Kα resonance fluorescence in Al, Ti, Cu and potential applications for X-ray sources

Science.gov (United States)

Nahar, Sultana N.; Pradhan, Anil K.

2015-04-01

The Kα resonance fluorescence (RFL) effect via photoabsorptions of inner shell electrons as the element goes through multiple ionization states is studied. We demonstrate that the resonances observed recently in Kα (1s-2p) fluorescence in aluminum plasmas by using a high-intensity X-ray free-electron laser [1] are basically K-shell resonances in hollow atoms going through multiple ionization states at resonant energies as predicted earlier for gold and iron ions [2]. These resonances are formed below the K-shell ionization edge and shift toward higher energies with ionization states, as observed. Fluorescence emission intensities depend on transition probabilities for each ionization stage of the given element for all possible Kα (1 s → 2 p) transition arrays. The present calculations for resonant photoabsorptions of Kα photons in Al have reproduced experimentally observed features. Resonant cross sections and absorption coefficients are presented for possible observation of Kα RFL in the resonant energy ranges of 4.5-5.0 keV for Ti ions and 8.0-8.7 keV for Cu ions respectively. We suggest that theoretically the Kα RFL process may be driven to enhance the Auger cycle by a twin-beam monochromatic X-ray source, tuned to the K-edge and Kα energies, with potential applications such as the development of narrow-band biomedical X-ray devices.

Fluorescence resonance energy transfer imaging of CFP/YFP labeled NDH in cyanobacterium cell

International Nuclear Information System (INIS)

Ji Dongmei; Lv Wei; Huang Zhengxi; Xia Andong; Xu Min; Ma Weimin; Mi Hualing; Ogawa Teruo

2007-01-01

The laser confocal scanning microscopy combined with time-correlated single photon counting imaging technique to obtain fluorescence intensity and fluorescence lifetime images for fluorescence resonance energy transfer measurement is reported. Both the fluorescence lifetime imaging microscopy (FLIM) and intensity images show inhomogeneous cyan fluorescent protein and yellow fluorescent protein (CFP /YFP) expression or inhomogeneous energy transfer between CFP and YFP over whole cell. The results presented in this work show that FLIM could be a potential method to reveal the structure-function behavior of NAD(P)H dehydrogenase complexes in living cell

Imaging atoms from resonance fluorescence spectrum beyond the diffraction limit

Science.gov (United States)

Liao, Zeyang; Al-Amri, Mohammad; Zubairy, M. Suhail

2014-03-01

We calculate the resonance fluorescence spectrum of a linear chain of two-level atoms driven by a gradient coherent laser field. The result shows that we can determine the positions of atoms from the spectrum even when the atoms locate within subwavelength range and the dipole-dipole interaction is significant. This far-field resonance fluorescence localization microscopy method does not require point-by-point scanning and it may be more time-efficient. We also give a possible scheme to extract the position information in an extended region without requiring more peak power of laser. We also briefly discuss how to do a 2D imaging based on our scheme. This work is supported by grants from the King Abdulaziz City for Science and Technology (KACST) and the Qatar National Research Fund (QNRF) under the NPRP project.

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.

Resonance fluorescence spectra of a three-level atom driven by two strong laser fields

International Nuclear Information System (INIS)

Peng Jinsheng.

1986-12-01

The resonance fluorescence of a three-level atom interacted with two high-power laser fields is investigated in strong field approximation. The fluorescence distribution is obtained by means of the theory of dressing transformation. (author). 15 refs, 2 figs

Preparation and characterization of alginate based-fluorescent magnetic nanoparticles for fluorescence/magnetic resonance multimodal imaging applications

Science.gov (United States)

Kwon, Yong-Su; Choi, Kee-Bong; Lim, Hyungjun; Lee, Sunghwi; Lee, Jae-Jong

2018-06-01

Simple and versatile methodologies have been reported that customize the surface of superparamagnetic iron oxide (SPIO) nanoparticles and impart additional fluorescence capabilities to these contrast agents. Herein, we present the rational design, synthesis, characterization, and biological applications of a new magnetic-based fluorescent probe. The dual modality imaging protocol was developed by labeling fluorophore with alginate natural polymers that have excellent biocompatibility and biodegradability, and using gelification method to form nanocomposites containing SPIO. The formation of alginate-based fluorescent magnetic (AFM) nanoparticles was observed in spherical and elliptical forms with a diameter of less than 500 nm by a transmission electron microscope (TEM). The fluorescent wavelength band in the range of 560 nm was also confirmed in the UV–visible spectrophotometer. In this study, we demonstrate that the multi-tasking design of AFM nanoparticles provides an ideal platform for building balanced dual-image probes of magnetic resonance imaging and optical imaging.

Enhanced escape rate for Hg 254 nm resonance radiation in fluorescent lamps

International Nuclear Information System (INIS)

Lawler, James E; Raizen, Mark G

2013-01-01

The potential of the low-cost MAGIS isotopic separation method to improve fluorescent lamp efficacy is explored using resonance radiation transport simulations. New Hg isotopic mixes are discovered that yield escape rates for 254 nm Hg I resonance radiation equal to 117% to 122% of the rate for a natural isotopic mix under the same lamp conditions. (paper)

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...

Magnetic resonance tracking of fluorescent nanodiamond fabrication

International Nuclear Information System (INIS)

Shames, A I; Panich, A M; Osipov, V Yu; Vul’, A Ya; Boudou, J P; Treussart, F; Von Bardeleben, H J

2015-01-01

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  ×  10 18  spins/g of singlet (S = 1/2) substitutional nitrogen defects P1, as well as sp 3 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  ×  10 17  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  ×  10 19  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

Homogeneous non-competitive bioaffinity assay based on fluorescence resonance energy transfer

International Nuclear Information System (INIS)

Kokko, Tiina; Kokko, Leena; Soukka, Tero; Loevgren, Timo

2007-01-01

A homogeneous non-competitive assay principle for measurement of small analytes based on quenching of fluorescence is described. Fluorescence resonance energy transfer (FRET) occurs between the donor, intrinsically fluorescent europium(III)-chelate conjugated to streptavidin, and the acceptor, quencher dye conjugated to biotin derivative when the biotin-quencher is bound to Eu-streptavidin. Fluorescence can be measured only from those streptavidins that are bound to biotin of the sample, while the fluorescence of the streptavidins that are not occupied by biotin are quenched by quencher-biotin conjugates. The quenching efficiencies of the non-fluorescent quencher dyes were over 95% and one dye molecule was able to quench the fluorescence of more than one europium(III)-chelate. This, however, together with the quadrovalent nature of streptavidin limited the measurable range of the assay to 0.2-2 nmol L -1 . In this study we demonstrated that FRET could be used to design a non-competitive homogeneous assay for a small analyte resulting in equal performance with competitive heterogeneous assay

Metal Nanoparticles/Porous Silicon Microcavity Enhanced Surface Plasmon Resonance Fluorescence for the Detection of DNA

Directory of Open Access Journals (Sweden)

Jiajia Wang

2018-02-01

Full Text Available A porous silicon microcavity (PSiMC with resonant peak wavelength of 635 nm was fabricated by electrochemical etching. Metal nanoparticles (NPs/PSiMC enhanced fluorescence substrates were prepared by the electrostatic adherence of Au NPs that were distributed in PSiMC. The Au NPs/PSiMC device was used to characterize the target DNA immobilization and hybridization with its complementary DNA sequences marked with Rhodamine red (RRA. Fluorescence enhancement was observed on the Au NPs/PSiMC device substrate; and the minimum detection concentration of DNA ran up to 10 pM. The surface plasmon resonance (SPR of the MC substrate; which is so well-positioned to improve fluorescence enhancement rather the fluorescence enhancement of the high reflection band of the Bragg reflector; would welcome such a highly sensitive in biosensor.

Metal Nanoparticles/Porous Silicon Microcavity Enhanced Surface Plasmon Resonance Fluorescence for the Detection of DNA.

Science.gov (United States)

Wang, Jiajia; Jia, Zhenhong

2018-02-23

A porous silicon microcavity (PSiMC) with resonant peak wavelength of 635 nm was fabricated by electrochemical etching. Metal nanoparticles (NPs)/PSiMC enhanced fluorescence substrates were prepared by the electrostatic adherence of Au NPs that were distributed in PSiMC. The Au NPs/PSiMC device was used to characterize the target DNA immobilization and hybridization with its complementary DNA sequences marked with Rhodamine red (RRA). Fluorescence enhancement was observed on the Au NPs/PSiMC device substrate; and the minimum detection concentration of DNA ran up to 10 pM. The surface plasmon resonance (SPR) of the MC substrate; which is so well-positioned to improve fluorescence enhancement rather the fluorescence enhancement of the high reflection band of the Bragg reflector; would welcome such a highly sensitive in biosensor.

Nuclear Resonance Fluorescence and Isotopic Mapping of Containers

Science.gov (United States)

Johnson, Micah S.; McNabb, Dennis P.

2009-03-01

National security programs have expressed interest in developing systems to isotopically map shipping containers, fuel assemblies, and waste barrels for various materials including special nuclear material (SNM). Current radiographic systems offer little more than an ambiguous density silhouette of a container's contents. In this paper we will present a system being developed at LLNL to isotopically map containers using the nuclear resonance fluorescence (NRF) method. Recent experimental measurements on NRF strengths in SNM are discussed.

In situ detection of atomic and molecular iodine using Resonance and Off-Resonance Fluorescence by Lamp Excitation: ROFLEX

Directory of Open Access Journals (Sweden)

J. C. Gómez Martín

2011-01-01

Full Text Available We demonstrate a new instrument for in situ detection of atmospheric iodine atoms and molecules based on atomic and molecular resonance and off-resonance ultraviolet fluorescence excited by lamp emission. The instrument combines the robustness, light weight, low power consumption and efficient excitation of radio-frequency discharge light sources with the high sensitivity of the photon counting technique. Calibration of I₂ fluorescence is achieved via quantitative detection of the molecule by Incoherent Broad Band Cavity-enhanced Absorption Spectroscopy. Atomic iodine fluorescence signal is calibrated by controlled broad band photolysis of known I₂ concentrations in the visible spectral range at atmospheric pressure. The instrument has been optimised in laboratory experiments to reach detection limits of 1.2 pptv for I atoms and 13 pptv for I₂, for S/N = 1 and 10 min of integration time. The ROFLEX system has been deployed in a field campaign in northern Spain, representing the first concurrent observation of ambient mixing ratios of iodine atoms and molecules in the 1–350 pptv range.

Time-resolved resonance fluorescence spectroscopy for study of chemical reactions in laser-induced plasmas.

Science.gov (United States)

Liu, Lei; Deng, Leimin; Fan, Lisha; Huang, Xi; Lu, Yao; Shen, Xiaokang; Jiang, Lan; Silvain, Jean-François; Lu, Yongfeng

2017-10-30

Identification of chemical intermediates and study of chemical reaction pathways and mechanisms in laser-induced plasmas are important for laser-ablated applications. Laser-induced breakdown spectroscopy (LIBS), as a promising spectroscopic technique, is efficient for elemental analyses but can only provide limited information about chemical products in laser-induced plasmas. In this work, time-resolved resonance fluorescence spectroscopy was studied as a promising tool for the study of chemical reactions in laser-induced plasmas. Resonance fluorescence excitation of diatomic aluminum monoxide (AlO) and triatomic dialuminum monoxide (Al 2 O) was used to identify these chemical intermediates. Time-resolved fluorescence spectra of AlO and Al 2 O were used to observe the temporal evolution in laser-induced Al plasmas and to study their formation in the Al-O 2 chemistry in air.

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

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Zimmermann Timo

2009-11-01

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

Let's Exploit Available Knowledge on Vegetation Fluorescence

Science.gov (United States)

Magnani, Federico; Raddi, Sabrina; Mohammed, Gina; Middleton, Elizabeth M.

2014-01-01

The potential to measure vegetation fluorescence from space (1) and to derive from it direct information on the gross primary productivity (GPP) of terrestrial ecosystems is probably the most thrilling development in remote sensing and global ecology of recent years, as it moves Earth observation techniques from the detection of canopy biophysics (e.g., fraction of absorbed radiation) and biochemistry (chlorophyll and nitrogen content) to the realm of ecosystem function. The existence of a functional relationship between fluorescence and photosynthesis has been elucidated over the last decade by several laboratories, notably as part of the preliminary studies of the European Space Agency Fluorescence Explorer (FLEX) Earth Explorer Mission. The empirical observation presented by Guanter et al. (2) of a linear relationship between fluorescence radiance and GPP, however, provides the first experimental confirmation of the feasibility of the approach— already thoroughly tested at leaf level—at the desired scale, despite the confounding effects associated with the satellite detection of such a faint signal. A word of clarification is needed here. The use of fluorescence as a probe of leaf photochemistry has been a staple of plant ecophysiology for decades, rooted in a sound understanding of photosynthetic energy dissipation. However, most past studies had to rely for the interpretation of results on active (pulse-saturated) techniques, making them unsuitable for remote-sensing applications. Over recent years, however, novel process based models have been developed for the interpretation of steady-state, solar-induced fluorescence at the leaf to canopy scale (3). We are therefore in a position to move beyond the mere empirical observation of an association between GPP and fluorescence radiance. In particular, Guanter et al. (2) base their analysis on the assumption of a constant ratio between photosynthetic and fluorescence light use efficiencies (equation 3 in ref

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

Nuclear resonance fluorescence of {sup 203,205}Tl

Energy Technology Data Exchange (ETDEWEB)

Pfeifer, Fabian; Fritzsche, Matthias; Pietralla, Norbert; Savran, Deniz; Weller, Henry; Zweidinger, Markus [Institut fuer Kernphysik, Technische Universitaet, Darmstadt (Germany); Rusev, Gencho; Tonchev, Anton P.; Tornow, Werner [Triangle Universities Nuclear Laboratory, Duke University, Durham (United States); Zilges, Andreas [Institut fuer Kernphysik, Universitaet Koeln (Germany)

2009-07-01

In order to investigate the dipole strength distribution in Thalium isotopes we have studied Nuclear Resonance Fluorescence of a sample composed of natural Thallium (consisting of 30% {sup 203}Tl and 70% {sup 205}Tl). Unpolarized bremsstrahlung with photo energies up to 7.5 MeV was used at the High Intensity Photon Setup (HIPS) at S-DALINAC at the IKP Darmstadt. 24 fluorescent {gamma}-ray transitions were observed, 19 of them for the first time. For the assignment of the polarity of two prominent {gamma}-ray transitions, one at 4.7 MeV and one at 4.9 MeV, the polarized photon beam of the High Intensity {gamma}-ray Source (HI{gamma}S) at Duke University was used. The experiment at HI{gamma}S revealed the existence of a photo-excited state of {sup 205}Tl at an excitation energy of 4.971 MeV that exhibits a transition to the first excited state at 203 keV.

A dark-field microscope for background-free detection of resonance fluorescence from single semiconductor quantum dots operating in a set-and-forget mode.

Science.gov (United States)

Kuhlmann, Andreas V; Houel, Julien; Brunner, Daniel; Ludwig, Arne; Reuter, Dirk; Wieck, Andreas D; Warburton, Richard J

2013-07-01

Optically active quantum dots, for instance self-assembled InGaAs quantum dots, are potentially excellent single photon sources. The fidelity of the single photons is much improved using resonant rather than non-resonant excitation. With resonant excitation, the challenge is to distinguish between resonance fluorescence and scattered laser light. We have met this challenge by creating a polarization-based dark-field microscope to measure the resonance fluorescence from a single quantum dot at low temperature. We achieve a suppression of the scattered laser exceeding a factor of 10(7) and background-free detection of resonance fluorescence. The same optical setup operates over the entire quantum dot emission range (920-980 nm) and also in high magnetic fields. The major development is the outstanding long-term stability: once the dark-field point has been established, the microscope operates for days without alignment. The mechanical and optical designs of the microscope are presented, as well as exemplary resonance fluorescence spectroscopy results on individual quantum dots to underline the microscope's excellent performance.

A dark-field microscope for background-free detection of resonance fluorescence from single semiconductor quantum dots operating in a set-and-forget mode

International Nuclear Information System (INIS)

Kuhlmann, Andreas V.; Houel, Julien; Warburton, Richard J.; Brunner, Daniel; Ludwig, Arne; Reuter, Dirk; Wieck, Andreas D.

2013-01-01

Optically active quantum dots, for instance self-assembled InGaAs quantum dots, are potentially excellent single photon sources. The fidelity of the single photons is much improved using resonant rather than non-resonant excitation. With resonant excitation, the challenge is to distinguish between resonance fluorescence and scattered laser light. We have met this challenge by creating a polarization-based dark-field microscope to measure the resonance fluorescence from a single quantum dot at low temperature. We achieve a suppression of the scattered laser exceeding a factor of 10 7 and background-free detection of resonance fluorescence. The same optical setup operates over the entire quantum dot emission range (920–980 nm) and also in high magnetic fields. The major development is the outstanding long-term stability: once the dark-field point has been established, the microscope operates for days without alignment. The mechanical and optical designs of the microscope are presented, as well as exemplary resonance fluorescence spectroscopy results on individual quantum dots to underline the microscope's excellent performance

Graphene-based absorber exploiting guided mode resonances in one-dimensional gratings.

Science.gov (United States)

Grande, M; Vincenti, M A; Stomeo, T; Bianco, G V; de Ceglia, D; Aközbek, N; Petruzzelli, V; Bruno, G; De Vittorio, M; Scalora, M; D'Orazio, A

2014-12-15

A one-dimensional dielectric grating, based on a simple geometry, is proposed and investigated to enhance light absorption in a monolayer graphene exploiting guided mode resonances. Numerical findings reveal that the optimized configuration is able to absorb up to 60% of the impinging light at normal incidence for both TE and TM polarizations resulting in a theoretical enhancement factor of about 26 with respect to the monolayer graphene absorption (≈2.3%). Experimental results confirm this behavior showing CVD graphene absorbance peaks up to about 40% over narrow bands of a few nanometers. The simple and flexible design points to a way to realize innovative, scalable and easy-to-fabricate graphene-based optical absorbers.

Resonance fluorescence based two- and three-dimensional atom localization

Science.gov (United States)

Wahab, Abdul; Rahmatullah; Qamar, Sajid

2016-06-01

Two- and three-dimensional atom localization in a two-level atom-field system via resonance fluorescence is suggested. For the two-dimensional localization, the atom interacts with two orthogonal standing-wave fields, whereas for the three-dimensional atom localization, the atom interacts with three orthogonal standing-wave fields. The effect of the detuning and phase shifts associated with the corresponding standing-wave fields is investigated. A precision enhancement in position measurement of the single atom can be noticed via the control of the detuning and phase shifts.

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

Resonance fluorescence spectra of three-level atoms in a squeezed vacuum

International Nuclear Information System (INIS)

Ferguson, M.R.; Ficek, Z.; Dalton, B.J.

1996-01-01

The fluorescence field from one of the two allowed transitions in a three-level atom can sense squeezed fluctuations of a vacuum field coupled to the other transition. We examine the fluorescence spectra of strongly driven three-level atoms in Λ, V, and cascade configurations in which one of the two one-photon transitions is coupled to a finite-bandwidth squeezed vacuum field, when the bandwidth is much smaller than the difference in the atomic transition frequencies, though much larger than atomic decay rates and Rabi frequencies of the driving fields. The driving fields are on one-photon resonance, and the squeezed vacuum field is generated by a degenerate parameter oscillator. Details are only given for the Λ configuration. The extension to the V and cascade configurations is straightforward. We find that in all configurations the fluorescence spectra of the transition not coupled to the squeezed vacuum field are composed of five lines, one central and two pairs of sidebands, with intensities and widths strongly influenced by the squeezed vacuum field. However, only the central component and the outer sidebands exhibit a dependence on the squeezing phase. We also examine the fluorescence spectrum for the cascade configuration with a squeezed vacuum field on resonance with the two-photon transition between the ground and the most excited states and now generated by a nondegenerate parametric oscillator. In this case, where the squeezed vacuum field can be made coupled to both transitions, all spectral lines depend on the squeezing phase. The spectral features are explained in terms of the dressed-atom model of the system. We show that the coherent mixing of the atomic states by the strong driving fields modifies transition rates between the dressed states, which results in the selective phase dependence of the spectral features. copyright 1996 The American Physical Society

A wireless interrogation system exploiting narrowband acoustic resonator for remote physical quantity measurement

Energy Technology Data Exchange (ETDEWEB)

Friedt, J.-M [SENSeOR, 32 Avenue de l' Observatoire, 25044 Besancon (France); Droit, C.; Martin, G.; Ballandras, S. [Department of Time and Frequency, FEMTO-ST, 32 Avenue de l' Observatoire, 25044 Besancon (France)

2010-01-15

Monitoring physical quantities using acoustic wave devices can be advantageously achieved using the wave characteristic dependence to various parametric perturbations (temperature, stress, and pressure). Surface acoustic wave (SAW) resonators are particularly well suited to such applications as their resonance frequency is directly influenced by these perturbations, modifying both the phase velocity and resonance conditions. Moreover, the intrinsic radio frequency (rf) nature of these devices makes them ideal for wireless applications, mainly exploiting antennas reciprocity and piezoelectric reversibility. In this paper, we present a wireless SAW sensor interrogation unit operating in the 434 MHz centered ISM band--selected as a tradeoff between antenna dimensions and electromagnetic wave penetration in dielectric media--based on the principles of a frequency sweep network analyzer. We particularly focus on the compliance with the ISM standard which reveals complicated by the need for switching from emission to reception modes similarly to radar operation. In this matter, we propose a fully digital rf synthesis chain to develop various interrogation strategies to overcome the corresponding difficulties and comply with the above-mentioned standard. We finally assess the reader interrogation range, accuracy, and dynamics.

A wireless interrogation system exploiting narrowband acoustic resonator for remote physical quantity measurement

International Nuclear Information System (INIS)

Friedt, J.-M; Droit, C.; Martin, G.; Ballandras, S.

2010-01-01

Monitoring physical quantities using acoustic wave devices can be advantageously achieved using the wave characteristic dependence to various parametric perturbations (temperature, stress, and pressure). Surface acoustic wave (SAW) resonators are particularly well suited to such applications as their resonance frequency is directly influenced by these perturbations, modifying both the phase velocity and resonance conditions. Moreover, the intrinsic radio frequency (rf) nature of these devices makes them ideal for wireless applications, mainly exploiting antennas reciprocity and piezoelectric reversibility. In this paper, we present a wireless SAW sensor interrogation unit operating in the 434 MHz centered ISM band--selected as a tradeoff between antenna dimensions and electromagnetic wave penetration in dielectric media--based on the principles of a frequency sweep network analyzer. We particularly focus on the compliance with the ISM standard which reveals complicated by the need for switching from emission to reception modes similarly to radar operation. In this matter, we propose a fully digital rf synthesis chain to develop various interrogation strategies to overcome the corresponding difficulties and comply with the above-mentioned standard. We finally assess the reader interrogation range, accuracy, and dynamics.

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.

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

Science.gov (United States)

Barty, Christopher P. J. [Hayward, CA; Hartemann, Frederic V [San Ramon, CA; McNabb, Dennis P [Alameda, CA; Pruet, Jason A [Brentwood, CA

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.

Fluorescence-enhanced gadolinium-doped zinc oxide quantum dots for magnetic resonance and fluorescence imaging.

Science.gov (United States)

Liu, Yanlan; Ai, Kelong; Yuan, Qinghai; Lu, Lehui

2011-02-01

We report here the development of Gd-doped ZnO quantum dots (QDs) as dual modal fluorescence and magnetic resonance imaging nanoprobes. They are fabricated in a simple, versatile and environmentally friendly method, not only decreasing the difficulty and complexity, but also avoiding the increase of particle's size brought about by silica coating procedure in the synthesis of nanoprobes reported previously. These nanoprobes, with exceptionally small size and enhanced fluorescence resulting from the Gd doping, can label successfully the HeLa cells in short time and present no evidence of toxicity or adverse affect on cell growth even at the concentration up to 1 mm. These results show that such nanoprobes have low toxicity, especially in comparison with the traditional PEGylated CdSe/ZnS or CdSe/CdS QDs. In MRI studies, they exert strong positive contrast effect with a large longitudinal relaxivity (r(1)) of water proton of 16 mm(-1) s(-1). Their capability of imaging HeLa cells with MRI implies that they have great potential as MRI contrast agents. Combining the high sensitivity of fluorescence imaging with high spatial resolution of MRI, We expect that the as-prepared Gd-doped Zno QDs can provide a better reliability of the collected data and find promising applications in biological, medical and other fields. Copyright © 2010 Elsevier Ltd. All rights reserved.

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

International Nuclear Information System (INIS)

Zou, Lu; Sui, Ning; Wang, Ying-Hui; Qian, Cheng; Ma, Yu-Guang; Zhang, Han-Zhuang

2015-01-01

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

Sub-Poissonian photon statistics in time-dependent collective resonance fluorescence

International Nuclear Information System (INIS)

Buzek, V.; Tran Quang; Lan, L.H.

1989-10-01

We have discussed the photon statistics of the spectral components of N-atom time-dependent resonance fluorescence. It is shown that in contrast to the stationary limit, sub-Poissonian photon statistics in the sidebands occur for any number N of atoms including the case N >> 1. Reduction in Maldel's parameters Q ±1 is found with increasing numbers of atoms. The typical time for the presence of sub-Poissonian statistics is proportional to 1/N. (author). 31 refs, 1 fig

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

Science.gov (United States)

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

2015-04-01

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

Resonance Fluorescence of a Trapped Four-Level Atom with Bichromatic Driving

International Nuclear Information System (INIS)

Bergou, J.; Jakob, M.; Abranyos, Y.

1999-01-01

The resonance fluorescence spectrum of a bichromatically driven four-level atom is polarization dependent. Very narrow lines occur in the incoherent parts of the spectrum for polarization directions which are different from that of the driving fields. The degree of squeezing has a maximum of 56% which should make it easily observable. The second-order correlation function exhibits anti bunching for zero time delay and strong super bunching for certain values of the interaction parameter and time delay. For these parameters resonant two-photon emission takes place in the form of polarization entangled photon pairs. The system can be a novel source of photons in the EPR and/or Bell states. Some experiments will be proposed which make use of this unique source. (Authors)

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.

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

Science.gov (United States)

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

2016-12-15

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

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.

Correlated quadratures of resonance fluorescence and the generalized uncertainty relation

Science.gov (United States)

Arnoldus, Henk F.; George, Thomas F.; Gross, Rolf W. F.

1994-01-01

Resonance fluorescence from a two-state atom has been predicted to exhibit quadrature squeezing below the Heisenberg uncertainty limit, provided that the optical parameters (Rabi frequency, detuning, laser linewidth, etc.) are chosen carefully. When the correlation between two quadratures of the radiation field does not vanish, however, the Heisenberg limit for quantum fluctuations might be an unrealistic lower bound. A generalized uncertainty relation, due to Schroedinger, takes into account the possible correlation between the quadrature components of the radiation, and it suggests a modified definition of squeezing. We show that the coherence between the two levels of a laser-driven atom is responsible for the correlation between the quadrature components of the emitted fluorescence, and that the Schrodinger uncertainty limit increases monotonically with the coherence. On the other hand, the fluctuations in the quadrature field diminish with an increasing coherence, and can disappear completely when the coherence reaches 1/2, provided that certain phase relations hold.

Folic acid-targeted magnetic Tb-doped CeF3 fluorescent nanoparticles as bimodal probes for cellular fluorescence and magnetic resonance imaging.

Science.gov (United States)

Ma, Zhi-Ya; Liu, Yu-Ping; Bai, Ling-Yu; An, Jie; Zhang, Lin; Xuan, Yang; Zhang, Xiao-Shuai; Zhao, Yuan-Di

2015-10-07

Magnetic fluorescent nanoparticles (NPs) have great potential applications for diagnostics, imaging and therapy. We developed a facile polyol method to synthesize multifunctional Fe3O4@CeF3:Tb@CeF3 NPs with small size (CA) to obtain carboxyl-functionalized NPs (Fe3O4@CeF3:Tb@CeF3-COOH). Folic acid (FA) as an affinity ligand was then covalently conjugated onto NPs to yield Fe3O4@CeF3:Tb@CeF3-FA NPs. They were then applied as multimodal imaging agents for simultaneous in vitro targeted fluorescence imaging and magnetic resonance imaging (MRI) of HeLa cells with overexpressed folate receptors (FR). The results indicated that these NPs had strong luminescence and enhanced T2-weighted MR contrast and would be promising candidates as multimodal probes for both fluorescence and MRI imaging.

Photon-number statistics in resonance fluorescence

Science.gov (United States)

Lenstra, D.

1982-12-01

The theory of photon-number statistics in resonance fluorescence is treated, starting with the general formula for the emission probability of n photons during a given time interval T. The results fully confirm formerly obtained results by Cook that were based on the theory of atomic motion in a traveling wave. General expressions for the factorial moments are derived and explicit results for the mean and the variance are given. It is explicitly shown that the distribution function tends to a Gaussian when T becomes much larger than the natural lifetime of the excited atom. The speed of convergence towards the Gaussian is found to be typically slow, that is, the third normalized central moment (or the skewness) is proportional to T-12. However, numerical results illustrate that the overall features of the distribution function are already well represented by a Gaussian when T is larger than a few natural lifetimes only, at least if the intensity of the exciting field is not too small and its detuning is not too large.

Resonance fluorescence and quantum jumps in single atoms: Testing the randomness of quantum mechanics

International Nuclear Information System (INIS)

Erber, T.; Hammerling, P.; Hockney, G.; Porrati, M.; Putterman, S.; La Jolla Institute, La Jolla, California 92037; Department of Physics, University of California, Los Angeles, California 90024)

1989-01-01

When a single trapped 198 Hg + ion is illuminated by two lasers, each tuned to an approximate transition, the resulting fluorescence switches on and off in a series of pulses resembling a bistable telegraph. This intermittent fluorescence can also be obtained by optical pumping with a single laser. Quantum jumps between successive atomic levels may be traced directly with multiple-resonance fluorescence. Atomic transition rates and photon antibunching distributions can be inferred from the pulse statistics and compared with quantum theory. Stochastic tests also indicate that the quantum telegraphs are good random number generators. During periods when the fluorescence is switched off, the radiationless atomic currents that generate the telegraph signals can be adjusted by varying the laser illumination: if this coherent evolution of the wave functions is sustained over sufficiently long time intervals, novel interactive precision measurements, near the limits of the time-energy uncertainty relations, are possible. Copyright 1989 Academic Press, Inc

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

International Nuclear Information System (INIS)

Allen, Lucy R; Paci, Emanuele

2010-01-01

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

Resonance fluorescence microscopy via three-dimensional atom localization

Science.gov (United States)

Panchadhyayee, Pradipta; Dutta, Bibhas Kumar; Das, Nityananda; Mahapatra, Prasanta Kumar

2018-02-01

A scheme is proposed to realize three-dimensional (3D) atom localization in a driven two-level atomic system via resonance fluorescence. The field arrangement for the atom localization involves the application of three mutually orthogonal standing-wave fields and an additional traveling-wave coupling field. We have shown the efficacy of such field arrangement in tuning the spatially modulated resonance in all directions. Under different parametric conditions, the 3D localization patterns originate with various shapes such as sphere, sheets, disk, bowling pin, snake flute, flower vase. High-precision localization is achieved when the radiation field detuning equals twice the combined Rabi frequencies of the standing-wave fields. Application of a traveling-wave field of suitable amplitude at optimum radiation field detuning under symmetric standing-wave configuration leads to 100% detection probability even in sub-wavelength domain. Asymmetric field configuration is also taken into consideration to exhibit atom localization with appreciable precision compared to that of the symmetric case. The momentum distribution of the localized atoms is found to follow the Heisenberg uncertainty principle under the validity of Raman-Nath approximation. The proposed field configuration is suitable for application in the study of atom localization in an optical lattice arrangement.

Nuclear Resonance Fluorescence off 54Cr: The Onset of the Pygmy Dipole Resonance

Science.gov (United States)

Ries, P. C.; Beck, T.; Beller, J.; Krishichayan; Gayer, U.; Isaak, J.; Löher, B.; Mertes, L.; Pai, H.; Pietralla, N.; Romig, C.; Savran, D.; Schilling, M.; Tornow, W.; Werner, V.; Zweidinger, M.

2016-06-01

Low-lying electric and magnetic dipole excitations (E1 and M1) below the neutron separation threshold, particularly the Pygmy Dipole Resonance (PDR), have drawn considerable attention in the last years. So far, mostly moderately heavy nuclei in the mass regions around A = 90 and A = 140 were examined with respect to the PDR. In the present work, the systematics of the PDR have been extended by measuring excitation strengths and parity quantum numbers of J = 1 states in lighter nuclei near A = 50 in order to gather information on the onset of the PDR. The nuclei 50,52,54Cr and 48,50Ti were examined via bremsstrahlung produced at the DArmstadt Superconducting electron Linear Accelerator (S-DALINAC) with photon energies up to 9.7 MeV with the method of nuclear resonance fluorescence. Numerous excited states were observed, many of which for the first time. The parity quantum numbers of these states have been determined at the High Intensity Gamma-ray Source (HIγS) of the Triangle Universities Nuclear Laboratory in Durham, NC, USA. Informations to the methods and the experimental setups will be provided and the results on 54Cr achieved will be discussed with respect to the onset of the PDR.

Advances in Spiropyrans/Spirooxazines and Applications Based on Fluorescence Resonance Energy Transfer (FRET with Fluorescent Materials

Directory of Open Access Journals (Sweden)

Hongyan Xia

2017-12-01

Full Text Available Studies on the following were reviewed: (1 the structure of spiropyrans and spirooxazines (two kinds of spiro compounds under external stimuli and (2 the construction and applications of composite systems based on fluorescence resonance energy transfer (FRET with fluorescent materials. When treated with different stimuli (light, acids and bases, solvents, metal ions, temperature, redox potential, and so on, spiropyrans/spirooxazines undergo transformations between the ring-closed form (SP, the ring-opened merocyanine (MC form, and the protonated ring-opened form (MCH. This is due to the breakage of the spiro C–O bond and the protonation of MC, along with a color change. Various novel, multifunctional materials based on photochromic spiropyrans and spirooxazines have been successfully developed because of the vastly differently physiochemical properties posssed by the SP, MC and MCH forms. Among the three different structural forms, the MC form has been studied most extensively. The MC form not only gives complexes with various inorganic particles, biological molecules, and organic chemicals but also acts as the energy acceptor (of energy from fluorescent molecules during energy transfer processes that take place under proper conditions. Furthermore, spiropyran and spirooxazine compounds exhibit reversible physicochemical property changes under proper stimuli; this provides more advantages compared with other photochromic compounds. Additionally, the molecular structures of spiropyrans and spirooxazines can be easily modified and extended, so better compounds can be obtained to expand the scope of already known applications. Described in detail are: (1 the structural properties of spiropyrans and spirooxazines and related photochromic mechanisms; (2 composite systems based on spiropyrans and spirooxazines, and (3 fluorescent materials which have potential applications in sensing, probing, and a variety of optical elements.

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.

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

International Nuclear Information System (INIS)

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

2011-01-01

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

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

Development of a dielectrophoresis-assisted surface plasmon resonance fluorescence biosensor for detection of bacteria

Science.gov (United States)

Kuroda, Chiaki; Iizuka, Ryota; Ohki, Yoshimichi; Fujimaki, Makoto

2018-05-01

To detect biological substances such as bacteria speedily and accurately, a dielectrophoresis-assisted surface plasmon resonance (SPR) fluorescence biosensor is being developed. Using Escherichia coli as a target organism, an appropriate voltage frequency to collect E. coli cells on indium tin oxide quadrupole electrodes by dielectrophoresis is analyzed. Then, E. coli is stained with 4‧,6-diamidino-2-phenylindole (DAPI). To clearly detect fluorescence signals from DAPI-stained E. coli cells, the sensor is optimized so that we can excite SPR on Al electrodes by illuminating 405 nm photons. As a result, the number of fluorescence signals is increased on the electrodes by the application of a low-frequency voltage. This indicates that E. coli cells with a lower permittivity than the surrounding water are collected by negative dielectrophoresis onto the electrodes where the electric field strength is lowest.

Exploiting fluorescence for multiplex immunoassays on protein microarrays

International Nuclear Information System (INIS)

Herbáth, Melinda; Balogh, Andrea; Matkó, János; Papp, Krisztián; Prechl, József

2014-01-01

Protein microarray technology is becoming the method of choice for identifying protein interaction partners, detecting specific proteins, carbohydrates and lipids, or for characterizing protein interactions and serum antibodies in a massively parallel manner. Availability of the well-established instrumentation of DNA arrays and development of new fluorescent detection instruments promoted the spread of this technique. Fluorescent detection has the advantage of high sensitivity, specificity, simplicity and wide dynamic range required by most measurements. Fluorescence through specifically designed probes and an increasing variety of detection modes offers an excellent tool for such microarray platforms. Measuring for example the level of antibodies, their isotypes and/or antigen specificity simultaneously can offer more complex and comprehensive information about the investigated biological phenomenon, especially if we take into consideration that hundreds of samples can be measured in a single assay. Not only body fluids, but also cell lysates, extracted cellular components, and intact living cells can be analyzed on protein arrays for monitoring functional responses to printed samples on the surface. As a rapidly evolving area, protein microarray technology offers a great bulk of information and new depth of knowledge. These are the features that endow protein arrays with wide applicability and robust sample analyzing capability. On the whole, protein arrays are emerging new tools not just in proteomics, but glycomics, lipidomics, and are also important for immunological research. In this review we attempt to summarize the technical aspects of planar fluorescent microarray technology along with the description of its main immunological applications. (topical review)

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

Science.gov (United States)

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

2015-12-15

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

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

International Nuclear Information System (INIS)

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

2007-01-01

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

Fluorescence Resonance Energy Transfer in Polydiacetylene Liposomes

Science.gov (United States)

Li, Xuelian; Matthews, Shelton; Kohli, Punit

2009-01-01

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

Tunneling induced dark states and the controllable resonance fluorescence spectrum in quantum dot molecules

International Nuclear Information System (INIS)

Tian, Si-Cong; Tong, Cun-Zhu; Ning, Yong-Qiang; Qin, Li; Liu, Yun; Wan, Ren-Gang

2014-01-01

Optical spectroscopy, a powerful tool for probing and manipulating quantum dots (QDs), has been used to investigate the resonance fluorescence spectrum from linear triple quantum dot molecules controlled by tunneling, using atomic physics methods. Interesting features such as quenching and narrowing of the fluorescence are observed. In such molecules the tunneling between the quantum dots can also induce a dark state. The results are explained by the transition properties of the dressed states generated by the coupling of the laser and the tunneling. Unlike the atomic system, in such quantum dot molecules quantum coherence can be induced using tunneling, requiring no coupling lasers, which will allow tunneling controllable quantum dot molecules to be applied to quantum optics and photonics. (paper)

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

Science.gov (United States)

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

2018-04-01

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

Multifunctional PHPMA-Derived Polymer for Ratiometric pH Sensing, Fluorescence Imaging, and Magnetic Resonance Imaging.

Science.gov (United States)

Su, Fengyu; Agarwal, Shubhangi; Pan, Tingting; Qiao, Yuan; Zhang, Liqiang; Shi, Zhengwei; Kong, Xiangxing; Day, Kevin; Chen, Meiwan; Meldrum, Deirdre; Kodibagkar, Vikram D; Tian, Yanqing

2018-01-17

In this paper, we report synthesis and characterization of a novel multimodality (MRI/fluorescence) probe for pH sensing and imaging. A multifunctional polymer was derived from poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA) and integrated with a naphthalimide-based-ratiometric fluorescence probe and a gadolinium-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid complex (Gd-DOTA complex). The polymer was characterized using UV-vis absorption spectrophotometry, fluorescence spectrofluorophotometry, magnetic resonance imaging (MRI), and confocal microscopy for optical and MRI-based pH sensing and cellular imaging. In vitro labeling of macrophage J774 and esophageal CP-A cell lines shows the polymer's ability to be internalized in the cells. The transverse relaxation time (T 2 ) of the polymer was observed to be pH-dependent, whereas the spin-lattice relaxation time (T 1 ) was not. The pH probe in the polymer shows a strong fluorescence-based ratiometric pH response with emission window changes, exhibiting blue emission under acidic conditions and green emission under basic conditions, respectively. This study provides new materials with multimodalities for pH sensing and imaging.

Laser-excited Fluorescence And Electron-spin Resonance Of Er3+ In Polycrystalline Alcl3

OpenAIRE

Ceotto G.; Pires M.A.; Sanjurjo J.A.; Rettori C.; Barberis G.E.

1990-01-01

The green fluorescence transitions among the levels corresponding to the 4S3/2 and 4I15/2 configurations of Er3+ diluted in AlCl3 have been measured using laser excitation. The data allow us to determine the crystalline-field splittings of these levels and, in turn, the spin-Hamiltonian parameters. The electron-paramagnetic-resonance spectrum observed at low temperatures is in good agreement with that expected from these parameters. © 1990 The American Physical Society.

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.

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

Science.gov (United States)

Sahoo, Harekrushna; Roccatano, Danilo; Zacharias, Martin; Nau, Werner M

2006-06-28

Fluorescence resonance energy transfer (FRET) between tryptophan (Trp) as donor and 2,3-diazabicyclo[2.2.2]oct-2-ene (Dbo) as acceptor was studied by steady-state and time-resolved fluorescence spectroscopy. The unique feature of this FRET pair is its exceptionally short Förster radius (10 A), which allows one to recover distance distributions in very short structureless peptides. The technique was applied to Trp-(GlySer)n-Dbo-NH2 peptides with n = 0-10, for which the average probe/quencher distance ranged between 8.7 and 13.7 A experimentally (in propylene glycol, analysis according to wormlike chain model) and 8.6-10.2 A theoretically (for n = 0-6, GROMOS96 molecular dynamics simulations). The larger FRET efficiency in steady-state compared to time-resolved fluorescence experiments was attributed to a static quenching component, suggesting that a small but significant part (ca. 10%) of the conformations are already in van der Waals contact when excitation occurs.

Enhanced absorption in Au nanoparticles/a-Si:H/c-Si heterojunction solar cells exploiting Au surface plasmon resonance

Energy Technology Data Exchange (ETDEWEB)

Losurdo, Maria; Giangregorio, Maria M.; Bianco, Giuseppe V.; Sacchetti, Alberto; Capezzuto, Pio; Bruno, Giovanni [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR, via Orabona 4, 70126 Bari (Italy)

2009-10-15

Au nanoparticles (NPs)/(n-type)a-Si:H/(p-type)c-Si heterojunctions have been deposited combining plasma-enhanced chemical-vapour deposition (PECVD) with Au sputtering. We demonstrate that a density of {proportional_to}1.3 x 10{sup 11} cm{sup -2} of Au nanoparticles with an approximately 20 nm diameter deposited onto (n-type)a-Si:H/(p-type)c-Si heterojunctions enhance performance exploiting the improved absorption of light by the surface plasmon resonance of Au NPs. In particular, Au NPs/(n-type)a-Si:H/(p-type)c-Si show an enhancement of 20% in the short-circuit current, J{sub SC}, 25% in the power output, P{sub max} and 3% in the fill factor, FF, compared to heterojunctions without Au NPs. Structures have been characterized by spectroscopic ellipsometry, atomic force microscopy and current-voltage (I-V) measurements to correlate the plasmon resonance-induced enhanced absorption of light with photovoltaic performance. (author)

Some secrets of fluorescent proteins: distinct bleaching in various mounting fluids and photoactivation of cyan fluorescent proteins at YFP-excitation.

Science.gov (United States)

Malkani, Naila; Schmid, Johannes A

2011-04-07

The use of spectrally distinct variants of green fluorescent protein (GFP) such as cyan or yellow mutants (CFP and YFP, respectively) is very common in all different fields of life sciences, e.g. for marking specific proteins or cells or to determine protein interactions. In the latter case, the quantum physical phenomenon of fluorescence resonance energy transfer (FRET) is exploited by specific microscopy techniques to visualize proximity of proteins. When we applied a commonly used FRET microscopy technique--the increase in donor (CFP)-fluorescence after bleaching of acceptor fluorophores (YFP), we obtained good signals in live cells, but very weak signals for the same samples after fixation and mounting in commercial microscopy mounting fluids. This observation could be traced back to much faster bleaching of CFP in these mounting media. Strikingly, the opposite effect of the mounting fluid was observed for YFP and also for other proteins such as Cerulean, TFP or Venus. The changes in photostability of CFP and YFP were not caused by the fixation but directly dependent on the mounting fluid. Furthermore we made the interesting observation that the CFP-fluorescence intensity increases by about 10-15% after illumination at the YFP-excitation wavelength--a phenomenon, which was also observed for Cerulean. This photoactivation of cyan fluorescent proteins at the YFP-excitation can cause false-positive signals in the FRET-microscopy technique that is based on bleaching of a yellow FRET acceptor. Our results show that photostability of fluorescent proteins differs significantly for various media and that CFP bleaches significantly faster in commercial mounting fluids, while the opposite is observed for YFP and some other proteins. Moreover, we show that the FRET microscopy technique that is based on bleaching of the YFP is prone to artifacts due to photoactivation of cyan fluorescent proteins under these conditions.

Nanoantenna array-induced fluorescence enhancement and reduced lifetimes

DEFF Research Database (Denmark)

Bakker, R. M.; Drachev, V. P.; Liu, Z.

2008-01-01

Enhanced fluorescence is observed from dye molecules interacting with optical nanoantenna arrays. Elliptical gold dimers form individual nanoantennae with tunable plasmon resonances depending upon the geometry of the two particles and the size of the gap between them. A fluorescent dye, Rhodamine...... 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...

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

Science.gov (United States)

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

2018-02-06

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

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

Science.gov (United States)

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

2014-01-01

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

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

International Nuclear Information System (INIS)

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

2006-01-01

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

Photonic reagents for concentration measurement of flu-orescent proteins with overlapping spectra

Science.gov (United States)

Goun, Alexei; Bondar, Denys I.; Er, Ali O.; Quine, Zachary; Rabitz, Herschel A.

2016-05-01

By exploiting photonic reagents (i.e., coherent control by shaped laser pulses), we employ Optimal Dynamic Discrimination (ODD) as a novel means for quantitatively characterizing mixtures of fluorescent proteins with a large spectral overlap. To illustrate ODD, we simultaneously measured concentrations of in vitro mixtures of Enhanced Blue Fluorescent Protein (EBFP) and Enhanced Cyan Fluorescent Protein (ECFP). Building on this foundational study, the ultimate goal is to exploit the capabilities of ODD for parallel monitoring of genetic and protein circuits by suppressing the spectral cross-talk among multiple fluorescent reporters.

Measurement of a heavy-hole hyperfine interaction in InGaAs quantum dots using resonance fluorescence.

Science.gov (United States)

Fallahi, P; Yilmaz, S T; Imamoğlu, A

2010-12-17

We measure the strength and the sign of hyperfine interaction of a heavy hole with nuclear spins in single self-assembled quantum dots. Our experiments utilize the locking of a quantum dot resonance to an incident laser frequency to generate nuclear spin polarization. By monitoring the resulting Overhauser shift of optical transitions that are split either by electron or exciton Zeeman energy with respect to the locked transition using resonance fluorescence, we find that the ratio of the heavy-hole and electron hyperfine interactions is -0.09 ± 0.02 in three quantum dots. Since hyperfine interactions constitute the principal decoherence source for spin qubits, we expect our results to be important for efforts aimed at using heavy-hole spins in quantum information processing.

Resonant Scanning with Large Field of View Reduces Photobleaching and Enhances Fluorescence Yield in STED Microscopy.

Science.gov (United States)

Wu, Yong; Wu, Xundong; Lu, Rong; Zhang, Jin; Toro, Ligia; Stefani, Enrico

2015-10-01

Photobleaching is a major limitation of superresolution Stimulated Depletion Emission (STED) microscopy. Fast scanning has long been considered an effective means to reduce photobleaching in fluorescence microscopy, but a careful quantitative study of this issue is missing. In this paper, we show that the photobleaching rate in STED microscopy can be slowed down and the fluorescence yield be enhanced by scanning with high speed, enabled by using large field of view in a custom-built resonant-scanning STED microscope. The effect of scanning speed on photobleaching and fluorescence yield is more remarkable at higher levels of depletion laser irradiance, and virtually disappears in conventional confocal microscopy. With ≥6 GW∙cm(-2) depletion irradiance, we were able to extend the fluorophore survival time of Atto 647N and Abberior STAR 635P by ~80% with 8-fold wider field of view. We confirm that STED Photobleaching is primarily caused by the depletion light acting upon the excited fluorophores. Experimental data agree with a theoretical model. Our results encourage further increasing the linear scanning speed for photobleaching reduction in STED microscopy.

Fluorescent scattering by molecules embedded in small particles

International Nuclear Information System (INIS)

1982-01-01

Studies are reported in these areas: double resonance in fluorescent and Raman scattering; surface enhanced Raman scattering; fluorescence by molecules embedded in small particles; fluorescence by a liquid droplet; and fluorescence by conical pits in surfaces

Highly fluorescent carbon dots as nanoprobes for sensitive and selective determination of 4-nitrophenol in surface waters

International Nuclear Information System (INIS)

Ahmed, Gaber Hashem Gaber; Laíño, Rosana Badía; Calzón, Josefa Angela García; García, Marta Elena Díaz

2015-01-01

We report on the synthesis of carbon dots (C-dots) by thermal carbonization of a mixture of ethyleneglycol bis-(2-aminoethyl ether)-N,N,N’,N’-tetraacetic acid (EGTA) and tris(hydroxymethyl)aminomethane (Tris). The resulting C-dots were characterized by X-ray diffraction, proton and carbon nuclear magnetic resonance, FTIR and fluorescence spectroscopy, and high-resolution TEM. The data reveal that the C-dots are mainly capped with hydroxy and carbonyl groups and are highly fluorescent with an emission peak that shifts from 427 to 438 nm if the excitation wavelength is increased from 310 to 360–370 nm. Fluorescence is quenched by 4-nitrophenol (4-NP), and this effect was exploited to design a simple and rapid protocol for the determination of 4-NP. The detection limit is 28 nM and the linear range extends from 0.1 to 50 μM. The method was successfully applied to the determination of 4-NP in spiked river and sea waters. (author)

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

Science.gov (United States)

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

2017-10-13

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

Theory of electrically controlled resonant tunneling spin devices

Science.gov (United States)

Ting, David Z. -Y.; Cartoixa, Xavier

2004-01-01

We report device concepts that exploit spin-orbit coupling for creating spin polarized current sources using nonmagnetic semiconductor resonant tunneling heterostructures, without external magnetic fields. The resonant interband tunneling psin filter exploits large valence band spin-orbit interaction to provide strong spin selectivity.

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)

Jang, Haeyun; Lee, Chaedong; Nam, Gi-Eun; Quan, Bo; Choi, Hyuck Jae; Yoo, Jung Sun; Piao, Yuanzhe

2016-01-01

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.

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.

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.

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

Science.gov (United States)

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

2015-10-15

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

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.

Generally Applicable Transformation Protocols for Fluorescent Nanodiamond Internalization into Cells

NARCIS (Netherlands)

Hemelaar, Simon R; van der Laan, Kiran J; Hinterding, Sophie R; Koot, Manon V; Ellermann, Else; Perona-Martinez, Felipe P; Roig, David; Hommelet, Severin; Novarina, Daniele; Takahashi, Hiroki; Chang, Michael; Schirhagl, Romana

2017-01-01

Fluorescent nanodiamonds (FNDs) are promising nanoprobes, owing to their stable and magnetosensitive fluorescence. Therefore they can probe properties as magnetic resonances, pressure, temperature or strain. The unprecedented sensitivity of diamond defects can detect the faint magnetic resonance of

Dynamic Measurement of Tumor Vascular Permeability and Perfusion using a Hybrid System for Simultaneous Magnetic Resonance and Fluorescence Imaging.

Science.gov (United States)

Ren, Wuwei; Elmer, Andreas; Buehlmann, David; Augath, Mark-Aurel; Vats, Divya; Ripoll, Jorge; Rudin, Markus

2016-04-01

Assessing tumor vascular features including permeability and perfusion is essential for diagnostic and therapeutic purposes. The aim of this study was to compare fluorescence and magnetic resonance imaging (MRI)-based vascular readouts in subcutaneously implanted tumors in mice by simultaneous dynamic measurement of tracer uptake using a hybrid fluorescence molecular tomography (FMT)/MRI system. Vascular permeability was measured using a mixture of extravascular imaging agents, GdDOTA and the dye Cy5.5, and perfusion using a mixture of intravascular agents, Endorem and a fluorescent probe (Angiosense). Dynamic fluorescence reflectance imaging (dFRI) was integrated into the hybrid system for high temporal resolution. Excellent correspondence between uptake curves of Cy5.5/GdDOTA and Endorem/Angiosense has been found with correlation coefficients R > 0.98. The two modalities revealed good agreement regarding permeability coefficients and centers-of-gravity of the imaging agent distribution. The FMT/dFRI protocol presented is able to accurately map physiological processes and poses an attractive alternative to MRI for characterizing tumor neoangiogenesis.

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

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

Science.gov (United States)

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

2013-10-01

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

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

Science.gov (United States)

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

2009-10-07

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

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.

Hybrid confocal Raman fluorescence microscopy on single cells using semiconductor quantum dots

NARCIS (Netherlands)

van Manen, H.J.; Otto, Cornelis

2007-01-01

We have overcome the traditional incompatibility of Raman microscopy with fluorescence microscopy by exploiting the optical properties of semiconductor fluorescent quantum dots (QDs). Here we present a hybrid Raman fluorescence spectral imaging approach for single-cell microscopy applications. We

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

Science.gov (United States)

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

2012-01-18

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

Spectrophotometry near the atmospheric cutoff of the strongest Bowen resonance fluorescence lines of O III in two planetary nebulae

Science.gov (United States)

O'Dell, C. R.; Opal, Chet B.

1989-01-01

Spectrophotometric results are presented for the stronger, well-resolved Bowen O III resonance fluorescence emission lines in the planetary nebulae 7027 and NGC 7662 down to and including the intrinsically strong line at 3133 A. These data are combined with results from the IUE atlas of spectra and similar results for the longer wavelength lines by Likkel and Aller (1986) to give the first full coverage of the Bowen lines. Good agreement is found with fluorescence theory for the primary cascade lines, except for the Likkel and Aller results. The efficiency of conversion of the exciting He II Ly-alpha into O III lines is determined, and values comparable to other planetary nebulae are found.

Measurement of changes in nuclear charge radii of 2r by laser-induced resonance fluorescence

International Nuclear Information System (INIS)

Gangrskij, Yu.P.; Zemlyanoj, S.G.; Marinova, K.P.; Markov, B.N.; Khoang Tkhi Kim Khueh; Chan Kong Tam; Kul'dzhanov, B.K.

1987-01-01

The optical isotopic shifts of Zr stable isotopes have been measured in three atomic transitions of type 4d 2 5s 2 → 4d 2 5s5p using the technique of laser-induced resonance fluorescence. The changes of nuclear mean-square charge radius Δ 2 > have been determined. The extracted values of Δ 2 > are compared to predictions of the droplet model. It is shown that the droplet model calculations can be made to agree with the experimental results, if changes of nuclear dynamical octupole deformation and of surface diffuseness parameter are taken into account

Fluorescence resonance energy transfer between perylene and riboflavin in micellar solution and analytical application on determination of vitamin B2

International Nuclear Information System (INIS)

Bhattar, S.L.; Kolekar, G.B.; Patil, S.R.

2008-01-01

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 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 2 directly from pharmaceutical tablets

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

International Nuclear Information System (INIS)

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

2007-01-01

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

Wideband Low Noise Amplifiers Exploiting Thermal Noise Cancellation

NARCIS (Netherlands)

Bruccoleri, F.; Klumperink, Eric A.M.; Nauta, Bram

2005-01-01

Low Noise Amplifiers (LNAs) are commonly used to amplify signals that are too weak for direct processing for example in radio or cable receivers. Traditionally, low noise amplifiers are implemented via tuned amplifiers, exploiting inductors and capacitors in resonating LC-circuits. This can render

Spectroscopy and nonclassical fluorescence properties of single trapped Ba+ ions

International Nuclear Information System (INIS)

Bolle, J.

1998-06-01

This thesis reports on the setup and application of an experimental apparatus for spectroscopic and quantum optical investigations of a single Barium ion in a Paul trap. The realization of the apparatus, which consists of the ion trap in ultra high vacuum, two laser systems, and a photon counting detection system, is described in detail, with particular consideration of the noise sources like stray light and laser frequency instabilities. The two lasers at 493 nm and 650 nm needed to continuously excite resonance fluorescence from the Barium ion have been realized using diode lasers only. The preparation of a single localized Barium ion is described, in particular its optical cooling with the laser light and the minimization of induced vibration in the trapping potential. The purely quantum mechanical property of antibunching is observed by measuring the intensity correlation function of resonance fluorescence from the trapped and cooled ion. Interference properties of the single ion resonance fluorescence are investigated with a Mach-Zehnder interferometer. From the measured high-contrast interference signal it is proven that each individual fluorescence photon interferes with itself. The fluorescence excitation spectrum, on varying one laser frequency, is also measured and exhibits dark resonances. These measurements are compared to calculations based on optical Bloch equations for the 8 atomic levels involved. Future experiments, in particular the detection of reduced quantum fluctuations (squeezing) in one quadrature component of the resonance fluorescence, are discussed. (author)

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

Science.gov (United States)

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

2015-10-20

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

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

Science.gov (United States)

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

2013-10-01

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

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. Copyright © 2014 John Wiley & Sons, Ltd.

Fluorescence fluctuation spectroscopy (FFS)

CERN Document Server

Tetin, Sergey

2012-01-01

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

Mid-infrared plasmonic resonances exploiting heavily-doped Ge on Si

Science.gov (United States)

Biagioni, P.; Sakat, E.; Baldassarre, L.; Calandrini, E.; Samarelli, A.; Gallacher, K.; Frigerio, J.; Isella, G.; Paul, D. J.; Ortolani, M.

2015-03-01

We address the behavior of mid-infrared localized plasmon resonances in elongated germanium antennas integrated on silicon substrates. Calculations based on Mie theory and on the experimentally retrieved dielectric constant allow us to study the tunability and the figures of merit of plasmon resonances in heavily-doped germanium and to preliminarily compare them with those of the most established plasmonic material, gold.

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.

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

Science.gov (United States)

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

2018-05-29

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

Study of the dispersion phenomena connected with the absorption by recoilless nuclear resonance fluorescence; Etude des phenomenes de dispersion lies a l'absorption resonnante sans recul des noyaux atomiques

Energy Technology Data Exchange (ETDEWEB)

Imbert, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1965-12-01

In nuclear resonance fluorescence as in the optical field abnormal dispersion curves are related to the absorption lines. It is possible, by using quadrupolar or magnetic splitting of the line in the case of recoilless resonance fluorescence (Moessbauer effect) to obtain differential dispersion effects between the two orthogonal linear or the two inverse circular components of the incident gamma radiation. These effects induce bi-refraction phenomena or Faraday rotation on the gamma beam, which have been studied on Fe-57 enriched absorbers. (author) [French] Comme dans le domaine optique, aux raies d'absorption de fluorescence resonnante des noyaux atomiques sont associees des courbes de dispersion anormale. Les decompositions des raies d'absorption de fluorescence resonnante sans recul (raies Moessbauer) par couplage quadrupolaire ou effet Zeeman permettent d'obtenir des effets dispersifs differentiels entre composantes lineaires orthogonales ou circulaires inverses du rayonnement gamma incident. Ces effets se traduisent par des phenomenes de birefringence ou de rotation Faraday, qui ont pu etre etudies sur des milieux enrichis en fer-57. (auteur)

Structure and dynamics of olefin radical cation aggregates. Time-resolved fluorescence detected magnetic resonance

International Nuclear Information System (INIS)

Desrosiers, M.F.; Trifunac, A.D.

1986-01-01

The time-resolved EPR spectra and thus the structure and dynamics of transient hydrocarbon radical cations are obtained by the pulse radiolysis-fluorescence detected magnetic resonance (FDMR) technique. Here the authors report the observation of short-lived radical cations from olefins. FDMR-EPR spectra of radical cations from tetramethylethylene and cyclohexadiene are illustrated. The olefin radical cations, FDMR spectra are concentration-dependent, since dimerization with neutral molecules takes place at higher (>10 -2 M) olefin concentration. Rate constants for the dimerization reaction are derived and the effect of solvent viscosity on aggregate formation is demonstrated. By monitoring the further reactions of dimer cations the authors have obtained EPR evidence for previously unobserved higher-order (multimer) radical cation aggregates of olefins. 16 references, 5 figures

Method of using a nuclear magnetic resonance spectroscopy standard. [SO/sub 2/ in gases by fluorescence

Science.gov (United States)

Spicer, L.D.; Bennett, D.W.; Davis, J.F.

1983-05-09

(CH/sub 3/)/sub 3/SiNSO is produced by the reaction of ((CH/sub 3/)/sub 3/SI)/sub 2/NH with SO/sub 2/. Also produced in the reaction are ((CH/sub 3/)/sub 3/Si)/sub 2/O and a new solid compound (NH/sub 4/)((CH/sub 3/)/sub 3/SiOSO/sub 2/). Both (CH/sub 3/)/sub 3/SiNSO and (NH/sub 4/)((CH/sub 3/)/sub 3/SiOSO/sub 2/) have fluorescent properties. The reaction of the subject invention is used in a method of measuring the concentration of SO/sub 2/ pollutants in gases. By the method, a sample of gas is bubbled through a solution of ((CH/sub 3/)/sub 3/Si)/sub 2/NH, whereby any SO/sub 2/ present in the gas will react to produce the two fluorescent products. The measured fluorescence of these products can then be used to calculate the concentration of SO/sub 2/ in the original gas sample. The solid product (NH/sub 4/)((CH/sub 3/)/sub 3/SiOSO/sub 2/) may be used as a standard in solid state NMR spectroscopy, wherein the resonance peaks of either /sup 1/H, /sup 13/C, /sup 15/N, or /sup 29/Si may be used as a reference.

Monte Carlo treatment of resonance-radiation imprisonment in fluorescent lamps—revisited

Science.gov (United States)

Anderson, James B.

2016-12-01

We reported in 1985 a Monte Carlo treatment of the imprisonment of the 253.7 nm resonance radiation from mercury in the mercury-argon discharge of fluorescent lamps. The calculated spectra of the emitted radiation were found in good agreement with measured spectra. The addition of the isotope mercury-196 to natural mercury was found, also in agreement with experiments, to increase lamp efficiency. In this paper we report the extension of the earlier work with increased accuracy, analysis of photon exit-time distributions, recycling of energy released in quenching, analysis of dynamic similarity for different lamp sizes, variation of Mrozowski transfer rates, prediction and analysis of the hyperfine ultra-violet spectra, and optimization of tailored mercury isotope mixtures for increased lamp efficiency. The spectra were found insensitive to the extent of quenching and recycling. The optimized mixtures were found to increase efficiencies by as much as 5% for several lamp configurations. Optimization without increasing the mercury-196 fraction was found to increase efficiencies by nearly 1% for several configurations.

Monte Carlo treatment of resonance-radiation imprisonment in fluorescent lamps—revisited

International Nuclear Information System (INIS)

Anderson, James B

2016-01-01

We reported in 1985 a Monte Carlo treatment of the imprisonment of the 253.7 nm resonance radiation from mercury in the mercury–argon discharge of fluorescent lamps. The calculated spectra of the emitted radiation were found in good agreement with measured spectra. The addition of the isotope mercury-196 to natural mercury was found, also in agreement with experiments, to increase lamp efficiency. In this paper we report the extension of the earlier work with increased accuracy, analysis of photon exit-time distributions, recycling of energy released in quenching, analysis of dynamic similarity for different lamp sizes, variation of Mrozowski transfer rates, prediction and analysis of the hyperfine ultra-violet spectra, and optimization of tailored mercury isotope mixtures for increased lamp efficiency. The spectra were found insensitive to the extent of quenching and recycling. The optimized mixtures were found to increase efficiencies by as much as 5% for several lamp configurations. Optimization without increasing the mercury-196 fraction was found to increase efficiencies by nearly 1% for several configurations. (paper)

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

International Nuclear Information System (INIS)

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

2003-01-01

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

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

Science.gov (United States)

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

2010-11-01

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

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

International Nuclear Information System (INIS)

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

2017-01-01

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

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

Science.gov (United States)

Mishra, Ashish K.

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

Recent developments in multimodality fluorescence imaging probes

Directory of Open Access Journals (Sweden)

Jianhong Zhao

2018-05-01

Full Text Available Multimodality optical imaging probes have emerged as powerful tools that improve detection sensitivity and accuracy, important in disease diagnosis and treatment. In this review, we focus on recent developments of optical fluorescence imaging (OFI probe integration with other imaging modalities such as X-ray computed tomography (CT, magnetic resonance imaging (MRI, positron emission tomography (PET, single-photon emission computed tomography (SPECT, and photoacoustic imaging (PAI. The imaging technologies are briefly described in order to introduce the strengths and limitations of each techniques and the need for further multimodality optical imaging probe development. The emphasis of this account is placed on how design strategies are currently implemented to afford physicochemically and biologically compatible multimodality optical fluorescence imaging probes. We also present studies that overcame intrinsic disadvantages of each imaging technique by multimodality approach with improved detection sensitivity and accuracy. KEY WORDS: Optical imaging, Fluorescence, Multimodality, Near-infrared fluorescence, Nanoprobe, Computed tomography, Magnetic resonance imaging, Positron emission tomography, Single-photon emission computed tomography, Photoacoustic imaging

Resonance Energy Transfer between protein and rhamnolipid capped ZnS quantum dots: Application in in-gel staining of proteins

Science.gov (United States)

Janakiraman, Narayanan; Mohan, Abhilash; Kannan, Ashwin; Pennathur, Gautam

The interaction of proteins with quantum dots is an interesting field of research. These interactions occur at the nanoscale. We have probed the interaction of Bovine Serum Albumin (BSA) and Candida rugosa lipase (CRL) with rhamnolipid capped ZnS (RhlZnSQDs) using absorption and fluorescence spectroscopy. Optical studies on mixtures of RhlZnSQDs and proteins resulted in Förster's Resonance Energy Transfer (FRET) from proteins to QDs. This phenomenon has been exploited to detect proteins in agarose gel electrophoresis. The activity of the CRL was unaffected on the addition of QDs as revealed by zymography.

A plasmonic biosensor with single-molecule sensitivity

NARCIS (Netherlands)

Zijlstra, P.; Paulo, P.M.R.; Yuan, H.; Khatua, S.; Yorulmaz, M.; Orrit, M.

2013-01-01

The plasmon resonance of a single metal nanoparticle induces an enhancement of the local electromagnetic field. We exploit this field enhancement to detect single molecules that are (1) poorly fluorescent or (2) completely non-fluorescent.

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-06-22

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

Probing Enzyme-Surface Interactions via Protein Engineering and Single-Molecule Techniques

Science.gov (United States)

2017-06-26

SECURITY CLASSIFICATION OF: The overall objective of this research was to exploit protein engineering and fluorescence single-molecule methods to...enhance our understanding of the interaction of proteins and surfaces. Given this objective, the specific aims of this research were to: 1) exploit the...incorporation of unnatural amino acids in proteins to introduce single-molecule probes (i.e., fluorophores for fluorescence resonance energy transfer

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

International Nuclear Information System (INIS)

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

2012-01-01

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

Fluorescence studies on 2-(het)aryl perimidine derivatives

Energy Technology Data Exchange (ETDEWEB)

Giani, Arianna Maria [Dipartimento di Scienze del Farmaco, Università degli Studi del Piemonte Orientale “A. Avogadro”, Largo Donegani 2/3, I-28100 Novara (Italy); Lamperti, Marco; Maspero, Angelo; Cimino, Alessandro [Dipartimento di Scienza e Alta Tecnologia, Università degli Studi dell’Insubria, Via Valleggio 11, I-22100 Como (Italy); Negri, Roberto; Giovenzana, Giovanni Battista [Dipartimento di Scienze del Farmaco, Università degli Studi del Piemonte Orientale “A. Avogadro”, Largo Donegani 2/3, I-28100 Novara (Italy); Palmisano, Giovanni [Dipartimento di Scienza e Alta Tecnologia, Università degli Studi dell’Insubria, Via Valleggio 11, I-22100 Como (Italy); Nardo, Luca, E-mail: luca.nardo@unimib.it [Dipartimento di Medicina e Chirurgia, Università degli Studi di Milano-Bicocca, Via Cadore 48, I-20900 Monza (Italy)

2016-11-15

Perimidines are extensively studied for their different therapeutic properties, including antiulcer, antifungal, antimicrobial, immunosuppressive and anticancer activities. Moreover, their heterocyclic structure embodies the naphthalene moiety, exploited in bio-imaging and biomolecules staining due to its high fluorescence. In this work we present the spectroscopic characterization of a family of perimidine derivatives, in order to obtain information potentially useful for the design of compounds combining biological activity and detectable fluorescence in physiological environment.

Few-body system and particle resonances

International Nuclear Information System (INIS)

Mubarak, Ahmad.

1979-01-01

Techniques of few-body system in nuclear physics are exploited to analyze the spectrum of the T resonance and its family. Their relation to nuclear resonances are established so as to apply few-body dynamical techniques in the dynamical structure of particles carrying the truth quantum number. (author)

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

Science.gov (United States)

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

2000-01-01

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

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

Science.gov (United States)

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

2013-11-19

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

Comparative in vivo mucoadhesion studies of thiomer formulations using magnetic resonance imaging and fluorescence detection.

Science.gov (United States)

Albrecht, K; Greindl, M; Kremser, C; Wolf, C; Debbage, P; Bernkop-Schnürch, A

2006-09-28

The aim of this study was to compare different oral delivery systems based on the thiolated polymer polycarbophil-cysteine (PCP-Cys) and to provide evidence for the validity of the hypothesis that unhydrated polymers provide better mucoadhesion in vivo. To achieve dry polymer application, a new, experimental dosage form named Eutex (made of Eudragit L100-55 and latex) capsule has been developed. Magnetic resonance imaging was used to localize the point of release of the thiolated polymer from the application forms via the positive magnetic resonance signal from a gadolinium complex (Gd-DTPA). In vivo mucoadhesion was determined by ascertaining the residence time of the fluorescence-tagged thiomer on intestinal mucosa after 3 h. Results showed that in comparison to conventional application forms the Eutex capsules led to 1.9-fold higher mucoadhesive properties of PCP-Cys when compared to application with a conventional enteric-coated capsule, and to 1.4-fold higher mucoadhesion when compared to administration with an enteric-coated tablet of the thiomer. The findings of this study should contribute to the understanding of mucoadhesion and mucoadhesion influencing parameters in vivo and should therefore be of considerable interest for the development of future mucoadhesive oral drug delivery dosage forms.

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

International Nuclear Information System (INIS)

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

2012-01-01

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

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

International Nuclear Information System (INIS)

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

2013-01-01

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

Ion Cyclotron Resonance Facility (ICR)

Data.gov (United States)

Federal Laboratory Consortium — his facility is charged with developing and exploiting the unique capabilities of Fourier Transform Ion Cyclotron Resonance (FT-ICR) mass spectrometry, and leads the...

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

Science.gov (United States)

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

2017-05-04

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

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

Directory of Open Access Journals (Sweden)

Adriana K. Carmona

2009-09-01

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

Contrast Induced by a Static Magnetic Field for Improved Detection in Nanodiamond Fluorescence Microscopy

Science.gov (United States)

Singam, Shashi K. R.; Motylewski, Jaroslaw; Monaco, Antonina; Gjorgievska, Elena; Bourgeois, Emilie; Nesládek, Milos; Giugliano, Michele; Goovaerts, Etienne

2016-12-01

Diamond nanoparticles with negatively charged nitrogen-vacancy (NV) centers are highly efficient nonblinking emitters that exhibit spin-dependent intensity. An attractive application of these emitters is background-free fluorescence microscopy exploiting the fluorescence quenching induced either by resonant microwaves (RMWs) or by an applied static magnetic field (SMF). Here, we compare RMW- and SMF-induced contrast measurements over a wide range of optical excitation rates for fluorescent nanodiamonds (FNDs) and for NV centers shallowly buried under the (100)-oriented surface of a diamond single crystal (SC). Contrast levels are found to be systematically lower in the FNDs than in the SC. At low excitation rates, the RMW contrast initially rises to a maximum (up to 7% in FNDs and 13% in the SC) but then decreases steadily at higher intensities. Conversely, the SMF contrast increases from approximately 12% at low excitation rates to high values of 20% and 38% for the FNDs and SC, respectively. These observations are well described in a rate-equations model for the charged NV defect using parameters in good agreement with the literature. The SMF approach yields higher induced contrast in image collection under commonly applied optical excitation. Unlike the RMW method, there is no thermal load exerted on the aqueous media in biological samples in the SMF approach. We demonstrate imaging by SMF-induced contrast in neuronal cultures incorporating FNDs (i) in a setup for patch-clamp experiments in parallel with differential-interference-contrast microscopy, (ii) after a commonly used staining procedure as an illustration of the high selectivity against background fluorescence, and (iii) in a confocal fluorescence microscope in combination with bright-field microscopy.

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. Copyright © 2015 Elsevier B.V. All rights reserved.

Exploiting Non-Markovianity for Quantum Control.

Science.gov (United States)

Reich, Daniel M; Katz, Nadav; Koch, Christiane P

2015-07-22

Quantum technology, exploiting entanglement and the wave nature of matter, relies on the ability to accurately control quantum systems. Quantum control is often compromised by the interaction of the system with its environment since this causes loss of amplitude and phase. However, when the dynamics of the open quantum system is non-Markovian, amplitude and phase flow not only from the system into the environment but also back. Interaction with the environment is then not necessarily detrimental. We show that the back-flow of amplitude and phase can be exploited to carry out quantum control tasks that could not be realized if the system was isolated. The control is facilitated by a few strongly coupled, sufficiently isolated environmental modes. Our paradigmatic example considers a weakly anharmonic ladder with resonant amplitude control only, restricting realizable operations to SO(N). The coupling to the environment, when harnessed with optimization techniques, allows for full SU(N) controllability.

A deep cavitand with a fluorescent wall functions as an ion sensor.

Science.gov (United States)

Berryman, Orion B; Sather, Aaron C; Rebek, Julius

2011-10-07

The synthesis and characterization of a deep cavitand bearing a fluorescent benzoquinoxaline wall is reported. Noncovalent host-guest recognition events are exploited to sense small charged molecules including acetylcholine. The cavitand also exhibits an anion dependent change in fluorescence that is used to differentiate halide ions in solution. © 2011 American Chemical Society

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

Science.gov (United States)

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

2007-07-15

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

Complicated Fermi-type vibronic resonance: Untangling of the single-site quasi-line fluorescence excitation spectra of a methylated dibenzoporphin

International Nuclear Information System (INIS)

Arabei, S.M.; Kuzmitsky, V.A.; Solovyov, K.N.

2008-01-01

The quasi-line low-temperature (4.2 K) fluorescence excitation spectra of 2,3,12,13-tetramethyldibenzo[g,q]porphin introduced into an n-octane matrix have been measured in the range of the S 2 0 electronic transition at selective fluorescence monitoring for the two main types of impurity centers (sites). A characteristic feature of these spectra is that a conglomerate of quasi-lines - a structured complex band - is observed instead of one 0-0 quasi-line of the S 2 0 transition. In this band, the intensity distributions for the two main sites considerably differ from each other. The occurrence of such conglomerates is interpreted as a result of nonadiabatic vibrational-electronic interaction between the vibronic S 2 and S 1 states (the complex vibronic analogue of the Fermi resonance). The frequencies and intensities of individual transitions determined from the deconvolution of complex conglomerates are used as the initial data for solving the inverse spectroscopic problem: the determination of the unperturbed electronic and vibrational levels of states involved in the resonance and the vibronic-interaction matrix elements between them. This problem is solved with a method developed previously. The experimental results and their analysis are compared to the analogous data obtained earlier for meso-tetraazaporphin and meso-tetrapropylporphin. The energy intervals between the S 2 and S 1 electronic levels (ΔE S 2 S 1 ) of the two main types of impurity centers formed by molecules of a given porphyrin in the crystal matrix are found to significantly differ from each other, the values of this difference (δΔE S 2 S 1 ) being considerably greater for tetramethyldibenzoporphin, δΔE S 2 S 1 =228cm -1 , than for the two other porphyrins. At the same time, the energies of the unperturbed vibrational states of the S 1 electronic level participating in the resonance are very close to each other for these two sites

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

Directory of Open Access Journals (Sweden)

Shaowei Ding

2015-06-01

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

Optically trapped atomic resonant devices for narrow linewidth spectral imaging

Science.gov (United States)

Qian, Lipeng

This thesis focuses on the development of atomic resonant devices for spectroscopic applications. The primary emphasis is on the imaging properties of optically thick atomic resonant fluorescent filters and their applications. In addition, this thesis presents a new concept for producing very narrow linewidth light as from an atomic vapor lamp pumped by a nanosecond pulse system. This research was motivated by application for missile warning system, and presents an innovative approach to a wide angle, ultra narrow linewidth imaging filter using a potassium vapor cell. The approach is to image onto and collect the fluorescent photons emitted from the surface of an optically thick potassium vapor cell, generating a 2 GHz pass-band imaging filter. This linewidth is narrow enough to fall within a Fraunhefer dark zone in the solar spectrum, thus make the detection solar blind. Experiments are conducted to measure the absorption line shape of the potassium resonant filter, the quantum efficiency of the fluorescent behavior, and the resolution of the fluorescent image. Fluorescent images with different spatial frequency components are analyzed by using a discrete Fourier transform, and the imaging capability of the fluorescent filter is described by its Modulation Transfer Function. For the detection of radiation that is spectrally broader than the linewidth of the potassium imaging filter, the fluorescent image is seen to be blurred by diffuse fluorescence from the slightly off resonant photons. To correct this, an ultra-thin potassium imaging filter is developed and characterized. The imaging property of the ultra-thin potassium imaging cell is tested with a potassium seeded flame, yielding a resolution image of ˜ 20 lines per mm. The physics behind the atomic resonant fluorescent filter is radiation trapping. The diffusion process of the resonant photons trapped in the atomic vapor is theoretically described in this thesis. A Monte Carlo method is used to simulate the

Problems of fluorescent imaging and its solution using nanofluorophores. Part I: Advantages of fluorescent nanoparticles over conventional organic fluorophores

International Nuclear Information System (INIS)

Zhelev, Z.; Hadjidekov, G.; Zlateva, G.; Spasov, L.; Bakalova, R.

2011-01-01

The application of fluorescence in deep-tissue imaging is rapidly expanding in fast several years. The progress in fluorescent molecular probes and fluorescent imaging techniques gives an opportunity to detect single cells and even molecules in live organisms. The highly sensitive and high-speed fluorescent molecular sensors and detection devices allow the application of fluorescence in functional imaging. With development of novel bright fluorophores based on nano-technologies and fluorescence scanners with high spatial and temporal resolution, the fluorescent imaging has a potential to become an alternative of the other non-invasive imaging techniques as magnetic resonance imaging, positron-emission tomography, X-ray, computing tomography. This review outlines the current status and future trends of fluorescent nanoparticles - quantum dots (QDs), as a new generation of fluorophores in experimental and pre-clinical fluorescent imaging diagnostic. Part 1 focuses on the advantages of quantum dots over conventional organic fluorophores and defines the major requirements to the 'perfect' fluorophore for fluorescent deep-tissue imaging diagnostic. The analysis is based on the limitations of fluorescent imaging in vivo and overcome by using quantum dots

Exploiting multicompartment effects in triple-echo steady-state T2 mapping for fat fraction quantification.

Science.gov (United States)

Liu, Dian; Steingoetter, Andreas; Curcic, Jelena; Kozerke, Sebastian

2018-01-01

To investigate and exploit the effect of intravoxel off-resonance compartments in the triple-echo steady-state (TESS) sequence without fat suppression for T 2 mapping and to leverage the results for fat fraction quantification. In multicompartment tissue, where at least one compartment is excited off-resonance, the total signal exhibits periodic modulations as a function of echo time (TE). Simulated multicompartment TESS signals were synthesized at various TEs. Fat emulsion phantoms were prepared and scanned at the same TE combinations using TESS. In vivo knee data were obtained with TESS to validate the simulations. The multicompartment effect was exploited for fat fraction quantification in the stomach by acquiring TESS signals at two TE combinations. Simulated and measured multicompartment signal intensities were in good agreement. Multicompartment effects caused erroneous T 2 offsets, even at low water-fat ratios. The choice of TE caused T 2 variations of as much as 28% in cartilage. The feasibility of fat fraction quantification to monitor the decrease of fat content in the stomach during digestion is demonstrated. Intravoxel off-resonance compartments are a confounding factor for T 2 quantification using TESS, causing errors that are dependent on the TE. At the same time, off-resonance effects may allow for efficient fat fraction mapping using steady-state imaging. Magn Reson Med 79:423-429, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Electrical Modulation of Fano Resonance in Plasmonic Nanostructures Using Graphene

DEFF Research Database (Denmark)

Emani, Naresh K.; Chung, Ting-Fung; Kildishev, Alexander V.

2014-01-01

Pauli blocking of interband transistions gives rise to tunable optical properties in single layer graphene (SLG). This effect is exploited in a graphene-nanoantenna hybrid device where Fano resonant plasmonic nanostructures are fabricated on top of a graphene sheet. The use of Fano resonant eleme......-element simulations. Our approach can be used for development of next generation of tunable plasmonic and hybrid nanophotonic devices.......Pauli blocking of interband transistions gives rise to tunable optical properties in single layer graphene (SLG). This effect is exploited in a graphene-nanoantenna hybrid device where Fano resonant plasmonic nanostructures are fabricated on top of a graphene sheet. The use of Fano resonant...... elements enhances the interaction of incident radiation with the graphene sheet and enables efficient electrical modulation of the plasmonic resonance. We observe electrically controlled damping in the Fano resonances occurring at approximately 2 μm, and the results are verified by full-wave 3D finite...

Analytical insights into optimality and resonance in fish swimming

Science.gov (United States)

Kohannim, Saba; Iwasaki, Tetsuya

2014-01-01

This paper provides analytical insights into the hypothesis that fish exploit resonance to reduce the mechanical cost of swimming. A simple body–fluid fish model, representing carangiform locomotion, is developed. Steady swimming at various speeds is analysed using optimal gait theory by minimizing bending moment over tail movements and stiffness, and the results are shown to match with data from observed swimming. Our analysis indicates the following: thrust–drag balance leads to the Strouhal number being predetermined based on the drag coefficient and the ratio of wetted body area to cross-sectional area of accelerated fluid. Muscle tension is reduced when undulation frequency matches resonance frequency, which maximizes the ratio of tail-tip velocity to bending moment. Finally, hydrodynamic resonance determines tail-beat frequency, whereas muscle stiffness is actively adjusted, so that overall body–fluid resonance is exploited. PMID:24430125

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

International Nuclear Information System (INIS)

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

2016-01-01

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

Engineering of a genetically encodable fluorescent voltage sensor exploiting fast Ci-VSP voltage-sensing movements.

Science.gov (United States)

Lundby, Alicia; Mutoh, Hiroki; Dimitrov, Dimitar; Akemann, Walther; Knöpfel, Thomas

2008-06-25

Ci-VSP contains a voltage-sensing domain (VSD) homologous to that of voltage-gated potassium channels. Using charge displacement ('gating' current) measurements we show that voltage-sensing movements of this VSD can occur within 1 ms in mammalian membranes. Our analysis lead to development of a genetically encodable fluorescent protein voltage sensor (VSFP) in which the fast, voltage-dependent conformational changes of the Ci-VSP voltage sensor are transduced to similarly fast fluorescence read-outs.

The interaction of fluorescent nanodiamond probes with cellular media

NARCIS (Netherlands)

Hemelaar, Simon R; Nagl, Andreas; Bigot, François; Rodriquez Garcia, Melissa; de Vries, Marcel P; Chipaux, Mayeul; Schirhagl, Romana

Fluorescent nanodiamonds (FNDs) are promising tools to image cells, bioanalytes and physical quantities such as temperature, pressure, and electric or magnetic fields with nanometer resolution. To exploit their potential for intracellular applications, the FNDs have to be brought into contact with

Random search for a dark resonance

DEFF Research Database (Denmark)

Kiilerich, Alexander Holm; Mølmer, Klaus

A pair of resonant laser fields can drive a three-level system into a dark state where it ceases to absorb and emit radiation due to destructive interference. We propose a scheme to search for this resonance by randomly changing the frequency of one of the fields each time a fluorescence photon...

Stepwise synthesis of cubic Au-AgCdS core-shell nanostructures with tunable plasmon resonances and fluorescence.

Science.gov (United States)

Liu, Xiao-Li; Liang, Shan; Nan, Fan; Pan, Yue-Yue; Shi, Jun-Jun; Zhou, Li; Jia, Shuang-Feng; Wang, Jian-Bo; Yu, Xue-Feng; Wang, Qu-Quan

2013-10-21

Cubic Au-AgCdS core-shell nanostructures were synthesized through cation exchange method assisted by tributylphosphine (TBP) as a phase-transfer agent. Among intermediate products, Au-Ag core-shell nanocubes exhibited many high-order plasmon resonance modes related to the special cubic shape, and these plasmon bands red-shifted along with the increasing of particle size. The plasmon band of Au core first red-shifted and broadened at the step of Au-Ag₂S and then blue-shifted and narrowed at the step of Au-AgCdS. Since TBP was very crucial for the efficient conversion from Ag₂S to CdS, we found that both absorption and fluorescence of the final products could be controlled by TBP.

Engineering of a genetically encodable fluorescent voltage sensor exploiting fast Ci-VSP voltage-sensing movements.

Directory of Open Access Journals (Sweden)

Alicia Lundby

2008-06-01

Full Text Available Ci-VSP contains a voltage-sensing domain (VSD homologous to that of voltage-gated potassium channels. Using charge displacement ('gating' current measurements we show that voltage-sensing movements of this VSD can occur within 1 ms in mammalian membranes. Our analysis lead to development of a genetically encodable fluorescent protein voltage sensor (VSFP in which the fast, voltage-dependent conformational changes of the Ci-VSP voltage sensor are transduced to similarly fast fluorescence read-outs.

Quantification of Material Fluorescence and Light Scattering Cross Sections Using Ratiometric Bandwidth-Varied Polarized Resonance Synchronous Spectroscopy.

Science.gov (United States)

Xu, Joanna Xiuzhu; Hu, Juan; Zhang, Dongmao

2018-05-25

Presented herein is the ratiometric bandwidth-varied polarized resonance synchronous spectroscopy (BVPRS2) method for quantification of material optical activity spectra. These include the sample light absorption and scattering cross-section spectrum, the scattering depolarization spectrum, and the fluorescence emission cross-section and depolarization spectrum in the wavelength region where the sample both absorbs and emits. This ratiometric BVPRS2 spectroscopic method is a self-contained technique capable of quantitatively decoupling material fluorescence and light scattering signal contribution to its ratiometric BVPRS2 spectra through the linear curve-fitting of the ratiometric BVPRS2 signal as a function of the wavelength bandwidth used in the PRS2 measurements. Example applications of this new spectroscopic method are demonstrated with materials that can be approximated as pure scatterers, simultaneous photon absorbers/emitters, simultaneous photon absorbers/scatterers, and finally simultaneous photon absorbers/scatterers/emitters. Because the only instruments needed for this ratiometric BVPRS2 technique are the conventional UV-vis spectrophotometer and spectrofluorometer, this work should open doors for routine decomposition of material UV-vis extinction spectrum into its absorption and scattering component spectra. The methodology and insights provided in this work should be of broad significance to all chemical research that involves photon/matter interactions.

Superior optical nonlinearity of an exceptional fluorescent stilbene dye

Energy Technology Data Exchange (ETDEWEB)

He, Tingchao [College of Physics Science and Technology, Shenzhen University, Shenzhen 518060 (China); Division of Physics and Applied Physics, Centre for Disruptive Photonic Technologies (CDPT), School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 (Singapore); Sreejith, Sivaramapanicker; Zhao, Yanli [Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 (Singapore); Gao, Yang; Grimsdale, Andrew C. [School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore 639798 (Singapore); Lin, Xiaodong, E-mail: linxd@szu.edu.cn, E-mail: hdsun@ntu.edu.sg [College of Physics Science and Technology, Shenzhen University, Shenzhen 518060 (China); Sun, Handong, E-mail: linxd@szu.edu.cn, E-mail: hdsun@ntu.edu.sg [Division of Physics and Applied Physics, Centre for Disruptive Photonic Technologies (CDPT), School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 (Singapore)

2015-03-16

Strong multiphoton absorption and harmonic generation in organic fluorescent chromophores are, respectively, significant in many fields of research. However, most of fluorescent chromophores fall short of the full potential due to the absence of the combination of such different nonlinear upconversion behaviors. Here, we demonstrate that an exceptional fluorescent stilbene dye could exhibit efficient two- and three-photon absorption under the excitation of femtosecond pulses in solution phase. Benefiting from its biocompatibility and strong excited state absorption behavior, in vitro two-photon bioimaging and superior optical limiting have been exploited, respectively. Simultaneously, the chromophore could generate efficient three-photon excited fluorescence and third-harmonic generation (THG) when dispersed into PMMA film, circumventing the limitations of classical fluorescent chromophores. Such chromophore may find application in the production of coherent light sources of higher photon energy. Moreover, the combination of three-photon excited fluorescence and THG can be used in tandem to provide complementary information in biomedical studies.

Nitrogen fluorescence in air for observing extensive air showers

CERN Document Server

Keilhauer, B; Fraga, M; Matthews, J; Sakaki, N; Tameda, Y; Tsunesada, Y; Ulrich, A

2012-01-01

Extensive air showers initiate the fluorescence emissions from nitrogen molecules in air. The UV-light is emitted isotropically and can be used for observing the longitudinal development of extensive air showers in the atmosphere over tenth of kilometers. This measurement technique is well-established since it is exploited for many decades by several cosmic ray experiments. However, a fundamental aspect of the air shower analyses is the description of the fluorescence emission in dependence on varying atmospheric conditions. Different fluorescence yields affect directly the energy scaling of air shower reconstruction. In order to explore the various details of the nitrogen fluorescence emission in air, a few experimental groups have been performing dedicated measurements over the last decade. Most of the measurements are now finished. These experimental groups have been discussing their techniques and results in a series of \\emph{Air Fluorescence Workshops} commenced in 2002. At the 8$^{\\rm{th}}$ Air Fluoresc...

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.

Kinetics of intercalation of fluorescent probes in magnesium–aluminium layered double hydroxide within a multiscale reaction–diffusion framework

Science.gov (United States)

Saliba, Daniel

2016-01-01

We report the synthesis of magnesium–aluminium layered double hydroxide (LDH) using a reaction–diffusion framework (RDF) that exploits the multiscale coupling of molecular diffusion with chemical reactions, nucleation and growth of crystals. In an RDF, the hydroxide anions are allowed to diffuse into an organic gel matrix containing the salt mixture needed for the precipitation of the LDH. The chemical structure and composition of the synthesized magnesium–aluminium LDHs are determined using powder X-ray diffraction (PXRD), thermo-gravimetric analysis, differential scanning calorimetry, solid-state nuclear magnetic resonance (SSNMR), Fourier transform infrared and energy dispersive X-ray spectroscopy. This novel technique also allows the investigation of the mechanism of intercalation of some fluorescent probes, such as the neutral three-dimensional rhodamine B (RhB) and the negatively charged two-dimensional 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS), using in situ steady-state fluorescence spectroscopy. The incorporation of these organic dyes inside the interlayer region of the LDH is confirmed via fluorescence microscopy, solid-state lifetime, SSNMR and PXRD. The activation energies of intercalation of the corresponding molecules (RhB and HPTS) are computed and exhibit dependence on the geometry of the involved probe (two or three dimensions), the charge of the fluorescent molecule (anionic, cationic or neutral) and the cationic ratio of the corresponding LDH. This article is part of the themed issue ‘Multiscale modelling at the physics–chemistry–biology interface’. PMID:27698034

Kinetics of intercalation of fluorescent probes in magnesium-aluminium layered double hydroxide within a multiscale reaction-diffusion framework

Science.gov (United States)

Saliba, Daniel; Al-Ghoul, Mazen

2016-11-01

We report the synthesis of magnesium-aluminium layered double hydroxide (LDH) using a reaction-diffusion framework (RDF) that exploits the multiscale coupling of molecular diffusion with chemical reactions, nucleation and growth of crystals. In an RDF, the hydroxide anions are allowed to diffuse into an organic gel matrix containing the salt mixture needed for the precipitation of the LDH. The chemical structure and composition of the synthesized magnesium-aluminium LDHs are determined using powder X-ray diffraction (PXRD), thermo-gravimetric analysis, differential scanning calorimetry, solid-state nuclear magnetic resonance (SSNMR), Fourier transform infrared and energy dispersive X-ray spectroscopy. This novel technique also allows the investigation of the mechanism of intercalation of some fluorescent probes, such as the neutral three-dimensional rhodamine B (RhB) and the negatively charged two-dimensional 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS), using in situ steady-state fluorescence spectroscopy. The incorporation of these organic dyes inside the interlayer region of the LDH is confirmed via fluorescence microscopy, solid-state lifetime, SSNMR and PXRD. The activation energies of intercalation of the corresponding molecules (RhB and HPTS) are computed and exhibit dependence on the geometry of the involved probe (two or three dimensions), the charge of the fluorescent molecule (anionic, cationic or neutral) and the cationic ratio of the corresponding LDH. This article is part of the themed issue 'Multiscale modelling at the physics-chemistry-biology interface'.

Refractive index sensing using Fluorescence Lifetime Imaging (FLIM)

International Nuclear Information System (INIS)

Jones, Carolyn; Suhling, Klaus

2006-01-01

The fluorescence lifetime is a function of the refractive index of the fluorophore's environment, for example in the case of the biologically important green fluorescent protein (GFP). In order to address the question whether this effect can be exploited to image the local environment of specific proteins in cell biology, we need to determine the distance over which the fluorophore's lifetime is sensitive to the refractive index. To this end, we employ Fluorescence Lifetime Imaging (FLIM) of fluorescein in NaOH buffer at an interface. This approach allows us to map the fluorescence lifetime as a function of distance from a buffer/air and buffer/oil interface. Preliminary data show that the fluorescence lifetime of fluorescein increases near a buffer/air interface and decreases near a buffer/oil interface. The range over which this fluorescence lifetime change occurs is found to be of the order several μm which is consistent with a theoretical model based on the full width at half maximum of the emission spectrum proposed by Toptygin

Blinking fluorescence of single donor-acceptor pairs: important role of "dark'' states in resonance energy transfer via singlet levels.

Science.gov (United States)

Osad'ko, I S; Shchukina, A L

2012-06-01

The influence of triplet levels on Förster resonance energy transfer via singlet levels in donor-acceptor (D-A) pairs is studied. Four types of D-A pair are considered: (i) two-level donor and two-level acceptor, (ii) three-level donor and two-level acceptor, (iii) two-level donor and three-level acceptor, and (iv) three-level donor and three-level acceptor. If singlet-triplet transitions in a three-level acceptor molecule are ineffective, the energy transfer efficiency E=I_{A}/(I_{A}+I_{D}), where I_{D} and I_{A} are the average intensities of donor and acceptor fluorescence, can be described by the simple theoretical equation E(F)=FT_{D}/(1+FT_{D}). Here F is the rate of energy transfer, and T_{D} is the donor fluorescence lifetime. In accordance with the last equation, 100% of the donor electronic energy can be transferred to an acceptor molecule at FT_{D}≫1. However, if singlet-triplet transitions in a three-level acceptor molecule are effective, the energy transfer efficiency is described by another theoretical equation, E(F)=F[over ¯](F)T_{D}/[1+F[over ¯](F)T_{D}]. Here F[over ¯](F) is a function of F depending on singlet-triplet transitions in both donor and acceptor molecules. Expressions for the functions F[over ¯](F) are derived. In this case the energy transfer efficiency will be far from 100% even at FT_{D}≫1. The character of the intensity fluctuations of donor and acceptor fluorescence indicates which of the two equations for E(F) should be used to find the value of the rate F. Therefore, random time instants of photon emission in both donor and acceptor fluorescence are calculated by the Monte Carlo method for all four types of D-A pair. Theoretical expressions for start-stop correlators (waiting time distributions) in donor and acceptor fluorescence are derived. The probabilities w_{N}^{D}(t) and w_{N}^{A}(t) of finding N photons of donor and acceptor fluorescence in the time interval t are calculated for various values of the energy

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

International Nuclear Information System (INIS)

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

2009-01-01

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

Parallel ion flow velocity measurement using laser induced fluorescence method in an electron cyclotron resonance plasma

International Nuclear Information System (INIS)

Yoshimura, Shinji; Okamoto, Atsushi; Terasaka, Kenichiro; Ogiwara, Kohei; Tanaka, Masayoshi Y.; Aramaki, Mitsutoshi

2010-01-01

Parallel ion flow velocity along a magnetic field has been measured using a laser induced fluorescence (LIF) method in an electron cyclotron resonance (ECR) argon plasma with a weakly-diverging magnetic field. To measure parallel flow velocity in a cylindrical plasma using the LIF method, the laser beam should be injected along device axis; however, the reflection of the incident beam causes interference between the LIF emission of the incident and reflected beams. Here we present a method of quasi-parallel laser injection at a small angle, which utilizes the reflected beam as well as the incident beam to obtain the parallel ion flow velocity. Using this method, we observed an increase in parallel ion flow velocity along the magnetic field. The acceleration mechanism is briefly discussed on the basis of the ion fluid model. (author)

Comparison of nuclear electric resonance and nuclear magnetic resonance in integer and fractional quantum Hall states

International Nuclear Information System (INIS)

Tomimatsu, Toru; Shirai, Shota; Hashimoto, Katsushi; Sato, Ken; Hirayama, Yoshiro

2015-01-01

Electric-field-induced nuclear resonance (NER: nuclear electric resonance) involving quantum Hall states (QHSs) was studied at various filling factors by exploiting changes in nuclear spins polarized at quantum Hall breakdown. Distinct from the magnetic dipole interaction in nuclear magnetic resonance, the interaction of the electric-field gradient with the electric quadrupole moment plays the dominant role in the NER mechanism. The magnitude of the NER signal strongly depends on whether electronic states are localized or extended. This indicates that NER is sensitive to the screening capability of the electric field associated with QHSs

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

Directory of Open Access Journals (Sweden)

Guanhua Du

2011-12-01

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

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

Science.gov (United States)

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

2006-03-01

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

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...

Bright and photostable nitrogen-vacancy fluorescence from unprocessed detonation nanodiamond.

Science.gov (United States)

Reineck, P; Capelli, M; Lau, D W M; Jeske, J; Field, M R; Ohshima, T; Greentree, A D; Gibson, B C

2017-01-05

Bright and photostable fluorescence from nitrogen-vacancy (NV) centers is demonstrated in unprocessed detonation nanodiamond particle aggregates. The optical properties of these particles is analyzed using confocal fluorescence microscopy and spectroscopy, time resolved fluorescence decay measurements, and optically detected magnetic resonance experiments. Two particle populations with distinct optical properties are identified and compared to high-pressure high-temperature (HPHT) fluorescent nanodiamonds. We find that the brightness of one detonation nanodiamond particle population is on the same order as that of highly processed fluorescent 100 nm HPHT nanodiamonds. Our results may open the path to a simple and up-scalable route for the production of fluorescent NV nanodiamonds for use in bioimaging applications.

Alternate gram staining technique using a fluorescent lectin.

Science.gov (United States)

Sizemore, R K; Caldwell, J J; Kendrick, A S

1990-01-01

Fluorescence-labeled wheat germ agglutinin binds specifically to N-acetylglucosamine in the outer peptidoglycan layer of gram-positive bacteria. The peptidoglycan layer of gram-negative bacteria is covered by a membrane and is not labeled by the lectin. By exploiting this phenomenon, an alternative Gram staining technique has been developed. Images PMID:1697149

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-07-15

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

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

Science.gov (United States)

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

2012-01-03

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

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

Science.gov (United States)

Singharoy, Dipti; Bhattacharya, Subhash Chandra

2017-12-01

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

A Brief Introduction to Single-Molecule Fluorescence Methods.

Science.gov (United States)

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

2018-01-01

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

Statistical uncertainties of nondestructive assay for spent nuclear fuel by using nuclear resonance fluorescence

Energy Technology Data Exchange (ETDEWEB)

Shizuma, Toshiyuki, E-mail: shizuma.toshiyuki@jaea.go.jp [Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Hayakawa, Takehito; Angell, Christopher T.; Hajima, Ryoichi [Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Minato, Futoshi; Suyama, Kenya [Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Seya, Michio [Integrated Support Center for Nuclear Nonproliferation and Nuclear Security, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1198 (Japan); Johnson, Micah S. [Lawrence Livermore National Laboratory, 7000 East Ave. Livermore, CA 94550 (United States); Department of Physics and Astronomy, San Jose State University, One Washington Square, San Jose, CA 9519 (United States); McNabb, Dennis P. [Lawrence Livermore National Laboratory, 7000 East Ave. Livermore, CA 94550 (United States)

2014-02-11

We estimated statistical uncertainties of a nondestructive assay system using nuclear resonance fluorescence (NRF) for spent nuclear fuel including low-concentrations of actinide nuclei with an intense, mono-energetic photon beam. Background counts from radioactive materials inside the spent fuel were calculated with the ORIGEN2.2-UPJ burn-up computer code. Coherent scattering contribution associated with Rayleigh, nuclear Thomson, and Delbrück scattering was also considered. The energy of the coherent scattering overlaps with that of NRF transitions to the ground state. Here, we propose to measure NRF transitions to the first excited state to avoid the coherent scattering contribution. Assuming that the total NRF cross-sections are in the range of 3–100 eV b at excitation energies of 2.25, 3.5, and 5 MeV, statistical uncertainties of the NRF measurement were estimated. We concluded that it is possible to assay 1% actinide content in the spent fuel with 2.2–3.2% statistical precision during 4000 s measurement time for the total integrated cross-section of 30 eV b at excitation energies of 3.5–5 MeV by using a photon beam with an intensity of 10{sup 6} photons/s/eV. We also examined both the experimental and theoretical NRF cross-sections for actinide nuclei. The calculation based on the quasi-particle random phase approximation suggests the existence of strong magnetic dipole resonances at excitation energies ranging from 2 to 6 MeV with the scattering cross-sections of tens eV b around 5 MeV in {sup 238}U.

Resonance – Journal of Science Education | Indian Academy of ...

Indian Academy of Sciences (India)

Home; Journals; Resonance – Journal of Science Education. Deepa Khushalani. Articles written in Resonance – Journal of Science Education. Volume 23 Issue 3 March 2018 pp 355-369 General Article. Exploiting Sun's Energy Effectively as a Source of Renewable Energy · Deepa Khushalani · More Details Abstract ...

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

Science.gov (United States)

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

2005-01-01

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

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

Science.gov (United States)

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

2002-01-01

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

Consensual exploitation : the moral wrong in exploitation and legal restrictions on consensual exploitative transactions

OpenAIRE

van der Neut, Wendy

2014-01-01

This thesis is about so-­‐called consensual exploitative transactions: transactions to which all parties agree voluntarily, and which are beneficial for all parties, but which are still widely considered exploitative, and for that reason legally restricted in many countries. The thesis asks two main questions: 1. What is wrong with consensual exploitation? 2.What implications does the answer to this question have for the legal restriction of consensual transactions ...

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

Science.gov (United States)

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

2015-03-15

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

Synthesis and bio-applications of targeted magnetic-fluorescent composite nanoparticles

International Nuclear Information System (INIS)

Xia, Hui; Tong, Ruijie; Song, Yanling; Xiong, Fang; Li, Jiman; Wang, Shichao; Fu, Huihui; Wen, Jirui; Li, Dongze; Zeng, Ye; Zhao, Zhiwei; Wu, Jiang

2017-01-01

Magnetic-fluorescent nanoparticles have a tremendous potential in biology. As the benefits of these materials gained recognition, increasing attention has been given to the conjugation of magnetic-fluorescent nanoparticles with targeting ligands. The magnetic and fluorescent properties of nanoparticles offer several functionalities, including imaging, separation, and visualization, while the presence of a targeting ligand allows for selective cell and tissue targeting. In this review, methods for the synthesis of targeted magnetic-fluorescent nanoparticles are explored, and recent applications of these nanocomposites to the detection and separation of biomolecules, fluorescent and magnetic resonance imaging, and cancer diagnosis and treatment will be summarized. As these materials are further optimized, targeted magnetic-fluorescent nanoparticles hold great promise for the diagnosis and treatment of some diseases.

Synthesis and bio-applications of targeted magnetic-fluorescent composite nanoparticles

Science.gov (United States)

Xia, Hui; Tong, Ruijie; Song, Yanling; Xiong, Fang; Li, Jiman; Wang, Shichao; Fu, Huihui; Wen, Jirui; Li, Dongze; Zeng, Ye; Zhao, Zhiwei; Wu, Jiang

2017-04-01

Magnetic-fluorescent nanoparticles have a tremendous potential in biology. As the benefits of these materials gained recognition, increasing attention has been given to the conjugation of magnetic-fluorescent nanoparticles with targeting ligands. The magnetic and fluorescent properties of nanoparticles offer several functionalities, including imaging, separation, and visualization, while the presence of a targeting ligand allows for selective cell and tissue targeting. In this review, methods for the synthesis of targeted magnetic-fluorescent nanoparticles are explored, and recent applications of these nanocomposites to the detection and separation of biomolecules, fluorescent and magnetic resonance imaging, and cancer diagnosis and treatment will be summarized. As these materials are further optimized, targeted magnetic-fluorescent nanoparticles hold great promise for the diagnosis and treatment of some diseases.

Synthesis and bio-applications of targeted magnetic-fluorescent composite nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Xia, Hui; Tong, Ruijie [Sichuan University, West China Medical Center (China); Song, Yanling [Shenyang University of Chemical Technology, College of Pharmaceutical and Biological Engineering (China); Xiong, Fang [Sichuan University, West China College of Stomatology (China); Li, Jiman [Sichuan Cancer Hospital, Pathology Department (China); Wang, Shichao; Fu, Huihui; Wen, Jirui; Li, Dongze; Zeng, Ye; Zhao, Zhiwei, E-mail: zzw2002400@126.com; Wu, Jiang, E-mail: jw@scu.edu.cn [Sichuan University, West China Medical Center (China)

2017-04-15

Magnetic-fluorescent nanoparticles have a tremendous potential in biology. As the benefits of these materials gained recognition, increasing attention has been given to the conjugation of magnetic-fluorescent nanoparticles with targeting ligands. The magnetic and fluorescent properties of nanoparticles offer several functionalities, including imaging, separation, and visualization, while the presence of a targeting ligand allows for selective cell and tissue targeting. In this review, methods for the synthesis of targeted magnetic-fluorescent nanoparticles are explored, and recent applications of these nanocomposites to the detection and separation of biomolecules, fluorescent and magnetic resonance imaging, and cancer diagnosis and treatment will be summarized. As these materials are further optimized, targeted magnetic-fluorescent nanoparticles hold great promise for the diagnosis and treatment of some diseases.

Exploiting jet binning to identify the initial state of high-mass resonances

Science.gov (United States)

Ebert, Markus A.; Liebler, Stefan; Moult, Ian; Stewart, Iain W.; Tackmann, Frank J.; Tackmann, Kerstin; Zeune, Lisa

2016-09-01

If a new high-mass resonance is discovered at the Large Hadron Collider, model-independent techniques to identify the production mechanism will be crucial to understand its nature and effective couplings to Standard Model particles. We present a powerful and model-independent method to infer the initial state in the production of any high-mass color-singlet system by using a tight veto on accompanying hadronic jets to divide the data into two mutually exclusive event samples (jet bins). For a resonance of several hundred GeV, the jet binning cut needed to discriminate quark and gluon initial states is in the experimentally accessible range of several tens of GeV. It also yields comparable cross sections for both bins, making this method viable already with the small event samples available shortly after a discovery. Theoretically, the method is made feasible by utilizing an effective field theory setup to compute the jet cut dependence precisely and model independently and to systematically control all sources of theoretical uncertainties in the jet binning, as well as their correlations. We use a 750 GeV scalar resonance as an example to demonstrate the viability of our method.

Exploiting jet binning to identify the initial state of high-mass resonances

International Nuclear Information System (INIS)

Ebert, Markus A.; Liebler, Stefan; Tackmann, Frank J.; Tackmann, Kerstin; Moult, Ian; Stewart, Iain W.; Zeune, Lisa

2016-05-01

If a new high-mass resonance is discovered at the Large Hadron Collider, model-independent techniques to identify the production mechanism will be crucial to understand its nature and effective couplings to Standard Model particles. We present a powerful and model-independent method to infer the initial state in the production of any high-mass color-singlet system by using a tight veto on accompanying hadronic jets to divide the data into two mutually exclusive event samples (jet bins). For a resonance of several hundred GeV, the jet binning cut needed to discriminate quark and gluon initial states is in the experimentally accessible range of several tens of GeV. It also yields comparable cross sections for both bins, making this method viable already with the small event samples available shortly after a discovery. Theoretically, the method is made feasible by utilizing an effective field theory setup to compute the jet cut dependence precisely and model-independently and to systematically control all sources of theoretical uncertainties in the jet binning, as well as their correlations. We use a 750 GeV scalar resonance as an example to demonstrate the viability of our method.

Fluorescence imaging as a diagnostic of M-band x-ray drive condition in hohlraum with fluorescent Si targets

International Nuclear Information System (INIS)

Li, Qi; Hu, Zhimin; Yao, Li; Huang, Chengwu; Yuan, Zheng; Zhao, Yang; Xiong, Gang; Qing, Bo; Lv, Min; Zhu, Tuo; Deng, Bo; Li, Jin; Wei, Minxi; Zhan, Xiayu; Li, Jun; Yang, Yimeng; Su, Chunxiao; Yang, Guohong; Zhang, Jiyan; Li, Sanwei

2017-01-01

Fluorescence imaging of surrogate Si-doped CH targets has been used to provide a measurement for drive condition of high-energy x-ray (i.e. M-band x-ray) drive symmetry upon the capsule in hohlraum on Shenguang-II laser facility. A series of experiments dedicated to the study of photo-pumping and fluorescence effect in Si-plasma are presented. To investigate the feasibility of fluorescence imaging in Si-plasma, an silicon plasma in Si-foil target is pre-formed at ground state by the soft x-ray from a half-hohlraum, which is then photo-pumped by the K-shell lines from a spatially distinct laser-produced Si-plasma. The resonant Si photon pump is used to improve the fluorescence signal and cause visible image in the Si-foil. Preliminary fluorescence imaging of Si-ball target is performed in both Si-doped and pure Au hohlraum. The usual capsule at the center of the hohlraum is replaced with a solid Si-doped CH-ball (Si-ball). Since the fluorescence is proportional to the photon pump upon the Si-plasma, high-energy x-ray drive symmetry is equal to the fluorescence distribution of the Si-ball. (paper)

Studies of fluorescence and Auger decay following inner-shell photoionization

International Nuclear Information System (INIS)

Levin, J.C.; Armen, G.B.

2004-01-01

Near inner-shell absorption edges, Auger and fluorescence spectra which characterize the first step of a complex cascade process exhibit properties which are well described by radiationless and radiative resonant Raman scattering theory. We present comparisons of our recent data and theory for Auger decay of argon K vacancies, xenon L vacancies, and of fluorescence decay of xenon L vacancies. A theoretical unification of Auger decay and fluorescence decay is presented which clarifies the similarities and differences between the two processes

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

DEFF Research Database (Denmark)

Gholami, Somayeh; Kompany Zare, Mohsen

2013-01-01

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

Resonant metallic nanostructures for enhanced terahertz spectroscopy

KAUST Repository

Toma, A.; Tuccio, S.; Prato, M.; De Donato, F.; Perucchi, A.; Di Pietro, P.; Marras, S.; Liberale, Carlo; Zaccaria, R. Proietti; De Angelis, F.; Manna, L.; Lupi, S.; Di Fabrizio, Enzo M.; Razzari, L.

2015-01-01

We present our recent studies on terahertz resonant dipole nanoantennas. Exploiting the localization and enhancement capabilities of these devices, we introduce an effective method to perform terahertz spectroscopy on an extremely small number

Polarization of fluorescence: a probe of molecular autoionization

International Nuclear Information System (INIS)

Leroi, G.E.; Dehmer, J.L.; Parr, A.C.; Poliakoff, E.D.

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 CO 2 and CS 2 are presented as examples

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

Energy Technology Data Exchange (ETDEWEB)

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

2012-10-15

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

Two photon versus one photon fluorescence excitation in whispering gallery mode microresonators

International Nuclear Information System (INIS)

Pastells, Carme; Marco, M.-Pilar; Merino, David; Loza-Alvarez, Pablo; Pasquardini, Laura; Lunelli, Lorenzo; Pederzolli, Cecilia; Daldosso, Nicola; Farnesi, Daniele; Berneschi, Simone; Righini, Giancarlo C.; Quercioli, Franco; Nunzi Conti, Gualtiero; Soria, Silvia

2016-01-01

We investigate the feasibility of both one photon and two photon fluorescence excitation using whispering gallery mode microresonators. We report the linear and non linear fluorescence real-time detection of labeled IgG covalently bonded to the surface of a silica whispering gallery mode resonator (WGMR). The immunoreagents have been immobilized onto the surface of the WGMR sensor after being activated with an epoxy silane and an orienting layer. The developed immunosensor presents great potential as a robust sensing device for fast and early detection of immunoreactions. We also investigate the potential of microbubbles as nonlinear enhancement platform. The dyes used in these studies are dylight800, tetramethyl rhodamine isothiocyanate, rhodamine 6G and fluorescein. All measurements were performed in a modified confocal microscope. - Highlights: • One photon fluorescence overlaps with the semiconductor pump laser gain bandwidth. • We report on the feasibility to excite two photon fluorescence in microbubble resonators. • Our functionalization process maintains a good quality factor of the microresonator.

Two photon versus one photon fluorescence excitation in whispering gallery mode microresonators

Energy Technology Data Exchange (ETDEWEB)

Pastells, Carme; Marco, M.-Pilar [Nanobiotechnology for Diagnostics Group (Nb4Dg), IQAC-CSIC, 08034 Barcelona (Spain); CIBER de Bioingeniería, Biomateriales y Nanomedicina, 08034 Barcelona (Spain); Merino, David; Loza-Alvarez, Pablo [ICFO-Institut de Ciències Fotòniques, Castelldefels, 08860 Barcelona (Spain); Pasquardini, Laura [Fondazione Bruno Kessler, 38123 Povo, TN (Italy); Lunelli, Lorenzo [Fondazione Bruno Kessler, 38123 Povo, TN (Italy); IBF-CNR, 38123 Povo, TN (Italy); Pederzolli, Cecilia [Fondazione Bruno Kessler, 38123 Povo, TN (Italy); Daldosso, Nicola [Department of Computer Science, University of Verona, Strada le Grazie 15, 37134 Verona (Italy); Farnesi, Daniele [CNR-IFAC “Nello Carrara” Institute of Applied Physics, 50019 Sesto Fiorentino, FI (Italy); Museo Storico della Fisica e Centro Studi e Ricerche “E. Fermi”, 00184 Roma (Italy); Berneschi, Simone [CNR-IFAC “Nello Carrara” Institute of Applied Physics, 50019 Sesto Fiorentino, FI (Italy); Righini, Giancarlo C. [CNR-IFAC “Nello Carrara” Institute of Applied Physics, 50019 Sesto Fiorentino, FI (Italy); Museo Storico della Fisica e Centro Studi e Ricerche “E. Fermi”, 00184 Roma (Italy); Quercioli, Franco [CNR-INO National Institute of Optics, Sesto Fiorentino, FI (Italy); Nunzi Conti, Gualtiero [CNR-IFAC “Nello Carrara” Institute of Applied Physics, 50019 Sesto Fiorentino, FI (Italy); Soria, Silvia, E-mail: s.soria@ifac.cnr.it [CNR-IFAC “Nello Carrara” Institute of Applied Physics, 50019 Sesto Fiorentino, FI (Italy)

2016-02-15

We investigate the feasibility of both one photon and two photon fluorescence excitation using whispering gallery mode microresonators. We report the linear and non linear fluorescence real-time detection of labeled IgG covalently bonded to the surface of a silica whispering gallery mode resonator (WGMR). The immunoreagents have been immobilized onto the surface of the WGMR sensor after being activated with an epoxy silane and an orienting layer. The developed immunosensor presents great potential as a robust sensing device for fast and early detection of immunoreactions. We also investigate the potential of microbubbles as nonlinear enhancement platform. The dyes used in these studies are dylight800, tetramethyl rhodamine isothiocyanate, rhodamine 6G and fluorescein. All measurements were performed in a modified confocal microscope. - Highlights: • One photon fluorescence overlaps with the semiconductor pump laser gain bandwidth. • We report on the feasibility to excite two photon fluorescence in microbubble resonators. • Our functionalization process maintains a good quality factor of the microresonator.

Time-resolved UV-excited microarray reader for fluorescence energy transfer (FRET) measurements

Science.gov (United States)

Orellana, Adelina; Hokkanen, Ari P.; Pastinen, Tomi; Takkinen, Kristina; Soderlund, Hans

2001-05-01

Analytical systems based on immunochemistry are largely used in medical diagnostics and in biotechnology. There is a significant pressure to develop the present assay formats to become easier to use, faster, and less reagent consuming. Further developments towards high density array--like multianalyte measurement systems would be valuable. To this aim we have studied the applicability of fluorescence resonance energy transfer and time-resolved fluorescence resonance energy transfer in immunoassays on microspots and in microwells. We have used engineered recombinant antibodies detecting the pentameric protein CRP as a model analyte system, and tested different assay formats. We describe also the construction of a time-resolved scanning epifluorometer with which we could measure the FRET interaction between the slow fluorescence decay from europium chelates and its energy transfer to the rapidly decaying fluorophore Cy5.

Comparison of different Bremsstrahlung converters and collimators for Nuclear Resonance Fluorescence setup at IFUSP

International Nuclear Information System (INIS)

Lopez, P.N; Corrales, Y.; Manso Guevara, M.V; Martins, M.N.

2007-01-01

Nuclear Resonance Fluorescence (NRF) setup will install in the new electron accelerator, which is in final stage of installation at the Physics Institute of Sao Paulo University (IFUSP). The Bremsstrahlung facility and the setup for photon scattering should be designed such that the background radiation caused by scattering photons and the production of neutrons is minimized. In this order the Monte Carlo simulation studies show the best options for the different elements of the NRF setup, and how to link these elements to the particularities of the irradiation room. In the present stage the simulations has been included the studies of different Bremsstrahlung converters and collimators. Several materials (Ta, W, Au, Nb, Cu) for Bremsstrahlung converters were studied. Detailed analyses of intensity as well as the opening angles of Bremsstrahlung radiation were carried out, for different converter thickness. For the collimator two materials (Cu and Pb) were studied in the simulations. Several opening angles and thickness (40 - 100 cm) were studied. The Bremsstrahlung beam collimation for different energy bins, and the photon scattering from the collimator ,were used as quality parameters of the collimators. (Author)

Induced Förster resonance energy transfer by encapsulation of DNA-scaffold based probes inside a plant virus based protein cage

Science.gov (United States)

de Ruiter, Mark V.; Overeem, Nico J.; Singhai, Gaurav; Cornelissen, Jeroen J. L. M.

2018-05-01

Insight into the assembly and disassembly of viruses can play a crucial role in developing cures for viral diseases. Specialized fluorescent probes can benefit the study of interactions within viruses, especially during cell studies. In this work, we developed a strategy based on Förster resonance energy transfer (FRET) to study the assembly of viruses without labeling the exterior of viruses. Instead, we exploit their encapsulation of nucleic cargo, using three different fluorescent ATTO dyes linked to single-stranded DNA oligomers, which are hybridised to a longer DNA strand. FRET is induced upon assembly of the cowpea chlorotic mottle virus, which forms monodisperse icosahedral particles of about 22 nm, thereby increasing the FRET efficiency by a factor of 8. Additionally, encapsulation of the dyes in virus-like particles induces a two-step FRET. When the formed constructs are disassembled, this FRET signal is fully reduced to the value before encapsulation. This reversible behavior makes the system a good probe for studying viral assembly and disassembly. It, furthermore, shows that multi-component supramolecular materials are stabilized in the confinement of a protein cage.

Resonant metallic nanostructures for enhanced terahertz spectroscopy

KAUST Repository

Toma, A.

2015-11-12

We present our recent studies on terahertz resonant dipole nanoantennas. Exploiting the localization and enhancement capabilities of these devices, we introduce an effective method to perform terahertz spectroscopy on an extremely small number of nano-objects.

Cryogenic Preamplifiers for Magnetic Resonance Imaging

DEFF Research Database (Denmark)

Johansen, Daniel H.; Sanchez-Heredia, Juan D.; Petersen, Jan R.

2018-01-01

Pursuing the ultimate limit of detection in magnetic resonance imaging (MRI) requires cryogenics to decrease the thermal noise of the electronic circuits. As cryogenic coils for MRI are slowly emerging cryogenic preamplifiers are required to fully exploit their potential. A cryogenic preamplifier...

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

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.

Fluorescent S-layer fusion proteins

International Nuclear Information System (INIS)

Kainz, B.

2010-01-01

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

Mode Coupling and Nonlinear Resonances of MEMS Arch Resonators for Bandpass Filters

KAUST Repository

Hajjaj, Amal Z.

2017-01-30

We experimentally demonstrate an exploitation of the nonlinear softening, hardening, and veering phenomena (near crossing), where the frequencies of two vibration modes get close to each other, to realize a bandpass filter of sharp roll off from the passband to the stopband. The concept is demonstrated based on an electrothermally tuned and electrostatically driven MEMS arch resonator operated in air. The in-plane resonator is fabricated from a silicon-on-insulator wafer with a deliberate curvature to form an arch shape. A DC current is applied through the resonator to induce heat and modulate its stiffness, and hence its resonance frequencies. We show that the first resonance frequency increases up to twice of the initial value while the third resonance frequency decreases until getting very close to the first resonance frequency. This leads to the phenomenon of veering, where both modes get coupled and exchange energy. We demonstrate that by driving both modes nonlinearly and electrostatically near the veering regime, such that the first and third modes exhibit softening and hardening behavior, respectively, sharp roll off from the passband to the stopband is achievable. We show a flat, wide, and tunable bandwidth and center frequency by controlling the electrothermal actuation voltage.

Microring resonator based modulator made by direct photodefinition of an electro-optic polymer

NARCIS (Netherlands)

Lam, Nghi Q.; Balakrishnan, M.; Faccini, M.; Diemeer, Mart; Klein, E.J.; Sengo, G.; Sengo, G.; Driessen, A.; Verboom, Willem; Reinhoudt, David

2008-01-01

A laterally coupled microring resonator was fabricated by direct photodefinition of negative photoresist SU8, containing tricyanovinylidenediphenylaminobenzene chromophore, by exploiting the low ultraviolet absorption window of this chromophore. The ring resonator was first photodefined by slight

Fluorescent nanodiamond-bacteriophage conjugates maintain host specificity.

Science.gov (United States)

Trinh, Jimmy T; Alkahtani, Masfer H; Rampersaud, Isaac; Rampersaud, Arfaan; Scully, Marlan; Young, Ryland F; Hemmer, Philip; Zeng, Lanying

2018-06-01

Rapid identification of specific bacterial strains within clinical, environmental, and food samples can facilitate the prevention and treatment of disease. Fluorescent nanodiamonds (FNDs) are being developed as biomarkers in biology and medicine, due to their excellent imaging properties, ability to accept surface modifications, and lack of toxicity. Bacteriophages, the viruses of bacteria, can have exquisite specificity for certain hosts. We propose to exploit the properties of FNDs and phages to develop phages conjugated with FNDs as long-lived fluorescent diagnostic reagents. In this study, we develop a simple procedure to create such fluorescent probes by functionalizing the FNDs and phages with streptavidin and biotin, respectively. We find that the FND-phage conjugates retain the favorable characteristics of the individual components and can discern their proper host within a mixture. This technology may be further explored using different phage/bacteria systems, different FND color centers and alternate chemical labeling schemes for additional means of bacterial identification and new single-cell/virus studies. © 2018 Wiley Periodicals, Inc.

Engineering and exploitation of a fluorescent HIV-1 gp120 for live cell CD4 binding assays

Energy Technology Data Exchange (ETDEWEB)

Costantini, Lindsey M. [Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461 (United States); Irvin, Susan C. [Department of Pediatrics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461 (United States); Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461 (United States); Kennedy, Steven C. [Department of Pediatrics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461 (United States); Guo, Feng [Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461 (United States); Goldstein, Harris; Herold, Betsy C. [Department of Pediatrics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461 (United States); Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461 (United States); Snapp, Erik L., E-mail: erik-lee.snapp@einstein.yu.edu [Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461 (United States)

2015-02-15

The HIV-1 envelope glycoprotein, gp120, binds the host cell receptor, CD4, in the initial step of HIV viral entry and infection. This process is an appealing target for the development of inhibitory drugs and neutralizing antibodies. To study gp120 binding and intracellular trafficking, we engineered a fluorescent fusion of the humanized gp120 JRFL HIV-1 variant and GFP. Gp120-sfGFP is glycosylated with human sugars, robustly expressed, and secreted from cultured human cells. Protein dynamics, quality control, and trafficking can be visualized in live cells. The fusion protein can be readily modified with different gp120 variants or fluorescent proteins. Finally, secreted gp120-sfGFP enables a sensitive and easy binding assay that can quantitatively screen potential inhibitors of gp120-CD4 binding on live cells via fluorescence imaging or laser scanning cytometry. This adaptable research tool should aid in studies of gp120 cell biology and the development of novel anti-HIV drugs. - Highlights: • Development of fluorescent protein labeled HIV-1 envelope gp120. • Imaging of gp120 dynamics and trafficking in live cells. • Quantitative visual assay of antibody-mediated inhibition of gp120 binding to CD4 on live cells.

Engineering and exploitation of a fluorescent HIV-1 gp120 for live cell CD4 binding assays

International Nuclear Information System (INIS)

Costantini, Lindsey M.; Irvin, Susan C.; Kennedy, Steven C.; Guo, Feng; Goldstein, Harris; Herold, Betsy C.; Snapp, Erik L.

2015-01-01

The HIV-1 envelope glycoprotein, gp120, binds the host cell receptor, CD4, in the initial step of HIV viral entry and infection. This process is an appealing target for the development of inhibitory drugs and neutralizing antibodies. To study gp120 binding and intracellular trafficking, we engineered a fluorescent fusion of the humanized gp120 JRFL HIV-1 variant and GFP. Gp120-sfGFP is glycosylated with human sugars, robustly expressed, and secreted from cultured human cells. Protein dynamics, quality control, and trafficking can be visualized in live cells. The fusion protein can be readily modified with different gp120 variants or fluorescent proteins. Finally, secreted gp120-sfGFP enables a sensitive and easy binding assay that can quantitatively screen potential inhibitors of gp120-CD4 binding on live cells via fluorescence imaging or laser scanning cytometry. This adaptable research tool should aid in studies of gp120 cell biology and the development of novel anti-HIV drugs. - Highlights: • Development of fluorescent protein labeled HIV-1 envelope gp120. • Imaging of gp120 dynamics and trafficking in live cells. • Quantitative visual assay of antibody-mediated inhibition of gp120 binding to CD4 on live cells

A Fluorescent Thermometer Based on a Pyrene-Labeled Thermoresponsive Polymer

Directory of Open Access Journals (Sweden)

Ulrich S. Schubert

2010-08-01

Full Text Available Thermoresponsive polymers that undergo a solubility transition by variation of the temperature are important materials for the development of ‘smart’ materials. In this contribution we exploit the solubility phase transition of poly(methoxy diethylene glycol methacrylate, which is accompanied by a transition from hydrophilic to hydrophobic, for the development of a fluorescent thermometer. To translate the polymer phase transition into a fluorescent response, the polymer was functionalized with pyrene resulting in a change of the emission based on the microenvironment. This approach led to a soluble polymeric fluorescent thermometer with a temperature range from 11 °C to 21 °C. The polymer phase transition that occurs during sensing is studied in detail by dynamic light scattering.

Plasmonic enhancement of ultraviolet fluorescence

Science.gov (United States)

Jiao, Xiaojin

Plasmonics relates to the interaction between electromagnetic radiation and conduction electrons at metallic interfaces or in metallic nanostructures. Surface plasmons are collective electron oscillations at a metal surface, which can be manipulated by shape, texture and material composition. Plasmonic applications cover a broad spectrum from visible to near infrared, including biosensing, nanolithography, spectroscopy, optoelectronics, photovoltaics and so on. However, there remains a gap in this activity in the ultraviolet (UV, research. Motivating factors in the study of UV Plasmonics are the direct access to biomolecular resonances and native fluorescence, resonant Raman scattering interactions, and the potential for exerting control over photochemical reactions. This dissertation aims to fill in the gap of Plasmonics in the UV with efforts of design, fabrication and characterization of aluminium (Al) and magnesium (Mg) nanostructures for the application of label-free bimolecular detection via native UV fluorescence. The first contribution of this dissertation addresses the design of Al nanostructures in the context of UV fluorescence enhancement. A design method that combines analytical analysis with numerical simulation has been developed. Performance of three canonical plasmonic structures---the dipole antenna, bullseye nanoaperture and nanoaperture array---has been compared. The optimal geometrical parameters have been determined. A novel design of a compound bullseye structure has been proposed and numerically analyzed for the purpose of compensating for the large Stokes shift typical of UV fluorescence. Second, UV lifetime modification of diffusing molecules by Al nanoapertures has been experimentally demonstrated for the first time. Lifetime reductions of ~3.5x have been observed for the high quantum yield (QY) laser dye p-terphenyl in a 60 nm diameter aperture with 50 nm undercut. Furthermore, quantum-yield-dependence of lifetime reduction has been

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...

A comparison of rapid-scanning X-ray fluorescence mapping and magnetic resonance imaging to localize brain iron distribution

International Nuclear Information System (INIS)

McCrea, Richard P.E.; Harder, Sheri L.; Martin, Melanie; Buist, Richard; Nichol, Helen

2008-01-01

The clinical diagnosis of many neurodegenerative disorders relies primarily or exclusively on observed behaviors rather than measurable physical tests. One of the hallmarks of Alzheimer disease (AD) is the presence of amyloid-containing plaques associated with deposits of iron, copper and/or zinc. Work in other laboratories has shown that iron-rich plaques can be seen in the mouse brain in vivo with magnetic resonance imaging (MRI) using a high-field strength magnet but this iron cannot be visualized in humans using clinical magnets. To improve the interpretation of MRI, we correlated iron accumulation visualized by X-ray fluorescence spectroscopy, an element-specific technique with T1, T2, and susceptibility weighted MR (SWI) in a mouse model of AD. We show that SWI best shows areas of increased iron accumulation when compared to standard sequences

The Ethics of Exploitation

Directory of Open Access Journals (Sweden)

Paul McLaughlin

2008-11-01

Full Text Available Philosophical inquiry into exploitation has two major deficiencies to date: it assumes that exploitation is wrong by definition; and it pays too much attention to the Marxian account of exploitation. Two senses of exploitation should be distinguished: the ‘moral’ or pejorative sense and the ‘non-moral’ or ‘non-prejudicial’ sense. By demonstrating the conceptual inadequacy of exploitation as defined in the first sense, and by defining exploitation adequately in the latter sense, we seek to demonstrate the moral complexity of exploitation. We contend, moreover, that moral evaluation of exploitation is only possible once we abandon a strictly Marxian framework and attempt, in the long run, to develop an integral ethic along Godwinian lines.

Financial Exploitation Is Associated With Structural and Functional Brain Differences in Healthy Older Adults.

Science.gov (United States)

Spreng, R Nathan; Cassidy, Benjamin N; Darboh, Bri S; DuPre, Elizabeth; Lockrow, Amber W; Setton, Roni; Turner, Gary R

2017-10-01

Age-related brain changes leading to altered socioemotional functioning may increase vulnerability to financial exploitation. If confirmed, this would suggest a novel mechanism leading to heightened financial exploitation risk in older adults. Development of predictive neural markers could facilitate increased vigilance and prevention. In this preliminary study, we sought to identify structural and functional brain differences associated with financial exploitation in older adults. Financially exploited older adults (n = 13, 7 female) and a matched cohort of older adults who had been exposed to, but avoided, a potentially exploitative situation (n = 13, 7 female) were evaluated. Using magnetic resonance imaging, we examined cortical thickness and resting state functional connectivity. Behavioral data were collected using standardized cognitive assessments, self-report measures of mood and social functioning. The exploited group showed cortical thinning in anterior insula and posterior superior temporal cortices, regions associated with processing affective and social information, respectively. Functional connectivity encompassing these regions, within default and salience networks, was reduced, while between network connectivity was increased. Self-reported anger and hostility was higher for the exploited group. We observed financial exploitation associated with brain differences in regions involved in socioemotional functioning. These exploratory and preliminary findings suggest that alterations in brain regions implicated in socioemotional functioning may be a marker of financial exploitation risk. Large-scale, prospective studies are necessary to validate this neural mechanism, and develop predictive markers for use in clinical practice. © The Author 2017. Published by Oxford University Press on behalf of The Gerontological Society of America.

Combined X-ray fluorescence and absorption computed tomography using a synchrotron beam

International Nuclear Information System (INIS)

Hall, C

2013-01-01

X-ray computed tomography (CT) and fluorescence X-ray computed tomography (FXCT) using synchrotron sources are both useful tools in biomedical imaging research. Synchrotron CT (SRCT) in its various forms is considered an important technique for biomedical imaging since the phase coherence of SR beams can be exploited to obtain images with high contrast resolution. Using a synchrotron as the source for FXCT ensures a fluorescence signal that is optimally detectable by exploiting the beam monochromaticity and polarisation. The ability to combine these techniques so that SRCT and FXCT images are collected simultaneously, would bring distinct benefits to certain biomedical experiments. Simultaneous image acquisition would alleviate some of the registration difficulties which comes from collecting separate data, and it would provide increased information about the sample: functional X-ray images from the FXCT, with the morphological information from the SRCT. A method is presented for generating simultaneous SRCT and FXCT images. Proof of principle modelling has been used to show that it is possible to recover a fluorescence image of a point-like source from an SRCT apparatus by suitably modulating the illuminating planar X-ray beam. The projection image can be successfully used for reconstruction by removing the static modulation from the sinogram in the normal flat and dark field processing. Detection of the modulated fluorescence signal using an energy resolving detector allows the position of a fluorescent marker to be obtained using inverse reconstruction techniques. A discussion is made of particular reconstruction methods which might be applied by utilising both the CT and FXCT data.

Resonance Energy Transfer Molecular Imaging Application in Biomedicine

Directory of Open Access Journals (Sweden)

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

2016-11-01

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

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

International Nuclear Information System (INIS)

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

2005-01-01

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

Tunable Magnetic Resonance in Microwave Spintronics Devices

Science.gov (United States)

Chen, Yunpeng; Fan, Xin; Xie, Yunsong; Zhou, Yang; Wang, Tao; Wilson, Jeffrey D.; Simons, Rainee N.; Chui, Sui-Tat; Xiao, John Q.

2015-01-01

Magnetic resonance is one of the key properties of magnetic materials for the application of microwave spintronics devices. The conventional method for tuning magnetic resonance is to use an electromagnet, which provides very limited tuning range. Hence, the quest for enhancing the magnetic resonance tuning range without using an electromagnet has attracted tremendous attention. In this paper, we exploit the huge exchange coupling field between magnetic interlayers, which is on the order of 4000 Oe and also the high frequency modes of coupled oscillators to enhance the tuning range. Furthermore, we demonstrate a new scheme to control the magnetic resonance frequency. Moreover, we report a shift in the magnetic resonance frequency as high as 20 GHz in CoFe based tunable microwave spintronics devices, which is 10X higher than conventional methods.

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.

Extraction of information on macromolecular interactions from fluorescence micro-spectroscopy measurements in the presence and absence of FRET

Science.gov (United States)

Raicu, Valerică

2018-06-01

Investigations of static or dynamic interactions between proteins or other biological macromolecules in living cells often rely on the use of fluorescent tags with two different colors in conjunction with adequate theoretical descriptions of Förster Resonance Energy Transfer (FRET) and molecular-level micro-spectroscopic technology. One such method based on these general principles is FRET spectrometry, which allows determination of the quaternary structure of biomolecules from cell-level images of the distributions, or spectra of occurrence frequency of FRET efficiencies. Subsequent refinements allowed combining FRET frequency spectra with molecular concentration information, thereby providing the proportion of molecular complexes with various quaternary structures as well as their binding/dissociation energies. In this paper, we build on the mathematical principles underlying FRET spectrometry to propose two new spectrometric methods, which have distinct advantages compared to other methods. One of these methods relies on statistical analysis of color mixing in subpopulations of fluorescently tagged molecules to probe molecular association stoichiometry, while the other exploits the color shift induced by FRET to also derive geometric information in addition to stoichiometry. The appeal of the first method stems from its sheer simplicity, while the strength of the second consists in its ability to provide structural information.

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

Energy Technology Data Exchange (ETDEWEB)

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

2007-09-21

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

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

International Nuclear Information System (INIS)

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

2007-01-01

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

Fluorescence and Magnetic Resonance Dual-Modality Imaging-Guided Photothermal and Photodynamic Dual-Therapy with Magnetic Porphyrin-Metal Organic Framework Nanocomposites

Science.gov (United States)

Zhang, Hui; Li, Yu-Hao; Chen, Yang; Wang, Man-Man; Wang, Xue-Sheng; Yin, Xue-Bo

2017-03-01

Phototherapy shows some unique advantages in clinical application, such as remote controllability, improved selectivity, and low bio-toxicity, than chemotherapy. In order to improve the safety and therapeutic efficacy, imaging-guided therapy seems particularly important because it integrates visible information to speculate the distribution and metabolism of the probe. Here we prepare biocompatible core-shell nanocomposites for dual-modality imaging-guided photothermal and photodynamic dual-therapy by the in situ growth of porphyrin-metal organic framework (PMOF) on Fe3O4@C core. Fe3O4@C core was used as T2-weighted magnetic resonance (MR) imaging and photothermal therapy (PTT) agent. The optical properties of porphyrin were well remained in PMOF, and PMOF was therefore selected for photodynamic therapy (PDT) and fluorescence imaging. Fluorescence and MR dual-modality imaging-guided PTT and PDT dual-therapy was confirmed with tumour-bearing mice as model. The high tumour accumulation of Fe3O4@C@PMOF and controllable light excitation at the tumour site achieved efficient cancer therapy, but low toxicity was observed to the normal tissues. The results demonstrated that Fe3O4@C@PMOF was a promising dual-imaging guided PTT and PDT dual-therapy platform for tumour diagnosis and treatment with low cytotoxicity and negligible in vivo toxicity.

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

Science.gov (United States)

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

2015-05-15

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

State-dependent fluorescence of neutral atoms in optical potentials

Science.gov (United States)

Martinez-Dorantes, M.; Alt, W.; Gallego, J.; Ghosh, S.; Ratschbacher, L.; Meschede, D.

2018-02-01

Recently we have demonstrated scalable, nondestructive, and high-fidelity detection of the internal state of 87Rb neutral atoms in optical dipole traps using state-dependent fluorescence imaging [M. Martinez-Dorantes, W. Alt, J. Gallego, S. Ghosh, L. Ratschbacher, Y. Völzke, and D. Meschede, Phys. Rev. Lett. 119, 180503 (2017), 10.1103/PhysRevLett.119.180503]. In this paper we provide experimental procedures and interpretations to overcome the detrimental effects of heating-induced trap losses and state leakage. We present models for the dynamics of optically trapped atoms during state-dependent fluorescence imaging and verify our results by comparing Monte Carlo simulations with experimental data. Our systematic study of dipole force fluctuations heating in optical traps during near-resonant illumination shows that off-resonant light is preferable for state detection in tightly confining optical potentials.

pH-responsive diblock copolymers with two different fluorescent labels for simultaneous monitoring of micellar self-assembly and degree of protonation

DEFF Research Database (Denmark)

Madsen, Jeppe; Madden, George; Themistou, Efrosyni

2018-01-01

methacrylate [PyMA] is statistically copolymerized with glycerolmonomethacrylate (GMA) to introduce a suitable fluorescent label. The chain-ends of the PDPA block are labelled with cresylviolet perchlorate [CV] by exploiting the spin trap properties of this dye molecule. Below pH 6, fluorescence from both...

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

Science.gov (United States)

Yuan, Shizhuang; Su, Wei; Wang, Enju

2017-09-01

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

Line broadening in multiphoton processes with a resonant intermediate transition

International Nuclear Information System (INIS)

Wang, C.C.; James, J.V.; Xia, J.

1983-01-01

The linewidth of the excitation spectrum for multiphoton ionization is found to be broadened much more severely than the cascade fluorescence originating from the resonant intermediate level. These results are due to the mutual effects of the ionizing and resonating transitions, which are not properly accounted for in perturbative treatments

Molecules for Fluorescence Detection of Specific Chemicals

Science.gov (United States)

Fedor, Steve

2008-01-01

A family of fluorescent dye molecules has been developed for use in on-off fluorescence detection of specific chemicals. By themselves, these molecules do not fluoresce. However, when exposed to certain chemical analytes in liquid or vapor forms, they do fluoresce (see figure). These compounds are amenable to fixation on or in a variety of substrates for use in fluorescence-based detection devices: they can be chemically modified to anchor them to porous or non-porous solid supports or can be incorporated into polymer films. Potential applications for these compounds include detection of chemical warfare agents, sensing of acidity or alkalinity, and fluorescent tagging of proteins in pharmaceutical research and development. These molecules could also be exploited for use as two-photon materials for photodynamic therapy in the treatment of certain cancers and other diseases. A molecule in this family consists of a fluorescent core (such as an anthracene or pyrene) attached to two end groups that, when the dye is excited by absorption of light, transfer an electron to the core, thereby quenching the fluorescence. The end groups can be engineered so that they react chemically with certain analytes. Upon reaction, electrons on the end groups are no longer available for transfer to the core and, consequently, the fluorescence from the core is no longer quenched. The chemoselectivity of these molecules can be changed by changing the end groups. For example, aniline end groups afford a capability for sensing acids or acid halides (including those contained in chemical warfare agents). Pyridine or bipyridyl end groups would enable sensing of metal ions. Other chemicals that can be selectively detected through suitable choice of end groups include glucose and proteins. Moreover, the fluorescent cores can be changed to alter light-absorption and -emission characteristics: anthracene cores fluoresce at wavelengths around 500 nm, whereas perylene cores absorb and emit at

Fluorescence imaging of soybean flavonol isolines

Science.gov (United States)

Kim, Moon S.; Lee, Edward H.; Mulchi, Charles L.; McMurtrey, James E., III; Chappelle, Emmett W.; Rowland, Randy A.

1998-07-01

region of the spectrum when excited with radiation in the blue region of the spectrum. Thus, green fluorescence emission due to kaempferol glycosides excited by the blue fluorescent compounds with UV excitation (resonance energy excitation) could become a factor in the fluorescence studies of in vivo plants.

UV-Vis Ratiometric Resonance Synchronous Spectroscopy for Determination of Nanoparticle and Molecular Optical Cross Sections.

Science.gov (United States)

Nettles, Charles B; Zhou, Yadong; Zou, Shengli; Zhang, Dongmao

2016-03-01

Demonstrated herein is a UV-vis Ratiometric Resonance Synchronous Spectroscopic (R2S2, pronounced as "R-two-S-two" for simplicity) technique where the R2S2 spectrum is obtained by dividing the resonance synchronous spectrum of a NP-containing solution by the solvent resonance synchronous spectrum. Combined with conventional UV-vis measurements, this R2S2 method enables experimental quantification of the absolute optical cross sections for a wide range of molecular and nanoparticle (NP) materials that range optically from pure photon absorbers or scatterers to simultaneous photon absorbers and scatterers, simultaneous photon absorbers and emitters, and all the way to simultaneous photon absorbers, scatterers, and emitters in the UV-vis wavelength region. Example applications of this R2S2 method were demonstrated for quantifying the Rayleigh scattering cross sections of solvents including water and toluene, absorption and resonance light scattering cross sections for plasmonic gold nanoparticles, and absorption, scattering, and on-resonance fluorescence cross sections for semiconductor quantum dots (Qdots). On-resonance fluorescence quantum yields were quantified for the model molecular fluorophore Eosin Y and fluorescent Qdots CdSe and CdSe/ZnS. The insights and methodology presented in this work should be of broad significance in physical and biological science research that involves photon/matter interactions.

A nonlinear plasmonic resonator for three-state all-optical switching

KAUST Repository

Amin, Muhammad

2014-01-01

A nonlinear plasmonic resonator design is proposed for three-state all-optical switching at frequencies including near infrared and lower red parts of the spectrum. The tri-stable response required for three-state operation is obtained by enhancing nonlinearities of a Kerr medium through multiple (higher order) plasmons excited on resonator\\'s metallic surfaces. Indeed, simulations demonstrate that exploitation of multiple plasmons equips the proposed resonator with a multi-band tri-stable response, which cannot be obtained using existing nonlinear plasmonic devices that make use of single mode Lorentzian resonances. Multi-band three-state optical switching that can be realized using the proposed resonator has potential applications in optical communications and computing. © 2014 Optical Society of America.

Satellite-detected fluorescence reveals global physiology of ocean phytoplankton

Directory of Open Access Journals (Sweden)

M. J. Behrenfeld

2009-05-01

Full Text Available Phytoplankton photosynthesis links global ocean biology and climate-driven fluctuations in the physical environment. These interactions are largely expressed through changes in phytoplankton physiology, but physiological status has proven extremely challenging to characterize globally. Phytoplankton fluorescence does provide a rich source of physiological information long exploited in laboratory and field studies, and is now observed from space. Here we evaluate the physiological underpinnings of global variations in satellite-based phytoplankton chlorophyll fluorescence. The three dominant factors influencing fluorescence distributions are chlorophyll concentration, pigment packaging effects on light absorption, and light-dependent energy-quenching processes. After accounting for these three factors, resultant global distributions of quenching-corrected fluorescence quantum yields reveal a striking consistency with anticipated patterns of iron availability. High fluorescence quantum yields are typically found in low iron waters, while low quantum yields dominate regions where other environmental factors are most limiting to phytoplankton growth. Specific properties of photosynthetic membranes are discussed that provide a mechanistic view linking iron stress to satellite-detected fluorescence. Our results present satellite-based fluorescence as a valuable tool for evaluating nutrient stress predictions in ocean ecosystem models and give the first synoptic observational evidence that iron plays an important role in seasonal phytoplankton dynamics of the Indian Ocean. Satellite fluorescence may also provide a path for monitoring climate-phytoplankton physiology interactions and improving descriptions of phytoplankton light use efficiencies in ocean productivity models.

Detecting aromatic compounds on planetary surfaces using ultraviolet time-resolved fluorescence spectroscopy

Science.gov (United States)

Eshelman, E.; Daly, M. G.; Slater, G.; Cloutis, E.

2018-02-01

Many aromatic organic molecules exhibit strong and characteristic fluorescence when excited with ultraviolet radiation. As laser excitation in the ultraviolet generates both fluorescence and resonantly enhanced Raman scattering of aromatic vibrational modes, combined Raman and fluorescence instruments have been proposed to search for organic compounds on Mars. In this work the time-resolved fluorescence of a suite of 24 compounds composed of 2-5 ringed alternant, non-alternant, and heterocyclic PAHs was measured. Fluorescence instrumentation with similar specifications to a putative flight instrument was capable of observing the fluorescence decay of these compounds with a sub-ns resolution. Incorporating time-resolved capabilities was also found to increase the ability to discriminate between individual PAHs. Incorporating time-resolved fluorescence capabilities into an ultraviolet gated Raman system intended for a rover or lander can increase the ability to detect and characterize PAHs on planetary surfaces.

Using biharmonic laser pumping for preparation of pure and entangled multiexciton states in clusters of resonantly interacting fluorescent centres

International Nuclear Information System (INIS)

Basieva, I.T.; Basiev, T.T.; Dietler, G.; Pukhov, K.K.; Sekatskii, S.K.

2007-01-01

Use of a biharmonic laser pumping for preparation of pure and entangled multiexciton states in dimers and tetramers of resonantly interacting fluorescent particles is analysed. Special emphasis is given to the preparation of all possible pure exciton states and their maximally entangled Bell states. The general results are illustrated using as an example the pair and quartet centres of neodymium ions in calcium fluoride (M- and N-centres), where all necessary experimental information concerning the interactions and decoherence is available, and experimental preparation of Bell vacuum-single exciton and vacuum-biexciton states has been recently demonstrated. These results can be easily rescaled for the cases of quantum dots and dye molecules. Numerical results are compared with the analytical results obtained for a particular case of the biharmonic excitation of dimers. Excellent agreement between these approaches is demonstrated

Wideband MEMS Resonator Using Multifrequency Excitation

KAUST Repository

Jaber, Nizar; Ramini, Abdallah; Al Hennawi, Qais M.; Younis, Mohammad I.

2016-01-01

We demonstrate the excitation of combination resonances of additive and subtractive types and their exploitations to realize a large bandwidth micro-machined resonator of large amplitude even at higher harmonic modes of vibrations. The investigation is conducted on a Microelectromechanical systems (MEMS) clamped-clamped microbeam fabricated using polyimide as a structural layer coated with nickel from top and chromium and gold layers from bottom. The microbeam is excited by a two-source harmonic excitation, where the first frequency source is swept around the targeted resonance (first or third mode of vibration) while the second source frequency is kept fixed. We report for the first time a large bandwidth and large amplitude response near the higher order modes of vibration. Also, we show that by properly tuning the frequency and amplitude of the excitation force, the frequency bandwidth of the resonator is controlled.

Wideband MEMS Resonator Using Multifrequency Excitation

KAUST Repository

Jaber, Nizar

2016-03-09

We demonstrate the excitation of combination resonances of additive and subtractive types and their exploitations to realize a large bandwidth micro-machined resonator of large amplitude even at higher harmonic modes of vibrations. The investigation is conducted on a Microelectromechanical systems (MEMS) clamped-clamped microbeam fabricated using polyimide as a structural layer coated with nickel from top and chromium and gold layers from bottom. The microbeam is excited by a two-source harmonic excitation, where the first frequency source is swept around the targeted resonance (first or third mode of vibration) while the second source frequency is kept fixed. We report for the first time a large bandwidth and large amplitude response near the higher order modes of vibration. Also, we show that by properly tuning the frequency and amplitude of the excitation force, the frequency bandwidth of the resonator is controlled.

Travelling-wave resonant four-wave mixing breaks the limits of cavity-enhanced all-optical wavelength conversion.

Science.gov (United States)

Morichetti, Francesco; Canciamilla, Antonio; Ferrari, Carlo; Samarelli, Antonio; Sorel, Marc; Melloni, Andrea

2011-01-01

Wave mixing inside optical resonators, while experiencing a large enhancement of the nonlinear interaction efficiency, suffers from strong bandwidth constraints, preventing its practical exploitation for processing broad-band signals. Here we show that such limits are overcome by the new concept of travelling-wave resonant four-wave mixing (FWM). This approach combines the efficiency enhancement provided by resonant propagation with a wide-band conversion process. Compared with conventional FWM in bare waveguides, it exhibits higher robustness against chromatic dispersion and propagation loss, while preserving transparency to modulation formats. Travelling-wave resonant FWM has been demonstrated in silicon-coupled ring resonators and was exploited to realize a 630-μm-long wavelength converter operating over a wavelength range wider than 60 nm and with 28-dB gain with respect to a bare waveguide of the same physical length. Full compatibility of the travelling-wave resonant FWM with optical signal processing applications has been demonstrated through signal retiming and reshaping at 10 Gb s(-1).

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

Gastrin-releasing peptide receptor-targeted gadolinium oxide-based multifunctional nanoparticles for dual magnetic resonance/fluorescent molecular imaging of prostate cancer

Directory of Open Access Journals (Sweden)

Cui DT

2017-09-01

Full Text Available Danting Cui,1 Xiaodan Lu,1 Chenggong Yan,1 Xiang Liu,1 Meirong Hou,1 Qi Xia,2 Yikai Xu,1 Ruiyuan Liu2,3 1Department of Medical Imaging Center, Nanfang Hospital, Southern Medical University, Guangzhou, People’s Republic of China; 2School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, People’s Republic of China; 3School of Biomedical Engineering, Southern Medical University, Guangzhou, People’s Republic of China Abstract: Bombesin (BBN, an analog of gastrin-releasing peptide (GRP, specifically binds to GRP receptors, which are overexpressed in human prostate cancer (PC. Here, we synthesized a BBN-modified gadolinium oxide (Gd2O3 nanoprobe containing fluorescein (Gd2O3-5(6-carboxyfluorescein [FI]-polyethylene glycol [PEG]-BBN for targeted magnetic resonance (MR/optical dual-modality imaging of PC. The Gd2O3-FI-PEG-BBN nanoparticles exhibited a relatively uniform particle size with an average diameter of 52.3 nm and spherical morphology as depicted by transmission electron microscopy. The longitudinal relaxivity (r1 of Gd2O3-FI-PEG-BBN (r1 =4.23 mM–1s–1 is comparable to that of clinically used Magnevist (Gd-DTPA. Fluorescence microscopy and in vitro cellular MRI demonstrated GRP receptor-specific and enhanced cellular uptake of the Gd2O3-FI-PEG-BBN in PC-3 tumor cells. Moreover, Gd2O3-FI-PEG-BBN showed more remarkable contrast enhancement than the corresponding nontargeted Gd2O3-FI-PEG according to in vivo MRI and fluorescent imaging. Tumor immunohistochemical analysis further demonstrated improved accumulation of the targeted nanoprobe in tumors. BBN-conjugated Gd2O3 may be a promising nanoplatform for simultaneous GRP receptor-targeted molecular cancer diagnosis and antitumor drug delivery in future clinical applications. Keywords: magnetic resonance imaging, gadolinium oxide, bombesin, gastrin-releasing peptide receptor, molecular imaging

Detection of internal fields in double-metal terahertz resonators

DEFF Research Database (Denmark)

Mitrofanov, Oleg; Han, Zhanghua; Ding, Fei

2017-01-01

Terahertz (THz) double-metal plasmonic resonators enable enhanced light-matter coupling by exploiting strong field confinement. The double-metal design however restricts access to the internal fields. We propose and demonstrate a method for spatial mapping and spectroscopic analysis of the internal...... electromagnetic fields in double-metal plasmonic resonators. We use the concept of image charges and aperture-type scanning near-field THz time-domain microscopy to probe the fields confined within the closed resonator. The experimental method opens doors to studies of light-matter coupling in deeply sub...

Highly Tunable Electrostatic Nanomechanical Resonators

KAUST Repository

Kazmi, Syed Naveed Riaz

2017-11-24

There has been significant interest towards highly tunable resonators for on-demand frequency selection in modern communication systems. Here, we report highly tunable electrostatically actuated silicon-based nanomechanical resonators. In-plane doubly-clamped bridges, slightly curved as shallow arches due to residual stresses, are fabricated using standard electron beam lithography and surface nanomachining. The resonators are designed such that the effect of mid-plane stretching dominates the softening effect of the electrostatic force. This is achieved by controlling the gap-to-thickness ratio and by exploiting the initial curvature of the structure from fabrication. We demonstrate considerable increase in the resonance frequency of nanoresonators with the dc bias voltages up to 108% for 180 nm thick structures with a transduction gap of 1 $mu$m separating them from the driving/sensing electrodes. The experimental results are found in good agreement with those of a nonlinear analytical model based on the Euler-Bernoulli beam theory. As a potential application, we demonstrate a tunable narrow band-pass filter using two electrically coupled nanomechanical arch resonators with varied dc bias voltages.

Highly Tunable Electrostatic Nanomechanical Resonators

KAUST Repository

Kazmi, Syed Naveed Riaz; Hajjaj, Amal Z.; Hafiz, Md Abdullah Al; Da Costa, Pedro M. F. J.; Younis, Mohammad I.

2017-01-01

There has been significant interest towards highly tunable resonators for on-demand frequency selection in modern communication systems. Here, we report highly tunable electrostatically actuated silicon-based nanomechanical resonators. In-plane doubly-clamped bridges, slightly curved as shallow arches due to residual stresses, are fabricated using standard electron beam lithography and surface nanomachining. The resonators are designed such that the effect of mid-plane stretching dominates the softening effect of the electrostatic force. This is achieved by controlling the gap-to-thickness ratio and by exploiting the initial curvature of the structure from fabrication. We demonstrate considerable increase in the resonance frequency of nanoresonators with the dc bias voltages up to 108% for 180 nm thick structures with a transduction gap of 1 $mu$m separating them from the driving/sensing electrodes. The experimental results are found in good agreement with those of a nonlinear analytical model based on the Euler-Bernoulli beam theory. As a potential application, we demonstrate a tunable narrow band-pass filter using two electrically coupled nanomechanical arch resonators with varied dc bias voltages.

Intrinsic fluorescence biomarkers in cells treated with chemopreventive drugs

Science.gov (United States)

Kirkpatrick, Nathaniel D.; Brands, William R.; Zou, Changping; Brewer, Molly A.; Utzinger, Urs

2005-03-01

Non-invasive monitoring of cellular metabolism offers promising insights into areas ranging from biomarkers for drug activity to cancer diagnosis. Fluorescence spectroscopy can be utilized in order to exploit endogenous fluorophores, typically metabolic co-factors nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD), and estimate the redox status of the sample. Fluorescence spectroscopy was applied to follow metabolic changes in epithelial ovarian cells as well as bladder epithelial cancer cells during treatment with a chemopreventive drug that initiates cellular quiescence. Fluorescence signals consistent with NADH, FAD, and tryptophan were measured to monitor cellular activity, redox status, and protein content. Cells were treated with varying concentrations of N-4-(hydroxyphenyl) retinamide (4-HPR) and measured in a stable environment with a sensitive fluorescence spectrometer. A subset of measurements was completed on a low concentration of cells to demonstrate feasibility for medical application such as in bladder or ovary washes. Results suggest that all of the cells responded with similar dose dependence but started at different estimated redox ratio baseline levels correlating with cell cycle, growth inhibition, and apoptosis assays. NADH and tryptophan related fluorescence changed significantly while FAD related fluorescence remained unaltered. Fluorescence data collected from approximately 1000 - 2000 cells, comparable to a bladder or ovary wash, was measurable and useful for future experiments. This study suggests that future intrinsic biomarker measurements may need to be most sensitive to changes in NADH and tryptophan related fluorescence while using FAD related fluorescence to help estimate the baseline redox ratio and predict response to chemopreventive agents.

Image-guided cancer surgery using near-infrared fluorescence

Science.gov (United States)

Vahrmeijer, Alexander L.; Hutteman, Merlijn; van der Vorst, Joost R.; van de Velde, C.J.H.; Frangioni, John V.

2013-01-01

Paradigm shifts in surgery arise when surgeons are empowered to perform surgery faster, better, and/or less expensively. Optical imaging that exploits invisible near-infrared fluorescent light has the potential to improve cancer surgery outcomes while minimizing anesthesia time and lowering healthcare costs. Because of this, the last few years have witnessed an explosion of proof-of-concept clinical trials in the field. In this review, we introduce the concept of near-infrared fluorescence imaging for cancer surgery, review the clinical trial literature to date, outline the key issues pertaining to imaging system and contrast agent optimization, discuss limitations and leverage, and provide a framework for making the technology available for the routine care of cancer patients in the near future. PMID:23881033

Polarization control of intermediate state absorption in resonance-mediated multi-photon absorption process

International Nuclear Information System (INIS)

Xu, Shuwu; Yao, Yunhua; Jia, Tianqing; Ding, Jingxin; Zhang, Shian; Sun, Zhenrong; Huang, Yunxia

2015-01-01

We theoretically and experimentally demonstrate the control of the intermediate state absorption in an (n + m) resonance-mediated multi-photon absorption process by the polarization-modulated femtosecond laser pulse. An analytical solution of the intermediate state absorption in a resonance-mediated multi-photon absorption process is obtained based on the time-dependent perturbation theory. Our theoretical results show that the control efficiency of the intermediate state absorption by the polarization modulation is independent of the laser intensity when the transition from the intermediate state to the final state is coupled by the single-photon absorption, but will be affected by the laser intensity when this transition is coupled by the non-resonant multi-photon absorption. These theoretical results are experimentally confirmed via a two-photon fluorescence control in (2 + 1) resonance-mediated three-photon absorption of Coumarin 480 dye and a single-photon fluorescence control in (1 + 2) resonance-mediated three-photon absorption of IR 125 dye. (paper)

Compact Dual-Band Zeroth-Order Resonance Antenna

International Nuclear Information System (INIS)

Xu He-Xiu; Wang Guang-Ming; Gong Jian-Qiang

2012-01-01

A novel microstrip zeroth-order resonator (ZOR) antenna and its equivalent circuit model are exploited with two zeroth-order resonances. It is constructed based on a resonant-type composite right/left handed transmission line (CRLH TL) using a Wunderlich-shaped extended complementary single split ring resonator pair (W-ECSSRRP) and a series capacitive gap. The gap either can be utilized for double negative (DNG) ZOR antenna or be removed to engineer a simplified elision-negative ZOR (ENG) antenna. For verification, a DNG ZOR antenna sample is fabricated and measured. Numerical and experimental results agree well with each other, indicating that the omnidirectional radiations occur at two frequency bands which are accounted for by two shunt branches in the circuit model. The size of the antenna is 49% more compact than its previous counterpart. The superiority of W-ECSSRRP over CSSRRP lies in the lower fundamental resonance of the antenna by 38.2% and the introduction of a higher zeroth-order resonance. (fundamental areas of phenomenology(including applications))

Raman and fluorescence contributions to the resonant inelastic soft x-ray scattering on LaAlO3/SrTiO3 heterostructures

Science.gov (United States)

Pfaff, F.; Fujiwara, H.; Berner, G.; Yamasaki, A.; Niwa, H.; Kiuchi, H.; Gloskovskii, A.; Drube, W.; Gabel, J.; Kirilmaz, O.; Sekiyama, A.; Miyawaki, J.; Harada, Y.; Suga, S.; Sing, M.; Claessen, R.

2018-01-01

We present a detailed study of the Ti 3 d carriers at the interface of LaAlO3/SrTiO3 heterostructures by high-resolution resonant inelastic soft x-ray scattering (RIXS), with special focus on the roles of overlayer thickness and oxygen vacancies. Our measurements show the existence of interfacial Ti 3 d electrons already below the critical thickness for conductivity. The (total) interface charge carrier density increases up to a LaAlO3 overlayer thickness of 6 unit cells before it levels out. Furthermore, we observe strong Ti 3 d charge carrier doping by oxygen vacancies. The RIXS data combined with photoelectron spectroscopy and transport measurements indicate the simultaneous presence of localized and itinerant charge carriers. At variance with previous interpretations, we show that in our excitation energy dependent RIXS measurements the amounts of localized and itinerant Ti 3 d electrons in the ground state do not scale with the intensities of the Raman and fluorescence peaks, respectively. Rather, we attribute the observation of either Raman components or fluorescence signal to the specific nature of the intermediate state reached in the RIXS excitation process.

Calibrating the photo-thermal response of magneto-fluorescent gold nanoshells.

Science.gov (United States)

Biswal, Nrusingh C; Ayala-Orzoco, Ciceron; Halas, Naomi J; Joshi, Amit

2011-01-01

We report the photothermal response and Near Infrared (NIR) imaging sensitivities of magneto-fluorescent silica core gold nanocomplexes designed for molecular image guided thermal therapy of cancer. Approximately 160 nm Silica core gold nanoshells were designed to provide NIR fluorescent and Magnetic Resonance (MR) contrast by incorporating FDA approved dye indocyanine green (ICG) and iron-oxide within an outer silica epilayer. The imaging and therapeutic sensitivity, and the stability of fluorescence contrast for 12 microliters of suspension (containing approximately 7.9 × 10(8) or 1.3 femtoMole nanoshells) buried at depths of 2-8 mm in tissue mimicking scattering media is reported.

Dipole Resonances of 76Ge

Science.gov (United States)

Ilieva, R. S.; Cooper, N.; Werner, V.; Rusev, G.; Pietralla, N.; Kelly, J. H.; Tornow, W.; Yates, S. W.; Crider, B. P.; Peters, E.

2013-10-01

Dipole resonances in 76Ge have been studied using the method of Nuclear Resonance Fluorescence (NRF). The experiment was performed using the Free Electron Laser facility at HI γS/TUNL, which produced linearly polarised quasi-monoenergetic photons in the 4-9 MeV energy range. Photon strength, in particular dipole strength, is an important ingredient in nuclear reaction calculations, and recent interest in its study has been stimulated by observations of a pygmy dipole resonance near the neutron separation energy Sn of certain nuclei. Furthermore, 76Ge is a candidate for 0 ν 2 β -decay. The results are complimentary to a relevant experiment done at TU Darmstadt using Bremsstrahlung beams. Single-resonance parities and a preliminary estimate of the total photo-excitation cross section will be presented. This work was supported by the U.S. DOE under grant no. DE-FG02-91ER40609.

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

NARCIS (Netherlands)

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

2017-01-01

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

Resonance fluorescence spectrum of a p-doped quantum dot coupled to a metallic nanoparticle

Science.gov (United States)

Carreño, F.; Antón, M. A.; Arrieta-Yáñez, Francisco

2013-11-01

The resonance fluorescence spectrum (RFS) of a hybrid system consisting of a p-doped semiconductor quantum dot (QD) coupled to a metallic nanoparticle (MNP) is analyzed. The quantum dot is described as a four-level atomlike system using the density matrix formalism. The lower levels are Zeeman-split hole spin states and the upper levels correspond to positively charged excitons containing a spin-up, spin-down hole pair and a spin electron. A linearly polarized laser field drives two of the optical transitions of the QD and produces localized surface plasmons in the nanoparticle, which act back upon the QD. The frequencies of these localized plasmons are very different along the two principal axes of the nanoparticle, thus producing an anisotropic modification of the spontaneous emission rates of the allowed optical transitions, which is accompanied by very minor local field corrections. This manifests into dramatic modifications in the RFS of the hybrid system in contrast to the one obtained for the isolated QD. The RFS is analyzed as a function of the nanoparticle's aspect ratio, the external magnetic field applied in the Voigt geometry, and the Rabi frequency of the driving field. It is shown that the spin of the QD is imprinted onto certain sidebands of the RFS, and that the signal at these sidebands can be optimized by engineering the shape of the MNP.

A nonlinear plasmonic resonator for three-state all-optical switching

KAUST Repository

Amin, Muhammad; Farhat, Mohamed; Bagci, Hakan

2014-01-01

A nonlinear plasmonic resonator design is proposed for three-state all-optical switching at frequencies including near infrared and lower red parts of the spectrum. The tri-stable response required for three-state operation is obtained by enhancing nonlinearities of a Kerr medium through multiple (higher order) plasmons excited on resonator's metallic surfaces. Indeed, simulations demonstrate that exploitation of multiple plasmons equips the proposed resonator with a multi-band tri-stable response, which cannot be obtained using existing nonlinear plasmonic devices that make use of single mode Lorentzian resonances. Multi-band three-state optical switching that can be realized using the proposed resonator has potential applications in optical communications and computing. © 2014 Optical Society of America.

Significantly improving nuclear resonance fluorescence non-destructive assay by using the integral resonance transmission method and photofission

International Nuclear Information System (INIS)

Angell, Christopher T.; Hayakawa, Takehito; Shizuma, Toshiyuki; Hajima, Ryoichi

2013-01-01

Non-destructive assay (NDA) of 239 Pu in spent nuclear fuel or melted fuel using a γ-ray beam is possible using self absorption and the integral resonance transmission method. The method uses nuclear resonance absorption where resonances in 239 Pu remove photons from the beam, and the selective absorption is detected by measuring the decrease in scattering in a witness target placed in the beam after the fuel, consisting of the isotope of interest, namely 239 Pu. The method is isotope specific, and can use photofission or scattered γ-rays to assay the 239 Pu. It overcomes several problems related to NDA of melted fuel, including the radioactivity of the fuel, and the unknown composition and geometry. This talk will explain the general method, and how photofission can be used to assay specific isotopes, and present example calculations. (author)

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

Science.gov (United States)

Zhang, Hongyan; Lv, Jie; Jia, Zhenhong

2017-05-10

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

Exploring the resonant vibration of thin plates: Reconstruction of Chladni patterns and determination of resonant wave numbers.

Science.gov (United States)

Tuan, P H; Wen, C P; Chiang, P Y; Yu, Y T; Liang, H C; Huang, K F; Chen, Y F

2015-04-01

The Chladni nodal line patterns and resonant frequencies for a thin plate excited by an electronically controlled mechanical oscillator are experimentally measured. Experimental results reveal that the resonant frequencies can be fairly obtained by means of probing the variation of the effective impedance of the exciter with and without the thin plate. The influence of the extra mass from the central exciter is confirmed to be insignificant in measuring the resonant frequencies of the present system. In the theoretical aspect, the inhomogeneous Helmholtz equation is exploited to derive the response function as a function of the driving wave number for reconstructing experimental Chladni patterns. The resonant wave numbers are theoretically identified with the maximum coupling efficiency as well as the maximum entropy principle. Substituting the theoretical resonant wave numbers into the derived response function, all experimental Chladni patterns can be excellently reconstructed. More importantly, the dispersion relationship for the flexural wave of the vibrating plate can be determined with the experimental resonant frequencies and the theoretical resonant wave numbers. The determined dispersion relationship is confirmed to agree very well with the formula of the Kirchhoff-Love plate theory.

In Vivo Deep Tissue Fluorescence and Magnetic Imaging Employing Hybrid Nanostructures.

Science.gov (United States)

Ortgies, Dirk H; de la Cueva, Leonor; Del Rosal, Blanca; Sanz-Rodríguez, Francisco; Fernández, Nuria; Iglesias-de la Cruz, M Carmen; Salas, Gorka; Cabrera, David; Teran, Francisco J; Jaque, Daniel; Martín Rodríguez, Emma

2016-01-20

Breakthroughs in nanotechnology have made it possible to integrate different nanoparticles in one single hybrid nanostructure (HNS), constituting multifunctional nanosized sensors, carriers, and probes with great potential in the life sciences. In addition, such nanostructures could also offer therapeutic capabilities to achieve a wider variety of multifunctionalities. In this work, the encapsulation of both magnetic and infrared emitting nanoparticles into a polymeric matrix leads to a magnetic-fluorescent HNS with multimodal magnetic-fluorescent imaging abilities. The magnetic-fluorescent HNS are capable of simultaneous magnetic resonance imaging and deep tissue infrared fluorescence imaging, overcoming the tissue penetration limits of classical visible-light based optical imaging as reported here in living mice. Additionally, their applicability for magnetic heating in potential hyperthermia treatments is assessed.

X-ray fluorescence/Auger-electron coincidence spectroscopy of vacancy cascades in atomic argon

International Nuclear Information System (INIS)

Arp, U.

1996-01-01

Argon L 2.3 -M 2.3 M 2.3 Auger-electron spectra were measured in coincidence with Kα fluorescent x-rays in studies of Ar K-shell vacancy decays at several photon energies above the K-threshold and on the 1s-4p resonance in atomic argon. The complex spectra recorded by conventional electron spectroscopy are greatly simplified when recorded in coincidence with fluorescent x-rays, allowing a more detailed analysis of the vacancy cascade process. The resulting coincidence spectra are compared with Hartree-Fock calculations which include shake-up transitions in the resonant case. Small energy shifts of the coincidence electron spectra are attributed to post-collision interaction with 1s photoelectrons

Resonant Tunneling Spin Pump

Science.gov (United States)

Ting, David Z.

2007-01-01

The resonant tunneling spin pump is a proposed semiconductor device that would generate spin-polarized electron currents. The resonant tunneling spin pump would be a purely electrical device in the sense that it would not contain any magnetic material and would not rely on an applied magnetic field. Also, unlike prior sources of spin-polarized electron currents, the proposed device would not depend on a source of circularly polarized light. The proposed semiconductor electron-spin filters would exploit the Rashba effect, which can induce energy splitting in what would otherwise be degenerate quantum states, caused by a spin-orbit interaction in conjunction with a structural-inversion asymmetry in the presence of interfacial electric fields in a semiconductor heterostructure. The magnitude of the energy split is proportional to the electron wave number. Theoretical studies have suggested the possibility of devices in which electron energy states would be split by the Rashba effect and spin-polarized currents would be extracted by resonant quantum-mechanical tunneling.

Theory of analytical curves in atomic fluorescence flame spectrometry

NARCIS (Netherlands)

Hooymayers, H.P.

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

A portable UV-fluorescence multispectral imaging system for the analysis of painted surfaces

Science.gov (United States)

Comelli, Daniela; Valentini, Gianluca; Nevin, Austin; Farina, Andrea; Toniolo, Lucia; Cubeddu, Rinaldo

2008-08-01

A portable fluorescence multispectral imaging system was developed and has been used for the analysis of artistic surfaces. The imaging apparatus exploits two UV lamps for fluorescence excitation and a liquid crystal tunable filter coupled to a low-noise charge coupled device as the image detector. The main features of the system are critically presented, outlining the assets, drawbacks, and practical considerations of portability. A multivariate statistical treatment of spectral data is further considered. Finally, the in situ analysis with the new apparatus of recently restored Renaissance wall paintings is presented.

Origins of fluorescence in evolved bacteriophytochromes.

Science.gov (United States)

Bhattacharya, Shyamosree; Auldridge, Michele E; Lehtivuori, Heli; Ihalainen, Janne A; Forest, Katrina T

2014-11-14

Use of fluorescent proteins to study in vivo processes in mammals requires near-infrared (NIR) biomarkers that exploit the ability of light in this range to penetrate tissue. Bacteriophytochromes (BphPs) are photoreceptors that couple absorbance of NIR light to photoisomerization, protein conformational changes, and signal transduction. BphPs have been engineered to form NIR fluorophores, including IFP1.4, Wi-Phy, and the iRFP series, initially by replacement of Asp-207 by His. This position was suggestive because its main chain carbonyl is within hydrogen-bonding distance to pyrrole ring nitrogens of the biliverdin chromophore, thus potentially functioning as a crucial transient proton sink during photoconversion. To explain the origin of fluorescence in these phytofluors, we solved the crystal structures of IFP1.4 and a comparison non-fluorescent monomeric phytochrome DrCBDmon. Met-186 and Val-288 in IFP1.4 are responsible for the formation of a tightly packed hydrophobic hub around the biliverdin D ring. Met-186 is also largely responsible for the blue-shifted IFP1.4 excitation maximum relative to the parent BphP. The structure of IFP1.4 revealed decreased structural heterogeneity and a contraction of two surface regions as direct consequences of side chain substitutions. Unexpectedly, IFP1.4 with Asp-207 reinstalled (IFPrev) has a higher fluorescence quantum yield (∼9%) than most NIR phytofluors published to date. In agreement, fluorescence lifetime measurements confirm the exceptionally long excited state lifetimes, up to 815 ps, in IFP1.4 and IFPrev. Our research helps delineate the origin of fluorescence in engineered BphPs and will facilitate the wide-spread adoption of phytofluors as biomarkers. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

Near resonant absorption by atoms in intense, fluctuating fields: [Progress report

International Nuclear Information System (INIS)

1989-01-01

During the present grant period preparations for photon echo studies of the role of phase fluctuations of an optical driving field resonant with the 1 S 0 - 3 P 1 transition in 174 Yb are moving forward. This experimental study emphasizes the role of fluctuations as a decorrelating mechanism on a phased array of excited atoms. Improvements in laser stabilization and in the quality of the fluctuation spectrum have been carried out and the first spectroscopic measurements will be carried out during this grant year. In response to an important recent theoretical study we have also applied the phase fluctuation synthesizing capability to the study of the atomic sodium resonance fluorescence line profile, driven by a phase fluctuating laser. The measured fluctuations in the fluorescence, characterized in terms of the standard deviation of the fluorescence intensity, have an unexpected and strong dependence on detuning of the driving laser

Polarization Multiplexing of Fluorescent Emission Using Multiresonant Plasmonic Antennas.

Science.gov (United States)

De Leo, Eva; Cocina, Ario; Tiwari, Preksha; Poulikakos, Lisa V; Marqués-Gallego, Patricia; le Feber, Boris; Norris, David J; Prins, Ferry

2017-12-26

Combining the ability to localize electromagnetic fields at the nanoscale with a directional response, plasmonic antennas offer an effective strategy to shape the far-field pattern of coupled emitters. Here, we introduce a family of directional multiresonant antennas that allows for polarization-resolved spectral identification of fluorescent emission. The geometry consists of a central aperture surrounded by concentric polygonal corrugations. By varying the periodicity of each axis of the polygon individually, this structure can support multiple resonances that provide independent control over emission directionality for multiple wavelengths. Moreover, since each resonant wavelength is directly mapped to a specific polarization orientation, spectral information can be encoded in the polarization state of the out-scattered beam. To demonstrate the potential of such structures in enabling simplified detection schemes and additional functionalities in sensing and imaging applications, we use the central subwavelength aperture as a built-in nanocuvette and manipulate the fluorescent response of colloidal-quantum-dot emitters coupled to the multiresonant antenna.

Targeting pancreatic cancer with magneto-fluorescent theranostic gold nanoshells.

Science.gov (United States)

Chen, Wenxue; Ayala-Orozco, Ciceron; Biswal, Nrusingh C; Perez-Torres, Carlos; Bartels, Marc; Bardhan, Rizia; Stinnet, Gary; Liu, Xian-De; Ji, Baoan; Deorukhkar, Amit; Brown, Lisa V; Guha, Sushovan; Pautler, Robia G; Krishnan, Sunil; Halas, Naomi J; Joshi, Amit

2014-01-01

We report a magneto-fluorescent theranostic nanocomplex targeted to neutrophil gelatinase-associated lipocalin (NGAL) for imaging and therapy of pancreatic cancer. Gold nanoshells resonant at 810 nm were encapsulated in silica epilayers doped with iron oxide and the near-infrared (NIR) dye indocyanine green, resulting in theranostic gold nanoshells (TGNS), which were subsequently conjugated with antibodies targeting NGAL in AsPC-1-derived xenografts in nude mice. Anti-NGAL-conjugated TGNS specifically targeted pancreatic cancer cells in vitro and in vivo providing contrast for both NIR fluorescence and T2-weighted MRI with higher tumor contrast than can be obtained using long-circulating, but nontargeted, PEGylated nanoparticles. The nanocomplexes also enabled highly specific cancer cell death via NIR photothermal therapy in vitro. TGNS with embedded NIR and magnetic resonance contrasts can be specifically targeted to pancreatic cancer cells with expression of early disease marker NGAL, and enable molecularly targeted imaging and photothermal therapy.

Chromophore Structure of Photochromic Fluorescent Protein Dronpa: Acid-Base Equilibrium of Two Cis Configurations.

Science.gov (United States)

Higashino, Asuka; Mizuno, Misao; Mizutani, Yasuhisa

2016-04-07

Dronpa is a novel photochromic fluorescent protein that exhibits fast response to light. The present article is the first report of the resonance and preresonance Raman spectra of Dronpa. We used the intensity and frequency of Raman bands to determine the structure of the Dronpa chromophore in two thermally stable photochromic states. The acid-base equilibrium in one photochromic state was observed by spectroscopic pH titration. The Raman spectra revealed that the chromophore in this state shows a protonation/deprotonation transition with a pKa of 5.2 ± 0.3 and maintains the cis configuration. The observed resonance Raman bands showed that the other photochromic state of the chromophore is in a trans configuration. The results demonstrate that Raman bands selectively enhanced for the chromophore yield valuable information on the molecular structure of the chromophore in photochromic fluorescent proteins after careful elimination of the fluorescence background.

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

Science.gov (United States)

Smith, Clint; Tatineni, Balaji; Anderson, John; Tepper, Gary

2006-10-01

Fluorescence resonance energy transfer (FRET) is a process in which energy is transferred nonradiatively from one fluorophore (the donor) in an excited electron state to another, the chromophore (the acceptor). FRET is distinctive in its ability to reveal the presence of specific recognition of select targets such as the nerve agent stimulant Methyl Salicylate (MES) upon spectroscopic excitation. We introduce a surface imprinted and non-imprinted thin film that underwent AC-Electrospray ionization for donor-acceptor pair(s) bound to InGaP quantum dots and mesoporous silicate nanoparticles. The donor-acceptor pair used in this investigation included MES (donor) and 6-(fluorescein-5-(and-6)- carboxamido) hexanoic acid, succinimidyl ester bound to InGaP quantum dots (acceptor). MES was then investigated as a donor to various acceptor fluorophore: InGaP: mesoporous silicate nanoparticle layers.

Ultrafast electrical control of a resonantly driven single photon source

International Nuclear Information System (INIS)

Cao, Y.; Bennett, A. J.; Ellis, D. J. P.; Shields, A. J.; Farrer, I.; Ritchie, D. A.

2014-01-01

We demonstrate generation of a pulsed stream of electrically triggered single photons in resonance fluorescence, by applying high frequency electrical pulses to a single quantum dot in a p-i-n diode under resonant laser excitation. Single photon emission was verified, with the probability of multiple photon emission reduced to 2.8%. We show that despite the presence of charge noise in the emission spectrum of the dot, resonant excitation acts as a “filter” to generate narrow bandwidth photons

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.

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

Science.gov (United States)

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

2013-10-01

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

The Response of HeLa Cells to Fluorescent NanoDiamond Uptake

NARCIS (Netherlands)

Hemelaar, Simon R; Saspaanithy, Babujhi; L'Hommelet, Severin R M; Perona Martinez, Felipe P; van der Laan, Kiran J; Schirhagl, Romana

2018-01-01

Fluorescent nanodiamonds are promising probes for nanoscale magnetic resonance measurements. Their physical properties predict them to have particularly useful applications in intracellular analysis. Before using them in intracellular experiments however, it should be clear whether diamond particles

Hacking the art of exploitation

CERN Document Server

Erickson, Jon

2003-01-01

A comprehensive introduction to the techniques of exploitation and creative problem-solving methods commonly referred to as "hacking," Hacking: The Art of Exploitation is for both technical and non-technical people who are interested in computer security. It shows how hackers exploit programs and write exploits, instead of just how to run other people's exploits. Unlike many so-called hacking books, this book explains the technical aspects of hacking, including stack based overflows, heap based overflows, string exploits, return-into-libc, shellcode, and cryptographic attacks on 802.11b.

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.

Concentration Dependence of Gold Nanoparticles for Fluorescence Enhancement

Science.gov (United States)

Solomon, Joel; Wittmershaus, Bruce

Noble metal nanoparticles possess a unique property known as surface plasmon resonance in which the conduction electrons oscillate due to incoming light, dramatically increasing their absorption and scattering of light. The oscillating electrons create a varying electric field that can affect nearby molecules. The fluorescence and photostability of fluorophores can be enhanced significantly when they are near plasmonic nanoparticles. This effect is called metal enhanced fluorescence (MEF). MEF from two fluorescence organic dyes, Lucifer Yellow CH and Riboflavin, was measured with different concentrations of 50-nm colloidal gold nanoparticles (Au-NP). The concentration range of Au-NP was varied from 2.5 to 250 pM. To maximize the interaction, the dyes were chosen so their emission spectra had considerable overlap with the absorption spectra of the Au-NP, which is common in MEF studies. If the dye molecules are too close to the surface of Au-NP, fluorescence quenching can occur instead of MEF. To try to observe this difference, silica-coated Au-NP were compared to citrate-based Au-NP; however, fluorescence quenching was observed with both Au-NP. This material is based upon work supported by the National Science Foundation under Grant Number NSF-ECCS-1306157.

Fluorescence Spectroscopy Approaches for the Development of a Real-Time Organophosphate Detection System Using an Enzymatic Sensor

Directory of Open Access Journals (Sweden)

Paola Carullo

2015-02-01

Full Text Available Organophosphates are organic substances that contain a phosphoryl or a thiophosphoryl bond. They are mainly used around the world as pesticides, but can also be used as chemical warfare agents. Their detection is normally entrusted to techniques like GC- and LC-MS that, although sensitive, do not allow their identification on site and in real time. We have approached their identification by exploiting the high-affinity binding of these compounds with the esterase 2 from Alicyclobacillus acidocaldarius. Using an in silico analysis to evaluate the binding affinities of the enzyme with organophosphate inhibitors, like paraoxon, and other organophosphate compounds, like parathion, chlorpyriphos, and other organophosphate thio-derivatives, we have designed fluorescence spectroscopy experiments to study the quenching of the tryptophan residues after esterase 2 binding with the organophosphate pesticides. The changes in the fluorescence signals permitted an immediate and quantitative identification of these compounds from nano- to picomolar concentrations. A fluorescence based polarity-sensitive probe (ANS was also employed as a means to understand the extent of the interactions involved, as well as to explore other ways to detect organophosphate pesticides. Finally, we designed a framework for the development of a biosensor that exploits fluorescence technology in combination with a sensitive and very stable bio-receptor.

Exploitation of Labour and Exploitation of Commodities: a “New Interpretation”

OpenAIRE

Veneziani, Roberto; Yoshihara, Naoki

2011-01-01

In the standard Okishio-Morishima approach, the existence of profits is proved to be equivalent to the exploitation of labour. Yet, it can also be proved that the existence of profits is equivalent to the ‘exploitation’ of any good. Labour and commodity exploitation are just different numerical representations of the productiveness of the economy. This paper presents an alternative approach to exploitation theory which is related to the New Interpretation (Duménil 1980; Foley 1982). In this a...

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

Science.gov (United States)

Algar, W Russ; Krull, Ulrich J

2009-01-06

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

Biosensing by WGM Microspherical Resonators

Directory of Open Access Journals (Sweden)

Giancarlo C. Righini

2016-06-01

Full Text Available Whispering gallery mode (WGM microresonators, thanks to their unique properties, have allowed researchers to achieve important results in both fundamental research and engineering applications. Among the various geometries, microspheres are the simplest 3D WGM resonators; the total optical loss in such resonators can be extremely low, and the resulting extraordinarily high Q values of 108–109 lead to high energy density, narrow resonant-wavelength lines and a lengthy cavity ringdown. They can also be coated in order to better control their properties or to increase their functionality. Their very high sensitivity to changes in the surrounding medium has been exploited for several sensing applications: protein adsorption, trace gas detection, impurity detection in liquids, structural health monitoring of composite materials, detection of electric fields, pressure sensing, and so on. In the present paper, after a general introduction to WGM resonators, attention is focused on spherical microresonators, either in bulk or in bubble format, to their fabrication, characterization and functionalization. The state of the art in the area of biosensing is presented, and the perspectives of further developments are discussed.

[Analysis of fluorescence spectrum of petroleum-polluted water].

Science.gov (United States)

Huang, Miao-Fen; Song, Qing-Jun; Xing, Xu-Feng; Jian, Wei-Jun; Liu, Yuan; Zhao, Zu-Long

2014-09-01

In four ratio experiments, natural waters, sampled from the mountain reservoir and the sea water around Dalian city, were mixed with the sewage from petroleum refinery and petroleum exploitation plants. The fluorescence spectra of water samples containing only chromophoric dissolved organic matters(CDOM), samples containing only petroleum, and samples containing a mixture of petroleum and CDOM were analyzed, respectively. The purpose of this analysis is to provide a basis for determining the contribution of petroleum substances and CDOM to the total absorption coefficient of the petroleum-contaminated water by using fluorescence technique. The results showed that firstly, CDOM in seawater had three main fluorescence peaks at Ex: 225-230 nm/Em: 320-330 nm, Ex: 280 nm/Em: 340 nm and Ex: 225-240 nm/Em: 430-470 nm, respectively, and these may arise from the oceanic chlorophyll. CDOM in natural reservoir water had two main fluorescence peaks at EX: 240- 260 nm/Em: 420-450 nm and Ex: 310~350 nm/Em: 420--440 nm, respectively, and these may arise from the terrestrial sources; secondly, the water samples containing only petroleum extracted with n-hexane had one to three fluorescence spectral peaksat Ex: 220-240 nm/Em: 320-340 nm, Ex: 270-290 nm/Em: 310-340 nm and Ex: 220-235 nm/Em: 280-310 nm, respectively, caused by their hydrocarbon component; finally, the water samples containing both petroleum and CDOM showed a very strong fluorescence peak at Ex: 230-250 nm/Em: 320-370 nm, caused by the combined effect of CDOM and petroleum hydrocarbons.

Exploitation and disadvantage

NARCIS (Netherlands)

Ferguson, B.

2016-01-01

According to some accounts of exploitation, most notably Ruth Sample's (2003) degradation-based account and Robert Goodin's (1987) vulnerability-based account, exploitation occurs when an advantaged party fails to constrain their advantage in light of another's disadvantage, regardless of the cause

Nuclear structure studies on medium-heavy mass nuclei using the method of nuclear resonance fluorescence; Kernstrukturuntersuchungen in mittelschweren Atomkernen mit der Methode der Kernresonanzfluoreszenz

Energy Technology Data Exchange (ETDEWEB)

Zweidinger, Markus

2016-06-22

In the present work the dipole strength distribution in the stable even-even isotopes {sup 92}Zr and {sup 94}Zr is investigated. To excite the nuclei from the ground state to an excited state, real photons are used. This method is called Nuclear Resonance Fluorescence. The measurements were performed at two different setups. The first one is the Darmstadt High Intensity Photon Setup (DHIPS). At DHIPS the measurements yield information about the spin quantum number and the integrated cross section. The second part of the experiments took place at the High Intensity γ-ray Source (HIγS). Here, information about the parity quantum number and the averaged branching ratio of the excited state is accessible. In total, 105 dipole excited states in the nucleus {sup 92}Zr and 124 in the isotope {sup 94}Zr are observed, most of them for the first time. The extracted dipole strength distribution is investigated for the existence of the pygmy dipole resonance that was observed in neighboring nuclei. Furthermore, in previously performed experiments on the isotope {sup 90}Zr, the spin-flip M1 resonance was observed as well. Therefore, also the magnetic dipole strength is investigated. Further, by comparison with global systematics, the two-phonon state is identified. Additionally, the averaged branching ratio is compared to the results of theoretical calculations in the framework of the statistical model.

Near-infrared II fluorescence for imaging hindlimb vessel regeneration with dynamic tissue perfusion measurement.

Science.gov (United States)

Hong, Guosong; Lee, Jerry C; Jha, Arshi; Diao, Shuo; Nakayama, Karina H; Hou, Luqia; Doyle, Timothy C; Robinson, Joshua T; Antaris, Alexander L; Dai, Hongjie; Cooke, John P; Huang, Ngan F

2014-05-01

Real-time vascular imaging that provides both anatomic and hemodynamic information could greatly facilitate the diagnosis of vascular diseases and provide accurate assessment of therapeutic effects. Here, we have developed a novel fluorescence-based all-optical method, named near-infrared II (NIR-II) fluorescence imaging, to image murine hindlimb vasculature and blood flow in an experimental model of peripheral arterial disease, by exploiting fluorescence in the NIR-II region (1000-1400 nm) of photon wavelengths. Because of the reduced photon scattering of NIR-II fluorescence compared with traditional NIR fluorescence imaging and thus much deeper penetration depth into the body, we demonstrated that the mouse hindlimb vasculature could be imaged with higher spatial resolution than in vivo microscopic computed tomography. Furthermore, imaging during 26 days revealed a significant increase in hindlimb microvascular density in response to experimentally induced ischemia within the first 8 days of the surgery (Pimaging make it a useful imaging tool for murine models of vascular disease. © 2014 American Heart Association, Inc.

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.

Cooperative fluorescence from a strongly driven dilute cloud of atoms

DEFF Research Database (Denmark)

Ott, Johan Raunkjær; Wubs, Martijn; Lodahl, Peter

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 driving fields. Furthermore, we compute the inelastic component of the light scattered by a cloud...

Enhancement of single-molecule fluorescence signals by colloidal silver nanoparticles in studies of protein translation.

Science.gov (United States)

Bharill, Shashank; Chen, Chunlai; Stevens, Benjamin; Kaur, Jaskiran; Smilansky, Zeev; Mandecki, Wlodek; Gryczynski, Ignacy; Gryczynski, Zygmunt; Cooperman, Barry S; Goldman, Yale E

2011-01-25

Metal-enhanced fluorescence (MEF) increased total photon emission of Cy3- and Cy5-labeled ribosomal initiation complexes near 50 nm silver particles 4- and 5.5-fold, respectively. Fluorescence intensity fluctuations above shot noise, at 0.1-5 Hz, were greater on silver particles. Overall signal-to-noise ratio was similar or slightly improved near the particles. Proximity to silver particles did not compromise ribosome function, as measured by codon-dependent binding of fluorescent tRNA, dynamics of fluorescence resonance energy transfer between adjacent tRNAs in the ribosome, and tRNA translocation induced by elongation factor G.

Enhancement of Single Molecule Fluorescence Signals by Colloidal Silver Nanoparticles in Studies of Protein Translation

Science.gov (United States)

Bharill, Shashank; Chen, Chunlai; Stevens, Benjamin; Kaur, Jaskiran; Smilansky, Zeev; Mandecki, Wlodek; Gryczynski, Ignacy; Gryczynski, Zygmunt; Cooperman, Barry S.; Goldman, Yale E.

2011-01-01

Metal enhanced fluorescence (MEF) increased total photon emission of Cy3- and Cy5-labeled ribosomal initiation complexes near 50 nm silver particles 4- and 5.5-fold respectively. Fluorescence intensity fluctuations above shot noise, at 0.1 – 5 Hz, were greater on silver particles. Overall signal to noise ratio was similar or slightly improved near the particles. Proximity to silver particles did not compromise ribosome function, as measured by codon-dependent binding of fluorescent tRNA, dynamics of fluorescence resonance energy transfer between adjacent tRNAs in the ribosome, and tRNA translocation induced by elongation factor G. PMID:21158483

Fluorescent magnetic hybrid nanoprobe for multimodal bioimaging

Energy Technology Data Exchange (ETDEWEB)

Koktysh, Dmitry [Department of Chemistry, Vanderbilt University, Station B 351822, Nashville, TN 37235 (United States); Bright, Vanessa; Pham, Wellington, E-mail: dmitry.koktysh@vanderbilt.edu, E-mail: wellington.pham@vanderbilt.edu [Institute of Imaging Science, Vanderbilt University, 1161 21st Avenue South AA, 1105 MCN, Nashville, TN 37232 (United States)

2011-07-08

A fluorescent magnetic hybrid imaging nanoprobe (HINP) was fabricated by the conjugation of superparamagnetic Fe{sub 3}O{sub 4} nanoparticles and visible light emitting ({approx}600 nm) fluorescent CdTe/CdS quantum dots (QDs). The assembly strategy used the covalent linking of the oxidized dextran shell of magnetic particles to the glutathione ligands of QDs. The synthesized HINP formed stable water-soluble colloidal dispersions. The structure and properties of the particles were characterized by transmission electron and atomic force microscopy, energy dispersive x-ray analysis and inductively coupled plasma optical emission spectroscopy, dynamic light scattering analysis, optical absorption and photoluminescence spectroscopy, and fluorescent imaging. The luminescence imaging region of the nanoprobe was extended to the near-infrared (NIR) ({approx}800 nm) by conjugation of the superparamagnetic nanoparticles with synthesized CdHgTe/CdS QDs. Cadmium, mercury based QDs in HINP can be easily replaced by novel water-soluble glutathione stabilized AgInS{sub 2}/ZnS QDs to present a new class of cadmium-free multimodal imaging agents. The observed NIR photoluminescence of fluorescent magnetic nanocomposites supports their use for bioimaging. The developed HINP provides dual-imaging channels for simultaneous optical and magnetic resonance imaging.

Smart phone based bacterial detection using bio functionalized fluorescent nanoparticles

International Nuclear Information System (INIS)

Rajendran, Vinoth Kumar; Bakthavathsalam, Padmavathy; Ali, Baquir Mohammed Jaffar

2014-01-01

We are describing immunochromatographic test strips with smart phone-based fluorescence readout. They are intended for use in the detection of the foodborne bacterial pathogens Salmonella spp. and Escherichia coli O157. Silica nanoparticles (SiNPs) were doped with FITC and Ru(bpy), conjugated to the respective antibodies, and then used in a conventional lateral flow immunoassay (LFIA). Fluorescence was recorded by inserting the nitrocellulose strip into a smart phone-based fluorimeter consisting of a light weight (40 g) optical module containing an LED light source, a fluorescence filter set and a lens attached to the integrated camera of the cell phone in order to acquire high-resolution fluorescence images. The images were analysed by exploiting the quick image processing application of the cell phone and enable the detection of pathogens within few minutes. This LFIA is capable of detecting pathogens in concentrations as low as 10 5 cfu mL −1 directly from test samples without pre-enrichment. The detection is one order of magnitude better compared to gold nanoparticle-based LFIAs under similar condition. The successful combination of fluorescent nanoparticle-based pathogen detection by LFIAs with a smart phone-based detection platform has resulted in a portable device with improved diagnosis features and having potential application in diagnostics and environmental monitoring. (author)

Quantum dots versus organic fluorophores in fluorescent deep-tissue imaging--merits and demerits.

Science.gov (United States)

Bakalova, Rumiana; Zhelev, Zhivko; Gadjeva, Veselina

2008-12-01

The use of fluorescence in deep-tissue imaging is rapidly expanding in last several years. The progress in fluorescent molecular probes and fluorescent imaging techniques gives an opportunity to detect single cells and even molecular targets in live organisms. The highly sensitive and high-speed fluorescent molecular sensors and detection devices allow the application of fluorescence in functional imaging. With the development of novel bright fluorophores based on nanotechnologies and 3D fluorescence scanners with high spatial and temporal resolution, the fluorescent imaging has a potential to become an alternative of the other non-invasive imaging techniques as magnetic resonance imaging, positron-emission tomography, X-ray, computing tomography. The fluorescent imaging has also a potential to give a real map of human anatomy and physiology. The current review outlines the advantages of fluorescent nanoparticles over conventional organic dyes in deep-tissue imaging in vivo and defines the major requirements to the "perfect fluorophore". The analysis proceeds from the basic principles of fluorescence and major characteristics of fluorophores, light-tissue interactions, and major limitations of fluorescent deep-tissue imaging. The article is addressed to a broad readership - from specialists in this field to university students.

An Experimental Study of the Fluorescence Spectrum of Cesium Atoms in the Presence of a Buffer Gas

Science.gov (United States)

Davydov, V. G.; Kulyasov, V. N.

2018-01-01

A direct experiment is performed to determine the quantum efficiency of a cesium fluorescence filter. The fluorescence spectra of cesium atoms are recorded under excitation of the upper states of the second resonance doublet with a Bell-Bloom cesium lamp. Introduction of different noble gases into the cell with cesium leads to the appearance of additional fluorescence photons. It is found that a fluorescence filter based on atomic cesium vapor with addition of helium in the working cell has the highest efficiency and response rate of all known fluorescence filters based on alkali-metal atomic vapors.

Biopharmaceutical production: Applications of surface plasmon resonance biosensors.

Science.gov (United States)

Thillaivinayagalingam, Pranavan; Gommeaux, Julien; McLoughlin, Michael; Collins, David; Newcombe, Anthony R

2010-01-15

Surface plasmon resonance (SPR) permits the quantitative analysis of therapeutic antibody concentrations and impurities including bacteria, Protein A, Protein G and small molecule ligands leached from chromatography media. The use of surface plasmon resonance has gained popularity within the biopharmaceutical industry due to the automated, label free, real time interaction that may be exploited when using this method. The application areas to assess protein interactions and develop analytical methods for biopharmaceutical downstream process development, quality control, and in-process monitoring are reviewed. 2009 Elsevier B.V. All rights reserved.

Generally Applicable Transformation Protocols for Fluorescent Nanodiamond Internalization into Cells.

Science.gov (United States)

Hemelaar, Simon R; van der Laan, Kiran J; Hinterding, Sophie R; Koot, Manon V; Ellermann, Else; Perona-Martinez, Felipe P; Roig, David; Hommelet, Severin; Novarina, Daniele; Takahashi, Hiroki; Chang, Michael; Schirhagl, Romana

2017-07-19

Fluorescent nanodiamonds (FNDs) are promising nanoprobes, owing to their stable and magnetosensitive fluorescence. Therefore they can probe properties as magnetic resonances, pressure, temperature or strain. The unprecedented sensitivity of diamond defects can detect the faint magnetic resonance of a single electron or even a few nuclear spins. However, these sensitivities are only achieved if the diamond probe is close to the molecules that need to be detected. In order to utilize its full potential for biological applications, the diamond particle has to enter the cell. Some model systems, like HeLa cells, readily ingest particles. However, most cells do not show this behavior. In this article we show for the first time generally applicable methods, which are able to transport fluorescent nanodiamonds into cells with a thick cell wall. Yeast cells, in particular Saccharomyces cerevisiae, are a favored model organism to study intracellular processes including aging on a cellular level. In order to introduce FNDs in these cells, we evaluated electrical transformation and conditions of chemical permeabilization for uptake efficiency and viability. 5% DMSO (dimethyl sulfoxide) in combination with optimized chemical transformation mix leads to high uptake efficiency in combination with low impact on cell biology. We have evaluated all steps in the procedure.

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

Science.gov (United States)

Ran, Yong

2008-01-01

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

Multimodal optical coherence tomography and fluorescence lifetime imaging with interleaved excitation sources for simultaneous endogenous and exogenous fluorescence.

Science.gov (United States)

Shrestha, Sebina; Serafino, Michael J; Rico-Jimenez, Jesus; Park, Jesung; Chen, Xi; Zhaorigetu, Siqin; Walton, Brian L; Jo, Javier A; Applegate, Brian E

2016-09-01

Multimodal imaging probes a variety of tissue properties in a single image acquisition by merging complimentary imaging technologies. Exploiting synergies amongst the data, algorithms can be developed that lead to better tissue characterization than could be accomplished by the constituent imaging modalities taken alone. The combination of optical coherence tomography (OCT) with fluorescence lifetime imaging microscopy (FLIM) provides access to detailed tissue morphology and local biochemistry. The optical system described here merges 1310 nm swept-source OCT with time-domain FLIM having excitation at 355 and 532 nm. The pulses from 355 and 532 nm lasers have been interleaved to enable simultaneous acquisition of endogenous and exogenous fluorescence signals, respectively. The multimodal imaging system was validated using tissue phantoms. Nonspecific tagging with Alexa Flour 532 in a Watanbe rabbit aorta and active tagging of the LOX-1 receptor in human coronary artery, demonstrate the capacity of the system for simultaneous acquisition of OCT, endogenous FLIM, and exogenous FLIM in tissues.

Learning Metasploit exploitation and development

CERN Document Server

Balapure, Aditya

2013-01-01

A practical, hands-on tutorial with step-by-step instructions. The book will follow a smooth and easy-to-follow tutorial approach, covering the essentials and then showing the readers how to write more sophisticated exploits.This book targets exploit developers, vulnerability analysts and researchers, network administrators, and ethical hackers looking to gain advanced knowledge in exploitation development and identifying vulnerabilities. The primary goal is to take readers wishing to get into more advanced exploitation discovery and reaching the next level.Prior experience exploiting basic st

A Graphene Oxide-Based Fluorescent Aptasensor for the Turn-on Detection of CCRF-CEM.

Science.gov (United States)

Tan, Jie; Lai, Zongqiang; Zhong, Liping; Zhang, Zhenghua; Zheng, Rong; Su, Jing; Huang, Yong; Huang, Panpan; Song, Hui; Yang, Nuo; Zhou, Sufang; Zhao, Yongxiang

2018-04-01

A convenient, low-cost, and highly sensitive fluorescent aptasensor for detection of leukemia has been developed based on graphene oxide-aptamer complex (GO-apt). Graphene oxide (GO) can absorb carboxyfluorescein-labeled Sgc8 aptamer (FAM-apt) by π-π stacking and quench the fluorescence through fluorescence resonance energy transfer (FRET). In the absence of Sgc8 target cell CCRF-CEM, the fluorescence is almost all quenched. Conversely, when the CCRF-CEM cells are added, the quenched fluorescence can be recovered rapidly and significantly. Therefore, based on the change of fluorescence signals, we can detect the number of CCRF-CEM cells in a wide range from 1 × 10 2 to 1 × 10 7  cells/mL with a limit of detection (LOD) of 10 cells/mL. Therefore, this strategy of graphene oxide-based fluorescent aptasensor may be promising for the detection of cancer.

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

Science.gov (United States)

Şen, Esra; Meral, Kadem; Atılgan, Serdar

2016-01-11

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

Anthropology of sexual exploitation

Directory of Open Access Journals (Sweden)

Lalić Velibor

2009-01-01

Full Text Available In this paper, the authors observe sexual exploitation from an anthropological perspective. They analyze the rational, ethical, emotional and mythological dimensions of human sexuality. Consequently, after setting the phenomenon in a social and historical context, sexual exploitation is closely observed in the contemporary age. Based on thoughts of relevant thinkers, they make the conclusion that the elimination of sexual exploitation is not an utterly legal issue, but political and economical issues as well. Namely, legal norms are not sufficient to overcome sexual exploitation, but, political and economical relationships in contemporary societies, which will be based on sincere equal opportunities must be established.

Functionalized graphene oxide/Fe3O4 hybrids for cellular magnetic resonance imaging and fluorescence labeling.

Science.gov (United States)

Zhou, Chaohui; Wu, Hui; Wang, Mingliang; Huang, Chusen; Yang, Dapeng; Jia, Nengqin

2017-09-01

In this work, we developed a T 2 -weighted contrast agent based on graphene oxide (GO)/Fe 3 O 4 hybrids for efficient cellular magnetic resonance imaging (MRI). The GO/Fe 3 O 4 hybrids were obtained by combining with co-precipitation method and pyrolysis method. The structural, surface and magnetic characteristics of the hybrids were systematically characterized by transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), AFM, Raman, FT-IR and XRD. The GO/Fe 3 O 4 hybrids were functionalized by modifying with anionic and cationic polyelectrolyte through layer-by-layer assembling. The fluorescence probe fluorescein isothiocyanate (FITC) was further loaded on the surface of functionalized GO/Fe 3 O 4 hybrids to trace the location of GO/Fe 3 O 4 hybrids in cells. Functionalized GO/Fe 3 O 4 hybrids possess good hydrophilicity, less cytotoxicity, high MRI enhancement with the relaxivity (r 2 ) of 493mM -1 s -1 as well as cellular MRI contrast effect. These obtained results indicated that the functionalized GO/Fe 3 O 4 hybrids could have great potential to be utilized as cellular MRI contrast agents for tumor early diagnosis and monitoring. Copyright © 2017 Elsevier B.V. All rights reserved.

Enhanced 3D fluorescence live cell imaging on nanoplasmonic substrate

International Nuclear Information System (INIS)

Gartia, Manas Ranjan; Hsiao, Austin; Logan Liu, G; Sivaguru, Mayandi; Chen Yi

2011-01-01

We have created a randomly distributed nanocone substrate on silicon coated with silver for surface-plasmon-enhanced fluorescence detection and 3D cell imaging. Optical characterization of the nanocone substrate showed it can support several plasmonic modes (in the 300-800 nm wavelength range) that can be coupled to a fluorophore on the surface of the substrate, which gives rise to the enhanced fluorescence. Spectral analysis suggests that a nanocone substrate can create more excitons and shorter lifetime in the model fluorophore Rhodamine 6G (R6G) due to plasmon resonance energy transfer from the nanocone substrate to the nearby fluorophore. We observed three-dimensional fluorescence enhancement on our substrate shown from the confocal fluorescence imaging of chinese hamster ovary (CHO) cells grown on the substrate. The fluorescence intensity from the fluorophores bound on the cell membrane was amplified more than 100-fold as compared to that on a glass substrate. We believe that strong scattering within the nanostructured area coupled with random scattering inside the cell resulted in the observed three-dimensional enhancement in fluorescence with higher photostability on the substrate surface.

Enhanced 3D fluorescence live cell imaging on nanoplasmonic substrate

Energy Technology Data Exchange (ETDEWEB)

Gartia, Manas Ranjan [Department of Nuclear, Plasma and Radiological Engineering, University of Illinois, Urbana, IL 61801 (United States); Hsiao, Austin; Logan Liu, G [Department of Bioengineering, University of Illinois, Urbana, IL 61801 (United States); Sivaguru, Mayandi [Institute for Genomic Biology, University of Illinois, Urbana, IL 61801 (United States); Chen Yi, E-mail: loganliu@illinois.edu [Department of Electrical and Computer Engineering, University of Illinois, Urbana, IL 61801 (United States)

2011-09-07

We have created a randomly distributed nanocone substrate on silicon coated with silver for surface-plasmon-enhanced fluorescence detection and 3D cell imaging. Optical characterization of the nanocone substrate showed it can support several plasmonic modes (in the 300-800 nm wavelength range) that can be coupled to a fluorophore on the surface of the substrate, which gives rise to the enhanced fluorescence. Spectral analysis suggests that a nanocone substrate can create more excitons and shorter lifetime in the model fluorophore Rhodamine 6G (R6G) due to plasmon resonance energy transfer from the nanocone substrate to the nearby fluorophore. We observed three-dimensional fluorescence enhancement on our substrate shown from the confocal fluorescence imaging of chinese hamster ovary (CHO) cells grown on the substrate. The fluorescence intensity from the fluorophores bound on the cell membrane was amplified more than 100-fold as compared to that on a glass substrate. We believe that strong scattering within the nanostructured area coupled with random scattering inside the cell resulted in the observed three-dimensional enhancement in fluorescence with higher photostability on the substrate surface.

Endogenous Fluorescence Signatures in Living Pluripotent Stem Cells Change with Loss of Potency

Science.gov (United States)

Squirrell, Jayne M.; Fong, Jimmy J.; Ariza, Carlos A.; Mael, Amber; Meyer, Kassondra; Shevde, Nirupama K.; Roopra, Avtar; Lyons, Gary E.; Kamp, Timothy J.; Eliceiri, Kevin W.; Ogle, Brenda M.

2012-01-01

The therapeutic potential of stem cells is limited by the non-uniformity of their phenotypic state. Thus it would be advantageous to noninvasively monitor stem cell status. Driven by this challenge, we employed multidimensional multiphoton microscopy to quantify changes in endogenous fluorescence occurring with pluripotent stem cell differentiation. We found that global and cellular-scale fluorescence lifetime of human embryonic stem cells (hESC) and murine embryonic stem cells (mESC) consistently decreased with differentiation. Less consistent were trends in endogenous fluorescence intensity with differentiation, suggesting intensity is more readily impacted by nuances of species and scale of analysis. What emerges is a practical and accessible approach to evaluate, and ultimately enrich, living stem cell populations based on changes in metabolism that could be exploited for both research and clinical applications. PMID:22952742

Far-Red Fluorescent Probe for Imaging of Vicinal Dithiol-Containing Proteins in Living Cells Based on a pKa Shift Mechanism.

Science.gov (United States)

Zhang, Shengrui; Chen, Guojun; Wang, Yuanyuan; Wang, Qin; Zhong, Yaogang; Yang, Xiao-Feng; Li, Zheng; Li, Hua

2018-02-20

Vicinal dithiol-containing proteins (VDPs) play fundamental roles in intracellular redox homeostasis and are responsible for many diseases. In this work, we report a far-red fluorescence turn-on probe MCAs for VDPs exploiting the pK a shift of the imine functionality of the probe. MCAs is composed of a merocyanine Schiff base as the fluorescent reporter and a cyclic 1,3,2-dithiarsenolane as the specific ligand for VDPs. The imine pK a of MCAs is 4.8, and it exists predominantly in the Schiff base (SB) form at physiological pH. Due to the absence of a resonating positive charge, it absorbs at a relatively short wavelength and is essentially nonfluorescent. Upon selective binding to reduced bovine serum albumin (rBSA, selected as the model protein), MCAs was brought from aqueous media to the binding pockets of the protein, causing a large increase in pK a value of MCAs (pK a = 7.1). As a result, an increase in the protonated Schiff base (PSB) form of MCAs was observed at the physiological pH conditions, which in turn leads to a bathochromically shifted chromophore (λ abs = 634 nm) and a significant increase in fluorescence intensity (λ em = 657 nm) simultaneously. Furthermore, molecular dynamics simulations indicate that the salt bridges formed between the iminium in MCAs and the residues D72 and D517 in rBSA resist the dissociation of proton from the probe, thus inducing an increase of the pK a value. The proposed probe shows excellent sensitivity and specificity toward VDPs over other proteins and biologically relevant species and has been successfully applied for imaging of VDPs in living cells. We believe that the present pK a shift switching strategy may facilitate the development of new fluorescent probes that are useful for a wide range of applications.

Intensity and pressure dependence of resonance fluorescence of OH induced by a tunable UV laser

Science.gov (United States)

Killinger, D. K.; Wang, C. C.; Hanabusa, M.

1976-01-01

The intensity and pressure dependence of the fluorescence spectrum of OH in the presence of N2 and H2O molecules was studied. Saturation of the absorption transition was observed at low pressures, and the corresponding fluorescence signal was found to vary as the square root of the exciting intensity. This observed dependence agreed with the predicted dependence which took into account the presence of laser modes in the spectrum of the exciting radiation. With full laser power incident, a saturation parameter as high as 3 x 10 to the 5th was observed. The fluorescence spectrum was found to peak at 3145 and at 3090 A, with the relative peak intensities dependent upon gas pressures and upon the particular rotational electronic transition used for excitation. It is concluded that vibrational relaxation of the electronically excited OH due to water vapor in the system plays a dominant role in determining the observed fluorescence spectrum.

Deep-tissue reporter-gene imaging with fluorescence and optoacoustic tomography: a performance overview.

Science.gov (United States)

Deliolanis, Nikolaos C; Ale, Angelique; Morscher, Stefan; Burton, Neal C; Schaefer, Karin; Radrich, Karin; Razansky, Daniel; Ntziachristos, Vasilis

2014-10-01

A primary enabling feature of near-infrared fluorescent proteins (FPs) and fluorescent probes is the ability to visualize deeper in tissues than in the visible. The purpose of this work is to find which is the optimal visualization method that can exploit the advantages of this novel class of FPs in full-scale pre-clinical molecular imaging studies. Nude mice were stereotactically implanted with near-infrared FP expressing glioma cells to from brain tumors. The feasibility and performance metrics of FPs were compared between planar epi-illumination and trans-illumination fluorescence imaging, as well as to hybrid Fluorescence Molecular Tomography (FMT) system combined with X-ray CT and Multispectral Optoacoustic (or Photoacoustic) Tomography (MSOT). It is shown that deep-seated glioma brain tumors are possible to visualize both with fluorescence and optoacoustic imaging. Fluorescence imaging is straightforward and has good sensitivity; however, it lacks resolution. FMT-XCT can provide an improved rough resolution of ∼1 mm in deep tissue, while MSOT achieves 0.1 mm resolution in deep tissue and has comparable sensitivity. We show imaging capacity that can shift the visualization paradigm in biological discovery. The results are relevant not only to reporter gene imaging, but stand as cross-platform comparison for all methods imaging near infrared fluorescent contrast agents.

In Vivo Imaging of Nitric Oxide by Magnetic Resonance Imaging Techniques

Directory of Open Access Journals (Sweden)

Rakesh Sharma

2014-01-01

Full Text Available Nitric oxide (NO biosensors are novel tools for real-time bioimaging of tissue oxygen changes and physiological monitoring of tissue vasculature. Nitric oxide behavior further enhances its role in mapping signal transduction at the molecular level. Spectrometric electron paramagnetic resonance (EPR and fluorometric imaging are well known techniques with the potential for in vivo bioimaging of NO. In tissues, NO is a specific target of nitrosyl compounds for chemical reaction, which provides a unique opportunity for application of newly identified NO biosensors. However, the accuracy and sensitivity of NO biosensors still need to be improved. Another potential magnetic resonance technique based on short term NO effects on proton relaxation enhancement is magnetic resonance imaging (MRI, and some NO biosensors may be used as potent imaging contrast agents for measurement of tumor size by MRI combined with fluorescent imaging. The present review provides supporting information regarding the possible use of nitrosyl compounds as NO biosensors in MRI and fluorescent bioimaging showing their measurement limitations and quantitative accuracy. These new approaches open a perspective regarding bioimaging of NO and the in vivo elucidation of NO effects by magnetic resonance techniques.

The exploitation argument against commercial surrogacy.

Science.gov (United States)

Wilkinson, Stephen

2003-04-01

This paper discusses the exploitation argument against commercial surrogacy: the claim that commercial surrogacy is morally objectionable because it is exploitative. The following questions are addressed. First, what exactly does the exploitation argument amount to? Second, is commercial surrogacy in fact exploitative? Third, if it were exploitative, would this provide a sufficient reason to prohibit (or otherwise legislatively discourage) it? The focus throughout is on the exploitation of paid surrogates, although it is noted that other parties (e.g. 'commissioning parents') may also be the victims of exploitation. It is argued that there are good reasons for believing that commercial surrogacy is often exploitative. However, even if we accept this, the exploitation argument for prohibiting (or otherwise legislatively discouraging) commercial surrogacy remains quite weak. One reason for this is that prohibition may well 'backfire' and lead to potential surrogates having to do other things that are more exploitative and/or more harmful than paid surrogacy. It is concluded therefore that those who oppose exploitation should (rather than attempting to stop particular practices like commercial surrogacy) concentrate on: (a) improving the conditions under which paid surrogates 'work'; and (b) changing the background conditions (in particular, the unequal distribution of power and wealth) which generate exploitative relationships.

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

Science.gov (United States)

Arvand, Majid; Mirroshandel, Aazam A

2017-10-15

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

Fluorescent turn-on determination of the activity of peptidases using peptide templated gold nanoclusters

International Nuclear Information System (INIS)

Luo, Junjun; Wang, Liqiang; Zeng, Ke; Shen, Congcong; Qian, Pin; Yang, Minghui; Rasooly, Avraham; Qu, Fengli

2016-01-01

The fluorescence intensity of gold nanoclusters (AuNCs) is inversely related to the length of a peptide immobilized on its surface. This finding has been exploited to design a turn-on fluorescent method for the determination of the activity of peptidase. The β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) was chosen as a model peptidase. BACE1 cleaves the peptide substrates on AuNCs, and the fluorescence intensity of the AuNCs (at exCitation/emission wavelengths of 320/405 nm) carrying the rest of the cleaved peptide is significantly higher than that of the AuNCs with uncleaved peptide. Transmission electron microscopy revealed a decrease in the size of the AuNCs which is assumed cause fluorescence enhancement. The assay was applied to the determination of BACE1 activity in spiked cell lysates, and recoveries were between 96.9 and 104.0 %. (author)

Is Chemically Synthesized Graphene ‘Really’ a Unique Substrate for SERS and Fluorescence Quenching?

Science.gov (United States)

Sil, Sanchita; Kuhar, Nikki; Acharya, Somnath; Umapathy, Siva

2013-11-01

We demonstrate observation of Raman signals of different analytes adsorbed on carbonaceous materials, such as, chemically reduced graphene, graphene oxide (GO), multi-walled carbon nanotube (MWCNT), graphite and activated carbon. The analytes selected for the study were Rhodamine 6G (R6G) (in resonant conditions), Rhodamine B (RB), Nile blue (NBA), Crystal Violet (CV) and acetaminophen (paracetamol). All the analytes except paracetamol absorb and fluoresce in the visible region. In this article we provide experimental evidence of the fact that observation of Raman signals of analytes on such carbonaceous materials are more due to resonance effect, suppression of fluorescence and efficient adsorption and that this property in not unique to graphene or nanotubes but prevalent for various type of carbon materials.

Is Chemically Synthesized Graphene ‘Really’ a Unique Substrate for SERS and Fluorescence Quenching?

Science.gov (United States)

Sil, Sanchita; Kuhar, Nikki; Acharya, Somnath; Umapathy, Siva

2013-01-01

We demonstrate observation of Raman signals of different analytes adsorbed on carbonaceous materials, such as, chemically reduced graphene, graphene oxide (GO), multi-walled carbon nanotube (MWCNT), graphite and activated carbon. The analytes selected for the study were Rhodamine 6G (R6G) (in resonant conditions), Rhodamine B (RB), Nile blue (NBA), Crystal Violet (CV) and acetaminophen (paracetamol). All the analytes except paracetamol absorb and fluoresce in the visible region. In this article we provide experimental evidence of the fact that observation of Raman signals of analytes on such carbonaceous materials are more due to resonance effect, suppression of fluorescence and efficient adsorption and that this property in not unique to graphene or nanotubes but prevalent for various type of carbon materials. PMID:24275718

Exploitability Assessment with TEASER

Science.gov (United States)

2017-05-01

for architectural neutral taint analysis on top of LLVM and QEMU. POC Proof of Concept : Demonstration of an exploit on a program . vii RCE Remote Code...bug with a Proof of Concept (POC), or input to a program demonstrating the ability to use a bug to exploit the application, to demonstrate the...often leads to either computationally difficult constraint solving problems or taint explosion. Given the computational difficulty of exploit

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.

Active molecular plasmonics: tuning surface plasmon resonances by exploiting molecular dimensions

Science.gov (United States)

Chen, Kai; Leong, Eunice Sok Ping; Rukavina, Michael; Nagao, Tadaaki; Liu, Yan Jun; Zheng, Yuebing

2015-06-01

Molecular plasmonics explores and exploits the molecule-plasmon interactions on metal nanostructures to harness light at the nanoscale for nanophotonic spectroscopy and devices. With the functional molecules and polymers that change their structural, electrical, and/or optical properties in response to external stimuli such as electric fields and light, one can dynamically tune the plasmonic properties for enhanced or new applications, leading to a new research area known as active molecular plasmonics (AMP). Recent progress in molecular design, tailored synthesis, and self-assembly has enabled a variety of scenarios of plasmonic tuning for a broad range of AMP applications. Dimension (i.e., zero-, two-, and threedimensional) of the molecules on metal nanostructures has proved to be an effective indicator for defining the specific scenarios. In this review article, we focus on structuring the field of AMP based on the dimension of molecules and discussing the state of the art of AMP. Our perspective on the upcoming challenges and opportunities in the emerging field of AMP is also included.

Active molecular plasmonics: tuning surface plasmon resonances by exploiting molecular dimensions

Directory of Open Access Journals (Sweden)

Chen Kai

2015-06-01

Full Text Available Molecular plasmonics explores and exploits the molecule–plasmon interactions on metal nanostructures to harness light at the nanoscale for nanophotonic spectroscopy and devices. With the functional molecules and polymers that change their structural, electrical, and/or optical properties in response to external stimuli such as electric fields and light, one can dynamically tune the plasmonic properties for enhanced or new applications, leading to a new research area known as active molecular plasmonics (AMP. Recent progress in molecular design, tailored synthesis, and self-assembly has enabled a variety of scenarios of plasmonic tuning for a broad range of AMP applications. Dimension (i.e., zero-, two-, and threedimensional of the molecules on metal nanostructures has proved to be an effective indicator for defining the specific scenarios. In this review article, we focus on structuring the field of AMP based on the dimension of molecules and discussing the state of the art of AMP. Our perspective on the upcoming challenges and opportunities in the emerging field of AMP is also included.

The Value of 5-Aminolevulinic Acid in Low-grade Gliomas and High-grade Gliomas Lacking Glioblastoma Imaging Features: An Analysis Based on Fluorescence, Magnetic Resonance Imaging, 18F-Fluoroethyl Tyrosine Positron Emission Tomography, and Tumor Molecular Factors.

Science.gov (United States)

Jaber, Mohammed; Wölfer, Johannes; Ewelt, Christian; Holling, Markus; Hasselblatt, Martin; Niederstadt, Thomas; Zoubi, Tarek; Weckesser, Matthias; Stummer, Walter

2016-03-01

Approximately 20% of grade II and most grade III gliomas fluoresce after 5-aminolevulinic acid (5-ALA) application. Conversely, approximately 30% of nonenhancing gliomas are actually high grade. The aim of this study was to identify preoperative factors (ie, age, enhancement, 18F-fluoroethyl tyrosine positron emission tomography [F-FET PET] uptake ratios) for predicting fluorescence in gliomas without typical glioblastomas imaging features and to determine whether fluorescence will allow prediction of tumor grade or molecular characteristics. Patients harboring gliomas without typical glioblastoma imaging features were given 5-ALA. Fluorescence was recorded intraoperatively, and biopsy specimens collected from fluorescing tissue. World Health Organization (WHO) grade, Ki-67/MIB-1 index, IDH1 (R132H) mutation status, O-methylguanine DNA methyltransferase (MGMT) promoter methylation status, and 1p/19q co-deletion status were assessed. Predictive factors for fluorescence were derived from preoperative magnetic resonance imaging and F-FET PET. Classification and regression tree analysis and receiver-operating-characteristic curves were generated for defining predictors. Of 166 tumors, 82 were diagnosed as WHO grade II, 76 as grade III, and 8 as glioblastomas grade IV. Contrast enhancement, tumor volume, and F-FET PET uptake ratio >1.85 predicted fluorescence. Fluorescence correlated with WHO grade (P fluorescing grade III gliomas was higher than in nonfluorescing tumors, whereas in fluorescing and nonfluorescing grade II tumors, no differences were noted. Age, tumor volume, and F-FET PET uptake are factors predicting 5-ALA-induced fluorescence in gliomas without typical glioblastoma imaging features. Fluorescence was associated with an increased Ki-67/MIB-1 index and high-grade pathology. Whether fluorescence in grade II gliomas identifies a subtype with worse prognosis remains to be determined.

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

Science.gov (United States)

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

2015-06-01

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

Two questions about surrogacy and exploitation.

Science.gov (United States)

Wertheimer, Alan

1992-01-01

In this article I will consider two related questions about surrogacy and exploitation: (1) Is surrogacy exploitative? (2) If surrogacy is exploitative, what is the moral force of this exploitation? Briefly stated, I shall argue that whether surrogacy is exploitative depends on whether exploitation must be harmful to the exploited party or whether (as I think) there can be mutually advantageous exploitation. It also depends on some facts about surrogacy about which we have little reliable evidence and on our philosophical view on what counts as a harm to the surrogate. Our answer to the second question will turn in part on the account of exploitation we invoke in answering the first question and in part on the way in which we resolve some other questions about the justification of state interference. I shall suggest, however, that if surrogacy is a form of voluntary and mutually advantageous exploitation, then there is a strong presumption that surrogacy contracts should be permitted and even enforceable, although that presumption may be overridden on other grounds.

Synchrotron radiation resonance Raman spectroscopy (SR3S)

International Nuclear Information System (INIS)

Hester, R.E.

1979-01-01

The use of normal Raman spectroscopy and resonance Raman spectroscopy to study the structure of molecular species and the nature of their chemical bonds is discussed. The availability of a fully tunable radiation source (the Synchrotron Radiation Source) extending into the ultraviolet raises the possibility of using synchrotron radiation resonance Raman spectroscopy as a sensitive and specific analytical probe. The pulsed nature of the SRS beam may be exploited for time-resolved resonance Raman spectroscopy and its high degree of polarization could be very helpful in the interpretation of spectra. The possibilities are considered under the headings: intensity requirements and comparison with other sources; some applications (e.g. structure of proteins; study of iron-porphyrin unit; study of chlorophylls). (U.K.)

Magnetic resonance imaging for the exploitation of bubble-enhanced heating by high-intensity focused ultrasound: a feasibility study in ex vivo liver.

Science.gov (United States)

Elbes, Delphine; Denost, Quentin; Robert, Benjamin; Köhler, Max O; Tanter, Mickaël; Bruno, Quesson

2014-05-01

Bubble-enhanced heating (BEH) may be exploited to improve the heating efficiency of high-intensity focused ultrasound in liver and to protect tissues located beyond the focal point. The objectives of this study, performed in ex vivo pig liver, were (i) to develop a method to determine the acoustic power threshold for induction of BEH from displacement images measured by magnetic resonance acoustic radiation force imaging (MR-ARFI), and (ii) to compare temperature distribution with MR thermometry for HIFU protocols with and without BEH. The acoustic threshold for generation of BEH was determined in ex vivo pig liver from MR-ARFI calibration curves of local tissue displacement resulting from sonication at different powers. Temperature distributions (MR thermometry) resulting from "conventional" sonications (20 W, 30 s) were compared with those from "composite" sonications performed at identical parameters, but after a HIFU burst pulse (0.5 s, acoustic power over the threshold for induction of BEH). Displacement images (MR-ARFI) were acquired between sonications to measure potential modifications of local tissue displacement associated with modifications of tissue acoustic characteristics induced by the burst HIFU pulse. The acoustic threshold for induction of BEH corresponded to a displacement amplitude of approximately 50 μm in ex vivo liver. The displacement and temperature images of the composite group exhibited a nearly spherical pattern, shifted approximately 4 mm toward the transducer, in contrast to elliptical shapes centered on the natural focal position for the conventional group. The gains in maximum temperature and displacement values were 1.5 and 2, and the full widths at half-maximum of the displacement data were 1.7 and 2.2 times larger than in the conventional group in directions perpendicular to ultrasound propagation axes. Combination of MR-ARFI and MR thermometry for calibration and exploitation of BEH appears to increase the efficiency and safety

Exploit Kit traffic analysis

OpenAIRE

Καπίρης, Σταμάτης; Kapiris, Stamatis

2017-01-01

Exploit kits have become one of the most widespread and destructive threat that Internet users face on a daily basis. Since the first actor, which has been categorized as exploit kit, namely MPack, appeared in 2006, we have seen a new era on exploit kit variants compromising popular websites, infecting hosts and delivering destructive malware, following an exponentially evolvement to date. With the growing threat landscape, large enterprises to domestic networks, have starte...

Exploiting NiTi shape memory alloy films in design of tunable high frequency microcantilever resonators

Science.gov (United States)

Stachiv, I.; Sittner, P.; Olejnicek, J.; Landa, M.; Heller, L.

2017-11-01

Shape memory alloy (SMA) films are very attractive materials for microactuators because of their high energy density. However, all currently developed SMA actuators utilize martensitic transformation activated by periodically generated heating and cooling; therefore, they have a slow actuation speed, just a few Hz, which restricts their use in most of the nanotechnology applications such as high frequency microcantilever based physical and chemical sensors, atomic force microscopes, or RF filters. Here, we design tunable high frequency SMA microcantilevers for nanotechnology applications. They consist of a phase transforming NiTi SMA film sputtered on the common elastic substrate material; in our case, it is a single-crystal silicon. The reversible tuning of microcantilever resonant frequencies is then realized by intentionally changing the Young's modulus and the interlayer stress of the NiTi film by temperature, while the elastic substrate guarantees the high frequency actuation (up to hundreds of kHz) of the microcantilever. The experimental results qualitatively agree with predictions obtained from the dedicated model based on the continuum mechanics theory and a phase characteristic of NiTi. The present design of SMA microcantilevers expands the capability of current micro-/nanomechanical resonators by enabling tunability of several consecutive resonant frequencies.

Fluorescence diffuse optical tomography: benefits of using the time-resolved modality

International Nuclear Information System (INIS)

Ducros, Nicolas

2009-01-01

Fluorescence diffuse optical tomography enables the three-dimensional reconstruction of fluorescence markers injected within a biological tissue, with light in the near infrared range. The simple continuous modality uses steady excitation light and operates from the measurements at different positions of the attenuation of the incident beam. This technique is low-cost, non-ionizing, and easy to handle, but subject to low resolution for thick tissues due to diffusion. Hopefully, the time-resolved modality, which provides the time of flight of any detected photon, could overcome this limitation and pave the way to clinical applications. This thesis aims at determining the best way to exploit the time resolved information and at quantifying the advantages of this modality over the standard continuous wave one. Model deviations must be carefully limited when ill-posed problems as fluorescence diffuse optical tomography are considered. As a result, we have first addressed the modelling part of the problem. We have shown that the photons density models to good approximation the measurable quantity that is the quantity measured by an actual acquisition set-up. Then, the moment-based reconstruction scheme has been thoroughly evaluated by means of a theoretical analysis of the moments properties. It was found that the moment-based approach requires high photon counts to be profitable compared to the continuous wave modality. Last, a novel wavelet-based approach, which enables an improved reconstruction quality, has been introduced. This approach has shown good ability to exploit the temporal information at lower photon counts. (author) [fr

Fluorescence Quenching of Alpha-Fetoprotein by Gold Nanoparticles: Effect of Dielectric Shell on Non-Radiative Decay

Science.gov (United States)

Zhu, Jian; Li, Jian-Jun; Wang, A.-Qing; Chen, Yu; Zhao, Jun-Wu

2010-09-01

Fluorescence quenching spectrometry was applied to study the interactions between gold colloidal nanoparticles and alpha-fetoprotein (AFP). Experimental results show that the gold nanoparticles can quench the fluorescence emission of adsorbed AFP effectively. Furthermore, the intensity of fluorescence emission peak decreases monotonously with the increasing gold nanoparticles content. A mechanism based on surface plasmon resonance-induced non-radiative decay was investigated to illuminate the effect of a dielectric shell on the fluorescence quenching ability of gold nanoparticles. The calculation results show that the increasing dielectric shell thickness may improve the monochromaticity of fluorescence quenching. However, high energy transfer efficiency can be obtained within a wide wavelength band by coating a thinner dielectric shell.

Real time detection of antibody-antigen interaction using a laser scanning confocal imaging-surface plasmon resonance system

International Nuclear Information System (INIS)

Zhang Hong-Yan; Yang Li-Quan; Ning Ting-Yin; Liu Wei-Min; Sun Jia-Yu; Wang Peng-Fei; Meng Lan; Nie Jia-Cai

2012-01-01

A laser scanning confocal imaging-surface plasmon resonance (LSCI-SPR) instrument integrated with a wavelength-dependent surface plasmon resonance (SPR) sensor and a laser scanning confocal microscopy (LSCM) is built to detect the bonding process of human IgG and fluorescent-labeled affinity purified antibodies in real time. The shifts of resonant wavelength at different reaction time stages are obtained by SPR, corresponding well with the changes of the fluorescence intensity collected by using LSCM. The instrument shows the merits of the combination and complementation of the SPR and LSCM, with such advantages as quantificational analysis, high spatial resolution and real time monitor, which are of great importance for practical applications in biosensor and life science. (general)

Lead-silicate glass optical microbubble resonator

Energy Technology Data Exchange (ETDEWEB)

Wang, Pengfei, E-mail: pengfei.wang@dit.ie [Photonics Research Centre, Dublin Institute of Technology, Kevin Street, Dublin 8 (Ireland); Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ (United Kingdom); Ward, Jonathan; Yang, Yong; Chormaic, Síle Nic [Light-Matter Interactions Unit, OIST Graduate University, 1919-1 Tancha, Onna-son, Okinawa 904-0495 (Japan); Feng, Xian; Brambilla, Gilberto [Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ (United Kingdom); Farrell, Gerald [Photonics Research Centre, Dublin Institute of Technology, Kevin Street, Dublin 8 (Ireland)

2015-02-09

Microbubble whispering gallery resonators have the potential to become key components in a variety of active and passive photonic circuit devices by offering a range of significant functionalities. Here, we report on the fabrication, optical characterization, and theoretical analysis of lead-silicate glass and optical microbubble resonators. Evanescent field coupling to the microbubbles was achieved using a 1 μm diameter, silica microfiber at a wavelength of circa 775 nm. High Q-factor modes were efficiently excited in both single-stem and two-stem, lead-silicate glass, and microbubble resonators, with bubble diameters of 38 μm (single-stem) and 48 μm (two-stem). Whispering gallery mode resonances with Q-factors as high as 2.3 × 10{sup 5} (single-stem) and 7 × 10{sup 6} (two-stem) were observed. By exploiting the high-nonlinearity of the lead-silicate glass, this work will act as a catalyst for studying a range of nonlinear optical effects in microbubbles, such as Raman scattering and four-wave mixing, at low optical powers.

Fluorescent genetic barcoding in mammalian cells for enhanced multiplexing capabilities in flow cytometry.

Science.gov (United States)

Smurthwaite, Cameron A; Hilton, Brett J; O'Hanlon, Ryan; Stolp, Zachary D; Hancock, Bryan M; Abbadessa, Darin; Stotland, Aleksandr; Sklar, Larry A; Wolkowicz, Roland

2014-01-01

The discovery of the green fluorescent protein from Aequorea victoria has revolutionized the field of cell and molecular biology. Since its discovery a growing panel of fluorescent proteins, fluorophores and fluorescent-coupled staining methodologies, have expanded the analytical capabilities of flow cytometry. Here, we exploit the power of genetic engineering to barcode individual cells with genes encoding fluorescent proteins. For genetic engineering, we utilize retroviral technology, which allows for the expression of ectopic genetic information in a stable manner in mammalian cells. We have genetically barcoded both adherent and nonadherent cells with different fluorescent proteins. Multiplexing power was increased by combining both the number of distinct fluorescent proteins, and the fluorescence intensity in each channel. Moreover, retroviral expression has proven to be stable for at least a 6-month period, which is critical for applications such as biological screens. We have shown the applicability of fluorescent barcoded multiplexing to cell-based assays that rely themselves on genetic barcoding, or on classical staining protocols. Fluorescent genetic barcoding gives the cell an inherited characteristic that distinguishes it from its counterpart. Once cell lines are developed, no further manipulation or staining is required, decreasing time, nonspecific background associated with staining protocols, and cost. The increasing number of discovered and/or engineered fluorescent proteins with unique absorbance/emission spectra, combined with the growing number of detection devices and lasers, increases multiplexing versatility, making fluorescent genetic barcoding a powerful tool for flow cytometry-based analysis. © 2013 International Society for Advancement of Cytometry.

Regarding light resonance interpretations of the B decay anomalies

Science.gov (United States)

Bishara, Fady; Haisch, Ulrich; Monni, Pier Francesco

2017-09-01

We sketch a novel method to search for light di-leptonic resonances by exploiting precision measurements of Drell-Yan production. Motivated by the recent hints of lepton flavor universality violation in B →K*ℓ+ℓ-, we illustrate our proposal by studying the case of spin-1 resonances that couple to muons and have masses in the range of a few GeV. We show that the existing LHC data on p p →Z/γ* →μ+μ- put nontrivial constraints on light di-muon resonance interpretations of B decay anomalies in a model-independent fashion. The impact of our proposal on the long-standing discrepancy in the anomalous magnetic moment of the muon is also briefly discussed.

Noise-exploitation and adaptation in neuromorphic sensors

Science.gov (United States)

Hindo, Thamira; Chakrabartty, Shantanu

2012-04-01

Even though current micro-nano fabrication technology has reached integration levels where ultra-sensitive sensors can be fabricated, the sensing performance (resolution per joule) of synthetic systems are still orders of magnitude inferior to those observed in neurobiology. For example, the filiform hairs in crickets operate at fundamental limits of noise; auditory sensors in a parasitoid fly can overcome fundamental limitations to precisely localize ultra-faint acoustic signatures. Even though many of these biological marvels have served as inspiration for different types of neuromorphic sensors, the main focus these designs have been to faithfully replicate the biological functionalities, without considering the constructive role of "noise". In man-made sensors device and sensor noise are typically considered as a nuisance, where as in neurobiology "noise" has been shown to be a computational aid that enables biology to sense and operate at fundamental limits of energy efficiency and performance. In this paper, we describe some of the important noise-exploitation and adaptation principles observed in neurobiology and how they can be systematically used for designing neuromorphic sensors. Our focus will be on two types of noise-exploitation principles, namely, (a) stochastic resonance; and (b) noise-shaping, which are unified within our previously reported framework called Σ▵ learning. As a case-study, we describe the application of Σ▵ learning for the design of a miniature acoustic source localizer whose performance matches that of its biological counterpart(Ormia Ochracea).

Distributed fluorescent optical fiber proximity sensor: Towards a proof of concept

Science.gov (United States)

Gălătuș, Ramona; Faragó, Paul; Miluski, Piotr; Valles, Juan-Antonio

2018-06-01

Fluorescent fibers are optical fibers which emit light as a response to an incident phenomenon, usually an incident light. Operation depends on the doping dyes, which determine specific fluorescence and optical characteristics useful in the development of optical sensors. In this work we propose a low-cost distributed proximity sensor implemented using a red fluorescent fiber, to provide a security option for a surface plasmon resonance system. Operation of the proposed sensor relies on having the incident illumination intensity varied by the presence or absence of an obstacle in the vicinity of the sensing element. This will influence the radiated fluorescence accordingly. The proposed setup for the implementation of the optical proximity sensor assumes having a high brightness LED deployed for axial fiber illumination and a blue LED for side illumination. Electronic processing then accounts for gain and digitization. Measurement results of the prototype validate the proposed concept.

Predictability, Force and (Anti-)Resonance in Complex Object Control.

Science.gov (United States)

Maurice, Pauline; Hogan, Neville; Sternad, Dagmar

2018-04-18

Manipulation of complex objects as in tool use is ubiquitous and has given humans an evolutionary advantage. This study examined the strategies humans choose when manipulating an object with underactuated internal dynamics, such as a cup of coffee. The object's dynamics renders the temporal evolution complex, possibly even chaotic, and difficult to predict. A cart-and-pendulum model, loosely mimicking coffee sloshing in a cup, was implemented in a virtual environment with a haptic interface. Participants rhythmically manipulated the virtual cup containing a rolling ball; they could choose the oscillation frequency, while the amplitude was prescribed. Three hypotheses were tested: 1) humans decrease interaction forces between hand and object; 2) humans increase the predictability of the object dynamics; 3) humans exploit the resonances of the coupled object-hand system. Analysis revealed that humans chose either a high-frequency strategy with anti-phase cup-and-ball movements or a low-frequency strategy with in-phase cup-and-ball movements. Counter Hypothesis 1, they did not decrease interaction force; instead, they increased the predictability of the interaction dynamics, quantified by mutual information, supporting Hypothesis 2. To address Hypothesis 3, frequency analysis of the coupled hand-object system revealed two resonance frequencies separated by an anti-resonance frequency. The low-frequency strategy exploited one resonance, while the high-frequency strategy afforded more choice, consistent with the frequency response of the coupled system; both strategies avoided the anti-resonance. Hence, humans did not prioritize interaction force, but rather strategies that rendered interactions predictable. These findings highlight that physical interactions with complex objects pose control challenges not present in unconstrained movements.

A dansyl-rhodamine ratiometric fluorescent probe for Hg2+ based on FRET mechanism.

Science.gov (United States)

Xie, Puhui; Guo, Fengqi; Wang, Lingyu; Yang, Sen; Yao, Denghui; Yang, Guoyu

2015-03-01

Based on resonance energy transfer (FRET) from dansyl to rhodamine 101, a new fluorescent probe (compound 1) containing rhodamine 101 and a dansyl unit was synthesized for detecting Hg(2+) through ratiometric sensing in DMSO aqueous solutions. This probe shows a fast, reversible and selective response toward Hg(2+) in a wide pH range. Hg(2+) induced ring-opening reactions of the spirolactam rhodamine moiety of 1, leading to the formation of fluorescent derivatives that can serve as the FRET acceptors. Very large stokes shift (220 nm) was observed in this case. About 97-fold increase in fluorescence intensity ratio was observed upon its binding with Hg(2+).

Laser induced fluorescence spectroscopy for FTU

International Nuclear Information System (INIS)

Hughes, T.P.

1995-07-01

Laser induced fluorescence spectroscopy (LIFS) is based on the absorption of a short pulse of tuned laser light by a group of atoms and the observation of the resulting fluorescence radiation from the excited state. Because the excitation is resonant it is very efficient, and the fluorescence can be many times brighter than the normal spontaneous emission, so low number densities of the selected atoms can be detected and measured. Good spatial resolution can be achieved by using a narrow laser beam. If the laser is sufficiently monochromatic, and it can be tuned over the absorption line profile of the selected atoms, information can also be obtained about the velocities of the atoms from the Doppler effect which can broaden and shift the line. In this report two topics are examined in detail. The first is the effect of high laser irradiance, which can cause 'power broadening' of the apparent absorption line profile. The second is the effect of the high magnetic field in FTU. Detailed calculations are given for LIFS of neutral iron and molybdenum atoms, including the Zeeman effect, and the implementation of LIFS for these atoms on FTU is discussed

In Vivo Dual-Modality Fluorescence and Magnetic Resonance Imaging-Guided Lymph Node Mapping with Good Biocompatibility Manganese Oxide Nanoparticles

Directory of Open Access Journals (Sweden)

Yonghua Zhan

2017-12-01

Full Text Available Multifunctional manganese oxide nanoparticles (NPs with impressive enhanced T1 contrast ability show great promise in biomedical diagnosis. Herein, we developed a dual-modality imaging agent system based on polyethylene glycol (PEG-coated manganese oxide NPs conjugated with organic dye (Cy7.5, which functions as a fluorescence imaging (FI agent as well as a magnetic resonance imaging (MRI imaging agent. The formed Mn3O4@PEG-Cy7.5 NPs with the size of ~10 nm exhibit good colloidal stability in different physiological media. Serial FI and MRI studies that non-invasively assessed the bio-distribution pattern and the feasibility for in vivo dual-modality imaging-guided lymph node mapping have been investigated. In addition, histological and biochemical analyses exhibited low toxicity even at a dose of 20 mg/kg in vivo. Since Mn3O4@PEG-Cy7.5 NPs exhibited desirable properties as imaging agents and good biocompatibility, this work offers a robust, safe, and accurate diagnostic platform based on manganese oxide NPs for tumor metastasis diagnosis.

In vivo self-bio-imaging of tumors through in situ biosynthesized fluorescent gold nanoclusters

Science.gov (United States)

Wang, Jianling; Zhang, Gen; Li, Qiwei; Jiang, Hui; Liu, Chongyang; Amatore, Christian; Wang, Xuemei

2013-01-01

Fluorescence imaging in vivo allows non-invasive tumor diagnostic thus permitting a direct monitoring of cancer therapies progresses. It is established herein that fluorescent gold nanoclusters are spontaneously biosynthesized by cancerous cell (i.e., HepG2, human hepatocarcinoma cell line; K562, leukemia cell line) incubated with micromolar chloroauric acid solutions, a biocompatible molecular Au(III) species. Gold nanoparticles form by Au(III) reduction inside cells cytoplasms and ultimately concentrate around their nucleoli, thus affording precise cell imaging. Importantly, this does not occur in non-cancerous cells, as evidenced with human embryo liver cells (L02) used as controls. This dichotomy is exploited for a new strategy for in vivo self-bio-imaging of tumors. Subcutaneous injections of millimolar chloroauric acid solution near xenograft tumors of the nude mouse model of hepatocellular carcinoma or chronic myeloid leukemia led to efficient biosynthesis of fluorescent gold nanoclusters without significant dissemination to the surrounding normal tissues, hence allowing specific fluorescent self-bio-marking of the tumors.

A molecular-sized optical logic circuit for digital modulation of a fluorescence signal

Science.gov (United States)

Nishimura, Takahiro; Tsuchida, Karin; Ogura, Yusuke; Tanida, Jun

2018-03-01

Fluorescence measurement allows simultaneous detection of multiple molecular species by using spectrally distinct fluorescence probes. However, due to the broad spectra of fluorescence emission, the multiplicity of fluorescence measurement is generally limited. To overcome this limitation, we propose a method to digitally modulate fluorescence output signals with a molecular-sized optical logic circuit by using optical control of fluorescence resonance energy transfer (FRET). The circuit receives a set of optical inputs represented with different light wavelengths, and then it switches high and low fluorescence intensity from a reporting molecule according to the result of the logic operation. By using combinational optical inputs in readout of fluorescence signals, the number of biomolecular species that can be identified is increased. To implement the FRET-based circuits, we designed two types of basic elements, YES and NOT switches. An YES switch produces a high-level output intensity when receiving a designated light wavelength input and a low-level intensity without the light irradiation. A NOT switch operates inversely to the YES switch. In experiments, we investigated the operation of the YES and NOT switches that receive a 532-nm light input and modulate the fluorescence intensity of Alexa Fluor 488. The experimental result demonstrates that the switches can modulate fluorescence signals according to the optical input.

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

Science.gov (United States)

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

2017-07-19

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

In vivo tomographic imaging with fluorescence and MRI using tumor-targeted dual-labeled nanoparticles

Directory of Open Access Journals (Sweden)

Zhang Y

2013-12-01

Full Text Available Yue Zhang,1 Bin Zhang,1 Fei Liu,1,2 Jianwen Luo,1,3 Jing Bai1 1Department of Biomedical Engineering, School of Medicine, 2Tsinghua-Peking Center for Life Sciences, 3Center for Biomedical Imaging Research, Tsinghua University, Beijing, People's Republic of China Abstract: Dual-modality imaging combines the complementary advantages of different modalities, and offers the prospect of improved preclinical research. The combination of fluorescence imaging and magnetic resonance imaging (MRI provides cross-validated information and direct comparison between these modalities. Here, we report on the application of a novel tumor-targeted, dual-labeled nanoparticle (NP, utilizing iron oxide as the MRI contrast agent and near infrared (NIR dye Cy5.5 as the fluorescent agent. Results of in vitro experiments verified the specificity of the NP to tumor cells. In vivo tumor targeting and uptake of the NPs in a mouse model were visualized by fluorescence and MR imaging collected at different time points. Quantitative analysis was carried out to evaluate the efficacy of MRI contrast enhancement. Furthermore, tomographic images were also acquired using both imaging modalities and cross-validated information of tumor location and size between these two modalities was revealed. The results demonstrate that the use of dual-labeled NPs can facilitate the dual-modal detection of tumors, information cross-validation, and direct comparison by combing fluorescence molecular tomography (FMT and MRI. Keywords: dual-modality, fluorescence molecular tomography (FMT, magnetic resonance imaging (MRI, nanoparticle

Linear all-optical signal processing using silicon micro-ring resonators

DEFF Research Database (Denmark)

Ding, Yunhong; Ou, Haiyan; Xu, Jing

2016-01-01

Silicon micro-ring resonators (MRRs) are compact and versatile devices whose periodic frequency response can be exploited for a wide range of applications. In this paper, we review our recent work on linear all-optical signal processing applications using silicon MRRs as passive filters. We focus...

A new measure of interpersonal exploitativeness

Directory of Open Access Journals (Sweden)

Amy B. Brunell

2013-05-01

Full Text Available Measures of exploitativeness evidence problems with validity and reliability. The present set of studies assessed a new measure (the Interpersonal Exploitativeness Scale that defines exploitativeness in terms of reciprocity. In Studies 1 and 2, 33 items were administered to participants. Exploratory and Confirmatory Factor Analysis demonstrated that a single factor consisting of six items adequately assess interpersonal exploitativeness. Study 3 results revealed that the Interpersonal Exploitativeness Scale was positively associated with normal narcissism, pathological narcissism, psychological entitlement, and negative reciprocity and negatively correlated with positive reciprocity. In Study 4, participants competed in a commons dilemma. Those who scored higher on the Interpersonal Exploitativeness Scale were more likely to harvest a greater share of resources over time, even while controlling for other relevant variables, such as entitlement. Together, these studies show the Interpersonal Exploitativeness Scale to be a valid and reliable measure of interpersonal exploitativeness. The authors discuss the implications of these studies.

Development and exploitation of optical diagnoses based on radicals fluorescence. Application to automotive engines; Developpement et exploitation de diagnostics optiques bases sur la fluorescence de radicaux. Application aux moteurs automobiles

Energy Technology Data Exchange (ETDEWEB)

Auge, M.

2005-12-15

During this PhD, we have developed an optical technique based on radicals fluorescence. The objective was to obtain more information on combustion phenomena. We first have applied the OH and HCHO PLIF technique simultaneously in laminar premixed counter-flow flames under pressure. With this technique, we have obtained the local heat release rate of the flame and an estimation of the laminar flame speed and the thickness of the flame for different fuels and pressure. We have then applied this technique on a Diesel fuel jet in combustion placed in a high pressure cell to understand the different phenomena occurring. Then PLIF at 355 nm was applied in direct and indirect injection spark ignition engine to detect the unburned. We have demonstrated the high potential of the technique used during this PhD to obtain local heat release rate of a flame. We have also progressed in our comprehension of the phenomena occurring during the combustion processes. (author)

HAI-178 antibody-conjugated fluorescent magnetic nanoparticles for targeted imaging and simultaneous therapy of gastric cancer

Science.gov (United States)

Wang, Can; Bao, Chenchen; Liang, Shujing; Zhang, Lingxia; Fu, Hualin; Wang, Yutian; Wang, Kan; Li, Chao; Deng, Min; Liao, Qiande; Ni, Jian; Cui, Daxiang

2014-05-01

The successful development of safe and highly effective nanoprobes for targeted imaging and simultaneous therapy of in vivo gastric cancer is a great challenge. Herein we reported for the first time that anti-α-subunit of ATP synthase antibody, HAI-178 monoclonal antibody-conjugated fluorescent magnetic nanoparticles, was successfully used for targeted imaging and simultaneous therapy of in vivo gastric cancer. A total of 172 specimens of gastric cancer tissues were collected, and the expression of α-subunit of ATP synthase in gastric cancer tissues was investigated by immunohistochemistry method. Fluorescent magnetic nanoparticles were prepared and conjugated with HAI-178 monoclonal antibody, and the resultant HAI-178 antibody-conjugated fluorescent magnetic nanoparticles (HAI-178-FMNPs) were co-incubated with gastric cancer MGC803 cells and gastric mucous GES-1 cells. Gastric cancer-bearing nude mice models were established, were injected with prepared HAI-178-FMNPs via tail vein, and were imaged by magnetic resonance imaging and small animal fluorescent imaging system. The results showed that the α-subunit of ATP synthase exhibited high expression in 94.7% of the gastric cancer tissues. The prepared HAI-178-FMNPs could target actively MGC803 cells, realized fluorescent imaging and magnetic resonance imaging of in vivo gastric cancer, and actively inhibited growth of gastric cancer cells. In conclusion, HAI-178 antibody-conjugated fluorescent magnetic nanoparticles have a great potential in applications such as targeted imaging and simultaneous therapy of in vivo early gastric cancer cells in the near future.

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

International Nuclear Information System (INIS)

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

2013-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2013-11-15

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

Time delayed K sup + N reactions and exotic baryon resonances

CERN Document Server

Kelkar, N G; Khemchandani, K P

2003-01-01

Evidence and hints, from both the theoretical and experimental sides, of exotic baryon resonances with B = S, have been with us for the last 30 years. The poor status of the general acceptance of these Z* resonances is partly due to the prejudice against penta-quark baryons and partly due to the opinion that a proof of the existence of exotic states must be rigorous. This can refer to the quality and amount of data gathered, and also to the analytical methods applied in the study of these resonances. It then seems mandatory that all possibilities and aspects be exploited. We do that by analysing the time delay in K sup + N scattering, encountering clear signals of the exotic Z* resonances close to the pole values found in partial wave analyses.

Thousand-fold enhancement of single-molecule fluorescence near a single gold nanorod

NARCIS (Netherlands)

Yuan, H.; Khatua, S.; Zijlstra, P.; Yorulmaz, M.; Orrit, M.

2013-01-01

Single molecules: Large enhancements of single-molecule fluorescence up to 1100 times by using synthesized gold nanorods are reported (see picture). This high enhancement is achieved by selecting a dye with its adsorption and emission close to the surface plasmon resonance of the gold nanorods

A Starting Point for Fluorescence-Based Single-Molecule Measurements in Biomolecular Research

Directory of Open Access Journals (Sweden)

Alexander Gust

2014-09-01

Full Text Available Single-molecule fluorescence techniques are ideally suited to provide information about the structure-function-dynamics relationship of a biomolecule as static and dynamic heterogeneity can be easily detected. However, what type of single-molecule fluorescence technique is suited for which kind of biological question and what are the obstacles on the way to a successful single-molecule microscopy experiment? In this review, we provide practical insights into fluorescence-based single-molecule experiments aiming for scientists who wish to take their experiments to the single-molecule level. We especially focus on fluorescence resonance energy transfer (FRET experiments as these are a widely employed tool for the investigation of biomolecular mechanisms. We will guide the reader through the most critical steps that determine the success and quality of diffusion-based confocal and immobilization-based total internal reflection fluorescence microscopy. We discuss the specific chemical and photophysical requirements that make fluorescent dyes suitable for single-molecule fluorescence experiments. Most importantly, we review recently emerged photoprotection systems as well as passivation and immobilization strategies that enable the observation of fluorescently labeled molecules under biocompatible conditions. Moreover, we discuss how the optical single-molecule toolkit has been extended in recent years to capture the physiological complexity of a cell making it even more relevant for biological research.

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

Science.gov (United States)

Chou, Cheng-Chung; Huang, Yi-Han

2012-01-01

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

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

Science.gov (United States)

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

2016-07-07

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

Comment on ’Single Pentacene Molecules Detected by Fluorescence Excitation in a P-Terphenyl Crystal’

Science.gov (United States)

1990-12-10

8217 NO 11 TITLE (include Security Classification) Comment on "Single Pentacene Molecules Detected by Fluorescence Excitation in a p-Terphenyl Crystal" 12...8217 {Continue on reverse it necessary and identify by block numboer) Using h--,Ihly efficient Fluorescence excitation spectroscov of individual pentacene ...molecular impurities in p-terphenvl crystals, we have observed that some pentacene defects exhibit spcntaneous spectral jumps in their resonance frequency at

Resonance Raman and optical dephasing study of tricarbocyanine dyes

NARCIS (Netherlands)

Ashworth, SH; Kummrow, A; Lenz, K

Fluorescence lineshape analysis based on resonance Raman spectra of the dye HITCI was used to determine the details and magnitude of the vibrational part of the line broadening function, Forced light scattering (FLS) was applied to measure optical dephasing of HITCI in ethylene glycol, pumping at

EXPLOITATION OF GRANITE BOULDER

Directory of Open Access Journals (Sweden)

Ivan Cotman

1994-12-01

Full Text Available The processes of forming, petrography, features, properties and exploitation of granite boulders are described. The directional drilling and black powder blasting is the succesful method in exploitation of granite boulders (boulder technology (the paper is published in Croatian.

Solidly mounted resonators aging under harsh environmental conditions

International Nuclear Information System (INIS)

Ivira, B; Fillit, R Y; Ndagijimana, F; Benech, Ph; Boussey, J; Parat, G; Ancey, P

2006-01-01

A contribution to reliability studies of Solidly Mounted Resonators (SMR) submitted to harsh environments such as temperature and humidity is presented. Electrical, structural and chemical monitoring of representative parameters is performed by means of RF, DC characterizations and also X-ray diffraction coupled to X-fluorescence to assess aging in microstructures. Results indicate that humidity affects samples stronger than high temperature. From viewpoint of robustness, non-negligible effects of SiO 2 mass-loading on antiresonance and resonance frequencies are reported. Drifts of parameters for a lonely resonator and filter transmission are both in good accordance. Finally, the need of a full sheet passivation layer is demonstrated in order to protect metals and Aluminum Nitride (AlN) against oxidation and pollutant compounds respectively

Rapid creation of distant entanglement by multi-photon resonant fluorescence

Science.gov (United States)

Cohen, Guy Z.; Sham, L. J.

2014-03-01

We study a simple, effective and robust method for entangling two separate stationary quantum dot spin qubits with high fidelity using multi-photon Gaussian state. The fluorescence signals from the two dots interfere at a beam splitter. The bosonic nature of photons leads, in analogy with the Hong-Ou-Mandel (HOM) effect, to selective pairing of photon holes (photon absences in the fluorescent signals). By the HOM effect, two photon holes with the same polarization end up at the same beam splitter output. As a result, two odd photon number detections at the outgoing beams, which must correspond to two photon holes with different polarizations, herald entanglement creation. The robustness of the Gaussian states is evidenced by the ability to compensate for photon absorption and noise by a moderate increase in the number of photons at the input. We calculate the entanglement generation rate in the ideal, non-ideal and near-ideal detector regimes and find substantial improvement over single-photon schemes in all three regimes. Fast and efficient spin-spin entanglement creation can form the basis for a scalable quantum dot quantum computing network. Our predictions can be tested using current experimental capabilities. This research was supported by the U.S. Army Research Office MURI award W911NF0910406, by NSF grant PHY-1104446 and by ARO (IARPA, W911NF-08-1-0487). The authors thank D. G. Steel for useful discussions.

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

International Nuclear Information System (INIS)

Amniai, Laziza; Lippens, Guy; Landrieu, Isabelle

2011-01-01

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.

Biophysical influence of coumarin 35 on bovine serum albumin: Spectroscopic study

Science.gov (United States)

Bayraktutan, Tuğba; Onganer, Yavuz

2017-01-01

The binding mechanism and protein-fluorescence probe interactions between bovine serum albumin (BSA) and coumarin 35 (C35) was investigated by using UV-Vis absorption and fluorescence spectroscopies since they remain major research topics in biophysics. The spectroscopic data indicated that a fluorescence quenching process for BSA-C35 system was occurred. The fluorescence quenching processes were analyzed using Stern-Volmer method. In this regard, Stern-Volmer quenching constants (KSV) and binding constants were calculated at different temperatures. The distance r between BSA (donor) and C35 (acceptor) was determined by exploiting fluorescence resonance energy transfer (FRET) method. Synchronous fluorescence spectra were also studied to observe information about conformational changes. Moreover, thermodynamics parameters were calculated for better understanding of interactions and conformational changes of the system.

New fluorescent probes for detection and characterization of amyloid fibrils

Science.gov (United States)

Gorbenko, Galyna; Trusova, Valeriya; Kirilova, Elena; Kirilov, Georgiy; Kalnina, Inta; Vasilev, Aleksey; Kaloyanova, Stefka; Deligeorgiev, Todor

2010-08-01

The applicability of the novel fluorescent probes, aminoderivative of benzanthrone ABM, squaraine dye SQ-1 and polymethine dye V2 to identification and structural analysis of amyloid fibrils has been evaluated using the lysozyme model system in which fibrillar aggregates have been formed in concentrated ethanol solution. The association constant, binding stoichiometry and molar fluorescence of the bound dye have been determined. ABM was found to surpass classical amyloid marker ThT in the sensitivity to the presence of fibrillar aggregates. Resonance energy transfer measurements involving ABM-SQ-1 and SQ-1-V2 donor-acceptor pairs yielded the limits for fractal-like dimension of lysozyme fibrils.

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...... polymer optical fiber for an excitation and emission wavelength of 550 nm and 650nm, respectively. The model suggests an increase of a factor of 1.6 to 4 in the collected fluorescent power for an ideal CPC tip, as compared to the plane-cut fiber tip for fiber lengths between 5 and 45mm...

Antiphase dual-color correlation in a reactant-product pair imparts ultrasensitivity in reaction-linked double-photoswitching fluorescence imaging.

Science.gov (United States)

Wan, Wei; Zhu, Ming-Qiang; Tian, Zhiyuan; Li, Alexander D Q

2015-04-08

A pair of reversible photochemical reactions correlates their reactant and product specifically, and such a correlation uniquely distinguishes their correlated signal from others that are not linked by this reversible reaction. Here a nanoparticle-shielded fluorophore is photodriven to undergo structural dynamics, alternating between a green-fluorescence state and a red-fluorescence state. As time elapses, the fluorophore can be in either state but not both at the same time. Thus, the red fluorescence is maximized while the green fluorescence is minimized and vice versa. Such an antiphase dual-color (AD) corelationship between the red and green fluorescence maxima as well as between their minima can be exploited to greatly improve the signal-to-noise ratio, thus enhancing the ultimate detection limit. Potential benefits of this correlation include elimination of all interferences originating from single-color dyes and signal amplification of AD photoswitching molecules by orders of magnitude.

Wave energy extraction by coupled resonant absorbers.

Science.gov (United States)

Evans, D V; Porter, R

2012-01-28

In this article, a range of problems and theories will be introduced that will build towards a new wave energy converter (WEC) concept, with the acronym 'ROTA' standing for resonant over-topping absorber. First, classical results for wave power absorption for WECs constrained to operate in a single degree of freedom will be reviewed and the role of resonance in their operation highlighted. Emphasis will then be placed on how the introduction of further resonances can improve power take-off characteristics by extending the range of frequencies over which the efficiency is close to a theoretical maximum. Methods for doing this in different types of WECs will be demonstrated. Coupled resonant absorbers achieve this by connecting a WEC device equipped with its own resonance (determined from a hydrodynamic analysis) to a new system having separate mass/spring/damper characteristics. It is shown that a coupled resonant effect can be realized by inserting a water tank into a WEC, and this idea forms the basis of the ROTA device. In essence, the idea is to exploit the coupling between the natural sloshing frequencies of the water in the internal tank and the natural resonance of a submerged buoyant circular cylinder device that is tethered to the sea floor, allowing a rotary motion about its axis of attachment.

Fluorescence Enhancement on Large Area Self-Assembled Plasmonic-3D Photonic Crystals.

Science.gov (United States)

Chen, Guojian; Wang, Dongzhu; Hong, Wei; Sun, Lu; Zhu, Yongxiang; Chen, Xudong

2017-03-01

Discontinuous plasmonic-3D photonic crystal hybrid structures are fabricated in order to evaluate the coupling effect of surface plasmon resonance and the photonic stop band. The nanostructures are prepared by silver sputtering deposition on top of hydrophobic 3D photonic crystals. The localized surface plasmon resonance of the nanostructure has a symbiotic relationship with the 3D photonic stop band, leading to highly tunable characteristics. Fluorescence enhancements of conjugated polymer and quantum dot based on these hybrid structures are studied. The maximum fluorescence enhancement for the conjugated polymer of poly(5-methoxy-2-(3-sulfopropoxy)-1,4-phenylenevinylene) potassium salt by a factor of 87 is achieved as compared with that on a glass substrate due to the enhanced near-field from the discontinuous plasmonic structures, strong scattering effects from rough metal surface with photonic stop band, and accelerated decay rates from metal-coupled excited state of the fluorophore. It is demonstrated that the enhancement induced by the hybrid structures has a larger effective distance (optimum thickness ≈130 nm) than conventional plasmonic systems. It is expected that this approach has tremendous potential in the field of sensors, fluorescence-imaging, and optoelectronic applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Imaging Live Drosophila Brain with Two-Photon Fluorescence Microscopy

Science.gov (United States)

Ahmed, Syeed Ehsan

Two-photon fluorescence microscopy is an imaging technique which delivers distinct benefits for in vivo cellular and molecular imaging. Cyclic adenosine monophosphate (cAMP), a second messenger molecule, is responsible for triggering many physiological changes in neural system. However, the mechanism by which this molecule regulates responses in neuron cells is not yet clearly understood. When cAMP binds to a target protein, it changes the structure of that protein. Therefore, studying this molecular structure change with fluorescence resonance energy transfer (FRET) imaging can shed light on the cAMP functioning mechanism. FRET is a non-radiative dipole-dipole coupling which is sensitive to small distance change in nanometer scale. In this study we have investigated the effect of dopamine in cAMP dynamics in vivo. In our study two-photon fluorescence microscope was used for imaging mushroom bodies inside live Drosophila melanogaster brain and we developed a method for studying the change in cyclic AMP level.

Room-temperature single-photon sources with definite circular and linear polarizations based on single-emitter fluorescence in liquid crystal hosts

International Nuclear Information System (INIS)

Winkler, Justin M; Lukishova, Svetlana G; Bissell, Luke J

2013-01-01

Definite circular and linear polarizations of room-temperature single-photon sources, which can serve as polarization bases for quantum key distribution, are produced by doping planar-aligned liquid crystal hosts with single fluorescence emitters. Chiral 1-D photonic bandgap microcavities for a single handedness of circularly polarized light were prepared from both monomeric and oligomeric cholesteric liquid crystals. Fluorescent emitters, such as nanocrystal quantum dots, nitrogen vacancy color centers in nanodiamonds, and rare-earth ions in nanocrystals, were doped into these microcavity structures and used to produce circularly polarized fluorescence of definite handedness. Additionally, we observed circularly polarized resonances in the spectrum of nanocrystal quantum dot fluorescence at the edge of the cholesteric microcavity's photonic stopband. For this polarization we obtained a ∼4.9 enhancement of intensity compared to the polarization of the opposite handedness that propagates without photonic bandgap microcavity effects. Such a resonance is indicative of coupling of quantum dot fluorescence to the cholesteric microcavity mode. We have also used planar-aligned nematic liquid crystal hosts to align DiI dye molecules doped into the host, thereby providing a single-photon source of linear polarization of definite direction. Antibunching is demonstrated for fluorescence of nanocrystal quantum dots, nitrogen vacancy color centers, and dye molecules in these liquid crystal structures.

A Geant4-based Simulation to Evaluate the Feasibility of Using Nuclear Resonance Fluorescence (NRF) in Determining Atomic Compositions of Body Tissue in Cancer Diagnostics and Irradiation

Science.gov (United States)

Gilbo, Yekaterina; Wijesooriya, Krishni; Liyanage, Nilanga

2017-01-01

Customarily applied in homeland security for identifying concealed explosives and chemical weapons, NRF (Nuclear Resonance Fluorescence) may have high potential in determining atomic compositions of body tissue. High energy photons incident on a target excite the target nuclei causing characteristic re-emission of resonance photons. As the nuclei of each isotope have well-defined excitation energies, NRF uniquely indicates the isotopic content of the target. NRF radiation corresponding to nuclear isotopes present in the human body is emitted during radiotherapy based on Bremsstrahlung photons generated in a linear electron accelerator. We have developed a Geant4 simulation in order to help assess NRF capabilities in detecting, mapping, and characterizing tumors. We have imported a digital phantom into the simulation using anatomical data linked to known chemical compositions of various tissues. Work is ongoing to implement the University of Virginia's cancer center treatment setup and patient geometry, and to collect and analyze the simulation's physics quantities to evaluate the potential of NRF for medical imaging applications. Preliminary results will be presented.

Two-Dimensional Edge Detection by Guided Mode Resonant Metasurface

Science.gov (United States)

Saba, Amirhossein; Tavakol, Mohammad Reza; Karimi-Khoozani, Parisa; Khavasi, Amin

2018-05-01

In this letter, a new approach to perform edge detection is presented using an all-dielectric CMOS-compatible metasurface. The design is based on guided-mode resonance which provides a high quality factor resonance to make the edge detection experimentally realizable. The proposed structure that is easy to fabricate, can be exploited for detection of edges in two dimensions due to its symmetry. Also, the trade-off between gain and resolution of edge detection is discussed which can be adjusted by appropriate design parameters. The proposed edge detector has also the potential to be used in ultrafast analog computing and image processing.

X-ray resonant Raman scattering cross sections of Mn, Fe, Cu and Zn

International Nuclear Information System (INIS)

Sanchez, Hector Jorge; Valentinuzzi, MarIa Cecilia; Perez, Carlos

2006-01-01

X-ray fluorescence spectra present singular characteristics produced by the different scattering processes. When atoms are irradiated with incident energy lower and close to an absorption edge, scattering peaks appear due to an inelastic process known as resonant Raman scattering. It constitutes an important contribution to the background of the fluorescent line. The resonant Raman scattering must be taken into account in the determination of low concentration contaminants, especially when the elements have proximate atomic numbers. The values of the mass attenuation coefficients experimentally obtained when materials are analysed with monochromatic x-ray beams under resonant conditions differ from the theoretical values (between 5% and 10%). This difference is due, in part, to the resonant Raman scattering. Monochromatic synchrotron radiation was used to study the Raman effect on pure samples of Mn, Fe, Cu and Zn. Energy scans were carried out in different ranges of energy near the absorption edge of the target element. As the Raman peak has a non-symmetric shape, theoretical models for the differential cross section, convoluted with the instrument function, were used to determine the RRS cross section as a function of the incident energy

Contact replacement for NMR resonance assignment.

Science.gov (United States)

Xiong, Fei; Pandurangan, Gopal; Bailey-Kellogg, Chris

2008-07-01

Complementing its traditional role in structural studies of proteins, nuclear magnetic resonance (NMR) spectroscopy is playing an increasingly important role in functional studies. NMR dynamics experiments characterize motions involved in target recognition, ligand binding, etc., while NMR chemical shift perturbation experiments identify and localize protein-protein and protein-ligand interactions. The key bottleneck in these studies is to determine the backbone resonance assignment, which allows spectral peaks to be mapped to specific atoms. This article develops a novel approach to address that bottleneck, exploiting an available X-ray structure or homology model to assign the entire backbone from a set of relatively fast and cheap NMR experiments. We formulate contact replacement for resonance assignment as the problem of computing correspondences between a contact graph representing the structure and an NMR graph representing the data; the NMR graph is a significantly corrupted, ambiguous version of the contact graph. We first show that by combining connectivity and amino acid type information, and exploiting the random structure of the noise, one can provably determine unique correspondences in polynomial time with high probability, even in the presence of significant noise (a constant number of noisy edges per vertex). We then detail an efficient randomized algorithm and show that, over a variety of experimental and synthetic datasets, it is robust to typical levels of structural variation (1-2 AA), noise (250-600%) and missings (10-40%). Our algorithm achieves very good overall assignment accuracy, above 80% in alpha-helices, 70% in beta-sheets and 60% in loop regions. Our contact replacement algorithm is implemented in platform-independent Python code. The software can be freely obtained for academic use by request from the authors.

Exploiting VM/XA

International Nuclear Information System (INIS)

Boeheim, C.

1990-03-01

The Stanford Linear Accelerator Center has recently completed a conversion to IBM's VM/XA SP Release 2 operating system. The primary physics application had been constrained by the previous 16 megabyte memory limit. Work is underway to enable this application to exploit the new features of VM/XA. This paper presents a brief tutorial on how to convert an application to exploit VM/XA and discusses some of the SLAC experiences in doing so. 13 figs

Principles of nuclear magnetic resonance (NMR) - current state of the art

International Nuclear Information System (INIS)

Lerski, R.A.

1985-01-01

Nuclear magnetic resonance (NMR) imaging has progressed rapidly from laboratory curiosity to commercial exploitation and clinical application in the space of only three years. The physical principles underlying the technique are described and the equipment requirements outlined. The question of optimal magnetic field strength is discussed. (author)

Experimental realization of extraordinary acoustic transmission using Helmholtz resonators

Directory of Open Access Journals (Sweden)

Brian C. Crow

2015-02-01

Full Text Available The phenomenon of extraordinary acoustic transmission through a solid barrier with an embedded Helmholtz resonator (HR is demonstrated. The Helmholtz resonator consists of an embedded cavity and two necks that protrude, one on each side of the barrier. Extraordinary transmission occurs for a narrow spectral range encompassing the resonant frequency of the Helmholtz resonator. We show that an amplitude transmission of 97.5% is achieved through a resonator whose neck creates an open area of 6.25% of the total barrier area. In addition to the enhanced transmission, we show that there is a smooth, continuous phase transition in the transmitted sound as a function of frequency. The frequency dependent phase transition is used to experimentally realize slow wave propagation for a narrow-band Gaussian wave packet centered at the maximum transmission frequency. The use of parallel pairs of Helmholtz resonators tuned to different resonant frequencies is experimentally explored as a means of increasing the transmission bandwidth. These experiments show that because of the phase transition, there is always a frequency between the two Helmholtz resonant frequencies at which destructive interference occurs whether the resonances are close or far apart. Finally, we explain how the phase transition associated with Helmholtz-resonator-mediated extraordinary acoustic transmission can be exploited to produce diffractive acoustic components including sub-wavelength thickness acoustic lenses.

Silicon photonic resonator for label-free bio-sensing application

Science.gov (United States)

Udomsom, Suruk; Mankong, Ukrit; Theera-Umpon, Nipon; Ittipratheep, Nattapol; Umezawa, Toshimasa; Matsumoto, Atsushi; Yamamoto, Naokatsu

2018-03-01

In medical diagnostics there is an increasing demand for biosensors that can specifically detect biological analytes in a fluid. Especially label-free sensing, consistings of a transducer with biorecognition molecules immobilized on its surface without relying on fluorescent dye. In this paper we study the design and fabrication of a silicon nanowire photonic ring resonator and its feasibility as a biosensor. We have simulated and fabricated racetrack ring resonators which have a few tenths of micrometer gap, up to 0.5 μm between the input / output waveguides and the resonators. It is found that the devices can be designed with large Q factors. Sensitivity to biomaterial detection has been simulated for antibody (goat anti-mouse IgG) - antigen (mouse IgG) using 3-dimensional Finite Difference Time Domain technique. The simulated results show that the ring resonator has a response 15 nm resonance shift per refractive index unit. Antibody coating method is also discussed in this paper which can be applied to other antibody-antigen types.

Autonomous Supervision and Control of Parametric Roll Resonance

DEFF Research Database (Denmark)

Galeazzi, Roberto

therefore two objectives. The first is to develop methods for detection of the inception of parametric roll resonance. The second is to develop control strategies to stabilize the motion after parametric roll has started. Stabilisation of parametric roll resonance points to two possible courses of action...... strategies are then combined to stabilise parametric roll resonance within few roll cycles. Limitations on the maximum stabilisable roll angle are analysed and linked to the ii slew rate saturation and hydrodynamic stall characteristics of the fin stabilisers. The study on maximum stabilisable roll angle...... leads to the requirements for early detection. Two novel detectors are proposed, which work within a shorttime prediction horizon, and issue early warnings of parametric roll inception within few roll cycles from its onset. The main idea behind these detection schemes is that of exploiting the link...

Proximal Sensing of Plant-Pathogen Interactions in Spring Barley with Three Fluorescence Techniques

Directory of Open Access Journals (Sweden)

Georg Leufen

2014-06-01

Full Text Available In the last years fluorescence spectroscopy has come to be viewed as an essential approach in key research fields of applied plant sciences. However, the quantity and particularly the quality of information produced by different equipment might vary considerably. In this study we investigate the potential of three optical devices for the proximal sensing of plant-pathogen interactions in four genotypes of spring barley. For this purpose, the fluorescence lifetime, the image-resolved multispectral fluorescence and selected indices of a portable multiparametric fluorescence device were recorded at 3, 6, and 9 days after inoculation (dai from healthy leaves as well as from leaves inoculated with powdery mildew (Blumeria graminis or leaf rust (Puccinia hordei. Genotype-specific responses to pathogen infections were revealed already at 3 dai by higher fluorescence mean lifetimes in the spectral range from 410 to 560 nm in the less susceptible varieties. Noticeable pathogen-induced modifications were also revealed by the ‘Blue-to-Far-Red Fluorescence Ratio’ and the ‘Simple Fluorescence Ratio’. Particularly in the susceptible varieties the differences became more evident in the time-course of the experiment i.e., following the pathogen development. The relevance of the blue and green fluorescence to exploit the plant-pathogen interaction was demonstrated by the multispectral fluorescence imaging system. As shown, mildewed leaves were characterized by exceptionally high blue fluorescence, contrasting the values observed in rust inoculated leaves. Further, we confirm that the intensity of green fluorescence depends on the pathogen infection and the stage of disease development; this information might allow a differentiation of both diseases. Moreover, our results demonstrate that the detection area might influence the quality of the information, although it had a minor impact only in the current study. Finally, we highlight the relevance of

The economics of exploiting gas hydrates

International Nuclear Information System (INIS)

Döpke, Lena-Katharina; Requate, Till

2014-01-01

We investigate the optimal exploitation of methane hydrates, a recent discovery of methane resources under the sea floor, mainly located along the continental margins. Combustion of methane (releasing CO2) and leakage through blow-outs (releasing CH4) contribute to the accumulation of greenhouse gases. A second externality arises since removing solid gas hydrates from the sea bottom destabilizes continental margins and thus increases the risk of marine earthquakes. We show that in such a model three regimes can occur: i) resource exploitation will be stopped in finite time, and some of the resource will stay in situ, ii) the resource will be used up completely in finite time, and iii) the resource will be exhausted in infinite time. We also show how to internalize the externalities by policy instruments. - Highlights: • We set up a model of optimal has hydrate exploitation • We incorporate to types of damages: contribution to global warming and geo-hazards • We characterize optimal exploitation paths and study decentralization with an exploitation tax. • Three regimes can occur: • i) exploitation in finite time and some of the stock remaining in situ, • ii) exploitation in finite time and the resource will be exhausted, • iii) exploitation and exhaustion in infinite time

Far from Equilibrium Percolation, Stochastic and Shape Resonances in the Physics of Life

Directory of Open Access Journals (Sweden)

Antonio Bianconi

2011-10-01

Full Text Available Key physical concepts, relevant for the cross-fertilization between condensed matter physics and the physics of life seen as a collective phenomenon in a system out-of-equilibrium, are discussed. The onset of life can be driven by: (a the critical fluctuations at the protonic percolation threshold in membrane transport; (b the stochastic resonance in biological systems, a mechanism that can exploit external and self-generated noise in order to gain efficiency in signal processing; and (c the shape resonance (or Fano resonance or Feshbach resonance in the association and dissociation processes of bio-molecules (a quantum mechanism that could play a key role to establish a macroscopic quantum coherence in the cell.

Laser stabilisation for velocity-selective atomic absorption

NARCIS (Netherlands)

Meijer, H.A.J.; Meulen, H.P. van der; Ditewig, F.; Wisman, C.J.; Morgenstern, R.

1987-01-01

A relatively simple method is described for stabilising a dye laser at a frequency ν = ν0 + νc in the vicinity of an atomic resonance frequency ν0. The Doppler effect is exploited by looking for atomic fluorescence when a laser beam is crossed with an atomic beam at certain angles αi. Absolute

Terahertz sensing of highly absorptive water-methanol mixtures with multiple resonances in metamaterials.

Science.gov (United States)

Chen, Min; Singh, Leena; Xu, Ningning; Singh, Ranjan; Zhang, Weili; Xie, Lijuan

2017-06-26

Terahertz sensing of highly absorptive aqueous solutions remains challenging due to strong absorption of water in the terahertz regime. Here, we experimentally demonstrate a cost-effective metamaterial-based sensor integrated with terahertz time-domain spectroscopy for highly absorptive water-methanol mixture sensing. This metamaterial has simple asymmetric wire structures that support multiple resonances including a fundamental Fano resonance and higher order dipolar resonance in the terahertz regime. Both the resonance modes have strong intensity in the transmission spectra which we exploit for detection of the highly absorptive water-methanol mixtures. The experimentally characterized sensitivities of the Fano and dipole resonances for the water-methanol mixtures are found to be 160 and 305 GHz/RIU, respectively. This method provides a robust route for metamaterial-assisted terahertz sensing of highly absorptive chemical and biochemical materials with multiple resonances and high accuracy.

Sensitized fluorescence in thallium induced in collisions with Hg(6/sup 3/P/sub 1/) atoms

Energy Technology Data Exchange (ETDEWEB)

Wade, M K; Czajkowski, M; Krause, L [Windsor Univ., Ontario (Canada). Dept. of Physics

1978-07-01

The transfer of excitation from excited mercury atoms to ground-state thallium atoms was investigated using techniques of sensitized fluorescence. A Hg-Tl vapor mixture contained in a quartz cell was irradiated with Hg 2537 A resonance radiation which caused the mercury atoms to become excited to the 6/sup 3/P/sub 1/ state. Subsequent collisions between the Hg(6/sup 3/P/sub 1/) and Tl(6/sup 2/Psub(1/2)) atoms resulted in the population of the 8/sup 2/Ssub(1/2), 6/sup 2/D, and 7/sup 2/Ssub(1/2) thallium states, whose decay gave rise to sensitized fluorescence of wavelengths 3231, 3520, 3776, and 5352 A. Intensity measurements on the sensitized fluorescence and on the Hg 2537 A resonance fluorescence, observed at right angles to the direction of excitation, yielded cross sections of 3.0, 0.3, and 0.05 A/sup 2/ for collisional excitation transfer from Hg(6/sup 3/P/sub 1/) to the 8/sup 2/Ssub(1/2), 6/sup 2/D, and 7/sup 2/Ssub(1/2) states in thallium, respectively. The results are fully consistent with previously determined cross sections for excitation transfer in other binary metallic vapor systems.

Parallel scan hyperspectral fluorescence imaging system and biomedical application for microarrays

International Nuclear Information System (INIS)

Liu Zhiyi; Ma Suihua; Liu Le; Guo Jihua; He Yonghong; Ji Yanhong

2011-01-01

Microarray research offers great potential for analysis of gene expression profile and leads to greatly improved experimental throughput. A number of instruments have been reported for microarray detection, such as chemiluminescence, surface plasmon resonance, and fluorescence markers. Fluorescence imaging is popular for the readout of microarrays. In this paper we develop a quasi-confocal, multichannel parallel scan hyperspectral fluorescence imaging system for microarray research. Hyperspectral imaging records the entire emission spectrum for every voxel within the imaged area in contrast to recording only fluorescence intensities of filter-based scanners. Coupled with data analysis, the recorded spectral information allows for quantitative identification of the contributions of multiple, spectrally overlapping fluorescent dyes and elimination of unwanted artifacts. The mechanism of quasi-confocal imaging provides a high signal-to-noise ratio, and parallel scan makes this approach a high throughput technique for microarray analysis. This system is improved with a specifically designed spectrometer which can offer a spectral resolution of 0.2 nm, and operates with spatial resolutions ranging from 2 to 30 μm . Finally, the application of the system is demonstrated by reading out microarrays for identification of bacteria.

In vivo colocalization of 2-nitroimidazole EF5 fluorescence intensity and electron paramagnetic resonance oximetry in mouse tumors

International Nuclear Information System (INIS)

Mahy, Pierre; Bast, Marc de; Gallez, Bernard; Gueulette, John; Koch, Cameron J.; Scalliet, Pierre; Gregoire, Vincent

2003-01-01

Background and purpose: The primary objective of this study was to establish in vivo the relationship between 2-2-nitro-1H-imidazol-1yl-N-(2,2,3,3,3-pentafluoropropyl)-acetamide (EF5) adduct formation and intratumoral oxygen concentrations measured by electron paramagnetic resonance (EPR) in a tumor model mimicking a clinical situation. The secondary objective was an attempt to calibrate in situ the immunofluorescence (IF) signal with EPR oximetry. Materials and methods: IM syngeneic fibrosarcoma (NFSA) bearing C3H mice were used. Three days after injection of a paramagnetic charcoal into the tumor, the mice were anesthetized, injected with the hypoxic marker EF5, and monitored every 20 min for 3 h with a low-frequency EPR spectrometer. Animals were allowed to breath either under 21 or 100% O 2 . Tumors were then harvested, frozen, cut into sections including the charcoal and processed for EF5 adducts detection using monoclonal antibodies. Slices were viewed with a fluorescence microscope and 190x140 μm areas surrounding the charcoal were digitized and analyzed with the NIH-Image and Adobe Photoshop TM software. The fluorescence intensity (FI) was measured in the whole pictures and in strips of 10 μm around the charcoal. Results: EF5 binding increased with decreasing pO 2 , most substantially at pO 2 below 5 mm Hg. Baseline (ambient air) pO 2 reached 3.2±2.1 mm Hg in NFSA tumors. It increased to 9.8±3.2 mm Hg under 100% O 2 . A statistically significant correlation was observed on an individual tumor basis between the FI in the first 10 μm strip around the charcoal and the pO 2 determined by EPR oximetry (Wilcoxon signed rank test: P 2 in an in vivo environment under biologically-relevant pO 2 values of less than 10 mm Hg

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

Science.gov (United States)

Sahoo, Harekrushna; Nau, Werner M

2007-03-26

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

Magnetic resonance and porous materials

International Nuclear Information System (INIS)

McDonald, P.; Strange, J.

1998-01-01

Mention the words magnetic resonance to your medical advisor and he or she will immediately think of a multi-million pound scanner that peers deep into the brain. A chemist, on the other hand, will imagine a machine that costs several hundred thousand pounds and produces high-resolution spectra for chemical analysis. Food technologists will probably think of a bench-top instrument for determining moisture content, while an oil prospector will envisage a device that can be operated several kilometres down an oil well. To a physicist the term is more likely to conjure up a mental picture of nuclear spins precessing in a magnetic field. These examples illustrate the diverse aspects of a phenomenon discovered by physicists over 50 years ago. Electron spin resonance was first discovered by Russian scientists, and nuclear magnetic resonance was discovered in the US shortly afterwards by Ed Purcell at Harvard University and Felix Bloch at Stanford University. Today, nuclear magnetic resonance (NMR) is the most widely used technique. Modern NMR machines are making it possible to probe microstructure and molecular movement in materials as diverse as polymers, cements, rocks, soil and foods. NMR allows the distribution of different components in a material to be determined with a resolution approaching 1μm, although the signal can be sensitive to even smaller lengthscales. In this article the authors describe how physicists are still developing magnetic resonance to exploit a range of new applications. (UK)

Scattering-Type Surface-Plasmon-Resonance Biosensors

Science.gov (United States)

Wang, Yu; Pain, Bedabrata; Cunningham, Thomas; Seshadri, Suresh

2005-01-01

Biosensors of a proposed type would exploit scattering of light by surface plasmon resonance (SPR). Related prior biosensors exploit absorption of light by SPR. Relative to the prior SPR biosensors, the proposed SPR biosensors would offer greater sensitivity in some cases, enough sensitivity to detect bioparticles having dimensions as small as nanometers. A surface plasmon wave can be described as a light-induced collective oscillation in electron density at the interface between a metal and a dielectric. At SPR, most incident photons are either absorbed or scattered at the metal/dielectric interface and, consequently, reflected light is greatly attenuated. The resonance wavelength and angle of incidence depend upon the permittivities of the metal and dielectric. An SPR sensor of the type most widely used heretofore includes a gold film coated with a ligand a substance that binds analyte molecules. The gold film is thin enough to support evanescent-wave coupling through its thickness. The change in the effective index of refraction at the surface, and thus the change in the SPR response, increases with the number of bound analyte molecules. The device is illuminated at a fixed wavelength, and the intensity of light reflected from the gold surface opposite the ligand-coated surface is measured as a function of the angle of incidence. From these measurements, the angle of minimum reflection intensity is determined

Picocyanobacteria and deep-ocean fluorescent dissolved organic matter share similar optical properties

Science.gov (United States)

Zhao, Zhao; Gonsior, Michael; Luek, Jenna; Timko, Stephen; Ianiri, Hope; Hertkorn, Norbert; Schmitt-Kopplin, Philippe; Fang, Xiaoting; Zeng, Qinglu; Jiao, Nianzhi; Chen, Feng

2017-05-01

Marine chromophoric dissolved organic matter (CDOM) and its related fluorescent components (FDOM), which are widely distributed but highly photobleached in the surface ocean, are critical in regulating light attenuation in the ocean. However, the origins of marine FDOM are still under investigation. Here we show that cultured picocyanobacteria, Synechococcus and Prochlorococcus, release FDOM that closely match the typical fluorescent signals found in oceanic environments. Picocyanobacterial FDOM also shows comparable apparent fluorescent quantum yields and undergoes similar photo-degradation behaviour when compared with deep-ocean FDOM, further strengthening the similarity between them. Ultrahigh-resolution mass spectrometry (MS) and nuclear magnetic resonance spectroscopy reveal abundant nitrogen-containing compounds in Synechococcus DOM, which may originate from degradation products of the fluorescent phycobilin pigments. Given the importance of picocyanobacteria in the global carbon cycle, our results indicate that picocyanobacteria are likely to be important sources of marine autochthonous FDOM, which may accumulate in the deep ocean.

Exploitation in International Paid Surrogacy Arrangements

OpenAIRE

Wilkinson, Stephen

2015-01-01

Abstract Many critics have suggested that international paid surrogacy is exploitative. Taking such concerns as its starting point, this article asks: (1) how defensible is the claim that international paid surrogacy is exploitative and what could be done to make it less exploitative? (2) In the light of the answer to (1), how strong is the case for prohibiting it? Exploitation could in principle be dealt with by improving surrogates' pay and conditions. However, doing so may exacerbate probl...

Cy5.5 conjugated MnO nanoparticles for magnetic resonance/near-infrared fluorescence dual-modal imaging of brain gliomas.

Science.gov (United States)

Chen, Ning; Shao, Chen; Li, Shuai; Wang, Zihao; Qu, Yanming; Gu, Wei; Yu, Chunjiang; Ye, Ling

2015-11-01

The fusion of molecular and anatomical modalities facilitates more reliable and accurate detection of tumors. Herein, we prepared the PEG-Cy5.5 conjugated MnO nanoparticles (MnO-PEG-Cy5.5 NPs) with magnetic resonance (MR) and near-infrared fluorescence (NIRF) imaging modalities. The applicability of MnO-PEG-Cy5.5 NPs as a dual-modal (MR/NIRF) imaging nanoprobe for the detection of brain gliomas was investigated. In vivo MR contrast enhancement of the MnO-PEG-Cy5.5 nanoprobe in the tumor region was demonstrated. Meanwhile, whole-body NIRF imaging of glioma bearing nude mouse exhibited distinct tumor localization upon injection of MnO-PEG-Cy5.5 NPs. Moreover, ex vivo CLSM imaging of the brain slice hosting glioma indicated the preferential accumulation of MnO-PEG-Cy5.5 NPs in the glioma region. Our results therefore demonstrated the potential of MnO-PEG-Cy5.5 NPs as a dual-modal (MR/NIRF) imaging nanoprobe in improving the diagnostic efficacy by simultaneously providing anatomical information from deep inside the body and more sensitive information at the cellular level. Copyright © 2015 Elsevier Inc. All rights reserved.

Fluorescence imaging of tryptophan and collagen cross-links to evaluate wound closure ex vivo

Science.gov (United States)

Wang, Ying; Ortega-Martinez, Antonio; Farinelli, Bill; Anderson, R. R.; Franco, Walfre

2016-02-01

Wound size is a key parameter in monitoring healing. Current methods to measure wound size are often subjective, time-consuming and marginally invasive. Recently, we developed a non-invasive, non-contact, fast and simple but robust fluorescence imaging (u-FEI) method to monitor the healing of skin wounds. This method exploits the fluorescence of native molecules to tissue as functional and structural markers. The objective of the present study is to demonstrate the feasibility of using variations in the fluorescence intensity of tryptophan and cross-links of collagen to evaluate proliferation of keratinocyte cells and quantitate size of wound during healing, respectively. Circular dermal wounds were created in ex vivo human skin and cultured in different media. Two serial fluorescence images of tryptophan and collagen cross-links were acquired every two days. Histology and immunohistology were used to validate correlation between fluorescence and epithelialization. Images of collagen cross-links show fluorescence of the exposed dermis and, hence, are a measure of wound area. Images of tryptophan show higher fluorescence intensity of proliferating keratinocytes forming new epithelium, as compared to surrounding keratinocytes not involved in epithelialization. These images are complementary since collagen cross-links report on structure while tryptophan reports on function. HE and immunohistology show that tryptophan fluorescence correlates with newly formed epidermis. We have established a fluorescence imaging method for studying epithelialization processes during wound healing in a skin organ culture model, our approach has the potential to provide a non-invasive, non-contact, quick, objective and direct method for quantitative measurements in wound healing in vivo.

Electrothermal Frequency Modulated Resonator for Mechanical Memory

KAUST Repository

Hafiz, Md Abdullah Al

2016-08-18

In this paper, we experimentally demonstrate a mechanical memory device based on the nonlinear dynamics of an electrostatically actuated microelectromechanical resonator utilizing an electrothermal frequency modulation scheme. The microstructure is deliberately fabricated as an in-plane shallow arch to achieve geometric quadratic nonlinearity. We exploit this inherent nonlinearity of the arch and drive it at resonance with minimal actuation voltage into the nonlinear regime, thereby creating softening behavior, hysteresis, and coexistence of states. The hysteretic frequency band is controlled by the electrothermal actuation voltage. Binary values are assigned to the two allowed dynamical states on the hysteretic response curve of the arch resonator with respect to the electrothermal actuation voltage. Set-and-reset operations of the memory states are performed by applying controlled dc pulses provided through the electrothermal actuation scheme, while the read-out operation is performed simultaneously by measuring the motional current through a capacitive detection technique. This novel memory device has the advantages of operating at low voltages and under room temperature. [2016-0043

Anisotropic resonator analysis using the Fourier-Bessel mode solver

Science.gov (United States)

Gauthier, Robert C.

2018-03-01

A numerical mode solver for optical structures that conform to cylindrical symmetry using Faraday's and Ampere's laws as starting expressions is developed when electric or magnetic anisotropy is present. The technique builds on the existing Fourier-Bessel mode solver which allows resonator states to be computed exploiting the symmetry properties of the resonator and states to reduce the matrix system. The introduction of anisotropy into the theoretical frame work facilitates the inclusion of PML borders permitting the computation of open ended structures and a better estimation of the resonator state quality factor. Matrix populating expressions are provided that can accommodate any material anisotropy with arbitrary orientation in the computation domain. Several example of electrical anisotropic computations are provided for rationally symmetric structures such as standard optical fibers, axial Bragg-ring fibers and bottle resonators. The anisotropy present in the materials introduces off diagonal matrix elements in the permittivity tensor when expressed in cylindrical coordinates. The effects of the anisotropy of computed states are presented and discussed.

Fluorescent quenching immune chromatographic strips with quantum dots and upconversion nanoparticles as fluorescent donors for visual detection of sulfaquinoxaline in foods of animal origin

International Nuclear Information System (INIS)

Hu, Gaoshuang; Sheng, Wei; Li, Jingmin; Zhang, Yan; Wang, Junping; Wang, Shuo

2017-01-01

In this study, two novel fluorescence quenching immune chromatographic strips (FQICS) were developed to detect sulfaquinoxaline (SQX) in foods of animal origin. These proposed FQICSs were based on fluorescence resonance energy transfer (FRET) from fluorescence donors (quantum dots or upconversion nanoparticles) to fluorescence acceptors (colloidal gold nanoparticles). Compared with traditional colloidal gold-based immune chromatographic strips (ICS), these FQICSs showed positive correlation between the fluorescent signals and the targets, and allowed user to get test results from weak fluorescent signals. The visual detection limits of these two FQICSs were both 1 ng mL −1 in standard solution and 8 μg kg −1 in samples, while the visual detection limit of the colloidal gold-based ICS was 10 ng mL −1 in standard solution and 80 μg kg −1 in samples. Besides, the results we obtained by the use of FQICS showed high agreement with those obtained by the use of commercial ELISA kits, indicating the good accuracy of these strips. As a conclusion, these proposed FQICS based on quantum dots and upconversion nanoparticles can be applied in sensitive, rapid and on-site detection of SQX in foods of animal origin. - Highlights: • Two novel FQICS based on FRET were developed for the first time. • QDs and UCNPs were used as fluorescent donors in the FQICS. • The proposed FQICS showed low LOD compared with traditional ICS. • The proposed FQICS were applied in real samples analysis. • The proposed FQICS were verified by commercial ELISA kits.

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

Science.gov (United States)

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

2014-06-01

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

Fluorescent pH sensor based on Ag@SiO2 core-shell nanoparticle.

Science.gov (United States)

Bai, Zhenhua; Chen, Rui; Si, Peng; Huang, Youju; Sun, Handong; Kim, Dong-Hwan

2013-06-26

We have demonstrated a novel method for the preparation of a fluorescence-based pH sensor by combining the plasmon resonance band of Ag core and pH sensitive dye (HPTS). A thickness-variable silica shell is placed between Ag core and HPTS dye to achieve the maximum fluorescence enhancement. At the shell thickness of 8 nm, the fluorescence intensity increases 4 and 9 times when the sensor is excited at 405 and 455 nm, respectively. At the same time, the fluorescence intensity shows a good sensitivity toward pH value in the range of 5-9, and the ratio of emission intensity at 513 nm excited at 455 nm to that excited at 405 nm versus the pH value in the range of 5-9 is determined. It is believed that the present pH sensor has the potential for determining pH real time in the biological sample.

Profits and Exploitation: A Reappraisal

OpenAIRE

Yoshihara, Naoki; Veneziani, Roberto

2011-01-01

This paper provides a mathematical analysis of the Marxian theory of the exploitation of labour in general equilibrium models. The two main definitions of Marxian exploitation in the literature, proposed by Morishima (1974) and Roemer (1982), respectively, are analysed in the context of general convex economies. It is shown that, contrary to the received view, in general these definitions do not preserve the so-called Fundamental Marxian Theorem (FMT), which states that the exploitation of la...

Increased fluorescence of PbS quantum dots in photonic crystals by excitation enhancement

Science.gov (United States)

Barth, Carlo; Roder, Sebastian; Brodoceanu, Daniel; Kraus, Tobias; Hammerschmidt, Martin; Burger, Sven; Becker, Christiane

2017-07-01

We report on the enhanced fluorescence of lead sulfide quantum dots interacting with leaky modes of slab-type silicon photonic crystals. The photonic crystal slabs were fabricated, supporting leaky modes in the near infrared wavelength range. Lead sulfite quantum dots which are resonant in the same spectral range were prepared in a thin layer above the slab. We selectively excited the leaky modes by tuning the wavelength and angle of incidence of the laser source and measured distinct resonances of enhanced fluorescence. By an appropriate experiment design, we ruled out directional light extraction effects and determined the impact of enhanced excitation. Three-dimensional numerical simulations consistently explain the experimental findings by strong near-field enhancements in the vicinity of the photonic crystal surface. Our study provides a basis for systematic tailoring of photonic crystals used in biological applications such as biosensing and single molecule detection, as well as quantum dot solar cells and spectral conversion applications.

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.

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

International Nuclear Information System (INIS)

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

1997-01-01

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

Feasibility study for airborne fluorescence/reflectivity lidar bathymetry

Science.gov (United States)

Steinvall, Ove; Kautsky, Hans; Tulldahl, Michael; Wollner, Erika

2012-06-01

There is a demand from the authorities to have good maps of the coastal environment for their exploitation and preservation of the coastal areas. The goal for environmental mapping and monitoring is to differentiate between vegetation and non-vegetated bottoms and, if possible, to differentiate between species. Airborne lidar bathymetry is an interesting method for mapping shallow underwater habitats. In general, the maximum depth range for airborne laser exceeds the possible depth range for passive sensors. Today, operational lidar systems are able to capture the bottom (or vegetation) topography as well as estimations of the bottom reflectivity using e.g. reflected bottom pulse power. In this paper we study the possibilities and advantages for environmental mapping, if laser sensing would be further developed from single wavelength depth sounding systems to include multiple emission wavelengths and fluorescence receiver channels. Our results show that an airborne fluorescence lidar has several interesting features which might be useful in mapping underwater habitats. An example is the laser induced fluorescence giving rise to the emission spectrum which could be used for classification together with the elastic lidar signal. In the first part of our study, vegetation and substrate samples were collected and their spectral reflectance and fluorescence were subsequently measured in laboratory. A laser wavelength of 532 nm was used for excitation of the samples. The choice of 532 nm as excitation wavelength is motivated by the fact that this wavelength is commonly used in bathymetric laser scanners and that the excitation wavelengths are limited to the visual region as e.g. ultraviolet radiation is highly attenuated in water. The second part of our work consisted of theoretical performance calculations for a potential real system, and comparison of separability between species and substrate signatures using selected wavelength regions for fluorescence sensing.

THz Pyro-Optical Detector Based on LiNbO3 Whispering Gallery Mode Microdisc Resonator

Science.gov (United States)

Cosci, Alessandro; Cerminara, Matteo; Nunzi Conti, Gualtiero; Soria, Silvia; Righini, Giancarlo C.; Pelli, Stefano

2017-01-01

This study analyzes the capabilities of a LiNbO3 whispering gallery mode microdisc resonator as a potential bolometer detector in the THz range. The resonator is theoretically characterized in the stationary regime by its thermo-optic and thermal coefficients. Considering a Q-factor of 107, a minimum detectable power of 20 μW was evaluated, three orders of magnitude above its noise equivalent power. This value opens up the feasibility of exploiting LiNbO3 disc resonators as sensitive room-temperature detectors in the THz range. PMID:28134857

Quantum measurement and orientation tracking of fluorescent nanodiamonds inside living cells

Science.gov (United States)

McGuinness, L. P.; Yan, Y.; Stacey, A.; Simpson, D. A.; Hall, L. T.; MacLaurin, D.; Prawer, S.; Mulvaney, P.; Wrachtrup, J.; Caruso, F.; Scholten, R. E.; Hollenberg, L. C. L.

2011-06-01

Fluorescent particles are routinely used to probe biological processes. The quantum properties of single spins within fluorescent particles have been explored in the field of nanoscale magnetometry, but not yet in biological environments. Here, we demonstrate optically detected magnetic resonance of individual fluorescent nanodiamond nitrogen-vacancy centres inside living human HeLa cells, and measure their location, orientation, spin levels and spin coherence times with nanoscale precision. Quantum coherence was measured through Rabi and spin-echo sequences over long (>10 h) periods, and orientation was tracked with effective 1° angular precision over acquisition times of 89 ms. The quantum spin levels served as fingerprints, allowing individual centres with identical fluorescence to be identified and tracked simultaneously. Furthermore, monitoring decoherence rates in response to changes in the local environment may provide new information about intracellular processes. The experiments reported here demonstrate the viability of controlled single spin probes for nanomagnetometry in biological systems, opening up a host of new possibilities for quantum-based imaging in the life sciences.

Ratiometric fluorescence polarization as a cytometric functional parameter: theory and practice

International Nuclear Information System (INIS)

Yishai, Yitzhak; Fixler, Dror; Cohen-Kashi, Meir; Zurgil, Naomi; Deutsch, Mordechai

2003-01-01

The use of ratiometric fluorescence polarization (RFP) as a functional parameter in monitoring cellular activation is suggested, based on the physical phenomenon of fluorescence polarization dependency on emission wavelengths in multiple (at least binary) solutions. The theoretical basis of this dependency is thoroughly discussed and examined via simulation. For simulation, aimed to imitate a fluorophore-stained cell, real values of the fluorescence spectrum and polarization of different single fluorophore solutions were used. The simulation as well as the experimentally obtained values of RFP indicated the high sensitivity of this measure. Finally, the RFP parameter was utilized as a cytometric measure in three exemplary cellular bioassays. In the first, the apoptotic effect of oxLDL in a human Jurkat FDA-stained T cell line was monitored by RFP. In the second, the interaction between cell surface membrane receptors of human T lymphocyte cells was monitored by RFP measurements as a complementary means to the fluorescence resonance energy transfer (FRET) technique. In the third bioassay, cellular thiol level of FDA- and CMFDA-labelled Jurkat T cells was monitored via RFP

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

2013-07-01

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.

Redefining Exploitation

DEFF Research Database (Denmark)

Agarwala, Rina

2016-01-01

This article examines how self-employed workers are organizing in the garments and waste collection industries in India. Although the question of who is profiting from self-employed workers’ labor is complex, the cases outlined in this paper highlight telling instances of how some self......-employed workers are organizing as workers. They are fighting labor exploitation by redefining the concept to include additional exploitation axes (from the state and middle class) and forms (including sexual). In doing so, they are redefining potential solutions, including identities and material benefits, to fit...... their unique needs. By expanding the category of “workers” beyond those defined by a narrow focus on a standard employer-employee relationship, these movements are also fighting exclusion from earlier labor protections by increasing the number of entitled beneficiaries. These struggles provide an important...

Fluorescent nanoscale detection of biotin-streptavidin interaction using near-field scanning optical microscopy

International Nuclear Information System (INIS)

Park, Hyun Kyu; Chung, Bong Hyun; Gokarna, Anisha; Hulme, John P; Park, Hyun Gyu

2008-01-01

We describe a nanoscale strategy for detecting biotin-streptavidin binding using near-field scanning optical microscopy (NSOM) that exploits the fluorescence properties of single polydiacetylene (PDA) liposomes. NSOM is more useful to observe nanomaterials having optical properties with the help of topological information. We synthesized amine-terminated 10,12-pentacosadiynoic acid (PCDA) monomer (PCDA-NH 2 ) and used this derivatized monomer to prepare PCDA liposomes. PCDA-NH 2 liposomes were immobilized on an aldehyde-functionalized glass surface followed by photopolymerization by using a 254 nm light source. To measure the biotin-streptavidin binding, we conjugated photoactivatable biotin to immobilized PCDA-NH 2 liposomes by UV irradiation (365 nm) and subsequently allowed them to interact with streptavidin. We analyzed the fluorescence using a fluorescence scanner and observed single liposomes using NSOM. The average height and NSOM signal observed in a single liposome after binding were ∼31.3 to 8.5 ± 0.5 nm and 0.37 to 0.16 ± 0.6 kHz, respectively. This approach, which has the advantage of not requiring a fluorescent label, could prove highly beneficial for single molecule detection technology

Label free selective detection of estriol using graphene oxide-based fluorescence sensor

Science.gov (United States)

Kushwaha, H. S.; Sao, Reshma; Vaish, Rahul

2014-07-01

Water-soluble and fluorescent Graphene oxide (GO) is biocompatible, easy, and economical to synthesize. Interestingly, GO is also capable of quenching fluorescence. On the basis of its fluorescence and quenching abilities, GO has been reported to serve as an energy acceptor in a fluorescence resonance energy transfer (FRET) sensor. GO-based FRET biosensors have been widely reported for sensing of proteins, nucleic acid, ATP (Adenosine triphosphate), etc. GO complexes with fluorescent dyes and enzymes have been used to sense metal ions. Graphene derivatives have been used for sensing endocrine-disrupting chemicals like bisphenols and chlorophenols with high sensitivity and good reproducibility. On this basis, a novel GO based fluorescent sensor has been successfully designed to detect estriol with remarkable selectivity and sensitivity. Estriol is one of the three estrogens in women and is considered to be medically important. Estriol content of maternal urine or plasma acts as an important screening marker for estimating foetal growth and development. In addition, estriol is also used as diagnostic marker for diseases like breast cancer, osteoporosis, neurodegenerative and cardiovascular diseases, insulin resistance, lupus erythematosus, endometriosis, etc. In this present study, we report for the first time a rapid, sensitive with detection limit of 1.3 nM, selective and highly biocompatible method for label free detection of estriol under physiological conditions using fluorescence assay.

A hybrid segmentation approach for geographic atrophy in fundus auto-fluorescence images for diagnosis of age-related macular degeneration.

Science.gov (United States)

Lee, Noah; Laine, Andrew F; Smith, R Theodore

2007-01-01

Fundus auto-fluorescence (FAF) images with hypo-fluorescence indicate geographic atrophy (GA) of the retinal pigment epithelium (RPE) in age-related macular degeneration (AMD). Manual quantification of GA is time consuming and prone to inter- and intra-observer variability. Automatic quantification is important for determining disease progression and facilitating clinical diagnosis of AMD. In this paper we describe a hybrid segmentation method for GA quantification by identifying hypo-fluorescent GA regions from other interfering retinal vessel structures. First, we employ background illumination correction exploiting a non-linear adaptive smoothing operator. Then, we use the level set framework to perform segmentation of hypo-fluorescent areas. Finally, we present an energy function combining morphological scale-space analysis with a geometric model-based approach to perform segmentation refinement of false positive hypo- fluorescent areas due to interfering retinal structures. The clinically apparent areas of hypo-fluorescence were drawn by an expert grader and compared on a pixel by pixel basis to our segmentation results. The mean sensitivity and specificity of the ROC analysis were 0.89 and 0.98%.

Laser-induced fluorescence studies of premalignant and benign lesions in the female genital tract

Science.gov (United States)

af Klinteberg, Claes; Wang, Ingrid; Lindquist, Charlotta; Vaitkuviene, Aurelija; Svanberg, Katarina

1997-12-01

Laser-induced fluorescence (LIF) was studied in vivo from premalignant and benign lesions in the female genital tract, in particular the cervix. The aim of the study was to investigate the possibilities to differentiate cervical intraepithelial neoplasia (CIN) from normal tissue by means of two different fluorescence modalities. Most of the patients were given a low dose (5 mg/kg bw) of (delta) -amino levulinic acid (ALA). The ALA was orally administered 2 - 4 hours prior to the investigation. During this time, the ALA is transformed to the strongly fluorescent protoporphyrin IX (PpIX) via the haem cycle. Excitation light with a wavelength of 405 nm was used to excite the PpIX fluorescence. Excess amounts of PpIX were accumulated preferentially in diseased tissue. However, the variability in the PpIX accumulation from patient to patient was large. By using excitation light at 337 nm, the endogenous fluorophores are more efficiently excited. Therefore, this excitation modality was exploited for studying spectral characteristics of the autofluorescence in different tissue types. The spectra obtained were evaluated by forming fluorescence intensity ratios. The tissue types were grouped according to the histopathological examination. A correlation with the fluorescence ratios was performed. Some problems with the classification remain, mostly due to the difficulties in obtaining histopathologic evaluation of the biopsies at the exact location of the LIF measurements.

Tunable Resonators for Nonlinear Modal Interactions

KAUST Repository

Ramini, Abdallah; Hajjaj, Amal Z.; Younis, Mohammad I.

2016-01-01

Understanding the various mechanisms of nonlinear mode coupling in micro and nano resonators has become an imminent necessity for their successful implementation in practical applications. However, consistent, repeatable, and flexible experimental procedures to produce nonlinear mode coupling are lacking, and hence research into well-controlled experimental conditions is crucial. Here, we demonstrate well-controlled and repeatable experiments to study nonlinear mode coupling among micro and nano beam resonators. Such experimental approach can be applied to other micro and nano structures to help study their nonlinear interactions and exploit them for higher sensitive and less noisy responses. Using electrothermal tuning and electrostatic excitation, we demonstrate three different kinds of nonlinear interactions among the first and third bending modes of vibrations of slightly curved beams (arches): two-one internal resonance, three-one internal resonance, and mode veering (near crossing). The experimental procedure is repeatable, highly flexible, do not require special or precise fabrication, and is conducted in air and at room temperature. This approach can be applied to other micro and nano structures, which come naturally curved due to fabrication imperfections, such as CNTs, and hence lays the foundation to deeply investigate the nonlinear mode coupling in these structures in a consistent way.

Tunable Resonators for Nonlinear Modal Interactions

KAUST Repository

Ramini, Abdallah

2016-10-04

Understanding the various mechanisms of nonlinear mode coupling in micro and nano resonators has become an imminent necessity for their successful implementation in practical applications. However, consistent, repeatable, and flexible experimental procedures to produce nonlinear mode coupling are lacking, and hence research into well-controlled experimental conditions is crucial. Here, we demonstrate well-controlled and repeatable experiments to study nonlinear mode coupling among micro and nano beam resonators. Such experimental approach can be applied to other micro and nano structures to help study their nonlinear interactions and exploit them for higher sensitive and less noisy responses. Using electrothermal tuning and electrostatic excitation, we demonstrate three different kinds of nonlinear interactions among the first and third bending modes of vibrations of slightly curved beams (arches): two-one internal resonance, three-one internal resonance, and mode veering (near crossing). The experimental procedure is repeatable, highly flexible, do not require special or precise fabrication, and is conducted in air and at room temperature. This approach can be applied to other micro and nano structures, which come naturally curved due to fabrication imperfections, such as CNTs, and hence lays the foundation to deeply investigate the nonlinear mode coupling in these structures in a consistent way.

Vibration-synchronized magnetic resonance imaging for the detection of myocardial elasticity changes.

Science.gov (United States)

Elgeti, Thomas; Tzschätzsch, Heiko; Hirsch, Sebastian; Krefting, Dagmar; Klatt, Dieter; Niendorf, Thoralf; Braun, Jürgen; Sack, Ingolf

2012-04-01

Vibration synchronized magnetic resonance imaging of harmonically oscillating tissue interfaces is proposed for cardiac magnetic resonance elastography. The new approach exploits cardiac triggered cine imaging synchronized with extrinsic harmonic stimulation (f = 22.83 Hz) to display oscillatory tissue deformations in magnitude images. Oscillations are analyzed by intensity threshold-based image processing to track wave amplitude variations over the cardiac cycle. In agreement to literature data, results in 10 volunteers showed that endocardial wave amplitudes during systole (0.13 ± 0.07 mm) were significantly lower than during diastole (0.34 ± 0.14 mm, P magnetic resonance imaging improves the temporal resolution of magnetic resonance elastography as it overcomes the use of extra motion encoding gradients, is less sensitive to susceptibility artifacts, and does not suffer from dynamic range constraints frequently encountered in phase-based magnetic resonance elastography. Copyright © 2012 Wiley Periodicals, Inc.

Impurity studies in fusion devices using laser-fluorescence-spectroscopy

International Nuclear Information System (INIS)

Husinsky, W.R.

1980-08-01

Resonance fluorescence excitation of neutral atoms using tunable radiation from dye lasers offers a number of unique advantages for impurity studies in fusion devices. Using this technique, it is possible to perform local, time-resolved measurements of the densities and velocity distributions of metallic impurities in fusion devices without disturbing the plasma. Velocities are measured by monitoring the fluorescence intensity while tuning narrow bandwidth laser radiation through the Doppler - broadened absorbtion spectrum of the transition. The knowledge of the velocity distribution of neutral impurities is particularly useful for the determination of impurity introduction mechanisms. The laser fluorescence technique will be described in terms of its application to metallic impurities in fusion devices and related laboratory experiments. Particular attention will be given to recent results from the ISX-B tokamak using pulsed dye lasers where detection sensitivities for neutral Fe of 10 6 atoms/cm 3 with a velocity resolution of 600 m/sec (0.1 eV) have been achieved. Techniques for exciting plasma particles (H,D) will also be discussed

Oil leakage detection for electric power equipment based on ultraviolet fluorescence effect

Science.gov (United States)

Zhang, Jing; Wang, Jian-hui; Xu, Bin; Huang, Zhi-dong; Huang, Lan-tao

2018-03-01

This paper presents a method to detect the oil leakage of high voltage power equipment based on ultraviolet fluorescence effect. The method exploits the principle that the insulating oil has the fluorescent effect under the irradiation of specific ultraviolet light. The emission spectrum of insulating oil under excitation light with different wavelengths is measured and analyzed first. On this basis, a portable oil leakage detective device for high voltage power equipment is designed and developed with a selected 365 nm ultraviolet as the excitation light and the low light level camera as the fluorescence image collector. Then, the feasibility of the proposed method and device in different conditions is experimentally verified in the laboratory environment. Finally, the developed oil leakage detective device is applied to 500 kV Xiamen substation and Quanzhou substation. And the results show that the device can detect the oil leakage of high voltage electrical equipment quickly and conveniently even under the condition of a slight oil leakage especially in the low light environment.

Microring resonator based modulator made by direct photodefinition of an electro-optic polymer

Science.gov (United States)

Balakrishnan, M.; Faccini, M.; Diemeer, M. B. J.; Klein, E. J.; Sengo, G.; Driessen, A.; Verboom, W.; Reinhoudt, D. N.

2008-04-01

A laterally coupled microring resonator was fabricated by direct photodefinition of negative photoresist SU8, containing tricyanovinylidenediphenylaminobenzene chromophore, by exploiting the low ultraviolet absorption window of this chromophore. The ring resonator was first photodefined by slight cross-linking. Thereafter, poling (to align the chromophores) and further cross-linking (to increase the glass transition temperature) were simultaneously carried out. The material showed excellent photostability and the electro-optic modulation with an r33 of 11pm/V was demonstrated at 10MHz.

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

International Nuclear Information System (INIS)

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

2015-01-01

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

Two-point active microrheology in a viscous medium exploiting a motional resonance excited in dual-trap optical tweezers

Science.gov (United States)

Paul, Shuvojit; Kumar, Randhir; Banerjee, Ayan

2018-04-01

Two-point microrheology measurements from widely separated colloidal particles approach the bulk viscosity of the host medium more reliably than corresponding single-point measurements. In addition, active microrheology offers the advantage of enhanced signal to noise over passive techniques. Recently, we reported the observation of a motional resonance induced in a probe particle in dual-trap optical tweezers when the control particle was driven externally [Paul et al., Phys. Rev. E 96, 050102(R) (2017), 10.1103/PhysRevE.96.050102]. We now demonstrate that the amplitude and phase characteristics of the motional resonance can be used as a sensitive tool for active two-point microrheology to measure the viscosity of a viscous fluid. Thus, we measure the viscosity of viscous liquids from both the amplitude and phase response of the resonance, and demonstrate that the zero crossing of the phase response of the probe particle with respect to the external drive is superior compared to the amplitude response in measuring viscosity at large particle separations. We compare our viscosity measurements with those using a commercial rheometer and obtain an agreement ˜1 % . The method can be extended to viscoelastic material where the frequency dependence of the resonance may provide further accuracy for active microrheological measurements.

Exploration, Exploitation, and Organizational Coordination Mechanisms

Directory of Open Access Journals (Sweden)

Silvio Popadiuk

2016-03-01

Full Text Available This paper presents an empirical relationship among exploration, exploitation, and organizational coordination mechanisms, classified as the centralization of decision-making, formalization, and connectedness. In order to analyze the findings of this survey, we used two techniques: Principal Component Analysis (PCA and Partial Least Squares Path Modeling (PLS-PM. Our analysis was supported by 249 answers from managers of companies located in Brazil (convenience sampling. Contrary to expectations, centralization and exploitation were negatively associated. Our data supports the research hypothesis that formalization is positively associated with exploitation. Although the relationship between formalization and exploration were significant, the result is contrary to the research hypothesis that we made. The relationships among connectedness and exploitation, and connectedness and exploration were both positive and significant. This relationship means that the more connectedness increases, the higher the likelihood of exploitation and exploration.

Fluorescence properties of Yb3+-Er3+ co-doped phosphate glasses containing silver nanoparticles

Science.gov (United States)

Martínez Gámez, Ma A.; Vallejo H, Miguel A.; Kiryanov, A. V.; Licea-Jiménez, L.; Lucio M, J. L.; Pérez-García, S. A.

2018-04-01

Er3+-Yb3+ co-doped phosphate glasses containing silver nitrate (SN), were fabricated. Transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS) analyses were used to evidence the nucleation and presence of silver nanoparticles (SNP). The basic parameters of the glasses were inspected by means of absorption and fluorescence spectra, and fluorescence lifetimes under excitation at 916 nm (in-band of Yb3+), and at 406 nm (in-band of surface plasmon resonance given by the presence of SNP). The spectra as well as estimates for the basic parameters defining the lasing/amplifying potential of the glasses were studied as a function of SN concentration. The experimental results indicate that by increasing the SN content an enhancement of Er3+/Yb3+ fluorescence takes place.

Calibrating the imaging and therapy performance of magneto-fluorescent gold nanoshells for breast cancer

Science.gov (United States)

Dowell, Adam; Chen, Wenxue; Biswal, Nrusingh; Ayala-Orozco, Ciceron; Giuliano, Mario; Schiff, Rachel; Halas, Naomi J.; Joshi, Amit

2012-03-01

Gold nanoshells with NIR plasmon resonance can be modified to simultaneously enhance conjugated NIR fluorescence dyes and T2 contrast of embedded iron-oxide nanoparticles, and molecularly targeted to breast and other cancers. We calibrated the theranostic performance of magneto-fluorescent nanoshells, and contrasted the performance of molecularly targeted and untargeted nanoshells for breast cancer therapy, employing MCF-7L and their HER2 overexpressing derivative MCF-7/HER2-18 breast cancer cells as in vitro model systems. Silica core gold nanoshells with plasmon resonance on ~810 nm were doped with NIR dye ICG and ~10 nm iron-oxide nanoparticles in a ~20 nm epilayer of silica. A subset of nanoshells was conjugated to antibodies targeting HER2. Cell viability with varying laser power levels in presence and absence of bare and HER2-targeted nanoshells was assessed by calcein and propidium iodide staining. For MCF-7L cells, increasing power resulted in increased cell death (F=5.63, p=0.0018), and bare nanoshells caused more cell death than HER2-targeted nanoshells or laser treatment alone (F=30.13, pmagneto-fluorescent nanocomplexes for imaging and therapy of breast cancer cells, and the advantages of targeting receptors unique to cancer cells.

Pulse Double-Resonance EPR Techniques for the Study of Metallobiomolecules.

Science.gov (United States)

Cox, Nicholas; Nalepa, Anna; Pandelia, Maria-Eirini; Lubitz, Wolfgang; Savitsky, Anton

2015-01-01

Electron paramagnetic resonance (EPR) spectroscopy exploits an intrinsic property of matter, namely the electron spin and its related magnetic moment. This can be oriented in a magnetic field and thus, in the classical limit, acts like a little bar magnet. Its moment will align either parallel or antiparallel to the field, giving rise to different energies (termed Zeeman splitting). Transitions between these two quantized states can be driven by incident microwave frequency radiation, analogous to NMR experiments, where radiofrequency radiation is used. However, the electron Zeeman interaction alone provides only limited information. Instead, much of the usefulness of EPR is derived from the fact that the electron spin also interacts with its local magnetic environment and thus can be used to probe structure via detection of nearby spins, e.g., NMR-active magnetic nuclei and/or other electron spin(s). The latter is exploited in spin labeling techniques, an exciting new area in the development of noncrystallographic protein structure determination. Although these interactions are often smaller than the linewidth of the EPR experiment, sophisticated pulse EPR methods allow their detection. A number of such techniques are well established today and can be broadly described as double-resonance methods, in which the electron spin is used as a reporter. Below we give a brief description of pulse EPR methods, particularly their implementation at higher magnetic fields, and how to best exploit them for studying metallobiomolecules. © 2015 Elsevier Inc. All rights reserved.

Fluorescence-Free Biosensor Methods in Detection of Food Pathogens with a Special Focus on Listeria monocytogenes

Directory of Open Access Journals (Sweden)

Rajeswaran Radhakrishnan

2017-12-01

Full Text Available Food pathogens contaminate food products that allow their growth on the shelf and also under refrigerated conditions. Therefore, it is of utmost importance to lower the limit of detection (LOD of the method used and to obtain the results within hours to few days. Biosensor methods exploit the available technologies to individuate and provide an approximate quantification of the bacteria present in a sample. The main bottleneck of these methods depends on the aspecific binding to the surfaces and on a change in sensitivity when bacteria are in a complex food matrix with respect to bacteria in a liquid food sample. In this review, we introduce surface plasmon resonance (SPR, new advancements in SPR techniques, and electrochemical impedance spectroscopy (EIS, as fluorescence-free biosensing technologies for detection of L. monocytogenes in foods. The application of the two methods has facilitated L. monocytogenes detection with LOD of 1 log CFU/mL. Further advancements are envisaged through the combination of biosensor methods with immunoseparation of bacteria from larger volumes, application of lab-on-chip technologies, and EIS sensing methods for multiplex pathogen detection. Validation efforts are being conducted to demonstrate the robustness of detection, reproducibility and variability in multi-site installations.

Rapid and sensitive detection of clenbuterol using a fluorescence nanosensor based on diazo coupling mechanism

Science.gov (United States)

Thanh Hop Tran, Thi; Huong Do, Thi Mai; Hoang, Mai Ha; Tuyen Nguyen, Duc; Le, Quang Tuan; Nghia Nguyen, Duc; Ngo, Trinh Tung

2015-01-01

In this paper, the fluorescence resonance energy transfer (FRET) effect has been used for fabrication of nanosensor for the detection of clenbuterol. In the nanosensor, the CdTe quantum dots (QDs) are the donors while the acceptor is the super-macromolecule formed by the diazoation coupling mechanism between diazo clenbuterol and naphthylethylene diamine. Changes in fluorescence intensities of nanosensor were used to determine the clenbuterol concentration. We have successfully fabricated a nanosensor for detection of clenbuterol sensible to clenbuterol concentration of 10-12 g ml-1.

Sensitive and selective tumor imaging with novel and highly activatable fluorescence probes

International Nuclear Information System (INIS)

Urano, Yasuteru

2008-01-01

Selective and sensitive tumor imaging in vivo is one of the most requested methodologies in medical sciences. Although several imaging modalities have been developed including positron emission tomography (PET) and magnetic resonance (MR) imaging for the detection of tumors, none of these modalities can activate the signals upon being accumulated or uptaken to tumor sites. Among these modalities, only optical fluorescence imaging has a marked advantage, that is, their signals can be dramatically increased upon detecting some biological features. In this short review, I will introduce some recent strategies for activatable optical fluorescence imaging of tumors, and discuss their advantages over other modalities. (author)

Azadioxatriangulenium: a long fluorescence lifetime fluorophore for large biomolecule binding assay

International Nuclear Information System (INIS)

Sørensen, Thomas Just; Thyrhaug, Erling; Szabelski, Mariusz; Gryczynski, Ignacy; Gryczynski, Zygmunt; Luchowski, Rafal; Laursen, Bo W

2013-01-01

Of the many optical bioassays available, sensing by fluorescence anisotropy has great advantages as it provides a sensitive, instrumentally simple, ratiometric method of detection. However, it is hampered by a severe limitation, as the emission lifetime of the label needs to be comparable to the correlation lifetime (tumbling time) of the biomolecule which is labelled. For proteins of moderate size this is on the order of 20–200 ns, which due to practical issues currently limits the choice of labels to the dansyl-type dyes and certain aromatic dyes. These have the significant drawback of UV/blue absorption and emission as well as an often significant solvent sensitivity. Here, we report the synthesis and characterization of a new fluorescent label for high molecular weight biomolecule assay based on the azadioxatriangulenium motif. The NHS ester of the long fluorescence lifetime, red-emitting fluorophore: azadioxatriangulenium (ADOTA-NHS) was conjugated to anti-rabbit Immunoglobulin G (antiIgG). The long fluorescence lifetime was exploited to determine the correlation time of the high molecular weight antibody and its complex with rabbit Immunoglobulin G (IgG) with steady-state fluorescence anisotropy and time-resolved methods: solution phase immuno-assay was performed following either steady-state or time-resolved fluorescence anisotropy. By performing a variable temperature experiment it was determined that the binding of the ligand resulted in an increase in correlation time of more than 75%, and an increase in the steady-state anisotropy of 18%. The results show that the triangulenium class of dyes can be used in anisotropy assay to detect binding events involving biomolecules of far larger size than what is possible with most other red-emitting organic dyes. (paper)

Azadioxatriangulenium: a long fluorescence lifetime fluorophore for large biomolecule binding assay

Science.gov (United States)

Just Sørensen, Thomas; Thyrhaug, Erling; Szabelski, Mariusz; Luchowski, Rafal; Gryczynski, Ignacy; Gryczynski, Zygmunt; Laursen, Bo W.

2013-06-01

Of the many optical bioassays available, sensing by fluorescence anisotropy has great advantages as it provides a sensitive, instrumentally simple, ratiometric method of detection. However, it is hampered by a severe limitation, as the emission lifetime of the label needs to be comparable to the correlation lifetime (tumbling time) of the biomolecule which is labelled. For proteins of moderate size this is on the order of 20-200 ns, which due to practical issues currently limits the choice of labels to the dansyl-type dyes and certain aromatic dyes. These have the significant drawback of UV/blue absorption and emission as well as an often significant solvent sensitivity. Here, we report the synthesis and characterization of a new fluorescent label for high molecular weight biomolecule assay based on the azadioxatriangulenium motif. The NHS ester of the long fluorescence lifetime, red-emitting fluorophore: azadioxatriangulenium (ADOTA-NHS) was conjugated to anti-rabbit Immunoglobulin G (antiIgG). The long fluorescence lifetime was exploited to determine the correlation time of the high molecular weight antibody and its complex with rabbit Immunoglobulin G (IgG) with steady-state fluorescence anisotropy and time-resolved methods: solution phase immuno-assay was performed following either steady-state or time-resolved fluorescence anisotropy. By performing a variable temperature experiment it was determined that the binding of the ligand resulted in an increase in correlation time of more than 75%, and an increase in the steady-state anisotropy of 18%. The results show that the triangulenium class of dyes can be used in anisotropy assay to detect binding events involving biomolecules of far larger size than what is possible with most other red-emitting organic dyes.

The decay pattern of the Pygmy Dipole Resonance of 140Ce

Directory of Open Access Journals (Sweden)

B. Löher

2016-05-01

Full Text Available The decay properties of the Pygmy Dipole Resonance (PDR have been investigated in the semi-magic N=82 nucleus 140Ce using a novel combination of nuclear resonance fluorescence and γ–γ coincidence techniques. Branching ratios for transitions to low-lying excited states are determined in a direct and model-independent way both for individual excited states and for excitation energy intervals. Comparison of the experimental results to microscopic calculations in the quasi-particle phonon model exhibits an excellent agreement, supporting the observation that the Pygmy Dipole Resonance couples to the ground state as well as to low-lying excited states. A 10% mixing of the PDR and the [21+×PDR] is extracted.

The decay pattern of the Pygmy Dipole Resonance of 140Ce

Science.gov (United States)

Löher, B.; Savran, D.; Aumann, T.; Beller, J.; Bhike, M.; Cooper, N.; Derya, V.; Duchêne, M.; Endres, J.; Hennig, A.; Humby, P.; Isaak, J.; Kelley, J. H.; Knörzer, M.; Pietralla, N.; Ponomarev, V. Yu.; Romig, C.; Scheck, M.; Scheit, H.; Silva, J.; Tonchev, A. P.; Tornow, W.; Wamers, F.; Weller, H.; Werner, V.; Zilges, A.

2016-05-01

The decay properties of the Pygmy Dipole Resonance (PDR) have been investigated in the semi-magic N = 82 nucleus 140Ce using a novel combination of nuclear resonance fluorescence and γ-γ coincidence techniques. Branching ratios for transitions to low-lying excited states are determined in a direct and model-independent way both for individual excited states and for excitation energy intervals. Comparison of the experimental results to microscopic calculations in the quasi-particle phonon model exhibits an excellent agreement, supporting the observation that the Pygmy Dipole Resonance couples to the ground state as well as to low-lying excited states. A 10% mixing of the PDR and the [21+ × PDR ] is extracted.

Open source tools for fluorescent imaging.

Science.gov (United States)

Hamilton, Nicholas A

2012-01-01

As microscopy becomes increasingly automated and imaging expands in the spatial and time dimensions, quantitative analysis tools for fluorescent imaging are becoming critical to remove both bottlenecks in throughput as well as fully extract and exploit the information contained in the imaging. In recent years there has been a flurry of activity in the development of bio-image analysis tools and methods with the result that there are now many high-quality, well-documented, and well-supported open source bio-image analysis projects with large user bases that cover essentially every aspect from image capture to publication. These open source solutions are now providing a viable alternative to commercial solutions. More importantly, they are forming an interoperable and interconnected network of tools that allow data and analysis methods to be shared between many of the major projects. Just as researchers build on, transmit, and verify knowledge through publication, open source analysis methods and software are creating a foundation that can be built upon, transmitted, and verified. Here we describe many of the major projects, their capabilities, and features. We also give an overview of the current state of open source software for fluorescent microscopy analysis and the many reasons to use and develop open source methods. Copyright © 2012 Elsevier Inc. All rights reserved.

Hybrid system for in vivo real-time planar fluorescence and volumetric optoacoustic imaging

Science.gov (United States)

Chen, Zhenyue; Deán-Ben, Xosé Luís.; Gottschalk, Sven; Razansky, Daniel

2018-02-01

Fluorescence imaging is widely employed in all fields of cell and molecular biology due to its high sensitivity, high contrast and ease of implementation. However, the low spatial resolution and lack of depth information, especially in strongly-scattering samples, restrict its applicability for deep-tissue imaging applications. On the other hand, optoacoustic imaging is known to deliver a unique set of capabilities such as high spatial and temporal resolution in three dimensions, deep penetration and spectrally-enriched imaging contrast. Since fluorescent substances can generate contrast in both modalities, simultaneous fluorescence and optoacoustic readings can provide new capabilities for functional and molecular imaging of living organisms. Optoacoustic images can further serve as valuable anatomical references based on endogenous hemoglobin contrast. Herein, we propose a hybrid system for in vivo real-time planar fluorescence and volumetric optoacoustic tomography, both operating in reflection mode, which synergistically combines the advantages of stand-alone systems. Validation of the spatial resolution and sensitivity of the system were first carried out in tissue mimicking phantoms while in vivo imaging was further demonstrated by tracking perfusion of an optical contrast agent in a mouse brain in the hybrid imaging mode. Experimental results show that the proposed system effectively exploits the contrast mechanisms of both imaging modalities, making it especially useful for accurate monitoring of fluorescence-based signal dynamics in highly scattering samples.

Quantitative magnetic resonance micro-imaging methods for pharmaceutical research.

Science.gov (United States)

Mantle, M D

2011-09-30

The use of magnetic resonance imaging (MRI) as a tool in pharmaceutical research is now well established and the current literature covers a multitude of different pharmaceutically relevant research areas. This review focuses on the use of quantitative magnetic resonance micro-imaging techniques and how they have been exploited to extract information that is of direct relevance to the pharmaceutical industry. The article is divided into two main areas. The first half outlines the theoretical aspects of magnetic resonance and deals with basic magnetic resonance theory, the effects of nuclear spin-lattice (T(1)), spin-spin (T(2)) relaxation and molecular diffusion upon image quantitation, and discusses the applications of rapid magnetic resonance imaging techniques. In addition to the theory, the review aims to provide some practical guidelines for the pharmaceutical researcher with an interest in MRI as to which MRI pulse sequences/protocols should be used and when. The second half of the article reviews the recent advances and developments that have appeared in the literature concerning the use of quantitative micro-imaging methods to pharmaceutically relevant research. Copyright © 2010 Elsevier B.V. All rights reserved.

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-04-15

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

Organization of fluorescent cholesterol analogs in lipid bilayers - lessons from cyclodextrin extraction.

Science.gov (United States)

Milles, Sigrid; Meyer, Thomas; Scheidt, Holger A; Schwarzer, Roland; Thomas, Lars; Marek, Magdalena; Szente, Lajos; Bittman, Robert; Herrmann, Andreas; Günther Pomorski, Thomas; Huster, Daniel; Müller, Peter

2013-08-01

To characterize the structure and dynamics of cholesterol in membranes, fluorescent analogs of the native molecule have widely been employed. The cholesterol content in membranes is in general manipulated by using water-soluble cyclodextrins. Since the interactions between cyclodextrins and fluorescent-labeled cholesterol have not been investigated in detail so far, we have compared the cyclodextrin-mediated membrane extraction of three different fluorescent cholesterol analogs (one bearing a NBD and two bearing BODIPY moieties). Extraction of these analogs was followed by measuring the Förster resonance energy transfer between a rhodamine moiety linked to phosphatidylethanolamine and the labeled cholesterol. The extraction kinetics revealed that the analogs are differently extracted from membranes. We examined the orientation of the analogs within the membrane and their influence on lipid condensation using NMR and EPR spectroscopies. Our data indicate that the extraction of fluorescent sterols from membranes is determined by several parameters, including their impact on lipid order, their hydrophobicity, their intermolecular interactions with surrounding lipids, their orientation within the bilayer, and their affinity with the exogenous acceptor. Copyright © 2013 Elsevier B.V. All rights reserved.

A virus-MIPs fluorescent sensor based on FRET for highly sensitive detection of JEV.

Science.gov (United States)

Liang, Caishuang; Wang, Huan; He, Kui; Chen, Chunyan; Chen, Xiaoming; Gong, Hang; Cai, Changqun

2016-11-01

Major stumbling blocks in the recognition and detection of virus are the unstable biological recognition element or the complex detection means. Here a fluorescent sensor based on virus-molecular imprinted polymers (virus-MIPs) was designed for specific recognition and highly sensitive detection of Japanese encephalitis virus (JEV). The virus-MIPs were anchored on the surface of silica microspheres modified by fluorescent dye, pyrene-1-carboxaldehyde (PC). The fluorescence intensity of PC can be enhanced by the principle of fluorescence resonance energy transfer (FRET), where virus acted as energy donor and PC acted as energy acceptor. The enhanced fluorescence intensity was proportional to the concentration of virus in the range of 24-960pM, with a limit of detection (LOD, 3σ) of 9.6pM, and the relative standard deviation was 1.99%. In additional, the specificity study confirmed the resultant MIPs has high-selectivity for JEV. This sensor would become a new key for the detection of virus because of its high sensitive, simple operation, high stability and low cost. Copyright © 2016. Published by Elsevier B.V.

Nitroxide radicals as contrast substances for magnetic resonance imaging diagnostics. Part 1

International Nuclear Information System (INIS)

Zhelev, Z.

2016-01-01

In last ten years, there is a significant progress in the selective and localized detection of redox-active compounds in the cells, tissues, and intact organisms. This progress is due to the development of new synthetic and genetically encoded redox-sensitive contrast substances, as well as due to the improvement of the techniques for their imaging: fluorescent, chemiluminescent, magnetic resonance, nuclear, ultrasonic. One of the most attractive redox-sensitive contrast substances are cyclic (stable) nitroxide radicals. They can be visualized and analyzed in vitro and in vivo by a variety of magnetic resonance techniques - electron-paramagnetic resonance imaging (EPRI), magnetic resonance imaging (MRI), Overhauser-enhanced MRI (OMRI). This review describes the merits and demerits of the nitroxide-enhanced EPR and MRI and the perspectives for their application in biomedical studies and clinical practice. The article is intended for a wide range of readers - from students to specialists in the field. Key words: Magnetic Resonance Imaging (MRI). Electron-Paramagnetic Resonance (EPR). Overhauser-Enhanced MRI (O MRI). Nitroxide

Coherent Population Trapping Resonances in Cs Atomic Vapor Layers of Micrometric Thickness

Directory of Open Access Journals (Sweden)

A. Krasteva

2011-01-01

Full Text Available We report on a novel behavior of the electromagnetically induced absorption (EIA resonance observed on the D2 line of Cs for atoms confined in cells with micrometric thickness. With the enhancement of light intensity, the EIA resonance amplitude suffers from fast reduction, and even at very low intensity (W < 1 mW/cm2, resonance sign reversal takes place and electromagnetically induced transparency (EIT resonance is observed. Similar EIA resonance transformation to EIT one is not observed in conventional cm-size cells. A theoretical model is proposed to analyze the physical processes behind the EIA resonance sign reversal with light intensity. The model involves elastic interactions between Cs atoms as well as elastic interaction of atom micrometric-cell windows, both resulting in depolarization of excited state which can lead to the new observations. The effect of excited state depolarization is confirmed also by the fluorescence (absorption spectra measurement in micrometric cells with different thicknesses.

Interaction between resonances through autoionization continua near the 4s-threshold in KrII

International Nuclear Information System (INIS)

Demekhin, Ph V; Petrov, I D; Lagutin, B M; Sukhorukov, V L; Vollweiler, F; Klumpp, S; Ehresmann, A; Schartner, K-H; Schmoranzer, H

2005-01-01

The interaction between resonances through autoionization continua and the interaction between autoionization continua were investigated theoretically and experimentally for the photoionization process of the 4p- and 4s-shells and for the population of 4p 4 ( 3 P)5s 4 P J , 4p 4 ( 3 P)5s 2 P J and 4p 4 ( 3 P)4d 4 D J satellites of KrII. Cross sections for the satellite production and the angular distribution parameter of the fluorescence radiation were measured by photon-induced fluorescence spectroscopy after excitationx with linearly polarized monochromatized synchrotron radiation at exciting-photon energies between 28.45 eV and 29.95 eV with an exciting-photon energy resolution of 10 meV (FWHM). Measured cross sections are in good agreement with the computed ones. A refined assignment of resonances in the proximity of the 4s 1 4p 6 5p resonance was performed. It was concluded that there is a strong influence of the core rearrangement, of the interaction between resonances through the autoionization continua and of the interaction between autoionization continua, on the investigated processes on the basis of the observed good overall agreement between the computed and measured quantities

Establishing a cellular FRET-based fluorescence plate reader assay to monitor proNGF-induced cross-linking of sortilin and the neurotrophin receptor p75(NTR)

DEFF Research Database (Denmark)

Skeldal, Sune; Kjaergaard, Maj M; Alwasel, Saleh

2015-01-01

the vps10p domain receptor sortilin and the neurotrophin receptor p75(NTR). However, proNGF-induced receptor complex formation has been difficult to directly assess other than by western blotting. We here describe a fluorescence resonance energy transfer (FRET) based fluorescence plate reader assay...

Metal complex-based templates and nanostructures for magnetic resonance/optical multimodal imaging agents

NARCIS (Netherlands)

Galindo Millan, Jealemy

2012-01-01

In this thesis, new approaches directed towards simple and functional imaging agents (IAs) for magnetic resonance (MR) and fluorescence multimodal imaging are proposed. In Chapter 3, hybrid silver nanostructures (hAgNSs), grown using a polyamino carboxylic acid scaffold, namely

A three-step reconstruction method for fluorescence molecular tomography based on compressive sensing

DEFF Research Database (Denmark)

Zhu, Yansong; Jha, Abhinav K.; Dreyer, Jakob K.

2017-01-01

Fluorescence molecular tomography (FMT) is a promising tool for real time in vivo quantification of neurotransmission (NT) as we pursue in our BRAIN initiative effort. However, the acquired image data are noisy and the reconstruction problem is ill-posed. Further, while spatial sparsity of the NT...... matrix coherence. The resultant image data are input to a homotopy-based reconstruction strategy that exploits sparsity via ℓ1 regularization. The reconstructed image is then input to a maximum-likelihood expectation maximization (MLEM) algorithm that retains the sparseness of the input estimate...... and improves upon the quantitation by accurate Poisson noise modeling. The proposed reconstruction method was evaluated in a three-dimensional simulated setup with fluorescent sources in a cuboidal scattering medium with optical properties simulating human brain cortex (reduced scattering coefficient: 9.2 cm-1...

MM-wave cyclotron auto-resonance maser for plasma heating

Science.gov (United States)

Ceccuzzi, S.; Dattoli, G.; Di Palma, E.; Doria, A.; Gallerano, G. P.; Giovenale, E.; Mirizzi, F.; Spassovsky, I.; Ravera, G. L.; Surrenti, V.; Tuccillo, A. A.

2014-02-01

Heating and Current Drive systems are of outstanding relevance in fusion plasmas, magnetically confined in tokamak devices, as they provide the tools to reach, sustain and control burning conditions. Heating systems based on the electron cyclotron resonance (ECRH) have been extensively exploited on past and present machines DEMO, and the future reactor will require high frequencies. Therefore, high power (≥1MW) RF sources with output frequency in the 200 - 300 GHz range would be necessary. A promising source is the so called Cyclotron Auto-Resonance Maser (CARM). Preliminary results of the conceptual design of a CARM device for plasma heating, carried out at ENEA-Frascati will be presented together with the planned R&D development.

Vesicular perylene dye nanocapsules as supramolecular fluorescent pH sensor systems.

Science.gov (United States)

Zhang, Xin; Rehm, Stefanie; Safont-Sempere, Marina M; Würthner, Frank

2009-11-01

Water-soluble, self-assembled nanocapsules composed of a functional bilayer membrane and enclosed guest molecules can provide smart (that is, condition responsive) sensors for a variety of purposes. Owing to their outstanding optical and redox properties, perylene bisimide chromophores are interesting building blocks for a functional bilayer membrane in a water environment. Here, we report water-soluble perylene bisimide vesicles loaded with bispyrene-based energy donors in their aqueous interior. These loaded vesicles are stabilized by in situ photopolymerization to give nanocapsules that are stable over the entire aqueous pH range. On the basis of pH-tunable spectral overlap of donors and acceptors, the donor-loaded polymerized vesicles display pH-dependent fluorescence resonance energy transfer from the encapsulated donors to the bilayer dye membrane, providing ultrasensitive pH information on their aqueous environment with fluorescence colour changes covering the whole visible light range. At pH 9.0, quite exceptional white fluorescence could be observed for such water-soluble donor-loaded perylene vesicles.

Detection of norovirus virus-like particles using a surface plasmon resonance-assisted fluoroimmunosensor optimized for quantum dot fluorescent labels.

Science.gov (United States)

Ashiba, Hiroki; Sugiyama, Yuki; Wang, Xiaomin; Shirato, Haruko; Higo-Moriguchi, Kyoko; Taniguchi, Koki; Ohki, Yoshimichi; Fujimaki, Makoto

2017-07-15

A highly sensitive biosensor to detect norovirus in environment is desired to prevent the spread of infection. In this study, we investigated a design of surface plasmon resonance (SPR)-assisted fluoroimmunosensor to increase its sensitivity and performed detection of norovirus virus-like particles (VLPs). A quantum dot fluorescent dye was employed because of its large Stokes shift. The sensor design was optimized for the CdSe-ZnS-based quantum dots. The optimal design was applied to a simple SPR-assisted fluoroimmunosensor that uses a sensor chip equipped with a V-shaped trench. Excitation efficiency of the quantum dots, degree of electric field enhancement by SPR, and intensity of autofluorescence of a substrate of the sensor chip were theoretically and experimentally evaluated to maximize the signal-to-noise ratio. As the result, an excitation wavelength of 390nm was selected to excite SPR on an Al film of the sensor chip. The sandwich assay of norovirus VLPs was performed using the designed sensor. Minimum detectable concentration of 0.01ng/mL, which corresponds to 100 virus-like particles included in the detection region of the V-trench, was demonstrated. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

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

Science.gov (United States)

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

2013-12-01

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

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

Directory of Open Access Journals (Sweden)

Noremylia Mohd Bakhori

2013-12-01

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

Optical micro-bubble resonators as promising biosensors

Science.gov (United States)

Giannetti, A.; Barucci, A.; Berneschi, S.; Cosci, A.; Cosi, F.; Farnesi, D.; Nunzi Conti, G.; Pelli, S.; Soria, S.; Tombelli, S.; Trono, C.; Righini, G. C.; Baldini, F.

2015-05-01

Recently, optical micro-bubble resonators (OMBRs) have gained an increasing interest in many fields of photonics thanks to their particular properties. These hollow microstructures can be suitable for the realization of label - free optical biosensors by combining the whispering gallery mode (WGM) resonator properties with the intrinsic capability of integrated microfluidics. In fact, the WGMs are morphology-dependent modes: any change on the OMBR inner surface (due to chemical and/or biochemical binding) causes a shift of the resonance position and reduces the Q factor value of the cavity. By measuring this shift, it is possible to obtain information on the concentration of the analyte to be detected. A crucial step for the development of an OMBR-based biosensor is constituted by the functionalization of its inner surface. In this work we report on the development of a physical and chemical process able to guarantee a good homogeneity of the deposed bio-layer and, contemporary, to preserve a high quality factor Q of the cavity. The OMBR capability of working as bioassay was proved by different optical techniques, such as the real time measurement of the resonance broadening after each functionalization step and fluorescence microscopy.

Wafer scale formation of monocrystalline silicon-based Mie resonators via silicon-on-insulator dewetting.

Science.gov (United States)

Abbarchi, Marco; Naffouti, Meher; Vial, Benjamin; Benkouider, Abdelmalek; Lermusiaux, Laurent; Favre, Luc; Ronda, Antoine; Bidault, Sébastien; Berbezier, Isabelle; Bonod, Nicolas

2014-11-25

Subwavelength-sized dielectric Mie resonators have recently emerged as a promising photonic platform, as they combine the advantages of dielectric microstructures and metallic nanoparticles supporting surface plasmon polaritons. Here, we report the capabilities of a dewetting-based process, independent of the sample size, to fabricate Si-based resonators over large scales starting from commercial silicon-on-insulator (SOI) substrates. Spontaneous dewetting is shown to allow the production of monocrystalline Mie-resonators that feature two resonant modes in the visible spectrum, as observed in confocal scattering spectroscopy. Homogeneous scattering responses and improved spatial ordering of the Si-based resonators are observed when dewetting is assisted by electron beam lithography. Finally, exploiting different thermal agglomeration regimes, we highlight the versatility of this technique, which, when assisted by focused ion beam nanopatterning, produces monocrystalline nanocrystals with ad hoc size, position, and organization in complex multimers.

In Vivo Lighted Fluorescence via Fenton Reaction: Approach for Imaging of Hydrogen Peroxide in Living Systems.

Science.gov (United States)

Liu, Changhui; Chen, Weiju; Qing, Zhihe; Zheng, Jing; Xiao, Yue; Yang, Sheng; Wang, Lili; Li, Yinhui; Yang, Ronghua

2016-04-05

By virtue of its high sensitivity and rapidity, Fenton reaction has been demonstrated as a powerful tool for in vitro biochemical analysis; however, in vivo applications of Fenton reaction still remain to be exploited. Herein, we report, for the first time, the design, formation and testing of Fenton reaction for in vivo fluorescence imaging of hydrogen peroxide (H2O2). To realize in vivo fluorescence imaging of H2O2 via Fenton reaction, a functional nanosphere, Fc@MSN-FDNA/PTAD, is fabricated from mesoporous silica nanoparticle (MSN), a Fenton reagent of ferrocene (Fc), ROX-labeled DNA (FDNA), and a cationic perylene derivative (PTAD). The ferrocene molecules are locked in the pore entrances of MSN, and exterior of MSN is covalently immobilized with FDNA. As a key part, PTAD acts as not only the gatekeeper of MSN but also the efficient quencher of ROX. H2O2 can permeate into the nanosphere and react with ferrocene to product hydroxyl radical (·OH) via Fenton reaction, which cleaves FDNA to detach ROX from PTAD, thus in turn, lights the ROX fluorescence. Under physiological condition, H2O2 can be determined from 5.0 nM to 1.0 μM with a detection limit of 2.4 nM. Because of the rapid kinetics of Fenton reaction and high specificity for H2O2, the proposed method meets the requirement for real applications. The feasibility of Fc@MSN-FDNA/PTAD for in vivo applications is demonstrated for fluorescence imaging of exogenous and endogenous H2O2 in cells and mice. We expect that this work will not only contribute to the H2O2-releated studies but also open up a new way to exploit in vivo Fenton reaction for biochemical research.

Smart detection of microRNAs through fluorescence enhancement on a photonic crystal.

Science.gov (United States)

Pasquardini, L; Potrich, C; Vaghi, V; Lunelli, L; Frascella, F; Descrovi, E; Pirri, C F; Pederzolli, C

2016-04-01

The detection of low abundant biomarkers, such as circulating microRNAs, demands innovative detection methods with increased resolution, sensitivity and specificity. Here, a biofunctional surface was implemented for the selective capture of microRNAs, which were detected through fluorescence enhancement directly on a photonic crystal. To set up the optimal biofunctional surface, epoxy-coated commercially available microscope slides were spotted with specific anti-microRNA probes. The optimal concentration of probe as well as of passivating agent were selected and employed for titrating the microRNA hybridization. Cross-hybridization of different microRNAs was also tested, resulting negligible. Once optimized, the protocol was adapted to the photonic crystal surface, where fluorescent synthetic miR-16 was hybridized and imaged with a dedicated equipment. The photonic crystal consists of a dielectric multilayer patterned with a grating structure. In this way, it is possible to take advantage from both a resonant excitation of fluorophores and an angularly redirection of the emitted radiation. As a result, a significant fluorescence enhancement due to the resonant structure is collected from the patterned photonic crystal with respect to the outer non-structured surface. The dedicated read-out system is compact and based on a wide-field imaging detection, with little or no optical alignment issues, which makes this approach particularly interesting for further development such as for example in microarray-type bioassays. Copyright © 2016 Elsevier B.V. All rights reserved.

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.

An aptamer-based fluorescence bio-sensor for chiral recognition of arginine enantiomers.

Science.gov (United States)

Yuan, Haiyan; Huang, Yunmei; Yang, Jidong; Guo, Yuan; Zeng, Xiaoqing; Zhou, Shang; Cheng, Jiawei; Zhang, Yuhui

2018-07-05

In this study, a novel aptamer - based fluorescence bio-sensor (aptamer-AuNps) was developed for chiral recognition of arginine (Arg) enantiomers based on aptamer and gold nanoparticles (AuNps). Carboxyfluorescein (FAM) labeled aptamers (Apt) were absorbed on AuNps and their fluorescence intensity could be significantly quenched by AuNps based on fluorescence resonance energy transfer (FRET). Once d-Arg or l-Arg were added into the above solution, the aptamer specifically bind to Arg enantiomers and released from AuNps, so the fluorescence intensity of d-Arg system and l-Arg system were all enhanced. The affinity of Apt to l-Arg is tighter to d-Arg, so the enhanced fluorescence signals of l-Arg system was stronger than d-Arg system. What's more, the enhanced fluorescence were directly proportional to the concentration of d-Arg and l-Arg ranging from 0-300 nM and 0-400 nM with related coefficients of 0.9939 and 0.9952, respectively. Furthermore, the method was successfully applied to detection l-Arg in human urine samples with satisfactory results. Eventually, a simple "OR" logic gate with d-Arg &l-Arg as inputs and AuNps aggregation state as outputs was fabricated, which can help us understand the chiral recognition process deeply. Copyright © 2018 Elsevier B.V. All rights reserved.

Breaking the color barrier - a multi-selective antibody reporter offers innovative strategies of fluorescence detection.

Science.gov (United States)

Gallo, Eugenio; Jarvik, Jonathan W

2017-08-01

A novel bi-partite fluorescence platform exploits the high affinity and selectivity of antibody scaffolds to capture and activate small-molecule fluorogens. In this report, we investigated the property of multi-selectivity activation by a single antibody against diverse cyanine family fluorogens. Our fluorescence screen identified three cell-impermeant fluorogens, each with unique emission spectra (blue, green and red) and nanomolar affinities. Most importantly, as a protein fusion tag to G-protein-coupled receptors, the antibody biosensor retained full activity - displaying bright fluorogen signals with minimal background on live cells. Because fluorogen-activating antibodies interact with their target ligands via non-covalent interactions, we were able to perform advanced multi-color detection strategies on live cells, previously difficult or impossible with conventional reporters. We found that by fine-tuning the concentrations of the different color fluorogen molecules in solution, a user may interchange the fluorescence signal (onset versus offset), execute real-time signal exchange via fluorogen competition, measure multi-channel fluorescence via co-labeling, and assess real-time cell surface receptor traffic via pulse-chase experiments. Thus, here we inform of an innovative reporter technology based on tri-color signal that allows user-defined fluorescence tuning in live-cell applications. © 2017. Published by The Company of Biologists Ltd.

Deep UV Native Fluorescence Imaging of Antarctic Cryptoendolithic Communities

Science.gov (United States)

Storrie-Lombardi, M. C.; Douglas, S.; Sun, H.; McDonald, G. D.; Bhartia, R.; Nealson, K. H.; Hug, W. F.

2001-01-01

An interdisciplinary team at the Jet Propulsion Laboratory Center for Life Detection has embarked on a project to provide in situ chemical and morphological characterization of Antarctic cryptoendolithic microbial communities. We present here in situ deep ultraviolet (UV) native fluorescence and environmental scanning electron microscopy images transiting 8.5 mm into a sandstone sample from the Antarctic Dry Valleys. The deep ultraviolet imaging system employs 224.3, 248.6, and 325 nm lasers to elicit differential fluorescence and resonance Raman responses from biomolecules and minerals. The 224.3 and 248.6 nm lasers elicit a fluorescence response from the aromatic amino and nucleic acids. Excitation at 325 nm may elicit activity from a variety of biomolecules, but is more likely to elicit mineral fluorescence. The resultant fluorescence images provide in situ chemical and morphological maps of microorganisms and the associated organic matrix. Visible broadband reflectance images provide orientation against the mineral background. Environmental scanning electron micrographs provided detailed morphological information. The technique has made possible the construction of detailed fluorescent maps extending from the surface of an Antarctic sandstone sample to a depth of 8.5 mm. The images detect no evidence of microbial life in the superficial 0.2 mm crustal layer. The black lichen component between 0.3 and 0.5 mm deep absorbs all wavelengths of both laser and broadband illumination. Filamentous deep ultraviolet native fluorescent activity dominates in the white layer between 0.6 mm and 5.0 mm from the surface. These filamentous forms are fungi that continue into the red (iron-rich) region of the sample extending from 5.0 to 8.5 mm. Using differential image subtraction techniques it is possible to identify fungal nuclei. The ultraviolet response is markedly attenuated in this region, apparently from the absorption of ultraviolet light by iron-rich particles coating

Analysis of plastid number, size, and distribution in Arabidopsis plants by light and fluorescence microscopy.

Science.gov (United States)

Pyke, Kevin

2011-01-01

Methods are described which allow one to observe chloroplasts in mesophyll cells from leaves of Arabidopsis, determine their number per cell, measure their area, and determine a value for chloroplast coverage inside mesophyll cells. Non-green plastids can also be imaged either by using staining, or by exploiting fluorescent proteins targeted to the plastid in non-green parts of the plant, such as the roots, in transgenic Arabidopsis.

A near-infrared fluorescent bioassay for thrombin using aptamer-modified CuInS2 quantum dots

International Nuclear Information System (INIS)

Lin, Zihan; Hu, Tianyu; Liu, Ziping; Su, Xingguang; Pan, Dong

2015-01-01

We describe a near-infrared (NIR) fluorescent thrombin assay using a thrombin-binding aptamer (TBA) and Zn(II)-activated CuInS 2 quantum dots (Q-dots). The fluorescence of Zn(II)-activated Q-dots is quenched by the TBA via photoinduced electron transfer, but if thrombin is added, it will bind to TBA to form G-quadruplexes and the Q-dots are released. As a result, the fluorescence intensity of the system is restored. This effect was exploited to design an assay for thrombin whose calibration plot, under optimum conditions, is linear in the 0.034 to 102 nmol L −1 concentration range, with a 12 pmol L −1 detection limit. The method is fairly simple, fast, and due to its picomolar detection limits holds great potential in the diagnosis of diseases associated with coagulation abnormalities and certain kinds of cancer. (author)

Preventing Raman Lasing in High-Q WGM Resonators

Science.gov (United States)

Savchenkov, Anatoliy; Matsko, Andrey; Strekalov, Dmitry; Maleki, Lute

2007-01-01

A generic design has been conceived to suppress the Raman effect in whispering- gallery-mode (WGM) optical resonators that have high values of the resonance quality factor (Q). Although it is possible to exploit the Raman effect (even striving to maximize the Raman gain to obtain Raman lasing), the present innovation is intended to satisfy a need that arises in applications in which the Raman effect inhibits the realization of the full potential of WGM resonators as frequency-selection components. Heretofore, in such applications, it has been necessary to operate high-Q WGM resonators at unattractively low power levels to prevent Raman lasing. (The Raman-lasing thresholds of WGM optical resonators are very low and are approximately proportional to Q(sup -2)). Heretofore, two ways of preventing Raman lasting at high power levels have been known, but both entail significant disadvantages: A resonator can be designed so that the optical field is spread over a relatively large mode volume to bring the power density below the threshold. For any given combination of Q and power level, there is certain mode volume wherein Raman lasing does not start. Unfortunately, a resonator that has a large mode volume also has a high spectral density, which is undesirable in a typical photonic application. A resonator can be cooled to the temperature of liquid helium, where the Raman spectrum is narrower and, therefore, the Raman gain is lower. However, liquid-helium cooling is inconvenient. The present design overcomes these disadvantages, making it possible to operate a low-spectral-density (even a single-mode) WGM resonator at a relatively high power level at room temperature, without risk of Raman lasing.

Simultaneous detection of transgenic DNA by surface plasmon resonance imaging with potential application to gene doping detection.

Science.gov (United States)

Scarano, Simona; Ermini, Maria Laura; Spiriti, Maria Michela; Mascini, Marco; Bogani, Patrizia; Minunni, Maria

2011-08-15

Surface plasmon resonance imaging (SPRi) was used as the transduction principle for the development of optical-based sensing for transgenes detection in human cell lines. The objective was to develop a multianalyte, label-free, and real-time approach for DNA sequences that are identified as markers of transgenosis events. The strategy exploits SPRi sensing to detect the transgenic event by targeting selected marker sequences, which are present on shuttle vector backbone used to carry out the transfection of human embryonic kidney (HEK) cell lines. Here, we identified DNA sequences belonging to the Cytomegalovirus promoter and the Enhanced Green Fluorescent Protein gene. System development is discussed in terms of probe efficiency and influence of secondary structures on biorecognition reaction on sensor; moreover, optimization of PCR samples pretreatment was carried out to allow hybridization on biosensor, together with an approach to increase SPRi signals by in situ mass enhancement. Real-time PCR was also employed as reference technique for marker sequences detection on human HEK cells. We can foresee that the developed system may have potential applications in the field of antidoping research focused on the so-called gene doping.

Resonance Polarization and Phase-Mismatched CARS of Pheophytin b Excited in the Qy Band

NARCIS (Netherlands)

de Boeij, W.P.; Lucassen, G.W.; Lucassen, Gerald; Otto, Cornelis; Greve, Jan

1993-01-01

Resonance polarization and phase-mismatched coherent anti-Stokes Raman scattering (CARS) measurements were performed on pheophytin b dissolved in acetone excited in the Qy absorption band, where strong broad fluorescence makes spontaneous Raman spectroscopy impossible. The phase-mismatching

Fluorescence lidar measurements at the archaeological site House of Augustus at Palatino, Rome

Science.gov (United States)

Raimondi, Valentina; Alisi, Chiara; Barup, Kerstin; Bracciale, Maria Paola; Broggi, Alessandra; Conti, Cinzia; Hällström, Jenny; Lognoli, David; Palombi, Lorenzo; Santarelli, Maria Laura; Sprocati, Anna Rosa

2013-10-01

Early diagnostics and documentation fulfill an essential role for an effective planning of conservation and restoration of cultural heritage assets. In particular, remote sensing techniques that do not require the use of scaffolds or lifts, such as fluoresence lidar, can provide useful information to obtain an overall assessment of the status of the investigated surfaces and can be exploited to address analytical studies in selected areas. Here we present the results of a joint Italian-Swedish project focused on documenting and recording the status of some sections of the part closed to the public by using fluorescence hyperspectral imaging lidar. The lidar used a tripled-frequency Nd:YAG laser emitting at 355 nm as excitation source and an intensified, gated 512x512-pixel CCD as detector. The lidar had imaging capabilities thanks to a computer-controlled scanning mirror. The fluorescence characteristics of fresco wall paintings were compared to those of fresco fragments found at the same archaeological site and separately examined in the lab using FT-IR and Raman techniques for the identification of pigments. The fluorescence lidar was also used to remotely detect the growth of phototrophic biodeteriogens on the walls. The fluorescence lidar data were compared with results from biological sampling, cultivation and laboratory analysis by molecular techniques.

Laplacian manifold regularization method for fluorescence molecular tomography

Science.gov (United States)

He, Xuelei; Wang, Xiaodong; Yi, Huangjian; Chen, Yanrong; Zhang, Xu; Yu, Jingjing; He, Xiaowei

2017-04-01

Sparse regularization methods have been widely used in fluorescence molecular tomography (FMT) for stable three-dimensional reconstruction. Generally, ℓ1-regularization-based methods allow for utilizing the sparsity nature of the target distribution. However, in addition to sparsity, the spatial structure information should be exploited as well. A joint ℓ1 and Laplacian manifold regularization model is proposed to improve the reconstruction performance, and two algorithms (with and without Barzilai-Borwein strategy) are presented to solve the regularization model. Numerical studies and in vivo experiment demonstrate that the proposed Gradient projection-resolved Laplacian manifold regularization method for the joint model performed better than the comparative algorithm for ℓ1 minimization method in both spatial aggregation and location accuracy.

Photoresponse of 60Ni below 10-MeV excitation energy: Evolution of dipole resonances in fp-shell nuclei near N=Z

Science.gov (United States)

Scheck, M.; Ponomarev, V. Yu.; Fritzsche, M.; Joubert, J.; Aumann, T.; Beller, J.; Isaak, J.; Kelley, J. H.; Kwan, E.; Pietralla, N.; Raut, R.; Romig, C.; Rusev, G.; Savran, D.; Schorrenberger, L.; Sonnabend, K.; Tonchev, A. P.; Tornow, W.; Weller, H. R.; Zilges, A.; Zweidinger, M.

2013-10-01

Background: Within the last decade, below the giant dipole resonance the existence of a concentration of additional electric dipole strength has been established. This accumulation of low-lying E1 strength is commonly referred to as pygmy dipole resonance (PDR).Purpose: The photoresponse of 60Ni has been investigated experimentally and theoretically to test the evolution of the PDR in a nucleus with only a small neutron excess. Furthermore, the isoscalar and isovector M1 resonances were investigated.Method: Spin-1 states were excited by exploiting the (γ,γ') nuclear resonance fluorescence technique with unpolarized continuous bremsstrahlung as well as with fully linearly polarized, quasimonochromatic, Compton-backscattered laser photons in the entrance channel of the reaction.Results: Up to 10 MeV a detailed picture of J=1 levels was obtained. For the preponderant number of the individual levels spin and parity were firmly assigned. Furthermore, branching ratios, transition widths, and reduced B(E1) or B(M1) excitation probability were calculated from the measured scattering cross sections. A comparison with theoretical results obtained within the quasiparticle phonon model allows an insight into the microscopic structure of the observed states.Conclusions: Below 10 MeV the directly observed E1 strength [∑B(E1)↑=(153.8±9.5) e2(fm)2] exhausts 0.5% of the Thomas-Reiche-Kuhn sum rule. This value increases to 0.8% of the sum rule [∑B(E1)↑=(250.9±31.1) e2(fm)2] when indirectly observed branches to lower-lying levels are considered. Two accumulations of M1 excited spin-1 states near 8 and 9 MeV excitation energy are identified as isoscalar and isovector M1 resonances dominated by proton and neutron f7/2→f5/2 spin-flip excitations. The B(M1)↑ strength of these structures accumulates to 3.94(27)μN2.