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Sample records for time-resolved fluorescence spectroscopy

  1. Time-resolved Hyperspectral Fluorescence Spectroscopy using Frequency Modulated Excitation

    SciTech Connect

    ,; Neill, M

    2012-07-01

    An intensity-modulated excitation light source is used together with a micro channel plate intensified CCD (ICCD) detector gated at a slightly different frequency to generate a beat frequency from a fluorescent sample. The addition of a spectrograph produces a hyperspectral time-resolved data product where the resulting beat frequency is detected with a low frame rate camera. Measuring the beat frequency of the spectrum as a function of time allows separation of the excited fluorescence from ambient constant light sources. The excitation and detector repetition rates are varied over a range of discrete frequencies, and the phase shift of the beat wave maps out the emission decay rate(s).

  2. Time-resolved FRET fluorescence spectroscopy of visible fluorescent protein pairs.

    PubMed

    Visser, A J W G; Laptenok, S P; Visser, N V; van Hoek, A; Birch, D J S; Brochon, J-C; Borst, J W

    2010-01-01

    Förster resonance energy transfer (FRET) is a powerful method for obtaining information about small-scale lengths between biomacromolecules. Visible fluorescent proteins (VFPs) are widely used as spectrally different FRET pairs, where one VFP acts as a donor and another VFP as an acceptor. The VFPs are usually fused to the proteins of interest, and this fusion product is genetically encoded in cells. FRET between VFPs can be determined by analysis of either the fluorescence decay properties of the donor molecule or the rise time of acceptor fluorescence. Time-resolved fluorescence spectroscopy is the technique of choice to perform these measurements. FRET can be measured not only in solution, but also in living cells by the technique of fluorescence lifetime imaging microscopy (FLIM), where fluorescence lifetimes are determined with the spatial resolution of an optical microscope. Here we focus attention on time-resolved fluorescence spectroscopy of purified, selected VFPs (both single VFPs and FRET pairs of VFPs) in cuvette-type experiments. For quantitative interpretation of FRET-FLIM experiments in cellular systems, details of the molecular fluorescence are needed that can be obtained from experiments with isolated VFPs. For analysis of the time-resolved fluorescence experiments of VFPs, we have utilised the maximum entropy method procedure to obtain a distribution of fluorescence lifetimes. Distributed lifetime patterns turn out to have diagnostic value, for instance, in observing populations of VFP pairs that are FRET-inactive. PMID:19693494

  3. Excitation emission and time-resolved fluorescence spectroscopy of selected varnishes used in historical musical instruments.

    PubMed

    Nevin, Austin; Echard, Jean-Philippe; Thoury, Mathieu; Comelli, Daniela; Valentini, Gianluca; Cubeddu, Rinaldo

    2009-11-15

    The analysis of various varnishes from different origins, which are commonly found on historical musical instruments was carried out for the first time with both fluorescence excitation emission spectroscopy and laser-induced time-resolved fluorescence spectroscopy. Samples studied include varnishes prepared using shellac, and selected diterpenoid and triterpenoid resins from plants, and mixtures of these materials. Fluorescence excitation emission spectra have been collected from films of naturally aged varnishes. In parallel, time-resolved fluorescence spectroscopy of varnishes provides means for discriminating between short- (less than 2.0 ns) and long-lived (greater than 7.5 ns) fluorescence emissions in each of these complex materials. Results suggest that complementary use of the two non destructive techniques allows a better understanding of the main fluorophores responsible for the emission in shellac, and further provides means for distinguishing the main classes of other varnishes based on differences in fluorescence lifetime behaviour. Spectrofluorimetric data and time resolved spectra presented here may form the basis for the interpretation of results from future in situ fluorescence examination and time resolved fluorescence imaging of varnished musical instruments. PMID:19782228

  4. Multispectral scanning time-resolved fluorescence spectroscopy (TRFS) technique for intravascular diagnosis

    PubMed Central

    Xie, Hongtao; Bec, Julien; Liu, Jing; Sun, Yang; Lam, Matthew; Yankelevich, Diego R.; Marcu, Laura

    2012-01-01

    This study describes a scanning time-resolved fluorescence spectroscopy (TRFS) system designed to continuously acquire fluorescence emission and to reconstruct fluorescence lifetime images (FLIM) from a luminal surface by using a catheter-based optical probe with rotary joint and pull-back device. The ability of the system to temporally and spectrally resolve the fluorescence emission from tissue was validated using standard dyes and tissue phantoms (e.g., ex vivo pig aorta phantom). Current results demonstrate that this system is capable to reliably resolve the fluorescence emission of multiple fluorophores located in the lumen; and suggest its potential for intravascular detection of distinct biochemical features of atherosclerotic plaques. PMID:22808425

  5. 256 × 2 SPAD line sensor for time resolved fluorescence spectroscopy.

    PubMed

    Krstajić, Nikola; Levitt, James; Poland, Simon; Ameer-Beg, Simon; Henderson, Robert

    2015-03-01

    We present a CMOS chip 256 × 2 single photon avalanche diode (SPAD) line sensor, 23.78 µm pitch, 43.7% fill factor, custom designed for time resolved emission spectroscopy (TRES). Integrating time-to-digital converters (TDCs) implement on-chip mono-exponential fluorescence lifetime pre-calculation allowing timing of 65k photons/pixel at 200 Hz line rate at 40 ps resolution using centre-of-mass method (CMM). Per pixel time-correlated single-photon counting (TCSPC) histograms can also be generated with 320 ps bin resolution. We characterize performance in terms of dark count rate, instrument response function and lifetime uniformity for a set of fluorophores with lifetimes ranging from 4 ns to 6 ns. Lastly, we present fluorescence lifetime spectra of multicolor microspheres and skin autofluorescence acquired using a custom built spectrometer. In TCSPC mode, time-resolved spectra are acquired within 5 minutes whilst in CMM mode spectral lifetime signatures are acquired within 2 ms for fluorophore in cuvette and 200 ms for skin autofluorescence. We demonstrate CMOS line sensors to be a versatile tool for time-resolved fluorescence spectroscopy by providing parallelized and flexible spectral detection of fluorescence decay. PMID:25836796

  6. Design and evaluation of a device for fast multispectral time-resolved fluorescence spectroscopy and imaging

    SciTech Connect

    Yankelevich, Diego R.; Department of Biomedical Engineering, University of California, 451 Health Sciences Drive, Davis, California 95616 ; Ma, Dinglong; Liu, Jing; Sun, Yang; Sun, Yinghua; Bec, Julien; Marcu, Laura; Elson, Daniel S.

    2014-03-15

    The application of time-resolved fluorescence spectroscopy (TRFS) to in vivo tissue diagnosis requires a method for fast acquisition of fluorescence decay profiles in multiple spectral bands. This study focusses on development of a clinically compatible fiber-optic based multispectral TRFS (ms-TRFS) system together with validation of its accuracy and precision for fluorescence lifetime measurements. It also presents the expansion of this technique into an imaging spectroscopy method. A tandem array of dichroic beamsplitters and filters was used to record TRFS decay profiles at four distinct spectral bands where biological tissue typically presents fluorescence emission maxima, namely, 390, 452, 542, and 629 nm. Each emission channel was temporally separated by using transmission delays through 200 μm diameter multimode optical fibers of 1, 10, 19, and 28 m lengths. A Laguerre-expansion deconvolution algorithm was used to compensate for modal dispersion inherent to large diameter optical fibers and the finite bandwidth of detectors and digitizers. The system was found to be highly efficient and fast requiring a few nano-Joule of laser pulse energy and <1 ms per point measurement, respectively, for the detection of tissue autofluorescent components. Organic and biological chromophores with lifetimes that spanned a 0.8–7 ns range were used for system validation, and the measured lifetimes from the organic fluorophores deviated by less than 10% from values reported in the literature. Multi-spectral lifetime images of organic dye solutions contained in glass capillary tubes were recorded by raster scanning the single fiber probe in a 2D plane to validate the system as an imaging tool. The lifetime measurement variability was measured indicating that the system provides reproducible results with a standard deviation smaller than 50 ps. The ms-TRFS is a compact apparatus that makes possible the fast, accurate, and precise multispectral time-resolved fluorescence lifetime measurements of low quantum efficiency sub-nanosecond fluorophores.

  7. Design and evaluation of a device for fast multispectral time-resolved fluorescence spectroscopy and imaging.

    PubMed

    Yankelevich, Diego R; Ma, Dinglong; Liu, Jing; Sun, Yang; Sun, Yinghua; Bec, Julien; Elson, Daniel S; Marcu, Laura

    2014-03-01

    The application of time-resolved fluorescence spectroscopy (TRFS) to in vivo tissue diagnosis requires a method for fast acquisition of fluorescence decay profiles in multiple spectral bands. This study focusses on development of a clinically compatible fiber-optic based multispectral TRFS (ms-TRFS) system together with validation of its accuracy and precision for fluorescence lifetime measurements. It also presents the expansion of this technique into an imaging spectroscopy method. A tandem array of dichroic beamsplitters and filters was used to record TRFS decay profiles at four distinct spectral bands where biological tissue typically presents fluorescence emission maxima, namely, 390, 452, 542, and 629 nm. Each emission channel was temporally separated by using transmission delays through 200 μm diameter multimode optical fibers of 1, 10, 19, and 28 m lengths. A Laguerre-expansion deconvolution algorithm was used to compensate for modal dispersion inherent to large diameter optical fibers and the finite bandwidth of detectors and digitizers. The system was found to be highly efficient and fast requiring a few nano-Joule of laser pulse energy and <1 ms per point measurement, respectively, for the detection of tissue autofluorescent components. Organic and biological chromophores with lifetimes that spanned a 0.8-7 ns range were used for system validation, and the measured lifetimes from the organic fluorophores deviated by less than 10% from values reported in the literature. Multi-spectral lifetime images of organic dye solutions contained in glass capillary tubes were recorded by raster scanning the single fiber probe in a 2D plane to validate the system as an imaging tool. The lifetime measurement variability was measured indicating that the system provides reproducible results with a standard deviation smaller than 50 ps. The ms-TRFS is a compact apparatus that makes possible the fast, accurate, and precise multispectral time-resolved fluorescence lifetime measurements of low quantum efficiency sub-nanosecond fluorophores. PMID:24689603

  8. Design and evaluation of a device for fast multispectral time-resolved fluorescence spectroscopy and imaging

    PubMed Central

    Yankelevich, Diego R.; Ma, Dinglong; Liu, Jing; Sun, Yang; Sun, Yinghua; Bec, Julien; Elson, Daniel S.; Marcu, Laura

    2014-01-01

    The application of time-resolved fluorescence spectroscopy (TRFS) to in vivo tissue diagnosis requires a method for fast acquisition of fluorescence decay profiles in multiple spectral bands. This study focusses on development of a clinically compatible fiber-optic based multispectral TRFS (ms-TRFS) system together with validation of its accuracy and precision for fluorescence lifetime measurements. It also presents the expansion of this technique into an imaging spectroscopy method. A tandem array of dichroic beamsplitters and filters was used to record TRFS decay profiles at four distinct spectral bands where biological tissue typically presents fluorescence emission maxima, namely, 390, 452, 542, and 629 nm. Each emission channel was temporally separated by using transmission delays through 200 ?m diameter multimode optical fibers of 1, 10, 19, and 28 m lengths. A Laguerre-expansion deconvolution algorithm was used to compensate for modal dispersion inherent to large diameter optical fibers and the finite bandwidth of detectors and digitizers. The system was found to be highly efficient and fast requiring a few nano-Joule of laser pulse energy and <1 ms per point measurement, respectively, for the detection of tissue autofluorescent components. Organic and biological chromophores with lifetimes that spanned a 0.87 ns range were used for system validation, and the measured lifetimes from the organic fluorophores deviated by less than 10% from values reported in the literature. Multi-spectral lifetime images of organic dye solutions contained in glass capillary tubes were recorded by raster scanning the single fiber probe in a 2D plane to validate the system as an imaging tool. The lifetime measurement variability was measured indicating that the system provides reproducible results with a standard deviation smaller than 50 ps. The ms-TRFS is a compact apparatus that makes possible the fast, accurate, and precise multispectral time-resolved fluorescence lifetime measurements of low quantum efficiency sub-nanosecond fluorophores. PMID:24689603

  9. Probing Ternary Complex Equilibria of Crown Ether Ligands by Time-Resolved Fluorescence Spectroscopy

    PubMed Central

    2015-01-01

    Ternary complex formation with solvent molecules and other adventitious ligands may compromise the performance of metal-ion-selective fluorescent probes. As Ca(II) can accommodate more than 6 donors in the first coordination sphere, commonly used crown ether ligands are prone to ternary complex formation with this cation. The steric strain imposed by auxiliary ligands, however, may result in an ensemble of rapidly equilibrating coordination species with varying degrees of interaction between the cation and the specific donor atoms mediating the fluorescence response, thus diminishing the change in fluorescence properties upon Ca(II) binding. To explore the influence of ligand architecture on these equilibria, we tethered two structurally distinct aza-15-crown-5 ligands to pyrazoline fluorophores as reporters. Due to ultrafast photoinduced electron-transfer (PET) quenching of the fluorophore by the ligand moiety, the fluorescence decay profile directly reflects the species composition in the ground state. By adjusting the PET driving force through electronic tuning of the pyrazoline fluorophores, we were able to differentiate between species with only subtle variations in PET donor abilities. Concluding from a global analysis of the corresponding fluorescence decay profiles, the coordination species composition was indeed strongly dependent on the ligand architecture. Altogether, the combination of time-resolved fluorescence spectroscopy with selective tuning of the PET driving force represents an effective analytical tool to study dynamic coordination equilibria and thus to optimize ligand architectures for the design of high-contrast cation-responsive fluorescence switches. PMID:25313708

  10. Structure and dynamics of a DNA: polymerase complex by time-resolved fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Millar, David P.; Benkovic, Stephen J.

    1990-05-01

    The interaction of a fluorescent DNA primer:template with the Klenow fragment of DNA polymerase I has been studied in solution using time-resolved fluorescence spectroscopy. The excited-state decay behavior and internal reorientation dynamics of a dansyl sulfonamide probe connected by a propyl chain to a modified uridine base in the primer strand were very sensitive to the local probe environment and exhibited characteristic changes upon binding of Kienow fragment to the DNA and elongation of the primer strand. Between 5 and 7 bases of duplex DNA upstream of the 3' primer terminus were protected from the solvent by the Kienow fragment and the strength of DNA:protein contacts varied within this region, being strongest at the 3' primer terminus. About 5% of the substrates were bound in a second spatially distinct site on the enzyme. Site-directed mutagenesis of the Kienow fragment was consistent with this being the active site for 3'->5' exonuclease activity.

  11. Time-resolved fluorescence polarization spectroscopy of visible and near infrared dyes in picosecond dynamics

    NASA Astrophysics Data System (ADS)

    Pu, Yang; Alfano, Robert R.

    2015-03-01

    Near-infrared (NIR) dyes absorb and emit light within the range from 700 to 900 nm have several benefits in biological studies for one- and/or two-photon excitation for deeper penetration of tissues. These molecules undergo vibrational and rotational motion in the relaxation of the excited electronic states, Due to the less than ideal anisotropy behavior of NIR dyes stemming from the fluorophores elongated structures and short fluorescence lifetime in picosecond range, no significant efforts have been made to recognize the theory of these dyes in time-resolved polarization dynamics. In this study, the depolarization of the fluorescence due to emission from rotational deactivation in solution will be measured with the excitation of a linearly polarized femtosecond laser pulse and a streak camera. The theory, experiment and application of the ultrafast fluorescence polarization dynamics and anisotropy are illustrated with examples of two of the most important medical based dyes. One is NIR dye, namely Indocyanine Green (ICG) and is compared with Fluorescein which is in visible range with much longer lifetime. A set of first-order linear differential equations was developed to model fluorescence polarization dynamics of NIR dye in picosecond range. Using this model, the important parameters of ultrafast polarization spectroscopy were identified: risetime, initial time, fluorescence lifetime, and rotation times.

  12. Time-resolved laser fluorescence spectroscopy of UO2(CO3)3(4-).

    PubMed

    Jung, E C; Cho, H-R; Baik, M H; Kim, H; Cha, W

    2015-11-21

    The objective of the present study is to examine the luminescence characteristics of UO2(CO3)3(4-) in detail using time-resolved laser fluorescence spectroscopy. The peak wavelengths and lifetime of UO2(CO3)3(4-) were determined at room temperature using the two excitation laser wavelengths of 266 and 448 nm. The peak wavelengths in the luminescence spectrum exhibited hypsochromic shifts compared with those of UO2(2+). The lifetime determined from several samples containing various uranium concentrations was 8.9 ± 0.8 ns. Explanations for the hindrance to the observation of the luminescence spectrum of UO2(CO3)3(4-) in previous investigations are discussed. The representative experimental parameters, which might interrupt the measurement of weak luminescence, are the insertion delay time of the detection device, the overlapped luminescence of the background materials and the primary inner filter effect in the sample solution. PMID:26460936

  13. Time-resolved confocal fluorescence spectroscopy reveals the structure and metabolic state of epithelial tissue

    NASA Astrophysics Data System (ADS)

    Wu, Yicong; Zheng, Wei; Qu, Jianan Y.

    2007-02-01

    Autofluorescence spectroscopy has been a widely explored technique for in vivo and noninvasive diagnosis of pre-cancer lesions in epithelium where 90% cancers originate. For extracting more accurate fluorescence information for cancer diagnosis, depth-resolved fluorescence measurements are crucial to assess NADH and FAD in non-keratinized epithelial layer and collagen in stromal layer, respectively. In this study, we achieved the depth-resolved fluorescence spectral measurements of squamous epithelial tissue based on confocal technique. We found that in non-keratinized epithelial layer the fluorescence signals excited at 405 nm were the combination of NADH and FAD fluorescence and could be used for evaluating the redox ratio. Moreover, we found that confocal time-resolved autofluorescence measurements of epithelial tissue with 405 nm excitations could provide the information on the layered tissue structure. All depth-resolved autofluorescence decays were accurately fitted with a dual-exponential function consisting of a short lifetime (0.4 ~ 0.6 ns) and a long lifetime (3 ~ 4 ns) components. The short lifetime component dominated the decay of non-keratinzied epithelial fluorescence while the decay of the signals from keratinized epithelium and stroma were mainly determined by the long lifetime component. The ratio of the amplitudes of two components could be used to differentiate the layered structure of epithelial tissue. In general, the results in this study demonstrated that the combined depth- and timeresolved fluorescence measurements can produce the information on the layered structure and localized biochemistry of epithelial tissue for the diagnosis of tissue pathology.

  14. Time-resolved spectroscopy of the intrinsic fluorescence of nucleic acid species

    NASA Astrophysics Data System (ADS)

    Daniels, Malcolm; Hart, Lucas P.; Ho, Paul S.; Ballini, Jean-Pierre; Vigny, Paul

    1990-05-01

    Polarization and lifetime studies have shown that the fluorescence from nucleic acid species is complex, both at the individual chromophore level and because of the effect of stacking interactions on the electronic states. Recent work aimed at elucidating some aspects of this behavior by decay analysis and time-resolved spectroscopy is surveyed. Experimental work has been carried out using the ACO synchrotron at LURE, France) with time-correlated single photon counting, or a frequency-doubled N2-pumped dye laser, pulse width 700 ps, with fast-gated (100 ps width) analog detection and signal averaging. Decay curves are treated by global analysis using the Marquardt non-linear least-squares algorithm (synchrotron data) or the SPLMOD program (EMBO), which carries out a non-linear leastsquares minimization using cubic splines, for the laser data. Resolution of the decay data gives a model-based estimate of the number of components and their lifetimes. This information is then used to deconvolute timewindowed spectra (time-delayed spectra) into the time-resolved spectra. It is a particular feature of the combination of delayed photon counting with the continuous wavelength distribution of pulsed synchrotron radiation that excitation spectra correlating with emissions of different lifetimes can be obtained by uninterrupted repetitive scanning over a wide range of exciting wavelengths, in the present work from 230 nm to 354 urn. Such time-delayed excitation spectra can also be deconvoluted into components corresponding to the various time-resolved emission spectra. Examples of these three types of information viz resolved lifetimes, time-resolved emission spectra and their excitation spectra are presented and discussed for the following systems. I. adenosine; 6N, 6N-dimethyladenosine; protonated adenosine; this work shows the role of rotamers in the excited state behavior of this chromophore and demonstrates the forbidden nature of the lowest excited state. II. d(AT); d(TA); we observe the sequence dependence of emission from the stacked state which has been observed previously in polarization studies and an unusual excitation spectrum. III. d(CG); poly d(CG), "B"-DNA structure; single crystal duplex d(CG)3, "Z"-DNA structure. Distinctive differences are observed between the stacked emissions from the "B" and "Z" structures which we attribute to different overlapping of the stacked bases.

  15. Time-resolved fluorescence spectroscopy and ultrasound backscatter microscopy for nondestructive evaluation of vascular grafts

    PubMed Central

    Fatakdawala, Hussain; Griffiths, Leigh G.; Humphrey, Sterling; Marcu, Laura

    2014-01-01

    Abstract. Quantitative and qualitative evaluations of structure and composition are important in monitoring development of engineered vascular tissue both in vitro and in vivo. Destructive techniques are an obstacle for performing time-lapse analyses from a single sample or animal. This study demonstrates the ability of time-resolved fluorescence spectroscopy (TRFS) and ultrasound backscatter microscopy (UBM), as nondestructive and synergistic techniques, for compositional and morphological analyses of tissue grafts, respectively. UBM images and integrated backscatter coefficients demonstrate the ability to visualize and quantify postimplantation changes in vascular graft biomaterials such as loss of the external elastic lamina and intimal/medial thickening over the grafted region as well as graft integration with the surrounding tissue. TRFS results show significant changes in spectra, average lifetime, and fluorescence decay parameters owing to changes in collagen, elastin, and cellular content between normal and grafted tissue regions. These results lay the foundation for the application of a catheter-based technique for in vivo evaluation of vascular grafts using TRFS and UBM. PMID:25147960

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

    PubMed

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

    2015-08-01

    Photosynthetic organisms change the quantity and/or quality of their pigment-protein complexes and the interactions among these complexes in response to light conditions. In the present study, we analyzed light adaptation of the unicellular red alga Cyanidioschyzon merolae, whose pigment composition is similar to that of cyanobacteria because its phycobilisomes (PBS) lack phycoerythrin. C. merolae were grown under different light qualities, and their responses were measured by steady-state absorption, steady-state fluorescence, and picosecond time-resolved fluorescence spectroscopies. Cells were cultivated under four monochromatic light-emitting diodes (blue, green, yellow, and red), and changes in pigment composition and energy transfer were observed. Cells grown under blue and green light increased their relative phycocyanin levels compared with cells cultured under white light. Energy-transfer processes to photosystem I (PSI) were sensitive to yellow and red light. The contribution of direct energy transfer from PBS to PSI increased only under yellow light, while red light induced a reduction in energy transfer from photosystem II to PSI and an increase in energy transfer from light-harvesting chlorophyll protein complex I to PSI. Differences in pigment composition, growth, and energy transfer under different light qualities are discussed. PMID:25577254

  17. Intraoperative delineation of primary brain tumors using time-resolved fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Butte, Pramod V.; Fang, Qiyin; Jo, Javier A.; Yong, William H.; Pikul, Brian K.; Black, Keith L.; Marcu, Laura

    2010-03-01

    The goal of this study is to determine the potential of time-resolved laser-induced fluorescence spectroscopy (TR-LIFS) as an adjunctive tool for delineation of brain tumor from surrounding normal tissue in order to assist the neurosurgeon in near-complete tumor excision. A time-domain TR-LIFS prototype apparatus (gated photomultiplier detection, fast digitizer) was used for recording tissue autofluorescence in normal cortex (NC), normal white matter (NWM), and various grades of gliomas intraoperatively. Tissue fluorescence was induced with a pulsed nitrogen laser (337 nm, 700 ps), and the intensity decay profiles were recorded in the 360- to 550-nm spectral range (10-nm interval). Histopathological analysis (hematoxylin & eosin) of the biopsy samples taken from the site of TR-LIFS measurements was used for validation of spectroscopic results. Preliminary results on 17 patients demonstrate that normal cortex (N=16) and normal white matter (N=3) show two peaks of fluorescence emission at 390 nm (lifetime=1.8+/-0.3 ns) and 460 nm (lifetime=0.8+/-0.1 ns). The 390-nm emission peak is absent in low-grade glioma (N=5; lifetime=1.1 ns) and reduced in high-grade glioma (N=9; lifetime=1.7+/-0.4 ns). The emission characteristics at 460 nm in all tissues correlated with the nicotinamide adenine dinucleotide fluorescence (peak: 440 to 460 nm lifetime: 0.8 to 1.0 ns). These findings demonstrate the potential of using TR-LIFS as a tool for enhanced delineation of brain tumors during surgery. In addition, this study evaluates similarities and differences between TR-LIFS signatures of brain tumors obtained in vivo and those previously reported in ex vivo brain tumor specimens.

  18. Adsorption of Uranyl on Gibbsite: A Time-Resolved Laser-Induced Fluorescence Spectroscopy Study

    SciTech Connect

    Chang, Hyun-shik; Korshin, Gregory V.; Wang, Zheming; Zachara, John M.

    2006-02-15

    Uranyl adsorbed on gibbsite at pH 4.0-8.0 and ionic strengths (ISs) 0.001-0.4 M (NaClO4) in the absence of carbonate was studied using time-resolved laser-induced fluorescence spectroscopy (TRLIFS) under cryogenic conditions. TRLIFS data showed the presence of several distinct emission components. Their contributions were determined using the evolving factor analysis approach. Four components denoted as species A, B, C, and D were discerned. Each of them was characterized by a characteristic response to pH and IS changes and also by a unique combination of the values of the fundamental transition energy E0,0, vibronic spacing E, and half-width of the vibronic lines W. Species A and B were major contributors to the overall emission. They were mainly affected by the pH and predominated below and above pH 5.0, respectively. In contrast with that, the contribution of species C was noticeable only at IS = 0.001 M, while it was suppressed or absent at high IS values. It was concluded that species A and B are likely to correspond to inner-sphere surface aluminol complexes AlO-(UO2)+ and AlO-(UO2)OH, while species C was hypothesized to correspond to electrostatically bound uranyl complexes (predominantly [UO2(OH)3]-).

  19. Time-Resolved Light Scattering and Fluorescence Spectroscopy in Biomedical and Model Random Media

    NASA Astrophysics Data System (ADS)

    Das, Bidyut Baran

    Optical spectroscopy, light scattering and ultrafast time-gated imaging have been shown to offer novel approaches to study the optical characteristics of various biomedical and other random media. Fluorescence spectra from human malignant and nonmalignant breast tissues were measured at 300 nm excitation and a significant spectral difference was found between the two tissue types by using the ratio of fluorescence intensities at 340 and 440 nm. Optical density measurements on thin breast tissues show that the scattering cross-sections of breast tissues are relatively constant over the visible and the uv region. Transport mean free paths and the absorption lengths for various tissues and model random media were measured using time-resolved transmission. The scattering coefficients for human breast and chicken tissues were found to remain relatively constant in 570-630 nm wavelength region while they change significantly at 1064 nm. Chicken breast and fat tissues were found to be good models for human breast tissues as the values of the optical parameters of the two tissue types are about the same. The less scattering observed at 1064 nm makes tissues more transparent in the NIR region making it easier to image in thick tissues. Time-resolved backscattering measurements show that the scattering and the absorption parameters of a random medium can be obtained accurately in a two-fiber configuration as long as the radial distance is more than about seven times the transport mean free path of the sample. The single point source-detection configuration provides a tool to diagnose breast malignancy though it fails to give accurate values of the optical parameters of tissues. This failure is attributed to the invalidity of the diffusion approximation in this experimental configuration. A 2.5 mm thin chicken fat strip was imaged inside a 40 mm thick chicken breast tissue using snake photons at 625 nm with ultrafast time-gated detection. A simple model to describe the effect of small objects embedded inside a highly scattering medium on the attenuation of snake photons is developed.

  20. Time resolved fluorescence spectroscopy of quercetin and morin complexes with Al 3+

    NASA Astrophysics Data System (ADS)

    Gutierrez, Amanda C.; Gehlen, Marcelo H.

    2002-01-01

    The association process of Al 3+ with quercetin and morin in methanol was studied by electronic absorption and emission spectroscopies. The number of species in solution with different absorption spectra were determined by the method of Rank analysis of the absorbance matrix, and the stoichiometries of the complexes were evaluated using the Job method. The number of fluorescent species in solution were calculated from the Rank analysis method of the time resolved emission spectra (TRES), and compared with a global analysis of the decay surface using a proper multi-exponential decay model. The association of Al 3+ with morin gives rise to two complexes with 1:1 and 2:1 (morin: Al 3+) stoichiometries, but in both species the association of the cation involves the carbonyl and 3-hydroxyl groups of the pyrone ring. The fluorescence decay surface of this system is biexponential and the lifetimes of the 1:1 and 2:1 complexes are 4.3 and 2.0 ns, respectively. The association of Al 3+ with quercetin forms preferentially two complexes with 1:1 and 1:2 (quercetin: Al 3+) stoichiometries where the first cation binds to the site of the pyrone ring but the second one is bound to the cathecol group of the molecule. However, the multichelation character of the quercetin ligand allows larger aggregates to be formed, thereby the species Al 2Q 3 is also detected in methanol. The lifetime of the 1:1 complex is about 2.7 ns, while for 1:2 and 3:2 complexes the lifetimes measured are 3.5 and 1.8 ns, respectively.

  1. Detection of rhodopsin dimerization in situ by PIE-FCCS, a time-resolved fluorescence spectroscopy.

    PubMed

    Smith, Adam W

    2015-01-01

    Rhodopsin self-associates in the plasma membrane. At low concentrations, the interactions are consistent with a monomer-dimer equilibrium (Comar et al., J Am Chem Soc 136(23):8342-8349, 2014). At high concentrations in native tissue, higher-order clusters have been observed (Fotiadis et al., Nature 421:127-128, 2003). The physiological role of rhodopsin dimerization is still being investigated, but it is clear that a quantitative assessment is essential to determining the function of rhodopsin clusters in vision. To quantify rhodopsin interactions, I will outline the theory and methodology of a specialized time-resolved fluorescence spectroscopy for measuring membrane protein-protein interactions called pulsed-interleaved excitation fluorescence cross-correlation spectroscopy (PIE-FCCS). The strength of this technique is its ability to quantify rhodopsin interactions in situ (i.e., a live cell plasma membrane). There are two reasons for restricting the scope to live cell membranes. First, the compositional heterogeneity of the plasma membrane creates a complex milieu with thousands of lipid, protein, and carbohydrate species. This makes it difficult to infer quaternary interactions from detergent solubilized samples or construct a model phospholipid bilayer that recapitulates all of the interactions present in native membranes. Second, organizational structure and dynamics is a key feature of the plasma membrane, and fixation techniques like formaldehyde cross-linking and vitrification will modulate the interactions. PIE-FCCS is based on two-color fluorescence imaging with time-correlated single-photon counting (TCSPC) (Becker et al., Rev Sci Instrum 70:1835-1841, 1999). By time-tagging every detected photon, the data can be analyzed as a fluorescence intensity distribution, fluorescence lifetime histogram, or fluorescence (cross-)correlation spectra (FCS/FCCS) (Becker, Advanced time-correlated single-photon counting techniques, Springer, Berlin, 2005). These analysis tools can then be used to quantify protein concentration, mobility, clustering, and Förster resonance energy transfer (FRET). In this paper I will focus on PIE-FCCS, which interleaves two wavelength excitation events in time so that the effects of spectral cross-talk and FRET can be isolated. In this way it is possible to characterize monomer-dimer-oligomer equilibria with high accuracy (Müller et al., Biophys J 89:3508-3522, 2005). Currently, PIE-FCCS requires a customized equipment configuration that will be described below. There is an excellent protocol that outlines traditional FCCS on a commercially available instrument (Bacia and Schwille, Nat Protoc 2:2842-2856, 2007). The PIE-FCCS approach is a relatively recent advance in FCCS that has been used in live cell assays to quantify lipid-anchored protein clustering (Triffo et al., J Am Chem Soc 134:10833-10842, 2012), epidermal growth factor receptor dimerization (Endres et al., Cell 152:543-556, 2013), and recently the dimerization of opsin (Comar et al., J Am Chem Soc 136(23):8342-8349, 2014). This paper will outline the theory and instrumentation requirements for PIE-FCCS, as well as the data collection and analysis process. PMID:25697526

  2. Time-resolved fluorescence spectroscopy of white-spot caries in human enamel.

    PubMed

    Ferretti de Oliveira, Fernanda; Ito, Amando Siuiti; Bachmann, Luciano

    2010-04-20

    The objective is to differentiate noncavitated caries enamel through time-resolved fluorescence and to find excitation and emission parameters that can be applied in future clinical practice for detection of caries lesions that are not clearly visible to the professional. Sixteen human teeth with noncavitiated white-spot caries were selected for this work. Fluorescence intensity decay was measured by using an apparatus based on the time-correlated single-photon counting method. An optical fiber bundle was employed for sample excitation (440 nm), and the fluorescence collected by the same bundle (500 nm) was registered. The average lifetime for sound enamel was 7.93+/-0.09, 2.46+/-0.04, and 0.51+/-0.02 ns, whereas for the carious enamel the lifetimes were 4.84+/-0.06, 1.35+/-0.02, and 0.16+/-0.01 ns. It was concluded that it is possible to differentiate between carious and sound regions by time-resolved fluorescence and that, although the origin of enamel fluorescence is still uncertain, the lifetime values seem to be typical of fluorophores like collagen I. PMID:20411003

  3. Time-resolved and steady-state fluorescence spectroscopy from bacteria subjected to bactericidal agents

    NASA Astrophysics Data System (ADS)

    Katz, Alvin; Alimova, Alexandra; Siddique, Masood; Savage, Howard E.; Shah, Mahendra; Rosen, Richard; Alfano, Robert

    2004-03-01

    The time-resolved and steady-state changes in fluorescence were investigated from one spore-forming (Bacillus subtilis) and four non-spore forming (Escherichia coli, Staphylococcus aureus, Enterococcus faecalis, and Pseudomonas aeruginosa) bacteria subjected to different bactericidal agents. The bactericidal agents were sodium hypochlorite (bleach) hydrogen peroxide, formaldehyde, and UV light exposure. Application of sodium hypochlorite resulted in an almost total lose of fluorescence signal and large decrease in the optical density of the bacterial suspension. Addition of hydrogen peroxide resulted in a 35% decrease in emission intensity fom the Sa and an 85-95% decrease for the other bacteria. Ultraviolet light exposure resulted in a 5-35% decrease in the emission intensity of the tryptophan band. The addition of formaldehyde to the bacteria did not result in significant changes in the steady-state emission intensity, but did shift the tryptophan emission peak position to shorter wavelengths by 3 to 5 nm. Time-resolved fluorescence measurements showed that the fluorescence lifetime of tryptophan in the bacteria could not be described by a single exponential decay, and was similar to that of tryptophan in neutral aqueous solution. Upon addition of formaldehyde to the Gram positive bacteria (Bs and Sa) the strength of the short lifetime component increased dramatically, while for the Gram negative bacteria, a smaller increase was observed. These fluorescence changes reflect the different mechanisms of the bactericidal agents and may provide a useful tool to monitor the effectiveness of disinfectants.

  4. Drug/protein interactions studied by time-resolved fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Gustavsson, Thomas; Markovitsi, Dimitra; Vay, Ignacio; Bonanca, Paula; Jimnez, M. C.; Miranda, Miguel A.

    2014-09-01

    We report here on a recent time-resolved fluorescence study [1] of the interaction between flurbiprofen (FBP), a chiral non-steroidal anti-inflammatory drug, and human serum albumin (HSA), the main transport protein in the human body. We compare the results obtained for the drug-protein complex with those of various covalently linked flurbiprofentryptophan dyads having well-defined geometries. In all cases stereoselective dynamic fluorescence quenching is observed, varying greatly from one system to another. In addition, the fluorescence anisotropy decays also display a clear stereoselectivity. For the drug-protein complexes, this can be interpreted in terms of the protein microenvironment playing a significant role in the conformational relaxation of FBP, which is more restricted in the case of the (R)- enantiomer.

  5. Analysis of hydrocarbon-bearing fluid inclusions (HCFI) using time-resolved fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Przyjalgowski, Milosz A.; Ryder, Alan G.; Feely, Martin; Glynn, Thomas J.

    2005-06-01

    Hydrocarbon-bearing fluid inclusions (HCFI) are microscopic cavities within rocks that are filled with petroleum oil, the composition of which may not have changed since the trapping event. Thus, the composition of that entrapped oil can provide information about the formation and evolution of the oil reservoir. This type of information is important to the petroleum production and exploration industries. Crude oil fluorescence originates from the presence of cyclic aromatic compounds and the nature of the emission is governed by the chemical composition of the oil. Fluorescence based methods are widely used for analysis of crude oil because they offer robust, non-contact and non-destructive measurement options. The goal of our group is the development of a non-destructive analytical method for HCFI using time-resolved fluorescence methods. In broad terms, crude oil fluorescence behavior is governed by the concentration of quenching species and the distribution of fluorophores. For the intensity averaged fluorescence lifetime, the best correlations have been found between polar or alkane concentrations, but these are not suitable for robust, quantitative analysis. We have recently started to investigate another approach for characterizing oils by looking at Time-resolved Emission Spectra (TRES). TRES are constructed from intensities sampled at discrete times during the fluorescence decay of the sample. In this study, TRES, from a series of 10 crude oils from the Middle East, have been measured at discrete time gates (0.5 ns, 1 ns, 2 ns, 4 ns) over the 450-700 nm wavelength range. The spectral changes in TRES, such as time gate dependent Stokes' shift and spectral broadening, are analyzed in the context of energy transfer rates. In this work, the efficacy of using TRES for fingerprinting individual oils and HCFI is also demonstrated.

  6. A novel time-resolved laser fluorescence spectroscopy system for research on complexation of uranium(IV).

    PubMed

    Lehmann, S; Geipel, G; Grambole, G; Bernhard, G

    2009-09-01

    To date only a small number of studies have investigated the chemical speciation of complexes and the fluorescence properties of metal ions whose emitted fluorescence lifetime is in the range of only few nanoseconds. This is due to a lack of advanced methods which allow the conduction of these measurements. In the current study we set up a new time-resolved laser fluorescence spectroscopy system with which the fluorescence properties of metal ions with very short fluorescence lifetimes such as uranium(IV) and its compounds can be investigated. By studying the fluorescence properties of uranium(IV) in perchloric acid, we showed uranium(IV) to have a detection limit of 5 x 10(-7)M and a fluorescence decay time of 2.74+/-0.36 ns. We further investigated the fluorescence properties of uranium(IV) during the reaction with fluoride and applied our novel laser system to study the complexation of uranium(IV) with fluoride. Our data revealed the formation of a 1:1 complex of uranium(IV) and fluoride. The corresponding complex formation constant of uranium(IV) fluoride UF(3+) was found to be log beta(0)=9.43+/-1.94. Our results demonstrate that our novel time-resolved laser fluorescence spectroscopy system can successfully conduct speciation measurements of metal ions and their compounds with very short-lived fluorescence lifetimes. Using this laser system, it is possible to analytically investigate such elements and compounds in environmentally relevant concentration ranges. PMID:19442574

  7. [Discrimination of Crude Oil Samples Using Laser-Induced Time-Resolved Fluorescence Spectroscopy].

    PubMed

    Han, Xiao-shuang; Liu, De-qing; Luan, Xiao-ning; Guo, Jin-jia; Liu, Yong-xin; Zheng, Rong-er

    2016-02-01

    The Laser-induced fluorescence spectra combined with pattern recognition method has been widely applied in discrimination of different spilled oil, such as diesel, gasoline, and crude oil. However, traditional three-dimension fluorescence analysis method, which is not adapted to requirement of field detection, is limited to laboratory investigatio ns. The development of oil identification method for field detection is significant to quick response and operation of oil spill. In this paper, a new method based on laser-induced time-resolved fluorescence combined with support vector machine (SVM) model was introduced to discriminate crude oil samples. In this method, time-resolved spectra data was descended into two dimensions with selecting appropriate range in time and wavelength domains respectively to form a SVM data base. It is found that the classification accurate rate increased with an appropriate selection. With a selected range from 54 to 74 ns in time domain, the classification accurate rate has been increased from 83.3% (without selection) to 88.1%. With a selected wavelength range of 387.00~608.87 nm, the classification accurate rate of suspect oil was improved from 84% (without selection) to 100%. Since the detection delay of fluorescence lidar fluctuates due to wave and platform swing, the identification method with optimizing in both time and wavelength domains could offer a better flexibility for field applications. It is hoped that the developed method could provide some useful reference with data reduction for classification of suspect crude oil in the future development. PMID:27209747

  8. Time-resolved and steady-state fluorescence spectroscopy for the assessment of skin photoaging process

    NASA Astrophysics Data System (ADS)

    D´Almeida, Camila de Paula; Campos, Carolina; Saito Nogueira, Marcelo; Pratavieira, Sebastião.; Kurachi, Cristina

    2015-06-01

    pathology. The optical properties of these intrinsic fluorophores respond to the microenvironment and the metabolic status, thus making fluorescence spectroscopy a valuable tool to study the conditions of biological tissues. The purpose of this study is to investigate the hairless mice skin metabolic changes during the photoaging process through lifetime and fluorescence measurements targeting NADH and FAD. Two lasers centered at 378 nm and 445 nm, respectively, perform excitation of NADH and FAD. The fluorescence acquisition is carried out at mice dorsal and ventral regions throughout the photoaging protocol and aging process. Differences in fluorescence and lifetime data between young and photoaged mice measurements were observed. The endogenous fluorescence spectrum of photoaged dorsal skin showed an increase compared to young and aged skin. Lifetime of bound NADH and free FAD presented an increase in the first week that continued until the end of the protocol. Aging process is being investigated to complement the information obtained from fluorescence data and lifetime of photoaging process.

  9. Detection of cancer cells in prostate tissue with time-resolved fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Gerich, C. E.; Opitz, J.; Toma, M.; Sergon, M.; Füssel, S.; Nanke, R.; Fehre, J.; Wirth, M.; Baretton, G.; Schreiber, J.

    2011-03-01

    Goals: Improving cancer diagnosis is one of the important challenges at this time. The precise differentiation between benign and malignant tissue is in the oncology and oncologic surgery of the utmost significance. A new diagnostic system, that facilitates the decision which tissue has to be removed, would be appreciated. In previous studies many attempts were made to use tissue fluorescence for cancer recognition. However, no clear correlation was found between tissue type and fluorescence parameters like time and wavelength dependent fluorescence intensity I(t, λ). The present study is focused on cooperative behaviour of cells in benign or malignant prostates tissue reflecting differences in their metabolism. Material and Methods: 50 prostate specimens were obtained directly after radical prostatectomy and from each specimen 6 punch biopsies were taken. Time-resolved fluorescence spectra were recorded for 4 different measurement points for each biopsy. The pathologist evaluated each measurement point separately. An algorithm was developed to determine a relevant parameter of the time dependent fluorescence data (fractal dimension DF ). The results of the finding and the DF -value were correlated for each point and then analysed with statistical methods. Results: A total of 1200 measurements points were analysed. The optimal algorithm and conditions for discrimination between malignant and non-malignant tissue areas were found. The correct classification could be stated in 93.4% of analysed points. The ROC-curve (AUC = 0.94) confirms the chosen statistical method as well as it informs about the specificity (0.94) and sensitivity (0.90). Conclusion: The new method seems to offer a very helpful diagnostic tool for pathologists as well as for surgery.

  10. TIME-RESOLVED VIBRATIONAL SPECTROSCOPY

    SciTech Connect

    Andrei Tokmakoff, MIT; Paul Champion, Northeastern University; Edwin J. Heilweil, NIST; Keith A. Nelson, MIT; Larry Ziegler, Boston University

    2009-05-14

    This document contains the Proceedings from the 14th International Conference on Time-Resolved Vibrational Spectroscopy, which was held in Meredith, NH from May 9-14, 2009. The study of molecular dynamics in chemical reaction and biological processes using time-resolved spectroscopy plays an important role in our understanding of energy conversion, storage, and utilization problems. Fundamental studies of chemical reactivity, molecular rearrangements, and charge transport are broadly supported by the DOE’s Office of Science because of their role in the development of alternative energy sources, the understanding of biological energy conversion processes, the efficient utilization of existing energy resources, and the mitigation of reactive intermediates in radiation chemistry. In addition, time-resolved spectroscopy is central to all five of DOE’s grand challenges for fundamental energy science. The Time-Resolved Vibrational Spectroscopy conference is organized biennially to bring the leaders in this field from around the globe together with young scientists to discuss the most recent scientific and technological advances. The latest technology in ultrafast infrared, Raman, and terahertz spectroscopy and the scientific advances that these methods enable were covered. Particular emphasis was placed on new experimental methods used to probe molecular dynamics in liquids, solids, interfaces, nanostructured materials, and biomolecules.

  11. In vivo detection of macrophages in a rabbit atherosclerotic model by time-resolved laser-induced fluorescence spectroscopy.

    PubMed

    Marcu, Laura; Fang, Qiyin; Jo, Javier A; Papaioannou, Thanassis; Dorafshar, Amir; Reil, Todd; Qiao, Jian-Hua; Baker, J Dennis; Freischlag, Julie A; Fishbein, Michael C

    2005-08-01

    Accumulation of numerous macrophages in the fibrous cap is a key identifying feature of plaque inflammation and vulnerability. This study investigates the use of time-resolved laser-induced fluorescence spectroscopy (TR-LIFS) as a potential tool for detection of macrophage foam cells in the intima of atherosclerotic plaques. Experiments were conducted in vivo on 14 New Zealand rabbits (6 control, 8 hypercholesterolemic) following aortotomy to expose the intimal luminal surface of the aorta. Tissue autofluorescence was induced with a nitrogen pulse laser (337 nm, 1 ns). Lesions were histologically classified by the percent of collagen or macrophage foam cells as well as thickness of the intima. Using parameters derived from the time-resolved fluorescence emission of plaques, we determined that intima rich in macrophage foam cells can be distinguished from intima rich in collagen with high sensitivity (>85%) and specificity (>95%). This study demonstrates, for the first time, that a time-resolved fluorescence-based technique can differentiate and demark macrophage content versus collagen content in vivo. Our results suggest that TR-LIFS technique can be used in clinical applications for identification of inflammatory cells important in plaque formation and rupture. PMID:16039283

  12. Synthesis of Ag clusters in microemulsions: A time-resolved UV vis and fluorescence spectroscopy study

    NASA Astrophysics Data System (ADS)

    Ledo, Ana; Martínez, F.; López-Quintela, M. A.; Rivas, J.

    2007-09-01

    The combined use of the microemulsion technique and the kinetic control allows the preparation of small silver clusters. By using UV-vis and fluorescence spectroscopy the main stages by which the clusters grow, before the formation of nanoparticles, were elucidated. Transmission electron microscopy (TEM) and scanning tunnelling microscopy (STM) were used to further characterize the samples. Two main stages were clearly identified, which are associated with: (1) the formation of Ag n clusters with n<10, which self-aggregate into one atom high 2D nanodiscs of 3.2 nm size and (2) Ag n clusters, which self-aggregate into 3D nanostructures of 1.5 nm in size. The fluorescence properties observed with both stages show that the formed clusters are small enough to display a molecule-like behaviour.

  13. Solvation dynamics of coumarin 153 embedded in AOT + phenol organogels studied by time-resolved fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Nishiyama, Katsura; Takata, Kei; Watanabe, Keiichi; Shigematsu, Hirotake

    2012-03-01

    We investigate solvation dynamics of organogel utilizing ps-ns fluorescence spectroscopy. The organogel studied in this Letter comprises bis(2-ethylhexyl) sulfosuccinate (AOT) and p-chlorophenol in the m-xylene solvent, that produce an organogel architecture with self-assembly. Within the organogel, an emitting probe, coumarin 153 (C153), is embedded. We then obtain dynamic response functions of solvation derived from the time-resolved fluorescence spectra of C153. We propose that total energy of the C153-organogel system relaxes with a relaxation time of 3.9 ns, whereas the entire rearrangement of the organogel structure around C153 is achieved with that of 6.1 ns, respectively.

  14. Coherent photon interference elimination and spectral correction in femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy.

    PubMed

    Dang, Wei; Mao, Pengcheng; Weng, Yuxiang

    2013-07-01

    We report an improved setup of femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy (FNOPAS) with a 210 fs temporal response. The system employs a Cassegrain objective to collect and focus fluorescence photons, which eliminates the interference from the coherent photons in the fluorescence amplification by temporal separation of the coherent photons and the fluorescence photons. The gain factor of the Cassegrain objective-assisted FNOPAS is characterized as 1.24 10(5) for Rhodamine 6G. Spectral corrections have been performed on the transient fluorescence spectra of Rhodamine 6G and Rhodamine 640 in ethanol by using an intrinsic calibration curve derived from the spectrum of superfluorescence, which is generated from the amplification of the vacuum quantum noise. The validity of spectral correction is illustrated by comparisons of spectral shape and peak wavelength between the corrected transient fluorescence spectra of these two dyes acquired by FNOPAS and their corresponding standard reference spectra collected by the commercial streak camera. The transient fluorescence spectra of the Rhodamine 6G were acquired in an optimized phase match condition, which gives a deviation in the peak wavelength between the retrieved spectrum and the reference spectrum of 1.0 nm, while those of Rhodamine 640 were collected in a non-optimized phase match condition, leading to a deviation in a range of 1.0-3.0 nm. Our results indicate that the improved FNOPAS can be a reliable tool in the measurement of transient fluorescence spectrum for its high temporal resolution and faithfully corrected spectrum. PMID:23902042

  15. Coherent photon interference elimination and spectral correction in femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy

    NASA Astrophysics Data System (ADS)

    Dang, Wei; Mao, Pengcheng; Weng, Yuxiang

    2013-07-01

    We report an improved setup of femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy (FNOPAS) with a 210 fs temporal response. The system employs a Cassegrain objective to collect and focus fluorescence photons, which eliminates the interference from the coherent photons in the fluorescence amplification by temporal separation of the coherent photons and the fluorescence photons. The gain factor of the Cassegrain objective-assisted FNOPAS is characterized as 1.24 × 105 for Rhodamine 6G. Spectral corrections have been performed on the transient fluorescence spectra of Rhodamine 6G and Rhodamine 640 in ethanol by using an intrinsic calibration curve derived from the spectrum of superfluorescence, which is generated from the amplification of the vacuum quantum noise. The validity of spectral correction is illustrated by comparisons of spectral shape and peak wavelength between the corrected transient fluorescence spectra of these two dyes acquired by FNOPAS and their corresponding standard reference spectra collected by the commercial streak camera. The transient fluorescence spectra of the Rhodamine 6G were acquired in an optimized phase match condition, which gives a deviation in the peak wavelength between the retrieved spectrum and the reference spectrum of 1.0 nm, while those of Rhodamine 640 were collected in a non-optimized phase match condition, leading to a deviation in a range of 1.0-3.0 nm. Our results indicate that the improved FNOPAS can be a reliable tool in the measurement of transient fluorescence spectrum for its high temporal resolution and faithfully corrected spectrum.

  16. Homogeneous time-resolved G protein-coupled receptor-ligand binding assay based on fluorescence cross-correlation spectroscopy.

    PubMed

    Antoine, Thomas; Ott, David; Ebell, Katharina; Hansen, Kerrin; Henry, Luc; Becker, Frank; Hannus, Stefan

    2016-06-01

    G protein-coupled receptors (GPCRs) mediate many important physiological functions and are considered as one of the most successful therapeutic target classes for a wide spectrum of diseases. Drug discovery projects generally benefit from a broad range of experimental approaches for screening compound libraries and for the characterization of binding modes of drug candidates. Owing to the difficulties in solubilizing and purifying GPCRs, assay formats have been so far mainly limited to cell-based functional assays and radioligand binding assays. In this study, we used fluorescence cross-correlation spectroscopy (FCCS) to analyze the interaction of detergent-solubilized receptors to various types of GPCR ligands: endogenous peptides, small molecules, and a large surrogate antagonist represented by a blocking monoclonal antibody. Our work demonstrates the suitability of the homogeneous and time-resolved FCCS assay format for a robust, high-throughput determination of receptor-ligand binding affinities and kinetic rate constants for various therapeutically relevant GPCRs. PMID:26954998

  17. Modified diglycol-amides for actinide separation: solvent extraction and time-resolved laser fluorescence spectroscopy complexation studies

    SciTech Connect

    Wilden, A.; Modolo, G.; Lange, S.; Sadowski, F.; Bosbach, D.; Beele, B.B.; Panak, P.J.; Skerencak-Frech, A.; Geist, A.; Iqbal, M.; Verboom, W.

    2013-07-01

    In this work, the back-bone of the diglycolamide-structure of the TODGA extractant was modified by adding one or two methyl groups to the central methylene carbon-atoms. The influence of these structural modifications on the extraction behavior of trivalent actinides and lanthanides and other fission products was studied in solvent extraction experiments. The addition of methyl groups to the central methylene carbon atoms leads to reduced distribution ratios, also for Sr(II). This reduced extraction efficiency for Sr(II) is beneficial for process applications, as the co-extraction of Sr(II) can be avoided, resulting in an easier process design. The use of these modified diglycol-amides in solvent extraction processes is discussed. Furthermore, the complexation of Cm(III) and Eu(III) to the ligands was studied using Time-Resolved-Laser-Fluorescence-Spectroscopy (TRLFS). The complexes were characterized by slope analysis and conditional stability constants were determined.

  18. Short-term light adaptation of a cyanobacterium, Synechocystis sp. PCC 6803, probed by time-resolved fluorescence spectroscopy.

    PubMed

    Akimoto, Seiji; Yokono, Makio; Yokono, Erina; Aikawa, Shimpei; Kondo, Akihiko

    2014-08-01

    In photosynthetic organisms, the interactions among pigment-protein complexes change in response to light conditions. In the present study, we analyzed the transfer of excitation energy from the phycobilisome (PBS) and photosystem (PS) II to PSI in the cyanobacterium Synechocystis sp. PCC 6803. After 20 min of dark adaptation, Synechocystis cells were illuminated for 5 min with strong light with different spectral profiles, blue, green, two kinds of red, and white light. After illumination, the energy-transfer characteristics were evaluated using steady-state fluorescence and picosecond time-resolved fluorescence spectroscopy techniques. The fluorescence rise and decay curves were analyzed by global analysis to obtain fluorescence decay-associated spectra, followed by spectral component analysis. Under illumination with strong light, the contribution of the energy transfer from the PSII to PSI (spillover) became greater, and that of the energy transfer from the PBS to PSI decreased; the former change was larger than the latter. The energy transfer pathway to PSI was sensitive to red light. We discuss the short-term adaptation of energy-transfer processes in Synechocystis under strong-light conditions. PMID:24495908

  19. In Situ Planetary Mineralogy Using Simultaneous Time Resolved Fluorescence and Raman Spectroscopy

    NASA Technical Reports Server (NTRS)

    Blacksberg, J.; Rossman , G.R.

    2011-01-01

    Micro-Raman spectroscopy is one of the primary methods of mineralogical analysis in the laboratory, and more recently in the field. Because of its versatility and ability to interrogate rocks in their natural form it is one of the front runners for the next generation of in situ instruments designed to explore adverse set of solar system bodies (e.g. Mars, Venus, the Moon, and other primitive bodies such as asteroids and the Martian moons Phobos and Deimos), as well as for pre-selection of rock and soil samples for potential cache and return missions.

  20. Time resolved fluorescence of naproxen in organogel medium

    NASA Astrophysics Data System (ADS)

    Burguete, M. Isabel; Izquierdo, M. Angeles; Galindo, Francisco; Luis, Santiago V.

    2008-07-01

    The interaction between non-steroidal anti-inflammatory drug naproxen and the self assembled fibrillar network created by a low molecular weight organogelator has been probed by means of time resolved fluorescence spectroscopy.

  1. Nanosecond time-resolved emission spectroscopy of a fluorescence probe adsorbed to L-alpha-egg lecithin vesicles.

    PubMed

    Easter, J H; DeToma, R P; Brand, L

    1976-06-01

    Nanosecond time-resolved emission spectra (TRES) are fluorescence emission spectra obtained at discrete times during the fluorescence decay. The complete data-set obtainable is a surface representing the intensity at all wavelengths and times during the emission decay time. When 2-p-toluidinonaphthalene-6-sulfonate (2,6 p-TNS) is adsorbed to egg lecithin vesicles, an excited-state reaction associated with energetic changes of the emitting species occurs on the nanosecond time scale. Convolution of the fluorescence decay with the excitation response introduces an artifact in the time-dependent spectra. A precedure is described by which this artifact can be eliminated. The data for the generation of time-resolved emission spectra are obtained with a computer-interfaced instrument based on the single-photon counting method. PMID:945086

  2. Multi-channel lock-in amplifier assisted femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy with efficient rejection of superfluorescence background

    SciTech Connect

    Mao, Pengcheng; Wang, Zhuan; Dang, Wei; Weng, Yuxiang

    2015-12-15

    Superfluorescence appears as an intense background in femtosecond time-resolved fluorescence noncollinear optical parametric amplification spectroscopy, which severely interferes the reliable acquisition of the time-resolved fluorescence spectra especially for an optically dilute sample. Superfluorescence originates from the optical amplification of the vacuum quantum noise, which would be inevitably concomitant with the amplified fluorescence photons during the optical parametric amplification process. Here, we report the development of a femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectrometer assisted with a 32-channel lock-in amplifier for efficient rejection of the superfluorescence background. With this spectrometer, the superfluorescence background signal can be significantly reduced to 1/300–1/100 when the seeding fluorescence is modulated. An integrated 32-bundle optical fiber is used as a linear array light receiver connected to 32 photodiodes in one-to-one mode, and the photodiodes are further coupled to a home-built 32-channel synchronous digital lock-in amplifier. As an implementation, time-resolved fluorescence spectra for rhodamine 6G dye in ethanol solution at an optically dilute concentration of 10{sup −5}M excited at 510 nm with an excitation intensity of 70 nJ/pulse have been successfully recorded, and the detection limit at a pump intensity of 60 μJ/pulse was determined as about 13 photons/pulse. Concentration dependent redshift starting at 30 ps after the excitation in time-resolved fluorescence spectra of this dye has also been observed, which can be attributed to the formation of the excimer at a higher concentration, while the blueshift in the earlier time within 10 ps is attributed to the solvation process.

  3. Multi-channel lock-in amplifier assisted femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy with efficient rejection of superfluorescence background.

    PubMed

    Mao, Pengcheng; Wang, Zhuan; Dang, Wei; Weng, Yuxiang

    2015-12-01

    Superfluorescence appears as an intense background in femtosecond time-resolved fluorescence noncollinear optical parametric amplification spectroscopy, which severely interferes the reliable acquisition of the time-resolved fluorescence spectra especially for an optically dilute sample. Superfluorescence originates from the optical amplification of the vacuum quantum noise, which would be inevitably concomitant with the amplified fluorescence photons during the optical parametric amplification process. Here, we report the development of a femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectrometer assisted with a 32-channel lock-in amplifier for efficient rejection of the superfluorescence background. With this spectrometer, the superfluorescence background signal can be significantly reduced to 1/300-1/100 when the seeding fluorescence is modulated. An integrated 32-bundle optical fiber is used as a linear array light receiver connected to 32 photodiodes in one-to-one mode, and the photodiodes are further coupled to a home-built 32-channel synchronous digital lock-in amplifier. As an implementation, time-resolved fluorescence spectra for rhodamine 6G dye in ethanol solution at an optically dilute concentration of 10(-5)M excited at 510 nm with an excitation intensity of 70 nJ/pulse have been successfully recorded, and the detection limit at a pump intensity of 60 μJ/pulse was determined as about 13 photons/pulse. Concentration dependent redshift starting at 30 ps after the excitation in time-resolved fluorescence spectra of this dye has also been observed, which can be attributed to the formation of the excimer at a higher concentration, while the blueshift in the earlier time within 10 ps is attributed to the solvation process. PMID:26724012

  4. Multi-channel lock-in amplifier assisted femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy with efficient rejection of superfluorescence background

    NASA Astrophysics Data System (ADS)

    Mao, Pengcheng; Wang, Zhuan; Dang, Wei; Weng, Yuxiang

    2015-12-01

    Superfluorescence appears as an intense background in femtosecond time-resolved fluorescence noncollinear optical parametric amplification spectroscopy, which severely interferes the reliable acquisition of the time-resolved fluorescence spectra especially for an optically dilute sample. Superfluorescence originates from the optical amplification of the vacuum quantum noise, which would be inevitably concomitant with the amplified fluorescence photons during the optical parametric amplification process. Here, we report the development of a femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectrometer assisted with a 32-channel lock-in amplifier for efficient rejection of the superfluorescence background. With this spectrometer, the superfluorescence background signal can be significantly reduced to 1/300-1/100 when the seeding fluorescence is modulated. An integrated 32-bundle optical fiber is used as a linear array light receiver connected to 32 photodiodes in one-to-one mode, and the photodiodes are further coupled to a home-built 32-channel synchronous digital lock-in amplifier. As an implementation, time-resolved fluorescence spectra for rhodamine 6G dye in ethanol solution at an optically dilute concentration of 10-5M excited at 510 nm with an excitation intensity of 70 nJ/pulse have been successfully recorded, and the detection limit at a pump intensity of 60 μJ/pulse was determined as about 13 photons/pulse. Concentration dependent redshift starting at 30 ps after the excitation in time-resolved fluorescence spectra of this dye has also been observed, which can be attributed to the formation of the excimer at a higher concentration, while the blueshift in the earlier time within 10 ps is attributed to the solvation process.

  5. Effect of ouabain on metabolic oxidative state in living cardiomyocytes evaluated by time-resolved spectroscopy of endogenous NAD(P)H fluorescence

    NASA Astrophysics Data System (ADS)

    Chorvatova, Alzbeta; Elzwiei, Fathia; Mateasik, Anton; Chorvat, Dusan

    2012-10-01

    Time-resolved spectrometry of endogenous nicotinamide dinucleotide phosphate [NAD(P)H] fluorescence is a useful method to evaluate metabolic oxidative state in living cells. Ouabain is a well-known pharmaceutical drug used in the treatment of cardiovascular disease, the effects of which on myocardial metabolism were recently demonstrated. Mechanisms implicated in these actions are still poorly understood. We investigate the effect of ouabain on the metabolic oxidative state of living cardiac cells identified by time-resolved fluorescence spectroscopy of mitochondrial NAD(P)H. Spectral unmixing is used to resolve individual NAD(P)H fluorescence components. Ouabain decreased the integral intensity of NAD(P)H fluorescence, leading to a reduced component amplitudes ratio corresponding to a change in metabolic state. We also noted that lactate/pyruvate, affecting the cytosolic NADH gradient, increased the effect of ouabain on the component amplitudes ratio. Cell oxidation levels, evaluated as the percentage of oxidized NAD(P)H, decreased exponentially with rising concentrations of the cardiac glycoside. Ouabain also stimulated the mitochondrial NADH production. Our study sheds a new light on the role that ouabain plays in the regulation of metabolic state, and presents perspective on a noninvasive, pharmaceutical approach for testing the effect of drugs on the mitochondrial metabolism by means of time-resolved fluorescence spectroscopy in living cells.

  6. Fluorescence-suppressed time-resolved Raman spectroscopy of pharmaceuticals using complementary metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) detector.

    PubMed

    Rojalin, Tatu; Kurki, Lauri; Laaksonen, Timo; Viitala, Tapani; Kostamovaara, Juha; Gordon, Keith C; Galvis, Leonardo; Wachsmann-Hogiu, Sebastian; Strachan, Clare J; Yliperttula, Marjo

    2016-01-01

    In this work, we utilize a short-wavelength, 532-nm picosecond pulsed laser coupled with a time-gated complementary metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) detector to acquire Raman spectra of several drugs of interest. With this approach, we are able to reveal previously unseen Raman features and suppress the fluorescence background of these drugs. Compared to traditional Raman setups, the present time-resolved technique has two major improvements. First, it is possible to overcome the strong fluorescence background that usually interferes with the much weaker Raman spectra. Second, using the high photon energy excitation light source, we are able to generate a stronger Raman signal compared to traditional instruments. In addition, observations in the time domain can be performed, thus enabling new capabilities in the field of Raman and fluorescence spectroscopy. With this system, we demonstrate for the first time the possibility of recording fluorescence-suppressed Raman spectra of solid, amorphous and crystalline, and non-photoluminescent and photoluminescent drugs such as caffeine, ranitidine hydrochloride, and indomethacin (amorphous and crystalline forms). The raw data acquired by utilizing only the picosecond pulsed laser and a CMOS SPAD detector could be used for identifying the compounds directly without any data processing. Moreover, to validate the accuracy of this time-resolved technique, we present density functional theory (DFT) calculations for a widely used gastric acid inhibitor, ranitidine hydrochloride. The obtained time-resolved Raman peaks were identified based on the calculations and existing literature. Raman spectra using non-time-resolved setups with continuous-wave 785- and 532-nm excitation lasers were used as reference data. Overall, this demonstration of time-resolved Raman and fluorescence measurements with a CMOS SPAD detector shows promise in diverse areas, including fundamental chemical research, the pharmaceutical setting, process analytical technology (PAT), and the life sciences. Graphical abstract Time-resolved Raman measurement of a pharmaceutical sample using the complementary metal-oxide semiconductor (CMOS) single photon avalanche diode (SPAD) detector technology. PMID:26549117

  7. Time-resolved photoelectron spectroscopy of liquids.

    PubMed

    Buchner, Franziska; Lübcke, Andrea; Heine, Nadja; Schultz, Thomas

    2010-11-01

    We present a novel setup for the investigation of ultrafast dynamic processes in a liquid jet using time-resolved photoelectron spectroscopy. A magnetic-bottle type spectrometer with a high collection efficiency allows the very sensitive detection of photoelectrons emitted from a 10 μm thick liquid jet. This translates into good signal/noise ratio and rapid data acquisition making femtosecond time-resolved experiments feasible. We describe the experimental setup, a detailed spectrometer characterization based on the spectroscopy of nitric oxide in the gas phase, and results from femtosecond time-resolved experiments on sodium iodide solutions. The latter experiments reveal the formation and evolution of the solvated electron and we characterize two distinct spectral components corresponding to initially thermalized and unthermalized solvated electrons. The absence of dark states in photoionization, the direct measurement of electron binding energies, and the ability to resolve dynamic processes on the femtosecond time scale make time-resolved photoelectron spectroscopy from the liquid jet a very promising method for the characterization of photochemical processes in liquids. PMID:21133461

  8. Time-resolved fluorescence decay measurements for flowing particles

    DOEpatents

    Deka, C.; Steinkamp, J.A.

    1999-06-01

    Time-resolved fluorescence decay measurements are disclosed for flowing particles. An apparatus and method for the measurement and analysis of fluorescence for individual cells and particles in flow are described, wherein the rapid measurement capabilities of flow cytometry and the robust measurement and analysis procedures of time-domain fluorescence lifetime spectroscopy are combined. A pulse-modulated CW laser is employed for excitation of the particles. The characteristics and the repetition rate of the excitation pulses can be readily adjusted to accommodate for fluorescence decays having a wide range of lifetimes. 12 figs.

  9. Time-resolved fluorescence decay measurements for flowing particles

    DOEpatents

    Deka, Chiranjit; Steinkamp, John A.

    1999-01-01

    Time-resolved fluorescence decay measurements for flowing particles. An apparatus and method for the measurement and analysis of fluorescence for individual cells and particles in flow are described, wherein the rapid measurement capabilities of flow cytometry and the robust measurement and analysis procedures of time-domain fluorescence lifetime spectroscopy are combined. A pulse-modulated cw laser is employed for excitation of the particles. The characteristics and the repetition rate of the excitation pulses can be readily adjusted to accommodate for fluorescence decays having a wide range of lifetimes.

  10. Time-resolved multiple probe spectroscopy

    SciTech Connect

    Greetham, G. M.; Sole, D.; Clark, I. P.; Parker, A. W.; Pollard, M. R.; Towrie, M.

    2012-10-15

    Time-resolved multiple probe spectroscopy combines optical, electronic, and data acquisition capabilities to enable measurement of picosecond to millisecond time-resolved spectra within a single experiment, using a single activation pulse. This technology enables a wide range of dynamic processes to be studied on a single laser and sample system. The technique includes a 1 kHz pump, 10 kHz probe flash photolysis-like mode of acquisition (pump-probe-probe-probe, etc.), increasing the amount of information from each experiment. We demonstrate the capability of the instrument by measuring the photolysis of tungsten hexacarbonyl (W(CO){sub 6}) monitored by IR absorption spectroscopy, following picosecond vibrational cooling of product formation through to slower bimolecular diffusion reactions on the microsecond time scale.

  11. Time-resolved Raman spectroscopy for in situ planetary mineralogy.

    PubMed

    Blacksberg, Jordana; Rossman, George R; Gleckler, Anthony

    2010-09-10

    Planetary mineralogy can be revealed through a variety of remote sensing and in situ investigations that precede any plans for eventual sample return. We briefly review those techniques and focus on the capabilities for on-surface in situ examination of Mars, Venus, the Moon, asteroids, and other bodies. Over the past decade, Raman spectroscopy has continued to develop as a prime candidate for the next generation of in situ planetary instruments, as it provides definitive structural and compositional information of minerals in their natural geological context. Traditional continuous-wave Raman spectroscopy using a green laser suffers from fluorescence interference, which can be large (sometimes saturating the detector), particularly in altered minerals, which are of the greatest geophysical interest. Taking advantage of the fact that fluorescence occurs at a later time than the instantaneous Raman signal, we have developed a time-resolved Raman spectrometer that uses a streak camera and pulsed miniature microchip laser to provide picosecond time resolution. Our ability to observe the complete time evolution of Raman and fluorescence spectra in minerals makes this technique ideal for exploration of diverse planetary environments, some of which are expected to contain strong, if not overwhelming, fluorescence signatures. We discuss performance capability and present time-resolved pulsed Raman spectra collected from several highly fluorescent and Mars-relevant minerals. In particular, we have found that conventional Raman spectra from fine grained clays, sulfates, and phosphates exhibited large fluorescent signatures, but high quality spectra could be obtained using our time-resolved approach. PMID:20830184

  12. Fully automated deconvolution method for on-line analysis of time-resolved fluorescence spectroscopy data based on an iterative Laguerre expansion technique

    NASA Astrophysics Data System (ADS)

    Dabir, Aditi S.; Trivedi, Chintan A.; Ryu, Yeontack; Pande, Paritosh; Jo, Javier A.

    2009-03-01

    Time-resolved fluorescence spectroscopy (TRFS) is a powerful analytical tool for quantifying the biochemical composition of organic and inorganic materials. The potential of TRFS for tissue diagnosis has been recently demonstrated. To facilitate the translation of TRFS to the clinical arena, algorithms for online TRFS data analysis are essential. A fast model-free TRFS deconvolution algorithm based on the Laguerre expansion method has previously been introduced. One limitation of this method, however, is the need to heuristically select two parameters that are crucial for the accurate estimation of the fluorescence decay: the Laguerre parameter α and the expansion order. Here, a new implementation of the Laguerre deconvolution method is introduced, in which a nonlinear least-square optimization of the Laguerre parameter α is performed, and the optimal expansion order is selected based on a minimum description length criterion (MDL). In addition, estimation of the zero-time delay between the recorded instrument response and fluorescence decay is also performed based on normalized mean square error criterion (NMSE). The method is validated on experimental data from fluorescence lifetime standards, endogenous tissue fluorophores, and human tissue. The proposed automated Laguerre deconvolution method will facilitate online applications of TRFS, such as real-time clinical tissue diagnosis.

  13. Time-resolved detection of aromatic compounds on planetary surfaces by ultraviolet laser induced fluorescence and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Raman spectroscopic instruments are highly capable in the search for organics on Mars due to the potential to perform rapid and nondestructive measurements on unprepared samples. Upcoming and future Raman instruments are likely to also incorporate laser-induced fluorescence (LIF) capabilities, which can be added for modest cost and complexity. We demonstrate that it is possible to obtain sub-ns fluorescence lifetime measurements of Mars-relevant organics and minerals if a fast time-gating capability is used with an intensified detector and a short ultraviolet laser pulse. This serves a primary purpose of discriminating mineral from short-lived (less than 10 ns) organic fluorescence, considered a potential biosignature. Additionally, lifetime measurements may assist in determining if more than one fluorescing species is present and provide information concerning the molecular structure as well as the local environment. Fast time-gating is also useful at longer visible or near-IR wavelengths, as this approach increases the sensitivity of the instrument to organic material by removing the majority of the fluorescence background from the Raman signal and reducing the effect of ambient light.

  14. ESIPT and photodissociation of 3-hydroxychromone in solution: photoinduced processes studied by static and time-resolved UV/Vis, fluorescence, and IR spectroscopy.

    PubMed

    Chevalier, Katharina; Grün, Anneken; Stamm, Anke; Schmitt, Yvonne; Gerhards, Markus; Diller, Rolf

    2013-11-01

    The spectral properties of fluorescence sensors such as 3-hydroxychromone (3-HC) and its derivatives are sensitive to interaction with the surrounding medium as well as to substitution. 3-HC is a prototype system for other derivatives because it is the basic unit of all flavonoides undergoing ESIPT and is not perturbed by a substituent. In this study, the elementary processes and intermediate states in the photocycle of 3-HC as well as its anion were identified and characterized by the use of static and femtosecond time-resolved spectroscopy in different solvents (methylcyclohexane, acetonitrile, ethanol, and water at different pH). Electronic absorption and fluorescence spectra and lifetimes of the intermediate states were obtained for the normal, tautomer and anionic excited state, while mid-IR vibrational spectra yielded structural information on ground and excited states of 3-HC. A high sensitivity on hydrogen-bonding perturbations was observed, leading to photoinduced anion formation in water, while in organic solvents, different processes are suggested, including slow picosecond ESIPT and contribution of the trans-structure excited state or a different stable solvation state with different direction of OH. The formation of the latter could be favored by the lack of a substituent increasing contact points for specific solute-solvent interactions at the hydroxyl group compared to substituted derivatives. The effect of substituents has to be considered for the design of future fluorescence sensors based on 3-HC. PMID:24083478

  15. In vivo validation of a bimodal technique combining time-resolved fluorescence spectroscopy and ultrasonic backscatter microscopy for diagnosis of oral carcinoma

    NASA Astrophysics Data System (ADS)

    Sun, Yang; Xie, Hongtao; Liu, Jing; Lam, Matthew; Chaudhari, Abhijit J.; Zhou, Feifei; Bec, Julien; Yankelevich, Diego R.; Dobbie, Allison; Tinling, Steven L.; Gandour-Edwards, Regina F.; Monsky, Wayne L.; Gregory Farwell, D.; Marcu, Laura

    2012-11-01

    Tissue diagnostic features generated by a bimodal technique integrating scanning time-resolved fluorescence spectroscopy (TRFS) and ultrasonic backscatter microscopy (UBM) are investigated in an in vivo hamster oral carcinoma model. Tissue fluorescence is excited by a pulsed nitrogen laser and spectrally and temporally resolved using a set of filters/dichroic mirrors and a fast digitizer, respectively. A 41-MHz focused transducer (37-μm axial, 65-μm lateral resolution) is used for UBM scanning. Representative lesions of the different stages of carcinogenesis show that fluorescence characteristics complement ultrasonic features, and both correlate with histological findings. These results demonstrate that TRFS-UBM provide a wealth of co-registered, complementary data concerning tissue composition and structure as it relates to disease status. The direct co-registration of the TRFS data (sensitive to surface molecular changes) with the UBM data (sensitive to cross-sectional structural changes and depth of tumor invasion) is expected to play an important role in pre-operative diagnosis and intra-operative determination of tumor margins.

  16. Energy transfer in the primary stages of the photosynthetic process investigated by picosecond time resolved fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Pellegrino, F.

    The fate of the absorbed light energy in the primary stages of the photosynthetic process was studied. In particular, the energy transfer in the accessory pigment complex consisting of carotenoids, Chl. a and Chl. b in higher green plants and phycobiliproteins in blue-green algae were investigated. These accessory pigments are responsible for the highly efficient transfer of the excitation energy to the photochemically active reaction center traps. The risetime, decay time, fluorescence depolarization, temperature and intensity dependence of the fluoresence emission from higher green plant and algal photosystems were directly measured. Excitation was provided by single picosecond laser pulses, as well as a train of pulses at 530 nm, within an intensity range of 10 to the 12th power to 10 to the 16th power photons/sq cm per pulse.

  17. Fluorescence-detected wave packet interferometry: Time resolved molecular spectroscopy with sequences of femtosecond phase-locked pulses

    NASA Astrophysics Data System (ADS)

    Scherer, Norbert F.; Carlson, Roger J.; Matro, Alexander; Du, Mei; Ruggiero, Anthony J.; Romero-Rochin, Victor; Cina, Jeffrey A.; Fleming, Graham R.; Rice, Stuart A.

    1991-08-01

    We introduce a novel spectroscopic technique which utilizes a two-pulse sequence of femtosecond duration phase-locked optical laser pulses to resonantly excite vibronic transitions of a molecule. In contrast with other ultrafast pump-probe methods, in this experiment a definite optical phase angle between the pulses is maintained while varying the interpulse delay with interferometric precision. For the cases of in-phase, in-quadrature, and out-of-phase pulse pairs, respectively, the optical delay is controlled to positions that are integer, integer plus one quarter, and integer plus one half multiples of the wavelength of a selected Fourier component. In analogy with a double slit optical interference experiment, the two the two pulse experiments reported herein involve the preparation and quantum interference of two nuclear wave packet amplitudes state of a molecule. These experiments are designed to be sensitive to the total phase evolution of the wave packet prepared by the initial pulse. The direct determination of wave packet phase evolution is possible because phase locking effectively transforms the interferogram to a frame which is referenced to the optical carrier frequency, thereby eliminating the high (optical) frequency modulations. This has the effect of isolating the rovibrational molecular dynamics. The phase locking scheme is demonstrated for molecular iodine. The excited state population following the passage of both pulses is detected as the resultant two-beam dependent fluorescence emission from the B state. The observed signals have periodically recurring features that result from the vibrational dynamics of the molecule on the electronically excited potential energy surface. In addition, coherent interference effects cause the magnitude and sign of the periodic features to be strongly modulated. The two-pulse phase-locked interferograms are interpreted herein by use of a simple analytic model, by first order perturbation theory and by quantum mechanical wave packet calculations. We find the form of the interferogram to be determined by the ground state level from which the amplitude originates, the deviation from impulsive preparation of the wave packet due to nonzero pulse duration, the frequency and anharmonicity of the target vibrational levels in the B state, and the detuning of the phase-locked frequency from resonance. The dependence of the interferogram on the phase-locked frequency and phase angle is investigated in detail.

  18. Time-Resolved Synchronous Fluorescence for Biomedical Diagnosis

    PubMed Central

    Zhang, Xiaofeng; Fales, Andrew; Vo-Dinh, Tuan

    2015-01-01

    This article presents our most recent advances in synchronous fluorescence (SF) methodology for biomedical diagnostics. The SF method is characterized by simultaneously scanning both the excitation and emission wavelengths while keeping a constant wavelength interval between them. Compared to conventional fluorescence spectroscopy, the SF method simplifies the emission spectrum while enabling greater selectivity, and has been successfully used to detect subtle differences in the fluorescence emission signatures of biochemical species in cells and tissues. The SF method can be used in imaging to analyze dysplastic cells in vitro and tissue in vivo. Based on the SF method, here we demonstrate the feasibility of a time-resolved synchronous fluorescence (TRSF) method, which incorporates the intrinsic fluorescent decay characteristics of the fluorophores. Our prototype TRSF system has clearly shown its advantage in spectro-temporal separation of the fluorophores that were otherwise difficult to spectrally separate in SF spectroscopy. We envision that our previously-tested SF imaging and the newly-developed TRSF methods will combine their proven diagnostic potentials in cancer diagnosis to further improve the efficacy of SF-based biomedical diagnostics. PMID:26404289

  19. Time-resolved fluorescence lifetime for cutaneous melanoma detection.

    PubMed

    Pires, Layla; Nogueira, Marcelo Saito; Pratavieira, Sebastião; Moriyama, Lilian Tan; Kurachi, Cristina

    2014-09-01

    Melanoma is the most aggressive skin cancer type. It is characterized by pigmented lesions with high tissue invasion and metastatic potential. The early detection of melanoma is extremely important to improve patient prognosis and survival rate, since it can progress to the deadly metastatic stage. Presently, the melanoma diagnosis is based on the clinical analysis of the macroscopic lesion characteristics such as shape, color, borders following the ABCD rules. The aim of this study is to evaluate the time-resolved fluorescence lifetime of NADH and FAD molecules to detect cutaneous melanoma in an experimental in vivo model. Forty-two lesions were analyzed and the data was classified using linear discriminant analysis, a sensitivity of 99.4%, specificity of 97.4% and accuracy of 98.4% were achieved. These results show the potential of this fluorescence spectroscopy for melanoma detection. PMID:25401022

  20. Ultrafast time-resolved vibrational spectroscopies of carotenoids in photosynthesis.

    PubMed

    Hashimoto, Hideki; Sugisaki, Mitsuru; Yoshizawa, Masayuki

    2015-01-01

    This review discusses the application of time-resolved vibrational spectroscopies to the studies of carotenoids in photosynthesis. The focus is on the ultrafast time regime and the study of photophysics and photochemistry of carotenoids by femtosecond time-resolved stimulated Raman and four-wave mixing spectroscopies. This article is part of a Special Issue entitled: Vibrational spectroscopies and bioenergetic systems. PMID:25223589

  1. Time-resolved photo-phonon spectroscopy

    NASA Astrophysics Data System (ADS)

    Lisin, V. N.; Shegeda, A. M.

    2006-03-01

    A rather simple method is discussed to study at once optical absorption spectra, excited-states nonradiative relaxation and propagation of the nonequilibrium phonons emitted during this process in doped dielectrics. The technique utilizes the time-resolved superconductive bolometer detection of these phonons at temperature T=2 K and optical excitation with a pulsed tunable dye laser. Observed, at fixed delay time after the laser pulse action, excitation spectra of the phonons well coincide with already known absorption spectra of both single doped ions and pairs of the nearest neighbors. In some crystals both the satellite lines and uncontrollable impurities lines (Nd 3+ in system LaF 3:Pr 3+) are well resolved in the phonon excitation spectra. This talks about high sensitivity of the used method. Time evolution of the phonon excitation spectra contains in itself the information on energy transfer mechanisms and has allowed to reveal the new types of doped ion cites (Cr 3+ in ruby). The study of a time dependence of bolometer signal versus the phonon propagation distance at fixed laser wave length has allowed to determine nonradiative relaxation time, a phonon propagation type and parameters of the phonon scattering rates.

  2. Time-resolved optical fluorescence spectroscopy of heterogeneous turbid media with special emphasis on brain tissue structures including diseased regions: A sensitivity analysis

    NASA Astrophysics Data System (ADS)

    Vaudelle, Fabrice; L'huillier, Jean-Pierre

    2013-09-01

    Fluorescence-enhanced optical imaging based on near-infrared light provides a promising tool to differentiate diseased lesions from normal tissue. However, the measurement sensitivity of the fluorescence signals acquired at the output surface of the tissue is greatly influenced by the tissue structure, the optical properties, the location and the size of the target. In this paper, we present a numerical model based on the Monte Carlo method that allows to simulate time-resolved reflectance signals acquired on the surface of the scalp of a human head model bearing a fluorescent diseased region (tumor, glioma). The influence of tumor depth, tumor size and tumor shape evolution on the computed signals are analyzed by taking into account the multi-layered tissue structure. The simulations show that the mean-time-of-flight and the difference between two mean-times acquired at two source-detector distances are both relevant to this problem type. Furthermore, the simulations suggest that the use of the difference between mean-flight-times may be interesting to probe scattering changes that occur in the cerebrospinal fluid (CSF).

  3. Time-resolved spectroscopy and imaging

    NASA Astrophysics Data System (ADS)

    Chance, Britton

    1995-05-01

    In response to the conference organizer's request, I am presenting a summary of the current status of medical optical imaging and spectroscopy. This is a topic which is advancing rapidly and on which there have been a number of conferences recently, and yet there has not been presented an overview of the field and some idea of what the advantages and disadvantages of the photon diffusion technology may be. Thus, this paper emphasizes diffusion waves for spectroscopy and imaging deep within the tissue and, at the same time, for providing specificity information of both absorption and scattering. In achieving this goal, I will not be able to cite all of the advantages of technologies that view the superficial layers of skin, retina, etc., on the one hand, nor those that measure the photons that have been scattered minimally on the transit between input and output. One of the main reasons for this is that specificity of the optical methods requires all of the information available: absorption and scattering of intrinsic signals naturally in the tissue, and of extrinsic signal due to contrast agents that have been artificially lodged in strategic tissue volumes. Since this paper is essentially the transcript of a lecture, it is not proposed as a topic review and does not contain full-scale bibliographic references, some of which may be found in a recent review elsewhere. This paper highlights what we all might accomplish in order to bring to bear with maximal effectiveness the optical method for altering the outcome of medical problems. I have not emphasized the mathematics of photon diffusion so well represented by the papers of this symposium volume. The achievable goals of the optical methods are to speed detection, improve diagnosis, guide therapy, and what appears in the minds of most, contribute to the improvement of medical economics. In order to fulfill these objectives, we will in the end have to demonstrate by lengthy and expensive clinical studies that the medical devices we develop are really what we think they are as determined by accepted procedures for clinical studies. This is a difficult and expensive route and one track along which many technologies will 'fall by the wayside'. However, our technology is maturing: we are obtaining numbers for important medical problems. It is indeed difficult to make these kinds of contributions; medical devices are not new. The choice of methods is manifold and the niches or windows of opportunity are circumscribed.

  4. Seventh international conference on time-resolved vibrational spectroscopy

    SciTech Connect

    Dyer, R.B.; Martinez, M.A.D.; Shreve, A.; Woodruff, W.H.

    1997-04-01

    The International Conference on Time-Resolved Vibrational Spectroscopy (TRVS) is widely recognized as the major international forum for the discussion of advances in this rapidly growing field. The 1995 conference was the seventh in a series that began at Lake Placid, New York, 1982. Santa Fe, New Mexico, was the site of the Seventh International Conference on Time-Resolved Vibrational Spectroscopy, held from June 11 to 16, 1995. TRVS-7 was attended by 157 participants from 16 countries and 85 institutions, and research ranging across the full breadth of the field of time-resolved vibrational spectroscopy was presented. Advances in both experimental capabilities for time-resolved vibrational measurements and in theoretical descriptions of time-resolved vibrational methods continue to occur, and several sessions of the conference were devoted to discussion of these advances and the associated new directions in TRVS. Continuing the interdisciplinary tradition of the TRVS meetings, applications of time-resolved vibrational methods to problems in physics, biology, materials science, and chemistry comprised a large portion of the papers presented at the conference.

  5. Time resolved imaging microscopy. Phosphorescence and delayed fluorescence imaging.

    PubMed Central

    Marriott, G; Clegg, R M; Arndt-Jovin, D J; Jovin, T M

    1991-01-01

    An optical microscope capable of measuring time resolved luminescence (phosphorescence and delayed fluorescence) images has been developed. The technique employs two phase-locked mechanical choppers and a slow-scan scientific CCD camera attached to a normal fluorescence microscope. The sample is illuminated by a periodic train of light pulses and the image is recorded within a defined time interval after the end of each excitation period. The time resolution discriminates completely against light scattering, reflection, autofluorescence, and extraneous prompt fluorescence, which ordinarily decrease contrast in normal fluorescence microscopy measurements. Time resolved image microscopy produces a high contrast image and particular structures can be emphasized by displaying a new parameter, the ratio of the phosphorescence to fluorescence. Objects differing in luminescence decay rates are easily resolved. The lifetime of the long lived luminescence can be measured at each pixel of the microscope image by analyzing a series of images that differ by a variable time delay. The distribution of luminescence decay rates is displayed directly as an image. Several examples demonstrate the utility of the instrument and the complementarity it offers to conventional fluorescence microscopy. Images FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 PMID:1723311

  6. Optical oxygen sensor based on time-resolved fluorescence

    NASA Astrophysics Data System (ADS)

    Chu, Cheng-Shane; Chu, Ssu-Wei

    2015-07-01

    A new, simple signal processing, low-cost technique for the fabrication of a portable oxygen sensor based on time-resolved fluorescence is described. The sensing film uses the oxygen sensing dye platinum meso-tetra (pentfluorophenyl) porphyrin (PtTFPP) embedded in a polymer matrix. The experimental results reveal that the PtTFPP-doped oxygen sensor has a sensitivity of 2.2 in the 0-100% range. A preparation procedure for coating the photodiodes with the oxygen sensor film that produces repetitive and reliable sensing devices is proposed. The developed time-resolved optical oxygen sensor is portable, low-cost, has simple signal processing, and lacks optical filter elements. It is a cost-effective alternative to traditional electrochemical-based oxygen sensors and provides a platform for other optical based sensors.

  7. Multimode Surface Functional Group Determination: Combining Steady-State and Time-Resolved Fluorescence with X-ray Photoelectron Spectroscopy and Absorption Measurements for Absolute Quantification.

    PubMed

    Fischer, Tobias; Dietrich, Paul M; Unger, Wolfgang E S; Rurack, Knut

    2016-01-19

    The quantitative determination of surface functional groups is approached in a straightforward laboratory-based method with high reliability. The application of a multimode BODIPY-type fluorescence, photometry, and X-ray photoelectron spectroscopy (XPS) label allows estimation of the labeling ratio, i.e., the ratio of functional groups carrying a label after reaction, from the elemental ratios of nitrogen and fluorine. The amount of label on the surface is quantified with UV/vis spectrophotometry based on the molar absorption coefficient as molecular property. The investigated surfaces with varying density are prepared by codeposition of 3-(aminopropyl)triethoxysilane (APTES) and cyanoethyltriethoxysilane (CETES) from vapor. These surfaces show high functional group densities that result in significant fluorescence quenching of surface-bound labels. Since alternative quantification of the label on the surface is available through XPS and photometry, a novel method to quantitatively account for fluorescence quenching based on fluorescence lifetime (τ) measurements is shown. Due to the complex distribution of τ on high-density surfaces, the stretched exponential (or Kohlrausch) function is required to determine representative mean lifetimes. The approach is extended to a commercial Rhodamine B isothiocyanate (RITC) label, clearly revealing the problems that arise from such charged labels used in conjunction with silane surfaces. PMID:26695740

  8. Steady-state and time-resolved fluorometry of fluorescent pollutants and heavy metal complexes

    NASA Astrophysics Data System (ADS)

    Resch, Ute; Rurack, Knut

    1997-05-01

    Time-resolved laser-induced fluorescence spectroscopy is one of the most sensitive optical methods which is well suited for on-line in situ analysis. Here, three examples for the steady- state and time-resolved fluorescence analysis of environmentally important analytes, the fluorescent monoaromatic hydrocarbons benzene, toluene, and xylene as well as non fluorescent heavy metal ions forming a fluorescent complex with a cation coordinating fluorescence probe, are presented and the potential of both methods is discussed. For BTX, various mixtures of the spectrally similar compounds B, T, and X showing different fluorescence lifetimes were studied with both methods. As an example for fluorometric metal ion analysis, the fluorescence probe BP(OH)2 (2,2'-bipyridyl- 3,3'-diol) was employed for the determination of d10 metal ions in water and the newly developed fluorescence probe APTA for the detection of Cu(II). Cation complexation of BP(OH2 yields spectrally very similar complexes which differ in their fluorescence lifetimes. Complexation of APTA to Cu(II) leads to small spectral changes and a strong increase in fluorescence quantum yield and lifetime. For the analytes studied, a comparison of the detection limits, standard deviations, and linear dynamic range of both methods clearly demonstrates the analytical potential of time-resolved fluorometry.

  9. Time-resolved fluorescence anisotropies in mixed surfactant solutions

    SciTech Connect

    McCarroll, M.E.; Joly, A.G.; Wang, Z.; Friedrich, D.M.; Wandruszka, R. von

    1999-10-01

    Time-resolved fluorescence anisotropy decays of solutions of Triton X-114 (TX-114) with various amounts of sodium dodecyl sulfate (SDS) were measured using the emission both from the surfactant itself and from added perylene. In the former case, the monomer and aggregate species of the surfactant were spectroscopically isolated and were shown to have significantly different rotational correlation times. The rotational diffusion of perylene in micellar TX-114 with small amounts of added SDS appeared to have a component with a very short correlation time. The anisotropy decay curves showed the existence of limiting anisotropies (r{sub {infinity}}), indicating hindered probe rotation in the micellar environment. At higher SDS concentrations, the fast-decaying component slowed down and the limiting anisotropy decreased substantially, suggesting some migration of the probe to the interior of the micelle.

  10. ULTRA: A Unique Instrument for Time-Resolved Spectroscopy.

    PubMed

    Greetham, Gregory M; Burgos, Pierre; Cao, Qian; Clark, Ian P; Codd, Peter S; Farrow, Richard C; George, Michael W; Kogimtzis, Moschos; Matousek, Pavel; Parker, Anthony W; Pollard, Mark R; Robinson, David A; Xin, Zhi-Jun; Towrie, Michael

    2010-12-01

    We report the development of a high-sensitivity time-resolved infrared and Raman spectrometer with exceptional experimental flexibility based on a 10-kHz synchronized dual-arm femtosecond and picosecond laser system. Ultrafast high-average-power titanium sapphire lasers and optical parametric amplifiers provide wavelength tuning from the ultraviolet (UV) to the mid-infrared region. Customized silicon, indium gallium arsenide, and mercury cadmium telluride linear array detectors are provided to monitor the probe laser intensity in the UV to mid-infrared wavelength range capable of measuring changes in sample absorbance of ΔOD ~ 10(-5) in 1 second. The system performance is demonstrated for the time-resolved infrared, two-dimensional (2D) infrared, and femtosecond stimulated Raman spectroscopy techniques with organometallic intermediates, organic excited states, and the dynamics of the tertiary structure of DNA. PMID:21144146

  11. A sensitive time-resolved fluorescent immunoassay for metallothionein protein.

    PubMed

    Butcher, Heather; Kennette, Wendy; Collins, Olga; Demoor, Janice; Koropatnick, James

    2003-01-15

    Metallothioneins (MTs) are a family of low molecular weight metal-binding proteins induced by a broad range of stress conditions, including exposure to transition metal ions. Biochemical and immunological methods to measure MT protein levels in tissues and cultured cells have been reported, but accuracy and sensitivity is impeded by high background levels, low specificity of currently available reagents, and relatively laborious and time-consuming multistep procedures. To address these difficulties, a protocol has been developed to measure MT protein levels using a competitive solid phase assay based on dissociation enhanced lanthanide fluoroimmuno (DELFIA) detection of anti-MT monoclonal antibody bound to solid phase MT. This assay allows time-resolved detection of antibody binding, based on binding and exchange of different lanthanide chelates followed by fluorescent detection, designed to reduce background fluorescence and increase sensitivity. The method allows measurement of low MT levels that are undetectable using current radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) protocols, and yields reproducible results with low background over a wide range of MT concentrations. Improved sensitivity of MT protein detection is of value in toxicological measurement of stress responses and assessment of MT expression and function. PMID:12505728

  12. A 0.18-µm CMOS Array Sensor for Integrated Time-Resolved Fluorescence Detection

    PubMed Central

    Huang, Ta-chien D.; Sorgenfrei, Sebastian; Gong, Ping; Levicky, Rastislav; Shepard, Kenneth L.

    2010-01-01

    This paper describes the design of an active, integrated CMOS sensor array for fluorescence applications which enables time-gated, time-resolved fluorescence spectroscopy. The 64-by-64 array is sensitive to photon densities as low as 8.8 × 106 photons/cm2 with 64-point averaging and, through a differential pixel design, has a measured impulse response of better than 800 ps. Applications include both active microarrays and high-frame-rate imagers for fluorescence lifetime imaging microscopy. PMID:20436922

  13. Sensitive, time-resolved, broadband spectroscopy of single transient processes

    NASA Astrophysics Data System (ADS)

    Fjodorow, Peter; Baev, Ivan; Hellmig, Ortwin; Sengstock, Klaus; Baev, Valery M.

    2015-09-01

    Intracavity absorption spectroscopy with a broadband Er3+-doped fiber laser is applied to time-resolved measurements of transient gain and absorption in electrically excited Xe and Kr plasmas. The achieved time resolution for broadband spectral recording of a single process is 25 µs. For pulsed-periodic processes, the time resolution is limited by the laser pulse duration, which is set here to 3 µs. This pulse duration also predefines the effective absorption path length, which amounts to 900 m. The presented technique can be applied to multicomponent analysis of single transient processes such as shock tube experiments, pulse detonation engines, or explosives.

  14. Time-resolved fluorescence spectroscopy investigation of the effect of 4-hydroxynonenal on endogenous NAD(P)H in living cardiac myocytes

    NASA Astrophysics Data System (ADS)

    Chorvatova, Alzbeta; Aneba, Swida; Mateasik, Anton; Chorvat, Dusan; Comte, Blandine

    2013-06-01

    Lipid peroxidation is a major biochemical consequence of the oxidative deterioration of polyunsaturated lipids in cell membranes and causes damage to membrane integrity and loss of protein function. 4-hydroxy-2-nonenal (HNE), one of the most reactive products of n-6 polyunsaturated fatty acid peroxidation of membrane phospholipids, has been shown to be capable of affecting both nicotinamide adenine dinucleotide (phosphate) reduced [NAD(P)H] as well as NADH production. However, the understanding of its effects in living cardiac cells is still lacking. Our goal was to therefore investigate HNE effects on NAD(P)H noninvasively in living cardiomyocytes. Spectrally resolved lifetime detection of endogenous fluorescence, an innovative noninvasive technique, was employed. Individual fluorescence components were resolved by spectral linear unmixing approach. Gathered results revealed that HNE reduced the amplitude of both resolved NAD(P)H components in a concentration-dependent manner. In addition, HNE increased flavoprotein fluorescence and responsiveness of the NAD(P)H component ratio to glutathione reductase (GR) inhibitor. HNE also increased the percentage of oxidized nucleotides and decreased maximal NADH production. Presented data indicate that HNE provoked an important cell oxidation by acting on NAD(P)H regulating systems in cardiomyocytes. Understanding the precise role of oxidative processes and their products in living cells is crucial for finding new noninvasive tools for biomedical diagnostics of pathophysiological states.

  15. Time-resolved fluorescence spectroscopy of two-photon laser-excited 8p, 9p, 5f, and 6f levels in neutral xenon

    SciTech Connect

    Eichhorn, Christoph; Loehle, Stefan; Knapp, Andreas; Fritzsche, Stephan; Auweter-Kurtz, Monika

    2009-08-15

    Laser-induced fluorescence of two-photon excited 8p, 9p, J=0,2 and 5f, 6f, J=2 levels in neutral xenon has been investigated in the pressure regime between 4 and 120 Pa. Radiative lifetimes and collisional deactivation rates have been deduced especially for the 5f[3/2]{sub 2}, 5f[5/2]{sub 2}, and 8p[1/2]{sub 0} levels using the Stern-Volmer approach. The spontaneous lifetimes for 5f[3/2]{sub 2}, 5f[5/2]{sub 2}, and 8p[1/2]{sub 0} levels are 94, 78, and 207 ns, respectively. These lifetimes have been calculated also by applying extended multiconfiguration Dirac-Fock wave functions and are found in agreement with experiment within 10-25%.

  16. Nonselective and polarization effects in time-resolved optogalvanic spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhechev, D.; Steflekova, V.

    2016-02-01

    Three interfering effects in optogalvanic (OG) spectroscopy are identified in a hollow cathode discharge (HCD) - OG detector. The laser beam is found to generate two nonselective processes, namely photoelectron emission (PE) from the cathode surface with a sub-breakdown bias applied, and nonresonant space ionization. The convolution of these galvanic contributions was determined experimentally as an instrumental function and a deconvolution procedure to determine the actual OG signal was developed. Specific plasma conductance is detected dependent on the polarization of the laser beam irradiating. Linearly/circularly polarized light beam is found to induce OG signals differ in amplitude (and their shape parameters in the time-resolved OG signals (TROGS)). The phenomena coherence and specific conductance are found to be in causal relationship. The additional conductance due to coherent states of atoms manifests itself as an intrinsic instrumental property of OG detector.

  17. Time-resolved vibrational spectroscopy of a molecular shuttle.

    PubMed

    Panman, Matthijs R; Bodis, Pavol; Shaw, Danny J; Bakker, Bert H; Newton, Arthur C; Kay, Euan R; Leigh, David A; Buma, Wybren Jan; Brouwer, Albert M; Woutersen, Sander

    2012-02-14

    Time-resolved vibrational spectroscopy is used to investigate the inter-component motion of an ultraviolet-triggered two-station molecular shuttle. The operation cycle of this molecular shuttle involves several intermediate species, which are observable in the amide I and amide II regions of the mid-IR spectrum. Using ab initio calculations on specific parts of the rotaxane, and by comparing the transient spectra of the normal rotaxane with that of the N-deuterated version, we can assign the observed vibrational modes of each species occurring during the shuttling cycle in an unambiguous way. The complete time- and frequency-dependent data set is analyzed using singular value decomposition (SVD). Using a kinetic model to describe the time-dependent concentrations of the transient species, we derive the absorption spectra associated with each stage in the operation cycle of the molecular shuttle, including the recombination of the charged species. PMID:22033540

  18. Time-resolved Spectroscopy of AL Comae Berenices

    NASA Astrophysics Data System (ADS)

    Howell, Steve B.; Hauschildt, Peter; Dhillon, V. S.

    1998-02-01

    We present time-resolved spectroscopy for AL Com, one of the faintest known tremendous outburst amplitude dwarf novae (TOADs). Using newly produced models for a white dwarf and red secondary, we show that the star AL Com has orbitally phase-resolved broad absorption features of yet unidentified origin and an optically thin accretion disk. Radial velocities measured from the few spectra available show essentially no motion of the white dwarf, leading to a strict upper limit on the secondary mass of <=0.18 Msolar, with a likely value of 0.04-0.09 Msolar. This agrees well with recent theoretical arguments placing the TOADs as post-period minimum cataclysmic variables.

  19. Recombinant human O6-alkylguanine-DNA alkyltransferase (AGT), Cys145-alkylated AGT and Cys145 --> Met145 mutant AGT: comparison by isoelectric focusing, CD and time-resolved fluorescence spectroscopy.

    PubMed Central

    Federwisch, M; Hassiepen, U; Bender, K; Dewor, M; Rajewsky, M F; Wollmer, A

    1997-01-01

    Isoelectric focusing, CD, steady-state and time-resolved fluorescence spectroscopy were used to compare the native recombinant human DNA-repair protein O6-alkylguanine-DNA alkyltransferase (AGT) with AGT derivatives methylated or benzylated on Cys145 or modified by site-directed mutagenesis at the active centre (Met145 mutant). The AGT protein is approximately spherical with highly constrained Trp residues, but is not stabilized by disulphide bridges. In contrast with native AGT, alkylated AGT precipitated at 25 degrees C but remained monomeric at 4 degrees C. As revealed by isoelectric focusing, pI changed from 8.2 (AGT) to 8. 4 (Cys145-methylated AGT) and 8.6 (Cys145-benzylated AGT). The alpha-helical content of the Met145 mutant was decreased by approx. 5% and Trp residues were partially liberated. Although non-covalent binding of O6-benzylguanine did not alter the secondary structure of AGT, its alpha-helical content was increased by approx. 2% on methylation and by approx. 4% on benzylation, altogether indicating a small conformational change in AGT on undergoing alkylation. No signal sequences have been found in AGT that mark it for polyubiquitination. Therefore the signal for AGT degradation remains to be discovered. PMID:9164873

  20. A Clinical Tissue Oximeter Using NIR Time-Resolved Spectroscopy.

    PubMed

    Fujisaka, Shin-ichi; Ozaki, Takeo; Suzuki, Tsuyoshi; Kamada, Tsuyoshi; Kitazawa, Ken; Nishizawa, Mitsunori; Takahashi, Akira; Suzuki, Susumu

    2016-01-01

    The tNIRS-1, a new clinical tissue oximeter using NIR time-resolved spectroscopy (TRS), has been developed. The tNIRS-1 measures oxygenated, deoxygenated and total hemoglobin and oxygen saturation in living tissues. Two-channel TRS measurements are obtained using pulsed laser diodes (LD) at three wavelengths, multi-pixel photon counters (MPPC) for light detection, and time-to-digital converters (TDC) for time-of-flight photon measurements. Incorporating advanced semiconductor devices helped to make the design of this small-size, low-cost and low-power TRS instrument possible. In order to evaluate the correctness and reproducibility of measurement data obtained with the tNIRS-1, a study using blood phantoms and healthy volunteers was conducted to compare data obtained from a conventional SRS device and data from an earlier TRS system designed for research purposes. The results of the study confirmed the correctness and reproducibility of measurement data obtained with the tNIRS-1. Clinical evaluations conducted in several hospitals demonstrated a high level of usability in clinical situations and confirmed the efficacy of measurement data obtained with the tNIRS-1. PMID:26782242

  1. Time-resolved EPR spectroscopy in a Unix environment.

    PubMed

    Lacoff, N M; Franke, J E; Warden, J T

    1990-02-01

    A computer-aided time-resolved electron paramagnetic resonance (EPR) spectrometer implemented under version 2.9 BSD Unix was developed by interfacing a Varian E-9 EPR spectrometer and a Biomation 805 waveform recorder to a PDP-11/23A minicomputer having MINC A/D and D/A capabilities. Special problems with real-time data acquisition in a multiuser, multitasking Unix environment, addressing of computer main memory for the control of hardware devices, and limitation of computer main memory were resolved, and their solutions are presented. The time-resolved EPR system and the data acquisition and analysis programs, written entirely in C, are described. Furthermore, the benefits of utilizing the Unix operating system and the C language are discussed, and system performance is illustrated with time-resolved EPR spectra of the reaction center cation in photosystem 1 of green plant photosynthesis. PMID:2155913

  2. Planetary Surface Exploration Using Time-Resolved Laser Spectroscopy on Rovers and Landers

    NASA Astrophysics Data System (ADS)

    Blacksberg, Jordana; Alerstam, Erik; Maruyama, Yuki; Charbon, Edoardo; Rossman, George

    2013-04-01

    Planetary surface exploration using laser spectroscopy has become increasingly relevant as these techniques become a reality on Mars surface missions. The ChemCam instrument onboard the Curiosity rover is currently using laser induced breakdown spectroscopy (LIBS) on a mast-mounted platform to measure elemental composition of target rocks. The RLS Raman Spectrometer is included on the payload for the ExoMars mission to be launched in 2018 and will identify minerals and organics on the Martian surface. We present a next-generation instrument that builds on these widely used techniques to provide a means for performing both Raman spectroscopy and LIBS in conjunction with microscopic imaging. Microscopic Raman spectroscopy with a laser spot size smaller than the grains of interest can provide surface mapping of mineralogy while preserving morphology. A very small laser spot size (~ 1 µm) is often necessary to identify minor phases that are often of greater interest than the matrix phases. In addition to the difficulties that can be posed by fine-grained material, fluorescence interference from the very same material is often problematic. This is particularly true for many of the minerals of interest that form in environments of aqueous alteration and can be highly fluorescent. We use time-resolved laser spectroscopy to eliminate fluorescence interference that can often make it difficult or impossible to obtain Raman spectra. As an added benefit, we have found that with small changes in operating parameters we can include microscopic LIBS using the same hardware. This new technique relies on sub-ns, high rep-rate lasers with relatively low pulse energy and compact solid state detectors with sub-ns time resolution. The detector technology that makes this instrument possible is a newly developed Single-Photon Avalanche Diode (SPAD) sensor array based on Complementary Metal-Oxide Semiconductor (CMOS) technology. The use of this solid state time-resolved detector offers a significant reduction in size, weight, power, and overall complexity - making time resolved detection feasible for planetary applications. We will discuss significant advances leading to the feasibility of a compact time-resolved spectrometer. We will present results on planetary analog minerals to demonstrate the instrument performance including fluorescence rejection and combined Raman-LIBS capability.

  3. Glucose sensing by time-resolved fluorescence of sol-gel immobilized glucose oxidase.

    PubMed

    Esposito, Rosario; Della Ventura, Bartolomeo; De Nicola, Sergio; Altucci, Carlo; Velotta, Raffaele; Mita, Damiano Gustavo; Lepore, Maria

    2011-01-01

    A monolithic silica gel matrix with entrapped glucose oxidase (GOD) was constructed as a bioactive element in an optical biosensor for glucose determination. Intrinsic fluorescence of free and immobilised GOD was investigated in the visible range in presence of different glucose concentrations by time-resolved spectroscopy with time-correlated single-photon counting detector. A three-exponential model was used for analysing the fluorescence transients. Fractional intensities and mean lifetime were shown to be sensitive to the enzymatic reaction and were used for obtaining calibration curve for glucose concentration determination. The sensing system proposed achieved high resolution (up to 0.17 mM) glucose determination with a detection range from 0.4 mM to 5 mM. PMID:22163807

  4. Monitoring tissue metabolism via time-resolved laser fluorescence

    NASA Astrophysics Data System (ADS)

    Maerz, Holger K.; Buchholz, Rainer; Emmrich, Frank; Fink, Frank; Geddes, Clive L.; Pfeifer, Lutz; Raabe, Ferdinand; Marx, Uwe

    1999-05-01

    Most assays for drug screening are monitoring the metabolism of cells by detecting the NADH content, which symbolize its metabolic activity, indirectly. Nowadays, the performance of a LASER enables us to monitor the metabolic state of mammalian cells directly and on-line by using time-resolved autofluorescence detection. Therefore, we developed in combination with tissue engineering, an assay for monitoring minor toxic effects of volatile organic compounds (VOC), which are accused of inducing Sick Building Syndrome (SBS). Furthermore, we used the Laserfluoroscope (LF) for pharmacological studies on human bone marrow in vitro with special interest in chemotherapy simulation. In cancer research and therapy, the effect of chemostatica in vitro in the so-called oncobiogram is being tested; up to now without great success. However, it showed among other things that tissue structure plays a vital role. Consequently, we succeeded in simulating a chemotherapy in vitro on human bone marrow. Furthermore, after tumor ektomy we were able to distinguish between tumoric and its surrounding healthy tissue by using the LF. With its sensitive detection of metabolic changes in tissues the LF enables a wide range of applications in biotechnology, e.g. for quality control in artificial organ engineering or biocompatability testing.

  5. Subpicosecond time-resolved absorption spectroscopy of alkali halide crystals

    NASA Astrophysics Data System (ADS)

    Thoma, Eben Daniel

    1997-12-01

    Relaxation of fundamental electronic excitation (electron-hole pairs and excitons) in perfect insulators can result in lattice defect formation via self-induced carrier localization (self-trapping). The potential for localization of electronic energy to the unit cell dimension is determined primarily by the strength of charge carrier to lattice phonon coupling. An effective tool for investigating the formation and evolution of radiation induced defects is pump-probe transient absorption spectroscopy. In our formulation of this technique, the 2nd,/ 3rd or 4th harmonics of an amplified 855 nm, 130 fs laser pulse are used to create electron-hole pairs in the sample via two-photon absorption. After the pump beam creates the excitation, the leftover fundamental (or 2nd harmonic) is used to generate a white-light continuum which is used as a probe for the excitation induced absorption. Control over the arrival time of the excitation pulse with respect to the pump pulse is achieved via a path length adjustment. Radiation induced absorption can currently be measured for probe delays of 0 to about 250 ps. This technique allows for observation of the evolution of localized species formation and transient behaviors with as high as 100 fs time resolution. This thesis describes the construction and operation of a subpicosecond transient absorption spectrometer. Included in this description are issues of special data interpretation and analysis which must be considered when working with intrinsic excitation of wide-gap metal halides in the high intensity, subpicosecond regime. Specifically, we have realized that a particular nonlinear mixing of the pump and probe laser (TPCCA) can produce a signal which is easily misinterpreted for a radiation induced defect absorption. This phenomena most likely accounts for a misidentification of the initial absorption signal in several of the alkali halides which have been published by other research groups. This misinterpretation leads to an erroneous conclusion on the nature of the initial self-induced carrier localization in these materials. This thesis additionally presents results on time- resolved defect formation in a variety of alkali halide samples including the first published results in the picosecond regimes for SrF2, AgCl, CsBr, and CsI.

  6. Time-Resolved Spectroscopy of Active Binary Stars

    NASA Technical Reports Server (NTRS)

    Brown, Alexander

    2000-01-01

    This NASA grant covered EUVE observing and data analysis programs during EUVE Cycle 5 GO observing. The research involved a single Guest Observer project 97-EUVE-061 "Time-Resolved Spectroscopy of Active Binary Stars". The grant provided funding that covered 1.25 months of the PI's salary. The activities undertaken included observation planning and data analysis (both temporal and spectral). This project was awarded 910 ksec of observing time to study seven active binary stars, all but one of which were actually observed. Lambda-And was observed on 1997 Jul 30 - Aug 3 and Aug 7-14 for a total of 297 ksec; these observations showed two large complex flares that were analyzed by Osten & Brown (1999). AR Psc, observed for 350 ksec on 1997 Aug 27 - Sep 13, showed only relatively small flares that were also discussed by Osten & Brown (1999). EUVE observations of El Eri were obtained on 1994 August 24-28, simultaneous with ASCA X-ray spectra. Four flares were detected by EUVE with one of these also observed simultaneously, by ASCA. The other three EUVE observations were of the stars BY Dra (1997 Sep 22-28), V478 Lyr (1998 May 18-27), and sigma Gem (1998 Dec 10-22). The first two stars showed a few small flares. The sigma Gem data shows a beautiful complete flare with a factor of ten peak brightness compared to quiescence. The flare rise and almost all the decay phase are observed. Unfortunately no observations in other spectral regions were obtained for these stars. Analysis of the lambda-And and AR Psc observations is complete and the results were published in Osten & Brown (1999). Analysis of the BY Dra, V478 Lyr and sigma Gem EUVE data is complete and will be published in Osten (2000, in prep.). The El Eri EUV analysis is also completed and the simultaneous EUV/X-ray study will be published in Osten et al. (2000, in prep.). Both these latter papers will be submitted in summer 2000. All these results will form part of Rachel Osten's PhD thesis.

  7. Analysis of time-resolved fluorescence anisotropy decays.

    PubMed Central

    Cross, A J; Fleming, G R

    1984-01-01

    We discuss the analysis of time-correlated single photon counting measurements of fluorescence anisotropy. Particular attention was paid to the statistical properties of the data. The methods used previously to analyze these experiments were examined and a new method was proposed in which parallel- and perpendicular-polarized fluorescence curves were fit simultaneously. The new method takes full advantage of the statistical properties of the measured curves; and, in some cases, it is shown to be more sensitive than other methods to systematic errors present in the data. Examples were presented using experimental and simulated data. The influence of fitting range on extracted parameters and statistical criteria for evaluating the quality of fits are also discussed. PMID:6743756

  8. Time-resolved fluorescence measurements using stroboscopic excitation

    NASA Astrophysics Data System (ADS)

    Matthews, Daniel R.; Summers, Huw D.; Njoh, Kerenza; Errington, Rachel J.; Smith, Paul J.; Ameer-Beg, Simon; Vojnovic, Boris

    2005-08-01

    We report on the development of a simple technique for obtaining time-domain information using dc detection of fluorescence. We show that this is feasible for assays where a change in lifetime of an indicator occurs in reaction to an analyte, in fluorescence resonance energy transfer for example, and could be particularly useful for assays performed in the scaled-down environment of a "lab-on-a-chip". A rate equation model is presented which allows an objective analysis of the relative importance of the key measurement parameters: optical saturation of the fluorophore and excitation pulse characteristics. We present a comparison of the model with a cuvette based analysis of a carbocyanine dye where the excitation source is a 650 nm wavelength, self-pulsing AlGaInP laser diode.

  9. Time resolved laser induced fluorescence measurements: Considerations when using Nd:YAG based system

    NASA Astrophysics Data System (ADS)

    Rabasovic, Maja S.; Sevic, Dragutin; Terzic, Mira; Marinkovic, Bratislav P.

    2012-05-01

    Time-resolved laser-induced fluorescence (TR-LIF) and the laser induced breakdown spectroscopy (LIBS) have been shown to be methods which are fast and sensitive to provide information about the constituents in analyzed samples. TR-LIF and LIBS have similar hardware requirements. In this paper, we analyze some characteristics of TR-LIF/LIBS system implemented in our laboratory, considering the fact that the excitation part of the system is based on Nd:YAG laser and Optical Parametric Oscillator (OPO). The laser is more than powerful enough (365 mJ at 1064 nm, variable OPO output >5 mJ) for LIBS, but somehow slow (the length of fundamental laser harmonic output pulse is about 5 ns) for fluorescence measurements in our present area of interest, namely plants and food products. Fortunately, the pulse length of tunable OPO output (320-475 nm) is less then 1 ns, so by means of a correct deconvolution procedure it is possible to measure the fluorescence lifetimes in the range as small as a few nanoseconds. The fluorescence detection part of our system is based on picosecond streak camera. Using the fluorescent dyes (Rhodamine B and Fluorescein) ethanol solutions we verified the analyzing capabilities of our TR-LIF system.

  10. Time-resolved fluorescence measurements of actin-phalloidin interactions

    NASA Astrophysics Data System (ADS)

    Helms, Michael K.; French, Todd E.

    2000-03-01

    Compounds that interact with the cytoskeleton affect mobility and division, making them useful for treatment of certain types of cancer. Actin binding drugs such as the phallotoxins (small, bicyclic peptides) bind to and stabilize actin polymers (F-actin) without binding to actin monomers (G-actin). It has been shown that the intensity of fluorescently labeled phallotoxins such as fluorescein- phalloidin and rhodamine-phalloidin increases upon bind F- actin. We used LJL BioSystems' new FLAReTM technology to measure excited state lifetime changes of fluorescein- phalloidin and rhodamine-phalloidin upon binding to F- actin.

  11. Time-resolved diffuse optical spectroscopy of small tissue samples

    NASA Astrophysics Data System (ADS)

    Taroni, Paola; Comelli, Daniela; Farina, Andrea; Pifferi, Antonio; Kienle, Alwin

    2007-07-01

    Time-resolved transmittance measurements were performed in the wavelength range of 610 or 700 to 1050 nm on phantom slabs and bone tissue cubes of different sizes. The data were best fitted with solutions of the diffusion equation for an infinite slab and for a parallelepiped to investigate how size and optical properties of the samples affect the results obtained with the two models. When small samples are considered, the slab model overestimates both optical coefficients, especially the absorption. The parallelepiped model largely compensates for the small sample size and performs much better also when the absorption spectra are interpreted with the Beer's law to estimate bone tissue composition.

  12. Time-resolved fluorescence and ultrafast energy transfer in a zinc (hydr)oxide-graphite oxide mesoporous composite

    NASA Astrophysics Data System (ADS)

    Secor, Jeff; Narinesingh, Veeshan; Seredych, Mykola; Giannakoudakis, Dimitrios A.; Bandosz, Teresa; Alfano, Robert R.

    2015-01-01

    Ultrafast energy decay kinetics of a zinc (hydr)oxide-graphite oxide (GO) composite is studied via time-resolved fluorescence spectroscopy. The time-resolved emission is spectrally decomposed into emission regions originating from the zinc (hydr)oxide optical gap, surface, and defect states of the composite material. The radiative lifetime of deep red emission becomes an order of magnitude longer than that of GO alone while the radiative lifetime of the zinc optical gap is shortened in the composite. An energy transfer scheme from the zinc (hydr)oxide to GO is considered.

  13. Integrated multimodal microscopy, time-resolved fluorescence, and optical-trap rheometry: toward single molecule mechanobiology

    PubMed Central

    Gullapalli, Ramachandra R.; Tabouillot, Tristan; Mathura, Rishi; Dangaria, Jhanvi H.; Butler, Peter J.

    2011-01-01

    Cells respond to forces through coordinated biochemical signaling cascades that originate from changes in single-molecule structure and dynamics and proceed to large-scale changes in cellular morphology and protein expression. To enable experiments that determine the molecular basis of mechanotransduction over these large time and length scales, we construct a confocal molecular dynamics microscope (CMDM). This system integrates total-internal-reflection fluorescence (TIRF), epifluorescence, differential interference contrast (DIC), and 3-D deconvolution imaging modalities with time-correlated single-photon counting (TCSPC) instrumentation and an optical trap. Some of the structures hypothesized to be involved in mechanotransduction are the glycocalyx, plasma membrane, actin cytoskeleton, focal adhesions, and cell-cell junctions. Through analysis of fluorescence fluctuations, single-molecule spectroscopic measurements [e.g., fluorescence correlation spectroscopy (FCS) and time-resolved fluorescence] can be correlated with these subcellular structures in adherent endothelial cells subjected to well-defined forces. We describe the construction of our multimodal microscope in detail and the calibrations necessary to define molecular dynamics in cell and model membranes. Finally, we discuss the potential applications of the system and its implications for the field of mechanotransduction. PMID:17343487

  14. Time-resolved fluorescence spectroscopic study of flavin fluorescence in purified enzymes of bioluminescent bacteria

    NASA Astrophysics Data System (ADS)

    Vetrova, Elena; Kudryasheva, N.; Cheng, K.

    2006-10-01

    Time-resolved fluorescence intensity and anisotropy decay measurements have been used to study the environment and rotational mobility of endogenous flavin in two purified enzymes of bioluminescent bacteria, Luciferase from Photobacterium leiognathi and NAD(P)H:FMN-oxidoreductase from Vibrio fischeri. We compared the time-resolved fluorescence parameters, intensity decay lifetimes, rotational correlation times, and their fractional contribution, of the endogeneous flavin fluorescence in each of the two enzymes in the presence or absence of quinones of different structures and redox potentials. The endogeneous flavin exhibited multi-exponential decay characteristics as compared to a single decay lifetime of around 5 ns for free flavin, suggesting a complex and heterogeneous environment of flavin bound to the enzyme. In addition, a significant increase in the rotational correlation time and a certain degree of ordering of the molecule were observed for endogenous flavin when compared to a single and fast rotational correlation time of 150 ps of free flavin. Quinone significantly altered both the lifetime and rotational characteristics of endogenous flavin suggesting specific interactions of quinones to the endogeneous flavin in the bacterial enzyme.

  15. Time-resolved phase-sensitive second harmonic generation spectroscopy

    NASA Astrophysics Data System (ADS)

    Nowakowski, Paweł J.; Woods, David A.; Bain, Colin D.; Verlet, Jan R. R.

    2015-02-01

    A methodology based on time-resolved, phase-sensitive second harmonic generation (SHG) for probing the excited state dynamics of species at interfaces is presented. It is based on an interference measurement between the SHG from the sample and a local oscillator generated at a reference together with a lock-in measurement to remove the large constant offset from the interference. The technique is characterized by measuring the phase and excited state dynamics of the dye malachite green at the water/air interface. The key attributes of the technique are that the observed signal is directly proportional to sample concentration, in contrast to the quadratic dependence from non-phase sensitive SHG, and that the real and imaginary parts of the 2nd order non-linear susceptibility can be determined independently. We show that the method is highly sensitive and can provide high quality excited state dynamics in short data acquisition times.

  16. Time-resolved spectroscopy of low-dimensional semiconductor structures

    NASA Astrophysics Data System (ADS)

    Murphy, Joseph R.

    This dissertation is a survey of ultrafast time-resolved optical measurements conducted on a variety of low-dimensional semiconductor systems to further the understanding of the dynamic behavior in the following systems: ZnMnTe/ZnSe quantum dots, ZnTe/ZnMnSe quantum dots, InGaAs quantum wells, CdMnSe colloidal quantum dots, multi-shell CdSe/CdMnS/CdS colloidal nanoplatelets, and graphene and graphene-related solutions and films. Using time-resolved photoluminescence to study epitaxially-grown ZnTe and ZnMnTe quantum dots in corresponding ZnMnSe and ZnSe matrices, the location dependence of manganese ions in respect to magnetic polaron formation is shown. The structure with manganese ions located in the matrix exhibited magnetic polaron behavior consistent with previous literature, whereas the structure with the magnetic ions located within the quantum dots exhibited unconventional magnetic polaron properties. These properties, including temperature and magnetic field insensitivity, were explained through the use of a model that predicted an increased internal magnetic field due to a decreased effective volume of the magnetic polaron and a higher effective temperature due to laser heating. Magneto-time-resolved photoluminescence measurements on a system of colloidal CdMnSe quantum dots show that the magnetic polaron properties differ significantly from the epitaxially grown quantum dots. First the timescales at which the magnetic polaron forms and the polarization saturates are different by more than an order of magnitude, and second, the magnetic polaron energy exhibited step-like behavior as the strength of the externally applied magnetic field is increased. The field dependent MP formation energy that is observed experimentally is explained as due to the breaking of the antiferromagnetic coupling of Mn dimers within the QDs. This model is further verified by the observation of quantized behavior in the Zeeman energy splitting. Through the use of magneto-photoluminescence measurements of InGaAs quantum wells, the observation of optical Aharonov-Bohm oscillations were identified in the photoluminescence emission intensity. This effect, generally observed in type-II systems, was unexpected in a quantum well structure, however the recombinations dynamics were identified through the use of a lifetime comparison with samples that did not contain indium and cross-sectional scanning tunneling microscopy that show indium rich islands within the quantum well layer. Analysis of the oscillations yielded a value of 17.3 nm for the exciton radius for sample 1 and 14.8 nm for sample 2. Magneto-photoluminescence is used to probe the behavior of a series of coreshell- shell CdSe/CdMnS/CdS nanoplatelets. This study shows that the magnetic character of the nanoplatelets is directly related to the wave function overlap of the regions containing manganese ions. The atomically-precise synthesis of these nanoplatelets allows for the placement of magnetic ions in specific monolayers of these two-dimensional heterostructures and the optical characterization identifies how this placement affects the magneto-optical properties. A surprising result is that in some magnetic samples with limited carrier wave function overlap of the regions containing manganese ions, the magneto-optical properties more closely resemble those of non-magnetic samples. Using time-resolved differential transmission, the carrier lifetime in several graphene related structures is determined. In these measurements, the changes in transmission are too small to measure using conventional techniques, therefore a background-free technique is required to obtain the necessary sensitivity. These measurement yielded carrier lifetimes ranging from 0.4 ps to 12 ps depending on the composition of the structure and the form it was measured as i.e., in solution or film.

  17. Time-resolved phase-sensitive second harmonic generation spectroscopy.

    PubMed

    Nowakowski, Paweł J; Woods, David A; Bain, Colin D; Verlet, Jan R R

    2015-02-28

    A methodology based on time-resolved, phase-sensitive second harmonic generation (SHG) for probing the excited state dynamics of species at interfaces is presented. It is based on an interference measurement between the SHG from the sample and a local oscillator generated at a reference together with a lock-in measurement to remove the large constant offset from the interference. The technique is characterized by measuring the phase and excited state dynamics of the dye malachite green at the water/air interface. The key attributes of the technique are that the observed signal is directly proportional to sample concentration, in contrast to the quadratic dependence from non-phase sensitive SHG, and that the real and imaginary parts of the 2nd order non-linear susceptibility can be determined independently. We show that the method is highly sensitive and can provide high quality excited state dynamics in short data acquisition times. PMID:25725724

  18. Optical biopsy of benign and malignant tissue by time resolved spectroscopy.

    PubMed

    Masilamani, V; Das, B B; Secor, J; AlSalhi, M; Devanesan, S; Prasad, S; Rabah, D; Alfano, R R

    2013-12-01

    Pathological condition of malignant tissue could be analyzed by spectral domain or time domain spectroscopy, the two being the complementary to each other in optical biopsy (OB) of cancer. This paper reports results of time resolved emission spectroscopy (TRS) of 24 excised tissue samples of breast and prostate (normal control = 12; benign = 4; malignant = 8), employing a 390 nm, 100 fs, Ti-Sapphire laser pulses.The fluorescence decay times were measured using streak camera and the resultant data were fitted for single and bi-exponential decays with reliability of 97%. Our results show the distinct difference between normal, benign and malignant tissues mostly due to the emission spectra of Nicotinamide Adenine Dinucleotide (NADH), Flavin Mononucleotide (FAD) and also due to the heterogeneity of micro environments associated with the diseased tissues. In this short report, fit is also shown that TRS of breast tissues are similar to those of prostate tissues. PMID:23745786

  19. Study of minerals, organic, and biogenic materials through time-resolved Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Garcia, Christopher S.; Abedin, M. Nurul; Ismail, Syed; Sharma, Shiv K.; Misra, Anupam K.; Nguyen, Trac; Elsayed-Ali, Hani

    2009-05-01

    A compact remote Raman spectroscopy system was developed at NASA Langley Research center and was previously demonstrated for its ability to identify chemical composition of various rocks and minerals. In this study, the Raman sensor was utilized to perform time-resolved Raman studies of various samples such as minerals and rocks, Azalea leaves, and a few fossil samples. The Raman sensor utilizes a pulsed 532 nm Nd:YAG laser as excitation source, a 4-inch telescope to collect the Raman-scattered signal from a sample several meters away, a spectrograph equipped with a holographic grating, and a gated intensified CCD (ICCD) camera system. Time resolved Raman measurements were carried out by varying the gate delay with fixed short gate width of the ICCD camera, allowing measurement of both Raman signals and fluorescence signals. Rocks and mineral samples were characterized, including marble, which contains CaCO3. Analysis of the results reveals the short (~10-13 s) lifetime of the Raman process and shows that the Raman spectra of some mineral samples contain fluorescence emission due to organic impurities. Also analyzed were a green (pristine) and a yellow (decayed) sample of Gardenia leaves. It was observed that the fluorescence signals from the green and yellow leaf samples showed stronger signals compared to the Raman lines. It was also observed that the fluorescence of the green leaf was more intense and had a shorter lifetime than that of the yellow leaf. For the fossil samples, Raman shifted lines could not be observed due to the presence of very strong short-lived fluorescence.

  20. Studies of Minerals, Organic and Biogenic Materials through Time-Resolved Raman Spectroscopy

    NASA Technical Reports Server (NTRS)

    Garcia, Christopher S.; Abedin, M. Nurul; Ismail, Syed; Sharma, Shiv K.; Misra, Anupam K.; Nyugen, Trac; Elsayed-Ali, hani

    2009-01-01

    A compact remote Raman spectroscopy system was developed at NASA Langley Research center and was previously demonstrated for its ability to identify chemical composition of various rocks and minerals. In this study, the Raman sensor was utilized to perform time-resolved Raman studies of various samples such as minerals and rocks, Azalea leaves and a few fossil samples. The Raman sensor utilizes a pulsed 532 nm Nd:YAG laser as excitation source, a 4-inch telescope to collect the Raman-scattered signal from a sample several meters away, a spectrograph equipped with a holographic grating, and a gated intensified CCD (ICCD) camera system. Time resolved Raman measurements were carried out by varying the gate delay with fixed short gate width of the ICCD camera, allowing measurement of both Raman signals and fluorescence signals. Rocks and mineral samples were characterized including marble, which contain CaCO3. Analysis of the results reveals the short (approx.10-13 s) lifetime of the Raman process, and shows that Raman spectra of some mineral samples contain fluorescence emission due to organic impurities. Also analyzed were a green (pristine) and a yellow (decayed) sample of Gardenia leaves. It was observed that the fluorescence signals from the green and yellow leaf samples showed stronger signals compared to the Raman lines. Moreover, it was also observed that the fluorescence of the green leaf was more intense and had a shorter lifetime than that of the yellow leaf. For the fossil samples, Raman shifted lines could not be observed due the presence of very strong short-lived fluorescence.

  1. Study of photon migration depths with time-resolved spectroscopy.

    PubMed

    Cui, W; Wang, N; Chance, B

    1991-11-01

    In this study a light-shielding plate with a hole was placed in an intralipid emulsion. The probability distribution for photons emitted from a surface light source, passing through the hole at different depths, and reaching a surface detector at the other side of the plate was experimentally assessed. We provide qualitative verification for a model derived by Weiss et al. [J. Mod. Opt. 36, 349 (1989)] that the migration depths for the measured photons follow a distribution in depth and that this distribution has a maximum probability at a describable depth beneath the surface. This agreement, corroborated by a parallel study, suggests that we may have assessed the maximum migration depth distribution of photons that reached the detector and that the random walk model may describe the maximum migration depth distribution. The experimental results indicate that photons with the same path lengths within the medium reach a wide range of depths and suggest difficulties in resolving optical structure with time-resolved measurement. The results also provide experimental evidence that, for a given source-detector separation, the photons that migrate deeper have longer mean path lengths with larger variation in their path lengths. PMID:19784091

  2. Solution dynamics of p21ras proteins bound with fluorescent nucleotides: a time-resolved fluorescence study.

    PubMed

    Hazlett, T L; Moore, K J; Lowe, P N; Jameson, D M; Eccleston, J F

    1993-12-14

    The solution dynamics of normal and transforming p21ras proteins in both the GTP- and GDP-bound forms were examined with time-resolved fluorescence spectroscopy. The fluorescent 2'(3')-O-(N-methylanthraniloyl) derivatives (mant derivatives) of GTP, dGTP, and GDP and the aminocoumarin and fluorescein derivatives of GTP and GDP were synthesized and used as reporter groups. The fluorescence lifetimes at 5 degrees C of the mant nucleotide derivatives increased from approximately 4 ns in solution to approximately 9 ns when bound to p21ras. At 30 degrees C, there was a 7.8% difference in lifetime between normal p21ras.mantGTP and p21ras.mantGDP, but no difference between similar complexes of the [Asp-12]p21ras protein. These data are consistent with steady-state fluorescence intensity differences among p21ras.mantGTP, p21ras.mantGDP, and the free nucleotides. Rotational correlation times for the mantGTP- and mantGDP-bound p21 proteins, N-ras, K-ras, and H-ras, were similar at 26 ns (5 degrees C), which is significantly longer than the 15-ns rotational correlation time predicted for a globular 21,000-Da protein. The p21-bound fluorescein and aminocoumarin nucleotide derivatives reported correlation times of 19 and 29 ns, respectively. Global analysis of the three fluorophore.p21 complexes with linked protein rotational correlation functions were best fit with a common rotational correlation time of 28 ns. Gel permeation chromatography of the GDP and mantGDP complexes of normal p21N-ras also showed greater apparent molecular weights than were expected in both cases, demonstrating that the high rotational correlation times obtained from time-resolved fluorescence measurements were not a result of the introduction of the fluorophore.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8257693

  3. Time-resolved laser-induced fluorescence study on dyes used in DNA sequencing

    SciTech Connect

    Chang, Kaisyang; Force, R.K. )

    1993-01-01

    Research on the time-resolved fluorescence of fluorescein isothiocyanate, NBD, tetramethylrhodamine isothiocyanate, and Texas Red - the dyes used for fluorescence-based DNA sequencing - is described. Mean fluorescence lifetiems in both aqueous buffer solution and 5.3%T, 4.8%C polyacrylamide gel were determined as a function of excitation wave-lengths at 337, 470, and 550 nm and were found to be 3.5, 1.1, 2.5, and 4.3 ns; the detection limits are 10, 200, 200 and 200 amol for FITC, NBD, TEMR, and T. Red, respectively. Comparisons of fluorescence parameters between the conjugated dyes and the free dyes are also reported. Results on the optimization of the excitation source wavelengths to improve sensitivity and reduce background scattering in polyacrylamide gel are also reported. Time-resolved fluorescence was successfully applied to resolve spectral overlapping of emissions in both solution and in polyacrylamide gel. 12 refs., 6 figs., 1 tab.

  4. Time-resolved fluorescence of the single tryptophan of Bacillus stearothermophilus phosphofructokinase.

    PubMed Central

    Kim, S J; Chowdhury, F N; Stryjewski, W; Younathan, E S; Russo, P S; Barkley, M D

    1993-01-01

    The fluorescence of the single tryptophan in Bacillus stearothermophilus phosphofructokinase was characterized by steady-state and time-resolved techniques. The enzyme is a tetramer of identical subunits, which undergo a concerted allosteric transition. Time-resolved emission spectral data were fitted to discrete and distributed lifetime models. The fluorescence decay is a double exponential with lifetimes of 1.6 and 4.4 ns and relative amplitudes of 40 and 60%. The emission spectra of both components are identical with maxima at 327 nm. The quantum yield is 0.31 +/- 0.01. The shorter lifetime is independent of temperature; the longer lifetime has weak temperature dependence with activation energy of 1 kcal/mol. The fluorescence intensity and decay are the same in H2O and D2O solutions, indicating that the indole ring is not accessible to bulk aqueous solution. The fluorescence is not quenched significantly by iodide, but it is quenched by acrylamide with bimolecular rate constant of 5 x 10(8) M-1 s-1. Static and dynamic light scattering measurements show that the enzyme is a tetramer in solution with hydrodynamic radius of 40 A. Steady-state and time-resolved fluorescence anisotropies indicate that the tryptophan is immobile. The allosteric transition has little effect on the fluorescence properties. The fluorescence results are related to the x-ray structure. PMID:8369432

  5. Plastique: A synchrotron radiation beamline for time resolved fluorescence in the frequency domain

    NASA Astrophysics Data System (ADS)

    De Stasio, Gelsomina; Zema, N.; Antonangeli, F.; Savoia, A.; Parasassi, T.; Rosato, N.

    1991-06-01

    PLASTIQUE is the only synchrotron radiation beamline in the world that performs time resolved fluorescence experiments in frequency domain. These experiments are extremely valuable sources of information on the structure and dynamics of molecules. We describe the beamline and some initial data.

  6. Fast dynamics in protein folding: Time-resolved fluorescence and absorbance studies of polypeptide reconfigurations

    NASA Astrophysics Data System (ADS)

    Pabit, Sersita Suzette A.

    We are at an era where we are beginning to understand the physical aspects of protein folding. The energy landscape theory of protein folding explains why protein-folding reactions are so rapid compared to random search. The high friction limit of Kramers theory for diffusion-driven reactions best describes protein folding kinetics. However, key biophysical questions remain, particularly in folding dynamics at fast time scales. Why do some protein molecules fold so fast? What physical parameters control the folding rates near the speed limit? We contributed to understanding protein folding at fast time scales by developing and improving techniques to probe submillisecond kinetics and by studying the fastest-folding protein systems: tryptophan cage and the compact late-stage intermediate of ferrocytochrome c. We studied fast dynamics in protein folding by time-resolved fluorescence and absorbance measurements. We fabricated and characterized a submillisecond laminar-flow mixing device that allows UV-excitation and observation of kinetic fluorescence changes in peptides with picomolar sample consumption. Together with equilibrium circular dichroism and fluorescence measurements, we used temperature-jump data to characterize the two-state folding of the designed miniprotein tryptophan cage. We have applied laser flash photolysis to the heme-CO bond and used nanosecond-resolved transient absorption spectroscopy to look at the fast M → N folding transitions in ferrocytochrome c. We are currently developing experiments based on triplet-triplet energy transfer to do time-resolved optical absorption measurements on reconfigurations of tryptophan-containing proteins and peptides. The miniprotein tryptophan cage folds in 4 microseconds and sets the conditions for fast folding: a two-state reaction, a weak folding activation energy barrier, a nearly optimized free energy landscape, and pre-organized structures in the unfolded state. In ferrocytochrome c, the folding time from a compact configuration is 12 microseconds in water. Analysis of the solvent viscosity-dependence of the folding time using a model based on Kramers rate theory allowed us to identify two limiting time scales in protein folding: the time scale for solvent-coupled reorganizations and the time scale controlled by the internal friction within the protein molecule.

  7. Theory of time-resolved Raman scattering and fluorescence emission from semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Kabuss, Julia; Werner, Stefan; Hoffmann, Axel; Hildebrandt, Peter; Knorr, Andreas; Richter, Marten

    2010-02-01

    We present a microscopic description of time-resolved Raman scattering and fluorescence emission of a coupled phonon-quantum dot system. Using density matrix formalism and higher-order Born approximation, the optical emission and scattering spectra of an InGaAs/GaAs-quantum dot are calculated for stationary and pulsed optical excitation. By means of their characteristic decay times, contributions such as Rayleigh, Raman, and fluorescence can be distinguished.

  8. Fluorescence lifetime imaging from time resolved measurements using a shape-based approach.

    PubMed

    Alvarez, Diego; Medina, Paúl; Moscoso, Miguel

    2009-05-25

    We present a novel fluorescent tomography algorithm to estimate the spatial distribution of fluorophores and the fluorescence lifetimes from surface time resolved measurements. The algorithm is a hybridization of the level set technique for recovering the distributions of distinct fluorescent markers with a gradient method for estimating their lifetimes. This imaging method offers several advantages compared to more traditional pixel-based techniques as, for example, well defined boundaries and a better resolution of the images. The numerical experiments show that our imaging method gives rise to accurate reconstructions in the presence of data noise and fluorescence background even for complicated fluorophore distributions in several-centimiter-thick biological tissue. PMID:19466134

  9. Use of Time-Resolved Fluorescence to Monitor Bioactive Compounds in Plant Based Foodstuffs.

    PubMed

    Lemos, M Adília; Sárniková, Katarína; Bot, Francesca; Anese, Monica; Hungerford, Graham

    2015-01-01

    The study of compounds that exhibit antioxidant activity has recently received much interest in the food industry because of their potential health benefits. Most of these compounds are plant based, such as polyphenolics and carotenoids, and there is a need to monitor them from the field through processing and into the body. Ideally, a monitoring technique should be non-invasive with the potential for remote capabilities. The application of the phenomenon of fluorescence has proved to be well suited, as many plant associated compounds exhibit fluorescence. The photophysical behaviour of fluorescent molecules is also highly dependent on their microenvironment, making them suitable probes to monitor changes in pH, viscosity and polarity, for example. Time-resolved fluorescence techniques have recently come to the fore, as they offer the ability to obtain more information, coupled with the fact that the fluorescence lifetime is an absolute measure, while steady state just provides relative and average information. In this work, we will present illustrative time-resolved measurements, rather than a comprehensive review, to show the potential of time-resolved fluorescence applied to the study of bioactive substances. The aim is to help assess if any changes occur in their form, going from extraction via storage and cooking to the interaction with serum albumin, a principal blood transport protein. PMID:26132136

  10. Use of Time-Resolved Fluorescence to Monitor Bioactive Compounds in Plant Based Foodstuffs

    PubMed Central

    Lemos, M. Adília; Sárniková, Katarína; Bot, Francesca; Anese, Monica; Hungerford, Graham

    2015-01-01

    The study of compounds that exhibit antioxidant activity has recently received much interest in the food industry because of their potential health benefits. Most of these compounds are plant based, such as polyphenolics and carotenoids, and there is a need to monitor them from the field through processing and into the body. Ideally, a monitoring technique should be non-invasive with the potential for remote capabilities. The application of the phenomenon of fluorescence has proved to be well suited, as many plant associated compounds exhibit fluorescence. The photophysical behaviour of fluorescent molecules is also highly dependent on their microenvironment, making them suitable probes to monitor changes in pH, viscosity and polarity, for example. Time-resolved fluorescence techniques have recently come to the fore, as they offer the ability to obtain more information, coupled with the fact that the fluorescence lifetime is an absolute measure, while steady state just provides relative and average information. In this work, we will present illustrative time-resolved measurements, rather than a comprehensive review, to show the potential of time-resolved fluorescence applied to the study of bioactive substances. The aim is to help assess if any changes occur in their form, going from extraction via storage and cooking to the interaction with serum albumin, a principal blood transport protein. PMID:26132136

  11. Ultrafast time-resolved spectroscopy of the light-harvesting complex 2 (LH2) from the photosynthetic bacterium Thermochromatium tepidum

    SciTech Connect

    Niedzwiedzki, Dariusz M.; Fuciman, Marcel; Kobayashi, Masayuki; Frank, Harry A.; Blankenship, Robert E.

    2011-10-08

    The light-harvesting complex 2 from the thermophilic purple bacterium Thermochromatium tepidum was purified and studied by steady-state absorption and fluorescence, sub-nanosecond-time-resolved fluorescence and femtosecond time-resolved transient absorption spectroscopy. The measurements were performed at room temperature and at 10 K. The combination of both ultrafast and steady-state optical spectroscopy methods at ambient and cryogenic temperatures allowed the detailed study of carotenoid (Car)-to-bacteriochlorophyll (BChl) as well BChl-to-BChl excitation energy transfer in the complex. The studies show that the dominant Cars rhodopin (N = 11) and spirilloxanthin (N = 13) do not play a significant role as supportive energy donors for BChl a. This is related with their photophysical properties regulated by long π-electron conjugation. On the other hand, such properties favor some of the Cars, particularly spirilloxanthin (N = 13) to play the role of the direct quencher of the excited singlet state of BChl.

  12. Localization of fluorescence marked prostate tumor with time- resolved diffuse optical tomography

    NASA Astrophysics Data System (ADS)

    Hervé, Lionel; Laidevant, Aurélie; Lecordier, Ludovic; Guyon, Laurent; Debourdeau, Mathieu; Boutet, Jérôme; Dinten, Jean-Marc

    2010-02-01

    To increase prostate cancer diagnosis sensibility, we propose to add an optical modality to an US biopsy tool to localize fluorophore marked tumors. Optical signals are acquired on a time-resolved acquisition chain composed by a 770 nm femtosecond laser source and a four channels TCSPC device. The fluorescence concentration is reconstructed by using intensity and mean time of flight acquired from each time-resolved source-detector signal. Validation experiments are performed on a phantom mimicking prostate both on its optical and ultrasound properties with 10 μmol/L ICG 1 cm deep double fluorescent inclusions to simulate marked tumors. An exhaustive search algorithm succeeded in reconstructing the two distinct fluorescence dots with correct locations.

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

    NASA Astrophysics Data System (ADS)

    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.

  14. A fluorescence LIDAR sensor for hyper-spectral time-resolved remote sensing and mapping.

    PubMed

    Palombi, Lorenzo; Alderighi, Daniele; Cecchi, Giovanna; Raimondi, Valentina; Toci, Guido; Lognoli, David

    2013-06-17

    In this work we present a LIDAR sensor devised for the acquisition of time resolved laser induced fluorescence spectra. The gating time for the acquisition of the fluorescence spectra can be sequentially delayed in order to achieve fluorescence data that are resolved both in the spectral and temporal domains. The sensor can provide sub-nanometric spectral resolution and nanosecond time resolution. The sensor has also imaging capabilities by means of a computer-controlled motorized steering mirror featuring a biaxial angular scanning with 200 μradiant angular resolution. The measurement can be repeated for each point of a geometric grid in order to collect a hyper-spectral time-resolved map of an extended target. PMID:23787661

  15. Frame-Transfer Gating Raman Spectroscopy for Time-Resolved Multiscalar Combustion Diagnostics

    NASA Technical Reports Server (NTRS)

    Nguyen, Quang-Viet; Fischer, David G.; Kojima, Jun

    2011-01-01

    Accurate experimental measurement of spatially and temporally resolved variations in chemical composition (species concentrations) and temperature in turbulent flames is vital for characterizing the complex phenomena occurring in most practical combustion systems. These diagnostic measurements are called multiscalar because they are capable of acquiring multiple scalar quantities simultaneously. Multiscalar diagnostics also play a critical role in the area of computational code validation. In order to improve the design of combustion devices, computational codes for modeling turbulent combustion are often used to speed up and optimize the development process. The experimental validation of these codes is a critical step in accepting their predictions for engine performance in the absence of cost-prohibitive testing. One of the most critical aspects of setting up a time-resolved stimulated Raman scattering (SRS) diagnostic system is the temporal optical gating scheme. A short optical gate is necessary in order for weak SRS signals to be detected with a good signal- to-noise ratio (SNR) in the presence of strong background optical emissions. This time-synchronized optical gating is a classical problem even to other spectroscopic techniques such as laser-induced fluorescence (LIF) or laser-induced breakdown spectroscopy (LIBS). Traditionally, experimenters have had basically two options for gating: (1) an electronic means of gating using an image intensifier before the charge-coupled-device (CCD), or (2) a mechanical optical shutter (a rotary chopper/mechanical shutter combination). A new diagnostic technology has been developed at the NASA Glenn Research Center that utilizes a frame-transfer CCD sensor, in conjunction with a pulsed laser and multiplex optical fiber collection, to realize time-resolved Raman spectroscopy of turbulent flames that is free from optical background noise (interference). The technology permits not only shorter temporal optical gating (down to <1 s, in principle), but also higher optical throughput, thus resulting in a substantial increase in measurement SNR.

  16. Halide (Cl(super -)) Quenching of Quinine Sulfate Fluorescence: A Time-Resolved Fluorescence Experiment for Physical Chemistry

    ERIC Educational Resources Information Center

    Gutow, Jonathan H.

    2005-01-01

    The time-resolved fluorescence experiment investigating the halide quenching of fluorescence from quinine sulfate in water is described. The objectives of the experiment include reinforcing student understanding of the kinetics of competing pathways, making connections with microscopic theories of kinetics through comparison of experimental and

  17. Halide (Cl(super -)) Quenching of Quinine Sulfate Fluorescence: A Time-Resolved Fluorescence Experiment for Physical Chemistry

    ERIC Educational Resources Information Center

    Gutow, Jonathan H.

    2005-01-01

    The time-resolved fluorescence experiment investigating the halide quenching of fluorescence from quinine sulfate in water is described. The objectives of the experiment include reinforcing student understanding of the kinetics of competing pathways, making connections with microscopic theories of kinetics through comparison of experimental and…

  18. Multiplexed analysis using time-resolved near-IR fluorescence for the detection of genomic material

    NASA Astrophysics Data System (ADS)

    Stryjewski, Wieslaw J.; Soper, Steven A.; Lassiter, Suzzane; Davis, Lloyd M.

    2002-06-01

    While fluorescence continues to be an important tool in genomics, new challenges are being encountered due to increased efforts toward miniaturization reducing detection volumes and the need for screening multiple targets simultaneously. We have initiated work on developing time- resolved near-IR fluorescence as an additional tool for the multiplexed analyses of DNA, either for sequencing or mutation detection. We have fabricated simple and compact time-resolved fluorescence microscopes for reading fluorescence from electrophoresis or DNA microarrays. These microscopes consist of solid-state diode lasers and diode detectors and due to their compact size, the optical components and laser head can be mounted on high-speed micro-translational stages to read fluorescence from either multi-channel capillary electrophoresis instruments or micro fabricated DNA sorting devices. The detector is configured in a time-correlated single photon counting format to allow acquisition of fluorescence lifetimes on-the-fly during data acquisition in the limit of low counting statistics. In multiplexed analyses, lifetime discrimination serves as a method for dye-reporter identification using only a single readout channel. Also, coupled to multi-color systems, lifetime identification can significantly increase the number of probes monitored in a single instrument. In this work, near-IR fluorescence, including dye-labels and hardware, will be discussed as well as the implementation of near-IR fluorescence in DNA sequencing using slab gel electrophoresis and DNA microarrays.

  19. CMOS Time-Resolved, Contact, and Multispectral Fluorescence Imaging for DNA Molecular Diagnostics

    PubMed Central

    Guo, Nan; Cheung, Ka Wai; Wong, Hiu Tung; Ho, Derek

    2014-01-01

    Instrumental limitations such as bulkiness and high cost prevent the fluorescence technique from becoming ubiquitous for point-of-care deoxyribonucleic acid (DNA) detection and other in-field molecular diagnostics applications. The complimentary metal-oxide-semiconductor (CMOS) technology, as benefited from process scaling, provides several advanced capabilities such as high integration density, high-resolution signal processing, and low power consumption, enabling sensitive, integrated, and low-cost fluorescence analytical platforms. In this paper, CMOS time-resolved, contact, and multispectral imaging are reviewed. Recently reported CMOS fluorescence analysis microsystem prototypes are surveyed to highlight the present state of the art. PMID:25365460

  20. Time-resolved fluorescence in immunocytochemical detection of prostate-specific antigen in prostatic tissue sections.

    PubMed

    Bjartell, A; Laine, S; Pettersson, K; Nilsson, E; Lövgren, T; Lilja, H

    1999-01-01

    Chelates with fluorescent lanthanides such as europium and terbium are widely used in immunofluorometric assays, e.g. for the measurement of different molecular forms of prostate-specific antigen (PSA) in serum for detection and monitoring of prostate cancer. These chelates have also been introduced as non-radioactive labels in immunocytochemistry and in situ hybridization. In the present study, sections of non-malignant prostate were investigated using monoclonal IgGs against PSA. Detection of specific immunostaining employing time-resolved fluorescence with europium-labeled streptavidin was compared with conventional detection by streptavidin conjugated to horse-radish peroxidase. The high PSA concentration in the tissue produced high intensity, specific time-resolved fluorescence signals in the epithelial cells of the prostate gland without disturbance from non-specific tissue autofluorescense. This allowed short exposure times to be used which resulted in insignificant photobleaching. Two of the three europium-chelates evaluated yielded high signal intensities. Counterstaining was found to be optimal with Gill No. 1-Haematoxylin solution and Merckoglas was the best mounting medium for the europium chelates tested. In conclusion, time-resolved fluorescence imaging is an attractive alternative to conventional detection of streptavidin conjugated to horse-radish peroxidase, as it provides linear, high intensity, specific signals subsequent to the decay of non-specific tissue autofluorescence. PMID:10405822

  1. Identifying Fossil Biosignatures and Minerals in Mars Analog Materials Using Time-Resolved Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    Shkolyar, S.; Farmer, J.; Alerstam, E.; Maruyama, Y.; Blacksberg, J.

    2013-12-01

    Mars sample return has been identified as a top priority in the planetary science decadal survey. A Mars sample selection and caching mission would be the likely first step in this endeavor. Such a mission would aim to select and prioritize for return to Earth aqueously formed geological samples present at a selected site on Mars, based upon their potential for biosignature capture and preservation. If evidence of past life exists and is found, it is likely to come via the identification of fossilized carbonaceous matter of biological origin (kerogen) found in the selected samples analyzed in laboratories after return to Earth. Raman spectroscopy is considered one of the primary techniques for analyzing materials in situ and selecting the most promising samples for Earth return. We have previously performed a pilot study to better understand the complexities of identifying kerogen using Raman spectroscopy. For the study, we examined a variety of Mars analog materials representing a broad range of mineral compositions and kerogen maturities. The study revealed that kerogen identification in many of the most promising lithologies is often impeded by background fluorescence that originates from long (>10 ns to ms) and short (<1 ns) lifetime fluorophores in both the mineral matrixes and preserved organic matter in the samples. This work explores the potential for time-gated Raman spectroscopy to enable clear kerogen and mineral identifications in such samples. The JPL time-resolved Raman system uses time gating to reduce background fluorescence. It uses a custom-built SPAD (single photon avalanche diode) detector, featuring a 1-ns time-gate, and electronically variable gate delay. Results for a range of fluorescent samples show that the JPL system reduces fluorescence, allowing the identification of both kerogen and mineral components more successfully than with conventional Raman systems. In some of the most challenging samples, the detection of organic matter is hindered by a combination of short lifetime fluorescence and weak Raman scattering coming from preserved kerogen grains. Fluorescence Lifetime Imaging Microscopy (FLIM) measurements were also performed to characterize the lifetimes of both components in the samples and to inform future system improvements such as shorter time gating. Here, we will discuss the results, along with identified challenges to the consistent and reliable in situ identification of kerogen in samples on Mars.

  2. Feasibility analysis of an epidermal glucose sensor based on time-resolved fluorescence

    NASA Astrophysics Data System (ADS)

    Katika, Kamal M.; Pilon, Laurent

    2007-06-01

    The goal of this study is to test the feasibility of using an embedded time-resolved fluorescence sensor for monitoring glucose concentration. Skin is modeled as a multilayer medium with each layer having its own optical properties and fluorophore absorption coefficients, lifetimes, and quantum yields obtained from the literature. It is assumed that the two main fluorophores contributing to the fluorescence at these excitation and emission wavelengths are nicotinamide adenine dinucleotide (NAD)H and collagen. The intensity distributions of excitation and fluorescent light in skin are determined by solving the transient radiative transfer equation by using the modified method of characteristics. The fluorophore lifetimes are then recovered from the simulated fluorescence decays and compared with the actual lifetimes used in the simulations. Furthermore, the effect of adding Poissonian noise to the simulated decays on recovering the lifetimes was studied. For all cases, it was found that the fluorescence lifetime of NADH could not be recovered because of its negligible contribution to the overall fluorescence signal. The other lifetimes could be recovered to within 1.3% of input values. Finally, the glucose concentrations within the skin were recovered to within 13.5% of their actual values, indicating a possibility of measuring glucose concentrations by using a time-resolved fluorescence sensor.

  3. Time-Resolved Fluorescence in Lipid Bilayers: Selected Applications and Advantages over Steady State

    PubMed Central

    Amaro, Mariana; Šachl, Radek; Jurkiewicz, Piotr; Coutinho, Ana; Prieto, Manuel; Hof, Martin

    2014-01-01

    Fluorescence methods are versatile tools for obtaining dynamic and topological information about biomembranes because the molecular interactions taking place in lipid membranes frequently occur on the same timescale as fluorescence emission. The fluorescence intensity decay, in particular, is a powerful reporter of the molecular environment of a fluorophore. The fluorescence lifetime can be sensitive to the local polarity, hydration, viscosity, and/or presence of fluorescence quenchers/energy acceptors within several nanometers of the vicinity of a fluorophore. Illustrative examples of how time-resolved fluorescence measurements can provide more valuable and detailed information about a system than the time-integrated (steady-state) approach will be presented in this review: 1), determination of membrane polarity and mobility using time-dependent spectral shifts; 2), identification of submicroscopic domains by fluorescence lifetime imaging microscopy; 3), elucidation of membrane leakage mechanisms from dye self-quenching assays; and 4), evaluation of nanodomain sizes by time-resolved Förster resonance energy transfer measurements. PMID:25517142

  4. Subcellular localization-dependent changes in EGFP fluorescence lifetime measured by time-resolved flow cytometry

    PubMed Central

    Gohar, Ali Vaziri; Cao, Ruofan; Jenkins, Patrick; Li, Wenyan; Houston, Jessica P.; Houston, Kevin D.

    2013-01-01

    Intracellular protein transport and localization to subcellular regions are processes necessary for normal protein function. Fluorescent proteins can be fused to proteins of interest to track movement and determine localization within a cell. Currently, fluorescence microscopy combined with image processing is most often used to study protein movement and subcellular localization. In this contribution we evaluate a high-throughput time-resolved flow cytometry approach to correlate intracellular localization of human LC3 protein with the fluorescence lifetime of enhanced green fluorescent protein (EGFP). Subcellular LC3 localization to autophagosomes is a marker of the cellular process called autophagy. In breast cancer cells expressing native EGFP and EGFP-LC3 fusion proteins, we measured the fluorescence intensity and lifetime of (i) diffuse EGFP (ii) punctate EGFP-LC3 and (iii) diffuse EGFP-ΔLC3 after amino acid starvation to induce autophagy-dependent LC3 localization. We verify EGFP-LC3 localization with low-throughput confocal microscopy and compare to fluorescence intensity measured by standard flow cytometry. Our results demonstrate that time-resolved flow cytometry can be correlated to subcellular localization of EGFP fusion proteins by measuring changes in fluorescence lifetime. PMID:24010001

  5. BHHST: An improved lanthanide chelate for time-resolved fluorescence applications

    NASA Astrophysics Data System (ADS)

    Connally, Russell; Jin, Dayong; Piper, James

    2005-04-01

    The detection of the waterborne pathogens Giardia lamblia and Cryptosporidium parvum in environmental water bodies requires concentration of large volumes of water due to the low dose required for infection. The highly concentrated (10,000-fold) water sample is often rich in strongly autofluorescent algae, organic debris and mineral particles that can obscure immunofluorescently labeled (oo)cysts during analysis. Time-resolved fluorescence techniques exploit the long fluorescence lifetimes of lanthanide chelates (ms) to differentiate target fluorescence from background autofluorescence (ns). Relatively simple instrumentation can be used to enhance the signal-to-noise ratio (S/N) of labelled target. Time-resolved fluorescence techniques exploit the large difference in lifetime by briefly exciting fluorescence from the sample using a pulsed excitation source. Capture of the resulting fluorescence emission is delayed until the more rapidly decaying autofluorescence has faded beyond detection, whereon the much stronger and slower fading emission from labelled target is collected. BHHCT is a tetradentate beta-diketone chelate that is activated to bind with protein (antibody) as the chlorosulfonate. The high activity of this residue makes conjugations difficult to control and can lead to the formation of unstable immunoconjugates. To overcome these limitations a 5-atom hydrophylic molecular tether was attached to BHHCT via the chlorosulfonate and the BHHCT derivative was then activated to bind to proteins as the succinimide. The new compound (BHHST) could be prepared in high purity and was far more stable than the chlorosulfonate on storage. A high activity immunocojugate was prepared against Cryptosporidium that yielded an 8-fold increase in SNR using a lab-built time-resolved fluorescence microscope.

  6. Multicolor Photometry and Time-resolved Spectroscopy of Two sdBV Stars

    NASA Astrophysics Data System (ADS)

    Reed, M. D.; O'Toole, S. J.; Telting, J. H.; Østensen, R. H.; Heber, U.; Barlow, B. N.; Reichart, D. E.; Nysewander, M. C.; LaCluyze, A. P.; Ivarsen, K. M.; Haislip, J. B.; Bean, J.

    2012-03-01

    Observational mode constraints have mostly been lacking for short period pulsating sdB stars, yet such identifications are vital to constrain models. Time-resolved spectroscopy and multicolor photometry have been employed with mixed results for short-period pulsating sdB stars. Time-resolved spectroscopy has successfully measured radial velocity, temperature, and gravity variations in six pulsators, yet interpreting results is far from straightforward. Multicolor photometry requires extremely high precision to discern between low-degree modes, yet has been used effectively to eliminate high-degree modes. Combining radial velocity (RV) and multicolor measurements has also been shown as an effective means of constraining mode identifications. We present preliminary results for Feige 48 and EC 01541-1409 using both time-resolved spectroscopy and multicolor photometry and an initial examination of their pulsation modes using the atmospheric codes BRUCE and KYLIE.

  7. A continuous time-resolved fluorescence assay for identification of BACE1 inhibitors.

    PubMed

    Porcari, Valentina; Magnoni, Letizia; Terstappen, Georg C; Fecke, Wolfgang

    2005-06-01

    The aspartic protease beta-site amyloid precursor protein cleaving enzyme 1 (BACE1) mediates the production of the neurotoxic amyloid beta peptide and is therefore considered an important drug target for treatment of Alzheimer's disease. We describe a new homogeneous time-resolved fluorescence quenching assay for the identification of BACE1 inhibitors that is characterized by minimal compound interference and allows both kinetic and end-point measurements. A fluorescent Eu-chelate as fluorescent donor, coupled to the N-terminus of a peptide containing the amyloid precursor protein Swedish mutation with a quenching molecule at the C-terminus as acceptor, is used as substrate. Upon peptide cleavage by BACE1, the energy transfer between donor and acceptor molecules is interrupted, leading to increased fluorescence emission of the donor. Compound interference, a common problem in fluorescence assays, is minimized with this technology because of the large Stoke's shift and the time-resolved fluorescence emission of the Eu-chelate. The assay reproduced IC50 values of known inhibitors and detected them also as hits in a screening campaign. A high signal-to-noise ratio of 289 and a Z' factor of 0.76 make this assay suitable for high-throughput screening. PMID:15971990

  8. Time-resolved fluorescence ligand binding for G protein-coupled receptors.

    PubMed

    Emami-Nemini, Alexander; Roux, Thomas; Leblay, Marion; Bourrier, Emmanuel; Lamarque, Laurent; Trinquet, Eric; Lohse, Martin J

    2013-01-01

    G protein-coupled receptors (GPCRs) and their ligands are traditionally characterized by radioligand-binding experiments. These experiments yield excellent quantitative data, but have low temporal and spatial resolution. In addition, the use of radioligands presents safety concerns. Here we provide a general procedure for an alternative approach with high temporal and spatial resolution, based on Tb(+)-labeled fluorescent receptor ligands and time-resolved fluorescence resonance energy transfer (TR-FRET). This protocol and its design are detailed here for the parathyroid hormone receptor, a class B GPCR, and its fluorescently labeled 34-amino acid peptide ligand, but it can be easily modified for other receptors and their appropriately labeled ligands. We discuss three protocol options that use Tb(+)-labeled fluorescent ligands: a time-resolved fluorescence separation option that works on native receptors but requires separation of bound and unbound ligand; a TR-FRET option using SNAP-tag-labeled receptors for high-throughput screening; and a TR-FRET option that uses fluorescently labeled antibodies directed against an epitope engineered into the Flag-labeled receptors' N terminus. These protocol options can be used as standard procedures with very high signal-to-background ratios in order to characterize ligands and their receptors in living cells and in cell membranes via straightforward plate-reader measurements. PMID:23764938

  9. Computational modeling of time-resolved fluorescence transport in turbid media for non-invasive clinical diagnostics

    NASA Astrophysics Data System (ADS)

    Vishwanath, Karthik

    Fluorescence spectroscopy and imaging methods, including fluorescence lifetime sensing, are being developed for a variety of non-invasive clinical diagnostic procedures, including applications to early cancer diagnosis. Here, both the theoretical developments and experimental validations of a versatile, numerical Monte Carlo code that models photon migration in turbid media to include simulations of time-resolved fluorescence transport are presented. The developed numerical model was used to study, for the first time, the dependence of time-resolved fluorescence signals emanating from turbid media on the optical transport coefficients, fluorophore properties and source-detector configurations in single-layered turbid media as well as more complex multi-layered turbid media. The numerical codes presented here can be adapted to model a wide range of experimental techniques measuring the optical responses of biological tissues to laser irradiation and are demonstrated here for two specific applications (a) to model time-resolved fluorescence dynamics in human colon tissues and (b) to extract the frequency-dependent optical responses of a model adult human head to an incident laser-source whose intensity was harmonically modulated i.e. simulating frequency-domain measurements. Specifically, measurements of time-resolved fluorescence decays from a previous clinical study aimed toward detecting differences in tissue pathologies in patients undergoing gastro-intestinal endoscopy were simulated using the Monte Carlo model and results demonstrated that variations in tissue optical transport coefficients (absorption and scattering) alone could not account for the fluorescence decay differences detected between tissue pathologies in vivo. However, variations in fluorescence decay time as large as those detected clinically between normal and pre-malignant tissues (of 2 ns) could be accounted for by simulated variations in tissue morphology or biochemistry while intrinsic fluorophore lifetimes were held constant. Potential applications of the numerical code for the construction of optimized fiber-probes for efficient clinical diagnostics and the reconstruction of tissue optical properties to match experimental measurements, possibly in real-time via the use of heuristic scaling procedures, are discussed.

  10. Time-resolvable fluorescent conjugates for the detection of pathogens in environmental samples containing autofluorescent material

    NASA Astrophysics Data System (ADS)

    Connally, Russell; Veal, Duncan; Piper, James A.

    2003-07-01

    Water is routinely monitored for environmental pathogens such a Cryptosporidium and Giardia using immunofluorescence microscopy (IFM). Autofluorescence can greatly diminish an operators capacity to resolve labeled pathogens from non-specific background. Naturally fluorescing components (autofluorophores) encountered in biological samples typically have fluorescent lifetimes (τ) of less than 100 nanoseconds and their emissions may be excluded through use of time-resolved fluorescence microscopy (TRFM). TRFM relies on the large differences in τ between autofluorescent molecules and long-lived lanthanide chelates. In TRFM, targets labeled with a time-resolvable fluorescent immunoconjugate are excited by an intense (UV) light pulse. A short delay is imposed to permit the decay of autofluorescence before capture of luminescence from the excited chelate using an image intensified CCD camera. In our experience, autofluorescence can be reduced to insignificant levels with a consequent 30-fold increase in target visibility using TRFM techniques. We report conjugation of a novel europium chelate to a monoclonal antibody specific for Giardia lamblia and use of the immunoconjugate for TRFM studies. Initial attempts to conjugate the same chelate to a monoclonal antibody directed against Cryptosporidium parvum led to poorly fluorescent constructs that were prone to denature and precipitate. We successfully conjugated BHHCT to anti-mouse polyvalent immunoglobulin and used this construct to overcome the difficulties in direct labeling of the anti-Cryptosporidium antibody. Both Giardia and Cryptosporidium were labeled using the anti-mouse protocol with a subsequent 20-fold and 6.6-fold suppression of autofluorescence respectively. A rapid protocol for conjugating and purifying the immunoconjugate was found and methods of quantifying the fluorescence to protein ratio determined. Performance of our TRFM was dependent on the quality and brightness of the immunoconjugate and optimization of the conjugation process is necessary to reap the full benefit of time-resolved techniques.

  11. Molecular diffusivity measurement through an alumina membrane using time-resolved fluorescence imaging

    NASA Astrophysics Data System (ADS)

    Kennard, Raymond; DeSisto, William J.; Mason, Michael D.

    2010-11-01

    We present a simple fluorescence imaging method for measuring the time-resolved concentration of a fluorescent molecule diffusing through an anodic alumina membrane with a pore diameter of 20 nm. From the concentration breakthrough curve, the molecular diffusivity of the fluorophore was extracted. The experimentally determined diffusivity was three orders of magnitude lower than reported bulk values. Due to the relative simplicity and ease of use, this method can be applied to provide fundamental information for biomolecular separations applications. One feature of this method is the high sensitivity at intercellular volumes broadening its application to drug delivery and controlled cell growth.

  12. Standoff Time-Resolved Laser-Based Spectroscopy Tools for Sample Characterization and Biosignature Detection

    NASA Astrophysics Data System (ADS)

    Gasda, P. J.; Acosta-Maeda, T.; Lucey, P. G.; Misra, A. K.; Sharma, S. K.; Taylor, J.

    2014-12-01

    The NASA Mars2020 rover will be searching for signs of past habitability and past life on Mars. Additionally, the rover mission will prepare a cache of highly significant samples for a future sample return mission. NASA requires these samples to be well characterized; the instruments on the rover must be capable of fine-scale in situ mineralogical or elemental analysis with emphasis on biosignature detection or characterization. We have been developing multiple standoff laser-based instruments at the University of Hawaii, Manoa that are capable of fine-scale in situ chemical analysis and biosignatures detection. By employing a time-resolved spectroscopy, we can perform elemental analysis with Laser-Induced Breakdown Spectroscopy (LIBS), mineral and organic analysis with Raman spectroscopy, and biosignature detection with Laser-Induced Fluorescence (LIF). Each of these techniques share the same optics and detection equipment, allowing us to integrate them into a single, compact instrument. High time-resolution (~100 ns/pulse) is the key to this instrument; with it, the detector only records data when the signal is the brightest. Spectra can be taken during the day, LIBS can be measured without a plasma light background, and the Raman signal can be separated from the mineral fluorescence signal. Since bio-organics have very short fluorescence lifetimes, the new instrument can be used to unambiguously detect bio-organics. The prototype uses a low power (0.5 mJ/pulse) 532 nm laser with a detection limit of < 30 ppm of organics in a sample of Antarctica Dry Valley soil measured from 8 m. Another LIF instrument under development in our lab, called the Biofinder, takes advantage of the extremely intense fluorescence signal produced by organics by using a wide laser spot and a camera to produce LIF images of wide area (25 cm area from 2 m distance with 2 mm/pixel resolution). The Biofinder can quickly assess the area around the rover (at 10 frames/s) by imaging sample cores, drill holes, or outcrops, and then allow the slower but more precise instruments on the rover to characterize the regions of interest. Either of these prototypes would be ideally suited for future NASA missions, including human exploration missions. The next iterations of the instruments will be designed specifically for future astronaut explorers.

  13. Time-resolved fluorescence monitoring of cholesterol in peripheral blood mononuclear cells

    NASA Astrophysics Data System (ADS)

    Martinakova, Z.; Horilova, J.; Lajdova, I.; Marcek Chorvatova, A.

    2014-12-01

    Precise evaluation of intracellular cholesterol distribution is crucial for improving diagnostics of diseased states associated with cholesterol alteration. Time-resolved fluorescence techniques are tested for non-invasive investigation of cholesterol in living cells. Fluorescent probe NBD attached to cholesterol was employed to evaluate cholesterol distribution in peripheral blood mononuclear cells (PBMC) isolated from the human blood. Fluorescence Lifetime Imaging Microscopy (FLIM) was successfully applied to simultaneously monitor the spatial distribution and the timeresolved characteristics of the NBD-cholesterol fluorescence in PBMC. Gathered data are the first step in the development of a new perspective non-invasive diagnostic method for evaluation of cholesterol modifications in diseases associated with disorders of lipid metabolism.

  14. Two-Photon Absorption and Time-Resolved Stimulated Emission Depletion Spectroscopy of a New Fluorenyl Derivative

    PubMed Central

    Bondar, Mykhailo V.; Morales, Alma R.; Yue, Xiling; Luchita, Gheorghe; Przhonska, Olga V.; Kachkovsky, Olexy D.

    2012-01-01

    The synthesis, comprehensive linear photophysical characterization, two-photon absorption (2PA), steady-state and time-resolved stimulated emission depletion properties of a new fluorene derivative, (E)-1-(2-(di-p-tolylamino)-9,9-diethyl-9H-fluoren-7-yl)-3-(thiophen-2-yl)prop-2-en-1-one (1), are reported. The primary linear spectral properties, including excitation anisotropy, fluorescence lifetimes, and photostability, were investigated in a number of aprotic solvents at room temperature. The degenerate 2PA spectra of 1 were obtained with an open aperture Z-scan and two-photon induced fluorescence methods, using a 1-kHz femtosecond laser system, and maximum 2PA cross-sections of ~400–600 GM were obtained. The nature of the electronic absorption processes in 1 was investigated by DFT-based quantum chemical methods implemented in the Gaussian 09 program. The one- and two-photon stimulated emission spectra of 1 were measured over a broad spectral range using a femtosecond pump probe–based fluorescence quenching technique, while a new methodology for time-resolved fluorescence emission spectroscopy is proposed. An effective application of 1 in fluorescence bioimaging was demonstrated via one- and two-photon fluorescence microscopy images of HCT 116 cells containing the dye encapsulated micelles. PMID:22887914

  15. Time-resolved VUV spectroscopy in the EXTRAP-T2 reversed field pinch

    NASA Astrophysics Data System (ADS)

    Hedqvist, Anders; Rachlew-Källne, Elisabeth

    1998-09-01

    Time-resolved VUV spectroscopy has been used to investigate the effects of impurities in a reversed field pinch operating with a resistive shell. Results of electron temperature, impurity ion densities, particle confinement time and 0741-3335/40/9/004/img1 together with a description of the interpretation and the equipment are presented.

  16. Time-resolved optical spectroscopy of the chest: is it possible to probe the lung?

    NASA Astrophysics Data System (ADS)

    Quarto, G.; Farina, A.; Pifferi, A.; Taroni, P.; Miniati, M.

    2013-06-01

    Monte Carlo simulations and preliminary time-resolved spectroscopy measurements were performed to investigate the feasibility of the in vivo optical diagnostics of lung conditions and diseases. Absorption and reduced scattering properties of the chest, arising from in vivo spectral measurements on volunteers are presented.

  17. Time-resolved scanning system for double reflectance and transmittance fluorescence imaging of diffusive media

    NASA Astrophysics Data System (ADS)

    Brambilla, Marco; Spinelli, Lorenzo; Pifferi, Antonio; Torricelli, Alessandro; Cubeddu, Rinaldo

    2008-01-01

    In this work we present a novel diffuse fluorescence imaging system, based on time-resolved two-wavelength double reflectance and transmittance setup for slab geometry samples. We describe the hardware setup, showing its compactness and versatility and show the results on preliminary measurements on phantoms. We fully assessed the performances and the dynamic ranges of the system. We validated its ability of recovering the optical properties of the bulk medium, for samples with scattering and absorption coefficients similar to those of biological tissues and with thicknesses of about 2cm. Moreover we assess the linearity of the recorded signals against the fluorophore concentration, when it is homogeneously diffused in the phantom or concentrated inside a sealed inclusion. In both cases we observe again a fairly good linearity, over three orders of magnitude, from 10-8M to 10-5M. With the fluorescent inclusion we were also able to assess the imaging capabilities of the system, in terms of spatial resolution, which we appraise in about 3mm, and in terms of imaging sensitivity (the smallest quantity of fluorescent dye distinguishable from the homogeneous background), settled to 200fmol. Since the recorded data are time resolved, we could also estimate the dye fluorescence lifetime and build early and late time gate images. We finally discuss some of the criticalities of the proposed system and the developments we are currently carrying on in order to adapt it for in vivo measurements.

  18. Photophysical and photochemical properties of 4-thiouracil: time-resolved IR spectroscopy and DFT studies.

    PubMed

    Zou, Xiaoran; Dai, Xiaojuan; Liu, Kunhui; Zhao, Hongmei; Song, Di; Su, Hongmei

    2014-06-01

    Intensified research interests are posed with the thionucleobase 4-thiouracil (4-TU), due to its important biological function as site-specific photoprobe to detect RNA structures and nucleic acid-nucleic acid contacts. By means of time-resolved IR spectroscopy and density functional theory (DFT) studies, we have examined the unique photophysical and photochemical properties of 4-TU. It is shown that 4-TU absorbs UVA light and results in the triplet formation with a high quantum yield (0.9). Under N2-saturated anaerobic conditions, the reactive triplet undergoes mainly cross-linking, leading to the (5-4)/(6-4) pyrimidine-pyrimidone product. In the presence of O2 under aerobic conditions, the triplet 4-TU acts as an energy donor to produce singlet oxygen (1)O2 by triplet-triplet energy transfer. The highly reactive oxygen species (1)O2 then reacts readily with 4-TU, leading to the products of uracil (U) with a yield of 0.2 and uracil-6-sulfonate (U(SO3)) that is fluorescent at ~390 nm. The product formation pathways and product distribution are well rationalized by the joint B3LYP/6-311+G(d,p) calculations. From dynamics and mechanistic point of views, these results enable a further understanding for 4-TU acting as reactive precursors for photochemical reactions relevant to (1)O2, which has profound implications for photo cross-linking, DNA photodamage, as well as photodynamic therapy studies. PMID:24820207

  19. Host Sensitized Luminescence and Time-Resolved Spectroscopy of YVO4: Ho3+ Nanocrystals

    NASA Astrophysics Data System (ADS)

    Mahata, Manoj Kumar; Koppe, Tristan; Hofsss, Hans; Kumar, Kaushal; Vetter, Ulrich

    Rare earth doped phosphors have attracted much interest because of their high chemical durability and wide range of attractive applications. In this work, Ho3+ doped tetragonal YVO4 nanocrystals have been synthesized via a facile co-precipitation method. The phosphor was characterized by various methods including X-ray diffraction, photoluminescence, cathodoluminescence, time-resolved spectroscopy measurements. The frequency upconversion emission in the synthesized phosphor has been investigated under 800 nm laser excitation. UV-excited photoluminescence (PL) and cathodoluminescence (CL) measurements were performed at room temperature (300 K). A broad band which arises at ? 370-600 nm is attributed to the relaxation of VO43- groups from conduction band to valence band. Under UV-excitation, the presence of a sharp band at 550 nm due to the intra-4f transitions of the trivalent holmium ions suggests energy transfer from YVO4 host to RE ions. Luminescence measurements show that this material is suitable for field emission displays (FED) and fluorescent lamps. Also the conversion of UV radiation as well as IR radiation into the visible region suggests the application of this material for photon harvesting in solar cells.

  20. Time-resolved spectroscopy of endogenous NAD(P)H in Gluconobacter oxydans

    NASA Astrophysics Data System (ADS)

    Horilova, J.; Kromkova, K.; Bucko, M.; Illesova, A.; Vikartovska, A.; Stefuca, V.; Mateasik, A.; Chorvat, D.; Chorvatova, A.

    2013-02-01

    The genus Gluconobacter is frequently used for biotechnological and/or nanotechnological applications. We studied endogenous fluorescence of nicotinamide adenine dinucleotide (phosphate) (NAD(P)H), indicator of the oxidative metabolic state in mammalian cells, in Gluconobacter oxydans (G. oxydans). Time-resolved measurements (excitation by 375nm pulsed diode laser) were employed to record the bacterial fluorescence intensity, as well as its modifications by metabolic modulation. Results were gathered on fresh bacteria, on de-frozen ones, as well as on bacteria encapsulated in alginate beads. NAD(P)H fluorescence increased linearly with the concentration of bacteria. Freezing, which has little effect on the viability of bacteria or the concentration-dependent fluorescence rise, affected the temperature-dependence of NAD(P)H fluorescence. Sodium cyanide (10 mM) provoked significant rise in the NAD(P)H fluorescence, while dinitrophenol (200 μM) induced its decrease, confirming the bacterial NAD(P)H fluorescence sensitivity to modulators of electron transport chain. Gathered results demonstrate that endogenous NAD(P)H fluorescence can be successfully recorded in the bacterial strain G. oxydans using time-resolved measurements.

  1. Spectral reconstruction analysis for enhancing signal-to-noise in time-resolved spectroscopies

    NASA Astrophysics Data System (ADS)

    Wilhelm, Michael J.; Smith, Jonathan M.; Dai, Hai-Lung

    2015-09-01

    We demonstrate a new spectral analysis for the enhancement of the signal-to-noise ratio (SNR) in time-resolved spectroscopies. Unlike the simple linear average which produces a single representative spectrum with enhanced SNR, this Spectral Reconstruction analysis (SRa) improves the SNR (by a factor of ca. 0 . 6 √{ n } ) for all n experimentally recorded time-resolved spectra. SRa operates by eliminating noise in the temporal domain, thereby attenuating noise in the spectral domain, as follows: Temporal profiles at each measured frequency are fit to a generic mathematical function that best represents the temporal evolution; spectra at each time are then reconstructed with data points from the fitted profiles. The SRa method is validated with simulated control spectral data sets. Finally, we apply SRa to two distinct experimentally measured sets of time-resolved IR emission spectra: (1) UV photolysis of carbonyl cyanide and (2) UV photolysis of vinyl cyanide.

  2. Time-resolved tryptophan fluorescence in photosynthetic reaction centers from Rhodobacter sphaeroides

    NASA Technical Reports Server (NTRS)

    Godik, V. I.; Blankenship, R. E.; Causgrove, T. P.; Woodbury, N.

    1993-01-01

    Tryptophan fluorescence of reaction centers isolated from Rhodobacter sphaeroides, both stationary and time-resolved, was studied. Fluorescence kinetics were found to fit best a sum of four discrete exponential components. Half of the initial amplitude was due to a component with a lifetime of congruent to 60 ps, belonging to Trp residues, capable of efficient transfer of excitation energy to bacteriochlorophyll molecules of the reaction center. The three other components seem to be emitted by Trp ground-state conformers, unable to participate in such a transfer. Under the influence of intense actinic light, photooxidizing the reaction centers, the yield of stationary fluorescence diminished by congruent to 1.5 times, while the number of the kinetic components and their life times remained practically unchanged. Possible implications of the observed effects for the primary photosynthesis events are considered.

  3. Fluorescence time-resolved imaging system embedded in an ultrasound prostate probe.

    PubMed

    Laidevant, Aurélie; Hervé, Lionel; Debourdeau, Mathieu; Boutet, Jérôme; Grenier, Nicolas; Dinten, Jean-Marc

    2010-01-01

    Ultrasound imaging (US) of the prostate has a low specificity to distinguish tumors from the surrounding tissues. This limitation leads to systematic biopsies. Fluorescent diffuse optical imaging may represent an innovative approach to guide biopsies to tumors marked with high specificity contrast agents and therefore enable an early detection of prostate cancer. This article describes a time-resolved optical system embedded in a transrectal US probe, as well as the fluorescence reconstruction method and its performance. Optical measurements were performed using a pulsed laser, optical fibers and a time-resolved detection system. A novel fast reconstruction method was derived and used to locate a 45 µL ICG fluorescent inclusion at a concentration of 10 µM, in a liquid prostate phantom. Very high location accuracy (0.15 cm) was achieved after reconstruction, for different positions of the inclusion, in the three directions of space. The repeatability, tested with ten sequential measurements, was of the same order of magnitude. Influence of the input parameters (optical properties and lifetime) is presented. These results confirm the feasibility of using optical imaging for prostate guided biopsies. PMID:21326649

  4. Time-resolved imaging of fluorescent inclusions in optically turbid medium — phantom study

    NASA Astrophysics Data System (ADS)

    Kacprzak, M.; Liebert, A.; Sawosz, P.; Żołek, N.; Milej, D.; Maniewski, R.

    2010-03-01

    We present results of application of a time-resolved optical system for imaging of fluorescence excited in an inclusion containing indocyanine green (ICG), and located in optically turbid medium. The developed imaging system enabled simultaneous acquisition of fluorescence and diffusive reflectance. Eight independent time-resolved measurement channels based on time-correlated single photon counting technique were applied. In four of these channels, used for the fluorescence detection, sets of filters were applied in order to block the excitation light. Fast optomechanical switches allowed us to illuminate sequentially nine different spots on the surface of the studied object and finally 4×4 pixels maps at excitation and emission wavelengths were obtained. A liquid phantom used in this study consists of the fish tank filed with a solution ofmilk and water with black ink added to obtain optical properties in the range of the optical properties typical for the living tissue. A gel ball of a diameter of 5 mm with precisely controlled concentration of ICG was immersed in the liquid. The measurements were performed for inclusion located at different depths and for various ICG concentrations in the gel ball and in the surrounding liquid. The recorded distributions of times of arrival (DTA) of fluorescence photons and times of flight (DTOF) of diffusely reflected photons were analyzed by calculation of their statistical moments. We observed specific changes in moments of the measured DTAs as a function of depth of immersion of the fluorescent inclusion in the medium. We noted also that the changes of moments depend significantly on concentration of the dye in the fluorescence inclusion as well as in the surrounding liquid.

  5. High-performance time-resolved fluorescence by direct waveform recording

    PubMed Central

    Muretta, Joseph M.; Kyrychenko, Alexander; Ladokhin, Alexey S.; Kast, David J.; Gillispie, Gregory D.; Thomas, David D.

    2010-01-01

    We describe a high-performance time-resolved fluorescence (HPTRF) spectrometer that dramatically increases the rate at which precise and accurate subnanosecond-resolved fluorescence emission waveforms can be acquired in response to pulsed excitation. The key features of this instrument are an intense(1 μJ∕pulse), high-repetition rate (10 kHz), and short (1 ns full width at half maximum) laser excitation source and a transient digitizer (0.125 ns per time point) that records a complete and accurate fluorescence decay curve for every laser pulse. For a typical fluorescent sample containing a few nanomoles of dye, a waveform with a signal∕noise of about 100 can be acquired in response to a single laser pulse every 0.1 ms, at least 105 times faster than the conventional method of time-correlated single photon counting, with equal accuracy and precision in lifetime determination for lifetimes as short as 100 ps. Using standard single-lifetime samples, the detected signals are extremely reproducible, with waveform precision and linearity to within 1% error for single-pulse experiments. Waveforms acquired in 0.1 s (1000 pulses) with the HPTRF instrument were of sufficient precision to analyze two samples having different lifetimes, resolving minor components with high accuracy with respect to both lifetime and mole fraction. The instrument makes possible a new class of high-throughput time-resolved fluorescence experiments that should be especially powerful for biological applications, including transient kinetics, multidimensional fluorescence, and microplate formats. PMID:21034069

  6. [Characterization of Time-Resolved Laser-Induced Fluorescence from Crude Oil Samples].

    PubMed

    Liu, De-qing; Luan, Xiao-ning; Han, Xiao-shuang; Guo, Jin-jia; An, Ju-bai; Zheng, Rong-er

    2015-06-01

    To evaluate the feasibility of laser induced time-resolved fluorescence technique for in-situ detection of underwater suspended oil spill, extensive investigations have been carried out with different densities of crude oil samples from six different wells of Shengli Oilfield in this work. It was found that the fluorescence emission durations of these crude oil samples were almost the same, the Gate Pulse Delay of DDG (Digital Delay Generator) in the ICCD started at 52ns and ended at 82ns with a width (FWHM) of 10 ns. It appears that the peak location and lifetime of fluorescence for different crude oil samples varied with their densities, and those with similar densities shared a similar lifespan with the closer peak locations of fluorescence. It is also observed that the peak of fluorescence remained the same location before reaching the maximum intensity, subsequently shift to longer wavelength as fluorescence attenuated from maximum intensity with a red shift among 17-30 nm varied with samples. This demonstrated that the decay rate of fluorescent components in the crude oils was different, and energy transfer between these components might exist. It is hoped that those obtained results and characteristics could be the useful information for identification of suspended spilled-oil underwater. PMID:26601371

  7. Radiative lifetime measurements for some levels in Mn I and Ni I by time-resolved laser spectroscopy

    NASA Astrophysics Data System (ADS)

    Shang, Xue; Wang, Qian; Zhang, Feifei; Wang, Chong; Dai, Zhenwen

    2015-09-01

    Natural radiative lifetimes for 32 excited levels of Mn I and for 17 excited levels of Ni I were measured using time-resolved laser-induced fluorescence (TR-LIF) spectroscopy in laser-induced plasma. The energy regions are from 45,754.27 to 54,950.81 cm-1 for Mn I and from 28,578.018 to 50,851.199 cm-1 for Ni I. The uncertainties of all lifetime results are within 10%. To our best knowledge, 26 lifetime results of Mn I and 9 lifetime results of Ni I are reported for the first time.

  8. Multimodal imaging of vascular grafts using time-resolved fluorescence and ultrasound

    NASA Astrophysics Data System (ADS)

    Fatakdawala, Hussain; Griffiths, Leigh G.; Wong, Maelene L.; Humphrey, Sterling; Marcu, Laura

    2015-02-01

    The translation of engineered tissues into clinic requires robust monitoring of tissue development, both in vitro and in vivo. Traditional methods for the same are destructive, inefficient in time and cost and do not allow time-lapse measurements from the same sample or animal. This study reports on the ability of time-resolved fluorescence and ultrasound measurements for non-destructive characterization of explanted tissue engineered vascular grafts. Results show that TRFS and FLIm are able to assess alterations in luminal composition namely elastin, collagen and cellular (hyperplasia) content via changes in fluorescence lifetime values between normal and grafted tissue. These observations are complemented by structural changes observed in UBM pertaining to graft integration and intimal thickness over the grafted region. These results encourage the future application of a catheter-based technique that combines these imaging modalities for non-destructive characterization of vascular grafts in vivo.

  9. Probing local secondary structure by fluorescence: time-resolved and circular dichroism studies of highly purified neurotoxins.

    PubMed Central

    Dahms, T E; Szabo, A G

    1995-01-01

    The relationship between beta-sheet secondary structure and intrinsic tryptophan fluorescence parameters of erabutoxin b, alpha-cobratoxin, and alpha-bungarotoxin were examined. Nuclear magnetic resonance and x-ray crystallography have shown that these neurotoxins have comparable beta-sheet, beta-turn, and random coil secondary structures. Each toxin contains a single tryptophan (Trp) residue within its beta-sheet. The time-resolved fluorescence properties of native erabutoxin b and alpha-cobratoxin are best described by triple exponential decay kinetics, whereas native alpha-bungarotoxin exhibits more than four lifetimes. The disulphide bonds of each toxin were reduced to facilitate carboxymethylation and amidocarboxymethylation. The two different toxin derivatives of all three neurotoxins displayed triple exponential decay kinetics and were completely denatured as evidenced by circular dichroism (random coil). The concentration (c) values of the three fluorescence decay times (time-resolved fluorescence spectroscopy (TRFS)) were dramatically different from those of the native toxins. Each neurotoxin, treated with different concentrations of guanidinium hydrochloride (GuHCl), was studied both by circular dichroism and TRFS. Disappearance of the beta-sheet secondary structural features with increasing concentrations of GuHCl was accompanied by a shift in the relative contribution (c value) of each fluorescence decay time (TRFS). It was found that certain disulphide residues confer added stability to the beta-sheet secondary structure of these neurotoxins and that the center of the beta-sheet is last to unfold. These titrations show that Trp can be used as a very localized probe of secondary structure. Images FIGURE 1 PMID:8527671

  10. A Novel Europium Chelate Coated Nanosphere for Time-Resolved Fluorescence Immunoassay

    PubMed Central

    Shen, Yifeng; Xu, Shaohan; He, Donghua

    2015-01-01

    A novel europium ligand 2, 2’, 2’’, 2’’’-(4, 7-diphenyl-1, 10-phenanthroline-2, 9-diyl) bis (methylene) bis (azanetriyl) tetra acetic acid (BC-EDTA) was synthesized and characterized. It shows an emission spectrum peak at 610 nm when it is excited at 360 nm, with a large Stock shift (250 nm). It is covalently coated on the surface of a bare silica nanosphere containi free amino groups, using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-Hydroxysuccinimide. We also observed an interesting phenomenon that when BC-EDTA is labeled with a silica nanosphere, the chelate shows different excitation spectrum peaks of about 295 nm. We speculate that the carboxyl has a significant influence on its excitation spectrum. The BC-EDTA/Eu3+coated nanosphere could be used as a fluorescent probe for time-resolved fluorescence immunoassay. We labeled the antibody with the fluorescent nanosphere to develop a nanosphere based hepatitis B surface antigen as a time-resolved fluorescence immunoassay reagent, which is very easy to operate and eliminates potential contamination of Eu3+ contained in the environment. The analytical and functional sensitivities are 0.0037 μg/L and 0.08 μg/L (S/N≥2.0) respectively. The detection range is 0.08-166.67 μg/L, which is much wider than that of ELISA (0.2-5μg/L). It is comparable to the commercial dissociation-enhanced lanthanide fluoro-immunoassay system (DELFIA) reagents (0.2-145μg/L). We propose that it can fulfill clinical applications. PMID:26056826

  11. Mosaic DNA chip fabrication and its time-resolved fluorescence detection

    NASA Astrophysics Data System (ADS)

    He, Quanguo; Chen, Hong; Tang, Jianxin; Xiao, Pengfeng; He, Nongyue

    2004-12-01

    Lab-on-a-Chip (LOC) and ?-TAS (micro-total analytical system) are based on miniaturized integrated platforms that have the potential to revolutionize chemical, biological, and biochemical synthesis and analysis. Here, we demonstrated a process of fabricating a mosaic DNA chip and a corresponding detection method by time-resolved fluorescence (TRF) labeling. We synthesized oligonucleotide sequences in situ on glass slides directly, and then sliced them up into small pieces and patched up the pieces with different sequences to generate a mosaic DNA chip. With multiple BCPDA (BCPDA, abbreviated from 4,7-bis(chlorosulfophenyl)-1,10-phenanthroline-2,9-dicarboxylic acid) labeling method based on biotin-avidin amplification, we established a TRF detection format on the mosaic DNA chip. The detection method allows discriminatory signals for perfect match, one-base mismatch, two-base mismatch and three-base mismatch by TRF labeled hybridization, whereby Europium (III, Eu3+) was captured and released on the principle of complexation and dissociation interaction between BCPDA and Eu3+ solution when the BCPDA-tagged avidin and biotin-ended oligonucleotide sequence linked. The fluorescence spectra and related lifetimes were determined. Also, we compared the TRF detection mode with the conventional fluorescence one. These results showed the former is more reliable and stable than the latter, especially for the mosaic DNA chip. Likewise, by applying TRF probing (or labeling) to specific bio-systems, the discovery is of fundamental interest and has significant implications to time-resolved-fluorescence based detection on biosensor.

  12. Time-resolved emission spectroscopy of gadolinium vanadate ceramics (GdVO4:Bi3+)

    NASA Astrophysics Data System (ADS)

    Leppert, J.; Peudenier, S.; Bayer, E.; Grabmaier, B. C.; Blasse, G.

    1994-07-01

    The preparation of GdVO4:Bi3+ ceramics is indicated. Bismuth shows a strong tendency to evaporate during the sintering process. Time-resolved emission spectroscopy shows for sufficiently low Bi3+ concentrations subsequently: blue VO{4/3-}emission with a decay time corresponding to the transfer rate (106 s-1), yellow VO{4/3-}-Bi3+ emission, rare-earth impurity emission and VO{4/3-}-Bi3+ afterglow.

  13. Time-Resolved Kerr Rotation Spectroscopy of Spin Dynamics in a Quantum Hall System

    SciTech Connect

    Fukuoka, D.; Tanaka, N.; Oto, K.; Muro, K.; Hirayama, Y.; Kumada, N.; Yamaguchi, H.

    2010-01-04

    A Time-resolved Kerr rotation spectroscopy under selective excitation by narrow spectrum pump beam is applied to high-mobility two dimensional (2D) electrons. The large non-oscillating Kerr signal is ascribed to the formation of Skyrmions by photoexcited carrier, and is confirmed by the selective excitation in TRKR measurement. The collapse of the spin coherence (dip of T{sub 2}*) near nu = 1 may be related by the formation of Skyrmions and anti-Skyrmiosn pair under photoexcitation.

  14. Time-resolved magnetic circular dichroism spectroscopy of photolyzed carbonmonoxy cytochrome c oxidase (cytochrome aa3).

    PubMed Central

    Goldbeck, R A; Dawes, T D; Einarsdóttir, O; Woodruff, W H; Kliger, D S

    1991-01-01

    Nanosecond time-resolved magnetic circular dichroism (TRMCD) and time-resolved natural circular dichroism (TRCD) measurements of photolysis products of the CO complex of eukaryotic cytochrome c oxidase (CcO-CO) are presented. TRMCD spectra obtained at 100 ns and 10 microseconds after photolysis are diagnostic of pentacoordinate cytochrome a3Fe2+, as would be expected for simple photodissociation. Other time-resolved spectroscopies (UV-visible and resonance Raman), however, show evidence for unusual Fea3(2+) coordination after CO photolysis (Woodruff, W. H., O. Einarsdóttir, R. B. Dyer, K. A. Bagley, G. Palmer, S. J. Atherton, R. A. Goldbeck, T. D. Dawes, and D. S. Kliger. 1991. Proc. Nat. Acad. Sci. U.S.A. 88:2588-2592). Furthermore, time-resolved IR experiments have shown that photodissociated CO binds to CuB+ prior to recombining with Fea3(2+) (Dyer, R. B., O. Einarsdóttir, P. M. Killough, J. J. López-Garriga, and W. H. Woodruff. 1989. J. Am. Chem. Soc. 111:7657-7659). A model of the CcO-CO photolysis cycle which is consistent with all of the spectroscopic results is presented. A novel feature of this model is the coordination of a ligand endogenous to the protein to the Fe axial site vacated by the photolyzed CO and the simultaneous breaking of the Fe-imidazole(histidine) bond. PMID:1653049

  15. Probing interfacial electron dynamics with time-resolved X-ray spectroscopy

    NASA Astrophysics Data System (ADS)

    Neppl, Stefan

    2015-05-01

    Time-resolved core-level spectroscopy techniques using laser pulses to initiate and short X-ray pulses to probe photo-induced processes have the potential to provide electronic state- and atomic site-specific insight into fundamental electron dynamics at complex interfaces. We describe the implementation of femto- and picosecond time-resolved photoelectron spectroscopy at the Linac Coherent Light Source (LCLS) and at the Advanced Light Source (ALS) in order to follow light-driven electron dynamics at dye-semiconductor interfaces on femto- to nanosecond timescales, and from the perspective of individual atomic sites. A distinct transient binding-energy shift of the Ru3d photoemission lines originating from the metal centers of N3 dye-molecules adsorbed on nanoporous ZnO is observed 500 fs after resonant HOMO-LUMO excitation with a visible laser pulse. This dynamical chemical shift is accompanied by a characteristic surface photo-voltage response of the semiconductor substrate. The two phenomena and their correlation will be discussed in the context of electronic bottlenecks for efficient interfacial charge-transfer and possible charge recombination and relaxation pathways leading to the neutralization of the transiently oxidized dye following ultrafast electron injection. First steps towards in operando time-resolved X-ray absorption spectroscopy techniques to monitor interfacial chemical dynamics will be presented.

  16. A homogeneous single-label time-resolved fluorescence cAMP assay.

    PubMed

    Martikkala, Eija; Rozwandowicz-Jansen, Anita; Hänninen, Pekka; Petäjä-Repo, Ulla; Härmä, Harri

    2011-03-01

    G-protein-coupled receptors (GPCRs) are an important class of pharmaceutical drug targets. Functional high-throughput GPCR assays are needed to test an increasing number of synthesized novel drug compounds and their function in signal transduction processes. Measurement of changes in the cyclic adenosine monophosphate (cAMP) concentration is a widely used method to verify GPCR activation in the adenylyl cyclase pathway. Here, a single-label time-resolved fluorescence and high-throughput screening (HTS)-feasible method was developed to measure changes in cAMP levels in HEK293(i) cells overexpressing either β(2)-adrenergic or δ-opioid receptors. In the quenching resonance energy transfer (QRET) technique, soluble quenchers reduce the signal of unbound europium(III)-labeled cAMP in solution, whereas the antibody-bound fraction is fluorescent. The feasibility of this homogeneous competitive assay was proven by agonist-mediated stimulation of receptors coupled to either the stimulatory G(s) or inhibitory G(i) proteins. The reproducibility of the assays was excellent, and Z' values exceeded 0.7. The dynamic range, signal-to-background ratio, and detection limit were compared with a commercial time-resolved fluorescence resonance energy transfer (TR-FRET) assay. In both homogeneous assays, similar assay parameters were obtained when adenylyl cyclase was stimulated directly by forskolin or via agonist-mediated activation of the G(s)-coupled β(2)AR. The advantage of using the single-label approach relates to the cost-effectiveness of the QRET system compared with the two-label TR-FRET assay as there is no need for labeling of two binding partners leading to reduced requirements for assay optimization. PMID:21343601

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

    SciTech Connect

    Debreczeny, M.P.

    1994-05-01

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

  18. Energy transfer in Anabaena variabilis filaments under nitrogen depletion, studied by time-resolved fluorescence.

    PubMed

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

    2015-08-01

    Some filamentous cyanobacteria (including Anabaena) differentiate into heterocysts under nitrogen-depleted conditions. During differentiation, the phycobiliproteins and photosystem II in the heterocysts are gradually degraded. Nitrogen depletion induces changes in the pigment composition of both vegetative cells and heterocysts, which affect the excitation energy transfer processes. To investigate the changes in excitation energy transfer processes of Anabaena variabilis filaments grown in standard medium (BG11) and a nitrogen-free medium (BG110), we measured their steady-state absorption spectra, steady-state fluorescence spectra, and time-resolved fluorescence spectra (TRFS) at 77 K. TRFS were measured with a picosecond time-correlated single photon counting system. The pigment compositions of the filaments grown in BG110 changed throughout the growth period; the relative phycocyanin levels monotonically decreased, whereas the relative carotenoid (Car) levels decreased and then recovered to their initial value (at day 0), with formation of lower-energy Cars. Nitrogen starvation also altered the fluorescence kinetics of PSI; the fluorescence maximum of TRFS immediately after excitation occurred at 735, 740, and 730 nm after 4, 8, and 15 days growth in BG110, respectively. Based on these results, we discuss the excitation energy transfer dynamics of A. variabilis filaments under the nitrogen-depleted condition throughout the growth period. PMID:25596847

  19. Subpicosecond time-resolved fluorescence spectrometer using a Ti:sapphire laser

    NASA Astrophysics Data System (ADS)

    Ye, Tong; Chen, Yaodong; Tang, Jianming; Wang, Shuicai; Hou, Xun

    1995-04-01

    In this paper a subpicosecond time-resolved fluorescence spectra's measurement apparatus is presented. The principle of measurement is based on sum frequency in nonlinear crystal between the pump laser pulses and the fluorescence from sample stimulated by excitation laser pulses. The fluorescence decay can be obtained by varying time delay of the excitation laser pulses to the gating pulses. Adjusting the phasematching angle of nonlinear crystal records the fluorescence decay at various wavelengths. In this spectrometer, a CW mode-locked Ti:sapphire tunable laser is used, with approximately 100 fs pulse width and 82 MHz repetition. The IR light from the lasers is frequency doubled to excite the sample with the remained unconverted light used as gating pulses. A very thin BBO (500 micrometers ) is selected to be a sum frequency nonlinear crystal. The time resolution of the apparatus mainly depends on the pulse width of laser and the effects of group velocity in the crystal. The upconversion UV light is detected by a single photon counting system. The delay line driven by stepper motor is controlled by computer. This computer controls the course of experiments and accumulates data meanwhile. Some experimental results are also presented in study of dynamics of photosystem II reaction center which is isolated and purified from higher plants.

  20. Measurement of nanosecond time-resolved fluorescence with a directly gated interline CCD camera.

    PubMed

    Mitchell, A C; Wall, J E; Murray, J G; Morgan, C G

    2002-06-01

    CCD cameras coupled optically to gated image intensifiers have been used for fast time-resolved measurements for some years. Image intensifiers have disadvantages, however, and for some applications it would be better if the image sensor could be gated directly at high speed. Control of the 'charge drain' function on an interline-transfer CCD allows the sensor to be switched rapidly from an insensitive state. The temporal and spatial properties of the charge drain are explored in the present paper and it is shown that nanosecond time resolution with acceptable spatial uniformity can be achieved for a small commercial sensor. A fluorescence lifetime imaging system is demonstrated, based on a repetitively pulsed laser excitation source synchronized to the CCD control circuitry via a programmable delay unit. PMID:12067368

  1. Development of a Rapid Insulin Assay by Homogenous Time-Resolved Fluorescence

    PubMed Central

    Vallaghe, Julie; Gregor, Nathalie; Donthamsetti, Prashant; Harris, Paul E.; Pierre, Nicolas; Freyberg, Robin; Charrier-Savournin, Fabienne; Javitch, Jonathan A.; Freyberg, Zachary

    2016-01-01

    Direct measurement of insulin is critical for basic and clinical studies of insulin secretion. However, current methods are expensive and time-consuming. We developed an insulin assay based on homogenous time-resolved fluorescence that is significantly more rapid and cost-effective than current commonly used approaches. This assay was applied effectively to an insulin secreting cell line, INS-1E cells, as well as pancreatic islets, allowing us to validate the assay by elucidating mechanisms by which dopamine regulates insulin release. We found that dopamine functioned as a significant negative modulator of glucose-stimulated insulin secretion. Further, we showed that bromocriptine, a known dopamine D2/D3 receptor agonist and newly approved drug used for treatment of type II diabetes mellitus, also decreased glucose-stimulated insulin secretion in islets to levels comparable to those caused by dopamine treatment. PMID:26849707

  2. A CMOS Time-Resolved Fluorescence Lifetime Analysis Micro-System

    PubMed Central

    Rae, Bruce R.; Muir, Keith R.; Gong, Zheng; McKendry, Jonathan; Girkin, John M.; Gu, Erdan; Renshaw, David; Dawson, Martin D.; Henderson, Robert K.

    2009-01-01

    We describe a CMOS-based micro-system for time-resolved fluorescence lifetime analysis. It comprises a 16 × 4 array of single-photon avalanche diodes (SPADs) fabricated in 0.35 μm high-voltage CMOS technology with in-pixel time-gated photon counting circuitry and a second device incorporating an 8 × 8 AlInGaN blue micro-pixellated light-emitting diode (micro-LED) array bump-bonded to an equivalent array of LED drivers realized in a standard low-voltage 0.35 μm CMOS technology, capable of producing excitation pulses with a width of 777 ps (FWHM). This system replaces instrumentation based on lasers, photomultiplier tubes, bulk optics and discrete electronics with a PC-based micro-system. Demonstrator lifetime measurements of colloidal quantum dot and Rhodamine samples are presented. PMID:22291564

  3. New time-resolved micro-photoluminescence spectroscopy of natural and synthetic analogue minerals

    NASA Astrophysics Data System (ADS)

    Panczer, G.; Ollier, N.; Champagnon, B.; Gaft, M.

    2003-04-01

    Minerals as well as geomaterials often present light emissions under UV or visible excitations. This property called photoluminescence is due to low concentration impurities such as the rare earths, the transition elements and the lanthanides. The induced color is used for ore prospection but only spectroscopic analyses indicate the nature of the emitted centers. However natural samples contained numerous luminescent centers simultaneously and with regular steady-state measurements (such as in cathodoluminescence) all the emissions are often over lapping. In order to record the contributions of each separate center, it is possible to use time-resolved measurements based on the decay time of the emissions and using pulsed laser excitation. Some characteristic examples will be presented on apatites, zircons as well as gemstones. Geomaterials present as well micro scale heterogeneities (growth zoning, inclusions, devitrification, microphases...). Precise identification and optical effects of such heterogeneities have to be taken into account. To reach the microscale using photo luminescence studies, a microscope has be modified to allowed pulsed laser injection (from UV to visible), beam focus with micro scale resolution on the sample (<10 μm), as well as time resolved collection of micro fluorescence. Such equipment allows now undertaking time-resolved measurements of microphases. Applications on geomaterials will be presented.

  4. Non-contact characterization of bacteria by time-resolved fluorescence

    NASA Astrophysics Data System (ADS)

    Bouchard, Alain; Frechette, Julie; Long, William F.; Vernon, Marcia; Cormier, Jean-Francois; Vallee, Real; Mafu, Akier A.; Lemay, Marie-Josee

    2004-07-01

    Accurate real-time methods for the detection of pathogenic microorganisms in the agri-food industry would represent an improvement over standard methods of analysis. We are currently developing a non-contact, scanning optical system for the detection of bacteria on meat surfaces based on fluorescence lifetime and intensity measurements. The system detects autofluorescent light emitted by the naturally occurring fluorophores in bacteria. Potential expected advantages of this system include accurate and efficient 2D real-time mapping of bacterial contamination of surfaces, and elimination of sample-to-sample cross-contamination. Furthermore, as the technique only requires minimal sample preparation and handling, the chemical properties of the specimen are preserved. This article presents the preliminary results obtained from a time-resolved fluorescence imaging system for the characterization of a non-pathogenic gram-negative bacteria, Pseudomonas fluorescens. Additionally we present a particular application of the system of interest to the agri-food industry, demonstrating its potential as a real-time macroscopic imaging system for mapping bacterial contamination on meat surfaces. Initial results indicate that the combination of fluorescence lifetime and intensity measurements provides a means for characterizing biological media and for detecting microorganisms on surfaces.

  5. Time-resolved fluorescence and fluorescence anisotropy of calix[4]arene: Elucidation of the excitation energies of various conformers

    NASA Astrophysics Data System (ADS)

    Boo, Bong Hyun; Kim, Hyun Sook; Koh, Sang Gon; Lee, Minyung; No, Kwanghyun

    2013-01-01

    Fluorescence, fluorescence excitation, time-resolved fluorescence spectroscopic, time-dependent fluorescence anisotropy, and time-dependent (TD) DFT studies were carried out to elucidate the excitation energies, fluorescence decay kinetics, and excitation transfer dynamics of calix[4]arene. We found that TD DFT calculations help to analyze the absorption spectra by elucidating the variation of the oscillator strengths with the excitation energies of various conformers involved and to clarify their relative importance. The TD DFT calculations imply that a cone-shaped conformer plays the most important role in the absorption spectrum. Fluorescence in a methanol solvent has a lifetime of 3.11 ± 0.1 ns and the decay kinetics is not found to have particular propensity with respect to solvent polarity. When the molecules in a glass matrix at 77 K were excited by short laser pulses, fluorescence anisotropy was observed. From the time-dependent fluorescence anisotropy, we derived the energy transfer rate constant and fluorescence anisotropy decay time, respectively: ket=1.7×109 s-1, τh=0.59 ns.

  6. High throughput screening of beta-amyloid secretion inhibitors using homogenous time-resolved fluorescence.

    PubMed

    Albrecht, Hugo; Zbinden, Peter; Rizzi, Andrea; Villetti, Gino; Riccardi, Benedetta; Puccini, Paola; Catinella, Silvia; Imbimbo, Bruno P

    2004-12-01

    A cell-based assay using homogeneous time-resolved fluorescence has been developed for high throughput screening of putative beta-amyloid (Abeta)production inhibitors. In this assay, total Abeta is detected by simply adding two commercially available antibody complexes. The first was a biotinylated monoclonal antibody (4G8), specifically recognizing an epitope comprising the residues 17-24 of the Abetapeptide, complexed with europium cryptate-streptavidin conjugate. The second was a polyclonal antibody (BioS-N), raised against the N-terminus of the Abeta peptide, complexed with an allophycocyanin-anti rabbit antibody conjugate. Binding of the two complexes to the Abeta peptide brought europium cryptate (fluorescence donor) and allophycocyanin (fluorescence acceptor) into close proximity, consequently a fluorescent resonance energy transfer signal was produced upon excitation at 337 nm. The resulting fluorescence signal (665 nm) was then detected using a Discovery or a ViewLux reader. Detection of Abeta by the proposed method is possible at concentrations of approximately 1 nM. The method was employed for the detection of Abeta secreted from a stable transfected human neuroglioma cell line (H4) overexpressing a mutated form of the human amyloid precursor protein (APP695NL) and developed for robotic automation. At optimized conditions, signal-to-background ratios exceeding 5 and Z' factors around 0.7 were achieved in a 384-well format. High throughput screening of 56,913 potential Abeta production inhibitors led to identification of new non-cytotoxic and cell permeable compounds with potencies in the submicromolar range. PMID:15578936

  7. Time-resolved spectroscopy using a chopper wheel as a fast shutter

    SciTech Connect

    Wang, Shicong; Wendt, Amy E.; Boffard, John B.; Lin, Chun C.

    2015-01-15

    Widely available, small form-factor, fiber-coupled spectrometers typically have a minimum exposure time measured in milliseconds, and thus cannot be used directly for time-resolved measurements at the microsecond level. Spectroscopy at these faster time scales is typically done with an intensified charge coupled device (CCD) system where the image intensifier acts as a “fast” electronic shutter for the slower CCD array. In this paper, we describe simple modifications to a commercially available chopper wheel system to allow it to be used as a “fast” mechanical shutter for gating a fiber-coupled spectrometer to achieve microsecond-scale time-resolved optical measurements of a periodically pulsed light source. With the chopper wheel synchronized to the pulsing of the light source, the time resolution can be set to a small fraction of the pulse period by using a chopper wheel with narrow slots separated by wide spokes. Different methods of synchronizing the chopper wheel and pulsing of the light sources are explored. The capability of the chopper wheel system is illustrated with time-resolved measurements of pulsed plasmas.

  8. Accuracy limits in the determination of absolute optical properties using time-resolved NIR spectroscopy.

    PubMed

    Ntziachristos, V; Chance, B

    2001-06-01

    We assess typical systematic experimental errors involved in a time-resolved measurement as applied to NIR diffuse optical spectroscopy and investigate their effect on the quantification accuracy of the absorption and the reduced scattering coefficient. We demonstrate that common systematic experimental uncertainties may lead to quantification errors of 10% or more, even when excellent signal to noise ratio conditions exist and accurate photon propagation models are employed. We further demonstrate that the accuracy of the calculation depends nonlinearly on the optical properties of the medium measured. High scattering and low absorbing media can be quantified more accurately than media with low scattering or high absorption using measurements of the same signal to noise ratio. We further discuss curve-shape fitting schemes that aid in improving the quantification accuracy in the presence of experimental errors. Finally, we identify uncertainties that set quantification accuracy limits and we find temporal resolution as the ultimate limiting factor in the quantification accuracy achieved. Our findings suggest that temporal resolution of the order of 10 ps is necessary for quantifying the absorption and reduced scattering coefficient of diffuse media with accuracy better than 5% using curve fitting methods. In that sense this analysis can be used in time-resolved system design and in predicting the expected errors given the technology selected for time-resolved measurements. PMID:11439481

  9. Time-resolved spectroscopy using a chopper wheel as a fast shutter

    NASA Astrophysics Data System (ADS)

    Wang, Shicong; Wendt, Amy E.; Boffard, John B.; Lin, Chun C.

    2015-01-01

    Widely available, small form-factor, fiber-coupled spectrometers typically have a minimum exposure time measured in milliseconds, and thus cannot be used directly for time-resolved measurements at the microsecond level. Spectroscopy at these faster time scales is typically done with an intensified charge coupled device (CCD) system where the image intensifier acts as a "fast" electronic shutter for the slower CCD array. In this paper, we describe simple modifications to a commercially available chopper wheel system to allow it to be used as a "fast" mechanical shutter for gating a fiber-coupled spectrometer to achieve microsecond-scale time-resolved optical measurements of a periodically pulsed light source. With the chopper wheel synchronized to the pulsing of the light source, the time resolution can be set to a small fraction of the pulse period by using a chopper wheel with narrow slots separated by wide spokes. Different methods of synchronizing the chopper wheel and pulsing of the light sources are explored. The capability of the chopper wheel system is illustrated with time-resolved measurements of pulsed plasmas.

  10. Photodissociation of thioglycolic acid studied by femtosecond time-resolved transient absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Attar, Andrew R.; Blumling, Daniel E.; Knappenberger, Kenneth L.

    2011-01-01

    Steady-state and time-resolved spectroscopies were employed to study the photodissociation of both the neutral (HS-CH2-COOH) and doubly deprotonated (-S-CH2-COO-) forms of thioglycolic acid (TGA), a common surface-passivating ligand used in the aqueous synthesis and organization of semiconducting nanostructures. Room temperature UV-Vis absorption spectroscopy indicated strong absorption by the S1 and S2 excited states at 250 nm and 185 nm, respectively. The spectrum also contained a weaker absorption band that extended to approximately 550 nm, which was assigned to the π ^ * _{CO} leftarrow n_O transition. Femtosecond time-resolved transient absorption spectroscopy was performed on TGA using 400 nm excitation and a white-light continuum probe to provide the temporally and spectrally resolved data. Both forms of TGA underwent a photoinduced dissociation from the excited state to form an α-thiol-substituted acyl radical (α-TAR, S-CH2-CO•). For the acidic form of TGA, radical formation occurred with an apparent time constant of 60 ± 5 fs; subsequent unimolecular decay took 400 ± 60 fs. Similar kinetics were observed for the deprotonated form of TGA (70 ± 10 fs radical formation; 420 ± 40 fs decay). The production of the α-TAR was corroborated by the observation of its characteristic optical absorption. Time-resolved data indicated that the photoinduced dissociation of TGA via cleavage of the C-OH bond occurred rapidly (≤100 fs). The prevalence of TGA in aqueous semiconducting nanoparticles makes its absorption in the visible spectral region and subsequent dissociation key to understanding the behavior of nanoscale systems.

  11. Detection of Aerosol Particles by Time-Resolved Laser Induced Breakdown Spectroscopy and its Emission Properties

    NASA Astrophysics Data System (ADS)

    Nagasaki, S.; Tanaka, Y.; Kado, S.; Tanaka, S.

    2001-12-01

    Development of in-situ and real-time detection techniques for is strongly expected for the human health and public welfare. Particles of SPM size in the air can be exploded by a focused high power laser pulse, and the concentration and composition of the particles are observed by measuring the intensity and the spectra of plasma emission of the particles exploded. Laser induced breakdown spectroscopy is a conventional detection method based on this particle explosion. In the present work, the time-resolved technique was combined with the laser induced breakdown spectroscopic method, in order to improve the signal/noise ratio and efficiency. In this work, firstly, the time-resolved laser induced breakdown spectroscopy system was established in the laboratory and the CaCO3 particles flowing in the air was detected by measuring the Ca II emission at 396nm. Linear calibration curve was obtained between 1x10-4g/m3-5x10-4g/m3 for CaCO3 particles. Secondly, we studied whether TiO2 particles in the presence and in the absence of Eu on their surface could be distinguished by the time-resolved laser induced breakdown spectroscopy. It was found that the dependence of peak intensity of Ti I emission at 453 nm on the laser power consisted of two regions for low Eu loading and of one for high Eu loading. This difference is considered to be caused by different mechanisms in initial electron density formation, suggesting that TiO2 particles in the presence and in the absence of Eu on their surface was distinguished.

  12. Application of time-resolved resonance Raman spectroscopy to intramolecular electron transfer

    SciTech Connect

    Schoonover, J.R.; Strouse, G.F.; Chen, P.; Bates, D.; Meyer, T.J. )

    1993-06-09

    Time-resolved resonance Raman spectroscopy has been applied for the first time to the study of intramolecular electron transfer in a chromophore-quencher complex, based on a metal-to-ligand charge-transfer (MLCT) excited state. These measurements allow for (1) the identification of redox sites that are reached following excitation and (2) the inferring of structural information in short-lived intermediates. This technique is a more sensitive probe than transient absorption as shown by its application to the redox-separated complex shown below involving a pyridinium acceptor and a phenothiazine donor.

  13. Absorption spectroscopy of powdered materials using time-resolved diffuse optical methods.

    PubMed

    D'Andrea, Cosimo; Obraztsova, Ekaterina A; Farina, Andrea; Taroni, Paola; Lanzani, Guglielmo; Pifferi, Antonio

    2012-11-10

    In this paper a novel method, based on time-resolved diffuse optical spectroscopy, is proposed to measure the absorption of small amounts of nanostructured powder materials independent of scattering. Experimental validation, in the visible and near-infrared spectral range, has been carried out on India Inkparticles. The effectiveness of the technique to measure scattering-free absorption is demonstrated on carbon nanotubes. The comparison between the absorption spectra acquired by the proposed method and conventional measurements performed with a commercial spectrophotometer is discussed. PMID:23142900

  14. Nonlinear Raman Techniques in Femtosecond Time Resolved Spectroscopy for the Analysis and Control of Molecular Dynamics

    SciTech Connect

    Materny, Arnulf; Konradi, Jakow; Namboodiri, Vinu; Namboodiri, Mahesh; Scaria, Abraham

    2008-11-14

    The use of four-wave mixing techniques in femtosecond time-resolved spectroscopy has considerable advantages. Due to the many degrees of freedom offered e.g. by coherent anti-Stokes Raman scattering (CARS), the dynamics even of complex systems can be analyzed in detail. Using pulse shaping techniques in combination with a self-learning loop approach, molecular mode excitation can be controlled very efficiently in a multi-photon excitation process. Results obtained from the optimal control of CARS on {beta}-carotene are discussed.

  15. Time-resolved coherent Raman spectroscopy by high-speed pump-probe delay scanning.

    PubMed

    Domingue, S R; Winters, D G; Bartels, R A

    2014-07-15

    Using a spinning window pump-probe delay scanner, we demonstrate a means of acquiring time-resolved vibrational spectra at rates up to 700 Hz. The time-dependent phase shift accumulated by the probe pulse in the presence of a coherently vibrating sample gives rise to a Raman-induced frequency shifting readily detectable in a balanced detector. This rapid delay scanning system represents a 23-fold increase in averaging speed and is >10× faster than state-of-the-art voice coil delay lines. These advancements make pump-probe spectroscopy a more practical means of imaging complex media. PMID:25121667

  16. Time-resolved measurements of short-wavelength fluorescence from x-ray-excited ions.

    PubMed

    Kapteyn, H C; Murnane, M M; Falcone, R W

    1987-09-01

    We demonstrate a novel technique for time-resolved spectroscopic studies of highly excited ions. The technique uses a laser-produced plasma as a short-pulse, soft-x-ray light source with a high repetition rate. A Nd:YAG laser with a pulse duration of 90 psec, a pulse energy of 70 microJ, and repetition rate of 10(4) pulses per second is focused onto a rotating metal target. Soft x rays from the resulting plasma photoionize a gas surrounding the target, and fluorescence from the gas is detected by using a spectrometer and a high-speed photodetector. Using the technique of time-correlated photon counting, we determined the radiative lifetime and collisional quenching rate of the Xe III 5s(0)5p(6)(1)S(0) state by observing its fluorescence at 108.9 nm. A time resolution of better than 400 psec was obtained. We also measured relative Auger decay yields of a core hole state in xenon using a higher-energy laser-produced plasma light source at a lower repetition rate. PMID:19741832

  17. The singlet-oxygen-sensitized delayed fluorescence in mammalian cells: a time-resolved microscopy approach.

    PubMed

    Scholz, Marek; Biehl, Anna-Louisa; D?dic, Roman; Hla, Jan

    2015-04-01

    The present work provides a proof-of-concept that the singlet oxygen-sensitized delayed fluorescence (SOSDF) can be detected from individual living mammalian cells in a time-resolved microscopy experiment. To this end, 3T3 mouse fibroblasts incubated with 100 ?M TPPS4 or TMPyP were used and the microsecond kinetics of the delayed fluorescence (DF) were recorded. The analysis revealed that SOSDF is the major component of the overall DF signal. The microscopy approach enables precise control of experimental conditions - the DF kinetics are clearly influenced by the presence of the (1)O2 quencher (sodium azide), H2O/D2O exchange, and the oxygen concentration. Analysis of SOSDF kinetics, which was reconstructed as a difference DF kinetics between the unquenched and the NaN3-quenched samples, provides a cellular (1)O2 lifetime of ?? = 1-2 ?s and a TPPS4 triplet lifetime of ?T = 22 5 ?s in agreement with previously published values. The short SOSDF acquisition times, typically in the range of tens of seconds, enable us to study the dynamic cellular processes. It is shown that SOSDF lifetimes increase during PDT-like treatment, which may provide valuable information about changes of the intracellular microenvironment. SOSDF is proposed and evaluated as an alternative tool for (1)O2 detection in biological systems. PMID:25591544

  18. Time-resolved spectroscopy of the Mercury 6 3P1 state

    NASA Technical Reports Server (NTRS)

    Halstead, J. A.; Reeves, R. R.

    1981-01-01

    The time-resolved fluorescence was observed from the Hg 6 3P1 state under the influence of the earth's magnetic field and with applied fields of up to 14 G. Modulation of the fluorescence decay signal was observed as a function of both time and space and can be interpreted in terms of a classical precession of the excited atom about the magnetic field or as quantum beats resulting from interference between coherently populated Zeeman sublevels. This modulation was studied for each of the five resolvable components of the hyperfine structure separately. The fluorescence from the even isotopes was determined to be almost completely modulated while the fluorescence from the odd isotopes was only partially modulated. The frequency of modulation of the fluorescence from the mercury-202 isotope was observed as a function of the applied magnetic field and a value for the Lande factor of 1.46 + or - 0.03 was obtained. This is within experimental error of the accepted value of 1.486. In addition, the frequency of modulation as a function of applied magnetic field was determined for each of the three resolvable components with more than one contributing isotopic hyperfine line. An investigation of the effect of radiation trapping on the degree modulation was also made.

  19. Combined Raman and LIBS for Planetary Surface Exploration: Enhanced Science Return Enabled by Time-Resolved Laser Spectroscopy

    NASA Astrophysics Data System (ADS)

    Blacksberg, J.; Maruyama, Y.; Choukroun, M.; Charbon, E.; Rossman, G. R.

    2012-10-01

    We present a mineralogy tool that can potentially perform phase and elemental analysis on rock, soil, and regolith in an undisturbed geological setting. This is made possible by new developments in the field of time-resolved laser spectroscopy.

  20. Time-resolved excitation density dependent fluorescence of R-phycoerythrin single crystal

    NASA Astrophysics Data System (ADS)

    Wang, H. Z.; Zheng, X. G.; Zhao, F. L.; Gao, Z. L.; Yu, Z. X.; Zhu, J. C.; Jiang, L. J.; Zhang, J. P.; Liang, D. C.

    1994-05-01

    The fluorescence kinetics of a new single crystal, R-phycoerythrin (R-PE), has been studied by picosecond laser spectroscopy. An excitonic band, which is much more narrow than that of the molecular fluorescnece, is observed. At high pump density, superradiance of excitons in the bulk pure single crystal is recorded. The experimental results of fluorescence kinetics and exciton superradiance of R-PE crystal demonstrate that exciton energy transfer is natural, effective and rapid. It is concluded that excitons play an important role in energy transfer in the antennae of photosynthetic systems.

  1. Applications of immunomagnetic capture and time-resolved fluorescence detection for Salmonella enteriditis in liquid eggs

    NASA Astrophysics Data System (ADS)

    Tu, Shu-I.; Gehring, Andrew; Paoli, George

    2008-04-01

    An immuno sandwich method was evaluated for the detection of Salmonella in liquid eggs. Liquid eggs spiked with different out-break strains of Salmonella were mixed with proper enrichment media and incubated at 37 C for 4 to 20 h. After enrichment, immunomagnetic beads (IMB) coated with anti Salmonella antibodies were used to capture the bacteria. Samarium (Sm) labeled anti Salmonella antibodies were then used to form sandwiched complexes with IMB captured bacteria. Sandwiched Salmonella were then treated with Sm-chelator to allow the measurement of the released Sm by time-resolved fluorescence (TRF). The processes ranging from IMB capture to Sm chelation were performed using an automated KingFisher apparatus. With this approach, the presence of ~ 1 CFU of outbreak strains of Salmonella Enteritidis per egg (~50 g of liquid eggs) could be detected after enrichment for 20 h at 37 C. For higher levels of Salmonella Enteritidis contamination, e.g., 10 CFU per 50 g of liquid eggs, the enrichment time could be reduced to 5 h at 37 C. The results demonstrated that a combination of IMB capture and TRF measurement could be a rapid and sensitive method for Salmonella Enteritidis detection in liquid eggs.

  2. Time-resolved absorption and fluorescence from the bacteriorhodopsin photocycle in the nanosecond time regime

    PubMed Central

    Delaney, J. K.; Brack, T. L.; Atkinson, G. H.

    1993-01-01

    Picosecond transient absorption (PTA) in the 568-660-nm region is measured over the initial 80 ns of the bacteriorhodopsin photocycle. After photocycle initiation with 573-nm excitation (7-ps pulsewidth), these PTA data reflect the formation during the initial 40 ps of two long-recognized intermediates with red-shifted (relative to that of BR-570) absorption bands, namely J-625 and K-590. PTA signals at 568, 628, and 652 nm are unchanged for the remainder of the 80-ns photocycle interval measured, demonstrating that no other intermediates, including the proposed KL, are observable by absorption changes. Picosecond time-resolved fluorescence (PTRF), measured at 740 nm, is initiated by 7 ps excitation of the species present at various time delays after the photocycle begins. PTRF signals change rapidly over the initial 40 ps, reflecting, first, the depletion of the ground state BR-570 population and, subsequently, the formation of K-590. The PTRF signal then decreases monotonically with a time constant of 5.5 ± 0.5 ns from its maximum near a 50-ps delay until it reaches a minimum at a delay of ≈ 13 ns. For time delays between 13 and 80 ns, the PTRF signal remains unchanged and slightly higher than that measured from BR-570 alone. The rapid decrease in PTRF signals over the same photocycle interval in which the PTA signals remain unchanged suggests that the retinal-protein interactions involving electronically excited K-590 (K*) are being significantly altered. PMID:19431895

  3. Time-Resolved Photoluminescence Spectroscopy and Imaging: New Approaches to the Analysis of Cultural Heritage and Its Degradation

    PubMed Central

    Nevin, Austin; Cesaratto, Anna; Bellei, Sara; D'Andrea, Cosimo; Toniolo, Lucia; Valentini, Gianluca; Comelli, Daniela

    2014-01-01

    Applications of time-resolved photoluminescence spectroscopy (TRPL) and fluorescence lifetime imaging (FLIM) to the analysis of cultural heritage are presented. Examples range from historic wall paintings and stone sculptures to 20th century iconic design objects. A detailed description of the instrumentation developed and employed for analysis in the laboratory or in situ is given. Both instruments rely on a pulsed laser source coupled to a gated detection system, but differ in the type of information they provide. Applications of FLIM to the analysis of model samples and for the in-situ monitoring of works of art range from the analysis of organic materials and pigments in wall paintings, the detection of trace organic substances on stone sculptures, to the mapping of luminescence in late 19th century paintings. TRPL and FLIM are employed as sensors for the detection of the degradation of design objects made in plastic. Applications and avenues for future research are suggested. PMID:24699285

  4. Time-resolved photoluminescence spectroscopy and imaging: new approaches to the analysis of cultural heritage and its degradation.

    PubMed

    Nevin, Austin; Cesaratto, Anna; Bellei, Sara; D'Andrea, Cosimo; Toniolo, Lucia; Valentini, Gianluca; Comelli, Daniela

    2014-01-01

    Applications of time-resolved photoluminescence spectroscopy (TRPL) and fluorescence lifetime imaging (FLIM) to the analysis of cultural heritage are presented. Examples range from historic wall paintings and stone sculptures to 20th century iconic design objects. A detailed description of the instrumentation developed and employed for analysis in the laboratory or in situ is given. Both instruments rely on a pulsed laser source coupled to a gated detection system, but differ in the type of information they provide. Applications of FLIM to the analysis of model samples and for the in-situ monitoring of works of art range from the analysis of organic materials and pigments in wall paintings, the detection of trace organic substances on stone sculptures, to the mapping of luminescence in late 19th century paintings. TRPL and FLIM are employed as sensors for the detection of the degradation of design objects made in plastic. Applications and avenues for future research are suggested. PMID:24699285

  5. Wide-field time-resolved luminescence imaging and spectroscopy to decipher obliterated documents in forensic science

    NASA Astrophysics Data System (ADS)

    Suzuki, Mototsugu; Akiba, Norimitsu; Kurosawa, Kenji; Kuroki, Kenro; Akao, Yoshinori; Higashikawa, Yoshiyasu

    2016-01-01

    We applied a wide-field time-resolved luminescence (TRL) method with a pulsed laser and a gated intensified charge coupled device (ICCD) for deciphering obliterated documents for use in forensic science. The TRL method can nondestructively measure the dynamics of luminescence, including fluorescence and phosphorescence lifetimes, which prove to be useful parameters for image detection. First, we measured the TRL spectra of four brands of black porous-tip pen inks on paper to estimate their luminescence lifetimes. Next, we acquired the TRL images of 12 obliterated documents at various delay times and gate times of the ICCD. The obliterated contents were revealed in the TRL images because of the difference in the luminescence lifetimes of the inks. This method requires no pretreatment, is nondestructive, and has the advantage of wide-field imaging, which makes it is easy to control the gate timing. This demonstration proves that TRL imaging and spectroscopy are powerful tools for forensic document examination.

  6. Radiative lifetime measurements of some Tm I and Tm II levels by time-resolved laser spectroscopy

    NASA Astrophysics Data System (ADS)

    Tian, Yanshan; Wang, Xinghao; Yu, Qi; Li, Yongfan; Gao, Yang; Dai, Zhenwen

    2016-04-01

    Radiative lifetimes of 88 levels of Tm I in the energy range 22 791.176-48 547.98 cm-1 and 29 levels of Tm II in the range 27 294.79-65 612.85 cm-1 were measured by time-resolved laser-induced fluorescence spectroscopy in laser-ablation plasma. The lifetime values obtained are in the range from 15.4 to 7900 ns for Tm I and from 36.5 to 1000 ns for Tm II. To the best of our knowledge, 77 lifetimes of Tm I and 22 lifetimes of Tm II are reported for the first time. Good agreements between the present results and the previous experimental values were achieved for both Tm I and Tm II.

  7. The primary photophysics of the Avena sativa phototropin 1 LOV2 domain observed with time-resolved emission spectroscopy.

    PubMed

    van Stokkum, Ivo H M; Gauden, Magdalena; Crosson, Sean; van Grondelle, Rienk; Moffat, Keith; Kennis, John T M

    2011-01-01

    The phototropins are blue-light receptors that base their light-dependent action on the reversible formation of a covalent bond between a flavin mononucleotide (FMN) cofactor and a conserved cysteine in light, oxygen or voltage (LOV) domains. The primary reactions of the Avena sativa phototropin 1 LOV2 domain were investigated by means of time-resolved and low-temperature fluorescence spectroscopy. Synchroscan streak camera experiments revealed a fluorescence lifetime of 2.2 ns in LOV2. A weak long-lived component with emission intensity from 600 to 650 nm was assigned to phosphorescence from the reactive FMN triplet state. This observation allowed determination of the LOV2 triplet state energy level at physiological temperature at 16600 cm(-1). FMN dissolved in aqueous solution showed pH-dependent fluorescence lifetimes of 2.7 ns at pH 2 and 3.9-4.1 ns at pH 3-8. Here, too, a weak phosphorescence band was observed. The fluorescence quantum yield of LOV2 increased from 0.13 to 0.41 upon cooling the sample from 293 to 77 K. A pronounced phosphorescence emission around 600 nm was observed in the LOV2 domain between 77 and 120 K in the steady-state emission. PMID:21261629

  8. Time resolved optical biopsy spectroscopy of normal, benign and malignant tissues from NADH and FAD changes

    NASA Astrophysics Data System (ADS)

    Masilamani, V.; Das, B. B.; Secor, J.; AlSalhi, M.; Amer, S. B.; Farhat, K.; Rabah, D.; Alfano, R. R.

    2012-01-01

    Histo pathological examination is the gold standard to discriminate between benign and malignant growth of tissue. But this is invasive and stressful. Hence many non invasive imaging techniques, such as CT, MRI, PET, etc are employed, each having certain advantages and disadvantages. In this context optical biopsy is a newly emerging technique, since it employs non-ionizing radiation like light or laser, which could be shined directly or launched through optical fiber to reach any part of the body. This paper reports results of time resolved emission spectra of 24 excised tissue sample (normal control=12; benign=4; malignant=8) of breast and prostate, employing a 390nm, 100 fs, Ti-Sapphire laser pulses. The fluorescence decay times were measured using streak camera and fitted for single and bi- exponential decays with reliability of 97%. Our results show the distinct difference between normal, benign and malignant tissues attributed changes of NADH and FAD levels.

  9. Time-resolved optical spectroscopy of oriented muscle fibers specifically and covalently labeled with extrinsic optical probes

    NASA Astrophysics Data System (ADS)

    Hayden, David Ward

    1997-11-01

    The protein myosin transforms chemical energy, in the form of ATP, into mechanical force in muscle. The rotational motions of myosin play a central role in all models of muscle contraction. I investigated the rotations of myosin in contracting muscle using time- resolved phosphorescence anisotropy (TPA), a technique sensitive to rotations on the microsecond time scale. I developed the hardware, software and theory for four- polarization TPA, which returns four time-resolved anisotropies in contrast to a single anisotropy for standard TPA. The additional anisotropies constrain the possible dye orientations and myosin head motions. Four- polarization TPA on oriented scallop muscle fibers with an extrinsic probe on the light chain shows that the rigor (no ATP, no calcium) anisotropies are consistent with a static distribution of rigid, but partially disordered molecules. Addition of ATP, in the presence or absence of calcium, induces microsecond rotational motion in a fraction of the myosin molecules, while the rest retain rigor-like orientation. This result is consistent with recently-published electron paramagnetic resonance (EPR) results and provides details of the microsecond motion that EPR is unable to detect. A method for simulation of time-resolved TPA spectra and determination of initial and final anisotropies allows testing of models of myosin rotations. The TPA spectra of several models, including restricted rotational diffusion and the Lymn-Taylor models are shown. To show the generality of the derived equations, I apply them to a comparison of EPR and fluorescence polarization spectroscopy on similar samples to investigate whether there is one model that could explain the results reported by the two techniques.

  10. Microcontroller based resonance tracking unit for time resolved continuous wave cavity-ringdown spectroscopy measurements.

    PubMed

    Votava, Ondrej; Mašát, Milan; Parker, Alexander E; Jain, Chaithania; Fittschen, Christa

    2012-04-01

    We present in this work a new tracking servoloop electronics for continuous wave cavity-ringdown absorption spectroscopy (cw-CRDS) and its application to time resolved cw-CRDS measurements by coupling the system with a pulsed laser photolysis set-up. The tracking unit significantly increases the repetition rate of the CRDS events and thus improves effective time resolution (and/or the signal-to-noise ratio) in kinetics studies with cw-CRDS in given data acquisition time. The tracking servoloop uses novel strategy to track the cavity resonances that result in a fast relocking (few ms) after the loss of tracking due to an external disturbance. The microcontroller based design is highly flexible and thus advanced tracking strategies are easy to implement by the firmware modification without the need to modify the hardware. We believe that the performance of many existing cw-CRDS experiments, not only time-resolved, can be improved with such tracking unit without any additional modification to the experiment. PMID:22559518

  11. Microcontroller based resonance tracking unit for time resolved continuous wave cavity-ringdown spectroscopy measurements

    NASA Astrophysics Data System (ADS)

    Votava, Ondrej; Mašát, Milan; Parker, Alexander E.; Jain, Chaithania; Fittschen, Christa

    2012-04-01

    We present in this work a new tracking servoloop electronics for continuous wave cavity-ringdown absorption spectroscopy (cw-CRDS) and its application to time resolved cw-CRDS measurements by coupling the system with a pulsed laser photolysis set-up. The tracking unit significantly increases the repetition rate of the CRDS events and thus improves effective time resolution (and/or the signal-to-noise ratio) in kinetics studies with cw-CRDS in given data acquisition time. The tracking servoloop uses novel strategy to track the cavity resonances that result in a fast relocking (few ms) after the loss of tracking due to an external disturbance. The microcontroller based design is highly flexible and thus advanced tracking strategies are easy to implement by the firmware modification without the need to modify the hardware. We believe that the performance of many existing cw-CRDS experiments, not only time-resolved, can be improved with such tracking unit without any additional modification to the experiment.

  12. Modelling Time-Resolved Two-Dimensional Electronic Spectroscopy of the Primary Photoisomerization Event in Rhodopsin

    PubMed Central

    2015-01-01

    Time-resolved two-dimensional (2D) electronic spectra (ES) tracking the evolution of the excited state manifolds of the retinal chromophore have been simulated along the photoisomerization pathway in bovine rhodopsin, using a state-of-the-art hybrid QM/MM approach based on multiconfigurational methods. Simulations of broadband 2D spectra provide a useful picture of the overall detectable 2D signals from the near-infrared (NIR) to the near-ultraviolet (UV). Evolution of the stimulated emission (SE) and excited state absorption (ESA) 2D signals indicates that the S1 → SN (with N ≥ 2) ESAs feature a substantial blue-shift only after bond inversion and partial rotation along the cis → trans isomerization angle, while the SE rapidly red-shifts during the photoinduced skeletal relaxation of the polyene chain. Different combinations of pulse frequencies are proposed in order to follow the evolution of specific ESA signals. These include a two-color 2DVis/NIR setup especially suited for tracking the evolution of the S1 → S2 transitions that can be used to discriminate between different photochemical mechanisms of retinal photoisomerization as a function of the environment. The reported results are consistent with the available time-resolved pump–probe experimental data, and may be used for the design of more elaborate transient 2D electronic spectroscopy techniques. PMID:24794143

  13. Time-resolved photoemission spectroscopy on a metal/ferroelectric heterostructure

    NASA Astrophysics Data System (ADS)

    Rault, J. E.; Agnus, G.; Maroutian, T.; Pillard, V.; Lecoeur, Ph.; Niu, G.; Vilquin, B.; Silly, M. G.; Bendounan, A.; Sirotti, F.; Barrett, N.

    2013-10-01

    In thin-film ferroelectric (FE) capacitors the chemical and electronic structure of the electrode/FE interface can play a crucial role in determining the kinetics of polarization switching. We investigate the electronic structure of a Pt/BaTiO3/SrTiO3:Nb capacitor using time-resolved photoemission spectroscopy. The chemical, electronic, and depth sensitivity of core-level photoemission are used to probe the transient response of different parts of the upper electrode/ferroelectric interface to voltage-pulse-induced polarization reversal. The linear response of the electronic structure agrees quantitatively with a simple RC circuit model. The nonlinear response due to the polarization switch is demonstrated by the time-resolved response of the characteristic core levels of the electrode and the ferroelectric. Adjustment of the RC circuit model allows an estimation of the Pt/BaTiO3 (BTO) interface capacitance. The experiment shows that the interface capacitance is at least 100 times higher than the bulk capacitance of the BTO film, in qualitative agreement with theoretical predictions from the literature.

  14. Time-resolved detection of fluorescent light during inflow of ICG to the brain-a methodological study.

    PubMed

    Milej, Daniel; Gerega, Anna; Zołek, Norbert; Weigl, Wojciech; Kacprzak, Michał; Sawosz, Piotr; Mączewska, Joanna; Fronczewska, Katarzyna; Mayzner-Zawadzka, Ewa; Królicki, Leszek; Maniewski, Roman; Liebert, Adam

    2012-10-21

    It was reported that time-resolved reflectance measurements carried out during inflow and washout of an optical contrast agent may provide information on the blood supply to the brain cortex of human adults. It was also shown that a measurement of fluorescence excited in the dye circulating in the brain is feasible. Unfortunately, patterns of time-resolved fluorescence signals observed during in vivo measurements are difficult to interpret. The aim of this study was to analyze the influence of several factors on the fluorescence signals measured during in vivo experiments. A laboratory instrument for recording the distributions of arrival of fluorescence photons was constructed and optimized for measurements on humans. Monte Carlo simulations and laboratory measurements on liquid phantoms as well as in vivo measurements on healthy volunteers were carried out. An influence of source-detector separation, position of the source-detector pair on the head, as well as a dose of the injected indocyanine green (ICG) on the fluorescence signals were studied in detail. It was shown that even for a small dose of ICG (0.025 mg kg(-1)) the time-resolved signals can be successfully detected on the surface of the head. Strong influence of the studied factors on the fluorescence signals was observed. It was also noted that the changes in moments of distributions of arrival times of fluorescence photons depend on the anatomical structure of the tissues located between the source and the detector. PMID:23032301

  15. Time-resolved detection of fluorescent light during inflow of ICG to the brain—a methodological study

    NASA Astrophysics Data System (ADS)

    Milej, Daniel; Gerega, Anna; Żołek, Norbert; Weigl, Wojciech; Kacprzak, Michał; Sawosz, Piotr; Mączewska, Joanna; Fronczewska, Katarzyna; Mayzner-Zawadzka, Ewa; Królicki, Leszek; Maniewski, Roman; Liebert, Adam

    2012-10-01

    It was reported that time-resolved reflectance measurements carried out during inflow and washout of an optical contrast agent may provide information on the blood supply to the brain cortex of human adults. It was also shown that a measurement of fluorescence excited in the dye circulating in the brain is feasible. Unfortunately, patterns of time-resolved fluorescence signals observed during in vivo measurements are difficult to interpret. The aim of this study was to analyze the influence of several factors on the fluorescence signals measured during in vivo experiments. A laboratory instrument for recording the distributions of arrival of fluorescence photons was constructed and optimized for measurements on humans. Monte Carlo simulations and laboratory measurements on liquid phantoms as well as in vivo measurements on healthy volunteers were carried out. An influence of source-detector separation, position of the source-detector pair on the head, as well as a dose of the injected indocyanine green (ICG) on the fluorescence signals were studied in detail. It was shown that even for a small dose of ICG (0.025 mg kg-1) the time-resolved signals can be successfully detected on the surface of the head. Strong influence of the studied factors on the fluorescence signals was observed. It was also noted that the changes in moments of distributions of arrival times of fluorescence photons depend on the anatomical structure of the tissues located between the source and the detector.

  16. Picosecond time-resolved absorption and fluorescence dynamics in the artificial bacteriorhodopsin pigment BR6.11.

    PubMed Central

    Brack, T. L.; Delaney, J. K.; Atkinson, G. H.; Albeck, A.; Sheves, M.; Ottolenghi, M.

    1993-01-01

    The picosecond molecular dynamics in an artificial bacteriorhodopsin (BR) pigment containing a structurally modified all-trans retinal chromphore with a six-membered ring bridging the C11=C12-C13 positions (BR6.11) are measured by picosecond transient absorption and picosecond time-resolved fluorescence spectroscopy. Time-dependent intensity and spectral changes in absorption in the 570-650-nm region are monitored for delays as long as 5 ns after the 7-ps, 573-nm excitation of BR6.11. Two intermediates, J6.11 and K6.11/1, both with enhanced absorption to the red (> 600 nm) of the BR6.11 spectrum are observed within approximately 50 ps. The J6.11 intermediate decays with a time constant of 12 +/- 3 ps to form K6.11/1. The K6.11/1 intermediate decays with an approximately 100-ps time constant to form a third intermediate, K6.11/2, which is observed through diminished 650-nm absorption (relative to that of K6.11/1). No other transient absorption changes are found during the remainder of the initial 5-ns period of the BR6.11 photoreaction. Fluorescence in the 650-900-nm region is observed from BR6.11, K6.11/1, and K6.11/2, but no emission assignable to J6.11 is found. The BR6.11 fluroescence spectrum has a approximately 725-nm maximum which is blue-shifted by approximately 15 nm relative to that of native BR-570 and is 4.2 +/- 1.5 times larger in intensity (same sample optical density). No differences in the profile of the fluorescence spectra of BR6.11 and the intermediates K6.11/1 and K6.11/2 are observed. Following ground-state depletion of the BR6.11 population, the time-resolved fluroescence intensity monitored at 725 nm increases with two time constants, 12 +/- 3 and approximately 100 ps, both of which correlate well with changes in the picosecond transient absorption data. The resonance Raman spectrum of ground-state BR6.11, measured with low-energy, 560-nm excitation, is significantly different from the spectrum of native BR-570, thus confirming that the picosecond transient absorption and picosecond time resolved fluorescence data are assignable to BR6.11 and its photoreaction alone and not to BR-570 reformed during there constitution process (<5% of the BR6.11 sample could be attributed to native BR-570).The J6.11 and K6.11 absorption and fluorescence data presented here are generally analogous to those measured for native J-625 and K-590, respectively, and therefore, the primary events in the BR6.11 photoreaction can be correlated with those in the native BR photocycle. The BR6.11 photoreaction, however, exhibits important differences including slower formation rates for J and K intermediates as well as the presence of a second K intermediate. These results demonstrate that the restricted motion in the C11=C12-C13 region of retinal found in BR6.11 does not greatly change the overall photoreaction mechanism,but does alter the rates at which processes occur. PMID:8218919

  17. Femtosecond time-resolved impulsive stimulated Raman spectroscopy using sub-7-fs pulses: Apparatus and applications

    NASA Astrophysics Data System (ADS)

    Kuramochi, Hikaru; Takeuchi, Satoshi; Tahara, Tahei

    2016-04-01

    We describe details of the setup for time-resolved impulsive stimulated Raman spectroscopy (TR-ISRS). In this method, snapshot molecular vibrational spectra of the photoreaction transients are captured via time-domain Raman probing using ultrashort pulses. Our instrument features transform-limited sub-7-fs pulses to impulsively excite and probe coherent nuclear wavepacket motions, allowing us to observe vibrational fingerprints of transient species from the terahertz to 3000-cm-1 region with high sensitivity. Key optical components for the best spectroscopic performance are discussed. The TR-ISRS measurements for the excited states of diphenylacetylene in cyclohexane are demonstrated, highlighting the capability of our setup to track femtosecond dynamics of all the Raman-active fundamental molecular vibrations.

  18. Time-resolved picosecond spectroscopy of the resonant secondary radiation of F centers in KCl

    NASA Astrophysics Data System (ADS)

    Akiyama, N.; Nakahara, F.; Ohkura, H.

    1995-12-01

    The linear polarization (P HL) of hot luminescence (HL) composing of the resonant secondary radiation of the F centers has been measured using a time-resolved picosecond spectroscopy over the whole Stokes wavenumber Ω range. The P HL holds constant value of about 40% until the onset of ordinary luminescence (OL), from where it decreases to vanishingly small with decrease of Ω This implies that the optically excited F center relaxes down along the 2p-like adiabatic potential energy surface (APES) trough, and transits to the 2s-like APES trough to form the relaxed excited state (RES). The lattice relaxation time and the dynamical transition time are ultra fast estimated to be less than 15 psec.

  19. Isotope effect on hydrated electron relaxation dynamics studied with time-resolved liquid jet photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Elkins, Madeline H.; Williams, Holly L.; Neumark, Daniel M.

    2016-05-01

    The excited state relaxation dynamics of the solvated electron in H2O and D2O are investigated using time-resolved photoelectron spectroscopy in a liquid microjet. The data show that the initial excited state decays on a time scale of 75 ± 12 fs in H2O and 102 ± 8 fs in D2O, followed by slower relaxation on time scales of 400 ± 70 fs and 390 ± 70 fs that are isotopically invariant within the precision of our measurements. Based on the time evolution of the transient signals, the faster and slower time constants are assigned to p → s internal conversion (IC) of the hydrated electron and relaxation on the ground electronic state, respectively. This assignment is consistent with the non-adiabatic mechanism for relaxation of the hydrated electron and yields an isotope effect of 1.4 ± 0.2 for IC of the hydrated electron.

  20. Bayesian Comparison of Fit Parameters: An Application to Time-Resolved X-Ray Spectroscopy

    NASA Astrophysics Data System (ADS)

    Kashyap, V.

    Analysis of X-ray data of the stars AD Leo and Wolf 630, obtained with ROSAT provide important clues to the structure of the coronae on these low-mass, main-sequence stars. In particular, time-resolved X-ray spectroscopy of these stars allow us to derive estimates for the low- and high-temperature components of the plasma emission measures. Using Bayes' theorem, we show that the high-temperature components are correlated with the X-ray light-curves of the stars, while the low-temperature components are steady. Thus we are able to model the low-temperature emission as relatively compact, quiescent, static coronal loops, and the high-temperature emission as unstable flaring components.

  1. Time-resolved broadband cavity-enhanced absorption spectroscopy for chemical kinetics.

    SciTech Connect

    Sheps, Leonid; Chandler, David W.

    2013-04-01

    Experimental measurements of elementary reaction rate coefficients and product branching ratios are essential to our understanding of many fundamentally important processes in Combustion Chemistry. However, such measurements are often impossible because of a lack of adequate detection techniques. Some of the largest gaps in our knowledge concern some of the most important radical species, because their short lifetimes and low steady-state concentrations make them particularly difficult to detect. To address this challenge, we propose a novel general detection method for gas-phase chemical kinetics: time-resolved broadband cavity-enhanced absorption spectroscopy (TR-BB-CEAS). This all-optical, non-intrusive, multiplexed method enables sensitive direct probing of transient reaction intermediates in a simple, inexpensive, and robust experimental package.

  2. Time-resolved two-dimensional vibrational spectroscopy of a short α-helix in water

    NASA Astrophysics Data System (ADS)

    Woutersen, Sander; Hamm, Peter

    2001-10-01

    Nonlinear two-dimensional (2D) vibrational spectroscopy has been used to investigate the amide I band of an alanine-based 21-residue α-helical peptide in aqueous solution. Whereas the linear absorption spectrum consists of a single, broad amide I band, the 2D vibrational spectrum clearly reveals that this band is composed of two amide I transitions, which are assigned to the A and E1 modes. The A-E1 frequency splitting is found to be approximately 10 cm-1. We find that the amide I band is inhomogeneously broadened due to conformational disorder of the helix. The 2D line shapes can be well described using distributions of the dihedral angles (φ,ψ) around their average values with a width of 20°, confirming previous molecular-dynamics studies. Time-resolved 2D measurements show that the conformation fluctuates on a time scale of picoseconds.

  3. Optical properties of drying wood studied by time-resolved near-infrared spectroscopy.

    PubMed

    Konagaya, Keiji; Inagaki, Tetsuya; Kitamura, Ryunosuke; Tsuchikawa, Satoru

    2016-05-01

    We measured the optical properties of drying wood with the moisture contents ranging from 10% to 200%. By using time-resolved near-infrared spectroscopy, the reduced scattering coefficient μs' and absorption coefficient μa were determined independent of each other, providing information on the chemical and structural changes, respectively, of wood on the nanometer scale. Scattering from dry pores dominated, which allowed us to determine the drying process of large pores during the period of constant drying rate, and the drying process of smaller pores during the period of decreasing drying rate. The surface layer and interior of the wood exhibit different moisture states, which affect the scattering properties of the wood. PMID:27137569

  4. Exploring the Dynamics of Superconductors by Time-Resolved Far-Infrared Spectroscopy

    SciTech Connect

    Carr, G. L.; Lobo, R. P. S. M.; LaVeigne, J.; Reitze, D. H.; Tanner, D. B.

    2000-10-02

    We have examined the recombination of excess quasiparticles in superconducting Pb by time-resolved far-infrared spectroscopy using a pulsed synchrotron source. The energy gap shift calculated by Owen and Scalapino [Phys. Rev. Lett. 28, 1559 (1972)] is directly observed, as is the associated reduction in the Cooper pair density. The relaxation process involves a two-component decay; the faster ({approx}200 ps) is associated with the actual (effective) recombination process, while the slower ({approx}10 to 100ns) is due to heat transport across the film/substrate interface. The temperature dependence of the recombination process between 0.5T{sub c} and 0.85T{sub c} is in good agreement with theory.

  5. Time-resolved Fourier transform intracavity spectroscopy with a Cr2+:ZnSe laser.

    PubMed

    Picqu, Nathalie; Gueye, Fatou; Guelachvili, Guy; Sorokin, Evgeni; Sorokina, Irina T

    2005-12-15

    Intracavity laser absorption spectroscopy (ICLAS) with an evacuated Cr2+:ZnSe laser is performed with a high-resolution time-resolved Fourier transform interferometer with a minimum detectable absorption coefficient equal to 4 x 10(-9) cm(-1) Hz(-1/2) in the 2.5 microm region. This represents the extreme limit currently reached in the infrared by ICLAS with Doppler-limited resolution. The broad gain band of the crystal allows a spectral coverage at most equal to 125 nm, wide enough to see entire vibration bands. Weak CO2 bands observed up to now only in the Venusian atmosphere are recorded for the first time, to our knowledge, in a laboratory. An H2O detection limit down to 0.9 parts per billion by volume is also demonstrated. PMID:16389848

  6. Raman spectroscopy and time-resolved photoluminescence of BN and BxCyNz nanotubes

    SciTech Connect

    Wu, J.; Han, Wei-Qiang; Walukiewicz, W.; Ager III, J.W.; Shan, W.; Haller,E.E.; Zettl, A.

    2004-01-21

    We report Raman and time-resolved photoluminescence spectroscopic studies of multiwalled BN and B{sub x}C{sub y}N{sub z} nanotubes. The Raman spectroscopy shows that the as-grown B{sub x}C{sub y}N{sub z} charge recombination, respectively. Comparison of the photoluminescence of BN nanotubes to that decay process is characterized by two time constants that are attributed to intra- and inter-BN sheet nanotubes as predicted by theory. nanotubes are radially phase separated into BN shells and carbon shells. The photoluminescence of hexagonal BN is consistent with the existence of a spatially indirect band gap in multi-walled BN.

  7. Time resolved tunable diode laser absoption spectroscopy of dual High Power Impulse Magnetron Sputtering discharges

    NASA Astrophysics Data System (ADS)

    Do, Hoang Tung; Stranak, Vitezslav; Hippler, Rainer

    2014-08-01

    Time-resolved measurements have been performed during dual High Power Impulse Magnetron Sputtering (dual-HiPIMS) with two cathodes in a closed magnetic field configuration. The dual-HiPIMS system, operated at a repetition frequency f = 100 Hz and duty cycle of 1 %, was equipped with two different metallic targets (Ti, Cu). The effect of a delay between subsequent pulses on argon excited atom density and temperature was investigated by means of tunable diode laser absorption spectroscopy. It is shown that the peak densities of pulses vary strongly with the delay. We observed an enhancement of metastable density due to pre-ionization effect but more effective than that is the contribution of metal atoms which have smaller ionization energy compare to that of buffer gas atom. Associate with the enhancement of density, the temporal variation of metastable atom temperature in the Cu pulse also transforms from those of low current pulse into the high current one.

  8. Discovery of novel aromatase inhibitors using a homogeneous time-resolved fluorescence assay

    PubMed Central

    Ji, Jin-zi; Lao, Ke-jing; Hu, Jie; Pang, Tao; Jiang, Zhen-zhou; Yuan, Hao-liang; Miao, Jing-shan; Chen, Xin; Ning, Shan-shan; Xiang, Hua; Guo, Yu-meng; Yan, Ming; Zhang, Lu-yong

    2014-01-01

    Aim: Aromatase is an important target for drugs to treat hormone-dependent diseases, including breast cancer. The aim of this study was to develop a homogeneous time-resolved fluorescence (HTRF) aromatase assay suitable for high-throughput screening (HTS). Methods: A 384-well aromatase HTRF assay was established, and used to screen about 7000 compounds from a compound library. Anti-proliferation activity of the hit was evaluated using alamarBlue(R) assay in a hormone-dependent breast cancer cell line T47D. Molecular docking was conducted to elucidate the binding mode of the hit using the Discovery Studio program. Results: The Z′ value and signal to background (S/B) ratio were 0.74 and 5.4, respectively. Among the 7000 compounds, 4 hits (XHN22, XHN26, XHN27 and triptoquinone A) were found to inhibit aromatase with IC50 values of 1.60±0.07, 2.76±0.24, 0.81±0.08 and 45.8±11.3 μmol /L, respectively. The hits XHN22, XHN26 and XHN27 shared the same chemical scaffold of 4-imidazolyl quinoline. Moreover, the most potent hit XHN27 at 10 and 50 μmol/L inhibited the proliferation of T47D cells by 45.3% and 35.2%, respectively. The docking study revealed that XHN27 docked within the active site of aromatase and might form a hydrogen bond and had a π-cation interaction with amino acid residues of the protein. Conclusion: XHN27, an imidazolyl quinoline derivative of flavonoid, is a potent aromatase inhibitor with anti-proliferation activity against breast cancer in vitro. The established assay can be used in HTS for discovering novel aromatase inhibitor. PMID:25047514

  9. Study of aggregation induced emission of cyano-substituted oligo (p-phenylenevinylene) by femtosecond time resolved fluorescence

    NASA Astrophysics Data System (ADS)

    Yan, Zi-Qi; Yang, Zhi-Yong; Wang, Hai; Li, Ai-Wu; Wang, Li-Ping; Yang, Han; Gao, Bing-Rong

    2011-05-01

    The aggregation induced emission (AIE) mechanism of the cyano-substituted oligo (p-phenylenevinylene)1,4-bis [1-cyano-2-(4-(diphenylamino) phenyl) vinyl] benzene (TPCNDSB) is investigated by time resolved fluorescence technique. By reconstructing the time resolved emission spectra (TRES), it is found that in solvent of low polarity, the emission is mainly from the local emission (LE) state with high quantum yield, but in high polarity solvent, the emission is mainly from the intramolecular charge transfer (ICT) state, which is a relatively dark state, with low quantum yield. In crystal form, the restriction of transfer from LE state to ICT state results in efficient AIE.

  10. Highly sensitive detection of human papillomavirus type 16 DNA using time-resolved fluorescence microscopy and long lifetime probes

    NASA Astrophysics Data System (ADS)

    Wang, Xue F.; Periasamy, Ammasi; Wodnicki, Pawel; Siadat-Pajouh, M.; Herman, Brian

    1995-04-01

    We have been interested in the role of Human Papillomavirus (HPV) in cervical cancer and its diagnosis; to that end we have been developing microscopic imaging and fluorescent in situ hybridization (FISH) techniques to genotype and quantitate the amount of HPV present at a single cell level in cervical PAP smears. However, we have found that low levels of HPV DNA are difficult to detect accurately because theoretically obtainable sensitivity is never achieved due to nonspecific autofluorescence, fixative induced fluorescence of cells and tissues, and autofluorescence of the optical components in the microscopic system. In addition, the absorption stains used for PAP smears are intensely autofluorescent. Autofluorescence is a rapidly decaying process with lifetimes in the range of 1-100 nsec, whereas phosphorescence and delayed fluorescence have lifetimes in the range of 1 microsecond(s) ec-10 msec. The ability to discriminate between specific fluorescence and autofluorescence in the time-domain has improved the sensitivity of diagnostic test such that they perform comparably to, or even more sensitive than radioisotopic assays. We have developed a novel time-resolved fluorescence microscope to improve the sensitivity of detection of specific molecules of interest in slide based specimens. This time-resolved fluorescence microscope is based on our recently developed fluorescence lifetime imaging microscopy (FILM) in conjunction with the use of long lifetime fluorescent labels. By using fluorescence in situ hybridization and the long lifetime probe (europium), we have demonstrated the utility of this technique for detection of HPV DNA in cervicovaginal cells. Our results indicate that the use of time-resolved fluorescence microscopy and long lifetime probes increases the sensitivity of detection by removing autofluorescence and will thus lead to improved early diagnosis of cervical cancer. Since the highly sensitive detection of DNA in clinical samples using fluorescence in situ hybridization image is useful for the diagnosis of many other type of diseases, the system we have developed should find numerous applications for the diagnosis of disease states.

  11. Characterization of energetic and thermalized sputtered atoms in pulsed plasma using time-resolved tunable diode-laser induced fluorescence

    SciTech Connect

    Desecures, M.; Poucques, L. de; Easwarakhanthan, T.; Bougdira, J.

    2014-11-03

    In this work, a time-resolved tunable diode-laser (DL) induced fluorescence (TR-TDLIF) method calibrated by absorption spectroscopy has been developed in order to determine atom and flux velocity distribution functions (AVDF and FVDF) of the energetic and the thermalized atoms in pulsed plasmas. The experimental set-up includes a low-frequency (∼3 Hz) and high spectral-resolution DL (∼0.005 pm), a fast rise-time pulse generator, and a high power impulse magnetron sputtering (HiPIMS) system. The induced TR-TDLIF signal is recorded every 0.5 μs with a digital oscilloscope of a second-long trace. The technique is illustrated with determining the AVDF and the FVDF of a metastable state of the sputtered neutral tungsten atoms in the HiPIMS post-discharge. Gaussian functions describing the population of the four W isotopes were used to fit the measured TR-TDLIF signal. These distribution functions provide insight into transition from the energetic to thermalized regimes from the discharge onset. This technique may be extended with appropriate DLs to probe any species with rapidly changing AVDF and FVDF in pulsed and strongly oscillating plasmas.

  12. Characterization of energetic and thermalized sputtered atoms in pulsed plasma using time-resolved tunable diode-laser induced fluorescence

    NASA Astrophysics Data System (ADS)

    Desecures, M.; de Poucques, L.; Easwarakhanthan, T.; Bougdira, J.

    2014-11-01

    In this work, a time-resolved tunable diode-laser (DL) induced fluorescence (TR-TDLIF) method calibrated by absorption spectroscopy has been developed in order to determine atom and flux velocity distribution functions (AVDF and FVDF) of the energetic and the thermalized atoms in pulsed plasmas. The experimental set-up includes a low-frequency (˜3 Hz) and high spectral-resolution DL (˜0.005 pm), a fast rise-time pulse generator, and a high power impulse magnetron sputtering (HiPIMS) system. The induced TR-TDLIF signal is recorded every 0.5 μs with a digital oscilloscope of a second-long trace. The technique is illustrated with determining the AVDF and the FVDF of a metastable state of the sputtered neutral tungsten atoms in the HiPIMS post-discharge. Gaussian functions describing the population of the four W isotopes were used to fit the measured TR-TDLIF signal. These distribution functions provide insight into transition from the energetic to thermalized regimes from the discharge onset. This technique may be extended with appropriate DLs to probe any species with rapidly changing AVDF and FVDF in pulsed and strongly oscillating plasmas.

  13. Time-resolved fluorescence studies of a transmembrane peptide sequence of the dopamine D2 receptor

    NASA Astrophysics Data System (ADS)

    Williams, Valerie L.; Courtney, Scott H.; Schuster, David I.; Murphy, Randall B.

    1994-08-01

    Highly hydrophobic peptides in small unilamellar vesicles can be used to model membrane-embedded proteins such as the dopamine D2 receptor. The transmembrane domains of the dopamine D2 receptor are known to contain residues corresponding to the binding sites for natural receptor ligands. We have developed a model system consisting of a peptide whose sequence was taken from the transmembrane region of the dopamine D2 receptor and incorporated it into phospholipid bilayers. This polypeptide sequence, NH2-D-V-L-Y-S-A-F-T-W-L-G-Y-V-N-S-A-V-N-P-I-I-Y-T- T-F-N-V-CO2H, contains a single tryptophan residue, whose fluorescence properties provides an intrinsic probe of the microenvironment of the peptide within the bilayer. Purification of this highly hydrophobic peptide required the development of a novel alcohol-based reversed-phase HPLC solvent system. The vesicles were produces by cosonication of the peptide with dimyristoylphosphatidylcholine lipid and were characterized by electron microscopy and fluorescence spectroscopy. Time- correlated single photon counting was sued to measure the fluorescence anisotropy of the system as a function of temperature across the lipid phase transition range and as a function of the peptide/lipid ratio.

  14. Time-resolved in-situ quantum cascade laser absorption spectroscopy in dielectric barrier discharges

    NASA Astrophysics Data System (ADS)

    Welzel, S.; Brehmer, F.; van de Sanden, M. C. M.; Engeln, R.

    2013-09-01

    Modern mid-infrared laser sources, known as quantum cascade lasers (QCLs), provide a means for highly time-resolved absorption spectroscopy in the molecular ``fingerprint'' region. Pulsed distributed feedback QCLs are especially suited for diagnostic studies on transient plasmas as the time-resolution can be as good as a few tens of nanoseconds. Dielectric barrier discharges in CO2 operated in the mid-frequency (kHz) range were studied by means of in-situ QCL absorption spectroscopy in single and multiple-pass configuration. Different synchronisation schemes were applied to achieve phase-resolved measurements during individual AC cycles as well as to monitor molecular absorption signals during pulsed operation. Mixing ratios of CO in its electronic and vibrational ground state were of the order of a few percent and thus confirmed ex-situ studies of the effluent. Interestingly, the concentrations levels were changing only slowly in time, i.e. of the order of the residence time. A direct CO2-to-CO dissociation through electron impact appears very unlikely under these conditions. The kinetics of low-lying ro-vibrational states of CO2 along with the evolution of the CO concentration were measured on a sub-millisecond time-scale to establish the (rotational) gas temperatures.

  15. Cyclohexene Photo-oxidation over Vanadia Catalyst Analyzed by Time Resolved ATR-FT-IR Spectroscopy

    SciTech Connect

    Frei, Heinz; Mul, Guido; Wasylenko, Walter; Hamdy, M. Sameh; Frei, Heinz

    2008-06-04

    Vanadia was incorporated in the 3-dimensional mesoporous material TUD-1 with a loading of 2percent w/w vanadia. The performance in the selective photo-oxidation of liquid cyclohexene was investigated using ATR-FT-IR spectroscopy. Under continuous illumination at 458 nm a significant amount of product, i.e. cyclohexenone, was identified. This demonstrates for the first time that hydroxylated vanadia centers in mesoporous materials can be activated by visible light to induce oxidation reactions. Using the rapid scan method, a strong perturbation of the vanadyl environment could be observed in the selective oxidation process induced by a 458 nm laser pulse of 480 ms duration. This is proposed to be caused by interaction of the catalytic centre with a cyclohexenyl hydroperoxide intermediate. The restoration of the vanadyl environment could be kinetically correlated to the rate of formation of cyclohexenone, and is explained by molecular rearrangement and dissociation of the peroxide to ketone and water. The ketone diffuses away from the active center and ATR infrared probing zone, resulting in a decreasing ketone signal on the tens of seconds time scale after initiation of the photoreaction. This study demonstrates the high potential of time resolved ATR FT-IR spectroscopy for mechanistic studies of liquid phase reactions by monitoring not only intermediates and products, but by correlating the temporal behavior of these species to molecular changes of the vanadyl catalytic site.

  16. Time-resolved tuned diode laser absorption spectroscopy of pulsed plasma

    NASA Astrophysics Data System (ADS)

    Adámek, P.; Do, H. T.; Čada, M.; Hubička, Z.; Hippler, R.

    2014-05-01

    A novel method for time-resolved tuned diode laser absorption spectroscopy has been developed. In this paper, we describe in detail developed electronic module that controls time-resolution of laser absorption spectroscopy system. The TTL signal triggering plasma pulse is used for generation of two signals: the first one triggers the fine tuning of laser wavelength and second one controls time-defined signal sampling from absorption detector. The described method and electronic system enable us to investigate temporal evolution of sputtered particles in technological low-temperature plasma systems. The pulsed DC planar magnetron sputtering system has been used to verify this method. The 2" in diameter titanium target was sputtered in pure argon atmosphere. The working pressure was held at 2 Pa. All the experiments were carried out for pulse ON time fixed at 100 (is. When changing OFF time the discharge has operated between High Power Impulse Magnetron Sputtering regime and pulsed DC magnetron regime. The effect of duty cycle variation results in decrease of titanium atom density during ON time while length of OFF time elongates. We believe that observed effect is connected with higher degree of ionization of sputtered particles. As previously reported by Bohlmark et al., the measured optical emission spectra in HiPIMS systems were dominated by emission from titanium ions [1].

  17. Time-resolved reflectance spectroscopy for nondestructive assessment of fruit and vegetable quality

    NASA Astrophysics Data System (ADS)

    Torricelli, Alessandro; Spinelli, Lorenzo; Vanoli, Maristella; Rizzolo, Anna; Eccher Zerbini, Paola

    2007-09-01

    In the majority of food and feed, due to the microscopic spatial changes in the refractive index, visible (VIS) and near infrared (NIR) light undergoes multiple scattering events and the overall light distribution is determined more by scattering rather than absorption. Conventional steady state VIS/NIR reflectance spectroscopy can provide information on light attenuation, which depends both on light absorption and light scattering, but cannot discriminate these two effects. On the contrary, time-resolved reflectance spectroscopy (TRS) provides a complete optical characterisation of diffusive media in terms of their absorption coefficient and reduced scattering coefficient. From the assessment of the absorption and reduced scattering coefficients, information can then be derived on the composition and internal structure of the medium. Main advantages of the technique are the absolute non-invasiveness, the potentiality for non-contact measurements, and the capacity to probe internal properties with no influence from the skin. In this work we review the physical and technical issues related to the use of TRS for nondestructive quality assessment of fruit and vegetable. A laboratory system for broadband TRS, based on tunable mode-locked lasers and fast microchannel plate photomultiplier, and a portable setup for TRS measurements, based on pulsed diode lasers and compact metal-channel photomultiplier, will be described. Results on broadband optical characterisation of fruits and applications of TRS to the detection of internal defects in pears and to maturity assessment in nectarines will be presented.

  18. Multiwavelength time-resolved detection of fluorescence during the inflow of indocyanine green into the adult's brain.

    PubMed

    Gerega, Anna; Milej, Daniel; Weigl, Wojciech; Botwicz, Marcin; Zolek, Norbert; Kacprzak, Michal; Wierzejski, Wojciech; Toczylowska, Beata; Mayzner-Zawadzka, Ewa; Maniewski, Roman; Liebert, Adam

    2012-08-01

    Optical technique based on diffuse reflectance measurement combined with indocyanine green (ICG) bolus tracking is extensively tested as a method for clinical assessment of brain perfusion in adults at the bedside. Methodology of multiwavelength and time-resolved detection of fluorescence light excited in the ICG is presented and advantages of measurements at multiple wavelengths are discussed. Measurements were carried out: 1. on a physical homogeneous phantom to study the concentration dependence of the fluorescence signal, 2. on the phantom to simulate the dynamic inflow of ICG at different depths, and 3. in vivo on surface of the human head. Pattern of inflow and washout of ICG in the head of healthy volunteers after intravenous injection of the dye was observed for the first time with time-resolved instrumentation at multiple emission wavelengths. The multiwavelength detection of fluorescence signal confirms that at longer emission wavelengths, probability of reabsorption of the fluorescence light by the dye itself is reduced. Considering different light penetration depths at different wavelengths, and the pronounced reabsorption at longer wavelengths, the time-resolved multiwavelength technique may be useful in signal decomposition, leading to evaluation of extra- and intracerebral components of the measured signals. PMID:23224200

  19. Multiwavelength time-resolved detection of fluorescence during the inflow of indocyanine green into the adult's brain

    NASA Astrophysics Data System (ADS)

    Gerega, Anna; Milej, Daniel; Weigl, Wojciech; Botwicz, Marcin; Zolek, Norbert; Kacprzak, Michal; Wierzejski, Wojciech; Toczylowska, Beata; Mayzner-Zawadzka, Ewa; Maniewski, Roman; Liebert, Adam

    2012-08-01

    Optical technique based on diffuse reflectance measurement combined with indocyanine green (ICG) bolus tracking is extensively tested as a method for clinical assessment of brain perfusion in adults at the bedside. Methodology of multiwavelength and time-resolved detection of fluorescence light excited in the ICG is presented and advantages of measurements at multiple wavelengths are discussed. Measurements were carried out: 1. on a physical homogeneous phantom to study the concentration dependence of the fluorescence signal, 2. on the phantom to simulate the dynamic inflow of ICG at different depths, and 3. in vivo on surface of the human head. Pattern of inflow and washout of ICG in the head of healthy volunteers after intravenous injection of the dye was observed for the first time with time-resolved instrumentation at multiple emission wavelengths. The multiwavelength detection of fluorescence signal confirms that at longer emission wavelengths, probability of reabsorption of the fluorescence light by the dye itself is reduced. Considering different light penetration depths at different wavelengths, and the pronounced reabsorption at longer wavelengths, the time-resolved multiwavelength technique may be useful in signal decomposition, leading to evaluation of extra- and intracerebral components of the measured signals.

  20. Time-resolved laser-induced fluorescence diagnostics in a HIPIMS discharge

    NASA Astrophysics Data System (ADS)

    Britun, Nikolay; Palmucci, Maria; Konstantinidis, Stephanos; Snyders, Rony

    2012-09-01

    Laser-induced fluorescence (LIF) combined with resonant optical absorption spectroscopy (ROAS) were utilized for characterization of the Ar-Ti high-power impulse sputtering (HIPIMS) discharge at working pressures of 5 and 20 mTorr. The LIF measurements were performed during the plasma off-time. It was shown that the time-behavior of the measured densities depends strongly on the working pressure in the reactor as well as on the distance from the magnetron target. ROAS measurements indicates that the absolute ground state level density of Ti can reach ≈ 1011 cm-3 (at 20 mTorr, 10 μs pulse, and 12 kW of applied power per pulse). Generally, the obtained results indicate highly non-uniform spatial and temporal behavior of the sputtered species such as Ti and Ti+, which correlate with the results previously obtained in the other magnetron discharges.

  1. A Vinblastine Fluorescent Probe for Pregnane X Receptor in a Time-Resolved Fluorescence Resonance Energy Transfer Assay

    PubMed Central

    Lin, Wenwei; Chen, Taosheng

    2013-01-01

    The pregnane X receptor (PXR) regulates the metabolism and excretion of xenobiotics and endobiotics by regulating the expression of drug-metabolizing enzymes and transporters. The unique structure of PXR allows the binding of many drugs and drug leads to it, possibly causing undesired drug-drug interactions. Therefore, it is crucial to evaluate whether lead compounds bind to PXR. Fluorescence-based assays are preferred because of their sensitivity and non-radioactive nature. One fluorescent PXR probe is currently commercially available; however, because its chemical structure is not publicly disclosed, it is not optimal for studying ligand-PXR interactions. Here we report the characterization of BODIPY FL Vinblastine, generated by labeling vinblastine with the fluorophore 4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene (BODIPY FL), as a high-affinity ligand for human PXR with a Kd value of 673 nM. We provide evidence that BODIPY FL Vinblastine is a unique chemical entity different from either vinblastine or the fluorophore 4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene in its function as a high-affinity human PXR ligand. We describe a BODIPY FL Vinblastine-based human PXR Time-Resolved Fluorescence Resonance Energy Transfer assay, which was used to successfully test a panel of human PXR ligands. The BODIPY FL Vinblastine–based biochemical assay is suitable for high-throughput screening to evaluate whether lead compounds bind to PXR. PMID:24044991

  2. A field programmable gate array-based time-resolved scaler for collinear laser spectroscopy with bunched radioactive potassium beams

    SciTech Connect

    Rossi, D. M. Davis, M.; Ringle, R.; Rodriguez, J. A.; Ryder, C. A.; Schwarz, S.; Sumithrarachchi, C.; Zhao, S.; Minamisono, K. Barquest, B. R.; Bollen, G.; Hughes, M.; Strum, R.; Tarazona, D.; Cooper, K.; Hammerton, K.; Mantica, P. F.; Morrissey, D. J.

    2014-09-15

    A new data acquisition system including a Field Programmable Gate Array (FPGA) based time-resolved scaler was developed for laser-induced fluorescence and beam bunch coincidence measurements. The FPGA scaler was tested in a collinear laser-spectroscopy experiment on radioactive {sup 37}K at the BEam COoler and LAser spectroscopy (BECOLA) facility at the National Superconducting Cyclotron Laboratory at Michigan State University. A 1.29 μs bunch width from the buncher and a bunch repetition rate of 2.5 Hz led to a background suppression factor of 3.1 × 10{sup 5} in resonant photon detection measurements. The hyperfine structure of {sup 37}K and its isotope shift relative to the stable {sup 39}K were determined using 5 × 10{sup 4} s{sup −1} {sup 37}K ions injected into the BECOLA beam line. The obtained hyperfine coupling constants A({sup 2}S{sub 1/2}) = 120.3(1.4) MHz, A({sup 2}P{sub 1/2}) = 15.2(1.1) MHz, and A({sup 2}P{sub 3/2}) = 1.4(8) MHz, and the isotope shift δν{sup 39,} {sup 37} = −264(3) MHz are consistent with the previously determined values, where available.

  3. Cyclohexadiene Revisited: A Time-Resolved Photoelectron Spectroscopy and ab Initio Study.

    PubMed

    Schalk, Oliver; Geng, Ting; Thompson, Travis; Baluyot, Noel; Thomas, Richard D; Tapavicza, Enrico; Hansson, Tony

    2016-04-21

    We have reinvestigated the excited state dynamics of cyclohexa-1,3-diene (CHD) with time-resolved photoelectron spectroscopy and fewest switches surface hopping molecular dynamics based on linear response time-dependent density functional theory after excitation to the lowest lying ππ* (1B) state. The combination of both theory and experiment revealed several new results: First, the dynamics progress on one single excited state surface. After an incubation time of 35 ± 10 fs on the excited state, the dynamics proceed to the ground state in an additional 60 ± 10 fs, either via a conrotatory ring-opening to hexatriene or back to the CHD ground state. Moreover, ring-opening predominantly occurs when the wavepacket crosses the region of strong nonadiabatic coupling with a positive velocity in the bond alternation coordinate. After 100 fs, trajectories remaining in the excited state must return to the CHD ground state. This extra time delay induces a revival of the photoelectron signal and is an experimental confirmation of the previously formulated model of two parallel reaction channels with distinct time constants. Finally, our simulations suggest that after the initially formed cis-Z-cis HT rotamer the trans-Z-trans isomer is formed, before the thermodynamical equilibrium of three possible rotamers is reached after 1 ps. PMID:27018427

  4. Evidence for bandgap opening in buckled epitaxial graphene from ultrafast time-resolved terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Mihnev, Momchil T.; Wang, Feng; Liu, Gang; Rothwell, Sara; Cohen, Philip I.; Feldman, Leonard C.; Conrad, Edward H.; Norris, Theodore B.

    2015-10-01

    We utilize ultrafast time-resolved terahertz (THz) spectroscopy as a direct, sensitive, and non-contact all-optical probe to investigate the hot-carrier relaxation and cooling dynamics of buckled epitaxial graphene. This special form of graphene is grown epitaxially on nitrogen-seeded single-crystal silicon carbide (SiC( 000 1 ¯ )) substrates by thermal decomposition of Si atoms. The pre-deposited interfacial nitrogen atoms pin the first graphene layer to the SiC substrate, and cause it and subsequent graphene layers to buckle into nanoscale folds, which opens an energy gap of up to ˜0.7 eV. We observe a remarkable increase of up to two orders of magnitude in the relaxation rate of the THz carrier dynamics of this semiconducting form of epitaxial graphene relative to pristine epitaxial graphene, which we attribute to a large enhancement of the optical-phonon-mediated carrier cooling and recombination over a wide range of electron temperatures due to the finite bandgap. Our results suggest that the introduced bandgap is spatially non-homogenous, with local values close to the optical phonon energy of ˜200 meV, which allows the conduction and the valence band to be bridged by optical phonon emission. We also demonstrate that carrier relaxation times can be modified by orders of magnitude by careful bandgap engineering, which could find application in novel graphene-based devices that incorporate both metallic and semiconducting forms of graphene.

  5. Nonadiabatic Dynamics May Be Probed through Electronic Coherence in Time-Resolved Photoelectron Spectroscopy.

    PubMed

    Bennett, Kochise; Kowalewski, Markus; Mukamel, Shaul

    2016-02-01

    We present a hierarchy of Fermi golden rules (FGRs) that incorporate strongly coupled electronic/nuclear dynamics in time-resolved photoelectron spectroscopy (TRPES) signals at different levels of theory. Expansion in the joint electronic and nuclear eigenbasis yields the numerically most challenging exact FGR (eFGR). The quasistatic Fermi Golden Rule (qsFGR) neglects nuclear motion during the photoionization process but takes into account electronic coherences as well as populations initially present in the pumped matter as well as those generated internally by coupling between electronic surfaces. The standard semiclassical Fermi Golden Rule (scFGR) neglects the electronic coherences and the nuclear kinetic energy during the ionizing pulse altogether, yielding the classical Condon approximation. The coherence contributions depend on the phase-profile of the ionizing field, allowing coherent control of TRPES signals. The photoelectron spectrum from model systems is simulated using these three levels of theory. The eFGR and the qsFGR show temporal oscillations originating from the electronic or vibrational coherences generated as the nuclear wave packet traverses a conical intersection. These oscillations, which are missed by the scFGR, directly reveal the time-evolving splitting between electronic states of the neutral molecule in the curve-crossing regime. PMID:26691822

  6. Initial Process of Proton Transfer in Salicylideneaniline Studied by Time-Resolved Photoelectron Spectroscopy

    NASA Astrophysics Data System (ADS)

    Sekikawa, T.; Schalk, O.; Wu, G.; Boguslavskiy, A. E.; Stolow, A.

    Excited state intramolecular proton transfer (ESIPT) in salicylideneaniline (SA) molecules expanded in a supersonic gas jet has been investigated by femtosecond time-resolved photoelectron spectroscopy. Although ESIPT in SA was predicted to take place in a planar structure, the fattening process of a molecule from a twisted Franck-Condon state has never been resolved. Here, we identified the twisting motion of the anilino ring during the fattening process in the decay dynamics of the photoelectron yield, taking account of the energy surface of the S1(π, π ∗) state of the enol form and the potential surface of ESIPT calculated by a time-dependent density functional theory (TDDFT). The twisting motion was found to be slower in the bromide and methylated SAs, while that in the nitrated SA did not change significantly. These substitution effects are explained by the modification of the potential barriers by the substituents, also predicted by the TDDFT calculation, and support the assignment of the decay dynamics to the twisting motion of the anilino ring prior ESIPT.

  7. Noninvasive detection of concealed explosives: depth profiling through opaque plastics by time-resolved Raman spectroscopy.

    PubMed

    Petterson, Ingeborg E Iping; López-López, María; García-Ruiz, Carmen; Gooijer, Cees; Buijs, Joost B; Ariese, Freek

    2011-11-15

    The detection of explosives concealed behind opaque, diffusely scattering materials is a challenge that requires noninvasive analytical techniques for identification without having to manipulate the package. In this context, this study focuses on the application of time-resolved Raman spectroscopy (TRRS) with a picosecond pulsed laser and an intensified charge-coupled device (ICCD) detector for the noninvasive identification of explosive materials through several millimeters of opaque polymers or plastic packaging materials. By means of a short (250 ps) gate which can be delayed several hundred picoseconds after the laser pulse, the ICCD detector allows for the temporal discrimination between photons from the surface of a sample and those from deeper layers. TRRS was applied for the detection of the two main isomers of dinitrotoluene, 2,4-dinitrotoluene, and 2,6-dinitrotoluene as well as for various other components of explosive mixtures, including akardite II, diphenylamine, and ethyl centralite. Spectra were obtained through different diffuse scattering white polymer materials: polytetrafluoroethylene (PTFE), polyoxymethylene (POM), and polyethylene (PE). Common packaging materials of various thicknesses were also selected, including polystyrene (PS) and polyvinyl chloride (PVC). With the demonstration of the ability to detect concealed, explosives-related compounds through an opaque first layer, this study may have important applications in the security and forensic fields. PMID:21967622

  8. Time-resolved spectroscopy of LiF:Mg,Cu,P.

    PubMed

    Mathur, V K; Barkyoumb, J H; Jarrett, Andrew

    2006-01-01

    Time-resolved spectroscopy measurements of LiF:Mg,Cu,P luminescence are presented to obtain a better understanding of the emission characteristics of this material. The intensities and decay of the emission bands were studied as a function of annealing temperature and ionising radiation (gamma) dose. Two peaks in the emission were observed at 367 and 466 nm when excited by the 266 nm laser radiation. The luminescence spectrum under band-to-band X-ray excitation shows a dominant emission approximately 390-400 nm, which resembles the reported thermoluminescence emission and is clearly different from the spectrum obtained using the 266 nm pulsed laser excitation. Annealing of the material to 300 degrees C increases the intensity of the 367 and 466 nm emission bands by an order of magnitude as well as changes the relative intensity of the bands. Additional emission bands, which are not evident in the thermoluminescence emission spectra, are seen at longer wavelengths that also increase with dose. Possible explanations for the observed emission spectra are discussed in this paper. PMID:16644981

  9. Time-resolved X-ray Absorption Spectroscopy for Electron Transport Study in Warm Dense Gold

    NASA Astrophysics Data System (ADS)

    Lee, Jong-Won; Bae, Leejin; Engelhorn, Kyle; Heimann, Philip; Ping, Yuan; Barbrel, Ben; Fernandez, Amalia; Beckwith, Martha Anne; Cho, Byoung-Ick; GIST Team; IBS Team; LBNL Collaboration; SLAC Collaboration; LLNL Collaboration

    2015-11-01

    The warm dense Matter represents states of which the temperature is comparable to Fermi energy and ions are strongly coupled. One of the experimental techniques to create such state in the laboratory condition is the isochoric heating of thin metal foil with femtosecond laser pulses. This concept largely relies on the ballistic transport of electrons near the Fermi-level, which were mainly studied for the metals in ambient conditions. However, they were barely investigated in warm dense conditions. We present a time-resolved x-ray absorption spectroscopy measured for the Au/Cu dual layered sample. The front Au layer was isochorically heated with a femtosecond laser pulse, and the x-ray absorption changes around L-edge of Cu, which was attached on the backside of Au, was measured with a picosecond resolution. Time delays between the heating of the `front surface' of Au layer and the alternation of x-ray spectrum of Cu attached on the `rear surface' of Au indicate the energetic electron transport mechanism through Au in the warm dense conditions. IBS (IBS-R012-D1) and the NRF (No. 2013R1A1A1007084) of Korea.

  10. Optical analysis of cirrhotic liver by near infrared time resolved spectroscopy

    NASA Astrophysics Data System (ADS)

    Nishio, Toshihiro; Kitai, Toshiyuki; Miwa, Mitsuharu; Takahashi, Rei; Yamaoka, Yoshio

    1999-10-01

    The severity of liver cirrhosis was related with the optical properties of liver tissue. Various grades of liver cirrhosis were produced in rats by intraperitoneal injection of thioacetamide (TAA) for different periods: 4 weeks, 8 weeks, 12 weeks, and 16 weeks. Optical properties of the liver, absorption, coefficient ((mu) a) and scattering coefficient (microsecond(s) '), were measured by near-infrared time- resolved spectroscopy. Histological examination confirmed cirrhotic changes in the liver, which were more severe in rats with TAA administration for longer periods. The (mu) a increased in 4- and 8-week rats, and then decreased in 12- and 16-week rats. The (mu) a of blood-free liver decreased as liver cirrhosis progressed. The hemoglobin content in the liver calculated from the (mu) a values increased in 4- and 8-week rats and decreased in 12- and 16-week rats. The microsecond(s) ' decreased in the cirrhotic liver, probably reflecting the decrease in the mitochondria content. It was shown that (mu) a and microsecond(s) ' determination is useful to assess the severity of liver cirrhosis.

  11. Reactivity of Binuclear Tantalum Clusters on Silica: Characterization by Transient Time-Resolved Spectroscopy

    SciTech Connect

    Nemana, Sailendra; Sun, Junming; Gates, Bruce C.

    2008-05-08

    Binuclear tantalum clusters were synthesized from Ta(CH{sub 2}Ph){sub 5} (Ph is phenyl) on the surface of nonporous SiO{sub 2} (Aerosil), and their reactions with H{sub 2}, D{sub 2}, and ethylene were characterized by time-resolved infrared (IR), extended X-ray absorption fine structure (EXAFS), and X-ray absorption near edge spectroscopies. The EXAFS data indicate the formation in H{sub 2} of clusters with a Ta-Ta coordination number of approximately 1 and a bonding distance of 2.74 {angstrom}. Reactions of the supported clusters with D{sub 2} and H{sub 2} facilitate the interconversion of O-H and O-D groups on the SiO{sub 2} surface. Reaction of these clusters with ethylene led to their rapid fragmentation to give mononuclear tantalum complexes, as the tantalum was oxidized and new ligands formed, suggested by IR spectra to be ethyl. The results demonstrate a rough analogy between the chemistry of tantalum clusters on the SiO{sub 2} surface and their chemistry in solution. Because alkenes are suggested intermediates in the catalytic disproportionation of alkanes on supported tantalum, our results indicate how these intermediates might influence the nature of the catalytically active species.

  12. Hemodynamic measurements in deep brain tissues of humans by near-infrared time-resolved spectroscopy

    NASA Astrophysics Data System (ADS)

    Suzuki, Hiroaki; Oda, Motoki; Yamaki, Etsuko; Suzuki, Toshihiko; Yamashita, Daisuke; Yoshimoto, Kenji; Homma, Shu; Yamashita, Yutaka

    2014-03-01

    Using near-infrared time-resolved spectroscopy (TRS), we measured the human head in transmittance mode to obtain the optical properties, tissue oxygenation, and hemodynamics of deep brain tissues in 50 healthy adult volunteers. The right ear canal was irradiated with 3-wavelengths of pulsed light (760, 795, and 835nm), and the photons passing through the human head were collected at the left ear canal. Optical signals with sufficient intensity could be obtained from 46 of the 50 volunteers. By analyzing the temporal profiles based on the photon diffusion theory, we successfully obtained absorption coefficients for each wavelength. The levels of oxygenated hemoglobin (HbO2), deoxygenated hemoglobin (Hb), total hemoglobin (tHb), and tissue oxygen saturation (SO2) were then determined by referring to the hemoglobin spectroscopic data. Compared with the SO2 values for the forehead measurements in reflectance mode, the SO2 values of the transmittance measurements of the human head were approximately 10% lower, and tHb values of the transmittance measurements were always lower than those of the forehead reflectance measurements. Moreover, the level of hemoglobin and the SO2 were strongly correlated between the human head measurements in transmittance mode and the forehead measurements in the reflectance mode, respectively. These results demonstrated a potential application of this TRS system in examining deep brain tissues of humans.

  13. Monitoring brain temperature by time-resolved near-infrared spectroscopy: pilot study

    NASA Astrophysics Data System (ADS)

    Bakhsheshi, Mohammad Fazel; Diop, Mamadou; St. Lawrence, Keith; Lee, Ting-Yim

    2014-05-01

    Mild hypothermia (HT) is an effective neuroprotective strategy for a variety of acute brain injuries. However, the wide clinical adaptation of HT has been hampered by the lack of a reliable noninvasive method for measuring brain temperature, since core measurements have been shown to not always reflect brain temperature. The goal of this work was to develop a noninvasive optical technique for measuring brain temperature that exploits both the temperature dependency of water absorption and the high concentration of water in brain (80%-90%). Specifically, we demonstrate the potential of time-resolved near-infrared spectroscopy (TR-NIRS) to measure temperature in tissue-mimicking phantoms (in vitro) and deep brain tissue (in vivo) during heating and cooling, respectively. For deep brain tissue temperature monitoring, experiments were conducted on newborn piglets wherein hypothermia was induced by gradual whole body cooling. Brain temperature was concomitantly measured by TR-NIRS and a thermocouple probe implanted in the brain. Our proposed TR-NIRS method was able to measure the temperature of tissue-mimicking phantoms and brain tissues with a correlation of 0.82 and 0.66 to temperature measured with a thermometer, respectively. The mean difference between the TR-NIRS and thermometer measurements was 0.15°C±1.1°C for the in vitro experiments and 0.5°C±1.6°C for the in vivo measurements.

  14. [Photodissociation of Acetylene and Acetone using Step-Scan Time-Resolved FTIR Emission Spectroscopy

    NASA Technical Reports Server (NTRS)

    McLaren, Ian A.; Wrobel, Jacek D.

    1997-01-01

    The photodissociation of acetylene and acetone was investigated as a function of added quenching gas pressures using step-scan time-resolved FTIR emission spectroscopy. Its main components consist of Bruker IFS88, step-scan Fourier Transform Infrared (FTIR) spectrometer coupled to a flow cell equipped with Welsh collection optics. Vibrationally excited C2H radicals were produced from the photodissociation of acetylene in the unfocused experiments. The infrared (IR) emission from these excited C2H radicals was investigated as a function of added argon pressure. Argon quenching rate constants for all C2H emission bands are of the order of 10(exp -13)cc/molecule.sec. Quenching of these radicals by acetylene is efficient, with a rate constant in the range of 10(exp -11) cc/molecule.sec. The relative intensity of the different C2H emission bands did not change with the increasing argon or acetylene pressure. However, the overall IR emission intensity decreased, for example, by more than 50% when the argon partial pressure was raised from 0.2 to 2 Torr at fixed precursor pressure of 160mTorr. These observations provide evidence for the formation of a metastable C2H2 species, which are collisionally quenched by argon or acetylene. Problems encountered in the course of the experimental work are also described.

  15. Nanosecond Time-Resolved Polarization Spectroscopies: Tools for Probing Protein Reaction Mechanisms

    PubMed Central

    Chen, Eefei; Goldbeck, Robert A.; Kliger, David S.

    2010-01-01

    Polarization methods, introduced in the 1800’s, offered one of the earliest ways to examine protein structure. Since then, many other structure-sensitive probes have been developed, but circular dichroism (CD) remains a powerful technique because of its versatility and the specificity of protein structural information that can be explored. With improvements in time-resolution, from millisecond to picosecond CD measurements, it has proven to be an important tool for studying the mechanism of folding and function in many biomolecules. For example, nanosecond time-resolved CD (TRCD) studies of the sub-microsecond events of reduced cytochrome c folding have provided direct experimental evidence of kinetic heterogeneity, which is an inherent property of the diffusional nature of early folding dynamics on the energy landscape. In addition, TRCD has been applied to the study of many biochemical processes, such as ligand rebinding in hemoglobin and myoglobin and signaling state formation in photoactive yellow protein and prototropin 1 LOV2. The basic approach to TRCD has also been extended to include a repertoire of nanosecond polarization spectroscopies: optical rotatory dispersion (ORD), magnetic CD and ORD, and linear dichroism. This article will discuss the details of the polarization methods used in this laboratory, as well as the coupling of timeresolved ORD with the temperature-jump trigger so that protein folding can be studied in a larger number of proteins. PMID:20438842

  16. Time-resolved four-wave-mixing spectroscopy for inner-valence transitions.

    PubMed

    Ding, Thomas; Ott, Christian; Kaldun, Andreas; Blättermann, Alexander; Meyer, Kristina; Stooss, Veit; Rebholz, Marc; Birk, Paul; Hartmann, Maximilian; Brown, Andrew; Van Der Hart, Hugo; Pfeifer, Thomas

    2016-02-15

    Noncollinear four-wave-mixing (FWM) techniques at near-infrared (NIR), visible, and ultraviolet frequencies have been widely used to map vibrational and electronic couplings, typically in complex molecules. However, correlations between spatially localized inner-valence transitions among different sites of a molecule in the extreme ultraviolet (XUV) spectral range have not been observed yet. As an experimental step toward this goal, we perform time-resolved FWM spectroscopy with femtosecond NIR and attosecond XUV pulses. The first two pulses (XUV-NIR) coincide in time and act as coherent excitation fields, while the third pulse (NIR) acts as a probe. As a first application, we show how coupling dynamics between odd- and even-parity, inner-valence excited states of neon can be revealed using a two-dimensional spectral representation. Experimentally obtained results are found to be in good agreement with ab initio time-dependent R-matrix calculations providing the full description of multielectron interactions, as well as few-level model simulations. Future applications of this method also include site-specific probing of electronic processes in molecules. PMID:26872169

  17. Circumstellar Variations and Microflaring in FK Comae Berenices: Time-Resolved Balmer Line Spectroscopy

    NASA Astrophysics Data System (ADS)

    Oliveira, J. M.; Foing, B. H.; Gondoin, Ph.; Stempels, H. C.; Sonnentrucker, P.; Le Poole, R. S.; Ehrenfreund, P.; de Jong, J. A.; Schrijvers, C.; Henrichs, H.; ESA-MUSICOS Collaboration

    We present results from the analysis of spectra of the fast rotating giant FK Comae Berenices, obtained with the recently commissioned ESA-MUSICOS spectrograph at the INT and with the Aurelie spectrograph at the OHP. The Balmer lines broad emission is modelled as arising from structures extending up to 4 stellar radii. The absorption is modelled due to the presence of a shell of cold and dense gas (solar-like filaments), near the corotation radius, covering about 20% of the stellar disc. The extended emission is believed to arise in giant structures reminiscent of active loops or prominences. Time resolved Hα emission spectroscopy indicates that these structures undergo continuous microflaring. Based on data sets from May and November 1996 and May and June 1997, we describe different time scales for variability, from yearly rise of activity to hourly microflares. Based on observations with the ESA-MUSICOS spectrograph at the 2.5 m Isaac Newton Telescope, ING Observatory, Spain and with the Aurelie spectrograph at the 1.52 m Coude Telescope, Observatoire de Haute-Provence, France

  18. Probing Kinetic Mechanisms of Protein Function and Folding with Time-Resolved Natural and Magnetic Chiroptical Spectroscopies

    PubMed Central

    Kliger, David S.; Chen, Eefei; Goldbeck, Robert A.

    2012-01-01

    Recent and ongoing developments in time-resolved spectroscopy have made it possible to monitor circular dichroism, magnetic circular dichroism, optical rotatory dispersion, and magnetic optical rotatory dispersion with nanosecond time resolution. These techniques have been applied to determine structural changes associated with the function of several proteins as well as to determine the nature of early events in protein folding. These studies have required new approaches in triggering protein reactions as well as the development of time-resolved techniques for polarization spectroscopies with sufficient time resolution and sensitivity to probe protein structural changes. PMID:22312279

  19. Laser plasma x-ray source for ultrafast time-resolved x-ray absorption spectroscopy

    PubMed Central

    Miaja-Avila, L.; O'Neil, G. C.; Uhlig, J.; Cromer, C. L.; Dowell, M. L.; Jimenez, R.; Hoover, A. S.; Silverman, K. L.; Ullom, J. N.

    2015-01-01

    We describe a laser-driven x-ray plasma source designed for ultrafast x-ray absorption spectroscopy. The source is comprised of a 1 kHz, 20 W, femtosecond pulsed infrared laser and a water target. We present the x-ray spectra as a function of laser energy and pulse duration. Additionally, we investigate the plasma temperature and photon flux as we vary the laser energy. We obtain a 75 μm FWHM x-ray spot size, containing ∼106 photons/s, by focusing the produced x-rays with a polycapillary optic. Since the acquisition of x-ray absorption spectra requires the averaging of measurements from >107 laser pulses, we also present data on the source stability, including single pulse measurements of the x-ray yield and the x-ray spectral shape. In single pulse measurements, the x-ray flux has a measured standard deviation of 8%, where the laser pointing is the main cause of variability. Further, we show that the variability in x-ray spectral shape from single pulses is low, thus justifying the combining of x-rays obtained from different laser pulses into a single spectrum. Finally, we show a static x-ray absorption spectrum of a ferrioxalate solution as detected by a microcalorimeter array. Altogether, our results demonstrate that this water-jet based plasma source is a suitable candidate for laboratory-based time-resolved x-ray absorption spectroscopy experiments. PMID:26798792

  20. Laser plasma x-ray source for ultrafast time-resolved x-ray absorption spectroscopy.

    PubMed

    Miaja-Avila, L; O'Neil, G C; Uhlig, J; Cromer, C L; Dowell, M L; Jimenez, R; Hoover, A S; Silverman, K L; Ullom, J N

    2015-03-01

    We describe a laser-driven x-ray plasma source designed for ultrafast x-ray absorption spectroscopy. The source is comprised of a 1 kHz, 20 W, femtosecond pulsed infrared laser and a water target. We present the x-ray spectra as a function of laser energy and pulse duration. Additionally, we investigate the plasma temperature and photon flux as we vary the laser energy. We obtain a 75 μm FWHM x-ray spot size, containing ∼10(6) photons/s, by focusing the produced x-rays with a polycapillary optic. Since the acquisition of x-ray absorption spectra requires the averaging of measurements from >10(7) laser pulses, we also present data on the source stability, including single pulse measurements of the x-ray yield and the x-ray spectral shape. In single pulse measurements, the x-ray flux has a measured standard deviation of 8%, where the laser pointing is the main cause of variability. Further, we show that the variability in x-ray spectral shape from single pulses is low, thus justifying the combining of x-rays obtained from different laser pulses into a single spectrum. Finally, we show a static x-ray absorption spectrum of a ferrioxalate solution as detected by a microcalorimeter array. Altogether, our results demonstrate that this water-jet based plasma source is a suitable candidate for laboratory-based time-resolved x-ray absorption spectroscopy experiments. PMID:26798792

  1. Laser plasma x-ray source for ultrafast time-resolved x-ray absorption spectroscopy

    DOE PAGESBeta

    Miaja-Avila, L.; O'Neil, G. C.; Uhlig, J.; Cromer, C. L.; Dowell, M. L.; Jimenez, R.; Hoover, A. S.; Silverman, K. L.; Ullom, J. N.

    2015-03-02

    We describe a laser-driven x-ray plasma source designed for ultrafast x-ray absorption spectroscopy. The source is comprised of a 1 kHz, 20 W, femtosecond pulsed infrared laser and a water target. We present the x-ray spectra as a function of laser energy and pulse duration. Additionally, we investigate the plasma temperature and photon flux as we vary the laser energy. We obtain a 75 μm FWHM x-ray spot size, containing ~106 photons/s, by focusing the produced x-rays with a polycapillary optic. Since the acquisition of x-ray absorption spectra requires the averaging of measurements from >107 laser pulses, we also presentmore » data on the source stability, including single pulse measurements of the x-ray yield and the x-ray spectral shape. In single pulse measurements, the x-ray flux has a measured standard deviation of 8%, where the laser pointing is the main cause of variability. Further, we show that the variability in x-ray spectral shape from single pulses is low, thus justifying the combining of x-rays obtained from different laser pulses into a single spectrum. Finally, we show a static x-ray absorption spectrum of a ferrioxalate solution as detected by a microcalorimeter array. Altogether, our results demonstrate that this water-jet based plasma source is a suitable candidate for laboratory-based time-resolved x-ray absorption spectroscopy experiments.« less

  2. Laser plasma x-ray source for ultrafast time-resolved x-ray absorption spectroscopy

    SciTech Connect

    Miaja-Avila, L.; O'Neil, G. C.; Uhlig, J.; Cromer, C. L.; Dowell, M. L.; Jimenez, R.; Hoover, A. S.; Silverman, K. L.; Ullom, J. N.

    2015-03-02

    We describe a laser-driven x-ray plasma source designed for ultrafast x-ray absorption spectroscopy. The source is comprised of a 1 kHz, 20 W, femtosecond pulsed infrared laser and a water target. We present the x-ray spectra as a function of laser energy and pulse duration. Additionally, we investigate the plasma temperature and photon flux as we vary the laser energy. We obtain a 75 μm FWHM x-ray spot size, containing ~106 photons/s, by focusing the produced x-rays with a polycapillary optic. Since the acquisition of x-ray absorption spectra requires the averaging of measurements from >107 laser pulses, we also present data on the source stability, including single pulse measurements of the x-ray yield and the x-ray spectral shape. In single pulse measurements, the x-ray flux has a measured standard deviation of 8%, where the laser pointing is the main cause of variability. Further, we show that the variability in x-ray spectral shape from single pulses is low, thus justifying the combining of x-rays obtained from different laser pulses into a single spectrum. Finally, we show a static x-ray absorption spectrum of a ferrioxalate solution as detected by a microcalorimeter array. Altogether, our results demonstrate that this water-jet based plasma source is a suitable candidate for laboratory-based time-resolved x-ray absorption spectroscopy experiments.

  3. Measurements of hydroxyl concentrations and lifetimes in laminar flames using picosecond time-resolved laser-induced fluorescence.

    PubMed

    Reichardt, T A; Klassen, M S; King, G B; Laurendeau, N M

    1996-04-20

    Picosecond time-resolved laser-induced fluorescence (PITLIF) can potentially be used to obtain measurements of minor species concentrations in rapidly fluctuating flames. Previous studies demonstrated this potential for atomic sodium by monitoring the temporal fluorescence signal with both an equivalent-time and a real-time sampling method. In this developmental study, PITLIF is used to determine hydroxyl concentrations in laminar CH(4)-O(2)-N(2) flames by the measurement of both the integrated fluorescence signal and the fluorescence lifetime. The quenching environment can be monitored with real-time sampling, and thus the necessary quenching rate coefficient is obtained in 348 us, which is fast enough for use in many turbulent flows. Fluorescence lifetimes of OH are also measured at different equivalence ratios in laminar flames by the use of the equivalent-time sampling technique. These results compare favorably with predicted lifetimes based on relevant quenching cross sections and calculated species concentrations. PMID:21085341

  4. Time-Resolved Emission Reveals Ensemble of Emissive States as the Origin of Multicolor Fluorescence in Carbon Dots.

    PubMed

    Khan, Syamantak; Gupta, Abhishek; Verma, Navneet C; Nandi, Chayan K

    2015-12-01

    The origin of photoluminescence in carbon dots has baffled scientists since its discovery. We show that the photoluminescence spectra of carbon dots are inhomogeneously broadened due to the slower relaxation of the solvent molecules around it. This gives rise to excitation-dependent fluorescence that violates the Kasha-Vavilov rule. The time-resolved experiment shows significant energy redistribution, relaxation among the emitting states, and spectral migration of fluorescence spectra in the nanosecond time scale. The excitation-dependent multicolor emission in time-integrated spectra is typically governed by the relative population of these emitting states. PMID:26566016

  5. Time-resolved flavin adenine dinucleotide fluorescence study of the interaction between immobilized glucose oxidase and glucose.

    PubMed

    Esposito, Rosario; Delfino, Ines; Lepore, Maria

    2013-09-01

    Time-resolved fluorescence experiments have shown that flavin adenine dinucleotide (FAD) fluorescence emission of sol-gel immobilized glucose oxidase (GOD) exhibits a three-exponential decaying behaviour characterized by long- (about 2.0-3.0 ns), intermediate- (about 300 ps) and short- (less than 10 ps) lifetime, each one being characteristic of a peculiar conformational state of the FAD structure. In the present work time-resolved fluorescence is used to monitor FAD signals in the time interval immediately following the addition of glucose at various concentrations in order to detect the conformational changes occurring during the interaction between sol-gel immobilized GOD and glucose. The analysis of time-dependent fluorescence emission signal has shown that the FAD conformational state changes during the process from a configuration with a prevalence of the state characterized by the long lifetime to a configuration with increased contribution from the process with the intermediate lifetime. The time needed to complete this configuration change decreases with the concentration of added glucose. The results here reported indicate that time-resoled fluorescence can be extremely useful for a better understanding of solid phase biocatalysis that is particularly important in light of their clinical and biotechnological applications. PMID:23576005

  6. Time-resolved fluorescence of thioredoxin single-tryptophan mutants: modeling experimental results with minimum perturbation mapping

    NASA Astrophysics Data System (ADS)

    Silva, Norberto D., Jr.; Haydock, Christopher; Prendergast, Franklyn G.

    1994-08-01

    The time-resolved fluorescence decay of single tryptophan (Trp) proteins is typically described using either a distribution of lifetimes or a sum of two or more exponential terms. A possible interpretation for this fluorescence decay heterogeneity is the existence of different isomeric conformations of Trp about its (chi) +1) and (chi) +2) dihedral angles. Are multiple Trp conformations compatible with the remainder of the protein in its crystallographic configuration or do they require repacking of neighbor side chains? It is conceivable that isomers of the neighbor side chains interconvert slowly on the fluorescence timescale and contribute additional lifetime components to the fluorescence intensity. We have explored this possibility by performing minimum perturbation mapping simulations of Trp 28 and Trp 31 in thioredoxin (TRX) using CHARMm 22. Mappings of Trp 29 and Trp 31 give the TRX Trp residue energy landscape as a function of (chi) +1) and (chi) +2) dihedral angles. Time-resolved fluorescence intensity and anisotropy decay of mutant TRX (W28F and W31F) are measured and interpreted in light of the above simulations. Relevant observables, like order parameters and isomerization rates, can be derived from the minimum perturbation maps and compared with experiment.

  7. Persistent luminescence nanoprobe for biosensing and lifetime imaging of cell apoptosis via time-resolved fluorescence resonance energy transfer.

    PubMed

    Zhang, Lei; Lei, Jianping; Liu, Jintong; Ma, Fengjiao; Ju, Huangxian

    2015-10-01

    Time-resolved fluorescence technique can reduce the short-lived background luminescence and auto-fluorescence interference from cells and tissues by exerting the delay time between pulsed excitation light and signal acquisition. Here, we prepared persistent luminescence nanoparticles (PLNPs) to design a universal time-resolved fluorescence resonance energy transfer (TR-FRET) platform for biosensing, lifetime imaging of cell apoptosis and in situ lifetime quantification of intracellular caspase-3. Three kinds of PLNPs-based nanoprobes are assembled by covalently binding dye-labeled peptides or DNA to carboxyl-functionalized PLNPs for the efficient detection of caspase-3, microRNA and protein. The peptides-functionalized nanoprobe is also employed for fluorescence lifetime imaging to monitor cell apoptosis, which shows a dependence of cellular fluorescence lifetime on caspase-3 activity and thus leads to an in situ quantification method. This work provides a proof-of-concept for PLNPs-based TR-FRET analysis and demonstrates its potential in exploring dynamical information of life process. PMID:26232881

  8. Global and Time-Resolved Monitoring of Crop Photosynthesis with Chlorophyll Fluorescence

    NASA Technical Reports Server (NTRS)

    Guanter, Luis; Zhang, Yongguang; Jung, Martin; Joiner, Joanna; Voigt, Maximilian; Berry, Joseph A.; Frankenberg, Christian; Huete, Alfredo R.; Zarco-Tejada, Pablo; Lee, Jung-Eun; Moran, M. Susan; Ponce-Campos, Guillermo; Beer, Christian; Camps-Valls, Gustavo; Buchmann, Nina; Gianelle, Damiano; Klumpp, Katja; Cescatti, Alessandro; Baker, John M.; Griffis, Timothy J.

    2014-01-01

    Photosynthesis is the process by which plants harvest sunlight to produce sugars from carbon dioxide and water. It is the primary source of energy for all life on Earth; hence it is important to understand how this process responds to climate change and human impact. However, model-based estimates of gross primary production (GPP, output from photosynthesis) are highly uncertain, in particular over heavily managed agricultural areas. Recent advances in spectroscopy enable the space-based monitoring of sun-induced chlorophyll fluorescence (SIF) from terrestrial plants. Here we demonstrate that spaceborne SIF retrievals provide a direct measure of the GPP of cropland and grassland ecosystems. Such a strong link with crop photosynthesis is not evident for traditional remotely sensed vegetation indices, nor for more complex carbon cycle models. We use SIF observations to provide a global perspective on agricultural productivity. Our SIF-based crop GPP estimates are 50-75% higher than results from state-of-the-art carbon cycle models over, for example, the US Corn Belt and the Indo-Gangetic Plain, implying that current models severely underestimate the role of management. Our results indicate that SIF data can help us improve our global models for more accurate projections of agricultural productivity and climate impact on crop yields. Extension of our approach to other ecosystems, along with increased observational capabilities for SIF in the near future, holds the prospect of reducing uncertainties in the modeling of the current and future carbon cycle.

  9. Global and time-resolved monitoring of crop photosynthesis with chlorophyll fluorescence.

    PubMed

    Guanter, Luis; Zhang, Yongguang; Jung, Martin; Joiner, Joanna; Voigt, Maximilian; Berry, Joseph A; Frankenberg, Christian; Huete, Alfredo R; Zarco-Tejada, Pablo; Lee, Jung-Eun; Moran, M Susan; Ponce-Campos, Guillermo; Beer, Christian; Camps-Valls, Gustavo; Buchmann, Nina; Gianelle, Damiano; Klumpp, Katja; Cescatti, Alessandro; Baker, John M; Griffis, Timothy J

    2014-04-01

    Photosynthesis is the process by which plants harvest sunlight to produce sugars from carbon dioxide and water. It is the primary source of energy for all life on Earth; hence it is important to understand how this process responds to climate change and human impact. However, model-based estimates of gross primary production (GPP, output from photosynthesis) are highly uncertain, in particular over heavily managed agricultural areas. Recent advances in spectroscopy enable the space-based monitoring of sun-induced chlorophyll fluorescence (SIF) from terrestrial plants. Here we demonstrate that spaceborne SIF retrievals provide a direct measure of the GPP of cropland and grassland ecosystems. Such a strong link with crop photosynthesis is not evident for traditional remotely sensed vegetation indices, nor for more complex carbon cycle models. We use SIF observations to provide a global perspective on agricultural productivity. Our SIF-based crop GPP estimates are 50-75% higher than results from state-of-the-art carbon cycle models over, for example, the US Corn Belt and the Indo-Gangetic Plain, implying that current models severely underestimate the role of management. Our results indicate that SIF data can help us improve our global models for more accurate projections of agricultural productivity and climate impact on crop yields. Extension of our approach to other ecosystems, along with increased observational capabilities for SIF in the near future, holds the prospect of reducing uncertainties in the modeling of the current and future carbon cycle. PMID:24706867

  10. Global and time-resolved monitoring of crop photosynthesis with chlorophyll fluorescence

    PubMed Central

    Guanter, Luis; Zhang, Yongguang; Jung, Martin; Joiner, Joanna; Voigt, Maximilian; Berry, Joseph A.; Frankenberg, Christian; Huete, Alfredo R.; Zarco-Tejada, Pablo; Lee, Jung-Eun; Moran, M. Susan; Ponce-Campos, Guillermo; Beer, Christian; Camps-Valls, Gustavo; Buchmann, Nina; Gianelle, Damiano; Klumpp, Katja; Cescatti, Alessandro; Baker, John M.; Griffis, Timothy J.

    2014-01-01

    Photosynthesis is the process by which plants harvest sunlight to produce sugars from carbon dioxide and water. It is the primary source of energy for all life on Earth; hence it is important to understand how this process responds to climate change and human impact. However, model-based estimates of gross primary production (GPP, output from photosynthesis) are highly uncertain, in particular over heavily managed agricultural areas. Recent advances in spectroscopy enable the space-based monitoring of sun-induced chlorophyll fluorescence (SIF) from terrestrial plants. Here we demonstrate that spaceborne SIF retrievals provide a direct measure of the GPP of cropland and grassland ecosystems. Such a strong link with crop photosynthesis is not evident for traditional remotely sensed vegetation indices, nor for more complex carbon cycle models. We use SIF observations to provide a global perspective on agricultural productivity. Our SIF-based crop GPP estimates are 50–75% higher than results from state-of-the-art carbon cycle models over, for example, the US Corn Belt and the Indo-Gangetic Plain, implying that current models severely underestimate the role of management. Our results indicate that SIF data can help us improve our global models for more accurate projections of agricultural productivity and climate impact on crop yields. Extension of our approach to other ecosystems, along with increased observational capabilities for SIF in the near future, holds the prospect of reducing uncertainties in the modeling of the current and future carbon cycle. PMID:24706867

  11. Monitoring the birth of an electronic wavepacket in a molecule with attosecond time-resolved photoelectron spectroscopy.

    PubMed

    Perveaux, Aurelie; Lauvergnat, David; Gatti, Fabien; Halász, Gábor J; Vibók, Ágnes; Lasorne, Benjamin

    2014-09-25

    Numerical simulations are presented to validate the possible use of cutting-edge attosecond time-resolved photoelectron spectroscopy to observe in real time the creation of an electronic wavepacket and subsequent electronic motion in a neutral molecule photoexcited by a UV pump pulse within a few femtoseconds. PMID:25167166

  12. Probing Reaction Dynamics of Transition-Metal Complexes in Solution via Time-Resolved Soft X-ray Spectroscopy

    SciTech Connect

    Huse, Nils; Kim, Tae Kyu; Khalil, Munira; Jamula, Lindsey; McCusker, James K.; Schoenlein, Robert W.

    2010-05-02

    We report the first time-resolved soft x-ray measurements of solvated transition-metal complexes. L-edge spectroscopy directly probes dynamic changes in ligand-field splitting of 3d orbitals associated with the spin transition, and mediated by changes in ligand-bonding.

  13. Time-resolved stand-off UV-Raman spectroscopy for planetary exploration

    NASA Astrophysics Data System (ADS)

    Skulinova, M.; Lefebvre, C.; Sobron, P.; Eshelman, E.; Daly, M.; Gravel, J.-F.; Cormier, J.-F.; Châteauneuf, F.; Slater, G.; Zheng, W.; Koujelev, A.; Léveillé, R.

    2014-03-01

    The exploration of Mars, Europa and Enceladus has provided evidence that support the existence of present or past potentially habitable environments, which may shelter signatures of extinct or extant life. A search for further evidence for habitability or for life requires the development of sophisticated instruments and techniques that enable detailed investigations of locations, which are of great interest to planetary scientists and astrobiologists. Raman spectroscopy is a powerful and versatile technique; a rover based Raman Laser Spectrometer (RLS) operating at 532 nm excitation wavelength has been selected for the 2018 ExoMars mission. In this study, we demonstrate the feasibility of the utilisation of a time-resolved stand-off UV-Raman prototype for the detection and identification of pure organics, organics mixed in a quartz matrix and minerals that have been selected based on their potential relevance to astrobiology and planetary exploration. The samples of organics (β-carotene, L-ascorbic acid, thiamine hydrochloride, L-alanine, L-serine, thymine), carbonates (calcite, dolomite), sulfates (gypsum), silicates (quartz), and natural rock (an altered meta-volcanic rock featuring quartz inclusions) were analyzed at a distance of 6 m using a 355 nm excitation source and a gated intensified charged-coupled device (ICCD) as the detector. We were able to obtain spectra with clear Raman signals enabling unequivocal identification of all selected samples. We assert for the first time, that such an instrument can effectively identify minerals and a wide range of organics that may serve as geo- and biomarkers thus showing great potential for the exploration of planets and astrobiology.

  14. Evaluating steady-state and time-resolved fluorescence as a tool to study the behavior of asphaltene in toluene.

    PubMed

    Zhang, Hui Ting; Li, Rui; Yang, Zixin; Yin, Cindy-Xing; Gray, Murray R; Bohne, Cornelia

    2014-06-01

    A combination of steady-state fluorescence, fluorescence lifetime measurements and the determination of time-resolved emission spectra were employed to characterize asphaltene toluene solutions. Lifetime measurements were shown to be insensitive to the source of asphaltene or the alkane solvent from which asphaltene was precipitated. This insensitivity suggests that either the composition of Athabasca and Cold Lake asphaltene is very similar or that the fluorescence behavior is dominated by the same sub-set of fluorophores for the different samples. These results highlight the limitations in using fluorescence to characterize asphaltene solutions. Different dependencies were observed for the average lifetimes with the asphaltene concentration when measured at two different emission wavelengths (420 nm and 520 nm). This result suggests that different fluorophores underwent diverse interactions with other asphaltene molecules as the asphaltene concentration was raised, suggesting that models for asphaltene aggregation need to include molecular diversity. PMID:24722727

  15. Time-resolved fluorescence for breast cancer detection using an octreotate-indocyanine green derivative dye conjugate

    NASA Astrophysics Data System (ADS)

    Sordillo, Laura A.; Das, B. B.; Pu, Yang; Liang, Kexian; Milione, Giovanni; Sordillo, Peter P.; Achilefu, Sam; Alfano, R. R.

    2013-03-01

    Time-resolved fluorescence was used to investigate malignant and normal adjacent breast tissues stained with a conjugate of indocyanine green and octreotate. A marked increase in fluorescence lifetime intensity was seen in the breast cancer sample compared to the normal sample. The fluorescent lifetimes were also investigated and showed similar fluorescence decay curves in stained malignant and normal breast tissue. These results confirm that somatostatin receptors occur on human breast carcinomas, suggest that the presence of somatostatin receptors should be investigated as a marker of breast cancer aggressiveness, and suggest that this conjugate might be used to detect the presence of residual breast cancer after surgery, allowing better assessment of tumor margins and reducing the need for second or repeat biopsies in selected patients. These results may also provide clues for designing future treatment options for breast cancer patients.

  16. Site-specific measurement of water dynamics in the substrate pocket of ketosteroid isomerase using time-resolved vibrational spectroscopy.

    PubMed

    Jha, Santosh Kumar; Ji, Minbiao; Gaffney, Kelly J; Boxer, Steven G

    2012-09-20

    Little is known about the reorganization capacity of water molecules at the active sites of enzymes and how this couples to the catalytic reaction. Here, we study the dynamics of water molecules at the active site of a highly proficient enzyme, Δ(5)-3-ketosteroid isomerase (KSI), during a light-activated mimic of its catalytic cycle. Photoexcitation of a nitrile-containing photoacid, coumarin183 (C183), mimics the change in charge density that occurs at the active site of KSI during the first step of the catalytic reaction. The nitrile of C183 is exposed to water when bound to the KSI active site, and we used time-resolved vibrational spectroscopy as a site-specific probe to study the solvation dynamics of water molecules in the vicinity of the nitrile. We observed that water molecules at the active site of KSI are highly rigid, during the light-activated catalytic cycle, compared to the solvation dynamics observed in bulk water. On the basis of this result, we hypothesize that rigid water dipoles at the active site might help in the maintenance of the preorganized electrostatic environment required for efficient catalysis. The results also demonstrate the utility of nitrile probes in measuring the dynamics of local (H-bonded) water molecules in contrast to the commonly used fluorescence methods which measure the average behavior of primary and subsequent spheres of solvation. PMID:22931297

  17. Site-Specific Measurement of Water Dynamics in the Substrate Pocket of Ketosteroid Isomerase Using Time-Resolved Vibrational Spectroscopy

    PubMed Central

    Jha, Santosh Kumar; Ji, Minbiao; Gaffney, Kelly J.; Boxer, Steven G.

    2012-01-01

    Little is known about the reorganization capacity of water molecules at the active sites of enzymes and how this couples to the catalytic reaction. Here, we study the dynamics of water molecules at the active site of a highly proficient enzyme, Δ5-3-ketosteroid isomerase (KSI), during a light-activated mimic of its catalytic cycle. Photo-excitation of a nitrile containing photo-acid, coumarin183 (C183), mimics the change in charge density that occurs at the active site of KSI during the first step of the catalytic reaction. The nitrile of C183 is exposed to water when bound to the KSI active site, and we used time-resolved vibrational spectroscopy as a site-specific probe to study the solvation dynamics of water molecules in the vicinity of the nitrile. We observed that water molecules at the active site of KSI are highly rigid, during the light-activated catalytic cycle, compared to the solvation dynamics observed in bulk water. Based upon this result we hypothesize that rigid water dipoles at the active site might help in the maintenance of the pre-organized electrostatic environment required for efficient catalysis. The results also demonstrate the utility of nitrile probes in measuring the dynamics of local (H-bonded) water molecules in contrast to the commonly used fluorescence methods which measure the average behavior of primary and subsequent spheres of solvation. PMID:22931297

  18. Time-resolved resonance Raman spectroscopy of radiation-chemical processes. [Pulsed irradiation

    SciTech Connect

    Tripathi, G.N.R.

    1983-01-01

    A tunable pulsed laser Raman spectrometer for time resolved Raman studies of radiation-chemical processes is described. This apparatus utilizes the state of art optical multichannel detection and analysis techniques for data acquisition and electron pulse radiolysis for initiating the reactions. By using this technique the resonance Raman spectra of intermediates with absorption spectra in the 248-900 nm region, and mean lifetimes > 30 ns can be examined. This apparatus can be used to time resolve the vibrational spectral overlap between transients absorbing in the same region, and to follow their decay kinetics by monitoring the well resolved Raman peaks. For kinetic measurements at millisecond time scale, the Raman technique is preferable over optical absorption method where low frequency noise is quite bothersome. A time resolved Raman study of the pulse radiolytic oxidation of aqueous tetrafluorohydroquinone and p-methoxyphenol is briefly discussed. 15 references, 5 figures.

  19. Time-resolved spectroscopy of nucleic acid systems using synchrotron radiation from 230 nm to 354 nm

    NASA Astrophysics Data System (ADS)

    Daniels, Malcolm; Ballini, Jean-Pierre; Vigny, Paul

    1992-07-01

    The excited states of nucleic acids are complex, both at the individual chromophore level and because of the effect of stacking interactions on the electronic states. Considerable progress has been made recently by studying the lifetimes of the stacked states and by utilizing the technique of time-resolved spectroscopy. Experimental results obtained using the ACO synchrotron at LURE, Orsay, will be presented. Resolution of the decay data gives a model-based estimate of the number of emitting species and their lifetimes, and this information is then used to deconvolate experimental time-windowed spectra (time-delayed spectra) to give true time-resolved spectra. It is a unique feature of the synchrotron, compared with the laser, that the combination of delayed detection (photon counting) with the continuous wavelength distribution of the synchrotron allows the acquisition of excitation spectra by uninterrupted repetitive scanning over a wide range of UV exciting wavelengths, in the present work from 230 nm to 354 nm. Such time-delayed excitation spectra can also be deconvoluted into components corresponding to the various time-resolved emission spectra. In this way we are able to demonstrate for the first time that ground state stacking interactions are directly responsible for excimer-like emissions. Time-resolved emission spectra and time-resolved excitation spectra will be presented for the dinucleoside phosphate d(CG) and the synthetic alternating polynucleotide poly d(GC), a `B-type' DNA structure.

  20. Ultrafast dynamics in transparent fluids investigated via time-resolved third-order spectroscopy

    NASA Astrophysics Data System (ADS)

    Peng, Jian

    The ultrafast dynamics of near critical fluids and other transparent materials are investigated with time-resolved optical heterodyne detected (OHD) third-order spectroscopy. Among the main results of this dissertation are: supercritical fluctuations on a picosecond timescale are revealed by H2 rotational coherence decay; a giant acoustic response due to enhanced near critical compressibility is optically generated and characterized; a new pulse reconstruction algorithm is developed. The decay of J-specific Raman coherence birefringence of H2 rotors in supercritical CO2 (0.8 rhoc) are measured in order to understand the ˜picosecond timescale solvent fluctuations around the critical point. The H2 anisotropic Raman time correlation functions possess long-time exponential tails attributed to motional narrowing. Nonexponential early-time behavior indicates the inhomogeneities in anisotropic local potential interactions. Mixed classical nonadiabatic quantum molecular dynamics simulations are performed. The excellent agreement between experiment and the theoretical treatment supports the use of this methodology. Multiregional studies are conducted for mixtures ranging from gas-like to liquid-like densities. A non-monotonic dependence of the Raman coherence decay times and transition frequencies are observed. A novel third-order polarization due to accumulated acoustic grating is characterized in near critical CHF3 and CO2. The electrostrictively generated acoustic response is pi out of phase with the normal OKE birefringence. Repetition rate dependence identifies the accumulated origin of the phenomenon with an acoustic relaxation timescale of ˜100 ns. The combined effect of efficient coherence coupling excitation and accumulation results in a birefringent signal strength inversely dependent on the sound velocity to the fifth power. In contrast a single-pulse coherence coupling effect routinely observed in transparent media can be shown to originate from nuclear responses. Its impact on frequency selected dichroic Raman spectral density recovery is demonstrated for CCl4. For linearly-chirped pulses, the antisymmetric coherent coupling trace dominates the frequency integrated dichroism. Its absolute sign indicates the sign of the chirp. An assumption-free amplitude-phase reconstruction algorithm combining the coherent coupling dichroism, the intensity autocorrelation and the power spectrum is developed.

  1. Understanding THz and IR signals beneath time-resolved fluorescence from excited-state ab initio dynamics.

    PubMed

    Petrone, Alessio; Donati, Greta; Caruso, Pasquale; Rega, Nadia

    2014-10-22

    The detailed interpretation of time-resolved spectroscopic signals in terms of the molecular rearrangement during a photoreaction or a photophysical event is one of the most important challenges of both experimental and theoretical chemistry. Here we simulate a time-resolved fluorescence spectrum of a dye in aqueous solution, the N-methyl-6-oxyquinolinium betaine, and analyze it in terms of far IR and THz frequency contributions, providing a direct connection to specific molecular motions. To obtain this result, we build up an innovative and general approach based on excited state ab-initio molecular dynamics and a wavelet-based time-dependent frequency analysis of nonstationary signals. We obtain a nice agreement with key parameters of the solvent dynamics, such as the total Stokes shift and the Stokes shift relaxation times. As an important finding, we observe a strong change of specific solute-solvent interactions upon the electronic excitation, with the migration of about 1.5 water molecules from the first solvation shell toward the bulk. In spite of this event, the Stokes shift dynamics is ruled by collective solvent motions in the THz and far IR, which guide and modulate the strong rearrangement of the dye microsolvation. By the relaxation of THz and IR contributions to the emission signal, we can follow and understand in detail the molecularity of the process. The protocol presented here is, in principle, transferable to other time-resolved spectroscopic techniques. PMID:25243826

  2. Real-time TDDFT simulations of time-resolved core-level spectroscopies in solid state systems

    NASA Astrophysics Data System (ADS)

    Pemmaraju, Sri Chaitanya Das; Prendergast, David; Theory of Nanostructured Materials Facility Team

    The advent of sub-femtosecond time-resolved core-level spectroscopies based on high harmonic generated XUV pulses has enabled the study of electron dyanamics on characteristic femtosecond time-scales. Unambiguous interpretation of these powerful yet complex spectroscopies however requires the development of theoretical algorithms capable of modeling light-matter interaction across a wide energy range spanning both valence and core orbitals. In this context we present a recent implementation of the velocity-gauge formalism of real-time TDDFT within a linear combination of atomic orbital (LCAO) framework, which facilitates efficient numerical treatment of localized semi-core orbitals. Dynamics and spectra obtained from LCAO based simulations are compared to those from a real-space grid implementation. Potential applications are also illustrated by applying the method towards interpreting recent atto-second time-resolved IR-pump XUV-probe spectroscopies investigating sub-cycle excitation dynamics in bulk silicon.

  3. Transient Absorption and Time-Resolved Fluorescence Studies of Solvated Ruthenium Di-Bipyridine Pseudo-Halide Complexes

    NASA Astrophysics Data System (ADS)

    Compton, R.; Weidinger, D.; Owrutsky, J. C.

    2012-06-01

    Time-resolved IR and fluorescence measurements were performed to probe the vibrational and electronic properties, respectively, of ruthenium di-bipyridine pseudo-halide (Ru(Bpy){_2}(X){_2} (where X = CN, N{_3} or NCS)) complexes. Vibrational energy relaxation (VER) times were determined for the complexes dissolved in dimethyl sulfoxide (DMSO) with a trend in VER time of NCS > CN > N{_3}. A similar trend and comparable absolute rates for NCS- and N3- were previously observed by our group and others for simple inorganic anions in solution, suggesting a minimal contribution due to complexation. Measurements of the VER time of the CN complex in various solvents provide VER times in ethanol (42.3 ps) and DMSO (53.3 ps), which shows that protic solvents promote the relaxation. Time-resolved fluorescence measurements indicate a strong ligand dependence, with a factor of five decrease in the excited electronic state decay time from the CN (215 ns) to the NCS (39 ns) complex. A solvent dependence of the CN complex reveals a nearly 3-fold increase in the fluorescence decay time from acetonitrile (70 ns) to DMSO (215 ns).

  4. Time-resolved studies of fluorescence and band-edge charge carrier dynamics in In1-xGaxP colloidal quantum dots

    NASA Astrophysics Data System (ADS)

    Mikhailovsky, Alexander A.; Diana, Frederic S.; Kim, Sangcheol; Kramer, Edward J.; Petroff, Pierre M.; Gerbec, Jeffrey; Strouse, Geoffrey

    2005-08-01

    In this submission, we report on the results of spectroscopic studies of charge carrier dynamics in colloidal In1-xGaxP quantum dots (QDs) with low levels of Ga doping (x~1%). These QDs exhibit large global Stokes shift of fluorescence (up to 300 meV) along with high emission yield (up to 30% in solution and 25% in films under blue excitation at 300 K) after post-synthesis photo-chemical treatment. In order to reveal the nature of large fluorescence Stokes shift and study the band-edge carriers dynamics, we performed time-resolved measurements of emission and photo-induced absorption changes in QDs with different sizes and surface passivation. The work was focused on the studies of differences between QDs subjected to photochemical surface passivation and bare nanoparticles. Time-resolved absorption spectroscopy indicates that holes' trapping strongly depends on passivation of surface trap states and can even suppress Auger multiparticle recombination in poorly passivated nanoparticles. Transient fluorescence measurements in well-passivated nanoparticles demonstrate that at short delays (<2 ns), emission Stokes shift is almost twice smaller than in steady-state measurements and matches the emission band in unpassivated QDs. At longer delays, time-resolved emission matches the spectra obtained with continuous wave (CW) excitation. We propose that initially photoluminescence occurs from quantum-confined state and subsequent hole relaxation onto surface/interface sites gives rise to emission with large global Stokes shift. In poorly passivated QDs, holes escape quickly to deep-trap states that leads to formation of low-efficiency broad emission band red-shifted with respect to the excitonic PL band.

  5. Steady-state and time-resolved fluorescence studies of stripped Borage oil.

    PubMed

    Smyk, Bogdan; Amarowicz, Ryszard; Szabelski, Mariusz; Gryczynski, Ignacy; Gryczynski, Zygmunt

    2009-07-30

    In this study we explored the spectroscopic properties of Borage oil, particularly the use of fluorescence techniques to investigate the presence of conjugated fatty acids (CFAs). This research has important health and dietary applications. The absorption and fluorescence spectra of different CFAs and Borage oil in ethanol were measured. Time-domain fluorescence was employed to establish the life times of the samples. We found that Borage oil contains 1.2x10(-3) mol L(-1) of alpha-eleostearic acid or its isomer (i.e., a conjugated triene), 1.6x10(-4) mol L(-1) of cis-parinaric acid (i.e., a conjugated tetraene) and 1.1x10(-5) mol L(-1) of c-COPA (i.e., a conjugated pentaene). Because of the three-exponential fluorescence intensity decay for Borage oil, other fatty acids with a four conjugated double bond system could not be excluded. PMID:19523559

  6. Interaction between certain porphyrins and CdS colloids: A steady state and time resolved fluorescence quenching study

    NASA Astrophysics Data System (ADS)

    Jhonsi, M. Asha; Kathiravan, A.; Renganathan, R.

    2008-12-01

    The interaction between porphyrins namely, meso-tetrakis (4-methoxyphenyl)porphyrin (TMeOPP), protoporphyrin IX (PPIX) and Zinc(II) meso-tetraphenylporphyrin (ZnTPP) with colloidal CdS has been studied by using steady state and time resolved fluorescence quenching measurements. The porphyrins adsorbed on the surface of colloidal CdS due to electrostatic interaction. This adsorption leads to changes in the absorption spectra related to the complex formation. The apparent association constant ( Kapp) was in the order of 4.34-5.58 × 10 5 M -1 from the effect of colloidal CdS on the absorption spectra and 0.64-1.6 × 10 5 M -1 from fluorescence quenching data. Quenching is attributable mainly to static mechanism through ground state complex formation as confirmed by lifetime measurements.

  7. Dynamic structural changes in microbial membranes in response to high hydrostatic pressure analyzed using time-resolved fluorescence anisotropy measurement.

    PubMed

    Abe, Fumiyoshi

    2013-12-15

    High hydrostatic pressure has a profound physiological impact on lipid membranes, primarily resulting in tighter packing and restriction of acyl-chain motion. To fulfill membrane protein functions in high-pressure environments, deep-sea organisms possess specialized cell membranes. Although the effects of high-pressure on model membranes have been investigated in great detail, high-pressure-induced structural changes in living cell membranes remain to be elucidated. Of the spectroscopic techniques available to date, fluorescence anisotropy measurement is a common useful method that provides information on dynamic membrane properties. This mini-review focuses on pressure-induced changes in natural cell membranes, analyzed by means of high-pressure time-resolved fluorescence anisotropy measurement (HP-TRFAM). Specifically, the role of eicosapentaenoic acid in deep-sea piezophiles is described in terms of the structural integrity of the membrane under high pressure. PMID:23790318

  8. Quantification of joint inflammation in rheumatoid arthritis by time-resolved diffuse optical spectroscopy and tracer kinetic modeling

    NASA Astrophysics Data System (ADS)

    Ioussoufovitch, Seva; Morrison, Laura B.; Lee, Ting-Yim; St. Lawrence, Keith; Diop, Mamadou

    2015-03-01

    Rheumatoid arthritis (RA) is characterized by chronic synovial inflammation, which can cause progressive joint damage and disability. Diffuse optical spectroscopy (DOS) and imaging have the potential to become potent monitoring tools for RA. We devised a method that combined time-resolved DOS and tracer kinetics modeling to rapidly and reliably quantify blood flow in the joint. Preliminary results obtained from two animals show that the technique can detect joint inflammation as early as 5 days after onset.

  9. Global and time-resolved monitoring of crop photosynthesis with chlorophyll fluorescence

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Global monitoring of agricultural productivity is critical in a world under a continuous increase of food demand. Here we have used new spaceborne retrievals of chlorophyll fluorescence, an emission quantity intrinsically linked to photosynthesis, to derive spatially explicit photosynthetic uptake r...

  10. Improving SNR in Time-Resolved Spectroscopies Without Sacrificing Temporal-Resolution Application to the UV Photolysis of Methyl Cyanoformate

    NASA Astrophysics Data System (ADS)

    Wilhelm, Michael J.; Smith, Jonathan M.; Dai, HAI-LUNG

    2015-06-01

    We demonstrate a new analysis for the enhancement of the signal-to-noise ratio (SNR) in time-resolved spectroscopies, termed spectral reconstruction analysis (SRA). As distinct from a simple linear average which produces only a single} representative spectrum with enhanced SNR, SRA produces a comparable enhancement, but fully preserves the measured time-dependence. Specifically, given a series of (n) time-resolved spectra, SRA yields an approximate sqrt(n)} SNR enhancement for each of the original n-spectra. SRA operates by eliminating noise in the temporal domain, thereby significantly attenuating noise in the spectral domain, as follows (see Figure): Temporal profiles of each measured frequency are fit to capture the representative temporal evolutions, then time-resolved spectra are reconstructed by replacing the measured profiles with the fit profiles. In addition to simulated control data sets, we demonstrate SRA with experimentally measured time-resolved IR emission spectra, collected following the 193 nm photolysis of methyl cyanoformate (CH_3OC(O)CN). Of significance, we now show the appearance of resonances assignable to hydrogen cyanide (HCN), which were previously obscured in the noise of the measured spectra. The presence of HCN suggests the occurrence of a previously uncharacterized dissociation channel, likely involving a cyclic 5-center transition state.

  11. A dissociative fluorescence enhancement technique for one-step time-resolved immunoassays

    PubMed Central

    Mukkala, Veli-Matti; Hakala, Harri H. O.; Mäkinen, Pauliina H.; Suonpää, Mikko U.; Hemmilä, Ilkka A.

    2010-01-01

    The limitation of current dissociative fluorescence enhancement techniques is that the lanthanide chelate structures used as molecular probes are not stable enough in one-step assays with high concentrations of complexones or metal ions in the reaction mixture since these substances interfere with lanthanide chelate conjugated to the detector molecule. Lanthanide chelates of diethylenetriaminepentaacetic acid (DTPA) are extremely stable, and we used EuDTPA derivatives conjugated to antibodies as tracers in one-step immunoassays containing high concentrations of complexones or metal ions. Enhancement solutions based on different β-diketones were developed and tested for their fluorescence-enhancing capability in immunoassays with EuDTPA-labelled antibodies. Characteristics tested were fluorescence intensity, analytical sensitivity, kinetics of complex formation and signal stability. Formation of fluorescent complexes is fast (5 min) in the presented enhancement solution with EuDTPA probes withstanding strong complexones (ethylenediaminetetra acetate (EDTA) up to 100 mM) or metal ions (up to 200 μM) in the reaction mixture, the signal is intensive, stable for 4 h and the analytical sensitivity with Eu is 40 fmol/L, Tb 130 fmol/L, Sm 2.1 pmol/L and Dy 8.5 pmol/L. With the improved fluorescence enhancement technique, EDTA and citrate plasma samples as well as samples containing relatively high concentrations of metal ions can be analysed using a one-step immunoassay format also at elevated temperatures. It facilitates four-plexing, is based on one chelate structure for detector molecule labelling and is suitable for immunoassays due to the wide dynamic range and the analytical sensitivity. Figure   PMID:21161513

  12. Cell type and spatial location dependence of cytoplasmic viscosity measured by time-resolved fluorescence microscopy.

    PubMed

    Srivastava, A; Krishnamoorthy, G

    1997-04-15

    Information on the cell type and spatial location dependence of cytoplasmic viscosity would be very useful in understanding some of the processes occurring in the cell. For this purpose, fluorescent dye kiton red (sulforhodamine B) was loaded into a variety of cells such as Swiss 3T3 fibroblasts, human mononuclear cells, Sarcoma-180 tumor cells, Chinese hamster ovary cells, plant cells from Digitalis lanata, stamen hair cells of Tradescantia, and guard mother cells of Allium cepa. Space-resolved measurements of cytoplasmic viscosity were carried out by using an experimental set-up wherein a picosecond laser system was coupled with an epifluorescence microscope. The spatial resolution of this set-up was approximately 1.0 micron, and reliable dynamic fluorescence measurements could be obtained from 10(2) to 10(3) fluorescent molecules. Fluorescence lifetime measurements showed that a large fraction (approximately 70%) of kiton red was in the free form. Fluorescence anisotropy decay of kiton red in cells was analyzed by a two population (free and bound) model. The microviscosity of cytoplasm was estimated from the anisotropy decay kinetics of the free probe. It was found that the cytoplasmic viscosity is dependent on both the cell type and spatial location within a cell. Furthermore, both the average value of viscosity and spatial variation within a cell were larger in the plant cells when compared to the animal cells. Model studies in various simpler systems have shown that the higher viscosity observed in some part of the cell could be due to either physical restriction and/or the presence of high concentrations of small solutes and macromolecules. PMID:9143317

  13. Quantifying the cerebral metabolic rate of oxygen by combining diffuse correlation spectroscopy and time-resolved near-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Verdecchia, Kyle; Diop, Mamadou; Lee, Ting-Yim; St. Lawrence, Keith

    2013-02-01

    Preterm infants are highly susceptible to ischemic brain injury; consequently, continuous bedside monitoring to detect ischemia before irreversible damage occurs would improve patient outcome. In addition to monitoring cerebral blood flow (CBF), assessing the cerebral metabolic rate of oxygen (CMRO2) would be beneficial considering that metabolic thresholds can be used to evaluate tissue viability. The purpose of this study was to demonstrate that changes in absolute CMRO2 could be measured by combining diffuse correlation spectroscopy (DCS) with time-resolved near-infrared spectroscopy (TR-NIRS). Absolute CBF was determined using bolus-tracking TR-NIRS to calibrate the DCS measurements. Cerebral venous blood oxygenation (SvO2) was determined by multiwavelength TR-NIRS measurements, the accuracy of which was assessed by directly measuring the oxygenation of sagittal sinus blood. In eight newborn piglets, CMRO2 was manipulated by varying the anesthetics and by injecting sodium cyanide. No significant differences were found between the two sets of SvO2 measurements obtained by TR-NIRS or sagittal sinus blood samples and the corresponding CMRO2 measurements. Bland-Altman analysis showed a mean CMRO2 difference of 0.0268±0.8340 mL O2/100 g/min between the two techniques over a range from 0.3 to 4 mL O2/100 g/min.

  14. High-pressure-low-temperature cryostat designed for use with fourier transform infrared spectrometers and time-resolved infrared spectroscopy.

    PubMed

    Calladine, James A; Love, Ashley; Fields, Peter A; Wilson, Richard G M; George, Michael W

    2014-01-01

    The design for a new high-pressure-low-temperature infrared (IR) cell for performing experiments using conventional Fourier transform infrared or fast laser-based time-resolved infrared spectroscopy, in a range of solvents, is described. The design builds upon a commercially available compressor and cold end (Polycold PCC() and CryoTiger()), which enables almost vibration-free operation, ideal for use with sensitive instrumentation. The design of our cell and cryostat allows for the study of systems at temperatures from 77 to 310 K and at pressures up to 250 bar. The CaF2 windows pass light from the mid-IR to the ultraviolet (UV), enabling a number of experiments to be performed, such as Raman, UV-visible absorption spectroscopy, and time-resolved techniques where sample excitation/probing using continuous wave or pulsed lasers is required. We demonstrate the capabilities of this cell by detailing two different applications: (i) the reactivity of a range of Group V-VII organometallic alkane complexes using time-resolved spectroscopy on the millisecond timescale and (ii) the gas-to-liquid phase transition of CO2 at low temperature, which is applicable to measurements associated with transportation issues related to carbon capture and storage. PMID:24666949

  15. Time-resolved imaging system for fluorescence-guided surgery with lifetime imaging capability

    NASA Astrophysics Data System (ADS)

    Powolny, F.; Homicsko, K.; Sinisi, R.; Bruschini, Claudio E.; Grigoriev, E.; Homulle, H.; Prior, John O.; Hanahan, D.; Dubikovskaya, E.; Charbon, E.

    2014-05-01

    We present a single-photon camera for fluorescence imaging, with a time resolution better than 100ps, capable of providing both intensity and lifetime images. the camera was fabricated in standard CMOS technology. With this FluoCam we show the possibility to study sub-nanosecond fluorescence mechanisms. The FluoCam was used to characterize a near-infrared probe, indocyanine green, conjugated with multimeric cyclic pentapeptide (cRGD). The fluorescent probe-conjugated was used to target and mark tumors with better specificity, in particular aiming at targeting the integrins αvβ3 and αvβ5. As a first step towards clinical studies, preliminary results obtained in-vivo are presented. The first envisioned clinical application would be image-guided surgical oncology to help the surgeon to remove tumor tissue by a better discrimination from normal tissues and also to improve the detection of metastatic lymph nodes. A further application could be the in-vivo determination of the αvβ3 and αvβ5 targets to select patients for therapy with RGD chemotherapy conjugates.

  16. Gene expression analysis with an integrated CMOS microarray by time-resolved fluorescence detection

    PubMed Central

    Huang, Ta-chien D.; Paul, Sunirmal; Gong, Ping; Levicky, Rastislav; Kymissis, John; Amundson, Sally A.; Shepard, Kenneth L.

    2010-01-01

    DNA microarrays have proven extraordinarily powerful for differential expression studies across thousands of genes in a single experiment. Microarrays also have the potential for clinical applications, including the detection of infectious and immunological diseases and cancer, if they can be rendered both reliable and cost-effective. Here we report the first practical application of an active microarray based on integrated circuit technology, completely obviating the need for external measurement instrumentation while employing protocols compatible with traditional fluorescence-based surface bioassays. In a gene-expression biodosimetry study, we determine the differential activity of genes from leucocytes in irradiated human blood. Quantum dots are used as fluorescence labels to realize filterless, time-gated fluorescence detection on an active complementary metal-oxide-semiconductor (CMOS) microarray with 100-pM sensitivity. Improvements in surface chemistry should allow sensitivities that approach the microarray hardware limit of less than 10 pM. Techniques for covalent attachment of DNA capture strands to the CMOS active microarrays allow integrated sensors to be placed in immediate proximity to hybridized analyte strands, maximizing photon collection efficiencies. PMID:20392628

  17. Application of time-resolved fluorescence to the determination of metabolites

    NASA Astrophysics Data System (ADS)

    Murillo Pulgarín, J. A.; Alañón Molina, A.; Martínez Ferreras, F.

    2014-07-01

    A simple fluorescent methodology for the simultaneous determination of two major metabolites of acetylsalicylic acid - salicylic and gentisic acids - in pharmaceutical preparations and human urine is proposed. Due to the overlapping between the fluorescence spectra of both analytes, the use of the more selective fluorescence decay curves is proposed. Values of dependent instrumental variables affecting the signal-to-noise ratio were fixed with a simplex optimization procedure. A calibration matrix of thirteen standards plus two blank samples was processed using a partial least-squares (PLS) analysis. To assess the goodness of the proposed method, a prediction set of nine synthetic samples was analyzed, obtaining recovery percentages between 95% and 106%. Limits of detection, calculated by means of a new criterion, were 3.49 μg L-1 and 1.66 μg L-1 for salicylic and gentisic acids, respectively. The method was also tested in three pharmaceutical preparations containing salicylic acid, obtaining recovery percentages close to 100%. Finally, the simultaneous determination of both analytes in human urine samples was successfully carried out by the PLS-analysis of a matrix of thirteen standards plus five analyte blanks. Although spectra of analytes and urine overlap strongly, no extraction method neither prior separation of the analytes were needed.

  18. Characterization of hydroxyapatite by time-resolved luminescence and FTIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Grigorjeva, L.; Millers, D.; Smits, K.; Jankovica, Dz; Pukina, L.

    2013-12-01

    Time-resolved luminescence and FTIR absorption spectra of undoped and Eu and Ce doped hydroxyapatite nanocrystalline powders prepared by sol-gel method were studied. The luminescence band at 350-400 nm was detected and two decay times (11 ns and 38 ns) was determinated for Ce doped samples. The luminescence spectra and decay kinetics were analized for Eu doped nanopowders. The Eu3+ ion was incorporated in different Ca sites. The process of energy transfer to Eu3+ excited state (5D0) was detected from luminescence decay kinetics.

  19. Discrimination of molecular thin films by surface-sensitive time-resolved optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Peli, Simone; Nembrini, Nicola; Damin, Francesco; Chiari, Marcella; Giannetti, Claudio; Banfi, Francesco; Ferrini, Gabriele

    2015-10-01

    An optical discrimination technique, tailored to nanometric-sized, low optical absorbance molecular complexes adhering to thin metal films, is proposed and demonstrated. It is based on a time-resolved evanescent-wave detection scheme in conjunction with hierarchical cluster analysis and principal value decomposition. The present approach aims to differentiate among molecular films based on statistical methods, without using previous detailed knowledge of the physical mechanisms responsible for the detected signal. The technique is open to integration in lab-on-a-chip architectures and nanoscopy platforms for applications ranging from medical screening to material diagnostics.

  20. Development of time resolved x-ray spectroscopy in high intensity laser-plasma interactions

    SciTech Connect

    Notley, M. M.; Weber, R. L.; Fell, B.; Jeffries, J.; Freeman, R. R.; Mackinnon, A. J.; Dickson, R.; Hey, D.; Khattak, F.; Saiz, E. Garcia; Gregori, G.

    2006-10-15

    This article discusses the design of a novel time resolved von Hamos Bragg spectrometer to provide spectra in the region around the titanium K-{alpha} and He-{alpha} lines. The instrument consists of a highly oriented pyrolitic graphite mosaic crystal coupled to a picosecond x-ray streak camera. Measurements of the time dependent behavior from Ti foils illuminated with intense laser pulses can be used to improve the understanding of recombination dynamics, electron transport, and phase transitions in strongly coupled dense plasma. This is important for the modeling of the compression phase in inertial confinement fusion research and the study of astrophysical environments.

  1. Time resolved laser-induced fluorescence of electrosprayed ions confined in a linear quadrupole trap

    SciTech Connect

    Friedrich, Jochen; Fu Jinmei; Hendrickson, Christopher L.; Marshall, Alan G.; Wang Yisheng

    2004-11-01

    We have designed and constructed a linear quadrupole ion trap for the measurement of laser-induced fluorescence (LIF) of mass selected gas-phase ions produced by electrospray ionization. The instrument consists of a simple electrospray source, radiofrequency octopole guide, a dc quadrupole bender, a quadrupole mass filter, the linear quadrupole trap (which is equipped with optics for LIF collection and a channeltron ion detector), and several multielement focusing lenses. With this instrument, the LIF decay lifetime of gas-phase Rhodamine 640 radical cations is determined for the first time.

  2. Time-resolved effects of an electric field in recombination fluorescence

    SciTech Connect

    Borovkov, V.I.; Anishchik, S.V.; Anisimov, O.A.

    1995-12-01

    Quenching of the recombination fluorescence by an external electric field was investigated in hexane, tetradecane, and aqualane solutions of p-terphenyl and 2.5-diphenyloxazole irradiated with X-rays. The kinetics of the recombination fluorescence I(E,t) was measured in a nanosecond time scale and the quenching-efficiency curves Q(E,t) = 1 - I(E,t)/I(0,t) were plotted. The dependence Q(E,t) was shown to have the specific character Q(E,t) = f(pt), where p = AE{sup 2}D/r{sub c}{sup 2}. Here A is a constant dependent on the initial-distance distribution function of the charges, E is the electric field strength, D is a mutual diffusion coefficient of the recombining ions, and r{sub c} is the Onsager radius. The quadratic dependence of the parameter p on the electric field strength was shown to be a consequence of the diffusion-controlled reaction of ion recombination.

  3. Correlation of conformational heterogeneity of the tryptophyl side chain and time-resolved fluorescence intensity decay kinetics

    NASA Astrophysics Data System (ADS)

    Laws, William R.; Ross, J. B. Alexander

    1992-04-01

    The time-resolved fluorescence properties of a tryptophan residue should be useful for probing protein structure, function, and dynamics. To date, however, the non-single exponential fluorescence intensity decay kinetics for numerous peptides and proteins having a single tryptophan residue have not been adequately explained. Many possibilities have been considered and include: (1) contributions from the 1La and 1Lb states of indole; (2) excited-state hydrogen exchange; and (3) environmental heterogeneity from (chi) 1 and (chi) 2 rotamers. In addition, it has been suggested that generally many factors contribute to the decay and a distribution of probabilities may be more appropriate. Two recent results support multiple species due to conformational heterogeneity as the major contributor to complex kinetics. First, a rotationally constrained tryptophan analogue has fluorescence intensity decay kinetics that can be described by the sum of two exponentials with amplitudes comparable to the relative populations of the two rotational isomers. Second, the multiple exponentials observed for tyrosine-containing model compounds and peptides correlate with the (chi) 1 rotamer populations independently determined by 1H NMR. We now report similar correlations between rotamer populations and fluorescence intensity decay kinetics for a tryptophan analogue of oxytocin. It appears for this compound that either (chi) 2 rotations do not appreciably alter the indole environment, (chi) 2 rotations are rapid enough to average the observed dependence, or only one of two possible (chi) 2 populations is associated with each (chi) 1 rotamer.

  4. Experimental station for laser-based picosecond time-resolved x-ray absorption near-edge spectroscopy

    SciTech Connect

    Dorchies, F. Fedorov, N.; Lecherbourg, L.

    2015-07-15

    We present an experimental station designed for time-resolved X-ray Absorption Near-Edge Spectroscopy (XANES). It is based on ultrashort laser-plasma x-ray pulses generated from a table-top 100 mJ-class laser at 10 Hz repetition rate. A high transmission (10%–20%) x-ray beam line transport using polycapillary optics allows us to set the sample in an independent vacuum chamber, providing high flexibility over a wide spectral range from 0.5 up to 4 keV. Some XANES spectra are presented, demonstrating 1% noise level in only ∼1 mn and ∼100 cumulated laser shots. Time-resolved measurements are reported, indicating that the time resolution of the entire experimental station is 3.3 ± 0.6 ps rms.

  5. In vivo optical characterization of human tissues from 610 to 1010 nm by time-resolved reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Torricelli, Alessandro; Pifferi, Antonio; Taroni, Paola; Giambattistelli, Eleonora; Cubeddu, Rinaldo

    2001-08-01

    A fully automated system for time-resolved reflectance spectroscopy based on tunable mode-locked laser sources and on time-correlated single-photon counting for the detection of time-resolved reflectance data was applied to the evaluation of the optical properties of biological tissues (arm, abdomen and forehead) in vivo from 610 to 1010 nm. The scattering decreases progressively with increasing wavelength, while the absorption line shapes show the typical spectral features of the principal tissue components (haemoglobin, water and lipid), with different weights depending on the tissue type. The best fit of the absorption spectra measured in vivo with the spectra of the pure constituents yielded information on the percentage composition of the different tissues. The interpretation of transport scattering spectra with Mie theory provided information on tissue structure.

  6. Cellular Oxygen and Nutrient Sensing in Microgravity Using Time-Resolved Fluorescence Microscopy

    NASA Technical Reports Server (NTRS)

    Szmacinski, Henryk

    2003-01-01

    Oxygen and nutrient sensing is fundamental to the understanding of cell growth and metabolism. This requires identification of optical probes and suitable detection technology without complex calibration procedures. Under this project Microcosm developed an experimental technique that allows for simultaneous imaging of intra- and inter-cellular events. The technique consists of frequency-domain Fluorescence Lifetime Imaging Microscopy (FLIM), a set of identified oxygen and pH probes, and methods for fabrication of microsensors. Specifications for electronic and optical components of FLIM instrumentation are provided. Hardware and software were developed for data acquisition and analysis. Principles, procedures, and representative images are demonstrated. Suitable lifetime sensitive oxygen, pH, and glucose probes for intra- and extra-cellular measurements of analyte concentrations have been identified and tested. Lifetime sensing and imaging have been performed using PBS buffer, culture media, and yeast cells as a model systems. Spectral specifications, calibration curves, and probes availability are also provided in the report.

  7. TIME-RESOLVED ULTRAVIOLET SPECTROSCOPY OF THE M-DWARF GJ 876 EXOPLANETARY SYSTEM

    SciTech Connect

    France, Kevin; Froning, Cynthia S.; Linsky, Jeffrey L.; Tian, Feng; Roberge, Aki

    2012-05-10

    Extrasolar planets orbiting M-stars may represent our best chance to discover habitable worlds in the coming decade. The ultraviolet spectrum incident upon both Earth-like and Jovian planets is critically important for proper modeling of their atmospheric heating and chemistry. In order to provide more realistic inputs for atmospheric models of planets orbiting low-mass stars, we present new near- and far-ultraviolet (NUV and FUV) spectroscopy of the M-dwarf exoplanet host GJ 876 (M4V). Using the COS and STIS spectrographs on board the Hubble Space Telescope, we have measured the 1150-3140 A spectrum of GJ 876. We have reconstructed the stellar H I Ly{alpha} emission line profile, and find that the integrated Ly{alpha} flux is roughly equal to the rest of the integrated flux (1150-1210 A + 1220-3140 A) in the entire ultraviolet bandpass (F(Ly{alpha})/F(FUV+NUV) Almost-Equal-To 0.7). This ratio is {approx}2500 Multiplication-Sign greater than the solar value. We describe the ultraviolet line spectrum and report surprisingly strong fluorescent emission from hot H{sub 2} (T(H{sub 2}) > 2000 K). We show the light curve of a chromospheric + transition region flare observed in several far-UV emission lines, with flare/quiescent flux ratios {>=}10. The strong FUV radiation field of an M-star (and specifically Ly{alpha}) is important for determining the abundance of O{sub 2}-and the formation of biomarkers-in the lower atmospheres of Earth-like planets in the habitable zones of low-mass stars.

  8. Time-Resolved Ultraviolet Spectroscopy of The M-Dwarf GJ 876 Exoplanetary System

    NASA Technical Reports Server (NTRS)

    France, Kevin; Linsky, Jeffrey L.; Tian, Feng; Froning, Cynthia S.; Roberge, Aki

    2012-01-01

    Extrasolar planets orbiting M-stars may represent our best chance to discover habitable worlds in the coming decade. The ultraviolet spectrum incident upon both Earth-like and Jovian planets is critically important for proper modeling of their atmospheric heating and chemistry. In order to provide more realistic inputs for atmospheric models of planets orbiting low-mass stars, we present new near- and far-ultraviolet (NUV and FUV) spectroscopy of the M-dwarf exoplanet host GJ 876 (M4V). Using the COS and STIS spectrographs on board the Hubble Space Telescope, we have measured the 1150-3140 A spectrum of GJ 876. We have reconstructed the stellar H1 Ly alpha emission line profile, and find that the integrated Ly alpha flux is roughly equal to the rest of the integrated flux (1150-1210 A + 1220-3140 A) in the entire ultraviolet bandpass (F(Ly alpha)/F(FUV+NUV) equals approximately 0.7). This ratio is approximately 2500x greater than the solar value. We describe the ultraviolet line spectrum and report surprisingly strong fluorescent emission from hot H2 (T(H2) greater than 2000 K). We show the light curve of a chromospheric + transition region flare observed in several far-UV emission lines, with flare/quiescent flux ratios greater than or equal to 10. The strong FUV radiation field of an M-star (and specifically Ly alpha) is important for determining the abundance of O2--and the formation of biomarkers-in the lower atmospheres of Earth-like planets in the habitable zones of low-mass stars.

  9. The analysis of time resolved protein fluorescence in multi-tryptophan proteins

    NASA Astrophysics Data System (ADS)

    Engelborghs, Yves

    2001-09-01

    In the last decades, considerable progress has been made in the analysis of the fluorescence decay of proteins with more than one tryptophan. The construction of single tryptophan containing proteins has shown that the lifetimes of the wild type proteins are often the linear combinations of the family lifetimes of the contributing tryptophan residues. Additivity is not followed when energy transfer takes place among tryptophan residues or when the structure of the remaining protein is altered upon the modification. Progress has also been made in the interpretation of the value of the lifetime and the linkage with the immediate environment. Probably all the irreversible processes leading to return to the ground state have been catalogued and their rate constants are documented. Also, the process of electron transfer to the peptide carbonyl is becoming more and more documented and is linked to the rotameric state of tryptophan. Reversible excited state processes are also being considered, including reversible interconversions between rotamers. Interesting information about tryptophan and its environment comes also from anisotropy measurements for proteins in the native, the denatured and the molten globule states. Alterations of protein fluorescence due to the effects of ligand binding or side chain modifications can be analyzed via the ratio of the quantum yields of the modified protein and the reference state. Using the ratio of quantum yields and the (amplitude weighted) average lifetime, three factors can be identified: (1) a change in the apparent radiative rate constant reflecting either static quenching or an intrinsic change in the radiative properties; (2) a change in dynamic quenching; and (3) a change in the balance of the populations of the microstates or local static quenching.

  10. Architecture of Polyglutamine-containing Fibrils from Time-resolved Fluorescence Decay

    PubMed Central

    Röthlein, Christoph; Miettinen, Markus S.; Borwankar, Tejas; Bürger, Jörg; Mielke, Thorsten; Kumke, Michael U.; Ignatova, Zoya

    2014-01-01

    The disease risk and age of onset of Huntington disease (HD) and nine other repeat disorders strongly depend on the expansion of CAG repeats encoding consecutive polyglutamines (polyQ) in the corresponding disease protein. PolyQ length-dependent misfolding and aggregation are the hallmarks of CAG pathologies. Despite intense effort, the overall structure of these aggregates remains poorly understood. Here, we used sensitive time-dependent fluorescent decay measurements to assess the architecture of mature fibrils of huntingtin (Htt) exon 1 implicated in HD pathology. Varying the position of the fluorescent labels in the Htt monomer with expanded 51Q (Htt51Q) and using structural models of putative fibril structures, we generated distance distributions between donors and acceptors covering all possible distances between the monomers or monomer dimensions within the polyQ amyloid fibril. Using Monte Carlo simulations, we systematically scanned all possible monomer conformations that fit the experimentally measured decay times. Monomers with four-stranded 51Q stretches organized into five-layered β-sheets with alternating N termini of the monomers perpendicular to the fibril axis gave the best fit to our data. Alternatively, the core structure of the polyQ fibrils might also be a zipper layer with antiparallel four-stranded stretches as this structure showed the next best fit. All other remaining arrangements are clearly excluded by the data. Furthermore, the assessed dimensions of the polyQ stretch of each monomer provide structural evidence for the observed polyQ length threshold in HD pathology. Our approach can be used to validate the effect of pharmacological substances that inhibit or alter amyloid growth and structure. PMID:25092288

  11. Time-resolved positron annihilation spectroscopy study of relaxation dynamics of ion damage in fused quartz

    NASA Astrophysics Data System (ADS)

    Tsuchida, Hidetsugu; Mizuno, Shohei; Tsutsumi, Hironori; Kinomura, Atsushi; Suzuki, Ryoichi; Itoh, Akio

    2016-05-01

    Relaxation dynamics of ion damage in fused quartz is investigated by our newly developed pump–probe technique combining energetic ions (pump) with slow positrons (probe). This method enables determination of time-resolved positron lifetime. We study the time-dependent relaxation of ion damage, by analyzing the intensity variation in the ortho-positronium lifetime component associated with irradiation damage. For irradiation with 160 keV He ions in the temperature range of 300–573 K, the positron annihilation lifetime spectra are obtained as a function of time after ion irradiation. We observe that the relaxation time of ion damage is strongly influenced by specimen temperatures; the relaxation time constant is approximately 400 ms at room temperature (300 K) and becomes smaller with an increasing temperature. Analysis for the effect of temperature on damage accumulation reveals that the activation energy for thermal annealing of the observed damage is approximately 0.1 eV.

  12. Time-resolved spectroscopy of self-assembly of CCMV protein capsids

    NASA Astrophysics Data System (ADS)

    Moore, Jelyn; Aronzon, Dina; Manoharan, V. N.

    2008-10-01

    In order to gain a deeper understanding of the process a virus undergoes to assemble; the purpose of this study to time resolve the self-assembly of a virus. Cowpea Chlorotic Mottle virus (CCMV), an icosahedral type virus, can assemble without its genetic code (RNA) depending on its chemical and physical surroundings. The surface plasmon resonance (SPR) of colloidal gold particles is known to display a shift when the gold interacts with the proteins of a virus. Surface plasmon resonance is the free electron oscillation occurring at the surface of the gold particle resulting in a characteristic peak location at maximal absorbance and peak width. The shift results from the change in the refractive index of the particles as induced by the presence of the proteins. We hope to detect this shift through total internal reflection microscopy (TIRM). The accomplishments of this research are the completion of the TIR setup and the purification of the virus and its proteins.

  13. Time-resolved resonance Raman spectroscopy of bacteriorhodopsin on the millisecond timescale.

    PubMed Central

    Terner, J; Campion, A; El-Sayed, M A

    1977-01-01

    A simple technique is described that uses a continuous wave laser with electromechanical modulation to obtain time-resolved Raman spectra of transient species on the millisecond timescale. The time behavior of the vibrational bands of the intermediates involved in the proton pumping of bacteriorhodopsin is determined. From these results, along with resonance enhancement and power dependence studies, the bands that appear in the continuous wave Raman spectrum of bacteriorhodopsin can be assigned to three intermediates in the photochemical cycle of bacteriorhodopsin, bR570, bL550, and bM412. The Raman spectra of bR570 and bM412 are compared with published spectra of model Schiff bases of all-trans and 13-cis retinal. PMID:271946

  14. Time-Resolved X-ray Spectroscopy of the Massive Binary delta Ori

    NASA Astrophysics Data System (ADS)

    Nichols, Joy S.; Naze, Y.; Corcoran, M. F.; Pollock, A.; Moffat, A. F.; Ignace, R.; Waldron, W. L.; Evans, N. R.

    2014-01-01

    We have obtained 500 ks of Chandra HETG observations of the massive binary delta Ori (O9.5II+unseen companion), one of the fundamental calibrators of the mass-luminosity-radius relation in the upper HR diagram. The program is intended to map the emission line parameters as the secondary moves through the wind of the primary star. Custom extraction techniques have been developed to create 12 time-resolved 40 ks spectra from these observations, each of which is properly calibrated for time and temperature effects. Emission line fluxes for these time slice spectra are presented, as well as phase analysis of the variability of the fluxes. We discuss the interpretation of the resulting data, such as colliding winds and occultation of various temperature regimes of the primary wind by the secondary.

  15. Use of Time-Resolved Fluorescence To Improve Sensitivity and Dynamic Range of Gel-Based Proteomics.

    PubMed

    Sandberg, AnnSofi; Buschmann, Volker; Kapusta, Peter; Erdmann, Rainer; Wheelock, Åsa M

    2016-03-15

    Limitations in the sensitivity and dynamic range of two-dimensional gel electrophoresis (2-DE) are currently hampering its utility in global proteomics and biomarker discovery applications. In the current study, we present proof-of-concept analyses showing that introducing time-resolved fluorescence in the image acquisition step of in-gel protein quantification provides a sensitive and accurate method for subtracting confounding background fluorescence at the photon level. In-gel protein detection using the minimal difference gel electrophoresis workflow showed improvements in lowest limit of quantification in terms of CyDye molecules per pixel of 330-fold in the blue-green region (Cy2) and 8000-fold in the red region (Cy5) over conventional state-of-the-art image acquisition instrumentation, here represented by the Typhoon 9400 instrument. These improvements make possible the detection of low-abundance proteins present at sub-attomolar levels, thereby representing a quantum leap for the use of gel-based proteomics in biomarker discovery. These improvements were achieved using significantly lower laser powers and overall excitation times, thereby drastically decreasing photobleaching during repeated scanning. The single-fluorochrome detection limits achieved by the cumulative time-resolved emission two-dimensional electrophoresis (CuTEDGE) technology facilitates in-depth proteomics characterization of very scarce samples, for example, primary human tissue materials collected in clinical studies. The unique information provided by high-sensitivity 2-DE, including positional shifts due to post-translational modifications, may increase the chance to detect biomarker signatures of relevance for identification of disease subphenotypes. PMID:26854653

  16. Cerebral and Muscle Tissue Oxygenation During Incremental Cycling in Male Adolescents Measured by Time-Resolved Near-Infrared Spectroscopy.

    PubMed

    Ganesan, Goutham; Leu, Szu-Yun; Cerussi, Albert; Tromberg, Bruce; Cooper, Dan M; Galassetti, Pietro

    2016-05-01

    Near-infrared spectroscopy has long been used to measure tissue-specific O2 dynamics in exercise, but most published data have used continuous wave devices incapable of quantifying absolute Hemoglobin (Hb) concentrations. We used time-resolved near-infrared spectroscopy to study exercising muscle (Vastus Lateralis, VL) and prefrontal cortex (PFC) Hb oxygenation in 11 young males (15.3 ± 2.1 yrs) performing incremental cycling until exhaustion (peak VO2 = 42.7 ± 6.1 ml/min/kg, mean peak power = 181 ± 38 W). Time-resolved near-infrared spectroscopy measurements of reduced scattering (μs´) and absorption (μa) at three wavelengths (759, 796, and 833 nm) were used to calculate concentrations of oxyHb ([HbO2]), deoxy Hb ([HbR]), total Hb ([THb]), and O2 saturation (stO2). In PFC, significant increases were observed in both [HbO2] and [HbR] during intense exercise. PFC stO2% remained stable until 80% of total exercise time, then dropped (-2.95%, p = .0064). In VL, stO2% decreased until peak time (-6.8%, p = .01). Segmented linear regression identified thresholds for PFC [HbO2], [HbR], VL [THb]. There was a strong correlation between timing of second ventilatory threshold and decline in PFC [HbO2] (r = .84). These findings show that time-resolved near-infrared spectroscopy can be used to study physiological threshold phenomena in children during maximal exercise, providing insight into tissue specific hemodynamics and metabolism. PMID:26451845

  17. Full Genotyping of a Highly Polymorphic Human Gene Trait by Time-Resolved Fluorescence Resonance Energy Transfer

    PubMed Central

    Totè, Edoardo; Lamperti, Marco; Bondani, Maria; Salerno, Domenico; Cassina, Valeria; Nardo, Luca

    2014-01-01

    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. PMID:25215592

  18. Probing Reaction Dynamics of Transition-Metal Complexes in Solution via Time-Resolved X-ray Spectroscopy

    SciTech Connect

    Huse, Nils; Khalil, Munira; Kim, Tae Kyu; Smeigh, Amanda L.; Jamula, Lindsey; McCusker, James K.; Schoenlein, Robert W.

    2009-05-24

    We report measurements of the photo-induced Fe(II) spin crossover reaction dynamics in solution via time-resolved x-ray absorption spectroscopy. EXAFS measurements reveal that the iron?nitrogen bond lengthens by 0.21+-0.03 Angstrom in the high-spin transient excited state relative to the ground state. XANES measurements at the Fe L-edge show directly the influence of the structural change on the ligand-field splitting of the Fe(II) 3d orbitals associated with the spin transition.

  19. Multiplexed measurements by time resolved spectroscopy using colloidal CdSe/ZnS quantum dots

    NASA Astrophysics Data System (ADS)

    Kaiser, U.; Jimenez de Aberasturi, D.; Malinowski, R.; Amin, F.; Parak, W. J.; Heimbrodt, W.

    2014-01-01

    Multiplexed measurements of analytes in parallel is a topical demand in bioanalysis and bioimaging. An interesting alternative to commonly performed spectral multiplexing is lifetime multiplexing. In this Letter, we present a proof of principle of single-color lifetime multiplexing by coupling the same fluorophore to different nanoparticles. The effective lifetime of the fluorophores can be tuned by more than one order of magnitude due to resonance energy transfer from donor states. Measurements have been done on a model systems consisting of ATTO-590 dye molecules linked to either gold particles or to CdSe/ZnS core shell quantum dots. Both systems show the same luminescence spectrum of ATTO-590 dye emission in continuous wave excitation, but can be distinguished by means of time resolved measurements. The dye molecules bound to gold particles exhibit a mono-exponential decay with a lifetime of 4.5 ns, whereas the dye molecules bound to CdSe/ZnS dots show a nonexponential decay with a slow component of about 135 ns due to the energy transfer from the quantum dots. We demonstrate the fundamental possibility to determine the mixing ratio for dyes with equal luminescence spectra but very different transients. This opens up a pathway independent of the standard optical multiplexing with many different fluorophores emitting from the near ultraviolet to the near infrared spectral region.

  20. Photoenhancement of quantum dots and conjugates measured by time-resolved spectroscopy

    NASA Astrophysics Data System (ADS)

    Suffern, Diana; Cooper, Daniel; Carlini, Lina; Parbhoo, Rupesh; Bradforth, Stephen; Nadeau, Jay

    2009-02-01

    The response of solubilized quantum dot solutions to visible or UV irradiation is highly variable, and contradictory reports exist in the literature. Using several different preparations of core CdSe, core-shell CdSe/ZnS, and CdTe quantum dots (QDs), we investigated the time-resolved photoluminescence as a function of 400 nm irradiation. We found that photoenhancement and photodegradation were highly dependent upon irradiation power, with the QDs being highly stable at fluences of < 2 mW. However, great variability was seen among independent preparations of QDs, with fresher dots showing greater photostability than those that had been aged in organic solvent. Conjugation of dopamine to the QDs also led to variable effects, with some batches showing lifetime enhancement upon conjugation and others suppression. In all cases, QD-dopamine conjugates showed increased lifetimes upon irradiation, up to a maximum effect at ~ 5 min post irradiation at 2.4 mW. The antioxidant beta-mercaptoethanol also affected different batches of QDs differently; it prevented photoenhancement with certain batches but not others. We propose a mechanism of photoenhancement and surface oxidation that relates the variability to the number of solubilising groups on the QD surface. The potential of photoenhancement as a sensing mechanism in cells is proposed.

  1. Determination of Iron in Water Solution by Time-Resolved Femtosecond Laser-Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Sergey, S. Golik; Alexey, A. Ilyin; Michael, Yu. Babiy; Yulia, S. Biryukova; Vladimir, V. Lisitsa; Oleg, A. Bukin

    2015-11-01

    The influence of the energy of femtosecond laser pulses on the intensity of Fe I (371.99 nm) emission line and the continuous spectrum of the plasma generated on the surface of Fe3+ water solution by a Ti: sapphire laser radiation with pulse duration < 45 fs and energies up to 7 mJ is determined. A calibration curve was obtained for Fe3+ concentration range from 0.5 g/L to the limit of detection in water solution, and its saturation was detected for concentrations above 0.25 g/L, which is ascribed to self-absorption. The 3σ- limit of detection obtained for Fe in water solution is 2.6 mg/L in the case of 7 mJ laser pulse energy. It is found that an increase of laser pulse energy insignificantly affects on LOD in the time-resolved LIBS and leads to a slight improvement of the limit of detection. supported by the Russian Science Foundation (agreement #14-50-00034) (measurements of limit of detection), Russian Foundation for Basic Research (NK 15-32-20878/15) obtained in the frame of “Organization of Scientific Research” in the Far Eastern Federal University supported by Ministry of Education and Science of Russian Federation

  2. Time-resolved photoionization spectroscopy of mixed Rydberg-valence states: indole case study.

    PubMed

    Zawadzki, Magdalena M; Thompson, James O F; Burgess, Emma A; Paterson, Martin J; Townsend, Dave

    2015-10-28

    Time-resolved photoelectron imaging was used to study non-adiabatic relaxation dynamics in gas-phase indole following photo-excitation at 267 nm and 258 nm. Our data analysis was supported by various ab initio calculations using both coupled cluster and density functional methods. The highly differential energy- and angle-resolved information provided by our experimental approach provides extremely subtle details of the complex interactions occurring between several low-lying electronically excited states. In particular, new insight into the role and fate of the mixed Rydberg-valence 3s/πσ* state is revealed. This includes population residing on the excited state surface at large N-H separations for a relatively long period of time (∼1 ps) prior to dissociation and/or internal conversion. Our findings may, in part, be rationalized by considering the rapid evolution of this state's electronic character as the N-H stretching coordinate is extended - as extensively demonstrated in the supporting theory. Overall, our findings highlight a number of important general caveats regarding the nature of mixed Rydberg-valence excited states, their spectral signatures and detection sensitivity in photoionization measurements, and the evaluation of their overall importance in mediating electronic relaxation in a wide range of small model-chromophore systems providing bio-molecular analogues - a topic of considerable interest within the chemical dynamics community over the last decade. PMID:26394263

  3. Diffusion optical spectroscopy of cancerous and normal prostate tissues in time-resolved and frequency domain

    NASA Astrophysics Data System (ADS)

    Zhou, Kenneth J.; Pu, Yang; Chen, Jun

    2014-03-01

    It is well-known that light transport can be well described using Maxwell's electromagnetic theory. In biological tissue, the scattering particles cause the interaction of scattered waves from neighboring particles. Since such interaction cannot be ignored, multiple scattering occurs. The theoretical solution of multiple scattering is complicated. A suitable description is that the wavelike behavior of light is ignored and the transport of an individual photon is considered to be absorbed or scattered. This is known as the Radiative Transfer Equation (RTE) theory. Analytical solutions to the RTE that explicitly describes photon migration can be obtained by introducing some proper approximations. One of the most popular models used in the field of tissue optics is the Diffusion Approximation (DA). In this study, we report on the results of our initial study of optical properties of ex vivo normal and cancerous prostate tissues and how tissue parameters affect the near infrared light transporting in the two types of tissues. The time-resolved transport of light is simulated as an impulse isotropic point source of energy within a homogeneous unbounded medium with different absorption and scattering properties of cancerous and normal prostate tissues. Light source is also modulated sinusoidally to yield a varied fluence rate in frequency domain at a distant observation point within the cancerous and normal prostate tissues. Due to difference of the absorption and scattering coefficients between cancerous and normal tissues, the expansion of light pulse, intensity, phase are found to be different.

  4. Structural recovery in plastic crystals by time-resolved non-linear dielectric spectroscopy

    NASA Astrophysics Data System (ADS)

    Riechers, Birte; Samwer, Konrad; Richert, Ranko

    2015-04-01

    The dielectric relaxation of several different plastic crystals has been examined at high amplitudes of the ac electric fields, with the aim of exploring possible differences with respect to supercooled liquids. In all cases, the steady state high field loss spectrum appears to be widened, compared with its low field limit counterpart, whereas peak position and peak amplitude remain almost unchanged. This field induced change in the loss profile is explained on the basis of two distinct effects: an increased relaxation time due to reduced configurational entropy at high fields which affects the low frequency part of the spectrum, and accelerated dynamics at frequencies above the loss peak position resulting from the added energy that the sample absorbs from the external electric field. From the time-resolved assessment of the field induced changes in fictive temperatures at relatively high frequencies, we find that this structural recovery is slaved to the average rather than mode specific structural relaxation time. In other words, the very fast relaxation modes in the plastic crystal cannot adjust their fictive temperatures faster than the slower modes, the equivalent of time aging-time superposition. As a result, an explanation for this single fictive temperature must be consistent with positional order, i.e., translational motion or local density fluctuations do not govern the persistence time of local time constants.

  5. Multiplexed measurements by time resolved spectroscopy using colloidal CdSe/ZnS quantum dots

    SciTech Connect

    Kaiser, U.; Jimenez de Aberasturi, D.; Malinowski, R.; Amin, F.; Parak, W. J.; Heimbrodt, W.

    2014-01-27

    Multiplexed measurements of analytes in parallel is a topical demand in bioanalysis and bioimaging. An interesting alternative to commonly performed spectral multiplexing is lifetime multiplexing. In this Letter, we present a proof of principle of single-color lifetime multiplexing by coupling the same fluorophore to different nanoparticles. The effective lifetime of the fluorophores can be tuned by more than one order of magnitude due to resonance energy transfer from donor states. Measurements have been done on a model systems consisting of ATTO-590 dye molecules linked to either gold particles or to CdSe/ZnS core shell quantum dots. Both systems show the same luminescence spectrum of ATTO-590 dye emission in continuous wave excitation, but can be distinguished by means of time resolved measurements. The dye molecules bound to gold particles exhibit a mono-exponential decay with a lifetime of 4.5 ns, whereas the dye molecules bound to CdSe/ZnS dots show a nonexponential decay with a slow component of about 135 ns due to the energy transfer from the quantum dots. We demonstrate the fundamental possibility to determine the mixing ratio for dyes with equal luminescence spectra but very different transients. This opens up a pathway independent of the standard optical multiplexing with many different fluorophores emitting from the near ultraviolet to the near infrared spectral region.

  6. Time-resolved infrared spectroscopy of the lowest triplet state of thymine and thymidine

    NASA Astrophysics Data System (ADS)

    Hare, Patrick M.; Middleton, Chris T.; Mertel, Kristin I.; Herbert, John M.; Kohler, Bern

    2008-05-01

    Vibrational spectra of the lowest energy triplet states of thymine and its 2'-deoxyribonucleoside, thymidine, are reported for the first time. Time-resolved infrared (TRIR) difference spectra were recorded over seven decades of time from 300 fs to 3 μs using femtosecond and nanosecond pump-probe techniques. The carbonyl stretch bands in the triplet state are seen at 1603 and ˜1700 cm -1 in room-temperature acetonitrile- d3 solution. These bands and additional ones observed between 1300 and 1450 cm -1 are quenched by dissolved oxygen on a nanosecond time scale. Density-functional calculations accurately predict the difference spectrum between triplet and singlet IR absorption cross sections, confirming the peak assignments and elucidating the nature of the vibrational modes. In the triplet state, the C4 dbnd O carbonyl exhibits substantial single-bond character, explaining the large (˜70 cm -1) red shift in this vibration, relative to the singlet ground state. Femtosecond TRIR measurements unambiguously demonstrate that the triplet state is fully formed within the first 10 ps after excitation, ruling out a relaxed 1nπ ∗ state as the triplet precursor.

  7. Time-resolved spectroscopy and photometry of the eclipsing AM Herculis binary EXO 033319 - 2554. 2

    SciTech Connect

    Allen, R.G.; Berriman, G.; Smith, P.S.; Schmidt, G.D. )

    1989-12-01

    Time-resolved optical observations of the eclipsing AM Herculis binary EXO 033319 - 2554.2 are presented. High-speed photometry of an eclipse is presented and used to derive a new ephemeris for the system and to estimate the size of the region responsible for the cyclotron emission. Optical spectra that span the orbital cycle are presented, the cyclotron emission in these spectra is discussed, and the flux and radial velocity variations of H-beta, H-gamma, and He II 4686 A are examined. Models of the flux and radial velocity variations of the emission lines indicate that about half the line emission comes from low-velocity material that is about 1.4 x 10 to the 10th cm from the white dwarf. The rest comes from high-velocity material that is about 10 to the 10th cm from the white dwarf and is moving toward it at about 600 km/s. 13 refs.

  8. Effects of ligand binding on the conformation and internal dynamics in specific regions of porcine pancreatic phospholipase A2 with tryptophan as a probe: a study combinging time-resolved fluorescence spectroscopy and site-directed mutagenesis (same as p. 628)

    NASA Astrophysics Data System (ADS)

    Kuipers, Oscar; Vincent, Michel; Brochon, Jean-Claude; Verheij, Bert; de Haas, Gerard; Gallay, Jacques

    1990-05-01

    Exploration of the effect of ligand-protein interactions on conformational substates and internal dynamics in different regions of phospholipase A2 from porcine pancreas (PLA2), was performed by combining site-directed mutagenesis and time-resolved fluorescence measurements. The single tryptophan residue (Trp-3) in the wild type protein was replaced by a phenylalanine residue, whereafter Tip was substituted either for leucine-3 1 ,located in the calcium binding ioop, or for phenylalanine-94, located at the "back side" of the enzyme, in a-helix E (Dijkstra et al., J. Mol. Biol., 147, 97-123, 1981). Analyses by the Maximum Entropy Method (MEM) of the total fluorescence intensity decays, provide in each case a distribution of separate lifetime classes, which can be interpreted as reflecting the existence of discrete conformational substates in slow exchange with respect to the time-scale of the decay kinetics. The fluorescence decay of the W94 mutant is. dominated by an extremely short excited state lifetime of ~60 ps, probably arising from the presence of two proximate disulfide bridges. Time-resolved fluorescence anisotropy studies show that the Trp residue near the NH2 terminus (Trp-3) undergoes a more limited rotational motion than the Trp-3 1 located in the calcium binding loop. The widest angular rotation is observed at position 94, in a-helix E. Calcium binding displays the strongest influence on the lifetime distribution of Trp-3 1: a major local conformation corresponding to a lifetime class with a barycenter value of -5.5 ns and contributing to ~50% of the decay is selected. The conformations giving rise to the short lifetimes (τ1 and τ2 lifetime classes) become less important. The contribution of the third lifetime class (c3) stays at a constant value of 30%. In the presence of calcium, the amplitude of motion is wider than without the ion. There is virtually no effect of calcium binding on the lifetime distribution of the Trp residue at the 3 or the 94 position. Binding of the monomeric substrate analog n-dodecylphosphocholine (C12PN) in the presence of calcium hardly affects neither the Trp-3 excited state population distribution, nor its rotational dynamics. The binding of C12PN monomers to the W31 mutant further increases the contribution of the τ4 lifetime class at the expense of c2. A more restricted rotation of the Trp-3 1 residue is also induced. The binding of the micellar substrate analog n-hexadecylphosphocholine (C16PN) in the presence of calcium is very efficient in modifying the lifetime distribution of Trp-3. Essentially, one major broad lifetime population (centered at ~2.6 ns) is revealed by MEM analysis of the total intensity decay. The internal motion is slowed down and the angle of rotation is much smaller in this conformation. Neither the excited state lifetime distribution of Trp-31 nor its dynamics are affected by micelle binding relative to monomer binding. In conclusion, by placing a single Tip-residue at strategic positions along the peptide chain of PLA2, relevant to the binding of biological ligands, an excellent model system for the study of selective perturbations of conformational substates and internal dynamics is provided.

  9. Effects of ligand binding on the conformation and internal dynamics in specific regions of porcine pancreatic phospholipase A2 with tryptophan as a probe: a study combining time-resolved fluorescence spectroscopy and site-directed mutagenesis (same as p. 100)

    NASA Astrophysics Data System (ADS)

    Kuipers, Oscar; Vincent, Michel; Brochon, Jean-Claude; Verheij, Bert; de Haas, Gerard; Gallay, Jacques

    1990-05-01

    Exploration of the effect of ligand-protein interactions on conformational substates and internal dynamics in different regions of phospholipase A2 from porcine pancreas (PLA2), was performed by combining site-directed mutagenesis and time-resolved fluorescence measurements. The single tryptophan residue (Trp-3) in the wild type protein was replaced by a phenylalanine residue, whereafter Trp was substituted either for leucine-31 ,located in the calcium binding loop, or for phenylalanine-94, located at the "back side" of the enzyme, in a-helix E (Dijkstra et al., J. Mol. Biol., 147, 97-123, 1981). Analyses by the Maximum Entropy Method (MIEM) of the total fluorescence intensity decays, provide in each case a distribution of separate lifetime classes, which can be interpreted as reflecting the existence of discrete conformational substates in slow exchange with respect to the time-scale of the decay kinetics. The fluorescence decay of the W94 mutant is dominated by an extremely short excited state lifetime of ~60 ps, probably arising from the presence of two proximate disulfide bridges. Time-resolved fluorescence anisotropy studies show that the Trp residue near the NH2 terminus (Trp-3) undergoes a more limited rotational motion than the Trp-3 1 located in the calcium binding loop. The widest angular rotation is observed at position 94, in a-helix E. Calcium binding displays the strongest influence on the lifetime distribution of Trp-31: a major local conformation corresponding to a lifetime class with a barycenter value of ~5.5 ns and contributing to ~50% of the decay is selected. The conformations giving rise to the short lifetimes ((tau)1 and (tau)2 lifetime classes) become less important. The contribution of the third lifetime class (c3) stays at a constant value of 30%. In the presence of calcium, the amplitude of motion is wider than without the ion. There is virtually no effect of calcium binding on the lifetime distribution of the Trp residue at the 3 or the 94 position. Binding of the monomeric substrate analog n-dodecylphosphocholine (C12PN) in the presence of calcium hardly affects neither the Trp-3 excited state population distribution, nor its rotational dynamics. The binding of C12PN monomers to the W31 mutant further increases the contribution of the t4lifetime class at the expense of c2. A more restricted rotation of the Trp-31 residue is also induced. The binding of the micellar substrate analog n-hexadecylphosphocholine (C16PN) in the presence of calcium is very efficient in modifying the lifetime distribution of Trp-3. Essentially, one major broad lifetime population (centered at ~2.6 ns) is revealed by MEM analysis of the total intensity decay. The internal motion is slowed down and the angle of rotation is much smaller in this conformation. Neither the excited state lifetime distribution of Trp-31 nor its dynamics are affected by micelle binding relative to monomer binding. In conclusion, by placing a single Tip-residue at strategic positions along the peptide chain of PLA2, relevant to the binding of biological ligands, an excellent model system for the study of selective perturbations of conformational substates and internal dynamics is provided.

  10. Identifiability analysis of rotational diffusion tensor and electronic transition moments measured in time-resolved fluorescence depolarization experiment

    SciTech Connect

    Szubiakowski, Jacek P.

    2014-06-14

    The subject of this paper is studies of the deterministic identifiability of molecular parameters, such as rotational diffusion tensor components and orientation of electronic transition moments, resulting from the time-resolved fluorescence anisotropy experiment. In the most general case considered, a pair of perpendicularly polarized emissions enables the unique determination of all the rotational diffusion tensor's principal components. The influence of the tensor's symmetry and the associated degeneration of its eigenvalues on the identifiability of the electronic transitions moments is systematically investigated. The analysis reveals that independently of the rotational diffusion tensor's symmetry, the transition moments involved in photoselection and emission processes cannot be uniquely identified without a priori information about their mutual orientation or their orientation with respect to the principal axes of the tensor. Moreover, it is shown that increasing the symmetry of the rotational diffusion tensor deteriorates the degree of the transition moments identifiability. To obtain these results analytically, a novel approach to solve bilinear system of equations for Markov parameters is applied. The effect of the additional information, obtained from fluorescence measurements for different molecular mobilities, to improve the identifiability at various levels of analysis is shown. The effectiveness and reliability of the target analysis method for experimental determination of the molecular parameters is also discussed.

  11. A time-resolved fluorescence immunoassay for the ultrasensitive determination of diethylstilbestrol based on the double-codified gold nanoparticles.

    PubMed

    Wang, Longjun; Zhang, Yuanfu; Liu, Guofu; Zhang, Chunyan; Wang, Shuhao

    2014-11-01

    An ultrasensitive and selective method is presented for the determination of diethylstilbestrol (DES) using time-resolved fluorescence immunoassay (TRFIA) based on double-codified gold nanoparticles (DC-AuNPs). In this system, the DC-AuNPs, that are gold nanoparticles (AuNPs) modified with anti-DES antibody and SH-dsDNA-biotin, was regarded as signal amplifier. A competitive immunoreaction was performed on polystyrene microtitration plates, where the DES compete with the immobilized DES-ovalbumin on polystyrene microtitration plates to bind to anti-DES antibodies on DC-AuNPs, and the europium(III)-labeled streptavidin was added to link to the SH-dsDNA-biotin as a tracer. Fluorescence signal was amplified via the AuNPs and the biotin-streptavidin double amplification systems. Under the optimized condition, DES can be quantified by TRFIA. The linear range and the limit of detection of DES were 1.0×10(-6)-10ngmL(-1) and 0.4fgmL(-1), respectively. This method was applied to determine DES in beef sample, with the recoveries ranging from 88% to 105%. PMID:25091151

  12. Calculating singlet excited states: Comparison with fast time-resolved infrared spectroscopy of coumarins

    NASA Astrophysics Data System (ADS)

    Hanson-Heine, Magnus W. D.; Wriglesworth, Alisdair; Uroos, Maliha; Calladine, James A.; Murphy, Thomas S.; Hamilton, Michelle; Clark, Ian P.; Towrie, Michael; Dowden, James; Besley, Nicholas A.; George, Michael W.

    2015-04-01

    In contrast to the ground state, the calculation of the infrared (IR) spectroscopy of molecular singlet excited states represents a substantial challenge. Here, we use the structural IR fingerprint of the singlet excited states of a range of coumarin dyes to assess the accuracy of density functional theory based methods for the calculation of excited state IR spectroscopy. It is shown that excited state Kohn-Sham density functional theory provides a high level of accuracy and represents an alternative approach to time-dependent density functional theory for simulating the IR spectroscopy of singlet excited states.

  13. Time-resolved spectroscopy of charge transfer phenomena in organic solar cells

    NASA Astrophysics Data System (ADS)

    Gerhard, Marina; Arndt, Andreas; Quintilla, Aina; Rahimi-Iman, Arash; Lemmer, Uli; Koch, Martin

    2015-03-01

    Geminate recombination of photo-generated excitons represents a considerable loss mechanism in polymer solar cells. We apply time-resolved photoluminescence (TRPL) to study the radiative recombination which accompanies the process of charge generation. A streak camera is used, which is sensitive for both the photoluminescence (PL) from the initially excited singlet excitons and the weaker emission from charge transfer (CT) states. The latter are formed at internal interfaces when the polymer is blended with a fullerene acceptor. We draw a comparison between our results for two polymers, P3HT and PTB7, respectively, which were studied in blends with the fullerene derivative PCBM. In addition, pristine films were investigated, allowing for the identification of interfacial features in the blends. For both polymers, the PL of the singlet states was rapidly quenched in blends with PCBM. In P3HT, time constants of about 40 ps were recorded for the singlet exciton decay and related to exciton diffusion, whereas the PL of PTB7 was almost completely quenched within the first 3 ps. The decay rates of the emissive CT excitons were 2-3 orders of magnitude smaller than those of the singlet state. Yet, due to their slower dynamics (~ 500 ps), they could be separated from the superimposed singlet emission. The CT decay times in blends with P3HT exhibited no significant temperature dependence, indicating that thermally driven dissociation of emissive excitons is unlikely. For blends with PTB7, however, a faster decay of the CT emission was obtained at room temperature.

  14. TIME-RESOLVED SPECTROSCOPY OF THE POLAR EU CANCRI IN THE OPEN CLUSTER MESSIER 67

    SciTech Connect

    Williams, Kurtis A.; Howell, Steve B.; Bellini, Andrea; Rubin, Kate H. R.; Bolte, Michael E-mail: steve.b.howell@nasa.gov E-mail: psmith@as.arizona.edu E-mail: rubin@mpia.de

    2013-05-15

    We present time-resolved spectroscopic and polarimetric observations of the AM Her system EU Cnc. EU Cnc is located near the core of the old open cluster Messier 67; new proper motion measurements indicate that EU Cnc is indeed a member of the star cluster, and this system therefore is useful to constrain the formation and evolution of magnetic cataclysmic variables. The spectra exhibit two-component emission features with independent radial velocity variations as well as time-variable cyclotron emission indicating a magnetic field strength of 41 MG. The period of the radial velocity and cyclotron hump variations are consistent with the previously known photometric period, and the spectroscopic flux variations are consistent in amplitude with previous photometric amplitude measurements. The secondary star is also detected in the spectrum. We also present polarimetric imaging measurements of EU Cnc that show a clear detection of polarization, and the degree of polarization drops below our detection threshold at phases when the cyclotron emission features are fading or not evident. The combined data are all consistent with the interpretation that EU Cnc is a low-state polar in the cluster Messier 67. The mass function of the system gives an estimate of the accretor mass of M{sub WD} {>=} 0.68 M{sub Sun} with M{sub WD} Almost-Equal-To 0.83 M{sub Sun} for an average inclination. We are thus able to place a lower limit on the progenitor mass of the accreting white dwarf of {>=}1.43 M{sub Sun }.

  15. Infrared Absorption of CH3SONO Detected with Time-Resolved Fourier-Transform Spectroscopy

    NASA Astrophysics Data System (ADS)

    Lee, Yuan-Pern; Chen, Jin-Dah

    2011-06-01

    A step-scan Fourier-transform spectrometer coupled with a 6.4-m multipass absorption cell was employed to detect time-resolved infrared absorption spectra of reaction intermediates produced upon UV irradiation of a flowing mixture of CH3SSCH3 and NO2 in CO2. Irradiation of CH3SSCH3 at 248 nm produces CH3S radicals that subsequently react with NO2. Under a total pressure of 100 Torr, we observed bands near 1560 Cm-1, assignable to mainly the N=O stretching mode of CH3SONO, with a small contribution from CH3SNO2. Calculations with density-functional theory (B3LYP/aug-cc-pVTZ and B3P86/aug-cc-pVTZ) predicted the geometry, vibrational wavenumbers, and rotational parameters of CH3SONO and CH3SNO2. Based on these predicted rotational parameters, the simulated absorption band agrees satisfactorily with experimental results. Under a total pressure of 16 Torr, bands near 1560 and 1260 Cm-1 are assigned to NO2 asymmetric and symmetric stretching modes of CH3SNO2, respectively; the former is overlapped with the N=O stretching mode of CH3SONO. An additional band near 1070 Cm-1 is assigned to the S=O stretching mode of CH3SO, reported previously as a secondary product in the reaction of CH3S + O2. Reaction of CH3S + NO2 at high pressure clearly yields CH3SONO, rather than CH3SNO2, as a major product. L.-K. Chu and Y.-P. Lee, J. Chem. Phys. 133, 184303 (2010).

  16. Time-resolved Spectroscopy of the Polar EU Cancri in the Open Cluster Messier 67

    NASA Astrophysics Data System (ADS)

    Williams, Kurtis A.; Howell, Steve B.; Liebert, James; Smith, Paul S.; Bellini, Andrea; Rubin, Kate H. R.; Bolte, Michael

    2013-05-01

    We present time-resolved spectroscopic and polarimetric observations of the AM Her system EU Cnc. EU Cnc is located near the core of the old open cluster Messier 67; new proper motion measurements indicate that EU Cnc is indeed a member of the star cluster, and this system therefore is useful to constrain the formation and evolution of magnetic cataclysmic variables. The spectra exhibit two-component emission features with independent radial velocity variations as well as time-variable cyclotron emission indicating a magnetic field strength of 41 MG. The period of the radial velocity and cyclotron hump variations are consistent with the previously known photometric period, and the spectroscopic flux variations are consistent in amplitude with previous photometric amplitude measurements. The secondary star is also detected in the spectrum. We also present polarimetric imaging measurements of EU Cnc that show a clear detection of polarization, and the degree of polarization drops below our detection threshold at phases when the cyclotron emission features are fading or not evident. The combined data are all consistent with the interpretation that EU Cnc is a low-state polar in the cluster Messier 67. The mass function of the system gives an estimate of the accretor mass of M WD >= 0.68 M ⊙ with M WD ≈ 0.83 M ⊙ for an average inclination. We are thus able to place a lower limit on the progenitor mass of the accreting white dwarf of >=1.43 M ⊙. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  17. Time ResolvedSpectroscopy of the Eclipsing Old Nova DQ Her

    NASA Astrophysics Data System (ADS)

    Mastrantonio, E.; Bianchini, A.; Canterna, R.

    2003-12-01

    Time resolved Hα VPH spectroscopic observations of the old nova DQ Her (1934) were taken during an eclipse of the white dwarf primary using the 1.82 m Mt. Ekar telescope (Asiago, Italy). The lightcurves of the H-alpha and He I line emitting regions exhibit several interesting features, including an eclipse minimum 0.02P before that of the continuum, low flux levels just before eclipse ingress and a shoulder during eclipse egress (between 1.1P and 1.15P). The latter might suggest the emergence of an emitting region--possibly the accretion stream-- during the eclipse egress that was otherwise obscured. The apparent lack of a hot spot during our observations might be explained by the presence of solar-type magnetic cycles in the secondary star, causing the mass transfer rate of the accretion stream to decrease and its impact with the disk to be less energetic. Radial velocities of ˜ ±140 Km s-1 derived from the wings of the Hα profiles are consistent with the orbital motion of the white dwarf primary as suggested in the literature [1]. Instead, the peaks of the emission line seem to be formed by at least three components which, though undergoing partial eclipse, seem to change their relative intensities rather than the wavelength, as if they were emitted by regions that do not follow the orbital motion of the primary. This behavior is not obvious within the standard model of Cataclysmic Variables. This work has been supported by NSF REU site grant AST 0097356 (University of Wyoming).

  18. Time-resolved spectroscopy and photometry of the dwarf nova FS Aurigae in quiescence

    NASA Astrophysics Data System (ADS)

    Neustroev, V. V.

    2002-02-01

    We present results of non-simultaneous time-resolved photometric and spectroscopic observations of the little-studied dwarf nova FS Aur in quiescence. The spectrum of FS Aur shows strong and broad emission lines of hydrogen and He I, and of weaker He II lambda4686 and C III/N III blend, similar to other quiescent dwarf novae. All emission lines are single-peaked, however their form varies with orbital phase. Absorption lines from a late-type secondary are not detected. From the radial velocity measurements of the hydrogen lines Hβ and Hγ we determined a most probable orbital period P=0.059 deg +/- 0.002 deg. This period agrees well with the 0.0595 deg +/- 0.0001 deg estimate by Thorstensen et al. (1996). On the other hand, the period of photometric modulations is longer than the spectroscopic period and can be estimated as 3 hours. Longer time coverage during a single night is needed to resolve this problem. Using the semi-amplitude of the radial velocities, obtained from measurements of hydrogen and helium lines, and some empirical and theoretical relations we limited the basic parameters of the system: a mass ratio q >= 0.22, a primary mass M1=0.34-0.46 Msun, a secondary mass M2 <= 0.1 Msun, and an inclination angle i=51deg-65deg. Doppler tomography has shown at least two bright regions in the accretion disk of FS Aur. The first, brighter spot is located at phase about 0.6. The second spot is located opposite the first one and occupies an extensive area at phases about 0.85-1.15. Based on observations made at the Special Astrophysical Observatory, Nizhnij Arkhyz, Russia.

  19. Femtosecond time-resolved spectroscopy of phonon dynamics in organic molecular and ferroelectric crystals

    SciTech Connect

    Wiederrecht, G.P.

    1992-01-01

    The ultrafast time-resolved technique of impulsive stimulated Raman scattering (ISRS) is utilized to probe and manipulate low frequency phonons related to structural and chemical change in the solid state. The soft modes in the ferroelectric crystals KNbO[sub 3] and BaTiO[sub 3] are impulsively excited by ultrashort laser pulses and their time dependence accurately characterized as a function of temperature. In both crystals, the data show only the presence of the heavily damped soft mode and no relaxational modes of the same symmetry. Quantitative comparisons to other works are made and strong support for the eight site' model is found. Previously observed anomalous polariton dynamics in the related material LiTaO[sub 3] are also studied and explained through ISRS. The wavevector dependent appearance of a weak relaxational mode is observed and a quantitative explanation of the excess damping rate of the polariton is made. The advantages of ISRS over conventional Raman scattering techniques are illustrated. Novel femtoosecond pulse shaping techniques are utilized in conjunction with ISRS in the organic molecular crystal [alpha] perylene to demonstrate selective excitation of a desired lattice mode. By resonantly driving a particular phonon with a train of pulses spaced to match its vibrational period, mode selectively is achieved because other modes rapidly become out of phase with the excitation force. Multiple pulse experiments in LiTaO[sub 3], which allows for a far larger amount of energy to be deposited into lattice modes than [alpha]-perylene, are also discussed and explained in terms of the differing electronic responses of the two materials to the ultrashort pulses. The experiments have important consequences for selecting and amplifying the vibrational amplitudes of modes believed to be related to chemical and structural change.

  20. Time-resolved visible spectroscopy of laser-produced lithium plasmas

    SciTech Connect

    Bailey, J.; Tisone, G.C.; Hurst, M.J.; Morrison, R.L.; Bieg, K.W.

    1988-08-01

    We have measured time-resolved visible spectra emitted from a plasma formed when the output from a dye laser irradiates solid lithium. Such a plasma has potential as a source of lithium ions for ion-driven inertial confinement fusion, and it also provides a useful source for developing diagnostics. The laser delivered 0.5 J onto a 2--7-mm-diam spot, with a 900-ns pulse length. Experiments were performed with the wavelength tuned to the Li I 2s--2p resonance line at 6708 A and off resonance at 6728 A. The target was a 500--1000-A-thick Li film, vacuum evaporated in situ onto a substrate. The light from the plasma was coupled into the entrance slit of a 1-m Czerny--Turner spectrograph, and the output from the spectrograph was focused onto the input slit of a streak camera. The electron density was obtained from Stark-broadened widths of Li I 2p--4d, 2p--5d, and 2p--4s, and H I 2p--4d. An irradiance of 2 x 10/sup 6/ W/cm/sup 2/ at 6708 A resulted in a peak electron density of 3.9 x 10/sup 17/ cm/sup -3/. The density decreased at lower irradiance, with an intensity threshold of 5 x 10/sup 5/ W/cm/sup 2/ for producing an ionized plasma. The threshold for producing a plasma was higher with the laser tuned off resonance, although high-density lithium plasmas could still be formed at relatively low laser irradiance.

  1. Time-resolved visible spectroscopy of laser-produced lithium plasmas

    SciTech Connect

    Bailey, J.; Tisone, G.C.; Hurst, M.J.; Morrison, R.L.; Bieg, K.W.

    1988-01-01

    We have measured time-resolved visible spectra emitted from a plasma formed when the output from a dye laser irradiates solid lithium. Such a plasma has potential as a source of lithium ions for ion-driven inertial confiement fusion, and it also provides a useful source for developing diagnostics. The laser delivered 0.5 Joules onto a 2-7 mm diameter spot, with a 900-ns pulse length. Experiments were performed with the wavelength tuned to the Li I 2s-2p resonance line at 6708 )angstrom) and off-resonance at 6728 )angstrom). The target was a 500 to 1000 )angstrom) thick Li film, vacuum evaporated in situ onto a substrate. The light from the plasma was coupled into the entrance slit of a 1-m Czerny-Turner spctrometer, and the output from the spectrometer was focused onto the input slit of a steak camera. The electron density was obtained from Stark broadened widths of Li I 2p-4d, 2p-5d, 2p-4s, and H I 2p-4d. An irradiance of 2 x 10/sup 6/ wcm/sup 2/ at 6708)angstrom) resulted in a peak electron density of 3.9 x 10/sup 17/ cm/sup )minus/3). The density decreased at lower irradiance, with an intensity threshold of 5 x 10/sup 5/ Wcm/sup 2/ for producing an ionized plasma. The threshold for producing a plasma was higher with the laser tuned off resonance, although high density lithium plasmas could still be formed at relatively lower laser irradiance. 6 refs., 4 figs

  2. Time-resolved in situ measurement of mitochondrial malfunction by energy transfer spectroscopy

    NASA Astrophysics Data System (ADS)

    Schneckenburger, Herbert; Sailer, Reinhard; Strauss, Wolfgang S.; Lyttek, Marco; Stock, Karl; Zipfl, Peter

    2000-10-01

    To establish optical in situ detection of mitochondrial malfunction, nonradiative energy transfer from the coenzyme NADH to the mitochondrial marker rhodamine 123 (R123) was examined. Dual excitation of R123 via energy transfer from excited NADH molecules as well as by direct absorption of light results in two fluorescence signals whose ratio is a measure of mitochondrial NADH. A screening system was developed in which these signals are detected simultaneously using a time-gated (nanosecond) technique for energy transfer measurements and a frequency selective technique for direct excitation and fluorescence monitoring of R123. Optical and electronic components of the apparatus are described, and results obtained from cultivated endothelial cells are reported. The ratio of fluorescence intensities excited in the near ultraviolet and blue-green spectral ranges increased by a factor 1.5 or 1.35 after inhibition of the mitochondrial respiratory chain by rotenone at cytotoxic or noncytotoxic concentrations, respectively. Concomitantly the amount of mitochondrial NADH increased. Excellent linearity between the number of cells incubated with R123 and fluorescence intensity was found in suspension.

  3. Time-Resolved Spectroscopy With A Narrow-Band Pulsed Dye Laser At High Irradiances

    NASA Astrophysics Data System (ADS)

    van Bergen, A. R.; Hollander, Tj.; Alkemade, C. T.

    1985-03-01

    We measured the fluorescence spectrum of the Na-D lines in a sodium vapour cell filled with Ar gas, excited by an intense, nearly monochromatic laser near resonance. In this case the theory (dressed-atom model) predicts a line splitting dependent on the laser intensity.

  4. Time-resolved autofluorescence spectroscopy of the bronchial mucosa for the detection of early cancer: clinical results

    NASA Astrophysics Data System (ADS)

    Glanzmann, Thomas M.; Uehlinger, Pascal; Ballini, Jean-Pierre; Radu, Alexandre; Gabrecht, Tanja; Monnier, Philippe; van den Bergh, Hubert; Wagnieres, Georges A.

    2001-10-01

    Time-resolved measurements of endogenous tissue autofluorescence were carried out on the bronchial mucosa of 18 patients during endoscopy by the means of a optical fibre-based spectrometer. The objective was to assess the fluorescence lifetime as a new contrast parameter between normal and malignant tissue and to explain the origin of a previously observed contrast in fluorescence intensity. The intra- and interpatient variation of tissue autofluorescence intensity and decay on normal tissue was determined with the outcome that a strong fluctuation in autofluorescence intensity but not in lifetime was observed on the normal tissue. Preliminary results were obtained by comparing fluorescence decays on normal mucosa and dysplasia/carcinoma in situ. No significant change in fluorescence decay nor in spectrum between 510 and 650 nm was found. Measurements in parallel with an endoscopic autofluorescence imaging device, on the other hand, indicated a contrast in intensity and spectrum on the same lesions. This suggests that the spectral contrast might be due to an enhanced blood concentration in deeper lying layers of the lesion the optical fibre-based contact measurements are less sensitive to. The difference in intensity might be due to a lower concentration in fluorophores or to the thickening of the epithelium in the neoplastic mucous membrane. However, no indication for fluorescence quenching in the upper layers of the mucous membrane as the reason for the reduced fluorescence intensity was found. The fluorescence decays showed a quite stable behaviour with three decay times of 6.9 ns, 2.0 ns and 0.2 ns in the spectral range between 430 and 680 nm. This can be an indication that there is one dominant fluorophore involved, the calculated decay times suggest that it might be elastin. However, a slight spectral dependence of the fluorescence decays let presume that there is a contribution from other fluorophores, probably flavins and NADH.

  5. Quantitative measurement of optical parameters in normal breasts using time-resolved spectroscopy: in vivo results of 30 Japanese women

    NASA Astrophysics Data System (ADS)

    Suzuki, Kazunori; Yamashita, Yutaka; Ohta, Kazuyoshi; Kaneko, Masao; Yoshida, Masayuki; Chance, Britton

    1996-07-01

    Previous investigation has proved time-resolved spectroscopy to be applicable to measurement of optical parameters in the human breast. To increase knowledge of these properties in vivo, the optical parameters of healthy breasts were measured using time-resolved reflectance spectroscopy. A time-correlated single-photon counting method was used to obtain time-response curves for the breasts of 30 Japanese women. Values of (mu) a and (mu) s$' were analyzed by fitting the curves to the diffusion equation. The relationships of optical parameters to age, body mass index, thickness of the breast, number of pregnancies, and menstrual status were examined. The (mu) a and (mu) s' ranged from 0.0024 to 0.0078/mm and from 0.63 to 1.08/mm, respectively. The values of (mu) a and (mu) s' showed a high correlation with properties may be strongly influenced by changes in tissue components related to aging, menstrual status, and so on. This optical information will contribute to the investigation of photon migration in the human breast.

  6. Rate constant of exciton quenching of Ir(ppy)3 with hole measured by time-resolved luminescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Oyama, Shiho; Sakai, Heisuke; Murata, Hideyuki

    2016-03-01

    We observed the quenching of tris(2-phenylpyridinato)iridium(III) [Ir(ppy)3] excitons by polarons (holes or electrons) by time-resolved photoluminescence (PL) spectroscopy to clarify the dynamics of the triplet-polaron quenching of excitons. We employed a hole-only device (HOD) and an electron-only device (EOD), where the emitting layer consists of Ir(ppy)3 doped in 4,4‧-bis(carbazol-9-yl)biphenyl. Time-resolved PL spectroscopy of the EOD and HOD were measured under a constant current density. The results showed that the excitons of Ir(ppy)3 were significantly quenched only by holes. The PL decay curves of HOD were well fitted by the biexponential function, where lifetimes (τ1 and τ2) remain unchanged but the coefficient of each exponential term depends on hole current density. From the results, we proposed a model of exciton quenching where the exciton-hole quenching area expands with increasing hole current density. On the basis of the model, the triplet-polaron quenching rate constant Kq was determined.

  7. Probing reaction dynamics of transition-metal complexes in solution via time-resolved soft x-ray spectroscopy

    SciTech Connect

    Huse, N.; Kim, T.-K.; Khalil, M.; Jamula, L.; McCusker, J.K.; Schoenlein, R.W.

    2008-08-01

    We report the first time-resolved soft x-ray measurements of solvated transition-metal complexes. L-edge spectroscopy directly probes dynamic changes in ligand-field splitting of 3d orbitals associated with the spin transition, and mediated by changes in ligand-bonding. We report the first time-resolved soft x-ray spectroscopy of solution-phase molecular dynamics. Changes in ligand-field splitting and spin-state populations in 3d orbitals of the Fe{sup II} complex are directly probed via transient absorption changes of the Fe L{sub 2} and L{sub 3} edges following photo-induced metal-to-ligand charge transfer. With the emergence of high-flux ultrafast soft x-ray sources, details on interplay between atomic structure, electronic states, and spin contributions will be revealed. Our experimental approach opens the door to femtosecond soft x-ray investigations of liquid phase chemistry that have previously been inaccessible.

  8. Exciton dynamics in conjugated polymer photovoltaics: Steady-state and time-resolved optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Chasteen, Stephanie V.

    The performance of organic photovoltaics is severely limited by poor exciton dissociation and charge transport due in part to high rates of exciton recombination and low charge mobilities in polymers. This challenge can be partially overcome through the use of blended and layered heterojunctions. Such morphologies offer multiple exciton dissociation sites and separate charge pathways, thus limiting exciton recombination, and allowing for thicker, more absorbing, polymer films. I have performed photovoltaic device characterization and time-resolved and steady-state photoluminescence on a variety of donor-acceptor heterojunction. I have used these methods to understand excited state dynamics and how they affect device performance. As hole-transporters I use a derivative of poly-phenylene-vinylene (M3EH-PPV) and poly-3-hexylthiophene (P3HT). As electron-transporters I use the metal oxide titanium dioxide (TiO2), the electron-transporter CN-PPV, and a fullerene derivative (PCBM). These materials are layered and blended together to form donor-acceptor heterojunctions. All heterojunctions result in enhanced device performance, and 1:4 M3EH-PPV:PCBM resulted in the highest efficiencies. M3EH-PPV emission is characterized by single-chain excitations, and the decay is dominated by short components of 0.20 and 0.45 ns. CN-ether-PPV is dominated by interchain excited state species---ie., excimers---with a decay time of 14.0 ns. The broken conjugation imposed by the ether group affect the excited state, resulting in an excited state species that is particularly vulnerable to quenching. This has important ramifications for material design. Hole-transporting polymers blended and layered with CN-ether-PPV have high currents (Jsc up to 3.3 mA/cm2) and good quenching relative to CN-ether-PPV (˜90%) due to charge separation and generation, respectively. Hole-transporters blended with PCBM result in efficient devices (Jsc up to 14 mA/cm2) due to rapid charge transfer and the existence of charge percolation pathways caused by the presence of aggregates of PCBM. The size of the aggregates affects charge transport, and is highly dependent upon film processing and blend ratio. The best device performance does not necessarily correlate with the excited state lifetime, however. Morphological differences, such as charge pathways that enable efficient charge transport, often outweigh the effect of charge transfer. Suggestions for improvement of nanoscale morphology are given.

  9. Hydrogen-bond lifetime measured by time-resolved 2D-IR spectroscopy: N-methylacetamide in methanol

    NASA Astrophysics Data System (ADS)

    Woutersen, S.; Mu, Y.; Stock, G.; Hamm, P.

    2001-05-01

    2D vibrational spectroscopy is applied to investigate the equilibrium dynamics of hydrogen bonding of N-methylacetamide (NMA) dissolved in methanol- d4. For this particular solute-solvent system, roughly equal populations are found for two conformers of the solute-solvent complex, one of which forms a hydrogen bond from the CO group of NMA to the surrounding solvent, and one of which does not. Using time-resolved 2D-IR spectroscopy on the amide I band of NMA, the exchange between both conformers is resolved. Equilibration of each conformer is completed after 4.5 ps, while the formation and breaking of the hydrogen bond occurs on a slower, 10-15 ps time scale. This interpretation is supported by classical molecular-dynamics simulations of NMA in methanol. The calculations predict a 64% population of the hydrogen-bonded conformer and an average hydrogen-bond lifetime of ≈12 ps.

  10. Femtosecond Time-Resolved Single-Molecule Spectroscopy: Towards Probing Ultrafast Dynamics at Single Molecular Level Under Ambient Conditions

    NASA Astrophysics Data System (ADS)

    Fujiwara, Takashige; Lu, H. Peter

    2015-05-01

    The structure-function relationship is an important fundamental concept in the molecular sciences. Recent applications of ultrafast spectroscopy to single-molecular level provide a direct measurement of the inhomogeneity with respect to the electronic and chemical properties of the molecules in the microenvironment. In this poster, we present detailed experimental setups for the single color time-resolved pump-probe single molecule spectroscopy that we have developed in our laboratory. We demonstrated detections of the excited-state dynamics of electron transfer in interactions of dye molecules with nanoparticles at ambient conditions. Insights obtained and applications to probe single molecular orientations will be discussed. Center for Photochemical Sciences and Department of Chemistry.

  11. Quantitative Time-Resolved Fluorescence Imaging of Androgen Receptor and Prostate-Specific Antigen in Prostate Tissue Sections.

    PubMed

    Krzyzanowska, Agnieszka; Lippolis, Giuseppe; Helczynski, Leszek; Anand, Aseem; Peltola, Mari; Pettersson, Kim; Lilja, Hans; Bjartell, Anders

    2016-05-01

    Androgen receptor (AR) and prostate-specific antigen (PSA) are expressed in the prostate and are involved in prostate cancer (PCa). The aim of this study was to develop reliable protocols for reproducible quantification of AR and PSA in benign and malignant prostate tissue using time-resolved fluorescence (TRF) imaging techniques. AR and PSA were detected with TRF in tissue microarrays from 91 PCa patients. p63/ alpha-methylacyl-CoA racemase (AMACR) staining on consecutive sections was used to categorize tissue areas as benign or cancerous. Automated image analysis was used to quantify staining intensity. AR intensity was significantly higher in AMACR+ and lower in AMACR- cancer areas as compared with benign epithelium. The PSA intensity was significantly lower in cancer areas, particularly in AMACR- glands. The AR/PSA ratio varied significantly in the AMACR+ tumor cells as compared with benign glands. There was a trend of more rapid disease progression in patients with higher AR/PSA ratios in the AMACR- areas. This study demonstrates the feasibility of developing reproducible protocols for TRF imaging and automated image analysis to study the expression of AR and PSA in benign and malignant prostate. It also highlighted the differences in AR and PSA protein expression within AMACR- and AMACR+ cancer regions. PMID:27026295

  12. Europium Nanospheres-Based Time-Resolved Fluorescence for Rapid and Ultrasensitive Determination of Total Aflatoxin in Feed.

    PubMed

    Wang, Du; Zhang, Zhaowei; Li, Peiwu; Zhang, Qi; Ding, Xiaoxia; Zhang, Wen

    2015-12-01

    Immunochromatographic (IC) assays are considered suitable diagnostic tools for the determination of mycotoxins. A europium nanospheres-based time-resolved fluorescence immunoassay (Eu-Nano-TRFIA), based on a monoclonal antibody and a portable TRFIA reader, was developed to determine total aflatoxin (including aflatoxins B1, B2, G1, and G2) levels in feed samples. Under optimized conditions, the Eu-Nano-TRFIA method detected total aflatoxin within 12 min. It showed good linearity (R(2) > 0.985), LOD of 0.16 μg/kg, a wide dynamic range of 0.48-30.0 μg/kg, recovery rates of 83.9-113.9%, and coefficients of variation (CVs) of 3.5-8.8%. In the 397 samples from company and livestock farms throughout China, the detection rate was 78.3%, concentrations were 0.50-145.30 μg/kg, the highest total aflatoxin content was found in cottonseed meal, and corn was found to be the most commonly contaminated feed. This method could be a powerful alternative for the rapid and ultrasensitive determination of total aflatoxin in quality control and meet the required Chinese maximum residue limits. PMID:26565941

  13. A multicolor time-resolved fluorescence aptasensor for the simultaneous detection of multiplex Staphylococcus aureus enterotoxins in the milk.

    PubMed

    Huang, Yukun; Zhang, Hui; Chen, Xiujuan; Wang, Xiaole; Duan, Nuo; Wu, Shijia; Xu, Baocai; Wang, Zhouping

    2015-12-15

    Food safety is one of the most important public health issues worldwide. Foodborne illnesses caused by Staphylococcus aureus enterotoxins (SEs) commonly occur, affecting both developing and developed countries. In this study, multicolor lanthanide-doped time-resolved fluorescence nanoparticles labeled with aptamers were used as bioprobes, and graphene oxide (GO) was employed as a resonance energy acceptor. Based on the "turn down" strategy, the simultaneous detection of multiplex SEs was realized in a homogeneous solution. Under the optimal conditions, the developed method exhibited high sensitivity and selectivity to three serological types of enterotoxins, including type A, B, C1, with limits of detection below 1 ng mL(-1). The application of this bioassay in milk analysis with no sample dilution was also investigated, and the results of recovery rates covered from 92.76% to 114.58%, revealing that the developed method was accurate. Therefore, this detection aptasnesor can be a good candidate for multiplex analysis and screening with simple and effective operations. PMID:26141103

  14. Time-Resolved Areal-Density Measurements with Proton Spectroscopy in Spherical Implosions

    NASA Astrophysics Data System (ADS)

    Smalyuk, V. A.; Radha, P. B.; Delettrez, J. A.; Glebov, V. Yu.; Goncharov, V. N.; Meyerhofer, D. D.; Regan, S. P.; Roberts, S.; Sangster, T. C.; Soures, J. M.; Stoeckl, C.; Frenje, J. A.; Li, C. K.; Petrasso, R. D.; Séguin, F. H.

    2003-04-01

    The temporal history of the target areal-density near peak compression of direct-drive spherical target implosions has been inferred with 14.7-MeV deuterium-helium-3 D3He proton spectroscopy of the 60-beam, 30-kJ UV OMEGA laser system. The target areal-density grows by a factor of ˜8 during the time of neutron-production (˜400 ps) before reaching 123±16 mg/cm2 at peak compression in the implosion of a 950-μm-diam, 20-μm-thick plastic CH capsule filled with 4atm of D3He fuel.

  15. Space- and time-resolved coherent anti-Stokes Raman spectroscopy for combustion diagnostics.

    PubMed

    Marko, K A; Rimai, L

    1979-07-01

    The technique of coherent anti-Stokes Raman spectroscopy can be used to obtain spectra in or near the reaction zone of combustion systems with spatial resolution on the order of 0.1 mm and time resolution on the order of 10 nsec. The latter is achieved by recording the entire spectrum generated during a single laser pulse by a broadband Stokes beam, simultaneously, on a vidicon, whereas the former is achieved by a simplified variant of the crossedbeam phase-matching technique taking advantage of the radiation intensity distribution from a pump laser using an unstable resonator structure. PMID:19687852

  16. The H + OCS hot atom reaction - CO state distributions and translational energy from time-resolved infrared absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Nickolaisen, Scott L.; Cartland, Harry E.

    1993-01-01

    Time-resolved infrared diode laser spectroscopy has been used to probe CO internal and translational excitation from the reaction of hot H atoms with OCS. Product distributions should be strongly biased toward the maximum 1.4 eV collision energy obtained from 278 nm pulsed photolysis of HI. Rotations and vibrations are both colder than predicted by statistical density of states theory, as evidenced by large positive surprisal parameters. The bias against rotation is stronger than that against vibration, with measurable population as high as v = 4. The average CO internal excitation is 1920/cm, accounting for only 13 percent of the available energy. Of the energy balance, time-resolved sub-Doppler line shape measurements show that more than 38 percent appears as relative translation of the separating CO and SH fragments. Studies of the relaxation kinetics indicate that some rotational energy transfer occurs on the time scale of our measurements, but the distributions do not relax sufficiently to alter our conclusions. Vibrational distributions are nascent, though vibrational relaxation of excited CO is unusually fast in the OCS bath, with rates approaching 3 percent of gas kinetic for v = 1.

  17. Time-Resolved Broadband Cavity-Enhanced Absorption Spectroscopy behind Shock Waves.

    PubMed

    Matsugi, Akira; Shiina, Hiroumi; Oguchi, Tatsuo; Takahashi, Kazuo

    2016-04-01

    A fast and sensitive broadband absorption technique for measurements of high-temperature chemical kinetics and spectroscopy has been developed by applying broadband cavity-enhanced absorption spectroscopy (BBCEAS) in a shock tube. The developed method has effective absorption path lengths of 60-200 cm, or cavity enhancement factors of 12-40, over a wavelength range of 280-420 nm, and is capable of simultaneously recording absorption time profiles over an ∼32 nm spectral bandpass in a single experiment with temporal and spectral resolutions of 5 μs and 2 nm, respectively. The accuracy of the kinetic and spectroscopic measurements was examined by investigating high-temperature reactions and absorption spectra of formaldehyde behind reflected shock waves using 1,3,5-trioxane as a precursor. The rate constants obtained for the thermal decomposition reactions of 1,3,5-trioxane (to three formaldehyde molecules) and formaldehyde (to HCO + H) agreed well with the literature data. High-temperature absorption cross sections of formaldehyde between 280 and 410 nm have been determined at the post-reflected-shock temperatures of 955, 1265, and 1708 K. The results demonstrate the applicability of the BBCEAS technique to time- and wavelength-resolved sensitive absorption measurements at high temperatures. PMID:26990289

  18. Photosynthetic Dioxygen Formation Monitored by Time-Resolved X-Ray Spectroscopy

    NASA Astrophysics Data System (ADS)

    Haumann, Michael; Dau, Holger

    2007-02-01

    Photosynthetic water oxidation provides the dioxygen of the atmosphere. Its partial reactions proceed at a Mn4Ca complex bound to photosystem II of plants and cyanobacteria. Understanding the mechanism of this biological oxidation of water molecules to O2 is one of the major challenges in life sciences. We have developed and employed X-ray absorption Spectroscopy (XAS) techniques facilitating measurements on metalloenzymes at room temperature. By these techniques, we were able to resolve structural changes at the Mn ions, to follow oxidation-state changes in the microseconds time domain, and to detect a novel and likely crucial intermediate in the oxygen-evolving step of the catalytic cycle of the Mn complex. Based on the obtained results, we replace the classic S-state model of the catalytic cycle by a more elaborated reaction scheme which solves apparent inconsistencies of earlier models, explains a large body of experimental results, and provides a fresh twist in photosynthesis research.

  19. Real-Time Probing of Electron Dynamics Using Attosecond Time-Resolved Spectroscopy.

    PubMed

    Ramasesha, Krupa; Leone, Stephen R; Neumark, Daniel M

    2016-05-27

    Attosecond science has paved the way for direct probing of electron dynamics in gases and solids. This review provides an overview of recent attosecond measurements, focusing on the wealth of knowledge obtained by the application of isolated attosecond pulses in studying dynamics in gases and solid-state systems. Attosecond photoelectron and photoion measurements in atoms reveal strong-field tunneling ionization and a delay in the photoemission from different electronic states. These measurements applied to molecules have shed light on ultrafast intramolecular charge migration. Similar approaches are used to understand photoemission processes from core and delocalized electronic states in metal surfaces. Attosecond transient absorption spectroscopy is used to follow the real-time motion of valence electrons and to measure the lifetimes of autoionizing channels in atoms. In solids, it provides the first measurements of bulk electron dynamics, revealing important phenomena such as the timescales governing the switching from an insulator to a metallic state and carrier-carrier interactions. PMID:26980312

  20. Time-resolved spectroscopy measurements of hydrogen-alpha, -beta, and -gamma emissions

    SciTech Connect

    Parigger, Christian G.; Dackman, Matthew; Hornkohl, James O

    2008-11-01

    Hydrogen emission spectroscopy results are reported following laser-induced optical breakdown with infrared Nd:YAG laser radiation focused into a pulsed methane flow. Measurements of Stark-broadened atomic hydrogen-alpha, -beta, and -gamma lines show electron number densities of 0.3 to 4x10{sup 17} cm{sup -3} for time delays of 2.1 to 0.4 {mu}s after laser-induced optical breakdown. In methane flow, recombination molecular spectra of the {delta}{nu}=+2 progression of the C2 Swan system are discernable in the H{beta} and H{gamma} plasma emissions within the first few microseconds. The recorded atomic spectra indicate the occurrence of hydrogen self-absorption for pulsed CH4 flow pressures of 2.7x10{sup 5} Pa (25 psig) and 6.5x10{sup 5} Pa (80 psig)

  1. Time resolved imaging of laser induced ablation spectroscopy (LIAS) in TEXTOR and comparison with modeling

    NASA Astrophysics Data System (ADS)

    Gierse, N.; Tokar, M. Z.; Brezinsek, S.; Giesen, T. F.; Hubeny, M.; Huber, A.; Philipps, V.; Pospieszczyk, A.; Sergienko, G.; Wegner, J.; Xiao, Q.; Samm, U.; Linsmeier, Ch; the TEXTOR Team

    2016-02-01

    Laser based methods are investigated as in situ diagnostic for plasma facing materials (PFMs) in magnetic fusion research to study PFM composition and retention. In laser induced ablation spectroscopy (LIAS) the wall material is ablated by a laser beam. The released material enters the edge plasma region of a fusion experiment and the resulting optical emission is observed. To conclude from the observed photons to the number of ablated atoms, a detailed knowledge of the velocity distribution of the ablated material is required. In this work the LIAS emission in discharges at TEXTOR was studied using an Ametek Phantom v711 camera. In this paper a method is developed to conclude from the observed emission the velocity distribution of the ablated species. The obtained velocity distribution is used for our numerical LIAS model, demonstrating good agreement with our experimental observations. Implications are discussed.

  2. Rotational and Translational Dynamics of Rhodamine 6G in a Pyrrolidinium Ionic Liquid: A Combined Time-Resolved Fluorescence Anisotropy Decay and NMR Study

    SciTech Connect

    Guo, Jianchang; Han, Kee Sung; Mahurin, Shannon Mark; Baker, Gary A; Hillesheim, Patrick C; Dai, Sheng; Hagaman, Edward {Ed} W; Shaw, Robert W

    2012-01-01

    NMR spectroscopy and time-resolved fluorescence anisotropy decay (TRFAD) are two of the most commonly used methods to study solute-solvent interactions. However, only a few studies have been reported to date using a combined NMR and TRFAD approach to systematically investigate the overall picture of diffusional and rotational dynamics of both the solute and solvent. In this paper, we combined NMR and TRFAD to probe fluorescent rhodamine dyes in a pyrrolidinium-based room temperature ionic liquid (RTIL), an emergent environmentally-friendly solvent type used in several energy-related applications. A specific interaction of the R6G cation and [Tf2N]- anion was identified, resulting in near-stick boundary condition rotation of R6G in this RTIL. The diffusional rates of the R6G solute and [C4mpyr][Tf2N] solvent derived from 1H NMR suggest the rates are proportional to their corresponding hydrodynamic radii. The 1H and 13C NMR studies of self-rotational dynamics of [C4mpyr][Tf2N] showed that the self-rotational correlation time of [C4mpyr]+ is 47 2 ps at 300 K. At the same temperature, we find that the correlation time for N-CH3 rotation in [C4mpyr]+ is 77 2 ps, comparable to overall molecular reorientation. This slow motion is attributed to properties of the cation structure.

  3. Time-Resolved Twisting Dynamics in a Porphyrin Dimer Characterized by Two-Dimensional Electronic Spectroscopy.

    PubMed

    Camargo, Franco V A; Anderson, Harry L; Meech, Stephen R; Heisler, Ismael A

    2015-11-19

    Molecular conformational changes in electronic excited states play a key role in numerous light-activated processes. In the case of porphyrin oligomers intramolecular twisting influences energy and charge transport dynamics. Here we address the twisting reaction in both ground and excited states in a model porphyrin dimer, employing two-dimensional electronic spectroscopy (2D ES). By spreading the information over excitation and detection frequencies, cross-peaks reveal the twisting reaction in both the ground and excited states unambiguously and distinctly from other dynamics. A quasi-barrierless planarization reaction is observed in the excited state on a tens of picoseconds time scale. This is accompanied by a spectral narrowing, indicative of a reduction in conformational disorder. The reverse reaction is suppressed in the excited state due to a steep activation energy barrier. However, in the ground state the barrier is within the thermal energy distribution, and therefore contributions from reverse and forward reactions could be observed on the subnanosecond time scale. Crucially 2D ES enables simultaneous assessment of ground and excited state reactions through analysis of different spectral regions on the 2D spectral maps. PMID:26496469

  4. Structural dynamics of membrane proteins - time-resolved and surface-enhanced IR spectroscopy

    NASA Astrophysics Data System (ADS)

    Heberle, Joachim

    2013-03-01

    Membrane proteins are the target of more than 50% of all drugs and are encoded by about 30% of the human genome. Electrophysiological techniques, like patch-clamp, unravelled many functional aspects of membrane proteins but suffer from structural sensitivity. We have developed Surface Enhanced Infrared Difference Absorption Spectroscopy (SEIDAS) to probe potential-induced structural changes of a protein on the level of a monolayer. A novel concept is introduced to incorporate membrane proteins into solid supported lipid bilayers in an orientated manner via the affinity of the His-tag to the Ni-NTA terminated gold surface. General applicability of the methodological approach is shown by tethering photosystem II to the gold surface. In conjunction with hydrogenase, the basis is set towards a biomimetic system for hydrogen production. Recently, we succeeded to record IR difference spectra of a monolayer of sensory rhodopsin II under voltage-clamp conditions. This approach opens an avenue towards mechanistic studies of voltage-gated ion channels with unprecedented structural and temporal sensitivity. Initial vibrational studies on the novel light-gated channelrhodopsin-2 (ChR2) will be presented. ChR2 represents a versatile tool in the new field of optogenetics where physiological reactions are controlled by light.

  5. Direct Visualization of Excited-State Symmetry Breaking Using Ultrafast Time-Resolved Infrared Spectroscopy.

    PubMed

    Dereka, Bogdan; Rosspeintner, Arnulf; Li, Zhiquan; Liska, Robert; Vauthey, Eric

    2016-04-01

    Most symmetric quadrupolar molecules designed for two-photon absorption behave as dipolar molecules in the S1 electronic excited state. This is usually explained by a breakup of the symmetry in the excited state. However, the origin of this process and its dynamics are still not fully understood. Here, excited-state symmetry breaking in a quadrupolar molecule with a D-π-A-π-D motif, where D and A are electron donating and accepting units, is observed in real time using ultrafast transient infrared absorption spectroscopy. The nature of the relaxed S1 state was found to strongly depend on the solvent polarity: (1) in nonpolar solvents, it is symmetric and quadrupolar; (2) in weakly polar media, the quadrupolar state observed directly after excitation transforms to a symmetry broken S1 state with one arm bearing more excitation than the other; and (3) in highly polar solvents, the excited state evolves further to a purely dipolar S1 state with the excitation localized entirely on one arm. The time scales associated with the transitions between these states coincide with those of solvation dynamics, indicating that symmetry breaking is governed by solvent fluctuations. PMID:26986957

  6. A new angle into time-resolved photoacoustic spectroscopy: A layered prism cell increases experimental flexibility

    SciTech Connect

    Autrey, T.; Foster, N.S.; Klepzig, K.; Amonette, J.E.; Daschbach, J.L.

    1998-06-01

    A new pulsed photoacoustic calorimetry cell that uses transmission of light through a pair of dovetail prisms is discussed. The layered prism cell (LPC) combines the enhanced time-resolution capabilities of the {open_quotes}layered{close_quotes} front-face irradiation geometry with the zero-background and broadband flexibility of the classical cuvette geometry. This work provides a phenomenological description of photoinduced pressure changes to yield an analytical expression to calculate the magnitude of the photoinduced acoustic pressure wave in a series of solvents. The mechanical to electrical conversion efficiency for an ultrasonic transducer coupled to the LPC is presented to provide a comparison of the experimentally observed photoinduced acoustic signal amplitudes to the empirically calculated acoustic signal amplitudes. An analysis of the background signals due to absorption and electrostriction of the media provides insight into the issues of sensitivity and limitations of pulsed photoacoustic experiments. The LPC provides several benefits to increase the flexibility of the photoacoustic spectroscopy: (1) greater sensitivity, (2) enhanced time resolution, and (3) the ability to obtain kinetic data in complex solvent mixtures. Under optically dilute conditions in the layered cell geometry, the acoustic transient time, {tau}a, approaches zero because the photoinduced acoustic wave homogeneously expands against the walls of the photoacoustic cell. To demonstrate the unique capabilities of the LPC, rates of hydrogen abstraction by {ital tert}-butoxyl radical from solvent mixtures containing ethyl and methyl alcohol are presented. {copyright} {ital 1998 American Institute of Physics.} thinsp

  7. Five-dimensional optical instrumentation: combining polarimetry with time-resolved integral-field spectroscopy

    NASA Astrophysics Data System (ADS)

    Rodenhuis, M.; Snik, F.; van Harten, G.; Hoeijmakers, J.; Keller, C. U.

    2014-05-01

    We present implementations of optical instrumentation that records five dimensions of light: polarization state as a function of wavelength, two spatial dimensions, and time. We focus on the optimal integration of polarimetry within microlens-based integral-field spectroscopy. The polarimetric analyzer (or beam-splitter) and dispersing element could be implemented separately, but also amalgamated in the form of a polarization grating. We present optimizations for stacking the polarization-split spectra on a 2D detector. The polarimetric modulation can be performed in the temporal, the spatial or the spectral domain. Temporal modulation could be set up with achromatic optics conform the Stokes definition scheme, but a wide wavelength range generally demands a "polychromatic" modulation approach for which the modulation efficiency for all or some of the Stokes parameters is optimized at every wavelength. Spectral modulation (full-Stokes or optimized for linear polarization) yields instruments without any moving parts, for which all polarization information is obtained in one shot. We present first results from two polarimetric IFU instruments; the ExPo pIFU and LOUPE. The first is based on a rapid polychromatic modulator consisting of two FLCs and two fixed retarders, while the latter is based on spectral modulation for linear polarization. In addition to applications within astronomy and planetary science, we discuss remote-sensing applications for such instruments.

  8. Rebinding dynamics of NO to microperoxidase-8 probed by time-resolved vibrational spectroscopy.

    PubMed

    Lee, Taegon; Kim, Jooyoung; Park, Jaeheung; Pak, Youngshang; Kim, Hyojoon; Lim, Manho

    2016-02-21

    Femtosecond vibrational spectroscopy was used to probe the rebinding kinetics of NO to microperoxidase-8 (Mp), an ideal model system for the active site of ligand-binding heme proteins, including myoglobin and hemoglobin, after the photodeligation of MpNO in glycerol/water (G/W) solutions at 294 K. The geminate rebinding (GR) of NO to Mp in viscous solutions was highly efficient and ultrafast and negligibly dependent on the solution viscosity, which was adjusted by changing the glycerol content from 65% to 90% by volume in G/W mixtures. The kinetics of the GR of NO to Mp in viscous solutions was well represented by an exponential function with a time constant of ca. 11 ps. Although the kinetic traces of the GR of NO to Mp in solutions with three different viscosities (18, 81, and 252 cP) almost overlap, they show a slight difference early in the decay process. The kinetic traces were also described by the diffusion-controlled reaction theory with a Coulomb potential. Since the ligand is deligated in a neutral form, an ionic pair of NO(-) and Mp(+) may be produced before forming the Mp-NO bond by an electron transfer from Mp to NO as the deligated NO is sufficiently near to the Fe atom of Mp. The strong reactivity between NO and ferrous heme may arise from the Coulomb interaction between the reacting pair, which is consistent with the harpooning mechanism for NO binding to heme. PMID:26813691

  9. Time-resolved luminescence spectroscopy of self-trapped excitons in ladder type Br-bridged Pt complexes.

    PubMed

    Suemoto, T; Nakao, H; Nakajima, M; Kitagawa, H

    2011-06-14

    The out-of-phase and in-phase ladder type Br-bridged Pt complexes are investigated by time-resolved luminescence spectroscopy in pico- and femtosecond time regions. The observed luminescence spectra have peaks at 0.87 and 0.94 eV in out-of-phase and in-phase materials, respectively, and are assigned to self-trapped excitons. The wave-packet oscillations in self-trapped excitons (STE) are observed in both materials. The time-evolution curves are analyzed in terms of the secondary radiation theory of strongly coupled electron-phonon system. The period and dephasing time of oscillations as well as the lifetime and spectral shape of the STE luminescence are determined. The fast dephasing or cooling of the wave-packet motion observed in the in-phase type complex is ascribed to inter-chain interactions within the ladder. PMID:21682521

  10. Revealing the ultrafast charge carrier dynamics in organo metal halide perovskite solar cell materials using time resolved THz spectroscopy

    NASA Astrophysics Data System (ADS)

    Ponseca, C. S., Jr.; Sundström, V.

    2016-03-01

    Ultrafast charge carrier dynamics in organo metal halide perovskite has been probed using time resolved terahertz (THz) spectroscopy (TRTS). Current literature on its early time characteristics is unanimous: sub-ps charge carrier generation, highly mobile charges and very slow recombination rationalizing the exceptionally high power conversion efficiency for a solution processed solar cell material. Electron injection from MAPbI3 to nanoparticles (NP) of TiO2 is found to be sub-ps while Al2O3 NPs do not alter charge dynamics. Charge transfer to organic electrodes, Spiro-OMeTAD and PCBM, is sub-ps and few hundreds of ps respectively, which is influenced by the alignment of energy bands. It is surmised that minimizing defects/trap states is key in optimizing charge carrier extraction from these materials.

  11. Time Resolved Spectroscopy, High Sensitivity Power Spectrum & a Search for the X-Ray QPO in NGC 5548

    NASA Astrophysics Data System (ADS)

    Yaqoob, Tahir

    1999-09-01

    Controversy surrounds the EXOSAT discovery of a QPO (period ~500 s) in NGC 5548 due to the data being plagued by high background and instrumental systematics. If the NGC 5548 QPO is real, the implications for the physics of the X-ray emission mechanism and inner-most disk/black-hole system are enormous. AXAF provides the first opportunity to settle the issue, capable of yielding power spectra with unprecedented sensitivity, pushing the limit on finding new features. Using HETG/ACIS we will also perform time-resolved spectroscopy of the ionized absorption features and Fe-K emission line, search for energy-dependent time lags in the continuum, between the continuum and spectral features, and between the spectral features. These data will provide powerful constraints on models of AGN.

  12. Sol-to-Gel Transition in Fast Evaporating Systems Observed by in Situ Time-Resolved Infrared Spectroscopy.

    PubMed

    Innocenzi, Plinio; Malfatti, Luca; Carboni, Davide; Takahashi, Masahide

    2015-06-22

    The in situ observation of a sol-to-gel transition in fast evaporating systems is a challenging task and the lack of a suitable experimental design, which includes the chemistry and the analytical method, has limited the observations. We synthesise an acidic sol, employing only tetraethylorthosilicate, SiCl4 as catalyst and deuterated water; the absence of water added to the sol allows us to follow the absorption from the external environment and the evaporation of deuterated water. The time-resolved data, obtained by attenuated total reflection infrared spectroscopy on an evaporating droplet, enables us to identify four different stages during evaporation. They are linked to specific hydrolysis and condensation rates that affect the uptake of water from external environment. The second stage is characterized by a decrease in hydroxyl content, a fast rise of condensation rate and an almost stationary absorption of water. This stage has been associated with the sol-to-gel transition. PMID:25891296

  13. Hemodynamic Measurements of the Human Adult Head in Transmittance Mode by Near-Infrared Time-Resolved Spectroscopy.

    PubMed

    Suzuki, Hiroaki; Oda, Motoki; Ohmae, Etsuko; Suzuki, Toshihiko; Yamashita, Daisuke; Yoshimoto, Kenji; Homma, Shu; Yamashita, Yutaka

    2016-01-01

    Using a near-infrared time-resolved spectroscopy (TRS) system, we measured the human head in transmittance mode to obtain the optical properties and the hemodynamic changes of deep brain tissues in seven healthy adult volunteers during hyperventilation. For six out of seven volunteers, we obtained the optical signals with sufficient intensity within 10 sec. of sampling. We confirmed that it is possible to non-invasively measure the hemodynamic changes of the human head during hyperventilation, even in the transmittance measurements by the developed TRS system. These results showed that the level of deoxygenated hemoglobin was significantly increased, and the level of oxygenated and total hemoglobin and tissue oxygen saturation were also significantly decreased during hyperventilation. We expect that this TRS technique will be applied to clinical applications for measuring deep brain tissues and deep biological organs. PMID:26782238

  14. Time resolved diagnostics in CF4 / H2 plasmas by electron attachment mass spectrometry and optical emission spectroscopy.

    NASA Astrophysics Data System (ADS)

    Wagner, Hans-Erich; Meichsner, Juergen; Kroutilina, Valja; Lerch, Rene

    2000-10-01

    In the case of a parallel plate symmetrical 50 kHz low pressure discharge in CF4 - H2 mixtures (discharge current 10 - 40 mA, total pressure 10 - 30 Pa , hydrogen admixture 0 - 80 %, closed system) the main stable products (e.g. F_2, CF_4, C_2F_6, C_3F_8) of plasma chemical reactions have been time resolved investigated by the electron attachment mass spectrometry (EAMS), investigating them according their resonant electron attachment cross sections. The EAMS was realised by means of a HAL EQP 300 Hiden Analytical system, extended by the (-) RGA mode. The plasma chemical reaction kinetics is characterised by the time dependent consumption of molecular hydrogen and the production of higher molecular fluorocarbons. These measurements were completed by optical emission spectroscopy of electronic excited species (e.g. atomic fluorine, molecular hydrogen).

  15. Revealing the ultrafast charge carrier dynamics in organo metal halide perovskite solar cell materials using time resolved THz spectroscopy.

    PubMed

    Ponseca, C S; Sundström, V

    2016-03-17

    Ultrafast charge carrier dynamics in organo metal halide perovskite has been probed using time resolved terahertz (THz) spectroscopy (TRTS). Current literature on its early time characteristics is unanimous: sub-ps charge carrier generation, highly mobile charges and very slow recombination rationalizing the exceptionally high power conversion efficiency for a solution processed solar cell material. Electron injection from MAPbI3 to nanoparticles (NP) of TiO2 is found to be sub-ps while Al2O3 NPs do not alter charge dynamics. Charge transfer to organic electrodes, Spiro-OMeTAD and PCBM, is sub-ps and few hundreds of ps respectively, which is influenced by the alignment of energy bands. It is surmised that minimizing defects/trap states is key in optimizing charge carrier extraction from these materials. PMID:26763720

  16. Long-Lived Excited-State Dynamics of i-Motif Structures Probed by Time-Resolved Infrared Spectroscopy.

    PubMed

    Keane, Páraic M; Baptista, Frederico R; Gurung, Sarah P; Devereux, Stephen J; Sazanovich, Igor V; Towrie, Michael; Brazier, John A; Cardin, Christine J; Kelly, John M; Quinn, Susan J

    2016-05-01

    UV-generated excited states of cytosine (C) nucleobases are precursors to mutagenic photoproduct formation. The i-motif formed from C-rich sequences is known to exhibit high yields of long-lived excited states following UV absorption. Here the excited states of several i-motif structures have been characterized following 267 nm laser excitation using time-resolved infrared spectroscopy (TRIR). All structures possess a long-lived excited state of ∼300 ps and notably in some cases decays greater than 1 ns are observed. These unusually long-lived lifetimes are attributed to the interdigitated DNA structure which prevents direct base stacking overlap. PMID:26879336

  17. Excited-state dynamics of guanosine in aqueous solution revealed by time-resolved photoelectron spectroscopy: experiment and theory.

    PubMed

    Buchner, Franziska; Heggen, Berit; Ritze, Hans-Hermann; Thiel, Walter; Lbcke, Andrea

    2015-12-21

    Time-resolved photoelectron spectroscopy is performed on aqueous guanosine solution to study its excited-state relaxation dynamics. Experimental results are complemented by surface hopping dynamic simulations and evaluation of the excited-state ionization energy by Koopmans' theorem. Two alternative models for the relaxation dynamics are discussed. The experimentally observed excited-state lifetime is about 2.5 ps if the molecule is excited at 266 nm and about 1.1 ps if the molecule is excited at 238 nm. The experimental probe photon energy dependence of the photoelectron kinetic energy distribution suggests that the probe step is not vertical and involves a doubly-excited autoionizing state. PMID:26569639

  18. SIMULTANEOUS DETECTION OF ESCHERICHIA COLI 0157:H7 AND SALMONELLA TYPHIMURIUM IN FOODS USING IMMUNOMAGNETIC CAPTURE AND LANTHANIDE TIME-RESOLVED FLUORESCENCE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A time-resolved fluorescence procedure was developed to detect Escherichia coli O157:H7 and Salmonella typhimurium in ground meats. After a 4.5 hour enrichment period, streptavidin coated magnetic beads conjugated with biotin-labeled specific anti-bacteria antibodies were used to capture targeted ...

  19. SIMULTANEOUS DETECTION OF ESCHERICHIA COLI 0157:H7 AND SALMONELLA TYPHIMURIUM IN FOODS USING IMMUNOMAGNETIC CAPTURE AND LANTHANIDE TIME-RESOLVED FLUORESCENCE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A procedure, based on immunomagnetic capture and time-resolved fluorescence, was developed to detect Escherichia coli O157:H7 and Salmonella Typhimurium in ground meats and fresh sprouts. After a brief enrichment period, streptavidin coated magnetic beads conjugated with biotin-labeled specific ant...

  20. Ultrafast time-resolved absorption spectroscopy of geometric isomers of carotenoids

    NASA Astrophysics Data System (ADS)

    Niedzwiedzki, Dariusz M.; Sandberg, Daniel J.; Cong, Hong; Sandberg, Megan N.; Gibson, George N.; Birge, Robert R.; Frank, Harry A.

    2009-02-01

    The structures of a number of stereoisomers of carotenoids have been revealed in three-dimensional X-ray crystallographic investigations of pigment-protein complexes from photosynthetic organisms. Despite these structural elucidations, the reason for the presence of stereoisomers in these systems is not well understood. An important unresolved issue is whether the natural selection of geometric isomers of carotenoids in photosynthetic pigment-protein complexes is determined by the structure of the protein binding site or by the need for the organism to accomplish a specific physiological task. The association of cis isomers of a carotenoid with reaction centers and trans isomers of the same carotenoid with light-harvesting pigment-protein complexes has led to the hypothesis that the stereoisomers play distinctly different physiological roles. A systematic investigation of the photophysics and photochemistry of purified, stable geometric isomers of carotenoids is needed to understand if a relationship between stereochemistry and biological function exists. In this work we present a comparative study of the spectroscopy and excited state dynamics of cis and trans isomers of three different open-chain carotenoids in solution. The molecules are neurosporene ( n = 9), spheroidene ( n = 10), and spirilloxanthin ( n = 13), where n is the number of conjugated π-electron double bonds. The spectroscopic experiments were carried out on geometric isomers of the carotenoids purified by high performance liquid chromatography (HPLC) and then frozen to 77 K to inhibit isomerization. The spectral data taken at 77 K provide a high resolution view of the spectroscopic differences between geometric isomers. The kinetic data reveal that the lifetime of the lowest excited singlet state of a cis-isomer is consistently shorter than that of its corresponding all- trans counterpart despite the fact that the excited state energy of the cis molecule is typically higher than that of the trans molecule. Quantum theoretical calculations on an n = 9 linear polyene were carried out to examine this process. The calculations indicate that the electronic coupling terms are significantly higher for the cis isomer, and when combined with the Franck-Condon factors, predict internal conversion rates roughly double those of the all- trans species. The electronic effects more than offset the decrease in coupling efficiencies associated with the higher system origin energies and explain the observed shorter cis isomer lifetimes.

  1. Ultrafast Time-resolved Absorption Spectroscopy of Geometric Isomers of Carotenoids

    PubMed Central

    Niedzwiedzki, Dariusz M.; Sandberg, Daniel J.; Cong, Hong; Sandberg, Megan N.; Gibson, George N.; Birge, Robert R.; Frank, Harry A.

    2009-01-01

    The structures of a number of stereoisomers of carotenoids have been revealed in three-dimensional X-ray crystallographic investigations of pigment-protein complexes from photosynthetic organisms. Despite these structural elucidations, the reason for the presence of stereoisomers in these systems is not well understood. An important unresolved issue is whether the natural selection of geometric isomers of carotenoids in photosynthetic pigment-protein complexes is determined by the structure of the protein binding site or by the need for the organism to accomplish a specific physiological task. The association of cis isomers of a carotenoid with reaction centers and trans isomers of the same carotenoid with light-harvesting pigment-protein complexes has led to the hypothesis that the stereoisomers play distinctly different physiological roles. A systematic investigation of the photophysics and photochemistry of purified, stable geometric isomers of carotenoids is needed to understand if a relationship between stereochemistry and biological function exists. In this work we present a comparative study of the spectroscopy and excited state dynamics of cis and trans isomers of three different open-chain carotenoids in solution. The molecules are neurosporene (n=9), spheroidene (n=10), and spirilloxanthin (n=13), where n is the number of conjugated π-electron double bonds. The spectroscopic experiments were carried out on geometric isomers of the carotenoids purified by high performance liquid chromatography (HPLC) and then frozen to 77 K to inhibit isomerization. The spectral data taken at 77 K provide a high resolution view of the spectroscopic differences between geometric isomers. The kinetic data reveal that the lifetime of the lowest excited singlet state of a cis-isomer is consistently shorter than that of its corresponding all-trans counterpart despite the fact that the excited state energy of the cis molecule is typically higher than that of the trans molecule. Quantum theoretical calculations on an n=9 linear polyene were carried out to examine this process. The calculations indicate that the electronic coupling terms are significantly higher for the cis isomer, and when combined with the Franck-Condon factors, predict internal conversion rates roughly double those of the all-trans species. The electronic effects more than offset the decrease in coupling efficiencies associated with the higher system origin energies and explain the observed shorter cis isomer lifetimes. PMID:20161150

  2. Ultrafast time-resolved absorption spectroscopy of geometric isomers of carotenoids

    PubMed Central

    Niedzwiedzki, Dariusz M.; Sandberg, Daniel J.; Cong, Hong; Sandberg, Megan N.; Gibson, George N.; Birge, Robert R.; Frank, Harry A.

    2010-01-01

    The structures of a number of stereoisomers of carotenoids have been revealed in three-dimensional X-ray crystallographic investigations of pigment–protein complexes from photosynthetic organisms. Despite these structural elucidations, the reason for the presence of stereoisomers in these systems is not well understood. An important unresolved issue is whether the natural selection of geometric isomers of carotenoids in photosynthetic pigment–protein complexes is determined by the structure of the protein binding site or by the need for the organism to accomplish a specific physiological task. The association of cis isomers of a carotenoid with reaction centers and trans isomers of the same carotenoid with light-harvesting pigment–protein complexes has led to the hypothesis that the stereoisomers play distinctly different physiological roles. A systematic investigation of the photophysics and photochemistry of purified, stable geometric isomers of carotenoids is needed to understand if a relationship between stereochemistry and biological function exists. In this work we present a comparative study of the spectroscopy and excited state dynamics of cis and trans isomers of three different open-chain carotenoids in solution. The molecules are neurosporene (n = 9), spheroidene (n = 10), and spirilloxanthin (n = 13), where n is the number of conjugated π-electron double bonds. The spectroscopic experiments were carried out on geometric isomers of the carotenoids purified by high performance liquid chromatography (HPLC) and then frozen to 77 K to inhibit isomerization. The spectral data taken at 77 K provide a high resolution view of the spectroscopic differences between geometric isomers. The kinetic data reveal that the lifetime of the lowest excited singlet state of a cis-isomer is consistently shorter than that of its corresponding all-trans counterpart despite the fact that the excited state energy of the cis molecule is typically higher than that of the trans molecule. Quantum theoretical calculations on an n = 9 linear polyene were carried out to examine this process. The calculations indicate that the electronic coupling terms are significantly higher for the cis isomer, and when combined with the Franck–Condon factors, predict internal conversion rates roughly double those of the all-trans species. The electronic effects more than offset the decrease in coupling efficiencies associated with the higher system origin energies and explain the observed shorter cis isomer lifetimes. PMID:20174614

  3. Time-resolved spectroscopy of energy and electron transfer processes in the photosynthetic bacterium Heliobacillus mobilis.

    PubMed

    Lin, S; Chiou, H C; Kleinherenbrink, F A; Blankenship, R E

    1994-02-01

    The kinetics of excitation energy transfer and electron transfer processes within the membrane of Heliobacillus mobilis were investigated using femtosecond transient absorption difference spectroscopy at room temperature. The kinetics in the 725- to 865-nm region, upon excitation at 590 and 670 nm, were fit using global analysis. The fits returned three kinetic components with lifetimes of 1-2 ps and 27-30 ps, and a component that does not decay within several nanoseconds. The 1- to 2-ps component is attributed to excitation equilibration to form a thermally relaxed excited state. The 27- to 30-ps phase corresponds to the decay of the relaxed excited state to form a charge-separated state. The intrinsic energy and electron transfer rates were estimated using the experimental results and theoretical models for excitation migration and trapping dynamics. Taking into account the number of antenna pigments and their spectral distribution, an upper limit of 1.2 ps for the intrinsic time constant for charge separation in the reaction center is calculated. This upper limit corresponds with the trapping-limited case for excitation migration and trapping. Reduction of the primary electron acceptor A0 was observed in the 640 to 700 nm region using excitation at 780 nm. An instantaneous absorbance increase followed by a decay of about 30 ps was observed over a broad wavelength region due to the excited state absorption and decay of BChl g molecules in the antenna. In addition, a narrow bleaching band centered at 670 nm grows in with an apparent time constant of about 1.0 ps, superimposed on the 30-ps absorbance increase due to excited state absorption. Measurements on a longer time scale showed that besides the 670 nm pigment a BChl g molecule absorbing near 785 nm may be involved in the primary charge separation, and that this pigment may be in equilibrium with the 670 nm pigment. The bleaching bands at 670 nm and 785nm recovered with a time constant of about 600 ps, due to forward electron transport to a secondary electron acceptor. Energy and electron transfer properties of H. mobilis membranes are compared with Photosystem 1, to which the heliobacteria bear an evolutionary relationship. PMID:8161697

  4. Time-resolved visible and extreme ultraviolet spectroscopy of laser-produced tin plasma

    NASA Astrophysics Data System (ADS)

    O'Shay, Joseph Fred

    Previous experimental studies of laser-matter interactions have often been conducted without sufficient accuracy or attention to critical laser parameters. Moreover, much of the work published in the open literature lacks the essential theoretical underpinnings necessary to explain observations and provide predictive capability for future experiments. In this study, we use nanosecond-resolved spectroscopic techniques to investigate fundamental physics in laser-produced tin plasma, and overcome these shortcomings by implementing several metrological innovations to ensure the accuracy of experimental data. Furthermore, we present a side-by-side comparison of experimental results with computational modeling to advance our understanding of the many nonlinear, interrelated processes that occur within transient tin plasma. This dissertation is divided into three primary sections. In the first section, we study the physics governing the generation and early-time evolution of tin plasma in the low-irradiance regime: IL ˜ 4 x 1011 - 1 x 1012W/cm2 . A two-channel XUV photodiode spectrometer has been developed to measure tin plasma temperature, as well as diagnose radiation transport processes during the laser irradiation phase. During laser heating, the radiation spectrum from semi-infinite tin targets was found to approach the blackbody limit in the 10--80 nm spectral range. Through one-dimensional numerical modeling, this is shown to be due to the penetration of a radiative diffusion wave beyond the critical depth. Analysis of the time-dependent tin emission spectrum has shown that nearly 30% of the incident laser energy is converted to energetic photons in the spectral range of 15 < hv < 120 eV. The equilibrium radiation temperature, characteristic of the optically thick ablation front, has shown reasonable agreement with numerical predictions despite the model's limited dimensionality. The second part of this work examines the late-time hydrodynamics associated with the radiative plasma phase studied in the preceding section. Nanosecond-gated optical emission spectroscopy is employed to diagnose electron temperature, electron density, and propagation velocity of the ablation plume. In contrast to the large change in radiation temperature observed for a factor of three increase in laser intensity, it is found that the post-pulse plume hydrodynamics is not significantly affected for the same variation in irradiation conditions. At late times, the ion kinetic energy is found to exceed electron thermal energy by more than 100 times, which serves as a lower bound on the ratio to the ion thermal counterpart. The expanding laser-produced tin plasma is well described by a cylindrical hydrodynamic transport model; a comparison between time-integrated experimental and numerical plasma energy density has shown convergence to within a factor of two. At distances > 3 mm from the target, it was found that the heavy ion tin plasma transitions from Boltzmann to coronal equilibrium, rendering LTE assumptions in the spectral deconvolution procedure invalid. In the final section of this study, we investigate the radiative properties of tin ablation plasma as the laser irradiance is varied by more than an order of magnitude. The effect of increased focused laser energy is manifested in a weak scaling of radiation temperature, and a significant broadening of the emission lifetime at the highest laser intensities. It is found that the resulting radiation conversion efficiency is not a strong function of laser intensity within the parameter regime of this work. It is shown that agreement between experimental and simulated plasma conditions becomes progressively worse in the high-irradiance regime as the ionization and radiative transfer models play increasingly dominant roles in the plasma energetics.

  5. Quantitative determination of major capsaicinoids in serum by ELISA and time-resolved fluorescent immunoassay based on monoclonal antibodies.

    PubMed

    Yang, Qingqing; Zhu, Jianguo; Ma, Fei; Li, Peiwu; Zhang, Liangxiao; Zhang, Wen; Ding, Xiaoxia; Zhang, Qi

    2016-07-15

    To monitor capsaicinoids in serum on-site, three new monoclonal antibodies (mAbs) were firstly proposed using a conjugate of 4-[(4-hydroxy-3-methoxybenzyl) amino]-4-oxobutanoic acid as the immunogen. Among them, the YQQD8 mAb showed the highest sensitivity and cross-reactivity to major capsaicinoids, such as capsaicin, dihydrocapsaicin and N-vanillylnonanamide. A competitive indirect enzyme-linked immunosorbent assay (icELISA) and a time-resolved fluorescent immunochromatographic assay (TRFICA) were established based on this mAb. The linear range was 1.1-27.0ngmL(-1) for icELISA and 1.9-62.5ngmL(-1) for TRFICA and the limit of detection (LOD) of TRFICA was 1.5ngmL(-1). To decrease the interference of sample components and increase accuracy, serum samples were diluted four times before assays. As a result, the linear range of serum samples was 4.6-107.9ngmL(-1) for icELISA and 7.6-250.0ngmL(-1) for TRFICA. Both icELISA and TRFICA showed good recoveries (91.0-112.8% for icELISA and 87.6-111.5% for TRFICA) and concordant results in spiked experiments. Overall, this is the first report of immunoassay based on the mAbs for quantitative determination of major capsaicinoids, and the results demonstrate that both methods can meet the demands of rapid on-site assay for capsaicinoids in serum samples. PMID:26954788

  6. Conformational dynamics and intersubunit energy transfer in wild-type and mutant lipoamide dehydrogenase from Azotobacter vinelandii. A multidimensional time-resolved polarized fluorescence study.

    PubMed Central

    Bastiaens, P I; van Hoek, A; Benen, J A; Brochon, J C; Visser, A J

    1992-01-01

    Time-resolved fluorescence and fluorescence anisotropy data surfaces of flavin adenine dinucleotide bound to lipoamide dehydrogenase from Azotobacter vinelandii in 80% glycerol have been obtained by variation of excitation energy and temperature between 203 and 303 K. The fluorescence kinetics of a deletion mutant lacking 14 COOH-terminal amino acids were compared with the wild-type enzyme to study a possible interaction of the COOH-terminal tail with the active site of the enzyme. The flavin adenine dinucleotide fluorescence in both proteins exhibits a bimodal lifetime distribution as recovered by the maximum entropy method of data analysis. The difference in standard enthalpy and entropy of associated conformational substates was retrieved from the fractional contributions of the two lifetime classes. Activation energies of thermal quenching were obtained that confirm that the isoalloxazines in the deletion mutant are solvent accessible in contrast to the wild-type enzyme. Red-edge spectroscopy in conjunction with variation of temperature provides the necessary experimental axes to interpret the fluorescence depolarization in terms of intersubunit energy transfer rather than reorientational dynamics of the flavins. The results can be explained by a compartmental model that describes the anisotropy decay of a binary, inhomogeneously broadened, homoenergy transfer system. By using this model in a global analysis of the fluorescence anisotropy decay surface, the distance between and relative orientation of the two isoalloxazine rings are elucidated. For the wild-type enzyme, this geometrical information is in agreement with crystallographic data of the A. vinelandii enzyme, whereas the mutual orientation of the subunits in the deletion mutant is slightly altered. In addition, the ambiguity in the direction of the emission transition moment in the isoalloxazine ring is solved. The anisotropy decay parameters also provide information on electronic and dipolar relaxational properties of the flavin active site. The local environment of the prosthetic groups in the deletion mutant of the A. vinelandii enzyme is highly inhomogeneous, and a transition from slow to rapid dipolar relaxation is observed over the measured temperature range. In the highly homogeneous active site of the wild-type enzyme, dipolar relaxation is slowed down beyond the time scale of fluorescence emission at any temperature studied. Our results are in favor of a COOH-terminal polypeptide interacting with the active site, thereby shielding the isoalloxazines from the solvent. This biological system forms a very appropriate tool to test the validity of photophysical models describing homoenergy transfer. PMID:1420917

  7. Excited state dynamics in SO2. I. Bound state relaxation studied by time-resolved photoelectron-photoion coincidence spectroscopy

    NASA Astrophysics Data System (ADS)

    Wilkinson, Iain; Boguslavskiy, Andrey E.; Mikosch, Jochen; Bertrand, Julien B.; Wörner, Hans Jakob; Villeneuve, David M.; Spanner, Michael; Patchkovskii, Serguei; Stolow, Albert

    2014-05-01

    The excited state dynamics of isolated sulfur dioxide molecules have been investigated using the time-resolved photoelectron spectroscopy and time-resolved photoelectron-photoion coincidence techniques. Excited state wavepackets were prepared in the spectroscopically complex, electronically mixed ({tildeB})1B1/(Ã)1A2, Clements manifold following broadband excitation at a range of photon energies between 4.03 eV and 4.28 eV (308 nm and 290 nm, respectively). The resulting wavepacket dynamics were monitored using a multiphoton ionisation probe. The extensive literature associated with the Clements bands has been summarised and a detailed time domain description of the ultrafast relaxation pathways occurring from the optically bright ({tildeB})1B1 diabatic state is presented. Signatures of the oscillatory motion on the ({tildeB})1B1/(Ã)1A2 lower adiabatic surface responsible for the Clements band structure were observed. The recorded spectra also indicate that a component of the excited state wavepacket undergoes intersystem crossing from the Clements manifold to the underlying triplet states on a sub-picosecond time scale. Photoelectron signal growth time constants have been predominantly associated with intersystem crossing to the ({tildec})3B2 state and were measured to vary between 750 and 150 fs over the implemented pump photon energy range. Additionally, pump beam intensity studies were performed. These experiments highlighted parallel relaxation processes that occurred at the one- and two-pump-photon levels of excitation on similar time scales, obscuring the Clements band dynamics when high pump beam intensities were implemented. Hence, the Clements band dynamics may be difficult to disentangle from higher order processes when ultrashort laser pulses and less-differential probe techniques are implemented.

  8. Excited state non-adiabatic dynamics of pyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study

    SciTech Connect

    Wu, Guorong; Neville, Simon P.; Worth, Graham A.; Schalk, Oliver; Sekikawa, Taro; Ashfold, Michael N. R.; Stolow, Albert

    2015-02-21

    The dynamics of pyrrole excited at wavelengths in the range 242-217 nm are studied using a combination of time-resolved photoelectron spectroscopy and wavepacket propagations performed using the multi-configurational time-dependent Hartree method. Excitation close to the origin of pyrrole’s electronic spectrum, at 242 and 236 nm, is found to result in an ultrafast decay of the system from the ionization window on a single timescale of less than 20 fs. This behaviour is explained fully by assuming the system to be excited to the A{sub 2}(πσ{sup ∗}) state, in accord with previous experimental and theoretical studies. Excitation at shorter wavelengths has previously been assumed to result predominantly in population of the bright A{sub 1}(ππ{sup ∗}) and B{sub 2}(ππ{sup ∗}) states. We here present time-resolved photoelectron spectra at a pump wavelength of 217 nm alongside detailed quantum dynamics calculations that, together with a recent reinterpretation of pyrrole’s electronic spectrum [S. P. Neville and G. A. Worth, J. Chem. Phys. 140, 034317 (2014)], suggest that population of the B{sub 1}(πσ{sup ∗}) state (hitherto assumed to be optically dark) may occur directly when pyrrole is excited at energies in the near UV part of its electronic spectrum. The B{sub 1}(πσ{sup ∗}) state is found to decay on a timescale of less than 20 fs by both N-H dissociation and internal conversion to the A{sub 2}(πσ{sup ∗}) state.

  9. Solvatochromism and time-resolved fluorescence of the antitumor agent mitoxantrone and its analogues in solution and in DNA

    SciTech Connect

    Su Lin; Struve, W.S. )

    1991-03-21

    The electronic spectroscopy and fluorescence kinetics of 1,4-dihydroxy-5,8-(2-(2-((2-hydroxyethyl)amino)ethyl)amino)-9,10-anthracenedione (mitoxantrone) and three closely related analogues have been studied in several solvents. The small solvatochromic blue shifts of their visible charge-transfer absorption bands in protic solvents are dominated by interactions with a solvent H-bonding donor, rather than by dipole-dielectric solute-solvent electrostatics. These interactions are unrelated to the phenolic hydroxy groups or the distal N atoms on the side chains but must be localized to the carbonyl groups. The fluorescence decays of all four anthraquinones are controlled by subnanosecond nonradiative relaxation in all solvents studied. At least two decay mechanisms contribute to the observed fluorescence kinetics in solution: (a) subnanosecond internal conversion that is accelerated relative to that in 1,4-diaminoanthraquinone by the presence of the flexible 1,4-side chains in mitoxantrone and its analogues; (b) an additional decay mode that is accentuated in H-bonding solvents. A substantial normal isotope effect occurs in the fluorescence lifetimes of mitoxantrone in perdeuterated water and methanol but not in aprotic solvents. When bound to double-stranded calf thymus DNA, mitoxantrone displays a fluorescence lifetime similar to that in aprotic solvents, suggesting that H-bonding interactions with water are precluded by chromophore intercalation. DNA-bound ametantrone exhibits a lifetime longer than that in either H-bonding or aprotic solvents, indicating that immobilization of the side chains through binding of the distal N atoms to the DNA backbone may influence the decay kinetics. This technique therefore shows potential for elucidating the DNA binding modes for a large class of intercalative drugs.

  10. Characterization of post mortem arterial tissue using time-resolved photoacoustic spectroscopy at 436, 461 and 532 nm.

    PubMed

    Beard, P C; Mills, T N

    1997-01-01

    Time-resolved photoacoustic spectroscopy has been used to characterize post mortem arterial tissue for the purpose of discriminating between normal and atheromatous areas of tissue. Ultrasonic thermoelastic waves were generated in post mortem human aorta by the absorption of nanosecond laser pulses at 436, 461 and 532 nm produced by a frequency doubled Q-switched Nd:YAG laser in conjunction with a gas filled Raman cell. A PVDF membrane hydrophone was used to detect the thermoelastic waves. At 436 nm, differences in the photoacoustic signatures of normal tissue and atherorma were found to be highly variable. At 461 nm, there was a clear and reproducible difference between the photacoustic response of atheroma and normal tissue as a result of increased optical attenuation in atheroma. At 532 nm, the generation of subsurface thermoelastic waves provided a means of determining the structure and thickness of the tissue sample. It is suggested that pulsed photoacoustic spectroscopy at 461 and 532 nm may find application in characterizing arterial tissue in situ by providing information about both the composition and thickness of the vessel wall. PMID:9015817

  11. Probing the hydrogen-bond network of water via time-resolved soft x-ray spectroscopy

    SciTech Connect

    Huse, Nils; Wen, Haidan; Nordlund, Dennis; Szilagyi, Erzsi; Daranciang, Dan; Miller, Timothy A.; Nilsson, Anders; Schoenlein, Robert W.; Lindenberg, Aaron M.

    2009-04-24

    We report time-resolved studies of hydrogen bonding in liquid H2O, in response to direct excitation of the O-H stretch mode at 3 mu m, probed via soft x-ray absorption spectroscopy at the oxygen K-edge. This approach employs a newly developed nanofluidic cell for transient soft x-ray spectroscopy in liquid phase. Distinct changes in the near-edge spectral region (XANES) are observed, and are indicative of a transient temperature rise of 10K following transient laser excitation and rapid thermalization of vibrational energy. The rapid heating occurs at constant volume and the associated increase in internal pressure, estimated to be 8MPa, is manifest by distinct spectral changes that differ from those induced by temperature alone. We conclude that the near-edge spectral shape of the oxygen K-edge is a sensitive probe of internal pressure, opening new possibilities for testing the validity of water models and providing new insight into the nature of hydrogen bonding in water.

  12. Synthesis and Characterization of Time-resolved Fluorescence Probes for Evaluation of Competitive Binding to Melanocortin Receptors

    PubMed Central

    Alleti, Ramesh; Vagner, Josef; Dehigaspitiya, Dilani Chathurika; Moberg, Valerie E.; Elshan, N. G. R. D.; Tafreshi, Narges K.; Brabez, Nabila; Weber, Craig S.; Lynch, Ronald M.; Hruby, Victor J.; Gillies, Robert J.; Morse, David L.; Mash, Eugene A.

    2013-01-01

    Probes for use in time-resolved fluorescence competitive binding assays at melanocortin receptors based on the parental ligands MSH(4), MSH(7), and NDP-α-MSH were prepared by solid phase synthesis methods, purified, and characterized. The saturation binding of these probes was studied using HEK-293 cells engineered to overexpress the human melanocortin 4 receptor (hMC4R) as well as the human cholecystokinin 2 receptor (hCCK2R). The ratios of non-specific binding to total binding approached unity at high concentrations for each probe. At low probe concentrations, receptor-mediated binding and uptake was discernable, and so probe concentrations were kept as low as possible in determining Kd values. The Eu-DTPA-PEGO-MSH(4) probe exhibited low specific binding relative to non-specific binding, even at low nanomolar concentrations, and was deemed unsuitable for use in competition binding assays. The Eu-DTPA-PEGO probes based on MSH(7) and NDP-α-MSH exhibited Kd values of 27±3.9 nM and 4.2±0.48 nM, respectively, for binding with hMC4R. These probes were employed in competitive binding assays to characterize the interactions of hMC4R with monovalent and divalent MSH(4), MSH(7), and NDP-α-MSH constructs derived from squalene. Results from assays with both probes reflected only statistical enhancements, suggesting improper ligand spacing on the squalene scaffold for the divalent constructs. The Ki values from competitive binding assays that employed the MSH(7)-based probe were generally lower than the Ki values obtained when the probe based on NDP-α-MSH was employed, which is consistent with the greater potency of the latter probe. The probe based on MSH(7) was also competed with monovalent, divalent, and trivalent MSH(4) constructs that previously demonstrated multivalent binding in competitive binding assays against a variant of the probe based on NDP-α-MSH. Results from these assays confirm multivalent binding, but suggest a more modest increase in avidity for these MSH(4) constructs than was previously reported. PMID:23890524

  13. Study of fluorescence interaction and conformational changes of bovine serum albumin with histamine H₁ -receptor--drug epinastine hydrochloride by spectroscopic and time-resolved fluorescence methods.

    PubMed

    Ariga, Girish G; Naik, Praveen N; Nandibewoor, Sharanappa T; Chimatadar, Shivamurti A

    2015-11-01

    The fluorescence, ultraviolet (UV) absorption, time resolved techniques, circular dichroism (CD), and infrared spectral methods were explored as tools to investigate the interaction between histamine H1 drug, epinastine hydrochloride (EPN), and bovine serum albumin (BSA) under simulated physiological conditions. The experimental results showed that the quenching of the BSA by EPN was static quenching mechanism and also confirmed by lifetime measurements. The value of n close to unity indicated that one molecule of EPN was bound to protein molecule. The binding constants (K) at three different temperatures were calculated (7.1 × 10(4), 5.5 × 10(4), and 3.9 × 10(4) M(-1)). Based on the thermodynamic parameters (ΔH(0), ΔG(0), and ΔS(0)), the nature of binding forces operating between drug and protein was proposed. The site of binding of EPN in the protein was proposed to be Sudlow's site I based on displacement experiments using site markers viz, warfarin, ibuprofen, and digitoxin. Based on the Förster's theory of non-radiation energy transfer, the binding average distance, r between the donor (BSA) and acceptor (EPN) was evaluated and found to be 4.48 nm. The UV-visible, synchronous fluorescence, CD, and three-dimensional fluorescence spectral results revealed the changes in secondary structure of the protein upon its interaction with EPN. PMID:26215421

  14. Iron-carbonyl bond geometries of carboxymyoglobin and carboxyhemoglobin in solution determined by picosecond time-resolved infrared spectroscopy.

    PubMed Central

    Moore, J N; Hansen, P A; Hochstrasser, R M

    1988-01-01

    The iron-carbonyl geometries in carboxymyoglobin (MbCO) and carboxyhemoglobin (HbCO) in ambient temperature solution have been investigated using picosecond time-resolved infrared spectroscopy. Polarized infrared and visible beams were used to monitor the change in infrared absorbance of the bound CO stretch bands on photodissociation of the ligand. The ratio of the change in absorbance for perpendicular and parallel relative polarizations of the photolysis and infrared probe beams is directly related to the angle between the ligand bond axis and the normal to the heme plane. Ratios, and hence the angles, have been obtained for the configurations giving rise to the principal CO stretch infrared absorption bands of HbCO and MbCO: 18 degrees for the 1951 cm-1 band of HbCO; 20 degrees and 35 degrees, respectively, for the 1944 cm-1 and 1933 cm-1 bands of MbCO. Structures consistent with x-ray diffraction and the picosecond experiments reported here are proposed for MbCO and HbCO in which the Fe-C bond tilts to the heme normal and the Fe-C-O angle differs significantly from 180 degrees. PMID:3393531

  15. Eu(III)-Fulvic Acid Complexation: Evidence of Fulvic Acid Concentration Dependent Interactions by Time-Resolved Luminescence Spectroscopy.

    PubMed

    Kouhail, Yasmine Z; Benedetti, Marc F; Reiller, Pascal E

    2016-04-01

    Europium speciation is investigated by time-resolved luminescence spectroscopy (TRLS) in the presence of Suwannee River fulvic acid (SRFA). From complexation isotherms built at different total Eu(III) concentrations, pH values, ionic strength, and SRFA concentrations, it appears that two luminescence behaviors of Eu(III) are occurring. The first part, at the lowest CSRFA values, is showing the typical luminescence evolution of Eu(III) complexed by humic substances-that is, the increase of the asymmetry ratio between the (5)D0 → (7)F2 and (5)D0 → (7)F1 transitions up to a plateau-, and the occurrence of a biexponential decay-the first decay being faster than free Eu(3+). At higher CSRFA, a second luminescence mode is detected as the asymmetry ratio is increasing again after the previous plateau, and could correspond to the formation of another type of complex, and/or it can reflect a different spatial organization of complexed europium within the SRFA structure. The luminescence decay keeps on evolving but link to hydration number is not straightforward due to quenching mechanisms. The Eu(III) chemical environment evolution with CSRFA is also ionic strength dependent. These observations suggest that in addition to short-range interactions-intraparticulate complexation-, there might be interactions at longer range-interparticulate repulsion-between particles that are complexing Eu(III) at high CSRFA. These interactions are not yet accounted by the different complexation models. PMID:26926621

  16. HELIOS—A laboratory based on high-order harmonic generation of extreme ultraviolet photons for time-resolved spectroscopy

    SciTech Connect

    Plogmaker, S. E-mail: Joachim.Terschluesen@physics.uu.se Terschlüsen, J. A. E-mail: Joachim.Terschluesen@physics.uu.se Krebs, N.; Svanqvist, M.; Forsberg, J.; Cappel, U. B.; Rubensson, J.-E.; Siegbahn, H.; Söderström, J. E-mail: Joachim.Terschluesen@physics.uu.se

    2015-12-15

    In this paper, we present the HELIOS (High Energy Laser Induced Overtone Source) laboratory, an in-house high-order harmonic generation facility which generates extreme ultraviolet (XUV) photon pulses in the range of 15-70 eV with monochromatized XUV pulse lengths below 35 fs. HELIOS is a source for time-resolved pump-probe/two-color spectroscopy in the sub-50 fs range, which can be operated at 5 kHz or 10 kHz. An optical parametric amplifier is available for pump-probe experiments with wavelengths ranging from 240 nm to 20 000 nm. The produced XUV radiation is monochromatized by a grating in the so-called off-plane mount. Together with overall design parameters, first monochromatized spectra are shown with an intensity of 2 ⋅ 10{sup 10} photons/s (at 5 kHz) in the 29th harmonic, after the monochromator. The XUV pulse duration is measured to be <25 fs after monochromatization.

  17. HELIOS—A laboratory based on high-order harmonic generation of extreme ultraviolet photons for time-resolved spectroscopy

    NASA Astrophysics Data System (ADS)

    Plogmaker, S.; Terschlüsen, J. A.; Krebs, N.; Svanqvist, M.; Forsberg, J.; Cappel, U. B.; Rubensson, J.-E.; Siegbahn, H.; Söderström, J.

    2015-12-01

    In this paper, we present the HELIOS (High Energy Laser Induced Overtone Source) laboratory, an in-house high-order harmonic generation facility which generates extreme ultraviolet (XUV) photon pulses in the range of 15-70 eV with monochromatized XUV pulse lengths below 35 fs. HELIOS is a source for time-resolved pump-probe/two-color spectroscopy in the sub-50 fs range, which can be operated at 5 kHz or 10 kHz. An optical parametric amplifier is available for pump-probe experiments with wavelengths ranging from 240 nm to 20 000 nm. The produced XUV radiation is monochromatized by a grating in the so-called off-plane mount. Together with overall design parameters, first monochromatized spectra are shown with an intensity of 2 ṡ 1010 photons/s (at 5 kHz) in the 29th harmonic, after the monochromator. The XUV pulse duration is measured to be <25 fs after monochromatization.

  18. Time-resolved X-Ray Absorption Spectroscopy of a Cobalt-Based Hydrogen Evolution System for Artificial Photosynthesis

    NASA Astrophysics Data System (ADS)

    Moonshiram, Dooshaye; Gimbert, Carolina; Lehmann, Carl; Southworth, Stephen; Llobet, Antoni; Argonne National Laboratory Team; Institut Català d'Investigació Química Collaboration

    2015-03-01

    Production of cost-effective hydrogen gas through solar power is an important challenge of the Department of Energy among other global industry initiatives. In natural photosynthesis, the oxygen evolving complex(OEC) can carry out four-electron water splitting to hydrogen with an efficiency of around 60%. Although, much progress has been carried out in determining mechanistic pathways of the OEC, biomimetic approaches have not duplicated Nature's efficiency in function. Over the past years, we have witnessed progress in developments of light harvesting modules, so called chromophore/catalytic assemblies. In spite of reportedly high catalytic activity of these systems, quantum yields of hydrogen production are below 40 % when using monochromatic light. Proper understanding of kinetics and bond making/breaking steps has to be achieved to improve efficiency of hydrogen evolution systems. This project shows the timing implementation of ultrafast X-ray absorption spectroscopy to visualize in ``real time'' the photo-induced kinetics accompanying a sequence of redox reactions in a cobalt-based molecular photocatalytic system. Formation of a Co(I) species followed by a Co(III) hydride species all the way towards hydrogen evolution is shown through time-resolved XANES.

  19. Single-shot Raman spectroscopy and time-resolved reflectivity of a shocked TATB-based explosive

    NASA Astrophysics Data System (ADS)

    Hebert, Philippe; Saint-Amans, Charles; Doucet, Michel; de Resseguier, Thibaut

    2015-06-01

    Single-shot Raman spectroscopy experiments under shockwave loading were performed in order to get information on the initiation mechanisms that can lead to sustained detonation of a TATB-based explosive. Shocks up to 30 GPa were generated using a two-stage laser-driven flyer plate generator. The samples were confined by an optical window and shock pressure was maintained for at least 30 ns. Photon Doppler Velocimetry measurements were performed at the explosive/window interface to determine the shock pressure profile. Raman spectra were recorded as a function of shock pressure and the shifts of the principal modes were compared to static high-pressure measurements performed in a diamond anvil cell. Our shock data indicate the role of temperature effects on the H-bonding network present in TATB. Our Raman spectra also show a progressive extinction of the signal which disappears around 9 GPa. High-speed photography images reveal a simultaneous progressive darkening of the sample surface up to total opacity at 9 GPa. Time-resolved reflectivity measurements under shock compression seem to indicate that this opacity is due to a broadening of the absorption spectrum over the entire visible region.

  20. DC-magnetoencephalography and time-resolved near-infrared spectroscopy combined to study neuronal and vascular brain responses.

    PubMed

    Sander, T H; Liebert, A; Mackert, B M; Wabnitz, H; Leistner, S; Curio, G; Burghoff, M; Macdonald, R; Trahms, L

    2007-06-01

    The temporal relation between vascular and neuronal responses of the brain to external stimuli is not precisely known. For a better understanding of the neuro-vascular coupling changes in cerebral blood volume and oxygenation have to be measured simultaneously with neuronal currents. With this motivation modulation dc-magnetoencephalography was combined with multi-channel time-resolved near-infrared spectroscopy to simultaneously monitor neuronal and vascular parameters on a scale of seconds. Here, the technique is described, how magnetic and optical signals can be measured simultaneously. In a simple motor activation paradigm (alternating 30 s of finger movement with 30 s of rest for 40 min) both signals were recorded non-invasively over the motor cortex of eight subjects. The off-line averaged signals from both modalities showed distinct stimulation related changes. By plotting changes in oxy- or deoxyhaemoglobin as a function of magnetic field a characteristic trajectory was created, which was similar to a hysteresis loop. A parametric analysis allowed quantitative results regarding the timing of coupling: the vascular signal increased significantly slower than the neuronal signal. PMID:17664619

  1. Study of Heat Transfer Dynamics from Gold Nanorods to the Environment via Time-Resolved Infrared Spectroscopy.

    PubMed

    Nguyen, Son C; Zhang, Qiao; Manthiram, Karthish; Ye, Xingchen; Lomont, Justin P; Harris, Charles B; Weller, Horst; Alivisatos, A Paul

    2016-02-23

    Studying the local solvent surrounding nanoparticles is important to understanding the energy exchange dynamics between the particles and their environment, and there is a need for spectroscopic methods that can dynamically probe the solvent region that is in nearby contact with the nanoparticles. In this work, we demonstrate the use of time-resolved infrared spectroscopy to track changes in a vibrational mode of local water on the time scale of hundreds of picoseconds, revealing the dynamics of heat transfer from gold nanorods to the local water environment. We applied this probe to a prototypical plasmonic photothermal system consisting of organic CTAB bilayer capped gold nanorods, as well as gold nanorods coated with varying thicknesses of inorganic mesoporous-silica. The heat transfer time constant of CTAB capped gold nanorods is about 350 ps and becomes faster with higher laser excitation power, eventually generating bubbles due to superheating in the local solvent. Silica coating of the nanorods slows down the heat transfer and suppresses the formation of superheated bubbles. PMID:26840805

  2. A safe, low-cost, and portable instrumentation for bedside time-resolved picosecond near infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Amouroux, Marine; Uhring, Wilfried; Pebayle, Thierry; Poulet, Patrick; Marlier, Luc

    2009-07-01

    Continuous wave Near InfraRed Spectroscopy (NIRS) has been used successfully in clinical environments for several years to detect cerebral activation thanks to oxymetry (i.e. absorption of photons by oxy- and deoxy- hemoglobin) measurement. The goal of our group is to build a clinically-adapted time-resolved NIRS setup i.e. a setup that is compact and robust enough to allow bedside measurements and that matches safety requirements with human patients applications. Indeed our group has already shown that time resolution allows spatial resolution and improves sensitivity of cerebral activation detection. The setup is built with four laser diodes (excitation wavelengths: 685, 780, 830 and 870 nm) whose emitted light is injected into four optical fibers; detection of reflected photons is made through an avalanche photodiode and a high resolution timing module used to record Temporal Point Spread Functions (TPSF). Validation of the device was made using cylindrically-chaped phantoms with absorbing and/or scattering inclusions. Results show that recorded TPSF are typical both of scattering and absorbing materials thus demonstrating that our apparatus would detect variation of optical properties (absorption and scattering) deep within a diffusive media just like a cerebral activation represents a rise of absorption in the cortex underneath head surface.

  3. Testing the Physical Mechanisms of Gamma-Ray Bursts with Multi-Instrument Time-Resolved Spectroscopy

    NASA Technical Reports Server (NTRS)

    Briggs, Michael S.; Preece, Robert E.

    2001-01-01

    We have continued the project of time-resolved spectral analyses of gamma-ray bursts observed jointly by the BATSE and the Wide-Field Camera on board BeppoSAX. We are making progress understanding the systematic differences between the two data sets. These data comprise the most important joint analysis set for our project. In several meetings, we have reported on metal efforts to understand the blackbody portion of the time series of spectra from GRB970111. Clearly, a fading thermal component can provide a 'seed' spectrum for Compton upscattering. It is very likely the X-ray excess that has been observed previously in BATSE data alone continues into the X-ray band observed by the WFC. We have also made progress in joint fitting of BATSE Large Area Detector and Spectroscopy Detector data with that of the Total Absorption Scintillation Calorimeter (TASC) of the EGRET experiment on CGRO. The TASC data are important to understanding the high-energy response of the BATSE data. We have produced time-sequences of spectra for two important GRB with data from both instruments. The Summer workshop on GRBs at the Aspen Center for Physics provided an opportunity for in-depth discussion of our on-going work. To aid our effort, we continue to make improvements in our spectral analysis software, RMFIT (rewritten from WINGSPAN).

  4. Effects of Cosmetic Therapy on Cognitive Function in Elderly Women Evaluated by Time-Resolved Spectroscopy Study.

    PubMed

    Machida, A; Shirato, M; Tanida, M; Kanemaru, C; Nagai, S; Sakatani, K

    2016-01-01

    With the rapid increase in dementia in developed countries, it is important to establish methods for maintaining or improving cognitive function in elderly people. To resolve such problems, we have been developing a cosmetic therapy (CT) program for elderly women. However, the mechanism and limitations of CT are not yet clear. In order to clarify these issues, we employed time-resolved spectroscopy (TRS) to evaluate the effect of CT on prefrontal cortex (PFC) activity in elderly females with various levels of cognitive impairment. Based on the Mini-Mental State Examination (MMSE) score, the subjects were classified into mild (mean MMSE score: 24.1±3.8) and moderate (mean MMSE score: 10.3±5.8) cognitive impairment (CI) groups (p<0.0001). The mild CI group exhibited significantly larger baseline concentrations of oxy-Hb and t-Hb than the moderate CI group. CT significantly increased the baseline concentrations of oxy-Hb (p<0.002) and t-Hb (p<0.0013) in the left PFC in the mild CI group. In contrast, CT did not change the concentrations of oxy-Hb and t-Hb in the moderate CI group (p>0.05). These results suggest that CT affects cognitive function by altering PFC activity in elderly women with mild CI, but not moderate CI. PMID:26782224

  5. Two Types of Water at the Water-Surfactant Interface Revealed by Time-Resolved Vibrational Spectroscopy.

    PubMed

    Livingstone, Ruth A; Nagata, Yuki; Bonn, Mischa; Backus, Ellen H G

    2015-12-01

    The surfactant sodium dodecyl sulfate (SDS) is widely used as a detergent for both domestic and industrial applications. It forms a self-assembled monolayer on the surface of water. We report a microscopic model for the interaction between the surfactant and water and between water molecules at the interface, revealed using static and time-resolved two-dimensional sum frequency generation spectroscopy. Two distinct subensembles of water in the presence of this negatively charged SDS surfactant have been identified: those close to the SDS headgroup having fairly isolated O-H groups, i.e., localized O-H stretch vibrations, and those whose O-H stretch vibrations are delocalized, i.e., shared between multiple O-H bonds. The two subensembles are coupled, with subpicosecond energy transfer occurring between them. This is markedly different from O-H bonds at the air-water interface, which are less heterogeneous, and indicates that the water molecules that interact with the surfactant headgroups have hydrogen-bonding properties different from those of water molecules interacting with the other water molecules. PMID:26544087

  6. Communication: Ultrafast time-resolved ion photofragmentation spectroscopy of photoionization-induced proton transfer in phenol-ammonia complex

    SciTech Connect

    Shen, Ching-Chi; Tsai, Tsung-Ting; Ho, Jr-Wei; Chen, Yi-Wei; Cheng, Po-Yuan

    2014-11-07

    Photoionization-induced proton transfer (PT) in phenol-ammonia (PhOH-NH{sub 3}) complex has been studied using ultrafast time-resolved ion photofragmentation spectroscopy. Neutral PhOH-NH{sub 3} complexes prepared in a free jet are photoionized by femtosecond [1+1] resonance-enhanced multiphoton ionization via the S{sub 1} state, and the subsequent dynamics occurring in the cations is probed by delayed pulses that result in ion fragmentation. The observed temporal evolutions of the photofragmentation spectra are consistent with an intracomplex PT reaction. The experiments revealed that PT in [PhOH-NH{sub 3}]{sup +} cation proceeds in two distinct steps: an initial impulsive wave-packet motion in ∼70 fs followed by a slower relaxation of about 1 ps that stabilizes the system into the final PT configuration. These results indicate that for a barrierless PT system, even though the initial PT motions are impulsive and ultrafast, the reaction may take a much longer time scale to complete.

  7. Two-photon resonances in femtosecond time-resolved four-wave mixing spectroscopy: {beta}-carotene

    SciTech Connect

    Namboodiri, V.; Namboodiri, M.; Flachenecker, G.; Materny, A.

    2010-08-07

    Femtosecond time-resolved pump-degenerate four-wave mixing (pump-DFWM) spectroscopy has been used to study the ultrafast dynamics of {beta}-carotene involving several electronic and vibrational states. An initial pump pulse, resonant with the S{sub 0}-to-S{sub 2} transition, excites the molecular system and a DFWM process, resonant with the S{sub 1}-to-S{sub n} transition, is used to probe the relaxation pathways. The transient shows a peculiar decay behavior, which is due to the contributions of resonant DFWM signal of the excited S{sub 1} state, nonresonant DFWM signal of the ground S{sub 0} state and vibrational hot S{sub 0}{sup *} state, and the two-photon resonant DFWM signal of the ground S{sub 0} state. We have used a kinetic model including all the signal contributions to successfully fit the transient. The time constants extracted are in very good agreement with the known values for {beta}-carotene. For comparison, a two-pulse pump-probe experiment was performed measuring the transient absorption at the wavelength of the DFWM experiment.

  8. Sub-100ps single photoelectron time resolution of a strip silicon photomultiplier for time-resolved optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Shenyuan; Liu, Rongdan; Liang, Kun; Yang, Ru; Han, Dejun

    2015-10-01

    SiPM with epitaxial quenching resistors developed at NDL (Novel Device Laboratory, Beijing) could alleviate the conflict between large dynamic range and high photon detection efficiency (PDE). It can be used as low light level detector in various applications with excellent single photoelectron time resolution (SPTR) and photon counting capacity. SPTR is mainly determined by the intrinsic structure parameters of the SiPM. However, it is also limited to measurement setup, electronics readout and the ultra-small signal of single photoelectron level. In this work, we designed and fabricated a 1 mm × 1 mm strip SiPM array for possible applications in time-resolved optical spectroscopy. The SiPM array consists of sixteen 50 μm × 1 mm strip SiPM elements. Each element contains five hundred 6.5 μm × 6.5 μm micro avalanche photodiode (APD) cells with 10μm pitch. The strip SiPM demonstrated SPTR of 68 ps (FWHM), peak PDE of 17% around 450 nm and high photon number resolving and photon counting capability.

  9. Single water solvation dynamics in the 4-aminobenzonitrile-water cluster cation revealed by picosecond time-resolved infrared spectroscopy.

    PubMed

    Miyazaki, Mitsuhiko; Nakamura, Takashi; Wohlgemuth, Matthias; Mitrić, Roland; Dopfer, Otto; Fujii, Masaaki

    2015-11-28

    The dynamics of a solvent is important for many chemical and biological processes. Here, the migration dynamics of a single water molecule is triggered by the photoionization of the 4-aminobenzonitrile-water (4ABN-W) cluster and monitored in real time by picosecond time-resolved IR (ps TRIR) spectroscopy. In the neutral cluster, water is hydrogen-bonded to the CN group. When this CN-bound cluster is selectively ionized with an excess energy of 1238 cm(-1), water migrates with a lifetime of τ = 17 ps from the CN to the NH2 group, forming a more stable 4ABN(+)-W(NH) isomer with a yield of unity. By decreasing the ionization excess energy, the yield of the CN → NH2 reaction is reduced. The relatively slow migration in comparison to the ionization-induced solvent dynamics in the related acetanilide-water cluster cation (τ = 5 ps) is discussed in terms of the internal excess energy after photoionization and the shape of the potential energy surface. PMID:26490096

  10. Time-resolved terahertz spectroscopy of electrically conductive metal-organic frameworks doped with redox active species

    NASA Astrophysics Data System (ADS)

    Alberding, Brian G.; Heilweil, Edwin J.

    2015-09-01

    Metal-Organic Frameworks (MOFs) are three-dimensional coordination polymers that are well known for large pore surface area and their ability to adsorb molecules from both the gaseous and solution phases. In general, MOFs are electrically insulating, but promising opportunities for tuning the electronic structure exist because MOFs possess synthetic versatility; the metal and organic ligand subunits can be exchanged or dopant molecules can be introduced into the pore space. Two such MOFs with demonstrated electrical conductivity are Cu3(1,3,5-benzenetricarboxylate)2, a.k.a HKUST-1, and Cu[Ni(pyrazine-2,3-dithiolate)2]. Herein, these two MOFs have been infiltrated with the redox active species 7,7,8,8-tetracyanoquinodimethane (TCNQ) and iodine under solution phase conditions and shown to produce redox products within the MOF pore space. Vibrational bands assignable to TCNQ anion and triiodide anion have been observed in the Mid-IR and Terahertz ranges using FTIR Spectroscopy. The MOF samples have been further investigated by Time-Resolved Terehertz Spectroscopy (TRTS). Using this technique, the charge mobility, separation, and recombination dynamics have been followed on the picosecond time scale following photoexcitation with visible radiation. The preliminary results show that the MOF samples have small inherent photoconductivity with charge separation lifetimes on the order of a few picoseconds. In the case of HKUST-1, the MOF can also be supported by a TiO2 film and initial results show that charge injection into the TiO2 layer occurs with a comparable efficiency to the dye sensitizer N3, [cis-Bis(isothiocyanato)-bis(2,2'-bipyridyl-4,4'-dicarboxylato ruthenium(II)], and therefore this MOF has potential as a new light absorbing and charge conducting material in photovoltaic devices.

  11. Time-resolved photometry and spectroscopy of the new deeply-eclipsing SW Sextantis star HS 0728+6738

    NASA Astrophysics Data System (ADS)

    Rodríguez-Gil, P.; Gänsicke, B. T.; Barwig, H.; Hagen, H.-J.; Engels, D.

    2004-09-01

    We present time-resolved optical spectroscopy and photometry, and far-ultraviolet spectroscopy of HS 0728+6738, a cataclysmic variable discovered in the Hamburg Quasar Survey. We show that the system is a new eclipsing member of the SW Sex class of CVs with an orbital period of 3.21 h. We derive an orbital inclination of ˜ 85 ± 4° from the average eclipse profile, making HS 0728+6738 the highest inclination SW Sex star known. The optical and far-ultraviolet emission lines are not or only weakly occulted during the eclipse, indicating the presence of line-emission sites either far outside the Roche lobe of the primary or, more likely, above the orbital plane of the binary. The photometric light curves exhibit fast variability with a period of ˜7 min, which might be related to the spin of the white dwarf. Based in part on observations obtained at the German-Spanish Astronomical Center, Calar Alto, operated by the Max-Planck-Institut für Astronomie, Heidelberg, jointly with the Spanish National Commission for Astronomy, on observations made with the IAC80 telescope, operated on the island of Tenerife by the Instituto de Astrofísica de Canarias (IAC) at the Spanish Observatorio del Teide, on observations made at the Wendelstein Observatory, operated by the Universitäts-Sternwarte München, and on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  12. Nonlinear spectroscopy in the near-field: time resolved spectroscopy and subwavelength resolution non-invasive imaging

    NASA Astrophysics Data System (ADS)

    Namboodiri, Mahesh; Khan, Tahirzeb; Karki, Khadga; Kazemi, Mehdi Mohammad; Bom, Sidhant; Flachenecker, Günter; Namboodiri, Vinu; Materny, Arnulf

    2014-04-01

    The combination of near-field microscopy along with nonlinear optical spectroscopic techniques is presented here. The scanning near-field imaging technique can be integrated with nonlinear spectroscopic techniques to improve spatial and axial resolution of the images. Additionally, ultrafast dynamics can be probed down to nano-scale dimension. The review shows some examples for this combination, which resulted in an exciton map and vibrational contrast images with sub-wavelength resolution. Results of two-color femtosecond time-resolved pump-probe experiments using scanning near-field optical microscopy (SNOM) on thin films of the organic semiconductor 3,4,9,10 Perylenetetracarboxylic dianhydride (PTCDA) are presented. While nonlinear Raman techniques have been used to obtain highly resolved images in combination with near-field microscopy, the use of femtosecond laser pulses in electronic resonance still constitutes a big challenge. Here, we present our first results on coherent anti-Stokes Raman scattering (fs-CARS) with femtosecond laser pulses detected in the near-field using SNOM. We demonstrate that highly spatially resolved images can be obtained from poly(3-hexylthiophene) (P3HT) nano-structures where the fs-CARS process was in resonance with the P3HT absorption and with characteristic P3HT vibrational modes without destruction of the samples. Sub-diffraction limited lateral resolution is achieved. Especially the height resolution clearly surpasses that obtained with standard microCARS. These results will be the basis for future investigations of mode-selective dynamics in the near-field.

  13. Monitoring changes of cellular metabolism and microviscosity in vitro based on time-resolved endogenous fluorescence and its anisotropy decay dynamics

    NASA Astrophysics Data System (ADS)

    Zheng, Wei; Li, Dong; Qu, Jianan Y.

    2010-05-01

    Reduced nicotinamide adenine dinucleotide (NADH) is a well-known metabolic coenzyme and endogenous fluorophore. In this study, we develop a system that simultaneously measures time- and wavelength-resolved fluorescence to extract free and protein-bound NADH signals from total cellular fluorescence. We analyze temporal characteristics of NADH fluorescence in a mixture of NADH and lactate dehydrogenase (LDH) as well as in living cell samples. The results show that in both the NADH/LDH mixture and cell samples, a fraction of free NADH and protein-bound components can be identified. The extracted free and bound NADH signals are confirmed by time-resolved measurement of anisotropy decay of NADH fluorescence, based on the fact that free NADH is a small fluorescent molecule with much shorter rotational diffusion time than bound NADH. The ratio of free NADH signal to bound NADH signal is very different between normal and cancer cervical epithelial cells. In addition, the ratio changes significantly when the cell samples are treated with a mitochondrial inhibitor or uncoupler, demonstrating that the method is sensitive to monitor cellular metabolic activity. Finally, we demonstrate that the microviscosity for relatively small molecules such as NADH in cells could be extracted from wavelength- and time-resolved NADH fluorescence of living cell samples.

  14. Time-Resolved Laser-Induced Fluorescence Measurements of Ion Velocity Distribution in the Plume of a 6 kW Hall Thruster with Unperturbed Discharge Oscillations

    NASA Astrophysics Data System (ADS)

    Durot, Christopher; Gallimore, Alec

    2014-10-01

    We present laser-induced fluorescence (LIF) measurements of the time-resolved ion velocity distribution in the plume of a 6 kW laboratory Hall thruster. To our knowledge, these are the first measurements of time-resolved ion velocity distribution on completely unperturbed Hall thruster operating conditions. To date, time-resolved LIF measurements have been made on Hall thrusters with oscillations driven or perturbed to be amenable to averaging techniques that assume a periodic oscillation. Natural Hall thruster breathing and spoke oscillations, however, are not periodic due to chaotic variations in amplitude and frequency. Although the system averages over many periods of nonperiodic oscillation, it recovers the time-resolved signal in part by assuming that a constant transfer function exists relating discharge current and LIF signal and averaging over the transfer function itself (http://dx.doi.org/10.1063/1.4856635). The assumption of a constant transfer function has been validated for a Hall thruster and the technique is now applied to a Hall thruster for the first time.

  15. Photoexcited State Properties of H2-Porphyrin/C60-Based Rotaxanes as Studied by Time-Resolved EPR Spectroscopy

    PubMed Central

    Jakob, Manuela; Berg, Alexander; Levanon, Haim; Schuster, David I.; Megiatto, Jackson D.

    2011-01-01

    Light-driven intramolecular electron transfer (ET) and energy transfer (EnT) processes in two rotaxanes, the first containing two free base porphyrins and C60 fullerene moieties incorporated around a Cu(I)bisphenanthroline core ((H2P)2-Cu(I)(phen)2-C60) and a second rotaxane lacking the fullerene moiety ((H2P)2-Cu(I)(phen)2) were studied by X-band (9.5 GHz) time-resolved electron paramagnetic resonance (TREPR) spectroscopy. The experiments were performed in a frozen toluene and ethanol, and different phases of the nematic liquid crystal (E-7). It is demonstrated that the ET and EnT processes in the (H2P)2-Cu(I)(phen)2-C60 rotaxane in different media result in formation of the same charge separated state, namely (H2P)2•+-Cu(I)(phen)2•−-C60, while photoexcitation of the (H2P)2-Cu(I)(phen)2 rotaxane does not induce noticeable transfer processes in these matrices. The results are discussed in terms of the high conformational mobility of the rotaxanes, which enables changes in the molecular topography and resultant modification of the rates and routes of photoinduced processes occurring in these systems. The parameters of the transfer processes are compared with those obtained in our previous study of (ZnP)2-Cu(I)(phen)2-C60 and (ZnP)2-Cu(I)(phen) rotaxanes under the same experimental conditions. PMID:21528881

  16. Ultrafast excited-state dynamics in photochromic N-salicylideneaniline studied by femtosecond time-resolved REMPI spectroscopy

    SciTech Connect

    Okabe, Chie; Nakabayashi, Takakazu; Inokuchi, Yoshiya; Nishi, Nobuyuki; Sekiya, Hiroshi

    2004-11-15

    Ultrafast processes in photoexcited N-salicylideneaniline have been investigated with femtosecond time-resolved resonance-enhanced multiphoton ionization spectroscopy. The ion signals via the S{sub 1}(n,{pi}*) state of the enol form as well as the proton-transferred cis-keto form emerge within a few hundred femtoseconds after photoexcitation to the first S{sub 1}({pi},{pi}*) state of the enol form. This reveals that two ultrafast processes, excited-state intramolecular proton transfer (ESIPT) reaction and an internal conversion (IC) to the S{sub 1}(n,{pi}*) state, occur on a time scale less than a few hundred femtoseconds from the S{sub 1}({pi},{pi}*) state of the enol form. The rise time of the transient corresponding to the production of the proton-transferred cis-keto form is within 750 fs when near the red edge of the absorption is excited, indicating that the ESIPT reaction occurs within 750 fs. The decay time of the S{sub 1}({pi},{pi}*) state of the cis-keto form is 8.9 ps by exciting the enol form at 370 nm, but it dramatically decreases to be 1.5-1.6 ps for the excitation at 365-320 nm. The decrease in the decay time has been attributed to the opening of an efficient nonradiative channel; an IC from S{sub 1}({pi},{pi}*) to S{sub 1}(n,{pi}*) of the cis-keto form promotes the production of the trans-keto form as the final photochromic products. The two IC processes may provide opposite effect on the quantum yield of photochromic products: IC in the enol form may substantially reduce the quantum yield, but IC in the cis-keto form increase it.

  17. Photo-induced carrier generation and recombination dynamics probed by combining time-resolved microwave conductivity and transient absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Park, Jaehong; Reid, Obadiah G.; Rumbles, Garry

    2015-08-01

    We examined photoinduced charge-generation dynamics of the poly(3-hexylthiophene) (P3HT)/titanyl phthalocyanine (TiOPc) bilayer and the P3HT/TiOPc/C60 trilayer using the combination of flash-photolysis time-resolved microwave conductivity experiments (fp-TRMC) and classic pump-probe transient absorption (TA) spectroscopy following dominant excitation of the P3HT layer. The superlinear increase of φΣμ for the P3HT/TiOPc bilayer, compared to the φΣμ sum of each P3HT and TiOPc layer suggest photoinduced carrier-generation. Furthermore, the superlinear increase of φΣμ of the P3HT/TiOPc/C60 trilayer with respect to the each P3HT/TiOPc and TiOPc/C60 bilayers evinces charge migration from one interface to the other interface. In addition, with selective photoexcitation on the P3HT layer, both amorphous and H-aggregated P3HT domains participate in electron transfer ([P3HT*/TiOPc]-->[P3HT•+/TiOPc•-]), contrasting to the previous observation where with selective excitation of the TiOPc layer, only the H-aggregated P3HT domain involves in hole transfer ([P3HT/TiOPc-->[P3HT•+/TiOPc•-]) to produce P3HT•+/TiOPc•- in J. Phys. Chem. B 119(24), 7729--7739 (2015). These results under different excitation conditions are consistent with calculated energetic driving force (ΔECS) for charge generation which is -0.58 eV and -0.73 eV for amorphous and H-aggregated P3HT domains under the P3HT layer excitation, while 0.04 eV and -0.11 eV for amorphous and H-aggregated P3HT domains under the TiOPc layer excitation.

  18. Vibrational spectroscopy of excited electronic states in carotenoids in vivo. Picosecond time-resolved resonance Raman scattering.

    PubMed Central

    Hayashi, H; Noguchi, T; Tasumi, M; Atkinson, G H

    1991-01-01

    The vibrational spectroscopy and population dynamics of excited singlet (2(1)Ag), excited triplet (3B u), and the ground (1Ag) electronic states of carotenoids in chromatophores of Chromatium vinosum (mainly spirilloxanthin and rhodopin) and of the same carotenoids in benzene solutions are examined by picosecond time-resolved resonance Raman scattering. Coherent Stokes Raman scattering from the ground states of carotenoids in chromatophores also is observed. Resonance Raman spectra of in vitro rhodopin and spirilloxanthin when compared with in vivo data demonstrate that scattering from spirilloxanthin dominates the in vivo spectrum. Comparisons of the time-dependent intensities of 2(1)Ag and 1Ag resonance Raman bands from both in vitro and in vivo carotenoids suggest that vibrationally excited levels in 1Ag are populated directly by the decay of the 2(1)Ag state and that these levels relax into a thermalized distribution in less than 50 ps. The appearance of asymmetrically broadened, ground-state resonance Raman bands supports this conclusion. Formation of the 3Bu state is observed for carotenoids in chromatophores, but not for in vitro spirilloxanthin indicating that the 3Bu state is formed by fission processes originating from the spatial organization of pigments within chromatophores. The rate at which the intensities of 2(1)Ag resonance Raman bands decay is faster for the carotenoids in vivo than for those in vitro thereby indicating that additional relaxation channels (e.g., energy transfer to bacteriochlorophylls) are present in the chromatophore. The similarity of the in vivo and in vitro 2(1)Ag resonance Raman spectra shows that no significant modifications in the vibronic coupling has been caused by the chromatophore environment. PMID:1883940

  19. Reduction of O2 slow component by priming exercise: novel mechanistic insights from time-resolved near-infrared spectroscopy

    PubMed Central

    Fukuoka, Yoshiyuki; Poole, David C; Barstow, Thomas J; Kondo, Narihiko; Nishiwaki, Masato; Okushima, Dai; Koga, Shunsaku

    2015-01-01

    Novel time-resolved near-infrared spectroscopy (TR-NIRS), with adipose tissue thickness correction, was used to test the hypotheses that heavy priming exercise reduces the V?O2 slow component (V?O2SC) (1) by elevating microvascular [Hb] volume at multiple sites within the quadriceps femoris (2) rather than reducing the heterogeneity of muscle deoxygenation kinetics. Twelve subjects completed two 6-min bouts of heavy work rate exercise, separated by 6min of unloaded cycling. Priming exercise induced faster overall V?O2 kinetics consequent to a substantial reduction in the V?O2SC (0.270.12 vs. 0.110.09Lmin?1, P<0.05) with an unchanged primary V?O2 time constant. An increased baseline for the primed bout [total (Hb+Mb)] (197.521.6 vs. 210.722.5?molL?1, P<0.01), reflecting increased microvascular [Hb] volume, correlated significantly with the V?O2SC reduction. At multiple sites within the quadriceps femoris, priming exercise reduced the baseline and slowed the increase in [deoxy (Hb+Mb)]. Changes in the intersite coefficient of variation in the time delay and time constant of [deoxy (Hb+Mb)] during the second bout were not correlated with the V?O2SC reduction. These results support a mechanistic link between priming exercise-induced increase in muscle [Hb] volume and the reduced V?O2SC that serves to speed overall V?O2 kinetics. However, reduction in the heterogeneity of muscle deoxygenation kinetics does not appear to be an obligatory feature of the priming response. PMID:26109190

  20. Vibrational cooling dynamics of a [FeFe]-hydrogenase mimic probed by time-resolved infrared spectroscopy.

    PubMed

    Caplins, Benjamin W; Lomont, Justin P; Nguyen, Son C; Harris, Charles B

    2014-12-11

    Picosecond time-resolved infrared spectroscopy (TRIR) was performed for the first time on a dithiolate bridged binuclear iron(I) hexacarbonyl complex ([Fe₂(μ-bdt)(CO)₆], bdt = benzene-1,2-dithiolate) which is a structural mimic of the active site of the [FeFe]-hydrogenase enzyme. As these model active sites are increasingly being studied for their potential in photocatalytic systems for hydrogen production, understanding their excited and ground state dynamics is critical. In n-heptane, absorption of 400 nm light causes carbonyl loss with low quantum yield (<10%), while the majority (ca. 90%) of the parent complex is regenerated with biexponential kinetics (τ₁ = 21 ps and τ₂ = 134 ps). In order to understand the mechanism of picosecond bleach recovery, a series of UV-pump TRIR experiments were performed in different solvents. The long time decay (τ₂) of the transient spectra is seen to change substantially as a function of solvent, from 95 ps in THF to 262 ps in CCl₄. Broadband IR-pump TRIR experiments were performed for comparison. The measured vibrational lifetimes (T₁(avg)) of the carbonyl stretches were found to be in excellent correspondence to the observed τ₂ decays in the UV-pump experiments, signifying that vibrationally excited carbonyl stretches are responsible for the observed longtime decays. The fast spectral evolution (τ₁) was determined to be due to vibrational cooling of low frequency modes anharmonically coupled to the carbonyl stretches that were excited after electronic internal conversion. The results show that cooling of both low and high frequency vibrational modes on the electronic ground state give rise to the observed picosecond TRIR transient spectra of this compound, without the need to invoke electronically excited states. PMID:25426927

  1. Time-resolved photoelectron spectroscopy of a dinuclear Pt(II) complex: Tunneling autodetachment from both singlet and triplet excited states of a molecular dianion

    NASA Astrophysics Data System (ADS)

    Winghart, Marc-Oliver; Yang, Ji-Ping; Vonderach, Matthias; Unterreiner, Andreas-Neil; Huang, Dao-Ling; Wang, Lai-Sheng; Kruppa, Sebastian; Riehn, Christoph; Kappes, Manfred M.

    2016-02-01

    Time-resolved pump-probe photoelectron spectroscopy has been used to study the relaxation dynamics of gaseous [Pt2(μ-P2O5H2)4 + 2H]2- after population of its first singlet excited state by 388 nm femtosecond laser irradiation. In contrast to the fluorescence and phosphorescence observed in condensed phase, a significant fraction of the photoexcited isolated dianions decays by electron loss to form the corresponding monoanions. Our transient photoelectron data reveal an ultrafast decay of the initially excited singlet 1A2u state and concomitant rise in population of the triplet 3A2u state, via sub-picosecond intersystem crossing (ISC). We find that both of the electronically excited states are metastably bound behind a repulsive Coulomb barrier and can decay via delayed autodetachment to yield electrons with characteristic kinetic energies. While excited state tunneling detachment (ESETD) from the singlet 1A2u state takes only a few picoseconds, ESETD from the triplet 3A2u state is much slower and proceeds on a time scale of hundreds of nanoseconds. The ISC rate in the gas phase is significantly higher than in solution, which can be rationalized in terms of changes to the energy dissipation mechanism in the absence of solvent molecules. [Pt2(μ-P2O5H2)4 + 2H]2- is the first example of a photoexcited multianion for which ESETD has been observed following ISC.

  2. Time-resolved photoelectron spectroscopy of a dinuclear Pt(II) complex: Tunneling autodetachment from both singlet and triplet excited states of a molecular dianion.

    PubMed

    Winghart, Marc-Oliver; Yang, Ji-Ping; Vonderach, Matthias; Unterreiner, Andreas-Neil; Huang, Dao-Ling; Wang, Lai-Sheng; Kruppa, Sebastian; Riehn, Christoph; Kappes, Manfred M

    2016-02-01

    Time-resolved pump-probe photoelectron spectroscopy has been used to study the relaxation dynamics of gaseous [Pt2(μ-P2O5H2)4 + 2H](2-) after population of its first singlet excited state by 388 nm femtosecond laser irradiation. In contrast to the fluorescence and phosphorescence observed in condensed phase, a significant fraction of the photoexcited isolated dianions decays by electron loss to form the corresponding monoanions. Our transient photoelectron data reveal an ultrafast decay of the initially excited singlet (1)A2u state and concomitant rise in population of the triplet (3)A2u state, via sub-picosecond intersystem crossing (ISC). We find that both of the electronically excited states are metastably bound behind a repulsive Coulomb barrier and can decay via delayed autodetachment to yield electrons with characteristic kinetic energies. While excited state tunneling detachment (ESETD) from the singlet (1)A2u state takes only a few picoseconds, ESETD from the triplet (3)A2u state is much slower and proceeds on a time scale of hundreds of nanoseconds. The ISC rate in the gas phase is significantly higher than in solution, which can be rationalized in terms of changes to the energy dissipation mechanism in the absence of solvent molecules. [Pt2(μ-P2O5H2)4 + 2H](2-) is the first example of a photoexcited multianion for which ESETD has been observed following ISC. PMID:26851919

  3. Picosecond time-resolved fluorescence study on solute-solvent interaction of 2-aminoquinoline in room-temperature ionic liquids: aromaticity of imidazolium-based ionic liquids.

    PubMed

    Iwata, Koichi; Kakita, Minoru; Hamaguchi, Hiro-o

    2007-05-10

    Time-resolved fluorescence spectra and fluorescence anisotropy decay of 2-aminoquinoline (2AQ) have been measured in eight room-temperature ionic liquids, including five imidazolium-based aromatic ionic liquids and three nonaromatic ionic liquids. The same experiments have also been carried out in several ordinary molecular liquids for comparison. The observed time-resolved fluorescence spectra indicate the formation of pi-pi aromatic complexes of 2AQ in some of the aromatic ionic liquids but not in the nonaromatic ionic liquids. The fluorescence anisotropy decay data show unusually slow rotational diffusion of 2AQ in the aromatic ionic liquids, suggesting the formation of solute-solvent complexes. The probe 2AQ molecule is likely to be incorporated in the possible local structure of ionic liquids, and hence the anisotropy decays only through the rotation of the whole local structure, making the apparent rotational diffusion of 2AQ slow. The rotational diffusion time decreases rapidly by adding a small amount of acetonitrile to the solution. This observation is interpreted in terms of the local structure formation in the aromatic ionic liquids and its destruction by acetonitrile. No unusual behavior upon addition of acetonitrile has been found for the nonaromatic ionic liquids. It is argued that the aromaticity of the imidazolium cation plays a key role in the local structure formation in imidazolium-based ionic liquids. PMID:17428083

  4. Microsecond Time-Resolved Absorption Spectroscopy Used to Study CO Compounds of Cytochrome bd from Escherichia coli

    PubMed Central

    Siletsky, Sergey A.; Zaspa, Andrey A.; Poole, Robert K.; Borisov, Vitaliy B.

    2014-01-01

    Cytochrome bd is a tri-heme (b558, b595, d) respiratory oxygen reductase that is found in many bacteria including pathogenic species. It couples the electron transfer from quinol to O2 with generation of an electrochemical proton gradient. We examined photolysis and subsequent recombination of CO with isolated cytochrome bd from Escherichia coli in one-electron reduced (MV) and fully reduced (R) states by microsecond time-resolved absorption spectroscopy at 532-nm excitation. Both Soret and visible band regions were examined. CO photodissociation from MV enzyme possibly causes fast (τ<1.5 µs) electron transfer from heme d to heme b595 in a small fraction of the protein, not reported earlier. Then the electron migrates to heme b558 (τ∼16 µs). It returns from the b-hemes to heme d with τ∼180 µs. Unlike cytochrome bd in the R state, in MV enzyme the apparent contribution of absorbance changes associated with CO dissociation from heme d is small, if any. Photodissociation of CO from heme d in MV enzyme is suggested to be accompanied by the binding of an internal ligand (L) at the opposite side of the heme. CO recombines with heme d (τ∼16 µs) yielding a transient hexacoordinate state (CO-Fe2+-L). Then the ligand slowly (τ∼30 ms) dissociates from heme d. Recombination of CO with a reduced heme b in a fraction of the MV sample may also contribute to the 30-ms phase. In R enzyme, CO recombines to heme d (τ∼20 µs), some heme b558 (τ∼0.2–3 ms), and finally migrates from heme d to heme b595 (τ∼24 ms) in ∼5% of the enzyme population. Data are consistent with the recent nanosecond study of Rappaport et al. conducted on the membranes at 640-nm excitation but limited to the Soret band. The additional phases were revealed due to differences in excitation and other experimental conditions. PMID:24755641

  5. Nanosecond fluorescence spectroscopy

    SciTech Connect

    Leskovar, B.

    1985-03-01

    This article is a summary of a short course lecture given in conjunction with the 1984 Nuclear Science Symposium. Measuring systems for nanosecond fluorescence spectroscopy using single-photon counting techniques are presented. These involve systems based on relaxation-type spark gap light pulser and synchronously pumped mode-locked dye lasers. Furthermore, typical characteristics and optimization of operating conditions of the critical components responsible for the system time resolution are discussed. A short comparison of the most important deconvolution methods for numerical analysis of experimental data is given particularly with respect to the signal-to-noise ratio of the fluorescence signal. 22 refs., 8 figs.

  6. In-situ analysis of fruit anthocyanins by means of total internal reflectance, continuous wave and time-resolved spectroscopy

    NASA Astrophysics Data System (ADS)

    Zude, Manuela; Spinelli, Lorenzo; Dosche, Carsten; Torricelli, Alessandro

    2009-08-01

    In sweet cherry (Prunus avium), the red pigmentation is correlated with the fruit maturity stage and can be measured by non-invasive spectroscopy. In the present study, the influence of varying fruit scattering coefficients on the fruit remittance spectrum (cw) were corrected with the effective pathlength and refractive index in the fruit tissue obtained with distribution of time-of-flight (DTOF) readings and total internal reflection fluorescence (TIRF) analysis, respectively. The approach was validated on fruits providing variation in the scattering coefficient outside the calibration sample set. In the validation, the measuring uncertainty when non-invasively analyzing fruits with cw method in comparison with combined application of cw, DTOF, and TIRF measurements showed an increase in r2 up to 22.7 % with, however, high errors in all approaches.

  7. Tryptophan dynamics in the exploration of micro-conformational changes of refolded ?-lactoglobulin after thermal exposure: a steady state and time-resolved fluorescence approach.

    PubMed

    Halder, Umesh C; Chakraborty, Jishnu; Das, Niloy; Bose, Sayantan

    2012-04-01

    Refolding intermediates of proteins, including molten globules, are likely to undergo dynamic conformational transitions. In this work, thermal unfolding and refolding of bovine ?-lactoglobulin (?-lg) have been revisited to encounter such intermediate states. Lower thermal range (< 80C) was selected to avoid irreversible aggregate formation. The gross kinetic refolding as monitored with the fluorophore, Trp19, was likely to be reversible but alteration in time resolved fluorescence parameters ruled out the possibility of micro-structural reversibility for the refolded partner. Time resolved fluorescence showed that the refolded protein still lacks some intact native conformation. Far-UV CD signals lack the signature of any secondary structural distortion in global structural context whereas near-UV CD signals were strongly indicative of perturbation in micro-structure surrounding the aromatic moieties which hardly revives after cooling. Steady state anisotropy results showed successfully the break-down of dimer to monomer form of ?-lg within 50C temperature range and augmentation in anisotropy up on further thermal stress reflected the reorganization of tryptophan residues into more restricted and rigid micro-environment as well as irreversible disulfide-linked dimer formation. Reliability of conformational reversibility in the thermal unfolding-refolding is still enigmatic on micro and global structural perspectives. Intermediate state prior to the completion of refolding of thermally exposed ?-lg was identified through fluorescence studies. PMID:22342029

  8. Development and demonstration of table-top synchronized fast-scan femtosecond time-resolved spectroscopy system by single-shot scan photo detector array

    NASA Astrophysics Data System (ADS)

    Yabushita, Atsushi; Kao, Chih-Hsien; Lee, Yu-Hsien; Kobayashi, Takayoshi

    2015-07-01

    Ultrafast dynamics is generally studied by pump-probe method with laser pulse, which scans optical delay by motorized stage step by step. Using ultrashort laser pulse shorter than typical molecular vibration periods, the pump-probe measurement can study both of electronic dynamics and vibration dynamics simultaneously. The probe wavelength dependence of the ultrafast electronic and vibration dynamics (UEVD) helps us to distinguish the signal contributions from the dynamics of the electronic ground state and that of the electronic excited states, which elucidates primary reaction mechanism after photoexcitation. Meanwhile, the measurement time of UEVD spectroscopy takes too long time to be used in realistic application. In our previous work, we have developed multi-channel lock-in amplifying (MLA) detectors to study UEVD at all probe wavelengths simultaneously, and synchronized it with laser and fast-scan delay stage to scan the data in five seconds. It enabled us to study UEVD spectroscopy even for photo-fragile materials. However, the home-made MLA detectors required for the measurement is expensive and massive in size and weight, thus not suitable for general researchers in the field of ultrafast time-resolved spectroscopy. In the present work, we have developed a table-top synchronized fast-scan femtosecond time-resolved spectroscopy system using single shot scan line CCD. This system measures time-resolved trace at all probe wavelengths simultaneously in five seconds. The CCD-based fast-scan time-resolved spectroscopy system enables us to study ultrafast dynamics of various materials even biomaterials, which have been thought to be hard or even impossible to be studied in previous methods.

  9. Time-Resolved Down-Conversion of 2-Aminopurine in a DNA Hairpin: Fluorescence Anisotropy and Solvent Effects

    NASA Astrophysics Data System (ADS)

    Tourón Touceda, Patricia; Gelot, Thomas; Crégut, Olivier; Léonard, Jérémie; Haacke, Stefan

    2013-03-01

    Femtosecond fluorescence anisotropy decay measured by type II difference frequency generation provides new insight into the local structural dynamics of ΔP(-)PBS fragments of the HIV- 1 DNA primary binding sequence, labeled with 2-aminopurine.

  10. Selective nonpeptidic fluorescent ligands for oxytocin receptor: design, synthesis, and application to time-resolved FRET binding assay.

    PubMed

    Karpenko, Iuliia A; Margathe, Jean-François; Rodriguez, Thiéric; Pflimlin, Elsa; Dupuis, Elodie; Hibert, Marcel; Durroux, Thierry; Bonnet, Dominique

    2015-03-12

    The design and the synthesis of the first high-affinity fluorescent ligands for oxytocin receptor (OTR) are described. These compounds enabled the development of a TR-FRET based assay for OTR, readily amenable to high throughput screening. The validation of the assay was achieved by competition experiments with both peptide and nonpeptide OTR ligands as competitors. These probes represent the first selective fluorescent ligands for the oxytocin G protein-coupled receptor. PMID:25642985

  11. Determination of blood oxygenation in the brain by time-resolved reflectance spectroscopy: influence of the skin, skull, and meninges

    NASA Astrophysics Data System (ADS)

    Hielscher, Andreas H.; Liu, Hanli; Wang, Lihong V.; Tittel, Frank K.; Chance, Britton; Jacques, Steven L.

    1994-07-01

    Near infrared light has been used for the determination of blood oxygenation in the brain but little attention has been paid to the fact that the states of blood oxygenation in arteries, veins, and capillaries differ substantially. In this study, Monte Carlo simulations for a heterogeneous system were conducted, and near infrared time-resolved reflectance measurements were performed on a heterogeneous tissue phantom model. The model was made of a solid polyester resin, which simulates the tissue background. A network of tubes was distributed uniformly through the resin to simulate the blood vessels. The time-resolved reflectance spectra were taken with different absorbing solutions filled in the network. Based on the simulation and experimental results, we investigated the dependence of the absorption coefficient obtained from the heterogeneous system on the absorption of the actual absorbing solution filled in the tubes. We show that light absorption by the brain should result from the combination of blood and blood-free tissue background.

  12. Remarkable effects of solvent and substitution on the photo-dynamics of cytosine: a femtosecond broadband time-resolved fluorescence and transient absorption study.

    PubMed

    Ma, Chensheng; Cheng, Chopen Chan-Wut; Chan, Chris Tsz-Leung; Chan, Ruth Chau-Ting; Kwok, Wai-Ming

    2015-07-15

    Cytosine (Cyt) among all the nucleic acid bases features the most complex and least understood nonradiative deactivation, a process that is crucially important for its photostability. Herein, the excited state dynamics of Cyt and a series of its N1- and C5-derivatives, including the full set of Cyt nucleosides and nucleotides in DNA and RNA and the nucleosides of 5-methyl cytosine, 5-methylcytidine and 2'-deoxy-5-methylcytidine, have been investigated in water and in methanol employing femtosecond broadband time-resolved fluorescence coupled with fs transient absorption spectroscopy. The results reveal remarkable state-specific effects of the substitution and solvent in tuning distinctively the timescales and pathways of the nonradiative decays. For Cyt and the N1-derivatives, the nonradiative deactivations occur in a common two-state process through three channels, two from the light-absorbing ??* state with respectively the sub-picosecond (?0.2 ps) and the picosecond (?1.5 ps) time constant, and the third is due to an optically dark n?* state with the lifetime ranging from several to hundreds of picoseconds depending on solvents and substitutions. Compared to Cyt, the presence of the ribose or deoxyribose moiety at the N1 position of N1-derivatives facilitates the formation of the n?* at the sub-picosecond timescale and at the same time increases its lifetime by ?4-6 times in both water and methanol. In sharp contrast, the existence of the methyl group at the C5 position of the C5-derivatives eliminates completely the sub-picosecond ??* channel and the channel due to the n?*, but on the other hand slows down the decay of the ??* state which after relaxation exhibits a single time constant of ?4.1 to ?7.6 ps depending on solvents. Varying the solvent from water to methanol accelerates only slightly the decay of the ??* state in all the compounds; while for Cyt and its N1-derivatives, this change of solvent also retards strongly the n?* channel, prolongs its lifetime from such as ?7.7 ps in water to ?52 ps in methanol for Cyt and from ?30 ps in water to ?186 ps in methanol for deoxycytidine. The spectral signatures we obtained for the ??* and the n?* states allow unambiguous evidence for clarifying uncertainties in the excited states of Cyt and the derivatives. The results provide a unifying experimental characterization at an improved level of detail about the photophysics of Cyt and its analogues under biologically relevant conditions and may help in understanding the photostability as well as photo-damages of the bases and related DNAs. PMID:26126728

  13. Simultaneous determination of nabumetone and its principal metabolite in medicines and human urine by time-resolved fluorescence.

    PubMed

    Murillo Pulgarín, José Antonio; Alañón Molina, Aurelia; Martínez Ferreras, Fernando

    2012-11-01

    A simple fluorescent methodology for the simultaneous determination of nabumetone and its main metabolite, 6-methoxy-2-naphthylacetic acid (6-MNA), in pharmaceutical preparations and human urine is proposed. Due to the strong overlapping between the fluorescence spectra of both analytes, the use of fluorescence decay curves to resolve their mixture is proposed, since these curves are more selective. Values of dependent instrumental variables affecting the signal-to-noise ratio were fixed using a simplex optimization procedure. A factorial design with three levels per factor coupled to a central composite design was selected to obtain a calibration matrix of thirteen standards plus one blank sample that was processed using a partial least-squares (PLS) analysis. In order to assess the goodness of the proposed method, a prediction set of ten synthetic samples was analyzed, obtaining recovery percentages between 97 and 105%. Limits of detection, calculated by means of a new criterion, were 0.96 μg L(-1) and 0.88 μg L(-1) for nabumetone and 6-MNA, respectively. The method was also tested in the pharmaceutical preparation Relif, which contains nabumetone, obtaining recovery percentages close to 100%. Finally, the simultaneous determination of both analytes in human urine samples was successfully carried out by the PLS-analysis of a matrix of fifteen standards plus four analyte blanks and the use of the standard addition technique. Although urine shows native fluorescence, no extraction method or prior separation of the analytes was needed. PMID:22977877

  14. Femtosecond Time-Resolved Stimulated Raman Spectroscopy: Application to the Ultrafast Internal Conversion in β-Carotene†

    PubMed Central

    McCamant, David W.; Kukura, Philipp; Mathies, Richard A.

    2005-01-01

    We have developed the technique of femtosecond stimulated Raman spectroscopy (FSRS), which allows the rapid collection of high-resolution vibrational spectra on the femtosecond time scale. FSRS combines a sub-50 fs actinic pump pulse with a two-pulse stimulated Raman probe to obtain vibrational spectra whose frequency resolution limits are uncoupled from the time resolution. This allows the acquisition of spectra with <100 fs time resolution and <30 cm−1 frequency resolution. Additionally, FSRS is unaffected by background fluorescence, provides rapid (100 ms) acquisition times, and exhibits traditional spontaneous Raman line shapes. FSRS is used here to study the relaxation dynamics of β-carotene. Following optical excitation to S2 (1Bu+) the molecule relaxes in 160 fs to S1 (2Ag−) and then undergoes two distinct stages of intramolecular vibrational energy redistribution (IVR) with 200 and 450 fs time constants. These processes are attributed to rapid (200 fs) distribution of the internal conversion energy from the S1 C=C modes into a restricted bath of anharmonically coupled modes followed by complete IVR in 450 fs. FSRS is a valuable new technique for studying the vibrational structure of chemical reaction intermediates and transition states. PMID:16710440

  15. A high-throughput time-resolved mini-silicon photomultiplier with embedded fluorescence lifetime estimation in 0.13 μm CMOS.

    PubMed

    Tyndall, David; Rae, Bruce R; Li, David Day-Uei; Arlt, Jochen; Johnston, Abigail; Richardson, Justin A; Henderson, Robert K

    2012-12-01

    We describe a miniaturized, high-throughput, time-resolved fluorescence lifetime sensor implemented in a 0.13 m CMOS process, combining single photon detection, multiple channel timing and embedded pre-processing of fluorescence lifetime estimations on a single device. Detection is achieved using an array of single photon avalanche diodes (SPADs) arranged in a digital silicon photomultiplier (SiPM) architecture with 400 ps output pulses and a 10% fill-factor. An array of time-to-digital converters (TDCs) with ≈50 ps resolution records up to 8 photon events during each excitation period. Data from the TDC array is then processed using a centre-of-mass method (CMM) pre-calculation to produce fluorescence lifetime estimations in real-time. The sensor is believed to be the first reported implementation of embedded fluorescence lifetime estimation. The system is demonstrated in a practical laboratory environment with measurements of a variety of fluorescent dyes with different single exponential lifetimes, successfully showing the sensor's ability to overcome the classic pile-up limitation of time-correlated single photon counting (TCSPC) by over an order of magnitude. PMID:23853257

  16. Time-resolved spectroscopy of 5d-4f transitions in Pr3+ doped alkali-earth fluorides

    NASA Astrophysics Data System (ADS)

    Shendrik, R.; Radzhabov, E.; Nagirnyi, V.

    2010-11-01

    We measured time-resolved spectra and emission decay times under pulsed X-ray and synchrotron excitation in alkali-earth fluorides doped with Pr3+ ions. Two fast decay components were found in the emission spectra of BaF2-Pr3+ and SrF2-Pr3+ . These were 4 ns and 21 ns in BaF2-Pr3+ and 8 and 24 ns in SrF2-Pr3+. The intensity of the faster components 4 ns and 8 ns depended on concentration of Pr3+. Thus, the presence of aggregates might be the cause of such faster components.

  17. Time-resolved laser-induced fluorescence measurement of ion and neutral dynamics in a Hall thruster during ionization oscillations

    NASA Astrophysics Data System (ADS)

    Lucca Fabris, Andrea; Young, Christopher V.; Cappelli, Mark A.

    2015-12-01

    The paper presents spatially and temporally resolved laser-induced fluorescence (LIF) measurements of the xenon ion and neutral velocity distribution functions in a 400 W Hall thruster during natural ionization oscillations at 23 kHz, the so-called "breathing mode." Strong fluctuations in measured axial ion velocity throughout the discharge current cycle are observed at five spatial locations and the velocity maxima appear in the low current interval. The spatio-temporal evolution of the ion velocity distribution function suggests a propagating acceleration front undergoing periodic motion between the thruster exit plane and ˜1 cm downstream into the plume. The ion LIF signal intensity oscillates almost in phase with the discharge current, while the neutral fluorescence signal appears out of phase, indicating alternating intervals of strong and weak ionization.

  18. Time-resolved fluorescence anisotropy in degenerate two-state systems: the role of complex stochastic processes

    NASA Astrophysics Data System (ADS)

    Law, C. K.; Knox, R. S.; Eberly, J. H.

    1996-08-01

    We examine the Haken-Reineker-Strobl model of relaxation processes for a class of two-site systems. We permit the stochastic processes used to simulate reservoir noise in the model to be complex Hermitean, instead of purely real. We demonstrate in a specific case that this can open the possibility of identifying the precise meaning of the decay rate constants obtained from fluorescence anisotropy measurements.

  19. High-sensitivity time-resolved intracavity laser Fourier transform spectroscopy with vertical-cavity surface-emitting multiple-quantum-well lasers.

    PubMed

    Picqu, Nathalie; Guelachvili, Guy; Kachanov, Alexander A

    2003-03-01

    Spectra composed of hundreds of time components for absorption path lengths of up to 130 km have been recorded near 1050 nm by combination of two recent techniques, intracavity laser spectroscopy with vertical external cavity surface-emitting multiple-quantum-well lasers and time-resolved Fourier transform spectroscopy. A sensitivity of 1 x 10(-10) cm(-1) Hz(-1/2) is achieved for 10(4) simultaneously acquired spectral elements, 3 orders of magnitude better than the sensitivity obtained in previous similar experiments. Specific advantages of the method, especially for frequency and intensity metrology of weak absorption transitions, are discussed. PMID:12659429

  20. Time-resolved spectroscopic study of photofragment fluorescence in methane/air mixtures and its diagnostic implications

    NASA Astrophysics Data System (ADS)

    Jonsson, Malin; Borggren, Jesper; Aldén, Marcus; Bood, Joakim

    2015-09-01

    In this work 80-picosecond laser pulses of 266-nm wavelength with intensities up to (2.0 ± 0.5) × 1011 W/cm2 were used for fragmentation of methane/air gas mixtures at ambient pressure and temperature. Emission spectra are, for the first time, studied with ultrahigh temporal resolution using a streak camera. Fluorescence spectra from CH(A2Δ-X2Π, B2Σ--X2Π, C2Σ+-X2Π), CN(B2Σ+-X2Σ+, Δ v = 0 and Δ v = ±1), NH(A3Π--X3Σ-), OH(A2Σ+-X2Π) and N2 +(B2Σu + X2Σg + were recorded and analyzed. By fitting simulated spectra to high-resolution experimental spectra, rotational and vibrational temperatures are estimated, showing that CH(C), CN(B), NH(A), and OH(A) are formed in highly excited vibrational and rotational states. The fluorescence signal dependencies on laser intensity and CH4/air equivalence ratio were investigated as well as the fluorescence lifetimes. All fragments observed are formed within 200 ps after the arrival of the laser pulse and their fluorescence lifetimes are shorter than 1 ns, except for CN(B-X) Δ v = 0 whose lifetime is 2.0 ns. The CN(B-X) Δ v = 0 fluorescence was studied temporally under high spectral resolution, and it was found that the vibrational levels are not populated simultaneously, but with a rate that decreases with increasing vibrational quantum number. This observation indicates that the rate of the chemical reaction that forms the CN(B) fragments is decreasing with increasing vibrational state of the product. The results provide vital information for the application of laser diagnostic techniques based on strong UV excitation, as they show that such methods might not be entirely non-intrusive and suffering from spectral interferences, unless the laser intensity is kept sufficiently low. Finally, equivalence ratios were determined from "unknown" spectra using multivariate analysis, showing a good agreement with theoretical compositions with an error of 4 %. The method is expected to be a useful diagnostic tool for measurements of local equivalence ratios in for example combustion environments.

  1. Mapping of calf muscle oxygenation and haemoglobin content during dynamic plantar flexion exercise by multi-channel time-resolved near-infrared spectroscopy.

    PubMed

    Torricelli, Alessandro; Quaresima, Valentina; Pifferi, Antonio; Biscotti, Giovanni; Spinelli, Lorenzo; Taroni, Paola; Ferrari, Marco; Cubeddu, Rinaldo

    2004-03-01

    A compact and fast multi-channel time-resolved near-infrared spectroscopy system for tissue oximetry was developed. It employs semiconductor laser and fibre optics for delivery of optical signals. Photons are collected by eight 1 mm fibres and detected by a multianode photomultiplier. A time-correlated single photon counting board is used for the parallel acquisition of time-resolved reflectance curves. Estimate of the reduced scattering coefficient is achieved by fitting with a standard model of diffusion theory, while the modified Lambert-Beer law is used to assess the absorption coefficient. In vivo measurements were performed on five healthy volunteers to monitor spatial changes in calf muscle (medial and lateral gastrocnemius; MG, LG) oxygen saturation (SmO2) and total haemoglobin concentration (tHb) during dynamic plantar flexion exercise performed at 50% of the maximal voluntary contraction. At rest SmO2 was 73.0 +/- 0.9 and 70.5 +/- 1.7% in MG and LG, respectively (P = 0.045). At the end of the exercise, SmO2 decreased (69.1 +/- 1.8 and 63.8 +/- 2.1% in MG and LG, respectively; P < 0.01). The LG desaturation was greater than the MG desaturation (P < 0.02). These results strengthen the role of time-resolved near-infrared spectroscopy as a powerful tool for investigating the spatial and temporal features of muscle SmO2 and tHb. PMID:15070196

  2. Characterization of female breasts in vivo by time-resolved and spectroscopic measurements in the near infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Heusmann, Hans; Koelzer, Jochen G.; Mitic, Gerhard

    1996-10-01

    Time-resolved and spectroscopic in vivo measurements were performed to determine the optical properties of the female breast in transmission. The time-resolved measurements were carried out at different positions on the female breast with a Ti:sapphire laser using as synchroscan steak camera. A diffusion model was used to calculate the absorption coefficient (mu) A and the reduced scattering coefficient. In addition, spectroscopic in vivo measurements of more than 100 patients were performed in a wavelength range between 650 and 1000 nm. A variety of pathological alterations could be characterized by measuring patients of different ages, different breast sizes, and at carrying locations on the breast. The results indicate that besides the pure detection of the amount of blood in the neovascular network, the volume concentrations of water and fat model was developed that takes the volume percentages of fat and water, the concentration and oxygenation of hemoglobin, and the relevant optical parameters into account. Experiments were carried out with volunteers and patients in a clinical environment: typical observations are presented and analyzed statistically.

  3. Probing organometallic reactions by time-resolved infrared spectroscopy in solution and in the solid state using quantum cascade lasers.

    PubMed

    Calladine, James A; Horvath, Raphael; Davies, Andrew J; Wriglesworth, Alisdair; Sun, Xue-Zhong; George, Michael W

    2015-05-01

    The photochemistry and photophysics of metal carbonyl compounds (W(CO)6, Cp*Rh(CO)2 (Cp* = η(5)-C5Me5), and fac-[Re(CO)3(4,4'-bpy)2Br] [bpy = bipyridine]) have been examined on the nanosecond timescale using a time-resolved infrared spectrometer with an external cavity quantum cascade laser (QCL) as the infrared source. We show the photochemistry of W(CO)6 in alkane solution is easily monitored, and very sensitive measurements are possible with this approach, meaning it can monitor small transients with absorbance changes less than 10(-6) ΔOD. The C-H activation of Cp*Rh(CO)(C6H12) to form Cp*Rh(CO)(C6H11)H occurs within the first few tens of nanoseconds following photolysis, and we demonstrate that kinetics obtained following deconvolution are in excellent agreement with those measured using an ultrafast laser-based spectrometer. We also show that the high flux and tunability of QCLs makes them suited for solid-state and time-resolved measurements. PMID:25811673

  4. Time-resolved K α spectroscopy measurements of hot-electron equilibration dynamics in thin-foil solid targets: collisional and collective effects

    NASA Astrophysics Data System (ADS)

    Nilson, P. M.; Solodov, A. A.; Davies, J. R.; Theobald, W.; Mileham, C.; Stoeckl, C.; Begishev, I. A.; Zuegel, J. D.; Froula, D. H.; Betti, R.; Meyerhofer, D. D.

    2015-11-01

    Time-resolved K α spectroscopy measurements from high-intensity laser interactions with thin-foil solid targets are reviewed. Thin Cu foils were irradiated with 1-10 J, 1 ps pulses at focused intensities from 1018 to 1019 W cm-2. The experimental data show K α -emission pulse widths from 3 to 6 ps, increasing with laser intensity. The time-resolved K α -emission data are compared to a hot-electron transport and K α -production model that includes collisional electron-energy coupling, resistive heating, and electromagnetic field effects. The experimental data show good agreement with the model when a reduced ponderomotive scaling is used to describe the initial mean hot-electron energy over the relevant intensity range.

  5. Time-resolved Kα spectroscopy measurements of hot-electron equilibration dynamics in thin-foil solid targets: Collisional and collective effects

    SciTech Connect

    Nilson, P. M.; Solodov, A. A.; Davies, J. R.; Theobald, W.; Mileham, C.; Stoeckl, C.; Begishev, I. A.; Zuegel, J. D.; Froula, D. H.; Betti, R.; Meyerhofer, D. D.

    2015-09-25

    Time-resolved Kα spectroscopy measurements from high-intensity laser interactions with thin-foil solid targets are reviewed. Thin Cu foils were irradiated with 1- to 10-J, 1-ps pulses at focused intensities from 1018 to 1019 W/cm2. The experimental data show Kα-emission pulse widths from 3 to 6 ps, increasing with laser intensity. The time-resolved Kα-emission data are compared to a hot-electron transport and Kα-production model that includes collisional electron-energy coupling, resistive heating, and electromagnetic field effects. The experimental data show good agreement with the model when a reduced ponderomotive scaling is used to describe the initial mean hot-electron energy over the relevant intensity range.

  6. Employing time-resolved terahertz spectroscopy to analyze carrier dynamics in thin-film Cu{sub 2}ZnSn(S,Se){sub 4} absorber layers

    SciTech Connect

    Guglietta, Glenn W.; Baxter, Jason B.; Choudhury, Kaushik Roy; Caspar, Jonathan V.

    2014-06-23

    We report the application of time-resolved terahertz spectroscopy (TRTS) to measure photoexcited carrier lifetimes and mobility, and to determine recombination mechanisms in Cu{sub 2}ZnSn(S,Se){sub 4} (CZTSSe) thin films fabricated from nanocrystal inks. Ultrafast time resolution permits tracking the evolution of carrier density to determine recombination rates and mechanisms. The carrier generation profile was manipulated by varying the photoexcitation wavelength and fluence to distinguish between surface, Shockley-Read-Hall (SRH), radiative, and Auger recombination mechanisms and determine rate constants. Surface and SRH recombination are the dominant mechanisms for the air/CZTSSe/SiO{sub 2}/Si film stack. Diffusion to, and then recombination at, the air-CZTSSe interface occurred on the order of 100 picoseconds, while SRH recombination lifetimes were 1–2 nanoseconds. TRTS measurements can provide information that is complementary to conventional time-resolved photoluminescence measurements and can direct the design of efficient thin film photovoltaics.

  7. Time-resolvedspectroscopy measurements of hot-electron equilibration dynamics in thin-foil solid targets: Collisional and collective effects

    DOE PAGESBeta

    Nilson, P. M.; Solodov, A. A.; Davies, J. R.; Theobald, W.; Mileham, C.; Stoeckl, C.; Begishev, I. A.; Zuegel, J. D.; Froula, D. H.; Betti, R.; et al

    2015-09-25

    Time-resolvedspectroscopy measurements from high-intensity laser interactions with thin-foil solid targets are reviewed. Thin Cu foils were irradiated with 1- to 10-J, 1-ps pulses at focused intensities from 1018 to 1019 W/cm2. The experimental data show Kα-emission pulse widths from 3 to 6 ps, increasing with laser intensity. The time-resolved Kα-emission data are compared to a hot-electron transport and Kα-production model that includes collisional electron-energy coupling, resistive heating, and electromagnetic field effects. The experimental data show good agreement with the model when a reduced ponderomotive scaling is used to describe the initial mean hot-electron energy over the relevant intensitymore » range.« less

  8. Density relaxation and particle motion characteristics in a non-ionic deep eutectic solvent (acetamide + urea): Time-resolved fluorescence measurements and all-atom molecular dynamics simulations

    SciTech Connect

    Das, Anuradha; Das, Suman; Biswas, Ranjit

    2015-01-21

    Temperature dependent relaxation dynamics, particle motion characteristics, and heterogeneity aspects of deep eutectic solvents (DESs) made of acetamide (CH{sub 3}CONH{sub 2}) and urea (NH{sub 2}CONH{sub 2}) have been investigated by employing time-resolved fluorescence measurements and all-atom molecular dynamics simulations. Three different compositions (f) for the mixture [fCH{sub 3}CONH{sub 2} + (1 − f)NH{sub 2}CONH{sub 2}] have been studied in a temperature range of 328-353 K which is ∼120-145 K above the measured glass transition temperatures (∼207 K) of these DESs but much lower than the individual melting temperature of either of the constituents. Steady state fluorescence emission measurements using probe solutes with sharply different lifetimes do not indicate any dependence on excitation wavelength in these metastable molten systems. Time-resolved fluorescence anisotropy measurements reveal near-hydrodynamic coupling between medium viscosity and rotation of a dissolved dipolar solute. Stokes shift dynamics have been found to be too fast to be detected by the time-resolution (∼70 ps) employed, suggesting extremely rapid medium polarization relaxation. All-atom simulations reveal Gaussian distribution for particle displacements and van Hove correlations, and significant overlap between non-Gaussian (α{sub 2}) and new non-Gaussian (γ) heterogeneity parameters. In addition, no stretched exponential relaxations have been detected in the simulated wavenumber dependent acetamide dynamic structure factors. All these results are in sharp contrast to earlier observations for ionic deep eutectics with acetamide [Guchhait et al., J. Chem. Phys. 140, 104514 (2014)] and suggest a fundamental difference in interaction and dynamics between ionic and non-ionic deep eutectic solvent systems.

  9. Density relaxation and particle motion characteristics in a non-ionic deep eutectic solvent (acetamide + urea): time-resolved fluorescence measurements and all-atom molecular dynamics simulations.

    PubMed

    Das, Anuradha; Das, Suman; Biswas, Ranjit

    2015-01-21

    Temperature dependent relaxation dynamics, particle motion characteristics, and heterogeneity aspects of deep eutectic solvents (DESs) made of acetamide (CH3CONH2) and urea (NH2CONH2) have been investigated by employing time-resolved fluorescence measurements and all-atom molecular dynamics simulations. Three different compositions (f) for the mixture [fCH3CONH2 + (1 - f)NH2CONH2] have been studied in a temperature range of 328-353 K which is ∼120-145 K above the measured glass transition temperatures (∼207 K) of these DESs but much lower than the individual melting temperature of either of the constituents. Steady state fluorescence emission measurements using probe solutes with sharply different lifetimes do not indicate any dependence on excitation wavelength in these metastable molten systems. Time-resolved fluorescence anisotropy measurements reveal near-hydrodynamic coupling between medium viscosity and rotation of a dissolved dipolar solute. Stokes shift dynamics have been found to be too fast to be detected by the time-resolution (∼70 ps) employed, suggesting extremely rapid medium polarization relaxation. All-atom simulations reveal Gaussian distribution for particle displacements and van Hove correlations, and significant overlap between non-Gaussian (α2) and new non-Gaussian (γ) heterogeneity parameters. In addition, no stretched exponential relaxations have been detected in the simulated wavenumber dependent acetamide dynamic structure factors. All these results are in sharp contrast to earlier observations for ionic deep eutectics with acetamide [Guchhait et al., J. Chem. Phys. 140, 104514 (2014)] and suggest a fundamental difference in interaction and dynamics between ionic and non-ionic deep eutectic solvent systems. PMID:25612718

  10. Homodimerization of Amyloid Precursor Protein at the Plasma Membrane: A homoFRET Study by Time-Resolved Fluorescence Anisotropy Imaging

    PubMed Central

    Devauges, Viviane; Marquer, Catherine; Lécart, Sandrine; Cossec, Jack-Christophe; Potier, Marie-Claude; Fort, Emmanuel; Suhling, Klaus; Lévêque-Fort, Sandrine

    2012-01-01

    Classical FRET (Förster Resonance Energy Transfer) using two fluorescent labels (one for the donor and another one for the acceptor) is not efficient for studying the homodimerization of a protein as only half of the homodimers formed can be identified by this technique. We thus resorted to homoFRET detected by time-resolved Fluorescence Anisotropy IMaging (tr-FAIM). To specifically image the plasma membrane of living cells, an original combination of tr-FAIM and Total Internal Reflection Fluorescence Lifetime Imaging Microscope (TIRFLIM) was implemented. The correcting factor accounting for the depolarization due to the high numerical aperture (NA) objective, mandatory for TIRF microscopy, was quantified on fluorescein solutions and on HEK293 cells expressing enhanced Green Fluorescence Protein (eGFP). Homodimerization of Amyloid Precursor Protein (APP), a key mechanism in the etiology of Alzheimer’s disease, was measured on this original set-up. We showed, both in epifluorescence and under TIRF excitation, different energy transfer rates associated with the homodimerization of wild type APP-eGFP or of a mutated APP-eGFP, which forms constitutive dimers. This original set-up thus offers promising prospects for future studies of protein homodimerization in living cells in control and pathological conditions. PMID:22973448

  11. Exactly soluble model of the time-resolved fluorescence return to thermal equilibrium in many-particle systems after excitation

    NASA Astrophysics Data System (ADS)

    Czachor, Andrzej

    2016-02-01

    In this paper we consider the assembly of weakly interacting identical particles, where the occupation of single-particle energy-levels at thermal equilibrium is governed by statistics. The analytic form of the inter-energy-level jump matrix is derived and analytic solution of the related eigen-problem is given. It allows one to demonstrate the nature of decline in time of the energy emission (fluorescence, recombination) of such many-level system after excitation in a relatively simple and unifying way - as a multi-exponential de-excitation. For the system of L energy levels the number of the de-excitation lifetimes is L-1. The lifetimes depend on the energy level spectrum as a whole. Two- and three-level systems are considered in detail. The impact of the energy level degeneracy on the lifetimes is discussed.

  12. Charge separation in subcells of triple-junction solar cells revealed by time-resolved photoluminescence spectroscopy.

    PubMed

    Tex, David M; Imaizumi, Mitsuru; Kanemitsu, Yoshihiko

    2015-11-30

    We measure the excitation-wavelength and power dependence of time-resolved photoluminescence (PL) from the top InGaP subcell in a InGaP/GaAs/Ge triple-junction solar cell. The wavelength-dependent data reveals that the PL decays are governed by charge separation. A fast single-exponential PL decay is observed at low excitation power densities, which is the charge separation under short-circuit condition. Under strong excitation a bi-exponential PL decay is observed. Its slow component appears at early times, followed by a faster component at late times. The slow decay is the carrier recombination of the subcell. The following fast component is the charge separation process under reduced built-in potential near the operating point. The subcells electrical conversion efficiency close to the operating point is evaluated using this decay time constant. PMID:26698814

  13. Tracking the photodissociation dynamics of liquid nitromethane at 266 nm by femtosecond time-resolved broadband transient grating spectroscopy

    NASA Astrophysics Data System (ADS)

    Wu, Honglin; Song, Yunfei; Yu, Guoyang; Wang, Yang; Wang, Chang; Yang, Yanqiang

    2016-05-01

    Femtosecond time-resolved transient grating (TG) technique was employed to get insight into the photodissociation mechanism of liquid nitromethane (NM). Broadband white-light continuum was introduced as the probe to observe the evolution of electronic excited states of NM molecules and the formation of photodissociation products simultaneously. The reaction channel of liquid NM under 266 nm excitation was obtained that NM molecules in excited state S2 relax through two channels: about 73% relax to low lying S1 state through S2/S1 internal conversion with a time constant of 0.24 ps and then go back to the ground state through S1/S0 internal conversion; the other 27% will dissociate with a time constant of 2.56 ps. NO2 was found to be one of the products from the experimental TG spectra, which confirmed that C-N bond rupture was the primary dissociation channel of liquid NM.

  14. Investigation of verbal and visual working memory by multi-channel time-resolved functional near-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Contini, D.; Caffini, M.; Re, R.; Zucchelli, L.; Spinelli, L.; Basso Moro, S.; Bisconti, S.; Ferrari, M.; Quaresima, V.; Cutini, S.; Torricelli, A.

    2013-03-01

    Working memory (WM) is fundamental for a number of cognitive processes, such as comprehension, reasoning and learning. WM allows the short-term maintenance and manipulation of the information selected by attentional processes. The goal of this study was to examine by time-resolved fNIRS neural correlates of the verbal and visual WM during forward and backward digit span (DF and DB, respectively) tasks, and symbol span (SS) task. A neural dissociation was hypothesised between the maintenance and manipulation processes. In particular, a dorsolateral/ventrolateral prefrontal cortex (DLPFC/VLPFC) recruitment was expected during the DB task, whilst a lateralised involvement of Brodmann Area (BA) 10 was expected during the execution of the DF task. Thirteen subjects were monitored by a multi-channel, dual-wavelength (690 and 829 nm) time-resolved fNIRS system during 3 minutes long DF and DB tasks and 4 minutes long SS task. The participants' mean memory span was calculated for each task: DF: 6.46+/-1.05 digits; DB: 5.62+/-1.26 digits; SS: 4.69+/-1.32 symbols. No correlation was found between the span level and the heart rate data (measured by pulse oximeter). As expected, DB elicited a broad activated area, in the bilateral VLPFC and the right DLPFC, whereas a more localised activation was observed over the right hemisphere during either DF (BA 10) or SS (BA 10 and 44). The robust involvement of the DLPFC during DB, compared to DF, is compatible with previous findings and with the key role of the central executive subserving in manipulating processes.

  15. Time-resolved fluorescence resonance energy transfer shows that the bacterial multidrug ABC half-transporter BmrA functions as a homodimer.

    PubMed

    Dalmas, Olivier; Do Cao, Marie-Ange; Lugo, Miguel R; Sharom, Frances J; Di Pietro, Attilio; Jault, Jean-Michel

    2005-03-22

    Members of the ATP-binding cassette (ABC) transporters share the same basic architecture, with a four-core domain made of two transmembrane plus two nucleotide-binding domains. However, a supramolecular organization has been detected in some ABC transporters, which might be relevant to physiological regulation of substrate transport. Here, the oligomerization status of a bacterial half-ABC multidrug transporter, BmrA, was investigated. Each BmrA monomer containing a single cysteine residue introduced close to either the Walker A or the ABC signature motifs was labeled using two probes, 2-(4-maleimidoanilino)naphthalene-6-sulfonic acid (fluorescence donor) or 4-dimethylaminophenylazophenyl-4'-maleimide (fluorescence acceptor). Reconstitution into proteoliposomes of BmrA monomers labeled separately with either the fluorescence donor or the fluorescence acceptor allowed measurement of time-resolved fluorescence resonance energy transfer between the two probes, showing that efficient reassociation of the singly labeled BmrA monomers occurred upon reconstitution. The efficiency of energy transfer studied as a function of increasing concentration of BmrA-labeled with the fluorescence acceptor argues for a dimeric association of BmrA instead of a tetrameric one. Furthermore, the efficiency of energy transfer allowed estimation of the distances between the two bound probes. Results suggest that, in the resting state, BmrA in a lipid bilayer environment preferentially adopts a closed conformation similar to that found in the BtuCD crystal structure and that the presence of different effectors does not substantially modify its global conformation. PMID:15766260

  16. Time-resolved fluorescence sensing of pesticides chlorpyrifos, crotoxyphos and endosulfan by the luminescent Eu(III)-8-allyl-3-carboxycoumarin probe

    NASA Astrophysics Data System (ADS)

    Azab, Hassan A.; Khairy, Gasser M.; Kamel, Rasha M.

    2015-09-01

    This work describes the application of time resolved fluorescence in microtiter plates for investigating the interactions of europium-allyl-3-carboxycoumarin with pesticides chlorpyrifos, endosulfan and crotoxyphos. Stern-Volmer studies at different temperatures for chlorpyrifos and crotoxyphos shows dynamic and static quenching mechanisms respectively. Direct methods for the determination of the pesticides under investigation have been developed using the luminescence variations of the probe in solution. The detection limits are 6.53, 0.004, 3.72 μmol/L for chlorpyrifos, endosulfan, and crotoxyphos, respectively. The binding constants and thermodynamic parameters of the pesticides with probe were evaluated. A thermodynamic analysis showed that the reaction is spontaneous with negative ΔG. Effect of some relevant interferents on the detection of pesticides has been investigated. The new method was applied to the determination of the pesticides in different types of water samples (tap, mineral, and waste water).

  17. Time resolved laser induced fluorescence of the NH radical in low pressure N/sub 2/O flames

    SciTech Connect

    Copeland, R. A.; Wise, M. L.; Rensberger, K. J.; Crosley, D. R.

    1989-08-01

    Total removal rate constants from the NH(/ital A//sup 3//product//sub /ital i//) electronic state have been obtained in low pressure (/similar to/14-Torr) N/sub 2/O flames. The fluorescence decay constants and quantum yields /Phi/ depend on the temperature and composition at each position interrogated in the flame. In similar conditions, /Phi/ for NH(A/sup 3//product//sub u/) is significantly greater than that for other radicals CH(A/sup 2//Delta/ and B/sup 2//summation//sup /minus//) and OH(A/sup 2//summation//sup +/). A small decrease (/similar to/5%) in the electronic removal is observed with rotational excitation increasing from N/prime/ = 2 to 12 in the A state. Estimates of collisional quenching cross sections at flame temperatures are made for the important combustion species, H/sub 2/O, C/sub 3/H/sub 8/, C/sub 2/H/sub 4/, and C/sub 2/H/sub 2/.

  18. Tracking Local Conformational Changes of Ribonuclease A Using Picosecond Time-Resolved Fluorescence of the Six Tyrosine Residues

    PubMed Central

    Noronha, Melinda; Lima, João C.; Paci, Emanuele; Santos, Helena; Maçanita, António L.

    2007-01-01

    The six tyrosine residues of ribonuclease A (RNase A) are used as individual intrinsic probes for tracking local conformational changes during unfolding. The fluorescence decays of RNase A are well described by sums of three exponentials with decay times (τ1 = 1.7 ns, τ2 = 180 ps, and τ3 = 30 ps) and preexponential coefficients (A1 = 1, A2 = 1, and A3 = 4) at pH 7, 25°C. The decay times are controlled by photo-induced electron transfer from individual tyrosine residues to the nearest disulphide (–SS–), bridge, which is distance (R) dependent. We assign τ1 to Tyr-76 (R = 12.8 Å), τ2 to Tyr-115 (R = 6.9 Å), and τ3 to Tyr-25, Tyr-73, Tyr-92, and Tyr-97 (all four at R = 5.5 ± 0.3 Å) at 23°C. On the basis of this assignment, the results show that, upon thermal or chemical unfolding only Tyr-25, Tyr-92, and Tyr-76 undergo significant displacement from their nearest –SS– bridge. Despite reporting on different regions of the protein, the concordance between the transition temperatures, Tm, obtained from Tyr-76 (Tm = 59.2°C) and Tyr-25 and Tyr-92 (Tm = 58.2°C) suggests a single unfolding event in this temperature range that affects all these regions similarly. PMID:17384067

  19. Identifying the major intermediate species by combining time-resolved X-ray solution scattering and X-ray absorption spectroscopy.

    PubMed

    Kim, Kyung Hwan; Kim, Jeongho; Oang, Key Young; Lee, Jae Hyuk; Grolimund, Daniel; Milne, Christopher J; Penfold, Thomas J; Johnson, Steven L; Galler, Andreas; Kim, Tae Wu; Kim, Jong Goo; Suh, Deokbeom; Moon, Jiwon; Kim, Joonghan; Hong, Kiryong; Guérin, Laurent; Kim, Tae Kyu; Wulff, Michael; Bressler, Christian; Ihee, Hyotcherl

    2015-09-28

    Identifying the intermediate species along a reaction pathway is a first step towards a complete understanding of the reaction mechanism, but often this task is not trivial. There has been a strong on-going debate: which of the three intermediates, the CHI2 radical, the CHI2-I isomer, and the CHI2(+) ion, is the dominant intermediate species formed in the photolysis of iodoform (CHI3)? Herein, by combining time-resolved X-ray liquidography (TRXL) and time-resolved X-ray absorption spectroscopy (TR-XAS), we present strong evidence that the CHI2 radical is dominantly formed from the photolysis of CHI3 in methanol at 267 nm within the available time resolution of the techniques (∼20 ps for TRXL and ∼100 ps for TR-XAS). The TRXL measurement, conducted using the time-slicing scheme, detected no CHI2-I isomer within our signal-to-noise ratio, indicating that, if formed, the CHI2-I isomer must be a minor intermediate. The TR-XAS transient spectra measured at the iodine L1 and L3 edges support the same conclusion. The present work demonstrates that the application of these two complementary time-resolved X-ray methods to the same system can provide a detailed understanding of the reaction mechanism. PMID:26300122

  20. Effect of Ca2+ on the Steady-State and Time-Resolved Emission Properties of the Genetically Encoded Fluorescent Sensor CatchER

    PubMed Central

    2015-01-01

    We previously designed a calcium sensor CatchER (a GFP-based Calcium sensor for detecting high concentrations in the high calcium concentration environment such as ER) with a capability for monitoring calcium ion responses in various types of cells. Calcium binding to CatchER induces the ratiometric changes in the absorption spectra, as well as an increase in fluorescence emission at 510 nm upon excitation at both 395 and 488 nm. Here, we have applied the combination of the steady-state and time-resolved optical methods and Hydrogen/Deuterium isotope exchange to understand the origin of such calcium-induced optical property changes of CatchER. We first demonstrated that calcium binding results in a 44% mean fluorescence lifetime increase of the indirectly excited anionic chromophore. Thus, CatchER is the first protein-based calcium indicator with the single fluorescent moiety to show the direct correlation between the lifetime and calcium binding. Calcium exhibits a strong inhibition on the excited-state proton transfer nonadiabatic geminate recombination in protic (vs deuteric) medium. Analysis of CatchER crystal structures and the MD simulations reveal the proton transfer mechanism in which the disrupted proton migration path in CatchER is rescued by calcium binding. Our finding provides important insights for a strategy to design calcium sensors and suggests that CatchER could be a useful probe for FLIM imaging of calcium in situ. PMID:24836743

  1. Characterization of a hybrid diffuse correlation spectroscopy and time-resolved near-infrared spectroscopy system for real-time monitoring of cerebral blood flow and oxygenation

    NASA Astrophysics Data System (ADS)

    Verdecchia, K.; Diop, M.; Lee, A.; St. Lawrence, K.

    2015-03-01

    The combination of near-infrared spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS) offers the ability to provide real-time monitoring of cerebral oxygenation, blood flow and oxygen consumption. However, measuring these parameters accurately requires depth-sensitive techniques that can remove the effects of signal contamination from extracerebral tissues. Towards this goal, we developed and characterized a hybrid DCS/time-resolved (TR)-NIRS system. Both systems acquire data at three source-detector distances (SDD: 7, 20 and 30 mm) to provide depth sensitivity. The TR-NIRS system uses three pulsed lasers (760, 810, and 830 nm) to quantify tissue optical properties, and DCS uses one continuous-wave, long coherence length (>5 m) laser (785 nm) for blood flow monitoring. The stability of the TR-NIRS system was characterized by continuously measuring the instrument response function (IRF) for four hours, and a warmup period of two hours was required to reduce the coefficient of variation of the extracted optical properties to < 2%. The errors in the measured optical properties were <10% at SDDs of 20 and 30 mm; however, the error at 7 mm was greater due to the effects of the IRF. The number of DCS detectors at each SDD and the minimum count-rate (20 kHz per detector resulting in <10% uncertainty in the extracted blood flow index) were optimized using a homogenous phantom. The depth sensitivity was assessed using a two-layer phantom, with the flow rate in the bottom layer altered to mimic cerebral blood flow.

  2. Time-Resolved IR-Absorption Spectroscopy of Hot-Electron Dynamics in Satellite and Upper Conduction Bands in GaP

    NASA Technical Reports Server (NTRS)

    Cavicchia, M. A.; Alfano, R. R.

    1995-01-01

    The relaxation dynamics of hot electrons in the X6 and X7 satellite and upper conduction bands in GaP was directly measured by femtosecond UV-pump-IR-probe absorption spectroscopy. From a fit to the induced IR-absorption spectra the dominant scattering mechanism giving rise to the absorption at early delay times was determined to be intervalley scattering of electrons out of the X7 upper conduction-band valley. For long delay times the dominant scattering mechanism is electron-hole scattering. Electron transport dynamics of the upper conduction band of GaP has been time resolved.

  3. Probing Electronic and Vibrational Dynamics in Molecules by Time-Resolved Photoelectron, Auger-Electron, and X-ray Photon Scattering Spectroscopy

    PubMed Central

    Bennett, Kochise; Kowalewski, Markus; Mukamel, Shaul

    2015-01-01

    We present a unified description for time-resolved electron and photon scattering spectroscopies from molecules prepared in nonstationary states. Signals are expressed in terms of superoperator Green’s functions and a systematic procedure for treating various degrees of freedom consistently at different levels of theory is developed. The standard Fermi Golden Rule expressions for photelectron spectra, which are limited to broad, slowly-varying signals, are obtained as a limiting case of our more general theory that applies to broader parameter regimes. PMID:25730500

  4. Monitoring cellular metabolic pathways by wavelength- and time-resolved intracellular autofluorescence

    NASA Astrophysics Data System (ADS)

    Wu, Yicong; Zheng, Wei; Qu, Jianan Y.

    2007-07-01

    Autofluorescence spectroscopy has been a widely explored noninvasive technique to detect the precancerous development in epithelial tissue, where NADH and FAD fluorescence are metabolism related. In this study, we investigated the methods to monitor cellular metabolism based on the ratio of NADH over FAD fluorescence and the ratio of free NADH and protein-bound NADH fluorescence, respectively. The signals of free NADH, protein-bound NADH and FAD were isolated from the intracellular autofluorescence using wavelength- and time-resolved fluorescence spectroscopy. We demonstrated that the wavelength- and time-resolved intracellular autofluorescence can be used to monitor the cellular metabolic pathways and differentiate the normal cells from the cancer cells.

  5. Intraoperative monitoring of depth-dependent hemoglobin concentration changes during carotid endarterectomy by time-resolved spectroscopy

    NASA Astrophysics Data System (ADS)

    Sato, Chie; Yamaguchi, Takekane; Seida, Mitsuru; Ota, Yoshihisa; Yu, Iwae; Iguchi, Yoshinobu; Nemoto, Masahito; Hoshi, Yoko

    2007-05-01

    By measuring the adult human head during carotid endarterectomy, we investigate the depth sensitivity of two methods for deriving the absorption coefficient changes (Δμa) from time-resolved reflectance data to absorption changes in inhomogeneous media: (1) the curve-fitting method based on the diffusion equation (DE-fit method) and (2) the time-independent calculation based on the modified Lambert-Beer law (MLB method). Remarkable differences in the determined values of Δμa caused by clamping the external carotid artery and subsequently clamping the common carotid artery were observed between the methods. The DE-fit method was more sensitive to μa changes in cerebral tissues, whereas the MLB method was rather sensitive to μa changes in the extracerebral tissues. Our results indicated that the DE-fit was useful for monitoring the cerebral blood circulation and oxygenation during neurosurgical operations. In addition, the combined evaluation of μa changes with the DE-fit and MLB methods will provide us with more available information about the hemodynamic changes in the depth direction.

  6. Time resolved study of the emission enhancement mechanisms in orthogonal double-pulse laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Sanginés, R.; Sobral, H.

    2013-10-01

    The evolution of laser induced ablation plume on aluminum targets has been investigated in orthogonal pre-ablation double pulse scheme at atmospheric pressure from the earliest stages of plasma evolution. Time-resolved emission spectra from neutrals, singly- and doubly-ionized species obtained with the double pulse experiment have been compared with those from the single pulse configuration. Signal-to-noise enhancement reaches values of up to 15 depending on the analyzed species; and the lower the charge state the later its maximum signal-to-noise ratio is reached. Ablation plume dynamics was monitored from 10 ns after the plasma onset via shadowgraphy and fast-photography with narrow interference filters to follow the evolution of individual species. Results show that ionic species from the target are located at the plasma core while nitrogen from the background air is found at the plume peripheral. Initially both configurations exhibit similar ablation plume sizes and their expansions were successfully fitted with the strong explosion model for the first 500 ns. At later times a good agreement was obtained by using the drag model, which predicts that the plume expansion eventually stops due to interaction with the background gas particles. The emission enhancement measured in the double pulse scheme is discussed in terms of the models describing the plume dynamics.

  7. Probing early events in ferrous cytochrome c folding with time-resolved natural and magnetic circular dichroism spectroscopies.

    PubMed

    Chen, Eefei; Goldbeck, Robert A; Kliger, David S

    2009-10-01

    In a 1998 collaboration with Tony Fink, we coupled nanosecond circular dichroism methods (TRCD) with a CO-photolysis system for quickly triggering folding in cytochrome c (cyt c) in order to make the first time-resolved far-UV CD measurement of early secondary structure formation in a protein. The small signal observed in that initial study, approximately 10% of native helicity, became the seed for increasingly robust results from subsequent studies bringing additional natural and magnetic circular polarization dichroism and optical rotatory dispersion detection methods (e.g., TRORD, TRMCD, and TRMORD), coupled to fast photolysis and photoreduction triggers, to the study of early folding events. Nanosecond polarization methods are reviewed here in the context of the range of initiation methods and structure-sensitive probes currently available for fast folding studies. We also review the impact of experimental results from fast polarization studies on questions in folding dynamics such as the possibility of multiple folding pathways implied by energy landscape models, the sequence dependence of ultrafast helix formation, and the simultaneity of chain collapse and secondary structure formation implicit in molten globule models for kinetic folding intermediates. PMID:19538147

  8. Time-Resolved FT-IR Spectroscopy of CO Hydrogenation overSupported Ru Catalyst at 700K

    SciTech Connect

    Wasylenko, Walter; Frei, Heinz

    2006-02-13

    Time-resolved FT-IR spectra of carbon monoxide hydrogenation over alumina-supported ruthenium were recorded on the millisecond timescale at 703 K using various H{sub 2} concentrations (1 atm total pressure). Adsorbed carbon monoxide was detected along with gas phase products methane (3016 and 1306 cm{sup -1}), water (sharp bands from 1900 - 1300 cm{sup -1}), and carbon dioxide (2348 cm{sup -1}). No other surface species were detected other than adsorbed carbon monoxide. The rate of formation of methane (2.5 {+-} 0.4 s{sup -1}) coincides with the rate of formation of carbon dioxide (3.4 {+-} 0.6 s{sup -1}), and bands due to water are observed to grow in over time. These results establish that methane and carbon dioxide originate from the same intermediate. The adsorbed carbon monoxide band is broad and unsymmetrical with a maximum at 2010 cm{sup -1} in spectra observed at 36 ms that shifts over 3000 ms to 1960 cm{sup -1} due to decreasing amounts of adsorbed carbon monoxide. Kinetic analysis of the adsorbed carbon monoxide band reveals that only a portion of the band can be temporally linked to gas phase products that we observe over the first 1000 ms of catalysis. This result suggests that we are observing dispersive kinetics, which is most likely due to heterogeneity of the surface environment.

  9. Real-time baseline correction technique for MWIR and LWIR time-resolved photoluminescence spectroscopy (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Lin, Zhi-Yuan; Zhang, Yong-Hang

    2015-08-01

    The time-resolved photoluminescence (TRPL) measurement provides rich information about carrier dynamics and recombination mechanisms. However, TRPL measurements are quite challenging in mid-wave infrared (MWIR) and long-wave infrared (LWIR) regimes due to noise in photodetectors and data acquisition systems. Our analysis and experimental results show that the noise in a conventional TRPL system using a traditional averaging method is dominated by 1/f noise from 10 Hz to 3 kHz. The signal is also mixed with sub-Hertz noise associated with the boxcar baseline oscillation, commonly known as the "baseline drift" issue which results from numerous fluctuations in the system. A real-time baseline correction method is proposed and demonstrated to suppress these low frequency noise sources. The real-time baseline correction method is realized by modulating the signal. The modulation can be achieved by either electrical, mechanical, or optical approaches. Analysis indicates that the noise of this method is proportional to the noise spectral density at the modulation frequency, this argument is confirmed by the simulation results. The simulated noise achieved by the real-time baseline correction method is much lower than the traditional method. Experimental results show that the low frequency baseline oscillations associated with the traditional TRPL experiments are absent using the real-time baseline correction technique, and the noise of the measurement is significantly reduced. This work establishes a more efficient experimental method for TRPL measurements on weak MWIR and LWIR PL signals, such as the InAs/InAsSb type-II superlattice samples which are used here to demonstrate the proposed method.

  10. Building homogeneous time-resolved fluorescence resonance energy transfer assays for characterization of bivalent inhibitors of an inhibitor of apoptosis protein target.

    PubMed

    Chaudhry, Charu; Davis, Jonathan; Zhang, Yong; Posy, Shana; Lei, Ming; Shen, Henry; Yan, Chunhong; Devaux, Brigitte; Zhang, Litao; Blat, Yuval; Metzler, William; Borzilleri, Robert M; Talbott, Randy L

    2016-03-15

    XIAP (X-chromosome-linked inhibitor of apoptosis protein) is a central apoptosis regulator that blocks cell death by inhibiting caspase-3, caspase-7, and caspase-9 via binding interactions with the XIAP BIR2 and BIR3 domains (where BIR is baculovirus IAP repeat). Smac protein, in its dimeric form, effectively antagonizes XIAP by concurrently targeting both its BIR2 and BIR3 domains. Here we describe the development of highly sensitive homogeneous time-resolved fluorescence resonance energy transfer (HTRF) assays to measure binding affinities of potent bivalent peptidomimetic inhibitors of XIAP. Our results indicate that these assays can differentiate Smac-mimetic inhibitors with a wide range of binding affinities down to the picomolar range. Furthermore, we demonstrate the utility of these fluorescent tools for characterization of inhibitor off-rates, which as a crucial determinant of target engagement and cellular potency is another important parameter to guide optimization in a structure-based drug discovery effort. Our study also explores how increased inhibitor valency can lead to enhanced potency at multimeric proteins such as IAP. PMID:26743718

  11. A Q-switched Ho:YAG laser assisted nanosecond time-resolved T-jump transient mid-IR absorbance spectroscopy with high sensitivity

    NASA Astrophysics Data System (ADS)

    Li, Deyong; Li, Yunliang; Li, Hao; Wu, Xianyou; Yu, Qingxu; Weng, Yuxiang

    2015-05-01

    Knowledge of dynamical structure of protein is an important clue to understand its biological function in vivo. Temperature-jump (T-jump) time-resolved transient mid-IR absorbance spectroscopy is a powerful tool in elucidating the protein dynamical structures and the folding/unfolding kinetics of proteins in solution. A home-built setup of T-jump time-resolved transient mid-IR absorbance spectroscopy with high sensitivity is developed, which is composed of a Q-switched Cr, Tm, Ho:YAG laser with an output wavelength at 2.09 μm as the T-jump heating source, and a continuous working CO laser tunable from 1580 to 1980 cm-1 as the IR probe. The results demonstrate that this system has a sensitivity of 1 × 10-4 ΔOD for a single wavelength detection, and 2 × 10-4 ΔOD for spectral detection in amide I' region, as well as a temporal resolution of 20 ns. Moreover, the data quality coming from the CO laser is comparable to the one using the commercial quantum cascade laser.

  12. A Q-switched Ho:YAG laser assisted nanosecond time-resolved T-jump transient mid-IR absorbance spectroscopy with high sensitivity

    SciTech Connect

    Li, Deyong; Li, Yunliang; Li, Hao; Weng, Yuxiang; Wu, Xianyou; Yu, Qingxu

    2015-05-15

    Knowledge of dynamical structure of protein is an important clue to understand its biological function in vivo. Temperature-jump (T-jump) time-resolved transient mid-IR absorbance spectroscopy is a powerful tool in elucidating the protein dynamical structures and the folding/unfolding kinetics of proteins in solution. A home-built setup of T-jump time-resolved transient mid-IR absorbance spectroscopy with high sensitivity is developed, which is composed of a Q-switched Cr, Tm, Ho:YAG laser with an output wavelength at 2.09 μm as the T-jump heating source, and a continuous working CO laser tunable from 1580 to 1980 cm{sup −1} as the IR probe. The results demonstrate that this system has a sensitivity of 1 × 10{sup −4} ΔOD for a single wavelength detection, and 2 × 10{sup −4} ΔOD for spectral detection in amide I′ region, as well as a temporal resolution of 20 ns. Moreover, the data quality coming from the CO laser is comparable to the one using the commercial quantum cascade laser.

  13. A Q-switched Ho:YAG laser assisted nanosecond time-resolved T-jump transient mid-IR absorbance spectroscopy with high sensitivity.

    PubMed

    Li, Deyong; Li, Yunliang; Li, Hao; Wu, Xianyou; Yu, Qingxu; Weng, Yuxiang

    2015-05-01

    Knowledge of dynamical structure of protein is an important clue to understand its biological function in vivo. Temperature-jump (T-jump) time-resolved transient mid-IR absorbance spectroscopy is a powerful tool in elucidating the protein dynamical structures and the folding/unfolding kinetics of proteins in solution. A home-built setup of T-jump time-resolved transient mid-IR absorbance spectroscopy with high sensitivity is developed, which is composed of a Q-switched Cr, Tm, Ho:YAG laser with an output wavelength at 2.09 μm as the T-jump heating source, and a continuous working CO laser tunable from 1580 to 1980 cm(-1) as the IR probe. The results demonstrate that this system has a sensitivity of 1 × 10(-4) ΔOD for a single wavelength detection, and 2 × 10(-4) ΔOD for spectral detection in amide I' region, as well as a temporal resolution of 20 ns. Moreover, the data quality coming from the CO laser is comparable to the one using the commercial quantum cascade laser. PMID:26026512

  14. Time-resolved x-ray photoelectron spectroscopy techniques for real-time studies of interfacial charge transfer dynamics

    SciTech Connect

    Shavorskiy, Andrey; Hertlein, Marcus; Guo Jinghua; Tyliszczak, Tolek; Cordones, Amy; Vura-Weis, Josh; Siefermann, Katrin; Slaughter, Daniel; Sturm, Felix; Weise, Fabian; Khurmi, Champak; Belkacem, Ali; Weber, Thorsten; Gessner, Oliver; Bluhm, Hendrik; Strader, Matthew; Cho, Hana; Coslovich, Giacomo; Kaindl, Robert A.; Lin, Ming-Fu; and others

    2013-04-19

    X-ray based spectroscopy techniques are particularly well suited to gain access to local oxidation states and electronic dynamics in complex systems with atomic pinpoint accuracy. Traditionally, these techniques are applied in a quasi-static fashion that usually highlights the steady-state properties of a system rather than the fast dynamics that often define the system function on a molecular level. Novel x-ray spectroscopy techniques enabled by free electron lasers (FELs) and synchrotron based pump-probe schemes provide the opportunity to monitor intramolecular and interfacial charge transfer processes in real-time and with element and chemical specificity. Two complementary time-domain xray photoelectron spectroscopy techniques are presented that are applied at the Linac Coherent Light Source (LCLS) and the Advanced Light Source (ALS) to study charge transfer processes in N3 dye-sensitized ZnO semiconductor nanocrystals, which are at the heart of emerging light-harvesting technologies.

  15. Early Amyloidogenic Oligomerization Studied through Fluorescence Lifetime Correlation Spectroscopy

    PubMed Central

    Paredes, Jose M.; Casares, Salvador; Ruedas-Rama, Maria J.; Fernandez, Elena; Castello, Fabio; Varela, Lorena; Orte, Angel

    2012-01-01

    Amyloidogenic protein aggregation is a persistent biomedical problem. Despite active research in disease-related aggregation, the need for multidisciplinary approaches to the problem is evident. Recent advances in single-molecule fluorescence spectroscopy are valuable for examining heterogenic biomolecular systems. In this work, we have explored the initial stages of amyloidogenic aggregation by employing fluorescence lifetime correlation spectroscopy (FLCS), an advanced modification of conventional fluorescence correlation spectroscopy (FCS) that utilizes time-resolved information. FLCS provides size distributions and kinetics for the oligomer growth of the SH3 domain of α-spectrin, whose N47A mutant forms amyloid fibrils at pH 3.2 and 37 °C in the presence of salt. The combination of FCS with additional fluorescence lifetime information provides an exciting approach to focus on the initial aggregation stages, allowing a better understanding of the fibrillization process, by providing multidimensional information, valuable in combination with other conventional methodologies. PMID:22949804

  16. Top-hat cw-laser-induced time-resolved mode-mismatched thermal lens spectroscopy for quantitative analysis of low-absorption materials.

    PubMed

    Astrath, Nelson G C; Astrath, Francine B G; Shen, Jun; Zhou, Jianqin; Pedreira, Paulo R B; Malacarne, Luis C; Bento, Antonio C; Baesso, Mauro L

    2008-07-01

    Thermal lens spectroscopy is a highly sensitive and versatile photothermal technique for material analysis, providing optical and thermal properties. To use less expensive multimode non-Gaussian lasers for quantitative analysis of low-absorption materials, this Letter presents a theoretical model for time-resolved mode-mismatched thermal lens spectroscopy induced by a cw laser with a top-hat profile. The temperature profile in a sample was calculated, and the intensity of the probe beam center at the detector plane was also derived using the Fresnel diffraction theory. Experimental validation was performed with glass samples, and the results were found well consistent with literature values of the thermo-optical properties of the samples. PMID:18594666

  17. Time-resolved monitoring of flash-induced changes of fluorescence quantum yield and decay of delayed light emission in oxygen-evolving photosynthetic organisms.

    PubMed

    Steffen, R; Christen, G; Renger, G

    2001-01-01

    The present contribution describes a new experimental setup that permits time-resolved monitoring of the rise kinetics of the relative fluorescence yield, Phi(rel)(t), and simultaneously of the decay of delayed light emission, L(t), induced by strong actinic laser flashes. The results obtained by excitation of dark-adapted samples with a train of eight flashes reveal (a) in suspensions of spinach thylakoids, Phi(rel)(t) exhibits a typical period four oscillation that is characteristic for a dependence on the redox states S(i)() of the water oxidizing complex (WOC), (b) the relative extent of the unresolved "instantaneous" rise to the level (100 ns) at 100 ns and the maximum values of Phi(rel)(t) attained at about 45 s after each actinic flash, (45 s) synchronously oscillate and exhibit the largest values at flash nos. 1 and 5 and minima after flash nos. 2 and 3, (c) opposite effects are observed for the normalized extent of the rise kinetics in the 100 ns to 5 s time domain of relative fluorescence yield, Phi(rel)(5 s) - Phi(rel)(100 ns), i.e., both parameters attain minimum and maximum values after the first/fifth and second/third flash, respectively, and (d) analogous features for the "fast" and "slow" ns-kinetics of the fluorescence rise were observed in suspensions of Chlamydomas reinhardtii cells. A slight phase shift by one flash is ascribed to physiological differences. The applicability of this noninvasive technique to study reactions of photosystem II, especially the reduction kinetics of P680(*)(+) and their dependence on the redox state S(i)() of the WOC, is discussed. PMID:11141068

  18. Time-resolved characterization of a filamentary argon discharge at atmospheric pressure in a capillary using emission and absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Schröter, Sandra; Pothiraja, Ramasamy; Awakowicz, Peter; Bibinov, Nikita; Böke, Marc; Niermann, Benedikt; Winter, Jörg

    2013-11-01

    An argon/nitrogen (0.999/0.001) filamentary pulsed discharge operated at atmospheric pressure in a quartz tube is characterized using voltage-current measurements, microphotography, optical emission spectroscopy (OES) and absorption spectroscopy. Nitrogen is applied as a sensor gas for the purpose of OES diagnostic. The density of argon metastable atoms Ar(3P2) is determined using tunable diode laser absorption spectroscopy (TDLAS). Using a plasma chemical model the measured OES data are applied for the characterization of the plasma conditions. Between intense positive pulses the discharge current oscillates with a damped amplitude. It is established that an electric current flows in this discharge not only through a thin plasma filament that is observed in the discharge image but also through the whole cross section of the quartz tube. A diffuse plasma fills the quartz tube during a time between intense current pulses. Ionization waves are propagating in this plasma between the spike and the grounded area of the tube producing thin plasma channels. The diameter of these channels increases during the pause between the propagation of ionization waves probably because of thermal expansion and diffusion. Inside the channels electron densities of ˜2 × 1013 cm-3, argon metastable densities ˜1014 cm-3 and a reduced electric field about 10 Td are determined.

  19. Validation of a high-power, time-resolved, near-infrared spectroscopy system for measurement of superficial and deep muscle deoxygenation during exercise.

    PubMed

    Koga, Shunsaku; Barstow, Thomas J; Okushima, Dai; Rossiter, Harry B; Kondo, Narihiko; Ohmae, Etsuko; Poole, David C

    2015-06-01

    Near-infrared assessment of skeletal muscle is restricted to superficial tissues due to power limitations of spectroscopic systems. We reasoned that understanding of muscle deoxygenation may be improved by simultaneously interrogating deeper tissues. To achieve this, we modified a high-power (∼8 mW), time-resolved, near-infrared spectroscopy system to increase depth penetration. Precision was first validated using a homogenous optical phantom over a range of inter-optode spacings (OS). Coefficients of variation from 10 measurements were minimal (0.5-1.9%) for absorption (μa), reduced scattering, simulated total hemoglobin, and simulated O2 saturation. Second, a dual-layer phantom was constructed to assess depth sensitivity, and the thickness of the superficial layer was varied. With a superficial layer thickness of 1, 2, 3, and 4 cm (μa = 0.149 cm(-1)), the proportional contribution of the deep layer (μa = 0.250 cm(-1)) to total μa was 80.1, 26.9, 3.7, and 0.0%, respectively (at 6-cm OS), validating penetration to ∼3 cm. Implementation of an additional superficial phantom to simulate adipose tissue further reduced depth sensitivity. Finally, superficial and deep muscle spectroscopy was performed in six participants during heavy-intensity cycle exercise. Compared with the superficial rectus femoris, peak deoxygenation of the deep rectus femoris (including the superficial intermedius in some) was not significantly different (deoxyhemoglobin and deoxymyoglobin concentration: 81.3 ± 20.8 vs. 78.3 ± 13.6 μM, P > 0.05), but deoxygenation kinetics were significantly slower (mean response time: 37 ± 10 vs. 65 ± 9 s, P ≤ 0.05). These data validate a high-power, time-resolved, near-infrared spectroscopy system with large OS for measuring the deoxygenation of deep tissues and reveal temporal and spatial disparities in muscle deoxygenation responses to exercise. PMID:25840439

  20. Implementation of Time-Resolved Step-Scan Fourier Transform Infrared (FT-IR) Spectroscopy Using a kHz Repetition Rate Pump Laser

    PubMed Central

    MAGANA, DONNY; PARUL, DZMITRY; DYER, R. BRIAN; SHREVE, ANDREW P.

    2011-01-01

    Time-resolved step-scan Fourier transform infrared (FT-IR) spectroscopy has been shown to be invaluable for studying excited-state structures and dynamics in both biological and inorganic systems. Despite the established utility of this method, technical challenges continue to limit the data quality and more wide ranging applications. A critical problem has been the low laser repetition rate and interferometer stepping rate (both are typically 10 Hz) used for data acquisition. Here we demonstrate significant improvement in the quality of time-resolved spectra through the use of a kHz repetition rate laser to achieve kHz excitation and data collection rates while stepping the spectrometer at 200 Hz. We have studied the metal-to-ligand charge transfer excited state of Ru(bipyridine)3Cl2 in deuterated acetonitrile to test and optimize high repetition rate data collection. Comparison of different interferometer stepping rates reveals an optimum rate of 200 Hz due to minimization of long-term baseline drift. With the improved collection efficiency and signal-to-noise ratio, better assignments of the MLCT excited-state bands can be made. Using optimized parameters, carbonmonoxy myoglobin in deuterated buffer is also studied by observing the infrared signatures of carbon monoxide photolysis upon excitation of the heme. We conclude from these studies that a substantial increase in performance of ss-FT-IR instrumentation is achieved by coupling commercial infrared benches with kHz repetition rate lasers. PMID:21513597

  1. Time-resolved visible and infrared absorption spectroscopy data obtained using photosystem I particles with non-native quinones incorporated into the A1 binding site

    PubMed Central

    Makita, Hiroki; Hastings, Gary

    2016-01-01

    Time-resolved visible and infrared absorption difference spectroscopy data at both 298 and 77 K were obtained using cyanobacterial menB− mutant photosystem I particles with several non-native quinones incorporated into the A1 binding site. Data was obtained for photosystem I particles with phylloquinone (2-methyl-3-phytyl-1,4-naphthoquinone), 2-bromo-1,4-naphthoquinone, 2-chloro-1,4-naphthoquinone, 2-methyl-1,4-naphthoquinone, 2,3-dibromo-1,4-naphthoquinone, 2,3-dichloro-1,4-naphthoquinone, and 9,10-anthraquinone incorporated. Transient absorption data were obtained at 487 and 703 nm in the visible spectral range, and 1950–1100 cm−1 in the infrared region. Time constants obtained from fitting the time-resolved infrared and visible data are in good agreement. The measured time constants are crucial for the development of appropriate kinetic models that can describe electron transfer processes in photosystem I, “Modeling Electron Transfer in Photosystem I” Makita and Hastings (2016) [1]. PMID:27182540

  2. Quantitative characterization of optical and physiological parameters in normal breasts using time-resolved spectroscopy: in vivo results of 19 Singapore women

    NASA Astrophysics Data System (ADS)

    Mo, Weirong; Chan, Tryphena S. S.; Chen, Ling; Chen, Nanguang

    2009-11-01

    We report the quantitative measurements of optical and physiological parameters of normal breasts from 19 Singapore women by using time-resolved diffuse optical spectroscopy. Intrinsic absorption coefficient (?a) and reduced scattering coefficients (?s') of breasts were calculated from the time-resolved photon migration data. Physiology of breasts was characterized using the concentrations of oxyhemoglobin, deoxyhemoglobin, total hemoglobin (THC), and oxygenation saturation. On average, the experiment results showed that the ?a of young women (below 40 years old) was 36 to 38% greater than that of older women (above 40 years old) and that parameter THC was approximately 42% greater. Results also showed that the THC of premenopausal women was 24.3 ?Mol/L, which was approximately 69% larger than that of postmenopausal women at 14.1 ?Mol/L. Meanwhile, the ?a of premenopausal women was approximately 60% larger than that of postmenopausal women. Correlation analysis further showed that the optical and physiological parameters of breasts were strongly influenced by changes in the women's age, menopausal states, and body mass index. These in vivo experiment results will contribute to the breast tissue diagnosis between healthy and diseased breast tissues.

  3. Time-resolved visible and infrared absorption spectroscopy data obtained using photosystem I particles with non-native quinones incorporated into the A1 binding site.

    PubMed

    Makita, Hiroki; Hastings, Gary

    2016-06-01

    Time-resolved visible and infrared absorption difference spectroscopy data at both 298 and 77 K were obtained using cyanobacterial menB (-) mutant photosystem I particles with several non-native quinones incorporated into the A1 binding site. Data was obtained for photosystem I particles with phylloquinone (2-methyl-3-phytyl-1,4-naphthoquinone), 2-bromo-1,4-naphthoquinone, 2-chloro-1,4-naphthoquinone, 2-methyl-1,4-naphthoquinone, 2,3-dibromo-1,4-naphthoquinone, 2,3-dichloro-1,4-naphthoquinone, and 9,10-anthraquinone incorporated. Transient absorption data were obtained at 487 and 703 nm in the visible spectral range, and 1950-1100 cm(-1) in the infrared region. Time constants obtained from fitting the time-resolved infrared and visible data are in good agreement. The measured time constants are crucial for the development of appropriate kinetic models that can describe electron transfer processes in photosystem I, "Modeling Electron Transfer in Photosystem I" Makita and Hastings (2016) [1]. PMID:27182540

  4. Efficient Spectral Diffusion at the Air/Water Interface Revealed by Femtosecond Time-Resolved Heterodyne-Detected Vibrational Sum Frequency Generation Spectroscopy.

    PubMed

    Inoue, Ken-Ichi; Ishiyama, Tatsuya; Nihonyanagi, Satoshi; Yamaguchi, Shoichi; Morita, Akihiro; Tahara, Tahei

    2016-05-19

    Femtosecond vibrational dynamics at the air/water interface is investigated by time-resolved heterodyne-detected vibrational sum frequency generation (TR-HD-VSFG) spectroscopy and molecular dynamics (MD) simulation. The low- and high-frequency sides of the hydrogen-bonded (HB) OH stretch band at the interface are selectively excited with special attention to the bandwidth and energy of the pump pulses. Narrow bleach is observed immediately after excitation of the high-frequency side of the HB OH band at ∼3500 cm(-1), compared to the broad bleach observed with excitation of the low-frequency side at ∼3300 cm(-1). However, the time-resolved spectra observed with the two different excitations become very similar at 0.5 ps and almost indistinguishable by 1.0 ps. This reveals that efficient spectral diffusion occurs regardless of the difference of the pump frequency. The experimental observations are well-reproduced by complementary MD simulation. There is no experimental and theoretical evidence that supports extraordinary slow dynamics in the high-frequency side of the HB OH band, which was reported before. PMID:27120559

  5. Employing Time-Resolved Terahertz Spectroscopy to Analyze Carrier Dynamics in Cu2ZnSn(S,Se)4 Absorber Layers

    NASA Astrophysics Data System (ADS)

    Baxter, Jason; Guglietta, Glenn; Li, Siming; Roy Choudhury, Kaushik; Caspar, Jonathan; Bishop, Douglas; Lloyd, Michael; McCandless, Brian

    We report the application of time-resolved terahertz spectroscopy (TRTS) to measure photoexcited carrier lifetimes and mobility, and to determine recombination mechanisms in Cu2ZnSn(S,Se)4 (CZTSSe) thin films and single crystals. Ultrafast time resolution permits tracking the evolution of carrier density to determine recombination rates and mechanisms. The carrier generation profile was manipulated by varying the photoexcitation wavelength and fluence to distinguish between surface, Shockley-Read-Hall (SRH), radiative, and Auger recombination mechanisms and determine rate constants. Surface and SRH recombination are the dominant mechanisms for the air/CZTSSe/SiO2/Si film stack. Diffusion to, and then recombination at, the air-CZTSSe interface occurred on the order of 100 picoseconds, while SRH recombination lifetimes were 1 - 2 nanoseconds. Analogous measurements on single crystals reveal the effects of eliminating grain boundaries, reducing point defects and secondary phases, and applying surface treatments to reduce surface recombination velocity. TRTS measurements can provide information that is complementary to conventional time-resolved photoluminescence measurements and can direct the design of efficient thin film photovoltaics. Ref: Guglietta et al., APL, 2014. Nsf DMR-1507988.

  6. Development of a time-resolved fluorescence resonance energy transfer assay for cyclin-dependent kinase 4 and identification of its ATP-noncompetitive inhibitors.

    PubMed

    Lo, Mei-Chu; Ngo, Rachel; Dai, Kang; Li, Cong; Liang, Lingming; Lee, Josie; Emkey, Renee; Eksterowicz, John; Ventura, Manuel; Young, Stephen W; Xiao, Shou-Hua

    2012-02-15

    Protein kinases are recognized as important drug targets due to the pivotal roles they play in human disease. Many kinase inhibitors are ATP competitive, leading to potential problems with poor selectivity and significant loss of potency in vivo due to cellular ATP concentrations being much higher than K(m). Consequently, there has been growing interest in the development of ATP-noncompetitive inhibitors to overcome these problems. There are challenges to identifying ATP-noncompetitive inhibitors from compound library screens because ATP-noncompetitive inhibitors are often weaker and commonly excluded by potency-based hit selection criteria in favor of abundant and highly potent ATP-competitive inhibitors in screening libraries. Here we report the development of a time-resolved fluorescence resonance energy transfer (TR-FRET) assay for protein kinase cyclin-dependent kinase 4 (CDK4) and the identification of ATP-noncompetitive inhibitors by high-throughput screening after employing a strategy to favor this type of inhibitors. We also present kinetic characterization that is consistent with the proposed mode of inhibition. PMID:22056947

  7. A high-throughput screening-compatible homogeneous time-resolved fluorescence assay measuring the glycohydrolase activity of human poly(ADP-ribose) glycohydrolase.

    PubMed

    Stowell, Alexandra I J; James, Dominic I; Waddell, Ian D; Bennett, Neil; Truman, Caroline; Hardern, Ian M; Ogilvie, Donald J

    2016-06-15

    Poly(ADP-ribose) (PAR) polymers are transient post-translational modifications, and their formation is catalyzed by poly(ADP-ribose) polymerase (PARP) enzymes. A number of PARP inhibitors are in advanced clinical development for BRCA-mutated breast cancer, and olaparib has recently been approved for BRCA-mutant ovarian cancer; however, there has already been evidence of developed resistance mechanisms. Poly(ADP-ribose) glycohydrolase (PARG) catalyzes the hydrolysis of the endo- and exo-glycosidic bonds within the PAR polymers. As an alternative strategy, PARG is a potentially attractive therapeutic target. There is only one PARG gene, compared with 17 known PARP family members, and therefore a PARG inhibitor may have wider application with fewer compensatory mechanisms. Prior to the initiation of this project, there were no known existing cell-permeable small molecule PARG inhibitors for use as tool compounds to assess these hypotheses and no suitable high-throughput screening (HTS)-compatible biochemical assays available to identify start points for a drug discovery project. The development of this newly described high-throughput homogeneous time-resolved fluorescence (HTRF) assay has allowed HTS to proceed and, from this, the identification and advancement of multiple validated series of tool compounds for PARG inhibition. PMID:27036617

  8. A homogeneous time-resolved fluorescence-based high-throughput screening for discovery of inhibitors of Nef-sdAb19 interaction.

    PubMed

    Fan, Xiaoqin; Wei, Jinmei; Xiong, Haiting; Liu, Xiaohui; Benichou, Serge; Gao, Xuejuan; Liu, Langxia

    2015-10-01

    The human immunodeficiency virus (HIV) protein negative factor (Nef) is important for AIDS pathogenesis. An anti-Nef single-domain antibody (sdAb19) derived from camelids has been previously generated and shown to effectively block the physiological functions of Nef in vitro and in vivo in nef-transgenic mice. However, sdAb19 must be ectopically expressed within the target cell to be able to exert its neutralizing effect on Nef, while the extra-cellular administration method turned out to be ineffective. This might suggest a default of the stability or/and deliverability of sdAb19. The identification of small molecule compounds capable of inhibiting the Nef-sdAb19 interaction and mimicking the neutralizing activity of sdAb19 in vivo would therefore be the means of circumventing the problem encountered with sdAb19. Here we describe the development of a high-throughput screening method combining the homogeneous time-resolved fluorescence (HTRF) and the microscale thermophoresis (MST) techniques for the identification of small-molecule compounds inhibiting the Nef-sdAb19 interaction by binding to Nef protein. Eight small-molecule compounds have been selected for their ability to significantly inhibit the Nef-sdAb19 interaction and to bind to Nef. These molecules could be further assessed for their potential of being the Nef-neutralizing agents in the future. PMID:26315450

  9. A study of collisional quenching and radiation-trapping kinetics for Rb(5p) in the presence of methane and ethane using time-resolved fluorescence

    NASA Astrophysics Data System (ADS)

    Zameroski, Nathan D.; Rudolph, Wolfgang; Hager, Gordon D.; Hostutler, David A.

    2009-12-01

    An experimental study using time-resolved fluorescence techniques together with theoretical simulations has been conducted and used to determine the quenching cross-sections of rubidium-methane and rubidium-ethane. Radiation trapping was significant under many of the experimental conditions (temperatures 40-130 °C and pressures 50-700 Torr) and a detailed analysis of the interplay between radiation trapping and quenching kinetics was carried out. Modifications of the Holstein equation for radiation trapping were implemented to account for the quasi-2 level behaviour of the Rb atom for high buffer gas pressures, the absolute frequency-dependent absorption cross-section for Rb with variable buffer gas pressures which accounts for the hyperfine splitting of 87Rb and modification of the trapping factors so that radiation trapping and quenching by an additive quenching gas could be treated simultaneously. Experimental results supported by theoretical simulations bound the quenching cross-sections (σ) of methane and ethane at 40 °C to be σ <= 0.019 Å2 and σ <= 0.033 Å2, respectively. These values are nearly two orders of magnitude smaller than previously reported.

  10. Time-resolved, 3D, laser-induced fluorescence measurements of fine-structure passive scalar mixing in a tubular reactor

    NASA Astrophysics Data System (ADS)

    Van Vliet, E.; Van Bergen, S. M.; Derksen, J. J.; Portela, L. M.; Van den Akker, H. E. A.

    A three-dimensional, time-resolved, laser-induced fluorescence (3D-LIF) technique was developed to measure the turbulent (liquid-liquid) mixing of a conserved passive scalar in the wake of an injector inserted perpendicularly into a tubular reactor with Re=4,000. In this technique, a horizontal laser sheet was traversed in its normal direction through the measurement section. Three-dimensional scalar fields were reconstructed from the 2D images captured at consecutive, closely spaced levels by means of a high-speed CCD camera. The ultimate goal of the measurements was to assess the downstream development of the 3D scalar fields (in terms of the full scalar gradient vector field and its associated scalar energy dissipation rate) in an industrial flow with significant advection velocity. As a result of this advection velocity, the measured 3D scalar field is artificially ``skewed'' during a scan period. A method to correct for this skewing was developed, tested and applied. Analysis of the results show consistent physical behaviour.

  11. Time-resolved ultraviolet and optical spectroscopy of the pulsating X-ray source H2252-035

    NASA Technical Reports Server (NTRS)

    Cordova, F. A.; Fenimore, E. E.; Middleditch, J.; Mason, K. O.

    1983-01-01

    UV spectrophotometry and and optical spectroscopy of H2252-035, a close binary featuring a spinning, magnetized star, were carried out with instrumentation on the IUE satellite, in addition to ground-based observations from the Lick Observatory. An excess reddening was determined, with E(B-V) equal to 0.10. The spectrum from 1200-22,000 A was decomposed into a blackbody with a temperature of 13,400 K and a power law wavelength component, where the exponent is 2.74, which fits the excess UV and IR excesses. The exponent value is noted to be amenable to a disk model with a slight curvature because of its finite extent. The emission-line intensities were found to vary by a factor of two, with some of the variations accountable by a modulation in-phase with the optical continuum binary modulation.

  12. Applications of immunomagnetic capture and time-resolved fluorescence to detect outbreak Escherichia coli O157 and Salmonella in alfalfa sprouts

    NASA Astrophysics Data System (ADS)

    Tu, Shu-I.; Gordon, Marsha; Fett, William F.; Gehring, Andrew G.; Irwin, Peter L.

    2004-03-01

    Commercially available alfalfa seeds were inoculated with low levels (~ 4 CFU/g) of pathogenic bacteria. The inoculated seeds were then allowed to sprout in sterile tap water at 22°C. After 48 hours, the irrigation water and sprouts were separately transferred to bovine heart infusion (BHI) media. The microbes in the BHI samples were allowed to grow for 4 hours at 37°C and 160 rpm. Specific immunomagnetic beads (IMB) were then applied to capture the E.coli O157 and/or Salmonella in the growth media. Separation and concentration of IMB-captured pathogens were achieved using magnetic separators. The captured E. coli O157:H7 and Salmonella spp were further tagged with europium (Eu) labeled anti-E. coli O157 antibodies and samarium (Sm) labeled anti-Salmonella antibodies, respectively. After washing, the lanthanide labels were extracted out from the complexes by specific chelators to form strongly fluorescent chelates. The specific time-resolved fluorescence (TRF) associated with Eu or Sm was measured to estimate the extent of capture of the E. coli O157 and Salmonella, respectively. The results indicated that the approach could detect E. coli O157 and Salmonella enterica from the seeds inoculated with ~ 4 CFU/g of the pathogens. Non-targeted bacteria, e.g., Aeromonas and Citrobacter exhibited essentially no cross reactivity. Since the pathogen detection from the sprouts was achieved within 6 hours, the developed methodology could be use as a rapid, sensitive and specific screening process for E. coli O157 and Salmonella enterica in this popular salad food.

  13. Photoinduced electron transfer between 2-methylanthraquinone and triethylamine in an ionic liquid: Time-resolved EPR and transient absorption spectroscopy study

    NASA Astrophysics Data System (ADS)

    Zhu, Guanglai; Wang, Yu; Fu, Haiying; Xu, Xinsheng; Cui, Zhifeng; Ji, Xuehan; Wu, Guozhong

    2015-02-01

    Photoinduced electron transfer between 2-methylanthraquinone (MeAQ) and triethylamine (TEA) in a room-temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]), was investigated by comparing the time-resolved electron paramagnetic resonance (TR-EPR) spectroscopy and the transient absorption spectroscopy. The results of TR-EPR spectroscopy, in which MeAQ was 8 mmol L-1 and TEA was 150 mmol L-1, indicated that the transient radical would exist longer time in [bmim][PF6] than in acetonitrile. At the delay time of 8 μs after laser excitation, the TR-EPR signal transformed from an emissive peak into an absorptive peak when the experiment was performed in [bmim][PF6]. The results of the transient absorption spectroscopy, in which MeAQ was 0.1 mmol L-1 and TEA was 2.2 mmol L-1, showed that the efficiency and the rate of the photoinduced electron transfer reaction in [bmim][PF6] were obviously lower than that in acetonitrile. It was concluded that various factors, such as concentration, viscosity and local structural transformation of the solution, have an influence on the process of photoinduced electron transfer in [bmim][PF6].

  14. Transient Electrochemical Surface-Enhanced Raman Spectroscopy: A Millisecond Time-Resolved Study of an Electrochemical Redox Process.

    PubMed

    Zong, Cheng; Chen, Chan-Juan; Zhang, Meng; Wu, De-Yin; Ren, Bin

    2015-09-16

    The pursuit of techniques with a high time resolution together with molecular signature information at the electrochemical interfaces has never stopped in order to explicitly monitor and understand the dynamic electrochemical processes. Here, we developed a transient electrochemical surface-enhanced Raman spectroscopy (TEC-SERS) to monitor the structural evolution of surface species at a time resolution that equals the transient electrochemical methods (e.g., cyclic voltammetry and chronoamperometry), so that the Raman signal with the molecular signature information and the electrochemical current signal can be precisely correlated. The technique was employed to study the redox process of nile blue on Ag surfaces. We revealed an interesting two-rate constant process and a peculiar increase of the absolute intensity during the reduction of nile blue on the Ag surface, which both related to the dissociation of nile blue aggregates and the follow-up reduction. Therefore, we were able to uncover the processes that are impossible to observe by conventional steady state SERS methods. The ability to provide a time resolution shorter than the charging time of the double layer capacitance with molecular fingerprint information has unprecedented significance for investigation of both reversible and irreversible electrochemical processes. PMID:26325244

  15. Toward Femtosecond Time-Resolved Inner-Shell Transient Absorption Spectroscopy of Ultrafast Dynamics in Sulfur-Containing Molecules

    NASA Astrophysics Data System (ADS)

    Lin, Ming-Fu; Neumark, Daniel; Leone, Stephen; Gessner, Oliver

    2013-05-01

    Sulfur-containing compounds play an important role in many applications such as polythiophene-based organic solar cells or the removal of sulfur compounds by hydrodesulfurization in the petroleum industry. Ultrafast relaxation dynamics (e.g. dissociation, internal conversion and intersystem crossing) of sulfur-containing molecules after photoexcitation have attracted considerable attention as a pathway to a better understanding of the fundamental chemistry of these systems. The novel technique of extreme ultraviolet (XUV) femtosecond transient absorption spectroscopy provides real-time access to the time-dependent structure and transient electronic states of molecules in the vicinity of a specific atom. The usable photon energy range of a high-order harmonic based XUV transient absorption setup has been extended up to 180 eV, enabling measurements in the vicinity of the sulfur 2p edge (165 eV). This new capability opens the route to monitor ultrafast intramolecular dynamics from the unique perspective of well-localized sulfur atoms. Preliminary results will be presented on the photoinduced ultrafast ring-opening, dissociation and vibrational relaxation dynamics in gaseous thiophene (C4H4S) and carbon disulfide (CS2) . Work supported by DOE DE-AC02-05CH11231.

  16. Stopped flow apparatus for time-resolved Fourier transform infrared difference spectroscopy of biological macromolecules in 1H2O.

    PubMed

    Masuch, Ralf; Moss, David A

    2003-11-01

    Stopped flow spectroscopy is an established technique for acquiring kinetic data on dynamic processes in chemical and biochemical reactions, and Fourier transform infrared (FT-IR) techniques can provide particularly rich structural information on biological macromolecules. However, it is a considerable challenge to design an FT-IR stopped flow system with an optical path length low enough for work with aqueous (1H2O) solutions. The system presented here is designed for minimal sample volumes (approximately 5 microL) and allows simultaneous FT-IR rapid-scan and VIS measurements. The system employs a micro-structured diffusional mixer to achieve effective mixing on the millisecond time scale under moderate flow and pressure conditions, allowing measurements in a cell path length of less than 10 microns. This makes it possible to record spectra in 1H2O solutions over a wide spectral range. The system layout is also designed for a combination of kinetic and static measurements, in particular to obtain detailed information on the faster spectral changes occurring during the system dead time. A detailed characterization of the FT-IR stopped flow system is presented, including a demonstration of the alkaline conformational transition of cytochrome c as an example. PMID:14658156

  17. Time-resolved spectroscopy of a homogeneous dielectric barrier discharge for soft ionization driven by square wave high voltage.

    PubMed

    Horvatic, Vlasta; Michels, Antje; Ahlmann, Norman; Jestel, Günter; Veza, Damir; Vadla, Cedomil; Franzke, Joachim

    2015-10-01

    Helium capillary dielectric barrier discharge driven by the square wave-shaped high voltage was investigated spatially and temporally by means of optical emission spectroscopy. The finding of the previous investigation conducted with the sinusoidal-like high voltage was confirmed, i.e., the plasma in the jet and the plasma in the capillary constitute two temporally separated events. The plasma in the jet occurs prior to the discharge in the capillary and exists only during the positive half period of the applied high voltage. The time delay of the capillary discharge with respect to the discharge in the jet depended on the high voltage, and it was between 2.4 and 8.4 μs for the voltage amplitude change in the range from 1.96 to 2.31 kV, respectively. It was found that, compared to sinusoidal-like voltage, application of the square wave high voltage results with stronger (~6 times) He line emission in the jet, which makes the latter more favorable for efficient soft ionization. The use of the square wave high voltage enabled comparison of the currents (~1 mA) flowing in the capillary during the positive and negative high voltage periods, which yielded the estimation for the charge dissipated in the atmosphere ((4 ± 20 %) × 10(-11) C) through the plasma jet. PMID:26297466

  18. Intra-molecular mobility of charge carriers along oligogermane backbones studied by flash photolysis time-resolved microwave conductivity and transient optical spectroscopy techniques

    NASA Astrophysics Data System (ADS)

    Seki, Shu; Saeki, Akinori; Acharya, Anjali; Koizumi, Yoshiko; Tagawa, Seiichi; Mochida, Kunio

    2008-10-01

    Time-resolved microwave conductivity (TRMC) measurement has been performed for fullerene-doped thin films of oligo (dimethylgermane) at different excitation energies to evaluate the intra-molecular mobility of holes along their Ge backbones. Photo-induced electron transfer reaction between oligogermane and fullerene has been observed in the solution with a variety of solvent polarity using transient optical spectroscopy (TOS). The transient spectrum at 391 nm can be attributed to the radical cation of the oligomer under an excitation at 532-nm light, whereas the same spectrum (391 nm) is the overlapping of absorptions of radical cations and neutral radicals of oligogermanes upon exposure of 355-nm light in polar solvent. A combined TRMC and TOS experiments on the solutions of oligomer confirms the conductive transients originate from the radical cations on the backbone chains.

  19. Time-resolved soft-x-ray spectroscopy of a magnetic octupole transition in nickel-like xenon, cesium, and barium ions

    SciTech Connect

    Traebert, E.; Beiersdorfer, P.; Brown, G. V.; Boyce, K.; Kelley, R. L.; Kilbourne, C. A.; Porter, F. S.; Szymkowiak, A.

    2006-02-15

    A microcalorimeter with event mode capability for time-resolved soft-x-ray spectroscopy, and a high-resolution flat-field extreme ultraviolet spectrometer have been employed at the Livermore EBIT-I electron beam ion trap for observations and wavelength measurements of M1, E2, and M3 decays of long-lived levels in the Ni-like ions Xe{sup 26+}, Cs{sup 27+}, and Ba{sup 28+}. Of particular interest is the lowest excited level, 3d{sup 9}4s {sup 3}D{sub 3}, which can only decay via a magnetic octupole (M3) transition. For this level in Xe, an excitation energy of (590.40{+-}0.03 eV) and a level lifetime of (11.5{+-}0.5 ms) have been determined.

  20. Photodissociation of cyclopentadienyliron(II) arene cations: Detection and characterization of reactive intermediates by means of time-resolved laser spectroscopy

    SciTech Connect

    Chrisope, D.R.; Park, Kyungmi; Schuster, G.B. )

    1989-08-02

    Cyclopentadienyliron(II) arene cations ((CpFeArH){sup +}) exist in solution as a mixture of freely solvated ions and as ion pairs with an anionic counterion (X{sup {minus}}). Irradiation of either the free ion or the ion pair in solutions containing benzonitrile (PhCN) leads to loss of the arene ligand and formation of a tris-nitrile complex ((CpFe(PhCN){sub 3}){sup +}). Two important reactive intermediates are detected by time-resolved laser spectroscopy. One, formed from irradiation of the ion pair, is assigned as the ring-slipped {eta}{sup 4}-arene-Cp-iron compound covalently bound to its counterion. The other, formed from irradiation of freely solvated cations, is assigned as the coordinatively unsaturated ring-slipped Cp-iron-{eta}{sup 4}-arene compound. The role of these intermediates in the ligand-exchange reaction was examined.

  1. Atomic resolution mapping of the excited-state electronic structure of Cu2O with time-resolved x-ray absorption spectroscopy

    SciTech Connect

    Hillyard, P. W.; Kuchibhatla, S. V. N. T.; Glover, T. E.; Hertlein, M. P.; Huse, Nils; Nachimuthu, P.; Saraf, L. V.; Thevuthasan, S.; Gaffney, K. J.

    2010-05-02

    We have used time-resolved soft x-ray spectroscopy to investigate the electronic structure of optically excited cuprous oxide at the O K-edge and the Cu L3-edge. The 400 nm optical excitation shifts the Cu and O absorptions to lower energy, but does not change the integrated x-ray absorption significantly for either edge. The constant integrated x-ray absorption cross-section indicates that the conduction-band and valence-band edges have very similar Cu 3d and O 2p orbital contributions. The 2.1 eV optical band gap of Cu2O significantly exceeds the one eV shift in the Cu L3- and O K-edges absorption edges induced by optical excitation, demonstrating the importance of core-hole excitonic effects and valence electron screening in the x-ray absorption process.

  2. Atomic Resolution Mapping of the Excited-State Electronic Structure of Cu2O with Time-Resolved X-Ray Absorption Spectroscopy

    SciTech Connect

    Hillyard, Patrick B.; Kuchibhatla, Satyanarayana V N T; Glover, T. E.; Hertlein, M. P.; Huse, N.; Nachimuthu, Ponnusamy; Saraf, Laxmikant V.; Thevuthasan, Suntharampillai; Gaffney, Kelly J.

    2009-09-29

    We have used time-resolved soft x-ray spectroscopy to investigate the electronic structure of optically excited cuprous oxide at the O K-edge and the Cu L3-edge. The 400 nm optical excitation shifts the Cu and O absorptions to lower energy, but does not change the integrated x-ray absorption significantly for either edge. The constant integrated x-ray absorption cross-section indicates that that the conduction band and valence band edges have very similar Cu 3d and O 2p orbital contributions. The 2.1 eV optical band gap of Cu2O significantly exceeds the one eV shift in the Cu L3- and O K-edges absorption edges induced by optical excitation, demonstrating the importance of core-hole excitonic effects and valence electron screening in the x-ray absorption process.

  3. Femtosecond time resolved coherent anti-Stokes Raman spectroscopy of H(2)-N(2) mixtures in the Dicke regime: Experiments and modeling of velocity effects.

    PubMed

    Tran, H; Chaussard, F; Le Cong, N; Lavorel, B; Faucher, O; Joubert, P

    2009-11-01

    In this paper, we present measurements and modeling of femtosecond time resolved coherent anti-Stokes Raman spectroscopy (CARS) signal in H(2)-N(2) mixtures at low densities. Three approaches have been used to model the CARS response. The first is the usual sum of Voigt profiles. In the second approach, the speed dependent Voigt profile is used. In the last approach, a model of the temporal CARS signal is developed, which takes into account the velocity changes induced by collisions and the speed dependence of the collisional parameters. The velocity changes are modeled using the Keilson and Storer memory function; the radiator speed dependences of the collisional parameters are determined from their temperature dependences. The results obtained are consistent with previous studies in the frequency domain, showing that the changes of the velocity have important effects for the H(2)/N(2) system in the Dicke narrowing density regime. PMID:19895015

  4. Direct measurement of S-branch N2-H2 Raman linewidths using time-resolved pure rotational coherent anti-Stokes Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Bohlin, A.; Nordstrm, E.; Patterson, B. D.; Bengtsson, P.-E.; Kliewer, C. J.

    2012-08-01

    S-branch N2-H2 Raman linewidths have been measured in the temperature region 294-1466 K using time-resolved dual-broadband picosecond pure rotational coherent anti-Stokes Raman spectroscopy (RCARS). Data are extracted by mapping the dephasing rates of the CARS signal temporal decay. The J-dependent coherence decays are detected in the time domain by following the individual spectral lines as a function of probe delay. The linewidth data set was employed in spectral fits of N2 RCARS spectra recorded in binary mixtures of N2 and H2 at calibrated temperature conditions up to 661 K using a standard nanosecond RCARS setup. In this region, the set shows a deviation of less than 2% in comparison with thermocouples. The results provide useful knowledge for the applicability of N2 CARS thermometry on the fuel-side of H2 diffusion flames.

  5. Direct measurement of S-branch N2-H2 Raman linewidths using time-resolved pure rotational coherent anti-Stokes Raman spectroscopy.

    PubMed

    Bohlin, A; Nordström, E; Patterson, B D; Bengtsson, P-E; Kliewer, C J

    2012-08-21

    S-branch N(2)-H(2) Raman linewidths have been measured in the temperature region 294-1466 K using time-resolved dual-broadband picosecond pure rotational coherent anti-Stokes Raman spectroscopy (RCARS). Data are extracted by mapping the dephasing rates of the CARS signal temporal decay. The J-dependent coherence decays are detected in the time domain by following the individual spectral lines as a function of probe delay. The linewidth data set was employed in spectral fits of N(2) RCARS spectra recorded in binary mixtures of N(2) and H(2) at calibrated temperature conditions up to 661 K using a standard nanosecond RCARS setup. In this region, the set shows a deviation of less than 2% in comparison with thermocouples. The results provide useful knowledge for the applicability of N(2) CARS thermometry on the fuel-side of H(2) diffusion flames. PMID:22920115

  6. Observation of femtosecond-laser-induced ablation plumes of aluminum using space- and time-resolved soft x-ray absorption spectroscopy

    SciTech Connect

    Okano, Yasuaki; Oguri, Katsuya; Nishikawa, Tadashi; Nakano, Hidetoshi

    2006-11-27

    The dynamics of the laser ablation plume expansion of aluminum was investigated by using space- and time-resolved soft x-ray absorption spectroscopy. Blueshifts of the Al L-shell photoabsorption edge indicating the state of aluminum were observed in the plumes, which were generated by irradiating an aluminum target with 120 fs near-infrared pulses at an intensity of 10{sup 14} W/cm{sup 2}. The spatiotemporal evolution of the plumes exhibited a multilayer structure consisting of vaporized aluminum and condensed aluminum particles, following the expansion of plasma, with expansion velocities of 10{sup 4} m/s for the atomic state and 10{sup 3} m/s for the condensed state.

  7. Time-Resolved X-ray Spectroscopy in the Water Window: Elucidating Transient Valence Charge Distributions in an Aqueous Fe(II) Complex.

    PubMed

    Van Kuiken, Benjamin E; Cho, Hana; Hong, Kiryong; Khalil, Munira; Schoenlein, Robert W; Kim, Tae Kyu; Huse, Nils

    2016-02-01

    Time-resolved nitrogen-1s spectroscopy in the X-ray water window is presented as a novel probe of metal-ligand interactions and transient states in nitrogen-containing organic compounds. New information on iron(II) polypyridyl complexes via nitrogen core-level transitions yields insight into the charge density of the photoinduced high-spin state by comparing experimental results with time-dependent density functional theory. In the transient high-spin state, the 3d electrons of the metal center are more delocalized over the nearest-neighbor nitrogen atoms despite increased bond lengths. Our findings point to a strong coupling of electronic states with charge-transfer character, facilitating the ultrafast intersystem crossing cascade in these systems. The study also highlights the importance of local charge density measures to complement chemical interaction concepts of charge donation and back-bonding with molecular orbital descriptions of states. PMID:26727390

  8. Europium(III) complexed by HPSEC size-fractions of a vertisol humic acid: Small differences evidenced by time-resolved luminescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Reiller, Pascal E.; Brevet, Julien; Nebbioso, Antonio; Piccolo, Alessandro

    2011-03-01

    The size fractionation of a humic acid (HA) by high performance size exclusion chromatography (HPSEC) was used as a proxy for the filtration effect during HA transport through a porous medium with minimum specific chemical interactions. The modification of the Eu(III)-HA complexes' formation with the different size-fractions, as compared to the bulk HA, was studied in time-resolved luminescence spectroscopy (TRLS). Clear modifications in Eu(III)-HA complexes' structures were shown and related to the molecular characteristics of the separated size-fractions. The properties of most of size-fractions did not induce a major alteration of the affinity towards Eu(III). Only the most hydrophilic fractions eluted in the tail of the chromatographic peak, representing about 11% of total fractions-weight, gave some significantly different parameters. Using a simplistic complexation model, it was found that the available complexation sites decreased with the size reduction of humic fractions.

  9. Time-resolved soft-x-ray spectroscopy of a magnetic octupole transition in nickel-like xenon, cesium, and barium ions

    SciTech Connect

    Trabert, E; Beiersdorfer, P; Brown, G V; Boyce, K; Kelley, R L; Kilbourne, C A; Porter, F S; Szymkowiak, A

    2005-11-11

    A microcalorimeter with event mode capability for time-resolved soft-x-ray spectroscopy, and a high-resolution flat-field EUV spectrometer have been employed at the Livermore EBIT-I electron beam ion trap for observations and wavelength measurements of M1, E2, and M3 decays of long-lived levels in the Ni-like ions Xe{sup 26+}, Cs{sup 27+}, and Ba{sup 28+}. Of particular interest is the lowest excited level, 3d{sup 9}4s {sup 3}D{sub 3}, which can only decay via a magnetic octupole (M3) transition. For this level in Xe an excitation energy of (590.40 {+-} 0.03eV) and a level lifetime of (11.5 {+-} 0.5 ms) have been determined.

  10. Observation of transient iron(II) formation in dye-sensitized iron oxide nanoparticles by time-resolved x-ray spectroscopy.

    SciTech Connect

    Katz, J. E.; Gilbert, B.; Zhang, X.; Attenkofer, K.; Falcone, R. W.; Waychunas, G. A.

    2010-01-01

    The reduction of ferric iron in solid phase minerals leads to the mobilization of ferrous iron in the environment and is thus a crucial component of the global iron cycle. Despite the importance of this process, a mechanistic understanding of the structural and chemical changes that are caused by this electron transfer reaction is not established because the speed of the fundamental chemical steps renders them inaccessible to conventional study. Ultrafast time-resolved X-ray spectroscopy is a technique that can overcome this limitation and measure changes in oxidation state and structure occurring during chemical reactions that can be initiated by a fast laser pulse. We use this approach with {approx}100 ps resolution to monitor the speciation of Fe atoms in iron oxide nanoparticles following photoinduced electron transfer from a surface-bound photoactive dye molecule. These data represent the first direct real-time observation of the dynamics of ferrous ion formation and subsequent reoxidation in iron oxide.

  11. Time-resolved Spectroscopy of the Three Brightest and Hardest Short Gamma-ray Bursts Observed with the Fermi Gamma-ray Burst Monitor

    NASA Astrophysics Data System (ADS)

    Guiriec, Sylvain; Briggs, Michael S.; Connaugthon, Valerie; Kara, Erin; Daigne, Frédéric; Kouveliotou, Chryssa; van der Horst, Alexander J.; Paciesas, William; Meegan, Charles A.; Bhat, P. N.; Foley, Suzanne; Bissaldi, Elisabetta; Burgess, Michael; Chaplin, Vandiver; Diehl, Roland; Fishman, Gerald; Gibby, Melissa; Giles, Misty M.; Goldstein, Adam; Greiner, Jochen; Gruber, David; von Kienlin, Andreas; Kippen, Marc; McBreen, Sheila; Preece, Robert; Rau, Arne; Tierney, Dave; Wilson-Hodge, Colleen

    2010-12-01

    From 2008 July to 2009 October, the Gamma-ray Burst Monitor (GBM) on board the Fermi Gamma-ray Space Telescope has detected 320 gamma-ray bursts (GRBs). About 20% of these events are classified as short based on their T 90 duration below 2 s. We present here for the first time time-resolved spectroscopy at timescales as short as 2 ms for the three brightest short GRBs observed with GBM. The time-integrated spectra of the events deviate from the Band function, indicating the existence of an additional spectral component, which can be fit by a power law with index ~-1.5. The time-integrated E peak values exceed 2 MeV for two of the bursts and are well above the values observed in the brightest long GRBs. Their E peak values and their low-energy power-law indices (α) confirm that short GRBs are harder than long ones. We find that short GRBs are very similar to long ones, but with light curves contracted in time and with harder spectra stretched toward higher energies. In our time-resolved spectroscopy analysis, we find that the E peak values range from a few tens of keV up to more than 6 MeV. In general, the hardness evolutions during the bursts follow their flux/intensity variations, similar to long bursts. However, we do not always see the E peak leading the light-curve rises and confirm the zero/short average light-curve spectral lag below 1 MeV, already established for short GRBs. We also find that the time-resolved low-energy power-law indices of the Band function mostly violate the limits imposed by the synchrotron models for both slow and fast electron cooling and may require additional emission processes to explain the data. Finally, we interpreted these observations in the context of the current existing models and emission mechanisms for the prompt emission of GRBs.

  12. Surface vibrational relaxation of N2 studied by CO2 titration with time-resolved quantum cascade laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Marinov, D.; Lopatik, D.; Guaitella, O.; Hübner, M.; Ionikh, Y.; Röpcke, J.; Rousseau, A.

    2012-05-01

    A new method for determination of the wall de-excitation probability \\gamma _{N_2 } of vibrationally excited N2 on different surfaces exposed to low-pressure plasmas has been developed. A short dc discharge pulse of only a few milliseconds was applied to a mixture containing 0.05-1% of CO2 in N2 at a pressure of 133 Pa. Due to a nearly resonant fast vibrational transfer between N2(v) and the asymmetric ν3 mode of CO2 the vibrational excitation of these titrating molecules is an image of the degree of vibrational excitation of N2. In the afterglow, the vibrational relaxation of CO2 was monitored in situ using quantum cascade laser absorption spectroscopy. The experimental results were interpreted in terms of a numerical model of non-equilibrium vibrational kinetics in CO2-N2 mixtures. Heterogeneous relaxation was the main quenching process of N2(v) under the conditions of this study, which allowed determination of the value of \\gamma _{N_2 } from the best agreement between the experiment and the model. The new method is suitable for \\gamma _{N_2 } determination in a single plasma pulse with the discharge tube surface pretreated by a low-pressure plasma. The relaxation probability of the first vibrational level of nitrogen γ1 = (1.1 ± 0.15) × 10-3 found for Pyrex and silica is in reasonable agreement with the literature data. Using the new technique the N2(v = 1) quenching probability was measured on TiO2 surface, γ1 = (9 ± 1) × 10-3. A linear enhancement of the N2(v) wall deactivation probability with an increase in the admixture of CO2 was observed for all studied materials. In order to explain this effect, a vibrational energy transfer mechanism between N2(v) and adsorbed CO2 is proposed.

  13. FLIMX: A Software Package to Determine and Analyze the Fluorescence Lifetime in Time-Resolved Fluorescence Data from the Human Eye

    PubMed Central

    Klemm, Matthias; Schweitzer, Dietrich; Peters, Sven; Sauer, Lydia; Hammer, Martin; Haueisen, Jens

    2015-01-01

    Fluorescence lifetime imaging ophthalmoscopy (FLIO) is a new technique for measuring the in vivo autofluorescence intensity decays generated by endogenous fluorophores in the ocular fundus. Here, we present a software package called FLIM eXplorer (FLIMX) for analyzing FLIO data. Specifically, we introduce a new adaptive binning approach as an optimal tradeoff between the spatial resolution and the number of photons required per pixel. We also expand existing decay models (multi-exponential, stretched exponential, spectral global analysis, incomplete decay) to account for the layered structure of the eye and present a method to correct for the influence of the crystalline lens fluorescence on the retina fluorescence. Subsequently, the Holm-Bonferroni method is applied to FLIO measurements to allow for group comparisons between patients and controls on the basis of fluorescence lifetime parameters. The performance of the new approaches was evaluated in five experiments. Specifically, we evaluated static and adaptive binning in a diabetes mellitus patient, we compared the different decay models in a healthy volunteer and performed a group comparison between diabetes patients and controls. An overview of the visualization capabilities and a comparison of static and adaptive binning is shown for a patient with macular hole. FLIMX’s applicability to fluorescence lifetime imaging microscopy is shown in the ganglion cell layer of a porcine retina sample, obtained by a laser scanning microscope using two-photon excitation. PMID:26192624

  14. Ultrafast Nonlinear Spectroscopy of Red Fluorescent Proteins

    NASA Astrophysics Data System (ADS)

    Konold, Patrick Eugene

    Red-emitting homologues (RFPs) of the native Green Fluorescent Protein (GFP) with emission wavelengths beyond 650 nm are desirable probes for in vivo imaging experiments. They offer the potential for deeper tissue penetration and lower background scatter given a cleaner spectral window. However, bioimaging applications are hindered by poor photophysics ( e.g. low fluorescence quantum yield, high photobleaching), which limits experimental resolution and represents a significant obstacle towards utilization for low copy-number, long-duration imaging applications. In this thesis, a variety of femtosecond nonlinear electronic spectroscopies were employed jointly with site-directed mutagenesis to investigate the photophysical properties of RFPs. In one study, the molecular mechanism of red emission was pursued in two notable RFPs, mPlum and TagRFP675. Solvation dynamics observed with time-resolved transient grating spectroscopy were interpreted with the aid of molecular dynamics simulations to indicate that their red-emission is correlated with the ability of specific chromophore-sidechain hydrogen-bonding interactions to interconvert between direct and water-mediated states. In a second set of studies, two-dimensional double quantum coherence spectroscopy was used to probe the electronic transitions of mPlum. It was discovered that it displayed a response distinctly different from an organic dye in bulk solvent. Modeling indicate of these spectra indicate the spectral features may be attributed to the existence of multiple high-lying (n>1) excited states. The results provide new insight into the electronic structure of these widely used fluorescent probes.

  15. Transmission electron microscopy and time resolved optical spectroscopy study of the electronic and structural interactions of ZnO nanorods with bovine serum albumin.

    PubMed

    Klaumünzer, M; Weichsel, U; Mačković, M; Spiecker, E; Peukert, W; Kryschi, C

    2013-08-22

    The adsorption behavior and electronic interactions of bovine serum albumin (BSA) with ZnO nanorod surfaces were investigated using high-resolution transmission electron microscopy as well as stationary and time-resolved optical spectroscopy techniques. Transmission electron microscopy shows that ZnO nanorod surfaces are surrounded by a homogeneous amorphous BSA film with thicknesses between ~2.5 and 5.0 nm. The electronic structure and adsorption geometry of BSA were examined using high-angle annular dark field scanning transmission electron microscopy combined with electron energy loss spectroscopy. The adsorption process was observed to result into an unfolded conformation of BSA becoming predominantly bound in the side-on orientation at the ZnO surface. This adsorption mode of the BSA molecules allows for a strong interaction with surface states of the ZnO nanorods. T