, Dipti; Bhattacharya, Subhash Chandra

2017-12-01

Constrained environmental effect inside AOT reverse micellar media has been employed in this work to collect the information about energy transfer efficacy between sodium salt of anthracene 1,5 disulphonate (1,5-AS) with model transport proteins, bovine serum albumin (BSA), and human serum albumin (HSA). Steady state, time-resolved fluorescence and circular dichroism techniques have been used for this purpose and corresponding Fӧrster-type resonance energy transfer (FRET) from tryptophan residues to 1,5-AS indicates that 1,5-AS binds in the vicinity of the tryptophan residue (BSA and HSA) with equal strength. Indication of protein damage from fluorescence data and its confirmation has been measured from CD measurement. Molecular modeling study hereby plays a crucial role to predict the minimum energy docked conformation of the probe inside the protein environment. From the docked conformation the distance between 1,5-AS and tryptophan moiety of BSA/HSA has successfully explained the FRET possibility between them. A comparative modeling study between BSA and HSA with 1,5-AS assigning their binding site within specific amino acids plays a crucial role in support of the FRET study.

Distance distributions of short polypeptides recovered by fluorescence resonance energy transfer in the 10 A domain.

Science.gov (United States)

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.

Near infrared fluorescence and energy transfer in Ce/Nd Co-doped Ca{sub x}Sr{sub 1-x}S

Energy Technology Data Exchange (ETDEWEB)

Meng Jianxin, E-mail: tmjx@jnu.edu.c [Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China); Department of Chemistry, Jinan University, Guangzhou 510632 (China); Wan Wenjiao; Fan Lili; Yang Chuangtao; Chen Qingqing [Department of Chemistry, Jinan University, Guangzhou 510632 (China); Cao Liwei; Man Shiqing [Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China)

2011-01-15

Novel near infrared (NIR) phosphors Ca{sub x}Sr{sub 1-x}S:Ce{sup 3+},Nd{sup 3+} were synthesized by a solid state reaction. The NIR emission was realized through an efficient absorption by the allowed 4f-5d transition of Ce{sup 3+} and efficient energy transfer to Nd{sup 3+} via well-matched energy levels. Ce{sup 3+} and Nd{sup 3+} content in CaS/SrS was optimized. It was found that CaS:Ce{sup 3+},Nd{sup 3+} gave much stronger NIR emission than that of SrS:Ce{sup 3+},Nd{sup 3+}. Further studies on Ca{sub x}Sr{sub 1-x}S:Ce{sup 3+},Nd{sup 3+} indicated that both visible emission of Ce{sup 3+} and NIR emission of Nd{sup 3+} were observably affected by Ca/Sr ratio. The energy transfer efficiency, which can be estimated from fluorescence lifetime of Ce{sup 3+}, increased from 52% to 74% for the Ca{sub x}Sr{sub 1-x}S:Ce{sup 3+},Nd{sup 3+} (x=0 to 1) series, accompanied with a shift of maximal emission wavelength of Ce{sup 3+} from 482 to 505 nm. The results showed that overlap between emission spectrum of Ce{sup 3+} and excitation spectrum of Nd{sup 3+} plays an important role in the energy transfer efficiency, and Ce{sup 3+} emitting in green or blue-greenish region sensitized the Nd{sup 3+} NIR fluorescence emission more efficiently than that in blue region.

Hybrid Systems Based on Layered Silicate and Organic Dyes for Cascade Energy Transfer

Czech Academy of Sciences Publication Activity Database

Belušáková, S.; Lang, Kamil; Bujdák, J.

2015-01-01

Roč. 119, č. 38 (2015), s. 21784-21794 ISSN 1932-7447 Institutional support: RVO:61388980 Keywords : Cascade energy transfers * Multicomponent films * Resonance energy transfer * Spectral properties * Steady state fluorescence * Time-resolved fluorescence spectroscopy Subject RIV: CA - Inorganic Chemistry Impact factor: 4.509, year: 2015

Self-Assembled Fluorescent Nanoprobe Based on Forster Resonance Energy Transfer for Carbon Monoxide in Living Cells and Animals via Ligand Exchange.

Science.gov (United States)

Jia, Ruizhen; Song, Pengfei; Wang, Jingjing; Mai, Hengtang; Li, Sixian; Cheng, Yu; Wu, Song

2018-05-29

Carbon monoxide (CO) is recognized as a biologically essential gaseous neurotransmitter that modulates many physiological processes in living subjects. Currently reported fluorescent probes for CO imaging in cells basically utilize palladium related chemistry which requires complicated synthetic work. Herein we provide a new strategy to construct a fluorescent nanoprobe, NanoCO-1, based on the Forster resonance energy transfer (FRET) mechanism by entrapping the existing dirhodium complex as the energy acceptor and the CO recognition part, and a commonly used nitrobenzoxadiazole (NBD) dye as energy donor into a micelle formed by self-assembly. The exchange of ligands in the dirhodium complex by CO in the nanoprobe disrupts the FRET and leads to the turn-on of fluorescence. The merits of NanoCO-1 including good biocompatibility, selectivity, photostability, and low cytotoxity, render this nanoprobe ability to track CO in living cells, zebrafish embryo, and larvae. Our straightforward approach can be extended to establish the CO fluorescent probes based on adsorption of CO on a variety of metal derivatives.

Highly Sensitive Fluorescent Sensor for Cartap Based on Fluorescence Resonance Energy Transfer Between Gold Nanoparticles and Rhodamine B.

Science.gov (United States)

Dong, Liang; Hou, Changjun; Fa, Huanbao; Yang, Mei; Wu, Huixiang; Zhang, Liang; Huo, Danqun

2018-04-01

Cartap residue poses a great threat to human health and its derivatives would remain in soils, natural waters and other environmental domains for a long time. Herein, a simple, rapid and ultrasensitive analytical method for the determination of cartap based on fluorescence resonance energy transfer (FRET) between Au nanoparticles (AuNPs) and rhodamine B (RB) is first described. With the presence of citrate-stabilized AuNPs, the fluorescence of RB was remarkably quenched by AuNPs via FRET. The fluorescence of the AuNPs-RB system was recovered upon addition of cartap, cartap can be adsorbed on the surface of AuNPs due to its amino group that has good affinity with gold, which could induce the aggregation of AuNPs accompanying color change from red to blue. Thus, the FRET between AuNPs and RB was weakened and the PL intensity of RB was recovered accordingly. A good linear correlation for detection of RB was exhibited from 1 nM to 180 nM, and the detection limit reached 0.88 nM, which was much lower than the safety limit required by USA, UK and China. To the best of our knowledge, it has been the lowest detection ever without the aid of costly instrumentation. This method was successfully carried out for the assessment of cartap in real samples with satisfactory results, which revealed many advantages such as high sensitivity, low cost and non-time-consuming compared with traditional methods.

Energy transfer between surface-immobilized light-harvesting chlorophyll a/b complex (LHCII) studied by surface plasmon field-enhanced fluorescence spectroscopy (SPFS).

Science.gov (United States)

Lauterbach, Rolf; Liu, Jing; Knoll, Wolfgang; Paulsen, Harald

2010-11-16

The major light-harvesting chlorophyll a/b complex (LHCII) of the photosynthetic apparatus in green plants can be viewed as a protein scaffold binding and positioning a large number of pigment molecules that combines rapid and efficient excitation energy transfer with effective protection of its pigments from photobleaching. These properties make LHCII potentially interesting as a light harvester (or a model thereof) in photoelectronic applications. Most of such applications would require the LHCII to be immobilized on a solid surface. In a previous study we showed the immobilization of recombinant LHCII on functionalized gold surfaces via a 6-histidine tag (His tag) in the protein moiety. In this work the occurrence and efficiency of Förster energy transfer between immobilized LHCII on a functionalized surface have been analyzed by surface plasmon field-enhanced fluorescence spectroscopy (SPFS). A near-infrared dye was attached to some but not all of the LHC complexes, serving as an energy acceptor to chlorophylls. Analysis of the energy transfer from chlorophylls to this acceptor dye yielded information about the extent of intercomplex energy transfer between immobilized LHCII.

A new assay format for NF-kappaB based on a DNA triple helix and a fluorescence resonance energy transfer.

Science.gov (United States)

Altevogt, Dominik; Hrenn, Andrea; Kern, Claudia; Clima, Lilia; Bannwarth, Willi; Merfort, Irmgard

2009-10-07

Herein we report a feasibility study for a new concept to detect DNA binding protein NF-kappaB based on a DNA triple helix formation in combination with a fluorescence resonance energy transfer (FRET). The new principle avoids expensive antibodies and radioactivity and might have implications for assays of other DNA binding proteins.

Resonance energy transfer: Dye to metal nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Wari, M. N.; Pujar, G. H.; Inamdar, S. R., E-mail: him-lax3@yahoo.com [Laser Spectroscopy Programme, Department of Physics, Karnatak University, Dharwad-580003 (India)

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.

Detection of constitutive heterodimerization of the integrin Mac-1 subunits by fluorescence resonance energy transfer in living cells

International Nuclear Information System (INIS)

Fu Guo; Yang Huayan; Wang Chen; Zhang Feng; You Zhendong; Wang Guiying; He Cheng; Chen Yizhang; Xu Zhihan

2006-01-01

Macrophage differentiation antigen associated with complement three receptor function (Mac-1) belongs to β 2 subfamily of integrins that mediate important cell-cell and cell-extracellular matrix interactions. Biochemical studies have indicated that Mac-1 is a constitutive heterodimer in vitro. Here, we detected the heterodimerization of Mac-1 subunits in living cells by means of two fluorescence resonance energy transfer (FRET) techniques (fluorescence microscopy and fluorescence spectroscopy) and our results demonstrated that there is constitutive heterodimerization of the Mac-1 subunits and this constitutive heterodimerization of the Mac-1 subunits is cell-type independent. Through FRET imaging, we found that heterodimers of Mac-1 mainly localized in plasma membrane, perinuclear, and Golgi area in living cells. Furthermore, through analysis of the estimated physical distances between cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP) fused to Mac-1 subunits, we suggested that the conformation of Mac-1 subunits is not affected by the fusion of CFP or YFP and inferred that Mac-1 subunits take different conformation when expressed in Chinese hamster ovary (CHO) and human embryonic kidney (HEK) 293T cells, respectively

Comparison of the rate constants for energy transfer in the light-harvesting protein, C-phycocyanin, calculated from Foerster`s theory and experimentally measured by time-resolved fluorescence spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Debreczeny, Martin Paul [Univ. of California, Berkeley, CA (United States)

1994-05-01

We have measured and assigned rate constants for energy transfer between chromophores in the light-harvesting protein C-phycocyanin (PC), in the monomeric and trimeric aggregation states, isolated from Synechococcus sp. PCC 7002. In order to compare the measured rate constants with those predicted by Fdrster`s theory of inductive resonance in the weak coupling limit, we have experimentally resolved several properties of the three chromophore types ({beta}{sub 155} {alpha}{sub 84}, {beta}{sub 84}) found in PC monomers, including absorption and fluorescence spectra, extinction coefficients, fluorescence quantum yields, and fluorescence lifetimes. The cpcB/C155S mutant, whose PC is missing the {beta}{sub 155} chromophore, was, useful in effecting the resolution of the chromophore properties and in assigning the experimentally observed rate constants for energy transfer to specific pathways.

Targeting human c-Myc promoter duplex DNA with actinomycin D by use of multi-way analysis of quantum-dot-mediated fluorescence resonance energy transfer

DEFF Research Database (Denmark)

Gholami, Somayeh; Kompany Zare, Mohsen

2013-01-01

Actinomycin D (Act D), an oncogenic c-Myc promoter binder, interferes with the action of RNA polymerase. There is great demand for high-throughput technology able to monitor the activity of DNA-binding drugs. To this end, binding of 7-aminoactinomycin D (7AAD) to the duplex c-Myc promoter...... pairs resulted in efficient energy transfer from drug to QD via fluorescence resonance energy transfer (FRET). Multi-way analysis of the three-way data array obtained from titration experiments was performed by use of restricted Tucker3 and hard trilinear decomposition (HTD). These techniques enable...... the important advantage over univariate classical methods of enabling us to investigate the source of variance in the fluorescence signal of the DNA-drug complex. It was established that hard trilinear decomposition analysis of FRET-measured data overcomes the problem of rank deficiency, enabling calculation...

Long range energy transfer in graphene hybrid structures

International Nuclear Information System (INIS)

Gonçalves, Hugo; Bernardo, César; Moura, Cacilda; Belsley, Michael; Schellenberg, Peter; Ferreira, R A S; André, P S; Stauber, Tobias

2016-01-01

In this work we quantify the distance dependence for the extraction of energy from excited chromophores by a single layer graphene flake over a large separation range. To this end hybrid structures were prepared, consisting of a thin (2 nm) layer of a polymer matrix doped with a well chosen strongly fluorescent organic molecule, followed by an un-doped spacer layer of well-defined thicknesses made of the same polymer material and an underlying single layer of pristine, undoped graphene. The coupling strength is assessed through the variation of the fluorescence decay kinetics as a function of distance between the graphene and the excited chromophore molecules. Non-radiative energy transfer to the graphene was observed at distances of up to 60 nm; a range much greater than typical energy transfer distances observed in molecular systems. (paper)

Palladium Nanoparticles-Based Fluorescence Resonance Energy Transfer Aptasensor for Highly Sensitive Detection of Aflatoxin M₁ in Milk.

Science.gov (United States)

Li, Hui; Yang, Daibin; Li, Peiwu; Zhang, Qi; Zhang, Wen; Ding, Xiaoxia; Mao, Jin; Wu, Jing

2017-10-13

A highly sensitive aptasensor for aflatoxin M₁ (AFM₁) detection was constructed based on fluorescence resonance energy transfer (FRET) between 5-carboxyfluorescein (FAM) and palladium nanoparticles (PdNPs). PdNPs (33 nm) were synthesized through a seed-mediated growth method and exhibited broad and strong absorption in the whole ultraviolet-visible (UV-Vis) range. The strong coordination interaction between nitrogen functional groups of the AFM₁ aptamer and PdNPs brought FAM and PdNPs in close proximity, which resulted in the fluorescence quenching of FAM to a maximum extent of 95%. The non-specific fluorescence quenching caused by PdNPs towards fluorescein was negligible. After the introduction of AFM₁ into the FAM-AFM₁ aptamer-PdNPs FRET system, the AFM₁ aptamer preferentially combined with AFM₁ accompanied by conformational change, which greatly weakened the coordination interaction between the AFM₁ aptamer and PdNPs. Thus, fluorescence recovery of FAM was observed and a linear relationship between the fluorescence recovery and the concentration of AFM₁ was obtained in the range of 5-150 pg/mL in aqueous buffer with the detection limit of 1.5 pg/mL. AFM₁ detection was also realized in milk samples with a linear detection range from 6 pg/mL to 150 pg/mL. The highly sensitive FRET aptasensor with simple configuration shows promising prospect in detecting a variety of food contaminants.

A dark green fluorescent protein as an acceptor for measurement of Förster resonance energy transfer.

Science.gov (United States)

Murakoshi, Hideji; Shibata, Akihiro C E; Nakahata, Yoshihisa; Nabekura, Junichi

2015-10-15

Measurement of Förster resonance energy transfer by fluorescence lifetime imaging microscopy (FLIM-FRET) is a powerful method for visualization of intracellular signaling activities such as protein-protein interactions and conformational changes of proteins. Here, we developed a dark green fluorescent protein (ShadowG) that can serve as an acceptor for FLIM-FRET. ShadowG is spectrally similar to monomeric enhanced green fluorescent protein (mEGFP) and has a 120-fold smaller quantum yield. When FRET from mEGFP to ShadowG was measured using an mEGFP-ShadowG tandem construct with 2-photon FLIM-FRET, we observed a strong FRET signal with low cell-to-cell variability. Furthermore, ShadowG was applied to a single-molecule FRET sensor to monitor a conformational change of CaMKII and of the light oxygen voltage (LOV) domain in HeLa cells. These sensors showed reduced cell-to-cell variability of both the basal fluorescence lifetime and response signal. In contrast to mCherry- or dark-YFP-based sensors, our sensor allowed for precise measurement of individual cell responses. When ShadowG was applied to a separate-type Ras FRET sensor, it showed a greater response signal than did the mCherry-based sensor. Furthermore, Ras activation and translocation of its effector ERK2 into the nucleus could be observed simultaneously. Thus, ShadowG is a promising FLIM-FRET acceptor.

Sensitive and selective turn off-on fluorescence detection of heparin based on the energy transfer platform using the BSA-stabilized Au nanoclusters/amino-functionalized graphene oxide hybrids.

Science.gov (United States)

Lan, Jing; Zou, Hong Yan; Wang, Qiang; Zeng, Ping; Li, Yuan Fang; Huang, Cheng Zhi

2016-12-01

An ultra-sensitive and selective turn off-on fluorescence detection of heparin based on the energy transfer in the BSA-stabilized gold nanoclusters/amino-functionalized graphene oxide (BSA-AuNCs/NH 2 -GO) hybrids was successfully realized. The BSA-AuNCs containing amounts of carboxyl groups could be absorbed on the surface of NH 2 -GO through the electrostatic interaction, which resulted in the fluorescence quenching of BSA-AuNCs with high efficiency. However, heparin, possessing high density of negative charge, could compete with BSA-AuNCs to bind NH 2 -GO and block the energy transfer from BSA-AuNCs to NH 2 -GO. The fluorescence recovery of BSA-AuNCs was closely related to the amount of heparin and there was a good linear relationship between fluorescence recovery of BSA-AuNCs and heparin over the range of 100ng/mL to 30μg/mL with a detection limit of 40ng/mL. What's more, the fluorescence assay was successfully applied for heparin sensing in human serums and intracellular imaging. Copyright © 2016 Elsevier B.V. All rights reserved.

Resonance energy transfer based electrochemiluminescence and fluorescence sensing of riboflavin using graphitic carbon nitride quantum dots

International Nuclear Information System (INIS)

Wang, Huan; Ma, Qin; Wang, Yanfeng; Wang, Caihe; Qin, Dongdong; Shan, Duoliang; Chen, Jing; Lu, Xiaoquan

2017-01-01

Graphitic carbon nitride quantum dots (g-CNQDs) are rarely used in the field of electrochemiluminescence. In this paper, g-CNQDs have a strong and stable electrochemiluminescence (ECL) signal generated in the presence of co-reactant K 2 S 2 O 8 . The ECL signal of g-CNQDs was quenched by the mechanism of resonance energy transfer (RET) between donor g-CNQDs and receptor riboflavin (RF) that is proved by UV-vis absorption spectroscopy, electrochemiluminescence and fluorescence emission spectroscopy analysis technology. Therefore, we achieved detection of the riboflavin content in the drug tablets of vitamin B 2 using ECL and FL. The determination results of ECL showed that the riboflavin content of the drug vitamin B 2 (VB 2 ) tablets was consistent with the fluorescence (FL) analysis, with wider linear range of 0.02–11 μM and lower minimum detection limit of 0.63 nM (S/N = 3) than FL. Hence, the riboflavin content in human serum was further detected using ECL. The relative standard deviation is less than 6.5%, with an acceptable recovery of 95.33%–104.22%, which means that this sensor has potential applications in the actual sample analysis. As a new ECL luminary, g-CNQDs have opened a new field for the development and application of ECL sensor. - Highlights: • G-CNQDs proposed as a new luminophore for ECL. • ECL signal was strong and stable in the presence of co-reactant K 2 S 2 O 8 . • Based on the resonance energy transfer between g-CNQDs and riboflavin. • ECL has wider linear range and lower detection limit than FL.

Full genotyping of a highly polymorphic human gene trait by time-resolved fluorescence resonance energy transfer.

Directory of Open Access Journals (Sweden)

Edoardo Totè

Full Text Available The ability of detecting the subtle variations occurring, among different individuals, within specific DNA sequences encompassed in highly polymorphic genes discloses new applications in genomics and diagnostics. DQB1 is a gene of the HLA-II DQ locus of the Human Leukocyte Antigens (HLA system. The polymorphisms of the trait of the DQB1 gene including codons 52-57 modulate the susceptibility to a number of severe pathologies. Moreover, the donor-receiver tissue compatibility in bone marrow transplantations is routinely assessed through crossed genotyping of DQB and DQA. For the above reasons, the development of rapid, reliable and cost-effective typing technologies of DQB1 in general, and more specifically of the codons 52-57, is a relevant although challenging task. Quantitative assessment of the fluorescence resonance energy transfer (FRET efficiency between chromophores labelling the opposite ends of gene-specific oligonucleotide probes has proven to be a powerful tool to type DNA polymorphisms with single-nucleotide resolution. The FRET efficiency can be most conveniently quantified by applying a time-resolved fluorescence analysis methodology, i.e. time-correlated single-photon counting, which allows working on very diluted template specimens and in the presence of fluorescent contaminants. Here we present a full in-vitro characterization of the fluorescence responses of two probes when hybridized to oligonucleotide mixtures mimicking all the possible genotypes of the codons 52-57 trait of DQB1 (8 homozygous and 28 heterozygous. We show that each genotype can be effectively tagged by the combination of the fluorescence decay constants extrapolated from the data obtained with such probes.

Ion-ion interaction and energy transfer of 4+ transuranium ions in cerium tetrafluoride

International Nuclear Information System (INIS)

Liu, G.K.; Beitz, J.V.

1990-01-01

Dynamics of excited 5f electron states of the transuranium ions Cm 4+ and Bk 4+ in CeF 4 are compared. Based on time- and wavelength-resolved laser-induced fluorescence, excitation energy transfer processes have been probed. Depending on concentration and electronic energy level structure of the studied 4+ transuranium ion, the dominant energy transfer mechanisms were identified as cross relaxation, exciton-exciton annihilation, and trapping. Energy transfer rates derived from the fitting of the observed fluorescence decays to theoretical models, based on electric multipolar ion-ion interactions, are contrasted with prior studies of 4f states of 3+ lanthanide and 3d states of transition metal ions. 16 refs., 1 tab

Energy transfer in a mechanically trapped exciplex.

Science.gov (United States)

Klosterman, Jeremy K; Iwamura, Munetaka; Tahara, Tahei; Fujita, Makoto

2009-07-15

Host-guest complexes involving M(6)L(4) coordination cages can display unusual photoreactivity, and enclathration of the very large fluorophore bisanthracene resulted in an emissive, mechanically trapped intramolecular exciplex. Mechanically linked intramolecular exciplexes are important for understanding the dependence of energy transfer on donor-acceptor distance, orientation, and electronic coupling but are relatively unexplored. Steady-state and picosecond time-resolved fluorescence measurements have revealed that selective excitation of the encapsulated guest fluorophore results in efficient energy transfer from the excited guest to an emissive host-guest exciplex state.

Short range photoinduced electron transfer in proteins: QM-MM simulations of tryptophan and flavin fluorescence quenching in proteins

International Nuclear Information System (INIS)

Callis, Patrik R.; Liu Tiqing

2006-01-01

Hybrid quantum mechanical-molecular mechanics (dynamics) were performed on flavin reductase (Fre) and flavodoxin reductase (Fdr), both from Escherichia coli. Each was complexed with riboflavin (Rbf) or flavin mononucleotide (FMN). During 50 ps trajectories, the relative energies of the fluorescing state (S 1 ) of the isoalloxazine ring and the lowest charge transfer state (CT) were assessed to aid prediction of fluorescence lifetimes that are shortened due to quenching by electron transfer from tyrosine. The simulations for the four cases display a wide range in CT-S 1 energy gap caused by the presence of phosphate, other charged and polar residues, water, and by intermolecular separation between donor and acceptor. This suggests that the Gibbs energy change (ΔG 0 ) and reorganization energy (λ) for the electron transfer may differ in different flavoproteins

Analytical use of multi-protein Fluorescence Resonance Energy Transfer to demonstrate membrane-facilitated interactions within cytokine receptor complexes.

Science.gov (United States)

Krause, Christopher D; Izotova, Lara S; Pestka, Sidney

2013-10-01

Experiments measuring Fluorescence Resonance Energy Transfer (FRET) between cytokine receptor chains and their associated proteins led to hypotheses describing their organization in intact cells. These interactions occur within a larger protein complex or within a given nano-environment. To illustrate this complexity empirically, we developed a protocol to analyze FRET among more than two fluorescent proteins (multi-FRET). In multi-FRET, we model FRET among more than two fluorophores as the sum of all possible pairwise interactions within the complex. We validated our assumption by demonstrating that FRET among pairs within a fluorescent triplet resembled FRET between each pair measured in the absence of the third fluorophore. FRET between two receptor chains increases with increasing FRET between the ligand-binding chain (e.g., IFN-γR1, IL-10R1 and IFN-λR1) and an acylated fluorescent protein that preferentially resides within subsections of the plasma membrane. The interaction of IL-10R2 with IFN-λR1 or IL-10R1 results in decreased FRET between IL-10R2 and the acylated fluorescent protein. Finally, we analyzed FRET among four fluorescent proteins to demonstrate that as FRET between IFN-γR1 and IFN-γR2 or between IFN-αR1 and IFN-αR2c increases, FRET among other pairs of proteins changes within each complex. Copyright © 2013 Elsevier Ltd. All rights reserved.

Label-Free Detection of Sequence-Specific DNA Based on Fluorescent Silver Nanoclusters-Assisted Surface Plasmon-Enhanced Energy Transfer.

Science.gov (United States)

Ma, Jin-Liang; Yin, Bin-Cheng; Le, Huynh-Nhu; Ye, Bang-Ce

2015-06-17

We have developed a label-free method for sequence-specific DNA detection based on surface plasmon enhanced energy transfer (SPEET) process between fluorescent DNA/AgNC string and gold nanoparticles (AuNPs). DNA/AgNC string, prepared by a single-stranded DNA template encoded two emitter-nucleation sequences at its termini and an oligo spacer in the middle, was rationally designed to produce bright fluorescence emission. The proposed method takes advantage of two strategies. The first one is the difference in binding properties of single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) toward AuNPs. The second one is SPEET process between fluorescent DNA/AgNC string and AuNPs, in which fluorescent DNA/AgNC string can be spontaneously adsorbed onto the surface of AuNPs and correspondingly AuNPs serve as "nanoquencher" to quench the fluorescence of DNA/AgNC string. In the presence of target DNA, the sensing probe hybridized with target DNA to form duplex DNA, leading to a salt-induced AuNP aggregation and subsequently weakened SPEET process between fluorescent DNA/AgNC string and AuNPs. A red-to-blue color change of AuNPs and a concomitant fluorescence increase were clearly observed in the sensing system, which had a concentration dependent manner with specific DNA. The proposed method achieved a detection limit of ∼2.5 nM, offering the following merits of simple design, convenient operation, and low experimental cost because of no chemical modification, organic dye, enzymatic reaction, or separation procedure involved.

Resonance energy transfer based electrochemiluminescence and fluorescence sensing of riboflavin using graphitic carbon nitride quantum dots

Energy Technology Data Exchange (ETDEWEB)

Wang, Huan [Key Laboratory of Bioelectrochemistry & Environmental Analysis of Gansu Province, College of Chemistry & Chemical Engineering, Northwest Normal University, Lanzhou, Gansu 730070 (China); The Phytochemistry Key Laboratory of Tibetan Plateau of Qinghai Province, College of Pharmacy, Qinghai Nationalities University, Xining, Qinghai 810007 (China); Ma, Qin; Wang, Yanfeng; Wang, Caihe; Qin, Dongdong; Shan, Duoliang; Chen, Jing [Key Laboratory of Bioelectrochemistry & Environmental Analysis of Gansu Province, College of Chemistry & Chemical Engineering, Northwest Normal University, Lanzhou, Gansu 730070 (China); Lu, Xiaoquan, E-mail: luxq@nwnu.edu.cn [Key Laboratory of Bioelectrochemistry & Environmental Analysis of Gansu Province, College of Chemistry & Chemical Engineering, Northwest Normal University, Lanzhou, Gansu 730070 (China)

2017-06-22

Graphitic carbon nitride quantum dots (g-CNQDs) are rarely used in the field of electrochemiluminescence. In this paper, g-CNQDs have a strong and stable electrochemiluminescence (ECL) signal generated in the presence of co-reactant K{sub 2}S{sub 2}O{sub 8}. The ECL signal of g-CNQDs was quenched by the mechanism of resonance energy transfer (RET) between donor g-CNQDs and receptor riboflavin (RF) that is proved by UV-vis absorption spectroscopy, electrochemiluminescence and fluorescence emission spectroscopy analysis technology. Therefore, we achieved detection of the riboflavin content in the drug tablets of vitamin B{sub 2} using ECL and FL. The determination results of ECL showed that the riboflavin content of the drug vitamin B{sub 2} (VB{sub 2}) tablets was consistent with the fluorescence (FL) analysis, with wider linear range of 0.02–11 μM and lower minimum detection limit of 0.63 nM (S/N = 3) than FL. Hence, the riboflavin content in human serum was further detected using ECL. The relative standard deviation is less than 6.5%, with an acceptable recovery of 95.33%–104.22%, which means that this sensor has potential applications in the actual sample analysis. As a new ECL luminary, g-CNQDs have opened a new field for the development and application of ECL sensor. - Highlights: • G-CNQDs proposed as a new luminophore for ECL. • ECL signal was strong and stable in the presence of co-reactant K{sub 2}S{sub 2}O{sub 8}. • Based on the resonance energy transfer between g-CNQDs and riboflavin. • ECL has wider linear range and lower detection limit than FL.

Optical bar code recognition of methyl salicylate (MES) for environmental monitoring using fluorescence resonance energy transfer (FRET) on thin films

Science.gov (United States)

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.

Evaluation by fluorescence resonance energy transfer of the stability of nonviral gene delivery vectors under physiological conditions.

Science.gov (United States)

Itaka, Keiji; Harada, Atsushi; Nakamura, Kozo; Kawaguchi, Hiroshi; Kataoka, Kazunori

2002-01-01

The stability in physiological medium of polyplex- and lipoplex-type nonviral gene vectors was evaluated by detecting the conformational change of complexed plasmid DNA (pDNA) labeled simultaneously with fluorescein (energy donor) and X-rhodamine (energy acceptor) through fluorescence resonance energy transfer (FRET). Upon mixing with cationic components, such as LipofectAMINE, poly(L-lysine), and poly(ethylene glycol)-poly(L-lysine) block copolymer (PEG-PLys), the fluorescence spectrum of doubly labeled pDNA underwent a drastic change due to the occurrence of FRET between the donor-acceptor pair on pDNA taking a globular conformation (condensed state) through complexation. The measurement was carried out also in the presence of 20% serum, under which conditions FRET from condensed pDNA was clearly monitored without interference from coexisting components in the medium, allowing evaluation of the condensed state of pDNA in nonviral gene vectors under physiological conditions. Serum addition immediately induced a sharp decrease in FRET for the LipofectAMINE/pDNA (lipoplex) system, which was consistent with the sharp decrease in the transfection efficiency of the lipoplex system in serum-containing medium. In contrast, the PEG-PLys/pDNA polyplex (polyion complex micelle) system maintained appreciable transfection efficiency even in serum-containing medium, and FRET efficiency remained constant for up to 12 h, indicating the high stability of the polyion complex micelle under physiological conditions.

Lifetime-based optical sensor for high-level pCO2 detection employing fluorescence resonance energy transfer

International Nuclear Information System (INIS)

Bueltzingsloewen, Christoph von; McEvoy, Aisling K.; McDonagh, Colette; MacCraith, Brian D.

2003-01-01

An optical sensor for the measurement of high levels of carbon dioxide in gas phase has been developed. It is based on fluorescence resonance energy transfer (FRET) between a long-lifetime ruthenium polypyridyl complex and the pH-active disazo dye Sudan III. The donor luminophore and the acceptor dye are both immobilised in a hydrophobic silica sol-gel/ethyl cellulose hybrid matrix material. Tetraoctylammonium hydroxide (TOA-OH) is used as an internal buffering system. Fluorescence lifetime is measured in the frequency domain, using low-cost phase modulation measurement technology. The use of Sudan III as an acceptor dye has enabled the sensor to have a dynamic range up to 100% carbon dioxide. The sensor displays 11.2 deg. phase shift between the limit of detection (LOD) of 0.06 and 100% CO 2 with a resolution of better than 2%. The encapsulation in the silica/polymer hybrid material has provided the sensor with good mechanical and chemical stability. The effect of molecular oxygen, humidity and temperature on the sensor performance was studied in detail

Energy transfer from natural photosynthetic complexes to single-wall carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Wiwatowski, Kamil [Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka 5, 87-100 Torun (Poland); Dużyńska, Anna; Świniarski, Michał [Faculty of Physics, Warsaw University of Technology, Koszykowa 75, 00-662 Warsaw (Poland); Szalkowski, Marcin [Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka 5, 87-100 Torun (Poland); Zdrojek, Mariusz; Judek, Jarosław [Faculty of Physics, Warsaw University of Technology, Koszykowa 75, 00-662 Warsaw (Poland); Mackowski, Sebastian, E-mail: mackowski@fizyka.umk.pl [Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka 5, 87-100 Torun (Poland); Wroclaw Research Center EIT+, Stablowicka 147, Wroclaw (Poland); Kaminska, Izabela [Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka 5, 87-100 Torun (Poland)

2016-02-15

Combination of fluorescence imaging and spectroscopy results indicates that single-walled carbon nanotubes are extremely efficient quenchers of fluorescence emission associated with chlorophylls embedded in a natural photosynthetic complex, peridinin-chlorophyll-protein. When deposited on a network of the carbon nanotubes forming a thin film, the emission of the photosynthetic complexes diminishes almost completely. This strong reduction of fluorescence intensity is accompanied with dramatic shortening of the fluorescence lifetime. Concluding, such thin films of carbon nanotubes can be extremely efficient energy acceptors in structures involving biologically functional complexes. - Highlights: • Fluorescence imaging of carbon nanotube - based hybrid structure. • Observation of efficient energy transfer from chlorophylls to carbon nanotubes.

Graphene oxide based fluorescence resonance energy transfer and loop-mediated isothermal amplification for white spot syndrome virus detection.

Science.gov (United States)

Waiwijit, U; Phokaratkul, D; Kampeera, J; Lomas, T; Wisitsoraat, A; Kiatpathomchai, W; Tuantranont, A

2015-10-20

Graphene oxide (GO) is attractived for biological or medical applications due to its unique electrical, physical, optical and biological properties. In particular, GO can adsorb DNA via π-π stacking or non-covalent interactions, leading to fluorescence quenching phenomenon applicable for bio-molecular detection. In this work, a new method for white spot syndrome virus (WSSV)-DNA detection is developed based on loop-mediated isothermal amplification (LAMP) combined with fluorescence resonance energy transfer (FRET) between GO and fluorescein isothiocyanate-labeled probe (FITC-probe). The fluorescence quenching efficiency of FITC-probe was found to increase with increasing GO concentration and reached 98.7% at a GO concentration of 50 μg/ml. The fluorescence intensity of FITC-probe was recovered after hybridization with WSSV LAMP product with an optimal hybridization time of 10 min and increased accordingly with increasing amount of LAMP products. The detection limit was estimated to be as low as 10 copies of WSSV plasmid DNA or 0.6 fg of the total DNA extracted from shrimp infected with WSSV. In addition, no cross reaction was observed with other common shrimp viral pathogens. Therefore, the GO-FRET-LAMP technique is promising for fast, sensitive and specific detection of DNAs. Copyright © 2015 Elsevier B.V. All rights reserved.

Detection of influenza A virus based on fluorescence resonance energy transfer from quantum dots to carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Tian Junping [Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education, China), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024 (China); Zhao Huimin, E-mail: zhaohuim@dlut.edu.cn [Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education, China), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024 (China); Liu Meng; Chen Yaqiong; Quan Xie [Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education, China), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024 (China)

2012-04-20

Highlights: Black-Right-Pointing-Pointer The quantum dots-ssDNA probe was designed for the determination of virus DNA. Black-Right-Pointing-Pointer The fluorescence of quantum dots was effectively quenched by carbon nanotubes. Black-Right-Pointing-Pointer The addition of target H5N1 DNA restored the quenched fluorescence of quantum dots. Black-Right-Pointing-Pointer The proposed method exhibited high sensitivity and good selectivity for H5N1 DNA. - Abstract: In this paper, a simple and sensitive approach for H5N1 DNA detection was described based on the fluorescence resonance energy transfer (FRET) from quantum dots (QDs) to carbon nanotubes (CNTs) in a QDs-ssDNA/oxCNTs system, in which the QDs (CdTe) modified with ssDNA were used as donors. In the initial stage, with the strong interaction between ssDNA and oxCNTs, QDs fluorescence was effectively quenched. Upon the recognition of the target, the effective competitive bindings of it to QDs-ssDNA occurred, which decreased the interactions between the QDs-ssDNA and oxCNTs, leading to the recovery of the QDs fluorescence. The recovered fluorescence of QDs was linearly proportional to the concentration of the target in the range of 0.01-20 {mu}M with a detection limit of 9.39 nM. Moreover, even a single-base mismatched target with the same concentration of target DNA can only recover a limited low fluorescence of QDs, illustrating the good anti-interference performance of this QDs-ssDNA/oxCNTs system. This FRET platform in the QDs-ssDNA/oxCNTs system was facilitated to the simple, sensitive and quantitative detection of virus nucleic acids and could have a wide range of applications in molecular diagnosis.

Improving the spectral analysis of Fluorescence Resonance Energy Transfer in live cells: application to interferon receptors and Janus kinases.

Science.gov (United States)

Krause, Christopher D; Digioia, Gina; Izotova, Lara S; Pestka, Sidney

2013-10-01

The observed Fluorescence Resonance Energy Transfer (FRET) between fluorescently labeled proteins varies in cells. To understand how this variation affects our interpretation of how proteins interact in cells, we developed a protocol that mathematically separates donor-independent and donor-dependent excitations of acceptor, determines the electromagnetic interaction of donors and acceptors, and quantifies the efficiency of the interaction of donors and acceptors. By analyzing large populations of cells, we found that misbalanced or insufficient expression of acceptor or donor as well as their inefficient or reversible interaction influenced FRET efficiency in vivo. Use of red-shifted donors and acceptors gave spectra with less endogenous fluorescence but produced lower FRET efficiency, possibly caused by reduced quenching of red-shifted fluorophores in cells. Additionally, cryptic interactions between jellyfish FPs artefactually increased the apparent FRET efficiency. Our protocol can distinguish specific and nonspecific protein interactions even within highly constrained environments as plasma membranes. Overall, accurate FRET estimations in cells or within complex environments can be obtained by a combination of proper data analysis, study of sufficient numbers of cells, and use of properly empirically developed fluorescent proteins. Copyright © 2013 Elsevier Ltd. All rights reserved.

Smart Drug Delivery System-Inspired Enzyme-Linked Immunosorbent Assay Based on Fluorescence Resonance Energy Transfer and Allochroic Effect Induced Dual-Modal Colorimetric and Fluorescent Detection.

Science.gov (United States)

Miao, Luyang; Zhu, Chengzhou; Jiao, Lei; Li, He; Du, Dan; Lin, Yuehe; Wei, Qin

2018-02-06

Numerous analytical techniques have been undertaken for the detection of protein biomarkers because of their extensive and significant applications in clinical diagnosis, whereas there are few strategies to develop dual-readout immunosensors to achieve more accurate results. To the best of our knowledge, inspired by smart drug delivery system (DDS), a novel pH-responsive modified enzyme-linked immunosorbent assay (ELISA) was innovatively developed for the first time, realizing dual-modal colorimetric and fluorescent detection of cardiac troponin I (cTnI). Curcumin (CUR) was elaborately selected as a reporter molecule, which played the same role of drugs in DDS based on the following considerations: (1) CUR can be used as a kind of pH indicator by the inherited allochroic effect induced by basic pH value; (2) the fluorescence of CUR can be quenched by certain nanocarriers as the acceptor because of the occurrence of fluorescence resonance energy transfer (FRET), while recovered by the stimuli of basic pH value, which can produce "signal-on" fluorescence detection. Three-dimensional MoS 2 nanoflowers (3D-MoS 2 NFs) were employed in immobilizing CUR to constitute a nanoprobe for the determination of cTnI by virtue of good biocompatibility, high absorption capacity, and fluorescence quench efficiency toward CUR. The proposed DDS-inspired ELISA offered dual-modal colorimetric and fluorescent detection of cTnI, thereby meeting the reliable and precise analysis requirements. We believe that the developed dual-readout ELISA will create a new avenue and bring innovative inspirations for biological detections.

Photophysical properties and energy transfer mechanism of PFO/Fluorol 7GA hybrid thin films

Energy Technology Data Exchange (ETDEWEB)

Al-Asbahi, Bandar Ali, E-mail: alasbahibandar@gmail.com [School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia (UKM), 43600 Bangi, Selangor (Malaysia); Department of Physics, Faculty of Science, Sana' a University (Yemen); Jumali, Mohammad Hafizuddin Haji, E-mail: hafizhj@ukm.my [School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia (UKM), 43600 Bangi, Selangor (Malaysia); Yap, Chi Chin; Flaifel, Moayad Husein [School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia (UKM), 43600 Bangi, Selangor (Malaysia); Salleh, Muhamad Mat [Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia (UKM), 43600 Bangi, Selangor (Malaysia)

2013-10-15

Photophysical properties of poly (9,9′-di-n-octylfluorenyl-2.7-diyl) (PFO)/2-butyl-6- (butylamino)benzo [de] isoquinoline-1,3-dione (Fluorol 7GA) and energy transfer between them have been investigated. In this work, both PFO and Fluorol 7GA act as donor and acceptor, respectively. Based on the absorption and luminescence measurements, the photophysical and energy transfer properties such as fluorescence quantum yield (Φ{sub f}), fluorescence lifetime (τ), radiative rate constant (k{sub r}), non-radiative rate constant (k{sub nr}), quenching rate constant (k{sub SV}), energy transfer rate constant (k{sub ET}), energy transfer probability (P{sub DA}), energy transfer efficiency (η), critical concentration of acceptor (C{sub o}), energy transfer time (τ{sub ET}) and critical distance of energy transfer (R{sub o}) were calculated. Large values of k{sub SV}, k{sub ET} and R{sub o} suggested that Förster-type energy transfer was the dominant mechanism for the energy transfer between the excited donor and ground state acceptor molecules. It was observed that the Förster energy transfer together with the trapping process are crucial for performance improvement in ITO/(PFO/Fluorol7GA)/Al device. -- Highlights: • The efficient of energy transfer from PFO to Fluorol 7GA was evidenced. • The resonance energy transfer (Förster type) is the dominant mechanism. • Hsu et al. model was used to calculate Φ{sub f}, τ, k{sub r} and k{sub nr} of PFO thin film. • Several of the photophysical and energy transfer properties were calculated. • Trapping process and Förster energy transfer led to improve the device performance.

Nanophotonics: Energy Transfer towards Enhanced Luminescent Chemosensing

Directory of Open Access Journals (Sweden)

Roy Aad

2015-04-01

Full Text Available We discuss a recently proposed novel photonic approach for enhancing the fluorescence of extremely thin chemosensing polymer layers. We present theoretical and experimental results demonstrating the concept of gain-assisted waveguided energy transfer (G-WET on a very thin polymer nanolayer spincoated on an active ZnO thin film. The G-WET approach is shown to result in an 8-fold increase in polymer fluorescence. We then extend the G-WET concept to nanostructured media. The benefits of using active nanostructured substrates on the sensitivity and fluorescence of chemosensing polymers are discussed. Preliminary theoretical results on enlarged sensing surface and photonic band-gap are presented.

Nanophotonics: Energy Transfer towards Enhanced Luminescent Chemosensing

Science.gov (United States)

Aad, Roy; Couteau, Christophe; Lérondel, Gilles

2015-01-01

We discuss a recently proposed novel photonic approach for enhancing the fluorescence of extremely thin chemosensing polymer layers. We present theoretical and experimental results demonstrating the concept of gain-assisted waveguided energy transfer (G-WET) on a very thin polymer nanolayer spincoated on an active ZnO thin film. The G-WET approach is shown to result in an 8-fold increase in polymer fluorescence. We then extend the G-WET concept to nanostructured media. The benefits of using active nanostructured substrates on the sensitivity and fluorescence of chemosensing polymers are discussed. Preliminary theoretical results on enlarged sensing surface and photonic band-gap are presented. PMID:28788025

Exciplex formation and energy transfer in a self-assembled metal-organic hybrid system.

Science.gov (United States)

Haldar, Ritesh; Rao, K Venkata; George, Subi J; Maji, Tapas Kumar

2012-05-07

Exciting assemblies: A metal-organic self-assembly of pyrenebutyric acid (PBA), 1,10-phenanthroline (o-phen), and Mg(II) shows solid-state fluorescence originating from a 1:1 PBA-o-phen exciplex. This exciplex fluorescence is sensitized by another residual PBA chromophore through an excited-state energy-transfer process. The solvent polarity modulates the self-assembly and the corresponding exciplex as well as the energy transfer, resulting in tunable emission of the hybrid (see figure). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fluorescent strategy based on cationic conjugated polymer fluorescence resonance energy transfer for the quantification of 5-(hydroxymethyl)cytosine in genomic DNA.

Science.gov (United States)

Hong, Tingting; Wang, Tianlu; Guo, Pu; Xing, Xiwen; Ding, Fei; Chen, Yuqi; Wu, Jinjun; Ma, Jingwei; Wu, Fan; Zhou, Xiang

2013-11-19

DNA methylation is dynamically reprogrammed during early embryonic development in mammals. It can be explained partially by the discovery of 5-(hydroxymethyl)cytosine (5-hmC), 5-formylcytosine (5-fC), and 5-carboxylcytosine (5-caC), which are identified as key players involved in both active and passive demethylation pathways. As one of the ten-eleven translocation oxidation products, 5-hmC was found relatively abundant in neuron cells and embryonic stem cells. Herein we report a new method for 5-hmC quantification in genomic DNA based on CCP-FRET (cationic conjugated polymers act as the energy donor and induce fluorescence resonance energy transfer) assay combined with KRuO4 oxidation. 5-hmC in genomic DNA can be selectively transformed into 5-fC by the oxidation of KRuO4 and then labeled with hydroxylamine-BODIPY (BODIPY = 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) fluorophore through the reaction between 5-fC and hydroxylamine-BODIPY. After the fluorescently labeled DNA was captured by CCP through electrostatic interactions, a significant FRET between CCP and hydroxylamine-BODIPY fluorophore was observed. This CCP-FRET-based assay benefits from light-harvesting, large Stokes shift, and optical signal amplification properties of the CCP. Furthermore, this CCP-FRET-based assay was quite successfully demonstrated for the 5-hmC quantification in three types of cells (mESc, HeLa, HEK 293T), providing a much more convenient choice for 5-hmC quantification in genomic DNA.

Fluorescence resonance energy transfer (FRET-based subcellular visualization of pathogen-induced host receptor signaling

Directory of Open Access Journals (Sweden)

Zimmermann Timo

2009-11-01

Full Text Available Abstract Background Bacteria-triggered signaling events in infected host cells are key elements in shaping the host response to pathogens. Within the eukaryotic cell, signaling complexes are spatially organized. However, the investigation of protein-protein interactions triggered by bacterial infection in the cellular context is technically challenging. Here, we provide a methodological approach to exploit fluorescence resonance energy transfer (FRET to visualize pathogen-initiated signaling events in human cells. Results Live-cell microscopy revealed the transient recruitment of the Src family tyrosine kinase Hck upon bacterial engagement of the receptor carcinoembryonic antigen-related cell adhesion molecule 3 (CEACAM3. In cells expressing a CEACAM3 variant lacking the cytoplasmic domain, the Src homology 2 (SH2 domain of Hck (Hck-SH2 was not recruited, even though bacteria still bound to the receptor. FRET measurements on the basis of whole cell lysates revealed intimate binding between Hck-SH2 (using enhanced yellow fluorescent protein (YPet-Hck-SH2 and the tyrosine-phosphorylated enhanced cyan fluorescent protein-labeled cytoplasmic domain of wild-type CEACAM3 (CEACAM3 WT-CyPet and a flow cytometry-based FRET approach verified this association in intact cells. Using confocal microscopy and acceptor photobleaching, FRET between Hck-SH2 and CEACAM3 was localized to the sites of bacteria-host cell contact. Conclusion These data demonstrate not only the intimate binding of the SH2 domain of Hck to the tyrosine-phosphorylated cytoplasmic domain of CEACAM3 in intact cells, but furthermore, FRET measurements allow the subcellular localization of this process during bacterial infection. FRET-based assays are valuable tools to resolve bacteria-induced protein-protein interactions in the context of the intact host cell.

Quantitative time domain analysis of lifetime-based Förster resonant energy transfer measurements with fluorescent proteins: Static random isotropic fluorophore orientation distributions

DEFF Research Database (Denmark)

Alexandrov, Yuriy; Nikolic, Dino Solar; Dunsby, Christopher

2018-01-01

Förster resonant energy transfer (FRET) measurements are widely used to obtain information about molecular interactions and conformations through the dependence of FRET efficiency on the proximity of donor and acceptor fluorophores. Fluorescence lifetime measurements can provide quantitative...... into new software for fitting donor emission decay profiles. Calculated FRET parameters, including molar population fractions, are compared for the analysis of simulated and experimental FRET data under the assumption of static and dynamic fluorophores and the intermediate regimes between fully dynamic...... analysis of FRET efficiency and interacting population fraction. Many FRET experiments exploit the highly specific labelling of genetically expressed fluorescent proteins, applicable in live cells and organisms. Unfortunately, the typical assumption of fast randomization of fluorophore orientations...

On-chip transduction of nucleic acid hybridization using spatial profiles of immobilized quantum dots and fluorescence resonance energy transfer.

Science.gov (United States)

Tavares, Anthony J; Noor, M Omair; Vannoy, Charles H; Algar, W Russ; Krull, Ulrich J

2012-01-03

The glass surface of a glass-polydimethylsiloxane (PDMS) microfluidic channel was modified to develop a solid-phase assay for quantitative determination of nucleic acids. Electroosmotic flow (EOF) within channels was used to deliver and immobilize semiconductor quantum dots (QDs), and electrophoresis was used to decorate the QDs with oligonucleotide probe sequences. These processes took only minutes to complete. The QDs served as energy donors in fluorescence resonance energy transfer (FRET) for transduction of nucleic acid hybridization. Electrokinetic injection of fluorescent dye (Cy3) labeled oligonucleotide target into a microfluidic channel and subsequent hybridization (within minutes) provided the proximity for FRET, with emission from Cy3 being the analytical signal. The quantification of target concentration was achieved by measurement of the spatial length of coverage by target along a channel. Detection of femtomole quantities of target was possible with a dynamic range spanning an order of magnitude. The assay provided excellent resistance to nonspecific interactions of DNA. Further selectivity of the assay was achieved using 20% formamide, which allowed discrimination between a fully complementary target and a 3 base pair mismatch target at a contrast ratio of 4:1. © 2011 American Chemical Society

Investigation of Membrane Receptors' Oligomers Using Fluorescence Resonance Energy Transfer and Multiphoton Microscopy in Living Cells

Science.gov (United States)

Mishra, Ashish K.

Investigating quaternary structure (oligomerization) of macromolecules (such as proteins and nucleic acids) in living systems (in vivo) has been a great challenge in biophysics, due to molecular diffusion, fluctuations in several biochemical parameters such as pH, quenching of fluorescence by oxygen (when fluorescence methods are used), etc. We studied oligomerization of membrane receptors in living cells by means of Fluorescence (Forster) Resonance Energy Transfer (FRET) using fluorescent markers and two photon excitation fluorescence micro-spectroscopy. Using suitable FRET models, we determined the stoichiometry and quaternary structure of various macromolecular complexes. The proteins of interest for this work are : (1) sigma-1 receptor and (2) rhodopsin, are described as below. (1) Sigma-1 receptors are molecular chaperone proteins, which also regulate ion channels. S1R seems to be involved in substance abuse, as well as several diseases such as Alzheimer's. We studied S1R in the presence and absence of its ligands haloperidol (an antagonist) and pentazocine +/- (an agonist), and found that at low concentration they reside as a mixture of monomers and dimers and that they may form higher order oligomers at higher concentrations. (2) Rhodopsin is a prototypical G protein coupled receptor (GPCR) and is directly involved in vision. GPCRs form a large family of receptors that participate in cell signaling by responding to external stimuli such as drugs, thus being a major drug target (more than 40% drugs target GPCRs). Their oligomerization has been largely controversial. Understanding this may help to understand the functional role of GPCRs oligomerization, and may lead to the discovery of more drugs targeting GPCR oligomers. It may also contribute toward finding a cure for Retinitis Pigmentosa, which is caused by a mutation (G188R) in rhodopsin, a disease which causes blindness and has no cure so far. Comparing healthy rhodopsin's oligomeric structure with that

Fluorescence Resonance Energy Transfer Assay for High-Throughput Screening of ADAMTS1 Inhibitors

Directory of Open Access Journals (Sweden)

Guanhua Du

2011-12-01

Full Text Available A disintegrin and metalloprotease with thrombospondin type I motifs-1 (ADAMTS1 plays a crucial role in inflammatory joint diseases and its inhibitors are potential candidates for anti-arthritis drugs. For the purposes of drug discovery, we reported the development and validation of fluorescence resonance energy transfer (FRET assay for high-throughput screening (HTS of the ADAMTS1 inhibitors. A FRET substrate was designed for a quantitative assay of ADAMTS1 activity and enzyme kinetics studies. The assay was developed into a 50-µL, 384-well assay format for high throughput screening of ADAMTS1 inhibitors with an overall Z’ factor of 0.89. ADAMTS1 inhibitors were screened against a diverse library of 40,960 total compounds with the established HTS system. Four structurally related hits, naturally occurring compounds, kuwanon P, kuwanon X, albafuran C and mulberrofuran J, extracted from the Chinese herb Morus alba L., were identified for further investigation. The results suggest that this FRET assay is an excellent tool, not only for measurement of ADAMTS1 activity but also for discovery of novel ADAMTS1 inhibitors with HTS.

Fis protein induced λF-DNA bending observed by single-pair fluorescence resonance energy transfer

Science.gov (United States)

Chi-Cheng, Fu; Wunshain, Fann; Yuan Hanna, S.

2006-03-01

Fis, a site-specific DNA binding protein, regulates many biological processes including recombination, transcription, and replication in E.coli. Fis induced DNA bending plays an important role in regulating these functions and bending angle range from ˜50 to 95 dependent on the DNA sequence. For instance, the average bending angle of λF-DNA (26 bp, 8.8nm long, contained λF binding site on the center) measured by gel mobility shift assays was ˜ 94 . But the traditional method cannot provide information about the dynamics and the angle distribution. In this study, λF-DNA was labeled with donor (Alexa Fluor 546) and acceptor (Alexa Fluor 647) dyes on its two 5' ends and the donor-acceptor distances were measured using single-pair fluorescence resonance energy transfer (sp-FRET) with and without the present of Fis protein. Combing with structure information of Fis-DNA complex, the sp-FRET results are used to estimate the protein induced DNA bending angle distribution and dynamics.

Homogeneous competitive assay of ligand affinities based on quenching fluorescence of tyrosine/tryptophan residues in a protein via Főrster-resonance-energy-transfer

Science.gov (United States)

Xie, Yanling; Yang, Xiaolan; Pu, Jun; Zhao, Yunsheng; Zhang, Ying; Xie, Guoming; Zheng, Jun; Yuan, Huidong; Liao, Fei

2010-11-01

A new homogeneous competitive assay of ligand affinities was proposed based on quenching the fluorescence of tryptophan/tyrosine residues in a protein via Főrster-resonance-energy-transfer using a fluorescent reference ligand as the acceptor. Under excitation around 280 nm, the fluorescence of a protein or a bound acceptor was monitored upon competitive binding against a nonfluorescent candidate ligand. Chemometrics for deriving the binding ratio of the acceptor with either fluorescence signal was discussed; the dissociation constant ( Kd) of a nonfluorescent candidate ligand was calculated from its concentration to displace 50% binding of the acceptor. N-biotinyl-N'-(1-naphthyl)-ethylenediamine (BNEDA) and N-biotinyl-N'-dansyl-ethylenediamine (BDEDA) were used as the reference ligands and acceptors to streptavidin to test this new homogeneous competitive assay. Upon binding of an acceptor to streptavidin, there were the quench of streptavidin fluorescence at 340 nm and the characteristic fluorescence at 430 nm for BNEDA or at 525 nm for BDEDA. Kd of BNEDA and BDEDA was obtained via competitive binding against biotin. By quantifying BNEDA fluorescence, Kd of each tested nonfluorescent biotin derivative was consistent with that by quantifying streptavidin fluorescence using BNEDA or BDEDA as the acceptor. The overall coefficients of variation were about 10%. Therefore, this homogeneous competitive assay was effective and promising to high-throughput-screening.

∼2 μm fluorescence radiative dynamics and energy transfer between Er3+ and Tm3+ ions in silicate glass

International Nuclear Information System (INIS)

Li, Ming; Liu, Xueqiang; Guo, Yanyan; Hao, Wei; Hu, Lili; Zhang, Junjie

2014-01-01

Graphical abstract: - Highlights: • A Er 3+ /Tm 3+ co-doped silicate glass with good thermal stability (k gl = 0.402 for STE glass) is prepared. • Efficient ∼2 μm emission is observed under 808 nm and 980 nm laser excitation. • The glass structure and spectroscopic properties are confirmed by optical absorption, IR transmission, Raman and fluorescence studies. • The content of OH groups deceases efficiently after fluorine ions are introduced. • The energy transfer coefficient from Er 3+ to Tm 3+ in STFE glass is 13.39 × 10 −40 cm 6 /s. - Abstract: A Er 3+ /Tm 3+ co-doped silicate glass with good thermal stability is prepared by melt-quenching method. An efficient emission of ∼2 μm is observed under different selective laser excitations. The optical absorption and transmission spectra, Raman spectra, and emission spectra are tested to characterize ∼2 μm emission properties of Er 3+ /Tm 3+ co-doped silicate glasses and a reasonable energy transfer mechanism of ∼2 μm emission between Er 3+ and Tm 3+ ions is proposed. Based on the optical absorption spectra, the Judd–Ofelt parameters and radiative properties were calculated. Intense ∼2 μm emission is obtained from Er 3+ /Tm 3+ co-doped silicate glasses due to the efficient energy transfer from Er 3+ to Tm 3+ ions. The energy transfer coefficient from Er 3+ to Tm 3+ ions can reach as high as 13.39 × 10 −40 cm 6 /s. In addition, the population of the OH groups is decreased and the ∼2 μm emission is effectively enhanced with fluoride introduction. The emission property, together with good thermal property, indicates that Er 3+ /Tm 3+ co-doped silicate glass is a potential kind of laser glass for efficient ∼2 μm laser

The convergence of quantum-dot-mediated fluorescence resonance energy transfer and microfluidics for monitoring DNA polyplex self-assembly in real time

International Nuclear Information System (INIS)

Ho Yiping; Wang, T-H; Chen, Hunter H; Leong, Kam W

2009-01-01

We present a novel convergence of quantum-dot-mediated fluorescence resonance energy transfer (QD-FRET) and microfluidics, through which molecular interactions were precisely controlled and monitored using highly sensitive quantum-dot-mediated FRET. We demonstrate its potential in studying the kinetics of self-assembly of DNA polyplexes under laminar flow in real time with millisecond resolution. The integration of nanophotonics and microfluidics offers a powerful tool for elucidating the formation of polyelectrolyte polyplexes, which is expected to provide better control and synthesis of uniform and customizable polyplexes for future nucleic acid-based therapeutics.

Near-field effects and energy transfer in hybrid metal-oxide nanostructures.

Science.gov (United States)

Herr, Ulrich; Kuerbanjiang, Balati; Benel, Cahit; Papageorgiou, Giorgos; Goncalves, Manuel; Boneberg, Johannes; Leiderer, Paul; Ziemann, Paul; Marek, Peter; Hahn, Horst

2013-01-01

One of the big challenges of the 21st century is the utilization of nanotechnology for energy technology. Nanoscale structures may provide novel functionality, which has been demonstrated most convincingly by successful applications such as dye-sensitized solar cells introduced by M. Grätzel. Applications in energy technology are based on the transfer and conversion of energy. Following the example of photosynthesis, this requires a combination of light harvesting, transfer of energy to a reaction center, and conversion to other forms of energy by charge separation and transfer. This may be achieved by utilizing hybrid nanostructures, which combine metallic and nonmetallic components. Metallic nanostructures can interact strongly with light. Plasmonic excitations of such structures can cause local enhancement of the electrical field, which has been utilized in spectroscopy for many years. On the other hand, the excited states in metallic structures decay over very short lifetimes. Longer lifetimes of excited states occur in nonmetallic nanostructures, which makes them attractive for further energy transfer before recombination or relaxation sets in. Therefore, the combination of metallic nanostructures with nonmetallic materials is of great interest. We report investigations of hybrid nanostructured model systems that consist of a combination of metallic nanoantennas (fabricated by nanosphere lithography, NSL) and oxide nanoparticles. The oxide particles were doped with rare-earth (RE) ions, which show a large shift between absorption and emission wavelengths, allowing us to investigate the energy-transfer processes in detail. The main focus is on TiO2 nanoparticles doped with Eu(3+), since the material is interesting for applications such as the generation of hydrogen by photocatalytic splitting of water molecules. We use high-resolution techniques such as confocal fluorescence microscopy for the investigation of energy-transfer processes. The experiments are

Photoinduced energy and electron transfer in rubrene-benzoquinone and rubrene-porphyrin systems

KAUST Repository

Khan, Jafar Iqbal

2014-11-01

Excited-state electron and energy transfer from singlet excited rubrene (Ru) to benzoquinone (BQ) and tetra-(4-aminophenyl) porphyrin (TAPP) were investigated by steady-state absorption and emission, time-resolved transient absorption, and femtosecond (fs)-nanosecond (ns) fluorescence spectroscopy. The low reduction potential of BQ provides the high probability of electron transfer from the excited Ru to BQ. Steady-state and time-resolved results confirm such an excited electron transfer scenario. On the other hand, strong spectral overlap between the emission of Ru and absorption of TAPP suggests that energy transfer is a possible deactivation pathway of the Ru excited state.

Double-labeled donor probe can enhance the signal of fluorescence resonance energy transfer (FRET) in detection of nucleic acid hybridization

Science.gov (United States)

Okamura, Yukio; Kondo, Satoshi; Sase, Ichiro; Suga, Takayuki; Mise, Kazuyuki; Furusawa, Iwao; Kawakami, Shigeki; Watanabe, Yuichiro

2000-01-01

A set of fluorescently-labeled DNA probes that hybridize with the target RNA and produce fluorescence resonance energy transfer (FRET) signals can be utilized for the detection of specific RNA. We have developed probe sets to detect and discriminate single-strand RNA molecules of plant viral genome, and sought a method to improve the FRET signals to handle in vivo applications. Consequently, we found that a double-labeled donor probe labeled with Bodipy dye yielded a remarkable increase in fluorescence intensity compared to a single-labeled donor probe used in an ordinary FRET. This double-labeled donor system can be easily applied to improve various FRET probes since the dependence upon sequence and label position in enhancement is not as strict. Furthermore this method could be applied to other nucleic acid substances, such as oligo RNA and phosphorothioate oligonucleotides (S-oligos) to enhance FRET signal. Although the double-labeled donor probes labeled with a variety of fluorophores had unexpected properties (strange UV-visible absorption spectra, decrease of intensity and decay of donor fluorescence) compared with single-labeled ones, they had no relation to FRET enhancement. This signal amplification mechanism cannot be explained simply based on our current results and knowledge of FRET. Yet it is possible to utilize this double-labeled donor system in various applications of FRET as a simple signal-enhancement method. PMID:11121494

Graphene-based chemiluminescence resonance energy transfer for homogeneous immunoassay.

Science.gov (United States)

Lee, Joon Seok; Joung, Hyou-Arm; Kim, Min-Gon; Park, Chan Beum

2012-04-24

We report on chemiluminescence resonance energy transfer (CRET) between graphene nanosheets and chemiluminescent donors. In contrast to fluorescence resonance energy transfer, CRET occurs via nonradiative dipole-dipole transfer of energy from a chemiluminescent donor to a suitable acceptor molecule without an external excitation source. We designed a graphene-based CRET platform for homogeneous immunoassay of C-reactive protein (CRP), a key marker for human inflammation and cardiovascular diseases, using a luminol/hydrogen peroxide chemiluminescence (CL) reaction catalyzed by horseradish peroxidase. According to our results, anti-CRP antibody conjugated to graphene nanosheets enabled the capture of CRP at the concentration above 1.6 ng mL(-1). In the CRET platform, graphene played a key role as an energy acceptor, which was more efficient than graphene oxide, while luminol served as a donor to graphene, triggering the CRET phenomenon between luminol and graphene. The graphene-based CRET platform was successfully applied to the detection of CRP in human serum samples in the range observed during acute inflammatory stress.

Time-resolved studies of energy transfer from meso-tetrakis(N-methylpyridinium-4-yl)- porphyrin to 3,3'-diethyl-2,2'-thiatricarbocyanine iodide along deoxyribonucleic acid Chain.

Science.gov (United States)

Kakiuchi, Toshifumi; Ito, Fuyuki; Nagamura, Toshihiko

2008-04-03

The excitation energy transfer from meso-tetrakis(N-methylpyridinium-4-yl)porphyrin (TMPyP) to 3,3'-diethyl-2,2'-thiatricarbocyanine iodide (DTTCI) along the deoxyribonucleic acid (DNA) double strand was investigated by the steady-state absorption and fluorescence measurements and time-resolved fluorescence measurements. The steady-state fluorescence spectra showed that the near-infrared fluorescence of DTTCI was strongly enhanced up to 86 times due to the energy transfer from the excited TMPyP molecule in DNA buffer solution. Furthermore, we elucidated the mechanism of fluorescence quenching and enhancement by the direct observation of energy transfer using the time-resolved measurements. The fluorescence quenching of TMPyP chiefly consists of a static component due to the formation of complex and dynamic components due to the excitation energy transfer. In a heterogeneous one-dimensional system such as a DNA chain, it was proved that the energy transfer process only carries out within the critical distance based on the Förster theory and within a threshold value estimated from the modified Stern-Volmer equation. The present results showed that DNA chain is one of the most powerful tools for nanoassemblies and will give a novel concepts of material design.

The effect of the silver nanoparticles on the dynamics of singlet-singlet energy transfer of luminophores in thin films of polyvinyl alcohol

International Nuclear Information System (INIS)

Bryukhanov, V.V.; Samusev, I.G.; Slezhkin, V.A.; Tsibul'nikova, A.V.

2014-01-01

The effect of ablated silver nanoparticles (ANP) on the dynamics of non-radiative inductance-resonance energy transfer and phosphorescence in the donor-acceptor pair of molecules of eosin and methylene blue (MB) luminophores embedded in thin films of polyvinyl alcohol have been investigated. Increased fluorescence intensity of donor (eosin) and acceptor (MB) molecules, as well as a growth of the dipole-dipole transfer efficiency have been obtained under the resonant excitation of the silver ANP surface plasmons in the absorption band of the donor energy. The luminescence quantum yields and the fluorescence lifetimes have been measured. The energy transfer constants, degree of polarization and fluorescence anisotropy have been determined. (authors)

Highly-sensitive aptasensor based on fluorescence resonance energy transfer between l-cysteine capped ZnS quantum dots and graphene oxide sheets for the determination of edifenphos fungicide.

Science.gov (United States)

Arvand, Majid; Mirroshandel, Aazam A

2017-10-15

With the advantages of excellent optical properties and biocompatibility, single-strand DNA-functionalized quantum dots have been widely applied in biosensing and bioimaging. A new aptasensor with easy operation, high sensitivity, and high selectivity was developed by immobilizing the aptamer on water soluble l-cysteine capped ZnS quantum dots (QDs). Graphene oxide (GO) sheets are mixed with the aptamer-QDs. Consequently, the aptamer-conjugated QDs bind to the GO sheets to form a GO/aptamer-QDs ensemble. This aptasensor enables the energy transfer based on a fluorescence resonance energy transfer (FRET) from the QDs to the GO sheets, quenching the fluorescence of QDs. The GO/aptamer-QDs ensemble assay acts as a "turn-on'' fluorescent sensor for edifenphos (EDI) detection. When GO was replaced by EDI, the fluorescence of QDs was restored and its intensity was proportional to the EDI concentration. This GO-based aptasensor under the optimum conditions exhibited excellent analytical performance for EDI determination, ranging from 5×10 -4 to 6×10 -3 mg L -1 with the detection limit of 1.3×10 -4 mgL -1 . Furthermore, the designed aptasensor exhibited excellent selectivity toward EDI compared to other pesticides and herbicides with similar structures such as diazinon, heptachlor, endrin, dieldrin, butachlor and chlordane. Good reproducibility and precision (RSD =3.9%, n =10) of the assay indicates the high potential of the aptasensor for quantitative trace analysis of EDI. Moreover, the results demonstrate the applicability of the aptasensor for monitoring EDI fungicide in spiked real samples. Copyright © 2017 Elsevier B.V. All rights reserved.

A high-throughput fluorescence resonance energy transfer (FRET)-based endothelial cell apoptosis assay and its application for screening vascular disrupting agents

International Nuclear Information System (INIS)

Zhu, Xiaoming; Fu, Afu; Luo, Kathy Qian

2012-01-01

Highlights: ► An endothelial cell apoptosis assay using FRET-based biosensor was developed. ► The fluorescence of the cells changed from green to blue during apoptosis. ► This method was developed into a high-throughput assay in 96-well plates. ► This assay was applied to screen vascular disrupting agents. -- Abstract: In this study, we developed a high-throughput endothelial cell apoptosis assay using a fluorescence resonance energy transfer (FRET)-based biosensor. After exposure to apoptotic inducer UV-irradiation or anticancer drugs such as paclitaxel, the fluorescence of the cells changed from green to blue. We developed this method into a high-throughput assay in 96-well plates by measuring the emission ratio of yellow fluorescent protein (YFP) to cyan fluorescent protein (CFP) to monitor the activation of a key protease, caspase-3, during apoptosis. The Z′ factor for this assay was above 0.5 which indicates that this assay is suitable for a high-throughput analysis. Finally, we applied this functional high-throughput assay for screening vascular disrupting agents (VDA) which could induce endothelial cell apoptosis from our in-house compounds library and dioscin was identified as a hit. As this assay allows real time and sensitive detection of cell apoptosis, it will be a useful tool for monitoring endothelial cell apoptosis in living cell situation and for identifying new VDA candidates via a high-throughput screening.

Three-color confocal Förster (or fluorescence) resonance energy transfer microscopy: Quantitative analysis of protein interactions in the nucleation of actin filaments in live cells.

Science.gov (United States)

Wallrabe, Horst; Sun, Yuansheng; Fang, Xiaolan; Periasamy, Ammasi; Bloom, George S

2015-06-01

Experiments using live cell 3-color Förster (or fluorescence) resonance energy transfer (FRET) microscopy and corresponding in vitro biochemical reconstitution of the same proteins were conducted to evaluate actin filament nucleation. A novel application of 3-color FRET data is demonstrated, extending the analysis beyond the customary energy-transfer efficiency (E%) calculations. MDCK cells were transfected for coexpression of Teal-N-WASP/Venus-IQGAP1/mRFP1-Rac1, Teal-N-WASP/Venus-IQGAP1/mRFP1-Cdc42, CFP-Rac1/Venus-IQGAP1/mCherry-actin, or CFP-Cdc42/Venus-IQGAP1/mCherry-actin, and with single-label equivalents for spectral bleedthrough correction. Using confirmed E% as an entry point, fluorescence levels and related ratios were correlated at discrete accumulating levels at cell peripheries. Rising ratios of CFP-Rac1:Venus-IQGAP1 were correlated with lower overall actin fluorescence, whereas the CFP-Cdc42:Venus-IQGAP1 ratio correlated with increased actin fluorescence at low ratios, but was neutral at higher ratios. The new FRET analyses also indicated that rising levels of mRFP1-Cdc42 or mRFP1-Rac1, respectively, promoted or suppressed the association of Teal-N-WASP with Venus-IQGAP1. These 3-color FRET assays further support our in vitro results about the role of IQGAP1, Rac1, and Cdc42 in actin nucleation, and the differential impact of Rac1 and Cdc42 on the association of N-WASP with IQGAP1. In addition, this study emphasizes the power of 3-color FRET as a systems biology strategy for simultaneous evaluation of multiple interacting proteins in individual live cells. © 2015 International Society for Advancement of Cytometry.

Plasmon-enhanced energy transfer for improved upconversion of infrared radiation in doped-lanthanide nanocrystals

Science.gov (United States)

Sun, Qi; Mundoor, Haridas; Ribot, Josep; Singh, Vivek; Smalyukh, Ivan; Nagpal, Prashant

2014-03-01

Upconversion of infrared radiation into visible light has been investigated for applications in biological imaging and photovoltaics. However, low conversion efficiency due to small absorption cross-section for infrared light (Yb3+) , and slow rate of energy transfer (to Er3+ states) has prevented application of upconversion photoluminescence (UPL) for diffuse sunlight or imaging tissue samples. Here, we utilize resonant surface plasmon polaritons (SPP) waves to enhance UPL in doped-lanthanide nanocrystals. Our analysis indicates that SPP waves not only enhance the electromagnetic field, and hence weak Purcell effect, but also increases the rate of resonant energy transfer from Yb3+ to Er3+ ions by 6 fold. While we do observe strong metal mediated quenching (14 fold) of green fluorescence on flat metal surfaces, the nanostructured metal is resonant in the infrared, and hence enhances the nanocrystal UPL. This strong columbic effect on energy transfer can have important implications for other fluorescent and excitonic systems too.

Plasmon-enhanced energy transfer for improved upconversion of infrared radiation in doped-lanthanide nanocrystals.

Science.gov (United States)

Sun, Qi-C; Mundoor, Haridas; Ribot, Josep C; Singh, Vivek; Smalyukh, Ivan I; Nagpal, Prashant

2014-01-08

Upconversion of infrared radiation into visible light has been investigated for applications in photovoltaics and biological imaging. However, low conversion efficiency due to small absorption cross-section for infrared light (Yb(3+)), and slow rate of energy transfer (to Er(3+) states) has prevented application of upconversion photoluminescence (UPL) for diffuse sunlight or imaging tissue samples. Here, we utilize resonant surface plasmon polaritons (SPP) waves to enhance UPL in doped-lanthanide nanocrystals. Our analysis indicates that SPP waves not only enhance the electromagnetic field, and hence weak Purcell effect, but also increase the rate of resonant energy transfer from Yb(3+) to Er(3+) ions by 6 fold. While we do observe strong metal mediated quenching (14-fold) of green fluorescence on flat metal surfaces, the nanostructured metal is resonant in the infrared and hence enhances the nanocrystal UPL. This strong Coulombic effect on energy transfer can have important implications for other fluorescent and excitonic systems too.

A fluorescence resonance energy transfer-based approach for investigating late endosome-lysosome retrograde fusion events.

Science.gov (United States)

Kaufmann, A M; Goldman, S D B; Krise, J P

2009-03-01

Traditionally, lysosomes have been considered to be a terminal endocytic compartment. Recent studies suggest that lysosomes are quite dynamic, being able to fuse with other late endocytic compartments as well as with the plasma membrane. Here we describe a quantitative fluorescence energy transfer (FRET)-based method for assessing rates of retrograde fusion between terminal lysosomes and late endosomes in living cells. Late endosomes were specifically labeled with 800-nm latex beads that were conjugated with streptavidin and Alexa Fluor 555 (FRET donor). Terminal lysosomes were specifically labeled with 10,000-MW dextran polymers conjugated with biotin and Alexa Fluor 647 (FRET acceptor). Following late endosome-lysosome fusion, the strong binding affinity between streptavidin and biotin brought the donor and acceptor fluorophore molecules into close proximity, thereby facilitating the appearance of a FRET emission signal. Because apparent size restrictions in the endocytic pathway do not permit endocytosed latex beads from reaching terminal lysosomes in an anterograde fashion, the appearance of the FRET signal is consistent with retrograde transport of lysosomal cargo back to late endosomes. We assessed the efficiency of this transport step in fibroblasts affected by different lysosome storage disorders-Niemann-Pick type C, mucolipidosis type IV, and Sandhoff's disease, all of which have a similar lysosomal lipid accumulation phenotype. We report here, for the first time, that these disorders can be distinguished by their rate of transfer of lysosome cargos to late endosomes, and we discuss the implications of these findings for developing new therapeutic strategies.

Uphill energy transfer in photosystem I from Chlamydomonas reinhardtii. Time-resolved fluorescence measurements at 77 K.

Science.gov (United States)

Giera, Wojciech; Szewczyk, Sebastian; McConnell, Michael D; Redding, Kevin E; van Grondelle, Rienk; Gibasiewicz, Krzysztof

2018-04-04

Energetic properties of chlorophylls in photosynthetic complexes are strongly modulated by their interaction with the protein matrix and by inter-pigment coupling. This spectral tuning is especially striking in photosystem I (PSI) complexes that contain low-energy chlorophylls emitting above 700 nm. Such low-energy chlorophylls have been observed in cyanobacterial PSI, algal and plant PSI-LHCI complexes, and individual light-harvesting complex I (LHCI) proteins. However, there has been no direct evidence of their presence in algal PSI core complexes lacking LHCI. In order to determine the lowest-energy states of chlorophylls and their dynamics in algal PSI antenna systems, we performed time-resolved fluorescence measurements at 77 K for PSI core and PSI-LHCI complexes isolated from the green alga Chlamydomonas reinhardtii. The pool of low-energy chlorophylls observed in PSI cores is generally smaller and less red-shifted than that observed in PSI-LHCI complexes. Excitation energy equilibration between bulk and low-energy chlorophylls in the PSI-LHCI complexes at 77 K leads to population of excited states that are less red-shifted (by ~ 12 nm) than at room temperature. On the other hand, analysis of the detection wavelength dependence of the effective trapping time of bulk excitations in the PSI core at 77 K provided evidence for an energy threshold at ~ 675 nm, above which trapping slows down. Based on these observations, we postulate that excitation energy transfer from bulk to low-energy chlorophylls and from bulk to reaction center chlorophylls are thermally activated uphill processes that likely occur via higher excitonic states of energy accepting chlorophylls.

The use of Fluorescence Resonance Energy Transfer (FRET peptidesfor measurement of clinically important proteolytic enzymes

Directory of Open Access Journals (Sweden)

Adriana K. Carmona

2009-09-01

Full Text Available Proteolytic enzymes have a fundamental role in many biological processes and are associated with multiple pathological conditions. Therefore, targeting these enzymes may be important for a better understanding of their function and development of therapeutic inhibitors. Fluorescence Resonance Energy Transfer (FRET peptides are convenient tools for the study of peptidases specificity as they allow monitoring of the reaction on a continuous basis, providing a rapid method for the determination of enzymatic activity. Hydrolysis of a peptide bond between the donor/acceptor pair generates fluorescence that permits the measurement of the activity of nanomolar concentrations of the enzyme. The assays can be performed directly in a cuvette of the fluorimeter or adapted for determinations in a 96-well fluorescence plate reader. The synthesis of FRET peptides containing ortho-aminobenzoic acid (Abz as fluorescent group and 2, 4-dinitrophenyl (Dnp or N-(2, 4-dinitrophenylethylenediamine (EDDnp as quencher was optimized by our group and became an important line of research at the Department of Biophysics of the Federal University of São Paulo. Recently, Abz/Dnp FRET peptide libraries were developed allowing high-throughput screening of peptidases substrate specificity. This review presents the consolidation of our research activities undertaken between 1993 and 2008 on the synthesis of peptides and study of peptidases specificities.As enzimas proteolíticas têm um papel fundamental em muitos processos biológicos e estão associadas a vários estados patológicos. Por isso, o estudo da especificidade das peptidases pode ser importante para uma melhor compreensão da função destas enzimas e para o desenvolvimento de inibidores. Os substratos com supressão intramolecular de fluorescência constituem uma excelente ferramenta, pois permitem o monitoramento da reação de forma contínua, proporcionando um método prático e rápido para a determinação da

Sensitive turn-on fluorescent detection of tartrazine based on fluorescence resonance energy transfer.

Science.gov (United States)

Huang, Sheng Tian; Shi, Yan; Li, Nian Bing; Luo, Hong Qun

2012-01-18

We introduce a sensitive, rapid, label-free and general fluorescent method for the determination of tartrazine by competitive binding to reduced graphene oxide (rGO) against fluorescein, and the fluorescence recovery upon fluorescein desorption from rGO provides a quantitative readout for tartrazine, giving a detection limit of 0.53 ng mL(-1).

Reusable fluorescent sensor for captopril based on energy transfer from photoluminescent graphene oxide self-assembly multilayers to silver nanoparticles.

Science.gov (United States)

Sun, Xiangying; Liu, Bin; Li, Shuchun; Li, Fang

2016-05-15

In this work we designed a self-assembly multilayers, in which photoluminescent graphene oxide was employed as a fluorescence probe. This multilayers film can effectively recognize captopril by resonance energy transfer from graphite oxide to silver nanoparticles. A new interfacial sensing method for captopril with high signal to noise ratio was established, by means of that multilayers was quenched by silver nanoparticles and subsequently recovered by adding captopril. The linear relation between intensity and captopril concentration was good, and the detection limit was found to be 0.1578 μM. Also, this novel detection platform demonstrated intriguing reusable properties, and the sensor could be repeated more than ten times without obviously losing its sensing performance. Copyright © 2016 Elsevier B.V. All rights reserved.

From Dark to Light to Fluorescence Resonance Energy Transfer (FRET): Polarity-Sensitive Aggregation-Induced Emission (AIE)-Active Tetraphenylethene-Fused BODIPY Dyes with a Very Large Pseudo-Stokes Shift.

Science.gov (United States)

Şen, Esra; Meral, Kadem; Atılgan, Serdar

2016-01-11

The work presented herein is devoted to the fabrication of large Stokes shift dyes in both organic and aqueous media by combining dark resonance energy transfer (DRET) and fluorescence resonance energy transfer (FRET) in one donor-acceptor system. In this respect, a series of donor-acceptor architectures of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dyes substituted by one, two, or three tetraphenylethene (TPE) luminogens were designed and synthesised. The photophysical properties of these three chromophore systems were studied to provide insight into the nature of donor-acceptor interactions in both THF and aqueous media. Because the generation of emissive TPE donor(s) is strongly polarity dependent, due to its aggregation-induced emission (AIE) feature, one might expect the formation of appreciable fluorescence emission intensity with a very large pseudo-Stokes shift in aqueous media when considering FRET process. Interestingly, similar results were also recorded in THF for the chromophore systems, although the TPE fragment(s) of the dyes are non-emissive. The explanation for this photophysical behaviour lies in the DRET. This is the first report on combining two energy-transfer processes, namely, FRET and DRET, in one polarity-sensitive donor-acceptor pair system. The accuracy of the dark-emissive donor property of the TPE luminogen is also presented for the first time as a new feature for AIE phenomena. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A ratiometric fluorescent probe based on boron dipyrromethene and rhodamine Förster resonance energy transfer platform for hypochlorous acid and its application in living cells

International Nuclear Information System (INIS)

Liu, Ying; Zhao, Zhi-Min; Miao, Jun-Ying; Zhao, Bao-Xiang

2016-01-01

We have developed a ratiometric fluorescent probe BRT based on boron dipyrromethene (BODIPY) and rhodamine-thiohydrazide Förster resonance energy transfer (FRET) platform for sensing hypochlorous acid (HOCl) with high selectivity and sensitivity. The probe can detect HOCl in 15 s with the detection limit of 38 nM. Upon mixing with HOCl the fluorescence colour of probe BRT changed from green to orange. Moreover, probe BRT was applied to successfully monitor HOCl in living RAW 264.7 cells. - Highlights: • A probe based on BODIPY and rhodamine was developed for sensing HOCl. • The probe could sense HOCl in a ratiometric manner based on the FRET platform in PBS buffer solution. • The probe can detect HOCl in 15 s accompanied with a fluorescence colour change. • This probe was successfully used to monitor HOCl in living RAW 264.7 cells.

Exploiting energy transfer in hybrid metal and semiconductor nanoparticle systems for biosensing and energy harvesting

Energy Technology Data Exchange (ETDEWEB)

Mayilo, Sergiy

2009-06-19

In this work, gold and semiconductor nanoparticles are used as building blocks for nanostructures, in which energy transfer is investigated. Fluorescence quenching by gold nanoparticles is investigated and used to develop novel immunoassays for medically relevant molecules. The influence of gold nanoparticles on radiative and non-radiative rates of Cy3 and Cy3B dyes is studied here. A competitive, homogeneous immunoassay for digoxigenin and digoxin, a drug used to cure heart diseases, is developed. The assay has a limit of detection of 0.5 nM in buffer and 50 nM in serum. Time resolved spectroscopy reveals that the quenching is due to energy transfer with an efficiency of 70%. A homogeneous sandwich immunoassay for cardiac troponin T, an indicator of damage to the heart muscle, is developed. Gold nanoparticles and fluorophores are functionalized with anti-troponin T antibodies. In the presence of troponin T the nanoparticles and fluorophores form a sandwich structure, in which the dye fluorescence is quenched by a gold nanoparticle. The limit of detection of the immunoassay in buffer is 0.02 nM and 0.11 nM in serum. Energy transfer is demonstrated in clusters of CdTe nanocrystals assembled using three methods. In the first method, clusters of differently-sized water soluble CdTe nanocrystals capped by negatively charged mercaptoacid stabilizers are produced through electrostatic interactions with positively charged Ca{sup 2+} cations. The two other methods employ covalent binding through dithiols and thiolated DNA as linkers between nanocrystals. Energy transfer from smaller nanocrystals to larger nanocrystals in aggregates is demonstrated by means of steady-state and time-resolved photoluminescence spectroscopy, paving the way for nanocrystal-based light harvesting structures in solution. Multi-shell onion-like CdSe/ZnS/CdSe/ZnS nanocrystals are presented. The shade of the white light can be controlled by annealing the particles. Evidence for intra

A Quantitative Theoretical Framework For Protein-Induced Fluorescence Enhancement-Förster-Type Resonance Energy Transfer (PIFE-FRET).

Science.gov (United States)

Lerner, Eitan; Ploetz, Evelyn; Hohlbein, Johannes; Cordes, Thorben; Weiss, Shimon

2016-07-07

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.

Imaging of activated caspase-3 in living cell by fluorescence resonance energy transfer during photosensitization-induced apoptosis

Science.gov (United States)

Wu, Yunxia; Xing, Da; Chen, Qun; Tang, Yonghong

2005-01-01

Photodynamic therapy (PDT) is a novel and promising cancer treatment that employs a combination of a photosensitizing chemical and visible light, induces apoptosis in cell, and activation of caspase-3 is considered to be the final step in many apoptosis pathways. The changes of caspase-3 activation in cell during TNFα- and photodynamic therapy-induced apoptosis was measured by fluorescence resonance energy transfer (FRET) analysis. FRET probe consisting of fusions of an enhanced cyan fluorescent protein (ECFP), Venus and a linker peptide containing the caspase-3 cleavage sequence DEVD was utilized. Therefore, activated caspase-3 cleaved the linker peptide of FRET probe and disrupted the FRET signal. Human lung adenocarcinoma cell line (ASTC-a-1) were stably transfected with the plasmid (ECFP-DEVD-Venus) and then were treated by TNF-α and PDT, respectively. Experimental results indicated that caspase-3 activation resulted in cleavage of linker peptide and subsequent disruption of the FRET signal during TNFα- and photodynamic therapy-induced apoptosis, and that the activation of caspase-3 induced by photodynamic therapy was faster than that induce by TNF-α. The study supports that using FRET technique and different recombinant substrates as FRET probes could be used to detect the process of PDT-induced apoptosis and provide a new means to investigate apoptotic mechanism of PDT.

Probing intermolecular protein-protein interactions in the calcium-sensing receptor homodimer using bioluminescence resonance energy transfer (BRET)

DEFF Research Database (Denmark)

Jensen, Anders A.; Hansen, Jakob L; Sheikh, Søren P

2002-01-01

-induced intermolecular movements in the CaR homodimer using the new bioluminescence resonance energy transfer technique, BRET2, which is based on the transference of energy from Renilla luciferase (Rluc) to the green fluorescent protein mutant GFP2. We tagged CaR with Rluc and GFP2 at different intracellular locations...

A highly sensitive fluorescence resonance energy transfer aptasensor for staphylococcal enterotoxin B detection based on exonuclease-catalyzed target recycling strategy

International Nuclear Information System (INIS)

Wu, Shijia; Duan, Nuo; Ma, Xiaoyuan; Xia, Yu; Wang, Hongxin; Wang, Zhouping

2013-01-01

Graphical abstract: -- Highlights: •An ultrasensitive FRET aptasensor was developed for staphylococcal enterotoxin B determination. •SEB was recognized by SEB aptamer with high affinity and specificity. •The Mn 2+ doped NaYF 4 :Yb/Er UCNPs used as donor to quencher dye (BHQ 3 ) in new FRET. •The fluorescence intensity was prominently amplified using an exonuclease-catalyzed target recycling strategy. -- Abstract: An ultrasensitive fluorescence resonance energy transfer (FRET) bioassay was developed to detect staphylococcal enterotoxin B (SEB), a low molecular exotoxin, using an aptamer-affinity method coupled with upconversion nanoparticles (UCNPs)-sensing, and the fluorescence intensity was prominently enhanced using an exonuclease-catalyzed target recycling strategy. To construct this aptasensor, both fluorescence donor probes (complementary DNA 1 –UCNPs) and fluorescence quencher probes (complementary DNA 2 –Black Hole Quencher 3 (BHQ 3 )) were hybridized to an SEB aptamer, and double-strand oligonucleotides were fabricated, which quenched the fluorescence of the UCNPs via FRET. The formation of an aptamer–SEB complex in the presence of the SEB analyte resulted in not only the dissociation of aptamer from the double-strand DNA but also both the disruption of the FRET system and the restoration of the UCNPs fluorescence. In addition, the SEB was liberated from the aptamer–SEB complex using exonuclease I, an exonuclease specific to single-stranded DNA, for analyte recycling by selectively digesting a particular DNA (SEB aptamer). Based on this exonuclease-catalyzed target recycling strategy, an amplified fluorescence intensity could be produced using different SEB concentrations. Using optimized experimental conditions produced an ultrasensitive aptasensor for the detection of SEB, with a wide linear range of 0.001–1 ng mL −1 and a lower detection limit (LOD) of 0.3 pg mL −1 SEB (at 3σ). The fabricated aptasensor was used to measure SEB in a

Study of protein-probe complexation equilibria and protein-surfactant interaction using charge transfer fluorescence probe methyl ester of N,N-dimethylamino naphthyl acrylic acid

Energy Technology Data Exchange (ETDEWEB)

Mahanta, Subrata; Balia Singh, Rupashree; Bagchi, Arnab [Department of Chemistry University of Calcutta 92, A.P.C. Road, Kolkata 700009 (India); Nath, Debnarayan [Department of Physical Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Guchhait, Nikhil, E-mail: nguchhait@yahoo.co [Department of Chemistry University of Calcutta 92, A.P.C. Road, Kolkata 700009 (India)

2010-06-15

In this paper, we demonstrate the interaction between intramolecular charge transfer (ICT) probe-Methyl ester of N,N-dimethylamino naphthyl acrylic acid (MDMANA) with bovine serum albumin (BSA) using absorption and fluorescence emission spectroscopy. The nature of probe protein binding interaction, fluorescence resonance energy transfer from protein to probe and time resolved fluorescence decay measurement predict that the probe molecule binds strongly to the hydrophobic cavity of the protein. Furthermore, the interaction of the anionic surfactant sodium dodecyl sulphate (SDS) with water soluble protein BSA has been investigated using MDMANA as fluorescenece probe. The changes in the spectral characteristics of charge transfer fluorescence probe MDMANA in BSA-SDS environment reflects well the nature of the protein-surfactant binding interaction such as specific binding, non-cooperative binding, cooperative binding and saturation binding.

A fluorescence resonance energy transfer-based approach for investigating late endosome–lysosome retrograde fusion events

Science.gov (United States)

Kaufmann, A.M.; Goldman, S.D.B.; Krise, J.P.

2009-01-01

Traditionally, lysosomes have been considered to be a terminal endocytic compartment. Recent studies suggest that lysosomes are quite dynamic, being able to fuse with other late endocytic compartments as well as with the plasma membrane. Here we describe a quantitative fluorescence energy transfer (FRET)-based method for assessing rates of retrograde fusion between terminal lysosomes and late endosomes in living cells. Late endosomes were specifically labeled with 800-nm latex beads that were conjugated with streptavidin and Alexa Fluor 555 (FRET donor). Terminal lysosomes were specifically labeled with 10,000-MW dextran polymers conjugated with biotin and Alexa Fluor 647 (FRET acceptor). Following late endosome–lysosome fusion, the strong binding affinity between streptavidin and biotin brought the donor and acceptor fluorophore molecules into close proximity, thereby facilitating the appearance of a FRET emission signal. Because apparent size restrictions in the endocytic pathway do not permit endocytosed latex beads from reaching terminal lysosomes in an anterograde fashion, the appearance of the FRET signal is consistent with retrograde transport of lysosomal cargo back to late endosomes. We assessed the efficiency of this transport step in fibroblasts affected by different lysosome storage disorders—Niemann–Pick type C, mucolipidosis type IV, and Sandhoff’s disease, all of which have a similar lysosomal lipid accumulation phenotype. We report here, for the first time, that these disorders can be distinguished by their rate of transfer of lysosome cargos to late endosomes, and we discuss the implications of these findings for developing new therapeutic strategies. PMID:19109922

Time-resolved spectroscopy and fluorescence resonance energy transfer in the study of excimer laser damage of chromatin

Energy Technology Data Exchange (ETDEWEB)

Radu, L. [Department of Molecular Genetics and Radiobiology, Babes National Institute, Bucharest (Romania)], E-mail: lilianajradu@yahoo.fr; Mihailescu, I. [Department of Lasers, Laser, Plasma and Radiation Physics Institute, Bucharest (Romania); Radu, S. [Department of Computer Science, Polytechnics University, Bucharest (Romania); Gazdaru, D. [Department of Biophysics, Bucharest University (Romania)

2007-09-21

The analysis of chromatin damage produced by a 248 nm excimer laser radiation, for doses of 0.3-3 MJ/m{sup 2} was carried out by time-resolved spectroscopy and fluorescence resonance energy transfer (FRET). The chromatin was extracted from a normal and a tumoral tissue of Wistar rats. The decrease with laser dose of the relative contribution of the excited state lifetimes of ethidium bromide (EtBr) bounded to chromatin constitutes an evidence of the reduction of chromatin deoxyribonucleic acid (DNA) double-strand structure. FRET was performed from dansyl chloride to acridine orange, both coupled to chromatin. The increase of the average distance between these ligands, under the action of laser radiation, reflects a loosening of the chromatin structure. The radiosensitivity of tumor tissue chromatin is higher than that of a normal tissue. The determination of the chromatin structure modification in an excimer laser field can be of interest in laser therapy.

Time-resolved spectroscopy and fluorescence resonance energy transfer in the study of excimer laser damage of chromatin

International Nuclear Information System (INIS)

Radu, L.; Mihailescu, I.; Radu, S.; Gazdaru, D.

2007-01-01

The analysis of chromatin damage produced by a 248 nm excimer laser radiation, for doses of 0.3-3 MJ/m 2 was carried out by time-resolved spectroscopy and fluorescence resonance energy transfer (FRET). The chromatin was extracted from a normal and a tumoral tissue of Wistar rats. The decrease with laser dose of the relative contribution of the excited state lifetimes of ethidium bromide (EtBr) bounded to chromatin constitutes an evidence of the reduction of chromatin deoxyribonucleic acid (DNA) double-strand structure. FRET was performed from dansyl chloride to acridine orange, both coupled to chromatin. The increase of the average distance between these ligands, under the action of laser radiation, reflects a loosening of the chromatin structure. The radiosensitivity of tumor tissue chromatin is higher than that of a normal tissue. The determination of the chromatin structure modification in an excimer laser field can be of interest in laser therapy

Application of multivariate curve resolution for the study of folding processes of DNA monitored by fluorescence resonance energy transfer

International Nuclear Information System (INIS)

Kumar, Praveen; Kanchan, Kajal; Gargallo, Raimundo; Chowdhury, Shantanu

2005-01-01

The study described in the present article used fluorescence resonance energy transfer (FRET) to monitor the folding of a 31-mer cytosine-rich DNA segment, from the promoter region of the human c-myc oncogene. Spectroscopic FRET data recorded during experiments carried out in different experimental conditions were individually and simultaneously analyzed by multivariate curve resolution. The simultaneous analysis of several data matrices allowed the resolution of the system, removing most of the ambiguities related to factor analysis. From the results obtained, we report the evidence of the formation of two ordered conformations in acidic and neutral pH values, in addition to the disordered structure found at high temperatures. These ordered conformations could be related to cytosine-tetraplex structures showing different degrees of protonation in cytosine bases

Interfacial transduction of nucleic acid hybridization using immobilized quantum dots as donors in fluorescence resonance energy transfer.

Science.gov (United States)

Algar, W Russ; Krull, Ulrich J

2009-01-06

Fluorescence resonance energy transfer (FRET) using immobilized quantum dots (QDs) as energy donors was explored as a transduction method for the detection of nucleic acid hybridization at an interface. This research was motivated by the success of the QD-FRET-based transduction of nucleic acid hybridization in solution-phase assays. This new work represents a fundamental step toward the assembly of a biosensor, where immobilization of the selective chemistry on a surface is desired. After immobilizing QD-probe oligonucleotide conjugates on optical fibers, a demonstration of the retention of selectivity was achieved by the introduction of acceptor (Cy3)-labeled single-stranded target oligonucleotides. Hybridization generated the proximity required for FRET, and the resulting fluorescence spectra provided an analytical signal proportional to the amount of target. This research provides an important framework for the future development of nucleic acid biosensors based on QDs and FRET. The most important findings of this work are that (1) a QD-FRET solid-phase hybridization assay is viable and (2) a passivating layer of denatured bovine serum albumin alleviates nonspecific adsorption, ultimately resulting in (3) the potential for a reusable assay format and mismatch discrimination. In this, the first incarnation of a solid-phase QD-FRET hybridization assay, the limit of detection was found to be 5 nM, and the dynamic range was almost 2 orders of magnitude. Selective discrimination of the target was shown using a three-base-pairs mismatch from a fully complementary sequence. Despite a gradual loss of signal, reuse of the optical fibers over multiple cycles of hybridization and dehybridization was possible. Directions for further improvement of the analytical performance by optimizing the design of the QD-probe oligonucleotide interface are identified.

Interaction and energy transfer studies between bovine serum albumin and CdTe quantum dots conjugates: CdTe QDs as energy acceptor probes.

Science.gov (United States)

Kotresh, M G; Inamdar, L S; Shivkumar, M A; Adarsh, K S; Jagatap, B N; Mulimani, B G; Advirao, G M; Inamdar, S R

2017-06-01

In this paper, a systematic investigation of the interaction of bovine serum albumin (BSA) with water-soluble CdTe quantum dots (QDs) of two different sizes capped with carboxylic thiols is presented based on steady-state and time-resolved fluorescence measurements. Efficient Förster resonance energy transfer (FRET) was observed to occur from BSA donor to CdTe acceptor as noted from reduction in the fluorescence of BSA and enhanced fluorescence from CdTe QDs. FRET parameters such as Förster distance, spectral overlap integral, FRET rate constant and efficiency were determined. The quenching of BSA fluorescence in aqueous solution observed in the presence of CdTe QDs infers that fluorescence resonance energy transfer is primarily responsible for the quenching phenomenon. Bimolecular quenching constant (k q ) determined at different temperatures and the time-resolved fluorescence data provide additional evidence for this. The binding stoichiometry and various thermodynamic parameters are evaluated by using the van 't Hoff equation. The analysis of the results suggests that the interaction between BSA and CdTe QDs is entropy driven and hydrophobic forces play a key role in the interaction. Binding of QDs significantly shortened the fluorescence lifetime of BSA which is one of the hallmarks of FRET. The effect of size of the QDs on the FRET parameters are discussed in the light of FRET parameters obtained. Copyright © 2016 John Wiley & Sons, Ltd.

Visualization of Stereoselective Supramolecular Polymers by Chirality-Controlled Energy Transfer.

Science.gov (United States)

Sarkar, Aritra; Dhiman, Shikha; Chalishazar, Aditya; George, Subi J

2017-10-23

Chirality-driven self-sorting is envisaged to efficiently control functional properties in supramolecular materials. However, the challenge arises because of a lack of analytical methods to directly monitor the enantioselectivity of the resulting supramolecular assemblies. Presented herein are two fluorescent core-substituted naphthalene-diimide-based donor and acceptor molecules with minimal structural mismatch and they comprise strong self-recognizing chiral motifs to determine the self-sorting process. As a consequence, stereoselective supramolecular polymerization with an unprecedented chirality control over energy transfer has been achieved. This chirality-controlled energy transfer has been further exploited as an efficient probe to visualize microscopically the chirality driven self-sorting. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photoinduced charge and energy transfer in dye-doped conjugated polymers

International Nuclear Information System (INIS)

Veldman, Dirk; Bastiaansen, Jolanda J.A.M.; Langeveld-Voss, Bea M.W.; Sweelssen, Joergen; Koetse, Marc M.; Meskers, Stefan C.J.; Janssen, Rene A.J.

2006-01-01

Conjugated polymer-molecular dye blends of MDMO-PPV (poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene]) and PF1CVTP (poly[9,9-dioctylfluorene-2,7-diyl-alt-2,5-bis(2-thienyl-1-cyanovinyl) -1-(3',7= '-dimethyloctyloxy)-4-methoxybenzene-5'',5''-diyl]) with three dipyrrometheneboron difluoride (bodipy) dyes were studied by (time-resolved) fluorescence and photoinduced absorption spectroscopy to determine quantitatively the relation between the electronic HOMO and LUMO levels and the occurrence of energy or charge transfer after optical excitation. We find that for MDMO-PPV photoinduced charge transfer to the dyes occurs, while photoexcitation of PF1CVTP exclusively results in energy transfer. The differences can be rationalized by assuming that the energy of the charge separated state is 0.33-0.45 eV higher than the energy determined from oxidation and reduction potentials of donor and acceptor, respectively. This provides an important design rule to identify appropriate materials for polymer solar cells that can have a high open-circuit voltage

Energy transfer dynamics from individual semiconductor nanoantennae to dye molecules with implication to light-harvesting nanosystems

Science.gov (United States)

Shan, Guangcun; Hu, Mingjun; Yan, Ze; Li, Xin; Huang, Wei

2018-03-01

Semiconductor nanocrystals can be used as nanoscale optical antennae to photoexcite individual dye molecules in an ensemble via energy transfer mechanism. The theoretical framework developed by Förster and others describes how electronic excitation migrates in the photosynthetic apparatus of plants, algae, and bacteria from light absorbing pigments to reaction centers where light energy is utilized for the eventual conversion into chemical energy. Herein we investigate the effect of the average donor-acceptor spacing on the time-resolved fluorescence intensity and dynamics of single donor-acceptor pairs with the dye acceptor concentration decreasing by using quantum Monte-Carlo simulation of FRET dynamics. Our results validated that the spatial disorder controlling the microscopic energy transfer rates accounts for the scatter in donor fluorescence lifetimes and intensities, which provides a new design guideline for artificial light-harvesting nanosystems.

A graphene oxide based fluorescence resonance energy transfer (FRET) biosensor for ultrasensitive detection of botulinum neurotoxin A (BoNT/A) enzymatic activity.

Science.gov (United States)

Shi, Jingyu; Guo, Jiubiao; Bai, Gongxun; Chan, Chunyu; Liu, Xuan; Ye, Weiwei; Hao, Jianhua; Chen, Sheng; Yang, Mo

2015-03-15

Botulinum neurotoxins (BoNTs) are among the most potent toxic bacterial proteins for humans, which make them potential agents for bioterrorism. Therefore, an ultrasensitive detection of BoNTs and their active states is in great need as field-deployable systems for anti-terrorism applications. We report the construction of a novel graphene oxide (GO)-peptide based fluorescence resonance energy transfer (FRET) biosensor for ultrasensitive detection of the BoNT serotype A light chain (BoNT-LcA) protease activity. A green fluorescence protein (GFP) modified SNAP-25 peptide substrate (SNAP-25-GFP) was optimally designed and synthesized with the centralized recognition/cleavage sites. This FRET platform was constructed by covalent immobilization of peptide substrate on GO with BSA passivation which have advantages of low non-specific adsorption and high stability in protein abundant solution. BoNT-LcA can specifically cleave SNAP-25-GFP substrate covalently immobilized on GO to release the fragment with GFP. Based on fluorescence signal recovery measurement, the target BoNT-LcA was detected sensitively and selectively with the linear detection range from 1fg/mL to 1pg/mL. The limit of detection (LOD) for BoNT-LcA is around 1fg/mL. Copyright © 2014 Elsevier B.V. All rights reserved.

State-to-state dynamics of molecular energy transfer

Energy Technology Data Exchange (ETDEWEB)

Gentry, W.R.; Giese, C.F. [Univ. of Minnesota, Minneapolis (United States)

1993-12-01

The goal of this research program is to elucidate the elementary dynamical mechanisms of vibrational and rotational energy transfer between molecules, at a quantum-state resolved level of detail. Molecular beam techniques are used to isolate individual molecular collisions, and to control the kinetic energy of collision. Lasers are used both to prepare specific quantum states prior to collision by stimulated-emission pumping (SEP), and to measure the distribution of quantum states in the collision products by laser-induced fluorescence (LIF). The results are interpreted in terms of dynamical models, which may be cast in a classical, semiclassical or quantum mechanical framework, as appropriate.

Energy transfer from carotenoids to chlorophyll in blue-green, red and green algae and greening bean leaves

NARCIS (Netherlands)

Goedheer, J.C.

1969-01-01

From fluorescence action spectra, fluorescence spectra and absorption spectra measured at room temperature and at 77 °K of light petroleum (b.p. 40–60°)-treated and normal chloroplasts, it is concluded that: 1. 1. In blue-green and red algae energy transfer from β-carotene to chlorophyll occurs

Characterization and inhibition of norovirus proteases of genogroups I and II using a fluorescence resonance energy transfer assay

International Nuclear Information System (INIS)

Chang, Kyeong-Ok; Takahashi, Daisuke; Prakash, Om; Kim, Yunjeong

2012-01-01

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.

Time-resolved stimulated emission depletion and energy transfer dynamics in two-photon excited EGFP

Science.gov (United States)

Masters, T. A.; Robinson, N. A.; Marsh, R. J.; Blacker, T. S.; Armoogum, D. A.; Larijani, B.; Bain, A. J.

2018-04-01

Time and polarization-resolved stimulated emission depletion (STED) measurements are used to investigate excited state evolution following the two-photon excitation of enhanced green fluorescent protein (EGFP). We employ a new approach for the accurate STED measurement of the hitherto unmeasured degree of hexadecapolar transition dipole moment alignment ⟨α40 ⟩ present at a given excitation-depletion (pump-dump) pulse separation. Time-resolved polarized fluorescence measurements as a function of pump-dump delay reveal the time evolution of ⟨α40 ⟩ to be considerably more rapid than predicted for isotropic rotational diffusion in EGFP. Additional depolarization by homo-Förster resonance energy transfer is investigated for both ⟨α20 ⟩ (quadrupolar) and ⟨α40 ⟩ transition dipole alignments. These results point to the utility of higher order dipole correlation measurements in the investigation of resonance energy transfer processes.

Energy transfer and cross-relaxation in Tb3+-doped borosilicate glasses

International Nuclear Information System (INIS)

Kim, Jung Hwan; Sol, Jung Sik

1990-01-01

Energy transfer in Tb 3+ -doped borosilicate glasses has been studied by the analysis of fluorescence intensities and lifetimes of 5 D 3 and 5 D 4 states as a function of Tb 3+ concentration. It is shown that as the Tb 3+ concentration is increased the cross-relaxation produces high population of the 5 D 4 state at the expense of 5 D 3 . It is also found that this interaction is predominantly dipole-dipole transition with critical distance of 13 A. The critical distance for energy transfer 5 D 4 5 D 3 which is responsible for the quenching of 5 D 4 emission at high concentration of Tb 3+ ions is 4.5 A. (Author)

Rotational energy transfer of the A{sup 2}{Sigma}`({nu}`=1) state of OH

Energy Technology Data Exchange (ETDEWEB)

Beaud, P; Radi, P; Frey, H B; Mischler, B; Tzannis, A P; Gerber, T [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1997-06-01

Spectrally and temporally resolved laser excited fluorescence of OH is investigated in the picosecond time domain. The total rotational energy transfer (RET) rate from the excited state is determined from the experimental data. Simulated spectra obtained by modelling RET with the energy corrected sudden approximation agree well with the measured spectra. (author) 1 fig., 1 tab., 5 refs.

Selective fluorescence resonance energy transfer from serum albumins to a bio-active 3-pyrazolyl-2-pyrazoline derivative: A spectroscopic analysis

Energy Technology Data Exchange (ETDEWEB)

Sarkar, Arindam [Department of Chemistry, Jadavpur University, Kolkata 700032 (India); Bhattacharya, Subhash Chandra, E-mail: sbjuchem@yahoo.com [Department of Chemistry, Jadavpur University, Kolkata 700032 (India)

2012-10-15

A novel fluorescent probe and pharmaceutically significant: 3-pyrazolyl-2-pyrazoline derivative (PYZ) has been selected as an acceptor molecule for fluorescence resonance energy transfer (FRET) interaction with serum albumins. Steady state and time resolved fluorescence techniques were applied to elucidate the nature of interaction of PYZ with serum albumins (BSA and HSA). Negligible FRET mediated emission occurred in the case of HSA but an efficient FRET mediated emission resulted in case of BSA. To gain further insight into the FRET selectivity of PYZ with the proteins, FRET from L-tryptophan (donor; native tryptophan) to PYZ (acceptor) was performed with the aim of getting an idea about the steric restrictions imposed on PYZ by the other groups present in BSA and HSA. The studies revealed that the surface bound Trp-134 in BSA allows an efficient FRET process with PYZ while the buried Trp-214 in HSA does not. The unusual selectivity for FRET in case of PYZ and the serum albumins has also been attributed to the complex structure of PYZ due to the presence of bulkier phenyl moieties in it. The complex nature of the excited state photophysics of tryptophan (Trp) in proteins also accounts for this FRET selectivity of PYZ with BSA and HSA. - Highlights: Black-Right-Pointing-Pointer FRET from BSA/HSA to PYZ was monitored using steady state and time resolved fluorescence methods. Black-Right-Pointing-Pointer Efficient FRET process resulted in BSA-PYZ system in contrast with the HSA-PYZ system. Black-Right-Pointing-Pointer Surface bound Trp-134 in BSA facilitates the FRET process with PYZ than the buried Trp-214 in HSA. Black-Right-Pointing-Pointer Rigid and complex structure of PYZ also accounts for the FRET selectivity of PYZ with BSA/HSA.

Bio-Inspired Photon Absorption and Energy Transfer for Next Generation Photovoltaic Devices

Science.gov (United States)

Magsi, Komal

Nature's solar energy harvesting system, photosynthesis, serves as a model for photon absorption, spectra broadening, and energy transfer. Photosynthesis harvests light far differently than photovoltaic cells. These differences offer both engineering opportunity and scientific challenges since not all of the natural photon absorption mechanisms have been understood. In return, solar cells can be a very sensitive probe for the absorption characteristics of molecules capable of transferring charge to a conductive interface. The objective of this scientific work is the advancement of next generation photovoltaics through the development and application of natural photo-energy transfer processes. Two scientific methods were used in the development and application of enhancing photon absorption and transfer. First, a detailed analysis of photovoltaic front surface fluorescent spectral modification and light scattering by hetero-structure was conducted. Phosphor based spectral down-conversion is a well-known laser technology. The theoretical calculations presented here indicate that parasitic losses and light scattering within the spectral range are large enough to offset any expected gains. The second approach for enhancing photon absorption is based on bio-inspired mechanisms. Key to the utilization of these natural processes is the development of a detailed scientific understanding and the application of these processes to cost effective systems and devices. In this work both aspects are investigated. Dye type solar cells were prepared and tested as a function of Chlorophyll (or Sodium-Copper Chlorophyllin) and accessory dyes. Forster has shown that the fluorescence ratio of Chlorophyll is modified and broadened by separate photon absorption (sensitized absorption) through interaction with nearby accessory pigments. This work used the dye type solar cell as a diagnostic tool by which to investigate photon absorption and photon energy transfer. These experiments shed

Dexter energy transfer pathways.

Science.gov (United States)

Skourtis, Spiros S; Liu, Chaoren; Antoniou, Panayiotis; Virshup, Aaron M; Beratan, David N

2016-07-19

Energy transfer with an associated spin change of the donor and acceptor, Dexter energy transfer, is critically important in solar energy harvesting assemblies, damage protection schemes of photobiology, and organometallic opto-electronic materials. Dexter transfer between chemically linked donors and acceptors is bridge mediated, presenting an enticing analogy with bridge-mediated electron and hole transfer. However, Dexter coupling pathways must convey both an electron and a hole from donor to acceptor, and this adds considerable richness to the mediation process. We dissect the bridge-mediated Dexter coupling mechanisms and formulate a theory for triplet energy transfer coupling pathways. Virtual donor-acceptor charge-transfer exciton intermediates dominate at shorter distances or higher tunneling energy gaps, whereas virtual intermediates with an electron and a hole both on the bridge (virtual bridge excitons) dominate for longer distances or lower energy gaps. The effects of virtual bridge excitons were neglected in earlier treatments. The two-particle pathway framework developed here shows how Dexter energy-transfer rates depend on donor, bridge, and acceptor energetics, as well as on orbital symmetry and quantum interference among pathways.

A Dansyl Fluorescence-Based Assay for Monitoring Kinetics of Lipid Extraction and Transfer

Science.gov (United States)

Ran, Yong

2008-01-01

Lipid transfer proteins (LTPs) play important roles in cellular biology, and fluorescence spectroscopy has found wide range use as a facile means for time-resolved monitoring of protein-lipid interactions[1]. Here, we show how the fluorescence emission properties of dansyl-DHPE can be exploited to characterize lipid extraction and lipid transfer kinetics. The GM2 activator protein serves as an example LTP where the ability to independently characterize lipid extraction from donor vesicles, formation of a protein:lipid complex in solution, and release of lipid from the complex to acceptor liposomes is crucial for full kinetic characterization of lipid transfer. PMID:18694718

Electronic-excitation energy transfer in heterogeneous dye solutions under laser excitation

International Nuclear Information System (INIS)

Levshin, L.V.; Mukushev, B.T.; Saletskii, A.M.

1995-01-01

An experimental study has been made of electronic-excitation energy transfer (EEET) among dye molecules of different types for different exciting-fight wavelengths and temperatures. Upon selective laser excitation of the donor, the inhomogeneous broadening of molecular levels increases the probability of EEET from the donor to acceptor molecules. The efficiency of this process is directly proportional to the acceptor molecule concentration and is temperature dependent. The EEET is accompanied by the spectral migration of energy among donor molecules, which reduces the fluorescence quantum efficiency of the donor. Increasing the frequency of the exciting light decreases in the donor fluorescence quantum efficiency. An increase in the acceptor molecule concentration results in a decrease of the spectral migration of excitation in the donor molecule system. 5 refs., 5 figs

Influence of silver nanoparticles on relaxation processes and efficiency of dipole – dipole energy transfer between dye molecules in polymethylmethacrylate films

Energy Technology Data Exchange (ETDEWEB)

Bryukhanov, V V; Borkunov, R Yu; Tsarkov, M V [Immanuel Kant Baltic Federal University, Kaliningrad (Russian Federation); Konstantinova, E I; Slezhkin, V A [Kaliningrad State Technical University, Kaliningrad (Russian Federation)

2015-10-31

The fluorescence and phosphorescence of dyes in thin polymethylmethacrylate (PMMA) films in the presence of ablated silver nanoparticles has been investigated in a wide temperature range by methods of femtosecond and picosecond laser photoexcitation. The fluorescence and phosphorescence times, as well as spectral and kinetic characteristics of rhodamine 6G (R6G) molecules in PMMA films are measured in a temperature range of 80 – 330 K. The temperature quenching activation energy of the fluorescence of R6G molecules in the presence of ablated silver nanoparticles is found. The vibrational relaxation rate of R6G in PMMA films is estimated, the efficiency of the dipole – dipole electron energy transfer between R6G and brilliant green molecules (enhanced by plasmonic interaction with ablated silver nanoparticles) is analysed, and the constants of this energy transfer are determined. (nanophotonics)

Influence of silver nanoparticles on relaxation processes and efficiency of dipole – dipole energy transfer between dye molecules in polymethylmethacrylate films

International Nuclear Information System (INIS)

Bryukhanov, V V; Borkunov, R Yu; Tsarkov, M V; Konstantinova, E I; Slezhkin, V A

2015-01-01

The fluorescence and phosphorescence of dyes in thin polymethylmethacrylate (PMMA) films in the presence of ablated silver nanoparticles has been investigated in a wide temperature range by methods of femtosecond and picosecond laser photoexcitation. The fluorescence and phosphorescence times, as well as spectral and kinetic characteristics of rhodamine 6G (R6G) molecules in PMMA films are measured in a temperature range of 80 – 330 K. The temperature quenching activation energy of the fluorescence of R6G molecules in the presence of ablated silver nanoparticles is found. The vibrational relaxation rate of R6G in PMMA films is estimated, the efficiency of the dipole – dipole electron energy transfer between R6G and brilliant green molecules (enhanced by plasmonic interaction with ablated silver nanoparticles) is analysed, and the constants of this energy transfer are determined. (nanophotonics)

Leading coordinate analysis of reaction pathways in proton chain transfer: Application to a two-proton transfer model for the green fluorescent protein

International Nuclear Information System (INIS)

Wang Sufan; Smith, Sean C.

2006-01-01

The 'leading coordinate' approach to computing an approximate reaction pathway, with subsequent determination of the true minimum energy profile, is applied to a two-proton chain transfer model based on the chromophore and its surrounding moieties within the green fluorescent protein (GFP). Using an ab initio quantum chemical method, a number of different relaxed energy profiles are found for several plausible guesses at leading coordinates. The results obtained for different trial leading coordinates are rationalized through the calculation of a two-dimensional relaxed potential energy surface (PES) for the system. Analysis of the 2-D relaxed PES reveals that two of the trial pathways are entirely spurious, while two others contain useful information and can be used to furnish starting points for successful saddle-point searches. Implications for selection of trial leading coordinates in this class of proton chain transfer reactions are discussed, and a simple diagnostic function is proposed for revealing whether or not a relaxed pathway based on a trial leading coordinate is likely to furnish useful information

Vibrational energy flow through the green fluorescent protein-water interface: communication maps and thermal boundary conductance.

Science.gov (United States)

Xu, Yao; Leitner, David M

2014-07-17

We calculate communication maps for green fluorescent protein (GFP) to elucidate energy transfer pathways between the chromophore and other parts of the protein in the ground and excited state. The approach locates energy transport channels from the chromophore to remote regions of the protein via residues and water molecules that hydrogen bond to the chromophore. We calculate the thermal boundary conductance between GFP and water over a wide range of temperature and find that the interface between the protein and the cluster of water molecules in the β-barrel poses negligible resistance to thermal flow, consistent with facile vibrational energy transfer from the chromophore to the β-barrel waters observed in the communication maps.

Fluorescence fluctuation spectroscopy (FFS)

CERN Document Server

Tetin, Sergey

2012-01-01

This new volume of Methods in Enzymology continues the legacy of this premier serial with quality chapters authored by leaders in the field. This volume covers fluorescence fluctuation spectroscopy and includes chapters on such topics as Förster resonance energy transfer (fret) with fluctuation algorithms, protein corona on nanoparticles by FCS, and FFS approaches to the study of receptors in live cells. Continues the legacy of this premier serial with quality chapters authored by leaders in the field Covers fluorescence fluctuation spectroscopy Contains chapters on such topics as Förster resonance energy transfer (fret) with fluctuation algorithms, protein corona on nanoparticles by FCS, and FFS approaches to the study of receptors in live cells.

Biomolecule-to-fluorescent-color encoder: modulation of fluorescence emission via DNA structural changes

Science.gov (United States)

Nishimura, Takahiro; Ogura, Yusuke; Yamada, Kenji; Ohno, Yuko; Tanida, Jun

2014-01-01

A biomolecule-to-fluorescent-color (B/F) encoder for optical readout of biomolecular information is proposed. In the B/F encoder, a set of fluorescence wavelengths and their intensity levels are used for coding of a biomolecular signal. A hybridization chain reaction of hairpin DNAs labeled with fluorescent reporters was performed to generate the fluorescence color codes. The fluorescence is modulated via fluorescence resonance energy transfer, which is controlled by DNA structural changes. The results demonstrate that fluorescent color codes can be configured based on two wavelengths and five intensities using the B/F encoder, and the assigned codes can be retrieved via fluorescence measurements. PMID:25071950

Nonradiative inter- and intramolecular energy transfer from the aromatic donor anisole to a synthesized photoswitchable acceptor system.

Science.gov (United States)

Bardhan, Munmun; Bhattacharya, Sudeshna; Misra, Tapas; Mukhopadhyay, Rupa; De, Asish; Chowdhury, Joydeep; Ganguly, Tapan

2010-02-01

We report steady state and time resolved fluorescence measurements on acetonitrile (ACN) solutions of the model compounds, energy donor anisole (A) and a photoswitchable acceptor N,N'-1,2-phenylene di-p-tosylamide (B) and the multichromophore (M) where A and B are connected by a spacer containing both rigid triple (acetylenic) and flexible methylene bonds. Both steady state and time correlated single photon counting measurements demonstrate that though intermolecular energy transfer, of Forster type, between the donor and acceptor moieties occurs with rate 10(8)s(-1) but when these two reacting components are linked by a spacer (multichromophore, M) the observed transfer rate ( approximately 10(11)s(-1)) enhances. This seemingly indicates that the imposition of the spacer by inserting a triple bond may facilitate in the propagation of electronic excitation energy through bond. The time resolved fluorescence measurements along with the theoretical predictions using Configuration interaction singles (CIS) method by using 6-31G (d,p) basis set, implemented in the Gaussian package indicate the formations of the two excited conformers of B. The experimental findings made from the steady state and time resolved fluorescence measurements demonstrate that, though two different isomeric species of the acceptor B are formed in the excited singlet states, the prevailing singlet-singlet nonradiative energy transfer route was found from the donor A to the relatively longer-lived isomeric species of B. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Investigation of energy transfer in ion associates by the nanosecond multichannel analysis

International Nuclear Information System (INIS)

Ermolaev, V.L.; Kotlyar, I.P.; Turaeva, Z.N.; Shakhverdov, T.A.

1980-01-01

The one-photon counting method is used to study the kinetics of fluorescence attenuation of pyrenetetrasulfonate and eosin bound into associates with ions of rare-earth elements in dimethylsulfoxide. This attenuation is shown to be exponential for all cases. The disagreement is found between the values of quenching of associates fluorescence, which are detrmined from its quantum yield and the lifetime with full complexing of the ligand. The results obtained are interpreted based on the existence in the solution of two types of complexes (extraspherical and intraspherical)in equilibrium. Basis parameters of energy transfer in each complex are determined

Color optimization of conjugated-polymer/InGaN hybrid white light emitting diodes by incomplete energy transfer

International Nuclear Information System (INIS)

Chang, Chi-Jung; Lai, Chun-Feng; Madhusudhana Reddy, P.; Chen, Yung-Lin; Chiou, Wei-Yung; Chang, Shinn-Jen

2015-01-01

By using the wavelength conversion method, white light emitting diodes (WLEDs) were produced by applying mixtures of polysiloxane and fluorescent polymers on InGaN based light emitting diodes. UV curable organic–inorganic hybrid materials with high refractive index (1.561), compromised optical, thermal and mechanical properties was used as encapsulants. Red light emitting fluorescent FABD polymer (with 9,9-dioctylfluorene (F), anthracene (A) and 2,1,3-benzothiadiazole (B), and 4,7-bis(2-thienyl)-2,1,3-benzothiadiazole (D) repeating units) and green light emitting fluorescent FAB polymer were used as wavelength converters. The encapsulant/fluorescent polymer mixture and InGaN produce the white light by incomplete energy transfer mechanism. WLEDs with high color rendering index (CRI, about 93), and tunable correlated color temperature (CCT) properties can be produced by controlling the composition and chemical structures of encapsulating polymer and fluorescent polymer in hybrid materials, offering cool-white and neutral-white LEDs. - Highlights: • Highly efficient white light-emitting diodes (WLEDs) were produced. • Conjugated-polymer/InGaN hybrid WLEDs by incomplete energy transfer mechanism. • WLEDs with high color-rendering index and tunable correlated color temperature. • Polysiloxane encapsulant with superior optical, mechanical and thermal properties

Triplet-triplet energy transfer from a UV-A absorber butylmethoxydibenzoylmethane to UV-B absorbers.

Science.gov (United States)

Kikuchi, Azusa; Oguchi-Fujiyama, Nozomi; Miyazawa, Kazuyuki; Yagi, Mikio

2014-01-01

The phosphorescence decay of a UV-A absorber, 4-tert-butyl-4'-methoxydibenzolymethane (BMDBM) has been observed following a 355 nm laser excitation in the absence and presence of UV-B absorbers, 2-ethylhexyl 4-methoxycinnamate (octyl methoxycinnamate, OMC) and octocrylene (OCR) in ethanol at 77 K. The lifetime of the lowest excited triplet (T1) state of BMDBM is significantly reduced in the presence of OMC and OCR. The observed quenching of BMDBM triplet by OMC and OCR suggests that the intermolecular triplet-triplet energy transfer occurs from BMDBM to OMC and OCR. The T1 state of OCR is nonphosphorescent or very weakly phosphorescent. However, we have shown that the energy level of the T1 state of OCR is lower than that of the enol form of BMDBM. Our methodology of energy-donor phosphorescence decay measurements can be applied to the study of the triplet-triplet energy transfer between UV absorbers even if the energy acceptor is nonphosphorescent. In addition, the delayed fluorescence of BMDBM due to triplet-triplet annihilation was observed in the BMDBM-OMC and BMDBM-OCR mixtures in ethanol at 77 K. Delayed fluorescence is one of the deactivation processes of the excited states of BMDBM under our experimental conditions. © 2013 The American Society of Photobiology.

Efficient Fluorescence Resonance Energy Transfer between Quantum Dots and Gold Nanoparticles Based on Porous Silicon Photonic Crystal for DNA Detection.

Science.gov (United States)

Zhang, Hongyan; Lv, Jie; Jia, Zhenhong

2017-05-10

A novel assembled biosensor was prepared for detecting 16S rRNA, a small-size persistent specific for Actinobacteria. The mechanism of the porous silicon (PS) photonic crystal biosensor is based on the fluorescence resonance energy transfer (FRET) between quantum dots (QDs) and gold nanoparticles (AuNPs) through DNA hybridization, where QDs act as an emission donor and AuNPs serve as a fluorescence quencher. Results showed that the photoluminescence (PL) intensity of PS photonic crystal was drastically increased when the QDs-conjugated probe DNA was adhered to the PS layer by surface modification using a standard cross-link chemistry method. The PL intensity of QDs was decreased when the addition of AuNPs-conjugated complementary 16S rRNA was dropped onto QDs-conjugated PS. Based on the analysis of different target DNA concentration, it was found that the decrease of the PL intensity showed a good linear relationship with complementary DNA concentration in a range from 0.25 to 10 μM, and the detection limit was 328.7 nM. Such an optical FRET biosensor functions on PS-based photonic crystal for DNA detection that differs from the traditional FRET, which is used only in liquid. This method will benefit the development of a new optical FRET label-free biosensor on Si substrate and has great potential in biochips based on integrated optical devices.

A fluorescence resonance energy transfer (FRET) biosensor based on graphene quantum dots (GQDs) and gold nanoparticles (AuNPs) for the detection of mecA gene sequence of Staphylococcus aureus.

Science.gov (United States)

Shi, Jingyu; Chan, Chunyu; Pang, Yukting; Ye, Weiwei; Tian, Feng; Lyu, Jing; Zhang, Yu; Yang, Mo

2015-05-15

In this work, a novel fluorescence resonance energy transfer (FRET) biosensor based on graphene quantum dots (GQDs) and gold nanoparticles (AuNPs) pairs was developed for Staphylococcus aureus specific gene sequence detection. This FRET biosensor platform was realized by immobilization of capture probes on GQDs and conjugation of reporter probes on AuNPs. Target oligos then co-hybridized with capture probes and reporter probes to form a sandwich structure which brought GQDs and AuNPs to close proximity to trigger FRET effect. The fluorescence signals before and after addition of targets were measured and the fluorescence quenching efficiency could reach around 87% with 100 nM target oligo. The limit of detection (LOD) of this FRET biosensor was around 1 nM for S.aureus gene detection. Experiments with both single-base mismatched oligos and double-base mismatched oligos demonstrated the good sequence selectivity of this FRET biosensor. Copyright © 2014 Elsevier B.V. All rights reserved.

On-chip multiplexed solid-phase nucleic acid hybridization assay using spatial profiles of immobilized quantum dots and fluorescence resonance energy transfer.

Science.gov (United States)

Noor, M Omair; Tavares, Anthony J; Krull, Ulrich J

2013-07-25

A microfluidic based solid-phase assay for the multiplexed detection of nucleic acid hybridization using quantum dot (QD) mediated fluorescence resonance energy transfer (FRET) is described herein. The glass surface of hybrid glass-polydimethylsiloxane (PDMS) microfluidic channels was chemically modified to assemble the biorecognition interface. Multiplexing was demonstrated using a detection system that was comprised of two colors of immobilized semi-conductor QDs and two different oligonucleotide probe sequences. Green-emitting and red-emitting QDs were paired with Cy3 and Alexa Fluor 647 (A647) labeled oligonucleotides, respectively. The QDs served as energy donors for the transduction of dye labeled oligonucleotide targets. The in-channel assembly of the biorecognition interface and the subsequent introduction of oligonucleotide targets was accomplished within minutes using a combination of electroosmotic flow and electrophoretic force. The concurrent quantification of femtomole quantities of two target sequences was possible by measuring the spatial coverage of FRET sensitized emission along the length of the channel. In previous reports, multiplexed QD-FRET hybridization assays that employed a ratiometric method for quantification had challenges associated with lower analytical sensitivity arising from both donor and acceptor dilution that resulted in reduced energy transfer pathways as compared to single-color hybridization assays. Herein, a spatial method for quantification that is based on in-channel QD-FRET profiles provided higher analytical sensitivity in the multiplexed assay format as compared to single-color hybridization assays. The selectivity of the multiplexed hybridization assays was demonstrated by discrimination between a fully-complementary sequence and a 3 base pair sequence at a contrast ratio of 8 to 1. Copyright © 2013 Elsevier B.V. All rights reserved.

Photoinduced electron-transfer from imidazole derivative to nano-semiconductors.

Science.gov (United States)

Karunakaran, C; Jayabharathi, J; Jayamoorthy, K; Devi, K Brindha

2012-04-01

Bioactive imidazole derivative absorbs in the UV region at 305 nm. The interaction of imidazole derivative with nanoparticulate WO3, Fe2O3, Fe3O4, CuO, ZrO2 and Al2O3 has been studied by UV-visible absorption, FT-IR and fluorescence spectroscopies. The imidazole derivative adsorbs strongly on the surfaces of nanosemiconductor, the apparent binding constants for the association between nanomaterials and imidazole derivative have been determined from the fluorescence quenching. In the case of nanocrystalline insulator, fluorescence quenching through electron transfer from the excited state of the imidazole derivative to alumina is not possible. However, a possible mechanism for the quenching of fluorescence by the insulator is energy transfer, that is, energy transferred from the organic molecule to the alumina lattice. Based on Forster's non-radiation energy transfer theory, the distance between the imidazole derivative and nanoparticles (r0∼2.00 nm) as well as the critical energy transfer distance (R0∼1.70 nm) has been calculated. The interaction between the imidazole derivative and nanosurfaces occurs through static quenching mechanism. The free energy change (ΔGet) for electron transfer process has been calculated by applying Rehm-Weller equation. Copyright © 2012 Elsevier B.V. All rights reserved.

Energy transfer properties and mechanisms

International Nuclear Information System (INIS)

1991-01-01

This report discusses the energy transfer mechanisms in azulene, benzene, toluene, and isotopomers. Also discussed is the coupled energy reservoirs model, quantum effects in energy transfer, NO 2 energy transfer, densities of states, the reactant states model, and O 3 excited electronic states

Energy and charge transfer dynamics between Alq3 and CdSeS nanocrystals.

Science.gov (United States)

Zhang, Shuping; Liu, Yuqiang; Yang, Yanqiang

2010-03-01

The photoluminescence properties of the blend films consisting of organic small molecules and nanocrystals (NCs)--Alq3 and CdSeS NCs--were studied by steady-state and time-resolved photoluminescence (PL) spectroscopy with different excited wavelengths. Both the fluorescence intensity and lifetime are intensively dependent on the NC concentration. The detailed analysis of experiment data proves that Forster energy transfer from the Alq3 to the NCs exists simultaneously with the charge transfer and both compete with each other in the blend films.

Calculating the X-Ray Fluorescence from the Planet Mercury Due to High-Energy Electrons

Science.gov (United States)

Burbine, T. H.; Trombka, J. I.; Bergstrom, P. M., Jr.; Christon, S. P.

2005-01-01

The least-studied terrestrial planet is Mercury due to its proximity to the Sun, which makes telescopic observations and spacecraft encounters difficult. Our lack of knowledge about Mercury should change in the near future due to the recent launching of MESSENGER, a Mercury orbiter. Another mission (BepiColombo) is currently being planned. The x-ray spectrometer on MESSENGER (and planned for BepiColombo) can characterize the elemental composition of a planetary surface by measuring emitted fluorescent x-rays. If electrons are ejected from an atom s inner shell by interaction with energetic particles such as photons, electrons, or ions, electrons from an outer shell can transfer to the inner shell. Characteristic x-rays are then emitted with energies that are the difference between the binding energy of the ion in its excited state and that of the ion in its ground state. Because each element has a unique set of energy levels, each element emits x-rays at a unique set of energies. Electrons and ions usually do not have the needed flux at high energies to cause significant x-ray fluorescence on most planetary bodies. This is not the case for Mercury where high-energy particles were detected during the Mariner 10 flybys. Mercury has an intrinsic magnetic field that deflects the solar wind, resulting in a bow shock in the solar wind and a magnetospheric cavity. Electrons and ions accelerated in the magnetosphere tend to follow its magnetic field lines and can impact the surface on Mercury s dark side Modeling has been done to determine if x-ray fluorescence resulting from the impact of high-energy electrons accelerated in Mercury's magnetosphere can be detected by MESSENGER. Our goal is to understand how much bulk chemical information can be obtained from x-ray fluorescence measurements on the dark side of Mercury.

Donor-acceptor random copolyesters containing perylenebisimide (PBI) and oligo(p-phenylene vinylene) (OPV) by melt condensation polymerization: energy transfer studies.

Science.gov (United States)

Nisha, S Kumari; Asha, S K

2013-10-31

Novel copolyesters consisting of oligo(p-phenylene vinylene) (OPV) as donor (D) and perylenebisimide (PBI) as acceptor (A) were synthesized by melt polycondensation. Photoinduced energy transfer and photoinduced charge separation in these polyesters were studied in solution as well as in the solid state. Selective excitation of OPV moiety resulted in the energy transfer with >90% efficiency from OPV to PBI chromophore in the solution state. The direct excitation of PBI in the D-A copolyester resulted in reduced fluorescence emission of acceptor, indicating electron transfer between the D and A moieties. The effect of distance between donor and acceptor on the energy transfer efficiency from donor to acceptor was studied. Compared to a physical mixture of D and A polyesters alone, the energy transfer was 4 times more efficient in the D-A copolyester, highlighting the influence of covalently linking D and A in a single polymer chain. A strong fluorescence quenching (∼ 100%) of both chromophores in solid state indicated an efficient photoinduced charge transfer after photoexcitation of either D or A. Thus, OPV-PBI main chain copolyester is an excellent system for the study of energy- and electron-transfer processes in organic semiconductor. Reactive blend of D/A copolyester was also prepared by the transesterification reaction between D and A alone copolyesters. The energy transfer efficiency from D to A moiety upon selective excitation of D chromophore in the D/A copolyester blend was ∼4 times higher compared to a physical mixture of D and A alone copolyesters, which gave direct proof for the transesterification reaction in polyester/polyester reactive blending.

Hydrogen bond strengthening induces fluorescence quenching of PRODAN derivative by turning on twisted intramolecular charge transfer

Science.gov (United States)

Yang, Yonggang; Li, Donglin; Li, Chaozheng; Liu, YuFang; Jiang, Kai

2017-12-01

Researchers have proposed different effective mechanisms of hydrogen bonding (HB) on the fluorescence of 6-propionyl-2-dimethylaminonaphthalene (PRODAN) and its derivatives. Herein, excited state transition and dynamics analysis confirm that the fluorescence of PD (a derivative of PRODAN with ethyl replaced by 3-hydroxy-2,2-dimethylpropan) emits from the planar intramolecular charge transfer (PICT) state rather than twist ICT (TICT) state, because the fluorescence emission and surface hopping from the TICT state to the twist ground (T-S0) state is energy forbidden. Nevertheless, the strengthening of intramolecular-HB (intra-HB) and intermolecular-HB (inter-HB) of PD-(methanol)2 smooth the pathway of surface hopping from TICT to T-S0 state and the external conversion going to planar ground state by decreasing the energy difference of the two states. This smoothing changes the fluorescence state of PD-(methanol)2 to the TICT state in which fluorescence emission does not occur but surface hopping, leading to the partial fluorescence quenching of PD in methanol solvent. This conclusion is different from previous related reports. Moreover, the inter-HB strengthening of PD-methanol in PICT state induces the cleavage of intra-HB and a fluorescence red-shift of 54 nm compared to PD. This red-shift increases to 66 nm for PD-(methanol)2 for the strengthening of the one intra-HB and two inter-HBs. The dipole moments of PD-methanol and PD-(methanol)2 respectively increase about 10.3D and 8.1D in PICT state compared to PD. The synergistic effect of intra-HB and inter-HB induces partial quenching of PD in methanol solvent by turning on the TICT state and fluorescence red-shift. This work gives a reasonable description on the fluorescence red-shift and partial quenching of PD in methanol solvent, which will bring insight into the study of spectroscopic properties of molecules owning better spectral characteristics.

Turn-on fluorescence probes based on pyranine/viologen charge-transfer complexes for the determination of nucleotides

Energy Technology Data Exchange (ETDEWEB)

Schäferling, Michael, E-mail: Michael.schaeferling@utu.fi; Lang, Thomas; Schnettelker, Annette

2014-10-15

The formation of ground state charge-transfer complexes between pyranine (8-hydroxypyrene-1,3,6-trisulfonic acid) and viologen (paraquat) derivatives is utilized for the design of novel fluoroionophores for the determination of phosphate species, particularly of nucleotides. The strong quenching of the pyranine fluorescence by viologen-type charge transfer acceptors can be countermanded if these are functionalized with triethylammonium groups that serve as recognition elements for phosphate anions. We report on the fluorogenic responses of these water-soluble molecular probes in presence of different phosphates. Absorbance measurements give additional information on the charge transfer complex formation and the interaction with nucleotides. The experimental data show that these aggregates form attractive, simple and versatile fluorescence turn-on probes for nucleoside triphosphates. The reversibility of the fluorescence response is demonstrated by means of an enzymatic model assay using ATPase for the decomposition of adenosine triphosphate. - Highlights: • Pyranine/viologen charge-transfer complexes as molecular probe for ATP recognition. • Fluorescence turn on mechanism. • Selective compared to other nucleotides and phosphate anions. • Fast and reversible response applicable to monitor enzymatic reactions.

Physiological pH fiber-optic chemical sensor based on energy transfer. [Eosin and phenol red

Energy Technology Data Exchange (ETDEWEB)

Jordan, D.M.; Walt, D.R.; Milanovich, F.P.

1987-02-01

A fiber-optic sensor has been developed containing a fluorophore, eosin, and an absorber, phenol red, coimmobilized on the distal end of an optical fiber. When an argon laser is used to excite eosin with light of lambda 488 nm, a region of the spectrum where phenol red does not absorb, eosin emits light in a spectral region that overlaps significantly with the absorption spectru of the basic form of phenol red. Consequently, nonradiative energy transfer occurs from eosin (donor) to phenol red (acceptor). The amount of energy transfer increases as the pH increases resulting in a diminished fluorescence intensity. Thus, changes in the absorption of phenol red as a function of pH are detected as changes in the fluorescent signal. In this manner a pH sensor optimized for physiological pH measurement has been prepared. The fiber exhibits a precision of at least 0.01 pH units.

Enhancing molecular logic through modulation of temporal and spatial constraints with quantum dot-based systems that use fluorescent (Förster) resonance energy transfer

Science.gov (United States)

Claussen, Jonathan C.; Algar, W. Russ; Hildebrandt, Niko; Susumu, Kimihiro; Ancona, Mario G.; Medintz, Igor L.

2013-10-01

Luminescent semiconductor nanocrystals or quantum dots (QDs) contain favorable photonic properties (e.g., resistance to photobleaching, size-tunable PL, and large effective Stokes shifts) that make them well-suited for fluorescence (Förster) resonance energy transfer (FRET) based applications including monitoring proteolytic activity, elucidating the effects of nanoparticles-mediated drug delivery, and analyzing the spatial and temporal dynamics of cellular biochemical processes. Herein, we demonstrate how unique considerations of temporal and spatial constraints can be used in conjunction with QD-FRET systems to open up new avenues of scientific discovery in information processing and molecular logic circuitry. For example, by conjugating both long lifetime luminescent terbium(III) complexes (Tb) and fluorescent dyes (A647) to a single QD, we can create multiple FRET lanes that change temporally as the QD acts as both an acceptor and donor at distinct time intervals. Such temporal FRET modulation creates multi-step FRET cascades that produce a wealth of unique photoluminescence (PL) spectra that are well-suited for the construction of a photonic alphabet and photonic logic circuits. These research advances in bio-based molecular logic open the door to future applications including multiplexed biosensing and drug delivery for disease diagnostics and treatment.

Microspectroscopic Study of Liposome-to-cell Interaction Revealed by Förster Resonance Energy Transfer.

Science.gov (United States)

Yefimova, Svetlana L; Kurilchenko, Irina Yu; Tkacheva, Tatyana N; Kavok, Nataliya S; Todor, Igor N; Lukianova, Nataliya Yu; Chekhun, Vasyl F; Malyukin, Yuriy V

2014-03-01

We report the Förster resonance energy transfer (FRET)-labeling of liposomal vesicles as an effective approach to study in dynamics the interaction of liposomes with living cells of different types (rat hepatocytes, rat bone marrow, mouse fibroblast-like cells and human breast cancer cells) and cell organelles (hepatocyte nuclei). The in vitro experiments were performed using fluorescent microspectroscopic technique. Two fluorescent dyes (DiO as the energy donor and DiI as an acceptor) were preloaded in lipid bilayers of phosphatidylcholine liposomes that ensures the necessary distance between the dyes for effective FRET. The change in time of the donor and acceptor relative fluorescence intensities was used to visualize and trace the liposome-to-cell interaction. We show that FRET-labeling of liposome vesicles allows one to reveal the differences in efficiency and dynamics of these interactions, which are associated with composition, fluidity, and metabolic activity of cell plasma membranes.

Concentration Effect on Quenching of Chlorophyll a Fluorescence by All-Trans-β-Carotene in Photosynthesis

Directory of Open Access Journals (Sweden)

Chen Chen

2017-09-01

Full Text Available Absorption, fluorescence spectra of chlorophyll a (Chl-a and all-trans-β-carotene (β-Car mixing solution are investigated in different polarity and polarizability solvents. The carotenoids regulate the energy flow in photosynthesis by interaction with chlorophyll, leading to an observable reduction of Chl-a fluorescence. The fluorescence red shifts with the increasing solvent polarizability. The energy transfer in the Chl-a and β-Car system is proposed. The electron transfer should be dominant in quenching Chl-a fluorescence rather than the energy transfer in this system. Polar solvent with large polarizability shows high quenching efficiency. When dissolved in carbon tetrachloride, Chl-a presents red shift of absorption and blue shift of fluorescence spectra with increasing β-Car concentration, which implies a Chl-a conformational change.

Effect of enhanced Renilla luciferase and fluorescent protein variants on the Foerster distance of Bioluminescence resonance energy transfer (BRET)

Energy Technology Data Exchange (ETDEWEB)

Dacres, Helen, E-mail: helen.dacres@csiro.au [CSIRO Food Futures Flagship and Ecosystem Sciences, Canberra (Australia); Michie, Michelle; Wang, Jian [CSIRO Food Futures Flagship and Ecosystem Sciences, Canberra (Australia); Pfleger, Kevin D.G. [Laboratory for Molecular Endocrinology-GPCRs, Western Australian Institute for Medical Research (WAIMR) and Centre for Medical Research, The University of Western Australia, Perth (Australia); Trowell, Stephen C. [CSIRO Food Futures Flagship and Ecosystem Sciences, Canberra (Australia)

2012-08-31

Highlights: Black-Right-Pointing-Pointer First experimental determination of Foerster distance (R{sub 0}) for enhanced BRET systems. Black-Right-Pointing-Pointer Effect of brighter BRET components RLuc2, RLuc8 and Venus was assessed. Black-Right-Pointing-Pointer Using brighter BRET components substantially increased (25%) R{sub 0} of the BRET{sup 1} system. Black-Right-Pointing-Pointer Using brighter BRET components marginally increased (2-9%) R{sub 0} of the BRET{sup 2} system. Black-Right-Pointing-Pointer Brighter BRET components improve the different weaknesses of BRET{sup 1} and BRET{sup 2} systems. -- Abstract: Bioluminescence resonance energy transfer (BRET) is an important tool for monitoring macromolecular interactions and is useful as a transduction technique for biosensor development. Foerster distance (R{sub 0}), the intermolecular separation characterized by 50% of the maximum possible energy transfer, is a critical BRET parameter. R{sub 0} provides a means of linking measured changes in BRET ratio to a physical dimension scale and allows estimation of the range of distances that can be measured by any donor-acceptor pair. The sensitivity of BRET assays has recently been improved by introduction of new BRET components, RLuc2, RLuc8 and Venus with improved quantum yields, stability and brightness. We determined R{sub 0} for BRET{sup 1} systems incorporating novel RLuc variants RLuc2 or RLuc8, in combination with Venus, as 5.68 or 5.55 nm respectively. These values were approximately 25% higher than the R{sub 0} of the original BRET{sup 1} system. R{sub 0} for BRET{sup 2} systems combining green fluorescent proteins (GFP{sup 2}) with RLuc2 or RLuc8 variants was 7.67 or 8.15 nm, i.e. only 2-9% greater than the original BRET{sup 2} system despite being {approx}30-fold brighter.

Nucleic Acid Sandwich Hybridization Assay with Quantum Dot-Induced Fluorescence Resonance Energy Transfer for Pathogen Detection

Science.gov (United States)

Chou, Cheng-Chung; Huang, Yi-Han

2012-01-01

This paper reports a nucleic acid sandwich hybridization assay with a quantum dot (QD)-induced fluorescence resonance energy transfer (FRET) reporter system. Two label-free hemagglutinin H5 sequences (60-mer DNA and 630-nt cDNA fragment) of avian influenza viruses were used as the targets in this work. Two oligonucleotides (16 mers and 18 mers) that specifically recognize two separate but neighboring regions of the H5 sequences were served as the capturing and reporter probes, respectively. The capturing probe was conjugated to QD655 (donor) in a molar ratio of 10:1 (probe-to-QD), and the reporter probe was labeled with Alexa Fluor 660 dye (acceptor) during synthesis. The sandwich hybridization assay was done in a 20 μL transparent, adhesive frame-confined microchamber on a disposable, temperature-adjustable indium tin oxide (ITO) glass slide. The FRET signal in response to the sandwich hybridization was monitored by a homemade optical sensor comprising a single 400 nm UV light-emitting diode (LED), optical fibers, and a miniature 16-bit spectrophotometer. The target with a concentration ranging from 0.5 nM to 1 μM was successfully correlated with both QD emission decrease at 653 nm and dye emission increase at 690 nm. To sum up, this work is beneficial for developing a portable QD-based nucleic acid sensor for on-site pathogen detection. PMID:23211753

Extension of Light-Harvesting Ability of Photosynthetic Light-Harvesting Complex 2 (LH2) through Ultrafast Energy Transfer from Covalently Attached Artificial Chromophores.

Science.gov (United States)

Yoneda, Yusuke; Noji, Tomoyasu; Katayama, Tetsuro; Mizutani, Naoto; Komori, Daisuke; Nango, Mamoru; Miyasaka, Hiroshi; Itoh, Shigeru; Nagasawa, Yutaka; Dewa, Takehisa

2015-10-14

Introducing appropriate artificial components into natural biological systems could enrich the original functionality. To expand the available wavelength range of photosynthetic bacterial light-harvesting complex 2 (LH2 from Rhodopseudomonas acidophila 10050), artificial fluorescent dye (Alexa Fluor 647: A647) was covalently attached to N- and C-terminal Lys residues in LH2 α-polypeptides with a molar ratio of A647/LH2 ≃ 9/1. Fluorescence and transient absorption spectroscopies revealed that intracomplex energy transfer from A647 to intrinsic chromophores of LH2 (B850) occurs in a multiexponential manner, with time constants varying from 440 fs to 23 ps through direct and B800-mediated indirect pathways. Kinetic analyses suggested that B800 chromophores mediate faster energy transfer, and the mechanism was interpretable in terms of Förster theory. This study demonstrates that a simple attachment of external chromophores with a flexible linkage can enhance the light harvesting activity of LH2 without affecting inherent functions of energy transfer, and can achieve energy transfer in the subpicosecond range. Addition of external chromophores, thus, represents a useful methodology for construction of advanced hybrid light-harvesting systems that afford solar energy in the broad spectrum.

The anisotropy of fluorescence in ring units II: transfer integral fluctuations

International Nuclear Information System (INIS)

Herman, Pavel; Barvik, Ivan; Reiter, Michal

2005-01-01

The time dependence of the anisotropy of fluorescence after an impulsive excitation in the molecular ring (resembling the B850 ring of the purple bacterium Rhodopseudomonas acidophila) is calculated. Fast fluctuations of the environment are simulated by dynamic disorder and slow fluctuations by static disorder. Without dynamic disorder, modest degrees of static disorder are sufficient to cause the experimentally found initial drop of the anisotropy on a sub-100 fs time scale. In the present investigation we are comparing results for the time-dependent optical anisotropy of the molecular ring for three models of the static disorder: Gaussian disorder in the local energies (Model A), Gaussian disorder in the transfer integrals (Model B) and Gaussian disorder in radial positions of molecules (Model C). Both types of disorder-static and dynamic-are taken into account simultaneously

Energy transfer in plasmonic systems

International Nuclear Information System (INIS)

Pustovit, Vitaliy N; Urbas, Augustine M; Shahbazyan, Tigran V

2014-01-01

We present our results on energy transfer between donor and acceptor molecules or quantum dots near a plasmonic nanoparticle. In such systems, the Förster resonance energy transfer is strongly modified due to plasmon-mediated coupling between donors and acceptors. The transfer efficiency is determined by a competition between transfer, radiation and dissipation that depends sensitively on system parameters. When donor and accepror spectral bands overlap with dipole surface plasmon resonance, the dominant transfer mechanism is through plasmon-enhanced radiative coupling. When transfer takes place from an ensemble of donors to an acceptor, a cooperative amplification of energy transfer takes place in a wide range of system parameters. (paper)

Radiative transition, local field enhancement and energy transfer microcosmic mechanism of tellurite glasses containing Er3+, Yb3+ ions and Ag nanoparticles

International Nuclear Information System (INIS)

Zhang, Wenjun; Lin, Jian; Cheng, Mingzhao; Zhang, Shuo; Jia, Yujie; Zhao, Junhong

2015-01-01

Er 3+ -doped, Er 3+ /Yb 3+ co-doped tellurite glass with and without Ag NPs were synthesized by melt-quenching method. The high resolution transmission electron microscopy (HR-TEM) and selected area electron diffractions (SAED) manifest growth of Ag NPs. The UV–vis–NIR absorption spectroscopy and fluorescence spectroscopy were measured. The optical band gap and multiphonon relaxation rate constants were calculated. The electronic band structure and local density of state (DOS) of Ag NPs are calculated. The fluorescence emission and enhancement mechanism including localized surface plasmon resonance (LSPR) and energy transfer (ET) microcosmic mechanism were discussed. The electric field distributions of Ag NPs are emulated by FDTD solutions software. Local field enhancement (LFE) induced by LSPR and lightning rod effect was found to be responsible for the fluorescence enhancement while energy transfer from Ag NPs to rare-earth was considered ignorable in the samples without photoluminescent emission. - Highlights: • Tellurite glasses containing Er 3+ , Yb 3+ and Ag NPs are prepared. • Judd–Ofelt and multiphonon relaxation are calculated. • The electronic band structures of Ag NPs are calculated. • The energy transfer mechanism is discussed. • The plasmon resonance effect of Ag NPs is discussed

Intramolecular energy transfer at donor-acceptor interactions in model and biological membranes

International Nuclear Information System (INIS)

Umarova, Fatima T.

2011-01-01

Intramolecular triplet-triplet energy transfer between molecules of sensibilisator and photochrome for registration of protein interactions in the membrane preparation of Na,K-ATPase was investigated. Erythrosinithiocyanate (ERITC) was used as the triplet label of sensibilisator, and 4-acetoamido-4 -isothiocyanatostilbene-2,2 disullfonic acid (SITS) was used as the photochrome label. Na,K-ATPase preparations were covalently bound with ERITC in active centre of enzyme, and SITS molecules were covalently bound by NH2-groups. In model system, in chymotrypsinogene molecule, SITS and ERITC labels were used also. The cis-trans-isomerization of SITS was initiated by triplet-triplet energy transfer from light excited ERITC molecule to photochrome. The kinetics of isomerization was recorded by the SITS fluorescence measurements. The constant of rate of triplet-triplet energy transfer from ERITC to cis-isomers of SITS in Na,K-ATPase was determined as (3-7)x10 3 M -1 s -1 , and in model system it equals 1x 10 7 M 1 s -1 . The value of energy transfer between loos molecules of erythrosine and SITS in buffer solution equaled to 7x10 7 M -1 s -1 . This drop of R m y in the membrane preparation of Na,K-ATPase at 10 4 reflected the decrease in the frequency of label collisions caused by the increase in the media viscosity and steric hindrances. (author)

Gold and silver nanoparticles based superquenching of fluorescence: A review

Energy Technology Data Exchange (ETDEWEB)

Ghosh, Debanjana; Chattopadhyay, Nitin, E-mail: nitin.chattopadhyay@yahoo.com

2015-04-15

The short review highlights the recent advances on the gold and silver nanoparticles induced efficient quenching of fluorescence from various fluorophores looking at their promising use as optical rulers and chemo-/bio- sensors. The fluorescence quenching often leads to the increase in the Stern–Volmer constant (K{sub SV}~10{sup 7}–10{sup 10} mol{sup −1} dm{sup 3}) several orders of magnitude higher than the values observed for the normal photochemical quenching processes (~10{sup 2} mol{sup −1} dm{sup 3}). This amplified quenching has been termed as “super-quenching” or “hyper-quenching”. Energy transfer (ET) is established from the donor to the metal nanoparticles rationalizing these fast quenching processes. Considering the distance dependence of the ET process, Förster resonance energy transfer (FRET) and nanometal surface energy transfer (NSET) are ascribed to take place. These sensitive distance dependent phenomena serve as the spectroscopic ruler to measure the intra- or intermolecular distances between the interacting partners. In this account focus has been laid on the size dependent energy transfer and super- and hyper- quenching of the fluorescence of the donor moieties by the nanometals and their probable applications in sensing. Rationalization has been made for the nanoparticle induced huge enhancement in the quenching efficiency. The impact of this review lies in the possible application of these amplified quenching processes in designing high sensitive chemical and biological sensors. - Highlights: • Super efficient quenching of fluorescence of probes by gold and silver nanoparticles is highlighted. • The amplified fluorescence quenching of dyes and polymers is rationalized. • Energy transfer is assigned to be responsible for the efficient quenching process. • Amplified quenching has its potential use in designing sensitive chemical/biological sensors.

Gold and silver nanoparticles based superquenching of fluorescence: A review

International Nuclear Information System (INIS)

Ghosh, Debanjana; Chattopadhyay, Nitin

2015-01-01

The short review highlights the recent advances on the gold and silver nanoparticles induced efficient quenching of fluorescence from various fluorophores looking at their promising use as optical rulers and chemo-/bio- sensors. The fluorescence quenching often leads to the increase in the Stern–Volmer constant (K SV ~10 7 –10 10 mol −1 dm 3 ) several orders of magnitude higher than the values observed for the normal photochemical quenching processes (~10 2 mol −1 dm 3 ). This amplified quenching has been termed as “super-quenching” or “hyper-quenching”. Energy transfer (ET) is established from the donor to the metal nanoparticles rationalizing these fast quenching processes. Considering the distance dependence of the ET process, Förster resonance energy transfer (FRET) and nanometal surface energy transfer (NSET) are ascribed to take place. These sensitive distance dependent phenomena serve as the spectroscopic ruler to measure the intra- or intermolecular distances between the interacting partners. In this account focus has been laid on the size dependent energy transfer and super- and hyper- quenching of the fluorescence of the donor moieties by the nanometals and their probable applications in sensing. Rationalization has been made for the nanoparticle induced huge enhancement in the quenching efficiency. The impact of this review lies in the possible application of these amplified quenching processes in designing high sensitive chemical and biological sensors. - Highlights: • Super efficient quenching of fluorescence of probes by gold and silver nanoparticles is highlighted. • The amplified fluorescence quenching of dyes and polymers is rationalized. • Energy transfer is assigned to be responsible for the efficient quenching process. • Amplified quenching has its potential use in designing sensitive chemical/biological sensors

Analysis of energy transfer process based emission spectra of erbium doped germanate glasses for mid-infrared laser materials

International Nuclear Information System (INIS)

Cai, Muzhi; Wei, Tao; Zhou, Beier; Tian, Ying; Zhou, Jiajia; Xu, Shiqing; Zhang, Junjie

2015-01-01

Highlights: • Er 3+ doped germanate glass with good thermal stability were prepared. • Ionic boding nature was proved by bonding parameter calculation. • Mid-infrared fluorescent behaviors and energy transfer were investigated. • Rate equation and Dexter’s theory were utilized to elucidate 2.7 μm emission. - Abstract: Er 3+ activated germanate glass with good thermal stability was prepared. Bonding parameters have been calculated and the nature of ionic bonding of the germanate glass has been determined. Mid-infrared fluorescence was observed and corresponding radiative properties were investigated. For Er 3+ : 4 I 11/2 → 4 I 13/2 transition, high spontaneous radiative transition probability (30.09 s −1 ), large emission cross section ((14.84 ± 0.10) × 10 −21 cm 2 ) and superior gain performance were obtained from the prepared glass. Besides, energy transfer processes concerning the 2.7 μm emission were also discussed in detail. According to simplified rate equation and Dexter’s theory, energy transfer microscopic parameters were computed to elucidate observed 2.7 μm emissions. Results demonstrate that the prepared germanate glass possessing excellent spectroscopic properties might be an attractive candidate for mid-infrared laser or amplifier

Bioluminescence resonance energy transfer system for measuring dynamic protein-protein interactions in bacteria.

Science.gov (United States)

Cui, Boyu; Wang, Yao; Song, Yunhong; Wang, Tietao; Li, Changfu; Wei, Yahong; Luo, Zhao-Qing; Shen, Xihui

2014-05-20

Protein-protein interactions are important for virtually every biological process, and a number of elegant approaches have been designed to detect and evaluate such interactions. However, few of these methods allow the detection of dynamic and real-time protein-protein interactions in bacteria. Here we describe a bioluminescence resonance energy transfer (BRET) system based on the bacterial luciferase LuxAB. We found that enhanced yellow fluorescent protein (eYFP) accepts the emission from LuxAB and emits yellow fluorescence. Importantly, BRET occurred when LuxAB and eYFP were fused, respectively, to the interacting protein pair FlgM and FliA. Furthermore, we observed sirolimus (i.e., rapamycin)-inducible interactions between FRB and FKBP12 and a dose-dependent abolishment of such interactions by FK506, the ligand of FKBP12. Using this system, we showed that osmotic stress or low pH efficiently induced multimerization of the regulatory protein OmpR and that the multimerization induced by low pH can be reversed by a neutralizing agent, further indicating the usefulness of this system in the measurement of dynamic interactions. This method can be adapted to analyze dynamic protein-protein interactions and the importance of such interactions in bacterial processes such as development and pathogenicity. Real-time measurement of protein-protein interactions in prokaryotes is highly desirable for determining the roles of protein complex in the development or virulence of bacteria, but methods that allow such measurement are not available. Here we describe the development of a bioluminescence resonance energy transfer (BRET) technology that meets this need. The use of endogenous excitation light in this strategy circumvents the requirement for the sophisticated instrument demanded by standard fluorescence resonance energy transfer (FRET). Furthermore, because the LuxAB substrate decanal is membrane permeable, the assay can be performed without lysing the bacterial cells

76 FR 70547 - Energy Conservation Program: Energy Conservation Standards for Fluorescent Lamp Ballasts

Science.gov (United States)

2011-11-14

... the term ``fluorescent lamp,'' which EPCA defines as ``a low pressure mercury electric-discharge... discharge into light,'' and as including the four enumerated types of fluorescent lamps for which EPCA... Conservation Program: Energy Conservation Standards for Fluorescent Lamp Ballasts; Final Rule #0;#0;Federal...

Collisional energy transfer in Na(4p--3d)--He,H2 collisions

International Nuclear Information System (INIS)

Kleiber, P.D.; Wong, T.H.; Bililign, S.

1993-01-01

We have investigated the direct collisional energy transfer process Na*(4p)+M→Na*(3d)+M, where M=He,H 2 under gas cell conditions. We have measured the temporal profiles of the Na(3d--3p) sensitized fluorescence as a function of quenching gas pressure and fit the profiles to a two-state rate equation model to obtain the quenching rate coefficients from the Na*(4p) state. The total energy transfer rate coefficient out of the 4p state for He is small [(0.5±0.2)x10 -10 cm 3 /s]. The total quenching rate coefficient out of the 4p state is much larger for H 2 [(3.9±0.5)x10 -10 cm 3 /s]. Evidence suggests that the energy transfer rate coefficient for the 4p--3d process is ∼2.0x10 -10 cm 3 /s with the remainder of the 4p quenching being predominantly reactive. We also compare the far-red wing absorption line shapes for the NaHe and NaH 2 systems

Influence of relaxation processes in polymers on energy transfer by triplet levels

International Nuclear Information System (INIS)

Ibraev, N.Kh.; Zhunusbekov, A.M.

1996-01-01

Temperature influence on triplet-triplet (T-T) energy transfer between molecules of eosin and 3,4-benzopyrene is studied. Polyvenylbuteryl films have been used in capacity of polymer matrix. Calculation has being carried out on spectral-kinetic unit. It is revealed, that 3,4-benzopyrene triplets have been formed in polymer matrix after end of T-T energy transfer. These triplets join in a reaction of mixed triplet-triplet annihilation with non-blow out triplets of eosin and its sensitize slowed fluorescence (SF) of donor. This explains non-exponent character of eosin's dumping kinetics. Non-linear dependence of SF output ration to eosin phosphorescence output under presence of 3,4-benzopyrene molecules in film indicates on process of mixed annihilation. Fractal character of SF donor and acceptor has been evidenced about microscopical distribution of phosphor in polymer. 13 refs., 5 figs

Synthesis and systematic evaluation of dark resonance energy transfer (DRET)-based library and its application in cell imaging.

Science.gov (United States)

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. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Two-Dimensional Free Energy Surfaces for Electron Transfer Reactions in Solution

Directory of Open Access Journals (Sweden)

Shigeo Murata

2008-01-01

Full Text Available Change in intermolecular distance between electron donor (D and acceptor (A can induce intermolecular electron transfer (ET even in nonpolar solvent, where solvent orientational polarization is absent. This was shown by making simple calculations of the energies of the initial and final states of ET. In the case of polar solvent, the free energies are functions of both D-A distance and solvent orientational polarization. On the basis of 2-dimensional free energy surfaces, the relation of Marcus ET and exciplex formation is discussed. The transient effect in fluorescence quenching was measured for several D-A pairs in a nonpolar solvent. The results were analyzed by assuming a distance dependence of the ET rate that is consistent with the above model.

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

Science.gov (United States)

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

Förster resonance energy transfer between acridinediones and selected fluorophores—Medium dependence

Energy Technology Data Exchange (ETDEWEB)

Krishnaveni, R. [National Centre for Ultrafast Processes, University of Madras, Taramani Campus, Chennai-600113 (India); Ramamurthy, P., E-mail: prm60@hotmail.com [National Centre for Ultrafast Processes, University of Madras, Taramani Campus, Chennai-600113 (India)

2013-06-15

We report highly efficient Förster resonance energy transfer process between acridinedione dyes and basic fluorophores. FRET between free and β-cyclodextrin modified acridinediones as donors and fluorophoric dyes like safranine as acceptor were investigated in an alcoholic medium, polymer solution and a polymeric film. Efficiency of the processes were experimentally found by steady-state and time-resolved experiments for different donor and acceptor combinations. The associated spectral parameters viz., R{sup 0}, J(λ) were calculated, the Stern–Volmer relations based on fluorescence intensity and lifetime were constructed and the rates of energy transfer were calculated. The results indicated that the dominant mechanism responsible for the excitation energy transfer is that of resonance transfer due to long range dipole–dipole interaction and the process was found to be highly efficient when the medium was a constrained one as in the case of a polymeric film. A multifold enhancement in efficiency of energy transfer was also observed when the donor was a modified acridinedione when compared to a free acridinedione. The reason is attributed to the effective binding of the acceptor into the cavity of β-cyclodextrin. Highlights: ► FRET between acridinediones and fluorophoric acceptors were investigated. ► FRET analysis was carried out in methanol, a 5% PVA solution and in PVA matrix. ► FRET efficiency was maximum when the medium was PVA matrix. ► FRET efficiency was also more when β-CD modified ADR is used as the donor. ► Efficiency enhancement is due to the inclusion of acceptor into the cavity of β-CD.

Ultrafast energy transfer in dansylated POPAM--eosin complexes

Science.gov (United States)

Aumanen, Jukka; Lehtovuori, Viivi; Werner, Nicole; Richardt, Gabriele; van Heyst, Jeroen; Vögtle, Fritz; Korppi-Tommola, Jouko

2006-12-01

Excitation energy transfer (EET) in dendritic host-guest complexes has been studied. Three generations G2, G3 and G4 of dansyl substituted poly(propyleneamine) dendrimers (POPAM) were complexed with a fluorescent dye eosin in chloroform solution. Arrival of excitation from dansyls to eosin was monitored by femtosecond transient absorption spectroscopy. EET rates from the dansyls to eosin(s) are characterised by two time constants 1 ps and 6 ps independent of dendrimer generation. Relaxation processes in eosin were clearly faster when complexed with dendrimer than in solution. As several eosins are bound to G3 and G4 dendrimers, besides host-guest interaction, also eosin-eosin interactions may contribute to the faster relaxation observed in these complexes.

Energy transfer from a fluorescent hydrogel to a hosted fluorophore

NARCIS (Netherlands)

Montalti, Marco; Dolci, Luisa Stella; Prodi, Luca; Zaccheroni, Nelsi; Stuart, Marc C.A.; van Bommel, Kjeld C.; Friggeri, Arianna

2006-01-01

The fluorescent properties of a new 1,3,5-cyclohexyltricarboxamide-based low-molecular-weight hydrogelator (1) derivatized with one hydrophobic fluorophore and two hydrophilic substituents have been investigated. Gels of I are composed of long, nonbranched fibers of uniform diameter, as shown by

Energy transfers and magnetic energy growth in small-scale dynamo

KAUST Repository

Kumar, Rohit Raj

2013-12-01

In this letter we investigate the dynamics of magnetic energy growth in small-scale dynamo by studying energy transfers, mainly energy fluxes and shell-to-shell energy transfers. We perform dynamo simulations for the magnetic Prandtl number Pm = 20 on 10243 grid using the pseudospectral method. We demonstrate that the magnetic energy growth is caused by nonlocal energy transfers from the large-scale or forcing-scale velocity field to small-scale magnetic field. The peak of these energy transfers moves towards lower wave numbers as dynamo evolves, which is the reason why the integral scale of the magnetic field increases with time. The energy transfers U2U (velocity to velocity) and B2B (magnetic to magnetic) are forward and local. Copyright © EPLA, 2013.

Energy transfer by way of an exciplex intermediate in flexible boron dipyrromethene-based allosteric architectures.

Science.gov (United States)

Mula, Soumyaditya; Elliott, Kristopher; Harriman, Anthony; Ziessel, Raymond

2010-10-07

We have designed and synthesized a series of modular, dual-color dyes comprising a conventional boron dipyrromethene (Bodipy) dye, as a yellow emitter, and a Bodipy dye possessing extended conjugation that functions as a red emitter. A flexible tether of variable length, built from ethylene glycol residues, connects the terminal dyes. A critical design element of this type of dyad relates to a secondary amine linkage interposed between the conventional Bodipy and the tether. Cyclic voltammetry shows both Bodipy dyes to be electroactive and indicates that the secondary amine is quite easily oxidized. The ensuing fluorescence quenching is best explained in terms of the rapid formation of an intermediate charge-transfer state. In fact, exciplex-type emission is observed in weakly polar solvents and over a critical temperature range. In the dual-color dyes, direct excitation of the yellow emitter results in the appearance of red fluorescence, indicating that the exciplex is likely involved in the energy-transfer event, and provides for a virtual Stokes shift of 5000 cm(-1). Replacing the red emitter with a higher energy absorber (namely, pyrene) facilitates the collection of near-UV light and extends the virtual Stokes shift to 8000 cm(-1). Modulation of the efficacy of intramolecular energy transfer is achieved by preorganization of the connector in the presence of certain cations. This latter behavior, which is fully reversible, corresponds to an artificial allosteric effect.

Picosecond excitation energy transfer of allophycocyanin studied in solution and in crystals.

Science.gov (United States)

Ranjbar Choubeh, Reza; Sonani, Ravi R; Madamwar, Datta; Struik, Paul C; Bader, Arjen N; Robert, Bruno; van Amerongen, Herbert

2018-03-01

Cyanobacteria perform photosynthesis with the use of large light-harvesting antennae called phycobilisomes (PBSs). These hemispherical PBSs contain hundreds of open-chain tetrapyrrole chromophores bound to different peptides, providing an arrangement in which excitation energy is funnelled towards the PBS core from where it can be transferred to photosystem I and/or photosystem II. In the PBS core, many allophycocyanin (APC) trimers are present, red-light-absorbing phycobiliproteins that covalently bind phycocyanobilin (PCB) chromophores. APC trimers were amongst the first light-harvesting complexes to be crystallized. APC trimers have two spectrally different PCBs per monomer, a high- and a low-energy pigment. The crystal structure of the APC trimer reveals the close distance (~21 Å) between those two chromophores (the distance within one monomer is ~51 Å) and this explains the ultrafast (~1 ps) excitation energy transfer (EET) between them. Both chromophores adopt a somewhat different structure, which is held responsible for their spectral difference. Here we used spectrally resolved picosecond fluorescence to study EET in these APC trimers both in crystallized and in solubilized form. We found that not all closely spaced pigment couples consist of a low- and a high-energy pigment. In ~10% of the cases, a couple consists of two high-energy pigments. EET to a low-energy pigment, which can spectrally be resolved, occurs on a time scale of tens of picoseconds. This transfer turns out to be three times faster in the crystal than in the solution. The spectral characteristics and the time scale of this transfer component are similar to what have been observed in the whole cells of Synechocystis sp. PCC 6803, for which it was ascribed to EET from C-phycocyanin to APC. The present results thus demonstrate that part of this transfer should probably also be ascribed to EET within APC trimers.

Energy transfer in purple bacterial photosynthetic units from cells grown in various light intensities.

Science.gov (United States)

Niedzwiedzki, Dariusz M; Gardiner, Alastair T; Blankenship, Robert E; Cogdell, Richard J

2018-05-03

Three photosynthetic membranes, called intra-cytoplasmic membranes (ICMs), from wild-type and the ∆pucBA abce mutant of the purple phototrophic bacterium Rps. palustris were investigated using optical spectroscopy. The ICMs contain identical light-harvesting complex 1-reaction centers (LH1-RC) but have various spectral forms of light-harvesting complex 2 (LH2). Spectroscopic studies involving steady-state absorption, fluorescence, and femtosecond time-resolved absorption at room temperature and at 77 K focused on inter-protein excitation energy transfer. The studies investigated how energy transfer is affected by altered spectral features of the LH2 complexes as those develop under growth at different light conditions. The study shows that LH1 → LH2 excitation energy transfer is strongly affected if the LH2 complex alters its spectroscopic signature. The LH1 → LH2 excitation energy transfer rate modeled with the Förster mechanism and kinetic simulations of transient absorption of the ICMs demonstrated that the transfer rate will be 2-3 times larger for ICMs accumulating LH2 complexes with the classical B800-850 spectral signature (grown in high light) compared to the ICMs from the same strain grown in low light. For the ICMs from the ∆pucBA abce mutant, in which the B850 band of the LH2 complex is blue-shifted and almost degenerate with the B800 band, the LH1 → LH2 excitation energy transfer was not observed nor predicted by calculations.

Energy transfer and 2.0 μm emission in Tm{sup 3+}/Ho{sup 3+} co-doped α-NaYF{sub 4} single crystals

Energy Technology Data Exchange (ETDEWEB)

Feng, Zhigang; Yang, Shuo [Key laboratory of Photo-electronic Materials, Ningbo University, Ningbo, Zhejiang 315211 (China); Xia, Haiping, E-mail: hpxcm@nbu.edu.cn [Key laboratory of Photo-electronic Materials, Ningbo University, Ningbo, Zhejiang 315211 (China); Wang, Cheng; Jiang, Dongsheng; Zhang, Jian; Gu, Xuemei; Zhang, Yuepin [Key laboratory of Photo-electronic Materials, Ningbo University, Ningbo, Zhejiang 315211 (China); Chen, Baojiu, E-mail: bjchen@dlmu.edu.cn [Department of Physics, Dalian Maritime University, Dalian, Liaoning Province 116026 (China); Jiang, Haochuan [Ningbo Institute of Materials Technology and Engineering, the Chinese Academy of Sciences, Ningbo, Zhejiang 315211 (China)

2016-04-15

Highlights: • Cubic NaYF{sub 4} single crystals co-doped with ∼1.90 mol% Tm{sup 3+} and various Ho{sup 3+} concentrations were grown by Bridgman method. • The maximum fluorescence lifetime was 23.23 ms for Tm{sup 3+} (1.90 mol%)/Ho{sup 3+} (3.89 mol%) co-doped α-NaYF{sub 4}. • The obtained energy transfer rate (W{sub ET}) and energy transfer efficiency (η) of Tm{sup 3+}:{sup 3}F{sub 4} are 1077 s{sup −1} and 95.0%, respectively. • The maximum emission cross section reached 1.06 × 10{sup −20} cm{sup 2}. - Abstract: Cubic NaYF{sub 4} single crystals co-doped with ∼1.90 mol% Tm{sup 3+} and various Ho{sup 3+} concentrations were grown by Bridgman method. The energy transfer from Tm{sup 3+} to Ho{sup 3+} and the optimum fluorescence emission around 2.04 μm of Ho{sup 3+} ion were investigated based on the measured absorption spectra, emission spectra, emission cross section and decay curves under excitation of 800 nm LD. The emission intensity at 2.04 μm increased with the increase of Ho{sup 3+} concentration from 0.96 mol% to 3.89 mol% when the concentration of Tm{sup 3+} was held constantly at ∼1.90 mol%. Moreover, the maximum emission cross section reached 1.06 × 10{sup −20} cm{sup 2} and the maximum fluorescence lifetime was 23.23 ms for Tm{sup 3+}(1.90 mol%)/Ho{sup 3+}(3.89 mol%) co-doped one. According to the measured lifetime of Tm{sup 3+} single-doped and Tm{sup 3+}/Ho{sup 3+} co-doped samples, the maximum energy transfer efficiency of Tm{sup 3+}:{sup 3}F{sub 4} level was 95.0%. Analysis on the fluorescence dynamics indicated that electric dipole–dipole is dominant for the energy transfer from Tm{sup 3+} to Ho{sup 3+}.

Energy-transfer properties and mechanisms:

International Nuclear Information System (INIS)

Barker, J.R.

1988-02-01

This project continues the research on vibrational energy transfer involving large molecules. The motivation of the research is to advance knowledge concerning molecular energy in the electronic ground state so that meaningful predictions can be made. The experimental program will use several techniques on several different molecules with the aim of eliminating experimental artifacts and gaining more insight into energy transfer processes. The theoretical effort will be directed toward assessing the validity of the Biased Random Walk theory and toward developing simpler models that adequately describe the energy transfer process. 6 figs

Analysis of energy transfer process based emission spectra of erbium doped germanate glasses for mid-infrared laser materials

Energy Technology Data Exchange (ETDEWEB)

Cai, Muzhi; Wei, Tao; Zhou, Beier; Tian, Ying; Zhou, Jiajia; Xu, Shiqing, E-mail: shiqingxu@cjlu.edu.cn; Zhang, Junjie, E-mail: jjzhang@cjlu.edu.cn

2015-03-25

Highlights: • Er{sup 3+} doped germanate glass with good thermal stability were prepared. • Ionic boding nature was proved by bonding parameter calculation. • Mid-infrared fluorescent behaviors and energy transfer were investigated. • Rate equation and Dexter’s theory were utilized to elucidate 2.7 μm emission. - Abstract: Er{sup 3+} activated germanate glass with good thermal stability was prepared. Bonding parameters have been calculated and the nature of ionic bonding of the germanate glass has been determined. Mid-infrared fluorescence was observed and corresponding radiative properties were investigated. For Er{sup 3+}:{sup 4}I{sub 11/2}→{sup 4}I{sub 13/2} transition, high spontaneous radiative transition probability (30.09 s{sup −1}), large emission cross section ((14.84 ± 0.10) × 10{sup −21} cm{sup 2}) and superior gain performance were obtained from the prepared glass. Besides, energy transfer processes concerning the 2.7 μm emission were also discussed in detail. According to simplified rate equation and Dexter’s theory, energy transfer microscopic parameters were computed to elucidate observed 2.7 μm emissions. Results demonstrate that the prepared germanate glass possessing excellent spectroscopic properties might be an attractive candidate for mid-infrared laser or amplifier.

Quantum dot-dye hybrid systems for energy transfer applications

International Nuclear Information System (INIS)

Ren, Ting

2010-01-01

In this thesis, we focus on the preparation of energy transfer-based quantum dot (QD)-dye hybrid systems. Two kinds of QD-dye hybrid systems have been successfully synthesized: QD-silica-dye and QD-dye hybrid systems. In the QD-silica-dye hybrid system, multishell CdSe/CdS/ZnS QDs were adsorbed onto monodisperse Stoeber silica particles with an outer silica shell of thickness 2-24 nm containing organic dye molecules (Texas Red). The thickness of this dye layer has a strong effect on the total sensitized acceptor emission, which is explained by the increase in the number of dye molecules homogeneously distributed within the silica shell, in combination with an enhanced surface adsorption of QDs with increasing dye amount. Our conclusions were underlined by comparison of the experimental results with Monte-Carlo simulations, and by control experiments confirming attractive interactions between QDs and Texas Red freely dissolved in solution. New QD-dye hybrid system consisting of multishell QDs and organic perylene dyes have been synthesized. We developed a versatile approach to assemble extraordinarily stable QD-dye hybrids, which uses dicarboxylate anchors to bind rylene dyes to QD. This system yields a good basis to study the energy transfer between QD and dye because of its simple and compact design: there is no third kind of molecule linking QD and dye; no spacer; and the affinity of the functional group to the QD surface is strong. The FRET signal was measured for these complexes as a function of both dye to QD ratio and center-to-center distance between QD and dye by controlling number of covered ZnS layers. Data showed that fluorescence resonance energy transfer (FRET) was the dominant mechanism of the energy transfer in our QD-dye hybrid system. FRET efficiency can be controlled by not only adjusting the number of dyes on the QD surface or the QD to dye distance, but also properly choosing different dye and QD components. Due to the strong stability, our QD

Quantum dot-dye hybrid systems for energy transfer applications

Energy Technology Data Exchange (ETDEWEB)

Ren, Ting

2010-07-01

In this thesis, we focus on the preparation of energy transfer-based quantum dot (QD)-dye hybrid systems. Two kinds of QD-dye hybrid systems have been successfully synthesized: QD-silica-dye and QD-dye hybrid systems. In the QD-silica-dye hybrid system, multishell CdSe/CdS/ZnS QDs were adsorbed onto monodisperse Stoeber silica particles with an outer silica shell of thickness 2-24 nm containing organic dye molecules (Texas Red). The thickness of this dye layer has a strong effect on the total sensitized acceptor emission, which is explained by the increase in the number of dye molecules homogeneously distributed within the silica shell, in combination with an enhanced surface adsorption of QDs with increasing dye amount. Our conclusions were underlined by comparison of the experimental results with Monte-Carlo simulations, and by control experiments confirming attractive interactions between QDs and Texas Red freely dissolved in solution. New QD-dye hybrid system consisting of multishell QDs and organic perylene dyes have been synthesized. We developed a versatile approach to assemble extraordinarily stable QD-dye hybrids, which uses dicarboxylate anchors to bind rylene dyes to QD. This system yields a good basis to study the energy transfer between QD and dye because of its simple and compact design: there is no third kind of molecule linking QD and dye; no spacer; and the affinity of the functional group to the QD surface is strong. The FRET signal was measured for these complexes as a function of both dye to QD ratio and center-to-center distance between QD and dye by controlling number of covered ZnS layers. Data showed that fluorescence resonance energy transfer (FRET) was the dominant mechanism of the energy transfer in our QD-dye hybrid system. FRET efficiency can be controlled by not only adjusting the number of dyes on the QD surface or the QD to dye distance, but also properly choosing different dye and QD components. Due to the strong stability, our QD

Fluorescence resonance energy transfer between NaYF4:Yb,Tm upconversion nanoparticles and gold nanorods: Near-infrared responsive biosensor for streptavidin

International Nuclear Information System (INIS)

Zhang, Shuang; Wang, Jing; Xu, Wen; Chen, Boting; Yu, Wei; Xu, Lin; Song, Hongwei

2014-01-01

We represent a fluorescence resonance energy transfer (FRET) system using upconversion nanoparticles (UCNPs) and the gold nanorods (GNRs) as the energy donor–acceptor pair for directly determining streptavidin in near-infrared (NIR) region. NaYF 4 :Yb,Tm UCNPs, which had a strong emission at 800 nm under 980-nm excitation, were adopted as the energy donor. The GNRs, which demonstrated strong surface plasmon absorption around 800 nm, were chosen as acceptor to quench the 800 nm emissions of the UCNPs. There had the spectral overlap between the emission of the donor nanoparticles (UCNPs) and the absorption of the acceptor nanoparticles (GNRs). This UCNP-based FRET system was then used to determine the amount of streptavidin. In this system, NaYF 4 :Yb,Tm UCNPs conjugated with biotin, while GNRs conjugated with streptavidin. When added GNRs into UCNPs, the streptavidin were preferred to bind with biotin and decreased spacing between the donor and acceptor NPs. Consequently, FRET occurred and a linear relationship between the luminescence quenching efficiency and the concentration of streptavidin was obtained. Owing to the aforementioned merits of UCNPs as an energy donor and the strong quenching ability of GNRs, satisfactory analytical performances have been acquired. -- Highlights: • NaYF4:Yb,Tm and GNRs are as NIR energy donor and quenching acceptor for FRET. • Linkage between biotin and streptavidin make the distance between the donors and the acceptors short enough for FRET. • The FRET system in this work was applicable for the detection of streptavidin. • The donor and acceptor NPs can be modified by proper molecules for other biological molecules detection

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

Directory of Open Access Journals (Sweden)

Kenny F. Chou

2015-06-01

Full Text Available 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.

Use of a laser-induced fluorescence thermal imaging system for film cooling heat transfer measurement

Energy Technology Data Exchange (ETDEWEB)

Chyu, M.K. [Carnegie Mellon Univ., Pittsburgh, PA (United States)

1995-10-01

This paper describes a novel approach based on fluorescence imaging of thermographic phosphor that enables the simultaneous determination of both local film effectiveness and local heat transfer on a film-cooled surface. The film cooling model demonstrated consists of a single row of three discrete holes on a flat plate. The transient temperature measurement relies on the temperature-sensitive fluorescent properties of europium-doped lanthanum oxysulfide (La{sub 2}O{sub 2}S:EU{sup 3+}) thermographic phosphor. A series of full-field surface temperatures, mainstream temperatures, and coolant film temperatures were acquired during the heating of a test surface. These temperatures are used to calculate the heat transfer coefficients and the film effectiveness simultaneously. Because of the superior spatial resolution capability for the heat transfer data reduced from these temperature frames, the laser-induced fluorescence (LIF) imaging system, the present study observes the detailed heat transfer characteristics over a film-protected surface. The trend of the results agrees with those obtained using other conventional thermal methods, as well as the liquid crystal imaging technique. One major advantage of this technique is the capability to record a large number of temperature frames over a given testing period. This offers multiple-sample consistency.

Far-field RF energy transfer and harvesting

NARCIS (Netherlands)

Visser, H.J.; Vullers, R.; Briand, D.; Yeatman, E.; Roundy, S.

2015-01-01

This chapter deals with radio frequency (RF) energy transfer over a distance. After explaining the differences between nonradiative and radiative RF energy transfer, the chapter gives definitions for transfer and harvesting. Nonradiative RF energy transfer is mostly employed in inductive systems,

Photoinduced intramolecular charge transfer (ICT) reaction in trans-methyl p-(dimethylamino) cinnamate: A combined fluorescence measurement and quantum chemical calculations

Energy Technology Data Exchange (ETDEWEB)

Chakraborty, Amrita [Department of Chemistry, University of Calcutta, 92, A. P. C. Road, Kolkata 700009 (India); Kar, Samiran [Department of Organic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Guchhait, Nikhil [Department of Chemistry, University of Calcutta, 92, A. P. C. Road, Kolkata 700009 (India)], E-mail: nikhilg@postmark.net

2006-01-05

The photophysical behaviour of trans-methyl p-(dimethylamino) cinnamate (t-MDMAC) donor-acceptor system has been investigated by steady-state absorption and emission spectroscopy and quantum chemical calculations. The molecule t-MDMAC shows an emission from the locally excited state in non-polar solvents. In addition to weak local emission, a strong solvent dependent red shifted fluorescence in polar aprotic solvents is attributed to highly polar intramolecular charge transfer state. However, the formation of hydrogen-bonded clusters with polar protic solvents has been suggested from a linear correlation between the observed red shifted fluorescence band maxima with hydrogen bonding parameters ({alpha}). Calculations by ab initio and density functional theory show that the lone pair electron at nitrogen center is out of plane of the benzene ring in the global minimum ground state structure. In the gas phase, a potential energy surface along the twist coordinate at the donor (-NMe{sub 2}) and acceptor (-CH = CHCOOMe) sites shows stabilization of S{sub 1} state and destabilization S{sub 2} and S{sub 0} states. A similar potential energy calculation along the twist coordinate in acetonitrile solvent using non-equilibrium polarized continuum model also shows more stabilization of S{sub 1} state relative to other states and supports solvent dependent red shifted emission properties. In all types of calculations it is found that the nitrogen lone pair is delocalized over the benzene ring in the global minimum ground state and is localized on the nitrogen centre at the 90 deg. twisted configuration. The S{sub 1} energy state stabilization along the twist coordinate at the donor site and localized nitrogen lone pair at the perpendicular configuration support well the observed dual fluorescence in terms of proposed twisted intramolecular charge transfer (TICT) model.

Energy Transfer between Er3+ and Pr3+ for 2.7 μm Fiber Laser Material

Directory of Open Access Journals (Sweden)

Xiangtan Li

2014-01-01

Full Text Available Energy transfer mechanisms between Er3+ and Pr3+ in Er3+/Pr3+ codoped germinate glass are investigated in detail. Under 980 nm LD pumping, 2.7 μm fluorescence intensity enhanced greatly. Meanwhile, 1.5 μm lifetime and fluorescence were suppressed deeply due to the efficient energy transfer from Er3+:4I13/2 to Pr3+:3F3,4, which depopulates the 4I13/2 level and promotes the 2.7 μm transition effectively. The obvious change in J-O parameters indicates that Pr3+ influences the local environment of Er3+ significantly. The increased spontaneous radiative probability in Er3+/Pr3+ glass is further evidence for enhanced 4I11/2 → 4I13/2 transition. The Er3+:4I11/2→Pr3+:1G4 process is harmful to the population accumulation on 4I11/2 level, which inhibits the 2.7 μm emission. The microscopic energy transfer coefficient of Er3+:4I13/2→Pr3+:3F3,4 is 42.25 × 10−40 cm6/s, which is 11.5 times larger than that of Er3+:4I11/2→Pr3+:1G4. Both processes prefer to be non-phonon assisted, which is the main reason why Pr3+ is so efficient in Er3+:2.7 μm emission.

Characterization of energy response for photon-counting detectors using x-ray fluorescence

International Nuclear Information System (INIS)

Ding, Huanjun; Cho, Hyo-Min; Molloi, Sabee; Barber, William C.; Iwanczyk, Jan S.

2014-01-01

Purpose: To investigate the feasibility of characterizing a Si strip photon-counting detector using x-ray fluorescence. Methods: X-ray fluorescence was generated by using a pencil beam from a tungsten anode x-ray tube with 2 mm Al filtration. Spectra were acquired at 90° from the primary beam direction with an energy-resolved photon-counting detector based on an edge illuminated Si strip detector. The distances from the source to target and the target to detector were approximately 19 and 11 cm, respectively. Four different materials, containing silver (Ag), iodine (I), barium (Ba), and gadolinium (Gd), were placed in small plastic containers with a diameter of approximately 0.7 cm for x-ray fluorescence measurements. Linear regression analysis was performed to derive the gain and offset values for the correlation between the measured fluorescence peak center and the known fluorescence energies. The energy resolutions and charge-sharing fractions were also obtained from analytical fittings of the recorded fluorescence spectra. An analytical model, which employed four parameters that can be determined from the fluorescence calibration, was used to estimate the detector response function. Results: Strong fluorescence signals of all four target materials were recorded with the investigated geometry for the Si strip detector. The average gain and offset of all pixels for detector energy calibration were determined to be 6.95 mV/keV and −66.33 mV, respectively. The detector’s energy resolution remained at approximately 2.7 keV for low energies, and increased slightly at 45 keV. The average charge-sharing fraction was estimated to be 36% within the investigated energy range of 20–45 keV. The simulated detector output based on the proposed response function agreed well with the experimental measurement. Conclusions: The performance of a spectral imaging system using energy-resolved photon-counting detectors is very dependent on the energy calibration of the

Colorful Polyelectrolytes: An Atom Transfer Radical Polymerization Route to Fluorescent Polystyrene Sulfonate.

Science.gov (United States)

Huberty, Wayne; Tong, Xiaowei; Balamurugan, Sreelatha; Deville, Kyle; Russo, Paul S; Zhang, Donghui

2016-03-01

A labeled green fluorescent polystyrene sulfonate (LNaPSS) has been synthesized using atom transfer radical polymerization of a styrene sulfonate monomer with a fluorescent co-monomer, fluorescein thiocyanate-vinyl aniline. As a result this 100 % sulfonated polymer contains no hydrophobic patches along the chain backbone besides the fluorescent marker itself. The concentration of the fluorescent monomer was kept low to maintain the characteristic properties of the anionic polyelectrolyte, LNaPSS. ATRP conditions facilitated the production of polymers spanning a range of molecular weights from 35,000 to 175,000 in gram-scale batches with polydispersity indices of 1.01-1.24. Molecular weight increased with the monomer to initiator ratio. Gel permeation chromatography results show a unimodal distribution, and the polymer structure was also confirmed by (1)H NMR and FT-IR spectroscopy. Fluorescence spectroscopy confirmed covalent bonding of fluorescein isothiocyanate to the polymer, indicating that the polymer is suitable as a probe in fluorescence microscopy. To demonstrate this ability, the polymer was used to locate structural features in salt crystals formed during drying, as in the evaporation of sea mist. A second application to probe diffusion studies is also demonstrated.

Fluorescence spectral properties of outer antenna LHC II

CERN Document Server

He Jun Fang; Zhang, Shu; He Fang Tao; Ren Zhao You; Li Liang Bi; Kuang Ting Yun

2002-01-01

Outer antenna LHC II acts to absorb and transfer energy for photosynthesis. The authors studied the fluorescence properties of LHC II of spinach with scanning imaging fluorescence spectroscopy. After it had been excited by 514.5 nm laser, the integral fluorescence spectrum of LHC II was detected. It was shown that energy transfer existed between carotenoid and chlorophyll. Seven bands of LHC II fluorescence emission were resolved by Gauss combination, viz. 656.7, 664.6, 671.5, 677.2, 683.5, 689.6, 695.3 nm, and the percentages of them were 3.0%, 13.1%,13.3%, 21.1%, 13.2%, 33.3%, 3.0% respectively. The emission of 658.7 nm was attributed to chlorophyll b, the other emission bands were produced by chlorophyll a molecules with the maximum absorption 662, 670/671, 676, 680 nm and over 690 nm. The band 656.7 nm, whose percentage was 3.0%, shows that the most energy was absorbed by chlorophyll a. The percentage of band 689.6 nm was the most, which was possibly correlated with one type of self protective mechanism o...

Highly Sensitive and Selective Sensing of Free Bilirubin Using Metal-Organic Frameworks-Based Energy Transfer Process.

Science.gov (United States)

Du, Yaran; Li, Xiqian; Lv, Xueju; Jia, Qiong

2017-09-13

Free bilirubin, a key biomarker for jaundice, was detected with a newly designed fluorescent postsynthetically modified metal organic framework (MOF) (UIO-66-PSM) sensor. UiO-66-PSM was prepared based on the aldimine condensation reaction of UiO-66-NH 2 with 2,3,4-trihydroxybenzaldehyde. The fluorescence of UIO-66-PSM could be effectively quenched by free bilirubin via a fluorescent resonant energy transfer process, thus achieving its recognition of free bilirubin. It was the first attempt to design a MOF-based fluorescent probe for sensing free bilirubin. The probe exhibited fast response time, low detection limit, wide linear range, and high selectivity toward free bilirubin. The sensing system enabled the monitor of free bilirubin in real human serum. Hence, the reported free bilirubin sensing platform has potential applications for clinical diagnosis of jaundice.

In vivo dynamics of enterovirus protease revealed by fluorescence resonance emission transfer (FRET) based on a novel FRET pair

International Nuclear Information System (INIS)

Hsu, Y.-Y.; Liu, Y.-N.; Wang Wenyen; Kao, Fu-Jen; Kung, S.-H.

2007-01-01

An in vivo protease assay suitable for analysis by fluorescence resonance energy transfer (FRET) was developed on the basis of a novel FRET pair. The specifically designed fusion substrate consists of green fluorescent protein 2 (GFP 2 )-peptide-red fluorescent protein 2 (DsRed2), with a cleavage motif for the enterovirus 2A protease (2A pro ) embedded within the peptide region. FRET can be readily visualized in real-time from cells expressing the fusion substrate until a proteolytic cleavage by 2A pro from the input virus. The level of FRET decay is a function of the amount and infection duration of the inoculated virus as measured by a fluorometer assay. The FRET biosensor also responded well to other related enteroviruses but not to a phylogenetically distant virus. Western blot analysis confirmed the physical cleavage of the fusion substrate upon the infections. The study provides proof of principle for applying the FRET technology to diagnostics, screening procedures, and cell biological research

Graphene oxide based photoinduced charge transfer label-free near-infrared fluorescent biosensor for dopamine.

Science.gov (United States)

Chen, Jin-Long; Yan, Xiu-Ping; Meng, Kang; Wang, Shu-Feng

2011-11-15

While the super fluorescence quenching capacity of graphene and graphene oxide (GO) has been extensively employed to develop fluorescent sensors, their own unique fluorescence and its potential for chemo-/biosensing have seldom been explored. Here we report a GO-based photoinduced charge transfer (PCT) label-free near-infrared (near-IR) fluorescent biosensor for dopamine (DA). The multiple noncovalent interactions between GO and DA and the ultrafast decay at the picosecond range of the near-IR fluorescence of GO resulted in effective self-assembly of DA molecules on the surface of GO, and significant fluorescence quenching, allowing development of a PCT-based biosensor with direct readout of the near-IR fluorescence of GO for selective and sensitive detection of DA. The developed method gave a detection limit of 94 nM and a relative standard deviation of 2.0% for 11 replicate detections of 2.0 μM DA and was successfully applied to the determination of DA in biological fluids with quantitative recovery (98-115%).

Phosphorylation-induced conformational changes in short peptides probed by fluorescence resonance energy transfer in the 10A domain.

Science.gov (United States)

Sahoo, Harekrushna; Nau, Werner M

2007-03-26

Phosphorylation-induced conformational changes in short polypeptides were probed by a fluorescence resonance energy transfer (FRET) method by employing a short-distance FRET pair (R(0) approximately 10 A) based on tryptophan as natural donor and a 2,3-diazabicyclo[2.2.2]oct-2-ene-labeled asparagine (Dbo) as synthetic acceptor. Two substrates for kinases, LeuArgArgTrpSerLeuGly-Dbo (peptide I) and TrpLysArgThrLeuArgArg-Dbo (peptide II), were investigated, with serine and threonine, respectively, as phosphorylation sites. Steady-state and time-resolved fluorescence experiments in H(2)O revealed a decrease in FRET efficiency for peptide I and an increase for peptide II; this suggested that the effective distances between donor and acceptor increased and decreased, respectively. The same trends and similar absolute variations in effective donor-acceptor distances were observed in propylene glycol, a less polar and highly viscous solvent; this suggested that the variations are due to intrinsic structural preferences. Fitting of the time-resolved decay traces according to a distribution function model (Gaussian distribution) provided the mean donor-acceptor distances, which showed an increase upon phosphorylation for peptide I (from 9.7 to 10.5 A) and a decrease for peptide II (from 10.9 to 9.3 A) in H(2)O. The broadness (half-width) of the distributions, which provides a measure of the rigidity of the peptides, remained similar upon phosphorylation of peptide I (3.0 versus 3.1 A), but decreased for peptide II (from 3.1 to 0.73 A in H(2)O); this suggests a more compact, structured conformation upon phosphorylation of the latter peptide. The elongation of the peptide backbone (by ca. 0.7 A) for peptide I is attributed to an increase in steric demand upon phosphorylation, which favors an extended conformation. The contraction (by ca. 1.4 A) and structural rigidification of peptide II is attributed to attractive Coulombic interactions and hydrogen bonding between the

Molecular interaction and energy transfer between human serum albumin and bioactive component Aloe dihydrocoumarin

Science.gov (United States)

Zhang, Xiu-Feng; Xie, Ling; Liu, Yang; Xiang, Jun-Feng; Li, Lin; Tang, Ya-Lin

2008-10-01

Aloe dihydrocoumarin is an antioxidant and a candidate of immunomodulatory drug on the immune system and can balance physiological reactive oxygen species (ROS) levels which may be useful to maintain homeostasis. In order to explore the mechanism of drug action at a molecular level, the binding of Aloe dihydrocoumarin with human serum albumin (HSA) has been investigated by fluorescence, ultraviolet (UV), circular dichroism (CD) and Fourier transform infrared (FT-IR) spectroscopy, fluorescence dynamics, and molecular dynamic docking for the first time. We observed a quenching of fluorescence of HSA in the presence of Aloe dihydrocoumarin and also analyzed the quenching results using the Stern-Volmer equation and obtained high affinity binding to HSA. A Förster type fluorescence resonance energy transfer mechanism is involved in this quenching of Trp fluorescence by Aloe dihydrocoumarin. From the CD and FT-IR results, it is apparent that the interaction of Aloe dihydrocoumarin with HSA causes a conformational change of the protein, with the loss of α-helix stability and the gain of β-sheet and β-turn content. Data obtained by fluorescence spectroscopy, fluorescence dynamics, CD, and FT-IR experiments along with the docking studies suggest that Aloe dihydrocoumarin binds to residues located in subdomain IIA of HSA.

Development of a Fluorescence Resonance Energy Transfer (FRET)-Based DNA Biosensor for Detection of Synthetic Oligonucleotide of Ganoderma boninense.

Science.gov (United States)

Mohd Bakhori, Noremylia; Yusof, Nor Azah; Abdullah, Abdul Halim; Hussein, Mohd Zobir

2013-12-01

An optical DNA biosensor based on fluorescence resonance energy transfer (FRET) utilizing synthesized quantum dot (QD) has been developed for the detection of specific-sequence of DNA for Ganoderma boninense, an oil palm pathogen. Modified QD that contained carboxylic groups was conjugated with a single-stranded DNA probe (ssDNA) via amide-linkage. Hybridization of the target DNA with conjugated QD-ssDNA and reporter probe labeled with Cy5 allows for the detection of related synthetic DNA sequence of Ganoderma boninense gene based on FRET signals. Detection of FRET emission before and after hybridization was confirmed through the capability of the system to produce FRET at 680 nm for hybridized sandwich with complementary target DNA. No FRET emission was observed for non-complementary system. Hybridization time, temperature and effect of different concentration of target DNA were studied in order to optimize the developed system. The developed biosensor has shown high sensitivity with detection limit of 3.55 × 10(-9) M. TEM results show that the particle size of QD varies in the range between 5 to 8 nm after ligand modification and conjugation with ssDNA. This approach is capable of providing a simple, rapid and sensitive method for detection of related synthetic DNA sequence of Ganoderma boninense.

Development of a Fluorescence Resonance Energy Transfer (FRET-Based DNA Biosensor for Detection of Synthetic Oligonucleotide of Ganoderma boninense

Directory of Open Access Journals (Sweden)

Noremylia Mohd Bakhori

2013-12-01

Full Text Available An optical DNA biosensor based on fluorescence resonance energy transfer (FRET utilizing synthesized quantum dot (QD has been developed for the detection of specific-sequence of DNA for Ganoderma boninense, an oil palm pathogen. Modified QD that contained carboxylic groups was conjugated with a single-stranded DNA probe (ssDNA via amide-linkage. Hybridization of the target DNA with conjugated QD-ssDNA and reporter probe labeled with Cy5 allows for the detection of related synthetic DNA sequence of Ganoderma boninense gene based on FRET signals. Detection of FRET emission before and after hybridization was confirmed through the capability of the system to produce FRET at 680 nm for hybridized sandwich with complementary target DNA. No FRET emission was observed for non-complementary system. Hybridization time, temperature and effect of different concentration of target DNA were studied in order to optimize the developed system. The developed biosensor has shown high sensitivity with detection limit of 3.55 × 10−9 M. TEM results show that the particle size of QD varies in the range between 5 to 8 nm after ligand modification and conjugation with ssDNA. This approach is capable of providing a simple, rapid and sensitive method for detection of related synthetic DNA sequence of Ganoderma boninense.

Detection of Heteromers Formed by Cannabinoid CB1, Dopamine D2, and Adenosine A2A G-Protein-Coupled Receptors by Combining Bimolecular Fluorescence Complementation and Bioluminescence Energy Transfer

Science.gov (United States)

Navarro, Gemma; Carriba, Paulina; Gandí, Jorge; Ciruela, Francisco; Casadó, Vicent; Cortés, Antoni; Mallol, Josefa; Canela, Enric I.; Lluis, Carmen; Franco, Rafael

2008-01-01

Functional interactions in signaling occur between dopamine D2 (D2R) and cannabinoid CB1 (CB1R) receptors, between CB1R and adenosine A2A (A2AR) receptors, and between D2R and A2AR. Furthermore, direct molecular interactions have been reported for the pairs CB1R-D2R, A2AR-D2R, and CB1R-A2AR. Here a combination of bimolecular fluorescence complementation and bioluminescence energy transfer techniques was used to identify the occurrence of D2R-CB1R-A2AR hetero-oligomers in living cells. PMID:18956124

Detection of Heteromers Formed by Cannabinoid CB1, Dopamine D2, and Adenosine A2A G-Protein-Coupled Receptors by Combining Bimolecular Fluorescence Complementation and Bioluminescence Energy Transfer

Directory of Open Access Journals (Sweden)

Gemma Navarro

2008-01-01

Full Text Available Functional interactions in signaling occur between dopamine D2 (D2R and cannabinoid CB1 (CB1R receptors, between CB1R and adenosine A2A (A2AR receptors, and between D2R and A2AR. Furthermore, direct molecular interactions have been reported for the pairs CB1R-D2R, A2AR-D2R, and CB1R-A2AR. Here a combination of bimolecular fluorescence complementation and bioluminescence energy transfer techniques was used to identify the occurrence of D2R-CB1R-A2AR hetero-oligomers in living cells.

Excitation energy transfer between Light-harvesting complex II and Photosystem I in reconstituted membranes.

Science.gov (United States)

Akhtar, Parveen; Lingvay, Mónika; Kiss, Teréz; Deák, Róbert; Bóta, Attila; Ughy, Bettina; Garab, Győző; Lambrev, Petar H

2016-04-01

Light-harvesting complex II (LHCII), the major peripheral antenna of Photosystem II in plants, participates in several concerted mechanisms for regulation of the excitation energy and electron fluxes in thylakoid membranes. In part, these include interaction of LHCII with Photosystem I (PSI) enhancing the latter's absorption cross-section - for example in the well-known state 1 - state 2 transitions or as a long-term acclimation to high light. In this work we examined the capability of LHCII to deliver excitations to PSI in reconstituted membranes in vitro. Proteoliposomes with native plant thylakoid membrane lipids and different stoichiometric ratios of LHCII:PSI were reconstituted and studied by steady-state and time-resolved fluorescence spectroscopy. Fluorescence emission from LHCII was strongly decreased in PSI-LHCII membranes due to trapping of excitations by PSI. Kinetic modelling of the time-resolved fluorescence data revealed the existence of separate pools of LHCII distinguished by the time scale of energy transfer. A strongly coupled pool, equivalent to one LHCII trimer per PSI, transferred excitations to PSI with near-unity efficiency on a time scale of less than 10ps but extra LHCIIs also contributed significantly to the effective antenna size of PSI, which could be increased by up to 47% in membranes containing 3 LHCII trimers per PSI. The results demonstrate a remarkable competence of LHCII to increase the absorption cross-section of PSI, given the opportunity that the two types of complexes interact in the membrane. Copyright © 2016 Elsevier B.V. All rights reserved.

DEVELOPMENT OF EVALUATION OF A QUANTITATIVE VIDEO-FLUORESCENCE IMAGING SYSTEM AND FLUORESCENT TRACER FOR MEASURING TRANSFER OF PESTICIDE RESIDUES FROM SURFACES TO HANDS WITH REPEATED CONTACTS

Science.gov (United States)

A video imaging system and the associated quantification methods have been developed for measurement of the transfers of a fluorescent tracer from surfaces to hands. The highly fluorescent compound riboflavin (Vitamin B2), which is also water soluble and non-toxic, was chosen as...

Energy transfers and magnetic energy growth in small-scale dynamo

KAUST Repository

Kumar, Rohit Raj; Verma, Mahendra K.; Samtaney, Ravi

2013-01-01

In this letter we investigate the dynamics of magnetic energy growth in small-scale dynamo by studying energy transfers, mainly energy fluxes and shell-to-shell energy transfers. We perform dynamo simulations for the magnetic Prandtl number Pm = 20

Synthesis, photoluminescence and intramolecular energy transfer model of a dysprosium complex

Energy Technology Data Exchange (ETDEWEB)

Zhang Aiqin; Zhang Jiuli; Pan Qiliang; Wang Shuhua [College of Materials Science and Engineering, Taiyuan University of Technology, No. 79 West Yingze Street, Taiyuan, Shanxi 030024 (China); Key Laboratory of Interface Science and Engineering in Advanced Materials of Taiyuan University of Technology, Ministry of Education, Taiyuan, Shanxi 030024 (China); Jia Husheng, E-mail: Jia_Husheng@126.com [College of Materials Science and Engineering, Taiyuan University of Technology, No. 79 West Yingze Street, Taiyuan, Shanxi 030024 (China) and Key Laboratory of Interface Science and Engineering in Advanced Materials of Taiyuan University of Technology, Ministry of Education, Taiyuan, Shanxi 030024 (China); Xu Bingshe [College of Materials Science and Engineering, Taiyuan University of Technology, No. 79 West Yingze Street, Taiyuan, Shanxi 030024 (China); Key Laboratory of Interface Science and Engineering in Advanced Materials of Taiyuan University of Technology, Ministry of Education, Taiyuan, Shanxi 030024 (China)

2012-04-15

The energy of the highest occupied molecular orbital and the lowest unoccupied molecular orbital as well as their energy gaps, and the singlet and triplet state energy levels of 4-benzoylbenzoic acid (HL=4-BBA) and triphenylphosphine oxide (TPPO) were calculated with the Gaussian03 program package. The singlet state and triplet state energy levels were also estimated from the UV-vis absorption spectra and phosphorescence spectra. The results suggest that the calculated values approximately coincided with the experimental values. A Dy(III) complex was synthesized with 4-BBA as primary ligand and TPPO as neutral ligand. The structure of the complex was characterized by elemental analysis, {sup 1}H NMR spectrometry, and FTIR spectrometry. TG-DTG analysis indicates that the complex kept stable up to 305 Degree-Sign C. The photoluminescence properties were studied by fluorescence spectrometry. The results show that Dy(III) ion sensitized by 4-BBA and TPPO emitted characteristic peaks at 572 nm ({sup 4}F{sub 9/2}-{sup 6}H{sub 13/2}) and 480 nm ({sup 4}F{sub 9/2}-{sup 6}H{sub 15/2}), and its Commission Internationale de L'Eclairge coordinates were calculated as x=0.33 and y=0.38, being located in the white range. Intermolecular energy transfer process was discussed and energy transfer model was also proposed. - Highlights: Black-Right-Pointing-Pointer Quantum calculation provides theoretical method of ligand choice for rare earth. Black-Right-Pointing-Pointer The complex Dy(L){sub 3}(TPPO){sub 2} emitted white light. Black-Right-Pointing-Pointer The CIE coordinates were calculated as x=0.33 and y=0.38. Black-Right-Pointing-Pointer Energy transfer in Dy(L){sub 3}(TPPO){sub 2} followed Dexter electron exchange theory.

Förster resonance energy transfer demonstrates a flavonoid metabolon in living plant cells that displays competitive interactions between enzymes

NARCIS (Netherlands)

Crosby, K.C.; Pietraszewska-Bogiel, A.; Gadella (jr.), T.W.J.; Winkel, B.S.J.

2011-01-01

We have used Förster resonance energy transfer detected by fluorescence lifetime imaging microscopy (FLIM-FRET) to provide the first evidence from living plants cells for the existence of a flavonoid metabolon. The distribution of flux within this system may be regulated by the direct competition of

The mutation of carotenoids affects the energy transfer in LH2 light harvesting complexes from Rhodobacter sphaeroides 601 at room temperature

International Nuclear Information System (INIS)

Liu Weimin; Liu Yuan; Guo Lijun; Xu Chunhe; Qian Shixiong

2006-01-01

Energy transfer in two kinds of peripheral antenna complexes LH2 from Rhodobacter sphaeroides 601 was studied by absorption, fluorescence emission, time-resolved fluorescence and femtosecond transient absorption spectroscopy at room temperature. These two complexes are LH2 (RS601) and green carotenoid mutated LH2 (GM309). The obtained results demonstrate that: (a) compared with spheroidenes, which have ten carbon-carbon double bonds in native RS601, carotenoids in GM309 were identified as containing neurosporenes with nine carbon-carbon double bonds, which show a significant blue shift of ∼20 nm in the three absorption peaks because of the higher energy levels of neurosporene than those of spheroidene, (b) the higher energy levels of neurosporene in GM309 induce a lower B800 → B850 energy transfer rate and efficiency as compared to that in RS601 resulting from the relatively higher band gap between the donor of B800 and the bridge of the carotenoids (c) the same lifetime of the B850 excited singlet state is observed in these two LH2 complexes

Fluorescence resonance energy transfer between NaYF{sub 4}:Yb,Tm upconversion nanoparticles and gold nanorods: Near-infrared responsive biosensor for streptavidin

Energy Technology Data Exchange (ETDEWEB)

Zhang, Shuang; Wang, Jing; Xu, Wen; Chen, Boting; Yu, Wei; Xu, Lin; Song, Hongwei, E-mail: songhw@jlu.edu.cn

2014-03-15

We represent a fluorescence resonance energy transfer (FRET) system using upconversion nanoparticles (UCNPs) and the gold nanorods (GNRs) as the energy donor–acceptor pair for directly determining streptavidin in near-infrared (NIR) region. NaYF{sub 4}:Yb,Tm UCNPs, which had a strong emission at 800 nm under 980-nm excitation, were adopted as the energy donor. The GNRs, which demonstrated strong surface plasmon absorption around 800 nm, were chosen as acceptor to quench the 800 nm emissions of the UCNPs. There had the spectral overlap between the emission of the donor nanoparticles (UCNPs) and the absorption of the acceptor nanoparticles (GNRs). This UCNP-based FRET system was then used to determine the amount of streptavidin. In this system, NaYF{sub 4}:Yb,Tm UCNPs conjugated with biotin, while GNRs conjugated with streptavidin. When added GNRs into UCNPs, the streptavidin were preferred to bind with biotin and decreased spacing between the donor and acceptor NPs. Consequently, FRET occurred and a linear relationship between the luminescence quenching efficiency and the concentration of streptavidin was obtained. Owing to the aforementioned merits of UCNPs as an energy donor and the strong quenching ability of GNRs, satisfactory analytical performances have been acquired. -- Highlights: • NaYF4:Yb,Tm and GNRs are as NIR energy donor and quenching acceptor for FRET. • Linkage between biotin and streptavidin make the distance between the donors and the acceptors short enough for FRET. • The FRET system in this work was applicable for the detection of streptavidin. • The donor and acceptor NPs can be modified by proper molecules for other biological molecules detection.

Fast intramolecular electron transfer and dual fluorescence. Configurational change of the amino nitrogen (pyramidal→planar)

International Nuclear Information System (INIS)

Haar, Th. von der; Hebecker, A.; Il'Ichev, Yu.; Kuehnle, W.; Zachariasse, K. A.

1996-01-01

The fast excited state intramolecular charge transfer (ICT) and dual fluorescence observed with several 4-aminobenzonitriles is discussed. It is shown that the magnitude of the energy gap between the two lowest excited states determines the occurrence or absence of ICT. The photophysical behavior of a series of four 4-aminobenzonitriles in which the amino nitrogen atom is part of a four- to seven-membered heterocyclic ring, P4C to P7C, is studied by using time-resolved fluorescence measurements. The ICT rate constant strongly decreases with decreasing ring size. With P4C in diethyl ether ICT does not occur. This is attributed to the increase of the amino nitrogen inversion barrier with decreasing ring size. The change of the amino nitrogen from pyramidal to planar is considered to be an important reaction coordinate. The photophysics of the 4-aminobenzonitriles is different from that of other ICT systems such as donor/acceptor-substituted stilbenes and 9,9'-bianthryl, which are governed by the charge distribution and macroscopic Coulombic interaction in their CT states

Ultrafast Single and Multiexciton Energy Transfer in Semiconductor Nanoplatelets

Science.gov (United States)

Schaller, Richard

Photophysical processes such as fluorescence resonance energy transfer (FRET) enable optical antennas, wavelength down-conversion in light-emitting diodes (LEDs), and optical bio-sensing schemes. The rate and efficiency of this donor to acceptor transfer of excitation between chromophores dictates the utility of FRET and can unlock new device operation motifs including quantum-funnel solar cells and reduced gain thresholds. However, the fastest reported FRET time constants involving spherical quantum dots (QDs) (0.12-1 ns), do not outpace biexciton Auger recombination (0.01-0.1 ns), which impedes multiexciton-driven applications including electrically-pumped lasers and carrier-multiplication-enhanced photovoltaics. Precisely controlled, few-monolayer thick semiconductor nano-platelets with tens-of-nanometer diameters exhibit intense optical transitions and hundreds-of-picosecond Auger recombination, but heretofore lack FRET characterizations. We examine binary CdSe NPL solids and show that inter-plate FRET (~6-23 ps, presumably for co-facial arrangements) can occur 15-50 times faster than Auger recombination and demonstrate multiexcitonic FRET, making such materials ideal candidates for advanced technologies. This work was performed at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility under Contract No. DE-AC02-06CH11357.

Single particle transfer for quantitative analysis with total-reflection X-ray fluorescence spectrometry

International Nuclear Information System (INIS)

Esaka, Fumitaka; Esaka, Konomi T.; Magara, Masaaki; Sakurai, Satoshi; Usuda, Shigekazu; Watanabe, Kazuo

2006-01-01

The technique of single particle transfer was applied to quantitative analysis with total-reflection X-ray fluorescence (TXRF) spectrometry. The technique was evaluated by performing quantitative analysis of individual Cu particles with diameters between 3.9 and 13.2 μm. The direct quantitative analysis of the Cu particle transferred onto a Si carrier gave a discrepancy between measured and calculated Cu amounts due to the absorption effects of incident and fluorescent X-rays within the particle. By the correction for the absorption effects, the Cu amounts in individual particles could be determined with the deviation within 10.5%. When the Cu particles were dissolved with HNO 3 solution prior to the TXRF analysis, the deviation was improved to be within 3.8%. In this case, no correction for the absorption effects was needed for quantification

Light induced intramolecular electron and energy transfer events in rigidly linked borondipyrromethene: Corrole Dyad

Energy Technology Data Exchange (ETDEWEB)

Giribabu, Lingamallu, E-mail: giribabu@iict.res.in [Inorganic & Physical Chemistry Division, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500007, Telangana (India); Jain, Kanika [Department of Chemistry, School of Chemical Sciences & Pharmacy, Central University of Rajasthan, Kishangarh, Dist. Ajmer, Rajasthan 305817 (India); Sudhakar, Kolanu; Duvva, Naresh [Inorganic & Physical Chemistry Division, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500007, Telangana (India); Chitta, Raghu, E-mail: raghuchitta@curaj.ac.in [Department of Chemistry, School of Chemical Sciences & Pharmacy, Central University of Rajasthan, Kishangarh, Dist. Ajmer, Rajasthan 305817 (India)

2016-09-15

We have designed and synthesized a photo-induced energy/electron donor–acceptor conjugate comprising of corrole linked to BODIPY at the 5-position via ester linkage. The dyad was characterized by elemental analysis, MALDI-MS, UV-Visible, {sup 1}H NMR fluorescence spectroscopy (steady-state and time-resolved) as well as electrochemical methods. A comparison of the UV–visible and {sup 1}H NMR spectra of the dyad with those of the corresponding individual model compounds (i.e., BODIPY-CO{sub 2}H and BPFC-OH) reveal that there exist minimum π–π interactions between BODIPY and corrole π-planes. Quenched emission of BODIPY and corrole part of the dyad has been observed in five different solvents. Excitation spectral data provided evidence for an intramolecular excitation energy transfer (EET) from the singlet BODIPY to the corrole and an intramolecular photoinduced electron transfer (PET) from singlet state of corrole to ground state of BODIPY. Detailed analysis of the data suggests that Forster's dipole–dipole mechanism does not adequately explain this energy transfer but, an electron exchange mediated mechanism can, in principle, contribute to the intramolecular EET.

Preparation of fluorescent tocopherols for use in protein binding and localization with the alpha-tocopherol transfer protein.

Science.gov (United States)

Nava, Phillip; Cecchini, Matt; Chirico, Sara; Gordon, Heather; Morley, Samantha; Manor, Danny; Atkinson, Jeffrey

2006-06-01

Sixteen fluorescent analogues of the lipid-soluble antioxidant vitamin alpha-tocopherol were prepared incorporating fluorophores at the terminus of omega-functionalized 2-n-alkyl-substituted chromanols (1a-d and 4a-d) that match the methylation pattern of alpha-tocopherol, the most biologically active form of vitamin E. The fluorophores used include 9-anthroyloxy (AO), 7-nitrobenz-2-oxa-1,3-diazole (NBD), N-methyl anthranilamide (NMA), and dansyl (DAN). The compounds were designed to function as fluorescent reporter ligands for protein-binding and lipid transfer assays. The fluorophores were chosen to maximize the fluorescence changes observed upon moving from an aqueous environment (low fluorescence intensity) to an hydrophobic environment such as a protein's binding site (high fluorescence intensity). Compounds 9d (anthroyloxy) and 10d (nitrobenzoxadiazole), having a C9-carbon chain between the chromanol and the fluorophore, were shown to bind specifically and reversibly to recombinant human tocopherol transfer protein (alpha-TTP) with dissociation constants of approximately 280 and 60 nM, respectively, as compared to 25 nM for the natural ligand 2R,4'R,8'R-alpha-tocopherol. Thus, compounds have been prepared that allow the investigation of the rate of alpha-TTP-mediated inter-membrane transfer of alpha-tocopherol and to investigate the mechanism of alpha-TTP function at membranes of different composition.

Energy transfer dynamics in Light-Harvesting Dendrimers

Science.gov (United States)

Melinger, Joseph S.; McMorrow, Dale; Kleiman, Valeria D.

2002-03-01

We explore energy transfer dynamics in light-harvesting phenylacetylene symmetric and asymmetric dendrimers. Femtosecond pump-probe spectroscopy is used to probe the ultrafast dynamics of electronic excitations in these dendrimers. The backbone of the macromolecule consists of branches of increasing conjugation length, creating an energy gradient, which funnels energy to an accepting perylene trap. In the case of the symmetric dendrimer (nanostar), the energy transfer efficiency is known to approach nearly unity, although the nature and timescale of the energy transfer process is still unknown. For the asymmetric dendrimers, energy transfer efficiencies are very high, with the possibility of more complex transfer processes. We experimentally monitor the transport of excitons through the light-harvesting dendrimer. The transients show a number of components, with timescales ranging from <300fs to several tens of picoseconds, revealing the complex photophysics taking place in these macromolecules. We interpret our results in terms of the Förster mechanism in which energy transfer occurs through dipole-dipole interactions.

Recent Advances in Nanoparticle-Based Förster Resonance Energy Transfer for Biosensing, Molecular Imaging and Drug Release Profiling

Directory of Open Access Journals (Sweden)

Nai-Tzu Chen

2012-12-01

Full Text Available 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.

Fluorescence quenching of 9-cyanoanthracene in presence of zinc tetraphenylporphyrin in a polar liquid medium

International Nuclear Information System (INIS)

Mandal, Paulami; Tiwari, Sanat Kumar; Ganguly, Tapan; Sinha, Subrata

2009-01-01

Steady-state and time-resolved techniques are used to study photoinduced electron and/or excitational energy transfer processes involved within a novel donor (zinc tetraphenylporphyrin)-acceptor (9-cyanoanthracene) system in a polar liquid medium (acetonitrile) at the ambient temperature (300 K). After photoexcitation of 9-cyanoanthracene, its fluorescence emission as well as lifetime are found to be quenched in presence of zinc tetraphenylporphyrin. The fluorescence quenching is ascribed to be due to the combined effect of electron transfer from zinc tetraphenylporphyrin to 9-cyanoanthracene and energy transfer (radiative as well as non-radiative) from 9-cyanoanthracene to zinc tetraphenylporphyrin. The highly exergonic values of Gibbs free energy change for both forward electron transfer reaction (-1.15 eV) and charge recombination reaction (-1.94 eV) indicate the possibilities of occurrences of these two processes in the Marcus inverted region. The fluorescence quenching rate due to photoinduced electron transfer reaction is found to be close to the diffusion-controlled limit within the present donor-acceptor system upon excitation of the acceptor molecules.

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

Science.gov (United States)

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. Copyright © 2015 Elsevier Inc. All rights reserved.

Absorption and fluorescence spectroscopy of 3-hydroxy-3-phenyl-1-o-carboxyphenyltriazene and its copper (II), nickel (II) and zinc (II) complexes: a novel fluorescence sensor

International Nuclear Information System (INIS)

Ressalan, S.; Iyer, C.S.P.

2005-01-01

Absorption and fluorescence spectroscopic properties of 3-hydroxy-3-phenyl-1-o-carboxyphenyltriazene (HT) are studied. The mechanism of photo-induced electron transfer (PET) followed by energy transfer process of the ligand and the Cu (II), Ni (II) and Zn (II) metal complexes have been investigated. The excited state photo induced intramolecular hydrogen transfer from N-OH to triazene 1-nitrogen atom is explained. The effect of pH, solvent and concentration on the absorption and fluorescence of the ligand is studied and it has been found that the absorption and fluorescence of HT is highly pH, solvent and concentration dependent. Participation of the N-OH proton of HT in the solvent assisted O to N-proton transfer has also been proposed. The fluorescence band shift and changes in intensity is modulated by protonation and complexation with metal ions. This fluorophore can thus be used as a pH dependent and M (n+1)+ /M n+ redox on/off switchable molecular sensor

IR-FEL-induced green fluorescence protein (GFP) gene transfer into plant cell

CERN Document Server

Awazu, K; Tamiya, E

2002-01-01

A Free Electron Laser (FEL) holds potential for various biotechnological applications due to its characteristics such as flexible wavelength tunability, short pulse and high peak power. We could successfully introduce the Green Fluorescent Protein (GFP) gene into tobacco BY2 cells by IR-FEL laser irradiation. The irradiated area of the solution containing BY2 cells and plasmid was about 0.1 mm sup 2. FEL irradiation at a wavelength of 5.75 and 6.1 mu m, targeting absorption by the ester bond of the lipid and the amide I bond of the protein, respectively, was shown to cause the introduction of the fluorescent dye into the cell. On the other hand, transient expression of the GFP fluorescence was only observed after irradiation at 5.75 mu m. The maximum transfer efficiency was about 0.5%.

Transfer of energy in an atom

International Nuclear Information System (INIS)

Chemin, J.F.

2001-01-01

In most cases the nucleus does not interact with the electron cloud because its energy range is far higher, but in some rare cases electrons from the electron cloud and the nucleus may exchange energy: an electron may de-excite by transferring a part of its energy to the nucleus that becomes itself excited (nuclear excitation by electronic transfer or NEET), conversely electrons can receive energy from the nucleus (bound internal conversion or BIC). For the first time both energy transfers have been observed: a BIC process on a tellurium-125 atom by a French team and a NEET process on a gold-197 atom by a Japanese team. (A.C.)

Wireless energy transfer through non-resonant magnetic coupling

DEFF Research Database (Denmark)

Peng, Liang; Breinbjerg, Olav; Mortensen, Asger

2010-01-01

could be properly designed to minimize undesired energy dissipation in the source coil when the power receiver is out of the range. Our basic observation paves the way for more flexible design and fabrication of non-resonant mid-range wireless energy transfer systems, thus potentially impacting......We demonstrate by theoretical analysis and experimental verification that mid-range wireless energy transfer systems may take advantage of de-tuned coupling devices, without jeopardizing the energy transfer efficiency. Allowing for a modest de-tuning of the source coil, energy transfer systems...... practical implementations of wireless energy transfer....

Observation of the energy transfer sequence in an organic host–guest system of a luminescent polymer and a phosphorescent molecule

International Nuclear Information System (INIS)

Basel, Tek; Sun, Dali; Gautam, Bhoj; Valy Vardeny, Z.

2014-01-01

We used steady state optical spectroscopies such as photoluminescence and photoinduced absorption (PA), and magnetic-field PA (MPA) for studying the energy transfer dynamics in films and organic light emitting diodes (OLED) based on host–guest blends with different guest concentrations of the fluorescent polymer poly-[2-methoxy, 5-(2′-ethyl-hexyloxy)phenylene vinylene] (MEHPPV-host), and phosphorescent molecule PtII-tetraphenyltetrabenzoporphyrin [Pt(tpbp); guest]. We show that the energy transfer process between the excited states of the host polymer and guest molecule takes a ‘ping-pong’ type sequence, because the lowest guest triplet exciton energy, E T (guest), lies higher than that of the host, E T (host). Upon photon excitation the photogenerated singlet excitons in the host polymer chains first undergo a Förster resonant energy transfer process to the guest singlet manifold, which subsequently reaches E T (guest) by intersystem crossing. Because E T (guest)>E T (host) there is a subsequent Dexter type energy transfer from E T (guest) to E T (host). This energy transfer sequence has profound influence on the photoluminescence and electroluminescence emission spectra in both films and OLED devices based on the MEHPPV-Pt(tpbp) system. - Highlights: • We studied electroluminescence of OLEDs based on host–guest blends. • The emission efficiency decreases with the guest concentration. • We found a dominant Dexter energy transfer from the triplet(guest) to triplet(host). • Energy transfer occurs from the host to guest and back to the host again

Modulation of defect-mediated energy transfer from ZnO nanoparticles for the photocatalytic degradation of bilirubin

Directory of Open Access Journals (Sweden)

Tanujjal Bora

2013-11-01

Full Text Available In recent years, nanotechnology has gained significant interest for applications in the medical field. In this regard, a utilization of the ZnO nanoparticles for the efficient degradation of bilirubin (BR through photocatalysis was explored. BR is a water insoluble byproduct of the heme catabolism that can cause jaundice when its excretion is impaired. The photocatalytic degradation of BR activated by ZnO nanoparticles through a non-radiative energy transfer pathway can be influenced by the surface defect-states (mainly the oxygen vacancies of the catalyst nanoparticles. These were modulated by applying a simple annealing in an oxygen-rich atmosphere. The mechanism of the energy transfer process between the ZnO nanoparticles and the BR molecules adsorbed at the surface was studied by using steady-state and picosecond-resolved fluorescence spectroscopy. A correlation of photocatalytic degradation and time-correlated single photon counting studies revealed that the defect-engineered ZnO nanoparticles that were obtained through post-annealing treatments led to an efficient decomposition of BR molecules that was enabled by Förster resonance energy transfer.

Imaging molecular interactions in cells by dynamic and static fluorescence anisotropy (rFLIM and emFRET)

NARCIS (Netherlands)

Lidke, D.S.; Nagy, P.; Barisas, B.G.; Heintzmann, R.; Post, Janine Nicole; Lidke, K.A.; Clayton, A.H.A.; Arndt-jovin, D.J.; Jovin, T.M.

2003-01-01

We report the implementation and exploitation of fluorescence polarization measurements, in the form of anisotropy fluorescence lifetime imaging microscopy (rFLIM) and energy migration Förster resonance energy transfer (emFRET) modalities, for wide-field, confocal laser-scanning microscopy and flow

Radiative transport and collisional transfer of excitation energy in Cs vapors mixed with Ar or He

International Nuclear Information System (INIS)

Vadla, Cedomil; Horvatic, Vlasta; Niemax, Kay

2003-01-01

This paper is a review (with a few original additions) on the radiative transport and collisional transfer of energy in laser-excited cesium vapors in the presence of argon or helium. Narrow-band excitation of lines with Lorentz, Doppler and Voigt profiles is studied in order to calculate effective rates for pumping of spectral lines with profiles comprising inhomogeneous broadening components. The radiative transport of excitation energy is considered, and a new, simple and robust, but accurate theoretical method for quantitative treatment of radiation trapping in relatively optically thin media is presented. Furthermore, comprehensive lists of experimental values for the excitation energy transfer cross-sections related to thermal collisions in Cs-Ar and Cs-He mixtures are given. Within the collected cross-section data sets, specific regularities with respect to the energy defect, as well as the temperature, are discerned. A particular emphasis is put on the radiative and collisional processes important for the optimization of resonance-fluorescence imaging atomic filters based on Cs-noble gas systems

Distance-dependent energy transfer between indole and anthracene moieties in Langmuir Blodgett films

Science.gov (United States)

Saha, D. C.; Bhattacharjee, D.; Misra, T. N.

1998-09-01

1,2-Diphenyl indole (DPI) and 9,10-diphenyl anthracene (DPA) are non-amphiphilic molecules but form excellent LB films when mixed with stearic acid (SA). Spectroscopic investigations of these films indicate formation of aggregates of DPI and DPA in the mixed LB films. DPA has been used as the quencher of the fluorescence of the DPI donor. Distance-dependent energy transfer between donor and acceptor monolayers in the LB film, where they can be precisely separated by inert spacers of stearic acid layers of varied thickness, is shown to satisfy Khun's quadratic equation. This suggests that the donor excitations are delocalized. The large critical transfer distance estimated from the experimental results has been attributed to the formation of aggregates of the molecules in a LB monolayer.

Evolution of group 14 rhodamines as platforms for near-infrared fluorescence probes utilizing photoinduced electron transfer.

Science.gov (United States)

Koide, Yuichiro; Urano, Yasuteru; Hanaoka, Kenjiro; Terai, Takuya; Nagano, Tetsuo

2011-06-17

The absorption and emission wavelengths of group 14 pyronines and rhodamines, which contain silicon, germanium, or tin at the 10 position of the xanthene chromophore, showed large bathochromic shifts compared to the original rhodamines, owing to stabilization of the LUMO energy levels by σ*-π* conjugation between group 14 atom-C (methyl) σ* orbitals and a π* orbital of the fluorophore. These group 14 pyronines and rhodamines retain the advantages of the original rhodamines, including high quantum efficiency in aqueous media (Φ(fl) = 0.3-0.45), tolerance to photobleaching, and high water solubility. Group 14 rhodamines have higher values of reduction potential than other NIR light-emitting original rhodamines, and therefore, we speculated their NIR fluorescence could be controlled through the photoinduced electron transfer (PeT) mechanism. Indeed, we found that the fluorescence quantum yield (Φ(fl)) of Si-rhodamine (SiR) and Ge-rhodamine (GeR) could be made nearly equal to zero, and the threshold level for fluorescence on/off switching lies at around 1.3-1.5 V for the SiRs. This is about 0.1 V lower than in the case of TokyoGreens, in which the fluorophore is well established to be effective for PeT-based probes. That is to say, the fluorescence of SiR and GeR can be drastically activated by more than 100-fold through a PeT strategy. To confirm the validity of this strategy for developing NIR fluorescence probes, we employed this approach to design two kinds of novel fluorescence probes emitting in the far-red to NIR region, i.e., a series of pH-sensors for use in acidic environments and a Zn(2+) sensor. We synthesized these probes and confirmed that they work well.

Cholesterol-dependent energy transfer between fluorescent proteins-insights into protein proximity of APP and BACE1 in different membranes in Niemann-Pick type C disease cells.

Science.gov (United States)

von Einem, Bjoern; Weber, Petra; Wagner, Michael; Malnar, Martina; Kosicek, Marko; Hecimovic, Silva; Arnim, Christine A F von; Schneckenburger, Herbert

2012-11-26

Förster resonance energy transfer (FRET) -based techniques have recently been applied to study the interactions between β-site APP-cleaving enzyme-GFP (BACE1-GFP) and amyloid precursor protein-mRFP (APP-mRFP) in U373 glioblastoma cells. In this context, the role of APP-BACE1 proximity in Alzheimer's disease (AD) pathogenesis has been discussed. FRET was found to depend on intracellular cholesterol levels and associated alterations in membrane stiffness. Here, NPC1 null cells (CHO-NPC1-/-), exhibiting increased cholesterol levels and disturbed cholesterol transport similar to that observed in Niemann-Pick type C disease (NPC), were used to analyze the influence of altered cholesterol levels on APP-BACE1 proximity. Fluorescence lifetime measurements of whole CHO-wild type (WT) and CHO-NPC1-/- cells (EPI-illumination microscopy), as well as their plasma membranes (total internal reflection fluorescence microscopy, TIRFM), were performed. Additionally, generalized polarization (GP) measurements of CHO-WT and CHO-NPC1-/- cells incubated with the fluorescence marker laurdan were performed to determine membrane stiffness of plasma- and intracellular-membranes. CHO-NPC1-/- cells showed higher membrane stiffness at intracellular- but not plasma-membranes, equivalent to cholesterol accumulation in late endosomes/lysosomes. Along with higher membrane stiffness, the FRET efficiency between BACE1-GFP and APP-mRFP was reduced at intracellular membranes, but not within the plasma membrane of CHO-NPC1-/-. Our data show that FRET combined with TIRF is a powerful technique to determine protein proximity and membrane fluidity in cellular models of neurodegenerative diseases.

Vibrational relaxation and energy transfer of matrix isolated HCl and DCl

Energy Technology Data Exchange (ETDEWEB)

Wiesenfeld, J.M.

1977-12-01

Vibrational kinetic and spectroscopic studies have been performed on matrix-isolated HCl and DCl between 9 and 20 K. Vibrational relaxation rates for v = 2 and v = 1 were measured by a tunable infrared laser-induced, time-resolved fluorescence technique. In an Ar matrix, vibrational decay times are faster than radiative and it is found that HCl relaxes about 35 times more rapidly than CCl, in spite of the fact that HCl must transfer more energy to the lattice than DCl. This result is explained by postulating that the rate-determining step for vibrational relaxation produces a highly rotationally excited guest in a V yield R step; rotational relaxation into lattice phonons follows rapidly. HCl v = 1, but not v = 2, excitation rapidly diffuses through the sample by a resonant dipole-dipole vibrational energy transfer process. Molecular complexes, and in particular the HCl dimer, relax too rapidly for direct observation, less than or approximately 1 ..mu..s, and act as energy sinks in the energy diffusion process. The temperature dependence for all these processes is weak--less than a factor of two between 9 and 20 K. Vibrational relaxation of HCl in N/sub 2/ and O/sub 2/ matrices is unobservable, presumably due to rapid V yield V transfer to the host. A V yield R binary collision model for relaxation in solids is successful in explaining the HCl(DCl)/Ar results as well as results of other experimenters. The model considers relaxation to be the result of ''collisions'' due to molecular motion in quantized lattice normal modes--gas phase potential parameters can fit the matrix kinetic data.

Vibrational relaxation and energy transfer of matrix isolated HCl and DCl

International Nuclear Information System (INIS)

Wiesenfeld, J.M.

1977-12-01

Vibrational kinetic and spectroscopic studies have been performed on matrix-isolated HCl and DCl between 9 and 20 K. Vibrational relaxation rates for v = 2 and v = 1 were measured by a tunable infrared laser-induced, time-resolved fluorescence technique. In an Ar matrix, vibrational decay times are faster than radiative and it is found that HCl relaxes about 35 times more rapidly than CCl, in spite of the fact that HCl must transfer more energy to the lattice than DCl. This result is explained by postulating that the rate-determining step for vibrational relaxation produces a highly rotationally excited guest in a V yield R step; rotational relaxation into lattice phonons follows rapidly. HCl v = 1, but not v = 2, excitation rapidly diffuses through the sample by a resonant dipole-dipole vibrational energy transfer process. Molecular complexes, and in particular the HCl dimer, relax too rapidly for direct observation, less than or approximately 1 μs, and act as energy sinks in the energy diffusion process. The temperature dependence for all these processes is weak--less than a factor of two between 9 and 20 K. Vibrational relaxation of HCl in N 2 and O 2 matrices is unobservable, presumably due to rapid V yield V transfer to the host. A V yield R binary collision model for relaxation in solids is successful in explaining the HCl(DCl)/Ar results as well as results of other experimenters. The model considers relaxation to be the result of ''collisions'' due to molecular motion in quantized lattice normal modes--gas phase potential parameters can fit the matrix kinetic data

Stray energy transfer during endoscopy.

Science.gov (United States)

Jones, Edward L; Madani, Amin; Overbey, Douglas M; Kiourti, Asimina; Bojja-Venkatakrishnan, Satheesh; Mikami, Dean J; Hazey, Jeffrey W; Arcomano, Todd R; Robinson, Thomas N

2017-10-01

Endoscopy is the standard tool for the evaluation and treatment of gastrointestinal disorders. While the risk of complication is low, the use of energy devices can increase complications by 100-fold. The mechanism of increased injury and presence of stray energy is unknown. The purpose of the study was to determine if stray energy transfer occurs during endoscopy and if so, to define strategies to minimize the risk of energy complications. A gastroscope was introduced into the stomach of an anesthetized pig. A monopolar generator delivered energy for 5 s to a snare without contacting tissue or the endoscope itself. The endoscope tip orientation, energy device type, power level, energy mode, and generator type were varied to mimic in vivo use. The primary outcome (stray current) was quantified as the change in tissue temperature (°C) from baseline at the tissue closest to the tip of the endoscope. Data were reported as mean ± standard deviation. Using the 60 W coag mode while changing the orientation of the endoscope tip, tissue temperature increased by 12.1 ± 3.5 °C nearest the camera lens (p energy transfer (p = 0.04 and p = 0.002, respectively) as did utilizing the low-voltage cut mode (6.6 ± 0.5 °C, p energy transfer compared to a standard generator (1.5 ± 3.5 °C vs. 9.5 ± 0.8 °C, p energy is transferred within the endoscope during the activation of common energy devices. This could result in post-polypectomy syndrome, bleeding, or perforation outside of the endoscopist's view. Decreasing the power, utilizing low-voltage modes and/or an impedance-monitoring generator can decrease the risk of complication.

Energy transfer in turbulence under rotation

Science.gov (United States)

Buzzicotti, Michele; Aluie, Hussein; Biferale, Luca; Linkmann, Moritz

2018-03-01

It is known that rapidly rotating turbulent flows are characterized by the emergence of simultaneous upscale and downscale energy transfer. Indeed, both numerics and experiments show the formation of large-scale anisotropic vortices together with the development of small-scale dissipative structures. However the organization of interactions leading to this complex dynamics remains unclear. Two different mechanisms are known to be able to transfer energy upscale in a turbulent flow. The first is characterized by two-dimensional interactions among triads lying on the two-dimensional, three-component (2D3C)/slow manifold, namely on the Fourier plane perpendicular to the rotation axis. The second mechanism is three-dimensional and consists of interactions between triads with the same sign of helicity (homochiral). Here, we present a detailed numerical study of rotating flows using a suite of high-Reynolds-number direct numerical simulations (DNS) within different parameter regimes to analyze both upscale and downscale cascade ranges. We find that the upscale cascade at wave numbers close to the forcing scale is generated by increasingly dominant homochiral interactions which couple the three-dimensional bulk and the 2D3C plane. This coupling produces an accumulation of energy in the 2D3C plane, which then transfers energy to smaller wave numbers thanks to the two-dimensional mechanism. In the forward cascade range, we find that the energy transfer is dominated by heterochiral triads and is dominated primarily by interaction within the fast manifold where kz≠0 . We further analyze the energy transfer in different regions in the real-space domain. In particular, we distinguish high-strain from high-vorticity regions and we uncover that while the mean transfer is produced inside regions of strain, the rare but extreme events of energy transfer occur primarily inside the large-scale column vortices.

Quantitative analysis with energy dispersive X-ray fluorescence analyser

International Nuclear Information System (INIS)

Kataria, S.K.; Kapoor, S.S.; Lal, M.; Rao, B.V.N.

1977-01-01

Quantitative analysis of samples using radioisotope excited energy dispersive x-ray fluorescence system is described. The complete set-up is built around a locally made Si(Li) detector x-ray spectrometer with an energy resolution of 220 eV at 5.94 KeV. The photopeaks observed in the x-ray fluorescence spectra are fitted with a Gaussian function and the intensities of the characteristic x-ray lines are extracted, which in turn are used for calculating the elemental concentrations. The results for a few typical cases are presented. (author)

Light adaptation of the unicellular red alga, Cyanidioschyzon merolae, probed by time-resolved fluorescence spectroscopy.

Science.gov (United States)

Ueno, Yoshifumi; Aikawa, Shimpei; Kondo, Akihiko; Akimoto, Seiji

2015-08-01

Photosynthetic organisms change the quantity and/or quality of their pigment-protein complexes and the interactions among these complexes in response to light conditions. In the present study, we analyzed light adaptation of the unicellular red alga Cyanidioschyzon merolae, whose pigment composition is similar to that of cyanobacteria because its phycobilisomes (PBS) lack phycoerythrin. C. merolae were grown under different light qualities, and their responses were measured by steady-state absorption, steady-state fluorescence, and picosecond time-resolved fluorescence spectroscopies. Cells were cultivated under four monochromatic light-emitting diodes (blue, green, yellow, and red), and changes in pigment composition and energy transfer were observed. Cells grown under blue and green light increased their relative phycocyanin levels compared with cells cultured under white light. Energy-transfer processes to photosystem I (PSI) were sensitive to yellow and red light. The contribution of direct energy transfer from PBS to PSI increased only under yellow light, while red light induced a reduction in energy transfer from photosystem II to PSI and an increase in energy transfer from light-harvesting chlorophyll protein complex I to PSI. Differences in pigment composition, growth, and energy transfer under different light qualities are discussed.

Targeting Low-Energy Ballistic Lunar Transfers

Science.gov (United States)

Parker, Jeffrey S.

2010-01-01

Numerous low-energy ballistic transfers exist between the Earth and Moon that require less fuel than conventional transfers, but require three or more months of transfer time. An entirely ballistic lunar transfer departs the Earth from a particular declination at some time in order to arrive at the Moon at a given time along a desirable approach. Maneuvers may be added to the trajectory in order to adjust the Earth departure to meet mission requirements. In this paper, we characterize the (Delta)V cost required to adjust a low-energy ballistic lunar transfer such that a spacecraft may depart the Earth at a desirable declination, e.g., 28.5(white bullet), on a designated date. This study identifies the optimal locations to place one or two maneuvers along a transfer to minimize the (Delta)V cost of the transfer. One practical application of this study is to characterize the launch period for a mission that aims to launch from a particular launch site, such as Cape Canaveral, Florida, and arrive at a particular orbit at the Moon on a given date using a three-month low-energy transfer.

Fluorescence-Based Bioassays for the Detection and Evaluation of Food Materials

OpenAIRE

Nishi, Kentaro; Isobe, Shin-Ichiro; Zhu, Yun; Kiyama, Ryoiti

2015-01-01

We summarize here the recent progress in fluorescence-based bioassays for the detection and evaluation of food materials by focusing on fluorescent dyes used in bioassays and applications of these assays for food safety, quality and efficacy. Fluorescent dyes have been used in various bioassays, such as biosensing, cell assay, energy transfer-based assay, probing, protein/immunological assay and microarray/biochip assay. Among the arrays used in microarray/biochip assay, fluorescence-based mi...

Practical lesson of Photosynthesis: A demonstration of Hill reaction in chloroplasts with energy dissipation by fluorescence upon photosystems uncoupling or inhibition by Diuron herbicide

Directory of Open Access Journals (Sweden)

Vadim Ravara Viviani

2016-05-01

Full Text Available During photosynthesis, the photochemical electron transfer process is easily demonstrated by the Hill reaction, where artificial electron acceptors are reduced by active chloroplasts suspensions in the presence of light.  However, the destiny of luminous energy absorbed by chlorophyll molecules in uncoupled or damaged photosystems is not usually demonstrated. Here we provide an adaptation of the classical Hill reaction using intact spinach chloroplasts, which includes the visualization of energy dissipation by fluorescence in lysed chloroplasts, and a dose/effect response in photosystems inhibited by the herbicide DCMU. This laboratory lesson, which is aimed to biochemistry and biophysics for undergraduate courses of Chemistry, Biological, Environmental and Agricultural Sciences, provides the basic photochemical principles using the classical Hill reaction, and photophysical principles through the visualization of energy dissipation by chlorophyll fluorescence,  improving the understanding of the photosynthetic process, and introducing the concept of fluorescence and its applications as bioanalytical tool to monitor photosynthesis in plants and vegetal ecosystems.

Observation of the energy transfer sequence in an organic host–guest system of a luminescent polymer and a phosphorescent molecule

Energy Technology Data Exchange (ETDEWEB)

Basel, Tek; Sun, Dali; Gautam, Bhoj; Valy Vardeny, Z., E-mail: val@physics.utah.edu

2014-11-15

We used steady state optical spectroscopies such as photoluminescence and photoinduced absorption (PA), and magnetic-field PA (MPA) for studying the energy transfer dynamics in films and organic light emitting diodes (OLED) based on host–guest blends with different guest concentrations of the fluorescent polymer poly-[2-methoxy, 5-(2′-ethyl-hexyloxy)phenylene vinylene] (MEHPPV-host), and phosphorescent molecule PtII-tetraphenyltetrabenzoporphyrin [Pt(tpbp); guest]. We show that the energy transfer process between the excited states of the host polymer and guest molecule takes a ‘ping-pong’ type sequence, because the lowest guest triplet exciton energy, E{sub T}(guest), lies higher than that of the host, E{sub T}(host). Upon photon excitation the photogenerated singlet excitons in the host polymer chains first undergo a Förster resonant energy transfer process to the guest singlet manifold, which subsequently reaches E{sub T}(guest) by intersystem crossing. Because E{sub T}(guest)>E{sub T}(host) there is a subsequent Dexter type energy transfer from E{sub T}(guest) to E{sub T}(host). This energy transfer sequence has profound influence on the photoluminescence and electroluminescence emission spectra in both films and OLED devices based on the MEHPPV-Pt(tpbp) system. - Highlights: • We studied electroluminescence of OLEDs based on host–guest blends. • The emission efficiency decreases with the guest concentration. • We found a dominant Dexter energy transfer from the triplet(guest) to triplet(host). • Energy transfer occurs from the host to guest and back to the host again.

Low-Energy Ballistic Transfers to Lunar Halo Orbits

Science.gov (United States)

Parker, Jeffrey S.

2009-01-01

Recent lunar missions have begun to take advantage of the benefits of low-energy ballistic transfers between the Earth and the Moon rather than implementing conventional Hohmann-like lunar transfers. Both Artemis and GRAIL plan to implement low-energy lunar transfers in the next few years. This paper explores the characteristics and potential applications of many different families of low-energy ballistic lunar transfers. The transfers presented here begin from a wide variety of different orbits at the Earth and follow several different distinct pathways to the Moon. This paper characterizes these pathways to identify desirable low-energy lunar transfers for future lunar missions.

Energy transfer mechanism from Gd3+ to Sm3+ in K3Gd(PO4)2:Sm3+ phosphor

International Nuclear Information System (INIS)

Gupta, Palvi; Bedyal, A K; Kumar, Vinay; Khajuria, Y; Sharma, Vishal; Ntwaeaborwa, O M; Swart, H C

2015-01-01

Undoped K 3 Gd(PO 4 ) 2 and trivalent samarium (0.5–2.5 mol%) doped K 3 Gd(PO 4 ) 2 phosphors were synthesized by the solid-state method. The phase formation, optical and luminescence properties were investigated by x-ray diffraction (XRD), diffuse reflectance (DR) spectroscopy, and photoluminescence (PL) spectroscopy. The fluorescence decay spectra of the obtained phosphors were also recorded to study the energy transfer from sensitizer (Gd 3+ ) to activator (Sm 3+ ). Energy transfer effects from sensitizer to activator caused by rare-earth ions were mainly observed in the obtained PL and lifetime spectra. The decay curves of K 3 Gd(PO 4 ) 2 phosphor with different Sm 3+ ions concentrations were found to be non-exponential and the data is well fitted with the Inokuti–Hirayama (I–H) model. The energy transfer parameters such as critical distance for the transfer processes were determined. The Commission Internationale de l’Eclairage (CIE) chromatic coordinates and color-correlated temperature were also determined for the prepared phosphor. (paper)

Intramolecular Energy Transfer, Charge Transfer & Hydrogen Bond

Indian Academy of Sciences (India)

Ultrafast Dynamics of Chemical Reactions in Condensed Phase: Intramolecular Energy Transfer, Charge Transfer & Hydrogen Bond · PowerPoint Presentation · Slide 3 · Slide 4 · Slide 5 · Slide 6 · Slide 7 · Slide 8 · Slide 9 · Slide 10 · Slide 11 · Slide 12 · Slide 13 · Slide 14 · Slide 15 · Slide 16 · Slide 17 · Slide 18 · Slide 19.

Laser induced energy transfer

International Nuclear Information System (INIS)

Falcone, R.W.

1979-01-01

Two related methods of rapidly transferring stored energy from one excited chemical species to another are described. The first of these, called a laser induced collision, involves a reaction in which the energy balance is met by photons from an intense laser beam. A collision cross section of ca 10 - 17 cm 2 was induced in an experiment which demonstrated the predicted dependence of the cross section on wavelength and power density of the applied laser. A second type of laser induced energy transfer involves the inelastic scattering of laser radiation from energetically excited atoms, and subsequent absorption of the scattered light by a second species. The technique of producing the light, ''anti-Stokes Raman'' scattering of visible and infrared wavelength laser photons, is shown to be an efficient source of narrow bandwidth, high brightness, tunable radiation at vacuum ultraviolet wavelengths by using it to excite a rare gas transition at 583.7 A. In addition, this light source was used to make the first measurement of the isotopic shift of the helium metastable level at 601 A. Applications in laser controlled chemistry and spectroscopy, and proposals for new types of lasers using these two energy transfer methods are discussed

Spectral heterogeneity and carotenoid-to-bacteriochlorophyll energy transfer in LH2 light-harvesting complexes from Allochromatium vinosum.

Science.gov (United States)

Magdaong, Nikki M; LaFountain, Amy M; Hacking, Kirsty; Niedzwiedzki, Dariusz M; Gibson, George N; Cogdell, Richard J; Frank, Harry A

2016-02-01

Photosynthetic organisms produce a vast array of spectral forms of antenna pigment-protein complexes to harvest solar energy and also to adapt to growth under the variable environmental conditions of light intensity, temperature, and nutrient availability. This behavior is exemplified by Allochromatium (Alc.) vinosum, a photosynthetic purple sulfur bacterium that produces different types of LH2 light-harvesting complexes in response to variations in growth conditions. In the present work, three different spectral forms of LH2 from Alc. vinosum, B800-820, B800-840, and B800-850, were isolated, purified, and examined using steady-state absorption and fluorescence spectroscopy, and ultrafast time-resolved absorption spectroscopy. The pigment composition of the LH2 complexes was analyzed by high-performance liquid chromatography, and all were found to contain five carotenoids: lycopene, anhydrorhodovibrin, spirilloxanthin, rhodopin, and rhodovibrin. Spectral reconstructions of the absorption and fluorescence excitation spectra based on the pigment composition revealed significantly more spectral heterogeneity in these systems compared to LH2 complexes isolated from other species of purple bacteria. The data also revealed the individual carotenoid-to-bacteriochlorophyll energy transfer efficiencies which were correlated with the kinetic data from the ultrafast transient absorption spectroscopic experiments. This series of LH2 complexes allows a systematic exploration of the factors that determine the spectral properties of the bound pigments and control the rate and efficiency of carotenoid-to-bacteriochlorophyll energy transfer.

Energy dispersive X-Ray fluorescence spectrometric study of ...

African Journals Online (AJOL)

Energy dispersive X-Ray fluorescence spectrometric study of compositional differences in trace elements in dried Moringa oleifera leaves grown in two different agro-ecological locations in Ebonyi State, Nigeria.

Dynamics of energy transfer from lycopene to bacteriochlorophyll in genetically-modified LH2 complexes of Rhodobacter sphaeroides.

Science.gov (United States)

Hörvin Billsten, H; Herek, J L; Garcia-Asua, G; Hashøj, L; Polívka, T; Hunter, C N; Sundström, V

2002-03-26

LH2 complexes from Rb. sphaeroides were modified genetically so that lycopene, with 11 saturated double bonds, replaced the native carotenoids which contain 10 saturated double bonds. Tuning the S1 level of the carotenoid in LH2 in this way affected the dynamics of energy transfer within LH2, which were investigated using both steady-state and time-resolved techniques. The S1 energy of lycopene in n-hexane was determined to be approximately 12 500 +/- 150 cm(-1), by direct measurement of the S1-S2 transient absorption spectrum using a femtosecond IR-probing technique, thus placing an upper limit on the S1 energy of lycopene in the LH2 complex. Fluorescence emission and excitation spectra demonstrated that energy can be transferred from lycopene to the bacteriochlorophyll molecules within this LH2 complex. The energy-transfer dynamics within the mutant complex were compared to wild-type LH2 from Rb. sphaeroides containing the carotenoid spheroidene and from Rs. molischianum, in which lycopene is the native carotenoid. The results show that the overall efficiency for Crt --> B850 energy transfer is approximately 80% in lyco-LH2 and approximately 95% in WT-LH2 of Rb. sphaeroides. The difference in overall Crt --> BChl transfer efficiency of lyco-LH2 and WT-LH2 mainly relates to the low efficiency of the Crt S(1) --> BChl pathway for complexes containing lycopene, which was 20% in lyco-LH2. These results show that in an LH2 complex where the Crt S1 energy is sufficiently high to provide efficient spectral overlap with both B800 and B850 Q(y) states, energy transfer via the Crt S1 state occurs to both pigments. However, the introduction of lycopene into the Rb. sphaeroides LH2 complex lowers the S1 level of the carotenoid sufficiently to prevent efficient transfer of energy to the B800 Q(y) state, leaving only the Crt S1 --> B850 channel, strongly suggesting that Crt S1 --> BChl energy transfer is controlled by the relative Crt S1 and BChl Q(y) energies.

Transferência de energia entre corantes catiônicos em sistemas homogêneos

Directory of Open Access Journals (Sweden)

Oliveira Hueder Paulo Moisés de

2003-01-01

Full Text Available In this work, the energy transfer by dipole-dipole interaction between cationic dyes in n-alcohols (methanol, ethanol, 1-propanol and 1-butanol is studied by time resolved and steady state fluorescence measurements. The critical radii of energy transfer were determined by three independent methods; the spectral overlap, fluorescence decay profiles, and relative intensity measurements. In all solvents, R0 values of the dye pairs obtained from spectral overlap were between 40 to 90 Å. Steady state and time resolved fluorescence measurements resulted in values of R0 in the range of 50 - 80 Å, with good correlation of values.

Simple structured hybrid WOLEDs based on incomplete energy transfer mechanism: from blue exciplex to orange dopant

Science.gov (United States)

Zhang, Tianyou; Zhao, Bo; Chu, Bei; Li, Wenlian; Su, Zisheng; Yan, Xingwu; Liu, Chengyuan; Wu, Hairuo; Gao, Yuan; Jin, Fangming; Hou, Fuhua

2015-05-01

Exciplex is well known as a charge transfer state formed between electron-donating and electron-accepting molecules. However, exciplex based organic light emitting diodes (OLED) often performed low efficiencies relative to pure phosphorescent OLED and could hardly be used to construct white OLED (WOLED). In this work, a new mechanism is developed to realize efficient WOLED with extremely simple structure by redistributing the energy of triplet exciplex to both singlet exciplex and the orange dopant. The micro process of energy transfer could be directly examined by detailed photoluminescence decay measurement and time resolved photoluminescence analysis. This strategy overcomes the low reverse intersystem crossing efficiency of blue exciplex and complicated device structure of traditional WOLED, enables us to achieve efficient hybrid WOLEDs. Based on this mechanism, we have successfully constructed both exciplex-fluorescence and exciplex-phosphorescence hybrid WOLEDs with remarkable efficiencies.

Fluorescence resonance energy transfer between ZnSe ZnS quantum dots and bovine serum albumin in bioaffinity assays of anticancer drugs

Science.gov (United States)

Shu, Chang; Ding, Li; Zhong, Wenying

2014-10-01

In the current work, using ZnSe ZnS quantum dots (QDs) as representative nanoparticles, the affinities of seven anticancer drugs for bovine serum albumin (BSA) were studied using fluorescence resonance energy transfer (FRET). The FRET efficiency of BSA-QD conjugates can reach as high as 24.87% by electrostatic interaction. The higher binding constant (3.63 × 107 L mol-1) and number of binding sites (1.75) between ZnSe ZnS QDs and BSA demonstrated that the QDs could easily associate to plasma proteins and enhance the transport efficacy of drugs. The magnitude of binding constants (103-106 L mol-1), in the presence of QDs, was between drugs-BSA and drugs-QDs in agreement with common affinities of drugs for serum albumins (104-106 L mol-1) in vivo. ZnSe ZnS QDs significantly increased the affinities for BSA of Vorinostat (SAHA), Docetaxel (DOC), Carmustine (BCNU), Doxorubicin (Dox) and 10-Hydroxycamptothecin (HCPT). However, they slightly reduced the affinities of Vincristine (VCR) and Methotrexate (MTX) for BSA. The recent work will not only provide useful information for appropriately understanding the binding affinity and binding mechanism at the molecular level, but also illustrate the ZnSe ZnS QDs are perfect candidates for nanoscal drug delivery system (DDS).

Fluorescence quenching and photocatalytic degradation of textile dyeing waste water by silver nanoparticles

Science.gov (United States)

Kavitha, S. R.; Umadevi, M.; Janani, S. R.; Balakrishnan, T.; Ramanibai, R.

2014-06-01

Silver nanoparticles (Ag NPs) of different sizes have been prepared by chemical reduction method and characterized using UV-vis spectroscopy and transmission electron microscopy (HRTEM). Fluorescence spectral analysis showed that the quenching of fluorescence of textile dyeing waste water (TDW) has been found to decrease with decrease in the size of the Ag NPs. Experimental results show that the silver nanoparticles can quench the fluorescence emission of adsorbed TDW effectively. The fluorescence interaction between Ag NPs (acceptor) and TDW (donor) confirms the Förster Resonance Energy Transfer (FRET) mechanism. Long range dipole-dipole interaction between the excited donor and ground state acceptor molecules is the dominant mechanism responsible for the energy transfer. Furthermore, photocatalytic degradation of TDW was measured spectrophotometrically by using silver as nanocatalyst under UV light illumination. The kinetic study revealed that synthesized Ag NPs was found to be effective in degrading TDW.

Exciplex emission and photoinduced energy transfer as a function of cavity dimension in naphthalene-linked aza-crown ethers

International Nuclear Information System (INIS)

Roy, Mailrayee Basu; Samanta, Subhodip; Chattopadhyay, Gautam; Ghosh, Sanjib

2004-01-01

We report here the photophysical properties of two derivatives of N-(β-methylnaphthalene) aza-crown systems having different cavity dimensions. The aza-crown moiety is attached to β-position of naphthalene moiety by one >CH 2 unit in both the derivatives. The cavity size is found to have a pronounced effect on exciplex formation as well as energy transfer in the systems at room temperature and low temperature, respectively. Both the systems exhibit photoinduced electron transfer (PET) which is evident from their weaker fluorescence emission and their quenched singlet lifetimes as compared to that of free naphthalene. The systems also show a solvent sensitive red shifted broad structureless emission which is assigned to exciplex formation. The ratio of quantum yields of exciplex to monomer emission (phi (cursive,open) Greek Exp /phi (cursive,open) Greek M ) is lower in the smaller aza-crown (L1) as compared to that in the larger aza-crown (L2) implying a different geometry of the two systems in the excited state. Semi-emperical calculations performed on the systems also corroborate the different geometry of the two systems. Complexation of alkali metals, rare earth ions and protons by the aza-crown moiety results in enhancement of fluorescence emission due to blocking of PET. In the presence of protons, L1 exhibits a new emission due to excimer formation which has not been observed in L2 under similar conditions. The rare earth ion complexes of L1 and L2 at low temperature exhibit energy transfer from the lowest triplet state of naphthalene to the rare earth ion states, the extent of energy transfer being greater in the larger aza-crown (L2) as compared to that in smaller aza-crown system (L1)

Simulation study of two-energy X-ray fluorescence holograms reconstruction algorithm to remove twin images

International Nuclear Information System (INIS)

Xie Honglan; Hu Wen; Luo Hongxin; Deng Biao; Du Guohao; Xue Yanling; Chen Rongchang; Shi Shaomeng; Xiao Tiqiao

2008-01-01

Unlike traditional outside-source holography, X-ray fluorescence holography is carded out with fluorescent atoms in a sample as source light for holographic imaging. With the method, three-dimensional arrangement of atoms into crystals can be observed obviously. However, just like traditional outside-source holography, X-ray fluorescence holography suffers from the inherent twin-image problem, too. With a 27-Fe-atoms cubic lattice as model, we discuss in this paper influence of the photon energy of incident source in removing twin images in reconstructed atomic images by numerical simulation and reconstruction with two-energy X-ray fluorescence holography. The results indicate that incident X-rays of nearer energies have better effect of removing twin images. In the detector of X-ray holography, minimum difference of the two incident energies depends on energy resolution of the monochromator and detector, and for inside source X-ray holography, minimum difference of the two incident energies depends on difference of two neighboring fluorescent energies emitting from the element and energy resolution of detector. The spatial resolution of atomic images increases with the incident energies. This is important for experiments of X-ray fluorescence holography, which is being developed on Shanghai Synchrotron Radiation Facility. (authors)

Energy transfers in large-scale and small-scale dynamos

Science.gov (United States)

Samtaney, Ravi; Kumar, Rohit; Verma, Mahendra

2015-11-01

We present the energy transfers, mainly energy fluxes and shell-to-shell energy transfers in small-scale dynamo (SSD) and large-scale dynamo (LSD) using numerical simulations of MHD turbulence for Pm = 20 (SSD) and for Pm = 0.2 on 10243 grid. For SSD, we demonstrate that the magnetic energy growth is caused by nonlocal energy transfers from the large-scale or forcing-scale velocity field to small-scale magnetic field. The peak of these energy transfers move towards lower wavenumbers as dynamo evolves, which is the reason for the growth of the magnetic fields at the large scales. The energy transfers U2U (velocity to velocity) and B2B (magnetic to magnetic) are forward and local. For LSD, we show that the magnetic energy growth takes place via energy transfers from large-scale velocity field to large-scale magnetic field. We observe forward U2U and B2B energy flux, similar to SSD.

Concentration-dependent luminescence and energy transfer of flower-like Y2(MoO4)3:Dy3+ phosphor

International Nuclear Information System (INIS)

Tian Yue; Chen Baojiu; Tian Bining; Hua Ruinian; Sun Jiashi; Cheng Lihong; Zhong Haiyang; Li Xiangping; Zhang Jinsu; Zheng Yanfeng; Yu Tingting; Huang Libo; Meng Qingyu

2011-01-01

Highlights: → Flower-shaped Y 2 (MoO 4 ) 3 phosphors were prepared by a co-precipitation method. → The structure and morphology of the prepared phosphors were characterized. → Energy transfer between Dy 3+ was studied by Huang's theory, IH and Uitert's models. - Abstract: Flower-like Y 2 (MoO 4 ) 3 :Dy 3+ phosphors have been synthesized via a co-precipitation approach with the aid of β-cyclodextrin. The crystal structure and morphology of the phosphors were characterized by XRD (X-ray diffraction) and FE-SEM (field emission scanning electron microscopy), respectively. The excitation and emission properties of the phosphors were examined by fluorescence spectroscopy. The dependence of color coordinates on the Dy 3+ doping concentration was analyzed. The energy transfer mechanism between Dy 3+ ions was studied based on the Huang's theory, I-H and Van Uitert's models. It was concluded simultaneously from these three routes that the electric dipole-dipole interaction between Dy 3+ ions is the main physical mechanism for the energy transfers between Dy 3+ .

Visual prosthesis wireless energy transfer system optimal modeling.

Science.gov (United States)

Li, Xueping; Yang, Yuan; Gao, Yong

2014-01-16

Wireless energy transfer system is an effective way to solve the visual prosthesis energy supply problems, theoretical modeling of the system is the prerequisite to do optimal energy transfer system design. On the basis of the ideal model of the wireless energy transfer system, according to visual prosthesis application condition, the system modeling is optimized. During the optimal modeling, taking planar spiral coils as the coupling devices between energy transmitter and receiver, the effect of the parasitic capacitance of the transfer coil is considered, and especially the concept of biological capacitance is proposed to consider the influence of biological tissue on the energy transfer efficiency, resulting in the optimal modeling's more accuracy for the actual application. The simulation data of the optimal model in this paper is compared with that of the previous ideal model, the results show that under high frequency condition, the parasitic capacitance of inductance and biological capacitance considered in the optimal model could have great impact on the wireless energy transfer system. The further comparison with the experimental data verifies the validity and accuracy of the optimal model proposed in this paper. The optimal model proposed in this paper has a higher theoretical guiding significance for the wireless energy transfer system's further research, and provide a more precise model reference for solving the power supply problem in visual prosthesis clinical application.

Förster resonance energy transfer between α -Bi2O3 nanorods and rhodamine 6G in aqueous media for turn-off glucose-sensing application

International Nuclear Information System (INIS)

Balasubramanian, Karthikeyan

2017-01-01

The present study deals with the Förster resonance energy transfer (FRET) process that takes place between α -Bi 2 O 3 nanorods (BN), which function as a donor, and Rhodamine 6G, which (R6G) functions as an acceptor. Fluorescence of R6G situated at 550 nm is found to be enhanced due to this FRET behaviour with the increase of the number of acceptor concentrations. Apart from this, the rate of energy transfer also increased. It is found that a decrease in the donor–acceptor distance is assisting FRET. Steady state and time-resolved fluorescence studies are performed in two different excitation wavelengths and it shows the possible FRET behaviour where the average lifetime increases with the increase of acceptor concentrations. This pair is used to sense the glucose in nM concentrations. (paper)

Comparitive study of fluorescence lifetime quenching of rhodamine 6G by MoS2 and Au-MoS2

Science.gov (United States)

Shakya, Jyoti; Kasana, Parath; Mohanty, T.

2018-04-01

Time resolved fluorescence study of Rhodamine 6G (R6G) in the presence of Molybdenum disulfide (MoS2) nanosheets and gold doped MoS2 (Au-MoS2) have been carried out and discussed. We have analyzed the fluorescence decay curves of R6G and it is observed that Au-MoS2 is a better fluorescence lifetime quencher as compare to MoS2 nanosheets. Also, the energy transfer efficiency and energy transfer rate from R6G to MoS2 and Au-MoS2 has been calculated and found higher for Au-MoS2.

Two photon absorption energy transfer in the light-harvesting complex of photosystem II (LHC-II) modified with organic boron dye

Science.gov (United States)

Chen, Li; Liu, Cheng; Hu, Rui; Feng, Jiao; Wang, Shuangqing; Li, Shayu; Yang, Chunhong; Yang, Guoqiang

2014-07-01

The plant light-harvesting complexes of photosystem II (LHC-II) play important roles in collecting solar energy and transferring the energy to the reaction centers of photosystems I and II. A two photon absorption compound, 4-(bromomethyl)-N-(4-(dimesitylboryl)phenyl)-N-phenylaniline (DMDP-CH2Br), was synthesized and covalently linked to the LHC-II in formation of a LHC-II-dye complex, which still maintained the biological activity of LHC-II system. Under irradiation with femtosecond laser pulses at 754 nm, the LHC-II-dye complex can absorb two photons of the laser light effectively compared with the wild type LHC-II. The absorbed excitation energy is then transferred to chlorophyll a with an obvious fluorescence enhancement. The results may be interesting and give potentials for developing hybrid photosystems.

The security energy encryption in wireless power transfer

Science.gov (United States)

Sadzali, M. N.; Ali, A.; Azizan, M. M.; Albreem, M. A. M.

2017-09-01

This paper presents a concept of security in wireless power transfer (WPT) by applying chaos theory. Chaos theory is applied as a security system in order to safeguard the transfer of energy from a transmitter to the intended receiver. The energy encryption of the wireless power transfer utilizes chaos theory to generate the possibility of a logistic map for the chaotic security key. The simulation for energy encryption wireless power transfer system was conducted by using MATLAB and Simulink. By employing chaos theory, the chaotic key ensures the transmission of energy from transmitter to its intended receiver.

Fluorescent S-layer fusion proteins

International Nuclear Information System (INIS)

Kainz, B.

2010-01-01

This work describes the construction and characterisation of fluorescent S-layer fusion proteins used as building blocks for the fabrication of nanostructured monomolecular biocoatings on silica particles with defined fluorescence properties. The S-layer protein SgsE of Geobacillus stearothermophilus NRS 2004/3a was fused with the pH-dependant cyan, green and yellow variant of the green fluorescent protein (GFP) and the red fluorescent protein mRFP1. These fluorescent S-layer fusion proteins, acting as scaffold and optical sensing element simultaneously, were able to reassemble in solution and on silica particles forming 2D nanostructures with p2 lattice symmetry (a=11 ±0.5 nm, b=14 ±0.4 nm, g=80 ±1 o ). The pH-dependant fluorescence behaviour was studied with fluorimetry, confocal microscopy and flow cytometry. These fluorescent S-layer fusion proteins can be used as pH-sensor. 50% of the fluorescence intensity decreases at their calculated pKa values (pH6 - pH5). The fluorescence intensity of the GFP variants vanished completely between pH4 and pH3 whereas the chromophore of the red protein mRFP1 was only slightly affected in acidic conditions. At the isoelectric point of the S-layer coated silica particles (pH4.6 ±0.2) an increase in particle aggregation was detected by flow cytometry. The cyan and yellow fluorescent proteins were chosen to create a bi-fluorescent S-layer tandem fusion protein with the possibility for resonance energy transfer (FRET). A transfer efficiency of 20% and a molecular distance between the donor (ECFP) and acceptor (YFP) chromophores of around 6.2 nm could be shown. This bi-fluorescent ECFP-SgsE-YFP tandem fusion protein was able to reassemble on solid surfaces. The remarkable combination of fluorescence and self-assembly and the design of bi-functional S-layer tandem fusion protein matrices makes them to a promising tool in nanobiotechnology. (author) [de

Intramolecular ex vivo Fluorescence Resonance Energy Transfer (FRET of Dihydropyridine Receptor (DHPR β1a Subunit Reveals Conformational Change Induced by RYR1 in Mouse Skeletal Myotubes.

Directory of Open Access Journals (Sweden)

Dipankar Bhattacharya

Full Text Available The dihydropyridine receptor (DHPR β1a subunit is essential for skeletal muscle excitation-contraction coupling, but the structural organization of β1a as part of the macromolecular DHPR-ryanodine receptor type I (RyR1 complex is still debatable. We used fluorescence resonance energy transfer (FRET to probe proximity relationships within the β1a subunit in cultured skeletal myotubes lacking or expressing RyR1. The fluorescein biarsenical reagent FlAsH was used as the FRET acceptor, which exhibits fluorescence upon binding to specific tetracysteine motifs, and enhanced cyan fluorescent protein (CFP was used as the FRET donor. Ten β1a reporter constructs were generated by inserting the CCPGCC FlAsH binding motif into five positions probing the five domains of β1a with either carboxyl or amino terminal fused CFP. FRET efficiency was largest when CCPGCC was positioned next to CFP, and significant intramolecular FRET was observed for all constructs suggesting that in situ the β1a subunit has a relatively compact conformation in which the carboxyl and amino termini are not extended. Comparison of the FRET efficiency in wild type to that in dyspedic (lacking RyR1 myotubes revealed that in only one construct (H458 CCPGCC β1a -CFP FRET efficiency was specifically altered by the presence of RyR1. The present study reveals that the C-terminal of the β1a subunit changes conformation in the presence of RyR1 consistent with an interaction between the C-terminal of β1a and RyR1 in resting myotubes.

Interactive Joint Transfer of Energy and Information

DEFF Research Database (Denmark)

Popovski, Petar; Fouladgar, A. M.; Simeone, Osvaldo

2013-01-01

In some communication networks, such as passive RFID systems, the energy used to transfer information between a sender and a recipient can be reused for successive communication tasks. In fact, from known results in physics, any system that exchanges information via the transfer of given physical...... key design insights. Index Terms— Two-way channel, interactive communication, energy transfer, energy harvesting....... resources, such as radio waves, particles and qubits, can conceivably reuse, at least part, of the received resources. This paper aims at illustrating some of the new challenges that arise in the design of communication networks in which the signals exchanged by the nodes carry both information and energy...

Fluorescent Probes and Fluorescence (Microscopy Techniques — Illuminating Biological and Biomedical Research

Directory of Open Access Journals (Sweden)

Gregor P. C. Drummen

2012-11-01

Full Text Available Fluorescence, the absorption and re-emission of photons with longer wavelengths, is one of those amazing phenomena of Nature. Its discovery and utilization had, and still has, a major impact on biological and biomedical research, since it enables researchers not just to visualize normal physiological processes with high temporal and spatial resolution, to detect multiple signals concomitantly, to track single molecules in vivo, to replace radioactive assays when possible, but also to shed light on many pathobiological processes underpinning disease states, which would otherwise not be possible. Compounds that exhibit fluorescence are commonly called fluorochromes or fluorophores and one of these fluorescent molecules in particular has significantly enabled life science research to gain new insights in virtually all its sub-disciplines: Green Fluorescent Protein. Because fluorescent proteins are synthesized in vivo, integration of fluorescent detection methods into the biological system via genetic techniques now became feasible. Currently fluorescent proteins are available that virtually span the whole electromagnetic spectrum. Concomitantly, fluorescence imaging techniques were developed, and often progress in one field fueled innovation in the other. Impressively, the properties of fluorescence were utilized to develop new assays and imaging modalities, ranging from energy transfer to image molecular interactions to imaging beyond the diffraction limit with super-resolution microscopy. Here, an overview is provided of recent developments in both fluorescence imaging and fluorochrome engineering, which together constitute the “fluorescence toolbox” in life science research.

Dendritic multiporphyrin arrays as light-harvesting antennae: effects of generation number and morphology on intramolecular energy transfer.

Science.gov (United States)

Choi, Myung-Seok; Aida, Takuzo; Yamazaki, Tomoko; Yamazaki, Iwao

2002-06-17

A series of star- and cone-shaped dendritic multiporphyrin arrays, (nPZn)4PFB and (nPZn)1PFB, respectively, that contain energy-donating dendritic zinc porphyrin (PZn) wedges of different numbers (n = 1, 3, and 7) of the PZn units, attached to an energy-accepting free-base porphyrin (PFB) core, were synthesized by a convergent growth approach. For the cone-shaped series ((nPZn)1PFB), the efficiency of energy transfer (phi ENT) from the photoexcited PZn units to the focal PFB core, as evaluated from the fluorescence lifetimes of the PZn units, considerably decreased as the generation number increased: (1PZn)1PFB (86%), (3PZn)1PFB (66%), and (7PZn)1PFB (19%). In sharp contrast, the star-shaped series ((nPZn)4PFB) all showed high phi ENT values: (1PZn)4PFB (87%), (3PZn)4PFB (80%), and (7PZn)4PFB (71%). Energy transfer efficiencies of (3PZn)4-ester-PFB, (1PZn)4-ester-PFB, and (3PZn)1-ester-PFB, whose dendritic PZn wedges are connected by an ester linkage to the PFB core, were almost comparable to those of the corresponding ether-linked versions. Fluorescence depolarization (P) studies showed much lower P values for star-shaped (7PZn)4PFB and (3PZn)4PFB than cone-shaped (7PZn)1PFB and (3PZn)1PFB, respectively, indicating a highly efficient energy migration among the PZn units in the star-shaped series. Such a morphology-assisted photochemical event is probably responsible for the excellent light-harvesting activity of large (7PZn)4PFB molecules.

A planning framework for transferring building energy technologies

Energy Technology Data Exchange (ETDEWEB)

Farhar, B C; Brown, M A; Mohler, B L; Wilde, M; Abel, F H

1990-07-01

Accelerating the adoption of new and existing cost-effective technologies has significant potential to reduce the energy consumed in US buildings. This report presents key results of an interlaboratory technology transfer planning effort in support of the US Department of Energy's Office of Building Technologies (OBT). A guiding assumption for planning was that OBT's R D program should forge linkages with existing programs whose goals involved enhancing energy efficiency in buildings. An ad hoc Technology Transfer Advisory Group reviewed the existing analysis and technology transfer program, brainstormed technology transfer approaches, interviewed DOE program managers, identified applicable research results, and developed a framework that management could use in deciding on the best investments of technology transfer resources. Representatives of 22 organizations were interviewed on their views of the potential for transferring energy efficiency technologies through active linking with OBT. The report describes these programs and interview results; outlines OBT tools, technologies, and practices to be transferred; defines OBT audiences; identifies technology transfer functions and presents a framework devised using functions and audiences; presents some 60 example technology transfer activities; and documents the Advisory Group's recommendations. 37 refs., 3 figs., 12 tabs.

Pigment organization effects on energy transfer and Chl a emission imaged in the diatoms C. meneghiniana and P. tricornutum in vivo: a confocal laser scanning fluorescence (CLSF) microscopy and spectroscopy study.

Science.gov (United States)

Premvardhan, Lavanya; Réfrégiers, Matthieu; Büchel, Claudia

2013-09-26

The (auto)fluorescence from three diatom strains, Cyclotella meneghiniana (Cm), Phaeodactylum tricornutum 1a (Pt1a), and Phaeodactylum UTex (PtUTex), has been imaged in vivo to submicrometer resolution using confocal laser scanning fluorescence (CLSF) microscopy. The diatoms are excited at 473 and 532 nm, energy primarily absorbed by the carotenoid fucoxanthin (Fx) found within the fucoxanthin chlorophyll a/c proteins (FCPs). On the basis of the fluorescence spectra measured in each image voxel, we obtain information about the spatial and energetic distribution of the terminal Chl a emitters, localized in the FCPs and the reaction centers of the PSII protein complexes, and the nature and location of the primary absorbers that are linked to these emitters; 532 nm excites the highly efficient Fx(red) light harvesters, and lesser amounts of Fx(green)s, that are enriched in some FCPs and preferentially transfer energy to PSII, compared to 473 nm, which excites almost equal amounts of all three previously identified sets of Fx--Fx(red), Fx(green) and Fx(blue)--as well as Chl c. The heterogeneous Chl a emission observed from the (C)LSF images indicates that the different Fx's serve different final emitters in P. tricornutum and suggest, at least in C. meneghiniana , a localization of FCPs with relatively greater Fx(red) content at the chloroplast edges, but with overall higher FCP concentration in the interior of the plastid. To better understand our results, the concentration-dependent ensemble-averaged diatom solution spectra are compared to the (auto)fluorescence spectra of individual diatoms, which indicate that pigment packing effects at an intracellular level do affect the diatoms' spectral properties, in particular, concerning a 710 nm emission band apparent under stress conditions. A species-specific response of the spectral signature to the incident light is also discussed in terms of the presence of a silica shell in Cm but not in Pt1a nor PtUTex.

Certification of reference materials by energy-dispersive x-ray fluorescence spectrometry?

DEFF Research Database (Denmark)

Christensen, Leif Højslet; Heydorn, Kaj

1985-01-01

This paper studies the precision and accuracy that can be achieved using energy-dispersive x-ray fluorescence spectrometry for the determination of total sulphur content in BCR 38 Fly Ash issued by the European Community Bureau of Reference.......This paper studies the precision and accuracy that can be achieved using energy-dispersive x-ray fluorescence spectrometry for the determination of total sulphur content in BCR 38 Fly Ash issued by the European Community Bureau of Reference....

Non-typical fluorescence studies of excited and ground state proton and hydrogen transfer

KAUST Repository

Gil, Michał; Kijak, Michał; Piwonski, Hubert Marek; Herbich, Jerzy; Waluk, Jacek

2017-01-01

Fluorescence studies of tautomerization have been carried out for various systems that exhibit single and double proton or hydrogen translocation in various environments, such as liquid and solid condensed phases, ultracold supersonic jets, and finally, polymer matrices with single emitters.We focus on less explored areas of application of fluorescence for tautomerization studies, using porphycene, a porphyrin isomer, as an example. Fluorescence anisotropy techniques allow investigations of self-exchange reactions, where the reactant and product are formally identical. Excitation with polarized light makes it possible to monitor tautomerization in single molecules and to detect their three-dimensional orientation. Analysis of fluorescence from single vibronic levels of jet-isolated porphycene not only demonstrates coherent tunneling of two internal protons, but also indicates that the process is vibrational mode-specific. Next, we present bifunctional proton donoracceptor systems, molecules that are able, depending on the environment, to undergo excited state single intramolecular or double intermolecular proton transfer. For molecules that have donor and acceptor groups located in separate moieties linked by a single bond, excited state tautomerization can be coupled to mutual twisting of the two subunits.

Non-typical fluorescence studies of excited and ground state proton and hydrogen transfer

KAUST Repository

Gil, Michał

2017-02-03

Fluorescence studies of tautomerization have been carried out for various systems that exhibit single and double proton or hydrogen translocation in various environments, such as liquid and solid condensed phases, ultracold supersonic jets, and finally, polymer matrices with single emitters.We focus on less explored areas of application of fluorescence for tautomerization studies, using porphycene, a porphyrin isomer, as an example. Fluorescence anisotropy techniques allow investigations of self-exchange reactions, where the reactant and product are formally identical. Excitation with polarized light makes it possible to monitor tautomerization in single molecules and to detect their three-dimensional orientation. Analysis of fluorescence from single vibronic levels of jet-isolated porphycene not only demonstrates coherent tunneling of two internal protons, but also indicates that the process is vibrational mode-specific. Next, we present bifunctional proton donoracceptor systems, molecules that are able, depending on the environment, to undergo excited state single intramolecular or double intermolecular proton transfer. For molecules that have donor and acceptor groups located in separate moieties linked by a single bond, excited state tautomerization can be coupled to mutual twisting of the two subunits.

Unified interpretation of exciplex formation and marcus electron transfer on the basis of two-dimensional free energy surfaces.

Science.gov (United States)

Murata, Shigeo; Tachiya, M

2007-09-27

The mechanism of exciplex formation proposed in a previous paper has been refined to show how exciplex formation and Marcus electron transfer (ET) in fluorescence quenching are related to each other. This was done by making simple calculations of the free energies of the initial (DA*) and final (D+A-) states of ET. First it was shown that the decrease in D-A distance can induce intermolecular ET even in nonpolar solvents where solvent orientational polarization is absent, and that it leads to exciplex formation. This is consistent with experimental results that exciplex is most often observed in nonpolar solvents. The calculation was then extended to ET in polar solvents where the free energies are functions of both D-A distance and solvent orientational polarization. This enabled us to discuss both exciplex formation and Marcus ET in the same D-A pair and solvent on the basis of 2-dimensional free energy surfaces. The surfaces contain more information about the rates of these reactions, the mechanism of fluorescence quenching by ET, etc., than simple reaction schemes. By changing the parameters such as the free energy change of reaction, solvent dielectric constants, etc., one can construct the free energy surfaces for various systems. The effects of free energy change of reaction and of solvent polarity on the mechanism and relative importance of exciplex formation and Marcus ET in fluorescence quenching can be well explained. The free energy surface will also be useful for discussion of other phenomena related to ET reactions.

Energy transfer and color tunable emission in Tb3+,Eu3+ co-doped Sr3LaNa(PO4)3F phosphors.

Science.gov (United States)

Li, Shuo; Guo, Ning; Liang, Qimeng; Ding, Yu; Zhou, Huitao; Ouyang, Ruizhuo; Lü, Wei

2018-02-05

A group of color tunable Sr 3 LaNa(PO 4 ) 3 F:Tb 3+ ,Eu 3+ phosphors were prepared by conventional high temperature solid state method. The phase structures, luminescence properties, fluorescence lifetimes and energy transfer were investigated in detail. Under 369nm excitation, owing to efficient energy transfer of Tb 3+ →Eu 3+ , the emission spectra both have green emission of Tb 3+ and red emission of Eu 3+ . An efficient energy transfer occur in Tb 3+ , Eu 3+ co-doped Sr 3 LaNa(PO 4 ) 3 F phosphors. The most possible mechanism of energy transfer is dipole-dipole interaction by Dexter's theoretical model. The energy transfer of Tb 3+ and Eu 3+ was confirmed by the variations of emission and excitation spectra and Tb 3+ /Eu 3+ decay lifetimes in Sr 3 LaNa(PO 4 ) 3 F:Tb 3+ ,Eu 3+ . The color tone can tuned from yellowish-green through yellow and eventually to reddish-orange with fixed Tb 3+ content by changing Eu 3+ concentrations. The results show that the prepared Tb 3+ , Eu 3+ co-doped color tunable Sr 3 LaNa(PO 4 ) 3 F phosphor can be used for white LED. Copyright © 2017 Elsevier B.V. All rights reserved.

Energy transfer and color tunable emission in Tb3 +,Eu3 + co-doped Sr3LaNa(PO4)3F phosphors

Science.gov (United States)

Li, Shuo; Guo, Ning; Liang, Qimeng; Ding, Yu; Zhou, Huitao; Ouyang, Ruizhuo; Lü, Wei

2018-02-01

A group of color tunable Sr3LaNa(PO4)3F:Tb3 +,Eu3 + phosphors were prepared by conventional high temperature solid state method. The phase structures, luminescence properties, fluorescence lifetimes and energy transfer were investigated in detail. Under 369 nm excitation, owing to efficient energy transfer of Tb3 + → Eu3 +, the emission spectra both have green emission of Tb3 + and red emission of Eu3 +. An efficient energy transfer occur in Tb3 +, Eu3 + co-doped Sr3LaNa(PO4)3F phosphors. The most possible mechanism of energy transfer is dipole-dipole interaction by Dexter's theoretical model. The energy transfer of Tb3 + and Eu3 + was confirmed by the variations of emission and excitation spectra and Tb3 +/Eu3 + decay lifetimes in Sr3LaNa(PO4)3F:Tb3 +,Eu3 +. The color tone can tuned from yellowish-green through yellow and eventually to reddish-orange with fixed Tb3 + content by changing Eu3 + concentrations. The results show that the prepared Tb3 +, Eu3 + co-doped color tunable Sr3LaNa(PO4)3F phosphor can be used for white LED.

Paper-based solid-phase nucleic acid hybridization assay using immobilized quantum dots as donors in fluorescence resonance energy transfer.

Science.gov (United States)

Noor, M Omair; Shahmuradyan, Anna; Krull, Ulrich J

2013-02-05

A paper-based solid-phase assay is presented for transduction of nucleic acid hybridization using immobilized quantum dots (QDs) as donors in fluorescence resonance energy transfer (FRET). The surface of paper was modified with imidazole groups to immobilize QD-probe oligonucleotide conjugates that were assembled in solution. Green-emitting QDs (gQDs) were FRET-paired with Cy3 acceptor. Hybridization of Cy3-labeled oligonucleotide targets provided the proximity required for FRET-sensitized emission from Cy3, which served as an analytical signal. The assay exhibited rapid transduction of nucleic acid hybridization within minutes. Without any amplification steps, the limit of detection of the assay was found to be 300 fmol with the upper limit of the dynamic range at 5 pmol. The implementation of glutathione-coated QDs for the development of nucleic acid hybridization assay integrated on a paper-based platform exhibited excellent resistance to nonspecific adsorption of oligonucleotides and showed no reduction in the performance of the assay in the presence of large quantities of noncomplementary DNA. The selectivity of nucleic acid hybridization was demonstrated by single-nucleotide polymorphism (SNP) detection at a contrast ratio of 19 to 1. The reuse of paper over multiple cycles of hybridization and dehybridization was possible, with less than 20% reduction in the performance of the assay in five cycles. This work provides an important framework for the development of paper-based solid-phase QD-FRET nucleic acid hybridization assays that make use of a ratiometric approach for detection and analysis.

Is There Excitation Energy Transfer between Different Layers of Stacked Photosystem-II-Containing Thylakoid Membranes?

Science.gov (United States)

Farooq, Shazia; Chmeliov, Jevgenij; Trinkunas, Gediminas; Valkunas, Leonas; van Amerongen, Herbert

2016-04-07

We have compared picosecond fluorescence decay kinetics for stacked and unstacked photosystem II membranes in order to evaluate the efficiency of excitation energy transfer between the neighboring layers. The measured kinetics were analyzed in terms of a recently developed fluctuating antenna model that provides information about the dimensionality of the studied system. Independently of the stacking state, all preparations exhibited virtually the same value of the apparent dimensionality, d = 1.6. Thus, we conclude that membrane stacking does not affect the efficiency of the delivery of excitation energy toward the reaction centers but ensures a more compact organization of the thylakoid membranes within the chloroplast and separation of photosystems I and II.

Energy transfer mechanism between manganese and neodymium

Energy Technology Data Exchange (ETDEWEB)

Kumar, R [Department of Physics, Government Raza Post-Graduate College, Rampur 244901, U.P., India

1977-01-01

The mechanism of energy transfer between Mn/sup 2 +/ ..-->.. Nd/sup 3 +/ in barium borate glass has been investigated. The change in emission intensities and lifetimes of Mn/sup 2 +/ (donor) due to the presence of Nd/sup 3 +/ (acceptor) are observed. It has been concluded that the mechanism of energy transfer involves a nonradiative resonance process. The electrostatic multiple interaction responsible for the transfer is dipole-dipole in nature.

Modeling of the Dynamics of Non-radiative Energy Transfer in Tm3+, Tb3+: LiYF4-Based Electronic Materials

Science.gov (United States)

Castañeda-Miranda, A.; Castaño, V. M.

2017-08-01

The fluorescent decay of the levels 3H4 and 3F4 of Tm3+ in LiYF4 crystals doped with Tb3+ and Eu3+ was mathematically modeled to estimate the optimal doping levels to maximize the laser emission at 1.5 μm of the transition 3H4 → 3F4. The analysis is carried out both through the solution of the master energy transfer equations that govern the non-radiative processes of energy and Monte Carlo simulations. The analysis is improved with the experimental data of the fluorescence decay to include quadrupole and dipole interactions simultaneously. The importance of considering these interactions is that the optimal concentrations of impurities predicted for these luminescent systems are lower than those reported with the use of traditional models.

Spontaneous charged lipid transfer between lipid vesicles.

Science.gov (United States)

Richens, Joanna L; Tyler, Arwen I I; Barriga, Hanna M G; Bramble, Jonathan P; Law, Robert V; Brooks, Nicholas J; Seddon, John M; Ces, Oscar; O'Shea, Paul

2017-10-03

An assay to study the spontaneous charged lipid transfer between lipid vesicles is described. A donor/acceptor vesicle system is employed, where neutrally charged acceptor vesicles are fluorescently labelled with the electrostatic membrane probe Fluoresceinphosphatidylethanolamine (FPE). Upon addition of charged donor vesicles, transfer of negatively charged lipid occurs, resulting in a fluorescently detectable change in the membrane potential of the acceptor vesicles. Using this approach we have studied the transfer properties of a range of lipids, varying both the headgroup and the chain length. At the low vesicle concentrations chosen, the transfer follows a first-order process where lipid monomers are transferred presumably through the aqueous solution phase from donor to acceptor vesicle. The rate of transfer decreases with increasing chain length which is consistent with energy models previously reported for lipid monomer vesicle interactions. Our assay improves on existing methods allowing the study of a range of unmodified lipids, continuous monitoring of transfer and simplified experimental procedures.

Risk transfer via energy savings insurance

Energy Technology Data Exchange (ETDEWEB)

Mills, Evan

2001-10-01

Among the key barriers to investment in energy efficiency improvements are uncertainties about attaining projected energy savings and apprehension about potential disputes over these savings. The fields of energy management and risk management are thus intertwined. While many technical methods have emerged to manage performance risks (e.g. building commissioning), financial risk transfer techniques are less developed in the energy management arena than in other more mature segments of the economy. Energy Savings Insurance (ESI) - formal insurance of predicted energy savings - is one method of transferring financial risks away from the facility owner or energy services contractor. ESI offers a number of significant advantages over other forms of financial risk transfer, e.g. savings guarantees or performance bonds. ESI providers manage risk via pre-construction design review as well as post-construction commissioning and measurement and verification of savings. We found that the two mos t common criticisms of ESI - excessive pricing and onerous exclusions - are not born out in practice. In fact, if properly applied, ESI can potentially reduce the net cost of energy savings projects by reducing the interest rates charged by lenders, and by increasing the level of savings through quality control. Debt service can also be ensured by matching loan payments to projected energy savings while designing the insurance mechanism so that payments are made by the insurer in the event of a savings shortfall. We estimate the U.S. ESI market potential of $875 million/year in premium income. From an energy-policy perspective, ESI offers a number of potential benefits: ESI transfers performance risk from the balance sheet of the entity implementing the energy savings project, thereby freeing up capital otherwise needed to ''self-insure'' the savings. ESI reduces barriers to market entry of smaller energy services firms who do not have sufficiently strong balance

Energy transfer during the hydroentanglement of fibres

CSIR Research Space (South Africa)

Moyo, D

2012-10-01

Full Text Available .kashan.co.za] ABSTRACT The hydroentanglement of fibres is achieved by the energy of the high-velocity waterjets. This method is highly energy intensive and costly, hence the attempt to study the energy transfer during the process. Generally, the amount of energy used... in the nonwoven fabric strength were studied. In the study, the energies of the waterjets transferred to every fabric sample as a function of the waterjet pressure, machine speed, machine efficiency and the web area weight were quantified, and the resultant...

Resonant vibrational energy transfer in ice Ih

Energy Technology Data Exchange (ETDEWEB)

Shi, L.; Li, F.; Skinner, J. L. [Theoretical Chemistry Institute and Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706 (United States)

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.

Pumped energy transfer stations (STEP)

International Nuclear Information System (INIS)

Tournery, Jean-Francois

2015-12-01

As objectives of development are high for renewable energies (they are supposed to cover 50 per cent of new energy needs by 2035), pumped energy transfer stations are to play an important role in this respect. The author first discusses the consequences of the development of renewable energies on the exploitation of electric grids: issue of intermittency for some of them, envisaged solutions. Then, he addresses one of the solutions: the storage of electric power. He notices that increasing the potential energy of a volume of water is presently the most mature solution to face massive needs of the power system. Dams and pumped energy transfer stations represent now almost the whole installed storage power in the world. The author then presents these pumped energy transfer stations: principle, brief history (the first appeared in Italy and Switzerland at the end of the 1890's). He indicates the various parameters of assessment of such stations: maximum stored energy, installed power in pumping mode and turbine mode, time constant, efficiency, level of flexibility. He discusses economic issues. He describes and comments the operation of turbine-pump groups: ternary groups, reversible binary groups. He discusses barriers to be overcome and technical advances to be made for varying speed groups and for marine stations. He finally gives an overview (table with number of stations belonging to different power ranges, remarkable installations) of existing stations in China, USA, Japan, Germany, Austria, Spain, Portugal, Italy, Switzerland, France and UK, and indicate predictions regarding storage needs at the world level. Some data are finally indicated for the six existing French installations

Förster Resonance Energy Transfer (FRET) from Triton X-100 to 4-benzothiazol-2-yl-phenol: Varying FRET efficiency with CMC of the donor (Triton X-100)

International Nuclear Information System (INIS)

Paul, Bijan Kumar; Ganguly, Aniruddha; Karmakar, Saswati; Guchhait, Nikhil

2013-01-01

A heterocyclic compound viz., 4-benzothiazol-2-yl-phenol (4B2YP) has been synthesized and its photophysics have been examined through steady-state absorption, emission and time resolved emission spectroscopic techniques, in brief. Then 4B2YP has been exploited as an acceptor in the Förster Resonance Energy Transfer (FRET) process from photoexcited benzene aromatic nucleus of Triton X-100 (TX-100) surfactant. Dependence of the energy transfer efficiency on the donor concentration with respect to its critical micelle concentration (CMC) is clearly reflected in the study. High values of Stern–Volmer constant (K SV ) for quenching of the donor fluorescence in the presence of the acceptor suggest the operation of long-range dipole–dipole interaction in the course of energy transfer process, while the inference is aptly supported from time resolved fluorescence decay results. Experimental results show maximum FRET efficiency at the CMC of the donor (TX-100). -- Highlights: • FRET from neutral surfactant Triton X-100 to chromophore 4-benzothiazol-2-yl-phenol. • Steady state and time resolved spectroscopy. • Long-range dipole–dipole interaction responsible for FRET. • FRET efficiency as a measure of CMC of surfactant

Förster Resonance Energy Transfer (FRET) from Triton X-100 to 4-benzothiazol-2-yl-phenol: Varying FRET efficiency with CMC of the donor (Triton X-100)

Energy Technology Data Exchange (ETDEWEB)

Paul, Bijan Kumar, E-mail: bijan.paul.chem.cu@gmail.com [Department of Chemistry, University of Calcutta, 92 A.P.C. Road, Calcutta 700009 (India); Ganguly, Aniruddha [Department of Chemistry, University of Calcutta, 92 A.P.C. Road, Calcutta 700009 (India); Karmakar, Saswati [Department of Chemistry, Sree Chaitanya College, Habra, North 24 Parganas (India); Guchhait, Nikhil, E-mail: nguchhait@yahoo.com [Department of Chemistry, University of Calcutta, 92 A.P.C. Road, Calcutta 700009 (India)

2013-11-15

A heterocyclic compound viz., 4-benzothiazol-2-yl-phenol (4B2YP) has been synthesized and its photophysics have been examined through steady-state absorption, emission and time resolved emission spectroscopic techniques, in brief. Then 4B2YP has been exploited as an acceptor in the Förster Resonance Energy Transfer (FRET) process from photoexcited benzene aromatic nucleus of Triton X-100 (TX-100) surfactant. Dependence of the energy transfer efficiency on the donor concentration with respect to its critical micelle concentration (CMC) is clearly reflected in the study. High values of Stern–Volmer constant (K{sub SV}) for quenching of the donor fluorescence in the presence of the acceptor suggest the operation of long-range dipole–dipole interaction in the course of energy transfer process, while the inference is aptly supported from time resolved fluorescence decay results. Experimental results show maximum FRET efficiency at the CMC of the donor (TX-100). -- Highlights: • FRET from neutral surfactant Triton X-100 to chromophore 4-benzothiazol-2-yl-phenol. • Steady state and time resolved spectroscopy. • Long-range dipole–dipole interaction responsible for FRET. • FRET efficiency as a measure of CMC of surfactant.

Laser-excited fluorescence spectroscopy of oxide glasses

International Nuclear Information System (INIS)

Weber, M.J.

1977-01-01

Laser-induced fluorescence line narrowing was applied to investigate the local fields and interactions of paramagnetic ions in oxide glasses. Studies included the site dependence of energy levels, radiative and nonradiative transition probabilities, homogeneous line broadening, and ion--ion energy transfer of rare earth ions. These results and the experimental techniques are reviewed briefly; the use of paramagnetic ions other than the rare earths is also considered. Recently, laser-excited fluorescence spectroscopy was used to investigate modifications in the local structure of lithium borate glass caused by compositional changes and phase separation and the site dependence of nonradiative relaxation of paramagnetic ions by multiphonon processes. These results and their implications are discussed. 6 figures

Molecularly imprinted fluorescent probe based on FRET for selective and sensitive detection of doxorubicin

Energy Technology Data Exchange (ETDEWEB)

Xu, Zhifeng, E-mail: 897061147@qq.com [College of Chemistry and Materials Science, Hengyang Normal University, Key Laboratory of Functional Organometallic Materials of Hunan Province University, Hengyang 421008 (China); Deng, Peihong; Li, Junhua [College of Chemistry and Materials Science, Hengyang Normal University, Key Laboratory of Functional Organometallic Materials of Hunan Province University, Hengyang 421008 (China); Xu, Li [Department of Applied Chemistry, College of Materials and Energy, South China Agricultural University, Guangzhou 510642 (China); Tang, Siping [College of Chemistry and Materials Science, Hengyang Normal University, Key Laboratory of Functional Organometallic Materials of Hunan Province University, Hengyang 421008 (China)

2017-04-15

Highlights: • FRET-based molecularly imprinted probe for detection of doxorubicin was prepared. • The detection limit of the probe was 13.8 nM for doxorubicin. • The FRET-based probe had a higher selectivity for the template than ordinary MIMs. - Abstract: In this work, a new type of fluorescent probe for detection of doxorubicin has been constructed by the combined use of fluorescence resonance energy transfer (FRET) technology and molecular imprinting technique (MIT). Using doxorubicin as the template, the molecularly imprinted polymer thin layer was fabricated on the surfaces of carbon dot (CD) modified silica by sol-gel polymerization. The excitation energy of the fluorescent donor (CDs) could be transferred to the fluorescent acceptor (doxorubicin). The FRET based fluorescent probe demonstrated high sensitivity and selectivity for doxorubicin. The detection limit was 13.8 nM. The fluorescent probe was successfully applied for detecting doxorubicin in doxorubicin-spiked plasmas with a recovery of 96.8–103.8%, a relative standard deviation (RSD) of 1.3–2.8%. The strategy for construction of FRET-based molecularly imprinted materials developed in this work is very promising for analytical applications.

Electromagnetic Energy Absorption due to Wireless Energy Transfer: A Brief Review

Directory of Open Access Journals (Sweden)

Syafiq A.

2016-01-01

Full Text Available This paper reviews an implementation of evaluating compliance of wireless power transfer systems with respect to human electromagnetic exposure limits. Methods for both numerical analysis and measurements are discussed. The objective is to evaluate the rate of which energy is absorbed by the human body when exposed to a wireless energy transfer, although it can be referred to the absorption of other forms of energy by tissue. An exposure assessment of a representative wireless power transfer system, under a limited set of operating conditions, is provided in order to estimate the maximum SAR levels. The aim of this review is to conclude the possible side effect to the human body when utilizing wireless charging in daily life so that an early severe action can be taken when using wireless transfer.

Light harvesting via energy transfer in the dye solar cell

Energy Technology Data Exchange (ETDEWEB)

Siegers, Conrad

2007-11-09

ratio was varied between 1 and 9. The different donor acceptor sensitizers were then incorporated into dye solar cells. Additionally, cells were prepared by the coadsorption of [Ru(dcbpy)2(NCS)2] (N719), which is today's standard dye for DSC applications, and a carboxy-functionalized Fluorol. Hence DSCs resulted that were sensitized via (i) coadsorbed chromophores, (ii) the dyad, and (iii) above-mentioned polymers. The resulting devices were characterized via current-voltage, transmission and external quantum efficiency (EQE) measurements. The current-voltage measurements were carried out under simulated sunlight (AM1.5G) as well as under monochromatic blue and green illumination. This data allowed the calculation of the ratio of short circuit currents acquired under blue and green illumination, which indicates to what extent the current output of the solar cell may be enhanced by energy transfer. Furthermore, the energy transfer efficiency (ETE) was calculated from the DSC's spectral properties. All three concepts for the implementation of donor acceptor systems in the DSC revealed high ETEs (up to 90%). The introduction of an additional donor chromophore via coadsorption led to an increase of the monochromatic power conversion efficiency. The last-mentioned increase was more pronounced if covalently assembled donor acceptor sensitizers were used. The relative energy-transfer-mediated current gain was 21%, 24% and up to 179%, when coadsorbed chromophores, the dyad and donor acceptor polymers were used as sensitizers, respectively (in relation to the current generated by selective excitation of the acceptor component within the cell). These values confirm that energy transfer from fluorescent dyes being poor electron donors in themselves to good electroactive dyes (e.g. Ru-complexes) is also a viable process for light-to-electricity conversion in DSCs. Further optimization of the concepts investigated in this thesis (notably with respect to enhancing the light

Integrated analysis of energy transfers in elastic-wave turbulence.

Science.gov (United States)

Yokoyama, Naoto; Takaoka, Masanori

2017-08-01

In elastic-wave turbulence, strong turbulence appears in small wave numbers while weak turbulence does in large wave numbers. Energy transfers in the coexistence of these turbulent states are numerically investigated in both the Fourier space and the real space. An analytical expression of a detailed energy balance reveals from which mode to which mode energy is transferred in the triad interaction. Stretching energy excited by external force is transferred nonlocally and intermittently to large wave numbers as the kinetic energy in the strong turbulence. In the weak turbulence, the resonant interactions according to the weak turbulence theory produce cascading net energy transfer to large wave numbers. Because the system's nonlinearity shows strong temporal intermittency, the energy transfers are investigated at active and moderate phases separately. The nonlocal interactions in the Fourier space are characterized by the intermittent bundles of fibrous structures in the real space.

A Turn-On Fluorescent Sensor for Hg2+ Based on Graphene Oxide

Directory of Open Access Journals (Sweden)

Yong Wu He

2017-01-01

Full Text Available A graphene oxide- (GO- boradiazaindacenes (BODIPY charge-transfer complex (BGO has been easily synthesized, and the structure of BGO was confirmed by FT-IR and atomic force microscopy (AFM. Moreover, the BGO was found that could be used as a turn-on fluorescent sensor for Hg2+. Upon addition of Hg2+, the fluorescence of BGO would be enhanced since the energy transfer between BODIPY and GO was inhibited. The selectivity and the competition performance of BGO towards Hg2+ were good among other heavy metal ions.

Early kinetic intermediate in the folding of acyl-CoA binding protein detected by fluorescence labeling and ultrarapid mixing

DEFF Research Database (Denmark)

Teilum, Kaare; Maki, Kosuke; Kragelund, Birthe B

2002-01-01

showed a major increase in tryptophan-dansyl fluorescence energy transfer, indicating formation of a partially collapsed ensemble of states on the 100-micros time scale. A subsequent decrease in dansyl fluorescence is attributed to intramolecular quenching of donor fluorescence on formation of the native...

Lateral distribution of NBD-PC fluorescent lipid analogs in membranes probed by molecular dynamics-assisted analysis of Förster Resonance Energy Transfer (FRET) and fluorescence quenching.

Science.gov (United States)

Loura, Luís M S

2012-11-08

Förster resonance energy transfer (FRET) is a powerful tool used for many problems in membrane biophysics, including characterization of the lateral distribution of lipid components and other species of interest. However, quantitative analysis of FRET data with a topological model requires adequate choices for the values of several input parameters, some of which are difficult to obtain experimentally in an independent manner. For this purpose, atomistic molecular dynamics (MD) simulations can be potentially useful as they provide direct detailed information on transverse probe localization, relative probe orientation, and membrane surface area, all of which are required for analysis of FRET data. This is illustrated here for the FRET pairs involving 1,6-diphenylhexatriene (DPH) as donor and either 1-palmitoyl,2-(6-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino] hexanoyl)- sn-glycero-3-phosphocholine (C6-NBD-PC) or 1-palmitoyl,2-(12-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]dodecanoyl)-sn-glycero-3-phosphocholine (C12-NBD-PC) as acceptors, in fluid vesicles of 1,2-dipalmitoyl-sn-3-glycerophosphocholine (DPPC, 50 °C). Incorporation of results from MD simulations improves the statistical quality of model fitting to the experimental FRET data. Furthermore, the decay of DPH in the presence of moderate amounts of C12-NBD-PC (>0.4 mol%) is consistent with non-random lateral distribution of the latter, at variance with C6-NBD-PC, for which aggregation is ruled out up to 2.5 mol% concentration. These conclusions are supported by analysis of NBD-PC fluorescence self-quenching. Implications regarding the relative utility of these probes in membrane studies are discussed.

Plasmonic energy transfer in periodically doped graphene

International Nuclear Information System (INIS)

Silveiro, I; Manjavacas, A; Thongrattanasiri, S; García de Abajo, F J

2013-01-01

We predict unprecedentedly large values of the energy-transfer rate between an optical emitter and a layer of periodically doped graphene. The transfer exhibits divergences at photon frequencies corresponding to the Van Hove singularities of the plasmonic band structure of the graphene. In particular, we find flat bands associated with regions of vanishing doping charge, which appear in graphene when it is patterned through gates of spatially alternating signs, giving rise to intense transfer rate singularities. Graphene is thus shown to provide a unique platform for fast control of optical energy transfer via fast electrostatic inhomogeneous doping. (paper)

Ultrafast energy transport in a first-generation coumarin-tetraphenylporphyrin dendrimer

NARCIS (Netherlands)

Hania, Pieter; Heijs, D.J.; Bowden, T.; Pugzlys, A; van Esch, J; Knoester, J; Duppen, K

2004-01-01

Energy transfer in a newly synthesized coumarin-tetraphenylporphyrin donor-acceptor system was studied by time- and frequency-resolved fluorescence spectroscopy. The energy transfer kinetics was shown to be fast (transfer time ca. 500 fs) and efficient (quantum yield ca. 97%). The influence of

Design and fabrication of an aptasensor for chloramphenicol based on energy transfer of CdTe quantum dots to graphene oxide sheet

International Nuclear Information System (INIS)

Alibolandi, Mona; Hadizadeh, Farzin; Vajhedin, Fereshteh; Abnous, Khalil; Ramezani, Mohammad

2015-01-01

Detection and quantification of chloramphenicol have played essential roles in the effort to minimize food safety risk. Herein, a sophisticated “turn on” aptasensor based on aptamer–CdTe quantum dots (Apt–QDs) and graphene oxide (GO) was developed for chloramphenicol sensing. In this assay, the fluorescence of CdTe QDs–Apt was efficiently quenched through energy transfer from QDs–Apt to GO, and chloramphenicol was detected by recovering the quenched fluorescence due to specific binding between aptamer and chloramphenicol. The results indicated that the addition of a CdTe QDs-labeled aptamer to a GO solution (250 μg/mL) led to a high quenching efficiency, yielding over 90% fluorescence quenching. Using a series of chloramphenicol concentrations (0.1 to 10 nM) aptasensor provides a limit of detection and limit of quantification at 98 pM and 987 pM, respectively. Linearity of response over chloramphenicol was demonstrated (r > 0.99). Furthermore, the GO-based aptasensor exhibited excellent selectivity toward chloramphenicol compared to other synthetic drugs with similar structures such as thiamphenicol, metronidazole and nitrofurantoin. Good reproducibility and precision (RSD 4.73%, n = 10) of the assay indicates the ability of the aptasensor for routine quantitative trace analysis of chloramphenicol. Our results suggested that the prepared aptasensor was also well qualified for the detection of chloramphenicol in milk with a limit of detection of 0.2 ppb. - Highlights: • Aptasensor based on aptamer–QDs and GO was developed for chloramphenicol sensing. • The fluorescence of QDs–Apt was quenched through energy transfer from QDs to GO. • Chloramphenicol was detected by recovering the quenched fluorescence. • The limit of detection for chloramphenicol was calculated to be 98 pM. • The proposed aptasensor showed high sensitivity, selectivity and precision

Design and fabrication of an aptasensor for chloramphenicol based on energy transfer of CdTe quantum dots to graphene oxide sheet

Energy Technology Data Exchange (ETDEWEB)

Alibolandi, Mona; Hadizadeh, Farzin [Biotechnology Research Center, Mashhad University of Medical Sciences, Mashhad (Iran, Islamic Republic of); Vajhedin, Fereshteh [Department of Chemistry, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Abnous, Khalil, E-mail: Abnouskh@mums.ac.ir [Pharmaceutical Research Center, Mashhad University of Medical Sciences, Mashhad (Iran, Islamic Republic of); Ramezani, Mohammad, E-mail: Ramezanim@mums.ac.ir [Nanotechnology Research Center, Mashhad University of Medical Sciences, Mashhad (Iran, Islamic Republic of)

2015-03-01

Detection and quantification of chloramphenicol have played essential roles in the effort to minimize food safety risk. Herein, a sophisticated “turn on” aptasensor based on aptamer–CdTe quantum dots (Apt–QDs) and graphene oxide (GO) was developed for chloramphenicol sensing. In this assay, the fluorescence of CdTe QDs–Apt was efficiently quenched through energy transfer from QDs–Apt to GO, and chloramphenicol was detected by recovering the quenched fluorescence due to specific binding between aptamer and chloramphenicol. The results indicated that the addition of a CdTe QDs-labeled aptamer to a GO solution (250 μg/mL) led to a high quenching efficiency, yielding over 90% fluorescence quenching. Using a series of chloramphenicol concentrations (0.1 to 10 nM) aptasensor provides a limit of detection and limit of quantification at 98 pM and 987 pM, respectively. Linearity of response over chloramphenicol was demonstrated (r > 0.99). Furthermore, the GO-based aptasensor exhibited excellent selectivity toward chloramphenicol compared to other synthetic drugs with similar structures such as thiamphenicol, metronidazole and nitrofurantoin. Good reproducibility and precision (RSD 4.73%, n = 10) of the assay indicates the ability of the aptasensor for routine quantitative trace analysis of chloramphenicol. Our results suggested that the prepared aptasensor was also well qualified for the detection of chloramphenicol in milk with a limit of detection of 0.2 ppb. - Highlights: • Aptasensor based on aptamer–QDs and GO was developed for chloramphenicol sensing. • The fluorescence of QDs–Apt was quenched through energy transfer from QDs to GO. • Chloramphenicol was detected by recovering the quenched fluorescence. • The limit of detection for chloramphenicol was calculated to be 98 pM. • The proposed aptasensor showed high sensitivity, selectivity and precision.

1.8 μm luminescent properties and energy transfer of Yb{sup 3+}/Tm{sup 3+} co-doped α-NaYF{sub 4} single crystals

Energy Technology Data Exchange (ETDEWEB)

Feng, Zhigang [Key Laboratory of Photo-electronic Materials, Ningbo University, Ningbo, Zhejiang, 315211 (China); Xia, Haiping, E-mail: hpxcm@nbu.edu.cn [Key Laboratory of Photo-electronic Materials, Ningbo University, Ningbo, Zhejiang, 315211 (China); Wang, Cheng; Zhang, Zhixiong; Jiang, Dongsheng; Zhang, Jian; He, Shinan; Tang, Qingyang; Sheng, Qiguo; Gu, Xuemei; Zhang, Yuepin [Key Laboratory of Photo-electronic Materials, Ningbo University, Ningbo, Zhejiang, 315211 (China); Chen, Baojiu [Department of Physics, Dalian Maritime University, Dalian, Liaoning Province, 116026 (China); Jiang, Haochuan, E-mail: jianghaochuan@nimte.ac.cn [Ningbo Institute of Materials Technology and Engineering, The Chinese Academy of Sciences, Ningbo, Zhejiang, 315211 (China)

2016-09-25

This paper reports on successful preparation of α-NaYF{sub 4} single crystals co-doped with ∼1.9 mol% Tm{sup 3+} and various concentrations (3.85 mol%, 7.69 mol%, 11.54 mol%, 15.38 mol%) of Yb{sup 3+} by using a flux-Bridgman method. The fluorescence decay curve was measured to investigate the luminescent properties of the Yb{sup 3+}/Tm{sup 3+} co-doped α-NaYF{sub 4}, and the energy transfer process from Yb{sup 3+} to Tm{sup 3+}; the J-O intensity parameters of Tm{sup 3+} were further calculated and analyzed according to the absorption spectra. Results show that, an intense 1.8 μm emission was achieved with Yb{sup 3+} as sensitizer for Tm{sup 3+} in the α-NaYF{sub 4} single crystal under the excitation of 980 nm LD (Laser Diode) because of the strong energy transfer from Yb{sup 3+} to Tm{sup 3+}. The maximum emission intensity at 1.8 μm is obtained at about 15.38 mol% doping concentration of Yb{sup 3+} when the concentration of Tm{sup 3+} ions is fixed at ∼1.90 mol% in the current research. Moreover, the calculated maximum value of emission cross section at 1.8 μm is 1.63 × 10{sup −20} cm{sup 2} for 3.85 mol% Yb{sup 3+}/1.9 mol% Tm{sup 3+} sample, and the obtained energy transfer rate (W{sub ET}) and energy transfer efficiency (η) are 1543 s{sup −1} and 83.8%, respectively. Our analysis of the fluorescence dynamics indicates that electric dipole-dipole interaction is dominant for the energy transfer from Yb{sup 3+} ions to Tm{sup 3+} ions by using Inokuti-Hirayama’s model. - Highlights: • The Tm{sup 3+}/Yb{sup 3+} co-doped α-NaYF{sub 4} single crystals were grown by Bridgman method. • The 1.8 μm emission intensity is obtained at 15.38 mol% Yb{sup 3+}/1.90 mol% Tm{sup 3+} sample. • The maximum value of emission cross section at 1.8 μm is 1.63 × 10{sup −20} cm{sup 2}. • The energy transfer rate is 1543 s{sup −1} and energy transfer efficiency is 83.8%. • The physical mechanism for energy transfer from Yb{sup 3+} to Tm{sup 3+} ions

The Grover energy transfer algorithm for relativistic speeds

International Nuclear Information System (INIS)

Garcia-Escartin, Juan Carlos; Chamorro-Posada, Pedro

2010-01-01

Grover's algorithm for quantum search can also be applied to classical energy transfer. The procedure takes a system in which the total energy is equally distributed among N subsystems and transfers most of it to one marked subsystem. We show that in a relativistic setting the efficiency of this procedure can be improved. We will consider the transfer of relativistic kinetic energy in a series of elastic collisions. In this case, the number of steps of the energy transfer procedure approaches 1 as the initial velocities of the objects become closer to the speed of light. This is a consequence of introducing nonlinearities in the procedure. However, the maximum attainable transfer will depend on the particular combination of speed and number of objects. In the procedure, we will use N elements, as in the classical non-relativistic case, instead of the log 2 (N) states of the quantum algorithm.

Research Note: Energy dispersive x-ray fluorescence analysis ...

African Journals Online (AJOL)

Energy Dispersive X-Ray fluorescence (EDXRF) technique for the analysis of geological, biological and environmental samples is described. The technique has been applied in the analysis of 10 (geological, biological, environmental) standard reference materials. The accuracy and precision of the technique were attested ...

Utilizing microfluidics to synthesize polyethylene glycol microbeads for Förster resonance energy transfer based glucose sensing

Science.gov (United States)

Kantak, Chaitanya; Zhu, Qingdi; Beyer, Sebastian; Bansal, Tushar; Trau, Dieter

2012-01-01

Here, we utilize microfluidic droplet technology to generate photopolymerizeable polyethylene glycol (PEG) hydrogel microbeads incorporating a fluorescence-based glucose bioassay. A microfluidic T-junction and multiphase flow of fluorescein isothiocyanate dextran, tetramethyl rhodamine isothiocyanate concanavalin A, and PEG in water were used to generate microdroplets in a continuous stream of hexadecane. The microdroplets were photopolymerized mid-stream with ultraviolet light exposure to form PEG microbeads and were collected at the outlet for further analysis. Devices were prototyped in PDMS and generated highly monodisperse 72 ± 2 μm sized microbeads (measured after transfer into aqueous phase) at a continuous flow rate between 0.04 ml/h—0.06 ml/h. Scanning electron microscopy analysis was conducted to analyze and confirm microbead integrity and surface morphology. Glucose sensing was carried out using a Förster resonance energy transfer (FRET) based assay. A proportional fluorescence intensity increase was measured within a 1–10 mM glucose concentration range. Microfluidically synthesized microbeads encapsulating sensing biomolecules offer a quick and low cost method to generate monodisperse biosensors for a variety of applications including cell cultures systems, tissue engineering, etc. PMID:22655010

Ultrafast proton shuttling in Psammocora cyan fluorescent protein.

Science.gov (United States)

Kennis, John T M; van Stokkum, Ivo H M; Peterson, Dayna S; Pandit, Anjali; Wachter, Rebekka M

2013-09-26

Cyan, green, yellow, and red fluorescent proteins (FPs) homologous to green fluorescent protein (GFP) are used extensively as model systems to study fundamental processes in photobiology, such as the capture of light energy by protein-embedded chromophores, color tuning by the protein matrix, energy conversion by Förster resonance energy transfer (FRET), and excited-state proton transfer (ESPT) reactions. Recently, a novel cyan fluorescent protein (CFP) termed psamFP488 was isolated from the genus Psammocora of reef building corals. Within the cyan color class, psamFP488 is unusual because it exhibits a significantly extended Stokes shift. Here, we applied ultrafast transient absorption and pump-dump-probe spectroscopy to investigate the mechanistic basis of psamFP488 fluorescence, complemented with fluorescence quantum yield and dynamic light scattering measurements. Transient absorption spectroscopy indicated that, upon excitation at 410 nm, the stimulated cyan emission rises in 170 fs. With pump-dump-probe spectroscopy, we observe a very short-lived (110 fs) ground-state intermediate that we assign to the deprotonated, anionic chromophore. In addition, a minor fraction (14%) decays with 3.5 ps to the ground state. Structural analysis of homologous proteins indicates that Glu-167 is likely positioned in sufficiently close vicinity to the chromophore to act as a proton acceptor. Our findings support a model where unusually fast ESPT from the neutral chromophore to Glu-167 with a time constant of 170 fs and resulting emission from the anionic chromophore forms the basis of the large psamFP488 Stokes shift. When dumped to the ground state, the proton on neutral Glu is very rapidly shuttled back to the anionic chromophore in 110 fs. Proton shuttling in excited and ground states is a factor of 20-4000 faster than in GFP, which probably results from a favorable hydrogen-bonding geometry between the chromophore phenolic oxygen and the glutamate acceptor, possibly

Optical Energy Transfer and Conversion System

Science.gov (United States)

Hogan, Bartholomew P. (Inventor); Stone, William C. (Inventor)

2018-01-01

An optical energy transfer and conversion system comprising a fiber spooler and an electrical power extraction subsystem connected to the spooler with an optical waveguide. Optical energy is generated at and transferred from a base station through fiber wrapped around the spooler, and ultimately to the power extraction system at a remote mobility platform for conversion to another form of energy. The fiber spooler may reside on the remote mobility platform which may be a vehicle, or apparatus that is either self-propelled or is carried by a secondary mobility platform either on land, under the sea, in the air or in space.

Luminescence properties and energy transfer investigations of Sr_3Lu(PO_4)_3:Ce"3"+, Tb"3"+ phosphors

International Nuclear Information System (INIS)

Yang, Zaifa; Xu, Denghui; Sun, Jiayue; Du, Jiangnan; Gao, Xuedong

2016-01-01

Highlights: • A phosphor Sr_3Lu(PO_4)_3:Ce"3"+, Tb"3"+ for UV-based white LEDs was firstly synthesized successfully. • The phase structure and photoluminescence properties of samples were studied in detail. • The energy transfer process from Ce"3"+ to Tb"3"+ ions was illustrated in detail. • Sr_3Lu(PO_4)_3:Ce"3"+, Tb"3"+ phosphor has potential applications as an UV-convertible phosphor for white light emitting diodes. - Abstract: A series of Ce"3"+ or Tb"3"+ doped and Ce"3"+/Tb"3"+ co-doped Sr_3Lu(PO_4)_3 phosphors were prepared via the conventional high temperature solid-state reaction. The phase structure, photoluminescence and energy transfer properties of samples were studied in detail. The optimal proportion of Ce"3"+ single doping is 4 mol% with maximal fluorescence intensity. The Sr_3Lu(PO_4)_3:Ce"3"+, Tb"3"+ phosphor shows both a blue emission (428 nm) from Ce"3"+ and a yellowish-green emission (545 nm) from Tb"3"+ with considerable intensity under ultraviolet (UV) excitation (268 nm). The energy transfer from Ce"3"+ to Tb"3"+ ions takes place in the Sr_3Lu(PO_4)_3:Ce"3"+, Tb"3"+ phosphor on the basis of the analysis of the luminescence spectra. The energy transfer mechanism from Ce"3"+ to Tb"3"+ ions was proved to be dipole–dipole interaction. The energy transfer behaviors in Sr_3Lu(PO_4)_3:Ce"3"+, Tb"3"+ phosphor is also investigated by the lifetime measurement. The results show that this phosphor has potential applications for UV white-light LEDs.

The Grover energy transfer algorithm for relativistic speeds

Energy Technology Data Exchange (ETDEWEB)

Garcia-Escartin, Juan Carlos; Chamorro-Posada, Pedro, E-mail: juagar@yllera.tel.uva.e [Dpto. de TeorIa de la Senal y Comunicaciones e Ingenieria Telematica, Universidad de Valladolid, ETSI de Telecomunicacion, Campus Miguel Delibes, Paseo Belen 15, 47011 Valladolid (Spain)

2010-11-12

Grover's algorithm for quantum search can also be applied to classical energy transfer. The procedure takes a system in which the total energy is equally distributed among N subsystems and transfers most of it to one marked subsystem. We show that in a relativistic setting the efficiency of this procedure can be improved. We will consider the transfer of relativistic kinetic energy in a series of elastic collisions. In this case, the number of steps of the energy transfer procedure approaches 1 as the initial velocities of the objects become closer to the speed of light. This is a consequence of introducing nonlinearities in the procedure. However, the maximum attainable transfer will depend on the particular combination of speed and number of objects. In the procedure, we will use N elements, as in the classical non-relativistic case, instead of the log{sub 2}(N) states of the quantum algorithm.

Fluorescence spectral studies on interaction of fluorescent probes with Bovine Serum Albumin (BSA)

Energy Technology Data Exchange (ETDEWEB)

Ghosh, Kaushik, E-mail: ghoshfcy@iitr.ac.in; Rathi, Sweety; Arora, Deepshikha

2016-07-15

Interaction of 2-(1-(naphthale-1-ylimino)ethyl)phenol (1), 2-methoxy-4-(((4-methoxyphenyl)imino)methyl)phenol (2) and 2-methoxy-4-((naphthalene-1-ylimino)methyl)phenol (3) with Bovine Serum Albumin (BSA) was examined. Fluorescence spectral data were obtained from the probes by varying the concentration of BSA as well as from BSA by varying the concentration of probes. Synchronous fluorescence measurements were performed and binding constants of the probes were calculated. To understand mode of quenching, Stern–Volmer plot, absorption spectral studies and life time measurements were performed. Förster resonance energy transfer (FRET) was also scrutinized. - Highlights: • Schiff bases with pendant phenolato function and interaction with BSA. • Synchronous fluorescence studies and a preferred interaction with tryptophan. • Probable interaction of probes with Trp-213 residue in the hydrophobic cavity. • 1:1 binding stoichiometry of probes and BSA in Benesi–Hildebrand graph.

Fluorescence quenching of derivatives of anthracene by organic electron donors and acceptors in acetonitrile. Electron and proton transfer mechanism

Science.gov (United States)

Mac, Marek; Najbar, Jan; Wirz, Jakob

1995-03-01

Fluorescence quenching of anthracene derivatives by organic electron donors (amines) and acceptors was investigated using stationary fluorescence measurements. The dependence of log( kq) on Δ Get shows Rehm-Weller-type behavior. The formation of anion radicals of anthracene, bianthryl, and 9-cyanoanthracene was detected by flash photolysis in systems containing aromatic amines (aniline, 2-bromoaniline, 4-bromoaniline, N,N-dimethylaniline, 4-bromo-N,N-dimethylaniline, N,N-diethylaniline, and 1,4-diazabicyclo[2.2.2]octane). The radical yields decreased and triplet yields increased when bromo derivatives of amines were used as donor quenchers, indicating the heavy-atom effect on spin conversion within radical pairs. The importance of the heavy-atom effect decreased when the energy gap between the charge transfer and molecular triplet states was small. The formation of separated radicals decreased when primary amines were used as quenchers which indicated the existence of an additional path of deactivation of the radical pair. The behavior of amines as quenchers of bianthryl and anthracene is compared with that of inorganic anion quenchers.

Environment-sensitive quinolone demonstrating long-lived fluorescence and unusually slow excited-state intramolecular proton transfer kinetics

Czech Academy of Sciences Publication Activity Database

Zamotaiev, O. M.; Shvadchak, Volodymyr; Sych, T. P.; Melnychuk, N. A.; Yushchenko, Dmytro A.; Mely, Y.; Pivovarenko, V. G.

2016-01-01

Roč. 4, č. 3 (2016), č. článku 034004. ISSN 2050-6120 Institutional support: RVO:61388963 Keywords : quinolone * fluorescent probes * local polarity * hydration * excited-state intramolecular proton transfer * kinetics Subject RIV: CC - Organic Chemistry Impact factor: 2.656, year: 2016

Characterization of a spectrally diverse set of fluorescent proteins as FRET acceptors for mTurquoise2

NARCIS (Netherlands)

Mastop, M.; Bindels, D.S.; Shaner, N.C.; Postma, M.; Gadella, T.W.J.; Goedhart, J.

2017-01-01

The performance of Förster Resonance Energy Transfer (FRET) biosensors depends on brightness and photostability, which are dependent on the characteristics of the fluorescent proteins that are employed. Yellow fluorescent protein (YFP) is often used as an acceptor but YFP is prone to photobleaching

Interfacial chemistry and the design of solid-phase nucleic acid hybridization assays using immobilized quantum dots as donors in fluorescence resonance energy transfer.

Science.gov (United States)

Algar, W Russ; Krull, Ulrich J

2011-01-01

The use of quantum dots (QDs) as donors in fluorescence resonance energy transfer (FRET) offer several advantages for the development of multiplexed solid-phase QD-FRET nucleic acid hybridization assays. Designs for multiplexing have been demonstrated, but important challenges remain in the optimization of these systems. In this work, we identify several strategies based on the design of interfacial chemistry for improving sensitivity, obtaining lower limits of detection (LOD) and enabling the regeneration and reuse of solid-phase QD-FRET hybridization assays. FRET-sensitized emission from acceptor dyes associated with hybridization events at immobilized QD donors provides the analytical signal in these assays. The minimization of active sensing area reduces background from QD donor PL and allows the resolution of smaller amounts of acceptor emission, thus lowering the LOD. The association of multiple acceptor dyes with each hybridization event can enhance FRET efficiency, thereby improving sensitivity. Many previous studies have used interfacial protein layers to generate selectivity; however, transient destabilization of these layers is shown to prevent efficient regeneration. To this end, we report a protein-free interfacial chemistry and demonstrate the specific detection of as little as 2 pmol of target, as well as an improved capacity for regeneration.

Evaluation of critical distances for energy transfer between Pr{sup 3+} and Ce{sup 3+} in yttrium aluminium garnet

Energy Technology Data Exchange (ETDEWEB)

Zeng, Peng; Wei, Xiantao; Yin, Min; Chen, Yonghu, E-mail: yhuchen@ustc.edu.cn [Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, School of Physical Sciences, University of Science and Technology of China, No. 96 Jinzhai Road, Hefei, Anhui 230026 (China); Zhou, Shaoshuai [Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, School of Physical Sciences, University of Science and Technology of China, No. 96 Jinzhai Road, Hefei, Anhui 230026 (China); Department of Physics, Qufu Normal University, Qufu, Shandong 273165 (China)

2016-09-07

A series of Pr{sup 3+}/Ce{sup 3+} doped yttrium aluminium garnet (Y{sub 3}Al{sub 5}O{sub 12} or simply YAG) phosphors were synthesized to investigate the energy transfer between Pr{sup 3+} and Ce{sup 3+} for their potential application in a white light-emitting diode and quantum information storage and processing. The excitation and emission spectra of YAG:Pr{sup 3+}/Ce{sup 3+} were measured and analyzed, and it revealed that the reabsorption between Pr{sup 3+} and Ce{sup 3+} was so weak that it can be ignored, and the energy transfer from Pr{sup 3+} (5d) to Ce{sup 3+} (5d) and Ce{sup 3+} (5d) to Pr{sup 3+} ({sup 1}D{sub 2}) did occur. By analyzing the excitation and the emission spectra, the energy transfer from Pr{sup 3+} (5d) to Ce{sup 3+} (5d) and Ce{sup 3+} (5d) to Pr{sup 3+} ({sup 1}D{sub 2}) was examined in detail with an original strategy deduced from fluorescence dynamics and the Dexter energy transfer theory, and the critical distances of energy transfer were derived to be 7.9 Å and 4.0 Å for Pr{sup 3+} (5d) to Ce{sup 3+} (5d) and Ce{sup 3+} (5d) to Pr{sup 3+} ({sup 1}D{sub 2}), respectively. The energy transfer rates of the two processes of various concentrations were discussed and evaluated. Furthermore, for the purpose of sensing a single Pr{sup 3+} state with a Ce{sup 3+} ion, the optimal distance of Ce{sup 3+} from Pr{sup 3+} was evaluated as 5.60 Å, where the probability of success reaches its maximum value of 78.66%, and meanwhile the probabilities were evaluated for a series of Y{sup 3+} sites in a YAG lattice. These results will be of valuable reference for achievement of the optimal energy transfer efficiency in Pr{sup 3+}/Ce{sup 3+} doped YAG and other similar systems.

Charge-transfer-based terbium MOF nanoparticles as fluorescent pH sensor for extreme acidity.

Science.gov (United States)

Qi, Zewan; Chen, Yang

2017-01-15

Newly emerged metal organic frameworks (MOFs) have aroused the great interest in designing functional materials by means of its flexible structure and component. In this study, we used lanthanide Tb 3+ ions and small molecular ligands to design and assemble a kind of pH-sensitive MOF nanoparticle based on intramolecular-charge-transfer effect. This kind of made-to-order MOF nanoparticle for H + is highly specific and sensitive and could be used to fluorescently indicate pH value of strong acidic solution via preset mechanism through luminescence of Tb 3+ . The long luminescence lifetime of Tb 3+ allows eliminating concomitant non-specific fluorescence by time-revised fluorescence techniques, processing an advantage in sensing H + in biological media with strong autofluorescence. Our method showed a great potential of MOF structures in designing and constructing sensitive sensing materials for specific analytes directly via the assembly of functional ions/ligands. Copyright © 2016 Elsevier B.V. All rights reserved.

Energy Dispersive X-Ray Fluorescence Spectrometric Study of ...

African Journals Online (AJOL)

MBI

2017-06-11

Jun 11, 2017 ... Compositional Differences in Trace Elements in Dried Moringa oleifera ... Ti, Cu, Mo, Fe, Zn, Ni, Re, Eu and Pb using Energy Dispersive X-ray fluorescence ... Africa, Southeast Asia (Valdez-Solana et al., 2015). ... vegetable in many countries, including Nigeria .... of other elements in environmental samples.

A Brief Introduction to Single-Molecule Fluorescence Methods.

Science.gov (United States)

van den Wildenberg, Siet M J L; Prevo, Bram; Peterman, Erwin J G

2018-01-01

One of the more popular single-molecule approaches in biological science is single-molecule fluorescence microscopy, which will be the subject of the following section of this volume. Fluorescence methods provide the sensitivity required to study biology on the single-molecule level, but they also allow access to useful measurable parameters on time and length scales relevant for the biomolecular world. Before several detailed experimental approaches will be addressed, we will first give a general overview of single-molecule fluorescence microscopy. We start with discussing the phenomenon of fluorescence in general and the history of single-molecule fluorescence microscopy. Next, we will review fluorescent probes in more detail and the equipment required to visualize them on the single-molecule level. We will end with a description of parameters measurable with such approaches, ranging from protein counting and tracking, single-molecule localization super-resolution microscopy, to distance measurements with Förster Resonance Energy Transfer and orientation measurements with fluorescence polarization.

An estimate of spherical impactor energy transfer for mechanical frequency up-conversion energy harvester

Directory of Open Access Journals (Sweden)

L. R. Corr

2016-08-01

Full Text Available Vibration energy harvesters, which use the impact mechanical frequency up-conversion technique, utilize an impactor, which gains kinetic energy from low frequency ambient environmental vibrations, to excite high frequency systems that efficiently convert mechanical energy to electrical energy. To take full advantage of the impact mechanical frequency up-conversion technique, it is prudent to understand the energy transfer from the low frequency excitations, to the impactor, and finally to the high frequency systems. In this work, the energy transfer from a spherical impactor to a multi degree of freedom spring / mass system, due to Hertzian impact, is investigated to gain insight on how best to design impact mechanical frequency up-conversion energy harvesters. Through this academic work, it is shown that the properties of the contact (or impact area, i.e., radius of curvature and material properties, only play a minor role in energy transfer and that the equivalent mass of the target system (i.e., the spring / mass system dictates the total amount of energy transferred during the impact. The novel approach of utilizing the well-known Hertzian impact methodology to gain an understanding of impact mechanical frequency up-conversion energy harvesters has made it clear that the impactor and the high frequency energy generating systems must be designed together as one system to ensure maximum energy transfer, leading to efficient ambient vibration energy harvesters.

Binding analysis for interaction of diacetylcurcumin with β-casein nanoparticles by using fluorescence spectroscopy and molecular docking calculations

Science.gov (United States)

Mehranfar, Fahimeh; Bordbar, Abdol-Khalegh; Fani, Najme; Keyhanfar, Mehrnaz

2013-11-01

The interaction of diacetylcurcumin (DAC), as a novel synthetic derivative of curcumin, with bovine β-casein (an abundant milk protein that is highly amphiphilic and self assembles into stable micellar nanoparticles in aqueous solution) was investigated using fluorescence quenching experiments, Forster energy transfer measurements and molecular docking calculations. The fluorescence quenching measurements revealed the presence of a single binding site on β-casein for DAC with the binding constant value equals to (4.40 ± 0.03) × 104 M-1. Forster energy transfer measurements suggested that the distance between bound DAC and Trp143 residue is higher than the respective critical distance, hence, the static quenching is more likely responsible for fluorescence quenching other than the mechanism of non-radiative energy transfer. Our results from molecular docking calculations indicated that binding of DAC to β-casein predominantly occurred through hydrophobic contacts in the hydrophobic core of protein. Additionally, in vitro investigation of the cytotoxicity of free DAC and DAC-β-casein complex in human breast cancer cell line MCF7 revealed the higher cytotoxic effect of DAC-β-casein complex.

Ultrafast time-resolved carotenoid to-bacteriochlorophyll energy transfer in LH2 complexes from photosynthetic bacteria.

Science.gov (United States)

Cong, Hong; Niedzwiedzki, Dariusz M; Gibson, George N; LaFountain, Amy M; Kelsh, Rhiannon M; Gardiner, Alastair T; Cogdell, Richard J; Frank, Harry A

2008-08-28

Steady-state and ultrafast time-resolved optical spectroscopic investigations have been carried out at 293 and 10 K on LH2 pigment-protein complexes isolated from three different strains of photosynthetic bacteria: Rhodobacter (Rb.) sphaeroides G1C, Rb. sphaeroides 2.4.1 (anaerobically and aerobically grown), and Rps. acidophila 10050. The LH2 complexes obtained from these strains contain the carotenoids, neurosporene, spheroidene, spheroidenone, and rhodopin glucoside, respectively. These molecules have a systematically increasing number of pi-electron conjugated carbon-carbon double bonds. Steady-state absorption and fluorescence excitation experiments have revealed that the total efficiency of energy transfer from the carotenoids to bacteriochlorophyll is independent of temperature and nearly constant at approximately 90% for the LH2 complexes containing neurosporene, spheroidene, spheroidenone, but drops to approximately 53% for the complex containing rhodopin glucoside. Ultrafast transient absorption spectra in the near-infrared (NIR) region of the purified carotenoids in solution have revealed the energies of the S1 (2(1)Ag-)-->S2 (1(1)Bu+) excited-state transitions which, when subtracted from the energies of the S0 (1(1)Ag-)-->S2 (1(1)Bu+) transitions determined by steady-state absorption measurements, give precise values for the positions of the S1 (2(1)Ag-) states of the carotenoids. Global fitting of the ultrafast spectral and temporal data sets have revealed the dynamics of the pathways of de-excitation of the carotenoid excited states. The pathways include energy transfer to bacteriochlorophyll, population of the so-called S* state of the carotenoids, and formation of carotenoid radical cations (Car*+). The investigation has found that excitation energy transfer to bacteriochlorophyll is partitioned through the S1 (1(1)Ag-), S2 (1(1)Bu+), and S* states of the different carotenoids to varying degrees. This is understood through a consideration of the

Efficient near-field wireless energy transfer using adiabatic system variations

Energy Technology Data Exchange (ETDEWEB)

Hamam, Rafif E.; Karalis, Aristeidis; Joannopoulos, John D.; Soljacic, Marin

2017-11-28

Disclosed is a method for transferring energy wirelessly including transferring energy wirelessly from a first resonator structure to an intermediate resonator structure, wherein the coupling rate between the first resonator structure and the intermediate resonator structure is .kappa..sub.1B, transferring energy wirelessly from the intermediate resonator structure to a second resonator structure, wherein the coupling rate between the intermediate resonator structure and the second resonator structure is .kappa..sub.B2, and during the wireless energy transfers, adjusting at least one of the coupling rates .kappa..sub.1B and .kappa..sub.B2 to reduce energy accumulation in the intermediate resonator structure and improve wireless energy transfer from the first resonator structure to the second resonator structure through the intermediate resonator structure.

Ultrafast Energy Transfer in an Artificial Photosynthetic Antenna

Directory of Open Access Journals (Sweden)

van Grondelle R.

2013-03-01

Full Text Available We temporally resolved energy transfer kinetics in an artificial light-harvesting dyad composed of a phthalocyanine covalently linked to a carotenoid. Upon carotenoid photo-excitation, energy transfers within ≈100fs (≈52% efficiency to the phthalocyanine.

Photoinduced proton transfer coupled with energy transfer: Mechanism of sensitized luminescence of terbium ion by salicylic acid doped in polymer.

Science.gov (United States)

Misra, Vinita; Mishra, Hirdyesh

2008-06-28

In the present work, excited state intramolecular proton transfer (ESIPT) in salicylic acid (SA) monoanion and subsequent sensitization of Tb(3+) ion in polyvinyl alcohol (PVA) have been studied. The study has been carried out both by steady state and time domain fluorescence measurement techniques at room temperature. It is found that the SA completely ionizes and exists as monoanion in PVA. It exhibits a large Stokes shifted blue emission (10 000 cm(-1)) due to ESIPT and shows a decay time of 6.85 ns. On the other hand, Tb(3+) ion shows a very weak green emission and a decay time of approximately 641 mus in PVA film. Upon incorporating Tb(3+) ion in SA doped PVA film, both intensity and decay time of SA decrease and sensitized emission from Tb(+3) ion along with 3.8 mus rise time is observed. Energy transfer is found to take place both from excited singlet as well as triplet states. A brief description of the properties of the present system from the viewpoint of luminescent solar collector material is addressed.

Wireless energy transfer between anisotropic metamaterials shells

Energy Technology Data Exchange (ETDEWEB)

Díaz-Rubio, Ana; Carbonell, Jorge; Sánchez-Dehesa, José, E-mail: jsdehesa@upv.es

2014-06-15

The behavior of strongly coupled Radial Photonic Crystals shells is investigated as a potential alternative to transfer electromagnetic energy wirelessly. These sub-wavelength resonant microstructures, which are based on anisotropic metamaterials, can produce efficient coupling phenomena due to their high quality factor. A configuration of selected constitutive parameters (permittivity and permeability) is analyzed in terms of its resonant characteristics. The coupling to loss ratio between two coupled resonators is calculated as a function of distance, the maximum (in excess of 300) is obtained when the shells are separated by three times their radius. Under practical conditions an 83% of maximum power transfer has been also estimated. -- Highlights: •Anisotropic metamaterial shells exhibit high quality factors and sub-wavelength size. •Exchange of electromagnetic energy between shells with high efficiency is analyzed. •Strong coupling is supported with high wireless transfer efficiency. •End-to-end energy transfer efficiencies higher than 83% can be predicted.

Wireless energy transfer between anisotropic metamaterials shells

International Nuclear Information System (INIS)

Díaz-Rubio, Ana; Carbonell, Jorge; Sánchez-Dehesa, José

2014-01-01

The behavior of strongly coupled Radial Photonic Crystals shells is investigated as a potential alternative to transfer electromagnetic energy wirelessly. These sub-wavelength resonant microstructures, which are based on anisotropic metamaterials, can produce efficient coupling phenomena due to their high quality factor. A configuration of selected constitutive parameters (permittivity and permeability) is analyzed in terms of its resonant characteristics. The coupling to loss ratio between two coupled resonators is calculated as a function of distance, the maximum (in excess of 300) is obtained when the shells are separated by three times their radius. Under practical conditions an 83% of maximum power transfer has been also estimated. -- Highlights: •Anisotropic metamaterial shells exhibit high quality factors and sub-wavelength size. •Exchange of electromagnetic energy between shells with high efficiency is analyzed. •Strong coupling is supported with high wireless transfer efficiency. •End-to-end energy transfer efficiencies higher than 83% can be predicted

Elementary analysis by means of the x fluorescence and energy dispersion

International Nuclear Information System (INIS)

Jbeli, H.

1988-10-01

Three actualisation reports are shown, in the three first chapters, concerning the following subjects: x fluorescence principle, energy dispersive X ray spectroscopy and excitation spectrum characteristics. The matrice effects, the energy equivalence concept, and the correction methods of the interelement effects, related to a calibration curve, are discussed. For the last ones, it is shown that they are supplied to rough values. Quantitative analysis results are shown. A new possibility has been added to those of data processing program usually applied in quantitative analysis. In the second method applied in quantitative analysis, standard samples are used. In both methods an error appreciation analysis is carried out. It is shown that energy dispersive X fluorescence analysis can be applied to thin layers composition and thickness characterization [fr

Spectral Gap Energy Transfer in Atmospheric Boundary Layer

Science.gov (United States)

Bhushan, S.; Walters, K.; Barros, A. P.; Nogueira, M.

2012-12-01

Experimental measurements of atmospheric turbulence energy spectra show E(k) ~ k-3 slopes at synoptic scales (~ 600 km - 2000 km) and k-5/3 slopes at the mesoscales (theory, it is expected that a strong backward energy cascade would develop at the synoptic scale, and that circulation would grow infinitely. To limit this backward transfer, energy arrest at macroscales must be introduced. The most commonly used turbulence models developed to mimic the above energy transfer include the energy backscatter model for 2D turbulence in the horizontal plane via Large Eddy Simulation (LES) models, dissipative URANS models in the vertical plane, and Ekman friction for the energy arrest. One of the controversial issues surrounding the atmospheric turbulence spectra is the explanation of the generation of the 2D and 3D spectra and transition between them, for energy injection at the synoptic scales. Lilly (1989) proposed that the existence of 2D and 3D spectra can only be explained by the presence of an additional energy injection in the meso-scale region. A second issue is related to the observations of dual peak spectra with small variance in meso-scale, suggesting that the energy transfer occurs across a spectral gap (Van Der Hoven, 1957). Several studies have confirmed the spectral gap for the meso-scale circulations, and have suggested that they are enhanced by smaller scale vertical convection rather than by the synoptic scales. Further, the widely accepted energy arrest mechanism by boundary layer friction is closely related to the spectral gap transfer. This study proposes an energy transfer mechanism for atmospheric turbulence with synoptic scale injection, wherein the generation of 2D and 3D spectra is explained using spectral gap energy transfer. The existence of the spectral gap energy transfer is validated by performing LES for the interaction of large scale circulation with a wall, and studying the evolution of the energy spectra both near to and far from the wall

Dispersive X-ray fluorescence applications in energy in environmental problems diagnostic

International Nuclear Information System (INIS)

Odino, R.; Souto, B.; Roca, S.; Campomar, W.

1994-01-01

X-ray fluorescence energy was used to detect the grade of contamination due to a Portland cement factory. X-ray fluorescence was used to determine the incidence of a Portland cement plant in the quality of air in its surroundings. Many contaminants (Cu, Pb, Ni, Br) do not come from the Portland cement industry but other industries in the zone

Influence of donor-donor transport on excitation energy transfer

Energy Technology Data Exchange (ETDEWEB)

Pandey, K K; Joshi, H C; Pant, T C [Kumaun University, Nainital (India). Department of Physics

1989-01-01

Energy migration and transfer from acriflavine to rhodamine B and malachite green in poly (methylmethacrylate) have been investigated using the decay function analysis. It is found that the influence of energy migration in energy transfer can be described quite convincingly by making use of the theories of Loring, Andersen and Fayer (LAF) and Huber. At high acceptor concentration direct donor-acceptor transfer occurs through Forster mechanism. (author). 17 refs., 5 figs.

Dual-Recognition Förster Resonance Energy Transfer Based Platform for One-Step Sensitive Detection of Pathogenic Bacteria Using Fluorescent Vancomycin-Gold Nanoclusters and Aptamer-Gold Nanoparticles.

Science.gov (United States)

Yu, Mengqun; Wang, Hong; Fu, Fei; Li, Linyao; Li, Jing; Li, Gan; Song, Yang; Swihart, Mark T; Song, Erqun

2017-04-04

The effective monitoring, identification, and quantification of pathogenic bacteria is essential for addressing serious public health issues. In this study, we present a universal and facile one-step strategy for sensitive and selective detection of pathogenic bacteria using a dual-molecular affinity-based Förster (fluorescence) resonance energy transfer (FRET) platform based on the recognition of bacterial cell walls by antibiotic and aptamer molecules, respectively. As a proof of concept, Vancomycin (Van) and a nucleic acid aptamer were employed in a model dual-recognition scheme for detecting Staphylococcus aureus (Staph. aureus). Within 30 min, by using Van-functionalized gold nanoclusters and aptamer-modified gold nanoparticles as the energy donor and acceptor, respectively, the FRET signal shows a linear variation with the concentration of Staph. aureus in the range from 20 to 10 8 cfu/mL with a detection limit of 10 cfu/mL. Other nontarget bacteria showed negative results, demonstrating the good specificity of the approach. When employed to assay Staph. aureus in real samples, the dual-recognition FRET strategy showed recoveries from 99.00% to the 109.75% with relative standard derivations (RSDs) less than 4%. This establishes a universal detection platform for sensitive, specific, and simple pathogenic bacteria detection, which could have great impact in the fields of food/public safety monitoring and infectious disease diagnosis.

Generic mechanism of optimal energy transfer efficiency: a scaling theory of the mean first-passage time in exciton systems.

Science.gov (United States)

Wu, Jianlan; Silbey, Robert J; Cao, Jianshu

2013-05-17

An asymptotic scaling theory is presented using the conceptual basis of trapping-free subspace (i.e., orthogonal subspace) to establish the generic mechanism of optimal efficiency of excitation energy transfer in light-harvesting systems. A quantum state orthogonal to the trap will exhibit noise-assisted transfer, clarifying the significance of initial preparation. For such an initial state, the efficiency is enhanced in the weak damping limit (⟨t⟩ ∼ 1/Γ), and suppressed in the strong damping limit (⟨t⟩ ∼ Γ), analogous to Kramers turnover in classical rate theory. An interpolating expression ⟨t⟩ = A/Γ + B + CΓ quantitatively describes the trapping time over the entire range of the dissipation strength, and predicts the optimal efficiency at Γ(opt) ∼ J for homogenous systems. In the presence of static disorder, the scaling law of transfer time with respect to dephasing rate changes from linear to square root, suggesting a weaker dependence on the environment. The prediction of the scaling theory is verified in a symmetric dendrimer system by numerically exact quantum calculations. Though formulated in the context of excitation energy transfer, the analysis and conclusions apply in general to open quantum processes, including electron transfer, fluorescence emission, and heat conduction.

Energy transfer in reactive and non-reactive H2 + OH collisions

International Nuclear Information System (INIS)

Rashed, O.; Brown, N.J.

1985-04-01

We have used the methods of quasi-classical dynamics to compute energy transfer properties of non-reactive and reactive H 2 + OH collisions. Energy transfer has been investigated as function of translational temperature, reagent rotational energy, and reagent vibrational energy. The energy transfer mechanism is complex with ten types of energy transfer possible, and evidence was found for all types. There is much more exchange between the translational degree of freedom and the H 2 vibrational degree of freedom than there is between translation and OH vibration. Translational energy is transferred to the rotational degrees of freedom of each molecule. There is a greater propensity for the transfer of translation to OH rotation than H 2 rotation. In reactive collisions, increases in reagent translational temperature predominantly appear as vibrational energy in the water molecule. Energy transfer in non-reactive and reactive collisions does not depend strongly on the initial angular momentum in either molecule. In non-reactive collisions, vibrational energy is transferred to translation, to the rotational degree of freedom of the same molecule, and to the rotational and vibrational degrees of freedom of the other molecule. In reactive collisions, the major effect of increasing the vibrational energy in reagent molecules is that, on the average, the vibrational energy of the reagents appears as product vibrational energy. 18 refs., 16 figs., 6 tabs

A graphene oxide-based sensing platform for the label-free assay of DNA sequence and exonuclease activity via long range resonance energy transfer.

Science.gov (United States)

Jiang, Yixuan; Tian, Jianniao; Chen, Sheng; Zhao, Yanchun; Wang, Yuan; Zhao, Shulin

2013-07-01

Graphene oxide (GO) was introduced as an efficient quencher for label-free and sensitive detection of DNA. Probe DNA (pDNA) was mixed with ethidium bromide (EB) and graphene oxide (GO). The interaction between EB and GO led to the fluorescent quenching. Upon the recognition of the target, EB was intercalated into duplex DNA and kept away from GO, which significantly hindered the long range resonance energy transfer (LrRET) from EB to GO and, thus, increased the fluorescence of EB. The changes in fluorescent intensity produced a novel method for sensitivity, and specificity detection of the target. Based on the structure-switching of aptamers, this strategy could be conveniently extended for detection of other biomolecules, which had been demonstrated by the detection of exonuclease activity.

Energy-donor phosphorescence quenching study of triplet–triplet energy transfer between UV absorbers

International Nuclear Information System (INIS)

Kikuchi, Azusa; Nakabai, Yuya; Oguchi-Fujiyama, Nozomi; Miyazawa, Kazuyuki; Yagi, Mikio

2015-01-01

The intermolecular triplet–triplet energy transfer from a photounstable UV-A absorber, 4-tert-butyl-4′-methoxydibenzoylmethane (BMDBM), to UV-B absorbers, 2-ethylhexyl 4-methoxycinnamate (octyl methoxycinnamate, OMC), octocrylene (OCR) and dioctyl 4-methoxybenzylidenemalonate (DOMBM) has been observed using a 355 nm laser excitation in rigid solutions at 77 K. The decay curves of the energy-donor phosphorescence in the presence of the UV-B absorbers deviate from the exponential decay at the initial stage of the decay. The Stern–Volmer formulation is not valid in rigid solutions because molecular diffusion is impossible. The experimental results indicate that the rate constant of triplet–triplet energy transfer from BMDBM to the UV-B absorbers, k T–T , decreases in the following order: k T–T (BMDBM–DOMBM)>k T–T (BMDBM–OMC)≥k T–T (BMDBM–OCR). The presence of DOMBM enhances the photostability of the widely used combination of UV-A and UV-B absorbers, BMDBM and OCR. The effects of the triplet–triplet energy transfer on the photostability of BMDBM are discussed. - Highlights: • The intermolecular triplet–triplet energy transfer between UV absorbers was observed. • The phosphorescence decay deviates from exponential at the initial stage of decay. • The effects of triplet–triplet energy transfer on the photostability are discussed

Fluorescence properties of novel near-infrared phosphor CaSc{sub 2}O{sub 4}:Ce{sup 3+}, Nd{sup 3+}

Energy Technology Data Exchange (ETDEWEB)

Meng, J.X., E-mail: tmjx@jnu.edu.c [Department of Chemistry, Jinan University, Guangzhou 510632 (China); Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China); Zhang, F.J.; Peng, W.F.; Wan, W.J.; Xiao, Q.L.; Chen, Q.Q.; Cao, L.W. [Department of Chemistry, Jinan University, Guangzhou 510632 (China); Wang, Z.L. [School of Chemistry and Biotechnology, Yunnan Nationalities University, Kunming 650031 (China)

2010-10-15

Research highlights: Novel near-infrared (NIR) phosphor, CaSc{sub 2}O{sub 4}:Ce{sup 3+}, Nd{sup 3+}, was synthesized. The phosphor gives strong Nd{sup 3+} characteristic NIR emissions in the range of 880-930 nm. The NIR emission intensity gets a 200 times enhancement benefited from the efficient energy transfer from a co-doped Ce{sup 3+}. The energy transfer mechanism was also briefly based on detailed investigation on spectrum and fluorescence lifetime. - Abstract: Novel near-infrared (NIR) phosphor, CaSc{sub 2}O{sub 4}:Ce{sup 3+}, Nd{sup 3+}, was synthesized by co-precipitation method followed by firing at 1300 {sup o}C in reduced atmosphere. When irradiated with blue light, the phosphor gives strong Nd{sup 3+} characteristic NIR emissions in the range of 880-930 nm. The NIR emission intensity gets a 200 times enhancement by co-doping of Ce{sup 3+}. Detailed investigation on spectrum and fluorescence lifetimes indicated the NIR luminescence enhancement is obtained from an energy transfer process. The process initiates with efficient absorption of blue light by Ce{sup 3+} ions via an allowed 4f-5d transition, follow by efficient energy transfer from Ce{sup 3+} to Nd{sup 3+}, and emitting strong Nd{sup 3+} characteristic fluorescence.

Ratiometric, single-dye, pH-sensitive inhibited laser-induced fluorescence for the characterization of mixing and mass transfer

Science.gov (United States)

Lacassagne, Tom; Simoëns, Serge; El Hajem, Mahmoud; Champagne, Jean-Yves

2018-01-01

Inhibited planar laser-induced fluorescence (I-PLIF) techniques are widely used for heat and mass transfer studies in fluid mechanics. They allow the visualization of instantaneous two-dimensional field of a passive or reactive scalar, providing that this scalar acts as an inhibitor to the fluorescence of a specific molecule, and that this molecule is homogeneously mixed in the fluid at a known concentration. Local scalar values are deduced from fluorescence recordings thanks to preliminary calibration procedure. When confronted with non-optically thin systems, however, the knowledge of the excitation intensity distribution in the region of interest is also required, and this information is most of the time hard to obtain. To overcome that problem, two-color ratiometric PLIF techniques ( {I}^ {r}-PLIF) have been developed. In these methods, the ratio of two different fluorescence wavelengths triggered by the same excitation is used as an indicator of the scalar value. Such techniques have been used for temperature measurements in several studies but never, to the author's knowledge, for pH tracking and acid-base mixing, despite the frequent use of the one-color version in mass transfer studies. In the present work, a ratiometric pH-sensitive-inhibited PLIF technique ( {I}_ {pH}^ {r}-PLIF) using fluorescein sodium as a single dye and applicable to complex geometries and flows is developed. Theoretical considerations show that the ratio of the two-color fluorescence intensities should only depend on the dye's spectral quantum yield, itself pH-dependent. A detailed spectrofluorimetric study of fluorescein reveals that this ratio strictly increases with the pH for two well-chosen spectral bands (fluorescence colors). A similar trend is found when using sCmos cameras equipped with optical filters to record fluorescence signals. The method is then experimented on a test flow, a turbulent acidic jet injected in an initially pH-neutral volume of fluid. The results obtained

Time-resolved fluorescence of cationic dyes covalently bound to poly(methacrylic acid) in rigid media

Energy Technology Data Exchange (ETDEWEB)

Paulo Moises de Oliveira, Hueder [Instituto de Quimica de Sao Carlos, Universidade de Sao Paulo, Sao Carlos, SP (Brazil); Gehlen, Marcelo Henrique [Instituto de Quimica de Sao Carlos, Universidade de Sao Paulo, Sao Carlos, SP (Brazil)]. E-mail: marcelog@iqsc.usp.br

2006-12-15

Atactic poly(methacrylic acid) labeled with acridine and Nile blue (NB) were studied by photophysical techniques in bulk solid state and in solution-cast films over different surfaces (glass, ITO, and polymethylmethacrylate). In the systems with both dyes, energy transfer from acridine to NB occurs with an efficiency depending on the type of substrate (solid or film). The films are more disordered fluorescent rigid media than the bulk chromophoric or bichromophoric polymers, and this effect is ascribed to inhomogeneous distribution of the dyes in the film. This effect enhances dye bimolecular interactions and increases the energy transfer rates between acridine donor and NB acceptor. Bimodal distributions of donor fluorescence lifetimes are observed.

A simplified approach for the coupling of excitation energy transfer

Energy Technology Data Exchange (ETDEWEB)

Shi Bo [Hefei National Laboratory for Physical Science at Microscale, University of Science and Technology of China, Hefei 230026 (China); Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China); Gao Fang, E-mail: gaofang@iim.ac.cn [Institute of Intelligent Machines, Chinese Academy of Sciences, Hefei 230031 (China); State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang 110016 (China); Liang Wanzhen [Hefei National Laboratory for Physical Science at Microscale, University of Science and Technology of China, Hefei 230026 (China); Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China)

2012-02-06

Highlights: Black-Right-Pointing-Pointer We propose a simple method to calculate the coupling of singlet-to-singlet and triplet-to-triplet energy transfer. Black-Right-Pointing-Pointer Coulomb term are the major contribution to the coupling of singlet-to-singlet energy transfer. Black-Right-Pointing-Pointer Effect from the intermolecular charge-transfer states dorminates in triplet-to-triplet energy transfer. Black-Right-Pointing-Pointer This method can be expanded by including correlated wavefunctions. - Abstract: A simplified approach for computing the electronic coupling of nonradiative excitation-energy transfer is proposed by following Scholes et al.'s construction on the initial and final states [G.D. Scholes, R.D. Harcourt, K.P. Ghiggino, J. Chem. Phys. 102 (1995) 9574]. The simplification is realized through defining a set of orthogonalized localized MOs, which include the polarization effect of the charge densities. The method allows calculating the coupling of both the singlet-to-singlet and triplet-to-triplet energy transfer. Numerical tests are performed for a few of dimers with different intermolecular orientations, and the results demonstrate that Coulomb term are the major contribution to the coupling of singlet-to-singlet energy transfer whereas in the case of triplet-to-triplet energy transfer, the dominant effect is arisen from the intermolecular charge-transfer states. The present application is on the Hartree-Fock level. However, the correlated wavefunctions which are normally expanded in terms of the determinant wavefunctions can be employed in the similar way.

Risk transfer via energy savings insurance; TOPICAL

International Nuclear Information System (INIS)

Mills, Evan

2001-01-01

Among the key barriers to investment in energy efficiency improvements are uncertainties about attaining projected energy savings and apprehension about potential disputes over these savings. The fields of energy management and risk management are thus intertwined. While many technical methods have emerged to manage performance risks (e.g. building commissioning), financial risk transfer techniques are less developed in the energy management arena than in other more mature segments of the economy. Energy Savings Insurance (ESI) - formal insurance of predicted energy savings - is one method of transferring financial risks away from the facility owner or energy services contractor. ESI offers a number of significant advantages over other forms of financial risk transfer, e.g. savings guarantees or performance bonds. ESI providers manage risk via pre-construction design review as well as post-construction commissioning and measurement and verification of savings. We found that the two mos t common criticisms of ESI - excessive pricing and onerous exclusions - are not born out in practice. In fact, if properly applied, ESI can potentially reduce the net cost of energy savings projects by reducing the interest rates charged by lenders, and by increasing the level of savings through quality control. Debt service can also be ensured by matching loan payments to projected energy savings while designing the insurance mechanism so that payments are made by the insurer in the event of a savings shortfall. We estimate the U.S. ESI market potential of$875 million/year in premium income. From an energy-policy perspective, ESI offers a number of potential benefits: ESI transfers performance risk from the balance sheet of the entity implementing the energy savings project, thereby freeing up capital otherwise needed to ''self-insure'' the savings. ESI reduces barriers to market entry of smaller energy services firms who do not have sufficiently strong balance sheets to self

X-ray fluorescence holography and multiple-energy x-ray holography: A critical comparison of atomic images

International Nuclear Information System (INIS)

Len, P.M.; Gog, T.; Fadley, C.S.; Materlik, G.

1997-01-01

We compare x-ray fluorescence holography (XFH) and multiple-energy x-ray holography (MEXH), two techniques that have recently been used to obtain experimental three-dimensional atomic images. For single-energy holograms, these methods are equivalent by virtue of the optical reciprocity theorem. However, XFH can only record holographic information at the characteristic fluorescence energies of the emitting species, while MEXH can record holographic information at any energy above the fluorescent edge of the emitter, thus enabling the suppression of real-twin overlaps and other aberrations and artifacts in atomic images. copyright 1997 The American Physical Society

Characterization of fluorescence quenching in bifluorophoric protease substrates.

Science.gov (United States)

Packard, B Z; Toptygin, D D; Komoriya, A; Brand, L

1997-09-01

NorFES is a relatively rigid, bent undecapeptide which contains an amino acid sequence that is recognized by the serine protease elastase (AspAlaIleProNle downward arrow SerIleProLysGlyTyr ( downward arrow indicates the primary cleavage site)). Covalent attachment of a fluorophore on each side of NorFES's elastase cleavage site enables one to use a change of fluorescence intensity as a measure of enzymatic activity. In this study two bichromophoric NorFES derivatives, D-NorFES-A and D-NorFES-D, were prepared in which D (donor) was tetramethylrhodamine and A (acceptor) was rhodamine-X, two chromophores with characteristics suitable for energy transfer. Absorption and fluorescence spectra were obtained with both the intact and cleaved homodoubly, heterodoubly and singly labeled derivatives. It was found that both the homo and hetero doubly-labeled derivatives form ground-state complexes which exhibit exciton bands. The hetero labeled derivative exhibits little or no resonance energy transfer. Spectral measurements were also done in urea, which partially disrupts ground-state dimers.

Mid-range adiabatic wireless energy transfer via a mediator coil

International Nuclear Information System (INIS)

Rangelov, A.A.; Vitanov, N.V.

2012-01-01

A technique for efficient mid-range wireless energy transfer between two coils via a mediator coil is proposed. By varying the coil frequencies, three resonances are created: emitter–mediator (EM), mediator–receiver (MR) and emitter–receiver (ER). If the frequency sweeps are adiabatic and such that the EM resonance precedes the MR resonance, the energy flows sequentially along the chain emitter–mediator–receiver. If the MR resonance precedes the EM resonance, then the energy flows directly from the emitter to the receiver via the ER resonance; then the losses from the mediator are suppressed. This technique is robust against noise, resonant constraints and external interferences. - Highlights: ► Efficient and robust mid-range wireless energy transfer via a mediator coil. ► The adiabatic energy transfer is analogous to adiabatic passage in quantum optics. ► Wireless energy transfer is insensitive to any resonant constraints. ► Wireless energy transfer is insensitive to noise in the neighborhood of the coils.

Quenching of acridine orange fluorescence by salts in aqueous solutions: Effects of aggregation and charge transfer

Energy Technology Data Exchange (ETDEWEB)

Amado, A.M. [Departamento de Física, FFCLRP, USP (Brazil); Ramos, A.P. [Departamento de Química, FFCLRP, USP (Brazil); Silva, E.R. [Departamento de Física, FFCLRP, USP (Brazil); Borissevitch, I.E., E-mail: iouribor@usp.br [Departamento de Física, FFCLRP, USP (Brazil)

2016-10-15

Acridine orange (AO) is widely applied in biology and medicine as a fluorescence probe, an intracellular pH indicator, and a photosensitizer in photodynamic therapy due to its adequate spectroscopic characteristics and high affinity to biological structures. Being introduced in an organism, AO is dispersed in blood plasma characterized by high ionic strength (ca. 0.36 M in humans). We have investigated the effect of ionic strength upon AO spectral characteristics and fluorescence quenching. The effect of pH on these characteristics was also tested. Salts quench AO fluorescence, the quenching constant (k{sub q}) increasing with the AO concentration. Salts stimulate AO aggregation, the process depending weakly on the salt origin. On the other hand, k{sub q} does depend on the salt anion origin, increasing as the anion oxidation potential decreases, and is virtually independent of the cation origin. This means that at least two different mechanisms of the AO fluorescence quenching by salts exist: fluorescence intensity decrease due to AO aggregation and quenching by partial electron transfer from salt anion to AO molecule in its singlet excited state (the exciplex formation).

Multiplexed interfacial transduction of nucleic acid hybridization using a single color of immobilized quantum dot donor and two acceptors in fluorescence resonance energy transfer.

Science.gov (United States)

Algar, W Russ; Krull, Ulrich J

2010-01-01

A multiplexed solid-phase assay for the detection of nucleic acid hybridization was developed on the basis of a single color of immobilized CdSe/ZnS quantum dot (QD) as a donor in fluorescence resonance energy transfer (FRET). This work demonstrated that two channels of detection did not necessitate two different QD donors. Two probe oligonucleotides were coimmobilized on optical fibers modified with QDs, and a sandwich assay was used to associate the acceptor dyes with interfacial hybridization events without target labeling. FRET-sensitized acceptor emission provided an analytical signal that was concentration dependent down to 10 nM. Changes in the ratio of coimmobilized probe oligonucleotides were found to yield linear changes in the relative amounts of acceptor emission. These changes were compared to previous studies that used mixed films of two QD donors for two detection channels. The analysis indicated that probe dilution effects were primarily driven by changes in acceptor number density and that QD dilution effects or changes in mean donor-acceptor distance were secondary. Hybridization kinetics were found to be consistent between different ratios of coimmobilized probes, suggesting that hybridization in this type of system occurred via the accepted model for solid-phase hybridization, where adsorption and then diffusion at the solid interface drove hybridization.

AIEgens for dark through-bond energy transfer: design, synthesis, theoretical study and application in ratiometric Hg2+ sensing.

Science.gov (United States)

Chen, Yuncong; Zhang, Weijie; Cai, Yuanjing; Kwok, Ryan T K; Hu, Yubing; Lam, Jacky W Y; Gu, Xinggui; He, Zikai; Zhao, Zheng; Zheng, Xiaoyan; Chen, Bin; Gui, Chen; Tang, Ben Zhong

2017-03-01

A novel dark through-bond energy transfer (DTBET) strategy is proposed and applied as the design strategy to develop ratiometric Hg 2+ sensors with high performance. Tetraphenylethene ( TPE ) derivatives with aggregation-induced emission (AIE) characteristics are selected as dark donors to eliminate emission leakage from the donors. The TBET mechanism has been adopted since it experiences less influence from spectral overlapping than Förster resonance energy transfer (FRET), making it more flexible for developing cassettes with large pseudo-Stokes shifts. In this work, energy transfer from the TPE derivatives (dark donor) to a rhodamine moiety (acceptor) was illustrated through photophysical spectroscopic studies and the energy transfer efficiency (ETE) was found to be up to 99%. In the solution state, no emission from the donors was observed and large pseudo-Stokes shifts were achieved (>280 nm), which are beneficial for biological imaging. Theoretical calculations were performed to gain a deeper mechanistic insight into the DTBET process and the structure-property relationship of the DTBET cassettes. Ratiometric Hg 2+ sensors were rationally constructed based on the DTBET mechanism by taking advantage of the intense emission of TPE aggregates. The Hg 2+ sensors exhibited well resolved emission peaks. >6000-fold ratiometric fluorescent enhancement is also achieved and the detection limit was found to be as low as 0.3 ppb. This newly proposed DTBET mechanism could be used to develop novel ratiometric sensors for various analytes and AIEgens with DTBET characteristics will have great potential in various areas including light harvesting materials, environmental science, chemical sensing, biological imaging and diagnostics.

Nearly 100% triplet harvesting in conventional fluorescent dopant-based organic light-emitting devices through energy transfer from exciplex.

Science.gov (United States)

Liu, Xiao-Ke; Chen, Zhan; Zheng, Cai-Jun; Chen, Miao; Liu, Wei; Zhang, Xiao-Hong; Lee, Chun-Sing

2015-03-25

Nearly 100% triplet harvesting in conventional fluorophor-based organic light-emitting devices is realized through energy transfer from exciplex. The best C545T-doped device using the exciplex host exhibits a maximum current efficiency of 44.0 cd A(-1) , a maximum power efficiency of 46.1 lm W(-1) , and a maximum external quantum efficiency of 14.5%. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Dansyl-Rhodamine Based Fluorescent Probe for Detection of Hg2+ and Cu2.

Science.gov (United States)

Yuan, Shizhuang; Su, Wei; Wang, Enju

2017-09-01

A novel fluorescent probe based on dansyl-appended rhodamine B was developed. The probe can selectively recognize and sense Hg2+ and Cu2+ from other common metal ions by showing unique fluorescence and absorption characteristics. In MeCN/HEPES buffer solution, the probe gives a ratiometric fluorescent response to Hg2+, which was ascribed to the fluorescence resonance energy transfer from dansyl moiety to the ring-opened rhodamine B moiety, while the presence of Cu2+ causes fluorescence quenching. Beside the fluorescence change, the presence of Cu2+ and Hg2+ can induce intensive absorption at about 555 nm, which resulted in a color change from colorless to pink.

Mode-to-mode energy transfers in convective patterns

Indian Academy of Sciences (India)

Abstract. We investigate the energy transfer between various Fourier modes in a low- dimensional model for thermal convection. We have used the formalism of mode-to-mode energy transfer rate in our calculation. The evolution equations derived using this scheme is the same as those derived using the hydrodynamical ...

Quantum electrodynamics of resonant energy transfer in condensed matter

International Nuclear Information System (INIS)

Juzeliunas, G.; Andrews, D.L.

1994-01-01

A microscopic many-body QED theory for dipole-dipole resonance energy transfer has been developed from first principles. A distinctive feature of the theory is full incorporation of the dielectric effects of the supporting medium. The approach employs the concept of bath polaritons mediating the energy transfer. The transfer rate is derived in terms of the Green's operator corresponding to the polariton matrix Hamiltonian. In contrast to the more common lossless polariton models, the present theory accommodates an arbitrary number of energy levels for each molecule of the medium. This includes, a case of special interest, where the excitation energy spectrum of the bath molecules is sufficiently dense that it can be treated as a quasicontinuum in the energy region in question, as in the condensed phase normally results from homogeneous and inhomogeneous line broadening. In such a situation, the photon ''dressed'' by the medium polarization (the polariton) acquires a finite lifetime, the role of the dissipative subsystem being played by bath molecules. It is this which leads to the appearance of the exponential decay factor in the microscopically derived pair transfer rates. Accordingly, the problem associated with potentially infinite total ensemble rates, due to the divergent R -2 contribution, is solved from first principles. In addition, the medium modifies the distance dependence of the energy transfer function A(R) and also produces extra modifications due to screening contributions and local field effects. The formalism addresses cases where the surrounding medium is either absorbing or lossless over the range of energies transferred. In the latter case the exponential factor does not appear and the dielectric medium effect in the near zone reduces to that which is familiar from the theory of radiationless (Foerster) energy transfer

Comparison of static and microfluidic protease assays using modified bioluminescence resonance energy transfer chemistry.

Directory of Open Access Journals (Sweden)

Nan Wu

Full Text Available BACKGROUND: Fluorescence and bioluminescence resonance energy transfer (F/BRET are two forms of Förster resonance energy transfer, which can be used for optical transduction of biosensors. BRET has several advantages over fluorescence-based technologies because it does not require an external light source. There would be benefits in combining BRET transduction with microfluidics but the low luminance of BRET has made this challenging until now. METHODOLOGY: We used a thrombin bioprobe based on a form of BRET (BRET(H, which uses the BRET(1 substrate, native coelenterazine, with the typical BRET(2 donor and acceptor proteins linked by a thrombin target peptide. The microfluidic assay was carried out in a Y-shaped microfluidic network. The dependence of the BRET(H ratio on the measurement location, flow rate and bioprobe concentration was quantified. Results were compared with the same bioprobe in a static microwell plate assay. PRINCIPAL FINDINGS: The BRET(H thrombin bioprobe has a lower limit of detection (LOD than previously reported for the equivalent BRET(1-based version but it is substantially brighter than the BRET(2 version. The normalised BRET(H ratio of the bioprobe changed 32% following complete cleavage by thrombin and 31% in the microfluidic format. The LOD for thrombin in the microfluidic format was 27 pM, compared with an LOD of 310 pM, using the same bioprobe in a static microwell assay, and two orders of magnitude lower than reported for other microfluidic chip-based protease assays. CONCLUSIONS: These data demonstrate that BRET based microfluidic assays are feasible and that BRET(H provides a useful test bed for optimising BRET-based microfluidics. This approach may be convenient for a wide range of applications requiring sensitive detection and/or quantification of chemical or biological analytes.

pH-dependent fluorescence property of methyl red isomers in silver colloids

International Nuclear Information System (INIS)

Wong, Jian-How; Lee, Szetsen

2012-01-01

We report the use of silver (Ag) colloids in the spectroscopic differentiation of methyl red (MR) isomers (o-MR, m-MR, p-MR) by fluorescence techniques. Under different pH conditions, the formation of MR-Ag complex has an impact on the fluorescence band shapes and peak position shift, which are distinctive between MR isomers. The fluorescence quenching between 400 and 414 nm accompanied by simultaneous enhancement between 510 and 541 nm changes with pH are closely related to energy transfer efficiency and the interaction between the MR isomers and the Ag surface.

Photophysics and energy transfer studies of Alq3 confined in the voids of nanoporous anodic alumina.

Science.gov (United States)

Mohammadpour, Arash; Utkin, Ilya; Bodepudi, Srikrishna Chanakya; Kar, Piyush; Fedosejevs, Robert; Pramanik, Sandipan; Shankar, Karthik

2013-04-01

We report on a hierarchical nanoarchitecture wherein distinct chromophores are deterministically placed at two different types of sites in a nanoporous metal oxide framework. One chromophore, namely Tris(8-hydroxyquinoline)aluminium(III) (Alq3), is embedded in the 1-2 nm sized nanovoids of anodic aluminum oxide (AAO) and another chromophore (carboxyfluorescein or pyrenebutyric acid) is anchored in the form of a monolayer to the surface of the walls of the cylindrical nanopores (- 20 nm in diameter) of AAO. We found the luminescence maximum to occur at 492 nm, blueshifted by at least 18 nm from the value in solutions and thin films. The excited state decay of Alq3 molecules in nanovoids was found to be biexponential with a fast component of 338 ps and a slower component of 2.26 ns, different from Alq3 thin films and solutions. Using a combination of steady state and time-resolved luminescence studies, we found that efficient Forster-type resonance energy transfer (FRET) from Alq3 in the nanovoids to the carboxyfluorescein monolayer could be used to pump the emission of surface-bound chromophores. Conversely, the emission of nanovoid-confined Alq3 could be pumped by energy transfer from a pyrenebutyric acid monolayer. Such intra-nanoarchitecture interactions between chromophores deterministically placed in different spatial locations are important in applications such as organic light emitting diodes, chemical sensors, energy transfer fluorescent labels, light harvesting antennas and organic spintronics.

Risk transfer via energy savings insurance

OpenAIRE

Mills, Evan

2001-01-01

Among the key barriers to investment in energy efficiency improvements are uncertainties about attaining projected energy savings and apprehension about potential disputes over these savings. The fields of energy management and risk management are thus intertwined. While many technical methods have emerged to manage performance risks (e.g. building commissioning), financial risk transfer techniques are less developed in the energy management arena than in other more mature segments of t...

Förster-type energy transfer as a probe for changes in local fluctuations of the protein matrix.

Science.gov (United States)

Somogyi, B; Matkó, J; Papp, S; Hevessy, J; Welch, G R; Damjanovich, S

1984-07-17

Much evidence, on both theoretical and experimental sides, indicates the importance of local fluctuations (in energy levels, conformational substates, etc.) of the macromolecular matrix in the biological activity of proteins. We describe here a novel application of the Förster-type energy-transfer process capable of monitoring changes both in local fluctuations and in conformational states of macromolecules. A new energy-transfer parameter, f, is defined as an average transfer efficiency, [E], normalized by the actual average quantum efficiency of the donor fluorescence, [phi D]. A simple oscillator model (for a one donor-one acceptor system) is presented to show the sensitivity of this parameter to changes in amplitudes of local fluctuations. The different modes of averaging (static, dynamic, and intermediate cases) occurring for a given value of the average transfer rate, [kt], and the experimental requirements as well as limitations of the method are also discussed. The experimental tests were performed on the ribonuclease T1-pyridoxamine 5'-phosphate conjugate (a one donor-one acceptor system) by studying the change of the f parameter with temperature, an environmental parameter expectedly perturbing local fluctuations of proteins. The parameter f increased with increasing temperature as expected on the basis of the oscillator model, suggesting that it really reflects changes of fluctuation amplitudes (significant changes in the orientation factor, k2, as well as in the spectral properties of the fluorophores can be excluded by anisotropy measurements and spectral investigations). Possibilities of the general applicability of the method are also discussed.

Fluorescence resonance energy transfer measured by spatial photon migration in CdSe-ZnS quantum dots colloidal systems as a function of concentration

Energy Technology Data Exchange (ETDEWEB)

Azevedo, G.; Monte, A. F. G.; Reis, A. F.; Messias, D. N. [Laboratório de Espectroscopia Óptica, Instituto de Física, Universidade Federal de Uberlândia, Uberlândia, MG 38400-902 (Brazil)

2014-11-17

The study of the spatial photon migration as a function of the concentration brings into attention the problem of the energy transfer in quantum dot embedded systems. By measuring the photon propagation and its spatial dependence, it is possible to understand the whole dynamics in a quantum dot system, and also improve their concentration dependence to maximize energy propagation due to radiative and non-radiative processes. In this work, a confocal microscope was adapted to scan the spatial distribution of photoluminescence from CdSe-ZnS core-shell quantum dots in colloidal solutions. The energy migration between the quantum dots was monitored by the direct measurement of the photon diffusion length, according to the diffusion theory. We observed that the photon migration length decreases by increasing the quantum dot concentration, this kind of behavior has been regarded as a signature of Förster resonance energy transfer in the system.

Detection of Babesia canis vogeli and Hepatozoon canis in canine blood by a single-tube real-time fluorescence resonance energy transfer polymerase chain reaction assay and melting curve analysis.

Science.gov (United States)

Kongklieng, Amornmas; Intapan, Pewpan M; Boonmars, Thidarut; Thanchomnang, Tongjit; Janwan, Penchom; Sanpool, Oranuch; Lulitanond, Viraphong; Taweethavonsawat, Piyanan; Chungpivat, Sudchit; Maleewong, Wanchai

2015-03-01

A real-time fluorescence resonance energy transfer polymerase chain reaction (qFRET PCR) coupled with melting curve analysis was developed for detection of Babesia canis vogeli and Hepatozoon canis infections in canine blood samples in a single tube assay. The target of the assay was a region within the 18S ribosomal RNA gene amplified in either species by a single pair of primers. Following amplification from the DNA of infected dog blood, a fluorescence melting curve analysis was done. The 2 species, B. canis vogeli and H. canis, could be detected and differentiated in infected dog blood samples (n = 37) with high sensitivity (100%). The detection limit for B. canis vogeli was 15 copies of a positive control plasmid, and for H. canis, it was 150 copies of a positive control plasmid. The assay could simultaneously distinguish the DNA of both parasites from the DNA of controls. Blood samples from 5 noninfected dogs were negative, indicating high specificity. Several samples can be run at the same time. The assay can reduce misdiagnosis and the time associated with microscopic examination, and is not prone to the carryover contamination associated with the agarose gel electrophoresis step of conventional PCR. In addition, this qFRET PCR method would be useful to accurately determine the range of endemic areas or to discover those areas where the 2 parasites co-circulate. © 2015 The Author(s).

Theory of coherent resonance energy transfer

International Nuclear Information System (INIS)

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

2008-01-01

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.

Pair transfer processes probed at deep sub barrier energies

International Nuclear Information System (INIS)

Corradi, L.; Mason, P.; Fioretto, E.; Michelagnoli, C.; Stefanini, A.M.; Valiente-Dobon, J.J.; Szinler, S.; Jelavic-Malenica, D.; Soic, N.; Pollarolo, G.; Farnea, E.; Montagnoli, G.; Montanari, D.; Scarlassara, F.; Ur, C.A.; Gadea, A.; Haas, F.; Marginean, N.

2011-01-01

Multinucleon transfer cross sections in the system 40 Ca+ 96 Zr have been measured at bombarding energies ranging from the Coulomb barrier to ∼ 25% below. Target-like (lighter) recoils in inverse kinematics have been completely identified in A,Z and Q-value with the large solid angle magnetic spectrometer PRISMA. The experimental slopes of the neutron transfer probabilities at large internuclear separation are consistent with the values derived from the binding energies. A phenomenological interpretation of the transfer probabilities indicates the presence of enhanced values for the even number of neutron transfers. (authors)

Graphene and graphene-like two-denominational materials based fluorescence resonance energy transfer (FRET) assays for biological applications.

Science.gov (United States)

Tian, Feng; Lyu, Jing; Shi, Jingyu; Yang, Mo

2017-03-15

In the past decades, Förster resonance energy transfer (FRET) has been applied in many biological applications to reveal the biological information at the nanoscale. Recently, graphene and graphene-like two-dimensional (2D) nanomaterials started to be used in FRET assays as donors or acceptors including graphene oxide (GO), graphene quantum dot (GQD), graphitic-carbon nitride nanosheets (g-C 3 N 4 ) and transition metal dichalcogenides (e.g. MoS 2 , MnO 2, and WS 2 ). Due to the remarkable properties such as large surface to volume ratio, tunable energy band, photoluminescence and excellent biocompatibility, these 2D nanomaterials based FRET assays have shown great potential in various biological applications. This review summarizes the recent development of graphene and graphene-like 2D nanomaterials based FRET assays in applications of biosensing, bioimaging, and drug delivery monitoring. Copyright © 2016 Elsevier B.V. All rights reserved.

Power law scaling for rotational energy transfer

International Nuclear Information System (INIS)

Pritchard, D.E.; Smith, N.; Driver, R.D.; Brunner, T.A.

1979-01-01

We have applied a new scaling law to several sets of rotational energy transfer cross sections. The new law asserts that the square of the T-matrix depends on the amount of energy transferred as a power law. Two different kinds of angular momentum statistics are assumed, one corresponding to m/sub j/ being conserved and the other corresponding to m/sub j/ being completely randomized. Numerical fits are presented which demonstrate that the data follow the power law better than the widely used exponential gap law

Imaging and Manipulating Energy Transfer Among Quantum Dots at Individual Dot Resolution.

Science.gov (United States)

Nguyen, Duc; Nguyen, Huy A; Lyding, Joseph W; Gruebele, Martin

2017-06-27

Many processes of interest in quantum dots involve charge or energy transfer from one dot to another. Energy transfer in films of quantum dots as well as between linked quantum dots has been demonstrated by luminescence shift, and the ultrafast time-dependence of energy transfer processes has been resolved. Bandgap variation among dots (energy disorder) and dot separation are known to play an important role in how energy diffuses. Thus, it would be very useful if energy transfer could be visualized directly on a dot-by-dot basis among small clusters or within films of quantum dots. To that effect, we report single molecule optical absorption detected by scanning tunneling microscopy (SMA-STM) to image energy pooling from donor into acceptor dots on a dot-by-dot basis. We show that we can manipulate groups of quantum dots by pruning away the dominant acceptor dot, and switching the energy transfer path to a different acceptor dot. Our experimental data agrees well with a simple Monte Carlo lattice model of energy transfer, similar to models in the literature, in which excitation energy is transferred preferentially from dots with a larger bandgap to dots with a smaller bandgap.

Fluorescence resonance energy transfer-based real-time polymerase chain reaction method without DNA extraction for the genotyping of F5, F2, F12, MTHFR, and HFE.

Science.gov (United States)

Martinez-Serra, Jordi; Robles, Juan; Nicolàs, Antoni; Gutierrez, Antonio; Ros, Teresa; Amat, Juan Carlos; Alemany, Regina; Vögler, Oliver; Abelló, Aina; Noguera, Aina; Besalduch, Joan

2014-01-01

Blood samples are extensively used for the molecular diagnosis of many hematological diseases. The daily practice in a clinical laboratory of molecular diagnosis in hematology involves using a variety of techniques, based on the amplification of nucleic acids. Current methods for polymerase chain reaction (PCR) use purified genomic DNA, mostly isolated from total peripheral blood cells or white blood cells (WBC). In this paper we describe a real-time fluorescence resonance energy transfer-based method for genotyping directly from blood cells. Our strategy is based on an initial isolation of the WBCs, allowing the removal of PCR inhibitors, such as the heme group, present in the erythrocytes. Once the erythrocytes have been lysed, in the LightCycler(®) 2.0 Instrument, we perform a real-time PCR followed by a melting curve analysis for different genes (Factors 2, 5, 12, MTHFR, and HFE). After testing 34 samples comparing the real-time crossing point (CP) values between WBC (5×10(6) WBC/mL) and purified DNA (20 ng/μL), the results for F5 Leiden were as follows: CP mean value for WBC was 29.26±0.566 versus purified DNA 24.79±0.56. Thus, when PCR was performed from WBC (5×10(6) WBC/mL) instead of DNA (20 ng/μL), we observed a delay of about 4 cycles. These small differences in CP values were similar for all genes tested and did not significantly affect the subsequent analysis by melting curves. In both cases the fluorescence values were high enough, allowing a robust genotyping of all these genes without a previous DNA purification/extraction.

Coherent excitation-energy transfer and quantum entanglement in a dimer

International Nuclear Information System (INIS)

Liao Jieqiao; Sun, C. P.; Huang Jinfeng; Kuang Leman

2010-01-01

We study coherent energy transfer of a single excitation and quantum entanglement in a dimer, which consists of a donor and an acceptor modeled by two two-level systems. Between the donor and the acceptor, there exists a dipole-dipole interaction, which provides the physical mechanism for coherent energy transfer and entanglement generation. The donor and the acceptor couple to two independent heat baths with diagonal couplings that do not dissipate the energy of the noncoupling dimer. Special attention is paid to the effect on single-excitation energy transfer and entanglement generation of the energy detuning between the donor and the acceptor and the temperatures of the two heat baths. It is found that, the probability for single-excitation energy transfer largely depends on the energy detuning in the low temperature limit. Concretely, the positive and negative energy detunings can increase and decrease the probability at steady state, respectively. In the high temperature limit, however, the effect of the energy detuning on the probability is negligibly small. We also find that the probability is negligibly dependent on the bath temperature difference of the two heat baths. In addition, it is found that quantum entanglement can be generated in the process of coherent energy transfer. As the bath temperature increases, the generated steady-state entanglement decreases. For a given bath temperature, the steady-state entanglement decreases with the increase of the absolute value of the energy detuning.

Studying electron-PAG interactions using electron-induced fluorescence

Science.gov (United States)

Narasimhan, Amrit; Grzeskowiak, Steven; Ostrander, Jonathan; Schad, Jonathon; Rebeyev, Eliran; Neisser, Mark; Ocola, Leonidas E.; Denbeaux, Gregory; Brainard, Robert L.

2016-03-01

In extreme ultraviolet (EUV) lithography, 92 eV photons are used to expose photoresists. Typical EUV resists are organic-based and chemically amplified using photoacid generators (PAGs). Upon exposure, PAGs produce acids which catalyze reactions that result in changes in solubility. In EUV lithography, photo- and secondary electrons (energies of 10- 80 eV) play a large role in PAG acid-production. Several mechanisms for electron-PAG interactions (e.g. electron trapping, and hole-initiated chemistry) have been proposed. The aim of this study is to explore another mechanism - internal excitation - in which a bound PAG electron can be excited by receiving energy from another energetic electron, causing a reaction that produces acid. This paper explores the mechanism of internal excitation through the analogous process of electron-induced fluorescence, in which an electron loses energy by transferring that energy to a molecule and that molecule emits a photon rather than decomposing. We will show and quantify electron-induced fluorescence of several fluorophores in polymer films to mimic resist materials, and use this information to refine our proposed mechanism. Relationships between the molecular structure of fluorophores and fluorescent quantum yield may aid in the development of novel PAGs for EUV lithography.

A virus-MIPs fluorescent sensor based on FRET for highly sensitive detection of JEV.

Science.gov (United States)

Liang, Caishuang; Wang, Huan; He, Kui; Chen, Chunyan; Chen, Xiaoming; Gong, Hang; Cai, Changqun

2016-11-01

Major stumbling blocks in the recognition and detection of virus are the unstable biological recognition element or the complex detection means. Here a fluorescent sensor based on virus-molecular imprinted polymers (virus-MIPs) was designed for specific recognition and highly sensitive detection of Japanese encephalitis virus (JEV). The virus-MIPs were anchored on the surface of silica microspheres modified by fluorescent dye, pyrene-1-carboxaldehyde (PC). The fluorescence intensity of PC can be enhanced by the principle of fluorescence resonance energy transfer (FRET), where virus acted as energy donor and PC acted as energy acceptor. The enhanced fluorescence intensity was proportional to the concentration of virus in the range of 24-960pM, with a limit of detection (LOD, 3σ) of 9.6pM, and the relative standard deviation was 1.99%. In additional, the specificity study confirmed the resultant MIPs has high-selectivity for JEV. This sensor would become a new key for the detection of virus because of its high sensitive, simple operation, high stability and low cost. Copyright © 2016. Published by Elsevier B.V.

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

Directory of Open Access Journals (Sweden)

Shaowei Ding

2015-06-01

Full Text Available 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.

Photoluminescence Enhancement of Silole-Capped Silicon Quantum Dots Based on Förster Resonance Energy Transfer.

Science.gov (United States)

Kim, Seongwoong; Kim, Sungsoo; Ko, Young Chun; Sohn, Honglae

2015-07-01

Photoluminescent porous silicon were prepared by an electrochemical etch of n-type silicon under the illumination with a 300 W tungsten filament bulb for the duration of etch. The red photoluminescence emitting at 650 nm with an excitation wavelength of 450 nm is due to the quantum confinement of silicon quantum dots in porous silicon. HO-terminated red luminescent PS was obtained by an electrochemical treatment of fresh PS with the current of 150 mA for 60 seconds in water and sodium chloride. As-prepared PS was sonicated, fractured, and centrifuged in toluene solution to obtain photoluminescence silicon quantum dots. Dichlorotetraphenylsilole exhibiting an emission band at 520 nm was reacted with HO-terminated silicon quantum dots to give a silole-capped silicon quantum dots. The optical characterization of silole-derivatized silicon quantum dots was investigated by UV-vis and fluorescence spectrometer. The fluorescence emission efficiency of silole-capped silicon quantum dots was increased by about 2.5 times due to F6rster resonance energy transfer from silole moiety to silicon quantum dots.

Influence of different environments on the excited-state proton transfer and dual fluorescence of fisetin

Science.gov (United States)

Guharay, Jayanti; Dennison, S. Moses; Sengupta, Pradeep K.

1999-05-01

The influence of different protic and aprotic solvent environments on the excited-state intramolecular proton transfer (ESIPT) leading to a dual fluorescence behaviour of a biologically important, naturally occurring, polyhydroxyflavone, fisetin (3,3',4',7-tetrahydroxyflavone), has been investigated. The normal fluorescence band, in particular, is extremely sensitive to solvent polarity with νmax shifting from 24 510 cm -1 in dioxane ( ET(30)=36.0) to 20 790 cm -1 in methanol ( ET(30)=55.5). This is rationalized in terms of solvent dipolar relaxation process, which also accounts for the red edge excitation shifts (REES) observed in viscous environments such as glycerol at low temperatures. Significant solvent dependence of the tautomer fluorescence properties ( νmax, yield and decay kinetics) reveals the influence of external hydrogen bonding perturbation on the internal hydrogen bond of the molecule. These excited-state relaxation phenomena and their relevant parameters have been used to probe the microenvironment of fisetin in a membrane mimetic system, namely AOT reverse micelles in n-heptane at different water/surfactant molar ratio ( w0).

Development of real time detector for fluorescent particles applied to pollutant transfers characterization

International Nuclear Information System (INIS)

Prevost, C.

1996-06-01

The studies on aerosol transfer carried out in the field of staff protection and nuclear plants safety become more and more important. So techniques of pollutants simulation by specific tracers with the same aeraulic behaviour are an interesting tool in order to characterize their transfers. Resorting to aerosols tagged by a fluorescent dye allows to realize different studies in ventilation and filtration field. The feasibility of detection in real time for a particulate tracer is the main aim of this work. The need of such a technique is obvious because it can provide the specific aerosol behaviour. Furthermore, direct measurements in real time are required for model validation in calculation codes: they give the most realistic informations on interaction between contaminant and ventilation air flows. Up to now, the principle of fluorescent aerosol concentration measurement allows only an integral response in a delayed time, by means of sampling on filters and a fluorimetric analysis after a specific conditioning of these filters. In order to have the opportunity to detect in real time specific tracer, we have developed a new monitor able to count these particles on the following basis: fluorescent particles pass through a sampling nozzle up to a measurement chamber specially designed; sheath flow rate is defined to confine the test aerosol in the test aerosol in the sample flow rate at nozzle outlet; the interception of this stream by a highly focused laser beam allows aerosol detection and characterization particle by particle; the signature of a passing aerosol is the burst of photons that occurs when the fluoro-phore contained in the glycerol particle is excited by a light of adapted wavelength; these signals are transmitted to a photodetector by a patented optical arrangement. Then, an acquisition interfaced board connected to a computer, converts them into frequencies histograms. In the end, two kind of results could be provided simultaneously : the

Energy transfer in porous anodic alumina/rhodamine 110 nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Elhouichet, H., E-mail: habib.elhouichet@fst.rnu.tn [Laboratoire de Physico-Chimie des Materiaux Mineraux et leurs Applications, Centre National de Recherches en Sciences des Materiaux, B.P. 95, Hammam-Lif 2050 (Tunisia); Departement de Physique, Faculte des Sciences de Tunis, University of Tunis Elmanar 2092 Tunis (Tunisia); Harima, N.; Koyama, H. [Hyogo University of Teacher Education, Kato, Hyogo 673-1494 (Japan); Gaponenko, N.V. [Belarusian State University of Informatics and Radioelectronics, P. Browki St. 6, 220013 Minsk (Belarus)

2012-09-15

We have used porous anodic alumina (PAA) films as templates for embedding rhodamine 110 (Rh110) molecules and examined their photoluminescence (PL) properties in detail. The analysis of the polarization memory (PM) of PL strongly suggests that there is a significant energy transfer from PAA to Rh110 molecules. The effect of annealing the PAA layer on the PL properties of the nanocomposite has been studied. The results show that the energy transfer becomes more efficient in annealed PAA. - Highlights: Black-Right-Pointing-Pointer Porous anodic alumina-rhodamine 110 nanocomposites are elaborated. Black-Right-Pointing-Pointer Efficient energy transfer from the host to Rh110 molecules is evidenced from measurements of photoluminescence and degree of polarization memory spectra. Black-Right-Pointing-Pointer Thermal annealing of porous anodic alumina can improve the process of excitation transfer.

Designing of fluorescent and magnetic imprinted polymer for rapid, selective and sensitive detection of imidacloprid via activators regenerated by the electron transfer-atom transfer radical polymerization (ARGET-ATRP) technique

Science.gov (United States)

Kumar, Sunil; Karfa, Paramita; Madhuri, Rashmi; Sharma, Prashant K.

2018-05-01

In this work, we report on a dual-behavior electrochemical/optical sensor for sensitive determination of Imidacloprid by fluorescent dye (fluorescein, FL) and imprinted polymer modified europium doped superparamagnetic iron oxide nanoparticles (FL@SPIONs@MIP). The imidacloprid (IMD)-imprinted polymer was directly synthesized on the Eu-SPIONs surface via Activators regenerated by the electron transfer-atom transfer radical polymerization (ARGET-ATRP) technique. Preparation, characterization and application of the prepared FL@SPIONs@MIP were systematically investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), fluorescence spectroscopy and electrochemical techniques. The electrochemical experiments exhibited a remarkable selectivity of the prepared sensor towards IMD. Determination of IMD by the square wave stripping voltammetry method represented a wide linear range of 0.059-0.791 μg L-1 with a detection limit of 0.0125 μg L-1. In addition, the fluorescence method shows a linear range of 0.039-0.942 μg L-1 and LOD of 0.0108 μg L-1. The fluorescence property of prepared FL@SPIONs@MIP was used for rapid, on-spot but selective detection of IMD in real samples. The proposed electrode displayed excellent repeatability and long-term stability and was successfully applied for quantitative and trace level determination of IMD in several real samples.

Nuclear response functions at large energy and momentum transfer

International Nuclear Information System (INIS)

Bertozzi, W.; Moniz, E.J.; Lourie, R.W.

1991-01-01

Quasifree nucleon processes are expected to dominate the nuclear electromagnetic response function for large energy and momentum transfers, i.e., for energy transfers large compared with nuclear single particle energies and momentum transfers large compared with typical nuclear momenta. Despite the evident success of the quasifree picture in providing the basic frame work for discussing and understanding the large energy, large momentum nuclear response, the limits of this picture have also become quite clear. In this article a selected set of inclusive and coincidence data are presented in order to define the limits of the quasifree picture more quantitatively. Specific dynamical mechanisms thought to be important in going beyond the quasifree picture are discussed as well. 75 refs, 37 figs

Computational study of energy transfer in two-dimensional J-aggregates

International Nuclear Information System (INIS)

Gallos, Lazaros K.; Argyrakis, Panos; Lobanov, A.; Vitukhnovsky, A.

2004-01-01

We perform a computational analysis of the intra- and interband energy transfer in two-dimensional J-aggregates. Each aggregate is represented as a two-dimensional array (LB-film or self-assembled film) of two kinds of cyanine dyes. We consider the J-aggregate whose J-band is located at a shorter wavelength to be a donor and an aggregate or a small impurity with longer wavelength to be an acceptor. Light absorption in the blue wing of the donor aggregate gives rise to the population of its excitonic states. The depopulation of these states is possible by (a) radiative transfer to the ground state (b) intraband energy transfer, and (c) interband energy transfer to the acceptor. We study the dependence of energy transfer on properties such as the energy gap, the diagonal disorder, and the exciton-phonon interaction strength. Experimentally observable parameters, such as the position and form of luminescence spectrum, and results of the kinetic spectroscopy measurements strongly depend upon the density of states in excitonic bands, rates of energy exchange between states and oscillator strengths for luminescent transitions originating from these states

Energy technology transfer to developing countries

International Nuclear Information System (INIS)

Goldemberg, J.

1991-01-01

This paper gives some examples of how technology transfer can successfully be given to third world countries to allow them to benefit in their quest for economic growth and better standards of living through reduced energy consumption and environmental pollution. It also suggests methods by which obstacles such as high investment costs, lack of information, market demand, etc., can be overcome in order to motivate technological transfer by industrialized countries

Definition and determination of the triplet-triplet energy transfer reaction coordinate.

Science.gov (United States)

Zapata, Felipe; Marazzi, Marco; Castaño, Obis; Acuña, A Ulises; Frutos, Luis Manuel

2014-01-21

A definition of the triplet-triplet energy transfer reaction coordinate within the very weak electronic coupling limit is proposed, and a novel theoretical formalism is developed for its quantitative determination in terms of internal coordinates The present formalism permits (i) the separation of donor and acceptor contributions to the reaction coordinate, (ii) the identification of the intrinsic role of donor and acceptor in the triplet energy transfer process, and (iii) the quantification of the effect of every internal coordinate on the transfer process. This formalism is general and can be applied to classical as well as to nonvertical triplet energy transfer processes. The utility of the novel formalism is demonstrated here by its application to the paradigm of nonvertical triplet-triplet energy transfer involving cis-stilbene as acceptor molecule. In this way the effect of each internal molecular coordinate in promoting the transfer rate, from triplet donors in the low and high-energy limit, could be analyzed in detail.

Intramolecular singlet-singlet energy transfer in antenna-substituted azoalkanes.

Science.gov (United States)

Pischel, Uwe; Huang, Fang; Nau, Werner M

2004-03-01

Two novel azoalkane bichromophores and related model compounds have been synthesised and photophysically characterised. Dimethylphenylsiloxy (DPSO) or dimethylnaphthylsiloxy (DNSO) serve as aromatic donor groups (antenna) and the azoalkane 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) as the acceptor. The UV spectral window of DBO (250-300 nm) allows selective excitation of the donor. Intramolecular singlet-singlet energy transfer to DBO is highly efficient and proceeds with quantum yields of 0.76 with DPSO and 0.99 with DNSO. The photophysical and spectral properties of the bichromophoric systems suggest that energy transfer occurs through diffusional approach of the donor and acceptor within a van der Waals contact at which the exchange mechanism is presumed to dominate. Furthermore, akin to the behaviour of electron-transfer systems in the Marcus inverted region, a rate of energy transfer 2.5 times slower was observed for the system with the more favourable energetics, i.e. singlet-singlet energy transfer from DPSO proceeded slower than from DNSO, although the process is more exergonic for DPSO (-142 kJ mol(-1) for DPSO versus-67 kJ mol(-1) for DNSO).

pH-Responsive Fluorescence Enhancement in Graphene Oxide-Naphthalimide Nanoconjugates: A Fluorescence Turn-On Sensor for Acetylcholine.

Science.gov (United States)

Mangalath, Sreejith; Abraham, Silja; Joseph, Joshy

2017-08-22

A pH-sensitive, fluorescence "turn-on" sensor based on a graphene oxide-naphthalimide (GO-NI) nanoconjugate for the detection of acetylcholine (ACh) by monitoring the enzymatic activity of acetylcholinesterase (AChE) in aqueous solution is reported. These nanoconjugates were synthesized by covalently anchoring picolyl-substituted NI derivatives on the GO/reduced GO surface through a 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxysuccinimide coupling strategy, and the morphological and photophysical properties were studied in detail. Synergistic effects of π-π interactions between GO and the NI chromophore, and efficient photoinduced electron- and energy-transfer processes, were responsible for the strong quenching of fluorescence of these nanoconjugates, which were perturbed under acidic pH conditions, leading to significant enhancement of fluorescence emission. This nanoconjugate was successfully employed for the efficient sensing of pH changes caused by the enzymatic activity of AChE, thereby demonstrating its utility as a fluorescence turn-on sensor for ACh in the neurophysiological range. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Energy transfer from a superconducting magnet to an inductive load

International Nuclear Information System (INIS)

Onishi, Toshitada; Miura, Akinori.

1977-01-01

Experiments on energy transfer between two superconducting magnets have been carried out using an inductive energy transfer system similar to the flying capacitor system developed at the Karlsruhe Institute. In the present system the capacitor is grounded and diodes are used instead of thyristors, and a fraction of stored energy is transferred to the capacitor only when the relay connected in parallel to the magnet is switched off. The capacitor is expected to have no constraint in size, while in the flying capacitor system the capacitor is required to exceed a threshold size. Consequently it is possible to shorten the transfer time to some extent in comparison with the one in the flying capacitor system. Transfer experiments have been carried out using a storage magnet with inductance of 1.2H and a load of 0.41H. The capacitance is 200μF. It is possible to transfer 80.1% of the stored energy of 221 J into the load in less than about 0.35 seconds. (auth.)

Energy transfer in diatom/diatom molecular collisions

International Nuclear Information System (INIS)

Sohlberg, K.W.

1992-01-01

In a collision of two molecules, the translational energy of the collision may be redistributed into internal energy of rotation, vibration, or electron motion, in one or both of the colliding partners. In addition, internal energy in one or more of these modes may be open-quotes quenchedclose quotes into translation, leading to a superelastic collision. Such energy transfer may take place by a number of mechanisms. This energy transfer is of fundamental importance in understanding chemical reaction dynamics. Nearly all chemical reactions take place through a bimolecular collision process (or multiple bimolecular collisions) and the quantum state specificity of the reaction can have a major role in determining the kinetics of the reaction, In particular, the author has investigated vibrational energy transfer in collisions between two diatomic molecules. In addition to serving as models for all molecular collision process, gas phase collisions of these species are ubiquitous in atmospheric phenomena which are of critical importance in answering the current questions about the human induced degradation of the earth's atmospheric. Classical trajectory methods have been used to explore the excitation of vibrations in gas-phase collisions of the nitrogen molecular ion with its parent molecule. The near symmetry of the reactants is shown to result in a high probability that the two molecules are excited by an equal amount of energy. This provides a possible explanation of the molecular beam measurements which show that the total number of vibrational energy quanta excited in the collision is, with a high probability that the two molecules are excited by an equal amount of energy. This provides a possible explanation of the molecular beam measurements which show that the total number of vibrational energy quanta excited in the collision is, with a high probability, even

Fabrication and charge/energy-transfer study of 4,7-bis(4-triphenylamino)benzo- 2,1,3-thiadiazole/CuPc composite films

International Nuclear Information System (INIS)

Zhu Yuanyuan; Wei Xiao; Xue Minzhao; Zhang Qing; Sheng Qiaorong; Liu Yangang; Gu Shuangxi

2010-01-01

Composite films of 4,7-bis(4-triphenylamino)benzo-2,1,3-thiadiazole (TBT) and copper phthalocyanine (CuPc) are fabricated via protonation-coelectrophoretic deposition from nitromethane solutions of TBT/CuPc mixture in the presence of trifluoroacetic acid as a protonation reagent. A nanospheres-nanowires interpenetrating network structure is obtained when the molar percentage of TBT is 70%. Furthermore, the existence of TBT makes α-phased CuPc be partly transformed into the β-phase, and simultaneously, CuPc disorganizes the TBT unit cells. The blue shift on the absorption edge of TBT and the significant fluorescence quenching in the composite films indicate energy/charge transfer and donor-acceptor (D-A) heterojunction formation. Then these results are proved from another point of view: the mutual overlap of absorption and emission spectra of TBT and CuPc lead to a bidirectional Foerster resonance energy transfer at the interface; the molecular energy levels calculated from the results of cyclic voltammetry theoretically determine that there exist a D-A heterojunction and charge transfer from TBT to CuPc. Finally, from the investigation of the field-induced surface photovoltage spectra, it can be concluded that this charge transfer results in efficient dissociation of the photoinduced excitons in the composite films, followed by the generation of a strong photovoltage response.

Fabrication and charge/energy-transfer study of 4,7-bis(4-triphenylamino)benzo- 2,1,3-thiadiazole/CuPc composite films

Energy Technology Data Exchange (ETDEWEB)

Zhu Yuanyuan; Wei Xiao; Xue Minzhao; Zhang Qing; Sheng Qiaorong; Liu Yangang [School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Gu Shuangxi, E-mail: mzxue@sjtu.edu.c [Department of Chemistry, Fudan University, Shanghai 200433 (China)

2010-12-15

Composite films of 4,7-bis(4-triphenylamino)benzo-2,1,3-thiadiazole (TBT) and copper phthalocyanine (CuPc) are fabricated via protonation-coelectrophoretic deposition from nitromethane solutions of TBT/CuPc mixture in the presence of trifluoroacetic acid as a protonation reagent. A nanospheres-nanowires interpenetrating network structure is obtained when the molar percentage of TBT is 70%. Furthermore, the existence of TBT makes {alpha}-phased CuPc be partly transformed into the {beta}-phase, and simultaneously, CuPc disorganizes the TBT unit cells. The blue shift on the absorption edge of TBT and the significant fluorescence quenching in the composite films indicate energy/charge transfer and donor-acceptor (D-A) heterojunction formation. Then these results are proved from another point of view: the mutual overlap of absorption and emission spectra of TBT and CuPc lead to a bidirectional Foerster resonance energy transfer at the interface; the molecular energy levels calculated from the results of cyclic voltammetry theoretically determine that there exist a D-A heterojunction and charge transfer from TBT to CuPc. Finally, from the investigation of the field-induced surface photovoltage spectra, it can be concluded that this charge transfer results in efficient dissociation of the photoinduced excitons in the composite films, followed by the generation of a strong photovoltage response.

Energy transfers in dynamos with small magnetic Prandtl numbers

KAUST Repository

Kumar, Rohit

2015-06-25

We perform numerical simulation of dynamo with magnetic Prandtl number Pm = 0.2 on 10243 grid, and compute the energy fluxes and the shell-to-shell energy transfers. These computations indicate that the magnetic energy growth takes place mainly due to the energy transfers from large-scale velocity field to large-scale magnetic field and that the magnetic energy flux is forward. The steady-state magnetic energy is much smaller than the kinetic energy, rather than equipartition; this is because the magnetic Reynolds number is near the dynamo transition regime. We also contrast our results with those for dynamo with Pm = 20 and decaying dynamo. © 2015 Taylor & Francis.

Design of triads for probing the direct through space energy transfers in closely spaced assemblies.

Science.gov (United States)

Camus, Jean-Michel; Aly, Shawkat M; Fortin, Daniel; Guilard, Roger; Harvey, Pierre D

2013-08-05

Using a selective stepwise Suzuki cross-coupling reaction, two trimers built on three different chromophores were prepared. These trimers exhibit a D(^)A1-A2 structure where the donor D (octa-β-alkyl zinc(II)porphyrin either as diethylhexamethyl, 10a, or tetraethyltetramethyl, 10b, derivatives) through space transfers the S1 energy to two different acceptors, di(4-ethylbenzene) zinc(II)porphyrin (A1; acceptor 1) placed cofacial with D, and the corresponding free base (A2; acceptor 2), which is meso-meso-linked with A1. This structure design allows for the possibility of comparing two series of assemblies, 9a,b (D(^)A1) with 10a,b (D(^)Â1-A2), for the evaluation of the S1 energy transfer for the global process D*→A2 in the trimers. From the comparison of the decays of the fluorescence of D, the rates for through space energy transfer, kET for 10a,b (kET ≈ 6.4 × 10(9) (10a), 5.9 × 10(9) s(-1) (10b)), and those for the corresponding cofacial D(^)A1 systems, 9a,b, (kET ≈ 5.0 × 10(9) (9a), 4.7 × 10(9) s(-1) (9b)), provide an estimate for kET for the direct through space D*→A2 process (i.e., kET(D(^)A1-A2) - kET(D(^)A1) = kET(D*→A2) ∼ 1 × 10(9) s(-1)). This channel of relaxation represents ∼15% of kET for D*→A1.

Dansyl-Galactoside, a Fluorescent Probe of Active Transport in Bacterial Membrane Vesicles*

Science.gov (United States)