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Sample records for cell-based fluorescence resonance

  1. Development of a Cell-Based Fluorescence Resonance Energy Transfer Reporter for Bacillus anthracis Lethal Factor Protease

    Energy Technology Data Exchange (ETDEWEB)

    Kimura, R H; Steenblock, E R; Camarero, J A

    2007-03-22

    We report the construction of a cell-based fluorescent reporter for anthrax lethal factor (LF) protease activity using the principle of fluorescence resonance energy transfer (FRET). This was accomplished by engineering an Escherichia coli cell line to express a genetically encoded FRET reporter and LF protease. Both proteins were encoded in two different expression plasmids under the control of different tightly controlled inducible promoters. The FRET-based reporter was designed to contain a LF recognition sequence flanked by the FRET pair formed by CyPet and YPet fluorescent proteins. The length of the linker between both fluorescent proteins was optimized using a flexible peptide linker containing several Gly-Gly-Ser repeats. Our results indicate that this FRET-based LF reporter was readily expressed in E. coli cells showing high levels of FRET in vivo in the absence of LF. The FRET signal, however, decreased 5 times after inducing LF expression in the same cell. These results suggest that this cell-based LF FRET reporter may be used to screen genetically encoded libraries in vivo against LF.

  2. Magnetic resonance imaging and cell-based neurorestorative therapy after brain injury

    Institute of Scientific and Technical Information of China (English)

    Quan Jiang

    2016-01-01

    Restorative cell-based therapies for experimental brain injury, such as stroke and traumatic brain injury, substantially improve functional outcome. We discuss and review state of the art magnetic resonance im-aging methodologies and their applications related to cell-based treatment after brain injury. We focus on the potential of magnetic resonance imaging technique and its associated challenges to obtain useful new information related to cell migration, distribution, and quantitation, as well as vascular and neuronal remodeling in response to cell-based therapy after brain injury. The noninvasive nature of imaging might more readily help with translation of cell-based therapy from the laboratory to the clinic.

  3. Magnetic resonance imaging and cell-based neurorestorative therapy after brain injury

    Directory of Open Access Journals (Sweden)

    Quan Jiang

    2016-01-01

    Full Text Available Restorative cell-based therapies for experimental brain injury, such as stroke and traumatic brain injury, substantially improve functional outcome. We discuss and review state of the art magnetic resonance imaging methodologies and their applications related to cell-based treatment after brain injury. We focus on the potential of magnetic resonance imaging technique and its associated challenges to obtain useful new information related to cell migration, distribution, and quantitation, as well as vascular and neuronal remodeling in response to cell-based therapy after brain injury. The noninvasive nature of imaging might more readily help with translation of cell-based therapy from the laboratory to the clinic.

  4. Resonance fluorescence in a waveguide geometry

    OpenAIRE

    Kocabaş, Şukrü Ekin; Rephaeli, Eden; Fan, Shanhui

    2011-01-01

    PHYSICAL REVIEW A 85, 023817 (2012) Resonance fluorescence in a waveguide geometry S¸ ¨ukr¨u Ekin Kocabas¸,1,* Eden Rephaeli,2,† and Shanhui Fan3,‡ 1Department of Electrical & Electronics Engineering, Koc¸ University, Rumeli Feneri Yolu TR-34450 Sarıyer, ˙Istanbul, Turkey 2Department of Applied Physics, Stanford University, Stanford, California 94305, USA 3Ginzton Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California 94305, USA (Received...

  5. Fluorescence Resonance Energy Transfer (FRET) sensor

    OpenAIRE

    Hussain, Syed Arshad; Dey, Dibyendu; CHAKRABORTY, SEKHAR; Saha, Jaba; Roy, Arpan Datta; Chakraborty, Santanu; Debnath, Pintu; Bhattacharjee, D.

    2014-01-01

    The applications of Fluorescence resonance energy transfer (FRET) have expanded tremendously in the last 25 years, and the technique has become a staple technique in many biological and biophysical fields. FRET can be used as spectroscopic ruler in various areas such as structural elucidation of biological molecules and their interactions, in vitro assays, in vivo monitoring in cellular research, nucleic acid analysis, signal transduction, light harvesting, and metallic nanomaterials etc. Bas...

  6. Fluorescence Resonance Energy Transfer (FRET) sensor

    CERN Document Server

    Hussain, Syed Arshad; Chakraborty, Sekhar; Saha, Jaba; Roy, Arpan Datta; Chakraborty, Santanu; Debnath, Pintu; Bhattacharjee, D

    2014-01-01

    The applications of Fluorescence resonance energy transfer (FRET) have expanded tremendously in the last 25 years, and the technique has become a staple technique in many biological and biophysical fields. FRET can be used as spectroscopic ruler in various areas such as structural elucidation of biological molecules and their interactions, in vitro assays, in vivo monitoring in cellular research, nucleic acid analysis, signal transduction, light harvesting, and metallic nanomaterials etc. Based on the mechanism of FRET a variety of novel chemical sensors and Biosensors have been developed. This review highlights the recent applications of sensitive and selective ratiometric FRET based sensors.

  7. Surface Plasmon Resonance for Cell-Based Clinical Diagnosis

    Directory of Open Access Journals (Sweden)

    Yuhki Yanase

    2014-03-01

    Full Text Available Non-invasive real-time observations and the evaluation of living cell conditions and functions are increasingly demanded in life sciences. Surface plasmon resonance (SPR sensors detect the refractive index (RI changes on the surface of sensor chips in label-free and on a real-time basis. Using SPR sensors, we and other groups have developed techniques to evaluate living cells’ reactions in response to stimuli without any labeling in a real-time manner. The SPR imaging (SPRI system for living cells may visualize single cell reactions and has the potential to expand application of SPR cell sensing for clinical diagnosis, such as multi-array cell diagnostic systems and detection of malignant cells among normal cells in combination with rapid cell isolation techniques.

  8. Magnetic resonance tracking of fluorescent nanodiamond fabrication

    International Nuclear Information System (INIS)

    Magnetic resonance techniques (electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR)) are used for tracking the multi-stage process of the fabrication of fluorescent nanodiamonds (NDs) produced by high-energy electron irradiation, annealing, and subsequent nano-milling. Pristine commercial high pressure and high temperature microdiamonds (MDs) with mean size 150 μm contain ∼5  ×  1018 spins/g of singlet (S = 1/2) substitutional nitrogen defects P1, as well as sp3 C–C dangling bonds in the crystalline lattice. The half-field X-band EPR clearly shows (by the appearance of the intense ‘forbidden’ g = 4.26 line) that high-energy electron irradiation and annealing of MDs induce a large amount (∼5  ×  1017 spins/g) of triplet (S = 1) magnetic centers, which are identified as negatively charged nitrogen vacancy defects (NV−). This is supported by EPR observations of the ‘allowed’ transitions between Zeeman sublevels of the triplet state. After progressive milling of the fluorescent MDs down to an ultrasubmicron scale (≤100 nm), the relative abundance of EPR active NV− defects in the resulting fluorescent NDs (FND) substantially decreases and, vice versa, the content of C-inherited singlet defects correlatively increases. In the fraction of the finest FNDs (mean particle size <20 nm), which are contained in the dried supernatant of ultracentrifuged aqueous dispersion of FNDs, the NV− content is found to be reduced by one order of magnitude whereas the singlet defects content increases up to ∼2  ×  1019 spins/g. In addition, another triplet-type defect, which is characterized by the g = 4.00 ‘forbidden’ line, appears. On reduction of the particle size below the 20 nm limit, the ‘allowed’ EPR lines become practically unobservable, whereas the ‘forbidden’ lines remain as a reliable fingerprint of the presence of NV− centers in small ND systems. The same size reduction causes the

  9. Nuclear Resonance Fluorescence Using Different Photon Sources

    International Nuclear Information System (INIS)

    Nuclear resonance fluorescence (NRF) is a photon-based active interrogation approach that provides isotope-specific signatures that can be used to detect and characterize samples. As NRF systems are designed to address specific applications, an obvious first question to address is the type of photon source to be employed for the application. Our collaboration has conducted a series of NRF measurements using different photon sources to begin to examine this issue. The measurements were designed to be as similar as possible to facilitate a straightforward comparison of the different sources. Measurements were conducted with a high-duty factor electron accelerator using bremsstrahlung photons, with a pulsed linear accelerator using bremsstrahlung photons, and with a narrow bandwidth photon source using Compton backscattered photons. We present our observations on the advantages and disadvantages of each photon source type. Issues such as signal rate, the signal-to-noise ratio, and absorbed dose are discussed

  10. Distance dependence of fluorescence resonance energy transfer

    Indian Academy of Sciences (India)

    R S Swathi; K L Sebastian

    2009-09-01

    Deviations from the usual -6 dependence of the rate of fluorescence resonance energy transfer (FRET) on the distance between the donor and the acceptor have been a common scenario in the recent times. In this paper, we present a critical analysis of the distance dependence of FRET, and try to illustrate the non--6 type behaviour of the rate for the case of transfer from a localized electronic excitation on the donor, a dye molecule to three different energy acceptors with delocalized electronic excitations namely, graphene, a two-dimensional semiconducting sheet and the case of such a semiconducting sheet rolled to obtain a nanotube. We use simple analytic models to understand the distance dependence in each case.

  11. Nuclear Resonance Fluorescence for Materials Assay

    International Nuclear Information System (INIS)

    This paper discusses the use of nuclear resonance fluorescence (NRF) techniques for the isotopic and quantitative assaying of radioactive material. Potential applications include age-dating of an unknown radioactive source, pre- and post-detonation nuclear forensics, and safeguards for nuclear fuel cycles Examples of age-dating a strong radioactive source and assaying a spent fuel pin are discussed. The modeling work has been performed with the Monte Carlo radiation transport computer code MCNPX, and the capability to simulate NRF has bee added to the code. Discussed are the limitations in MCNPX?s photon transport physics for accurately describing photon scattering processes that are important contributions to the background and impact the applicability of the NRF assay technique.

  12. Potential Applications of Nuclear Resonance Fluorescence

    Science.gov (United States)

    Warren, Glen; Caggiano, Jac; Peplowski, Patrick

    2009-12-01

    Nuclear resonance fluorescence (NRF) is a photon-based active interrogation approach that provides isotope-specific signatures that can be used to detect and characterize samples. Photon energies are in the range of a few MeV, so that penetration through significant material is possible. Unlike other active interrogation techniques that are based on inducing fission, NRF is sensitive to a wide range of isotopes: for example 11B, 12C, 13C, 14N, 16O, 27Al, 208Pb, 235U, 238U and 239Pu just to name a few. NRF is most likely to outperform existing technologies for applications requiring isotopic information of sealed samples. Pacific Northwest National Laboratory is conducting a review of potential applications that could be addressed by NRF techniques. These applications cover a wide range of topics, from geo-location, to material assay, to safeguarding the nuclear fuel cycle. The objective of the project is to search for potential applications, define technical requirements, identify physical limitations, conduct an initial assessment of the technique and design a research approach for developing the applications. In this report, our current progress on will be presented.

  13. An Introduction to Fluorescence Resonance Energy Transfer (FRET)

    OpenAIRE

    Hussain, Syed Arshad

    2009-01-01

    Recent advances in Fluorescence Resonance Energy Transfer (FRET) provides a way to measure and understand different biological systems and molecular interactions in nanometer order. In this report the introduction and principle of the FRET process have been explained.

  14. Resonance fluorescence from quantum dots: beyond the Mollow triplet

    DEFF Research Database (Denmark)

    Lund, Anders Mølbjerg; Nielsen, Per Kær; Lorke, Michael;

    2011-01-01

    We show that the resonance fluorescence spectrum of a quantum dot excited by a strong pulse contains multiple peaks. An analytical model shows how the peak positions depend on pulse width and amplitude.......We show that the resonance fluorescence spectrum of a quantum dot excited by a strong pulse contains multiple peaks. An analytical model shows how the peak positions depend on pulse width and amplitude....

  15. Nuclear Resonance Fluorescence for Safeguards Applications

    Energy Technology Data Exchange (ETDEWEB)

    Ludewigt, Bernhard A; Quiter, Brian J; Ambers, Scott D

    2011-02-04

    In nuclear resonance fluorescence (NRF) measurements, resonances are excited by an external photon beam leading to the emission of {gamma} rays with specific energies that are characteristic of the emitting isotope. The promise of NRF as a non-destructive analysis technique (NDA) in safeguards applications lies in its potential to directly quantify a specific isotope in an assay target without the need for unfolding the combined responses of several fissile isotopes as often required by other NDA methods. The use of NRF for detection of sensitive nuclear materials and other contraband has been researched in the past. In the safeguards applications considered here one has to go beyond mere detection and precisely quantify the isotopic content, a challenge that is discussed throughout this report. Basic NRF measurement methods, instrumentation, and the analytical calculation of NRF signal strengths are described in Section 2. Well understood modeling and simulation tools are needed for assessing the potential of NRF for safeguards and for designing measurement systems. All our simulations were performed with the radiation transport code MCNPX, a code that is widely used in the safeguards community. Our initial studies showed that MCNPX grossly underestimated the elastically scattered background at backwards angles due to an incorrect treatment of Rayleigh scattering. While new, corrected calculations based on ENDF form factors showed much better agreement with experimental data for the elastic scattering of photons on an uranium target, the elastic backscatter is still not rigorously treated. Photonuclear scattering processes (nuclear Thomson, Delbruck and Giant Dipole Resonance scattering), which are expected to play an important role at higher energies, are not yet included. These missing elastic scattering contributions were studied and their importance evaluated evaluated against data found in the literature as discussed in Section 3. A transmission experiment

  16. Nuclear Resonance Fluorescence for Safeguards Applications

    International Nuclear Information System (INIS)

    In nuclear resonance fluorescence (NRF) measurements, resonances are excited by an external photon beam leading to the emission of γ rays with specific energies that are characteristic of the emitting isotope. The promise of NRF as a non-destructive analysis technique (NDA) in safeguards applications lies in its potential to directly quantify a specific isotope in an assay target without the need for unfolding the combined responses of several fissile isotopes as often required by other NDA methods. The use of NRF for detection of sensitive nuclear materials and other contraband has been researched in the past. In the safeguards applications considered here one has to go beyond mere detection and precisely quantify the isotopic content, a challenge that is discussed throughout this report. Basic NRF measurement methods, instrumentation, and the analytical calculation of NRF signal strengths are described in Section 2. Well understood modeling and simulation tools are needed for assessing the potential of NRF for safeguards and for designing measurement systems. All our simulations were performed with the radiation transport code MCNPX, a code that is widely used in the safeguards community. Our initial studies showed that MCNPX grossly underestimated the elastically scattered background at backwards angles due to an incorrect treatment of Rayleigh scattering. While new, corrected calculations based on ENDF form factors showed much better agreement with experimental data for the elastic scattering of photons on an uranium target, the elastic backscatter is still not rigorously treated. Photonuclear scattering processes (nuclear Thomson, Delbruck and Giant Dipole Resonance scattering), which are expected to play an important role at higher energies, are not yet included. These missing elastic scattering contributions were studied and their importance evaluated evaluated against data found in the literature as discussed in Section 3. A transmission experiment was

  17. A Cell-Based Fluorescent Assay to Detect the Activity of Shiga Toxin and Other Toxins That Inhibit Protein Synthesis

    Science.gov (United States)

    Escherichia coli O157:H7, a major cause of food-borne illness, produces Shiga toxins that block protein synthesis by inactivating the ribosome. In this chapter we describe a simple cell-based fluorescent assay to detect Shiga toxins and inhibitors of toxin activity. The assay can also be used to d...

  18. Resonance fluorescence from a telecom-wavelength quantum dot

    CERN Document Server

    Al-Khuzheyri, R; Huwer, J; Santana, T S; Szymanska, J Skiba-; Felle, M; Ward, M B; Stevenson, R M; Farrer, I; Tanner, M G; Hadfield, R H; Ritchie, D A; Shields, A J; Gerardot, B D

    2016-01-01

    We report on resonance fluorescence from a single quantum dot emitting at telecom wavelengths. We perform high-resolution spectroscopy and observe the Mollow triplet in the Rabi regime--a hallmark of resonance fluorescence. The measured resonance-fluorescence spectra allow us to rule out pure dephasing as a significant decoherence mechanism in these quantum dots. Combined with numerical simulations, the experimental results provide robust characterisation of charge noise in the environment of the quantum dot. Resonant control of the quantum dot opens up new possibilities for on-demand generation of indistinguishable single photons at telecom wavelengths as well as quantum optics experiments and direct manipulation of solid-state qubits in telecom-wavelength quantum dots.

  19. Investigation of Quenching Mechanism in Thermoreversible Fluorescent Recording Materials of Fluorescence Using Thermochromic Fluorescence Resonance Energy Transfer

    Science.gov (United States)

    Shuzo Hirata,; Martin Vacha,; Toshiyuki Watanabe,

    2010-05-01

    We demonstrated reversible thermosensitive recording of a fluorescent image (TRF) using a low-molecular-weight mixture consisting of a fluorescent dye, a fluoran dye, a developer, and a reversible matrix. In this material, reversible thermoresponsive disorder-crystal transition triggers a cyclical colorless-color change of a fluoran dye, which induces on-off switching of fluorescence resonance energy transfer (FRET) from a fluorescent dye to a fluoran dye. On-off switching of fluorescence is induced by heat-promoted off-on switching of FRET. Modulation of fluorescence is held at room temperature by utilizing thermal hysteresis, and nondestructive readout of the fluorescent image is accomplished in the presence of excitation light. Here, we investigate the on-off switching mechanism of fluorescence in this recording material. We analyzed the theoretical factor of emission quenching in the erasing state by comparing the theoretical overlap integral Ω between fluorescent dyes and fluoran dyes on the basis of the FRET theory with experimental emission contrast for various combinations of fluorescent dyes and fluoran dyes. It was proved that fluorescence on-off switching occurs mainly by concentration quenching due to the aggregation of fluorescent dyes and FRET from isolated fluorescent dyes to colored fluoran dyes. The key issue to obtain both high-contrast fluorescence and high fluorescence quantum yield is to control these two factors.

  20. Resonance fluorescence and electron spin in semiconductor quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yong

    2009-11-18

    The work presented in this dissertation contains the first observation of spin-resolved resonance fluorescence from a single quantum dot and its application of direct measurement of electron spin dynamics. The Mollow triplet and the Mollow quintuplet, which are the hallmarks of resonance fluorescence, are presented as the non-spin-resolved and spin-resolved resonance fluorescence spectrum, respectively. The negligible laser background contribution, the near pure radiative broadened spectrum and the anti-bunching photon statistics imply the sideband photons are background-free and near transform-limited single photons. This demonstration is a promising step towards the heralded single photon generation and electron spin readout. Instead of resolving spectrum, an alternative spin-readout scheme by counting resonance fluorescence photons under moderate laser power is demonstrated. The measurements of n-shot time-resolved resonance fluorescence readout are carried out to reveal electron spin dynamics of the measurement induced back action and the spin relaxation. Hyperfine interaction and heavy-light hole mixing are identified as the relevant mechanisms for the back action and phonon-assistant spin-orbit interaction dominates the spin relaxation. After a detailed discussion on charge-spin configurations in coupled quantum dots system, the single-shot readout on electron spin are proposed. (orig.)

  1. 基于TiO2和CdTe荧光共振能量转移的PDT体外灭活HL60细胞实验研究%Experimental Research on the PDT Vitro Inactivation of HL60 Cells Based on Fluorescence Resonance Energy Transfer between TiO2 and CdTe Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    罗有焕; 张卿; 陈丽; 艾保全; 熊建文

    2015-01-01

    为研究TiO2和CdTe量子点间荧光共振能量转移效率对PDT体外灭活HL60细胞的影响,本文以发射波长为407.8 nm的TiO2为供体,CdTe为受体,通过TiO2与CdTe超声混合构建荧光共振能量转移体系,研究了TiO2和CdTe量子点间荧光共振能量转移;其中体系中TiO2浓度为200μg/mL时,通过逐渐增加体系中CdTe浓度来观察供体TiO2荧光强度变化,根据Forster能量共振转移理论计算体系能量转移效率.之后将体系用于PDT体外灭活HL60细胞的实验研究,采用CCK-8法,结合酶联免疫检测仪进行细胞活性检测,得出不同浓度下体系的PDT灭活效率.发现当TiO2-CdTe体系荧光共振能量转移效率20.21%时,PDT灭活效率为53.75%,而当体系能量转移效率为6.77%时,灭活效率达到了71.54%,实验表明在一定浓度范围内,TiO2-CdTe混合体系荧光共振能量转移效率低时,PDT灭活效率更高.这可能是由于TiO2-CdTe之间能量共振转移低时,容易致使TiO2表面光生电子和空穴复合率降低,提高了二氧化钛的光催化活性,导致灭活效率增高.%A fluorescence resonance energy transfer system based on TiO2 and CdTe ultrasonic mix was built to study how fluorescence resonance energy transfer between TiO2 and CdTe quantum dots influence HL60 viability in PDT exper-iment.TiO2 with 407.8 nm emission wavelength was used as donor,and CdTe as acceptor.The intensity change of do-nor TiO2 was observed when the concentration of CdTe was increased in proportion,and the concentration of TiO2 re-mained at 200 μg/mL.The system energy transfer efficiency was calculated according to the theory of Forster energy transfer.The system was then applied in in vitro PDT experiment based on HL60 cells.With CCK-8 method,the cell vi-ability under different drug concentration was calculated.Our data showed that when the fluorescence resonance energy transfer efficiency of TiO2-CdTe hybrid system was 20.21%,the PDT inactivated efficiency was 53

  2. Fluorescence Resonance Energy Transfer Using Spiropyran and Diarylethene Photochromic Acceptors

    OpenAIRE

    E. A. Jares-Erijman; Irie, M.; Jovin, T M; Song, L.; Macareno, J.; GIORDANO, L.

    2000-01-01

    We describe the preparation and photophysical characterization of two model compounds designed to test a new approach for the quantitative determination of Fluorescence Resonance Energy Transfer (FRET) in biological systems. The method enables modulation of FRET by exploiting the unique reversible spectral properties of photochromic diarylethenes and spiropyrans to create switchable energy acceptors.

  3. New method for tissue indentification: resonance fluorescence spectroscopy

    Science.gov (United States)

    Neu, Walter

    1991-11-01

    The method proposed in this paper is based on the detection of resonantly enhanced fluorescence emission induced by a tunable dye laser. First test on anorganic samples exposed to air and to saline solution demonstrate the potential of this technique. A XeCl excimer-laser ((lambda) equals308 nm) pulse, guided by quartz fibers, causes an efficient ablation of the irradiated samples. The specific species to be detected in the ablation plume determines the wavelength of the narrow-band dye-laser radiation. Preferably, it is set to a strong transition of the selected ablation product. Taking into account the formation of the plume, the dye-laser pulse is applied with a certain delay in order to excite resonantly the chosen species in the plume. The resulting resonance fluorescence is then guided by optical fibers to an OMA system. Compared to the broad-band excimer-laser-indiced fluorescence during the ablation process, the resonance fluorescence signal shows a distinct and easily detectable sharp peak. The signal-to-background ratio is improved by one order of magnitude. The achieved increase in sensitivity as well as selectivity is for the benefit of a reliable identification of ablated tissue.

  4. Diagnosis of atherosclerotic tissue by resonance fluorescence spectroscopy

    Science.gov (United States)

    Neu, Walter; Haase, Karl K.; Tischler, Christian; Nyga, Ralf; Karsch, Karl R.

    1991-05-01

    Resonantly enhanced fluorescence emission induced by a tunable dye laser can be used for the identification of ablated atherosclerotic tissue. This method has been tested with anorganic samples exposed to air and to saline solution. A XeCl excimer laser pulse ((lambda) = 308 nm), delivered by a fused silica optical fiber, causes an efficient ablation of the irradiated samples. The wavelength of the narrow-band dye laser radiation is set to a strong transition of a specific species to be detected in the ablation plume. Taking into account the formation of the plume, the dye laser pulse is applied with a certain delay in order to excite resonantly the selected species in the plume. The resulting resonance fluorescence then is guided by optical fibers to an optical multi-channel analyzer system. Compared to the broad-band fluorescence during excimer laser ablation the resonance fluorescence signal shows a distinct and easily detectable sharp peak. The signal-to-background ratio is improved by one order of magnitude.

  5. Resonance fluorescence of a cold atom in a high-finesse resonator

    CERN Document Server

    Bienert, M; Torres, J M; Zippilli, S; Bienert, Marc; Morigi, Giovanna; Zippilli, Stefano

    2007-01-01

    We study the spectra of emission of a system composed by an atom, tightly confined inside a high-finesse resonator, when the atom is driven by a laser and is at steady state of the cooling dynamics induced by laser and cavity field. In general, the spectrum of resonance fluorescence and the spectrum at the cavity output contain complementary information about the dynamics undergone by the system. In certain parameter regimes, quantum interference effects between the scattering processes induced by cavity and laser field lead to the selective suppression of features of the resonance fluorescence spectrum, which are otherwise visible in the spectrum of laser-cooled atoms in free space.

  6. Far-red fluorescence gene reporter tomography for determination of placement and viability of cell-based gene therapies.

    Science.gov (United States)

    Lu, Yujie; Darne, Chinmay D; Tan, I-Chih; Zhu, Banghe; Hall, Mary A; Lazard, Zawaunyka W; Davis, Alan R; Simpson, Lashan; Sevick-Muraca, Eva M; Olmsted-Davis, Elizabeth A

    2013-10-01

    Non-invasive injectable cellular therapeutic strategies based on sustained delivery of physiological levels of BMP-2 for spinal fusion are emerging as promising alternatives, which could provide sufficient fusion without the associated surgical risks. However, these injectable therapies are dependent on bone formation occurring only at the specific target region. In this study, we developed and deployed fluorescence gene reporter tomography (FGRT) to provide information on in vivo cell localization and viability. This information is sought to confirm the ideal placement of the materials with respect to the area where early bone reaction is required, ultimately providing three dimensional data about the future fusion. However, because almost all conventional fluorescence gene reporters require visible excitation wavelengths, current in vivo imaging of fluorescent proteins is limited by high tissue absorption and confounding autofluorescence. We previously administered fibroblasts engineered to produce BMP-2, but is difficult to determine 3-D information of placement prior to bone formation. Herein we used the far-red fluorescence gene reporter, IFP1.4 to report the position and viability of fibroblasts and developed 3-D tomography to provide placement information. A custom small animal, far-red fluorescence tomography system integrated into a commercial CT scanner was used to assess IFP1.4 fluorescence and to demark 3-D placement of encapsulated fibroblasts with respect to the vertebrae and early bone formation as assessed from CT. The results from three experiments showed that the placement of the materials within the spine could be detected. This work shows that in vivo fluorescence gene reporter tomography of cell-based gene therapy is feasible and could help guide cell-based therapies in preclinical models.

  7. Using magnetic resonance imaging to evaluate dendritic cell-based vaccination.

    Directory of Open Access Journals (Sweden)

    Peter M Ferguson

    Full Text Available Cancer immunotherapy with antigen-loaded dendritic cell-based vaccines can induce clinical responses in some patients, but further optimization is required to unlock the full potential of this strategy in the clinic. Optimization is dependent on being able to monitor the cellular events that take place once the dendritic cells have been injected in vivo, and to establish whether antigen-specific immune responses to the tumour have been induced. Here we describe the use of magnetic resonance imaging (MRI as a simple, non-invasive approach to evaluate vaccine success. By loading the dendritic cells with highly magnetic iron nanoparticles it is possible to assess whether the injected cells drain to the lymph nodes. It is also possible to establish whether an antigen-specific response is initiated by assessing migration of successive rounds of antigen-loaded dendritic cells; in the face of a successfully primed cytotoxic response, the bulk of antigen-loaded cells are eradicated on-route to the node, whereas cells without antigen can reach the node unchecked. It is also possible to verify the induction of a vaccine-induced response by simply monitoring increases in draining lymph node size as a consequence of vaccine-induced lymphocyte trapping, which is an antigen-specific response that becomes more pronounced with repeated vaccination. Overall, these MRI techniques can provide useful early feedback on vaccination strategies, and could also be used in decision making to select responders from non-responders early in therapy.

  8. Development and validation of a simple cell-based fluorescence assay for dipeptidyl peptidase 1 (DPP1) activity.

    Science.gov (United States)

    Thong, Bob; Pilling, James; Ainscow, Edward; Beri, Raj; Unitt, John

    2011-01-01

    Dipeptidyl peptidase 1 (DPP1) (EC 3.4.14.1; also known as cathepsin C, cathepsin J, dipeptidyl aminopeptidase, and dipeptidyl aminotransferase) is a lysosomal cysteinyl protease of the papain family involved in the intracellular degradation of proteins. Isolated enzyme assays for DPP1 activity using a variety of synthetic substrates such as dipeptide or peptide linked to amino-methyl-coumarin (AMC) or other fluorophores are well established. There is, however, no report of a simple whole-cell-based assay for measuring lysosomal DPP1 activity other than the use of flow cytometry (fluorescence-activated cell sorting) or the use of invasive activity-based probes or the production of physiological products such as neutrophil elastase. The authors investigated a number of DPP1 fluorogenic substrates that have the potential to access the lysosome and enable the measurement of DPP1 enzyme activity in situ. They describe the development and evaluation of a simple noninvasive fluorescence assay for measuring DPP1 activity in fresh or cryopreserved human THP-1 cells using the substrate H-Gly-Phe-AFC (amino-fluoro-coumarin). This cell-based fluorescence assay can be performed in a 96-well plate format and is ideally suited for determining the cell potency of potential DPP1 enzyme inhibitors.

  9. Photon statistics and dynamics of Fluorescence Resonance Energy Transfer

    OpenAIRE

    Berglund, Andrew J.; Doherty, Andrew C.; Mabuchi, Hideo

    2002-01-01

    We report high time-resolution measurements of photon statistics from pairs of dye molecules coupled by fluorescence resonance energy transfer (FRET). In addition to quantum-optical photon antibunching, we observe photon bunching on a time scale of several nanoseconds. We show by numerical simulation that configuration fluctuations in the coupled fluorophore system could account for minor deviations of our data from predictions of basic Förster theory. With further characterization we believe...

  10. Resonance fluorescence of a trapped three-level atom

    CERN Document Server

    Bienert, M; Morigi, G; Bienert, Marc; Merkel, Wolfgang; Morigi, Giovanna

    2003-01-01

    We investigate theoretically the spectrum of resonance fluorescence of a harmonically trapped atom, whose internal transitions are $\\Lambda$--shaped and driven at two-photon resonance by a pair of lasers, which cool the center--of--mass motion. For this configuration, photons are scattered only due to the mechanical effects of the quantum interaction between light and atom. We study the spectrum of emission in the final stage of laser--cooling, when the atomic center-of-mass dynamics is quantum mechanical and the size of the wave packet is much smaller than the laser wavelength (Lamb--Dicke limit). We use the spectral decomposition of the Liouville operator of the master equation for the atomic density matrix and apply second order perturbation theory. We find that the spectrum of resonance fluorescence is composed by two narrow sidebands -- the Stokes and anti-Stokes components of the scattered light -- while all other signals are in general orders of magnitude smaller. For very low temperatures, however, th...

  11. Fluorescence assay for glycan expression on living cancer cells based on competitive strategy coupled with dual-functionalized nanobiocomposites.

    Science.gov (United States)

    Fu, Ying; Lu, Danqin; Lin, Bin; Sun, Qianqian; Liu, Kai; Xu, Lili; Zhang, Shengping; Hu, Chen; Wang, Chuangui; Xu, Zhiai; Zhang, Wen

    2013-11-21

    Cell surface glycans are a class of sophisticated biomolecules related to cancer development and progression, and their analysis is of great significance for early cancer diagnosis and treatment. In this paper, we proposed a fluorescence assay to evaluate glycan expression on living cancer cells based on a competitive strategy coupled with dual-functionalized nanobiocomposites. The competitive assay was conducted between living cancer cells and thiomannosyl derivatives using concanavalin A (Con A)-modified electrode as the interaction platform. To impart fluorescence signaling ability to competitive derivatives, quantum dots (QDs) were anchored on BSA-protected Au nanoparticles, and thiomannosyl derivatives were further immobilized on the nanoparticle surface through Au-S binding. Due to the spacing between QDs and Au nanoparticles by BSA, the {QDs-Au-BSA-mannose} nanobiocomposites maintained the fluorescence of QDs and showed binding ability with the Con A-modified electrode. Au nanorods (AuNRs)-modified electrode was used as an effective substrate to immobilize Con A. This assay was successfully applied to the analysis of two cancer cells lines (A549 and QGY-7701). The method is simple and shows promise for the study of glycan expression on living cancer cells.

  12. A cell-based fluorescent glucose transporter assay for SGLT2 inhibitor discovery

    OpenAIRE

    Yi Huan; Linyi Li; Quan Liu; Shuainan Liu; Zhufang Shen

    2013-01-01

    The sodium/glucose cotransporter 2 (SGLT2) is responsible for the majority of glucose reabsorption in the kidney, and currently, SGLT2 inhibitors are considered as promising hypoglycemic agents for the treatment of type 2 diabetes mellitus. By constructing CHO cell lines that stably express the human SGLT2 transmembrane protein, along with a fluorescent glucose transporter assay that uses 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]2-deoxyglucose (2-NBDG) as a glucose analog, we have develo...

  13. Fluorescence In situ Hybridization: Cell-Based Genetic Diagnostic and Research Applications.

    Science.gov (United States)

    Cui, Chenghua; Shu, Wei; Li, Peining

    2016-01-01

    Fluorescence in situ hybridization (FISH) is a macromolecule recognition technology based on the complementary nature of DNA or DNA/RNA double strands. Selected DNA strands incorporated with fluorophore-coupled nucleotides can be used as probes to hybridize onto the complementary sequences in tested cells and tissues and then visualized through a fluorescence microscope or an imaging system. This technology was initially developed as a physical mapping tool to delineate genes within chromosomes. Its high analytical resolution to a single gene level and high sensitivity and specificity enabled an immediate application for genetic diagnosis of constitutional common aneuploidies, microdeletion/microduplication syndromes, and subtelomeric rearrangements. FISH tests using panels of gene-specific probes for somatic recurrent losses, gains, and translocations have been routinely applied for hematologic and solid tumors and are one of the fastest-growing areas in cancer diagnosis. FISH has also been used to detect infectious microbias and parasites like malaria in human blood cells. Recent advances in FISH technology involve various methods for improving probe labeling efficiency and the use of super resolution imaging systems for direct visualization of intra-nuclear chromosomal organization and profiling of RNA transcription in single cells. Cas9-mediated FISH (CASFISH) allowed in situ labeling of repetitive sequences and single-copy sequences without the disruption of nuclear genomic organization in fixed or living cells. Using oligopaint-FISH and super-resolution imaging enabled in situ visualization of chromosome haplotypes from differentially specified single-nucleotide polymorphism loci. Single molecule RNA FISH (smRNA-FISH) using combinatorial labeling or sequential barcoding by multiple round of hybridization were applied to measure mRNA expression of multiple genes within single cells. Research applications of these single molecule single cells DNA and RNA FISH

  14. Performance of a Cyanobacteria Whole Cell-Based Fluorescence Biosensor for Heavy Metal and Pesticide Detection

    Directory of Open Access Journals (Sweden)

    Salmijah Surif

    2013-05-01

    Full Text Available Whole cell biosensors always face the challenge of low stability of biological components and short storage life. This paper reports the effects of poly(2-hydroxyethyl methacrylate (pHEMA immobilization on a whole cell fluorescence biosensor for the detection of heavy metals (Cu, Pb, Cd, and pesticides (dichlorophenoxyacetic acid (2,4-D, and chlorpyrifos. The biosensor was produced by entrapping the cyanobacterium Anabaena torulosa on a cellulose membrane, followed by applying a layer of pHEMA, and attaching it to a well. The well was then fixed to an optical probe which was connected to a fluorescence spectrophotometer and an electronic reader. The optimization of the biosensor using several factors such as amount of HEMA and drying temperature were undertaken. The detection limits of biosensor without pHEMA for Cu, Cd, Pb, 2,4-D and chlorpyrifos were 1.195, 0.027, 0.0100, 0.025 and 0.025 µg/L respectively. The presence of pHEMA increased the limits of detection to 1.410, 0.250, 0.500, 0.235 and 0.117 µg/L respectively. pHEMA is known to enhance the reproducibility of the biosensor with average relative standard deviation (RSD of ±1.76% for all the pollutants tested, 48% better than the biosensor without pHEMA (RSD = ±3.73%. In storability test with Cu 5 µg/L, the biosensor with pHEMA performed 11.5% better than the test without pHEMA on day-10 and 5.2% better on day-25. pHEMA is therefore a good candidate to be used in whole cell biosensors as it increases reproducibility and enhances biosensor storability.

  15. A Label-Free Microfluidic Biosensor for Activity Detection of Single Microalgae Cells Based on Chlorophyll Fluorescence

    Directory of Open Access Journals (Sweden)

    Junsheng Wang

    2013-11-01

    Full Text Available Detection of living microalgae cells is very important for ballast water treatment and analysis. Chlorophyll fluorescence is an indicator of photosynthetic activity and hence the living status of plant cells. In this paper, we developed a novel microfluidic biosensor system that can quickly and accurately detect the viability of single microalgae cells based on chlorophyll fluorescence. The system is composed of a laser diode as an excitation light source, a photodiode detector, a signal analysis circuit, and a microfluidic chip as a microalgae cell transportation platform. To demonstrate the utility of this system, six different living and dead algae samples (Karenia mikimotoi Hansen, Chlorella vulgaris, Nitzschia closterium, Platymonas subcordiformis, Pyramidomonas delicatula and Dunaliella salina were tested. The developed biosensor can distinguish clearly between the living microalgae cells and the dead microalgae cells. The smallest microalgae cells that can be detected by using this biosensor are 3 μm ones. Even smaller microalgae cells could be detected by increasing the excitation light power. The developed microfluidic biosensor has great potential for in situ ballast water analysis.

  16. Assessment of Nuclear Resonance Fluorescence for Spent Nuclear Fuel Assay

    Energy Technology Data Exchange (ETDEWEB)

    Quiter, Brian; Ludewigt, Bernhard; Ambers, Scott

    2011-06-30

    In nuclear resonance fluorescence (NRF) measurements, resonances are excited by an external photon beam leading to the emission of gamma rays with specific energies that are characteristic of the emitting isotope. NRF promises the unique capability of directly quantifying a specific isotope without the need for unfolding the combined responses of several fissile isotopes as is required in other measurement techniques. We have analyzed the potential of NRF as a non-destructive analysis technique for quantitative measurements of Pu isotopes in spent nuclear fuel (SNF). Given the low concentrations of 239Pu in SNF and its small integrated NRF cross sections, the main challenge in achieving precise and accurate measurements lies in accruing sufficient counting statistics in a reasonable measurement time. Using analytical modeling, and simulations with the radiation transport code MCNPX that has been experimentally tested recently, the backscatter and transmission methods were quantitatively studied for differing photon sources and radiation detector types. Resonant photon count rates and measurement times were estimated for a range of photon source and detection parameters, which were used to determine photon source and gamma-ray detector requirements. The results indicate that systems based on a bremsstrahlung source and present detector technology are not practical for high-precision measurements of 239Pu in SNF. Measurements that achieve the desired uncertainties within hour-long measurements will either require stronger resonances, which may be expressed by other Pu isotopes, or require quasi-monoenergetic photon sources with intensities that are approximately two orders of magnitude higher than those currently being designed or proposed.This work is part of a larger effort sponsored by the Next Generation Safeguards Initiative to develop an integrated instrument, comprised of individual NDA techniques with complementary features, that is fully capable of

  17. Imaging of surfaces by surface plasmon resonance and surface plasmon resonance-enhanced fluorescence

    Science.gov (United States)

    Thariani, Rahber A.

    An instrument system capable of concurrent imaging of surfaces by surface plasmon resonance microscopy (SPRM) and surface plasmon resonance-enhanced fluorescence (SPRF) is presented. A conventional laser pointer is adopted as a light source, and a reflective diffuser coupled to an acoustic transducer is used to remove speckle artifacts due to coherent beam interference. Both SPRM and SPRF systems are characterized, and a careful choice of widely available, inexpensive, off-the-shelf components allows the entire system to be constructed at low cost. A model streptavidin-biotin system is explored utilizing the different modalities of the instrument. Applications of the system include mobile, cost-effective point-of-care diagnostics system and research laboratories in resource-limited settings where cost efficacy is a prime concern.

  18. Construction of Cell-based Neurotransmitter Fluorescent Engineered Reporters (CNiFERs) for Optical Detection of Neurotransmitters In Vivo.

    Science.gov (United States)

    Lacin, Emre; Muller, Arnaud; Fernando, Marian; Kleinfeld, David; Slesinger, Paul A

    2016-01-01

    Cell-based neurotransmitter fluorescent engineered reporters (CNiFERs) provide a new tool for neuroscientists to optically detect the release of neurotransmitters in the brain in vivo. A specific CNiFER is created from a human embryonic kidney cell that stably expresses a specific G protein-coupled receptor, which couples to Gq/11 G proteins, and a FRET-based Ca(2+)-detector, TN-XXL. Activation of the receptor leads to an increase in the FRET signal. CNiFERs have nM sensitivity and a temporal response of seconds because a CNiFER clone utilizes the native receptor for a particular neurotransmitter, e.g., D2R for dopamine. CNiFERs are directly implanted into the brain, enabling them to sense neurotransmitter release with a spatial resolution of less than one hundred µm, making them ideal to measure volume transmission in vivo. CNiFERs can also be used to screen other drugs for potential cross-reactivity in vivo. We recently expanded the family of CNiFERs to include GPCRs that couple to Gi/o G proteins. CNiFERs are available for detecting acetylcholine (ACh), dopamine (DA) and norepinephrine (NE). Given that any GPCR can be used to create a novel CNiFER and that there are approximately 800 GPCRs in the human genome, we describe here the general procedure to design, realize, and test any type of CNiFER. PMID:27214050

  19. A novel cell-based duplex high-throughput screening assay combining fluorescent Ca(2+) measurement with homogeneous time-resolved fluorescence technology.

    Science.gov (United States)

    Kiss, László; Cselenyák, Attila; Varga, Ágnes; Visegrády, András

    2016-08-15

    Cell-based assays for G-protein-coupled receptor (GPCR) activation applied in high-throughput screening (HTS) monitor various readouts for second messengers or intracellular effectors. Recently, our understanding of diverging signaling pathways downstream of receptor activation and the capability of small molecules to selectively modulate signaling routes has increased substantially, underlining the importance of selecting appropriate readouts in cellular functional screens. To minimize the rate of false negatives in large-scale screening campaigns, it is crucial to maximize the chance of a ligand being detected, and generally applicable methods for detecting multiple analytes from a single well might serve this purpose. The few assays developed so far based on multiplexed GPCR readouts are limited to only certain applications and usually rely on genetic manipulations hindering screening in native or native-like cellular systems. Here we describe a more generally applicable and HTS-compatible homogeneous assay based on the combination of fluorometric detection of [Ca(2+)] with subsequent homogeneous time-resolved fluorescence (HTRF) cAMP readout in the same well. Besides describing development and validation of the assay, using a cell line recombinantly expressing the human PTH1 receptor screening of a small library is also presented, demonstrating the robustness and HTS compatibility of the novel paradigm. PMID:27235172

  20. A novel cell-based duplex high-throughput screening assay combining fluorescent Ca(2+) measurement with homogeneous time-resolved fluorescence technology.

    Science.gov (United States)

    Kiss, László; Cselenyák, Attila; Varga, Ágnes; Visegrády, András

    2016-08-15

    Cell-based assays for G-protein-coupled receptor (GPCR) activation applied in high-throughput screening (HTS) monitor various readouts for second messengers or intracellular effectors. Recently, our understanding of diverging signaling pathways downstream of receptor activation and the capability of small molecules to selectively modulate signaling routes has increased substantially, underlining the importance of selecting appropriate readouts in cellular functional screens. To minimize the rate of false negatives in large-scale screening campaigns, it is crucial to maximize the chance of a ligand being detected, and generally applicable methods for detecting multiple analytes from a single well might serve this purpose. The few assays developed so far based on multiplexed GPCR readouts are limited to only certain applications and usually rely on genetic manipulations hindering screening in native or native-like cellular systems. Here we describe a more generally applicable and HTS-compatible homogeneous assay based on the combination of fluorometric detection of [Ca(2+)] with subsequent homogeneous time-resolved fluorescence (HTRF) cAMP readout in the same well. Besides describing development and validation of the assay, using a cell line recombinantly expressing the human PTH1 receptor screening of a small library is also presented, demonstrating the robustness and HTS compatibility of the novel paradigm.

  1. On-Resonance Fluorescence, Resonance Rayleigh Scattering, and Ratiometric Resonance Synchronous Spectroscopy of Molecular- and Quantum Dot-Fluorophores.

    Science.gov (United States)

    Siriwardana, Kumudu; Nettles, Charles B; Vithanage, Buddhini C N; Zhou, Yadong; Zou, Shengli; Zhang, Dongmao

    2016-09-20

    Existing studies on molecular fluorescence have almost exclusively been focused on Stokes-shifted fluorescence spectroscopy (SSF) in which the emitted photon is detected at the wavelengths longer than that for the excitation photons. Information on fluorophore on-resonance fluorescence (ORF) and resonance Rayleigh scattering (RRS) is limited and often problematic due to the complex interplay of the fluorophore photon absorption, ORF emission, RRS, and solvent Rayleigh scattering. Reported herein is a relatively large-scale systematic study on fluorophore ORF and RRS using the conventional UV-vis extinction and SSF measurements in combination with the recently reported ratiometric resonance synchronous spectroscopic (R2S2, pronounced as "R-Two-S-Two") method. A series of fundamental parameters including fluorophore ORF cross sections and quantum yields have been quantified for the first time for a total of 12 molecular and 6 semiconductor quantum dot (QD) fluorophores. All fluorophore spectra comprise a well-defined Gaussian peak with a full width at half-maximum ranging from 4 to 30 nm. However, the RRS features of fluorophores differ drastically. The effect of fluorophore aggregation on its RRS, UV-vis, R2S2, and SSF spectra was also discussed. This work highlights the critical importance of the combined UV-vis extinction, SSF, and R2S2 spectroscopic measurements for material characterizations. The method and insights described in this work can be directly used for improving the reliability of RRS spectroscopic methods in chemical analysis. In addition, it should pave the way for developing novel R2S2-based analytical applications.

  2. Nuclear Resonance Fluorescence for Material Verification in Dismantlement

    International Nuclear Information System (INIS)

    Nuclear resonance fluorescence (NRF) is a well-established physical process that provides an isotope-specific signature that can be exploited for isotopic detection and characterization of samples. Pacific Northwest National Laboratory has been investigating possible applications of NRF for national security. Of the investigated applications, the verification of material in the dismantlement process is the most promising. Through a combination of benchmarking measurements and radiation transport modeling, we have shown that NRF techniques with existing bremsstrahlung photon sources and a modest detection system can be used to detect highly enriched uranium in the quantities and time limits relevant to the dismantlement process. Issues such as orientation, placement and material geometry do not significantly impact the sensitivity of the technique. We have also investigated how shielding of the uranium would be observed through non-NRF processes to enable the accurate assay of the material. This paper will discuss our findings on how NRF and photon-interrogation techniques may be applied to the material verification in the dismantlement process.

  3. Simulations of nuclear resonance fluorescence in GEANT4

    Energy Technology Data Exchange (ETDEWEB)

    Lakshmanan, Manu N., E-mail: mnL7@duke.edu [Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University Medical Center, Durham, NC (United States); Harrawood, Brian P. [Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University Medical Center, Durham, NC (United States); Rusev, Gencho [Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM (United States); Agasthya, Greeshma A.; Kapadia, Anuj J. [Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University Medical Center, Durham, NC (United States)

    2014-11-01

    The nuclear resonance fluorescence (NRF) technique has been used effectively to identify isotopes based on their nuclear energy levels. Specific examples of its modern-day applications include detecting spent nuclear waste and cargo scanning for homeland security. The experimental designs for these NRF applications can be more efficiently optimized using Monte Carlo simulations before the experiment is implemented. One of the most widely used Monte Carlo physics simulations is the open-source toolkit GEANT4. However, NRF physics has not been incorporated into the GEANT4 simulation toolkit in publicly available software. Here we describe the development and testing of an NRF simulation in GEANT4. We describe in depth the development and architecture of this software for the simulation of NRF in any isotope in GEANT4; as well as verification and validation testing of the simulation for NRF in boron. In the verification testing, the simulation showed agreement with the analytical model to be within 0.6% difference for boron and iron. In the validation testing, the simulation showed agreement to be within 20.5% difference with the experimental measurements for boron, with the percent difference likely due to small uncertainties in beam polarization, energy distribution, and detector composition.

  4. Controlled degradation stochastic resonance in adaptive averaging cell-based architectures

    OpenAIRE

    Aymerich Capdevila, Nivard; Cotofana, Sorin; Rubio Sola, Jose Antonio

    2013-01-01

    In this paper, we first analyze the degradation stochastic resonance (DSR) effect in the context of adaptive averaging (AD-AVG) architectures. The AD-AVG is the adaptive version of the well-known AVG architecture . It is an optimized fault-tolerant design for future technologies with very high rates of failures and defects. With system degradation the AD-AVG reliability is diminishing, as expected, but at a certain moment in time it increases due to the DSR occurrence, which is counterintuiti...

  5. Biomolecular interactions probed by fluorescence resonance energy transfer

    Science.gov (United States)

    Lange, Daniela Charlotte

    2000-09-01

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

  6. Titanium atom detection by resonance fluorescence excited with a nitrogen laser

    International Nuclear Information System (INIS)

    Coincidence of wave lengths of nitrogen laser basing lines and resonance transitions in titanium atom is investigated. It is shown that resonance fluorescence excited by nitrogen laser can be used for absolute titanium atom density measurements. Experiments on titanium atom detection in a vapour cloud formed under irradiation of a titanium target in vacuum by dye laser pulse, are conducted. Fluorescence extinguishing is observed under high evaporation power

  7. Direct observation of resonance tryptophan-to-chromophore energy transfer in visible fluorescent proteins

    NARCIS (Netherlands)

    Visser, NV; Borst, JW; Hink, MA; van Hoek, A; Visser, AJWG

    2005-01-01

    Visible fluorescent proteins from Aequorea victoria contain next to the fluorophoric group a single tryptophan residue. Both molecules form a single donor-acceptor pair for resonance energy transfer (RET) within the protein. Time-resolved fluorescence experiments using tryptophan excitation have sho

  8. Resonance Fluorescence in Two-Photon JC Models Analyzed by Supersymmetric Transformation

    Institute of Scientific and Technical Information of China (English)

    LIANG Xian-Ting; SUN Ming-Zhai

    2002-01-01

    Resonance fluorescences of two-photon two-level and two-photon three-level atoms driven by laser are investigated with supersymmetric transformation.It is shown that the spectrum of fluorescent light obtained from the supersymmetric transformation is more accurate and the physical process shown by this method is clearer than that from dress transformation.

  9. Emission wavelength tuning of fluorescence by fine structural control of optical metamaterials with Fano resonance

    Science.gov (United States)

    Moritake, Y.; Kanamori, Y.; Hane, K.

    2016-09-01

    We demonstrated fine emission wavelength tuning of quantum dot (QD) fluorescence by fine structural control of optical metamaterials with Fano resonance. An asymmetric-double-bar (ADB), which was composed of only two bars with slightly different bar lengths, was used to obtain Fano resonance in the optical region. By changing the short bar length of ADB structures with high dimensional accuracy in the order of 10 nm, resonant wavelengths of Fano resonance were controlled from 1296 to 1416 nm. Fluorescence of QDs embedded in a polymer layer on ADB metamaterials were modified due to coupling to Fano resonance and fine tuning from 1350 to 1376 nm was observed. Wavelength tuning of modified fluorescence was reproduced by analysis using absorption peaks of Fano resonance. Tuning range of modified fluorescence became narrow, which was interpreted by a simple Gaussian model and resulted from comparable FWHM in QD fluorescence and Fano resonant peaks. The results will help the design and fabrication of metamaterial devices with fluorophores such as light sources and biomarkers.

  10. Emission wavelength tuning of fluorescence by fine structural control of optical metamaterials with Fano resonance.

    Science.gov (United States)

    Moritake, Y; Kanamori, Y; Hane, K

    2016-09-13

    We demonstrated fine emission wavelength tuning of quantum dot (QD) fluorescence by fine structural control of optical metamaterials with Fano resonance. An asymmetric-double-bar (ADB), which was composed of only two bars with slightly different bar lengths, was used to obtain Fano resonance in the optical region. By changing the short bar length of ADB structures with high dimensional accuracy in the order of 10 nm, resonant wavelengths of Fano resonance were controlled from 1296 to 1416 nm. Fluorescence of QDs embedded in a polymer layer on ADB metamaterials were modified due to coupling to Fano resonance and fine tuning from 1350 to 1376 nm was observed. Wavelength tuning of modified fluorescence was reproduced by analysis using absorption peaks of Fano resonance. Tuning range of modified fluorescence became narrow, which was interpreted by a simple Gaussian model and resulted from comparable FWHM in QD fluorescence and Fano resonant peaks. The results will help the design and fabrication of metamaterial devices with fluorophores such as light sources and biomarkers.

  11. Optical resonance shifts in the fluorescence imaging of thermal and cold Rubidium atomic gases

    CERN Document Server

    Jenkins, S D; Javanainen, J; Bourgain, R; Jennewein, S; Sortais, Y R P; Browaeys, A

    2016-01-01

    We show that the resonance shifts in fluorescence of a cold gas of rubidium atoms substantially differ from those of thermal atomic ensembles that obey the standard continuous medium electrodynamics. The analysis is based on large-scale microscopic numerical simulations and experimental measurements of the resonance shifts in a steady-state response in light propagation.

  12. Magnification of photonic crystal fluorescence enhancement via TM resonance excitation and TE resonance extraction on a dielectric nanorod surface

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Hsin-Yu; Cunningham, Brian T [Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 1406 W Green Street, Urbana, IL 61801 (United States); Zhang Wei [Department of Material Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W Green Street, Urbana, IL 61801 (United States); Mathias, Patrick C, E-mail: bcunning@illinois.edu [Department of Bioengineering, University of Illinois at Urbana-Champaign, 1304 W Springfield Avenue, Urbana, IL 61801 (United States)

    2010-03-26

    Using a one-dimensional grating surface photonic crystal (PC), we experimentally demonstrate that the detection of fluorescent molecules on a PC surface can be substantially magnified through the combined effects of resonance-enhanced excitation of the fluorescent dye, resonance-enhanced extraction of the fluorescence emission and a dielectric nanorod surface coating increasing the surface area available for fluorophore-PC interaction. Enhanced excitation is obtained by engineering a high-Q TM resonant mode to efficiently couple with an incident TM-polarized {lambda} = 633 nm laser for exciting Cyanine-5 (Cy5). Enhanced extraction results from a low-Q TE resonance designed to spectrally overlap the Cy5 emission spectrum for channeling TE-polarized emission towards the detection instrument. The entire PC surface is coated with a porous film of TiO{sub 2} nanorods that allows more fluorophores to penetrate into the region of enhanced near-electric fields. Experimental results reveal a 588-fold enhancement in fluorescence intensity relative to an unpatterned glass surface.

  13. Emission dynamics in QD systems: from single QD resonance fluorescence to many-emitter laser switching

    DEFF Research Database (Denmark)

    Lorke, Michael; Lund, Anders Mølbjerg; Nielsen, Per Kær;

    2012-01-01

    and photonic confinement. This combination opens the possibility to exploit the Purcell effect to enhance and direct the photon emission. In this contribution, we investigate multiple facets of the emission dynamics in semiconductor QDs, ranging from the resonance fluorescence of QDs under pulsed excitation...... to the switch-on behavior of QD based nanolasers. Recently the resonance fluorescence from semicoductor QDs has recieved considerable attention [1]. We show that for the case of pulsed excitation the resonance fluorescence spectrum of a quantum dot contains multiple side peaks beyond those of the Mollow triplet...... evidence for the suggested physical explanation. Additionally, we investigate the dynamical properties of InGaAs QD based nanolasers, combining a microscopic treatment of carrier scattering with a quantum-kinetic description of the carrier-photon interaction that also allows to study the coherence...

  14. 基于荧光检测的新型细胞传感器%Novel Cell-based Biosensors Based on Measurement of Fluorescence

    Institute of Scientific and Technical Information of China (English)

    辛文文; 王景林

    2011-01-01

    The diagnosis of infectious diseases, the monitoring of environment and detection of potential bioterrorism agents greatly require a pathogen identification method with better combined speed, accuracy and sensitivity. Here, a kind of novel cell-based biosensors based on measurement of fluorescence is introduced, which could detect pathogens and other antigens by measuring fluorescent signals within minutes. It is based on the specifically bind character of antigens and antibodies and the theory of bioluminescence or chemiluminescence.The cell could emit light via calcium chemically fluorescent indicators such as Fluo-4, or calcium fluorescent proteins such as aequorin, green fluorescent protein. B cell-based biosensors and mast cell-based biosensors have been applied in some fields. This kind of biosensors has advantages in combined sensitivity, accuracy and speed,while it also has disadvantages such as cross reactivity and problems with cellular storage and maintenance. This is a promising kind of biosensors applied in the diagnosis of infectious diseases, the monitoring of environment and detection of potential bioterrorism agents.%主要介绍了一类基于荧光检测的新型细胞传感器,这类传感器利用免疫细胞表面分子特异性识别、结合抗原的特性和生物(或化学)发光技术,通过检测荧光信号在数分钟内达到检测病原体或其他抗原的目的.这类传感器的发光原理主要是利用钙离子敏感型化学荧光探针发光,如Fluo-4等,或钙离子敏感型发光蛋自发光,如水母发光蛋白、绿色荧光蛋白等.现在已经应用的主要是B细胞传感器和肥大细胞传感器.这类传感器具有灵敏度高、检测准确、反应速度快的优点.同时又存在交叉反应、细胞不易保存等不足之处.这类传感器在疾病诊断、环境监测、生物战剂检测等领域具有较大的应用前景.

  15. The stationary resonance fluorescence of a two-level atom in a cat-state field

    Science.gov (United States)

    Tomilin, V. A.; Il'ichov, L. V.

    2016-09-01

    We investigate the resonance fluorescence of a two-level atom placed in non-classical field which is a superposition of Glauber coherent states. The source of this superposition known under the common name of 'Schrödinger cat'-states is explicitly incorporated into the model. This let us to explore the stationary regime. In the strong (multiphoton) field limit the steady-state of the atom+photons system is found. We evaluated the spectrum of the resonance fluorescence. It appears to be one-component in contrast to the case with the classical external field.

  16. Monitoring p21 mRNA expression in living cell based on molecular beacon fluorescence increasing rate

    Institute of Scientific and Technical Information of China (English)

    TANG HongXing; YANG XiaoHai; WANG KeMin; TAN WeiHong; LIU Bin; HE LiFang; WANG Wei

    2008-01-01

    Studying the expression level of mRNA in living cells will offer tremendous opportunities for ad-vancement in cell biology research, disease diagnostics, and drug discovery. In this paper, a molecular beacon (MB) specific for the important tumor suppressor gene p21 has been designed and synthesized. The fluorescence signal was detected in real-time after the MB entered the cytoplasm of nasopharyn-geal carcinoma cells. After injecting the p21MB into nasopharyngeal carcinoma cell and p33-trans-fected nasopharyngeal carcinoma cell, the consistent increase of fluorescent signal intensity was de-tected in both cell lines, and maximum fluorescence intensity achieved in about 15 min. In about 4 min following microinjection, the fluorescence increasing rate was significantly different between these two cell lines, which indicate the different p21 mRNA expression levels. The results obtained in the real-time detection were also validated by RT-PCR. Analysis of the initial fluorescence increasing rate can effi-ciently reduce the side effect of enzyme and improve the accuracy in living cell mRNA detection.

  17. Determination of level widths in 15N using nuclear resonance fluorescence

    Directory of Open Access Journals (Sweden)

    Szücs T.

    2015-01-01

    Full Text Available Level widths in 15N have been measured with the nuclear resonance fluorescence (NRF technique. Solid nitrogen compounds, bremsstrahlung, and HPGe detectors have been used as target, beam, and detectors, respectively. The preliminarily level widths are in agreement with the literature values, but more precise.

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

    Science.gov (United States)

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

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

    Science.gov (United States)

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

  20. A fluorescence resonance energy transfer-based method for histone methyltransferases

    DEFF Research Database (Denmark)

    Devkota, Kanchan; Lohse, Brian; Nyby Jakobsen, Camilla;

    2015-01-01

    A simple dye–quencher fluorescence resonance energy transfer (FRET)-based assay for methyltransferases was developed and used to determine kinetic parameters and inhibitory activity at EHMT1 and EHMT2. Peptides mimicking the truncated histone H3 tail were functionalized in each end with a dye...

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

    Science.gov (United States)

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

    2016-01-01

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

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

    Science.gov (United States)

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

    2016-01-01

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

  3. Study on the interaction between diphenhydramine and erythrosin by absorption, fluorescence and resonance Rayleigh scattering spectra

    Institute of Scientific and Technical Information of China (English)

    TANG XiaoLing; LIU ZhongFang; LIU ShaoPu; HU XiaoLi

    2007-01-01

    In pH 4.5 Britton-Robinson (BR) buffer solution, erythrosin (ET) can react with diphenhydramine (DP) to form a 1:1 ion-association complex, which not only results in the change of the absorption spectra, but also results in the great enhancement of resonance Rayleigh scattering (RRS) and the quenching of fluorescence. Furthermore, a new RRS spectrum will appear, and the maximum RRS wavelength was located at about 580 nm.In this work, the spectral characteristics of the absorption, fluorescence and RRS, the optimum conditions of the reaction and the properties of an analytical chemistry were investigated. A sensitive, simple and new method for the determination of DP by using erythrosin as a probe has been developed. The detection limits for DP were 0.0020 μg/mL for RRS method, 0.088 μg/mL for absorption method and 0.094 μg/mL for fluorophotometry. There was a linear relationship between the absorbance, RRS and fluorescence intensities and the drug concentration in the range of 0.0067-2.0, 0.29-6.4 and 0.31-3.2 μg/mL, respectively. The effects of the interaction of diphenhydramine and erythrosin on the absorption, fluorescence and resonance Rayleigh scattering spectra were discussed. In light polarization experiment, the polarization of RRS at maximum wavelength was measured to be P = 0.9779, and it revealed that the RRS spectrum of DP-ET complex consists mostly of resonance scattering and few resonance fluorescence. In this study, enthalpy of formation and mean polarizability were calculated by AM1 quantum chemistry method. In addition, the reaction mechanism and the reasons for the enhancement of scattering spectra and the energy transfer between absorption, fluorescence and RRS were discussed.

  4. A Dual Readout Assay Based on Fluorescence Polarization and Time-Resolved Fluorescence Resonance Energy Transfer to Screen for RSK1 Inhibitors.

    Science.gov (United States)

    Jeong, Eun-mi; Lee, Mi Young; Lee, Jeong Hyun; Lee, Byung Ho; Oh, Kwang-Seok

    2016-01-01

    A dual readout assay based on fluorescence polarization (FP) and time-resolved fluorescence resonance energy transfer (TR-FRET) exhibits many advantages over single assay technology in terms of screening quality and efficiency. In this study, we developed a dual readout assay combining FP and TR-FRET to identify ribosomal S6 kinase 1 (RSK1) inhibitors. This dual readout assay can monitor both FP and TR-FRET signals from a single RSK1 kinase reaction by using the immobilized metal affinity for phosphochemical (IMAP)-based assay. The Z' value and signal to background (S/B) ratio were 0.85 and 4.0 using FP, and 0.79 and 10.6 using TR-FRET, which led to performance of a pilot library screening against the drug repositioning set consisting of 2320 compounds with a reasonable reproducibility. From this screening, we identified 16 compounds showing greater than 50% inhibition against RSK1 for both FP and TR-FRET; 6 compounds with greater than 50% inhibition only for FP; and 4 compounds with greater than 50% inhibition only for TR-FRET. In a cell-based functional assay to validate the hit compounds, 10 compounds identified only in a single assay had little effect on the RSK-mediated phosphorylation of liver kinase B1, whereas 5 compounds showing greater than 80% inhibition for both FP and TR-FRET reduced the phosphorylation of liver kinase B1. These results demonstrate that the dual readout assay can be used to identify hit compounds by subsequently monitoring both FP and TR-FRET signals from one RSK1 reaction. PMID:27040627

  5. Lambda/4 resonance of an optical monopole antenna probed by single molecule fluorescence.

    Science.gov (United States)

    Taminiau, Tim H; Moerland, Robert J; Segerink, Frans B; Kuipers, Laurens; van Hulst, Niek F

    2007-01-01

    We present a resonant optical nanoantenna positioned at the end of a metal-coated glass fiber near-field probe. Antenna resonances, excitation conditions, and field localization are directly probed in the near field by single fluorescent molecules and compared to finite integration technique simulations. It is shown that the antenna is equivalent to its radio frequency analogue, the monopole antenna. For the right antenna length and local excitation conditions, antenna resonances occur that lead to an enhanced localized field near the antenna apex. Direct mapping of this field with single fluorescent molecules reveals a spatial localization of 25 nm, demonstrating the importance of such antennas for nanometer resolution optical microscopy. PMID:17212435

  6. Fluorescence resonance energy transfer from tryptophan in human serum albumin to a bioactive indoloquinolizine system

    Indian Academy of Sciences (India)

    Paramita Das; Arabinda Mallick; Basudeb Haldar; Alok Chakrabarty; Nitin Chattopadhyay

    2007-03-01

    The interaction between a bioactive molecule, 3-acetyl-4-oxo-6,7-dihydro-12H indolo-[2,3-a] quinolizine (AODIQ), with human serum albumin (HSA) has been studied using steady-state absorption and fluorescence techniques. A 1 : 1 complex formation has been established and the binding constant () and free energy change for the process have been reported. The AODIQ-HSA complex results in fluorescence resonance energy transfer (FRET) from the tryptophan moiety of HSA to the probe. The critical energy-transfer distance (0) for FRET and the Stern-Volmer constant (sv) for the fluorescence quenching of the donor in the presence of the acceptor have been determined. Importantly, SV has been shown to be equal to the binding constant itself, implying that the fluorescence quenching arises only from the FRET process. The study suggests that the donor and the acceptor are bound to the same protein at different locations but within the quenching distance.

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

    Science.gov (United States)

    Makarov, Dmitrii E.; Plaxco, Kevin W.

    2009-01-01

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

  8. Global analysis of Förster resonance energy transfer in live cells measured by fluorescence lifetime imaging microscopy exploiting the rise time of acceptor fluorescence

    NARCIS (Netherlands)

    Laptenok, S.; Borst, J.W.; Mullen, K.M.; Stokkum, van I.H.M.; Visser, A.J.W.G.; Amerongen, van H.

    2010-01-01

    A methodology is described for the quantitative determination of Förster resonance energy transfer (FRET) in live cells using the rise time of acceptor fluorescence as determined with fluorescence lifetime imaging microscopy (FLIM). An advantage of this method is that only those molecules that are i

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

    Science.gov (United States)

    Branchini, Bruce

    2016-01-01

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

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

    Science.gov (United States)

    Branchini, Bruce

    2016-01-01

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

  11. Discrete deexcitations in 235U from Nuclear Resonance Fluorescence

    Science.gov (United States)

    Kwan, E.; Howell, C. R.; Raut, R.; Rusev, G.; Tonchev, A. P.; Tornow, W.; Adekola, A. S.; Hammond, S. L.; Karwowski, H. J.; Pedroni, R.; Kelley, J. H.

    2010-11-01

    Systematics of the even-even rare-earth nuclei suggest a concentration of M1 excitations peaking around 3 MeV with a ∑B(M1) strength of ˜3μN^2. In addition, a linear dependence on the square of the ground-state deformation was observed in the systematics of the ∑B(M1) strengths. The actinide region is interesting for investigation of the ``scissors'' mode of M1 excitations because it has neutron-rich nuclei with large deformations. Evidence of M1 resonances concentrated around 2.0-2.5 MeV were found in ^238U & ^232Th. A research program has been initiated at TUNL to measure dipole transitions in the actinide using HIγS. Nearly monoenergic & circular polarized γ-ray beams below 3.0 MeV was used to measure transitions in ^235U. More than 20 transitions were observed. The integrated cross sections, B(M1) strengths & branching transitions intensities will be presented and compared with previous measurements.

  12. Observing interferences between past and future quantum states in resonance fluorescence.

    Science.gov (United States)

    Campagne-Ibarcq, P; Bretheau, L; Flurin, E; Auffèves, A; Mallet, F; Huard, B

    2014-05-01

    The fluorescence of a resonantly driven superconducting qubit is measured in the time domain, providing a weak probe of the qubit dynamics. Prior preparation and final, single-shot measurement of the qubit allows us to average fluorescence records conditionally on past and future knowledge. The resulting interferences reveal purely quantum features characteristic of weak values. We demonstrate conditional averages that go beyond classical boundaries and probe directly the jump operator associated with relaxation. The experimental results are remarkably captured by a recent theory, which generalizes quantum mechanics to open quantum systems whose past and future are known. PMID:24856677

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

    Science.gov (United States)

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

    2006-01-01

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

  14. Correlation functions in resonance fluorescence with spectral resolution: Signal-processing approach

    Science.gov (United States)

    Shatokhin, Vyacheslav N.; Kilin, Sergei Ya.

    2016-09-01

    In the framework of the signal processing approach to single-atom resonance fluorescence with spectral resolution, we diagrammatically derive an analytical formula for arbitrary-order spectral correlation functions of the scattered fields that pass through Fabry-Perot interferometers. Our general expression is then applied to study correlation signals in the limit of well separated spectral lines of the resonance fluorescence spectrum. In particular, we study the normalized second-order temporal intensity correlation functions in the case of the interferometers tuned to the components of the spectrum and obtain interferential corrections to the approximate results derived in the secular limit. In addition, we explore purely spectral correlations and show that they can fully be understood in terms of the two-photon cascades down the dressed state ladder.

  15. Fluorescence resonance energy transfer between conjugated molecules infiltrated in three-dimensional opal photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Lu; Sui, Ning; Wang, Ying-Hui, E-mail: yinghui_wang@jlu.edu.cn; Qian, Cheng; Ma, Yu-Guang; Zhang, Han-Zhuang, E-mail: zhanghz@jlu.edu.cn

    2015-02-15

    Fluorescence resonance energy transfer (FRET) from Coumarin 6 (C-6) to Sulforhodamine B (S-B) infiltrated into opal PMMA (poly-methyl-methacrylate) photonic crystals (PCs) has been studied in detail. The intrinsic mesh micro-porous structure of opal PCs could increase the luminescent efficiency through inhibiting the intermolecular interaction. Meanwhile, its structure of periodically varying refractive indices could also modify the FRET through affecting the luminescence characteristics of energy donor or energy acceptor. The results demonstrate that the FRET efficiency between conjugated dyes was easily modified by opal PCs. - Highlights: • We investigate the fluorescence resonance energy transfer between two kinds of dyes. • These two kinds of dyes are infiltrated in PMMA opal photonic crystals. • The structure of opal PCs could improve the luminescent characteristics. • The structure of opal PCs could improve the energy transfer characteristics.

  16. Denaturation studies of active-site labeled papain using electron paramagnetic resonance and fluorescence spectroscopy.

    OpenAIRE

    Ping, Z A; Butterfiel, D A

    1991-01-01

    A spin-labeled p-chloromercuribenzoate (SL-PMB) and a fluorescence probe, 6-acryloyl-2-dimethylaminonaphthalene (Acrylodan), both of which bind to the single SH group located in the active site of papain, were used to investigate the interaction of papain (EC 3.4.22.2) with two protein denaturants. It was found that the active site of papain was highly stable in urea solution, but underwent a large conformational change in guanidine hydrochloride solution. Electron paramagnetic resonance and ...

  17. Fluorescence resonance energy transfer sensors for quantitative monitoring of pentose and disaccharide accumulation in bacteria

    Directory of Open Access Journals (Sweden)

    Looger Loren L

    2008-06-01

    Full Text Available Abstract Background Engineering microorganisms to improve metabolite flux requires detailed knowledge of the concentrations and flux rates of metabolites and metabolic intermediates in vivo. Fluorescence resonance energy transfer sensors represent a promising technology for measuring metabolite levels and corresponding rate changes in live cells. These sensors have been applied successfully in mammalian and plant cells but potentially could also be used to monitor steady-state levels of metabolites in microorganisms using fluorimetric assays. Sensors for hexose and pentose carbohydrates could help in the development of fermentative microorganisms, for example, for biofuels applications. Arabinose is one of the carbohydrates to be monitored during biofuels production from lignocellulose, while maltose is an important degradation product of starch that is relevant for starch-derived biofuels production. Results An Escherichia coli expression vector compatible with phage λ recombination technology was constructed to facilitate sensor construction and was used to generate a novel fluorescence resonance energy transfer sensor for arabinose. In parallel, a strategy for improving the sensor signal was applied to construct an improved maltose sensor. Both sensors were expressed in the cytosol of E. coli and sugar accumulation was monitored using a simple fluorimetric assay of E. coli cultures in microtiter plates. In the case of both nanosensors, the addition of the respective ligand led to concentration-dependent fluorescence resonance energy transfer responses allowing quantitative analysis of the intracellular sugar levels at given extracellular supply levels as well as accumulation rates. Conclusion The nanosensor destination vector combined with the optimization strategy for sensor responses should help to accelerate the development of metabolite sensors. The new carbohydrate fluorescence resonance energy transfer sensors can be used for in vivo

  18. Intracellular ribozyme-catalyzed trans-cleavage of RNA monitored by fluorescence resonance energy transfer.

    OpenAIRE

    Vitiello, D; Pecchia, D B; Burke, J M

    2000-01-01

    Small catalytic RNAs like the hairpin ribozyme are proving to be useful intracellular tools; however, most attempts to demonstrate trans-cleavage of RNA by ribozymes in cells have been frustrated by rapid cellular degradation of the cleavage products. Here, we describe a fluorescence resonance energy transfer (FRET) assay that directly monitors cleavage of target RNA in tissue-culture cells. An oligoribonucleotide substrate was modified to inhibit cellular ribonuclease degradation without int...

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

    Science.gov (United States)

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

    2008-06-01

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

  20. Resonance fluorescence spectra from coherently driven quantum dots coupled to slow-light photonic crystal waveguides

    Science.gov (United States)

    Roy-Choudhury, Kaushik; Mann, Nishan; Manson, Ross; Hughes, Stephen

    2016-06-01

    Using a polaron master equation approach, we investigate the resonance fluorescence spectra from coherently driven quantum dots (QDs) coupled to an acoustic phonon bath and photonic crystal waveguides with a rich local density of photon states (LDOS). Resonance fluorescence spectra from QDs in semiconductor crystals are known to show strong signatures of electron-phonon interactions, but when coupled to a structured photonic reservoir, the QD emission properties are also determined by the frequency dependence of the LDOS of the photon reservoir. Here, we investigate the simultaneous role of coupled photon and phonon baths on the characteristic Mollow triplet spectra from a strongly driven QD. As an example structured photonic reservoir, we first study a photonic crystal coupled cavity waveguide, and find that photons and phonons have counterinteracting effects near the upper mode edge of the coupled-cavity waveguide, thus establishing the importance of their separate roles in determining the emission spectra. The general theory is developed for arbitrary photonic reservoirs and is further applied to determine the resonance fluorescence spectra from a realistic, disordered W1 photonic crystal waveguide showing important photon-phonon interaction effects that are directly relevant to emerging experiments and theoretical proposals.

  1. Paper-based fluorescence resonance energy transfer assay for directly detecting nucleic acids and proteins.

    Science.gov (United States)

    Li, Hua; Fang, Xueen; Cao, Hongmei; Kong, Jilie

    2016-06-15

    Paper-based fluorescence resonance energy transfer assay (FRET) is gaining great interest in detecting macro-biological molecule. It is difficult to achieve conveniently and fast detection for macro-biological molecule. Herein, a graphene oxide (GO)-based paper chip (glass fiber) integrated with fluorescence labeled single-stranded DNA (ssDNA) for fast, inexpensive and direct detection of biological macromolecules (proteins and nucleic acids) has been developed. In this paper, we employed the Cy3/FAM-labeled ssDNA as the reporter and the GO as quencher and the original glass fiber paper as data acquisition substrates. The chip which was designed and fabricated by a cutting machine is a miniature biosensor that monitors fluorescence recovery from resonance energy transfer. The hybridization assays and fluorescence detection were all simplified, and the surface of the chip did not require immobilization or washing. A Nikon Eclipse was employed as excited resource and a commercial digital camera was employed for capturing digital images. This paper-based microfluidics chip has been applied in the detection of proteins and nucleic acids. The biosensing capability meets many potential requirements for disease diagnosis and biological analysis. PMID:26807518

  2. Resonance fluorescence of strongly driven two-level system coupled to multiple dissipative reservoirs

    Science.gov (United States)

    Yan, Yiying; Lü, Zhiguo; Zheng, Hang

    2016-08-01

    We present a theoretical formalism for resonance fluorescence radiating from a two-level system (TLS) driven by any periodic driving and coupled to multiple reservoirs. The formalism is derived analytically based on the combination of Floquet theory and Born-Markov master equation. The formalism allows us to calculate the spectrum when the Floquet states and quasienergies are analytically or numerically solved for simple or complicated driving fields. We can systematically explore the spectral features by implementing the present formalism. To exemplify this theory, we apply the unified formalism to comprehensively study a generic model that a harmonically driven TLS is simultaneously coupled to a radiative reservoir and a dephasing reservoir. We demonstrate that the significant features of the fluorescence spectra, the driving-induced asymmetry and the dephasing-induced asymmetry, can be attributed to the violation of detailed balance condition, and explained in terms of the driving-related transition quantities between Floquet-states and their steady populations. In addition, we find the distinguished features of the fluorescence spectra under the biharmonic and multiharmonic driving fields in contrast with that of the harmonic driving case. In the case of the biharmonic driving, we find that the spectra are significantly different from the result of the RWA under the multiple resonance conditions. By the three concrete applications, we illustrate that the present formalism provides a routine tool for comprehensively exploring the fluorescence spectrum of periodically strongly driven TLSs.

  3. Magnetic Separation-Assistant Fluorescence Resonance Energy Transfer Inhibition for Highly Sensitive Probing of Nucleolin.

    Science.gov (United States)

    Li, Yan-Ran; Liu, Qian; Hong, Zhangyong; Wang, He-Fang

    2015-12-15

    For the widely used "off-on" fluorescence (or phosphorescence) resonance energy transfer (FRET or PRET) system, the separation of donors and acceptors species was vital for enhancing the sensitivity. To date, separation of free donors from FRET/PRET inhibition systems was somewhat not convenient, whereas separation of the target-induced far-between acceptors has hardly been reported yet. We presented here a novel magnetic separation-assistant fluorescence resonance energy transfer (MS-FRET) inhibition strategy for highly sensitive detection of nucleolin using Cy5.5-AS1411 as the donor and Fe3O4-polypyrrole core-shell (Fe3O4@PPY) nanoparticles as the NIR quenching acceptor. Due to hydrophobic interaction and π-π stacking of AS1411 and PPY, Cy5.5-AS1411 was bound onto the surface of Fe3O4@PPY, resulting in 90% of fluorescence quenching of Cy5.5-AS1411. Owing to the much stronger specific interaction of AS1411 and nucleolin, the presence of nucleolin could take Cy5.5-AS1411 apart from Fe3O4@PPY and restore the fluorescence of Cy5.5-AS1411. The superparamagnetism of Fe3O4@PPY enabled all separations and fluorescence measurements complete in the same quartz cell, and thus allowed the convenient but accurate comparison of the sensitivity and fluorescence recovery in the cases of separation or nonseparation. Compared to nonseparation FRET inhibition, the separation of free Cy5.5-AS1411 from Cy5.5-AS1411-Fe3O4@PPY solution (the first magnetic separation, MS-1) had as high as 25-fold enhancement of the sensitivity, whereas further separation of the nucleolin-inducing far-between Fe3O4@PPY from the FRET inhibition solution (the second magnetic separation, MS-2) could further enhance the sensitivity to 35-fold. Finally, the MS-FRET inhibition assay displayed the linear range of 0.625-27.5 μg L(-1) (8.1-359 pM) and detection limit of 0.04 μg L(-1) (0.05 pM) of nucleolin. The fluorescence intensity recovery (the percentage ratio of the final restoring fluorescence intensity

  4. The Effect of Incoherent Population Pumping on Squeezing in Resonance Fluorescence

    Institute of Scientific and Technical Information of China (English)

    CHEN Zhaoyang; ZHANG Jingtao; XU Zhizhan

    2000-01-01

    The effect of incoherent population pumping on the steady-state population inversion and the quadrature squeezing spectra produced in the resonance fluorescence of a two-level atom is investigated. In the presence of incoherent population pumping, the steady-state population inversion is increased for small frequency detuning but is not changed for large frequency detuning. For resonant excitation at low intensities, the weak incoherent pumping degrades the degree of the squeezing and shifts the position of the maximum squeezing; for off-resonant excitation at strong intensities, the weak incoherent pumping hardly changes the squeezing spectra. But when the incoherent pumping is strong the squeezing may be completely destroyed for both cases.

  5. Amplification of the Signal Intensity of Fluorescence-Based Fiber-Optic Biosensors Using a Fabry-Perot Resonator Structure

    Directory of Open Access Journals (Sweden)

    Meng-Chang Hsieh

    2015-02-01

    Full Text Available Fluorescent biosensors have been widely used in biomedical applications. To amplify the intensity of fluorescence signals, this study developed a novel structure for an evanescent wave fiber-optic biosensor by using a Fabry-Perot resonator structure. An excitation light was coupled into the optical fiber through a laser-drilled hole on the proximal end of the resonator. After entering the resonator, the excitation light was reflected back and forth inside the resonator, thereby amplifying the intensity of the light in the fiber. Subsequently, the light was used to excite the fluorescent molecules in the reactive region of the sensor. The experimental results showed that the biosensor signal was amplified eight-fold when the resonator reflector was formed using a 92% reflective coating. Furthermore, in a simulation, the biosensor signal could be amplified 20-fold by using a 99% reflector.

  6. Intrinsic Tryptophan Fluorescence in the Detection and Analysis of Proteins: A Focus on Förster Resonance Energy Transfer Techniques

    Directory of Open Access Journals (Sweden)

    Amar B. T. Ghisaidoobe

    2014-12-01

    Full Text Available F resonance energy transfer (FRET occurs when the distance between a donor fluorophore and an acceptor is within 10 nm, and its application often necessitates fluorescent labeling of biological targets. However, covalent modification of biomolecules can inadvertently give rise to conformational and/or functional changes. This review describes the application of intrinsic protein fluorescence, predominantly derived from tryptophan (\\(\\uplambda_{\\textsc{ex}}\\sim\\ nm, \\(\\uplambda_{\\textsc{em}}\\sim\\ 350 nm, in protein-related research and mainly focuses on label-free FRET techniques. In terms of wavelength and intensity, tryptophan fluorescence is strongly influenced by its (or the proteinlocal environment, which, in addition to fluorescence quenching, has been applied to study protein conformational changes. Intrinsic F resonance energy transfer (iFRET, a recently developed technique, utilizes the intrinsic fluorescence of tryptophan in conjunction with target-specific fluorescent probes as FRET donors and acceptors, respectively, for real time detection of native proteins.

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

    Science.gov (United States)

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

    2015-08-01

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

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

    Science.gov (United States)

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

    2009-02-01

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

  9. Probing symmetry and symmetry breaking in resonant soft-x-ray fluorescence spectra of molecules

    Energy Technology Data Exchange (ETDEWEB)

    Glans, P.; Gunnelin, K.; Guo, J. [Uppsala Univ. (Sweden)] [and others

    1997-04-01

    Conventional non-resonant soft X-ray emission brings about information about electronic structure through its symmetry and polarization selectivity, the character of which is governed by simple dipole rules. For centro-symmetric molecules with the emitting atom at the inversion center these rules lead to selective emission through the required parity change. For the more common classes of molecules which have lower symmetry or for systems with degenerate core orbitals (delocalized over identical sites), it is merely the local symmetry selectivity that provides a probe of the local atomic orbital contribution to the molecular orbital. For instance, in X-ray spectra of first row species the intensities essentially map the p-density at each particular atomic site, and, in a molecular orbital picture, the contribution of the local p-type atomic orbitals in the LCAO description of the molecular orbitals. The situation is different for resonant X-ray fluorescence spectra. Here strict parity and symmetry selectivity gives rise to a strong frequency dependence for all molecules with an element of symmetry. In addition to symmetry selectivity the strong frequency dependence of resonant X-ray emission is caused by the interplay between the shape of a narrow X-ray excitation energy function and the lifetime and vibrational broadenings of the resonantly excited core states. This interplay leads to various observable effects, such as linear dispersion, resonance narrowing and emission line (Stokes) doubling. Also from the point of view of polarization selectivity, the resonantly excited X-ray spectra are much more informative than the corresponding non-resonant spectra. Examples are presented for nitrogen, oxygen, and carbon dioxide molecules.

  10. Novel fluorescent silica nanoparticle probe for Förster Resonance Energy Transfer

    Directory of Open Access Journals (Sweden)

    Mouhamad Khalil

    2014-04-01

    Full Text Available The preparation and utilization of a novel particulate label based on fluorescent hybrid silica nanoparticles are reported in this article. These fluorescent nanoparticles have shown several unique advantages over existing dye molecules, quantum dots, and latex-based fluorescent particles in easy preparation, good photostability and high sensitivity. Alexa Fluor® dyes, the leading and most trusted fluorescent dyes available today were used to make the grafting onto silica nanoparticles. Alexa Fluor® was modified with 3-aminopropyl-triethoxysilane (APS to provide reactive groups Alexa-APS. Alexa-APS can be grafted onto silica nanoparticles via silylation process. The silica nanoparticles were prepared by Stöber methods and treated by Etching to functionalized their surface. A mixture of Alexafluoro donor A488 and Alexafluoro acceptor A568 coated silica nanoparticles leads to the Förster Resonance Energy Transfer (FRET by excitation of the acceptor when the particles are distant by less than 10nm.

  11. Comparing implementations of magnetic-resonance-guided fluorescence molecular tomography for diagnostic classification of brain tumors

    Science.gov (United States)

    Davis, Scott C.; Samkoe, Kimberley S.; O'Hara, Julia A.; Gibbs-Strauss, Summer L.; Paulsen, Keith D.; Pogue, Brian W.

    2010-09-01

    Fluorescence molecular tomography (FMT) systems coupled to conventional imaging modalities such as magnetic resonance imaging (MRI) and computed tomography provide unique opportunities to combine data sets and improve image quality and content. Yet, the ideal approach to combine these complementary data is still not obvious. This preclinical study compares several methods for incorporating MRI spatial prior information into FMT imaging algorithms in the context of in vivo tissue diagnosis. Populations of mice inoculated with brain tumors that expressed either high or low levels of epidermal growth factor receptor (EGFR) were imaged using an EGF-bound near-infrared dye and a spectrometer-based MRI-FMT scanner. All data were spectrally unmixed to extract the dye fluorescence from the tissue autofluorescence. Methods to combine the two data sets were compared using student's t-tests and receiver operating characteristic analysis. Bulk fluorescence measurements that made up the optical imaging data set were also considered in the comparison. While most techniques were able to distinguish EGFR(+) tumors from EGFR(-) tumors and control animals, with area-under-the-curve values=1, only a handful were able to distinguish EGFR(-) tumors from controls. Bulk fluorescence spectroscopy techniques performed as well as most imaging techniques, suggesting that complex imaging algorithms may be unnecessary to diagnose EGFR status in these tissue volumes.

  12. Resonance fluorescence beyond the dipole approximation of a quantum dot in a plasmonic nanostructure

    Science.gov (United States)

    Yang, Chun-Jie; An, Jun-Hong

    2016-05-01

    The mesoscopic characteristics of a quantum dot (QD), which make the dipole approximation (DA) break down, provide a new dimension to manipulate light-matter interaction [M. L. Andersen et al., Nat. Phys. 7, 215 (2011)], 10.1038/nphys1870. Here we investigate the power spectrum and the second-order correlation property of the fluorescence from a resonantly driven QD placed on a planar metal. It is revealed that due to the pronounced QD spatial extension and the dramatic variation of the triggered surface plasmon near the metal, the fluorescence has a notable contribution from the quadrupole moment. The π -rotation symmetry of the fluorescence to the QD orientation under the DA is broken. By manipulating the QD orientation and quadrupole moment, the spectrum can be switched between the Mollow triplet and a single peak, and the fluorescence characterized by the antibunching in the second-order correlation function can be changed from the weak to the strong radiation regime. Our result is instructive for utilizing the unique mesoscopic effects to develop nanophotonic devices.

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

    Science.gov (United States)

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

    2015-06-15

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

  14. The Photochemical Study of HSA and BSA with Resonance Light-Scattering and Fluorescence Spectra

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The resonance light-scattering (RLS) of human serum albumin (HSA) and bovine serum albumin (BSA) is reported for the first time, and applied to study photochemical reaction of HSA and BSA. The fact of photocrosslinking self-association effect in HSA and BSA solutions is identified by the enhancement of RLS. The fluorescence quenching at about 350 nm and 700 nm proves that tryptophan (Trp) residues are one of the photochemical activity sites in HSA and BSA molecules. The Rayleigh scattering (RS) spectra of HSA and BSA that were neglected in fluorescence spectra before are found at about 296 nm, 592 nm and 888 nm for the first time, and are of adventageous to studying the aggregation of HSA or BSA. The possible photochemical reaction mechanism is also proposed.

  15. RecQ Helicase-catalyzed DNA Unwinding Detected by Fluorescence Resonance Energy Transfer

    Institute of Scientific and Technical Information of China (English)

    Xing-Dong ZHANG; Shuo-Xing DOU; Ping XIE; Peng-Ye WANG; Xu Guang XI

    2005-01-01

    A fluorometric assay was used to study the DNA unwinding kinetics induced by Escherichia coli RecQ helicase. This assay was based on fluorescence resonance energy transfer and carried out on stopped-flow, in which DNA unwinding was monitored by fluorescence emission enhancement of fluorescein resulting from helicase-catalyzed DNA unwinding. By this method, we determined the DNA unwinding rate of RecQ at different enzyme concentrations. We also studied the dependences of DNA unwinding magnitude and rate on magnesium ion concentration. We showed that this method could be used to determine the polarity of DNA unwinding. This assay should greatly facilitate further study of the mechanism for RecQcatalyzed DNA unwinding.

  16. Fabrication of a Multimodal Microbubble Platform for Magnetic Resonance, Ultrasound and Fluorescence Imaging Application.

    Science.gov (United States)

    Miao, Zhaohua; Guo, Caixin; Li, Zhenglin; Ke, Hengte; Dai, Zhifei

    2016-03-01

    Magnetic resonance (MR), ultrasound (US) and fluorescence imaging are the widely used diagnostic modalities for various experimental and clinical applications. A multimodal poly(lactic acid) microbubble (MB) integrated with the three imaging modalities was fabricated by adsorbing CdTe quantum dots (QDs) onto the surface and encapsulating superparamagnetic iron oxide (SPIO) nanoparticles into the core. The strong fluorescence of the multimodal MBs confirmed that QDs were successfully deposited onto the surface. The in vitro MRI contrasting capability of the multimodal MBs at various concentrations was evaluated by T2-weighted imaging. Furthermore, the in vitro and in vivo ultrasonography indicated that CdTe and SPIO-inclusive MBs maintained excellent ultrasound contrast property. These results implied that the nano-in-micro hybrid materials have the potential as a nanomedical platform for multimodal bioimaging.

  17. Measuring evaporation rates of laser-trapped droplets by use of fluorescent morphology-dependent resonances.

    Science.gov (United States)

    Pastel, R; Struthers, A

    2001-05-20

    Morphology-dependent resonances (MDRs) are used to measure accurately the evaporation rates of laser-trapped 1- to 2-mum droplets of ethylene glycol. Droplets containing 3 x 10(-5) M Rhodamine-590 laser dye are optically trapped in a 20-mum hollow fiber by two counterpropagating 150-mW, 800-nm laser beams. A weaker 532-nm laser excites the dye, and fluorescence emission is observed near 560 nm as the droplet evaporates. A complete series of first-order TE and TM MDRs dominates the fluorescent output. MDR mode identification sizes the droplets and provides accurate evaporation rates. We verify the automated MDR mode identification by counting fringes in a videotape of the experiment. The longitudinal spring constant of the trap, measured by analysis of the videotaped motion of droplets perturbed from the trap center, provides independent verification of the laser's intensity within the trap.

  18. Far-field resonance fluorescence from a dipole-interacting laser-driven cold atomic gas

    CERN Document Server

    Jones, Ryan; Olmos, Beatriz

    2016-01-01

    We analyze the temporal response of the fluorescence light that is emitted from a dense gas of cold atoms driven by a laser. When the average interatomic distance is smaller than the wavelength of the photons scattered by the atoms, the system exhibits strong dipolar interactions and collective dissipation. We solve the exact dynamics of small systems with different geometries and show how these collective features are manifest in the scattered light properties such as the photon emission rate, the power spectrum and the second-order correlation function. By calculating these quantities beyond the weak driving limit, we make progress in understanding the signatures of collective behavior in these many-body systems. Furthermore, we clarify the role of disorder on the resonance fluorescence, of direct relevance for recent experimental efforts that aim at the exploration of many-body effects in dipole-dipole interacting gases of atoms.

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

    Science.gov (United States)

    Anderson, Trevor; Weninger, Keith

    2008-10-01

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

  20. Gold/Silica biochips: applications to Surface Plasmon Resonance and fluorescence quenching

    CERN Document Server

    Mangeat, Thomas; Elie-Caille, Céline; Perrin, Maud; Boireau, Wilfrid; Pieralli, Christian; Wacogne, Bruno; 10.1134/S1054660X09020170

    2010-01-01

    We report Gold/Silica biochips for low cost biosensor devices. Firstly, the study of biochemical interactions on silica by means of Surface Plasmon Resonance (SPR) is presented. Secondly, Gold/Silica biochips are employed to reduce the strong quenching that occurs when a fluorophore is close to the gold surface. Furthermore, the control of the Silica-like thickness allows optimizing the distance between the metallic surface and the fluorophore in order to enhance the fluorescent signal. These results represent the first steps towards highly sensitive, specific and low cost biosensors based, for example, on Surface Plasmon Coupled Emission (SPCE) techniques.

  1. Nondestructive assay of Pu in spent fuel using nuclear resonance fluorescence with monochromatic gamma-rays

    International Nuclear Information System (INIS)

    We have proposed a nondestructive assay for Pu-239 in spent fuel assembly using nuclear resonance fluorescence with energy tunable monochromatic gamma-rays generated by Compton scattering of laser photons and high energy electrons. To demonstrate this method, we carried out nuclear experiments using available laser Compton scattering gamma-rays. We measured NRF gamma-rays of Pb-208 concealed in an iron box with a thickness of 15 mm using LCS gamma-rays at National Institute of Advanced Industrial Science and Technology. We also measured NRF gamma-rays of U-238 using LCS gamma-rays at Duke University. (author)

  2. Resonantly Enhanced Multi-Photon Ionization Spectrum of the Neutral Green Fluorescent Protein Chromophore

    OpenAIRE

    greenwood, jason; Miles, Jordan; De Camillis, Simone; Mulholland, Peter; Zhang, Lijuan; Parkes, Michael A.; Hailes, Helen C.; Fielding, Helen H.

    2014-01-01

    The photophysics of the green fluorescent protein is governed by the electronic structure of the chromophore at the heart of its β-barrel protein structure. We present the first two-color, resonance-enhanced, multiphoton ionization spectrum of the isolated neutral chromophore in vacuo with supporting electronic structure calculations. We find the absorption maximum to be 3.65 ± 0.05 eV (340 ± 5 nm), which is blue-shifted by 0.5 eV (55 nm) from the absorption maximum of the protein in its neut...

  3. Efficiency calibration of the ELBE nuclear resonance fluorescence setup using a proton beam

    Energy Technology Data Exchange (ETDEWEB)

    Trompler, Erik; Bemmerer, Daniel; Beyer, Roland; Erhard, Martin; Grosse, Eckart; Hannaske, Roland; Junghans, Arnd Rudolf; Marta, Michele; Nair, Chithra; Schwengner, R.; Wagner, Andreas; Yakorev, Dmitry [Forschungszentrum Dresden-Rossendorf (FZD), Dresden (Germany); Broggini, Carlo; Caciolli, Antonio; Menegazzo, Roberto [INFN Sezione di Padova, Padova (Italy); Fueloep, Zsolt; Gyuerky, Gyoergy; Szuecs, Tamas [Atomki, Debrecen (Hungary)

    2009-07-01

    The nuclear resonance fluorescence (NRF) setup at ELBE uses bremsstrahlung with endpoint energies up to 20 MeV. The setup consists of four 100% high-purity germanium detectors, each surrounded by a BGO escape-suppression shield and a lead collimator. The detection efficiency up to E{sub {gamma}}=12 MeV has been determined using the proton beam from the FZD Tandetron and well-known resonances in the {sup 11}B(p,{gamma}){sup 12}C, {sup 14}N(p,{gamma}){sup 15}O, and {sup 27}Al(p,{gamma}){sup 28}Si reactions. The deduced efficiency curve allows to check efficiency curves calculated with GEANT. Future photon-scattering work can be carried out with improved precision at high energy.

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

    Science.gov (United States)

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

    2007-02-01

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

  5. Intracellular ribozyme-catalyzed trans-cleavage of RNA monitored by fluorescence resonance energy transfer.

    Science.gov (United States)

    Vitiello, D; Pecchia, D B; Burke, J M

    2000-04-01

    Small catalytic RNAs like the hairpin ribozyme are proving to be useful intracellular tools; however, most attempts to demonstrate trans-cleavage of RNA by ribozymes in cells have been frustrated by rapid cellular degradation of the cleavage products. Here, we describe a fluorescence resonance energy transfer (FRET) assay that directly monitors cleavage of target RNA in tissue-culture cells. An oligoribonucleotide substrate was modified to inhibit cellular ribonuclease degradation without interfering with ribozyme cleavage, and donor (fluorescein) and acceptor (tetramethylrhodamine) fluorophores were introduced at positions flanking the cleavage site. In simple buffers, the intact substrate produces a strong FRET signal that is lost upon cleavage, resulting in a red-to-green shift in dominant fluorescence emission. Hairpin ribozyme and fluorescent substrate were microinjected into murine fibroblasts under conditions in which substrate cleavage can occur only inside the cell. A strong FRET signal was observed by fluorescence microscopy when substrate was injected, but rapid decay of the FRET signal occurred when an active, cognate ribozyme was introduced with the substrate. No acceleration in cleavage rates was observed in control experiments utilizing a noncleavable substrate, inactive ribozyme, or an active ribozyme with altered substrate specificity. Subsequently, the fluorescent substrates were injected into clonal cell lines that expressed cognate or noncognate ribozymes. A decrease in FRET signal was observed only when substrate was microinjected into cells expressing its cognate ribozyme. These results demonstrate trans-cleavage of RNA within mammalian cells, and provide an experimental basis for quantitative analysis of ribozyme activity and specificity within the cell. PMID:10786853

  6. Isotopic imaging via nuclear resonance fluorescence with laser-based Thomson radiation

    Science.gov (United States)

    Barty, Christopher P. J.; Hartemann, Frederic V.; McNabb, Dennis P.; Pruet, Jason A.

    2009-07-21

    The present invention utilizes novel laser-based, high-brightness, high-spatial-resolution, pencil-beam sources of spectrally pure hard x-ray and gamma-ray radiation to induce resonant scattering in specific nuclei, i.e., nuclear resonance fluorescence. By monitoring such fluorescence as a function of beam position, it is possible to image in either two dimensions or three dimensions, the position and concentration of individual isotopes in a specific material configuration. Such methods of the present invention material identification, spatial resolution of material location and ability to locate and identify materials shielded by other materials, such as, for example, behind a lead wall. The foundation of the present invention is the generation of quasimonochromatic high-energy x-ray (100's of keV) and gamma-ray (greater than about 1 MeV) radiation via the collision of intense laser pulses from relativistic electrons. Such a process as utilized herein, i.e., Thomson scattering or inverse-Compton scattering, produces beams having diameters from about 1 micron to about 100 microns of high-energy photons with a bandwidth of .DELTA.E/E of approximately 10E.sup.-3.

  7. ``Green'' functionalization of magnetic nanoparticles via tea polyphenol for magnetic resonance/fluorescent dual-imaging

    Science.gov (United States)

    Jiang, Wen; Lai, Kuilin; Liu, Kexia; Xia, Rui; Gao, Fabao; Wu, Yao; Gu, Zhongwei

    2014-01-01

    Tea polyphenol serves as an environmentally friendly ligand-exchange molecule to synthesize multifunctional metal-doped superparamagnetic iron oxide nanoparticles via a catechol-metal coordination interaction. The resultant particles not only exhibit excellent hydrophilicity and protein adsorption resistance, but also are applicable as magnetic resonance/fluorescent dual-imaging probes due to their high T2 relaxivity, autofluorescence and large cellular uptake.Tea polyphenol serves as an environmentally friendly ligand-exchange molecule to synthesize multifunctional metal-doped superparamagnetic iron oxide nanoparticles via a catechol-metal coordination interaction. The resultant particles not only exhibit excellent hydrophilicity and protein adsorption resistance, but also are applicable as magnetic resonance/fluorescent dual-imaging probes due to their high T2 relaxivity, autofluorescence and large cellular uptake. Electronic supplementary information (ESI) available: Additional information and figures (Fig. S1-S7), including experimental sections, characterization of the products, protein corona analysis, cytotoxicity and cellular uptake quantification. See DOI: 10.1039/c3nr05003c

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

    Science.gov (United States)

    Cao, Duojun; Qian, Ying

    2016-07-01

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

  9. Absorption, fluorescence and resonance Rayleigh scattering spectral characteristics of interaction of gold nanoparticle with safranine T

    Institute of Scientific and Technical Information of China (English)

    HE Youqiu; LIU Shaopu; LIU Qin; LIU Zhongfang; HU Xiaoli

    2005-01-01

    The interaction between gold nanoparticle and safranine T (ST) has been studied with resonance Rayleigh scattering (RRS) spectra, absorption and fluorescence spectra. In the pH 5 solution, citrate [(H2L)2-] self-assembles on the surface of positively-charged gold nanoparticle, which results in the [(Au)n(H2L)m]x- complex. In other words, one of carboxylate oxygens in (H2L)2- moves inward and combines with gold nanoparticle. The other carboxylate oxygens moves outward to form a supermolecular complex anion with x negative charges. Then by virtue of electrostatic attraction, hydrophobic force and charge transfer action, the complex anion binds with ST cation to form a new ion-association complex. Here (H2L)2- acts as a bridge. The formation of the complex results in the significant enhancement of RRS intensity, the appearance of new RRS spectrum, the red shift of plasma absorption band of gold nanoparticle as well as the decrease in the absorbance and fluorescence quenching for safranine T. In this work, the interaction between gold nanoparticle and ST on the RRS, absorption and fluorescence spectra has been investigated. The reason why RRS intensity increases greatly and the reaction mechanism have been inquired. The results show that RRS spectra can not only be used to study nanoparticle and reaction product, but also are a sensitive means to characterize and detect nanoparticles.

  10. Probing the graphite band structure with resonant soft-x-ray fluorescence

    Energy Technology Data Exchange (ETDEWEB)

    Carlisle, J.A.; Shirley, E.L.; Hudson, E.A. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    Soft x-ray fluorescence (SXF) spectroscopy using synchrotron radiation offers several advantages over surface sensitive spectroscopies for probing the electronic structure of complex multi-elemental materials. Due to the long mean free path of photons in solids ({approximately}1000 {angstrom}), SXF is a bulk-sensitive probe. Also, since core levels are involved in absorption and emission, SXF is both element- and angular-momentum-selective. SXF measures the local partial density of states (DOS) projected onto each constituent element of the material. The chief limitation of SXF has been the low fluorescence yield for photon emission, particularly for light elements. However, third generation light sources, such as the Advanced Light Source (ALS), offer the high brightness that makes high-resolution SXF experiments practical. In the following the authors utilize this high brightness to demonstrate the capability of SXF to probe the band structure of a polycrystalline sample. In SXF, a valence emission spectrum results from transitions from valence band states to the core hole produced by the incident photons. In the non-resonant energy regime, the excitation energy is far above the core binding energy, and the absorption and emission events are uncoupled. The fluorescence spectrum resembles emission spectra acquired using energetic electrons, and is insensitive to the incident photon`s energy. In the resonant excitation energy regime, core electrons are excited by photons to unoccupied states just above the Fermi level (EF). The absorption and emission events are coupled, and this coupling manifests itself in several ways, depending in part on the localization of the empty electronic states in the material. Here the authors report spectral measurements from highly oriented pyrolytic graphite.

  11. Vibrational techniques applied to photosynthesis: Resonance Raman and fluorescence line-narrowing.

    Science.gov (United States)

    Gall, Andrew; Pascal, Andrew A; Robert, Bruno

    2015-01-01

    Resonance Raman spectroscopy may yield precise information on the conformation of, and the interactions assumed by, the chromophores involved in the first steps of the photosynthetic process. Selectivity is achieved via resonance with the absorption transition of the chromophore of interest. Fluorescence line-narrowing spectroscopy is a complementary technique, in that it provides the same level of information (structure, conformation, interactions), but in this case for the emitting pigment(s) only (whether isolated or in an ensemble of interacting chromophores). The selectivity provided by these vibrational techniques allows for the analysis of pigment molecules not only when they are isolated in solvents, but also when embedded in soluble or membrane proteins and even, as shown recently, in vivo. They can be used, for instance, to relate the electronic properties of these pigment molecules to their structure and/or the physical properties of their environment. These techniques are even able to follow subtle changes in chromophore conformation associated with regulatory processes. After a short introduction to the physical principles that govern resonance Raman and fluorescence line-narrowing spectroscopies, the information content of the vibrational spectra of chlorophyll and carotenoid molecules is described in this article, together with the experiments which helped in determining which structural parameter(s) each vibrational band is sensitive to. A selection of applications is then presented, in order to illustrate how these techniques have been used in the field of photosynthesis, and what type of information has been obtained. This article is part of a Special Issue entitled: Vibrational spectroscopies and bioenergetic systems. PMID:25268562

  12. Multifunctional nanoprobe for cancer cell targeting and simultaneous fluorescence/magnetic resonance imaging.

    Science.gov (United States)

    Wei, Zhenzhen; Wu, Yafeng; Zhao, Yuewu; Mi, Li; Wang, Jintao; Wang, Jimin; Zhao, Jinjin; Wang, Lixin; Liu, Anran; Li, Ying; Wei, Wei; Zhang, Yuanjian; Liu, Songqin

    2016-09-28

    Multifunctional nanoprobes with distinctive magnetic and fluorescent properties are highly useful in accurate and early cancer diagnosis. In this study, nanoparticles of Fe3O4 core with fluorescent SiO2 shell (MFS) are synthesized by a facile improved Stöber method. These nanoparticles owning a significant core-shell structure exhibit good dispersion, stable fluorescence, low cytotoxicity and excellent biocompatibility. TLS11a aptamer (Apt1), a specific membrane protein for human liver cancer cells which could be internalized into cells, is conjugated to the MFS nanoparticles through the formation of amide bond working as a target-specific moiety. The attached TLS11a aptamers on nanoparticles are very stable and can't be hydrolyzed by DNA hydrolytic enzyme in vivo. Both fluorescence and magnetic resonance imaging show significant uptake of aptamer conjugated nanoprobe by HepG2 cells compared to 4T1, SGC-7901 and MCF-7 cells. In addition, with the increasing concentration of the nanoprobe, T2-weighted MRI images of the as-treated HepG2 cells are significantly negatively enhanced, indicating that a high magnetic field gradient is generated by MFS-Apt1 which has been specifically captured by HepG2 cells. The relaxivity of nanoprobe is calculated to be 11.5 mg(-1)s(-1). The MR imaging of tumor-bearing nude mouse is also confirmed. The proposed multifunctional nanoprobe with the size of sub-100 nm has the potential to provide real-time imaging in early liver cancer cell diagnosis. PMID:27619098

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

    Science.gov (United States)

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

    2012-02-01

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

  14. Iodinated oil-loaded, fluorescent mesoporous silica-coated iron oxide nanoparticles for magnetic resonance imaging/computed tomography/fluorescence trimodal imaging.

    Science.gov (United States)

    Xue, Sihan; Wang, Yao; Wang, Mengxing; Zhang, Lu; Du, Xiaoxia; Gu, Hongchen; Zhang, Chunfu

    2014-01-01

    In this study, a novel magnetic resonance imaging (MRI)/computed tomography (CT)/fluorescence trifunctional probe was prepared by loading iodinated oil into fluorescent mesoporous silica-coated superparamagnetic iron oxide nanoparticles (i-fmSiO4@SPIONs). Fluorescent mesoporous silica-coated superparamagnetic iron oxide nanoparticles (fmSiO4@SPIONs) were prepared by growing fluorescent dye-doped silica onto superparamagnetic iron oxide nanoparticles (SPIONs) directed by a cetyltrimethylammonium bromide template. As prepared, fmSiO4@SPIONs had a uniform size, a large surface area, and a large pore volume, which demonstrated high efficiency for iodinated oil loading. Iodinated oil loading did not change the sizes of fmSiO4@SPIONs, but they reduced the MRI T2 relaxivity (r2) markedly. I-fmSiO4@SPIONs were stable in their physical condition and did not demonstrate cytotoxic effects under the conditions investigated. In vitro studies indicated that the contrast enhancement of MRI and CT, and the fluorescence signal intensity of i-fmSiO4@SPION aqueous suspensions and macrophages, were intensified with increased i-fmSiO4@SPION concentrations in suspension and cell culture media. Moreover, for the in vivo study, the accumulation of i-fmSiO4@SPIONs in the liver could also be detected by MRI, CT, and fluorescence imaging. Our study demonstrated that i-fmSiO4@SPIONs had great potential for MRI/CT/fluorescence trimodal imaging. PMID:24904212

  15. Transmission Nuclear Resonance Fluorescence Measurements of 238U in Thick Targets

    Energy Technology Data Exchange (ETDEWEB)

    Quiter, Brian J.; Ludewigt, Bernhard A.; Mozin, Vladimir V.; Wilson, Cody; Korbly, Steve

    2010-08-31

    Transmission nuclear resonance fluorescence measurements were made on targets consisting of Pb and depleted U with total areal densities near 86 g/cm2. The 238U content n the targets varied from 0 to 8.5percent (atom fraction). The experiment demonstrates the capability of using transmission measurements as a non-destructive technique to identify and quantify the presence of an isotope in samples with thicknesses comparable to he average thickness of a nuclear fuel assembly. The experimental data also appear to demonstrate the process of notch refilling with a predictable intensity. Comparison of measured spectra to previous backscatter 238U measurements indicates general agreement in observed excited states. Two new 238U excited states and possibly a third state have also been observed.

  16. Design of narrow-band Compton scattering sources for nuclear resonance fluorescence

    Science.gov (United States)

    Albert, F.; Anderson, S. G.; Gibson, D. J.; Marsh, R. A.; Wu, S. S.; Siders, C. W.; Barty, C. P. J.; Hartemann, F. V.

    2011-05-01

    The design of narrow-band Compton scattering sources for specific applications using nuclear resonance fluorescence (NRF) is presented. NRF lines are extremely narrow (ΔE/Ẽ10-6) and require spectrally narrow sources to be excited selectively and efficiently. This paper focuses on the theory of spectral broadening mechanisms involved during Compton scattering of laser photons from relativistic electron beams. It is shown that in addition to the electron beam emittance, energy spread, and the laser parameters, nonlinear processes during the laser-electron interaction can have a detrimental effect on the gamma-ray source bandwidth, including a newly identified weakly nonlinear phase shift accumulated over the effective interaction duration. Finally, a design taking these mechanisms into consideration is outlined.

  17. Multiway study of hybridization in nanoscale semiconductor labeled DNA based on fluorescence resonance energy transfer

    DEFF Research Database (Denmark)

    Gholami, Somayeh; Kompany Zare, Mohsen

    2013-01-01

    The resolution of the ternary-binary complex competition of a target sequence and of its two complementary probes in sandwich DNA hybridization is reported. To achieve this goal, Fluorescence Resonance Energy Transfer (FRET) between oligonucleotide-functionalized quantum dot (QD) nanoprobes (QD...... donor-QD acceptor) upon hybridization with a label free target was monitored by two-dimensional photoluminescence excitation spectroscopy (2D-PLE). Detection of a target oligonucleotide strand, using sandwiched nanoassembly in a separation-free format, was performed with the appearance of a new feature...... in the photoluminescence excitation (PLE) plot. From the obtained data, energy transfer efficiency and Forster radius (R-0) were calculated. In particular, our results demonstrated that energy transfer by using QD donor-QD acceptor FRET pairs is more efficient in comparison with QD donor-organic dye acceptor pairs. Soft...

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

    Science.gov (United States)

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

    2014-01-01

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

  19. Development of L-lactate dehydrogenase biosensor based on porous silicon resonant microcavities as fluorescence enhancers.

    Science.gov (United States)

    Jenie, S N Aisyiyah; Prieto-Simon, Beatriz; Voelcker, Nicolas H

    2015-12-15

    The up-regulation of L-lactate dehydrogenase (LDH), an intracellular enzyme present in most of all body tissues, is indicative of several pathological conditions and cellular death. Herein, we demonstrate LDH detection using porous silicon (pSi) microcavities as a luminescence-enhancing optical biosensing platform. Non-fluorescent resazurin was covalently attached onto the pSi surface via thermal hydrocarbonisation, thermal hydrosylilation and acylation. Each surface modification step was confirmed by means of FTIR and the optical shifts of the resonance wavelength of the microcavity. Thermal hydrocarbonisation also afforded excellent surface stability, ensuring that the resazurin was not reduced on the pSi surface. Using a pSi microcavity biosensor, the fluorescence signal upon detection of LDH was amplified by 10 and 5-fold compared to that of a single layer and a detuned microcavity, respectively, giving a limit of detection of 0.08 U/ml. The biosensor showed a linear response between 0.16 and 6.5 U/ml, covering the concentration range of LDH in normal as well as damaged tissues. The biosensor was selective for LDH and did not produce a signal upon incubation with another NAD-dependant enzyme L-glutamic dehydrogenase. The use of the pSi microcavity as a sensing platform reduced reagent usage by 30% and analysis time threefold compared to the standard LDH assay in solution.

  20. Miniature fiber optic spectrometer-based quantitative fluorescence resonance energy transfer measurement in single living cells

    Science.gov (United States)

    Chai, Liuying; Zhang, Jianwei; Zhang, Lili; Chen, Tongsheng

    2015-03-01

    Spectral measurement of fluorescence resonance energy transfer (FRET), spFRET, is a widely used FRET quantification method in living cells today. We set up a spectrometer-microscope platform that consists of a miniature fiber optic spectrometer and a widefield fluorescence microscope for the spectral measurement of absolute FRET efficiency (E) and acceptor-to-donor concentration ratio (RC) in single living cells. The microscope was used for guiding cells and the spectra were simultaneously detected by the miniature fiber optic spectrometer. Moreover, our platform has independent excitation and emission controllers, so different excitations can share the same emission channel. In addition, we developed a modified spectral FRET quantification method (mlux-FRET) for the multiple donors and multiple acceptors FRET construct (mD˜nA) sample, and we also developed a spectra-based 2-channel acceptor-sensitized FRET quantification method (spE-FRET). We implemented these modified FRET quantification methods on our platform to measure the absolute E and RC values of tandem constructs with different acceptor/donor stoichiometries in single living Huh-7 cells.

  1. Raman and fluorescence characteristics of resonant inelastic X-ray scattering from doped superconducting cuprates.

    Science.gov (United States)

    Huang, H Y; Jia, C J; Chen, Z Y; Wohlfeld, K; Moritz, B; Devereaux, T P; Wu, W B; Okamoto, J; Lee, W S; Hashimoto, M; He, Y; Shen, Z X; Yoshida, Y; Eisaki, H; Mou, C Y; Chen, C T; Huang, D J

    2016-01-01

    Measurements of spin excitations are essential for an understanding of spin-mediated pairing for superconductivity; and resonant inelastic X-ray scattering (RIXS) provides a considerable opportunity to probe high-energy spin excitations. However, whether RIXS correctly measures the collective spin excitations of doped superconducting cuprates remains under debate. Here we demonstrate distinct Raman- and fluorescence-like RIXS excitations of Bi1.5Pb0.6Sr1.54CaCu2O(8+δ). Combining photon-energy and momentum dependent RIXS measurements with theoretical calculations using exact diagonalization provides conclusive evidence that the Raman-like RIXS excitations correspond to collective spin excitations, which are magnons in the undoped Mott insulators and evolve into paramagnons in doped superconducting compounds. In contrast, the fluorescence-like shifts are due primarily to the continuum of particle-hole excitations in the charge channel. Our results show that under the proper experimental conditions RIXS indeed can be used to probe paramagnons in doped high-Tc cuprate superconductors. PMID:26794437

  2. Drug transport mechanism of P-glycoprotein monitored by single molecule fluorescence resonance energy transfer

    Science.gov (United States)

    Ernst, S.; Verhalen, B.; Zarrabi, N.; Wilkens, S.; Börsch, M.

    2011-03-01

    In this work we monitor the catalytic mechanism of P-glycoprotein (Pgp) using single-molecule fluorescence resonance energy transfer (FRET). Pgp, a member of the ATP binding cassette family of transport proteins, is found in the plasma membrane of animal cells where it is involved in the ATP hydrolysis driven export of hydrophobic molecules. When expressed in the plasma membrane of cancer cells, the transport activity of Pgp can lead to the failure of chemotherapy by excluding the mostly hydrophobic drugs from the interior of the cell. Despite ongoing effort, the catalytic mechanism by which Pgp couples MgATP binding and hydrolysis to translocation of drug molecules across the lipid bilayer is poorly understood. Using site directed mutagenesis, we have introduced cysteine residues for fluorescence labeling into different regions of the nucleotide binding domains (NBDs) of Pgp. Double-labeled single Pgp molecules showed fluctuating FRET efficiencies during drug stimulated ATP hydrolysis suggesting that the NBDs undergo significant movements during catalysis. Duty cycle-optimized alternating laser excitation (DCO-ALEX) is applied to minimize FRET artifacts and to select the appropriate molecules. The data show that Pgp is a highly dynamic enzyme that appears to fluctuate between at least two major conformations during steady state turnover.

  3. Electron paramagnetic resonance and fluorescence spectra of Mg-doped ZnSe precursor nanoribbon bundles

    International Nuclear Information System (INIS)

    Manganese-doped ZnSe precursor (ZnSe·3en) nanoribbon bundles were prepared through a mixed solvothermal approach, which is time-saving and efficient compared with traditional route. Electron paramagnetic resonance (EPR) and Fluorescence spectra are used to confirm that the Mn impurities are embedded inside the ZnSe crystal lattice and partly substitute the place of Zn. Shown in fluorescence spectra, ZnSe has an emission peak centered at 588 nm and the introduction of Mn strongly increases the intensity of peak The internal Mn transition (4T1→6A1) which strongly increases the peak intensity depends on the average number of Mn atoms in the nanoparticals. As the Mn concentration increases, the peak intensity enhances. It has been clearly seen that EPR spectra of the sample have six hyperfine lines which are attributed to the Mn2+ ions. Strong signal and small background imply successful doping. A series of samples with different Mn concentration was prepared and studied. In the last, it's summarized a suitable conditions and Mn concentration which led to best doping. (authors)

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

    Science.gov (United States)

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

    2015-03-01

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

  5. A homogeneous time-resolved fluorescence resonance energy transfer assay for phosphatidylserine exposure on apoptotic cells.

    Science.gov (United States)

    Gasser, Jean-Philippe; Hehl, Michaela; Millward, Thomas A

    2009-01-01

    A simple, "mix-and-measure" microplate assay for phosphatidylserine (PtdSer) exposure on the surface of apoptotic cells is described. The assay exploits the fact that annexin V, a protein with high affinity and specificity for PtdSer, forms trimers and higher order oligomers on binding to membranes containing PtdSer. The transition from soluble monomer to cell-bound oligomer is detected using time-resolved fluorescence resonance energy transfer from europium chelate-labeled annexin V to Cy5-labeled annexin V. PtdSer detection is achieved by a single addition of a reagent mix containing labeled annexins and calcium ions directly to cell cultures in a 96-well plate, followed by a brief incubation before fluorescence measurement. The assay can be used to quantify PtdSer exposure on both suspension cells and adherent cells in situ. This method is simpler and faster than existing annexin V binding assays based on flow cytometry or microscopy, and it yields precise data with Z' values of 0.6-0.7. PMID:18835236

  6. High-sensitivity quantum dot-based fluorescence resonance energy transfer bioanalysis by capillary electrophoresis.

    Science.gov (United States)

    Li, Yong-Qiang; Wang, Jian-Hao; Zhang, Hai-Li; Yang, Jie; Guan, Li-Yun; Chen, Hong; Luo, Qing-Ming; Zhao, Yuan-Di

    2010-02-15

    Here a new method for high-sensitivity quantum dot (QD)-based fluorescence resonance energy transfer (FRET) bioanalysis was developed. In this method, capillary electrophoresis (CE) with fluorescence detection was applied. The FRET system consisted of water-soluble 532-nm emitting CdTe QDs donor and 632-nm emitting CdSe/ZnS QDs acceptor which were covalently conjugated with mouse IgG and goat anti-mouse IgG, respectively. The bio-affinity between antigen and antibody brought two kinds of QDs close enough to make the FRET happen between them. In the CE experiments, highly efficient separation of donor-acceptor immunocomplexes was obtained, and the process of FRET was monitored. Results showed that FRET efficiency obtained by CE (38.56-69.58%) improved substantially in comparison with that obtained by ensemble measurement (12.77-52.37%). The high efficient separation of donor-acceptor immunocomplexes and the possible conformation change of antigen and antibody, contributes to the lower analysis uncertainty (variance) and higher FRET efficiency obtained in CE and consequentially, this makes the analysis of FRET more sensitive. This novel CE-based technique can be easily extended to other FRET system based on QDs and may have potential application in the study of biomolecule conformation change. PMID:19914053

  7. Time-domain microfluidic fluorescence lifetime flow cytometry for high-throughput Förster resonance energy transfer screening.

    Science.gov (United States)

    Nedbal, Jakub; Visitkul, Viput; Ortiz-Zapater, Elena; Weitsman, Gregory; Chana, Prabhjoat; Matthews, Daniel R; Ng, Tony; Ameer-Beg, Simon M

    2015-02-01

    Sensing ion or ligand concentrations, physico-chemical conditions, and molecular dimerization or conformation change is possible by assays involving fluorescent lifetime imaging. The inherent low throughput of imaging impedes rigorous statistical data analysis on large cell numbers. We address this limitation by developing a fluorescence lifetime-measuring flow cytometer for fast fluorescence lifetime quantification in living or fixed cell populations. The instrument combines a time-correlated single photon counting epifluorescent microscope with microfluidics cell-handling system. The associated computer software performs burst integrated fluorescence lifetime analysis to assign fluorescence lifetime, intensity, and burst duration to each passing cell. The maximum safe throughput of the instrument reaches 3,000 particles per minute. Living cells expressing spectroscopic rulers of varying peptide lengths were distinguishable by Förster resonant energy transfer measured by donor fluorescence lifetime. An epidermal growth factor (EGF)-stimulation assay demonstrated the technique's capacity to selectively quantify EGF receptor phosphorylation in cells, which was impossible by measuring sensitized emission on a standard flow cytometer. Dual-color fluorescence lifetime detection and cell-specific chemical environment sensing were exemplified using di-4-ANEPPDHQ, a lipophilic environmentally sensitive dye that exhibits changes in its fluorescence lifetime as a function of membrane lipid order. To our knowledge, this instrument opens new applications in flow cytometry which were unavailable due to technological limitations of previously reported fluorescent lifetime flow cytometers. The presented technique is sensitive to lifetimes of most popular fluorophores in the 0.5-5 ns range including fluorescent proteins and is capable of detecting multi-exponential fluorescence lifetime decays. This instrument vastly enhances the throughput of experiments involving fluorescence

  8. Peptide-based fluorescence resonance energy transfer protease substrates for the detection and diagnosis of Bacillus species

    NARCIS (Netherlands)

    W.E. Kaman; A.G. van Hulst; P.T.W. van Alphen; S. Roffel; M.J. van der Schans; T. Merkel; A. van Belkum; F.J. Bikker

    2011-01-01

    We describe the development of a highly specific enzyme-based fluorescence resonance energy transfer (FRET) assay for easy and rapid detection both in vitro and in vivo of Bacillus spp., among which are the members of the B. cereus group. Synthetic substrates for B. anthracis proteases were designed

  9. Spectroscopy and photophysics of self-organized zinc porphyrin nanolayers. 3. Fluorescence detected magnetic resonance of triplet states

    NARCIS (Netherlands)

    Schaafsma, T.J.; Dag, I.; Sitters, R.; Glasbeek, M.; Lifshitz, E.

    2005-01-01

    Fluorescence detected magnetic resonance (FDMR) has been applied to ~25-nm-thick porphyrin films, containing ordered domains of zinc tetra-(p-octylphenyl)-porphyrin (ZnTOPP) spin-coated onto quartz slides. Illuminating the films at 1.4 K with 457.9-nm light from a continuous wave Ar+ laser produces

  10. Ratiometric fluorescent ion detection in water with high sensitivity via aggregation-mediated fluorescence resonance energy transfer using a conjugated polyelectrolyte as an optical platform.

    Science.gov (United States)

    Le, Van Sang; Kim, Boram; Lee, Wonho; Jeong, Ji-Eun; Yang, Renqiang; Woo, Han Young

    2013-05-14

    A cationic conjugated polyelectrolyte was designed and synthesized based on poly(fluorene-co-phenylene) containing 5 mol% benzothiadiazole (BT) as a low energy trap and 15-crown-5 as a recognizing group for potassium ions. A potassium ion can form a sandwich-type 2:1 Lewis acid-based complex with 15-crown-5, to cause the intermolecular aggregation of polymers. This facilitates inter-chain fluorescence resonance energy transfer (FRET) to a low-energy BT segment, resulting in fluorescent signal amplification, even at dilute analyte concentrations. Highly sensitive and selective detection of K(+) ions was demonstrated in water. The linear response of ratiometric fluorescent signal as a function of [K(+) ] allows K(+) quantification in a range of nanomolar concentrations with a detection limit of ≈0.7 × 10(-9) M. PMID:23417971

  11. Resonant inelastic scattering in dilute magnetic semiconductors by x-ray fluorescence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lawniczak-Jablonska, K. [Lawrence Berkeley National Lab., CA (United States)]|[Institute of Physics, Warsaw (Poland); Jia, J.J.; Underwood, J.H. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    As modern, technologically important materials have become more complex, element specific techniques have become invaluable in studying the electronic structure of individual components from the system. Soft x-ray fluorescence (SXF) and absorption (SXA) spectroscopies provide a unique means of measuring element and angular momentum density of electron states, respectively, for the valence and conducting bands in complex materials. X-ray absorption and the decay through x-ray emission are generally assumed to be two independent one-photon processes. Recent studies, however have demonstrated that SXF excited near the absorption threshold generate an array of spectral features that depend on nature of materials, particularly on the localization of excited states in s and d-band solids and that these two processes can no be longer treated as independent. Resonant SXF offers thus the new way to study the dynamics of the distribution of electronic valence states in the presence of a hole which is bound to the electron low lying in the conduction band. This process can simulate the interaction between hole-electron pair in wide gap semiconductors. Therefore such studies can help in understanding of transport and optics phenomena in the wide gap semiconductors. The authors report the result of Mn and S L-resonant emission in Zn{sub 1{minus}x}Mn{sub x}S (with x=0.2 and 0.3) and MnS as the energy of exciting radiation is tuned across the Mn and S L{sub 3,2} absorption edge, along with the resonant excited spectra from elemental Mn as a reference.

  12. Nuclear Resonance Fluorescence to Measure Plutonium Mass in Spent Nuclear Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Ludewigt, Bernhard A; Quiter, Brian J.; Ambers, Scott D.

    2011-01-14

    The Next Generation Safeguard Initiative (NGSI) of the U.S Department of Energy is supporting a multi-lab/university collaboration to quantify the plutonium (Pu) mass in spent nuclear fuel (SNF) assemblies and to detect the diversion of pins with non-destructive assay (NDA) methods. The following 14 NDA techniques are being studied: Delayed Neutrons, Differential Die-Away, Differential Die-Away Self-Interrogation, Lead Slowing Down Spectrometer, Neutron Multiplicity, Passive Neutron Albedo Reactivity, Total Neutron (Gross Neutron), X-Ray Fluorescence, {sup 252}Cf Interrogation with Prompt Neutron Detection, Delayed Gamma, Nuclear Resonance Fluorescence, Passive Prompt Gamma, Self-integration Neutron Resonance Densitometry, and Neutron Resonance Transmission Analysis. Understanding and maturity of the techniques vary greatly, ranging from decades old, well-understood methods to new approaches. Nuclear Resonance Fluorescence (NRF) is a technique that had not previously been studied for SNF assay or similar applications. Since NRF generates isotope-specific signals, the promise and appeal of the technique lies in its potential to directly measure the amount of a specific isotope in an SNF assay target. The objectives of this study were to design and model suitable NRF measurement methods, to quantify capabilities and corresponding instrumentation requirements, and to evaluate prospects and the potential of NRF for SNF assay. The main challenge of the technique is to achieve the sensitivity and precision, i.e., to accumulate sufficient counting statistics, required for quantifying the mass of Pu isotopes in SNF assemblies. Systematic errors, considered a lesser problem for a direct measurement and only briefly discussed in this report, need to be evaluated for specific instrument designs in the future. Also, since the technical capability of using NRF to measure Pu in SNF has not been established, this report does not directly address issues such as cost, size

  13. Nuclear Resonance Fluorescence to Measure Plutonium Mass in Spent Nuclear Fuel

    International Nuclear Information System (INIS)

    The Next Generation Safeguard Initiative (NGSI) of the U.S Department of Energy is supporting a multi-lab/university collaboration to quantify the plutonium (Pu) mass in spent nuclear fuel (SNF) assemblies and to detect the diversion of pins with non-destructive assay (NDA) methods. The following 14 NDA techniques are being studied: Delayed Neutrons, Differential Die-Away, Differential Die-Away Self-Interrogation, Lead Slowing Down Spectrometer, Neutron Multiplicity, Passive Neutron Albedo Reactivity, Total Neutron (Gross Neutron), X-Ray Fluorescence, 252Cf Interrogation with Prompt Neutron Detection, Delayed Gamma, Nuclear Resonance Fluorescence, Passive Prompt Gamma, Self-integration Neutron Resonance Densitometry, and Neutron Resonance Transmission Analysis. Understanding and maturity of the techniques vary greatly, ranging from decades old, well-understood methods to new approaches. Nuclear Resonance Fluorescence (NRF) is a technique that had not previously been studied for SNF assay or similar applications. Since NRF generates isotope-specific signals, the promise and appeal of the technique lies in its potential to directly measure the amount of a specific isotope in an SNF assay target. The objectives of this study were to design and model suitable NRF measurement methods, to quantify capabilities and corresponding instrumentation requirements, and to evaluate prospects and the potential of NRF for SNF assay. The main challenge of the technique is to achieve the sensitivity and precision, i.e., to accumulate sufficient counting statistics, required for quantifying the mass of Pu isotopes in SNF assemblies. Systematic errors, considered a lesser problem for a direct measurement and only briefly discussed in this report, need to be evaluated for specific instrument designs in the future. Also, since the technical capability of using NRF to measure Pu in SNF has not been established, this report does not directly address issues such as cost, size, development

  14. 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.

  15. Fluorescence resonance energy transfer in AOT/4-chlorophenol/m-xylene organogels

    Energy Technology Data Exchange (ETDEWEB)

    Dandapat, Manika; Mandal, Debabrata, E-mail: dmandal.chemistry@gmail.com

    2015-06-15

    Fluorescence Resonance Energy Transfer (FRET) between donor coumarins (C102 and C153) and acceptor Rhodamine 6G were studied in AOT/4-chlorophenol/m-xylene organogels. The gel comprises a three-dimensional network of fiber bundles trapping the m-xylene solvent. Each fiber is an aggregate of several strands, and each strand consists of a central columnar stack of the phenols, surrounded by AOT headgroups. Our acceptor is ionic so that it was concentrated near the polar center of the strand, while the neutral donors were likely distributed over a wider region. With C153 as donor, clear evidence of FRET (time-constant~100 ps) was found, which indicated that the donor and acceptor may reside in neighboring strands within the same fiber. However, with C102 as donor, FRET probably occurred over an ultrashort, sub-picosecond time-scale suggesting that the donor and acceptor in this case resided in close vicinity. Thus, C102 tends to localize near the polar centre of the strands, compared to the more hydrophobic C153, which prefers to occupy the relatively non-polar peripheral regions of the strands and fibers. - Highlights: • FRET between coumarin donors and Rhodamine 6G acceptor studied in AOT organogels. • With Coumarin 153 donor, a ~100 ps FRET component detected in both donor and acceptor fluorescence. • With Coumarin 102 donor, FRET component too short to be detected with a time-resolution of ~70 ps. • The FRET rates reveal crucial differences in donor–acceptor distances for the two coumarin donors.

  16. Improvement of the Mutation-Discrimination Threshold for Rare Point Mutations by a Separation-Free Ligase Detection Reaction Assay Based on Fluorescence Resonance Energy Transfer.

    Science.gov (United States)

    Hagihara, Kenta; Tsukagoshi, Kazuhiko; Nakajima, Chinami; Esaki, Shinsuke; Hashimoto, Masahiko

    2016-01-01

    We previously developed a separation-free ligase detection reaction assay based on fluorescence resonance energy transfer from a donor quantum dot to an acceptor fluorescent dye. This assay could successfully detect one cancer mutation among 10 wild-type templates. In the current study, the mutation-discrimination threshold was improved by one order of magnitude by replacing the original acceptor dye (Alexa Fluor 647) with another fluorescent dye (Cyanine 5) that was spectrally similar but more fluorescent. PMID:26960620

  17. Study on the interaction between diphenhydramine and erythrosin by absorption,fluorescence and resonance Rayleigh scattering spectra

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In pH 4.5 Britton-Robinson(BR)buffer solution,erythrosin(ET)can react with diphenhydramine(DP)to form a 1:1 ion-association complex,which not only results in the change of the absorption spectra,but also results in the great enhancement of resonance Rayleigh scattering(RRS)and the quenching of fluorescence.Furthermore,a new RRS spectrum will appear,and the maximum RRS wavelength was located at about 580 nm.In this work,the spectral characteristics of the absorption,fluorescence and RRS,the optimum conditions of the reaction and the properties of an analytical chemistry were inves- tigated.A sensitive,simple and new method for the determination of DP by using erythrosin as a probe has been developed.The detection limits for DP were 0.0020μg/mL for RRS method,0.088μg/mL for absorption method and 0.094μg/mL for fluorophotometry.There was a linear relationship between the absorbance,RRS and fluorescence intensities and the drug concentration in the range of 0.0067-2.0, 0.29-6.4 and 0.31-3.2μg/mL,respectively.The effects of the interaction of diphenhydramine and erythrosin on the absorption,fluorescence and resonance Rayleigh scattering spectra were discussed. In light polarization experiment,the polarization of RRS at maximum wavelength was measured to be P =0.9779,and it revealed that the RRS spectrum of DP-ET complex consists mostly of resonance scat- tering and few resonance fluorescence.In this study,enthalpy of formation and mean polarizability were calculated by AM1 quantum chemistry method.In addition,the reaction mechanism and the rea- sons for the enhancement of scattering spectra and the energy transfer between absorption,fluores- cence and RRS were discussed.

  18. Synthesis of a fluorescence resonance energy transfer-based probe containing a tricyclic nucleoside analog for single nucleotide polymorphism typing.

    Science.gov (United States)

    Hayai, Aya; Maeda, Yusuke; Ueno, Yoshihito

    2016-08-01

    Here, we report the synthesis of a fluorescence resonance energy transfer (FRET)-based probe for single nucleotide polymorphism (SNP) typing. The probe contains a fluorescent tricyclic base, 8-amino-3-(2,3-dihydroxypropyl)imidazo[4',5':5,6]pyrido[2,3-d]pyrimidine, as a donor molecule and 7-diethylaminocoumarin-3-carboxylic acid as an acceptor molecule. FRET was observed between the donor and acceptor molecules on the probe. The identity of the target bases on DNA and RNA strands could be determined using the probe. PMID:27329795

  19. 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.

  20. Investigation of Prolactin Receptor Activation and Blockade Using Time-Resolved Fluorescence Resonance Energy Transfer

    Directory of Open Access Journals (Sweden)

    Estelle eTallet

    2011-09-01

    Full Text Available The prolactin receptor (PRLR is emerging as a therapeutic target in oncology. Knowledge-based drug design led to the development of a pure PRLR antagonist (Del1-9-G129R-hPRL that was recently shown to prevent PRL-induced mouse prostate tumorogenesis. In humans, the first gain-of-function mutation of the PRLR (PRLRI146L was recently identified in breast tumor patients. At the molecular level, the actual mechanism of action of these two novel players in the PRL system remains elusive. In this study, we addressed whether constitutive PRLR activation (PRLRI146L or PRLR blockade (antagonist involved alteration of receptor oligomerization and/or of inter-chain distances compared to unstimulated and PRL-stimulated PRLR. Using a combination of various biochemical and spectroscopic approaches (co-IP, blue-native electrophoresis, BRET1, we demonstrated that preformed PRLR homodimers are altered neither by PRL- or I146L-induced receptor triggering, nor by antagonist-mediated blockade. These findings were confirmed using a novel time-resolved fluorescence resonance energy transfer (TR-FRET technology that allows monitoring distance changes between cell-surface tagged receptors. This technology revealed that PRLR blockade or activation did not involve detectable distance changes between extracellular domains of receptor chains within the dimer. This study merges with our previous structural investigations suggesting that the mechanism of PRLR activation solely involves intermolecular contact adaptations leading to subtle intramolecular rearrangements.

  1. Excited-State-Proton-Transfer-Triggered Fluorescence Resonance Energy Transfer: from 2-Naphthylamine to Phenosafranin

    Science.gov (United States)

    Ghosh, Debanjana; Bose, Debosreeta; Sarkar, Deboleena; Chattopadhyay, Nitin

    2009-09-01

    Excited-state proton transfer (ESPT) and fluorescence resonance energy transfer (FRET) have been linearly coupled leading to an efficient pH-sensitive energy transfer from 2-naphthylamine (2NA) to a potentially bioactive cationic phenazinium dye, phenosafranin (PSF). The prototropic product produced exclusively from the photoexcited 2NA in the presence of added alkali serves as the donor for the energy transfer process. The energy transfer process is turned on at pH ≥ 12, whereas the process is turned off at a pH lower than that. Within the range of pH 12 to 13, the energy transfer efficiency (E) has been shown to follow a linear relation with the solution pH establishing the governing role of pH of the solution on the energy transfer process. The energy transfer follows a long-range dipole-dipole interaction mechanism. The critical energy transfer distance (R0) and the distance between the acceptor and the donor (r) have been determined for the ESPT-promoted FRET process at an optimum pH of 13. The present study involving the coupled processes is simple but has its implication due to its potential to be exploited for designing a pH-sensitive molecular switch.

  2. Detection of Citrus tristeza virus by using fluorescence resonance energy transfer-based biosensor.

    Science.gov (United States)

    Shojaei, Taha Roodbar; Salleh, Mohamad Amran Mohd; Sijam, Kamaruzaman; Rahim, Raha Abdul; Mohsenifar, Afshin; Safarnejad, Reza; Tabatabaei, Meisam

    2016-12-01

    Due to the low titer or uneven distribution of Citrus tristeza virus (CTV) in field samples, detection of CTV by using conventional detection techniques may be difficult. Therefore, in the present work, the cadmium-telluride quantum dots (QDs) was conjugated with a specific antibody against coat protein (CP) of CTV, and the CP were immobilized on the surface of gold nanoparticles (AuNPs) to develop a specific and sensitive fluorescence resonance energy transfer (FRET)-based nanobiosensor for detecting CTV. The maximum FRET efficiency for the developed nano-biosensor was observed at 60% in AuNPs-CP/QDs-Ab ratio of 1:8.5. The designed system showed higher sensitivity and specificity over enzyme linked immunosorbent assay (ELISA) with a limit of detection of 0.13μgmL(-1) and 93% and 94% sensitivity and specificity, respectively. As designed sensor is rapid, sensitive, specific and efficient in detecting CTV, this could be envisioned for diagnostic applications, surveillance and plant certification program. PMID:27380305

  3. Quantitative imaging of cell-permeable magnetic resonance contrast agents using x-ray fluorescence.

    Science.gov (United States)

    Endres, Paul J; Macrenaris, Keith W; Vogt, Stefan; Allen, Matthew J; Meade, Thomas J

    2006-01-01

    The inability to transduce cellular membranes is a limitation of current magnetic resonance imaging probes used in biologic and clinical settings. This constraint confines contrast agents to extracellular and vascular regions of the body, drastically reducing their viability for investigating processes and cycles in developmental biology. Conversely, a contrast agent with the ability to permeate cell membranes could be used in visualizing cell patterning, cell fate mapping, gene therapy, and, eventually, noninvasive cancer diagnosis. Therefore, we describe the synthesis and quantitative imaging of four contrast agents with the capability to cross cell membranes in sufficient quantity for detection. Each agent is based on the conjugation of a Gd(III) chelator with a cellular transduction moiety. Specifically, we coupled Gd(III)-diethylenetriaminepentaacetic acid DTPA and Gd(III)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid with an 8-amino acid polyarginine oligomer and an amphipathic stilbene molecule, 4-amino-4'-(N,N-dimethylamino)stilbene. The imaging modality that provided the best sensitivity and spatial resolution for direct detection of the contrast agents is synchrotron radiation x-ray fluorescence (SR-XRF). Unlike optical microscopy, SR-XRF provides two-dimensional images with resolution 10(3) better than (153)Gd gamma counting, without altering the agent by organic fluorophore conjugation. The transduction efficiency of the intracellular agents was evaluated by T(1) analysis and inductively coupled plasma mass spectrometry to determine the efficacy of each chelate-transporter combination. PMID:17150161

  4. Phase-resolved x-ray ferromagnetic resonance measurements in fluorescence yield

    Energy Technology Data Exchange (ETDEWEB)

    Marcham, M. K.; Keatley, P. S.; Neudert, A.; Hicken, R. J.; Cavill, S. A.; Shelford, L. R.; van der Laan, G.; Telling, N. D.; Childress, J. R.; Katine, J. A.; Shafer, P.; Arenholz, E.

    2010-10-14

    Phase-resolved x-ray ferromagnetic resonance (XFMR) has been measured in fluorescence yield, extending the application of XFMR to opaque samples on opaque substrates. Magnetization dynamics were excited in a Co{sub 50}Fe{sub 50}(0.7)/Ni{sub 90}Fe{sub 10}(5) bilayer by means of a continuous wave microwave excitation, while x-ray magnetic circular dichroism (XMCD) spectra were measured stroboscopically at different points in the precession cycle. By tuning the x-ray energy to the L{sub 3} edges of Ni and Fe, the dependence of the real and imaginary components of the element specific magnetic susceptibility on the strength of an externally applied static bias field was determined. First results from measurements on a Co{sub 50}Fe{sub 50}(0.7)/Ni{sub 90}Fe{sub 10}(5)/Dy(1) sample confirm that enhanced damping results from the addition of the Dy cap.

  5. Forster Resonance Energy Transfer and Laser Fluorescent Analysis of Defects in DNA Double Helix

    CERN Document Server

    Bregadze, Vasil G; Giorgadze, Tamar G; Jaliashvili, Zaza V; Chkhaberidze, Jemal G; Monaselidze, Jamlet R; Khuskivadze, Temur B

    2013-01-01

    Real time laser induced fluorescence spectroscopy usage for microanalysis of DNA double helix defects is shown. The method is based on Forster resonance energy transfer (FRET) in intercalator-donor pair (acridine orange as a donor and ethidium bromide as an acceptor). Transition metal ions such as Cu(II), Cu(I), Ag(I), silver nanoparticles (AgNPs), photo- and thermo effects were used to cause double helix defects in DNA. FRET radii were experimentally estimated in background electrolyte solution (0.01 M NaNO3) and proved to be 3.9 +- 0.3 nm and the data are in satisfactory agreement with the theoretically calculated value Ro = 3.5 +- 0.3 nm. Concentration of DNA sites, exposed to Cu(II), Cu(I), Ag(I) ions, AgNPs impact as well as laser irradiation ({\\lambda} = 457 nm) and temperature, which are applicable for intercalation, were estimated in relative units. FRET method allows to estimate the concentration of double helix areas with high quality stability applicable for intercalation in DNA after it was subjec...

  6. Single-molecule-sensitive fluorescence resonance energy transfer in freely-diffusing attoliter droplets

    Energy Technology Data Exchange (ETDEWEB)

    Rahmanseresht, Sheema; Ramos, Kieran P.; Gamari, Ben D.; Goldner, Lori S., E-mail: lgoldner@physics.umass.edu [Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003 (United States); Milas, Peker [Department of Neuroscience, University of Wisconsin, Madison, Wisconsin 53705 (United States)

    2015-05-11

    Fluorescence resonance energy transfer (FRET) from individual, dye-labeled RNA molecules confined in freely-diffusing attoliter-volume aqueous droplets is carefully compared to FRET from unconfined RNA in solution. The use of freely-diffusing droplets is a remarkably simple and high-throughput technique that facilitates a substantial increase in signal-to-noise for single-molecular-pair FRET measurements. We show that there can be dramatic differences between FRET in solution and in droplets, which we attribute primarily to an altered pH in the confining environment. We also demonstrate that a sufficient concentration of a non-ionic surfactant mitigates this effect and restores FRET to its neutral-pH solution value. At low surfactant levels, even accounting for pH, we observe differences between the distribution of FRET values in solution and in droplets which remain unexplained. Our results will facilitate the use of nanoemulsion droplets as attoliter volume reactors for use in biophysical and biochemical assays, and also in applications such as protein crystallization or nanoparticle synthesis, where careful attention to the pH of the confined phase is required.

  7. Iodinated oil-loaded, fluorescent mesoporous silica-coated iron oxide nanoparticles for magnetic resonance imaging/computed tomography/fluorescence trimodal imaging

    Directory of Open Access Journals (Sweden)

    Xue S

    2014-05-01

    Full Text Available Sihan Xue,1 Yao Wang,1 Mengxing Wang,2 Lu Zhang,1 Xiaoxia Du,2 Hongchen Gu,1 Chunfu Zhang1,31School of Biomedical Engineering and Med-X Research Institute, Shanghai Jiao Tong University, 2Shanghai Key Laboratory of Magnetic Resonance, Department of Physics, East China Normal University, 3State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, People’s Republic of ChinaAbstract: In this study, a novel magnetic resonance imaging (MRI/computed tomography (CT/fluorescence trifunctional probe was prepared by loading iodinated oil into fluorescent mesoporous silica-coated superparamagnetic iron oxide nanoparticles (i-fmSiO4@SPIONs. Fluorescent mesoporous silica-coated superparamagnetic iron oxide nanoparticles (fmSiO4@SPIONs were prepared by growing fluorescent dye-doped silica onto superparamagnetic iron oxide nanoparticles (SPIONs directed by a cetyltrimethylammonium bromide template. As prepared, fmSiO4@SPIONs had a uniform size, a large surface area, and a large pore volume, which demonstrated high efficiency for iodinated oil loading. Iodinated oil loading did not change the sizes of fmSiO4@SPIONs, but they reduced the MRI T2 relaxivity (r2 markedly. I-fmSiO4@SPIONs were stable in their physical condition and did not demonstrate cytotoxic effects under the conditions investigated. In vitro studies indicated that the contrast enhancement of MRI and CT, and the fluorescence signal intensity of i-fmSiO4@SPION aqueous suspensions and macrophages, were intensified with increased i-fmSiO4@SPION concentrations in suspension and cell culture media. Moreover, for the in vivo study, the accumulation of i-fmSiO4@SPIONs in the liver could also be detected by MRI, CT, and fluorescence imaging. Our study demonstrated that i-fmSiO4@SPIONs had great potential for MRI/C/fluorescence trimodal imaging.Keywords: multifunctional probe, SPIONs, mesoporous silica

  8. Sensitive fluorescence assay of organophosphorus pesticides based on the fluorescence resonance energy transfer between CdTe quantum dots and porphyrin.

    Science.gov (United States)

    Xue, Gao; Yue, Zhao; Bing, Zhang; Yiwei, Tang; Xiuying, Liu; Jianrong, Li

    2016-08-01

    A sensitive and selective quantum dot (QD)-based fluorescence resonance energy transfer (FRET) biosensor was successfully fabricated for the detection of organophosphorus pesticides (OPs). 5,10,15,20-Tetra(4-pyridyl)porphyrin (TPyP) with meso-pyridyl substituents was bound to the surface of CdTe QDs to produce self-assembled nanosensors, and the process of FRET between QDs and TPyP occurred. However, the process of FRET was switched off with the addition of OPs, due to the combination between TPyP and OPs. The fluorescence intensity of TPyP (donor) would decrease gradually with the increasing concentration of OPs. Under optimal conditions, a linear correlation was established between the fluorescence intensity ratio ITPyP/IQDs and the concentration of paraoxon in the range of 9.09 × 10(-12)-1.09 × 10(-6) mol L(-1) with a detection limit of 3.15 × 10(-12) mol L(-1). The attractive sensitivity was obtained due to the efficient FRET and the superior fluorescence properties of QDs. The proposed method was successfully applied to the determination of the OPs in real fruit samples with satisfactory results. PMID:27305657

  9. Efficient stray-light suppression for resonance fluorescence in quantum dot micropillars using self-aligned metal apertures

    Science.gov (United States)

    Hopfmann, Caspar; Musiał, Anna; Maier, Sebastian; Emmerling, Monika; Schneider, Christian; Höfling, Sven; Kamp, Martin; Reitzenstein, Stephan

    2016-09-01

    Within this work we propose and demonstrate a technological approach to efficiently suppress excitation laser stray-light in resonance fluorescence experiments on quantum dot micropillars. To ensure efficient stray-light suppression, their fabrication process includes a planarization step and subsequent covering with a titanium mask to fabricate self-aligned apertures at the micropillar positions. These apertures aim to limit laser stray-light in the side-excitation vertical-detection configuration, while enabling detection of the optical signal through the top facet of the micropillars. The beneficial effects of these apertures are proven and quantitatively evaluated within a statistical study in which we determine and compare the stray-light suppression of 48 micropillars with and without metal apertures. Actual resonance fluorescence experiments on single quantum dots coupled to the cavity mode prove the relevance of the proposed approach and demonstrate that it will foster further studies on cavity quantum electrodynamics phenomena under coherent optical excitation.

  10. Early Detection of Trichinella spiralis in Muscle of Infected Mice by Real-Time Fluorescence Resonance Energy Transfer PCR

    OpenAIRE

    Tantrawatpan, Chairat; Intapan, Pewpan M.; Thanchomnang, Tongjit; Sanpool, Oranuch; Janwan, Penchom; Boonmars, Thidarut; Morakote, Nimit; Maleewong, Wanchai

    2013-01-01

    Real-time fluorescence resonance energy transfer (FRET) PCR and melting curve analysis using newly developed fluorophore-labeled hybridization probes were applied for the detection of Trichinella spiralis DNA in muscle of mice following oral inoculation with 300 T. spiralis larvae. The developed assay could detect and differentiate T. spiralis, Trichinella papuae, and Trichinella pseudospiralis DNAs by the different melting temperatures (Tm). The assay had a detection limit of 5×102 positive ...

  11. Investigation of Förster Resonance Energy Transfer (FRET) and Competition of Fluorescent Dyes on DNA Microparticles

    OpenAIRE

    Jieun Kim; Jae Sung Lee; Jong Bum Lee

    2015-01-01

    Fluorescent labeling is widely used to investigate the structural stability and changes to DNA nano- and microstructures. Despite this, the conventional method for observing DNA structures has several limitations in terms of cost-efficiency. This paper introduces a DNA spherical particle stained with DNA intercalating dyes (SYBR Green and SYTOX Orange) as tracers and reports the interaction between multiple dyes. The interference between the dyes was analyzed in terms of Förster resonance en...

  12. Switchable and selective detection of Zn2+ or Cd2+ in living cells based on 3'-O-substituted arrangement of benzoxazole-derived fluorescent probes.

    Science.gov (United States)

    Xu, Yongqian; Xiao, Liangliang; Sun, Shiguo; Pei, Zhichao; Pei, Yuxin; Pang, Yi

    2014-07-18

    Two benzoxazole-derived ESIPT fluorescent sensors and show highly selective detection of Zn(2+) and Cd(2+), respectively, in aqueous solution and living cells. The selectivity switching from Zn(2+) to Cd(2+) is attributed to the different binding mode which is dependent on the 3'-O-substituted arrangement.

  13. Ultrafast fluorescence resonance energy transfer in a bile salt aggregate: Excitation wavelength dependence

    Indian Academy of Sciences (India)

    Ujjwal Mandal; Subhadip Ghosh; Dibyendu Kumar Das; Aniruddha Adhikari; Shantanu Dey; Kankan Bhattacharyya

    2008-01-01

    Fluorescence resonance energy transfer (FRET) from Coumarin 153 (C153) to Rhodamine 6G (R6G) in a secondary aggregate of a bile salt (sodium deoxycholate, NaDC) is studied by femtosecond up-conversion. The emission spectrum of C153 in NaDC is analysed in terms of two spectra-one with emission maximum at 480 nm which corresponds to a non-polar and hydrophobic site and another with maximum at ∼ 530 nm which arises from a polar hydrophilic site. The time constants of FRET were obtained from the rise time of the emission of the acceptor (R6G). In the NaDC aggregate, FRET occurs in multiple time scales -4 ps and 3700 ps. The 4 ps component is assigned to FRET from a donor (D) to an acceptor (A) held at a close distance (DA ∼ 17 Å) inside the bile salt aggregate. The 3700 ps component corresponds to a donor-acceptor distance ∼ 48 Å. The long (3700 ps) component may involve diffusion of the donor. With increase in the excitation wavelength (ex) from 375 to 435 nm, the relative contribution of the ultrafast component of FRET (∼ 4 ps) increases from 3 to 40% with a concomitant decrease in the contribution of the ultraslow component (∼3700 ps) from 97 to 60%. The ex dependence is attributed to the presence of donors at different locations. At a long ex (435 nm) donors in the highly polar peripheral region are excited. A short ex (375 nm) `selects’ donor at a hydrophobic location.

  14. Noninvasive fluorescence resonance energy transfer imaging of in vivo premature drug release from polymeric nanoparticles.

    Science.gov (United States)

    Zou, Peng; Chen, Hongwei; Paholak, Hayley J; Sun, Duxin

    2013-11-01

    Understanding in vivo drug release kinetics is critical for the development of nanoparticle-based delivery systems. In this study, we developed a fluorescence resonance energy transfer (FRET) imaging approach to noninvasively monitor in vitro and in vivo cargo release from polymeric nanoparticles. The FRET donor dye (DiO or DiD) and acceptor dye (DiI or DiR) were individually encapsulated into poly(ethylene oxide)-b-polystyrene (PEO-PS) nanoparticles. When DiO (donor) nanoparticles and DiI (acceptor) nanoparticles were coincubated with cancer cells for 2 h, increased FRET signals were observed from cell membranes, suggesting rapid release of DiO and DiI to cell membranes. Similarly, increased FRET ratios were detected in nude mice after intravenous coadministration of DiD (donor) nanoparticles and DiR (acceptor) nanoparticles. In contrast, another group of nude mice i.v. administrated with DiD/DiR coloaded nanoparticles showed decreased FRET ratios. Based on the difference in FRET ratios between the two groups, in vivo DiD/DiR release half-life from PEO-PS nanoparticles was determined to be 9.2 min. In addition, it was observed that the presence of cell membranes facilitated burst release of lipophilic cargos while incorporation of oleic acid-coated iron oxide into PEO-PS nanoparticles slowed the release of DiD/DiR to cell membranes. The developed in vitro and in vivo FRET imaging techniques can be used to screening stable nanoformulations for lipophilic drug delivery.

  15. Study on molecular interactions between proteins on live cell membranes using quantum dot-based fluorescence resonance energy transfer.

    Science.gov (United States)

    Liu, Tian-Cai; Zhang, Hai-Li; Wang, Jian-Hao; Wang, Hai-Qiao; Zhang, Zhi-Hong; Hua, Xiao-Feng; Cao, Yuan-Cheng; Luo, Qing-Ming; Zhao, Yuan-Di

    2008-08-01

    Mouse anti-human CD71 monoclonal antibody (anti-CD71) was conjugated with red quantum dots (QDs; 5.3 nm, emission wavelength lambda(em) = 614 nm) and used to label HeLa cells successfully. Then green QD-labeled goat anti-mouse immunoglobulin G (IgG; the size of the green QDs was 2.2 nm; lambda(em) = 544 nm) was added to bind the red-QD-conjugated anti-CD71 on the cell surface by immunoreactions. Such interaction between anti-CD71 and IgG lasted 4 min and was observed from the fluorescence spectra: the fluorescence intensity of the "red" peak at 614 nm increased by 32%; meanwhile that of the "green" one at 544 nm decreased by 55%. The ratio of the fluorescence intensities (I(544 nm)/I(614 nm)) decreased from 0.5 to 0.2. The fluorescence spectra as well as cell imaging showed that fluorescence resonance energy transfer took place between these two kinds of QDs on the HeLa cells through interactions between the primary antibody and the secondary antibody. PMID:18537029

  16. A Cell-Based Internalization and Degradation Assay with an Activatable Fluorescence-Quencher Probe as a Tool for Functional Antibody Screening.

    Science.gov (United States)

    Li, Yan; Liu, Peter Corbett; Shen, Yang; Snavely, Marshall D; Hiraga, Kaori

    2015-08-01

    For the development of therapeutically potent anti-cancer antibody drugs, it is often important to identify antibodies that internalize into cells efficiently, rather than just binding to antigens on the cell surface. Such antibodies can mediate receptor endocytosis, resulting in receptor downregulation on the cell surface and potentially inhibiting receptor function and tumor growth. Also, efficient antibody internalization is a prerequisite for the delivery of cytotoxic drugs into target cells and is critical for the development of antibody-drug conjugates. Here we describe a novel activatable fluorescence-quencher pair to quantify the extent of antibody internalization and degradation in the target cells. In this assay, candidate antibodies were labeled with a fluorescent dye and a quencher. Fluorescence is inhibited outside and on the surface of cells, but activated upon endocytosis and degradation of the antibody. This assay enabled the development of a process for rapid characterization of candidate antibodies potentially in a high-throughput format. By employing an activatable secondary antibody, primary antibodies in purified form or in culture supernatants can be screened for internalization and degradation. Because purification of candidate antibodies is not required, this method represents a direct functional screen to identify antibodies that internalize efficiently early in the discovery process. PMID:26024945

  17. 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.

  18. Fluorescence resonance energy transfer (FRET) for DNA biosensors: FRET pairs and Foerster distances for various dye-DNA conjugates

    International Nuclear Information System (INIS)

    Fluorescence resonance energy transfer (FRET) between the extrinsic dye labels Cyanine 3 (Cy3), Cyanine 5 (Cy5), Carboxytetramethyl Rhodamine (TAMRA), Iowa Black Fluorescence Quencher (IabFQ), and Iowa Black RQ (IabRQ) has been studied. The Foerster distances for these FRET-pairs in single- and double-stranded DNA conjugates have been determined. In particular, it should be noted that the quantum yield of the donors Cy3 and TAMRA varies between single- and double-stranded DNA. While this alters the Foerster distance for a donor-acceptor pair, this also allows for detection of thermal denaturation events with a single non-intercalating fluorophore. The utility of FRET in the development of nucleic acid biosensor technology is illustrated by using TAMRA and IabRQ as a FRET pair in selectivity experiments. The differential quenching of TAMRA fluorescence by IabRQ in solution has been used to discriminate between 0 and 3 base pair mismatches at 60 deg. C for a 19 base sequence. At room temperature, the quenching of TAMRA fluorescence was not an effective indicator of the degree of base pair mismatch. There appears to be a threshold of duplex stability at room temperature which occurs beyond two base pair mismatches and reverses the observed trend in TAMRA fluorescence prior to that degree of mismatch. When this experimental system is transferred to a glass surface through covalent coupling and organosilane chemistry, the observed trend in TAMRA fluorescence at room temperature is similar to that obtained in bulk solution, but without a threshold of duplex stability. In addition to quenching of fluorescence by FRET, it is believed that several other quenching mechanisms are occurring at the surface

  19. Study on the interaction between fluoroquinolones and erythrosine by absorption, fluorescence and resonance Rayleigh scattering spectra and their application

    Science.gov (United States)

    Wang, Jian; Liu, Zhongfang; Liu, Jiangtao; Liu, Shaopu; Shen, Wei

    2008-03-01

    In pH 4.4-4.5 Britton-Robinson (BR) buffer solution, fluoroquinolone antibiotics (FLQs) including ciprofloxacin (CIP), norfloxacin (NOR), levofloxacin (LEV) and lomefloxacin (LOM) could react with erythrosine (Ery) to form 1:1 ion-association complexes, which not only resulted in the changes of the absorption spectra and the quenching of fluorescence, but also resulted in the great enhancement of resonance Rayleigh scattering (RRS). These offered some indications of the determination of fluoroquinolone antibiotics by spectrophotometric, fluorescence and resonance Rayleigh scattering methods. The detection limits for fluoroquinolone antibiotics were in the range of 0.097-0.265 μg/mL for absorption methods, 0.022-0.100 μg/mL for fluorophotometry and 0.014-0.027 μg/mL for RRS method, respectively. Among them, the RRS method had the highest sensitivity. In this work, the spectral characteristics of the absorption, fluorescence and RRS, the optimum conditions of the reactions and the properties of the analytical chemistry were investigated. The methods have been successfully applied to determination of some fluoroquinolone antibiotics in human urine samples and tablets. Taking CIP-Ery system as an example, the charge distribution, the enthalpy of formation and the mean polarizability were calculated by density function theory (DFT) method. In addition, the reasons for the enhancement of scattering spectra were discussed.

  20. Probing the Conformation of the Fibronectin III1–2 Domain by Fluorescence Resonance Energy Transfer*S⃞

    Science.gov (United States)

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

    2009-01-01

    Fibronectin (FN) matrix is crucial for cell and tissue functions during embryonic development, wound healing, and oncogenesis. Assembly of FN matrix fibrils requires FN domains that mediate interactions with integrin receptors and with other FN molecules. In addition, regulation of FN matrix assembly depends on the first two FN type III modules, III1 and III2, which harbor FN-binding sites. We propose that interactions between these two modules sequester FN-binding sites in soluble FN and that these sites become exposed by FN conformational changes during assembly. To test the idea that III1–2 has a compact conformation, we constructed CIIIY, a conformational sensor of III1–2 based on fluorescent resonance energy transfer between cyan and yellow fluorescent proteins conjugated at its N and C termini. We demonstrate energy transfer in CIIIY and show that fluorescent resonance energy transfer was eliminated by proteolysis and by treatment with mild denaturants that disrupted intramolecular interactions between the two modules. We also show that mutations of key charged residues resulted in conformational changes that exposed binding sites for the N-terminal 70-kDa FN fragment. Collectively, these results support a conformation-dependent mechanism for the regulation of FN matrix assembly by III1–2. PMID:19064996

  1. The inhibition of fluorescence resonance energy transfer between multicolor quantum dots for rapid and sensitive detection of Staphylococcus aureus

    Science.gov (United States)

    Wang, Beibei; Wang, Qi; Ma, Meihu; Cai, Zhaoxia

    2015-01-01

    In this paper, we constructed the fluorescence resonance energy transfer (FRET) system between two multi-color quantum dots (QDs) of two sizes for rapid and sensitive detection of Staphylococcus aureus. In this system, green-emitting QDs conjugated with rabbit anti-S. aureus antibodies were used as energy donors while orange-emitting QDs conjugated with goat-anti-rabbit IgG were used as energy acceptors to form FRET system. Pre-binding of Staphylococcus aureus (S. aureus) on the donor occupied the binding sites and thus blocked resonance energy transfer between two colors QDs, leading to the quenching fluorescence of the acceptor. The fluorescence of acceptor has a linear calibration graph with the concentrations of S. aureus from 52 to 2.6 × 105 CFU mL-1. The low detection limit was 10 CFU/mL. It was worth mentioning that the detection method of S. aureus had been applied to the analysis of apple juice and milk samples, which could potentially be developed into a sensor in the further study.

  2. Special characteristics of fluorescence and resonance Rayleigh scattering for cadmium telluride nanocrystal aqueous solution and its interactions with aminoglycoside antibiotics

    Institute of Scientific and Technical Information of China (English)

    LI TaiShan; LIU ShaoPu; LIU ZhongFang; HU XiaoLi; ZHANG LiPing

    2009-01-01

    CdTe nanocrystals (CdTe NCs) were achieved by reaction of CdCl2 with KHTe solution and were capped with sodium mercaptoacetate. The product was detected by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive spectroscopy (EDS), fluorescence spectra, ultraviolet-visible spectra and X-ray diffraction (XRD). The CdTe NCs are of cubic structure and the average size is about 5 nm. The fluorescence quantum yield of CdTe NCs aqueous solution increased from 37% to 97% after 20 d under room light. The maximum λem of fluorescence changed from 543 nm to 510 nm and the blue shift was 33 nm. CdTe NCs aqueous solution can be steady for at least 10 months at 4℃ in a refrigerator. The resonance Rayleigh scattering (RRS) of CdTe NCs in the aqueous solution was investigated. The maximum scattering peak was located at about 554 nm. The interactions of CdTe NCs with amikacin sulfate (AS) and micronomicin sulfate (MS) were in-vestigated respectively. The effects of AS and MS on fluorescence and RRS of CdTe NCs were analyzed. It was found that AS and MS quenched the photoluminescence of CdTe NCs and enhanced RRS of CdTe NCs. Under optimum conditions, there are linear relationships between quenching intensity (F0-F), intensity of RRS (1-10) and concentration of AS and MS. The detection limits (3σ) of AS and MS are re-spectively 3.4 ng.mL-1 and 2.6 ng.mL-1 by the fluorescence quenching method, and 15.2 ng.mL-1 and 14.0 ng.mL-1 by the RRS method. The methods have high sensitivity, thus CdTe NCs may be used as fluorescence probes and RRS probes for the detection of aminoglycoside antibiotics.

  3. Establishment and validation of whole-cell based fluorescence assays to identify anti-mycobacterial compounds using the Acanthamoeba castellanii-Mycobacterium marinum host-pathogen system.

    Directory of Open Access Journals (Sweden)

    Sébastien Kicka

    Full Text Available Tuberculosis is considered to be one of the world's deadliest disease with 2 million deaths each year. The need for new antitubercular drugs is further exacerbated by the emergence of drug-resistance strains. Despite multiple recent efforts, the majority of the hits discovered by traditional target-based screening showed low efficiency in vivo. Therefore, there is heightened demand for whole-cell based approaches directly using host-pathogen systems. The phenotypic host-pathogen assay described here is based on the monitoring of GFP-expressing Mycobacterium marinum during infection of the amoeba Acanthamoeba castellanii. The assay showed straight-forward medium-throughput scalability, robustness and ease of manipulation, demonstrating its qualities as an efficient compound screening system. Validation with a series of known antitubercular compounds highlighted the advantages of the assay in comparison to previously published macrophage-Mycobacterium tuberculosis-based screening systems. Combination with secondary growth assays based on either GFP-expressing D. discoideum or M. marinum allowed us to further fine-tune compound characterization by distinguishing and quantifying growth inhibition, cytotoxic properties and antibiotic activities of the compounds. The simple and relatively low cost system described here is most suitable to detect anti-infective compounds, whether they present antibiotic activities or not, in which case they might exert anti-virulence or host defense boosting activities, both of which are largely overlooked by classical screening approaches.

  4. Monitoring triplex DNA formation with fluorescence resonance energy transfer between a fluorophore-labeled probe and intercalating dyes.

    Science.gov (United States)

    Chiou, Chiuan-Chian; Chen, Shiau-Wen; Luo, Ji-Dung; Chien, Yu-Tzu

    2011-09-01

    Triplex-forming oligonucleotides (TFOs) are sequence-dependent DNA binders that may be useful for DNA targeting and detection. A sensitive and convenient method to monitor triplex formation by a TFO and its target DNA duplex is required for the application of TFO probes. Here we describe a novel design by which triplex formation can be monitored homogeneously without prelabeling the target duplex. The design uses a TFO probe tagged with a fluorophore that undergoes fluorescence resonance energy transfer with fluorescent dyes that intercalate into the target duplex. Through color compensation analysis, the specific emission of the TFO probe reveals the status of the triple helices. We used this method to show that triple helix formation with TFOs is magnesium dependent. We also demonstrated that the TFO probe can be used for detection of sequence variation in melting analysis and for DNA quantitation in real-time polymerase chain reaction. PMID:21609711

  5. DNAzyme-based biosensor for Cu(2+) ion by combining hybridization chain reaction with fluorescence resonance energy transfer technique.

    Science.gov (United States)

    Chen, Ying; Chen, Ling; Ou, Yidian; Wang, Zhenhua; Fu, Fengfu; Guo, Liangqia

    2016-08-01

    A novel signal amplification strategy based on Cu(2+)-dependent DNAzyme was developed for sensing Cu(2+) ion by combining hybridization chain reaction (HCR) with fluorescence resonance energy transfer (FRET) technique. In the presence of Cu(2+) ion, the substrate strands of Cu(2+)-dependent DNAzyme immobilized on magnetic beads were specifically cleaved and released. The released strands initiated the HCR process of hairpin H1 and H2 labeled with FAM as the donor and TAMRA as the acceptor, respectively. Long nicked dsDNA structures were self-assembled to bring the donor and the acceptor in close proximity, resulting in a FRET process. The relative ratio of fluorescent intensities of the acceptor and donor was used to quantitatively detect Cu(2+) ion with a limit of detection of 0.5nmolL(-1). This proposed biosensor was applied to detect Cu(2+) ion in tap water with satisfactory results. PMID:27216680

  6. Label-free distinguishing between neurons and glial cells based on two-photon excited fluorescence signal of neuron perinuclear granules

    Science.gov (United States)

    Du, Huiping; Jiang, Liwei; Wang, Xingfu; Liu, Gaoqiang; Wang, Shu; Zheng, Liqin; Li, Lianhuang; Zhuo, Shuangmu; Zhu, Xiaoqin; Chen, Jianxin

    2016-08-01

    Neurons and glial cells are two critical cell types of brain tissue. Their accurate identification is important for the diagnosis of psychiatric disorders such as depression and schizophrenia. In this paper, distinguishing between neurons and glial cells by using the two-photon excited fluorescence (TPEF) signals of intracellular intrinsic sources was performed. TPEF microscopy combined with TUJ-1 and GFAP immunostaining and quantitative image analysis demonstrated that the perinuclear granules of neurons in the TPEF images of brain tissue and the primary cultured cortical cells were a unique characteristic of neurons compared to glial cells which can become a quantitative feature to distinguish neurons from glial cells. With the development of miniaturized TPEF microscope (‘two-photon fiberscopes’) imaging devices, TPEF microscopy can be developed into an effective diagnostic and monitoring tool for psychiatric disorders such as depression and schizophrenia.

  7. Direct visualization of triplex DNA molecular dynamics by fluorescence resonance energy transfer and atomic force microscopy measurements

    Science.gov (United States)

    Chang, Chia-Ching; Lin, Po-Yen; Chen, Yen-Fu; Chang, Chia-Seng; Kan, Lou-Sing

    2007-11-01

    We have detected the dynamics of 17-mer DNA triplex dissociation mechanism at the molecular level. Fluorescence resonance energy transfer (FRET) was used as an indicator of intermolecular interaction in nanometer range, whereas atomic force microscopy (AFM) was employed to address single molecule with sub-angstrom precision. The maximum rupture force of DNA triplex was found at pH 4.65, consistent with macroscopic observations. These results indicated that the FRET together with an AFM detection system could be used to reveal the DNA triplex interaction in nanometer scale unambiguously.

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

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Kyeong-Ok [Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, KS 66506 (United States); Takahashi, Daisuke; Prakash, Om [Department of Biochemistry, Kansas State University, Manhattan, KS 66506 (United States); Kim, Yunjeong, E-mail: ykim@vet.ksu.edu [Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, KS 66506 (United States)

    2012-02-20

    Noroviruses are the major cause of food- or water-borne gastroenteritis outbreaks in humans. The norovirus protease that cleaves a large viral polyprotein to nonstructural proteins is essential for virus replication and an attractive target for antiviral drug development. Noroviruses show high genetic diversity with at least five genogroups, GI-GV, of which GI and GII are responsible for the majority of norovirus infections in humans. We cloned and expressed proteases of Norwalk virus (GI) and MD145 virus (GII) and characterized the enzymatic activities with fluorescence resonance energy transfer substrates. We demonstrated that the GI and GII proteases cleaved the substrates derived from the naturally occurring cleavage site in the open reading frame (ORF) 1 of G1 norovirus with similar efficiency, and that enzymatic activity of both proteases was inhibited by commercial protease inhibitors including chymostatin. The interaction of chymostatin to Norwalk virus protease was validated by nuclear magnetic resonance (NMR) spectroscopy.

  9. Time-Resolved Fluorescence Assays.

    Science.gov (United States)

    Ma, Chen-Ting; Sergienko, Eduard A

    2016-01-01

    Fluorescence-based detection techniques are popular in high throughput screening due to sensitivity and cost-effectiveness. Four commonly used techniques exist, each with distinct characteristics. Fluorescence intensity assays are the simplest to run, but suffer the most from signal interference. Fluorescence polarization assays show less interference from the compounds or the instrument, but require a design that results in change of fluorophore-containing moiety size and usually have narrow assay signal window. Fluorescence resonance energy transfer (FRET) is commonly used for detecting protein-protein interactions and is constrained not by the sizes of binding partners, but rather by the distance between fluorophores. Time-resolved fluorescence resonance energy transfer (TR-FRET), an advanced modification of FRET approach utilizes special fluorophores with long-lived fluorescence and earns its place near the top of fluorescent techniques list by its performance and robustness, characterized by larger assay window and minimized compound spectral interference. TR-FRET technology can be applied in biochemical or cell-based in vitro assays with ease. It is commonly used to detect modulation of protein-protein interactions and in detection of products of biochemical reactions and cellular activities. PMID:27316992

  10. Homogeneous detection of concanavalin A using pyrene-conjugated maltose assembled graphene based on fluorescence resonance energy transfer.

    Science.gov (United States)

    Chen, Qiushui; Wei, Weili; Lin, Jin-Ming

    2011-07-15

    In this work, we proposed a novel biosensor to homogeneously detect concanavalin A (ConA) using pyrene-conjugated maltose assembled graphene based on fluorescence resonance energy transfer (FRET). Maltose-grafted-aminopyrene (Mal-Apy) was synthesized and characterized by mass spectra, UV-vis and fluorescence spectra. The Mal-Apy was further employed for fluorescence switch and ConA recognition. When Mal-Apy was self-assembled on the surface of graphene by means of π-stacking interaction, its fluorescence was adequately quenched because the graphene acted as a "nanoquencher" of the pyrene rings due to FRET. As a result, in the presence of ConA, competitive binding of ConA with glucose destroyed the π-stacking interaction between the pyrene and graphene, thereby causing the fluorescence recovery. This method was demonstrated the selective sensing of ConA, and the linear range is 2.0 × 10⁻² to 1.0 μM with the linear equation y=1.029x + 0.284 (R = 0.996). The limit of detection for ConA was low to 0.8 nM, and the detection of ConA could be performed in 5 min, indicating that this method could be used for fast, sensitive, and selective sensing of ConA. Such data suggests that the graphene FRET platform is a great potential application for protein-carbohydrate studies, and would be widely applied in drug screening, bimolecular recognition and disease diagnosis. PMID:21621405

  11. 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.

  12. Measuring ligand-dependent and ligand-independent interactions between nuclear receptors and associated proteins using Bioluminescence Resonance Energy Transfer (BRET2)

    OpenAIRE

    Koterba, Kristen L.; Rowan, Brian G.

    2006-01-01

    Bioluminescent resonance energy transfer (BRET2) is a recently developed technology for the measurement of protein-protein interactions in a live, cell-based system. BRET2 is characterized by the efficient transfer of excited energy between a bioluminescent donor molecule (Renilla luciferase) and a fluorescent acceptor molecule (a mutant of Green Fluorescent Protein (GFP2)). The BRET2 assay offers advantages over fluorescence resonance energy transfer (FRET) because it does not require an ext...

  13. Collective resonance fluorescence in small and dense atom clouds: Comparison between theory and experiment

    CERN Document Server

    Jenkins, S D; Javanainen, J; Jennewein, S; Bourgain, R; Pellegrino, J; Sortais, Y R P; Browaeys, A

    2016-01-01

    We study the emergence of a collective optical response of a cold and dense $^{87}$Rb atomic cloud to a near-resonant low-intensity light when the atom number is gradually increased. Experimental observations are compared with microscopic stochastic simulations of recurrent scattering processes between the atoms that incorporate the atomic multilevel structure and the optical measurement setup. We analyze the optical response of an inhomogeneously-broadened gas and find that the experimental observations of the resonance line shifts and the total collected scattered light intensity in cold atom clouds substantially deviate from those of thermal atomic ensembles, indicating strong light-induced resonant dipole-dipole interactions between the atoms. At high densities, the simulations also predict a significantly slower decay of light-induced excitations in cold than in thermal atom clouds. The role of dipole-dipole interactions is discussed in terms of resonant coupling examples and the collective radiative exc...

  14. Folate-targeted gadolinium-lipid-based nanoparticles as a bimodal contrast agent for tumor fluorescent and magnetic resonance imaging.

    Science.gov (United States)

    Nakamura, Taro; Kawano, Kumi; Shiraishi, Kouichi; Yokoyama, Masayuki; Maitani, Yoshie

    2014-01-01

    To enhance tumor magnetic resonance imaging (MRI) signals via the selective accumulation of contrast agents, we prepared folate-modified gadolinium-lipid-based nanoparticles as MRI contrast agents. Folate-modified nanoparticles were comprised of polyethylene glycol (PEG)-lipid, gadolinium diethylenetriamine pentaacetic acid lipid, cationic cholesterol derivatives, folate-conjugated PEG-lipid, and Cy7-PEG-lipid. Folate receptor-mediated cellular nanoparticle association was examined in KB cells, which overexpress the folate receptor. The biodistribution of nanoparticles after their intravenous injection into KB tumor-bearing mice was measured. Mice were imaged through in vivo fluorescence imaging and MRI 24 h after nanoparticle injection, and the intensity enhancement of the tumor MRI signal was evaluated. Increased cellular association of folate-modified nanoparticles was inhibited by excess free folic acid, indicating that nanoparticle association was folate receptor-mediated. Irrespective of folate modification, the amount of nanoparticles in blood 24 h after injection was ca. 10% of the injected dose. Compared with non-modified nanoparticles, folate-modified nanoparticles exhibited significant accumulation in tumor tissues without altering other biodistribution, as well as enhanced tumor fluorescence and MRI signal intensity. The results support the feasibility of MRI- and in vivo fluorescence imaging-based tumor visualization using folate-modified nanoparticles and provide opportunities to develop folate targeting-based imaging applications.

  15. A homogeneous europium cryptate-based assay for the diagnosis of mutations by time-resolved fluorescence resonance energy transfer.

    Science.gov (United States)

    Lopez-Crapez, E; Bazin, H; Andre, E; Noletti, J; Grenier, J; Mathis, G

    2001-07-15

    Oligonucleotide ligation assay (OLA) is considered to be a very useful methodology for the detection and characterization of mutations, particularly for clinical purposes. The fluorescence resonance energy transfer between a fluorescent donor and a suitable fluorophore as acceptor has been applied in the past to several scientific fields. This technique is well adapted to nucleic acid analysis such as DNA sequencing, DNA hybridization and polymerase chain reaction. We describe here a homogeneous format based on the use of a rare earth cryptate label as donor: tris-bipyridine-Eu(3+). The long-lived fluorescence of this label makes it possible to reach a high sensitivity by using a time-resolved detection mode. A non-radiative energy transfer technology, known as time-resolved amplification of cryptate emission (TRACE((R))) characterized by a temporal and spectral selectivity has been developed. The TRACE((R)) detection of characterized single nucleotide polymorphism using the OLA for allelic discrimination is proposed. We demonstrate the potentialities of this OLA-TRACE((R)) methodology through the analysis of K-ras oncogene point mutations.

  16. Boronate Affinity Fluorescent Nanoparticles for Förster Resonance Energy Transfer Inhibition Assay of cis-Diol Biomolecules.

    Science.gov (United States)

    Wang, Shuangshou; Ye, Jin; Li, Xinglin; Liu, Zhen

    2016-05-17

    Förster resonance energy transfer (FRET) has been essential for many applications, in which an appropriate donor-acceptor pair is the key. Traditional dye-to-dye combinations remain the working horses but are rather nonspecifically susceptive to environmental factors (such as ionic strength, pH, oxygen, etc.). Besides, to obtain desired selectivity, functionalization of the donor or acceptor is essential but usually tedious. Herein, we present fluorescent poly(m-aminophenylboronic acid) nanoparticles (poly(mAPBA) NPs) synthesized via a simple procedure and demonstrate a FRET scheme with suppressed environmental effects for the selective sensing of cis-diol biomolecules. The NPs exhibited stable fluorescence properties, resistance to environmental factors, and a Förster distance comparable size, making them ideal donor for FRET applications. By using poly(mAPBA) NPs and adenosine 5'-monophosphate modified graphene oxide (AMP-GO) as a donor and an acceptor, respectively, an environmental effects-suppressed boronate affinity-mediated FRET system was established. The fluorescence of poly(mAPBA) NPs was quenched by AMP-GO while it was restored when a competing cis-diol compounds was present. The FRET system exhibited excellent selectivity and improved sensitivity toward cis-diol compounds. Quantitative inhibition assay of glucose in human serum was demonstrated. As many cis-diol compounds such as sugars and glycoproteins are biologically and clinically significant, the FRET scheme presented herein could find more promising applications. PMID:27089186

  17. Bimodal Fluorescence and Magnetic Resonance Imaging Using Water-Soluble Hexagonal NaYF4:Ce,Tb,Gd Nanocrystals

    Directory of Open Access Journals (Sweden)

    Wen Ting Ren

    2011-01-01

    Full Text Available The present study explored the feasibility of using hexagonal-phase NaYF4:Ce,Tb,Gd nanocrystals as bimodal probes for fluorescence and magnetic resonance (MR imaging. Using a facile and user-friendly strategy, the NaYF4:Ce,Tb,Gd nanocrystals were synthesized with good water dispensability, high quantum yield (26%, and decent MR T1 relaxivity (r1=2.87 mM−1 s−1. The NaYF4:Ce,Tb,Gd NCs conjugated by folic acid presented great efficiency in fluorescence imaging of C6 glioma cells in vitro. Meanwhile, in in vivo MR experiments on rats, the NaYF4:Ce,Tb,Gd NCs also significantly increased T1 signal in the liver, spleen, and kidney even with a low probe dose. The proposed NaYF4:Ce,Tb,Gd nanoprobes hold promise for simultaneous bimodal fluorescence and MR bioimaging.

  18. Magnetic resonance-coupled fluorescence tomography scanner for molecular imaging of tissue

    Science.gov (United States)

    Davis, Scott C.; Pogue, Brian W.; Springett, Roger; Leussler, Christoph; Mazurkewitz, Peter; Tuttle, Stephen B.; Gibbs-Strauss, Summer L.; Jiang, Shudong S.; Dehghani, Hamid; Paulsen, Keith D.

    2008-06-01

    A multichannel spectrally resolved optical tomography system to image molecular targets in small animals from within a clinical MRI is described. Long source/detector fibers operate in contact mode and couple light from the tissue surface in the magnet bore to 16 spectrometers, each containing two optical gratings optimized for the near infrared wavelength range. High sensitivity, cooled charge coupled devices connected to each spectrograph provide detection of the spectrally resolved signal, with exposure times that are automated for acquisition at each fiber. The design allows spectral fitting of the remission light, thereby separating the fluorescence signal from the nonspecific background, which improves the accuracy and sensitivity when imaging low fluorophore concentrations. Images of fluorescence yield are recovered using a nonlinear reconstruction approach based on the diffusion approximation of photon propagation in tissue. The tissue morphology derived from the MR images serves as an imaging template to guide the optical reconstruction algorithm. Sensitivity studies show that recovered values of indocyanine green fluorescence yield are linear to concentrations of 1nM in a 70mm diameter homogeneous phantom, and detection is feasible to near 10pM. Phantom data also demonstrate imaging capabilities of imperfect fluorophore uptake in tissue volumes of clinically relevant sizes. A unique rodent MR coil provides optical fiber access for simultaneous optical and MR data acquisition of small animals. A pilot murine study using an orthotopic glioma tumor model demonstrates optical-MRI imaging of an epidermal growth factor receptor targeted fluorescent probe in vivo.

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

    Science.gov (United States)

    Nikiforov, Theo T; Beechem, Joseph M

    2006-10-01

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

  20. A new biosensor for glucose determination in serum based on up-converting fluorescence resonance energy transfer.

    Science.gov (United States)

    Peng, Jianhong; Wang, Yuhui; Wang, Jialan; Zhou, Xin; Liu, Zhihong

    2011-10-15

    In this work, a new glucose sensor based on up-converting fluorescence resonance energy transfer (UC-FRET) was developed. Up-converting phosphors (UCPs, NaYF(4): Yb, Er), which were covalently labeled with Concanavalin A (ConA), were used as the energy donor with thiolated β-cyclodextrins (SH-β-CDs) functionalized gold nanoparticles as the energy acceptor. Due to the combination between ConA and SH-β-CDs, the energy donor and the acceptor were brought to close proximity, resulting in the quenching of the fluorescence of UCPs by gold nanoparticles. In the presence of glucose which competed with SH-β-CDs towards the binding sites of ConA, the biosensor (UCPs-ConA-SH-β-CDs-Au) was decomposed and the energy donor was separated from the acceptor. Therefore, the fluorescence of UCPs was restored dependent on the concentration of glucose. The increase of UCPs fluorescence intensity was proportional to glucose concentration within the range from 0.4 μM to 10μM in aqueous buffer, with a limit of detection (LOD) of 0.043 μM. A same linear range of glucose concentration was obtained in a human serum matrix (which was pretreated and thus contained no glucose) with a slightly higher LOD (0.065 μM). The glucose sensor was applied to real human serum samples with the results consistent with that of a classic hexokinase (HK) method, indicating that the UC-FRET biosensor was competent for directly sensing glucose in serum samples without optical interference, which benefited from the near infrared (NIR) excitation nature of UCPs. The results of this work suggested that the UC-FRET technique could be a promising alternative for detecting biomolecules in complex biological sample matrixes for diagnostic purposes. PMID:21852101

  1. Facile preparation of Gd3+ doped carbon quantum dots: Photoluminescence materials with magnetic resonance response as magnetic resonance/fluorescence bimodal probes

    Science.gov (United States)

    Ren, X. Y.; Yuan, X. X.; Wang, Y. P.; Liu, C. L.; Qin, Y.; Guo, L. P.; Liu, L. H.

    2016-07-01

    There are a few bimodal molecular imaging probes constructed by gadolinium (3+) ions in combination with carbon quantum dots (CQDs), and the reported ones show such obvious drawbacks as low luminous efficiency and weak MRI contrast. In the paper, a kind of CQDs photoluminescence materials with magnetic resonance response was prepared by hydrothermal method and employing gadopentetate monomeglumine (GdPM) as a precusor. Here, the GdPM plays a role of not only carbon source, but also gadolinium (3+) sources. When the GdPM aqueous solution with a concentration of 4 mg mL-1 was pyrolyzed under 220 °C and 2.0 MPa for 8 h, an optimal CQDs was obtained which are doped with gadolinium (3+) ions in both chelates and Gd2O3 (named as Gd3+-CQDs). The average diameter of the Gd3+-CQDs is about 1.6 nm, which show a high photoluminescence quantum yield of 7.1%, as well as high longitudinal relaxivity (r1) of 9.87 mM-1 s-1. And owing to the unconspicuous cell toxicity, the Gd3+-CQDs show big possibility for clinical application in magnetic resonance/fluorescence bimodal molecular imaging.

  2. Special characteristics of fluorescence and resonance Rayleigh scattering for cadmium telluride nanocrystal aqueous solution and its interactions with aminoglycoside antibiotics

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    CdTe nanocrystals(CdTe NCs) were achieved by reaction of CdCl2 with KHTe solution and were capped with sodium mercaptoacetate.The product was detected by transmission electron microscopy(TEM),high-resolution transmission electron microscopy(HRTEM),energy dispersive spectroscopy(EDS),fluorescence spectra,ultraviolet-visible spectra and X-ray diffraction(XRD).The CdTe NCs are of cubic structure and the average size is about 5 nm.The fluorescence quantum yield of CdTe NCs aqueous solution increased from 37% to 97% after 20 d under room light.The maximum λem of fluorescence changed from 543 nm to 510 nm and the blue shift was 33 nm.CdTe NCs aqueous solution can be steady for at least 10 months at 4℃ in a refrigerator.The resonance Rayleigh scattering(RRS) of CdTe NCs in the aqueous solution was investigated.The maximum scattering peak was located at about 554 nm.The interactions of CdTe NCs with amikacin sulfate(AS) and micronomicin sulfate(MS) were investigated respectively.The effects of AS and MS on fluorescence and RRS of CdTe NCs were analyzed.It was found that AS and MS quenched the photoluminescence of CdTe NCs and enhanced RRS of CdTe NCs.Under optimum conditions,there are linear relationships between quenching intensity(F0-F),intensity of RRS(I-I0) and concentration of AS and MS.The detection limits(3б) of AS and MS are respectively 3.4 ng·mL-1 and 2.6 ng·mL-1 by the fluorescence quenching method,and 15.2 ng·mL-1 and 14.0 ng·mL-1 by the RRS method.The methods have high sensitivity,thus CdTe NCs may be used as fluorescence probes and RRS probes for the detection of aminoglycoside antibiotics.

  3. Excitonic Heterodimer Formation in an HIV-1 Oligonucleotide Labeled with a Donor-Acceptor Pair Used for Fluorescence Resonance Energy Transfer

    OpenAIRE

    Bernacchi, Serena; Piémont, Etienne; Potier, Noelle; Van Dorsselaer, Alain; Mély, Yves

    2003-01-01

    In this study, we investigated the absorbance and fluorescence properties of cTAR, the complementary DNA sequence of the transactivation response element of the HIV-1 genome, doubly end-labeled by different dyes, 5(and 6)-carboxyfluorescein (Fl) and 5(and 6)-carboxytetramethylrhodamine (TMR), frequently used in fluorescence resonance energy transfer (FRET) studies. This oligonucleotide forms a stable stem-loop structure. The absorption spectrum of this species clearly differed from that of a ...

  4. Handheld Fluorescence Resonance Energy Transfer (FRET)-Aptamer Sensor for Bone Markers

    Science.gov (United States)

    Bruno, John G.

    2015-01-01

    Astronauts lose significant bone mass during lengthy space flights. NASA wishes to monitor this bone loss in order to develop nutritional and exercise countermeasures. Operational Technologies Corporation (OpTech) has developed a handheld device that quantifies bone loss in a spacecraft environment. The innovation works by adding fluorescent dyes and quenchers to aptamers to enable pushbutton, one-step bind-and-detect FRET assays that can be freeze-dried, rehydrated with body fluids, and used to quantify bone loss.

  5. Monochromatic X-ray propagation in multi-Z media for imaging and diagnostics including Kα Resonance Fluorescence

    Science.gov (United States)

    Westphal, Maximillian; Lim, Sara; Nahar, Sultana; Pradhan, Anil

    2016-05-01

    Aimed at monochromatic X-ray imaging and therapy, broadband, monochromatic, and quasi-monochromatic X-ray sources and propagation through low and high-Z (HZ) media were studied with numerically and experimentally. Monte Carlo simulations were performed using the software package Geant4, and a new code Photx, to simulate X-ray image contrast, depth of penetration, and total attenuation. The data show that monochromatic and quasi-monochromatic X-rays achieve improved contrast at lower absorbed radiation doses compared to conventional broadband 120 kV or CT scans. Experimental quasi-monochromatic high-intensity laser-produced plasma sources and monochromatic synchrotron beam data are compared. Physical processes responsible for X-ray photoexcitation and absorption are numerically modelled, including a novel mechanism for accelerating Kα resonance fluorescence via twin monochromatic X-ray beam. Potential applications are medical diagnostics and high-Z material detection. Acknowledgement: Ohio Supercomputer Center, Columbus, OH.

  6. Depth profiles of pulmonary surfactant protein B in phosphatidylcholine bilayers, studied by fluorescence and electron spin resonance spectroscopy

    DEFF Research Database (Denmark)

    Cruz, A; Casals, C; Plasencia, I;

    1998-01-01

    Pulmonary surfactant-associated protein B (SP-B) has been isolated from porcine lungs and reconstituted in bilayers of dipalmitoylphosphatidylcholine (DPPC) or egg yolk phosphatidylcholine (PC) to characterize the extent of insertion of the protein into phospholipid bilayers. The parameters...... for the interaction of SP-B with DPPC or PC using different reconstitution protocols have been estimated from the changes induced in the fluorescence emission spectrum of the single protein tryptophan. All the different reconstituted SP-B-phospholipid preparations studied had similar Kd values for the binding....... These differences in the extent of insertion lead to qualitative and quantitative differences in the effect of the protein on the mobility of the phospholipid acyl chains, as studied by spin-label electron spin resonance (ESR) spectroscopy, and could represent different functional stages in the surfactant cycle...

  7. Analysis of nuclear resonance fluorescence excitation measured with LaBr3(Ce) detectors near 2 MeV

    International Nuclear Information System (INIS)

    The performance of LaBr3(Ce) to measure nuclear resonance fluorescence (NRF) excitations is discussed in terms of limits of detection and in comparison with high-purity germanium (HPGe) detectors near the 2 MeV region where many NRF excitation levels from special nuclear materials are located. The NRF experiment was performed at the High Intensity γ-ray Source (HIγS) facility. The incident γ-rays, of 2.12 MeV energy, hit a B4C target to excite the 11B nuclei to the first excitation level. The statistical-sensitive non-linear peak clipping (SNIP) algorithm was implemented to eliminate the background and enhance the limits of detection for the spectra measured with LaBr3(Ce). Both detection and determination limits were deduced from the experimental data

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

    International Nuclear Information System (INIS)

    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% CO2 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

  9. Förster resonance energy transfer and protein-induced fluorescence enhancement as synergetic multi-scale molecular rulers

    Science.gov (United States)

    Ploetz, Evelyn; Lerner, Eitan; Husada, Florence; Roelfs, Martin; Chung, Sangyoon; Hohlbein, Johannes; Weiss, Shimon; Cordes, Thorben

    2016-09-01

    Advanced microscopy methods allow obtaining information on (dynamic) conformational changes in biomolecules via measuring a single molecular distance in the structure. It is, however, extremely challenging to capture the full depth of a three-dimensional biochemical state, binding-related structural changes or conformational cross-talk in multi-protein complexes using one-dimensional assays. In this paper we address this fundamental problem by extending the standard molecular ruler based on Förster resonance energy transfer (FRET) into a two-dimensional assay via its combination with protein-induced fluorescence enhancement (PIFE). We show that donor brightness (via PIFE) and energy transfer efficiency (via FRET) can simultaneously report on e.g., the conformational state of double stranded DNA (dsDNA) following its interaction with unlabelled proteins (BamHI, EcoRV, and T7 DNA polymerase gp5/trx). The PIFE-FRET assay uses established labelling protocols and single molecule fluorescence detection schemes (alternating-laser excitation, ALEX). Besides quantitative studies of PIFE and FRET ruler characteristics, we outline possible applications of ALEX-based PIFE-FRET for single-molecule studies with diffusing and immobilized molecules. Finally, we study transcription initiation and scrunching of E. coli RNA-polymerase with PIFE-FRET and provide direct evidence for the physical presence and vicinity of the polymerase that causes structural changes and scrunching of the transcriptional DNA bubble.

  10. Förster resonance energy transfer and protein-induced fluorescence enhancement as synergetic multi-scale molecular rulers.

    Science.gov (United States)

    Ploetz, Evelyn; Lerner, Eitan; Husada, Florence; Roelfs, Martin; Chung, SangYoon; Hohlbein, Johannes; Weiss, Shimon; Cordes, Thorben

    2016-01-01

    Advanced microscopy methods allow obtaining information on (dynamic) conformational changes in biomolecules via measuring a single molecular distance in the structure. It is, however, extremely challenging to capture the full depth of a three-dimensional biochemical state, binding-related structural changes or conformational cross-talk in multi-protein complexes using one-dimensional assays. In this paper we address this fundamental problem by extending the standard molecular ruler based on Förster resonance energy transfer (FRET) into a two-dimensional assay via its combination with protein-induced fluorescence enhancement (PIFE). We show that donor brightness (via PIFE) and energy transfer efficiency (via FRET) can simultaneously report on e.g., the conformational state of double stranded DNA (dsDNA) following its interaction with unlabelled proteins (BamHI, EcoRV, and T7 DNA polymerase gp5/trx). The PIFE-FRET assay uses established labelling protocols and single molecule fluorescence detection schemes (alternating-laser excitation, ALEX). Besides quantitative studies of PIFE and FRET ruler characteristics, we outline possible applications of ALEX-based PIFE-FRET for single-molecule studies with diffusing and immobilized molecules. Finally, we study transcription initiation and scrunching of E. coli RNA-polymerase with PIFE-FRET and provide direct evidence for the physical presence and vicinity of the polymerase that causes structural changes and scrunching of the transcriptional DNA bubble. PMID:27641327

  11. A fluorescence detected magnetic resonance investigation of the carotenoid triplet states associated with Photosystem II of isolated spinach thylakoid membranes

    CERN Document Server

    Santabarbara, S; Carbonera, D; Heathcote, P

    2005-01-01

    The carotenoid triplet populations associated with the fluorescence emission chlorophyll forms of Photosystem II have been investigated in isolated spinach thylakoid membranes by means of fluorescence detected magnetic resonance in zero field (FDMR). The spectra collected in the 680-690 nm emission range, have been fitted by a global analysis procedure. At least five different carotenoid triplet states coupled to the terminal emitting chlorophyll forms of PS II, peaking at 682 nm, 687 nm and 692 nm, have been characterised. The triplets associated with the outer antenna emission forms, at 682 nm, have zero field splitting parameters D = 0.0385 cm/sup -1/, E = 0.00367 cm/sup -1/; D = 0.0404 cm/sup -1/, E = 0.00379 cm/sup -1/ and D = 0.0386 cm/sup -1/, E = 0.00406 cm/sup -1/ which are very similar to those previously reported for the xanthophylls of the isolated LHC II complex. Therefore the FDMR spectra recorded in this work provide insights into the organisation of the LHC II complex in the unperturbed enviro...

  12. Early detection of Trichinella spiralis in muscle of infected mice by real-time fluorescence resonance energy transfer PCR.

    Science.gov (United States)

    Tantrawatpan, Chairat; Intapan, Pewpan M; Thanchomnang, Tongjit; Sanpool, Oranuch; Janwan, Penchom; Boonmars, Thidarut; Morakote, Nimit; Maleewong, Wanchai

    2013-09-01

    Real-time fluorescence resonance energy transfer (FRET) PCR and melting curve analysis using newly developed fluorophore-labeled hybridization probes were applied for the detection of Trichinella spiralis DNA in muscle of mice following oral inoculation with 300 T. spiralis larvae. The developed assay could detect and differentiate T. spiralis, Trichinella papuae, and Trichinella pseudospiralis DNAs by the different melting temperatures (Tm). The assay had a detection limit of 5 × 10(2) positive control plasmid copies, which was equivalent to 1 ng of T. spiralis DNA spiked into 250 mg of muscle sample. No fluorescence signal was detected when the technique was applied to the DNA of 27 parasites other than Trichinella spp. The assay could detect T. spiralis DNA in muscle at 7, 14, and 21 days postinoculation. The range, mean ± standard deviation, and median of the Tm values of all positive muscle tissue samples were 60.4-60.8, 60.6 ± 0.2, and 60.5, respectively. This assay provides an effective tool for the specific, sensitive, and high-throughput detection of T. spiralis DNA in muscle during the early stage of infection. In addition, the technique can be useful for epidemiologic surveillance in naturally infected wildlife. PMID:23808975

  13. Förster resonance energy transfer and protein-induced fluorescence enhancement as synergetic multi-scale molecular rulers

    Science.gov (United States)

    Ploetz, Evelyn; Lerner, Eitan; Husada, Florence; Roelfs, Martin; Chung, SangYoon; Hohlbein, Johannes; Weiss, Shimon; Cordes, Thorben

    2016-01-01

    Advanced microscopy methods allow obtaining information on (dynamic) conformational changes in biomolecules via measuring a single molecular distance in the structure. It is, however, extremely challenging to capture the full depth of a three-dimensional biochemical state, binding-related structural changes or conformational cross-talk in multi-protein complexes using one-dimensional assays. In this paper we address this fundamental problem by extending the standard molecular ruler based on Förster resonance energy transfer (FRET) into a two-dimensional assay via its combination with protein-induced fluorescence enhancement (PIFE). We show that donor brightness (via PIFE) and energy transfer efficiency (via FRET) can simultaneously report on e.g., the conformational state of double stranded DNA (dsDNA) following its interaction with unlabelled proteins (BamHI, EcoRV, and T7 DNA polymerase gp5/trx). The PIFE-FRET assay uses established labelling protocols and single molecule fluorescence detection schemes (alternating-laser excitation, ALEX). Besides quantitative studies of PIFE and FRET ruler characteristics, we outline possible applications of ALEX-based PIFE-FRET for single-molecule studies with diffusing and immobilized molecules. Finally, we study transcription initiation and scrunching of E. coli RNA-polymerase with PIFE-FRET and provide direct evidence for the physical presence and vicinity of the polymerase that causes structural changes and scrunching of the transcriptional DNA bubble. PMID:27641327

  14. A Study of the Nuclear Resonance Fluorescence Reaction Yield Dependence on the Target Thickness of 208PB

    Science.gov (United States)

    Negm, Hani; Daito, Izuru; Zen, Heishun; Kii, Toshiteru; Masuda, Kai; Hori, Toshitada; Ohgaki, Hideaki; Hajima, Ryoichi; Shizuma, Toshiyuki; Hayakawa, Takehito; Kikuzawa, Nobuhiro; Toyokawa, Hiroyuki

    2015-10-01

    We have been developing an active, non-destructive detection system based on nuclear resonance fluorescence (NRF) for inspecting special nuclear materials (SNMs) such as 235U in a container at a seaport. The study of the NRF yield dependence on the target thickness of SNMs is required to evaluate the performance of the inspection system. To this end, an NRF experiment has been performed using a laser Compton backscattering γ-ray beam line at New SUBARU in 208Pb. Cylindrical shaped natural lead targets with a 0.5 cm radius and varying thicknesses of 1.0, 1.44, and 3.05 cm were irradiated at a resonance energy of 7.332 MeV. The NRF yield was detected using two HPG detectors with relative efficiencies of 120% and 100% positioned at scattering angles of 90° and 130°, respectively, relative to the incident γ-ray beam. As a result, the NRF yield exhibited a saturation behavior for the thick lead target. An analytic treatment and Monte Carlo simulation using GEANT4 was performed to interpret the reaction yield (RY) of the NRF interaction. The simulation result is in good agreement with the experimental data for the target thickness dependence. The analytic treatment, the NRF RY model, is also in reasonable agreement.

  15. Identification of weak autoionizing resonances observed through fluorescence from the satellite states of Ar{sup +}

    Energy Technology Data Exchange (ETDEWEB)

    McLaughlin, K.W.; Yenen, O.; Samson, J.A.R. [Univ. of Nebraska, Lincoln, NE (United States)] [and others

    1997-04-01

    Photoionization accompanied by excitation of the residual ionic state violates an independent electron model since, according to QED, photons interact only with individual electrons. By allowing measurements at a threshold event with high resolution, the observation of the fluorescence from the decay of these excited states (satellite states) is a sensitive method in the study of electron-electron interactions, providing complementary information to photoelectron spectroscopy. In the measurements reported here, an atomic beam of argon has been photoionized with 34 to 39 eV synchrotron radiation at beamline 9.0.1 of the Advanced Light Source. This energy range encompasses the 3p{sup 4} [{sup 3}P] 4p {sup 4}P, {sup 2}P, and {sup 2}D as well as the [{sup 1}D]4p {sup 2}F satellite states of Ar{sup +}. By observing the fine-structure resolved fluorescence from these satellite states, new Rydberg series and extensions of previously known series have been resolved with an energy resolution of 3 meV. With the high photon flux available from the high resolution monochromator of beamline 9.0.1, even the weakly excited [{sup 3}P] 4p ({sup 2}S) ns,d autoionizing structure has been observed for the first time.

  16. Targeting T1 and T2 dual modality enhanced magnetic resonance imaging of tumor vascular endothelial cells based on peptides-conjugated manganese ferrite nanomicelles

    Science.gov (United States)

    Gong, Mingfu; Yang, Hua; Zhang, Song; Yang, Yan; Zhang, Dong; Li, Zhaohui; Zou, Liguang

    2016-01-01

    Tumor angiogenesis plays very important roles for tumorigenesis, tumor development, metastasis, and prognosis. Targeting T1/T2 dual modality magnetic resonance (MR) imaging of the tumor vascular endothelial cells (TVECs) with MR molecular probes can greatly improve diagnostic sensitivity and specificity, as well as helping to make an early diagnosis of tumor at the preclinical stage. In this study, a new T1 and T2 dual modality nanoprobe was successfully fabricated. The prepared nanoprobe comprise peptides CL 1555, poly(ε-caprolactone)-block-poly(ethylene glycol) amphiphilic copolymer shell, and dozens of manganese ferrite (MnFe2O4) nanoparticle core. The results showed that the hydrophobic MnFe2O4 nanoparticles were of uniform spheroidal appearance and narrow size distribution. Due to the self-assembled nanomicelles structure, the prepared probes were of high relaxivity of 281.7 mM−1 s−1, which was much higher than that of MnFe2O4 nanoparticles (67.5 mM 1 s−1). After being grafted with the targeted CD105 peptide CL 1555, the nanomicelles can combine TVECs specifically and make the labeled TVECs dark in T2-weighted MR imaging. With the passage on, the Mn2+ ions were released from MnFe2O4 and the size decreased gradually, making the signal intensity of the second and third passage of labeled TVECs increased in T1-weighted MR imaging. Our results demonstrate that CL-poly(ethylene glycol)-MnFe2O4 can conjugate TVECs and induce dark and bright contrast in MR imaging, and act as a novel molecular probe for T1- and T2-enhanced MR imaging of tumor angiogenesis. PMID:27578974

  17. Determination of metallothioneins by fluorescence and resonance light scattering strategies based on ciprofloxacin–Cu(II) system

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Lu [College of Public Health, University of South China, Hengyang 421001 (China); Wang, Yong-Sheng, E-mail: yongsheng.w@tom.com [College of Public Health, University of South China, Hengyang 421001 (China); Xue, Jin-Hua; Yang, Hui-Xian; Li, Qiu; Zhou, Bin; Wang, Jia-Cheng; Yin, Ji-Cheng; Wang, Yong-Song [College of Public Health, University of South China, Hengyang 421001 (China); Xiao, Xi-Lin [College of Chemistry and Chemical Engineering, University of South China, Hengyang 421001 (China)

    2013-06-15

    Based on ciprofloxacin (CIP)–Cu(II) system, the novel methods for the detection of metallothioneins (MTs) have been developed by fluorescence (FL) and resonance light scattering (RLS) strategies. The FL strategy avoids the label and derivatization steps in common methods, while the RLS strategy can be applied for determining bio-macromolecules and small molecules without native fluorescence. The response signals linearly correlated with the concentration of MTs over the ranges of 1.03×10{sup −8}–1.23×10{sup −6} mol L{sup −1} for FL, and of 2.56×10{sup −7}–1.54×10{sup −6} mol L{sup −1} for RLS. The limits of detection (LOD) are 3.1×10{sup −9} mol L{sup −1} for FL and 7.68×10{sup −8} mol L{sup −1} for RLS. This study represents the comparison of these two methods using the same CIP–Cu{sup 2+}–MTs system. They not only allow practical application for MTs detection but also serve as a potential choice for the operators according to their concrete needs. In addition, the mechanisms for FL and RLS enhancement of the system were also discussed. -- Highlights: ► Determination of MTs was developed based on CIP–Cu(II) system by FL and RLS strategies. ► FL strategy provides lower limit of detection and wider linear range, and avoids the label and derivatization steps. ► RLS strategy can be applied for determining bio-macromolecules and small molecules. ► The mechanism of interaction of MTs with CIP–Cu(II) chelate was discussed.

  18. Determination of metallothioneins by fluorescence and resonance light scattering strategies based on ciprofloxacin–Cu(II) system

    International Nuclear Information System (INIS)

    Based on ciprofloxacin (CIP)–Cu(II) system, the novel methods for the detection of metallothioneins (MTs) have been developed by fluorescence (FL) and resonance light scattering (RLS) strategies. The FL strategy avoids the label and derivatization steps in common methods, while the RLS strategy can be applied for determining bio-macromolecules and small molecules without native fluorescence. The response signals linearly correlated with the concentration of MTs over the ranges of 1.03×10−8–1.23×10−6 mol L−1 for FL, and of 2.56×10−7–1.54×10−6 mol L−1 for RLS. The limits of detection (LOD) are 3.1×10−9 mol L−1 for FL and 7.68×10−8 mol L−1 for RLS. This study represents the comparison of these two methods using the same CIP–Cu2+–MTs system. They not only allow practical application for MTs detection but also serve as a potential choice for the operators according to their concrete needs. In addition, the mechanisms for FL and RLS enhancement of the system were also discussed. -- Highlights: ► Determination of MTs was developed based on CIP–Cu(II) system by FL and RLS strategies. ► FL strategy provides lower limit of detection and wider linear range, and avoids the label and derivatization steps. ► RLS strategy can be applied for determining bio-macromolecules and small molecules. ► The mechanism of interaction of MTs with CIP–Cu(II) chelate was discussed

  19. Fluorescence enhancement using Fano-resonant a plasmonic nanostructure with selective functionalization of molecules at the electromagnetic hot spot (Presentation Recording)

    Science.gov (United States)

    Wang, Xiaolong; Martin, Olivier J. F.

    2015-09-01

    In recent years, one has paid significant attention to plasmonic nanostructures due to their potential for practical applications. Especially, in most plasmonic nanostructures, the local density of optical states is strongly enhanced and confined in the nanogap region - like for example in plasmonic antennas - which results in the so-called electromagnetic hot spots. In this work, we use 4-nanorod structures made with silver to generate and tune Fano resonances exhibiting an asymmetric and narrow lineshape. In such a system, a strongly enhanced electromagnetic field is created in the nanogap when the two antenna modes undergo destructive interference, i.e. at the Fano resonance. The local near field is thus strongly enhanced since most of the energy is not radiated into the far field at that wavelength. We will show that using a 4-nanorod structure in silver, we can easily tune the Fano resonance through the fluorescence spectrum of the molecule under study, thus exploring the different resonance conditions between the molecule absorption/emission bands and the plasmonic nanostructure; both the excitation and emission rates of the molecule can be enhanced when it is placed within the hot spot. To this end, we have developed a double electron beam lithography process to fabricate the plasmonic nanostructures and then selectively immobilize the molecule in the hot spot, in order to investigate the fluorescence enhancement under well-controlled conditions. The fluorescence enhancement is demonstrated by measuring the fluorescence lifetime and the fluorescence count rate. The experimental results are supported by theoretical modelling and numerical calculations with the Green's tensor method.

  20. Characterization of the AT180 epitope of phosphorylated Tau protein by a combined nuclear magnetic resonance and fluorescence spectroscopy approach

    Energy Technology Data Exchange (ETDEWEB)

    Amniai, Laziza [CNRS-UMR 8576 UGSF-IFR 147, Universite des Sciences et Technologies de Lille 1, 59655 Villeneuve d' Ascq Cedex (France); Lippens, Guy, E-mail: guy.lippens@univ-lille1.fr [CNRS-UMR 8576 UGSF-IFR 147, Universite des Sciences et Technologies de Lille 1, 59655 Villeneuve d' Ascq Cedex (France); Landrieu, Isabelle, E-mail: isabelle.landrieu@univ-lille1.fr [CNRS-UMR 8576 UGSF-IFR 147, Universite des Sciences et Technologies de Lille 1, 59655 Villeneuve d' Ascq Cedex (France)

    2011-09-09

    Highlights: {yields} pThr231 of the Tau protein is necessary for the binding of the AT180 antibody. {yields} pSer235 of the Tau protein does not interfere with the AT180 recognition of pThr231. {yields} Epitope mapping is efficiently achieved by combining NMR and FRET spectroscopy. -- Abstract: We present here the characterization of the epitope recognized by the AT180 monoclonal antibody currently used to define an Alzheimer's disease (AD)-related pathological form of the phosphorylated Tau protein. Some ambiguity remains as to the exact phospho-residue(s) recognized by this monoclonal: pThr231 or both pThr231 and pSer235. To answer this question, we have used a combination of nuclear magnetic resonance (NMR) and fluorescence spectroscopy to characterize in a qualitative and quantitative manner the phospho-residue(s) essential for the epitope recognition. Data from the first step of NMR experiments are used to map the residues bound by the antibodies, which were found to be limited to a few residues. A fluorophore is then chemically attached to a cystein residue introduced close-by the mapped epitope, at arginine 221, by mutagenesis of the recombinant protein. The second step of Foerster resonance energy transfer (FRET) between the AT180 antibody tryptophanes and the phospho-Tau protein fluorophore allows to calculate a dissociation constant Kd of 30 nM. We show that the sole pThr231 is necessary for the AT180 recognition of phospho-Tau and that phosphorylation of Ser235 does not interfere with the binding.

  1. Characterization of the AT180 epitope of phosphorylated Tau protein by a combined nuclear magnetic resonance and fluorescence spectroscopy approach

    International Nuclear Information System (INIS)

    Highlights: → pThr231 of the Tau protein is necessary for the binding of the AT180 antibody. → pSer235 of the Tau protein does not interfere with the AT180 recognition of pThr231. → Epitope mapping is efficiently achieved by combining NMR and FRET spectroscopy. -- Abstract: We present here the characterization of the epitope recognized by the AT180 monoclonal antibody currently used to define an Alzheimer's disease (AD)-related pathological form of the phosphorylated Tau protein. Some ambiguity remains as to the exact phospho-residue(s) recognized by this monoclonal: pThr231 or both pThr231 and pSer235. To answer this question, we have used a combination of nuclear magnetic resonance (NMR) and fluorescence spectroscopy to characterize in a qualitative and quantitative manner the phospho-residue(s) essential for the epitope recognition. Data from the first step of NMR experiments are used to map the residues bound by the antibodies, which were found to be limited to a few residues. A fluorophore is then chemically attached to a cystein residue introduced close-by the mapped epitope, at arginine 221, by mutagenesis of the recombinant protein. The second step of Foerster resonance energy transfer (FRET) between the AT180 antibody tryptophanes and the phospho-Tau protein fluorophore allows to calculate a dissociation constant Kd of 30 nM. We show that the sole pThr231 is necessary for the AT180 recognition of phospho-Tau and that phosphorylation of Ser235 does not interfere with the binding.

  2. Kinetics and thermodynamics of glycans and glycoproteins binding to Holothuria scabra lectin: a fluorescence and surface plasmon resonance spectroscopic study.

    Science.gov (United States)

    Gowda, Nagaraj M; Gaikwad, Sushama M; Khan, M Islam

    2013-11-01

    Holothuria scabra produces a monomeric lectin (HSL) of 182 kDa. HSL showed strong antibacterial activity and induced bacterial agglutination under in vitro conditions, indicating its role in animals' innate immune responses. Very few lectins have been reported from echinoderms and none of these lectins have been explored in detail for their sugar-binding kinetics. Affinity, kinetics and thermodynamic analysis of glycans and glycoproteins binding to HSL were studied by fluorescence and surface plasmon resonance spectroscopy. Lectin binds with higher affinity to O-linked than N-linked asialo glycans, and the affinities were relatively higher than that for sialated glycans and glycoproteins. T-antigen α-methyl glycoside was the most potent ligand having the highest affinity (Ka 8.32 ×10(7) M(-1)). Thermodynamic and kinetic analysis indicated that the binding of galactosyl Tn-antigen and asialo glycans is accompanied by an enthalpic contribution in addition to higher association rate coupled by low activation energy for the association process. Presence of sialic acid or protein matrix inhibits binding. Higher affinity of HSL for O-glycans than N-glycans had biological implications; since HSL specifically recognizes bacteria, which have mucin or O-glycan cognate on their cell surfaces and play a major role in animal innate immunity. Since, HSL had higher affinity to T-antigen, makes it a useful tool for cancer diagnostic purpose. PMID:23736907

  3. Dark-resonance Doppler cooling and high fluorescence in trapped Ca-43 ions at intermediate magnetic field

    CERN Document Server

    Allcock, D T C; Sepiol, M A; Janacek, H A; Ballance, C J; Steane, A M; Lucas, D M; Stacey, D N

    2015-01-01

    We demonstrate simple and robust methods for Doppler cooling and obtaining high fluorescence from trapped 43Ca+ ions at a magnetic field of 146 Gauss. This field gives access to a magnetic-field-independent "atomic clock" qubit transition within the ground level hyperfine structure of the ion, but also causes the complex internal structure of the 64 states relevant to Doppler cooling to be spread over many times the atomic transition line-width. Using a time-dependent optical Bloch equation simulation of the system we develop a simple scheme to Doppler-cool the ion on a two-photon dark resonance, which is robust to typical experimental variations in laser intensities, detunings and polarizations. We experimentally demonstrate cooling to a temperature of 0.3 mK, slightly below the Doppler limit for the corresponding two-level system, and then use Raman sideband laser cooling to cool further to the ground states of the ion's radial motional modes. These methods will enable two-qubit entangling gates with this i...

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

    Science.gov (United States)

    2016-01-01

    Single-molecule, protein-induced fluorescence enhancement (PIFE) serves as a molecular ruler at molecular distances inaccessible to other spectroscopic rulers such as Förster-type resonance energy transfer (FRET) or photoinduced electron transfer. In order to provide two simultaneous measurements of two distances on different molecular length scales for the analysis of macromolecular complexes, we and others recently combined measurements of PIFE and FRET (PIFE-FRET) on the single molecule level. PIFE relies on steric hindrance of the fluorophore Cy3, which is covalently attached to a biomolecule of interest, to rotate out of an excited-state trans isomer to the cis isomer through a 90° intermediate. In this work, we provide a theoretical framework that accounts for relevant photophysical and kinetic parameters of PIFE-FRET, show how this framework allows the extraction of the fold-decrease in isomerization mobility from experimental data, and show how these results provide information on changes in the accessible volume of Cy3. The utility of this model is then demonstrated for experimental results on PIFE-FRET measurement of different protein–DNA interactions. The proposed model and extracted parameters could serve as a benchmark to allow quantitative comparison of PIFE effects in different biological systems. PMID:27184889

  5. 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

    2016-07-01

    Single-molecule, protein-induced fluorescence enhancement (PIFE) serves as a molecular ruler at molecular distances inaccessible to other spectroscopic rulers such as Förster-type resonance energy transfer (FRET) or photoinduced electron transfer. In order to provide two simultaneous measurements of two distances on different molecular length scales for the analysis of macromolecular complexes, we and others recently combined measurements of PIFE and FRET (PIFE-FRET) on the single molecule level. PIFE relies on steric hindrance of the fluorophore Cy3, which is covalently attached to a biomolecule of interest, to rotate out of an excited-state trans isomer to the cis isomer through a 90° intermediate. In this work, we provide a theoretical framework that accounts for relevant photophysical and kinetic parameters of PIFE-FRET, show how this framework allows the extraction of the fold-decrease in isomerization mobility from experimental data, and show how these results provide information on changes in the accessible volume of Cy3. The utility of this model is then demonstrated for experimental results on PIFE-FRET measurement of different protein-DNA interactions. The proposed model and extracted parameters could serve as a benchmark to allow quantitative comparison of PIFE effects in different biological systems. PMID:27184889

  6. Fluorescence/bioluminescence resonance energy transfer techniques to study G-protein-coupled receptor activation and signaling.

    Science.gov (United States)

    Lohse, Martin J; Nuber, Susanne; Hoffmann, Carsten

    2012-04-01

    Fluorescence and bioluminescence resonance energy transfer (FRET and BRET) techniques allow the sensitive monitoring of distances between two labels at the nanometer scale. Depending on the placement of the labels, this permits the analysis of conformational changes within a single protein (for example of a receptor) or the monitoring of protein-protein interactions (for example, between receptors and G-protein subunits). Over the past decade, numerous such techniques have been developed to monitor the activation and signaling of G-protein-coupled receptors (GPCRs) in both the purified, reconstituted state and in intact cells. These techniques span the entire spectrum from ligand binding to the receptors down to intracellular second messengers. They allow the determination and the visualization of signaling processes with high temporal and spatial resolution. With these techniques, it has been demonstrated that GPCR signals may show spatial and temporal patterning. In particular, evidence has been provided for spatial compartmentalization of GPCRs and their signals in intact cells and for distinct physiological consequences of such spatial patterning. We review here the FRET and BRET technologies that have been developed for G-protein-coupled receptors and their signaling proteins (G-proteins, effectors) and the concepts that result from such experiments. PMID:22407612

  7. Thin solid europium(III) dye layers as donors in time-resolved fluorescence resonance energy transfer assays

    International Nuclear Information System (INIS)

    Lanthanide chelates and lanthanide nanoparticle labels are attractive donors for separation-free time-resolved fluorescence resonance energy transfer (TR-FRET) assays. In fully dyed nanoparticles, the inner volume of nanoparticle labels in TR-FRET assays are incapable of participating to energy transfer due to large distances to acceptors on the surface. Our interest was to study surface-based TR-FRET and, therefore, various europium(III) (Eu) chelate layers were investigated for TR-FRET efficiency. Eu(III) chelates incorporated in a siloxane layer, Eu(III) chelate covalently coupled on silanized surface and Eu(III) labeled protein surface were prepared and compared to nanoparticle-based TR-FRET. Energy transfer between the solid-phase donors and Cy5-labeled protein were obtained with signal-to-background ratios ranging from 1.2 to 9.9. In this study, a thin layer prepared using Eu(III)-labeled protein gave the most efficient TR-FRET. This thin donor layer was tested in a competitive separation-free immunoassay of human albumin (hAlb). hAlb was measured in a clinically relevant concentrations from 0.05 to 10 mg l-1 with the coefficient of variation ranging from 1.0% to 12.4%.

  8. Investigation of high-contrast velocity selective optical pumping resonance at the cycling transition of Cs using fluorescence technique

    Science.gov (United States)

    Dey, Saswati; Ray, Biswajit; Ghosh, Pradip Narayan; Cartaleva, Stefka; Slavov, Dimitar

    2015-12-01

    A high contrast (∼48%) Velocity Selective Optical Pumping (VSOP) resonance at the closed transition Fg=4→Fe=5 of Cs-D2 line is obtained in the fluorescence signal under co-propagating pump-probe configuration. We use a 5.2 μm cell operating at reduced temperature (∼55 °C) and the intensity of the pump-laser is kept lower than that of the probe-laser. The observed sharp narrow structure is suitable for side-arms frequency-locking of the cooling- (i.e. probe-) laser in a cold atom experiment, with possibility for "-Γ" to "-4Γ" red-detuning and "+Γ" to "+10Γ" blue-detuning using the standard properties of the commercially available electronics. We have developed a theoretical model corresponding to the thin cell, incorporating the atomic time-of-flight dependent optical pumping decay rate to describe the dimensional anisotropy of the thin cell. The model shows good qualitative agreement with the observation and simulates as well the cases of cells with smaller thickness. It also describes correctly the temperature dependence of the line broadening and shows the potential for further optimization and red-shift detuning above "-4Γ". It may be of interest for further development of miniaturized modules, like the recently developed portable small magneto-optical traps.

  9. Fluorescence resonance energy transfer (FRET) in chemistry and biology: Non-Förster distance dependence of the FRET rate

    Indian Academy of Sciences (India)

    Sangeeta Saini; Harjinder Singh; Biman Bagchi

    2006-01-01

    Fluorescence resonance energy transfer (FRET) is a popular tool to study equilibrium and dynamical properties of polymers and biopolymers in condensed phases and is now widely used in conjunction with single molecule spectroscopy. In the data analysis, one usually employs the Förster expression which predicts (1/6) distance dependence of the energy transfer rate. However, critical analysis shows that this expression can be of rather limited validity in many cases. We demonstrate this by explicitly considering a donor-acceptor system, polyfluorene (PF6)-tetraphenylporphyrin (TPP), where the size of both donor and acceptor is comparable to the distance separating them. In such cases, one may expect much weaker distance (as 1/2 or even weaker) dependence. We have also considered the case of energy transfer from a dye to a nanoparticle. Here we find 1/4 distance dependence at large separations, completely different from Förster. We also discuss recent application of FRET to study polymer conformational dynamics.

  10. 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

    2016-07-01

    Single-molecule, protein-induced fluorescence enhancement (PIFE) serves as a molecular ruler at molecular distances inaccessible to other spectroscopic rulers such as Förster-type resonance energy transfer (FRET) or photoinduced electron transfer. In order to provide two simultaneous measurements of two distances on different molecular length scales for the analysis of macromolecular complexes, we and others recently combined measurements of PIFE and FRET (PIFE-FRET) on the single molecule level. PIFE relies on steric hindrance of the fluorophore Cy3, which is covalently attached to a biomolecule of interest, to rotate out of an excited-state trans isomer to the cis isomer through a 90° intermediate. In this work, we provide a theoretical framework that accounts for relevant photophysical and kinetic parameters of PIFE-FRET, show how this framework allows the extraction of the fold-decrease in isomerization mobility from experimental data, and show how these results provide information on changes in the accessible volume of Cy3. The utility of this model is then demonstrated for experimental results on PIFE-FRET measurement of different protein-DNA interactions. The proposed model and extracted parameters could serve as a benchmark to allow quantitative comparison of PIFE effects in different biological systems.

  11. Monitoring of bystander effect of herpes simplex virus thymidine kinase/acyclovir system using fluorescence resonance energy transfer technique.

    Science.gov (United States)

    Xiong, Tao; Li, Yongjun; Ni, Fenge; Zhang, Feng

    2012-02-01

    Cytotoxic gene therapy mediated by gene transfer of the herpes simplex virus thymidine kinase (HSV-tk) gene followed by acyclovir (ACV) treatment has been reported to inhibit malignant tumor growth in a variety of studies. The magnitude of "bystander effect" is an essential factor for this anti-tumor approach in vivo. However, the mechanism by which HSV-tk/ACV brings "bystander effect" is poorly understood. In this report, the plasmid CD3 (ECFP-CRS-DsRed) and TK-GFP were transferred to the human adenoid cystic carcinoma line ACC-M cell line. The CD3-expressing cells apoptosis was monitored using fluorescence resonance energy transfer (FRET) technique. First, CD3 and TK-GFP co-expressing ACC-M cells apoptosis was monitored using FRET technique. The apoptosis was induced by ACV and initiated by caspase3. The FRET efficient was remarkably decreased and then disappeared during cellular apoptosis, which indicated that the TK-GFP expressing ACC-M cells apoptosis, induced by ACV, was via a caspase3-dependent pathway. Secondly, CD3 and TK-GFP mixed expressing ACC-M cells apoptosis, induced by ACV, were monitored using FRET technique. The apoptotic phenomena appeared in the CD3-expressing ACC-M cells. The results show that HSV-tk/ACV system killed ACC-M cells using its bystander effect. These results confirm that HSV-tk/ACV system is potential for cancer gene therapy.

  12. Enzymatic activity characterization of SARS coronavirus 3C-like protease by fluorescence resonance energy transfer technique

    Institute of Scientific and Technical Information of China (English)

    Shuai CHEN; Hua-liang JIANG; Li-li CHEN; Hai-bin LUO; Tao SUN; Jing CHEN; Fei YE; Jian-hua CAI; Jing-kang SHEN; Xu SHEN

    2005-01-01

    Aim: To characterize enzymatic activity of severe acute respiratory syndrome(SARS) coronavirus (CoV) 3C-like protease (3CLpro) and its four site-directed mutants. Methods: Based on the fluorescence resonance energy transfer (FRET)principle using 5-[(2'-aminoethyl)-amino] naphthelenesulfonic acid (EDANS) and 4-[[4-(dimethylamino) phenyl] azo] benzoic acid (Dabcyl) as the energy transfer pair, one fluorogenic substrate was designed for the evaluation of SARS-CoV 3CLpro proteolytic activity. Results: The kinetic parameters of the fluorogenic substrate have been determined as Km=404 μmol.L-1, kcat=1.08 min-1, and kcat/Km=2.7 gered activity switches, and site-directed mutagenesis analysis of SARS-CoV 3CLpro revealed that substitutions of His41, Cys145, and His163 resulted in complete loss of enzymatic activity, while replacement of Met162 with Ala caused strongly increased activity. Conclusion: This present work has provided valuable information for understanding the catalytic mechanism of SARS-CoV 3CLpro. This FRET-based assay might supply an ideal approach for the exploration SARSCoV 3CLpro putative inhibitors.

  13. Interfacial Chemistry and the Design of Solid-Phase Nucleic Acid Hybridization Assays Using Immobilized Quantum Dots as Donors in Fluorescence Resonance Energy Transfer

    OpenAIRE

    Ulrich J. Krull; W. Russ Algar

    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 th...

  14. 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.

  15. Determination of trace uranium by resonance fluorescence method coupled with photo-catalytic technology and dual cloud point extraction.

    Science.gov (United States)

    Li, Jiekang; Li, Guirong; Han, Qian

    2016-12-01

    In this paper, two kinds of salophens (Sal) with different solubilities, Sal1 and Sal2, have been respectively synthesized, and they all can combine with uranyl to form stable complexes: [UO2(2+)-Sal1] and [UO2(2+)-Sal2]. Among them, [UO2(2+)-Sal1] was used as ligand to extract uranium in complex samples by dual cloud point extraction (dCPE), and [UO2(2+)-Sal2] was used as catalyst for the determination of uranium by photocatalytic resonance fluorescence (RF) method. The photocatalytic characteristic of [UO2(2+)-Sal2] on the oxidized pyronine Y (PRY) by potassium bromate which leads to the decrease of RF intensity of PRY were studied. The reduced value of RF intensity of reaction system (ΔF) is in proportional to the concentration of uranium (c), and a novel photo-catalytic RF method was developed for the determination of trace uranium (VI) after dCPE. The combination of photo-catalytic RF techniques and dCPE procedure endows the presented methods with enhanced sensitivity and selectivity. Under optimal conditions, the linear calibration curves range for 0.067 to 6.57ngmL(-1), the linear regression equation was ΔF=438.0 c (ngmL(-1))+175.6 with the correlation coefficient r=0.9981. The limit of detection was 0.066ngmL(-1). The proposed method was successfully applied for the separation and determination of uranium in real samples with the recoveries of 95.0-103.5%. The mechanisms of the indicator reaction and dCPE are discussed.

  16. Determination of trace uranium by resonance fluorescence method coupled with photo-catalytic technology and dual cloud point extraction.

    Science.gov (United States)

    Li, Jiekang; Li, Guirong; Han, Qian

    2016-12-01

    In this paper, two kinds of salophens (Sal) with different solubilities, Sal1 and Sal2, have been respectively synthesized, and they all can combine with uranyl to form stable complexes: [UO2(2+)-Sal1] and [UO2(2+)-Sal2]. Among them, [UO2(2+)-Sal1] was used as ligand to extract uranium in complex samples by dual cloud point extraction (dCPE), and [UO2(2+)-Sal2] was used as catalyst for the determination of uranium by photocatalytic resonance fluorescence (RF) method. The photocatalytic characteristic of [UO2(2+)-Sal2] on the oxidized pyronine Y (PRY) by potassium bromate which leads to the decrease of RF intensity of PRY were studied. The reduced value of RF intensity of reaction system (ΔF) is in proportional to the concentration of uranium (c), and a novel photo-catalytic RF method was developed for the determination of trace uranium (VI) after dCPE. The combination of photo-catalytic RF techniques and dCPE procedure endows the presented methods with enhanced sensitivity and selectivity. Under optimal conditions, the linear calibration curves range for 0.067 to 6.57ngmL(-1), the linear regression equation was ΔF=438.0 c (ngmL(-1))+175.6 with the correlation coefficient r=0.9981. The limit of detection was 0.066ngmL(-1). The proposed method was successfully applied for the separation and determination of uranium in real samples with the recoveries of 95.0-103.5%. The mechanisms of the indicator reaction and dCPE are discussed. PMID:27380304

  17. Rocket observation of atomic oxygen and night airglow: Measurement of concentration with an improved resonance fluorescence technique

    Directory of Open Access Journals (Sweden)

    K. Kita

    Full Text Available An improved resonant fluorescence instrument for measuring atomic oxygen concentration was developed to avoid the Doppler effect and the aerodynamic shock effect due to the supersonic motion of a rocket. The shock effect is reduced by adopting a sharp wedge-shaped housing and by scanning of the detector field of view to change the distance between the scattering volume and the surface of the housing. The scanning enables us to determine absolute values of atomic oxygen concentration from relative variation of the scattered light signal due to the self-absorption. The instrument was calibrated in the laboratory, and the numerical simulation reproduced the calibration result. Using the instrument, the altitude profile of atomic oxygen concentration was observed by a rocket experiment at Uchinoura (31°N on 28 January 1992. The data obtained from the rocket experiment were not perfectly free from the shock effect, but errors due to the effect were reduced by the data analysis procedure. The observed maximum concentration was 3.8× 1011 cm–3 at altitudes around 94 km. The systematic error is estimated to be less than ±0.7×1011 cm–3 and the relative random error is less than±0.07× 1011 cm–3at the same altitudes. The altitude profile of the OI 557.7-nm airglow was also observed in the same rocket experiment. The maximum volume emission rate was found to be 150 photons cm–3 s–1 at 94 km. The observed altitude profiles are compared with the MSIS model and other in situ observations.

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

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiaoming; Fu, Afu [Division of Bioengineering, School of Chemical and Biomedical Engineering, Nanyang Technological University (Singapore); Luo, Kathy Qian, E-mail: kluo@ntu.edu.sg [Division of Bioengineering, School of Chemical and Biomedical Engineering, Nanyang Technological University (Singapore)

    2012-02-24

    Highlights: Black-Right-Pointing-Pointer An endothelial cell apoptosis assay using FRET-based biosensor was developed. Black-Right-Pointing-Pointer The fluorescence of the cells changed from green to blue during apoptosis. Black-Right-Pointing-Pointer This method was developed into a high-throughput assay in 96-well plates. Black-Right-Pointing-Pointer 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 Prime 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.

  19. 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)

    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.

  20. Terbium-doped gadolinium oxide nanoparticles prepared by laser ablation in liquid for use as a fluorescence and magnetic resonance imaging dual-modal contrast agent.

    Science.gov (United States)

    Chen, Fei; Chen, Min; Yang, Chuan; Liu, Jun; Luo, Ningqi; Yang, Guowei; Chen, Dihu; Li, Li

    2015-01-14

    Dual-modal lanthanide-doped gadolinium nanoparticles (NPs), which exhibit an excellent magnetic resonance imaging (MRI) spatial resolution and high fluorescence imaging (FI) sensitivity, have attracted tremendous attention in biotechnology and nanomedicine applications. In this paper, terbium (Tb) ion doped gadolinium oxide (Gd2O3:Tb) NPs with varied Tb concentrations were synthesized by a laser ablation in liquid (LAL) method. The characterization of the structure, morphology, and composition shows that these NPs are spherical with excellent crystallinity. The effects of Tb ion concentration on the visible green fluorescence and longitudinal relaxivity were investigated, indicating that the fluorescence properties were significantly influenced by the Tb ion concentration, but all samples were still efficient T1-weighted contrast agents. Furthermore, the optimum Tb doping concentration was determined to be 1%. The cell viability, cellular fluorescence imaging and in vivo MRI of this dual-modal nano-probe were studied, with the results revealing that the Gd2O3:Tb NPs did not have a significant cytotoxic effect, making them good candidates for use as a dual-modal contrast agent for MRI and fluorescence imaging.

  1. Fluorescence resonance energy transfer based immunosensing of human IgG by using quantum dot/GIgG-gold nanoparticles/IgG conjugation.

    Science.gov (United States)

    Luo, Lin; Liu, Zhao; Li, Jianjun; Zhu, Jian

    2014-06-01

    A novel immunosensor of human immune globulin (IgG) was fabricated based on the fluorescence transfer between luminescent semiconductor quantum dots (QDs) and gold nanoparticles (AuNPs). AuNPs and CdSe/ZnS QDs were respectively labeled with immune reaction pair:IgG and goat anti-human immunoglobulin (GIgG), by optimizing the conditions including pH value and protein amount. In the assembled QD-GIgG-IgG-AuNP fluorescence resonance energy transfer (FRET) immunocomplex system, the presence of AuNP-IgG directly reduced the fluorescence intensity of the GIgG conjugated QDs. As a result, the concentration of AuNP-IgG had a linear relationship with the fluorescence decrease in a range of 0-1.57 microg/mL. Furthermore, the mechanism of the QDs' fluorescence decay has also been discussed and attributed to the light-induced photobleaching. This novel sensing method achieves quantitative detection of trace proteins, suggesting the potential of biomolecule-AuNPs conjugation based analytical methods in further application. PMID:24738348

  2. Construction of fluorescence resonance energy transfer vectors and their application in study of structure and function of signal transducers and activators of transcription 1

    Institute of Scientific and Technical Information of China (English)

    Fujun Han; Yongfeng Luo; Nanhai Ge; Jun Xu

    2008-01-01

    Protein-protein interactions have been studied extensively by green fluorescent protein-based fluorescence resonance energy transfer (FRET). The fluorescent proteins (FP) can be fused either to the N- or C-terminus of a host protein, but it is difficult to predict which order will perturb the host protein the least and provide the largest FRET. Therefore, a researcher needs to fuse host proteins with FP at both the N- and C-termini and test every possible combination (N-N,N-C, or C-C) to promote the energy transfer efficiency.Consequently, researchers required to do many subelonings.Herein, we designed FRET vectors to make them more efficient. The expression vectors ofpCTP.YFP and pYFP-CFP were constructed with both cyan fluorescent protein (CFP)-yellow fluorescent protein (YFP) and YFP-CFP coding sequences flanked by two restriction enzyme sites, and with multiple cloning regions in the middle of both coding sequences. To select an optimal combination for FRET detection, we created plasmids encoding various fusion proteins of FP and signal transducers and activators of transcription 1 (STAT1). We found that the nuclear:cytoplasmic fluorescence intensity ratios of STAT1 -FP were significantly higher than those of FP-STAT1 at steady state,and fluorescence redistribution was only observed for STAT1-FP upon interferon gamma (IFNΥ) stimulation. In addition, positive FRET signals were only detected in the C-C interactions of STAT 1 homodimer. Taken together, these data indicate that fusing STATI at the N.terminus with Fpimpairs the interactions ofunphospborylated STAT1 homodimers and possibly diminishes its binding with DNA. In contrast, STATIFP was functional with respect to its activation. Moreover, the FRET vectors are able to facilitate FRET studies.

  3. In vivo magnetic resonance and fluorescence dual imaging of tumor sites by using dye-doped silica-coated iron oxide nanoparticles

    International Nuclear Information System (INIS)

    The difficulty in delineating tumor is a major obstacle for better outcomes in cancer treatment of patients. The use of single-imaging modality is often limited by inadequate sensitivity and resolution. Here, we present the synthesis and the use of monodisperse iron oxide nanoparticles coated with fluorescent silica nano-shells for fluorescence and magnetic resonance dual imaging of tumor. The as-synthesized core–shell nanoparticles were designed to improve the accuracy of diagnosis via simultaneous tumor imaging with dual imaging modalities by a single injection of contrast agent. The iron oxide nanocrystals (∼11 nm) were coated with Rhodamine B isothiocyanate-doped silica shells via reverse microemulsion method. Then, the core–shell nanoparticles (∼54 nm) were analyzed to confirm their size distribution by transmission electron microscopy and dynamic laser scattering. Photoluminescence spectroscopy was used to characterize the fluorescent property of the dye-doped silica shell-coated nanoparticles. The cellular compatibility of the as-prepared nanoparticles was confirmed by a trypan blue dye exclusion assay and the potential as a dual-imaging contrast agent was verified by in vivo fluorescence and magnetic resonance imaging. The experimental results show that the uniform-sized core–shell nanoparticles are highly water dispersible and the cellular toxicity of the nanoparticles is negligible. In vivo fluorescence imaging demonstrates the capability of the developed nanoparticles to selectively target tumors by the enhanced permeability and retention effects and ex vivo tissue analysis was corroborated this. Through in vitro phantom test, the core/shell nanoparticles showed a T2 relaxation time comparable to Feridex® with smaller size, indicating that the as-made nanoparticles are suitable for imaging tumor. This new dual-modality-nanoparticle approach has promised for enabling more accurate tumor imaging.

  4. In vivo magnetic resonance and fluorescence dual imaging of tumor sites by using dye-doped silica-coated iron oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Haeyun; Lee, Chaedong [Seoul National University, Program in Nano Science and Technology, Graduate School of Convergence Science and Technology (Korea, Republic of); Nam, Gi-Eun [University of Ulsan College of Medicine, Department of Radiology, Asan Medical Center (Korea, Republic of); Quan, Bo [Seoul National University, Program in Nano Science and Technology, Graduate School of Convergence Science and Technology (Korea, Republic of); Choi, Hyuck Jae [University of Ulsan College of Medicine, Department of Radiology, Asan Medical Center (Korea, Republic of); Yoo, Jung Sun [Seoul National University, Department of Transdisciplinary Studies, Graduate School of Convergence Science and Technology, Smart Humanity Convergence Center (Korea, Republic of); Piao, Yuanzhe, E-mail: parkat9@snu.ac.kr [Seoul National University, Program in Nano Science and Technology, Graduate School of Convergence Science and Technology (Korea, Republic of)

    2016-02-15

    The difficulty in delineating tumor is a major obstacle for better outcomes in cancer treatment of patients. The use of single-imaging modality is often limited by inadequate sensitivity and resolution. Here, we present the synthesis and the use of monodisperse iron oxide nanoparticles coated with fluorescent silica nano-shells for fluorescence and magnetic resonance dual imaging of tumor. The as-synthesized core–shell nanoparticles were designed to improve the accuracy of diagnosis via simultaneous tumor imaging with dual imaging modalities by a single injection of contrast agent. The iron oxide nanocrystals (∼11 nm) were coated with Rhodamine B isothiocyanate-doped silica shells via reverse microemulsion method. Then, the core–shell nanoparticles (∼54 nm) were analyzed to confirm their size distribution by transmission electron microscopy and dynamic laser scattering. Photoluminescence spectroscopy was used to characterize the fluorescent property of the dye-doped silica shell-coated nanoparticles. The cellular compatibility of the as-prepared nanoparticles was confirmed by a trypan blue dye exclusion assay and the potential as a dual-imaging contrast agent was verified by in vivo fluorescence and magnetic resonance imaging. The experimental results show that the uniform-sized core–shell nanoparticles are highly water dispersible and the cellular toxicity of the nanoparticles is negligible. In vivo fluorescence imaging demonstrates the capability of the developed nanoparticles to selectively target tumors by the enhanced permeability and retention effects and ex vivo tissue analysis was corroborated this. Through in vitro phantom test, the core/shell nanoparticles showed a T2 relaxation time comparable to Feridex{sup ®} with smaller size, indicating that the as-made nanoparticles are suitable for imaging tumor. This new dual-modality-nanoparticle approach has promised for enabling more accurate tumor imaging.

  5. In vitro observation of the molecular interaction between NodD and its inducer naringenin as monitored by fluorescence resonance energy transfer

    Institute of Scientific and Technical Information of China (English)

    Fengqing Li; Bihe Hou; Lei Chen; Zhujun Yao; Guofan Hong

    2008-01-01

    At initial stages in the Rhizobium legume symbiosis, most nodulation genes are controlled by NodD protein and plant inducers. Some genetic studies and other reports have suggested that NodD may be activated by its direct interaction with plant inducers. However, there has been no molecular evidence of such an inducing interaction. In this paper, we used fluorescence resonance energy transfer technique to see whether such an interaction exists between NodD and its activator, naringenin, in vitro. The tetracysteine motif (Cys-Cys-Pro-Gly-Cys-Cys) was genetically inserted into NodD to label NodD with 4′,5′-bis(1,3,2-dithioarsolan-2-yl) fluorescein (FlAsH). Naringenin was labeled with fluorescein by chemical linking. In the fluorescence resonance energy transfer experiments in vitro, the fluorescence intensity of one acceptor, NodD(90R6)-FlAsH, increased by 13%. This suggests that NodD may directly interact with inducer naringenin in vitro and that the reaction centre is likely near hinge region 1 of NodD.

  6. A general thiol assay based on the suppression of fluorescence resonance energy transfer in magnetic-resin core-shell nanospheres coated with gold nanoparticles

    International Nuclear Information System (INIS)

    A simple, rapid and sensitive fluorescence resonance energy transfer (FRET) method is presented for the determination of thiols. It is based on the thiol-induced enhancement effect of the surfactant sodium dodecyl sulfate (SDS) on the efficiency of fluorescence resonance energy transfer (FRET) in nanospheres consisting of a magnetic (Fe3O4) core and a phenol-formaldehyde resin (PFR) shell containing gold nanoparticles (AuNPs). The luminescence of the core-shell nanospheres at excitation/emission wavelengths of 390/445 nm, respectively, is quenched by the AuNPs which act as energy acceptors. The interaction of AuNPs with thiol compounds in the presence of SDS suppresses FRET and gives rise to a fluorescent signal whose intensity is proportional to the thiol concentration. The analytical features of seven thiols (homocysteine, thioglycolic acid, glutathione, dodecanethiol, cysteamine, cysteine and N-acetylcysteine) were studied. Detection limits are in the range from 0.14 to 0.49 μmol L−1. The precision of the method, expressed as the relative standard deviation, ranges from 0.4 to 4.9 %. The method was applied to the determination of total thiols in water samples with recovery values between 88.7 and 104.6 %. (author)

  7. Cell-based bioassays in microfluidic systems

    Science.gov (United States)

    Itle, Laura J.; Zguris, Jeanna C.; Pishko, Michael V.

    2004-12-01

    The development of cell-based bioassays for high throughput drug screening or the sensing of biotoxins is contingent on the development of whole cell sensors for specific changes in intracellular conditions and the integration of those systems into sample delivery devices. Here we show the feasibility of using a 5-(and-6)-carboxy SNARF-1, acetoxymethyl ester, acetate, a fluorescent dye capable of responding to changes in intracellular pH, as a detection method for the bacterial endotoxin, lipopolysaccharide. We used photolithography to entrap cells with this dye within poly(ethylene) glyocol diacrylate hydrogels in microfluidic channels. After 18 hours of exposure to lipopolysaccharide, we were able to see visible changes in the fluorescent pattern. This work shows the feasibility of using whole cell based biosensors within microfluidic networks to detect cellular changes in response to exogenous agents.

  8. Intercomparison of peroxy radical measurements obtained at atmospheric conditions by laser-induced fluorescence and electron spin resonance spectroscopy

    Directory of Open Access Journals (Sweden)

    A. Hofzumahaus

    2009-03-01

    Full Text Available Measurements of hydroperoxy radical (HO2 and organic peroxy radical (RO2 concentrations were performed by two different techniques in the atmospheric simulation chamber SAPHIR in Jülich, Germany. The first technique was the well-established Matrix Isolation Electron Spin Resonance (MIESR, which provides absolute measurements with a time resolution of 30 min and high accuracy (10%, 2 σ. The other technique, ROxLIF, has been newly developed. It is based on the selective chemical conversion of ROx radicals (HO2 and RO2 to OH, which is detected with high sensitivity by laser-induced fluorescence (LIF. ROxLIF is calibrated by quantitative photolysis of water vapor at 185 nm and provides ambient measurements at a temporal resolution of 1 min and accuracy of 20% (2 σ. The measurements of HO2 and RO2 obtained by the two techniques were compared for two types of atmospheric simulation experiments. In one experiment, HO2 and CH3O2 radicals were produced by photooxidation of methane in air at tropospheric conditions. In the second experiment, HO2 and C2H5O2 were produced by ozonolysis of 1-butene in air at dark conditions. The radical concentrations were within the range of 16 to 100 pptv for HO2 and 12 to 45 pptv for RO2. Good agreement was found in the comparison of the ROxLIF and MIESR measurements within their combined experimental uncertainties. Linear regressions to the combined data set yield slopes of 1.02±0.13 (1 σ for RO2 and 0.98±0.08 (1 σ for HO2 without significant offsets. The results confirm the calibration of the ROxLIF instrument and demonstrate that it can be applied with good accuracy for measurements of atmospheric peroxy radical concentrations.

  9. Absorption,fluorescence and resonance Rayleigh scattering spectra of hydrophobic hydrogen bonding of eosin Y/Triton X-100 nanoparticles and their analytical applications

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    In a weak acidic medium(pH 2.4-2.8),eosin Y molecules(H2L) could replace water molecules to associate with Triton X-100 to form hydrophobic hydrogen bonding complexes.These complexes could further aggregate to form nanoparticles through the squeezing action of the water phase and Van Der Waals force,resulting in changes in the absorption spectrum and fluorescence quenching of EY as well as the significant enhancement of resonance Rayleigh scattering.This enables the sensitive determination of Triton X-100 using the fading spectrophotometry,fluorescence quenching method and RRS method.Among them,the RRS method shows the highest sensitivity with a detection limit of 20.6 ng mL-1 for Triton X-100.The optimum experimental conditions and factors that affect the absorption,fluorescence and RRS spectra were tested.The effects of coexisting substances were investigated and the results showed good selectivity.Based on these results,new spectrophotometric methods,fluorescence quenching method and RRS method for the determination of Triton X-100,were established.The hydrogen bonding association of eosin Y with Triton X-100 and the formation of nanoparticles as well as their effects on related spectral characteristics were discussed utilizing infrared,transmission electron microscope technique and quantum chemical method.

  10. Fluorescence resonance energy transfer between perylene and riboflavin in micellar solution and analytical application on determination of vitamin B{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Bhattar, S.L.; Kolekar, G.B. [Fluorescence Spectroscopy Research Laboratory, Department of Chemistry, Shivaji University, Kolhapur 416 004, Maharashtra (India); Patil, S.R. [Fluorescence Spectroscopy Research Laboratory, Department of Chemistry, Shivaji University, Kolhapur 416 004, Maharashtra (India)], E-mail: srp_fsl@rediffmail.com

    2008-03-15

    Fluorescence resonance energy transfer (FRET) between perylene and riboflavin is studied in micellar solution of sodium dodecyl sulfate. The fluorescence of perylene is quenched by riboflavin and quenching is in accordance with Stern-Volmer relation. The efficiency of energy transfer is found to depend on the concentration of riboflavin. The value of critical energy transfer distance (R{sub 0}) calculated by using Foster relation is 32.13 A, and as it is less than 50 A, it indicates efficient energy transfer in the present system. The analytical relation was established between extent of sensitization and concentration of riboflavin, which helped to estimate vitamin B{sub 2} directly from pharmaceutical tablets.

  11. Efficient labeling in vitro with non-ionic gadolinium magnetic resonance imaging contrast agent and fluorescent transfection agent in bone marrow stromal cells of neonatal rats.

    Science.gov (United States)

    Li, Ying-Qin; Tang, Ying; Fu, Rao; Meng, Qiu-Hua; Zhou, Xue; Ling, Ze-Min; Cheng, Xiao; Tian, Su-Wei; Wang, Guo-Jie; Liu, Xue-Guo; Zhou, Li-Hua

    2015-07-01

    Although studies have been undertaken on gadolinium labeling-based molecular imaging in magnetic resonance imaging (MRI), the use of non-ionic gadolinium in the tracking of stem cells remains uncommon. To investigate the efficiency in tracking of stem cells with non-ionic gadolinium as an MRI contrast agent, a rhodamine-conjugated fluorescent reagent was used to label bone marrow stromal cells (BMSCs) of neonatal rats in vitro, and MRI scanning was undertaken. The fluorescent-conjugated cell uptake reagents were able to deliver gadodiamide into BMSCs, and cell uptake was verified using flow cytometry. In addition, the labeled stem cells with paramagnetic contrast medium remained detectable by an MRI monitor for a minimum of 28 days. The present study suggested that this method can be applied efficiently and safely for the labeling and tracking of bone marrow stromal cells in neonatal rats.

  12. Two-photon-excited fluorescence resonance energy transfer in an aqueous system of CdTe quantum dots and Rhodamine B

    International Nuclear Information System (INIS)

    Two-photon excited fluorescence resonance energy transfer (FRET) between CdTe quantum dots with different emission peaks and Rhodamine B in aqueous solution are investigated both experimentally and theoretically. The photoluminescence and lifetime are measured using a time-resolved fluorescence test system. The two-photon excited FRET efficiency is found to increase as the degree of spectral overlap of the emission spectrum of CdTe and the absorption spectrum of Rhodamine B increases, which is due to the increase of Forster radius of the sample. Moreover, FRET efficiency increases when the ratio of acceptor/donor concentration increases. The two-photon excited FRET efficiency was found to reach 40%

  13. Multimodal Mn-doped I-III-VI quantum dots for near infrared fluorescence and magnetic resonance imaging: from synthesis to in vivo application.

    OpenAIRE

    Sitbon, Gary; Bouccara, Sophie; Tasso, Mariana; Francois, Aurélie; Bezdetnaya, Lina; Marchal, Frédéric; Beaumont, Marine; Pons, Thomas

    2014-01-01

    The development of sensitive multimodal contrast agents is a key issue to provide better global, multi-scale images for diagnostic or therapeutic purposes. Here we present the synthesis of Zn-Cu-In-(S, Se)/Zn(1-x)Mn(x)S core-shell quantum dots (QDs) that can be used as markers for both near-infrared fluorescence imaging and magnetic resonance imaging (MRI). We first present the synthesis of Zn-Cu-In-(S, Se) cores coated with a thick ZnS shell doped with various proportions of Mn. Their emissi...

  14. Iodinated oil-loaded, fluorescent mesoporous silica-coated iron oxide nanoparticles for magnetic resonance imaging/computed tomography/fluorescence trimodal imaging

    OpenAIRE

    Xue S; Wang Y; Wang M; Zhang L; Du X; Gu H; Zhang C

    2014-01-01

    Sihan Xue,1 Yao Wang,1 Mengxing Wang,2 Lu Zhang,1 Xiaoxia Du,2 Hongchen Gu,1 Chunfu Zhang1,31School of Biomedical Engineering and Med-X Research Institute, Shanghai Jiao Tong University, 2Shanghai Key Laboratory of Magnetic Resonance, Department of Physics, East China Normal University, 3State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, People’s Republic of ChinaAbstract: In this...

  15. Interaction of poxvirus intracellular mature virion proteins with the TPR domain of kinesin light chain in live infected cells revealed by two-photon-induced fluorescence resonance energy transfer fluorescence lifetime imaging microscopy.

    Science.gov (United States)

    Jeshtadi, Ananya; Burgos, Pierre; Stubbs, Christopher D; Parker, Anthony W; King, Linda A; Skinner, Michael A; Botchway, Stanley W

    2010-12-01

    Using two-photon-induced fluorescence lifetime imaging microscopy, we corroborate an interaction (previously demonstrated by yeast two-hybrid domain analysis) of full-length vaccinia virus (VACV; an orthopoxvirus) A36 protein with the cellular microtubule motor protein kinesin. Quenching of enhanced green fluorescent protein (EGFP), fused to the C terminus of VACV A36, by monomeric red fluorescent protein (mDsRed), fused to the tetratricopeptide repeat (TPR) domain of kinesin, was observed in live chicken embryo fibroblasts infected with either modified vaccinia virus Ankara (MVA) or wild-type fowlpox virus (FWPV; an avipoxvirus), and the excited-state fluorescence lifetime of EGFP was reduced from 2.5 ± 0.1 ns to 2.1 ± 0.1 ns due to resonance energy transfer to mDsRed. FWPV does not encode an equivalent of intracellular enveloped virion surface protein A36, yet it is likely that this virus too must interact with kinesin to facilitate intracellular virion transport. To investigate possible interactions between innate FWPV proteins and kinesin, recombinant FWPVs expressing EGFP fused to the N termini of FWPV structural proteins Fpv140, Fpv168, Fpv191, and Fpv198 (equivalent to VACV H3, A4, p4c, and A34, respectively) were generated. EGFP fusions of intracellular mature virion (IMV) surface protein Fpv140 and type II membrane protein Fpv198 were quenched by mDsRed-TPR in recombinant FWPV-infected cells, indicating that these virion proteins are found within 10 nm of mDsRed-TPR. In contrast, and as expected, EGFP fusions of the IMV core protein Fpv168 did not show any quenching. Interestingly, the p4c-like protein Fpv191, which demonstrates late association with preassembled IMV, also did not show any quenching.

  16. Preparation of liposomes loaded with quantum dots, fluorescence resonance energy transfer studies, and near-infrared in-vivo imaging of mouse tissue

    International Nuclear Information System (INIS)

    We report on a simple, fast and convenient method to engineer lipid vesicles loaded with quantum dots (QDs) by incorporating QDs into a vesicle-type of lipid bilayer using a phase transfer reagent. Hydrophilic CdTe QDs and near-infrared (NIR) QDs of type CdHgTe were incorporated into liposomes by transferring the QDs from an aqueous solution into chloroform by addition of a surfactant. The QD-loaded liposomes display bright fluorescence, and the incorporation of the QDs into the lipid bilayer leads to enhanced storage stability and reduced sensitivity to UV irradiation. The liposomes containing the QD were applied to label living cells and to image mouse tissue in-vivo using a confocal laser scanning microscope, while NIR images of mouse tissue were acquired with an NIR fluorescence imaging system. We also report on the fluorescence resonance energy transfer (FRET) that occurs between the CdTe QDs (the donor) and the CdHgTe QDs (the acceptor), both contained in liposomes. Based on these data, this NIR FRET system shows promise as a tool that may be used to study the release of drug-loaded liposomes and their in vivo distribution. (author)

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

    Science.gov (United States)

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

    2016-01-01

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

  18. 1,3-Bis(2-chloroethyl)-1-nitrosourea-loaded bovine serum albumin nanoparticles with dual magnetic resonance-fluorescence imaging for tracking of chemotherapeutic agents.

    Science.gov (United States)

    Wei, Kuo-Chen; Lin, Feng-Wei; Huang, Chiung-Yin; Ma, Chen-Chi M; Chen, Ju-Yu; Feng, Li-Ying; Yang, Hung-Wei

    2016-01-01

    To date, knowing how to identify the location of chemotherapeutic agents in the human body after injection is still a challenge. Therefore, it is urgent to develop a drug delivery system with molecular imaging tracking ability to accurately understand the distribution, location, and concentration of a drug in living organisms. In this study, we developed bovine serum albumin (BSA)-based nanoparticles (NPs) with dual magnetic resonance (MR) and fluorescence imaging modalities (fluorescein isothiocyanate [FITC]-BSA-Gd/1,3-bis(2-chloroethyl)-1-nitrosourea [BCNU] NPs) to deliver BCNU for inhibition of brain tumor cells (MBR 261-2). These BSA-based NPs are water dispersible, stable, and biocompatible as confirmed by XTT cell viability assay. In vitro phantoms and in vivo MR and fluorescence imaging experiments show that the developed FITC-BSA-Gd/BCNU NPs enable dual MR and fluorescence imaging for monitoring cellular uptake and distribution in tumors. The T1 relaxivity (R1) of FITC-BSA-Gd/BCNU NPs was 3.25 mM(-1) s(-1), which was similar to that of the commercial T1 contrast agent (R1 =3.36 mM(-1) s(-1)). The results indicate that this multifunctional drug delivery system has potential bioimaging tracking of chemotherapeutic agents ability in vitro and in vivo for cancer therapy. PMID:27601895

  19. Super-resolution Localization and Defocused Fluorescence Microscopy on Resonantly Coupled Single-Molecule, Single-Nanorod Hybrids.

    Science.gov (United States)

    Su, Liang; Yuan, Haifeng; Lu, Gang; Rocha, Susana; Orrit, Michel; Hofkens, Johan; Uji-i, Hiroshi

    2016-02-23

    Optical antennas made of metallic nanostructures dramatically enhance single-molecule fluorescence to boost the detection sensitivity. Moreover, emission properties detected at the optical far field are dictated by the antenna. Here we study the emission from molecule-antenna hybrids by means of super-resolution localization and defocused imaging. Whereas gold nanorods make single-crystal violet molecules in the tip's vicinity visible in fluorescence, super-resolution localization on the enhanced molecular fluorescence reveals geometrical centers of the nanorod antenna instead. Furthermore, emission angular distributions of dyes linked to the nanorod surface resemble that of nanorods in defocused imaging. The experimental observations are consistent with numerical calculations using the finite-difference time-domain method.

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Butorin, S.M.; Guo, J.; Magnuson, M. [Uppsala Univ. (Sweden)] [and others

    1997-04-01

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

  2. Cooperative Resonance Interaction Between One-and Two-Photon Super-fluorescences Trough the Vacuum Field

    International Nuclear Information System (INIS)

    The theoretical approach takes in consideration the cooperative phenomena which appear between three particle in two-photon resonance in the process of single- and two- photon decay. This type of single- and two-quanta cooperative effect between three subsystems of radiators are described by master equation which takes into account three-particle cooperative resonance in the system. The resonance between the spontaneous emissions by two- and single photon transitions of three inverted radiators from the ensemble is proposed in order to accelerate the collective decay rate of the entangled photon pairs generated by the system. This effect is accompanied with the interferences between one-photon and two-quantum collective transitions of three inverted radiators from the ensemble. The three particle collective decay rate is defined in the description of three atomic correlation functions.

  3. Cooperative Resonance Interaction Between One-and Two-Photon Super-fluorescences Trough the Vacuum Field

    Science.gov (United States)

    Enaki, Nicolae A.

    2012-02-01

    The theoretical approach takes in consideration the cooperative phenomena which appear between three particle in two-photon resonance in the process of single- and two- photon decay. This type of single- and two-quanta cooperative effect between three subsystems of radiators are described by master equation which takes into account three-particle cooperative resonance in the system. The resonance between the spontaneous emissions by two- and single photon transitions of three inverted radiators from the ensemble is proposed in order to accelerate the collective decay rate of the entangled photon pairs generated by the system. This effect is accompanied with the interferences between one-photon and two-quantum collective transitions of three inverted radiators from the ensemble. The three particle collective decay rate is defined in the description of three atomic correlation functions.

  4. Cyclodextrin-Based Metal-Organic Nanotube as Fluorescent Probe for Selective Turn-On Detection of Hydrogen Sulfide in Living Cells Based on H2S-Involved Coordination Mechanism

    Science.gov (United States)

    Xin, Xuelian; Wang, Jingxin; Gong, Chuanfang; Xu, Hai; Wang, Rongming; Ji, Shijie; Dong, Hanxiao; Meng, Qingguo; Zhang, Liangliang; Dai, Fangna; Sun, Daofeng

    2016-01-01

    Hydrogen sulfide (H2S) has been considered as the third biologically gaseous messenger (gasotransmitter) after nitric oxide (NO) and carbon monoxide (CO). Fluorescent detection of H2S in living cells is very important to human health because it has been found that the abnormal levels of H2S in human body can cause Alzheimer’s disease, cancers and diabetes. Herein, we develop a cyclodextrin-based metal-organic nanotube, CD-MONT-2, possessing a {Pb14} metallamacrocycle for efficient detection of H2S. CD-MONT-2′ (the guest-free form of CD-MONT-2) exhibits turn-on detection of H2S with high selectivity and moderate sensitivity when the material was dissolved in DMSO solution. Significantly, CD-MONT-2′ can act as a fluorescent turn-on probe for highly selective detection of H2S in living cells. The sensing mechanism in the present work is based on the coordination of H2S as the auxochromic group to the central Pb(II) ion to enhance the fluorescence intensity, which is studied for the first time. PMID:26911657

  5. Cyclodextrin-Based Metal-Organic Nanotube as Fluorescent Probe for Selective Turn-On Detection of Hydrogen Sulfide in Living Cells Based on H2S-Involved Coordination Mechanism

    Science.gov (United States)

    Xin, Xuelian; Wang, Jingxin; Gong, Chuanfang; Xu, Hai; Wang, Rongming; Ji, Shijie; Dong, Hanxiao; Meng, Qingguo; Zhang, Liangliang; Dai, Fangna; Sun, Daofeng

    2016-02-01

    Hydrogen sulfide (H2S) has been considered as the third biologically gaseous messenger (gasotransmitter) after nitric oxide (NO) and carbon monoxide (CO). Fluorescent detection of H2S in living cells is very important to human health because it has been found that the abnormal levels of H2S in human body can cause Alzheimer’s disease, cancers and diabetes. Herein, we develop a cyclodextrin-based metal-organic nanotube, CD-MONT-2, possessing a {Pb14} metallamacrocycle for efficient detection of H2S. CD-MONT-2‧ (the guest-free form of CD-MONT-2) exhibits turn-on detection of H2S with high selectivity and moderate sensitivity when the material was dissolved in DMSO solution. Significantly, CD-MONT-2‧ can act as a fluorescent turn-on probe for highly selective detection of H2S in living cells. The sensing mechanism in the present work is based on the coordination of H2S as the auxochromic group to the central Pb(II) ion to enhance the fluorescence intensity, which is studied for the first time.

  6. pH-Responsive Tumor-Targetable Theranostic Nanovectors Based on Core Crosslinked (CCL Micelles with Fluorescence and Magnetic Resonance (MR Dual Imaging Modalities and Drug Delivery Performance

    Directory of Open Access Journals (Sweden)

    Sidan Tian

    2016-06-01

    Full Text Available The development of novel theranostic nanovectors is of particular interest in treating formidable diseases (e.g., cancers. Herein, we report a new tumor-targetable theranostic agent based on core crosslinked (CCL micelles, possessing tumor targetable moieties and fluorescence and magnetic resonance (MR dual imaging modalities. An azide-terminated diblock copolymer, N3-POEGMA-b-P(DPA-co-GMA, was synthesized via consecutive atom transfer radical polymerization (ATRP, where OEGMA, DPA, and GMA are oligo(ethylene glycolmethyl ether methacrylate, 2-(diisopropylaminoethyl methacrylate, and glycidyl methacrylate, respectively. The resulting diblock copolymer was further functionalized with DOTA(Gd (DOTA is 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakisacetic acid or benzaldehyde moieties via copper(I-catalyzed alkyne-azide cycloaddition (CuAAC chemistry, resulting in the formation of DOTA(Gd-POEGMA-b-P(DPA-co-GMA and benzaldehyde-POEGMA-b-P(DPA-co-GMA copolymers. The resultant block copolymers co-assembled into mixed micelles at neutral pH in the presence of tetrakis[4-(2-mercaptoethoxyphenyl]ethylene (TPE-4SH, which underwent spontaneous crosslinking reactions with GMA residues embedded within the micellar cores, simultaneously switching on TPE fluorescence due to the restriction of intramolecular rotation. Moreover, camptothecin (CPT was encapsulated into the crosslinked cores at neutral pH, and tumor-targeting pH low insertion peptide (pHLIP, sequence: AEQNPIYWARYADWLFTTPLLLLDLALLVDADEGTCG moieties were attached to the coronas through the Schiff base chemistry, yielding a theranostic nanovector with fluorescence and MR dual imaging modalities and tumor-targeting capability. The nanovectors can be efficiently taken up by A549 cells, as monitored by TPE fluorescence. After internalization, intracellular acidic pH triggered the release of loaded CPT, killing cancer cells in a selective manner. On the other hand, the nanovectors labeled with DOTA

  7. Observation of resonance fluorescence and the Mollow triplet from a coherently driven site-controlled quantum dot

    DEFF Research Database (Denmark)

    Unsleber, Sebastian; Maier, Sebastian; McCutcheon, Dara;

    2015-01-01

    Resonant excitation of solid state quantum emitters has the potential to deterministically excite a localized exciton while ensuring a maximally coherent emission. In this work, we demonstrate the coherent coupling of an exciton localized in a lithographically positioned, site-controlled semicond...

  8. Deep tissue fluorescence resonance energy transfer imaging and the application of the Bethe-Salpeter equation to non-diffusive wave propagation

    Science.gov (United States)

    Gaind, Vaibhav

    Fluorescence resonance energy transfer (FRET) has found many applications in in vitro imaging as an indicator of molecular activity. However, till now, in vivo FRET imaging has been restricted to near-surface multiphoton microscopy. Optical diffusion tomography (ODT) is an emerging tool for deep tissue imaging. In this work, FRET was incorporated in an ODT framework, thereby allowing FRET to be applied in deep tissue imaging. Using simulations and tissue phantom and small animal imaging experiments, the possibility of imaging molecular activity on the nanometer scale using macroscopic measurements is demonstrated. The diffusion equation model is limited to regions of high scatter and low absorption. The Bethe-Salpeter equation has been used extensively to explain various scattering phenomena and is more fundamental than the Boltzmann transport equation. In this work, the Bethe-Salpeter equation has been investigated for modeling photon transport in the non-diffusive regime.

  9. Self-assembled dual-modality contrast agents for non-invasive stem cell tracking via near-infrared fluorescence and magnetic resonance imaging.

    Science.gov (United States)

    Liu, Hong; Tan, Yan; Xie, Lisi; Yang, Lei; Zhao, Jing; Bai, Jingxuan; Huang, Ping; Zhan, Wugen; Wan, Qian; Zou, Chao; Han, Yali; Wang, Zhiyong

    2016-09-15

    Stem cells hold great promise for treating various diseases. However, one of the main drawbacks of stem cell therapy is the lack of non-invasive image-tracking technologies. Although magnetic resonance imaging (MRI) and near-infrared fluorescence (NIRF) imaging have been employed to analyse cellular and subcellular events via the assistance of contrast agents, the sensitivity and temporal resolution of MRI and the spatial resolution of NIRF are still shortcomings. In this study, superparamagnetic iron oxide nanocrystals and IR-780 dyes were co-encapsulated in stearic acid-modified polyethylenimine to form a dual-modality contrast agent with nano-size and positive charge. These resulting agents efficiently labelled stem cells and did not influence the cellular viability and differentiation. Moreover, the labelled cells showed the advantages of dual-modality imaging in vivo. PMID:27299677

  10. 1Application of Fluorescence Resonance Energy Transfer and Magnetic Twisting Cytometry to Quantitate Mechano-Chemical Signaling Activities in a Living Cell

    Science.gov (United States)

    Na, Sungsoo; Wang, Ning

    2009-01-01

    Mechanotransduction is the process by which living cells sense mechanical forces and then convert them into biochemical signaling. Recently we showed that mechanical stress is transduced from the cell surface to remote cytoplasmic sites within 0.3 s, which is at least 40 to 50 times faster than soluble factor-induced signal transduction, and the sites of mechanotransduction colocalize with sites where mechanical stress causes microtubule displacement. These results suggest that mechanotransduction employs mechanisms different from those of soluble factor-induced signal transduction. Here we describe a protocol that utilizes fluorescence resonance energy transfer (FRET) and a magnetic twisting cytometry (MTC) device to capture rapid mechano-chemical signaling activities in living cells. PMID:18728305

  11. Self-assembled dual-modality contrast agents for non-invasive stem cell tracking via near-infrared fluorescence and magnetic resonance imaging.

    Science.gov (United States)

    Liu, Hong; Tan, Yan; Xie, Lisi; Yang, Lei; Zhao, Jing; Bai, Jingxuan; Huang, Ping; Zhan, Wugen; Wan, Qian; Zou, Chao; Han, Yali; Wang, Zhiyong

    2016-09-15

    Stem cells hold great promise for treating various diseases. However, one of the main drawbacks of stem cell therapy is the lack of non-invasive image-tracking technologies. Although magnetic resonance imaging (MRI) and near-infrared fluorescence (NIRF) imaging have been employed to analyse cellular and subcellular events via the assistance of contrast agents, the sensitivity and temporal resolution of MRI and the spatial resolution of NIRF are still shortcomings. In this study, superparamagnetic iron oxide nanocrystals and IR-780 dyes were co-encapsulated in stearic acid-modified polyethylenimine to form a dual-modality contrast agent with nano-size and positive charge. These resulting agents efficiently labelled stem cells and did not influence the cellular viability and differentiation. Moreover, the labelled cells showed the advantages of dual-modality imaging in vivo.

  12. Preparation and Fluorescence Resonance Energy Transfer of Carbon Dots%碳点的制备及其荧光共振能量转移

    Institute of Scientific and Technical Information of China (English)

    张煌博; 曹学功; 孙向英

    2014-01-01

    Amino-modified carbon dots were synthesized by the low temperature carbonization of citric acid in the pres-ence of branched polyethylenimine in one step.The bright blue emission was observed under the excitation of ultraviolet rays.Fourier transform infrared spectroscopy and X-ray powder diffraction were used to characterize its structure.Mean-while,the fluorescence resonance energy transfer between amino-modified carbon dots and CdTe QDs in liquid or solid-liquid phase was studied.The results show that fluorescence resonance energy transfer efficiency in liquid is much larger than the solid-liquid phase and it also has a limit.%以枝状聚乙烯亚胺和柠檬酸为原料,低温熔融法一步合成水溶性的氨基化碳点,碳点在紫外光激发下发出明亮的蓝光。采用傅里叶变换红外光谱和 X 射线粉末衍射仪对其结构进行表征,并研究其与碲化镉量子点在液相和固液界面的荧光共振能量转移。实验结果表明:液相中的荧光共振能量转移效率远大于固液界面的荧光共振能量转移,且能量转移具有一定的限度。

  13. Development of a fluorescence resonance energy transfer assay for monitoring bacterial collagenase triple-helical peptidase activity

    OpenAIRE

    Tokmina-Roszyk, Michal; Tokmina-Roszyk, Dorota; Bhowmick, Manishabrata; Fields, Gregg B.

    2014-01-01

    Due to their efficiency in the hydrolysis of the collagen triple-helix, Clostridial histolyticum collagenases are utilized for isolation of cells from various tissues, including isolation of the human pancreatic islets. However, the instability of Clostridial collagenase I (Col G) results in a degraded Col G that has weak collagenolytic activity and an adverse effect on islet isolation and viability. A Föster resonance energy transfer (FRET) triple-helical peptide (fTHP) substrate has been de...

  14. Observation of resonance fluorescence and the Mollow triplet from a coherently driven site-controlled quantum dot

    DEFF Research Database (Denmark)

    Unsleber, Sebastian; Maier, Sebastian; McCutcheon, Dara;

    2015-01-01

    Resonant excitation of solid state quantum emitters has the potential to deterministically excite a localized exciton while ensuring a maximally coherent emission. In this work, we demonstrate the coherent coupling of an exciton localized in a lithographically positioned, site-controlled semicond......Resonant excitation of solid state quantum emitters has the potential to deterministically excite a localized exciton while ensuring a maximally coherent emission. In this work, we demonstrate the coherent coupling of an exciton localized in a lithographically positioned, site......-controlled semiconductor quantum dot to an external resonant laser field. For strong continuous-wave driving we observe the characteristic Mollow triplet and analyze the Rabi splitting and sideband widths as a function of driving strength and temperature. The sideband widths increase linearly with temperature...... and the square of the driving strength, which we explain via coupling of the exciton to longitudinal acoustic phonons. We also find an increase of the Rabi splitting with temperature, which indicates a temperature induced delocalization of the excitonic wave function resulting in an increase of the oscillator...

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

    Science.gov (United States)

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

    2016-08-16

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

  16. Study on the absorption and fluorescence and resonance Rayleigh scattering spectra of Cu (Ⅱ)-fluoroquinolone chelates with erythrosine and their applications

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In pH 4.2-5.0 Britton-Robinson buffer solution medium, fluoroquinolone antibiotics (FLQs), such as ciprofloxacin (CIP), norfloxacin (NOR), ofloxacin (OF), levofloxacin (LEV), lomefloxacin (LOM), and sparfloxacin (SPA), react with Cu (Ⅱ) to form chelate cations, which further bind with erythrosine to form the ion association complexes. They can result in the changes of the absorption spectra. Simultaneously, erythrosine fades obviously and the maximum fading wavelength is located at 526 nm. The fading reactions have high sensitivities. Thus, new spectrophotometries of determination for these drugs are developed. The ion-association reactions result in the quenching of fluorescence, which also have high sensitivities. The detection limits for six antibiotics are in the range of 7.1-12.2 μg·L-1. Furthermore, the reactions can result in the enhancement of resonance Rayleigh scattering (RRS). The maximum scattering peaks of six ion-association complexes are located at 566 nm, and there are two small RRS peaks at 333 nm and 287 nm. The detection limits for fluoroquinolone antibiotics are in the range of 1.70-3.10 μg·L-1 for RRS method. Among the above three methods, the RRS method has the highest sensitivity. In this work, we investigated the spectral characteristics of the absorption, fluorescence and RRS, the optimum conditions of the reactions, and the properties of the analytical chemistry. In addition, the mechanism of reactions were discussed by density function theory (DFT) and AM1 methods.

  17. Fluorescence characterization of co-immobilization-induced multi-enzyme aggregation in a polymer matrix using Förster resonance energy transfer (FRET): toward the metabolon biomimic.

    Science.gov (United States)

    Wu, Fei; Minteer, Shelley D

    2013-08-12

    Sequential metabolic enzymes can form supramolecular complexes named metabolons in vivo through enzyme-enzyme association or aggregation to facilitate efficient substrate channeling. By separately labeling enzymes with lysine-targeting carboxylic acid succinimidyl ester fluorophores of distinct excitation wavelengths, this research presents a quantitative study of polymer-entrapment-induced in vitro multi-enzyme aggregation from three Krebs cycle enzymes using Förster resonance energy transfer (FRET) to find potential polymer materials for immobilizing enzyme cascades and inducing the metabolon biomimic formation on electrodes. The effect of hydrophobic modification of linear polyethylenimine, Nafion, and chitosan polymers on metabolon formation has been investigated through photobleaching FRET imaging in addition to traditional steady-state fluorescence spectroscopy. By partially destroying FRET acceptors of longer excitation wavelength, increased fluorescence from dequenched donors of shorter excitation wavelength was measured and enzyme interactions in terms of energy-transfer efficiencies were mapped point by point. Results show that trimethyloctadecylammonium-modified Nafion works best in inducing multi-enzyme aggregation and exhibits a promising future in immobilized metabolon biomimics with the most uniform enzyme organization, as indicated by the protein distance distribution.

  18. 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.

  19. Mammalian Cell-Based Sensor System

    Science.gov (United States)

    Banerjee, Pratik; Franz, Briana; Bhunia, Arun K.

    Use of living cells or cellular components in biosensors is receiving increased attention and opens a whole new area of functional diagnostics. The term "mammalian cell-based biosensor" is designated to biosensors utilizing mammalian cells as the biorecognition element. Cell-based assays, such as high-throughput screening (HTS) or cytotoxicity testing, have already emerged as dependable and promising approaches to measure the functionality or toxicity of a compound (in case of HTS); or to probe the presence of pathogenic or toxigenic entities in clinical, environmental, or food samples. External stimuli or changes in cellular microenvironment sometimes perturb the "normal" physiological activities of mammalian cells, thus allowing CBBs to screen, monitor, and measure the analyte-induced changes. The advantage of CBBs is that they can report the presence or absence of active components, such as live pathogens or active toxins. In some cases, mammalian cells or plasma membranes are used as electrical capacitors and cell-cell and cell-substrate contact is measured via conductivity or electrical impedance. In addition, cytopathogenicity or cytotoxicity induced by pathogens or toxins resulting in apoptosis or necrosis could be measured via optical devices using fluorescence or luminescence. This chapter focuses mainly on the type and applications of different mammalian cell-based sensor systems.

  20. Study on the absorption and fluorescence and resonance Rayleigh scattering spectra of Cu (II)-fluoroquinolone chelates with erythrosine and their applications

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In pH 4.2-5.0 Britton-Robinson buffer solution medium, fluoroquinolone antibiotics (FLQs), such as ciprofloxacin (CIP), norfloxacin (NOR), ofloxacin (OF), levofloxacin (LEV), lomefloxacin (LOM), and sparfloxacin (SPA), react with Cu (II) to form chelate cations, which further bind with erythrosine to form the ion association complexes. They can result in the changes of the absorption spectra. Simultane- ously, erythrosine fades obviously and the maximum fading wavelength is located at 526 nm. The fad- ing reactions have high sensitivities. Thus, new spectrophotometries of determination for these drugs are developed. The ion-association reactions result in the quenching of fluorescence, which also have high sensitivities. The detection limits for six antibiotics are in the range of 7.1-12.2 μg·L?1. Furthermore, the reactions can result in the enhancement of resonance Rayleigh scattering (RRS). The maximum scattering peaks of six ion-association complexes are located at 566 nm, and there are two small RRS peaks at 333 nm and 287 nm. The detection limits for fluoroquinolone antibiotics are in the range of 1.70 -3.10 μg·L?1 for RRS method. Among the above three methods, the RRS method has the highest sen- sitivity. In this work, we investigated the spectral characteristics of the absorption, fluorescence and RRS, the optimum conditions of the reactions, and the properties of the analytical chemistry. In addi- tion, the mechanism of reactions were discussed by density function theory (DFT) and AM1 methods.

  1. Differential detection of Trichinella papuae, T. spiralis and T. pseudospiralis by real-time fluorescence resonance energy transfer PCR and melting curve analysis.

    Science.gov (United States)

    Tantrawatpan, Chairat; Intapan, Pewpan M; Thanchomnang, Tongjit; Lulitanond, Viraphong; Boonmars, Thidarut; Wu, Zhiliang; Morakote, Nimit; Maleewong, Wanchai

    2012-04-30

    Trichinellosis caused by nematodes of Trichinella spp. is a zoonotic foodborne disease. Three Trichinella species of the parasite including Trichinella spiralis, Trichinella papuae and Trichinella pseudospiralis, have been etiologic agents of human trichinellosis in Thailand. Definite diagnosis of this helminthiasis is based on a finding of the Trichinella larva (e) in a muscle biopsy. The parasite species or genotype can be determined using molecular methods, e.g., polymerase chain reaction (PCR). This study has utilized real-time fluorescence resonance energy transfer PCR (real-time FRET PCR) and a melting curve analysis for the differential diagnosis of trichinellosis. Three common Trichinella species in Thailand were studied using one set of primers and fluorophore-labeled hybridization probes specific for the small subunit of the mitochondrial ribosomal RNA gene. Using fewer than 35 cycles as the cut-off for positivity and using different melting temperatures (T(m)), this assay detected T. spiralis, T. papuae and T. pseudospiralis in muscle tissue and found the mean T(m) ± SD values to be 51.79 ± 0.06, 66.09 ± 0.46 and 51.46 ± 0.09, respectively. The analytical sensitivity of the technique enabled the detection of a single Trichinella larva of each species, and the detection limit for the target DNA sequence was 16 copies of positive control plasmid. A test of the technique's analytical specificity showed no fluorescence signal for a panel of 19 non-Trichinella parasites or for human and mouse genomic DNA. Due to the sensitivity and specificity of the detection of these Trichinella species, as well as the fast and high-throughput nature of these tools, this method has application potential in differentiating non-encapsulated larvae of T. papuae from T. spiralis and T. pseudospiralis in tissues of infected humans and animals. PMID:22037059

  2. Interfacial Chemistry and the Design of Solid-Phase Nucleic Acid Hybridization Assays Using Immobilized Quantum Dots as Donors in Fluorescence Resonance Energy Transfer

    Directory of Open Access Journals (Sweden)

    Ulrich J. Krull

    2011-06-01

    Full Text Available 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.

  3. X-ray fluorescence microscopy demonstrates preferential accumulation of a vanadium-based magnetic resonance imaging contrast agent in murine colonic tumors.

    Science.gov (United States)

    Mustafi, Devkumar; Ward, Jesse; Dougherty, Urszula; Bissonnette, Marc; Hart, John; Vogt, Stefan; Karczmar, Gregory S

    2015-01-01

    Contrast agents that specifically enhance cancers on magnetic resonance imaging (MRI) will allow earlier detection. Vanadium-based chelates (VCs) selectively enhance rodent cancers on MRI, suggesting selective uptake of VCs by cancers. Here we report x-ray fluorescence microscopy (XFM) of VC uptake by murine colon cancer. Colonic tumors in mice treated with azoxymethane/dextran sulfate sodium were identified by MRI. Then a gadolinium-based contrast agent and a VC were injected intravenously; mice were sacrificed and colons sectioned. VC distribution was sampled at 120 minutes after injection to evaluate the long-term accumulation. Gadolinium distribution was sampled at 10 minutes after injection due to its rapid washout. XFM was performed on 72 regions of normal and cancerous colon from five normal mice and four cancer-bearing mice. XFM showed that all gadolinium was extracellular, with similar concentrations in colon cancers and normal colon. In contrast, the average VC concentration was twofold higher in cancers versus normal tissue (p < .002). Cancers also contained numerous "hot spots" with intracellular VC concentrations sixfold higher than the concentration in normal colon (p < .0001). No hot spots were detected in normal colon. This is the first direct demonstration that VCs selectively accumulate in cancer cells and thus may improve cancer detection.

  4. Determination of the electromagnetic dipole strength distribution in medium-heavy atomic nuclei by means of nuclear resonance fluorescence; Bestimmung der elektromagnetischen Dipolstaerkeverteilung in mittelschweren Atomkernen mittels Kernresonanzfluoreszenz

    Energy Technology Data Exchange (ETDEWEB)

    Massarczyk, Ralph Jens

    2011-01-17

    During the last hundred years several models were developed to describe the configuration of nuclei. These models have to make predictions, which should be comparable with experiments. As a standard type of experiment the nuclear resonance fluorescence was established. A nucleus is excited by irradiation with photons. By emitting one or more photons the nucleus decays back to the ground state. With this method it is possible to measure energy levels and to determine the strength of their excitation. A continuum of unresolved peaks gives additional strength. The existing setup at the linear electron accelerator ELBE of the Forschungszentrum Dresden-Rossendorf uses bremsstrahlung, produced as a secondary beam in a thin Niobium foil. During the years 2008/09 experiments on the nuclei of {sup 86}Kr and {sup 136}Ba took place there. In this work they will be analyzed. Photon flux and efficiency determination have been done as well as simulations on detector response and non-nuclear scattered background events. For this purpose the GEANT4 package was used. Finally the resulting cross sections were corrected for branching and feeding.

  5. A novel ionic liquid-in-oil microemulsion composed of biologically acceptable components: an excitation wavelength dependent fluorescence resonance energy transfer study.

    Science.gov (United States)

    Mandal, Sarthak; Ghosh, Surajit; Banerjee, Chiranjib; Kuchlyan, Jagannath; Banik, Debasis; Sarkar, Nilmoni

    2013-03-21

    In this work we have reported the formulation of a novel ionic liquid-in-oil (IL/O) microemulsion where the polar core of the ionic liquid, 1-ethyl-3-methylimidazolium n-butylsulfate ([C2mim][C4SO4]), is stabilized by a mixture of two nontoxic nonionic surfactants, polyoxyethylene sorbitan monooleate (Tween-80) and sorbitan laurate (Span-20), in a biological oil phase of isopropyl myristate (IPM). The formation of the microemulsion droplets has been confirmed from the dynamic light scattering (DLS) and phase behavior study. To assess the dynamic heterogeneity of this tween-based IL/O microemulsion, we have performed an excitation wavelength dependent fluorescence resonance energy transfer (FRET) from coumarin 480 (C480) to rhodamine 6G (R6G). The multiple donor-acceptor (D-A) distances, ∼15, 30, and 45 Å, obtained from the rise times of the acceptor emission in the presence of a donor can be rationalized from the varying distribution of the donor, C480, in the different regions of the microemulsion system. With increasing the excitation wavelength from 375 to 408 nm, the contribution of the rise component of ∼240 ps which results the D-A distance of ∼30 Å increases significantly due to the enhanced contribution of the C480 probe molecules closer to the acceptor in the ionic liquid pool of the microemulsion. PMID:23445434

  6. Real-time PCR/MCA assay using fluorescence resonance energy transfer for the genotyping of resistance related DHPS-540 mutations in Plasmodium falciparum

    Directory of Open Access Journals (Sweden)

    Dujardin Jean-Claude

    2008-03-01

    Full Text Available Abstract Background Sulphadoxine-pyrimethamine has been abandoned as first- or second-line treatment by most African malaria endemic countries in favour of artemisinin-based combination treatments, but the drug is still used as intermittent preventive treatment during pregnancy. However, resistance to sulphadoxine-pyrimethamine has been increasing in the past few years and, although the link between molecular markers and treatment failure has not been firmly established, at least for pregnant women, it is important to monitor such markers. Methods This paper reports a novel sensitive, semi-quantitative and specific real-time PCR and melting curve analysis (MCA assay using fluorescence resonance energy transfer (FRET for the detection of DHPS-540, an important predictor for SP resistance. FRET/MCA was evaluated using 78 clinical samples from malaria patients and compared to PCR-RFLP. Results Sixty-two samples were in perfect agreement between both assays. One sample showed a small wild type signal with FRET/MCA that indicates a polyclonal infection. Four samples were not able to generate enough material in both assays to distinguish mutant from wild-type infection, six samples gave no signal in PCR-RFLP and five samples gave no amplification in FRET/MCA. Conclusion FRET/MCA is an effective tool for the identification of SNPs in drug studies and epidemiological surveys on resistance markers in general and DHPS-540 mutation in particular.

  7. Application of the laser induced fluorescence to the investigation of highly magnetized plasmas, heated by ion cyclotron resonance; Fluorescence induite par laser sur des plasmas fortement magnetises, chauffes par resonnance cyclotron ionique

    Energy Technology Data Exchange (ETDEWEB)

    Pailloux, A. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. des Procedes d`Enrichissement]|[Universite Louis Pasteur, 67 - Strasbourg (France)

    1997-12-31

    This work has been achieved in the frame of isotopic separation studies by in cyclotron resonance. For this purpose, in a highly magnetized (2 to 3 Tesla) and non-collisional (10{sup 12} ions/cm{sup 3}) plasma, composed of metallic ions, a wave near the ion cyclotron frequency is thrown in order to heat selectively a given species. A laser induced fluorescence (LIP) has been developed on barium and gadolinium plasmas. The Larmor gyration of ions greatly modifies the interaction, which has been modelled through the time-dependent Schroedinger equation. The obtained excitation probably has been integrated over all the ions excited in the measurement volume in order to check that the LIF still leads to the distribution function of ion velocities. The influence of the Larmor motion of ions on the spectral distribution of LIF has been derived both theoretically and experimentally. The LIF diagnostics has been achieved with a dye O`ring laser. The barium ion has been excited on the transition 6142 angstrom, using rhodamine 6G dye, and the gadolinium ion on the pseudo-triplet 3861 angstrom, using exalite dye. Data treatment has been developed taking into account the Zeeman effect and the different heating of isotopes. The ionic temperature (from 1 eV to some hundreds eV) has been measured as a function of radiofrequency heating. Our experimental results are in good agreement with the selective heating theory. Also, the ion velocity distribution function has been found locally Maxwellian. And the behaviour of the plasma has been studied as a function of control parameters of the plasma source. (author) 62 refs.

  8. 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

    Directory of Open Access Journals (Sweden)

    Luís M. S. Loura

    2012-11-01

    Full Text Available 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-ylamino] hexanoyl- sn-glycero-3-phosphocholine (C6-NBD-PC or 1-palmitoyl,2-(12-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-ylamino]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.

  9. 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

    2012-01-01

    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. PMID:23203080

  10. Optical-optical double resonance, laser induced fluorescence, and revision of the signs of the spin-spin constants of the boron carbide (BC) free radical

    International Nuclear Information System (INIS)

    The cold boron carbide free radical (BC X 4Σ−) has been produced in a pulsed discharge free jet expansion using a precursor mixture of trimethylborane in high pressure argon. High resolution laser induced fluorescence spectra have been obtained for the B 4Σ−–X 4Σ− and E 4Π–X 4Σ− band systems of both 11BC and 10BC. An optical-optical double resonance (OODR) scheme was implemented to study the finer details of both band systems. This involved pumping a single rotational level of the B state with one laser and then recording the various allowed transitions from the intermediate B state to the final E state with a second laser by monitoring the subsequent E–X ultraviolet fluorescence. In this fashion, we were able to prove unambiguously that, contrary to previous studies, the spin-spin constant λ is negative in the ground state and positive in the B 4Σ− excited state. It has been shown that λ″ < 0 is in fact expected based on a semiempirical second order perturbation theory calculation of the magnitude of the spin-spin constant. The OODR spectra have also been used to validate our assignments of the complex and badly overlapped E 4Π–X 4Σ− 0-0 and 1-0 bands of 11BC. The E–X 0-0 band of 10BC was found to be severely perturbed. The ground state main electron configuration is …3σ24σ25σ11π22π0 and the derived bond lengths show that there is a 0.03 Å contraction in the B state, due to the promotion of an electron from the 4σ antibonding orbital to the 5σ bonding orbital. In contrast, the bond length elongates by 0.15 Å in the E state, a result of promoting an electron from the 5σ bonding orbital to the 2π antibonding orbitals

  11. Optical-optical double resonance, laser induced fluorescence, and revision of the signs of the spin-spin constants of the boron carbide (BC) free radical

    Energy Technology Data Exchange (ETDEWEB)

    Sunahori, Fumie X. [Department of Chemistry and Physics, Franklin College, Franklin, Indiana 46131 (United States); Nagarajan, Ramya; Clouthier, Dennis J., E-mail: dclaser@uky.edu [Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055 (United States)

    2015-12-14

    The cold boron carbide free radical (BC X {sup 4}Σ{sup −}) has been produced in a pulsed discharge free jet expansion using a precursor mixture of trimethylborane in high pressure argon. High resolution laser induced fluorescence spectra have been obtained for the B {sup 4}Σ{sup −}–X {sup 4}Σ{sup −} and E {sup 4}Π–X {sup 4}Σ{sup −} band systems of both {sup 11}BC and {sup 10}BC. An optical-optical double resonance (OODR) scheme was implemented to study the finer details of both band systems. This involved pumping a single rotational level of the B state with one laser and then recording the various allowed transitions from the intermediate B state to the final E state with a second laser by monitoring the subsequent E–X ultraviolet fluorescence. In this fashion, we were able to prove unambiguously that, contrary to previous studies, the spin-spin constant λ is negative in the ground state and positive in the B {sup 4}Σ{sup −} excited state. It has been shown that λ″ < 0 is in fact expected based on a semiempirical second order perturbation theory calculation of the magnitude of the spin-spin constant. The OODR spectra have also been used to validate our assignments of the complex and badly overlapped E {sup 4}Π–X {sup 4}Σ{sup −} 0-0 and 1-0 bands of {sup 11}BC. The E–X 0-0 band of {sup 10}BC was found to be severely perturbed. The ground state main electron configuration is …3σ{sup 2}4σ{sup 2}5σ{sup 1}1π{sup 2}2π{sup 0} and the derived bond lengths show that there is a 0.03 Å contraction in the B state, due to the promotion of an electron from the 4σ antibonding orbital to the 5σ bonding orbital. In contrast, the bond length elongates by 0.15 Å in the E state, a result of promoting an electron from the 5σ bonding orbital to the 2π antibonding orbitals.

  12. Optical-optical double resonance, laser induced fluorescence, and revision of the signs of the spin-spin constants of the boron carbide (BC) free radical

    Science.gov (United States)

    Sunahori, Fumie X.; Nagarajan, Ramya; Clouthier, Dennis J.

    2015-12-01

    The cold boron carbide free radical (BC X 4Σ-) has been produced in a pulsed discharge free jet expansion using a precursor mixture of trimethylborane in high pressure argon. High resolution laser induced fluorescence spectra have been obtained for the B 4Σ--X 4Σ- and E 4Π-X 4Σ- band systems of both 11BC and 10BC. An optical-optical double resonance (OODR) scheme was implemented to study the finer details of both band systems. This involved pumping a single rotational level of the B state with one laser and then recording the various allowed transitions from the intermediate B state to the final E state with a second laser by monitoring the subsequent E-X ultraviolet fluorescence. In this fashion, we were able to prove unambiguously that, contrary to previous studies, the spin-spin constant λ is negative in the ground state and positive in the B 4Σ- excited state. It has been shown that λ″ < 0 is in fact expected based on a semiempirical second order perturbation theory calculation of the magnitude of the spin-spin constant. The OODR spectra have also been used to validate our assignments of the complex and badly overlapped E 4Π-X 4Σ- 0-0 and 1-0 bands of 11BC. The E-X 0-0 band of 10BC was found to be severely perturbed. The ground state main electron configuration is …3σ24σ25σ11π22π0 and the derived bond lengths show that there is a 0.03 Å contraction in the B state, due to the promotion of an electron from the 4σ antibonding orbital to the 5σ bonding orbital. In contrast, the bond length elongates by 0.15 Å in the E state, a result of promoting an electron from the 5σ bonding orbital to the 2π antibonding orbitals.

  13. Optical-optical double resonance, laser induced fluorescence, and revision of the signs of the spin-spin constants of the boron carbide (BC) free radical.

    Science.gov (United States)

    Sunahori, Fumie X; Nagarajan, Ramya; Clouthier, Dennis J

    2015-12-14

    The cold boron carbide free radical (BC X (4)Σ(-)) has been produced in a pulsed discharge free jet expansion using a precursor mixture of trimethylborane in high pressure argon. High resolution laser induced fluorescence spectra have been obtained for the B (4)Σ(-)-X (4)Σ(-) and E (4)Π-X (4)Σ(-) band systems of both (11)BC and (10)BC. An optical-optical double resonance (OODR) scheme was implemented to study the finer details of both band systems. This involved pumping a single rotational level of the B state with one laser and then recording the various allowed transitions from the intermediate B state to the final E state with a second laser by monitoring the subsequent E-X ultraviolet fluorescence. In this fashion, we were able to prove unambiguously that, contrary to previous studies, the spin-spin constant λ is negative in the ground state and positive in the B (4)Σ(-) excited state. It has been shown that λ″ < 0 is in fact expected based on a semiempirical second order perturbation theory calculation of the magnitude of the spin-spin constant. The OODR spectra have also been used to validate our assignments of the complex and badly overlapped E (4)Π-X (4)Σ(-) 0-0 and 1-0 bands of (11)BC. The E-X 0-0 band of (10)BC was found to be severely perturbed. The ground state main electron configuration is …3σ(2)4σ(2)5σ(1)1π(2)2π(0) and the derived bond lengths show that there is a 0.03 Å contraction in the B state, due to the promotion of an electron from the 4σ antibonding orbital to the 5σ bonding orbital. In contrast, the bond length elongates by 0.15 Å in the E state, a result of promoting an electron from the 5σ bonding orbital to the 2π antibonding orbitals.

  14. A Fluorescent Indicator for Imaging Lysosomal Zinc(II) with Förster Resonance Energy Transfer (FRET)-Enhanced Photostability and a Narrow Band of Emission

    Science.gov (United States)

    Sreenath, Kesavapillai; Yuan, Zhao; Allen, John R.

    2015-01-01

    We demonstrate a strategy to transfer the zinc(II) sensitivity of a fluoroionophore with low photostability and a broad emission band to a bright and photostable fluorophore with a narrow emission band. The two fluorophores are covalently connected to afford an intramolecular Förster resonance energy transfer (FRET) conjugate. The FRET donor in the conjugate is a zinc(II)-sensitive arylvinylbipyridyl fluoroionophore, the absorption and emission of which undergo bathochromic shifts upon zinc(II) coordination. When the FRET donor is excited, efficient intramolecular energy transfer occurs to result in the emission of the acceptor boron dipyrromethene (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene or BODIPY) as a function of zinc(II) concentration. The broad emission band of the donor/zinc(II) complex is transformed into the strong, narrow emission band of the BODIPY acceptor in the FRET conjugates, which can be captured within the narrow emission window that is preferred for multicolor imaging experiments. In addition to competing with other nonradiative decay processes of the FRET donor, the rapid intramolecular FRET of the excited FRET-conjugate molecule protects the donor fluorophore from photobleaching, thus enhancing the photostability of the indicator. FRET conjugates 3 and 4 contain aliphatic amino groups, which selectively target lysosomes in mammalian cells. This subcellular localization preference was verified by using confocal fluorescence microscopy, which also shows the zinc(II)-enhanced emission of 3 and 4 in lysosomes. It was further shown using two-color structured illumination microscopy (SIM), which is capable of extending the lateral resolution over the Abbe diffraction limit by a factor of two, that the morpholino-functionalized compound 4 localizes in the interior of lysosomes, rather than anchoring on the lysosomal membranes, of live HeLa cells. PMID:25382395

  15. Preliminary Study of the Efficacy of Using Nuclear Resonance Fluorescence with Quasi-Monoenergetic Gamma-Ray Sources for Nuclear Safeguards Assay

    International Nuclear Information System (INIS)

    We have studied the efficacy of using nuclear resonance fluorescence (NRF)-based techniques to assay spent nuclear fuel for Pu content using quasi-monoenergetic sources. We have developed two techniques to precisely determine the Pu content in a fuel rod/pin. One of our approaches is virtually free of systematic uncertainties. Using analytical models, we have determined the amount of time required to measure the Pu content in spent nuclear fuel rods and spent fuel assemblies to within 1% precision. We note that Pu content can be determined in a fuel assembly about as fast as in a single fuel pin. The performance of NRF-based assay techniques with improved photon sources, which are currently under development, will also estimated. For follow-on research we propose to: (1) Construct research prototype detection systems for both of the NRF-based assay systems proposed in this paper and measure their calibration curves; (2) Determine the systematic errors associated with both assay methods, explore ways to reduce the errors and fold the results into future performance calculations; (3) Develop an algorithm to assay a fuel assembly; (4) Perform validation measurements using a single pin and scaled assemblies; (5) Research and develop current-mode detection and/or threshold detection techniques to improve assay times; (6) Characterize the flux of newly constructed sources and fold the results into the calculations presented here to determine the feasibility of a variety of proposed sources; and (7) Collaborate with others in the safeguards community to build a prototype system and perform an NRF-based assay demonstration on spent fuel.

  16. Preliminary Study of the Efficacy of Using Nuclear Resonance Fluorescence with Quasi-Monoenergetic Gamma-Ray Sources for Nuclear Safeguards Assay

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, M S; McNabb, D P; Hall, J M; Gonzalez, J J

    2011-02-17

    We have studied the efficacy of using nuclear resonance fluorescence (NRF)-based techniques to assay spent nuclear fuel for Pu content using quasi-monoenergetic sources. We have developed two techniques to precisely determine the Pu content in a fuel rod/pin. One of our approaches is virtually free of systematic uncertainties. Using analytical models, we have determined the amount of time required to measure the Pu content in spent nuclear fuel rods and spent fuel assemblies to within 1% precision. We note that Pu content can be determined in a fuel assembly about as fast as in a single fuel pin. The performance of NRF-based assay techniques with improved photon sources, which are currently under development, will also estimated. For follow-on research we propose to: (1) Construct research prototype detection systems for both of the NRF-based assay systems proposed in this paper and measure their calibration curves; (2) Determine the systematic errors associated with both assay methods, explore ways to reduce the errors and fold the results into future performance calculations; (3) Develop an algorithm to assay a fuel assembly; (4) Perform validation measurements using a single pin and scaled assemblies; (5) Research and develop current-mode detection and/or threshold detection techniques to improve assay times; (6) Characterize the flux of newly constructed sources and fold the results into the calculations presented here to determine the feasibility of a variety of proposed sources; and (7) Collaborate with others in the safeguards community to build a prototype system and perform an NRF-based assay demonstration on spent fuel.

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

    International Nuclear Information System (INIS)

    Highlights: ► First experimental determination of Förster distance (R0) for enhanced BRET systems. ► Effect of brighter BRET components RLuc2, RLuc8 and Venus was assessed. ► Using brighter BRET components substantially increased (25%) R0 of the BRET1 system. ► Using brighter BRET components marginally increased (2–9%) R0 of the BRET2 system. ► Brighter BRET components improve the different weaknesses of BRET1 and BRET2 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. Förster distance (R0), the intermolecular separation characterized by 50% of the maximum possible energy transfer, is a critical BRET parameter. R0 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 R0 for BRET1 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 R0 of the original BRET1 system. R0 for BRET2 systems combining green fluorescent proteins (GFP2) with RLuc2 or RLuc8 variants was 7.67 or 8.15 nm, i.e. only 2–9% greater than the original BRET2 system despite being ∼30-fold brighter.

  18. Ultrafast resonance energy transfer from a site-specifically attached fluorescent chromophore reveals the folding of the N-terminal domain of CP29

    NARCIS (Netherlands)

    Oort, van B.F.; Murali, S.; Wientjes, E.; Koehorst, R.B.M.; Spruijt, R.B.; Hoek, van A.; Croce, R.; Amerongen, van H.

    2009-01-01

    The photosynthetic minor antenna complex CP29 of higher plants was singly mutated, overexpressed in Escherichia coli, selectively labeled with the fluorescent dye TAMRA at three positions in the N-terminal domain, and reconstituted with its natural pigments. Picosecond fluorescence experiments revea

  19. Nuclear magnetic resonance, fluorescence correlation spectroscopy and time-resolved fluorescence anisotropy studies of intermolecular interactions in bis(1-methyl-1H-imidazol-3-ium-3-yl)dihydroborate bis(trifluoromethylsulfonyl)amide and its mixtures with various cosolvents

    Science.gov (United States)

    Sahu, Prabhat Kumar; Nanda, Raju; Seth, Sudipta; Ghosh, Arindam; Sarkar, Moloy

    2016-09-01

    Keeping in mind the potential usefulness of mixed ionic liquid (IL)-cosolvents systems in several industrial applications, intermolecular interactions between a borate-based IL, bis(1-methyl-1H-imidazol-3-ium-3-yl)dihydroborate bis(trifluoromethylsulfonyl)amide ([BIMIMDBA][TF2N]), and its binary mixtures with several molecular solvents has been investigated through NMR and fluorescence spectroscopy. Analysis of the 1H chemical shifts (δ/ppm) and translational diffusion coefficients (D) of the IL in different solvent mixtures demonstrate interplay of nonspecific (ion-dipole) and specific (hydrogen bonding) interactions in governing the properties of these mixtures. Fluorescence correlation spectroscopy (FCS) and time-resolved fluorescence anisotropy data provide evidence in favour of different IL-solvent interaction for different IL-cosolvent systems.

  20. Fluorescence Resonance Energy Transfer Probe Based on Nano-Ag-EY-DNA System%基于纳米银-曙红Y-DNA的荧光共振能量转移探针

    Institute of Scientific and Technical Information of China (English)

    魏光成; 闫苗苗; 马丽英

    2012-01-01

    The resonance energy transfer between nano-Ag and eosin Y (EY)-DNA was studied by UV-Vis spectrophotometry, fluorospectrophotometry and electrophoresis with EY-DNA as fluorescence probe. The phenomenon of interaction between nano-Ag and EY-DNA was explained by the theory of fluorescence resonance energy transfer (FRET). It was found that the reaction of EY with DNA was due to inserting action, and the reaction between nano Ag and DNA was due to electrostatic action. The structure of DNA was changed after binding with EY and nano-Ag.%以曙红Y—DNA为荧光探针,运用紫外可见光谱法、荧光光谱法和电泳法研究了纳米银与曙红Y—DNA之间的共振能量转移,并应用能量共振转移的原理解释了纳米银及曙红Y与DNA之间的相互作用。结果表明,曙红Y与DNA的作用方式为嵌插作用,纳米银与DNA的作用方式为静电作用,曙红Y和纳米银结合到DNA上以后,导致了DNA结构的改变。

  1. Cell-based microfluidic platform for mimicking human olfactory system.

    Science.gov (United States)

    Lee, Seung Hwan; Oh, Eun Hae; Park, Tai Hyun

    2015-12-15

    Various attempts have been made to mimic the human olfactory system using human olfactory receptors (hORs). In particular, OR-expressed cell-based odorant detection systems mimic the smell sensing mechanism of humans, as they exploit endogenous cellular signaling pathways. However, the majority of such cell-based studies have been performed in the liquid phase to maintain cell viability, and liquid odorants were used as detection targets. Here, we present a microfluidic device for the detection of gaseous odorants which more closely mimics the human olfactory system. Cells expressing hOR were cultured on a porous membrane. The membrane was then flipped over and placed between two compartments. The upper compartment is the gaseous part where gaseous odorants are supplied, while the lower compartment is the aqueous part where viable cells are maintained in the liquid medium. Using this simple microfluidic device, we were able to detect gaseous odorant molecules by a fluorescence signal. The fluorescence signal was generated by calcium influx resulting from the interaction between odorant molecules and the hOR. The system allowed detection of gaseous odorant molecules in real-time, and the findings showed that the fluorescence responses increased dose-dependently in the range of 0-2 ppm odorant. In addition, the system can discriminate among gaseous odorant molecules. This microfluidic system closely mimics the human olfactory system in the sense that the submerged cells detect gaseous odorants.

  2. Surface plasmon resonance-enhanced fluorescence implementation of a single-step competition assay: demonstration of fatty acid measurement using an anti-fatty acid monoclonal antibody and a Cy5-labeled fatty acid.

    Science.gov (United States)

    Vareiro, Margarida M L M; Tranchant, Isabelle; Maplin, Sandra; Zak, Kris; Gani, M M; Slevin, Christopher J; Hailes, Helen C; Tabor, Alethea B; Cameron, Petra J; Jenkins, A Toby A; Williams, David E

    2008-06-15

    The development of a single-step, separation-free method for measurement of low concentrations of fatty acid using a surface plasmon resonance-enhanced fluorescence competition assay with a surface-bound antibody is described. The assay behavior was unexpectedly complex. A nonlinear coverage-dependent self-quenching of emission from surface-bound fluorescent label was deduced from the response kinetics and attributed to a surface plasmon-mediated energy transfer between adsorbed fluorophores, modified by the effects of plasmon interference. Principles of assay design to avoid complications from such effects are discussed. An anti-fatty acid mouse monoclonal antibody reacting to the alkyl chain was prepared and supported on a gold chip at a spacing appropriate for surface-plasmon field-enhanced fluorescence spectroscopy (SPEFS), by applying successively a self-assembled biotinylated monolayer, then streptavidin, then biotinylated protein A, and then the antibody, which was crosslinked to the protein A. Synthesis of a fluorescently (Cy5) tagged C-11 fatty acid is reported. SPEFS was used to follow the kinetics of the binding of the labeled fatty acid to the antibody, and to implement a competition assay with free fatty acid (undecanoic acid), sensitive at the 1 microM scale, a sensitivity limit caused by the low affinity of antibodies for free fatty acids, rather than the SPEFS technique itself. Free fatty acid concentration in human serum is in the range 0.1-1mM, suggesting that this measurement approach could be applied in a clinical diagnostic context. Finally, a predictive, theoretical model of fatty acid binding was developed that accounted for the observed "overshoot" kinetics.

  3. 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

    OpenAIRE

    Luís M. S. Loura

    2012-01-01

    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) simul...

  4. Analysis of the near-resonant fluorescence spectra of a single rubidium atom localized in a three-dimensional optical lattice

    CERN Document Server

    Kim, Wookrae; Kim, Jung-Ryul; Lee, Yea-Lee; Ihm, Jisoon; An, Kyungwon

    2010-01-01

    Supplementary information is presented on the recent work by W. Kim et al. on the matter-wave-tunneling-induced broadening in the near-resonant spectra of a single rubidium atom localized in a three-dimensional optical lattice in a strong Lamb-Dicke regime.

  5. 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

    investigated by use of 2D-photoluminescence emission (2D-PLE), and the resulting data were subjected to analysis by use of convenient and powerful multi-way approaches. Fluorescence measurements were performed by use of the quantum dot (QD)-conjugated c-Myc promoter. Intercalation of 7AAD within duplex base...... 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 of...... hybridization stability 1.0 x 10(8) mol(-1) L obtained were in good agreement with values reported in the literature. The analytical concentration of the QD-labeled DNA was determined by use of nonlinear fitting, without using external standard calibration samples. This study was a successful application of...

  6. Fluorescence Resonance Energy Transfer of the Tb(III)-Nd(III) Binary System in Molten LiCl-KCl Eutectic Salt

    International Nuclear Information System (INIS)

    The lanthanides act as a neutron poison in nuclear reactor with large neutron absorption cross section. For that reason, very low amount of lanthanides is required in the recovered U/TRU ingot product from pyrochemical process. In view of that, the investigation of thermodynamic properties and chemical behaviors of lanthanides in molten chloride salt are necessary to estimate the performance efficiency of pyrochemical process. However, there are uncertainties about knowledge and understanding of basic mechanisms in pyrochemical process, such as chemical speciation and redox behaviors due to the lack of in-situ monitoring methods for high temperature molten salt. The spectroscopic analysis is one of the probable techniques for in-situ qualitative and quantitative analysis. Recently, a few fluorescence spectroscopic measurements on single lanthanide element in molten LiCl-KCl eutectic have been investigated. The fluorescence intensity and the fluorescence lifetime of Tb(III) were decreased as increasing the concentration of Nd(III), demonstrating collisional quenching between donor ions and acceptor ions. The Forster distance (..0) of Tb(III)-Nd(III) binary system in molten LiCl-KCl eutectic was determined in the specific range of .... (0.1-1.0) and .. (1.387-1.496)

  7. Fluorescence Resonance Energy Transfer of the Tb(III)-Nd(III) Binary System in Molten LiCl-KCl Eutectic Salt

    Energy Technology Data Exchange (ETDEWEB)

    Kim, B. Y. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Yun, J. I. [KAIST, Daejeon (Korea, Republic of)

    2015-05-15

    The lanthanides act as a neutron poison in nuclear reactor with large neutron absorption cross section. For that reason, very low amount of lanthanides is required in the recovered U/TRU ingot product from pyrochemical process. In view of that, the investigation of thermodynamic properties and chemical behaviors of lanthanides in molten chloride salt are necessary to estimate the performance efficiency of pyrochemical process. However, there are uncertainties about knowledge and understanding of basic mechanisms in pyrochemical process, such as chemical speciation and redox behaviors due to the lack of in-situ monitoring methods for high temperature molten salt. The spectroscopic analysis is one of the probable techniques for in-situ qualitative and quantitative analysis. Recently, a few fluorescence spectroscopic measurements on single lanthanide element in molten LiCl-KCl eutectic have been investigated. The fluorescence intensity and the fluorescence lifetime of Tb(III) were decreased as increasing the concentration of Nd(III), demonstrating collisional quenching between donor ions and acceptor ions. The Forster distance (..0) of Tb(III)-Nd(III) binary system in molten LiCl-KCl eutectic was determined in the specific range of .... (0.1-1.0) and .. (1.387-1.496)

  8. Cell-Based Biosensors Principles and Applications

    CERN Document Server

    Wang, Ping

    2009-01-01

    Written by recognized experts the field, this leading-edge resource is the first book to systematically introduce the concept, technology, and development of cell-based biosensors. You find details on the latest cell-based biosensor models and novel micro-structure biosensor techniques. Taking an interdisciplinary approach, this unique volume presents the latest innovative applications of cell-based biosensors in a variety of biomedical fields. The book also explores future trends of cell-based biosensors, including integrated chips, nanotechnology and microfluidics. Over 140 illustrations hel

  9. Application of a real-time fluorescence resonance energy transfer polymerase chain reaction assay with melting curve analysis for the detection of Paragonimus heterotremus eggs in the feces of experimentally infected cats.

    Science.gov (United States)

    Tantrawatpan, Chairat; Intapan, Pewpan M; Thanchomnang, Tongjit; Sanpool, Oranuch; Janwan, Penchom; Lulitanond, Viraphong; Anamnart, Witthaya; Maleewong, Wanchai

    2013-09-01

    Paragonimus heterotremus is a medically important lung fluke that causes human and animal paragonimiasis in Southeast Asia, including Thailand. In the current study, a real-time fluorescence resonance energy transfer polymerase chain reaction (real-time FRET PCR) with melting curve analysis was developed and evaluated to detect P. heterotremus eggs in the feces of experimentally infected cats. The detection limit of this method for the P. heterotremus DNA sequence was 3 × 10(2) copies of the positive control plasmid and 10(-3) ng of P. heterotremus genomic DNA. The assay system could detect 10 eggs of P. heterotremus per gram of cat feces. No fluorescence signal was observed when DNA purified from 16 other organisms or genomic DNA from cats and human beings were tested. Real-time FRET PCR yielded positive results for all fecal samples from 17 P. heterotremus-infected cats and showed a negative relationship (r = -0.852, P Paragonimus species examined were divided into 4 groups by melting peak analysis. This assay can be useful for the detection of, and epidemiological studies on, P. heterotremus infection in endemic areas.

  10. Novel Mn3 [Co(CN)6]2@SiO2@Ag Core-Shell Nanocube: Enhanced Two-Photon Fluorescence and Magnetic Resonance Dual-Modal Imaging-Guided Photothermal and Chemo-therapy.

    Science.gov (United States)

    Wang, Dongdong; Guo, Zhen; Zhou, Jiajia; Chen, Jian; Zhao, Gaozheng; Chen, Ruhui; He, Mengni; Liu, Zhenbang; Wang, Haibao; Chen, Qianwang

    2015-11-25

    The versatile Mn3[Co(CN)6]2@SiO2@Ag core-shell NCs are prepared by a simple coprecipitation method. Ag nanoparticles with an average diameter of 12 nm deposited on the surface of Mn3[Co(CN)6]2@SiO2 through S-Ag bonding are fabricated in ethanol solution by reducing silver nitrate (AgNO3 ) with NaBH4 . The NCs possess T1 -T2 dual-modal magnetic resonance imaging ability. The inner Prussian blue analogs (PBAs) Mn3[Co(CN)6]2 exhibit bright two-photon fluorescence (TPF) imaging when excited at 730 nm. Moreover, the TPF imaging intensity displays 1.85-fold enhancement after loading of Ag nanoparticles. Besides, the sample also has multicolor fluorescence imaging ability under 403, 488, and 543 nm single photon excitation. The as-synthesized Mn3[Co(CN)6]2@SiO2@Ag NCs show a DOX loading capacity of 600 mg g(-1) and exhibit an excellent ability of near-infrared (NIR)-responsive drug release and photothermal therapy (PTT) which is induced from the relative high absorbance in NIR region. The combined chemotherapy and PTT against cancer cells in vitro test shows high therapeutic efficiency. The multimodal treatment and imaging could lead to this material a potential multifunctional system for biomedical diagnosis and therapy. PMID:26437078

  11. Fluorescence resonance energy transfer biosensors that detect Ran conformational changes and a Ran x GDP-importin-beta -RanBP1 complex in vitro and in intact cells.

    Science.gov (United States)

    Plafker, Kendra; Macara, Ian G

    2002-08-16

    The Ran GTPase plays a central role in nucleocytoplasmic transport. Association of Ran x GTP with transport carriers (karyopherins) triggers the loading/unloading of export or import cargo, respectively. The C-terminal tail of Ran x GTP is deployed in an extended conformation when associated with a Ran binding domain or importins. To monitor tail orientation, a Ran-GFP fusion was labeled with the fluorophore Alexa546. Fluorescence resonance energy transfer (FRET) occurs efficiently between the green fluorescent protein (GFP) and Alexa546 for Ran x GDP and Ran x GTP, suggesting that the tail is tethered in both states. However, Ran x GTP complexes with importin-beta, RanBP1, and Crm1 all show reduced FRET consistent with tail extension. Displacement of the C-terminal tail of Ran by karyopherins may be a general mechanism to facilitate RanBP1 binding. A Ran x GDP-RanBP1-importin-beta complex also displayed a low FRET signal. To detect this complex in vivo, a bipartite biosensor consisting of Ran-Alexa546 plus GST-GFP-RanBP1, was co-injected into the cytoplasm of cells. The Ran redistributed predominantly to the nucleus, and RanBP1 remained cytoplasmic. Nonetheless, a robust cytoplasmic FRET signal was detectable, which suggests that a significant fraction of cytoplasmic Ran.GDP may exist in a ternary complex with RanBP1 and importins.

  12. A dual-modal magnetic nanoparticle probe for preoperative and intraoperative mapping of sentinel lymph nodes by magnetic resonance and near infrared fluorescence imaging.

    Science.gov (United States)

    Zhou, Zhengyang; Chen, Hongwei; Lipowska, Malgorzata; Wang, Liya; Yu, Qiqi; Yang, Xiaofeng; Tiwari, Diana; Yang, Lily; Mao, Hui

    2013-07-01

    The ability to reliably detect sentinel lymph nodes for sentinel lymph node biopsy and lymphadenectomy is important in clinical management of patients with metastatic cancers. However, the traditional sentinel lymph node mapping with visible dyes is limited by the penetration depth of light and fast clearance of the dyes. On the other hand, sentinel lymph node mapping with radionucleotide technique has intrinsically low spatial resolution and does not provide anatomic details in the sentinel lymph node mapping procedure. This work reports the development of a dual modality imaging probe with magnetic resonance and near infrared imaging capabilities for sentinel lymph node mapping using magnetic iron oxide nanoparticles (10 nm core size) conjugated with a near infrared molecule with emission at 830 nm. Accumulation of magnetic iron oxide nanoparticles in sentinel lymph nodes leads to strong T2 weighted magnetic resonance imaging contrast that can be potentially used for preoperative localization of sentinel lymph nodes, while conjugated near infrared molecules provide optical imaging tracking of lymph nodes with a high signal to background ratio. The new magnetic nanoparticle based dual imaging probe exhibits a significant longer lymph node retention time. Near infrared signals from nanoparticle conjugated near infrared dyes last up to 60 min in sentinel lymph node compared to that of 25 min for the free near infrared dyes in a mouse model. Furthermore, axillary lymph nodes, in addition to sentinel lymph nodes, can be also visualized with this probe, given its slow clearance and sufficient sensitivity. Therefore, this new dual modality imaging probe with the tissue penetration and sensitive detection of sentinel lymph nodes can be applied for preoperative survey of lymph nodes with magnetic resonance imaging and allows intraoperative sentinel lymph node mapping using near infrared optical devices.

  13. Auxiliary pattern for cell-based OPC

    Science.gov (United States)

    Kahng, Andrew B.; Park, Chul-Hong

    2006-10-01

    The runtime of model-based optical proximity correction (OPC) tools has grown unacceptably with each successive technology generation, and has emerged as one of the major bottlenecks for turnaround time (TAT) of IC data preparation and manufacturing. The cell-based OPC approach improves runtime by performing OPC once per cell definition as opposed to once per cell instantiation in the layout. However, cell-based OPC does not comprehend inter-cell optical interactions that affect feature printability in a layout context. In this work, we propose auxiliary pattern-enabled cell-based OPC which can minimize the CD differences between cell-based OPC and model-based OPC. To enable effective insertion of auxiliary pattern (AP) in the design, we also propose a post-placement optimization of a standard cell block with respect to detailed placement. By dynamic programming-based placement perturbation, we achieve 100% AP applicability in designs with placement utilizations of cell-based OPC with AP can match gate edge placement error (EPE) count of model-based OPC within 4%. This is an improvement of 90%, on average, over cell-based OPC without APs. The AP-based OPC approach can reduce OPC runtimes versus model-based OPC by up to 40X in our benchmark designs. We can also achieve reduction of GDSII file size and ORC runtimes due to hierarchy maintenance of cell-based OPC.

  14. 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.

  15. Fourier Transform Near Infrared Microspectroscopy, Infrared Chemical Imaging, High-Resolution Nuclear Magnetic Resonance and Fluorescence Microspectroscopy Detection of Single Cancer Cells and Single Viral Particles

    CERN Document Server

    Baianu,I C; Hofmann, N E; Korban, S S; Lozano, P; You, T

    2004-01-01

    Single Cancer Cells from Human tumors are being detected and imaged by Fourier Transform Infrared (FT-IR), Fourier Transform Near Infrared (FT-NIR)Hyperspectral Imaging and Fluorescence Correlation Microspectroscopy. The first FT-NIR chemical, microscopic images of biological systems approaching one micron resolution are here reported. Chemical images obtained by FT-NIR and FT-IR Microspectroscopy are also presented for oil in soybean seeds and somatic embryos under physiological conditions. FT-NIR spectra of oil and proteins were obtained for volumes as small as two cubic microns. Related, HR-NMR analyses of oil contents in somatic embryos as well as 99% accurate calibrations are also presented here with nanoliter precision. Such high-resolution, 400 MHz H-1 NMR analyses allowed the selection of mutagenized embryos with higher oil content (e.g. >~20%) compared to the average levels in non-mutagenized control embryos. Moreover, developmental changes in single soybean seeds and/or somatic embryos may be monito...

  16. Near Infrared Microspectroscopy, Fluorescence Microspectroscopy, Infrared Chemical Imaging and High Resolution Nuclear Magnetic Resonance Analysis of Soybean Seeds, Somatic Embryos and Single Cells

    CERN Document Server

    Baianu, I C; Hofmann, N E; Korban, S S; Lozano, P; You, T; AOCS 94th Meeting, Kansas

    2002-01-01

    Novel methodologies are currently being developed and established for the chemical analysis of soybean seeds, embryos and single cells by Fourier Transform Infrared (FT-IR), Fourier Transform Near Infrared (FT-NIR) Microspectroscopy, Fluorescence and High-Resolution NMR (HR-NMR). The first FT-NIR chemical images of biological systems approaching one micron resolution are presented here. Chemical images obtained by FT-NIR and FT-IR Microspectroscopy are presented for oil in soybean seeds and somatic embryos under physiological conditions. FT-NIR spectra of oil and proteins were obtained for volumes as small as two cubic microns. Related, HR-NMR analyses of oil contents in somatic embryos are also presented here with nanoliter precision. Such 400 MHz 1H NMR analyses allowed the selection of mutagenized embryos with higher oil content (e.g. ~20%) compared to non-mutagenized control embryos. Moreover, developmental changes in single soybean seeds and/or somatic embryos may be monitored by FT-NIR with a precision ...

  17. Resonance Energy Transfer

    OpenAIRE

    Andrews, David; Bradshaw, David; Dinshaw, Rayomond; Scholes, Gregory

    2015-01-01

    Resonance energy transfer, also known as Förster- or fluorescence- resonance energy transfer, or electronic energy transfer, is a photonic process whose relevance in many major areas of science is reflected both by a wide prevalence of the effect and through numerous technical applications. The process, operating through an optical near-field mechanism, effects a transport of electronic excitation between physically distinct atomic or molecular components, based on transition dipole-dipole co...

  18. Biotoxin Detection Using Cell-Based Sensors

    OpenAIRE

    Pratik Banerjee; Spyridon Kintzios; Balabhaskar Prabhakarpandian

    2013-01-01

    Cell-based biosensors (CBBs) utilize the principles of cell-based assays (CBAs) by employing living cells for detection of different analytes from environment, food, clinical, or other sources. For toxin detection, CBBs are emerging as unique alternatives to other analytical methods. The main advantage of using CBBs for probing biotoxins and toxic agents is that CBBs respond to the toxic exposures in the manner related to actual physiologic responses of the vulnerable subjects. The results ob...

  19. Comparative Fluorescence Resonance Energy-Transfer Study in Pluronic Triblock Copolymer Micelle and Niosome Composed of Biological Component Cholesterol: An Investigation of Effect of Cholesterol and Sucrose on the FRET Parameters.

    Science.gov (United States)

    Roy, Arpita; Kundu, Niloy; Banik, Debasis; Sarkar, Nilmoni

    2016-01-14

    The formation of pluronic triblock copolymer (F127)-cholesterol-based niosome and its interaction with sugar (sucrose) molecules have been investigated. The morphology of F127-cholesterol -based niosome in the presence of sucrose has been successfully demonstrated using dynamic light scattering (DLS) and transmission electron microscopic (TEM) techniques. The DLS profiles and TEM images clearly suggest that the size of the niosome aggregates increases significantly in the presence of sucrose. In addition to structural characterization, a detailed comparative fluorescence resonance energy transfer (FRET) study has been carried out in these F127-containing aggregates, involving coumarin 153 (C153) as donor (D) and rhodamine 6G (R6G) as an acceptor (A) to monitor the dynamic heterogeneity of the systems. Besides, time-resolved anisotropy and fluorescence correlation spectroscopy measurements have been carried out to monitor the rotational and lateral diffusion motion in these F127-cholesterol-based aggregates using C153 and R6G, respectively. During the course of FRET study, we have observed multiple time constants of FRET inside the F127-cholesterol-based niosomes in contrast with the F127 micelle. This corresponds to the presence of more than one preferential donor-acceptor (D-A) distance in niosomes than in F127 micelle. FRET has also been successfully used to probe the effect of sucrose on the morphology of F127-cholesterol-based niosome. In the presence of sucrose, the time constant of FRET further increases as the D-A distances increase in sucrose-decorated niosome. Finally, the excitation-wavelength-dependent FRET studies have indicated that as the excitation of donor molecules varies from 408 to 440 nm the contribution of the faster rise component of the acceptor enhances considerably, which clearly establishes the dynamics heterogeneity of both systems. Our findings also indicate that FRET is completely intravesicular in nature in these block copolymer

  20. J Fluorescence

    OpenAIRE

    Resch-Genger, U.; Hoffmann, K.; Nietfeld, W; A. Engel; Neukammer, J.; Nitschke, R.; Ebert, P.; Macdonald, R

    2005-01-01

    The scope of this paper is to illustrate the need for an improved quality assurance in fluorometry. For this purpose, instrumental sources of error and their influences on the reliability and comparability of fluorescence data are highlighted for frequently used photoluminescence techniques ranging from conventional macro- and microfluorometry over fluorescence microscopy and flow cytometry to microarray technology as well as in vivo fluorescence imaging. Particularly, the need for and requir...

  1. Surface plasmon resonance in nano-gold antimony glass-ceramic dichroic nanocomposites: One-step synthesis and enhanced fluorescence application

    International Nuclear Information System (INIS)

    A single-step melt-quench in situ thermochemical reduction technique has been used to synthesize a new series of Auo nanoparticles embedded antimony glass-ceramic (K2O-B2O3-Sb2O3-ZnO) dichroic nanocomposites. X-ray and selected area electron diffractions manifest growth of Auo nanoparticles along (2 0 0) planes. The particle sizes obtained from X-ray diffraction patterns are found to vary in the range 4-21 nm. Dichroic behavior is attributed to the elliptical shape gold nanoparticles having aspect ratio 1.2, as observed from the transmission electron microscopy (TEM) images. The Auo nanoparticles exhibit surface plasmon resonance band (SPR) around 600 nm, which experiences red-shifts with increasing Au concentration. These nanocomposites when co-doped with Sm2O3 and excited at 949 nm, exhibit 2-fold intensification of 636 nm red emission transition (4G5/2 → 6H9/2) due to SPR induced local field enhancement of Auo nanoparticles and are promising materials for display applications.

  2. Label-free characterization of carbonic anhydrase-novel inhibitor interactions using surface plasmon resonance, isothermal titration calorimetry and fluorescence-based thermal shift assays.

    Science.gov (United States)

    Rogez-Florent, Tiphaine; Duhamel, Laetitia; Goossens, Laurence; Six, Perrine; Drucbert, Anne-Sophie; Depreux, Patrick; Danzé, Pierre-Marie; Landy, David; Goossens, Jean-François; Foulon, Catherine

    2014-01-01

    This work describes the development of biophysical unbiased methods to study the interactions between new designed compounds and carbonic anhydrase II (CAII) enzyme. These methods have to permit both a screening of a series of sulfonamide derivatives and the identification of a lead compound after a thorough study of the most promising molecules. Interactions data were collected using surface plasmon resonance (SPR) and thermal shift assay (TSA). In the first step, experiments were performed with bovine CAII isoform and were extended to human CAII. Isothermal titration calorimetry (ITC) experiments were also conducted to obtain thermodynamics parameters necessary for the processing of the TSA data. Results obtained with this reference methodology demonstrate the effectiveness of SPR and TSA. KD values obtained from SPR data were in perfect accordance with ITC. For TSA, despite the fact that the absolute values of KD were quite different, the same affinity scale was obtained for all compounds. The binding affinities of the analytes studied vary by more than 50 orders of magnitude; for example, the KD value determined by SPR were 6 ± 4 and 299 ± 25 nM for compounds 1 and 3, respectively. This paper discusses some of the theoretical and experimental aspects of the affinity-based methods and evaluates the protein consumption to develop methods for the screening of further new compounds. The double interest of SPR, that is, for screening and for the quick thorough study of the interactions parameters (ka , kd , and KD ), leads us to choose this methodology for the study of new potential inhibitors. PMID:24375583

  3. Label-free characterization of carbonic anhydrase-novel inhibitor interactions using surface plasmon resonance, isothermal titration calorimetry and fluorescence-based thermal shift assays.

    Science.gov (United States)

    Rogez-Florent, Tiphaine; Duhamel, Laetitia; Goossens, Laurence; Six, Perrine; Drucbert, Anne-Sophie; Depreux, Patrick; Danzé, Pierre-Marie; Landy, David; Goossens, Jean-François; Foulon, Catherine

    2014-01-01

    This work describes the development of biophysical unbiased methods to study the interactions between new designed compounds and carbonic anhydrase II (CAII) enzyme. These methods have to permit both a screening of a series of sulfonamide derivatives and the identification of a lead compound after a thorough study of the most promising molecules. Interactions data were collected using surface plasmon resonance (SPR) and thermal shift assay (TSA). In the first step, experiments were performed with bovine CAII isoform and were extended to human CAII. Isothermal titration calorimetry (ITC) experiments were also conducted to obtain thermodynamics parameters necessary for the processing of the TSA data. Results obtained with this reference methodology demonstrate the effectiveness of SPR and TSA. KD values obtained from SPR data were in perfect accordance with ITC. For TSA, despite the fact that the absolute values of KD were quite different, the same affinity scale was obtained for all compounds. The binding affinities of the analytes studied vary by more than 50 orders of magnitude; for example, the KD value determined by SPR were 6 ± 4 and 299 ± 25 nM for compounds 1 and 3, respectively. This paper discusses some of the theoretical and experimental aspects of the affinity-based methods and evaluates the protein consumption to develop methods for the screening of further new compounds. The double interest of SPR, that is, for screening and for the quick thorough study of the interactions parameters (ka , kd , and KD ), leads us to choose this methodology for the study of new potential inhibitors.

  4. Modulation of Intracellular Quantum Dot to Fluorescent Protein Förster Resonance Energy Transfer via Customized Ligands and Spatial Control of Donor–Acceptor Assembly

    Directory of Open Access Journals (Sweden)

    Lauren D. Field

    2015-12-01

    Full Text Available Understanding how to controllably modulate the efficiency of energy transfer in Förster resonance energy transfer (FRET-based assemblies is critical to their implementation as sensing modalities. This is particularly true for sensing assemblies that are to be used as the basis for real time intracellular sensing of intracellular processes and events. We use a quantum dot (QD donor -mCherry acceptor platform that is engineered to self-assemble in situ wherein the protein acceptor is expressed via transient transfection and the QD donor is microinjected into the cell. QD-protein assembly is driven by metal-affinity interactions where a terminal polyhistidine tag on the protein binds to the QD surface. Using this system, we show the ability to modulate the efficiency of the donor–acceptor energy transfer process by controllably altering either the ligand coating on the QD surface or the precise location where the QD-protein assembly process occurs. Intracellularly, a short, zwitterionic ligand mediates more efficient FRET relative to longer ligand species that are based on the solubilizing polymer, poly(ethylene glycol. We further show that a greater FRET efficiency is achieved when the QD-protein assembly occurs free in the cytosol compared to when the mCherry acceptor is expressed tethered to the inner leaflet of the plasma membrane. In the latter case, the lower FRET efficiency is likely attributable to a lower expression level of the mCherry acceptor at the membrane combined with steric hindrance. Our work points to some of the design considerations that one must be mindful of when developing FRET-based sensing schemes for use in intracellular sensing.

  5. Imaging protein complex formation in the autophagy pathway: analysis of the interaction of LC3 and Atg4BC74A in live cells using Förster resonance energy transfer and fluorescence recovery after photobleaching

    Science.gov (United States)

    Kraft, Lewis J.; Kenworthy, Anne K.

    2012-01-01

    The protein microtubule-associated protein 1, light chain 3 (LC3) functions in autophagosome formation and plays a central role in the autophagy pathway. Previously, we found LC3 diffuses more slowly in cells than is expected for a freely diffusing monomer, suggesting it may constitutively associate with a macromolecular complex containing other protein components of the pathway. In the current study, we used Förster resonance energy transfer (FRET) microscopy and fluorescence recovery after photobleaching (FRAP) to investigate the interactions of LC3 with Atg4BC74A, a catalytically inactive mutant of the cysteine protease involved in lipidation and de-lipidation of LC3, as a model system to probe protein complex formation in the autophagy pathway. We show Atg4BC74A is in FRET proximity with LC3 in both the cytoplasm and nucleus of living cells, consistent with previous biochemical evidence that suggests these proteins directly interact. In addition, overexpressed Atg4BC74A diffuses significantly more slowly than predicted based on its molecular weight, and its translational diffusion coefficient is significantly slowed upon coexpression with LC3 to match that of LC3 itself. Taken together, these results suggest Atg4BC74A and LC3 are contained within the same multiprotein complex and that this complex exists in both the cytoplasm and nucleoplasm of living cells.

  6. Cell-Based Therapies for Diabetic Complications

    Directory of Open Access Journals (Sweden)

    Stella Bernardi

    2012-01-01

    Full Text Available In recent years, accumulating experimental evidence supports the notion that diabetic patients may greatly benefit from cell-based therapies, which include the use of adult stem and/or progenitor cells. In particular, mesenchymal stem cells and the circulating pool of endothelial progenitor cells have so far been the most studied populations of cells proposed for the treatment of vascular complications affecting diabetic patients. We review the evidence supporting their use in this setting, the therapeutic benefits that these cells have shown so far as well as the challenges that cell-based therapies in diabetic complications put out.

  7. Fluorescent refrigeration

    Science.gov (United States)

    Epstein, Richard I.; Edwards, Bradley C.; Buchwald, Melvin I.; Gosnell, Timothy R.

    1995-01-01

    Fluorescent refrigeration is based on selective radiative pumping, using substantially monochromatic radiation, of quantum excitations which are then endothermically redistributed to higher energies. Ultimately, the populated energy levels radiatively deexcite emitting, on the average, more radiant energy than was initially absorbed. The material utilized to accomplish the cooling must have dimensions such that the exciting radiation is strongly absorbed, but the fluorescence may exit the material through a significantly smaller optical pathlength. Optical fibers and mirrored glasses and crystals provide this requirement.

  8. Radiation induced centers in irradiated SrB{sub 4}O{sub 7} doped europium and their role in thermally stimulated reactions: Thermally stimulated luminescence, fluorescence and electron paramagnetic resonance studies

    Energy Technology Data Exchange (ETDEWEB)

    Kadam, R.M.; Rajeswari, B., E-mail: rajibala@barc.gov.in; Mohapatra, M.; Porwal, N.K.; Hon, N.S.; Seshagiri, T.K.; Natarajan, V.

    2015-02-15

    Polycrystalline samples of strontium tetraborate (SrB{sub 4}O{sub 7}: SBO) samples doped with different concentrations of europium (0%, 0.05%, 1% and 2%) were synthesized using solid state reaction in air at high temperature. These samples were characterized by X-ray diffraction (XRD), photoluminescence (PL), thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) techniques. X-ray diffraction studies indicated that SrB{sub 4}O{sub 7} has orthorhombic structure with lattice parameters a=4.237±0.001, b=4.431±0.001, c=10.704±0.010, space group Pnm2{sub i}, Z=2. Thermally Stimulated Luminescence (TSL) investigations on the gamma irradiated sample showed an intense glow peak at 407 K and a weak glow peak at 500 K. The trap parameters namely activation energy (E), order of kinetics (b) and the frequency factor (s) for the main peak at 407 K were determined using the glow curve method. Fluorescence studies showed weak emission at ca 367 nm, which was attributed to f-d transition (4f{sup 6}5d-4f{sup 7}) of Eu{sup 2+} ions in the host lattice, whereas an intense emission in the range 570–650 nm was assigned to {sup 5}D{sub 0}→{sup 7}F{sub J}, J=0,1,2,3 and 4 transition of Eu{sup 3+} in the host lattice. The large value of I{sub (R)}/I{sub (O)} suggested that Eu{sup 3+} ions are situated at sites without center of inversion (lower symmetry) in SBO matrix. EPR studies suggested the formation of boron–oxygen hole trapped center viz, BOHC, electron trapped at oxygen vacancies and some impurity radicals like NO{sub 3}{sup 2−} and CO{sub 2}{sup −} radicals in SBO on irradiation. EPR temperature variation studies in the range 300–475 K on gamma irradiated europium doped samples, suggested a recombination process occurring between boronoxygen hole trapped species and electron trapped species and subsequently energy is transferred to Eu{sup 3+} ion, which on de-excitation yields thermally stimulated luminescence yielding an intense TSL glow

  9. Stem cell-based bone repair

    OpenAIRE

    Fei, Yurong; Xu, Ren-He; Hurley, Marja M.

    2012-01-01

    To accelerate bone repair, one strategy is to deliver the cells that make bone. The current review focuses on stem cell-based bone repair. Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) can self-renew unlimitedly and differentiate into the bone forming cells – osteoblasts. Scientists have been actively investigating culture conditions to stably and efficiently induce differentiation of these stem cells into osteoblasts. However, ESCs have the issues of ethnics, immune ...

  10. Fluorescence of Alexa Fluor dye tracks protein folding

    OpenAIRE

    Simon Lindhoud; Westphal, Adrie H.; Visser, Antonie J.W.G.; Jan Willem Borst; van Mierlo, Carlo P. M.

    2012-01-01

    Fluorescence spectroscopy is an important tool for the characterization of protein folding. Often, a protein is labeled with appropriate fluorescent donor and acceptor probes and folding-induced changes in Förster Resonance Energy Transfer (FRET) are monitored. However, conformational changes of the protein potentially affect fluorescence properties of both probes, thereby profoundly complicating interpretation of FRET data. In this study, we assess the effects protein folding has on fluoresc...

  11. CdTe量子点-铜酞菁复合体系荧光共振能量转移的研究∗%Fluorescence resonance energy transfer b etween CdTe quantum dots and copp er phthalo cyanine

    Institute of Scientific and Technical Information of China (English)

    何志聪; 李芳; 李牧野; 魏来

    2015-01-01

    The fluorescence resonance energy transfer in CdTe quantum dots (QDs)-copper phthalocyanine (CuPc) is inves-tigated by ultrafast time-resolved spectroscopy technique equipped with femtosecond laser (780 nm, 76 MHz, 130 fs). The results show that the fluorescence lifetime of CdTe QDs decreases with the increase of CuPc concentration, and the energy transfer efficiency is found to increase with the increase of CuPc concentration. Moreover, the influence of the laser excitation power on the energy transfer efficiency is also studied. It is found that transfer efficiency decreases as excitation laser power increases, the physical mechanism is the thermal activation in the high power and the excited state transitions of high order induced by two-photon. The energy transfer efficiency can reach 43.8%, when the laser power is 200 mW, via two-photon excitation. This study indicates that the CdTe QDs-CuPc composite system has high potential as the third generation of photosensitizers.%以波长为780 nm、重复频率为76 MHz、脉宽为130 fs的飞秒激光作为激发光源,采用超快时间分辨光谱技术研究了CdTe量子点-铜酞菁复合体系的荧光共振能量转移.实验结果表明,在780 nm的双光子激发条件下,复合体系中CdTe量子点的荧光寿命随着铜酞菁溶液浓度的增加而减少,荧光共振能量转移效率增加.同时也研究了激发功率对荧光共振能量转移效率的影响.结果表明,随着激发光功率的增加,复合体系溶液中CdTe量子点的荧光寿命增加,荧光共振能量转移效率减小,其物理机理是因为高激发功率下的热效应和由双光子诱导的高阶激发态的跃迁.当激发光功率为200 mW时,双光子荧光共振能量转移效率为43.8%.研究表明CdTe量子点-铜酞菁复合体系是非常有潜力的第三代光敏剂.

  12. Antibody-based fluorescent and fluorescent ratiometric indicators for detection of phosphotyrosine.

    Science.gov (United States)

    Huynh Nhat, Kim Phuong; Watanabe, Takayoshi; Yoshikoshi, Kensuke; Hohsaka, Takahiro

    2016-08-01

    Fluorescent indicators for protein phosphorylation are very important in not only fundamental biology but also biomedical applications. In this study, we developed novel fluorescent and fluorescent ratiometric indicators for detection of phosphotyrosine (pTyr) derivatives. A single-chain antibody variable fragment (scFv) against phosphotyrosine was fluorescent-labeled by incorporation of tetramethylrhodamine (TAMRA)-linked nonnatural amino acid at the N- or C-terminus. The TAMRA-labeled scFv showed fluorescence enhancement upon addition of pTyr-containing peptides based on antigen-dependent fluorescence quenching effect on TAMRA. The TAMRA-labeled scFv was further fused with enhanced green fluorescent protein (EGFP) to generate a double-labeled scFv for pTyr. In the absence of antigen, fluorescence resonance energy transfer (FRET) occurred from EGFP to TAMRA but TAMRA was quenched. The antigen-binding removed the quenching of TAMRA while FRET occurred without altering its efficiency. As a result of the FRET and antigen-dependent fluorescence quenching effect, the double-labeled scFv exhibited fluorescence ratio enhancement upon the antigen-binding. The fluorescent and fluorescent ratiometric indicators obtained in this study will become a novel tool for analysis of protein phosphorylation. Moreover, this strategy utilizes antibody derivatives, and therefore, can be easily applied to other antigen-antibody pairs to generate fluorescent ratiometric indicators for various target molecules. PMID:26896314

  13. Cell-Based Therapy for Silicosis.

    Science.gov (United States)

    Lopes-Pacheco, Miquéias; Bandeira, Elga; Morales, Marcelo M

    2016-01-01

    Silicosis is the most common pneumoconiosis globally, with higher prevalence and incidence in developing countries. To date, there is no effective treatment to halt or reverse the disease progression caused by silica-induced lung injury. Significant advances have to be made in order to reduce morbidity and mortality related to silicosis. In this review, we have highlighted the main mechanisms of action that cause lung damage by silica particles and summarized the data concerning the therapeutic promise of cell-based therapy for silicosis. PMID:27066079

  14. Cell-Based Therapy for Silicosis

    Directory of Open Access Journals (Sweden)

    Miquéias Lopes-Pacheco

    2016-01-01

    Full Text Available Silicosis is the most common pneumoconiosis globally, with higher prevalence and incidence in developing countries. To date, there is no effective treatment to halt or reverse the disease progression caused by silica-induced lung injury. Significant advances have to be made in order to reduce morbidity and mortality related to silicosis. In this review, we have highlighted the main mechanisms of action that cause lung damage by silica particles and summarized the data concerning the therapeutic promise of cell-based therapy for silicosis.

  15. Resonant Mode-hopping Micromixing.

    Science.gov (United States)

    Jang, Ling-Sheng; Chao, Shih-Hui; Holl, Mark R; Meldrum, Deirdre R

    2007-07-20

    A common micromixer design strategy is to generate interleaved flow topologies to enhance diffusion. However, problems with these designs include complicated structures and dead volumes within the flow fields. We present an active micromixer using a resonating piezoceramic/silicon composite diaphragm to generate acoustic streaming flow topologies. Circulation patterns are observed experimentally and correlate to the resonant mode shapes of the diaphragm. The dead volumes in the flow field are eliminated by rapidly switching from one discrete resonant mode to another (i.e., resonant mode-hop). Mixer performance is characterized by mixing buffer with a fluorescence tracer containing fluorescein. Movies of the mixing process are analyzed by converting fluorescent images to two-dimensional fluorescein concentration distributions. The results demonstrate that mode-hopping operation rapidly homogenized chamber contents, circumventing diffusion-isolated zones. PMID:19551159

  16. Sensitive-cell-based fish chromatophore biosensor

    Science.gov (United States)

    Plant, Thomas K.; Chaplen, Frank W.; Jovanovic, Goran; Kolodziej, Wojtek; Trempy, Janine E.; Willard, Corwin; Liburdy, James A.; Pence, Deborah V.; Paul, Brian K.

    2004-07-01

    A sensitive biosensor (cytosensor) has been developed based on color changes in the toxin-sensitive colored living cells of fish. These chromatophores are highly sensitive to the presence of many known and unknown toxins produced by microbial pathogens and undergo visible color changes in a dose-dependent manner. The chromatophores are immobilized and maintained in a viable state while potential pathogens multiply and fish cell-microbe interactions are monitored. Low power LED lighting is used to illuminate the chromatophores which are magnified using standard optical lenses and imaged onto a CCD array. Reaction to toxins is detected by observing changes is the total area of color in the cells. These fish chromatophores are quite sensitive to cholera toxin, Staphococcus alpha toxin, and Bordatella pertussis toxin. Numerous other toxic chemical and biological agents besides bacterial toxins also cause readily detectable color effects in chromatophores. The ability of the chromatophore cell-based biosensor to distinguish between different bacterial pathogens was examined. Toxin producing strains of Salmonella enteritis, Vibrio parahaemolyticus, and Bacillus cereus induced movement of pigmented organelles in the chromatophore cells and this movement was measured by changes in the optical density over time. Each bacterial pathogen elicited this measurable response in a distinctive and signature fashion. These results suggest a chromatophore cell-based biosensor assay may be applicable for the detection and identification of virulence activities associated with certain air-, food-, and water-borne bacterial pathogens.

  17. Cell-based strategies for vascular regeneration.

    Science.gov (United States)

    Zou, Tongqiang; Fan, Jiabing; Fartash, Armita; Liu, Haifeng; Fan, Yubo

    2016-05-01

    Vascular regeneration is known to play an essential role in the repair of injured tissues mainly through accelerating the repair of vascular injury caused by vascular diseases, as well as the recovery of ischemic tissues. However, the clinical vascular regeneration is still challenging. Cell-based therapy is thought to be a promising strategy for vascular regeneration, since various cells have been identified to exert important influences on the process of vascular regeneration such as the enhanced endothelium formation on the surface of vascular grafts, and the induction of vessel-like network formation in the ischemic tissues. Here are a vast number of diverse cell-based strategies that have been extensively studied in vascular regeneration. These strategies can be further classified into three main categories, including cell transplantation, construction of tissue-engineered grafts, and surface modification of scaffolds. Cells used in these strategies mainly refer to terminally differentiated vascular cells, pluripotent stem cells, multipotent stem cells, and unipotent stem cells. The aim of this review is to summarize the reported research advances on the application of various cells for vascular regeneration, yielding insights into future clinical treatment for injured tissue/organ. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1297-1314, 2016. PMID:26864677

  18. Biotoxin Detection Using Cell-Based Sensors

    Directory of Open Access Journals (Sweden)

    Pratik Banerjee

    2013-11-01

    Full Text Available Cell-based biosensors (CBBs utilize the principles of cell-based assays (CBAs by employing living cells for detection of different analytes from environment, food, clinical, or other sources. For toxin detection, CBBs are emerging as unique alternatives to other analytical methods. The main advantage of using CBBs for probing biotoxins and toxic agents is that CBBs respond to the toxic exposures in the manner related to actual physiologic responses of the vulnerable subjects. The results obtained from CBBs are based on the toxin-cell interactions, and therefore, reveal functional information (such as mode of action, toxic potency, bioavailability, target tissue or organ, etc. about the toxin. CBBs incorporate both prokaryotic (bacteria and eukaryotic (yeast, invertebrate and vertebrate cells. To create CBB devices, living cells are directly integrated onto the biosensor platform. The sensors report the cellular responses upon exposures to toxins and the resulting cellular signals are transduced by secondary transducers generating optical or electrical signals outputs followed by appropriate read-outs. Examples of the layout and operation of cellular biosensors for detection of selected biotoxins are summarized.

  19. Biotoxin detection using cell-based sensors.

    Science.gov (United States)

    Banerjee, Pratik; Kintzios, Spyridon; Prabhakarpandian, Balabhaskar

    2013-12-01

    Cell-based biosensors (CBBs) utilize the principles of cell-based assays (CBAs) by employing living cells for detection of different analytes from environment, food, clinical, or other sources. For toxin detection, CBBs are emerging as unique alternatives to other analytical methods. The main advantage of using CBBs for probing biotoxins and toxic agents is that CBBs respond to the toxic exposures in the manner related to actual physiologic responses of the vulnerable subjects. The results obtained from CBBs are based on the toxin-cell interactions, and therefore, reveal functional information (such as mode of action, toxic potency, bioavailability, target tissue or organ, etc.) about the toxin. CBBs incorporate both prokaryotic (bacteria) and eukaryotic (yeast, invertebrate and vertebrate) cells. To create CBB devices, living cells are directly integrated onto the biosensor platform. The sensors report the cellular responses upon exposures to toxins and the resulting cellular signals are transduced by secondary transducers generating optical or electrical signals outputs followed by appropriate read-outs. Examples of the layout and operation of cellular biosensors for detection of selected biotoxins are summarized. PMID:24335754

  20. The phenomenon of fluorescence in immunosensors.

    Science.gov (United States)

    Kłos-Witkowska, Aleksandra

    2016-01-01

    The phenomenon of fluorescence in immunosensors is described in this paper. Both structure and characteristics of biosensors and immunosensors are presented. Types of immunosensors and the response of bioreceptor layers to the reaction with analytes as well as measurements of electrochemical, piezoelectric and optical parameters in immunosensors are also presented. In addition, detection techniques used in studies of optical immunosensors based on light-matter interactions (absorbance, reflectance, dispersion, emission) such as: UV/VIS spectroscopy, reflectometric interference spectroscopy (RIfs), surface plasmon resonance (SPR), optical waveguide light-mode spectroscopy (OWLS), fluorescence spectroscopy. The phenomenon of fluorescence in immunosensors and standard configurations of immunoreactions between an antigen and an antibody (direct, competitive, sandwich, displacement) is described. Fluorescence parameters taken into account in analyses and fluorescence detection techniques used in research of immunosensors are presented. Examples of immunosensor applications are given. PMID:27192088

  1. Polarization of fluorescence: a probe of molecular autoionization

    Energy Technology Data Exchange (ETDEWEB)

    Leroi, G. E. [Michigan State Univ., East Lansing, MI (United States); Dehmer, Joseph L. [Argonne National Laboratory (ANL), Argonne, IL (United States); Parr, Albert C. [National Bureau of Standards, Washington, DC (United States); Poliakoff, E. D. [Boston Univ., MA (United States)

    1983-01-01

    The polarization of fluorescence from excited-state molecular photoions provides a direct probe of the photoionization dynamics and the symmetry signatures of autoionizing resonances. Measurements on CO₂ and CS₂ are presented as examples.

  2. A dual mode targeting probe for distinguishing HER2-positive breast cancer cells using silica-coated fluorescent magnetic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jia [Medical School Southeast University, Department of Ultrasonography, Zhongda Hospital (China); An, Yan-Li; Zang, Feng-Chao [Southeast University, Jiangsu Key Laboratory of Molecular and Functional Imaging (China); Zong, Shen-Fei; Cui, Yi-Ping, E-mail: cyp@seu.edu.cn [Southeast University, Advanced Photonics Center (China); Teng, Gao-Jun, E-mail: gjteng@vip.sina.com [Southeast University, Jiangsu Key Laboratory of Molecular and Functional Imaging (China)

    2013-10-15

    We report a composite nanoprobe based on silica-coated magnetic nanoparticles (NPs) for distinguishing breast cancers at different HER2 statuses. The nanoprobe has a core-shell structure, with Fe{sub 3}O{sub 4} NPs as the magnetic core and dye-embedded silica as the fluorescent shell, whose average size is about 150 nm. Besides, the outmost surfaces of the probes were modified with specific antibodies to endow the probe with a targeting ability. With such a structure, the nanoprobe can accomplish dual mode targeting of human breast cancer cells based on fluorescence and magnetic resonance imaging (MRI). In the experiments, three human breast cancer cell lines were used to test the targeting ability of the nanoprobe. Specifically, SKBR3 cells with a high HER2 expression level were used as the model target cells, while MCF7 cells with a lower HER2 expression levels and HER2-negative MDA-MB-231 cells were used as the controls. Both the fluorescence and MRI imaging results confirmed that the nanoprobe can distinguish three cancer cell lines with different HER2 expression levels. With the dual mode imaging and specific targeting properties, we anticipate that the presented nanoprobe may have a great potential in the diagnosis and treatment of cancerous diseases.

  3. Fluorescence detection: SPIE volume 743

    Energy Technology Data Exchange (ETDEWEB)

    Menzel, E.R.

    1987-01-01

    This book contains proceedings arranged into four sessions. They are: Fluorescence spectroscopic techniques; Fluorescence in analysis and materials characterization; Fluorescence in medicine and biochemistry; and Fluorescence in criminalistics.

  4. Development of a fluorescent substrate to measure hyaluronidase activity

    OpenAIRE

    Zhang, Li-Shu; Mummert, Mark E.

    2008-01-01

    A novel fluorescent substrate (termed FRET-HA) to quantitatively assess hyaluronidase activity was developed. Hyaluronan (HA), the major substrate for hyaluronidase, was dual labeled with fluorescein amine and rhodamine B amine. The fluorescein amine fluorescence signal was significantly quenched while the rhodamine B amine signal was significantly enhanced due to fluorescence resonance energy transfer (FRET). In the presence of bovine testes hyaluronidase, cleavage of HA disrupted FRET resul...

  5. Revealing the radiative and non-radiative relaxation rates of the fluorescent dye Atto488 in a λ/2 Fabry-Pérot-resonator by spectral and time resolved measurements

    Science.gov (United States)

    Konrad, Alexander; Metzger, Michael; Kern, Andreas M.; Brecht, Marc; Meixner, Alfred J.

    2016-07-01

    Using a Fabry-Pérot-microresonator with controllable cavity lengths in the λ/2-regime, we show the controlled modification of the vibronic relaxation dynamics of a fluorescent dye molecule in the spectral and time domain. By altering the photonic mode density around the fluorophores we are able to shape the fluorescence spectrum and enhance specifically the probability of the radiative transitions from the electronic excited state to distinct vibronic excited states of the electronic ground state. Analysis and correlation of the spectral and time resolved measurements by a theoretical model and a global fitting procedure allows us to reveal quantitatively the spectrally distributed radiative and non-radiative relaxation dynamics of the respective dye molecule under ambient conditions at the ensemble level.Using a Fabry-Pérot-microresonator with controllable cavity lengths in the λ/2-regime, we show the controlled modification of the vibronic relaxation dynamics of a fluorescent dye molecule in the spectral and time domain. By altering the photonic mode density around the fluorophores we are able to shape the fluorescence spectrum and enhance specifically the probability of the radiative transitions from the electronic excited state to distinct vibronic excited states of the electronic ground state. Analysis and correlation of the spectral and time resolved measurements by a theoretical model and a global fitting procedure allows us to reveal quantitatively the spectrally distributed radiative and non-radiative relaxation dynamics of the respective dye molecule under ambient conditions at the ensemble level. Electronic supplementary information (ESI) available. See DOI: 10.1039/C6NR02380K

  6. Fluorescent taggants with temporally coded signatures.

    Science.gov (United States)

    Wang, Siyang; Vyas, Raul; Dwyer, Chris

    2016-07-11

    In this paper, resonance energy transfer (RET) networks between chromophores are used to implement fluorescent taggants with temporally coded signatures. Because the temporal signature of such a fluorescent taggant is a phase-type distribution defined by the geometry of its RET network, the taggant design is not constrained by resolvable dyes and has a significantly larger coding capacity than spectrally or lifetime coded fluorescent taggants. Meanwhile, the detection process becomes highly efficient when the signatures are coded in the time domain. The taggant identification method is based on the multinomial distribution of detected photons and Maximum Likelihood Estimation, which guarantees high accuracy even with only a few hundred photons and also applies to a mixture of taggants in multiplex detection. Therefore, these temporally coded fluorescent taggants have great potential for both in situ and Lidar applications. PMID:27410827

  7. Plasmonic Molecular Nanohybrids—Spectral Dependence of Fluorescence Quenching

    Directory of Open Access Journals (Sweden)

    Maria Olejnik

    2012-01-01

    Full Text Available We demonstrate strong spectral dependence of the efficiency of fluorescence quenching in molecular systems composed of organic dyes and gold nanoparticles. In order to probe the coupling with metallic nanoparticles we use dyes with varied spectral overlap between the plasmon resonance and their absorption. Hybrid molecular structures were obtained via conjugation of metallic nanoparticles with the dyes using biotin-streptavidin linkage. For dyes featuring absorption above the plasmon excitation in gold nanoparticles, laser excitation induces minute changes in the fluorescence intensity and its lifetime for both conjugated and non-conjugated mixtures, which are the reference. In contrast, when the absorption of the dye overlaps with the plasmon resonance, the effect is quite dramatic, reaching 85% and 95% fluorescence quenching for non-conjugated and conjugated mixtures, respectively. The degree of fluorescence quenching strongly depends upon the concentration of metallic nanoparticles. Importantly, the origin of the fluorescence quenching is different in the case of the conjugated mixture, as evidenced by time-resolved fluorescence. For conjugated mixtures of dyes resonant with plasmon, excitation features two-exponential decay. This is in contrast to the single exponential decay measured for the off-resonant configuration. The results provide valuable insight into spectral dependence of the fluorescence quenching in molecular assemblies involving organic dyes and metallic nanoparticles.

  8. Nonlinear resonances

    CERN Document Server

    Rajasekar, Shanmuganathan

    2016-01-01

    This introductory text presents the basic aspects and most important features of various types of resonances and anti-resonances in dynamical systems. In particular, for each resonance, it covers the theoretical concepts, illustrates them with case studies, and reviews the available information on mechanisms, characterization, numerical simulations, experimental realizations, possible quantum analogues, applications and significant advances made over the years. Resonances are one of the most fundamental phenomena exhibited by nonlinear systems and refer to specific realizations of maximum response of a system due to the ability of that system to store and transfer energy received from an external forcing source. Resonances are of particular importance in physical, engineering and biological systems - they can prove to be advantageous in many applications, while leading to instability and even disasters in others. The book is self-contained, providing the details of mathematical derivations and techniques invo...

  9. Refractometric Sensing of Heavy Oils in Fluorescent Core Microcapillaries

    Directory of Open Access Journals (Sweden)

    Zamora V.

    2015-03-01

    Full Text Available The refractometric sensing of calibrated heavy oils (density > 1 000 kg/m3 is demonstrated using fluorescent-core microcapillaries. A 25-micron capillary channel was first coated with a high-index layer of fluorescent silicon Quantum Dots (QD. This QD film supports the development of cylindrical Whispering Gallery Mode (WGM resonances inside the capillary. Heavy oils spanning a wide range of refractive index were pumped into the capillary channel, causing large shifts in the fluorescence WGM resonant wavelengths. The sensitivity for heavy oils approached 250 nm per Refractive Index Unit (nm/RIU at the higher oil indices, which is the highest sensitivity so far observed for a refractometric sensor operating in the fluorescence mode. This suggests that fluorescent core microcapillaries may be a viable microfluidic alternative for refractometric or chemical sensing in various stages of oil and gas processing, monitoring and usage.

  10. A Caco-2 cell-based quantitative antioxidant activity assay for antioxidants.

    Science.gov (United States)

    Wan, Hongxia; Liu, Dong; Yu, Xiangying; Sun, Haiyan; Li, Yan

    2015-05-15

    A Caco-2 cell-based antioxidant activity (CAA) assay for quantitative evaluation of antioxidants was developed by optimizing seeding density and culture time of Caco-2 cells, incubation time and concentration of fluorescent probe (2',7'-dichlorofluorescin diacetate, DCFH-DA), incubation way and incubation time of antioxidants (pure phytochemicals) and DCFH-DA with cells, and detection time of fluorescence. Results showed that the CAA assay was of good reproducibility and could be used to evaluate the antioxidant activity of antioxidants at the following conditions: seeding density of 5 × 10(4)/well, cell culture time of 24h, co-incubation of 60 μM DCFH-DA and pure phytochemicals with Caco-2 cells for 20 min and fluorescence recorded for 90 min. Additionally, a significant correlation was observed between CAA values and rat plasma ORAC values following the intake of antioxidants for selected pure phytochemicals (R(2) = 0.815, p < 0.01), demonstrating the good biological relevance of CAA assay.

  11. Development of fluorescence-based high-throughput screening assays: choice of appropriate instrumentation

    Science.gov (United States)

    Burns, David J.; Alder, Elisabeth; Fan, Yi-Hong; McKeegan, Evelyn; Warrior, Usha; Beutel, Bruce

    1998-04-01

    Fluorescence-based assays have become increasingly popular in high throughput screening for a variety of reasons (e.g. sensitivity). However, new screening technologies are pushing the limits of conventional fluorescence plate readers. For example, instruments that have optical sensitivities beyond most of the commercially available plate readers are required to reproducibly measure the fluorescence generated by the green fluorescent protein (GFP)--a novel reporter gene. Also, miniaturization of screening formats (with densities higher than the conventional 96-well plate) requires high resolution instrumentation to measure fluorescence. Several assays based on optical fluorescence measurements have been developed and screened in our Biological Screening group. These assays include various fluorescence-based protease assays (standard end-point and kinetic modes) and a functional cell-based screen using the green fluorescent protein as a reporter gene. The choice of instrumentation was the critical factor in the performance and success of each of these arrays. Data will be presented for the cell- based reporter assay including the type of instrumentation (fluorescence plate readers; fluorescence imaging systems) used for detection of GFP fluorescence.

  12. Interaction between Potassium Sorbate and Bovine Serum Albumin Revealed by Fluorescence and Resonance Light Scattering Spectra%山梨酸钾与蛋白质相互作用的荧光和共振光散射光谱研究

    Institute of Scientific and Technical Information of China (English)

    胡勇; 扶雄; 陈旭东; 杨连生; 章明秋

    2009-01-01

    用荧光光谱和共振散射光谱(RLS)对山梨酸钾(PSA)与牛血清蛋白(BSA)在溶液中的相互作用进行了研究,探讨了PSA对BSA荧光和共振光散射猝灭的机理,测定了该反应的表观结合常数及结合位点数.在288和293 K时的表观结合常数分别为2.23×10~3和2.74×10~3 L·mol~(-1),其相应的结合位点数分别为1.02和0.99.利用热力学参数确定了分子间的作用力性质,作用过程是自发的,作用力主要是电子作用力.同步荧光光谱表明相互作用对蛋白质构象有一定的影响.基于Forster非辐射能量转移理论估算了山梨酸钾与蛋白质之间的结合距离.%The interaction between potassium sorbate (PSA) and bovine serum albumin (BSA) was investigated by fluorescence spectroscopy, resonance light-scattering (RLS) spectroscopy. The quenching mechanism was analyzed referring to PSA against the fluorescence and the resonance light scattering spectra of BSA. The apparent binding constants (K_A) between PSA and BSA were 2.23 × 10~3 L·mol~(-1) (288 K) , and 2.74 × 10~3 L·mol~(-1) (293 K) , respectively. The corresponding binding sites values (n) were 1.02 and 0.99.The changes of negative entropy change and enthalpy indicate that the interaction of PSA and BSA was driven mainly by electrostatic interactions. The binding process was a spontaneous process in which Gibbs free energy change was negative. The effect of PSA on the conformation of BSA was analyzed by synchronous fluorescence spectroscopy. Furthermore, the binding distance r =2.83 nm between PSA and BSA was obtained based on the mechanism of Forster non-radiation energy transfer.

  13. Cell-based Assays to Identify Inhibitors of Viral Disease

    Science.gov (United States)

    Green, Neil; Ott, Robert D.; Isaacs, Richard J.; Fang, Hong

    2009-01-01

    Background Antagonizing the production of infectious virus inside cells requires drugs that can cross the cell membrane without harming host cells. Objective It is therefore advantageous to establish intracellular potency of anti-viral drug candidates early in the drug-discovery pipeline. Methods To this end, cell-based assays are being developed and employed in high-throughput drug screening, ranging from assays that monitor replication of intact viruses to those that monitor activity of specific viral proteins. While numerous cell-based assays have been developed and investigated, rapid counter screens are also needed to define the specific viral targets of identified inhibitors and to eliminate nonspecific screening hits. Results/Conclusions Here, we describe the types of cell-based assays being used in antiviral drug screens and evaluate the equally important counter screens that are being employed to reach the full potential of cell-based high-throughput screening. PMID:19750206

  14. Reviews in fluorescence 2010

    CERN Document Server

    Geddes, Chris D

    2011-01-01

    ""Reviews in Fluorescence 2010"", the seventh volume of the book serial from Springer, serves as a comprehensive collection of current trends and emerging hot topics in the field of fluorescence and closely related disciplines. It summarizes the year's progress in fluorescence and its applications, with authoritative analytical reviews specialized enough to be attractive to professional researchers, yet also appealing to the wider audience of scientists in related disciplines of fluorescence. ""Reviews in Fluorescence"" offers an essential reference material for any lab working in the fluoresc

  15. Principles of fluorescence techniques

    CERN Document Server

    2016-01-01

    Fluorescence techniques are being used and applied increasingly in academics and industry. The Principles of Fluorescence Techniques course will outline the basic concepts of fluorescence techniques and the successful utilization of the currently available commercial instrumentation. The course is designed for students who utilize fluorescence techniques and instrumentation and for researchers and industrial scientists who wish to deepen their knowledge of fluorescence applications. Key scientists in the field will deliver theoretical lectures. The lectures will be complemented by the direct utilization of steady-state and lifetime fluorescence instrumentation and confocal microscopy for FLIM and FRET applications provided by leading companies.

  16. A Guide to Fluorescent Protein FRET Pairs

    Science.gov (United States)

    Bajar, Bryce T.; Wang, Emily S.; Zhang, Shu; Lin, Michael Z.; Chu, Jun

    2016-01-01

    Förster or fluorescence resonance energy transfer (FRET) technology and genetically encoded FRET biosensors provide a powerful tool for visualizing signaling molecules in live cells with high spatiotemporal resolution. Fluorescent proteins (FPs) are most commonly used as both donor and acceptor fluorophores in FRET biosensors, especially since FPs are genetically encodable and live-cell compatible. In this review, we will provide an overview of methods to measure FRET changes in biological contexts, discuss the palette of FP FRET pairs developed and their relative strengths and weaknesses, and note important factors to consider when using FPs for FRET studies. PMID:27649177

  17. A Guide to Fluorescent Protein FRET Pairs

    Directory of Open Access Journals (Sweden)

    Bryce T. Bajar

    2016-09-01

    Full Text Available Förster or fluorescence resonance energy transfer (FRET technology and genetically encoded FRET biosensors provide a powerful tool for visualizing signaling molecules in live cells with high spatiotemporal resolution. Fluorescent proteins (FPs are most commonly used as both donor and acceptor fluorophores in FRET biosensors, especially since FPs are genetically encodable and live-cell compatible. In this review, we will provide an overview of methods to measure FRET changes in biological contexts, discuss the palette of FP FRET pairs developed and their relative strengths and weaknesses, and note important factors to consider when using FPs for FRET studies.

  18. Fluorescence correlation spectroscopy

    NARCIS (Netherlands)

    M.A. Hink

    2015-01-01

    Fluorescence fluctuation spectroscopy techniques allow the quantification of fluorescent molecules present at the nanomolar concentration level. After a brief introduction to the technique, this chapter presents a protocol including background information in order to measure and quantify the molecul

  19. Fluorescent optical position sensor

    Science.gov (United States)

    Weiss, Jonathan D.

    2005-11-15

    A fluorescent optical position sensor and method of operation. A small excitation source side-pumps a localized region of fluorescence at an unknown position along a fluorescent waveguide. As the fluorescent light travels down the waveguide, the intensity of fluorescent light decreases due to absorption. By measuring with one (or two) photodetectors the attenuated intensity of fluorescent light emitted from one (or both) ends of the waveguide, the position of the excitation source relative to the waveguide can be determined by comparing the measured light intensity to a calibrated response curve or mathematical model. Alternatively, excitation light can be pumped into an end of the waveguide, which generates an exponentially-decaying continuous source of fluorescent light along the length of the waveguide. The position of a photodetector oriented to view the side of the waveguide can be uniquely determined by measuring the intensity of the fluorescent light emitted radially at that location.

  20. Fluorescent S-layer fusion proteins

    International Nuclear Information System (INIS)

    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 ±1o). 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)

  1. Droplet Enhanced Fluorescence for Ultrasensitive Detection Using Inkjet.

    Science.gov (United States)

    Zeng, Hulie; Katagiri, Daisuke; Ogino, Taisuke; Nakajima, Hizuru; Kato, Shungo; Uchiyama, Katsumi

    2016-06-21

    A fluorescence enhanced phenomenon was found within a micrometer-sized liquid droplet, and it was adopted to construct droplet enhanced fluorescence (DEF) for ultrasensitive fluorescence detection. In this paper, an inkjet was utilized to eject perfect spherical droplets to construct a microspherical resonator and to develop a DEF system. It was utilized to implement ultrasensitive fluorescence detection in a liquid specimen with a volume of several microliters. The DEF detection of fluorescent molecules, fluorescein sodium, was used as a model to validate the proposed enhanced fluorescence detection method. A low limit of detection (LOD) for fluorescein sodium of 124 pM was obtained. The sensitive detection of single stranded DNA (ssDNA) was experimentally completed, with a wide range of linearity with a LOD of 312 pM. The proposed mechanism can be used as an ultrasensitive detection technique for analyzing microliters of liquid samples. PMID:27282958

  2. Novel patient cell-based HTS assay for identification of small molecules for a lysosomal storage disease.

    Directory of Open Access Journals (Sweden)

    Haifeng Geng

    Full Text Available Small molecules have been identified as potential therapeutic agents for lysosomal storage diseases (LSDs, inherited metabolic disorders caused by defects in proteins that result in lysosome dysfunctional. Some small molecules function assisting the folding of mutant misfolded lysosomal enzymes that are otherwise degraded in ER-associated degradation. The ultimate result is the enhancement of the residual enzymatic activity of the deficient enzyme. Most of the high throughput screening (HTS assays developed to identify these molecules are single-target biochemical assays. Here we describe a cell-based assay using patient cell lines to identify small molecules that enhance the residual arylsulfatase A (ASA activity found in patients with metachromatic leukodystrophy (MLD, a progressive neurodegenerative LSD. In order to generate sufficient cell lines for a large scale HTS, primary cultured fibroblasts from MLD patients were transformed using SV40 large T antigen. These SV40 transformed (SV40t cells showed to conserve biochemical characteristics of the primary cells. Using a specific colorimetric substrate para-nitrocatechol sulfate (pNCS, detectable ASA residual activity were observed in primary and SV40t fibroblasts from a MLD patient (ASA-I179S cultured in multi-well plates. A robust fluorescence ASA assay was developed in high-density 1,536-well plates using the traditional colorimetric pNCS substrate, whose product (pNC acts as "plate fluorescence quencher" in white solid-bottom plates. The quantitative cell-based HTS assay for ASA generated strong statistical parameters when tested against a diverse small molecule collection. This cell-based assay approach can be used for several other LSDs and genetic disorders, especially those that rely on colorimetric substrates which traditionally present low sensitivity for assay-miniaturization. In addition, the quantitative cell-based HTS assay here developed using patient cells creates an

  3. Synthesis and high content cell-based profiling of simplified analogues of the microtubule stabilizer (+)-discodermolide.

    Science.gov (United States)

    Minguez, Jose M; Giuliano, Kenneth A; Balachandran, Raghavan; Madiraju, Charitha; Curran, Dennis P; Day, Billy W

    2002-12-01

    (+)-Discodermolide, a C24:4, trihydroxylated, octamethyl, carbamate-bearing fatty acid lactone originally isolated from a Caribbean sponge, has proven to be the most potent of the microtubule-stabilizing agents. Recent studies suggest that it or its analogues may have advantages over other classes of microtubule-stabilizing agents. (+)-Discodermolide's complex molecular architecture has made structure-activity relationship analysis in this class of compounds a formidable task. The goal of this study was to prepare simplified analogues of (+)-discodermolide and to analyze their biological activities to expand structure-activity relationships. A small library of analogues was prepared wherein the (+)-discodermolide methyl groups at C-14 and C-16 and the C-7 hydroxyl were removed, and the lactone was replaced by simple esters. The library components were analyzed for microtubule-stabilizing actions in vitro, antiproliferative activity against a small panel of human carcinoma cells, and cell signaling, microtubule architecture and mitotic spindle alterations by a multiparameter fluorescence cell-based screening technique. The results show that even drastic structural simplification can lead to analogues with actions related to microtubule targeting and signal transduction, but that these subtle effects were illuminated only through the high information content cell-based screen.

  4. Resonating Statements

    DEFF Research Database (Denmark)

    Hjelholt, Morten; Jensen, Tina Blegind

    2015-01-01

    IT projects are often complex arrangements of technological components, social actions, and organizational transformation that are difficult to manage in practice. This paper takes an analytical discourse perspective to explore the process of legitimizing IT projects. We introduce the concept...... of resonating statements to highlight how central actors navigate in various discourses over time. Particularly, the statements and actions of an IT project manager are portrayed to show how individuals can legitimize actions by connecting statements to historically produced discourses. The case study...... of an IT project in a Danish local government spans a two-year time period and demonstrates a double-loop legitimization process. First, resonating statements are produced to localize a national IT initiative to support the specificity of a local government discourse. Second, the resonating statements are used...

  5. Resonance conditions

    CERN Document Server

    Rebusco, P

    2005-01-01

    Non-linear parametric resonances occur frequently in nature. Here we summarize how they can be studied by means of perturbative methods. We show in particular how resonances can affect the motion of a test particle orbiting in the vicinity of a compact object. These mathematical toy-models find application in explaining the structure of the observed kHz Quasi-Periodic Oscillations: we discuss which aspects of the reality naturally enter in the theory, and which one still remain a puzzle.

  6. Resonance conditions

    Science.gov (United States)

    Rebusco, P.

    2005-11-01

    Non-linear parametric resonances occur frequently in nature. Here we summarize how they can be studied by means of perturbative methods. We show in particular how resonances can affect the motion of a test particle orbiting in the vicinity of a compact object. These mathematical toy-models find application in explaining the structure of the observed kHz Quasi-Periodic Oscillations: we show which aspects of the reality naturally enter in the theory, and which one still remain a puzzle.

  7. Baryon Resonances

    CERN Document Server

    Oset, E; Sun, Bao Xi; Vacas, M J Vicente; Ramos, A; Gonzalez, P; Vijande, J; Torres, A Martinez; Khemchandani, K

    2009-01-01

    In this talk I show recent results on how many excited baryon resonances appear as systems of one meson and one baryon, or two mesons and one baryon, with the mesons being either pseudoscalar or vectors. Connection with experiment is made including a discussion on old predictions and recent results for the photoproduction of the $\\Lambda(1405)$ resonance, as well as the prediction of one $1/2^+$ baryon state around 1920 MeV which might have been seen in the $\\gamma p \\to K^+ \\Lambda$ reaction.

  8. Baryon Resonances

    Energy Technology Data Exchange (ETDEWEB)

    Oset, E. [Departamento de Fisica Teorica and IFIC, Centro Mixto Universidad de Valencia-CSIC, Institutos de Investigacion de Paterna, Aptdo. 22085, 46071 Valencia (Spain); Sarkar, S. [Variable Energy Cyclotron Centre, 1/AF, Bidhannagar, Kolkata 700064 (India); Sun Baoxi [Institute of Theoretical Physics, College of Applied Sciences, Beijing University of Technology, Beijing 100124 (China); Vicente Vacas, M.J. [Departamento de Fisica Teorica and IFIC, Centro Mixto Universidad de Valencia-CSIC, Institutos de Investigacion de Paterna, Aptdo. 22085, 46071 Valencia (Spain); Ramos, A. [Departament d' Estructura i Constituents de la Materia and Institut de Ciencies del Cosmos, Universitat de Barcelona, 08028 Barcelona (Spain); Gonzalez, P. [Departamento de Fisica Teorica and IFIC, Centro Mixto Universidad de Valencia-CSIC, Institutos de Investigacion de Paterna, Aptdo. 22085, 46071 Valencia (Spain); Vijande, J. [Departamento de Fisica Atomica Molecular y Nuclear and IFIC, Centro Mixto Universidad de Valencia-CSIC, Institutos de Investigacion de Paterna, Aptdo. 22085, 46071 Valencia (Spain); Martinez Torres, A. [Departamento de Fisica Teorica and IFIC, Centro Mixto Universidad de Valencia-CSIC, Institutos de Investigacion de Paterna, Aptdo. 22085, 46071 Valencia (Spain); Khemchandani, K. [Centro de Fisica Computacional, Departamento de Fisica, Universidade de Coimbra, P-3004-516 Coimbra (Portugal)

    2010-04-01

    In this talk I show recent results on how many excited baryon resonances appear as systems of one meson and one baryon, or two mesons and one baryon, with the mesons being either pseudoscalar or vectors. Connection with experiment is made including a discussion on old predictions and recent results for the photoproduction of the {lambda}(1405) resonance, as well as the prediction of one 1/2{sup +} baryon state around 1920 MeV which might have been seen in the {gamma}p{yields}K{sup +}{lambda} reaction.

  9. Neuroaesthetic Resonance

    DEFF Research Database (Denmark)

    Brooks, Anthony Lewis

    2013-01-01

    tailored channeling of sensory stimulus aligned as ‘art-making’ and ‘game playing’ core experiences. Thus, affecting brain plasticity and human motoric-performance via the adaptability (plasticity) of digital medias result in closure of the human afferent-efferent neural feedback loop closure through...... the unencumbered motion-to-computer-generated activities - ‘Music Making’, ‘Painting’, ‘Robotic’ and ‘Video Game’ control. A focus of this position paper is to highlight how Aesthetic Resonance, in this context, relates to the growing body of research on Neuroaesthetics to evolve Neuroaesthetic Resonance....

  10. Cell-based biosensors: Towards the development of cellular monitoring

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Cell-based biosensors (CBBs), a research hotspot of biosensors, which treat living cells as sensing elements, can detect the functional information of biologically active analytes. They characterize with high sensitivity, excellent selectivity and rapid response, and have been applied in many fields, such as biomedicine, environmental monitoring and pharmaceutical screening. Recently cell-cultured technology, silicon microfabrication technology and genetic technology have promoted exploration of CBBs dramatically. To elucidate the novel research findings and applications of cell- based biosensors, this paper summarizes various research approaches, presents some challenges and proposes the research trends.

  11. Resonance Raman study of benzyl radical

    DEFF Research Database (Denmark)

    Langkilde, F.W.; Bajdor, K.; Wilbrandt, R.

    1992-01-01

    Time-resolved resonance Raman spectra are obtained of benzyl radicals created by laser flash photolysis of benzylchloride and diphenylacetone in solution. The spectra are obtained in resonance with the intense 2 2A2-1 B-2(2) transition of benzyl. The strong Raman bands are assigned to totally...... symmetric a1 modes. The remaining observed bands are tentatively assigned to fundamental modes of b1, a2, and b2 symmetry, and to overtones and combinations. The resonance Raman spectra are found to be quite different from previous fluorescence spectra of benzyl, and the origins of these differences are...

  12. Demonstration of a visual cell-based assay for screening glucose transporter 4 translocation modulators in real time

    Indian Academy of Sciences (India)

    Maleppillil Vavachan Vijayakumar; Amrendra Kumar Ajay; Manoj Kumar Bhat

    2010-12-01

    Insulin-stimulated translocation of glucose transporter 4 (GLUT4) to cell membrane leading to glucose uptake is the rate-limiting step in diabetes. It is also a defined target of antidiabetic drug research. Existing GLUT4 translocation assays are based on time-consuming immunoassays and are hampered by assay variability and low sensitivity. We describe a real-time, visual, cell-based qualitative GLUT4 translocation assay using CHO-HIRc-myc-GLUT4eGFP cells that stably express myc- and eGFP-tagged GLUT4 in addition to human insulin receptor (HIRc). GLUT4 translocation is visualized by live cell imaging based on GFP fluorescence by employing a cooled charge-coupled device camera attached to a fluorescent microscope. This video imaging method and further quantitative analysis of GLUT4 on the cell membrane provide rapid and foolproof visual evidence that this method is suitable for screening GLUT4 translocation modulators.

  13. Cooperative Fluorescence from a Strongly Driven Dilute Cloud of Atoms

    OpenAIRE

    Ott, Johan Raunkjær; Wubs, Martijn; Lodahl, Peter; Mortensen, N. Asger; Kaiser, R.

    2013-01-01

    We investigate cooperative fluorescence in a dilute cloud of strongly driven two-level emitters. Starting from the Heisenberg equations of motion, we compute the first-order scattering corrections to the saturation of the excited-state population and to the resonance-fluorescence spectrum, which both require going beyond the state-of-the-art linear-optics approach to describe collective phenomena. A dipole blockade is observed due to long-range dipole-dipole coupling that vanishes at stronger...

  14. Autostereogram resonators

    Science.gov (United States)

    Leavey, Sean; Rae, Katherine; Murray, Adam; Courtial, Johannes

    2012-09-01

    Autostereograms, or "Magic Eye" pictures, are repeating patterns designed to give the illusion of depth. Here we discuss optical resonators that create light patterns which, when viewed from a suitable position by a monocular observer, are autostereograms of the three-dimensional shape of one of the mirror surfaces.

  15. CdTe量子点与罗丹明B水溶液体系下的双光子激发荧光共振能量转移∗%Fluorescence resonance energy transfer in a aqueous system of CdTe quantum dots and Rho damine B with two-photon excitation

    Institute of Scientific and Technical Information of China (English)

    李牧野; 李芳; 魏来; 何志聪; 张俊佩; 韩俊波; 陆培祥

    2015-01-01

    采用时间分辨荧光光谱技术研究了在双光子激发下不同尺寸的量子点与罗丹明B 之间的荧光共振能量转移.研究结果表明,在800 nm的双光子激发条件下,体系间能量转移效率随着供体吸收光谱与受体荧光光谱的光谱重叠程度增加而增加;理论分析表明,供体和受体间的Förster半径增加是导致其双光子能量转移效率增大的物理原因.同时,研究了罗丹明B浓度对荧光共振能量转移效率的影响.研究结果表明,量子点的荧光寿命随着罗丹明B浓度的增加而减小;量子点与罗丹明B之间的荧光共振能量转移效率随着罗丹明B浓度的增加而增加;当罗丹明B浓度为3.0×10−5 mol·L−1时,双光子荧光共振能量转移效率为40.1%.%Fluorescence resonance energy transfer (FRET) is non-radiation energy transfer that occurs between a donor (D) molecule in an excited state and an acceptor (A) molecule in a ground state by dipole-dipole interactions. The efficiency of FRET is dependent on the extent of spectral overlap between the donor photoluminescence peak and the absorption spectrum of acceptor, the quantum yield of the donor, and the distance between the donor and acceptor molecules. Cur-rently, FRET is commonly used for determining the metal ion, analyzing the protein, biological molecular fluorescence probe, etc. In this study, the FRET between CdTe quantum dots (QDs) with different sizes and Rhodamine B (RhB) in aqueous solution is investigated by using the time-resolved fluorescence test system under two-photon excitation. In this two-photon FRET aqueous system, QD is used as donor while RhB as acceptor. The time resolved two-photon photo-luminescence and fluorescence lifetime measurements are performed for analyzing the two-photon-excited luminescence by using a titanium sapphire femtosecond laser with a wavelength of 800 nm, pulse width of 130 fs, repetition frequency of 76 MHz, with the power fixed at

  16. Fluorescent fiber diagnostics

    Science.gov (United States)

    Toeppen, John S.

    1994-01-01

    A fluorescent fiber (13) having a doped core (16) is pumped (11) by light (18) of a relatively short wavelength to produce fluorescence at a longer wavelength that is detected by detector (24). The level of fluorescence is monitored (26) and evaluated to provide information as to the excitation of the fiber (13) or the environment thereof. In particular, the level of intensity of the detected fluorescence may be used to measure the intensity of a light beam (18) passing axially through an optical fiber system (12) (FIG. 1 ), or the intensity of a light beam (46) passing radially through a fluorescent fiber (13) (FIG. 2 ), or the level of a fluid (32) in a tank (31) (FIG. 3 ), or a scintillation event (37) in a fluorescent fiber (13) pumped to produce amplification of the scintillation event (FIG. 4 ).

  17. Global Distribution of Businesses Marketing Stem Cell-Based Interventions.

    Science.gov (United States)

    Berger, Israel; Ahmad, Amina; Bansal, Akhil; Kapoor, Tanvir; Sipp, Douglas; Rasko, John E J

    2016-08-01

    A structured search reveals that online marketing of stem-cell-based interventions is skewed toward developed economies including the United States, Ireland, Australia, and Germany. Websites made broad, imprecise therapeutic claims and frequently failed to detail procedures. Widespread marketing poses challenges to regulators, bioethicists, and those seeking realistic hope from therapies. PMID:27494673

  18. Fluorescent minerals, a review

    Science.gov (United States)

    Modreski, P.J.; Aumente-Modreski, R.

    1996-01-01

    Fluorescent minerals are more than just an attractive novelty, and collecting them is a speciality for thousands of individuals who appreciate their beauty, rarity, and scientific value. Fluorescent properties can be used as an aid to mineral identification, locality determination, and distinction between natural and synthetic gemstones. This article gives an overview of those aspects of fluorescence that are of most interest to collectors, hobbyists, and mineralogists. -from Authors

  19. Development of a quantitative, cell-based, high-content screening assay for epidermal growth factor receptor modulators

    Institute of Scientific and Technical Information of China (English)

    Jue WANG; Xin XIE

    2007-01-01

    Aim: To develop a robust, cell-based, high-content screening (HCS) assay based on receptor internalization for the identification of novel modulators of the epidermal growth factor receptor (EGFR). Methods: Agonist-induced receptor internalization is part of the signaling cascade of EGFR. Fluorescent-tagged epidermal growth factor (EGF) was used to visualize the internalized receptorligand complex. The fluorescent intracellular spots were detected and measured with an ArrayScan HCS reader. Compounds that can competitively bind to EGFR or interfere with EGFR internalization process would result in a reduced number and intensity of intracellular fluorescent spots. This assay was validated,optimized, and applied to a large-scale screening of a library containing 48 000 synthetic compounds. Results: The competition between fluorescent EGF and unlabeled EGF reveals the IC50 of unlabeled EGF is approximately 0.2 nmol/L,which is comparable with other published reports. Thirteen compounds with a relatively high degree of interference with EGFR internalization were identified.One of the compounds was proven to be agonist of the EGFR since it induced phosphorylation of the receptor and extracellular signal-regulated protein kinase (ERK). Conclusion: This automated, objective, and easy-to-use assay provided abundant information, quantitative results, and demonstrated the potential use of HCS methods in searching membrane receptor modulators.

  20. Preclinical fluorescent mouse models of pancreatic cancer

    Science.gov (United States)

    Bouvet, Michael; Hoffman, Robert M.

    2007-02-01

    Here we describe our cumulative experience with the development and preclinical application of several highly fluorescent, clinically-relevant, metastatic orthotopic mouse models of pancreatic cancer. These models utilize the human pancreatic cancer cell lines which have been genetically engineered to selectively express high levels of the bioluminescent green fluorescent (GFP) or red fluorescent protein (RFP). Fluorescent tumors are established subcutaneously in nude mice, and tumor fragments are then surgically transplanted onto the pancreas. Locoregional tumor growth and distant metastasis of these orthotopic implants occurs spontaneously and rapidly throughout the abdomen in a manner consistent with clinical human disease. Highly specific, high-resolution, real-time visualization of tumor growth and metastasis may be achieved in vivo without the need for contrast agents, invasive techniques, or expensive imaging equipment. We have shown a high correlation between florescent optical imaging and magnetic resonance imaging in these models. Alternatively, transplantation of RFP-expressing tumor fragments onto the pancreas of GFP-expressing transgenic mice may be used to facilitate visualization of tumor-host interaction between the pancreatic tumor fragments and host-derived stroma and vasculature. Such in vivo models have enabled us to serially visualize and acquire images of the progression of pancreatic cancer in the live animal, and to demonstrate the real-time antitumor and antimetastatic effects of several novel therapeutic strategies on pancreatic malignancy. These fluorescent models are therefore powerful and reliable tools with which to investigate human pancreatic cancer and therapeutic strategies directed against it.

  1. Equal-potential interpretation of electrically induced resonances in metamaterials

    DEFF Research Database (Denmark)

    Peng, Liang; Mortensen, N. Asger

    2011-01-01

    We propose a general description of electrically induced resonances (EIR) in metamaterials (MMs) comprising subwavelength unit cells. Based on classical electrodynamics, we found that EIR is governed by an equal-potential effect. Our theory accounts for the EIR phenomena and can give a renewed...

  2. Fluorescent Nanoparticle Uptake for Brain Tumor Visualization

    Directory of Open Access Journals (Sweden)

    Rachel Tréhin

    2006-04-01

    Full Text Available Accurate delineation of tumor margins is vital to the successful surgical resection of brain tumors. We have previously developed a multimodal nanoparticle CLIO-Cy5.5, which is detectable by both magnetic resonance imaging and fluorescence, to assist in intraoperatively visualizing tumor boundaries. Here we examined the accuracy of tumor margin determination of orthotopic tumors implanted in hosts with differing immune responses to the tumor. Using a nonuser-based signal intensity method applied to fluorescent micrographs of 9L gliosarcoma green fluorescent protein (GFP tumors, mean overestimations of 2 and 24 µm were obtained using Cy5.5 fluorescence, compared to the true tumor margin determined by GFP fluorescence, in nude mice and rats, respectively. To resolve which cells internalized the nanoparticle and to quantitate degree of uptake, tumors were disaggregated and cells were analyzed by flow cytometry and fluorescence microscopy. Nanoparticle uptake was seen in both CD11b+ cells (representing activated microglia and macrophages and tumor cells in both animal models by both methods. CD11b+ cells were predominantly found at the tumor margin in both hosts, but were more pronounced at the margin in the rat model. Additional metastatic (CT26 colon and primary (Gli36 glioma brain tumor models likewise demonstrated that the nanoparticle was internalized both by tumor cells and by host cells. Together, these observations suggest that fluorescent nanoparticles provide an accurate method of tumor margin estimation based on a combination of tumor cell and host cell uptake for primary and metastatic tumors in animal model systems and offer potential for clinical translation.

  3. Recent Progress on Plasmon-Enhanced Fluorescence

    Directory of Open Access Journals (Sweden)

    Dong Jun

    2015-12-01

    Full Text Available The optically generated collective electron density waves on metal–dielectric boundaries known as surface plasmons have been of great scientific interest since their discovery. Being electromagnetic waves on gold or silver nanoparticle’s surface, localised surface plasmons (LSP can strongly enhance the electromagnetic field. These strong electromagnetic fields near the metal surfaces have been used in various applications like surface enhanced spectroscopy (SES, plasmonic lithography, plasmonic trapping of particles, and plasmonic catalysis. Resonant coupling of LSPs to fluorophore can strongly enhance the emission intensity, the angular distribution, and the polarisation of the emitted radiation and even the speed of radiative decay, which is so-called plasmon enhanced fluorescence (PEF. As a result, more and more reports on surface-enhanced fluorescence have appeared, such as SPASER-s, plasmon assisted lasing, single molecule fluorescence measurements, surface plasmoncoupled emission (SPCE in biological sensing, optical orbit designs etc. In this review, we focus on recent advanced reports on plasmon-enhanced fluorescence (PEF. First, the mechanism of PEF and early results of enhanced fluorescence observed by metal nanostructure will be introduced. Then, the enhanced substrates, including periodical and nonperiodical nanostructure, will be discussed and the most important factor of the spacer between molecule and surface and wavelength dependence on PEF is demonstrated. Finally, the recent progress of tipenhanced fluorescence and PEF from the rare-earth doped up-conversion (UC and down-conversion (DC nanoparticles (NPs are also commented upon. This review provides an introduction to fundamentals of PEF, illustrates the current progress in the design of metallic nanostructures for efficient fluorescence signal amplification that utilises propagating and localised surface plasmons.

  4. Recent Progress on Plasmon-Enhanced Fluorescence

    Science.gov (United States)

    Dong, Jun; Zhang, Zhenglong; Zheng, Hairong; Sun, Mentao

    2015-12-01

    The optically generated collective electron density waves on metal-dielectric boundaries known as surface plasmons have been of great scientific interest since their discovery. Being electromagnetic waves on gold or silver nanoparticle's surface, localised surface plasmons (LSP) can strongly enhance the electromagnetic field. These strong electromagnetic fields near the metal surfaces have been used in various applications like surface enhanced spectroscopy (SES), plasmonic lithography, plasmonic trapping of particles, and plasmonic catalysis. Resonant coupling of LSPs to fluorophore can strongly enhance the emission intensity, the angular distribution, and the polarisation of the emitted radiation and even the speed of radiative decay, which is so-called plasmon enhanced fluorescence (PEF). As a result, more and more reports on surface-enhanced fluorescence have appeared, such as SPASER-s, plasmon assisted lasing, single molecule fluorescence measurements, surface plasmoncoupled emission (SPCE) in biological sensing, optical orbit designs etc. In this review, we focus on recent advanced reports on plasmon-enhanced fluorescence (PEF). First, the mechanism of PEF and early results of enhanced fluorescence observed by metal nanostructure will be introduced. Then, the enhanced substrates, including periodical and nonperiodical nanostructure, will be discussed and the most important factor of the spacer between molecule and surface and wavelength dependence on PEF is demonstrated. Finally, the recent progress of tipenhanced fluorescence and PEF from the rare-earth doped up-conversion (UC) and down-conversion (DC) nanoparticles (NPs) are also commented upon. This review provides an introduction to fundamentals of PEF, illustrates the current progress in the design of metallic nanostructures for efficient fluorescence signal amplification that utilises propagating and localised surface plasmons.

  5. Development of a Cell-Based Functional Assay for the Detection of Clostridium botulinum Neurotoxin Types A and E

    Directory of Open Access Journals (Sweden)

    Uma Basavanna

    2013-01-01

    Full Text Available The standard procedure for definitive detection of BoNT-producing Clostridia is a culture method combined with neurotoxin detection using a standard mouse bioassay (MBA. The mouse bioassay is highly sensitive and specific, but it is expensive and time-consuming, and there are ethical concerns due to use of laboratory animals. Cell-based assays provide an alternative to the MBA in screening for BoNT-producing Clostridia. Here, we describe a cell-based assay utilizing a fluorescence reporter construct expressed in a neuronal cell model to study toxin activity in situ. Our data indicates that the assay can detect as little as 100 pM BoNT/A activity within living cells, and the assay is currently being evaluated for the analysis of BoNT in food matrices. Among available in vitro assays, we believe that cell-based assays are widely applicable in high-throughput screenings and have the potential to at least reduce and refine animal assays if not replace it.

  6. Recent developments in fluorescence-based microscopy applied in biomedical sciences

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The present short review aims to give an overview of the most recent de velopments in fluorescence microscopy and its applications in biomedical science s. Apart from improvements in well-established methods based on conventional fl u orescence microscopy and confocal microscopy (fluorescence in situ hybridisa tion (FISH), tyramide signal amplification (TSA) in immunocytochemistry, new fluorop hores), more recently introduced techniques like fluorescence resonance energy t ransfer (FRET), fluorescence recovery after photobleaching (FRAP), multiphoton m icroscopy and fluorescence correlation spectroscopy (FCS) will be discussed.

  7. Fluorescence in insects

    Science.gov (United States)

    Welch, Victoria L.; Van Hooijdonk, Eloise; Intrater, Nurit; Vigneron, Jean-Pol

    2012-10-01

    Fluorescent molecules are much in demand for biosensors, solar cells, LEDs and VCSEL diodes, therefore, considerable efforts have been expended in designing and tailoring fluorescence to specific technical applications. However, naturally occurring fluorescence of diverse types has been reported from a wide array of living organisms: most famously, the jellyfish Aequorea victoria, but also in over 100 species of coral and in the cuticle of scorpions, where it is the rule, rather than the exception. Despite the plethora of known insect species, comparatively few quantitative studies have been made of insect fluorescence. Because of the potential applications of natural fluorescence, studies in this field have relevance to both physics and biology. Therefore, in this paper, we review the literature on insect fluorescence, before documenting its occurrence in the longhorn beetles Sternotomis virescens, Sternotomis variabilis var. semi rufescens, Anoplophora elegans and Stellognatha maculata, the tiger beetles Cicindela maritima and Cicindela germanica and the weevil Pachyrrhynchus gemmatus purpureus. Optical features of insect fluorescence, including emitted wavelength, molecular ageing and naturally occurring combinations of fluorescence with bioluminescence and colour-producing structures are discussed.

  8. Fluorescence of atopic allergens

    NARCIS (Netherlands)

    Berrens, L.

    1967-01-01

    Purified atopic allergens have been found to emit flue fluorescence upon irradiation with ultraviolet light of 365 mμ wavelength. The maximum of fluorescence is in the region 445–490 mμ and the intensity is of the same order of magnitude for different atopic allergens. Synthetic model compounds, inc

  9. LEDs for fluorescence microscopy

    NARCIS (Netherlands)

    Young, I.T.; Garini, Y.; Dietrich, H.R.C.; Van Oel, W.; Liqui Lung, G.

    2004-01-01

    Traditional light sources for fluorescence microscopy have been mercury lamps, xenon lamps, and lasers. These sources have been essential in the development of fluorescence microscopy but each can have serious disadvantages: lack of near monochromaticity, heat generation, cost, lifetime of the light

  10. Stem Cell-Based Therapies for Ischemic Stroke

    Directory of Open Access Journals (Sweden)

    Lei Hao

    2014-01-01

    Full Text Available In recent years, stem cell-based approaches have attracted more attention from scientists and clinicians due to their possible therapeutical effect on stroke. Animal studies have demonstrated that the beneficial effects of stem cells including embryonic stem cells (ESCs, inducible pluripotent stem cells (iPSCs, neural stem cells (NSCs, and mesenchymal stem cell (MSCs might be due to cell replacement, neuroprotection, endogenous neurogenesis, angiogenesis, and modulation on inflammation and immune response. Although several clinical studies have shown the high efficiency and safety of stem cell in stroke management, mainly MSCs, some issues regarding to cell homing, survival, tracking, safety, and optimal cell transplantation protocol, such as cell dose and time window, should be addressed. Undoubtably, stem cell-based gene therapy represents a novel potential therapeutic strategy for stroke in future.

  11. Cell-Based Strategies for Meniscus Tissue Engineering

    OpenAIRE

    Wei Niu; Weimin Guo; Shufeng Han; Yun Zhu; Shuyun Liu; Quanyi Guo

    2016-01-01

    Meniscus injuries remain a significant challenge due to the poor healing potential of the inner avascular zone. Following a series of studies and clinical trials, tissue engineering is considered a promising prospect for meniscus repair and regeneration. As one of the key factors in tissue engineering, cells are believed to be highly beneficial in generating bionic meniscus structures to replace injured ones in patients. Therefore, cell-based strategies for meniscus tissue engineering play a ...

  12. Stem Cell-Based Therapeutics to Improve Wound Healing

    OpenAIRE

    Hu, Michael S.; Tripp Leavitt; Samir Malhotra; Dominik Duscher; Pollhammer, Michael S.; Walmsley, Graham G.; Zeshaan N. Maan; Alexander T. M. Cheung; Manfred Schmidt; Georg M. Huemer; Longaker, Michael T.; Peter Lorenz, H.

    2015-01-01

    Issues surrounding wound healing have garnered deep scientific interest as well as booming financial markets invested in novel wound therapies. Much progress has been made in the field, but it is unsurprising to find that recent successes reveal new challenges to be addressed. With regard to wound healing, large tissue deficits, recalcitrant wounds, and pathological scar formation remain but a few of our most pressing challenges. Stem cell-based therapies have been heralded as a promising mea...

  13. Safety issues in cell-based intervention trials

    OpenAIRE

    Dawson, Liza; Bateman-House, Alison S; Mueller Agnew, Dawn; Bok, Hilary; Brock, Dan W.; Chakravarti, Aravinda; Greene, Mark; King, Patricia A.; O'Brien, Stephen J.; Sachs, David H.; Schill, Kathryn E; Siegel, Andrew; Solter, Davor; Suter, Sonia M; Verfaillie, Catherine

    2003-01-01

    We report on the deliberations of an interdisciplinary group of experts in science, law, and philosophy who convened to discuss novel ethical and policy challenges in stem cell research. In this report we discuss the ethical and policy implications of safety concerns in the transition from basic laboratory research to clinical applications of cell-based therapies derived from stem cells. Although many features of this transition from lab to clinic are common to other therapies, three aspects ...

  14. Stem cell-based therapy in neural repair.

    Science.gov (United States)

    Hsu, Yi-Chao; Chen, Su-Liang; Wang, Dan-Yen; Chiu, Ing-Ming

    2013-01-01

    Cell-based therapy could aid in alleviating symptoms or even reversing the progression of neurodegenerative diseases and nerve injuries. Fibroblast growth factor 1 (FGF1) has been shown to maintain the survival of neurons and induce neurite outgrowth. Accumulating evidence suggests that combination of FGF1 and cell-based therapy is promising for future therapeutic application. Neural stem cells (NSCs), with the characteristics of self-renewal and multipotency, can be isolated from embryonic stem cells, embryonic ectoderm, and developing or adult brain tissues. For NSC clinical application, several critical problems remain to be resolved: (1) the source of NSCs should be personalized; (2) the isolation methods and protocols of human NSCs should be standardized; (3) the clinical efficacy of NSC transplants must be evaluated in more adequate animal models; and (4) the mechanism of intrinsic brain repair needs to be better characterized. In addition, the ideal imaging technique for tracking NSCs would be safe and yield high temporal and spatial resolution, good sensitivity and specificity. Here, we discuss recent progress and future development of cell-based therapy, such as NSCs, induced pluripotent stem cells, and induced neurons, in neurodegenerative diseases and peripheral nerve injuries. PMID:23806879

  15. Studies in atomic-fluorescence spectroscopy-V The fluorescence characteristics and determination of antimony.

    Science.gov (United States)

    Dagnall, R M; Thompson, K C; West, T S

    1967-10-01

    Atomic-fluorescence of antimony may be generated in an air-propane flame by nebulizing aqueous solutions of antimony salts whilst irradiating the flame by means of a microwave-excited electrode-less discharge tube operating at 30 W. The strongest fluorescence is exhibited by the (4)S(11 2 ) --> (4)P(1 3 ) 2311 A resonance line and weaker signals are observed at the 2068 and 2176 A resonance lines and at four intercombination lines, at 2598, 2671, 2770 and 2878 A. A process of thermally assisted direct-line fluorescence is postulated to account for the otherwise inexplicable intensity of the 2598 A line emission. Atomic-fluorescence spectroscopy at 2176 A permits the determination of antimony in the range 0.1-120 ppm with a detection limit of 0.05 ppm. With the same equipment and source, the range of measurement for atomic-absorption was 6-120 ppm and the detection limit was 1 ppm. No interferences were observed from 100-fold molar amounts of Cd, Co, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, NH(4), Pb and Zn or from arsenate, chloride, nitrate, phosphate and sulphate. PMID:18960212

  16. Theory of analytical curves in atomic fluorescence flame spectrometry

    NARCIS (Netherlands)

    Hooymayers, H.P.

    1968-01-01

    An explicit expression for the intensity of atomic resonance fluorescence as a function of atomic concentration in a flame is derived under certain idealized conditions. The expression is generally valid for a pure Doppler absorption line profile as well as for a combined Doppler and collisional bro

  17. Fluorescence and Spectral Imaging

    Directory of Open Access Journals (Sweden)

    Ralph S. DaCosta

    2007-01-01

    Full Text Available Early identification of dysplasia remains a critical goal for diagnostic endoscopy since early discovery directly improves patient survival because it allows endoscopic or surgical intervention with disease localized without lymph node involvement. Clinical studies have successfully used tissue autofluorescence with conventional white light endoscopy and biopsy for detecting adenomatous colonic polyps, differentiating benign hyperplastic from adenomas with acceptable sensitivity and specificity. In Barrett's esophagus, the detection of dysplasia remains problematic because of background inflammation, whereas in the squamous esophagus, autofluorescence imaging appears to be more dependable. Point fluorescence spectroscopy, although playing a crucial role in the pioneering mechanistic development of fluorescence endoscopic imaging, does not seem to have a current function in endoscopy because of its nontargeted sampling and suboptimal sensitivity and specificity. Other point spectroscopic modalities, such as Raman spectroscopy and elastic light scattering, continue to be evaluated in clinical studies, but still suffer the significant disadvantages of being random and nonimaging. A recent addition to the fluorescence endoscopic imaging arsenal is the use of confocal fluorescence endomicroscopy, which provides real-time optical biopsy for the first time. To improve detection of dysplasia in the gastrointestinal tract, a new and exciting development has been the use of exogenous fluorescence contrast probes that specifically target a variety of disease-related cellular biomarkers using conventional fluorescent dyes and novel potent fluorescent nanocrystals (i.e., quantum dots. This is an area of great promise, but still in its infancy, and preclinical studies are currently under way.

  18. Large Enhancement of Quantum Dot Fluorescence by Highly Scalable Nanoporous Gold

    OpenAIRE

    Zhang, Ling; Song, Yunke; Fujita, Takeshi; Zhang, Ye; Chen, Mingwei; Wang, Tza-Huei

    2013-01-01

    Nanoengineered metallic materials have been shown to have a number of exclusive physicochemical properties not available at neither larger (micro- and macroscopic) nor smaller (molecular) scales. Recently, these materials in particular have drawn significant attention due to their capability to enhance fluorescent signals of nearby fluorescent species through a phenomenon known as metal enhanced fluorescence (MEF). MEF originates from the localized surface plasmon resonance (LSPR), a collecti...

  19. Highly thermostable fluorescent proteins

    Science.gov (United States)

    Bradbury, Andrew M.; Waldo, Geoffrey S.; Kiss, Csaba

    2011-03-22

    Thermostable fluorescent proteins (TSFPs), methods for generating these and other stability-enhanced proteins, polynucleotides encoding such proteins, and assays and method for using the TSFPs and TSFP-encoding nucleic acid molecules are provided. The TSFPs of the invention show extremely enhanced levels of stability and thermotolerance. In one case, for example, a TSFP of the invention is so stable it can be heated to 99.degree. C. for short periods of time without denaturing, and retains 85% of its fluorescence when heated to 80.degree. C. for several minutes. The invention also provides a method for generating stability-enhanced variants of a protein, including but not limited to fluorescent proteins.

  20. Nanoantenna array-induced fluorescence enhancement and reduced lifetimes

    DEFF Research Database (Denmark)

    Bakker, R. M.; Drachev, V. P.; Liu, Z.;

    2008-01-01

    800, is uniformly embedded in a dielectric host that coats the nanoantennae. The nanoantennae act to enhance the dye absorption. In turn, emission from the dye drives the plasmon resonance of the antennae; the nanoantennae act to enhance the fluorescence signal and change the angular distribution...... of emission. These effects depend upon the overlap of the plasmon resonance with the excitation wavelength and the fluorescence emission band. A decreased fluorescence lifetime is observed along with highly polarized emission that displays the characteristics of the nanoantenna's dipole mode. Being able...... to engineer the emission of the dye-nanoantenna system is important for future device applications in both bio-sensing and nanoscale optoelectronic integration....

  1. Fluorescent carbon nanowires made by pyrolysis of DNA nanofibers and plasmon-assisted emission enhancement of their fluorescence.

    Science.gov (United States)

    Nakao, Hidenobu; Tokonami, Shiho; Yamamoto, Yojiro; Shiigi, Hiroshi; Takeda, Yoshihiko

    2014-10-14

    We report on a facile method for preparing fluorescent carbon nanowires (CNWs) with pyrolysis of highly aligned DNA nanofibers as carbon sources. Silver nanoparticle (AgNP)-doped CNWs were also produced using pyrolysis of DNA nanofibers with well-attached AgNPs, indicating emission enhancement assisted by localized plasmon resonances.

  2. CdTe量子点与罗丹明6G间的荧光共振能量转移机理研究%Study on Fluorescence Resonance Energy Transfer between CdTe Quantum Dots and Rhodamine 6G

    Institute of Scientific and Technical Information of China (English)

    罗建梅; 毕宁; 张曼君; 茶文丽; 梁建功; 陆冬莲

    2011-01-01

    本文在合成水溶性巯基乙酸修饰的CdTe量子点的基础上,研究了CdTe量子点与罗丹明6G之间的荧光共振能量转移.实验结果表明:构建的CdTe量子点(供体)-罗丹明6G(受体)荧光共振能量转移体系在磷酸盐缓冲溶液中有较好的转移效果.当磷酸缓冲溶液pH值为7.4,NaCl浓度为1.0 mol/L时,构建的CdTe量子点-罗丹明6G荧光共振能量转移效率为62%;罗丹明6G既能与CdTe量子点表面的修饰试剂作用,也能与CdTe量子点本身直接作用,其作用力为静电相互作用和配位作用.%CdTe quantum dots (QDs) were synthesized in aqueous medium by employing thioglycolic acid as a stabilizer. The fluorescence resonance energy transfer (FRET) between CdTe QDs and rhodamine 6G (Rh 6G) was investigated. The results showed that the energy transfer efficiency was 62% at pH=7.4 in 1.0 mol/L NaC1. Rh 6G molecules interacted not only with thioglycolic acid but also with the surface of CdTe QDs directly. The forces of the interaction were electrostatic interaction and coordinate interaction.

  3. Cell-Based Odorant Sensor Array for Odor Discrimination Based on Insect Odorant Receptors.

    Science.gov (United States)

    Termtanasombat, Maneerat; Mitsuno, Hidefumi; Misawa, Nobuo; Yamahira, Shinya; Sakurai, Takeshi; Yamaguchi, Satoshi; Nagamune, Teruyuki; Kanzaki, Ryohei

    2016-07-01

    The olfactory system of living organisms can accurately discriminate numerous odors by recognizing the pattern of activation of several odorant receptors (ORs). Thus, development of an odorant sensor array based on multiple ORs presents the possibility of mimicking biological odor discrimination mechanisms. Recently, we developed novel odorant sensor elements with high sensitivity and selectivity based on insect OR-expressing Sf21 cells that respond to target odorants by displaying increased fluorescence intensity. Here we introduce the development of an odorant sensor array composed of several Sf21 cell lines expressing different ORs. In this study, an array pattern of four cell lines expressing Or13a, Or56a, BmOR1, and BmOR3 was successfully created using a patterned polydimethylsiloxane film template and cell-immobilizing reagents, termed biocompatible anchor for membrane (BAM). We demonstrated that BAM could create a clear pattern of Sf21 sensor cells without impacting their odorant-sensing performance. Our sensor array showed odorant-specific response patterns toward both odorant mixtures and single odorant stimuli, allowing us to visualize the presence of 1-octen-3-ol, geosmin, bombykol, and bombykal as an increased fluorescence intensity in the region of Or13a, Or56a, BmOR1, and BmOR3 cell lines, respectively. Therefore, we successfully developed a new methodology for creating a cell-based odorant sensor array that enables us to discriminate multiple target odorants. Our method might be expanded into the development of an odorant sensor capable of detecting a large range of environmental odorants that might become a promising tool used in various applications including the study of insect semiochemicals and food contamination.

  4. Fluorescent filtered electrophosphorescence

    Science.gov (United States)

    Forrest, Stephen R.; Sun, Yiru; Giebink, Noel; Thompson, Mark E.

    2009-01-06

    The present invention relates to organic light emitting devices (OLEDs), and more specifically to OLEDS that emit light using a combination of fluorescent emitters and phosphorescent emitters for the efficient utilization of all of the electrically generated excitons.

  5. Plasmonic antennas and zero mode waveguides to enhance single molecule fluorescence detection and fluorescence correlation spectroscopy towards physiological concentrations

    CERN Document Server

    Punj, Deep; Moparthi, Satish Babu; de Torres, Juan; Grigoriev, Victor; Rigneault, Hervé; Wenger, Jérôme

    2014-01-01

    Single-molecule approaches to biology offer a powerful new vision to elucidate the mechanisms that underpin the functioning of living cells. However, conventional optical single molecule spectroscopy techniques such as F\\"orster fluorescence resonance energy transfer (FRET) or fluorescence correlation spectroscopy (FCS) are limited by diffraction to the nanomolar concentration range, far below the physiological micromolar concentration range where most biological reaction occur. To breach the diffraction limit, zero mode waveguides and plasmonic antennas exploit the surface plasmon resonances to confine and enhance light down to the nanometre scale. The ability of plasmonics to achieve extreme light concentration unlocks an enormous potential to enhance fluorescence detection, FRET and FCS. Single molecule spectroscopy techniques greatly benefit from zero mode waveguides and plasmonic antennas to enter a new dimension of molecular concentration reaching physiological conditions. The application of nano-optics...

  6. Fluorescent silver nanoparticles via exploding wire technique

    Indian Academy of Sciences (India)

    Alqudami Abdullah; S Annapoorni

    2005-11-01

    Aqueous solution containing spherical silver nanoparticles of 20–80 nm size have been generated using a newly developed novel electro-exploding wire (EEW) technique where thin silver wires have been exploded in double distilled water. Structural properties of the resulted nanoparticles have been studied by means of X-ray diffractometer (XRD) and transmission electron microscopy (TEM). The absorption spectrum of the aqueous solution of silver nanoparticles showed the appearance of a broad surface plasmon resonance (SPR) peak centered at a wavelength of 390 nm. The theoretically generated SPR peak seems to be in good agreement with the experimental one. Strong green fluorescence emission was observed from the water-suspended silver nanoparticles excited with light of wavelengths 340, 360 and 390 nm. The fluorescence of silver nanoparticles could be due to the excitation of the surface plasmon coherent electronic motion with the small size effect and the surface effect considerations.

  7. Resonant Nucleation

    CERN Document Server

    Gleiser, M; Gleiser, Marcelo; Howell, Rafael

    2004-01-01

    We investigate the role played by fast quenching on the decay of metastable (or false vacuum) states. Instead of the exponentially-slow decay rate per unit volume, $\\Gamma_{\\rm HN} \\sim \\exp[-E_b/k_BT]$ ($E_b$ is the free energy of the critical bubble), predicted by Homogeneous Nucleation theory, we show that under fast enough quenching the decay rate is, in fact, a power law $\\Gamma_{\\rm RN} \\sim [E_b/k_BT]^{-B}$, where $B$ is weakly sensitive to the temperature. We argue that the fast quench generates large-amplitude fluctuations about the metastable state which promote its rapid decay via parametric resonance. Possible decay mechanisms and their dependence on $E_b$ are proposed and illustrated in a (2+1)-dimensional scalar field model with an asymmetric double-well potential.

  8. Fluorescence enhancement in visible light: dielectric or noble metal?

    Science.gov (United States)

    Sun, S; Wu, L; Bai, P; Png, C E

    2016-07-28

    A high permittivity dielectric gives the impression of outperforming plasmonic noble metal in visible light fluorescence enhancement primarily because of its small loss. Nonetheless, the performances of these two platforms in various situations remain obscure due to the different optical confinement mechanisms as well as the complexity in the fluorescence enhancement process. This study presents a comprehensive comparison between these two platforms based on nanoparticles (NPs) to evaluate their capability and applicability in fluorescence enhancement by taking into account the fluorescence excitation rate, the quantum yield, the fluorophore wavelengths and Stokes shifts as well as the far field intensity. In a low permittivity sensing medium (e.g. air), the dielectric NP can achieve comparable or higher fluorescence enhancement than the metal NP due to its decent NP-enhanced excitation rate and larger quantum yield. In a relatively high permittivity sensing medium (e.g. water), however, there is a significant decrement of the excitation rate of the dielectric NP as the permittivity contrast decreases, leading to a smaller fluorescence enhancement compared to the metallic counterpart. Combining the fluorescence enhancement and the far field intensity studies, we further conclude that for both dielectric and plasmonic NPs, the optimal situation occurs when the fluorescence excitation wavelength, the fluorescence emission wavelength and the electric-dipole-mode of the dielectric NP (or the plasmonic resonance of the metal NP) are the same and all fall in the low conductivity region of the NP material. We also find that the electric-dipole-mode of the dielectric NP performs better than the magnetic-dipole-mode for fluorescence enhancement applications because only the electric-dipole-mode can be strongly excited by the routinely used fluorescent dyes and quantum dots, which behave as electric dipoles by nature. PMID:27374052

  9. Applied neutron resonance theory

    International Nuclear Information System (INIS)

    Utilisation of resonance theory in basic and applications-oriented neutron cross section work is reviewed. The technically important resonance formalisms, principal concepts and methods as well as representative computer programs for resonance parameter extraction from measured data, evaluation of resonance data, calculation of Doppler-broadened cross sections and estimation of level-statistical quantities from resonance parameters are described. (orig.)

  10. Dendritic cell-based cancer immunotherapy for colorectal cancer.

    Science.gov (United States)

    Kajihara, Mikio; Takakura, Kazuki; Kanai, Tomoya; Ito, Zensho; Saito, Keisuke; Takami, Shinichiro; Shimodaira, Shigetaka; Okamoto, Masato; Ohkusa, Toshifumi; Koido, Shigeo

    2016-05-01

    Colorectal cancer (CRC) is one of the most common cancers and a leading cause of cancer-related mortality worldwide. Although systemic therapy is the standard care for patients with recurrent or metastatic CRC, the prognosis is extremely poor. The optimal sequence of therapy remains unknown. Therefore, alternative strategies, such as immunotherapy, are needed for patients with advanced CRC. This review summarizes evidence from dendritic cell-based cancer immunotherapy strategies that are currently in clinical trials. In addition, we discuss the possibility of antitumor immune responses through immunoinhibitory PD-1/PD-L1 pathway blockade in CRC patients. PMID:27158196

  11. Dendritic cell-based cancer immunotherapy for colorectal cancer.

    Science.gov (United States)

    Kajihara, Mikio; Takakura, Kazuki; Kanai, Tomoya; Ito, Zensho; Saito, Keisuke; Takami, Shinichiro; Shimodaira, Shigetaka; Okamoto, Masato; Ohkusa, Toshifumi; Koido, Shigeo

    2016-05-01

    Colorectal cancer (CRC) is one of the most common cancers and a leading cause of cancer-related mortality worldwide. Although systemic therapy is the standard care for patients with recurrent or metastatic CRC, the prognosis is extremely poor. The optimal sequence of therapy remains unknown. Therefore, alternative strategies, such as immunotherapy, are needed for patients with advanced CRC. This review summarizes evidence from dendritic cell-based cancer immunotherapy strategies that are currently in clinical trials. In addition, we discuss the possibility of antitumor immune responses through immunoinhibitory PD-1/PD-L1 pathway blockade in CRC patients.

  12. Enhancing molecule fluorescence with asymmetrical plasmonic antennas.

    Science.gov (United States)

    Lu, Guowei; Liu, Jie; Zhang, Tianyue; Shen, Hongming; Perriat, Pascal; Martini, Matteo; Tillement, Olivier; Gu, Ying; He, Yingbo; Wang, Yuwei; Gong, Qihuang

    2013-07-21

    We propose and justify by the finite-difference time-domain method an efficient strategy to enhance the spontaneous emission of a fluorophore with a multi-resonance plasmonic antenna. The custom-designed asymmetrical antenna consists of two plasmonic nanoparticles with different sizes and is able to couple efficiently to free space light through multiple localized surface plasmon resonances. This design simultaneously permits a large near-field excitation near the antenna as well as a high quantum efficiency, which results in an unusual and significant enhancement of the fluorescence of a single emitter. Such an asymmetrical antenna presents intrinsic advantages over single particle or dimer based antennas made using two identical nanostructures. This promising concept can be exploited in the large domain of light-matter interaction processes involving multiple frequencies.

  13. Cell-Based Assay Design for High-Content Screening of Drug Candidates.

    Science.gov (United States)

    Nierode, Gregory; Kwon, Paul S; Dordick, Jonathan S; Kwon, Seok-Joon

    2016-02-01

    To reduce attrition in drug development, it is crucial to consider the development and implementation of translational phenotypic assays as well as decipher diverse molecular mechanisms of action for new molecular entities. High-throughput fluorescence and confocal microscopes with advanced analysis software have simplified the simultaneous identification and quantification of various cellular processes through what is now referred to as highcontent screening (HCS). HCS permits automated identification of modifiers of accessible and biologically relevant targets and can thus be used to detect gene interactions or identify toxic pathways of drug candidates to improve drug discovery and development processes. In this review, we summarize several HCS-compatible, biochemical, and molecular biology-driven assays, including immunohistochemistry, RNAi, reporter gene assay, CRISPR-Cas9 system, and protein-protein interactions to assess a variety of cellular processes, including proliferation, morphological changes, protein expression, localization, post-translational modifications, and protein-protein interactions. These cell-based assay methods can be applied to not only 2D cell culture but also 3D cell culture systems in a high-throughput manner. PMID:26428732

  14. Improvement of Bioactive Compound Classification through Integration of Orthogonal Cell-Based Biosensing Methods

    Directory of Open Access Journals (Sweden)

    Goran N. Jovanovic

    2007-01-01

    Full Text Available Lack of specificity for different classes of chemical and biological agents, and false positives and negatives, can limit the range of applications for cell-based biosensors. This study suggests that the integration of results from algal cells (Mesotaenium caldariorum and fish chromatophores (Betta splendens improves classification efficiency and detection reliability. Cells were challenged with paraquat, mercuric chloride, sodium arsenite and clonidine. The two detection systems were independently investigated for classification of the toxin set by performing discriminant analysis. The algal system correctly classified 72% of the bioactive compounds, whereas the fish chromatophore system correctly classified 68%. The combined classification efficiency was 95%. The algal sensor readout is based on fluorescence measurements of changes in the energy producing pathways of photosynthetic cells, whereas the response from fish chromatophores was quantified using optical density. Change in optical density reflects interference with the functioning of cellular signal transduction networks. Thus, algal cells and fish chromatophores respond to the challenge agents through sufficiently different mechanisms of action to be considered orthogonal.

  15. Antioxidant activity of polyphenolic myricetin in vitro cell-free and cell-based systems

    Directory of Open Access Journals (Sweden)

    Abolfazl Barzegar

    2016-06-01

    Full Text Available Myricetin (Myc is one of the most important flavonoids in diet due to its abundance in foods with the highest antioxidant activity. The antioxidant activity of Myc was studied in cell-free and cell-based systems to evaluate the ROS protection efficiency of Myc. The studies were based on the assessment of reducing power of Myc according to ferric ion reduction and intracellular ROS level measurement by assaying the cellular fluorescence intensity using dichlorodihydrofluorescein (DCF probe as an indicator for ROS in cells. Moreover, the antitoxic capability of Myc was assessed using MTT method. Data indicated that intracellular ROS are highly toxic and applying low concentration of Myc not only inhibited cellular ROS production but also was accompanying with the protection of cells against the highly toxic and the lethal effects of peroxide compounds. Because of strong correlation between cellular ROS and their cell toxic properties, the higher antioxidant potency of Myc in cell medium resulted in effectively blocking intracellular ROS and protecting cell death. This property is achieved by the help of high polar solubility and cell membrane permeability of Myc.

  16. Sorting live stem cells based on Sox2 mRNA expression.

    Directory of Open Access Journals (Sweden)

    Hans M Larsson

    Full Text Available While cell sorting usually relies on cell-surface protein markers, molecular beacons (MBs offer the potential to sort cells based on the presence of any expressed mRNA and in principle could be extremely useful to sort rare cell populations from primary isolates. We show here how stem cells can be purified from mixed cell populations by sorting based on MBs. Specifically, we designed molecular beacons targeting Sox2, a well-known stem cell marker for murine embryonic (mES and neural stem cells (NSC. One of our designed molecular beacons displayed an increase in fluorescence compared to a nonspecific molecular beacon both in vitro and in vivo when tested in mES and NSCs. We sorted Sox2-MB(+SSEA1(+ cells from a mixed population of 4-day retinoic acid-treated mES cells and effectively isolated live undifferentiated stem cells. Additionally, Sox2-MB(+ cells isolated from primary mouse brains were sorted and generated neurospheres with higher efficiency than Sox2-MB(- cells. These results demonstrate the utility of MBs for stem cell sorting in an mRNA-specific manner.

  17. MRI (Magnetic Resonance Imaging)

    Science.gov (United States)

    ... Procedures Medical Imaging MRI (Magnetic Resonance Imaging) MRI (Magnetic Resonance Imaging) Share Tweet Linkedin Pin it More sharing options ... 8 MB) Also available in Other Language versions . Magnetic Resonance Imaging (MRI) is a medical imaging procedure for making ...

  18. Lifetime estimation of moving subcellular objects in frequency-domain fluorescence lifetime imaging microscopy.

    Science.gov (United States)

    Roudot, Philippe; Kervrann, Charles; Blouin, Cedric M; Waharte, Francois

    2015-10-01

    Fluorescence lifetime is usually defined as the average nanosecond-scale delay between excitation and emission of fluorescence. It has been established that lifetime measurements yield numerous indications on cellular processes such as interprotein and intraprotein mechanisms through fluorescent tagging and Förster resonance energy transfer. In this area, frequency-domain fluorescence lifetime imaging microscopy is particularly appropriate to probe a sample noninvasively and quantify these interactions in living cells. The aim is then to measure the fluorescence lifetime in the sample at each location in space from fluorescence variations observed in a temporal sequence of images obtained by phase modulation of the detection signal. This leads to a sensitivity of lifetime determination to other sources of fluorescence variations such as intracellular motion. In this paper, we propose a robust statistical method for lifetime estimation for both background and small moving structures with a focus on intracellular vesicle trafficking. PMID:26479936

  19. Resonance Fluorescence from Semiconductor Quantum Dots: Beyond the Mollow Triplet

    DEFF Research Database (Denmark)

    Lund, Anders Mølbjerg; Nielsen, Per Kær; Lorke, Michael;

    2012-01-01

    analytical theory has been derived, which quantitatively accounts for the appearance and position of the peaks. This theory explains the physics responsible for the multiple peaks. By considering the time-dependent spectrum we demonstrate a time ordering of the side peaks, which is further evidence...

  20. Stem cell-based therapies for HIV/AIDS.

    Science.gov (United States)

    Pernet, Olivier; Yadav, Swati Seth; An, Dong Sung

    2016-08-01

    One of the current focuses in HIV/AIDS research is to develop a novel therapeutic strategy that can provide a life-long remission of HIV/AIDS without daily drug treatment and, ultimately, a cure for HIV/AIDS. Hematopoietic stem cell-based anti-HIV gene therapy aims to reconstitute the patient immune system by transplantation of genetically engineered hematopoietic stem cells with anti-HIV genes. Hematopoietic stem cells can self-renew, proliferate and differentiate into mature immune cells. In theory, anti-HIV gene-modified hematopoietic stem cells can continuously provide HIV-resistant immune cells throughout the life of a patient. Therefore, hematopoietic stem cell-based anti-HIV gene therapy has a great potential to provide a life-long remission of HIV/AIDS by a single treatment. Here, we provide a comprehensive review of the recent progress of developing anti-HIV genes, genetic modification of hematopoietic stem progenitor cells, engraftment and reconstitution of anti-HIV gene-modified immune cells, HIV inhibition in in vitro and in vivo animal models, and in human clinical trials. PMID:27151309

  1. Cell-Based Strategies for Meniscus Tissue Engineering

    Science.gov (United States)

    Niu, Wei; Guo, Weimin; Han, Shufeng; Zhu, Yun; Liu, Shuyun; Guo, Quanyi

    2016-01-01

    Meniscus injuries remain a significant challenge due to the poor healing potential of the inner avascular zone. Following a series of studies and clinical trials, tissue engineering is considered a promising prospect for meniscus repair and regeneration. As one of the key factors in tissue engineering, cells are believed to be highly beneficial in generating bionic meniscus structures to replace injured ones in patients. Therefore, cell-based strategies for meniscus tissue engineering play a fundamental role in meniscal regeneration. According to current studies, the main cell-based strategies for meniscus tissue engineering are single cell type strategies; cell coculture strategies also were applied to meniscus tissue engineering. Likewise, on the one side, the zonal recapitulation strategies based on mimicking meniscal differing cells and internal architectures have received wide attentions. On the other side, cell self-assembling strategies without any scaffolds may be a better way to build a bionic meniscus. In this review, we primarily discuss cell seeds for meniscus tissue engineering and their application strategies. We also discuss recent advances and achievements in meniscus repair experiments that further improve our understanding of meniscus tissue engineering. PMID:27274735

  2. Stem Cell-Based Cell Therapy for Glomerulonephritis

    Directory of Open Access Journals (Sweden)

    Meiling Jin

    2014-01-01

    Full Text Available Glomerulonephritis (GN, characterized by immune-mediated inflammatory changes in the glomerular, is a common cause of end stage renal disease. Therapeutic options for glomerulonephritis applicable to all cases mainly include symptomatic treatment and strategies to delay progression. In the attempt to yield innovative interventions fostering the limited capability of regeneration of renal tissue after injury and the uncontrolled pathological process by current treatments, stem cell-based therapy has emerged as novel therapy for its ability to inhibit inflammation and promote regeneration. Many basic and clinical studies have been performed that support the ability of various stem cell populations to ameliorate glomerular injury and improve renal function. However, there is a long way before putting stem cell-based therapy into clinical practice. In the present article, we aim to review works performed with respect to the use of stem cell of different origins in GN, and to discuss the potential mechanism of therapeutic effect and the challenges for clinical application of stem cells.

  3. Cell-Based Strategies for Meniscus Tissue Engineering

    Directory of Open Access Journals (Sweden)

    Wei Niu

    2016-01-01

    Full Text Available Meniscus injuries remain a significant challenge due to the poor healing potential of the inner avascular zone. Following a series of studies and clinical trials, tissue engineering is considered a promising prospect for meniscus repair and regeneration. As one of the key factors in tissue engineering, cells are believed to be highly beneficial in generating bionic meniscus structures to replace injured ones in patients. Therefore, cell-based strategies for meniscus tissue engineering play a fundamental role in meniscal regeneration. According to current studies, the main cell-based strategies for meniscus tissue engineering are single cell type strategies; cell coculture strategies also were applied to meniscus tissue engineering. Likewise, on the one side, the zonal recapitulation strategies based on mimicking meniscal differing cells and internal architectures have received wide attentions. On the other side, cell self-assembling strategies without any scaffolds may be a better way to build a bionic meniscus. In this review, we primarily discuss cell seeds for meniscus tissue engineering and their application strategies. We also discuss recent advances and achievements in meniscus repair experiments that further improve our understanding of meniscus tissue engineering.

  4. Regenerative feedback resonant circuit

    Science.gov (United States)

    Jones, A. Mark; Kelly, James F.; McCloy, John S.; McMakin, Douglas L.

    2014-09-02

    A regenerative feedback resonant circuit for measuring a transient response in a loop is disclosed. The circuit includes an amplifier for generating a signal in the loop. The circuit further includes a resonator having a resonant cavity and a material located within the cavity. The signal sent into the resonator produces a resonant frequency. A variation of the resonant frequency due to perturbations in electromagnetic properties of the material is measured.

  5. Resonances, resonance functions and spectral deformations

    International Nuclear Information System (INIS)

    The present paper is aimed at an analysis of resonances and resonance states from a mathematical point of view. Resonances are characterized as singular points of the analytically continued Lippman-Schwinger equation, as complex eigenvalues of the Hamiltonian with a purely outgoing, exponentially growing eigenfunction, and as poles of the S-matrix. (orig./HSI)

  6. Magnetic resonance angiography

    Science.gov (United States)

    MRA; Angiography - magnetic resonance ... Kwong RY. Cardiovascular Magnetic Resonance Imaging. In: Bonow RO, Mann DL, Zipes DP, Libby P, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine . ...

  7. Fluorescent image tracking velocimeter

    Science.gov (United States)

    Shaffer, Franklin D.

    1994-01-01

    A multiple-exposure fluorescent image tracking velocimeter (FITV) detects and measures the motion (trajectory, direction and velocity) of small particles close to light scattering surfaces. The small particles may follow the motion of a carrier medium such as a liquid, gas or multi-phase mixture, allowing the motion of the carrier medium to be observed, measured and recorded. The main components of the FITV include: (1) fluorescent particles; (2) a pulsed fluorescent excitation laser source; (3) an imaging camera; and (4) an image analyzer. FITV uses fluorescing particles excited by visible laser light to enhance particle image detectability near light scattering surfaces. The excitation laser light is filtered out before reaching the imaging camera allowing the fluoresced wavelengths emitted by the particles to be detected and recorded by the camera. FITV employs multiple exposures of a single camera image by pulsing the excitation laser light for producing a series of images of each particle along its trajectory. The time-lapsed image may be used to determine trajectory and velocity and the exposures may be coded to derive directional information.

  8. Fluorescence of Alexa fluor dye tracks protein folding.

    Directory of Open Access Journals (Sweden)

    Simon Lindhoud

    Full Text Available Fluorescence spectroscopy is an important tool for the characterization of protein folding. Often, a protein is labeled with appropriate fluorescent donor and acceptor probes and folding-induced changes in Förster Resonance Energy Transfer (FRET are monitored. However, conformational changes of the protein potentially affect fluorescence properties of both probes, thereby profoundly complicating interpretation of FRET data. In this study, we assess the effects protein folding has on fluorescence properties of Alexa Fluor 488 (A488, which is commonly used as FRET donor. Here, A488 is covalently attached to Cys69 of apoflavodoxin from Azotobacter vinelandii. Although coupling of A488 slightly destabilizes apoflavodoxin, the three-state folding of this protein, which involves a molten globule intermediate, is unaffected. Upon folding of apoflavodoxin, fluorescence emission intensity of A488 changes significantly. To illuminate the molecular sources of this alteration, we applied steady state and time-resolved fluorescence techniques. The results obtained show that tryptophans cause folding-induced changes in quenching of Alexa dye. Compared to unfolded protein, static quenching of A488 is increased in the molten globule. Upon populating the native state both static and dynamic quenching of A488 decrease considerably. We show that fluorescence quenching of Alexa Fluor dyes is a sensitive reporter of conformational changes during protein folding.

  9. Fluorescence of Alexa fluor dye tracks protein folding.

    Science.gov (United States)

    Lindhoud, Simon; Westphal, Adrie H; Visser, Antonie J W G; Borst, Jan Willem; van Mierlo, Carlo P M

    2012-01-01

    Fluorescence spectroscopy is an important tool for the characterization of protein folding. Often, a protein is labeled with appropriate fluorescent donor and acceptor probes and folding-induced changes in Förster Resonance Energy Transfer (FRET) are monitored. However, conformational changes of the protein potentially affect fluorescence properties of both probes, thereby profoundly complicating interpretation of FRET data. In this study, we assess the effects protein folding has on fluorescence properties of Alexa Fluor 488 (A488), which is commonly used as FRET donor. Here, A488 is covalently attached to Cys69 of apoflavodoxin from Azotobacter vinelandii. Although coupling of A488 slightly destabilizes apoflavodoxin, the three-state folding of this protein, which involves a molten globule intermediate, is unaffected. Upon folding of apoflavodoxin, fluorescence emission intensity of A488 changes significantly. To illuminate the molecular sources of this alteration, we applied steady state and time-resolved fluorescence techniques. The results obtained show that tryptophans cause folding-induced changes in quenching of Alexa dye. Compared to unfolded protein, static quenching of A488 is increased in the molten globule. Upon populating the native state both static and dynamic quenching of A488 decrease considerably. We show that fluorescence quenching of Alexa Fluor dyes is a sensitive reporter of conformational changes during protein folding.

  10. Improved Computational Model of Grid Cells Based on Column Structure

    Institute of Scientific and Technical Information of China (English)

    Yang Zhou; Dewei Wu; Weilong Li; Jia Du

    2016-01-01

    To simulate the firing pattern of biological grid cells, this paper presents an improved computational model of grid cells based on column structure. In this model, the displacement along different directions is processed by modulus operation, and the obtained remainder is associated with firing rate of grid cell. Compared with the original model, the improved parts include that: the base of modulus operation is changed, and the firing rate in firing field is encoded by Gaussian⁃like function. Simulation validates that the firing pattern generated by the improved computational model is more consistent with biological characteristic than original model. Besides, the firing pattern is badly influenced by the cumulative positioning error, but the computational model can also generate the regularly hexagonal firing pattern when the real⁃time positioning results are modified.

  11. Glial progenitor cell-based treatment of the childhood leukodystrophies

    DEFF Research Database (Denmark)

    Osorio, M Joana; Goldman, Steven A

    2016-01-01

    stem cell-derived human neural or glial progenitor cells may comprise a promising strategy for both structural remyelination and metabolic rescue. A broad variety of pediatric white matter disorders, including the primary hypomyelinating disorders, the lysosomal storage disorders, and the broader group...... genetic editing of pluripotent stem cells. Yet these challenges notwithstanding, the promise of glial progenitor cell-based treatment of the childhood myelin disorders offers hope to the many victims of this otherwise largely untreatable class of disease....... and astrocytes are the major affected cell populations, and are either structurally impaired or metabolically compromised through cell-intrinsic pathology, or are the victims of mis-accumulated toxic byproducts of metabolic derangement. In either case, glial cell replacement using implanted tissue or pluripotent...

  12. Cell-based screens and phenomics with fission yeast.

    Science.gov (United States)

    Rallis, Charalampos; Bähler, Jürg

    2016-01-01

    Next-generation sequencing approaches have considerably advanced our understanding of genome function and regulation. However, the knowledge of gene function and complex cellular processes remains a challenge and bottleneck in biological research. Phenomics is a rapidly emerging area, which seeks to rigorously characterize all phenotypes associated with genes or gene variants. Such high-throughput phenotyping under different conditions can be a potent approach toward gene function. The fission yeast Schizosaccharomyces pombe (S. pombe) is a proven eukaryotic model organism that is increasingly used for genomewide screens and phenomic assays. In this review, we highlight current large-scale, cell-based approaches used with S. pombe, including computational colony-growth measurements, genetic interaction screens, parallel profiling using barcodes, microscopy-based cell profiling, metabolomic methods and transposon mutagenesis. These diverse methods are starting to offer rich insights into the relationship between genotypes and phenotypes. PMID:26523839

  13. Cell-Based Microarrays for In Vitro Toxicology

    Science.gov (United States)

    Wegener, Joachim

    2015-07-01

    DNA/RNA and protein microarrays have proven their outstanding bioanalytical performance throughout the past decades, given the unprecedented level of parallelization by which molecular recognition assays can be performed and analyzed. Cell microarrays (CMAs) make use of similar construction principles. They are applied to profile a given cell population with respect to the expression of specific molecular markers and also to measure functional cell responses to drugs and chemicals. This review focuses on the use of cell-based microarrays for assessing the cytotoxicity of drugs, toxins, or chemicals in general. It also summarizes CMA construction principles with respect to the cell types that are used for such microarrays, the readout parameters to assess toxicity, and the various formats that have been established and applied. The review ends with a critical comparison of CMAs and well-established microtiter plate (MTP) approaches.

  14. A stem cell-based approach to cartilage repair.

    Science.gov (United States)

    Johnson, Kristen; Zhu, Shoutian; Tremblay, Matthew S; Payette, Joshua N; Wang, Jianing; Bouchez, Laure C; Meeusen, Shelly; Althage, Alana; Cho, Charles Y; Wu, Xu; Schultz, Peter G

    2012-05-11

    Osteoarthritis (OA) is a degenerative joint disease that involves the destruction of articular cartilage and eventually leads to disability. Molecules that promote the selective differentiation of multipotent mesenchymal stem cells (MSCs) into chondrocytes may stimulate the repair of damaged cartilage. Using an image-based high-throughput screen, we identified the small molecule kartogenin, which promotes chondrocyte differentiation (median effective concentration = 100 nM), shows chondroprotective effects in vitro, and is efficacious in two OA animal models. Kartogenin binds filamin A, disrupts its interaction with the transcription factor core-binding factor β subunit (CBFβ), and induces chondrogenesis by regulating the CBFβ-RUNX1 transcriptional program. This work provides new insights into the control of chondrogenesis that may ultimately lead to a stem cell-based therapy for osteoarthritis. PMID:22491093

  15. Comparison of Static and Microfluidic Protease Assays Using Modified Bioluminescence Resonance Energy Transfer Chemistry

    OpenAIRE

    Wu, Nan; Dacres, Helen; Anderson, Alisha; Stephen C Trowell; Zhu, Yonggang

    2014-01-01

    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...

  16. FLEX: fluorescence explorer

    NARCIS (Netherlands)

    Stoll, M.Ph.; Court, A.J.; Smorenburg, C.; Visser, H.; Crocco, L.; Heilimo, J.; Honig, A.

    1999-01-01

    FLEX is a scientifically driven space mission to provide demonstration/validation of the instrumentation and technique for measuring the natural fluorescence of vegetation in the Fraunhofer lines. The payload consists of high spectral resolution (0.1-0.3 nm) CCD imaging grating spectrometer with two

  17. Fluorescence Experiments with Quinine

    Science.gov (United States)

    O'Reilly, James E.

    1975-01-01

    Describes a series of experiments which illustrate the analytical capabilities of fluorescence, and outlines two straightforward analyses involving real analyses. These experiments are suitable for an undergraduate instrumental analysis course and require approximately six to seven hours of laboratory time. (MLH)

  18. Ultraviolet fluorescence monitor

    Energy Technology Data Exchange (ETDEWEB)

    Hargis, P.J. Jr.; Preppernau, B.L.; Aragon, B.P. [Sandia National Labs., Albuquerque, NM (United States). Laser, Optics and Remote Sensing Dept.

    1997-05-01

    A multispectral ultraviolet (UV) fluorescence imaging fluorometer and a pulsed molecular beam laser fluorometer were developed to detect volatile organic compounds of interest in environmental monitoring and drug interdiction applications. The UV fluorescence imaging fluorometer is a relatively simple instrument which uses multiple excitation wavelengths to measure the excitation/emission matrix for irradiated samples. Detection limits in the high part-per-million to low part-per-million range were measured for a number of volatile organic vapors in the atmosphere. Detection limits in the low part-per-million range were obtained using cryogenic cooling to pre-concentrate unknown samples before introducing them into the imaging fluorometer. A multivariate analysis algorithm was developed to analyze the excitation/emission matrix and used to determine the relative concentrations of species in computer synthesized mixtures containing up to five organic compounds. Analysis results demonstrated the utility of multispectral UV fluorescence in analytical measurements. A transportable UV fluorescence imaging fluorometer was used in two field tests. Field test results demonstrated that detection limits in the part-per-billion range were needed to reliably identify volatile organic compounds in realistic field test measurements. The molecular beam laser fluorometer, a more complex instrument with detection limits in the part-per-billion to part-per-trillion range, was therefore developed to satisfy detection sensitivity requirements for field test measurements. High-resolution spectroscopic measurements made with the molecular beam laser fluorometer demonstrated its utility in identifying volatile organic compounds in the atmosphere.

  19. Surface-Enhanced X-Ray Fluorescence

    Science.gov (United States)

    Anderson, Mark

    2010-01-01

    Surface-enhanced x-ray fluorescence (SEn-XRF) spectroscopy is a form of surface- enhanced spectroscopy that was conceived as a means of obtaining greater sensitivity in x-ray fluorescence (XRF) spectroscopy. As such, SEn-XRF spectroscopy joins the ranks of such other, longer-wavelength surface-enhanced spectroscopies as those based on surface-enhanced Raman scattering (SERS), surface-enhanced resonance Raman scattering (SERRS), and surfaceenhanced infrared Raman absorption (SEIRA), which have been described in previous NASA Tech Briefs articles. XRF spectroscopy has been used in analytical chemistry for determining the elemental compositions of small samples. XRF spectroscopy is rapid and quantitative and has been applied to a variety of metal and mineralogical samples. The main drawback of XRF spectroscopy as practiced heretofore is that sensitivity has not been as high as required for some applications. In SEn-XRF as in the other surface-enhanced spectroscopies, one exploits several interacting near-field phenomena, occurring on nanotextured surfaces, that give rise to local concentrations of incident far-field illumination. In this case, the far-field illumination comes from an x-ray source. Depending on the chemical composition and the geometry of a given nanotextured surface, these phenomena could include the lightning-rod effect (concentration of electric fields at the sharpest points on needlelike surface features), surface plasmon resonances, and grazing incidence geometric effects. In the far field, the observable effect of these phenomena is an increase in the intensity of the spectrum of interest - in this case, the x-ray fluorescence spectrum of chemical elements of interest that may be present within a surface layer at distances no more than a few nanometers from the surface.

  20. Green fluorescent protein: A perspective

    OpenAIRE

    Remington, S James

    2011-01-01

    A brief personal perspective is provided for green fluorescent protein (GFP), covering the period 1994–2011. The topics discussed are primarily those in which my research group has made a contribution and include structure and function of the GFP polypeptide, the mechanism of fluorescence emission, excited state protein transfer, the design of ratiometric fluorescent protein biosensors and an overview of the fluorescent proteins derived from coral reef animals. Structure-function relationship...

  1. Synthesis and Fluorescence Spectra of Triazolylcoumarin Fluorescent Dyes

    Institute of Scientific and Technical Information of China (English)

    PENG Xian-fu; LI Hong-qi

    2009-01-01

    Much attention is devoted to fluorescent dyes especially those with potential in versatile applications. Reactions under "click" conditions between nonfluorescent 3 - azidocoumarins and terminal alkynes produced 3 -(1, 2, 3- triazol- 1 - yl)cournarins, a novel type of fluorescent dyes with intense fluorescence. The structures of the new coumarins were characterized by 1H NMR, MS, and IR spectra. Fluorescence spectra measurement demonstrated excellent fluorescence performance of the triazolylcoumarins and this click reaction is a promising candidate for bioconjugation and bioimaging applications since both azide and alkynes are quite inert to biological systems.

  2. Fluorescence spectroscopy of dental calculus

    International Nuclear Information System (INIS)

    The aim of the present study was to investigate the fluorescence properties of dental calculus in comparison with the properties of adjacent unaffected tooth structure using both lasers and LEDs in the UV-visible range for fluorescence excitation. The influence of calculus color on the informative signal is demonstrated. The optimal spectral bands of excitation and registration of the fluorescence are determined

  3. Resonance and Neck Length for a Spherical Resonator

    Directory of Open Access Journals (Sweden)

    Emily Corning

    2011-06-01

    Full Text Available The relationship between the neck length of a spherical resonator and its period of fundamental resonance was investigated. This was done by measuring the frequency of fundamental resonance of the resonator at 6 different neck lengths. It was found that its resonance resembled Helmholtz resonance but was not that of ideal Helmholtz resonance.

  4. Tunable fluorescence from patterned silver nano-island arrays for sensitive sub-cell imaging

    International Nuclear Information System (INIS)

    Surface-enhanced fluorescence, a burgeoning technique in biological detection, provides largely enhanced fluorescence signal by exciting localized surfaces plasmons resonance with fluorescent dyes. Nanostructure and surroundings brings great impact on the emission signal, however, insufficient physics about the process limits further improvement on the nanostructure design. In this study, optical properties of Rhodamin-6G molecules on patterned silver nano-island arrays are tailored by precisely controlling the distance between the dyes and silver arrays. The fluorescence signal depends on the distance and the largest enhancement of 10 folds is achieved when the distance is 10 nm. The results are theoretically corroborated by finite difference time domain simulation and applied to cytoskeleton fluorescence imaging using phalloidin–fluorescein isothiocyanate. Our study provides insights into the physical mechanisms associated with the fluorescence enhancement and quenching, and our experiments suggest potential applications to high-sensitivity sub-cell imaging. (paper)

  5. Planar Resonators for Metamaterials

    Directory of Open Access Journals (Sweden)

    M. Blaha

    2012-09-01

    Full Text Available This paper presents the results of an investigation into a combination of electric and magnetic planar resonators in order to design the building element of a volumetric metamaterial showing simultaneously negative electric and magnetic polarizabilities under irradiation by an electromagnetic wave. Two combinations of particular planar resonators are taken into consideration. These planar resonators are an electric dipole, a split ring resonator and a double H-shaped resonator. The response of the single resonant particle composed of a resonator with an electric response and a resonator with a magnetic response is strongly anisotropic. Proper spatial arrangement of these particles can make the response isotropic. This is obtained by proper placement of six planar resonators on the surface of a cube that now represents a metamaterial unit cell. The cells are distributed in space with 3D periodicity.

  6. Femtosecond laser fluorescence and propagation in very dense potassium vapor.

    Science.gov (United States)

    Makdisi, Y; Kokaj, J; Afrousheh, K; Nair, R; Mathew, J; Pichler, G

    2013-12-16

    Femtosecond (fs) laser propagation and fluorescence of dense potassium vapor was studied, and the spectral region around the first and the second doublets of the principal series lines of potassium atoms was investigated. In our search we did not observe the conical emission in the far field, although it was previously observed in the case of rubidium. We discuss the possible reason of this unexpected result. The fluorescence spectrum revealed Rb impurity resonance lines in emission due to the collisional redistribution from the K(4p) levels into the Rb(5p) levels. In the forward propagation of 400 nm femtosecond light we observed the molecular band red shifted from potassium second doublet. However, no molecular spectrum was observed when the mode-locked fs laser light was discretely tuned within the wings of the first resonance lines, at 770 nm. PMID:24514609

  7. Plasmonic fluorescent quantum dots

    OpenAIRE

    Jin, Yongdong; Gao, Xiaohu

    2009-01-01

    Combining multiple discrete components into a single multifunctional nanoparticle could be useful in a variety of applications. Retaining the unique optical and electrical properties of each component after nanoscale integration is, however, a long-standing problem1,2. It is particularly difficult when trying to combine fluorophores such as semiconductor quantum dots with plasmonic materials such as gold, because gold and other metals can quench the fluorescence3,4. So far, the combination of...

  8. Magnetic fluorescent lamp

    Science.gov (United States)

    Berman, S.M.; Richardson R.W.

    1983-12-29

    The radiant emission of a mercury-argon discharge in a fluorescent lamp assembly is enhanced by providing means for establishing a magnetic field with lines of force along the path of electron flow through the bulb of the lamp assembly, to provide Zeeman splitting of the ultraviolet spectral line. Optimum results are obtained when the magnetic field strength causes a Zeeman splitting of approximately 1.7 times the thermal line width.

  9. [Safety monitoring of cell-based medicinal products (CBMPs)].

    Science.gov (United States)

    Funk, Markus B; Frech, Marion; Spranger, Robert; Keller-Stanislawski, Brigitte

    2015-11-01

    Cell-based medicinal products (CBMPs), a category of advanced-therapy medicinal products (ATMPs), are authorised for the European market by the European Commission by means of the centralized marketing authorisation. By conforming to the German Medicinal Products Act (Sec. 4b AMG), national authorisation can be granted by the Paul-Ehrlich-Institut in Germany exclusively for ATMPs not based on a routine manufacturing procedure. In both procedures, quality, efficacy, and safety are evaluated and the risk-benefit balance is assessed. For the centralised procedure, mainly controlled clinical trial data must be submitted, whereas the requirements for national procedures could be modified corresponding to the stage of development of the ATMP. After marketing authorization, the marketing authorization/license holder is obligated to report all serious adverse reactions to the competent authority and to provide periodic safety update reports. If necessary, post-authorization safety studies could be imposed. On the basis of these regulatory measures, the safety of advanced therapies can be monitored and improved.

  10. Neural stem cell-based treatment for neurodegenerative diseases.

    Science.gov (United States)

    Kim, Seung U; Lee, Hong J; Kim, Yun B

    2013-10-01

    Human neurodegenerative diseases such as Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS) and Alzheimer's disease (AD) are caused by a loss of neurons and glia in the brain or spinal cord. Neurons and glial cells have successfully been generated from stem cells such as embryonic stem cells (ESCs), mesenchymal stem cells (MSCs) and neural stem cells (NSCs), and stem cell-based cell therapies for neurodegenerative diseases have been developed. A recent advance in generation of a new class of pluripotent stem cells, induced pluripotent stem cells (iPSCs), derived from patients' own skin fibroblasts, opens doors for a totally new field of personalized medicine. Transplantation of NSCs, neurons or glia generated from stem cells in animal models of neurodegenerative diseases, including PD, HD, ALS and AD, demonstrates clinical improvement and also life extension of these animals. Additional therapeutic benefits in these animals can be provided by stem cell-mediated gene transfer of therapeutic genes such as neurotrophic factors and enzymes. Although further research is still needed, cell and gene therapy based on stem cells, particularly using neurons and glia derived from iPSCs, ESCs or NSCs, will become a routine treatment for patients suffering from neurodegenerative diseases and also stroke and spinal cord injury.

  11. A MULTISCALE, CELL-BASED FRAMEWORK FOR MODELING CANCER DEVELOPMENT

    Energy Technology Data Exchange (ETDEWEB)

    JIANG, YI [Los Alamos National Laboratory

    2007-01-16

    Cancer remains to be one of the leading causes of death due to diseases. We use a systems approach that combines mathematical modeling, numerical simulation, in vivo and in vitro experiments, to develop a predictive model that medical researchers can use to study and treat cancerous tumors. The multiscale, cell-based model includes intracellular regulations, cellular level dynamics and intercellular interactions, and extracellular level chemical dynamics. The intracellular level protein regulations and signaling pathways are described by Boolean networks. The cellular level growth and division dynamics, cellular adhesion and interaction with the extracellular matrix is described by a lattice Monte Carlo model (the Cellular Potts Model). The extracellular dynamics of the signaling molecules and metabolites are described by a system of reaction-diffusion equations. All three levels of the model are integrated through a hybrid parallel scheme into a high-performance simulation tool. The simulation results reproduce experimental data in both avasular tumors and tumor angiogenesis. By combining the model with experimental data to construct biologically accurate simulations of tumors and their vascular systems, this model will enable medical researchers to gain a deeper understanding of the cellular and molecular interactions associated with cancer progression and treatment.

  12. Stem cell-based therapies for acute radiation syndrome

    International Nuclear Information System (INIS)

    Exposure to high doses of ionizing radiation in the event of accidental or intentional incident such as nuclear/radiological terrorism can lead to debilitating injuries to multiple organs resulting in death within days depending on the amount of radiation dose and the quality of radiation. Unfortunately, there is not a single FDA-licensed drug approved against acute radiation injury. The RadStem Center for Medical Countermeasures against Radiation (RadStem CMGR) program at Einstein is developing stem cell-based therapies to treat acute radiation syndrome (ARS). We have demonstrated that intravenous transplantation of bone marrow-derived and adipose-derived stromal cells, consisting of a mixture of mesenchymal, endothelial and myeloid progenitors can mitigate mice exposed to whole body irradiation of 12 Gy or whole abdominal irradiation of up to 20 Gy. We identified a variety of growth and differentiation factors that individually is unable to improve survival of animals exposed to lethal irradiation, but when administered sequentially mitigates radiation injury and improves survival. We termed this phenomenon as synthetic survival and describe a new paradigm whereby the 'synthetic survival' of irradiated tissues can be promoted by systemic administration of growth factors to amplify residual stem cell clonogens post-radiation exposure, followed by a differentiation factor that favors tissue stem cell differentiation. Synthetic survival can be applied to mitigate lethal radiation injury in multiple organs following radiation-induced hematopoeitic, gastrointestinal and pulmonary syndromes. (author)

  13. [Safety monitoring of cell-based medicinal products (CBMPs)].

    Science.gov (United States)

    Funk, Markus B; Frech, Marion; Spranger, Robert; Keller-Stanislawski, Brigitte

    2015-11-01

    Cell-based medicinal products (CBMPs), a category of advanced-therapy medicinal products (ATMPs), are authorised for the European market by the European Commission by means of the centralized marketing authorisation. By conforming to the German Medicinal Products Act (Sec. 4b AMG), national authorisation can be granted by the Paul-Ehrlich-Institut in Germany exclusively for ATMPs not based on a routine manufacturing procedure. In both procedures, quality, efficacy, and safety are evaluated and the risk-benefit balance is assessed. For the centralised procedure, mainly controlled clinical trial data must be submitted, whereas the requirements for national procedures could be modified corresponding to the stage of development of the ATMP. After marketing authorization, the marketing authorization/license holder is obligated to report all serious adverse reactions to the competent authority and to provide periodic safety update reports. If necessary, post-authorization safety studies could be imposed. On the basis of these regulatory measures, the safety of advanced therapies can be monitored and improved. PMID:26391098

  14. Microbial fuel cell based on electroactive sulfate-reducing biofilm

    International Nuclear Information System (INIS)

    Highlights: ► Regulation and management of electricity generation by variation of residence time. ► Design of microbial fuel cell based on electroactive biofilm on zeolite. ► Engineering solution for removing of the obtained elemental sulfur. - abstract: A two chambered laboratory scale microbial fuel cell (MFC) has been developed, based on natural sulfate-reducing bacterium consortium in electroactive biofilm on zeolite. The MFC utilizes potassium ferricyanide in the cathode chamber as an electron acceptor that derives electrons from the obtained in anode chamber H2S. The molecular oxygen is finally used as a terminal electron acceptor at cathode compartment. The generated power density was 0.68 W m−2 with current density of 3.2 A m−2 at 150 Ω electrode resistivity. The hydrogen sulfide itself is produced by microbial dissimilative sulfate reduction process by utilizing various organic substrates. Finally, elemental sulfur was identified as the predominant final oxidation product in the anode chamber. It was removed from MFC through medium circulation and gathering in an external tank. This report reveals dependence relationship between the progress of general electrochemical parameters and bacterial sulfate-reduction rate. The presented MFC design can be used for simultaneous sulfate purification of mining drainage wastewater and generation of renewable electricity

  15. Preclinical safety testing for cell-based products using animals.

    Science.gov (United States)

    McBlane, James W

    2015-09-01

    The objectives of preclinical testing include to show why there might be therapeutic benefit in patients and to provide information on the product's toxicity. For cell-based products, given even once, there may be long term exposure and this could imply, unlike for conventional drugs, that all preclinical studies may be needed prior to first human use. The duration of exposure to cells should be studied in animals to guide toxicity assessments. Distribution of cells after administration by a route resembling that intended in humans should be studied to understand potential risks. Risk of tumour formation with the product may also need to be characterised. To the extent that this information can be generated by in vitro testing, studies in animals may not be needed and limitations on the capability of preclinical data to predict human toxicity are recognised: species-specificity make some cell products act only in humans and a human cell-product might be expected to be rejected by immunocompetent animals. Does this suggest testing in immunosuppressed animals or of development of an animal-cell product supposedly similar to the human cell product? No single answer seems to fit every situation.

  16. Regulations and guidelines governing stem cell based products: Clinical considerations

    Directory of Open Access Journals (Sweden)

    Bobby George

    2011-01-01

    Full Text Available The use of stem cells as medicines is a promising and upcoming area of research as they may be able to help the body to regenerate damaged or lost tissue in a host of diseases like Parkinson′s, multiple sclerosis, heart disease, liver disease, spinal cord damage, cancer and many more. Translating basic stem cell research into routine therapies is a complex multi-step process which entails the challenge related to managing the expected therapeutic benefits with the potential risks while complying with the existing regulations and guidelines. While in the United States (US and European Union (EU regulations are in place, in India, we do not have a well-defined regulatory framework for "stem cell based products (SCBP". There are several areas that need to be addressed as it is quite different from that of pharmaceuticals. These range from establishing batch consistency, product stability to product safety and efficacy through pre-clinical, clinical studies and marketing authorization. This review summarizes the existing regulations/guidelines in US, EU, India, and the associated challenges in developing SCBP with emphasis on clinical aspects.

  17. A novel multi-functional cell-based microphysiometer

    Institute of Scientific and Technical Information of China (English)

    XU Ying; XU Gaixia; LIU Qingjun; CAI Hua; LI Yan; LI Rong; WANG Ping

    2006-01-01

    This paper presents a novel multi-functional microphysiometer for simultaneous measurements of several extracellular ion concentrations and action potential measurement in living cells based on MLAPS (multi-light addressable potentiometric sensor). In the microphysiometer, sorts of sensitive membranes are illuminated in parallel with n light sources at working frequencies, and the response amplitudes of each frequency component can be measured on-line by parallel processing algorithm. In the experiments, the relations of the extracellular environmental H+, Na +, K +, Ca2 + under the effects of western medicines (dilantin, phenobarbital sodium) and Chinese drugs (scutellaria, medlar, hemlock parsley) were analyzed, and the effects of several drugs were evaluated. Moreover, the action potential signals of different cell types (cardiac myocytes and neurons) could be measured and analyzed by LAPS. By detecting these parameters, the system can monitor the real-time process of the cell metabolism and action potential, observe the functional responses of different kinds of membrane-bound receptors, and evaluate the activities of drugs.

  18. Integral resonator gyroscope

    Science.gov (United States)

    Shcheglov, Kirill V. (Inventor); Challoner, A. Dorian (Inventor); Hayworth, Ken J. (Inventor); Wiberg, Dean V. (Inventor); Yee, Karl Y. (Inventor)

    2008-01-01

    The present invention discloses an inertial sensor having an integral resonator. A typical sensor comprises a planar mechanical resonator for sensing motion of the inertial sensor and a case for housing the resonator. The resonator and a wall of the case are defined through an etching process. A typical method of producing the resonator includes etching a baseplate, bonding a wafer to the etched baseplate, through etching the wafer to form a planar mechanical resonator and the wall of the case and bonding an end cap wafer to the wall to complete the case.

  19. Fluorescent nanodiamond for biomedicine

    International Nuclear Information System (INIS)

    NV centers in diamond have gained strong interest as a novel tool for quantum information processing, quantum computing and quantum photonics. These applications are based on fluorescent and spin properties of NV-centres. However, in some conditions NV- can lose an electron and turn to NV0. The occupation of NV0 and NV- charge states depend on the position of their ground states with respect to the Fermi level and the mechanism of the charge transfer. Interestingly, that the charge switch has important implications on applications of fluorescent nanodiamond (fND) to nano-biology and nano-medicine. fND can be used for bio-marking and bio-tracking but also for the monitoring of targeted delivery to the cells. In this presentation we review the current state-of-the art for using fND particles for fluorescent bio imaging in cells and discuss the charge transfer and its luminescence stability by using ultra high sensitive spectroscopy methods to study the NV0 and NV- state occupation. (author)

  20. A new airborne formaldehyde instrument: Compact Formaldehyde Fluorescence Experiment (COFFEE)

    Science.gov (United States)

    Hanisco, T. F.; Bailey, S. A.; Swanson, A. K.; Wolfe, G. M., Jr.

    2014-12-01

    We present the operating principles of a new instrument designed for operation on small aircraft. The instrument uses a new non-resonant fluorescence technique to take advantage of compact industrial lasers to make a small, robust package that can measure formaldehyde at sensitivities better than 100 ppt in 1 second integration. The instrument is designed to fly on the Alphajet at NASA Ames but can be modified to fly on other small aircraft.

  1. Coumarin amide derivatives as fluorescence chemosensors for cyanide anions

    International Nuclear Information System (INIS)

    Four coumarin amide derivatives with 4-methyl coumarin or pyrene as terminal group have been synthesized. Their photophysical properties and recognition properties for cyanide anions have been examined. The results indicate that the compounds can recognize cyanide anions with obvious absorption and fluorescence spectra change, at the same time, obvious color and fluorescence change can be observed by naked eye. The in situ hydrogen nuclear magnetic resonance spectra and photophysical properties change confirm that Michael additions between the chemosensors and cyanide anions take place at the 4-position of coumarin. - Highlights: • Four coumarin amide derivatives with 4-methyl coumarin or pyrene as terminal group were synthesized. • The compounds can recognize cyanide anions with obvious absorption and fluorescence spectra change. • Michael additions between the chemosensors and cyanide anions take place at the 4-position of coumarin

  2. Make caffeine visible: a fluorescent caffeine "traffic light" detector.

    Science.gov (United States)

    Xu, Wang; Kim, Tae-Hyeong; Zhai, Duanting; Er, Jun Cheng; Zhang, Liyun; Kale, Anup Atul; Agrawalla, Bikram Keshari; Cho, Yoon-Kyoung; Chang, Young-Tae

    2013-01-01

    Caffeine has attracted abundant attention due to its extensive existence in beverages and medicines. However, to detect it sensitively and conveniently remains a challenge, especially in resource-limited regions. Here we report a novel aqueous phase fluorescent caffeine sensor named Caffeine Orange which exhibits 250-fold fluorescence enhancement upon caffeine activation and high selectivity. Nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy indicate that π-stacking and hydrogen-bonding contribute to their interactions while dynamic light scattering and transmission electron microscopy experiments demonstrate the change of Caffeine Orange ambient environment induces its fluorescence emission. To utilize this probe in real life, we developed a non-toxic caffeine detection kit and tested it for caffeine quantification in various beverages. Naked-eye sensing of various caffeine concentrations was possible based on color changes upon irradiation with a laser pointer. Lastly, we performed the whole system on a microfluidic device to make caffeine detection quick, sensitive and automated. PMID:23877095

  3. Coumarin amide derivatives as fluorescence chemosensors for cyanide anions

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Qianqian [School of Material Science and Engineering, Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials, University of Jinan, Jinan 250022, Shandong (China); Liu, Zhiqiang [State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, Shandong (China); Cao, Duxia, E-mail: duxiacao@ujn.edu.cn [School of Material Science and Engineering, Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials, University of Jinan, Jinan 250022, Shandong (China); Guan, Ruifang, E-mail: mse_guanrf@ujn.edu.cn [School of Material Science and Engineering, Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials, University of Jinan, Jinan 250022, Shandong (China); Wang, Kangnan; Shan, Yanyan; Xu, Yongxiao; Ma, Lin [School of Material Science and Engineering, Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials, University of Jinan, Jinan 250022, Shandong (China)

    2015-07-01

    Four coumarin amide derivatives with 4-methyl coumarin or pyrene as terminal group have been synthesized. Their photophysical properties and recognition properties for cyanide anions have been examined. The results indicate that the compounds can recognize cyanide anions with obvious absorption and fluorescence spectra change, at the same time, obvious color and fluorescence change can be observed by naked eye. The in situ hydrogen nuclear magnetic resonance spectra and photophysical properties change confirm that Michael additions between the chemosensors and cyanide anions take place at the 4-position of coumarin. - Highlights: • Four coumarin amide derivatives with 4-methyl coumarin or pyrene as terminal group were synthesized. • The compounds can recognize cyanide anions with obvious absorption and fluorescence spectra change. • Michael additions between the chemosensors and cyanide anions take place at the 4-position of coumarin.

  4. Modulation gamma resonance spectroscopy

    International Nuclear Information System (INIS)

    Possibility to control dynamic processes in a matter through gamma-resonance modulation by high-frequency external variable fields in excess of inverse lifetimes of the Moessbauer nuclei excited states, that is, within the megahertz frequency range lies in the heart of the modulation gamma-resonance spectroscopy. Through the use of the gamma-resonance process theoretical analysis methods and of the equation solution method for the density matrix with the secondary quantization of gamma-radiation field one attacks the problems dealing with the effect of both variable fields and relaxation on gamma-resonance. One has studied the gamma-radiation ultrasound modulation stages. One points out a peculiar role of the gamma-magnetic resonance effect in modulation gamma resonance spectroscopy formation. One forecasts development of the modulation gamma-resonance spectroscopy into the nonlinear gamma-resonance spectroscopy

  5. Neutron resonance averaging

    International Nuclear Information System (INIS)

    The principles of resonance averaging as applied to neutron capture reactions are described. Several illustrations of resonance averaging to problems of nuclear structure and the distribution of radiative strength in nuclei are provided. 30 refs., 12 figs

  6. Aspect ratio dependent fluorescence quenching of eosin Y by gold nanorods.

    Science.gov (United States)

    Weng, Guojun; Li, Jianjun; Zhang, Li; Zhao, Junwu

    2014-06-01

    Gold nanorods of different aspect ratios had been synthesized using seed mediated growth method. The formed gold nanorods had been characterized by the absorption and transmission electron microscopy (TEM) measurements. The obtained gold nanorods were used to study the quenched effect on fluorescence of Eosin Y. Experimental results revealed that Eosin Y molecules adsorbed on the metallic surfaces, suffering strong quenching of their fluorescence and the quenching efficiency was different for different aspect ratio. Using dielectric coated gold nanorods model, the probable mechanism of aspect ratio dependent quenching efficiency was obtained by numerical calculation based on fluorescence resonance energy transfer and quasi-static theory. The calculation results showed that the non-monotonic changing of fluorescence quenching was attributed to competing effects of aspect ratio and the dielectric constant of coated shell on surface plasmon resonance.

  7. Modeling and control of fuel cell based distributed generation systems

    Science.gov (United States)

    Jung, Jin Woo

    This dissertation presents circuit models and control algorithms of fuel cell based distributed generation systems (DGS) for two DGS topologies. In the first topology, each DGS unit utilizes a battery in parallel to the fuel cell in a standalone AC power plant and a grid-interconnection. In the second topology, a Z-source converter, which employs both the L and C passive components and shoot-through zero vectors instead of the conventional DC/DC boost power converter in order to step up the DC-link voltage, is adopted for a standalone AC power supply. In Topology 1, two applications are studied: a standalone power generation (Single DGS Unit and Two DGS Units) and a grid-interconnection. First, dynamic model of the fuel cell is given based on electrochemical process. Second, two full-bridge DC to DC converters are adopted and their controllers are designed: an unidirectional full-bridge DC to DC boost converter for the fuel cell and a bidirectional full-bridge DC to DC buck/boost converter for the battery. Third, for a three-phase DC to AC inverter without or with a Delta/Y transformer, a discrete-time state space circuit model is given and two discrete-time feedback controllers are designed: voltage controller in the outer loop and current controller in the inner loop. And last, for load sharing of two DGS units and power flow control of two DGS units or the DGS connected to the grid, real and reactive power controllers are proposed. Particularly, for the grid-connected DGS application, a synchronization issue between an islanding mode and a paralleling mode to the grid is investigated, and two case studies are performed. To demonstrate the proposed circuit models and control strategies, simulation test-beds using Matlab/Simulink are constructed for each configuration of the fuel cell based DGS with a three-phase AC 120 V (L-N)/60 Hz/50 kVA and various simulation results are presented. In Topology 2, this dissertation presents system modeling, modified space

  8. Dark resonances in the field of frequency shifted feedback laser radiation

    OpenAIRE

    Romanenko, V. I.; Romanenko, A. V.; Yatsenko, L. P.; Kazakov, G. A.; Litvinov, A. N.; Matisov, B. G.; Rozhdestvensky, Yu. V.

    2010-01-01

    We present a theory of dark resonances in a fluorescence of a three-level atom gas interacting with a polychromatic field of a frequency shifted feedback (FSF) laser. We show that conditions for the resonance observation are optimal when the phase relations between the laser spectral components provide generation of a light pulses train. We study analytically the field broadening and the light shift of the resonances.

  9. Dark resonances in the field of frequency-shifted feedback laser radiation

    Science.gov (United States)

    Romanenko, V. I.; Romanenko, A. V.; Yatsenko, L. P.; Kazakov, G. A.; Litvinov, A. N.; Matisov, B. G.; Rozhdestvensky, Yu V.

    2010-11-01

    We present a theory of dark resonances in fluorescence of a three-level atom gas interacting with a polychromatic field of a frequency-shifted feedback laser. We show that conditions for the resonance observation are optimal when the phase relations between the laser spectral components provide generation of a light pulse train. We study analytically the field broadening and the light shift of the resonances.

  10. Dark resonances in the field of frequency-shifted feedback laser radiation

    International Nuclear Information System (INIS)

    We present a theory of dark resonances in fluorescence of a three-level atom gas interacting with a polychromatic field of a frequency-shifted feedback laser. We show that conditions for the resonance observation are optimal when the phase relations between the laser spectral components provide generation of a light pulse train. We study analytically the field broadening and the light shift of the resonances.

  11. Dark resonances in the field of frequency-shifted feedback laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Romanenko, V I; Romanenko, A V; Yatsenko, L P [Institute of Physics, National Academy of Science of Ukraine, 46, Nauky Avenue, Kyiv 03028 (Ukraine); Kazakov, G A; Litvinov, A N; Matisov, B G [St Petersburg State Polytechnical University, 29, Polytechnicheskaya st, St. Petersburg 195251 (Russian Federation); Rozhdestvensky, Yu V, E-mail: vr@iop.kiev.u, E-mail: andrey.litvinov@mail.r [S I Vavilov State Optical Institute 12, Birzhevaya Liniya st, St Petersburg 199034 (Russian Federation)

    2010-11-14

    We present a theory of dark resonances in fluorescence of a three-level atom gas interacting with a polychromatic field of a frequency-shifted feedback laser. We show that conditions for the resonance observation are optimal when the phase relations between the laser spectral components provide generation of a light pulse train. We study analytically the field broadening and the light shift of the resonances.

  12. The promise of fuel cell-based automobiles

    Indian Academy of Sciences (India)

    A K Shukla; C L Jackson; K Scott

    2003-02-01

    Fuel cell-based automobiles have gained attention in the last few years due to growing public concern about urban air pollution and consequent environmental problems. From an analysis of the power and energy requirements of a modern car, it is estimated that a base sustainable power of $ca$. 50 kW supplemented with short bursts up to 80 kW will suffice in most driving requirements. The energy demand depends greatly on driving characteristics but under normal usage is expected to be 200 Wh/km. The advantages and disadvantages of candidate fuel-cell systems and various fuels are considered together with the issue of whether the fuel should be converted directly in the fuel cell or should be reformed to hydrogen onboard the vehicle. For fuel cell vehicles to compete successfully with conventional internal-combustion engine vehicles, it appears that direct conversion fuel cells using probably hydrogen, but possibly methanol, are the only realistic contenders for road transportation applications. Among the available fuel cell technologies, polymer–electrolyte fuel cells directly fueled with hydrogen appear to be the best option for powering fuel cell vehicles as there is every prospect that these will exceed the performance of the internal-combustion engine vehicles but for their first cost. A target cost of $ 50/kW would be mandatory to make polymer–electrolyte fuel cells competitive with the internal combustion engines and can only be achieved with design changes that would substantially reduce the quantity of materials used. At present, prominent car manufacturers are deploying important research and development efforts to develop fuel cell vehicles and are projecting to start production by 2005.

  13. High content cell-based assay for the inflammatory pathway

    Science.gov (United States)

    Mukherjee, Abhishek; Song, Joon Myong

    2015-07-01

    Cellular inflammation is a non-specific immune response to tissue injury that takes place via cytokine network orchestration to maintain normal tissue homeostasis. However chronic inflammation that lasts for a longer period, plays the key role in human diseases like neurodegenerative disorders and cancer development. Understanding the cellular and molecular mechanisms underlying the inflammatory pathways may be effective in targeting and modulating their outcome. Tumor necrosis factor alpha (TNF-α) is a pro-inflammatory cytokine that effectively combines the pro-inflammatory features with the pro-apoptotic potential. Increased levels of TNF-α observed during acute and chronic inflammatory conditions are believed to induce adverse phenotypes like glucose intolerance and abnormal lipid profile. Natural products e. g., amygdalin, cinnamic acid, jasmonic acid and aspirin have proven efficacy in minimizing the TNF-α induced inflammation in vitro and in vivo. Cell lysis-free quantum dot (QDot) imaging is an emerging technique to identify the cellular mediators of a signaling cascade with a single assay in one run. In comparison to organic fluorophores, the inorganic QDots are bright, resistant to photobleaching and possess tunable optical properties that make them suitable for long term and multicolor imaging of various components in a cellular crosstalk. Hence we tested some components of the mitogen activated protein kinase (MAPK) pathway during TNF-α induced inflammation and the effects of aspirin in HepG2 cells by QDot multicolor imaging technique. Results demonstrated that aspirin showed significant protective effects against TNF-α induced cellular inflammation. The developed cell based assay paves the platform for the analysis of cellular components in a smooth and reliable way.

  14. Magnetic Resonance Imaging (MRI)

    Science.gov (United States)

    ... How Can I Help a Friend Who Cuts? Magnetic Resonance Imaging (MRI) KidsHealth > For Teens > Magnetic Resonance Imaging (MRI) Print A A A Text Size What's ... Exam Safety Getting Your Results What Is MRI? Magnetic resonance imaging (MRI) is a type of safe, painless testing ...

  15. Controlling Parametric Resonance

    DEFF Research Database (Denmark)

    Galeazzi, Roberto; Pettersen, Kristin Ytterstad

    2012-01-01

    Parametric resonance is a resonant phenomenon which takes place in systems characterized by periodic variations of some parameters. While seen as a threatening condition, whose onset can drive a system into instability, this chapter advocates that parametric resonance may become an advantage if t...

  16. Spin coupling and resonance

    NARCIS (Netherlands)

    Zielinski, M.L.; van Lenthe, J.H.

    2008-01-01

    The resonating block localize wave function (RBLW) method is introduced, a resonating modification of the block localized wave functions introduced by Mo et al. [Mo, Y.; Peyerimhoff, S. D. J. Chem. Phys. 1998, 109, 1687].This approach allows the evaluation of resonance energies following Pauling’s r

  17. Imaging in cell-based therapy for neurodegenerative diseases

    International Nuclear Information System (INIS)

    Fetal cell transplantation for the treatment of Parkinson's and Huntington's diseases has been developed over the past two decades and is now in early clinical testing phase. Direct assessment of the graft's survival, integration into the host brain and impact on neuronal functions requires advanced in vivo neuroimaging techniques. Owing to its high sensitivity, positron emission tomography is today the most widely used tool to evaluate the viability and function of the transplanted tissue in the brain. Nuclear magnetic resonance techniques are opening new possibilities for imaging neurochemical events in the brain. The ultimate goal will be to use the combination of multiple imaging modalities for complete functional monitoring of the repair processes in the central nervous system. (orig.)

  18. Studies of crystalline water at low temperatures by selective laser excitation of impurity uranyl ion fluorescence

    International Nuclear Information System (INIS)

    Fine-structure fluorescence spectrum of uranyl aqueous solution is obtained for the first time at low temperatures. It is established that the uranyl local surrounding in crystals of ice is characterized by low ordering, more typical for glasses. Temperature dependence of the width of the fluorescence resonance 0-0 line is measured. This dependence at temperatures above 20 K is described by interaction with phonons within the frames of the Debye model

  19. DNA origami as a tool for single-molecule fluorescence studies

    OpenAIRE

    Stein, Ingo

    2012-01-01

    Single-molecule fluorescence studies have become a routine practice in laboratories worldwide. As an experimental tool, especially fluorescence resonance energy transfer (FRET) has helped to unravel conformational changes and interactions of biomolecules. With the DNA origami method a new technique to create nanoscale shapes with DNA as a building material was recently introduced. As shown in this work, DNA nanotechnology can be readily combined with single-molecule FRET experiments, opening ...

  20. Make Caffeine Visible: a Fluorescent Caffeine “Traffic Light” Detector

    OpenAIRE

    Wang Xu; Tae-Hyeong Kim; Duanting Zhai; Jun Cheng Er; Liyun Zhang; Anup Atul Kale; Bikram Keshari Agrawalla; Yoon-Kyoung Cho; Young-Tae Chang

    2013-01-01

    Caffeine has attracted abundant attention due to its extensive existence in beverages and medicines. However, to detect it sensitively and conveniently remains a challenge, especially in resource-limited regions. Here we report a novel aqueous phase fluorescent caffeine sensor named Caffeine Orange which exhibits 250-fold fluorescence enhancement upon caffeine activation and high selectivity. Nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy indicate that π-s...

  1. FRET-Based Localization of Fluorescent Protein Insertions Within the Ryanodine Receptor Type 1

    OpenAIRE

    Raina, Shweta A.; Jeffrey Tsai; Montserrat Samsó; Fessenden, James D.

    2012-01-01

    Fluorescent protein (FP) insertions have often been used to localize primary structure elements in mid-resolution 3D cryo electron microscopic (EM) maps of large protein complexes. However, little is known as to the precise spatial relationship between the location of the fused FP and its insertion site within a larger protein. To gain insights into these structural considerations, Förster resonance energy transfer (FRET) measurements were used to localize green fluorescent protein (GFP) inse...

  2. An efficient core-shell fluorescent silica nanoprobe for ratiometric fluorescence detection of pH in living cells.

    Science.gov (United States)

    Fu, Jingni; Ding, Changqin; Zhu, Anwei; Tian, Yang

    2016-08-01

    Intracellular pH plays a vital role in cell biology, including signal transduction, ion transport and homeostasis. Herein, a ratiometric fluorescent silica probe was developed to detect intracellular pH values. The pH sensitive dye fluorescein isothiocyanate isomer I (FITC), emitting green fluorescence, was hybridized with reference dye rhodamine B (RB), emitting red fluorescence, as a dual-emission fluorophore, in which RB was embedded in a silica core of ∼40 nm diameter. Moreover, to prevent fluorescence resonance energy transfer between FITC and RB, FITC was grafted onto the surface of core-shell silica colloidal particles with a shell thickness of 10-12 nm. The nanoprobe exhibited dual emission bands centered at 517 and 570 nm, under single wavelength excitation of 488 nm. RB encapsulated in silica was inert to pH change and only served as reference signals for providing built-in correction to avoid environmental effects. Moreover, FITC (λem = 517 nm) showed high selectivity toward H(+) against metal ions and amino acids, leading to fluorescence variation upon pH change. Consequently, variations of the two fluorescence intensities (Fgreen/Fred) resulted in a ratiometric pH fluorescent sensor. The specific nanoprobe showed good linearity with pH variation in the range of 6.0-7.8. It can be noted that the fluorescent silica probe demonstrated good water dispersibility, high stability and low cytotoxicity. Accordingly, imaging and biosensing of pH variation was successfully achieved in HeLa cells. PMID:27291898

  3. Fluorescence analyzer for lignin

    Science.gov (United States)

    Berthold, John W.; Malito, Michael L.; Jeffers, Larry

    1993-01-01

    A method and apparatus for measuring lignin concentration in a sample of wood pulp or black liquor comprises a light emitting arrangement for emitting an excitation light through optical fiber bundles into a probe which has an undiluted sensing end facing the sample. The excitation light causes the lignin concentration to produce fluorescent emission light which is then conveyed through the probe to analyzing equipment which measures the intensity of the emission light. Measures a This invention was made with Government support under Contract Number DOE: DE-FC05-90CE40905 awarded by the Department of Energy (DOE). The Government has certain rights in this invention.

  4. Fluorescent temperature sensor

    Science.gov (United States)

    Baker, Gary A [Los Alamos, NM; Baker, Sheila N [Los Alamos, NM; McCleskey, T Mark [Los Alamos, NM

    2009-03-03

    The present invention is a fluorescent temperature sensor or optical thermometer. The sensor includes a solution of 1,3-bis(1-pyrenyl)propane within a 1-butyl-1-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquid solvent. The 1,3-bis(1-pyrenyl)propane remains unassociated when in the ground state while in solution. When subjected to UV light, an excited state is produced that exists in equilibrium with an excimer. The position of the equilibrium between the two excited states is temperature dependent.

  5. Ovenized microelectromechanical system (MEMS) resonator

    Science.gov (United States)

    Olsson, Roy H; Wojciechowski, Kenneth; Kim, Bongsang

    2014-03-11

    An ovenized micro-electro-mechanical system (MEMS) resonator including: a substantially thermally isolated mechanical resonator cavity; a mechanical oscillator coupled to the mechanical resonator cavity; and a heating element formed on the mechanical resonator cavity.

  6. A fluorescence scanning electron microscope

    Directory of Open Access Journals (Sweden)

    Takaaki Kanemaru

    2010-01-01

    Full Text Available Fluorescence techniques are widely used in biological research to examine molecular localization, while electron microscopy can provide unique ultrastructural information. To date, correlative images from both fluorescence and electron microscopy have been obtained separately using two different instruments, i.e. a fluorescence microscope (FM and an electron microscope (EM. In the current study, a scanning electron microscope (SEM (JEOL JXA8600 M was combined with a fluorescence digital camera microscope unit and this hybrid instrument was named a fluorescence SEM (FL-SEM. In the labeling of FL-SEM samples, both Fluolid, which is an organic EL dye, and Alexa Fluor, were employed. We successfully demonstrated that the FL-SEM is a simple and practical tool for correlative fluorescence and electron microscopy.

  7. The TALE Fluorescence Detectors

    Science.gov (United States)

    Jui, Charles

    2009-05-01

    The TALE fluorescence detectors are designed to extend the threshold for fluorescence observation by TA down to 3x10^16 eV. It will comprise two main components. The first is a set of 24 telescopes working in stereo, with an existing TA FD station at ˜6 km separation. These will cover between 3-31 degrees in elevation and have azimuthal coverage maximizing the stereo aperture in the 10^18-10^19 eV energy range. The second component consists of 15 telescopes equipped with 4m diameter mirrors and covering the sky between 31 and 73 degrees in elevation. The larger mirror size pushes the physics threshold down to 3x10^16 eV, and provides view of the shower maximum for the lower energy events. The Tower detector will cover one quadrant in azimuth and operate in hybrid mode with the TALE infill array to provide redundant composition measurements from both shower maximum information and muon-to-electron ratio.

  8. Fluorescent calixarenes as molecular receptors

    OpenAIRE

    Lynam, Carol

    2002-01-01

    The synthesis of calixarene L1 is described. This molecular sensor incorporates a fluorescent naphthyl moiety, the necessary fluorophore for optical transduction, whose fluorescent intensity alters to differing degrees on binding of enantiomers. Means of distinguishing between enantiomers of a chiral molecule are of critical importance in many areas of analytical chemistry and biotechnology, particularly in drug design and synthesis. Fluorescent quenching studies of calixarene L1 in methanol ...

  9. Magnetic resonance energy and topological resonance energy.

    Science.gov (United States)

    Aihara, Jun-Ichi

    2016-04-28

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

  10. Laser Induced Fluorescence of the Iodine Ion

    Science.gov (United States)

    Hargus, William

    2014-10-01

    Iodine (I2) has been considered as a potential electrostatic spacecraft thruster propellant for approximately 2 decades, but has only recently been demonstrated. Energy conversion efficiency appears to be on par with xenon without thruster modification. Intriguingly, performance appears to exceed xenon at high acceleration potentials. As part of a continuing program for the development of non-intrusive plasma diagnostics for advanced plasma spacecraft propulsion, we have identified the I II 5d5D4 o state as metastable, and therefore containing a reservoir of excited state ions suitable for laser probing. The 5d5D4 o - 6p5P3 transition at 695.878 nm is convenient for diode laser excitation with the 5s5S2 o - 6p5P3 transition at 516.12 nm as an ideal candidate for non-resonant fluorescence collection. We have constructed a Penning type iodine microwave discharge lamp optimized for I II production for table-top measurements. This work demonstrates I II laser-induced fluorescence in a representative iodine discharge and will validate our previous theoretical work based on the limited available historical I II spectral data.

  11. Plasmonic-enhanced fluorescence emission using D-shape microstructured optical fiber

    International Nuclear Information System (INIS)

    Highly sensitive side-polished D-shaped optical fiber sensors have been fabricated based on surface plasmon resonance (SPR) technology. Current techniques in plasmonic-enhanced total internal reflection microscopy (TIRM) and evanescent wave microscopy, although advantageous, require cumbersome set-ups and encompass large coupling losses. A gold coated D-shaped optical fiber was demonstrated to provide fluorescence enhanced spectroscopy. Comparison was made between a gold coated and uncoated D-shaped microstructured optical fiber (MOF) with respect to excitation of Rhodamine B (Rh B). Results highlighted improved fluorescence emission intensity and heightened sensitivity in fluorescence spectroscopy in the gold coated device, indicating potential in enhanced bio-imaging applications.

  12. Directional fluorescence emission co-enhanced by localized and propagating surface plasmons for biosensing

    Science.gov (United States)

    Wang, Yi; Wu, Lin; Wong, Ten It; Bauch, Martin; Zhang, Qingwen; Zhang, Jinling; Liu, Xiaohu; Zhou, Xiaodong; Bai, Ping; Dostalek, Jakub; Liedberg, Bo

    2016-04-01

    We investigated the simultaneous excitation of localized surface plasmons (LSPs) and propagating surface plasmons (PSPs) on a thin metallic film with an array of nanoholes for the enhancement of fluorescence intensity in heterogeneous bioassays. Experiments supported by simulations reveal that the co-excitation of PSP and LSP modes on the nanohole array in a Kretschmann configuration allows for fluorescence enhancement of about 102 as compared to a flat Au surface irradiated off-resonance. Moreover, this fluorescence signal was about 3-fold higher on the substrate supporting both PSPs and LSPs than that on a flat surface where only PSPs were resonantly excited. Simulations also indicated the highly directional fluorescence emission as well as the high fluorescence collection efficiency on the nanohole array substrate. Our contribution attempts to de-convolute the origin of this enhancement and identify further ways to maximize the efficiency of surface plasmon-enhanced fluorescence spectroscopy for implementation in ultra-sensitive bioassays.We investigated the simultaneous excitation of localized surface plasmons (LSPs) and propagating surface plasmons (PSPs) on a thin metallic film with an array of nanoholes for the enhancement of fluorescence intensity in heterogeneous bioassays. Experiments supported by simulations reveal that the co-excitation of PSP and LSP modes on the nanohole array in a Kretschmann configuration allows for fluorescence enhancement of about 102 as compared to a flat Au surface irradiated off-resonance. Moreover, this fluorescence signal was about 3-fold higher on the substrate supporting both PSPs and LSPs than that on a flat surface where only PSPs were resonantly excited. Simulations also indicated the highly directional fluorescence emission as well as the high fluorescence collection efficiency on the nanohole array substrate. Our contribution attempts to de-convolute the origin of this enhancement and identify further ways to maximize

  13. Rapid global fitting of large fluorescence lifetime imaging microscopy datasets.

    Directory of Open Access Journals (Sweden)

    Sean C Warren

    Full Text Available Fluorescence lifetime imaging (FLIM is widely applied to obtain quantitative information from fluorescence signals, particularly using Förster Resonant Energy Transfer (FRET measurements to map, for example, protein-protein interactions. Extracting FRET efficiencies or population fractions typically entails fitting data to complex fluorescence decay models but such experiments are frequently photon constrained, particularly for live cell or in vivo imaging, and this leads to unacceptable errors when analysing data on a pixel-wise basis. Lifetimes and population fractions may, however, be more robustly extracted using global analysis to simultaneously fit the fluorescence decay data of all pixels in an image or dataset to a multi-exponential model under the assumption that the lifetime components are invariant across the image (dataset. This approach is often considered to be prohibitively slow and/or computationally expensive but we present here a computationally efficient global analysis algorithm for the analysis of time-correlated single photon counting (TCSPC or time-gated FLIM data based on variable projection. It makes efficient use of both computer processor and memory resources, requiring less than a minute to analyse time series and multiwell plate datasets with hundreds of FLIM images on standard personal computers. This lifetime analysis takes account of repetitive excitation, including fluorescence photons excited by earlier pulses contributing to the fit, and is able to accommodate time-varying backgrounds and instrument response functions. We demonstrate that this global approach allows us to readily fit time-resolved fluorescence data to complex models including a four-exponential model of a FRET system, for which the FRET efficiencies of the two species of a bi-exponential donor are linked, and polarisation-resolved lifetime data, where a fluorescence intensity and bi-exponential anisotropy decay model is applied to the analysis

  14. Green fluorescence of terbium ions in lithium fluoroborate glasses for fibre lasers and display devices

    Indian Academy of Sciences (India)

    G R DILLIP; C MADHUKAR REDDY; M RAJESH; SHIVANAND CHAURASIA; B DEVA PRASAD RAJU; S W JOO

    2016-06-01

    In this paper, for the first time, the visible fluorescence properties, resonance energy transfer mechanism responsible for non-radiative decay rates of ${}^5$D$_4$ $\\to$ ${}^7$F$_5$ transition and also quenching of fluorescence intensity of the ${}^5$D$_3$ $\\to$ ${}^7$F$_5$ transition of various concentrations of Tb$^{3+}$ ions in LBZLFB glasses are reported. Optical absorption, fluorescence spectra and quantum efficiencies are measured and analysed. Green fluorescence related to ${}^5$D$_4$ $\\to$ ${}^7$F$_5$ (548 nm) transition is registered under excitation of 378 nm of Tb$^{3+}$ ions. Based on excitation and fluorescence measurements, several spectroscopic parameters for Tb$^{3+}$ ions are examined as a function of concentration by Judd–Ofelt theory to judge the suitability of studied glasses for display devices and fibre lasers.

  15. Silica nanocapsules of fluorescent conjugated polymers and superparamagnetic nanocrystals for dual-mode cellular imaging.

    Science.gov (United States)

    Tan, Happy; Wang, Miao; Yang, Chang-Tong; Pant, Shilpa; Bhakoo, Kishore Kumar; Wong, Siew Yee; Chen, Zhi-Kuan; Li, Xu; Wang, John

    2011-06-01

    We describe here a facile and benign synthetic strategy to integrate the fluorescent behavior of conjugated polymers and superparamagnetic properties of iron oxide nanocrystals into silica nanocapsules, forming a new type of bifunctional magnetic fluorescent silica nanocapsule (BMFSN). The resultant BMFSNs are uniform, colloidally stable in aqueous medium, and exhibit the desired dual functionality of fluorescence and superparamagnetism in a single entity. Four conjugated polymers with different emissions were used to demonstrate the versatility of employing this class of fluorescent materials for the preparation of BMFSNs. The applicability of BMFSNs in cellular imaging was studied by incubating them with human liver cancer cells, the result of which demonstrated that the cells could be visualized by dual-mode fluorescence and magnetic resonance imaging. Furthermore, the superparamagnetic behavior of the BMFSNs was exploited for in vitro magnetic-guided delivery of the nanocapsules into the cancer cells, thereby highlighting their potential for targeting biomedical applications.

  16. Detection of brain tumors using fluorescence diffuse optical tomography and nanoparticles as contrast agents

    Science.gov (United States)

    Fortin, Pierre-Yves; Genevois, Coralie; Koenig, Anne; Heinrich, Emilie; Texier, Isabelle; Couillaud, Franck

    2012-12-01

    Near-infrared fluorescence-enhanced diffuse optical tomography (fDOT) is used to localize tumors in mice using fluorescent nanoparticles as a blood pool contrast agent. The infrared dye DiR is loaded in the lipid core of nontargeted nanoparticles (DiR-lipidots) and injected systemically via the tail vein in mice bearing U87 tumors. Distribution and time-course of DiR-lipidots are followed using in vivo fluorescence reflectance imaging and reveal enhanced fluorescent signal within the subcutaneous tumors up to seven days due to the enhanced permeability and retention effect. Tumor growth into the brain is followed using bioluminescent imaging, and tumor localization is further determined by magnetic resonance imaging. The fDOT provides three-dimensional fluorescent maps that allow for consistent localization for both subcutaneous and brain tumors.

  17. Resonance energy transfer: Dye to metal nanoparticles

    International Nuclear Information System (INIS)

    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

  18. 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.

  19. Polyacrylamide hydrogel encapsulated E. coli expressing metal-sensing green fluorescent protein as a potential tool for copper ion determination.

    Science.gov (United States)

    Tantimongcolwat, Tanawut; Isarankura-Na-Ayudhya, Chartchalerm; Srisarin, Apapan; Galla, Hans-Joachim; Prachayasittikul, Virapong

    2014-01-01

    A simple, inexpensive and field applicable metal determination system would be a powerful tool for the efficient control of metal ion contamination in various sources e.g. drinking-water, water reservoir and waste discharges. In this study, we developed a cell-based metal sensor for specific and real-time detection of copper ions. E. coli expressing metal-sensing green fluorescent protein (designated as TG1/(CG)6GFP and TG1/H6CdBP4GFP) were constructed and served as a metal analytical system. Copper ions were found to exert a fluorescence quenching effect, while zinc and cadmium ions caused minor fluorescence enhancement in the engineered bacterial suspension. To construct a user-friendly and reagentless metal detection system, TG1/H6CdBP4GFP and TG1/(CG)6GFP were encapsulated in polyacrylamide hydrogels that were subsequently immobilized on an optical fiber equipped with a fluorescence detection module. The sensor could be applied to measure metal ions by simply dipping the encapsulated bacteria into a metal solution and monitoring fluorescence changes in real time as a function of the metal concentration in solution. The sensor system demonstrated high specificity toward copper ions. The fluorescence intensities of the encapsulated TG1/(CG)6GFP and TG1/H6CdBP4GFP were quenched by approximately 70 % and 80 % by a high-dose of copper ions (50 mM), respectively. The level of fluorescence quenching exhibited a direct correlation with the copper concentration, with a linear correlation coefficient (r) of 0.99. The cell-based metal sensor was able to efficiently monitor copper concentrations ranging between 5 M and 50 mM, encompassing the maximum allowed copper contamination in drinking water (31.15 M) established by the WHO. Furthermore, the cell-based metal sensor could undergo prolonged storage for at least 2 weeks without significantly influencing the copper sensitivity. PMID:26417267

  20. Raman Scattering at Resonant or Near-Resonant Conditions: A Generalized Short-Time Approximation

    Institute of Scientific and Technical Information of China (English)

    Abdelsalam Mohammed; Yu-Ping Sun; Quan Miao; Hans (A)gren; Faris Gel'mukhanov

    2012-01-01

    We investigate the dynamics of resonant Raman scattering in the course of the frequency detuning.The dephasing in the time domain makes the scattering fast when the photon energy is tuned from the absorption resonance.This makes frequency detuning to act as a camera shutter with a regulated scattering duration and provides a practical tool of controlling the scattering time in ordinary stationary measurements.The theory is applied to resonant Raman spectra of a couple of few-mode model systems and to trans-1,3,5-hexatriene and guanine-cytosine (G-C) Watson-Crick base pairs (DNA) molecules.Besides some particular physical effects,the regime of fast scattering leads to a simplification of the spectrum as well as to the scattering theory itself.Strong overtones appear in the Raman spectra when the photon frequency is tuned in the resonant region,while in the mode of fast scattering,the overtones are gradually quenched when the photon frequency is tuned more than one vibrational quantum below the first absorption resonance.The detuning from the resonant region thus leads to a strong purification of the Raman spectrum from the contamination by higher overtones and soft modes and purifies the spectrum also in terms of avoidance of dissociation and interfering fluorescence decay of the resonant state.This makes frequency detuning a very useful practical tool in the analysis of the resonant Raman spectra of complex systems and considerably improves the prospects for using the Raman effect for detection of foreign substances at ultra-low concentrations.

  1. X-ray Fluorescence Sectioning

    CERN Document Server

    Cong, Wenxiang

    2012-01-01

    In this paper, we propose an x-ray fluorescence imaging system for elemental analysis. The key idea is what we call "x-ray fluorescence sectioning". Specifically, a slit collimator in front of an x-ray tube is used to shape x-rays into a fan-beam to illuminate a planar section of an object. Then, relevant elements such as gold nanoparticles on the fan-beam plane are excited to generate x-ray fluorescence signals. One or more 2D spectral detectors are placed to face the fan-beam plane and directly measure x-ray fluorescence data. Detector elements are so collimated that each element only sees a unique area element on the fan-beam plane and records the x-ray fluorescence signal accordingly. The measured 2D x-ray fluorescence data can be refined in reference to the attenuation characteristics of the object and the divergence of the beam for accurate elemental mapping. This x-ray fluorescence sectioning system promises fast fluorescence tomographic imaging without a complex inverse procedure. The design can be ad...

  2. Assessing Photosynthesis by Fluorescence Imaging

    Science.gov (United States)

    Saura, Pedro; Quiles, Maria Jose

    2011-01-01

    This practical paper describes a novel fluorescence imaging experiment to study the three processes of photochemistry, fluorescence and thermal energy dissipation, which compete during the dissipation of excitation energy in photosynthesis. The technique represents a non-invasive tool for revealing and understanding the spatial heterogeneity in…

  3. Excitonic surface lattice resonances

    Science.gov (United States)

    Humphrey, A. D.; Gentile, M. J.; Barnes, W. L.

    2016-08-01

    Electromagnetic resonances are important in controlling light at the nanoscale. The most studied such resonance is the surface plasmon resonance that is associated with metallic nanostructures. Here we explore an alternative resonance, the surface exciton-polariton resonance, one based on excitonic molecular materials. Our study is based on analytical and numerical modelling. We show that periodic arrays of suitable molecular nanoparticles may support surface lattice resonances that arise as a result of coherent interactions between the particles. Our results demonstrate that excitonic molecular materials are an interesting alternative to metals for nanophotonics; they offer the prospect of both fabrication based on supramolecular chemistry and optical functionality arising from the way the properties of such materials may be controlled with light.

  4. Resonance ionization spectroscopy 1986

    International Nuclear Information System (INIS)

    The paper presents the proceedings of the Third International Symposium on Resonance Ionization Spectroscopy and its Applications, held at the University College of Swansea, Wales, 1986. The Symposium is divided into eight main sections entitled: photophysics and spectroscopy, noble gas atom counting, resonance ionization mass spectrometry, materials and surface analysis, small molecules, medical and environmental applications, resonance ionization and materials separation, and elementary particles and nuclear physics. Thirty papers were chosen for INIS and indexed separately. (U.K.)

  5. Dynamically generated resonances

    CERN Document Server

    Oset, E; Sarkar, S; Sun, Bao Xi; Vacas, M J Vicente; González, P; Vijande, J; Jido, D; Sekihara, T; Torres, A Martinez; Khemchandani, K

    2009-01-01

    In this talk I report on recent work related to the dynamical generation of baryonic resonances, some made up from pseudoscalar meson-baryon, others from vector meson-baryon and a third type from two meson-one baryon systems. We can establish a correspondence with known baryonic resonances, reinforcing conclusions previously drawn and bringing new light on the nature of some baryonic resonances of higher mass.

  6. Time-resolved fluorescence spectroscopy

    International Nuclear Information System (INIS)

    This article addresses the evolution in time of light emitted by a molecular system after a brief photo-excitation. The authors first describe fluorescence from a photo-physical point of view and discuss the characterization of the excited state. Then, they explain some basic notions related to fluorescence characterization (lifetime and decays, quantum efficiency, so on). They present the different experimental methods and techniques currently used to study time-resolved fluorescence. They discuss basic notions of time resolution and spectral reconstruction. They briefly present some conventional methods: intensified Ccd cameras, photo-multipliers and photodiodes associated with a fast oscilloscope, and phase modulation. Other methods and techniques are more precisely presented: time-correlated single photon counting (principle, examples, and fluorescence lifetime imagery), streak camera (principle, examples), and optical methods like the Kerr optical effect (principle and examples) and fluorescence up-conversion (principle and theoretical considerations, examples of application)

  7. Optical Properties of Fluorescent Dyes

    Institute of Scientific and Technical Information of China (English)

    李戎; 陈东辉

    2001-01-01

    Fluorescent dyes have been widely used these years.Because of the special optical performance, conventional CCM systems seem to be unable to predict the recipes of fabrics dyed with fluorescent dyes. In order to enhance the functions of CCM systems, the optical properties of fluorescent dyes in their absorption region were investigated. It has been found that there was a fixed maximum absorption wavelength for each fluorescent dyes whatever its concentration is. Both absorption region and maximum absorption wavelength of the dyes in solution are the same to those in fabric, and that the absorption is directly proportional to the concentration of the dye. So the optical properties obtained in solutions cna be applied for describing the optics performance of fluorescent dyes in fabrics.

  8. Non-blinking quantum dot with a plasmonic nanoshell resonator.

    Science.gov (United States)

    Ji, Botao; Giovanelli, Emerson; Habert, Benjamin; Spinicelli, Piernicola; Nasilowski, Michel; Xu, Xiangzhen; Lequeux, Nicolas; Hugonin, Jean-Paul; Marquier, Francois; Greffet, Jean-Jacques; Dubertret, Benoit

    2015-02-01

    Colloidal semiconductor quantum dots are fluorescent nanocrystals exhibiting exceptional optical properties, but their emission intensity strongly depends on their charging state and local environment. This leads to blinking at the single-particle level or even complete fluorescence quenching, and limits the applications of quantum dots as fluorescent particles. Here, we show that a single quantum dot encapsulated in a silica shell coated with a continuous gold nanoshell provides a system with a stable and Poissonian emission at room temperature that is preserved regardless of drastic changes in the local environment. This novel hybrid quantum dot/silica/gold structure behaves as a plasmonic resonator with a strong Purcell factor, in very good agreement with simulations. The gold nanoshell also acts as a shield that protects the quantum dot fluorescence and enhances its resistance to high-power photoexcitation or high-energy electron beams. This plasmonic fluorescent resonator opens the way to a new family of plasmonic nanoemitters with robust optical properties. PMID:25581887

  9. Electron paramagnetic resonance

    CERN Document Server

    Al'tshuler, S A

    2013-01-01

    Electron Paramagnetic Resonance is a comprehensive text on the field of electron paramagnetic resonance, covering both the theoretical background and the results of experiment. This book is composed of eight chapters that cover theoretical materials and experimental data on ionic crystals, since these are the materials that have been most extensively studied by the methods of paramagnetic resonance. The opening chapters provide an introduction to the basic principles of electron paramagnetic resonance and the methods of its measurement. The next chapters are devoted to the theory of spectra an

  10. Two-dimensional fluorescence spectroscopy of laser-produced plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Harilal, Sivanandan S.; LaHaye, Nicole L.; Phillips, Mark C.

    2016-08-01

    We use a two-dimensional laser-induced fluorescence spectroscopy technique to measure the coupled absorption and emission properties of atomic species in plasmas produced via laser ablation of solid aluminum targets at atmospheric pressure. Emission spectra from the Al I 394.4 nm and Al I 396.15 nm transitions are measured while a frequency-doubled, continuous-wave, Ti:Sapphire laser is tuned across the Al I 396.15 nm transition. The resulting two-dimensional spectra show the energy coupling between the two transitions via increased emission intensity for both transitions during resonant absorption of the continuous-wave laser at one transition. Time-delayed and gated detection of the emission spectrum is used to isolate the resonantly-excited fluorescence emission from the thermally-excited emission from the plasma. In addition, the tunable continuous-wave laser measures the absorption spectrum of the Al transition with ultra-high resolution after the plasma has cooled, resulting in narrower spectral linewidths than observed in emission spectra. Our results highlight that fluorescence spectroscopy employing continuous-wave laser re-excitation after pulsed laser ablation combines benefits of both traditional emission and absorption spectroscopic methods.

  11. Improved "optical highlighter" probes derived from discosoma red fluorescent protein.

    Science.gov (United States)

    Robinson, Lisbeth C; Marchant, Jonathan S

    2005-02-01

    The tetrameric red fluorescent protein, DsRed, undergoes a rapid red to green color change evoked by short wavelength (lambda highlighter" probe for tracking live cells, organelles, and fusion proteins. This color change results from selective bleaching of the "mature" red-emitting species of DsRed and an enhancement of emission from the "immature" green species, likely caused by dequenching of fluorescence resonance energy transfer occurring within the protein tetramer. Here, we have examined the role of residues known to influence the rate and completeness of chromophore maturation on the cellular and biophysical properties of DsRed mutants. Surprisingly, a single amino acid mutation (N42Q) with increased basal green emission yet rapid chromophore maturation displayed a multiphoton-evoked color change that was brighter, more consistent, more vivid, and easier to evoke than DsRed, despite the larger proportion of green chromophores. Rapidly maturing mutants with more complete chromophore maturation, exhibited little color change and increased resistance to multiphoton bleaching. We describe improved optical and cell biological properties for two DsRed-derived variants which we showcase in photolabeling studies, and discuss these data in terms of implications for fluorescence resonance energy transfer-based probes.

  12. Shedding Some Light on Fluorescent Bulbs.

    Science.gov (United States)

    Guilbert, Nicholas R.

    1996-01-01

    Explores some of the principles behind the working of fluorescent bulbs using a specially prepared fluorescent bulb with the white inner fluorescent coating applied along only half its length. Discusses the spectrum, the bulb plasma, and light production. (JRH)

  13. Split ring resonator resonance assisted terahertz antennas

    CERN Document Server

    Galal, Hossam; Vitiello, Miriam S

    2016-01-01

    We report on the computational development of novel architectures of low impedance broadband antennas, for efficient detection of Terahertz (THz) frequency beams. The conceived Split Ring Resonator Resonance Assisted (SRR RA) antennas are based on both a capacitive and inductive scheme, exploiting a 200 Ohm and 400 Ohm impedance, respectively. Moreover, the impedance is tunable by varying the coupling parameters in the exploited geometry, allowing for better matching with the detector circuit for maximum power extraction. Our simulation results have been obtained by assuming a 1.5 THz operation frequency.

  14. Oligomerization of epidermal growth factor receptors (EGFR) on A431 cells studied by time-resolved fluorescence imaging microscopy: a stereochemical model for tyrosine kinase receptor activation

    NARCIS (Netherlands)

    Th.W.J. Gadella; T.M. Jovin

    1995-01-01

    The aggregation states of the epidermal growth factor receptor (EGFR) on single A431 human epidermoid carcinoma cells were assessed with two new techniques for determining fluorescence resonance en- ergy transfer: donor photobleaching fluorescence reso- nance energy transfer (pbFRET) microscopy and

  15. Rise-time of FRET-acceptor fluorescence tracks protein folding

    NARCIS (Netherlands)

    Lindhoud, S.; Westphal, A.H.; Van Mierlo, C.P.M.; Visser, A.J.W.G.; Borst, J.W.

    2014-01-01

    Uniform labeling of proteins with fluorescent donor and acceptor dyes with an equimolar ratio is paramount for accurate determination of Förster resonance energy transfer (FRET) efficiencies. In practice, however, the labeled protein population contains donor-labeled molecules that have no correspon

  16. Compound parabolic concentrator optical fiber tip for FRET-based fluorescent sensors

    DEFF Research Database (Denmark)

    Hassan, Hafeez Ul; Nielsen, Kristian; Aasmul, Soren;

    2015-01-01

    The Compound Parabolic Concentrator (CPC) optical fiber tip shape has been proposed for intensity based fluorescent sensors working on the principle of FRET (Förster Resonance Energy Transfer). A simple numerical Zemax model has been used to optimize the CPC tip geometry for a step-index multimode...

  17. High content screening for G protein-coupled receptors using cell-based protein translocation assays

    DEFF Research Database (Denmark)

    Grånäs, Charlotta; Lundholt, Betina Kerstin; Heydorn, Arne;

    2005-01-01

    the capability to probe GPCR function at the cellular level with better resolution than has previously been possible, and offer practical strategies for more definitive selectivity evaluation and counter-screening in the early stages of drug discovery. The potential of cell-based translocation assays for GPCR...... will continue to be valuable discovery tools, the most exciting developments in the field involve cell-based assays for GPCR function. Some cell-based discovery strategies, such as the use of beta-arrestin as a surrogate marker for GPCR function, have already been reduced to practice, and have been used...... as valuable discovery tools for several years. The application of high content cell-based screening to GPCR discovery has opened up additional possibilities, such as direct tracking of GPCRs, G proteins and other signaling pathway components using intracellular translocation assays. These assays provide...

  18. Far-field infrared super-resolution microscopy using picosecond time-resolved transient fluorescence detected IR spectroscopy

    Science.gov (United States)

    Sakai, Makoto; Kawashima, Yasutake; Takeda, Akihiro; Ohmori, Tsutomu; Fujii, Masaaki

    2007-05-01

    A new far-field infrared super-resolution microscopy combining laser fluorescence microscope and picosecond time-resolved transient fluorescence detected IR (TFD-IR) spectroscopy is proposed. TFD-IR spectroscopy is a kind of IR-visible/UV double resonance spectroscopy, and detects IR transitions by the transient fluorescence due to electronic transition originating from vibrationally excited level populated by IR light. IR images of rhodamine-6G solution and of fluorescent beads were clearly observed by monitoring the transient fluorescence. Super-resolution twice higher than the diffraction limit for IR light was achieved. The IR spectrum due to the transient fluorescence was also measured from spatial domains smaller than the diffraction limit.

  19. FLEX: fluorescence explorer

    Science.gov (United States)

    Stoll, Marc-Ph.; Court, Andrew; Smorenburg, Kees; Visser, Huib; Crocco, Luiggi; Heilimo, Jyro; Honig, Andre

    1999-12-01

    FLEX is a scientifically driven space mission to provide demonstration/validation of the instrumentation and technique for measuring the natural fluorescence of vegetation in the Fraunhofer lines. The payload consists of high spectral resolution (0.1 - 0.3 nm) CCD imaging grating spectrometer with two channels: one in the red (648 - 664 nm) and one in the blue (391 - 438 nm) for working with several Fraunhofer lines. The across track FOV is 8.4 degrees; ground spatial resolution is better than 0.5 X 0.5 km2. To increase the S/N ratio a steering mirror will be used, if necessary, to 'freeze' the image and also to provide plus or minus 4 degrees across track depointing. Calibration is made by viewing the sun via a diffuser plate switched into the telescope field of view. A separate CCD camera will allow cloud detection and scene identification. A TIR radiometer will provide simultaneous surface temperature measurements. The spacecraft, overall mass estimated at 200 kg, is derived from the ASI-MITA bus which provides all the necessary subsystems and stabilized platform. By use of on-board storage, ground requirements for satellite control and data link are minimized; the possibility of local stations for real time reception/distribution is also envisaged. Provisional orbit characteristics are: LEO sun synchronous, 500 - 900 km altitude. Priority will be given to highest revisit frequency on a sufficient number of selected test sites.

  20. Efficient isotropic magnetic resonators

    OpenAIRE

    Martin, O. J. F.; Gay-Balmaz, P.

    2002-01-01

    We study experimentally and numerically a novel three-dimensional magnetic resonator structure with high isotropy. It is formed by crossed split-ring resonators and has a response independent of the illumination direction in a specific plane. The utilization of such elements to build a finite left-handed medium is discussed. (C) 2002 American Institute of Physics.