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1

Emerging biomedical applications of time-resolved fluorescence spectroscopy  

NASA Astrophysics Data System (ADS)

Time-resolved fluorescence spectroscopy is presently regarded as a research tool in biochemistry, biophysics, and chemical physics. Advances in laser technology, the development of long-wavelength probes, and the use of lifetime-based methods are resulting in the rapid migration of time-resolved fluorescence to the clinical chemistry lab, to the patient's bedside, to flow cytometers, to the doctor's office, and even to home health care. Additionally, time-resolved imaging is now a reality in fluorescence microscopy, and will provide chemical imaging of a variety of intracellular analytes and/or cellular phenomena. In this overview paper we attempt to describe some of the opportunities available using chemical sensing based on fluorescence lifetimes, and to predict those applications of lifetime-based sensing which are most likely in the near future.

Lakowicz, Joseph R.; Szmacinski, Henryk; Koen, Peter A.

1994-07-01

2

IN SITU PLANETARY MINERALOGY USING SIMULTANEOUS TIME RESOLVED FLUORESCENCE AND RAMAN SPECTROSCOPY. J. Blacksberg1  

E-print Network

1. Image of our pulsed 532nm laser focusedIN SITU PLANETARY MINERALOGY USING SIMULTANEOUS TIME RESOLVED FLUORESCENCE AND RAMAN SPECTROSCOPY@gps.caltech.edu Introduction: Micro-Raman spectroscopy is one of the primary methods of mineralogical analysis

Rossman. George R.

3

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

Microsoft Academic Search

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

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

2009-01-01

4

Automation of the Laguerre Expansion Technique for Analysis of Time-resolved Fluorescence Spectroscopy Data  

E-print Network

Time-resolved fluorescence spectroscopy (TRFS) is a powerful analytical tool for quantifying the biochemical composition of organic and inorganic materials. The potentials of TRFS as nondestructive clinical tool for tissue diagnosis have been...

Dabir, Aditi Sandeep

2010-07-14

5

Classification of aortic atherosclerotic lesions with time-resolved fluorescence spectroscopy  

NASA Astrophysics Data System (ADS)

In this study, we examine the possibility of differentiating between classes of atherosclerotic lesions based on time- resolved fluorescence spectroscopy and we compare the performance of classification schemes that use either the time-resolved spectra or only the intensity spectra. Transient fluorescence emissions induced by pulsed nitrogen laser excitation was measured on 87 excised samples of human aorta. The samples were classified histologically using the AHA classification Predictor variables derived from the time-resolved spectra included the spectral intensities at 360-510 nm and parameters of a biexponential fit of the fluorescence impulse response function. Stepwise discriminant analysis using these predict variables showed that a few predictor variables sufficed to correctly classify 89 percent of the samples. Excluding the time- dependent decay and using only the spectral intensities, the percentage of correctly classified cases was significantly lower: 51 percent. These results establish that time- resolved fluorescence spectroscopy markedly improved on the performance of steady-state fluorescence spectroscopy for fine classification of atherosclerotic lesions.

Maarek, Jean-Michel I.; Marcu, Laura; Grundfest, Warren S.; Fishbein, Michael C.

1999-07-01

6

Time-resolved fluorescence spectroscopy for application to PAH contaminated areas and hydrogeological research  

SciTech Connect

A mobile fiber-optical sensor system for the on-line and in situ detection of aquatic fluorophores has been developed. By the use of time-resolved laser-induced fluorescence spectroscopy the determination of contaminants i.e. polycyclic aromatic hydrocarbons (PAH) or fluorescence tracers in various environments is possible. In both cases attempts to detect these substances in water by means of fluorescence spectroscopy are complicated by the low concentrations and the overlapping and featureless fluorescence spectroscopy are complicated by the low concentrations and the overlapping and featureless fluorescence spectra in combination with background fluorescence caused by further compounds e.g. humic material. By collecting the fluorescence decay time as an additional independent dimension, the analytical information is significantly increased, and to certain extent the determination of the desired analyte in complex natural matrices is possible. At a first application, the detection of pyrene (PYR) in real samples from a contaminated former coking plant site has been realized. The system is also best suitable for hydrogeological research. Here applications spread from the investigation of the fluorescence tracer migration in an artificial aquifer system to the determination of hydrogeological parameters at a domestic waste disposal.

Kotzick, R.; Haaszio, S.; Niessner, R. [Technical Univ. of Munich (Germany). Institute for Hydrochemistry

1995-12-31

7

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

NASA Astrophysics Data System (ADS)

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 0.8-7 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.

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

2014-03-01

8

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

SciTech Connect

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 0.8–7 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.

Yankelevich, Diego R. [Department of Electrical and Computer Engineering, University of California, 3101 Kemper Hall, Davis, California 95616 (United States) [Department of Electrical and Computer Engineering, University of California, 3101 Kemper Hall, Davis, California 95616 (United States); Department of Biomedical Engineering, University of California, 451 Health Sciences Drive, Davis, California 95616 (United States); Ma, Dinglong; Liu, Jing; Sun, Yang; Sun, Yinghua; Bec, Julien; Marcu, Laura, E-mail: lmarcu@ucdavis.edu [Department of Biomedical Engineering, University of California, 451 Health Sciences Drive, Davis, California 95616 (United States)] [Department of Biomedical Engineering, University of California, 451 Health Sciences Drive, Davis, California 95616 (United States); Elson, Daniel S. [Hamlyn Centre for Robotic Surgery, Department of Surgery and Cancer, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom)] [Hamlyn Centre for Robotic Surgery, Department of Surgery and Cancer, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom)

2014-03-15

9

Applications of time-resolved laser fluorescence spectroscopy to the environmental biogeochemistry of actinides.  

PubMed

Time-resolved laser fluorescence spectroscopy (TRLFS) is a useful means of identifying certain actinide species resulting from various biogeochemical processes. In general, TRLFS differentiates chemical species of a fluorescent metal ion through analysis of different excitation and emission spectra and decay lifetimes. Although this spectroscopic technique has largely been applied to the analysis of actinide and lanthanide ions having fluorescence decay lifetimes on the order of microseconds, such as UO , Cm, and Eu, continuing development of ultra-fast and cryogenic TRLFS systems offers the possibility to obtain speciation information on metal ions having room-temperature fluorescence decay lifetimes on the order of nanoseconds to picoseconds. The main advantage of TRLFS over other advanced spectroscopic techniques is the ability to determine in situ metal speciation at environmentally relevant micromolar to picomolar concentrations. In the context of environmental biogeochemistry, TRLFS has principally been applied to studies of (i) metal speciation in aqueous and solid phases and (ii) the coordination environment of metal ions sorbed to mineral and bacterial surfaces. In this review, the principles of TRLFS are described, and the literature reporting the application of this methodology to the speciation of actinides in systems of biogeochemical interest is assessed. Significant developments in TRLFS methodology and advanced data analysis are highlighted, and we outline how these developments have the potential to further our mechanistic understanding of actinide biogeochemistry. PMID:21546659

Collins, Richard N; Saito, Takumi; Aoyagi, Noboru; Payne, Timothy E; Kimura, Takaumi; Waite, T David

2011-01-01

10

Uptake of trivalent actinides (curium(III)) by hardened cement paste: a time-resolved laser fluorescence spectroscopy study  

Microsoft Academic Search

The curium(III) interaction with cement was investigated using time-resolved laser fluorescence spectroscopy at trace concentrations. Four different Cm(III) species were identified: a nonfluorescing species which corresponds to curium hydroxide real colloids, which were characterized in detail by laser-induced breakdown detection (LIBD), a fluorescing Cm(III)\\/portlandite sorption species, and two fluorescing Cm(III)\\/calcium silicate hydrate (CSH) species. From the fluorescence emission lifetimes it

Thorsten Stumpf; Clemens Walther; Erich Wieland; Thomas Fanghänel

2004-01-01

11

Application of time-resolved polarization fluorescence spectroscopy in the femtosecond range to photosynthetic systems.  

PubMed

Time-resolved polarization fluorescence spectroscopy in the femtosecond range was applied to a photosynthetic antenna system. Specific signals of excited states were obtained by simultaneous measurements of fluorescence rise and decay curves and polarized spectroscopy. Relaxation processes of carotenoids, energy transfer from carotenoids to chlorophyll (Chl) a, and energy migration among pigment pools of Chl a and Chl b were clearly resolved. Two new characteristics of carotenoid molecules were revealed only by anisotropy measurements. A new singlet excited state between the well known S2 (1Bu(+)) and S1 (2Ag(-)) states was resolved by an intermediary anisotropy (r(t) = 0.30) for siphonaxanthin in chloroplasts of Codium fragile. Time-dependent changes in anisotropy with an initial value of 0.52 (r(0) = 0.52) were recorded during the relaxation of lutein molecules in the light-harvesting complexes II of Arabidopsis thaliana, and this was interpreted as a strong interaction between two lutein molecules in the pigment-protein complexes. Other examples of the application of this method were also discussed. PMID:16643087

Akimoto, Seiji; Mimuro, Mamoru

2007-01-01

12

Intracellular localization of meso-tetraphenylporphine tetrasulphonate probed by time-resolved and microscopic fluorescence spectroscopy.  

PubMed

The effects of solvent pH on spectral properties and fluorescence decay kinetics were investigated in order to characterize the microenvironment of meso-tetraphenylporphine tetrasulphonate (TPPS4) taken up by cells. Steady-state absorption and fluorescence spectra of TPPS4 in buffer solutions of different pH were used to identify a ring protonated species at pH less than or equal to 4. This dictation could also be distinguished from the unprotonated form by its altered fluorescence decay time (3.5 vs. 11.4 ns). In addition, time-resolved spectroscopy gave some evidence of a monocationic species existing at pH 6-9. This was concluded from the occurrence of another component with a decay time of 5 ns. Measurements of the spectral and kinetic properties of the fluorescence emission of single epithelial cells (RR1022) incubated with TPPS4 indicated that the sensitizer was mainly localized in a microenvironment with a pH of 5, a value which occurs intracellularly only within lysosomes. Cells kept in the dark exhibited the characteristic spectra of both the dication and the neutral form. The fluorescence decay showed two components with decay times of 2.6 ns and 10.6 ns. Irradiation of the cells changed the decay times to 4.6 ns and 13.4 ns and the dication fluorescence emission peak vanished, which is in accordance with the results obtained from buffer solutions at pH greater than or equal to 6. Therefore, we deduce that the photodynamic action leads to a rupture of the lysosomes and that the sensitizer is released into the surrounding cytoplasm. PMID:1635012

Wessels, J M; Strauss, W; Seidlitz, H K; Rück, A; Schneckenburger, H

1992-02-28

13

Characterization of powellite-based solid solutions by site-selective time resolved laser fluorescence spectroscopy.  

PubMed

We present a comprehensive study of the solid solution system Ca2(MoO4)2-NaGd(MoO4)2 on the molecular scale, by means of site-selective time resolved laser fluorescence spectroscopy (TRLFS). Eu(3+) is used as a trace fluorescent probe, homogeneously substituting for Gd(3+) in the solid solution crystal structure. Site-selective TRLFS of a series of polycrystalline samples covering the whole composition range of the solid solution series from 10% substitution of Ca(2+) to the NaGd end-member reveals it to be homogeneous throughout the whole range. The trivalent ions are incorporated into the powellite structure in only one coordination environment, which exhibits a very strong ligand-metal interaction. Polarization-dependent measurements of a single crystal of NaGd(Eu)(MoO4)2 identify the coordination geometry to be of C2v point symmetry. The S4 symmetry of the Ca site within the powellite lattice can be transformed into C2v assuming minor motion in the first coordination sphere. PMID:23615970

Schmidt, Moritz; Heck, Stephanie; Bosbach, Dirk; Ganschow, Steffen; Walther, Clemens; Stumpf, Thorsten

2013-06-21

14

Complexation of curium(III) with hydroxamic acids investigated by time-resolved laser-induced fluorescence spectroscopy  

Microsoft Academic Search

The unknown complex formation of Cm(III) with two hydroxamic acids, salicylhydroxamic (SHA) and benzohydroxamic acid (BHA) was studied by time-resolved laser-induced fluorescence spectroscopy (TRLFS). Hydroxamate containing chelating substances have the potential to enhance the solubility and mobility of metals and radionuclides by forming complexes. We explored the fluorescence properties, lifetimes and individual fluorescence emission spectra of the formed Cm(III) hydroxamate

M. Glorius; H. Moll; G. Bernhard

2008-01-01

15

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

Microsoft Academic Search

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

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

2004-01-01

16

Conformational Analysis of DNA Repair Intermediates by Time-Resolved Fluorescence Spectroscopy  

NASA Astrophysics Data System (ADS)

DNA repair enzymes are essential for maintaining the integrity of the DNA sequence. Unfortunately, very little is known about how these enzymes recognize damaged regions along the helix. Structural analysis of cellular repair enzymes bound to DNA reveals that these enzymes are able to recognize DNA in a variety of conformations. However, the prevalence of these deformations in the absence of enzymes remains unclear, as small populations of DNA conformations are often difficult to detect by NMR and X-ray crystallography. Here, we used time-resolved fluorescence spectroscopy to examine the conformational dynamics of linear, nicked, gapped, and bulged DNA in the absence of protein enzymes. This analysis reveals that damaged DNA is polymorphic in nature and able to adopt multiple individual conformations. We show that DNA repair intermediates that contain a one-nucleotide gap and bulge have a significant propensity to adopt conformations in which the orphan base resides outside the DNA helix, while DNA structures damaged by a nick or two-nucleotide gap favor intrahelical conformations. Because changes in DNA conformation appear to guide the recognition of DNA repair enzymes, we suggest that the current approach could be used to study the mechanism of DNA repair.

Lin, Su; Horning, David P.; Szostak, Jack W.; Chaput, John C.

2009-08-01

17

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

NASA Astrophysics Data System (ADS)

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.

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

2004-03-01

18

Time-resolved fluorescence microscopy  

NASA Astrophysics Data System (ADS)

Fluorescence imaging techniques are powerful tools in the biological and biomedical sciences, because they are minimally invasive and can be applied to live cells and tissues. The fluorescence emission can be characterized not only by its intensity and position, by also by its fluorescence lifetime, polarization and wavelength. Fluorescence Lifetime Imaging (FLIM) in particular has emerged as a key technique to image the environment and interaction of specific proteins in living cells. Using a time-correlated single photon counting (TCSPC)-based FLIM set-up, we find that the fluorescence lifetime of GFP-tagged proteins in cells is a function of the refractive index of the medium the cells are suspended in. In addition, combining Fluorescence Recovery After Photobleaching (FRAP) of fluorescently labeled proteins of different sizes in sol gels with time-resolved fluorescence anisotropy measurements, we demonstrate that we can measure their lateral and rotational diffusion. This allows us to infer the size and connectivity of the pores in the sol gel matrix. Moreover, wide-field photon counting imaging, originally developed for astronomical applications, is a powerful imaging method because of its high sensitivity and excellent signal-to-noise ratio. It has a distinct advantage over CCD-based imaging due to the ability to time the arrival of individual photons. The potential of time-resolved wide-field photon counting imaging with a fast CMOS camera applied to luminescence microscopy is demonstrated.

Suhling, Klaus; Tregidgo, Carolyn; Sergent, Nicolas; Levitt, James A.; Pavlides, Alex; Green, Mark; Hungerford, Graham; Rei, Ana; Ferreira, M. Isabel C.

2007-09-01

19

Drug/protein interactions studied by time-resolved fluorescence spectroscopy  

NASA Astrophysics Data System (ADS)

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.

Gustavsson, Thomas; Markovitsi, Dimitra; Vayá, Ignacio; Bonancía, Paula; Jiménez, M. C.; Miranda, Miguel A.

2014-09-01

20

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

NASA Astrophysics Data System (ADS)

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, ?). 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.

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

2011-03-01

21

Fluorescence Instrument Response Standards in Two-Photon Time-Resolved Spectroscopy  

PubMed Central

We studied the fluorescence properties of several potential picosecond lifetime standards suitable for two-photon excitation from a Ti : sapphire femtosecond laser. The fluorescence emission of the selected fluorophores (rose bengal, pyridine 1, and LDS 798) covered the visible to near-infrared wavelength range from 550 to 850 nm. We suggest that these compounds can be used to measure the appropriate instrument response functions needed for accurate deconvolution of fluorescence lifetime data. Lifetime measurements with multiphoton excitation that use scatterers as a reference may fail to properly resolve fluorescence intensity decays. This is because of the different sensitivities of photodetectors in different spectral regions. Also, detectors often lose sensitivity in the near-infrared region. We demonstrate that the proposed references allow a proper reconvolution of measured lifetimes. We believe that picosecond lifetime standards for two-photon excitation will find broad applications in multiphoton spectroscopy and in fluorescence lifetime imaging microscopy (FLIM). PMID:20719056

LUCHOWSKI, RAFAL; SZABELSKI, MARIUSZ; SARKAR, PABAK; APICELLA, ELISA; MIDDE, KRISHNA; RAUT, SANGRAM; BOREJDO, JULIAN; GRYCZYNSKI, ZYGMUNT; GRYCZYNSKI, IGNACY

2011-01-01

22

Fluorescence instrument response standards in two-photon time-resolved spectroscopy.  

PubMed

We studied the fluorescence properties of several potential picosecond lifetime standards suitable for two-photon excitation from a Ti:sapphire femtosecond laser. The fluorescence emission of the selected fluorophores (rose bengal, pyridine 1, and LDS 798) covered the visible to near-infrared wavelength range from 550 to 850 nm. We suggest that these compounds can be used to measure the appropriate instrument response functions needed for accurate deconvolution of fluorescence lifetime data. Lifetime measurements with multiphoton excitation that use scatterers as a reference may fail to properly resolve fluorescence intensity decays. This is because of the different sensitivities of photodetectors in different spectral regions. Also, detectors often lose sensitivity in the near-infrared region. We demonstrate that the proposed references allow a proper reconvolution of measured lifetimes. We believe that picosecond lifetime standards for two-photon excitation will find broad applications in multiphoton spectroscopy and in fluorescence lifetime imaging microscopy (FLIM). PMID:20719056

Luchowski, Rafal; Szabelski, Mariusz; Sarkar, Pabak; Apicella, Elisa; Midde, Krishna; Raut, Sangram; Borejdo, Julian; Gryczynski, Zygmunt; Gryczynski, Ignacy

2010-08-01

23

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

NASA Astrophysics Data System (ADS)

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.

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

2007-09-01

24

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

NASA Astrophysics Data System (ADS)

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.

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

2012-03-01

25

Time-resolved laser-induced fluorescence spectroscopy as a diagnostic instrument in head and neck carcinoma  

PubMed Central

OBJECTIVE 1) Determine differences in lifetime fluorescence between normal and malignant tissue of the upper aerodigestive tract. 2) Evaluate the potential of time-resolved laser-induced fluorescence spectroscopy (TR-LIFS) as a diagnostic instrument for head and neck squamous cell carcinoma (HNSCC). STUDY DESIGN Cross-sectional study. SETTING University-based medical center. SUBJECTS AND METHODS Nine patients with suspected HNSCC were included. In the operating room, a nitrogen pulse laser (337 nm, 700 ps pulse width) was used to induce tissue autofluorescence of normal tissue and suspected malignant lesions. Spectral intensities and time-domain measurements were obtained and compared to the histopathology at each site. A total of 53 sites were measured. The fluorescence parameters that provided the most discrimination were determined. RESULTS Differences in spectral intensities allowed for discrimination between malignant and normal tissue. The spectral intensity of malignant tissue was lower than the normal tissue, and a shift of peak intensity to a longer wavelength was observed in the normalized spectrum of malignant tissue in the range of 360~660 nm. Multiple time-resolved fluorescence parameters provided the best diagnostic discrimination between normal tissue and carcinoma, including average lifetimes (i.e., at 390 nm: 1.7±0.06 ns for normal and 1.3±0.06 ns for tumor, P=0.0025), and the Laguerre coefficients, LEC-2 (i.e., at 460 nm: 0.135±0.001 for normal and 0.155±0.007 for tumor, P<0.05). CONCLUSION These findings highlight some of the differences in lifetime fluorescence between normal and malignant tissue. TR-LIFS has potential as a non-invasive diagnostic technique for HNSCC. PMID:20493355

Meier, Jeremy D.; Xie, Hongtao; Sun, Yang; Sun, Yinghua; Hatami, Nisa; Poirier, Brian; Marcu, Laura; Farwell, D. Gregory

2011-01-01

26

The study of polyplex formation and stability by time-resolved fluorescence spectroscopy of SYBR Green I-stained DNA.  

PubMed

Polyplexes are nanoparticles formed by the self-assembly of DNA/RNA and cationic polymers specifically designed to deliver exogenous genetic material to cells by a process called transfection. There is a general consensus that a subtle balance between sufficient extracellular protection and intracellular release of nucleic acids is a key factor for successful gene delivery. Therefore, there is a strong need to develop suitable tools and techniques for enabling the monitoring of the stability of polyplexes in the biological environment they face during transfection. In this work we propose time-resolved fluorescence spectroscopy in combination with SYBR Green I-DNA dye as a reliable tool for the in-depth characterization of the DNA/vector complexation state. As a proof of concept, we provide essential information on the assembly and disassembly of complexes formed between DNA and each of three cationic polymers, namely a novel promising chitosan-graft-branched polyethylenimine copolymer (Chi-g-bPEI), one of its building block 2 kDa bPEI and the gold standard transfectant 25 kDa bPEI. Our results highlight the higher information content provided by the time-resolved studies of SYBR Green I/DNA, as compared to conventional steady state measurements of ethidium bromide/DNA that enabled us to draw relationships among fluorescence lifetime, polyplex structural changes and transfection efficiency. PMID:25308511

D'Andrea, Cosimo; Pezzoli, Daniele; Malloggi, Chiara; Candeo, Alessia; Capelli, Giulio; Bassi, Andrea; Volonterio, Alessandro; Taroni, Paola; Candiani, Gabriele

2014-12-01

27

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

NASA Astrophysics Data System (ADS)

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.

Dang, Wei; Mao, Pengcheng; Weng, Yuxiang

2013-07-01

28

Picosecond time-resolved fluorescence spectroscopy of K-590 in the bacteriorhodopsin photocycle.  

PubMed Central

The fluorescence spectrum of a distinct isometric and conformational intermediate formed on the 10(-11) s time scale during the bacteriorhodopsin (BR) photocycle is observed at room temperature using a two laser, pump-probe technique with picosecond time resolution. The BR photocycle is initiated by pulsed (8 ps) excitation at 565 nm, whereas the fluorescence is generated by 4-ps laser pulses at 590 nm. The unstructured fluorescence extends from 650 to 880 nm and appears in the same general spectral region as the fluorescence spectrum assigned to BR-570. The transient fluorescence spectrum can be distinguished from that assigned to BR-570 by a larger emission quantum yield (approximately twice that of BR-570) and by a maximum intensity near 731 nm (shifted 17 nm to higher energy from the maximum of the BR-570 fluorescence spectrum). The fluorescence spectrum of BR-570 only is measured with low energy, picosecond pulsed excitation at 590 nm and is in good agreement with recent data in the literature. The assignment of the transient fluorescence spectrum to the K-590 intermediate is based on its appearance at time delays longer than 40 ps. The K-590 fluorescence spectrum remains unchanged over the entire 40-100-ps interval. The relevance of these fluorescence data with respect to the molecular mechanism used to model the primary processes in the BR photocycle also is discussed. PMID:2713439

Atkinson, G H; Blanchard, D; Lemaire, H; Brack, T L; Hayashi, H

1989-01-01

29

Time resolved fluorescence of CdSe nanocrystals using single molecule spectroscopy  

E-print Network

A wide variety of spectroscopic studies of CdSe nanocrystals (NCs) are presented in this thesis, all studying some aspect of the temporal evolution of NC fluorescence tinder different conditions. In particular the methods ...

Fisher, Brent R

2005-01-01

30

Development of a Time Resolved Fluorescence Spectroscopy System for Near Real-Time Clinical Diagnostic Applications  

E-print Network

as 25 picoseconds) resolution. Alternatively, a state diode pumped pulsed laser can be used for excitation to improve data collection speed. The TRFS system is capable of measuring a broad range of fluorescence emission spectra (visible to near infra...

Trivedi, Chintan A.

2010-07-14

31

Studying effects of capillary flow on membrane proteins by time-resolved fluorescence spectroscopy  

NASA Astrophysics Data System (ADS)

We wish to develop a biophysical understanding of the structure-function relationship of Tissue Factor (TF), the membrane-bound protein that triggers hemostasis and arterial thrombosis by essential activation of the enzyme Factor VIIa (VIIa). Catalysis by TF-bound VIIa occurs in the blood stream, and flow-dependent shear affects its enzyme kinetics. From the known structure of the TF:VIIa complex, the catalytic domain of VIIa could be as close as 1 nm or as far as 12 nm from the membrane surface depending on geometry under the influence of shear. As models of blood vessels, we use glass capillary tubes coated on the inside surface with a lipid bilayer containing TF. This setup permits two types of measurements as a function of flow: enzyme kinetics of TF:VIIa by a colorimetric assay; and analysis of the spatial and dynamic relationship of TF:VIIa with respect to the membrane surface. Time-resolved depolarization and resonance energy transfer are measured via a microscope using either direct or evanescent wave excitation. We demonstrate the feasibility of these experiments by using rhodamine-labelled phospholipids at probe densities down to approximately 300 molecules/micrometer2 in the presence or absence of the acceptor malachite green and by the emission anisotropy decay of probes in glycerol.

Sassaroli, Massimo; Uchiyama, Katsumi; Vaananen, Heikki; Dale, Robert E.; Giesen, Peter L. A.; Ross, J. B. Alexander

1998-05-01

32

Interaction of europium and nickel with calcite studied by Rutherford Backscattering Spectrometry and Time-Resolved Laser Fluorescence Spectroscopy  

NASA Astrophysics Data System (ADS)

This study aims at elucidating the mechanisms regulating the interaction of Eu and Ni with calcite (CaCO3). Calcite powders or single crystals (some mm sized) were put into contact with Eu or Ni solutions at concentrations ranging from 10-3 to 10-5 mol L-1 for Eu and 10-3 mol L-1 for Ni. The sorption durations ranged from 1 week to 1 month. Rutherford Backscattering Spectrometry (RBS) well adapted to discriminate incorporation processes such as: (i) adsorption or co precipitation at the mineral surfaces or, (ii) incorporation into the mineral structure (through diffusion for instance), has been carried out. Moreover, using the fluorescence properties of europium, the results have been compared to those obtained by Time-Resolved Laser Fluorescence Spectroscopy (TRLFS) on calcite powders. For the single crystals, complementary SEM observations of the mineral surfaces at low voltage were also performed. Results showed that Ni accumulates at the calcite surface whereas Eu is also incorporated at a greater depth. Eu seems therefore to be incorporated into two different states in calcite: (i) heterogeneous surface accumulation and (ii) incorporation at depth greater than 160 nm after 1 month of sorption. Ni was found to accumulate at the surface of calcite without incorporation.

Sabau, A.; Pipon, Y.; Toulhoat, N.; Lomenech, C.; Jordan, N.; Moncoffre, N.; Barkleit, A.; Marmier, N.; Brendler, V.; Surblé, S.; Giffaut, E.

2014-08-01

33

A computationally efficient model for simulating time-resolved fluorescence spectroscopy of thick biological tissues  

NASA Astrophysics Data System (ADS)

A computational model based on finite element method is derived to examine how the recorded time-dependent signals are related to the basic optical properties of a slab at both excitation and emission wavelengths. The model is based on a set of two time-dependent photon diffusion equations: -the transport of the pulsed laser source light (1 ps) and -the transport of the induced fluorescent light excited by the source. The coupling between these equations is due to a source term directly proportional to the scattered fluence rate at the same location. To solve this problem, the method proceeds following the Galerkin formulation, added to implicite finite difference scheme (Backward Euler) to integrate the resulting matrix formulation with respect to time. The meshed domain is two dimensional and takes into account the available boundary conditions relative to air-tissue interface (Robin boundary conditions). The computations are first carried out for a slab in which fluorophores are uniformly distributed, and afterwards devoted to the localization in depth of a fluorescent object (like a tumor) embedded within the slab.

L'Huillier, Jean-Pierre; Humeau, Anne

2004-09-01

34

Viscosity heterogeneity inside lipid bilayers of single-component phosphatidylcholine liposomes observed with picosecond time-resolved fluorescence spectroscopy.  

PubMed

A number of biochemical reactions proceed inside biomembranes. Because the rate of a chemical reaction is influenced by chemical properties of the reaction field, it is important to examine the chemical properties inside the biomembranes, or lipid bilayer membranes, for understanding biochemical reactions. In this study, we estimate viscosity inside the lipid bilayers of liposomes with picosecond time-resolved fluorescence spectroscopy. trans-Stilbene is solubilized in the lipid bilayers formed by phosphatidylcholines, DSPC, DOPC, DPPC, DMPC, and DLPC, with 18, 18, 16, 14, and 12 carbon atoms in their alkyl chains, respectively, and egg-PC. Viscosity inside the lipid bilayer is estimated from the photoisomerization rate constant and from the rotational relaxation time of the first excited singlet state of trans-stilbene. The effect of the hydrocarbon chain length and temperature on viscosity is examined. The presence of two solvation environments within the lipid bilayer is indicated from the two independent estimations. One environment is 30 to 290 times more viscous than the other. Even single-component lipid bilayers are likely to have heterogeneous structures. PMID:24967901

Nojima, Yuki; Iwata, Koichi

2014-07-24

35

Role of polyplex intermediate species on gene transfer efficiency: polyethylenimine-DNA complexes and time-resolved fluorescence spectroscopy.  

PubMed

Polyethylenimine (PEI) is a cationic DNA condensing polymer that facilitates gene transfer into the mammalian cells. The highest gene transfer with branched PEI is obtained at high nitrogen/phosphate (N/P) ratios with free PEI present. The small molecular weight PEI alone is not able to mediate DNA transfection. Here, we used recently developed time-resolved fluorescence spectroscopic method to study the mechanism of PEI-DNA complex formation and to investigate how free PEI, mean molecular weight, and branching of PEI affect the complexes. Analysis of fluorescence lifetimes and time-resolved spectra revealed that for both linear and branched high-molecular-weight PEI the complexation takes place in two steps, but the small-molecular-weight branched PEI complexed DNA at a single step. According to the binding constants obtained from time-resolved spectroscopic measurements, the affinity of N/P complexation per nitrogen atom is highest for LPEI and weakest for BPEI, whereas SPEI-DNA complexation showed intermediate values. Thus, the binding constant alone does not give adequate measure for transfection efficiency. On the other hand, the presence of intermediate states during the polyplex formation seems to be favorable for the gene transfection. Free PEI had no impact on the physical state of PEI-DNA complexes, even though it was essential for gene transfection in the cell culture. In conclusion, the molecular size and topology of PEI have direct influence on the DNA complexation but the free PEI does not. Free PEI must facilitate transfection at the cellular level and not via indirect effects on the PEI-DNA complexes. PMID:21291220

Ketola, Tiia-Maaria; Hanzlíková, Martina; Urtti, Arto; Lemmetyinen, Helge; Yliperttula, Marjo; Vuorimaa, Elina

2011-03-01

36

Photosystem II Does Not Possess a Simple Excitation Energy Funnel: Time-Resolved Fluorescence Spectroscopy Meets Theory  

PubMed Central

The experimentally obtained time-resolved fluorescence spectra of photosystem II (PS II) core complexes, purified from a thermophilic cyanobacterium Thermosynechococcus vulcanus, at 5–180 K are compared with simulations. Dynamic localization effects of excitons are treated implicitly by introducing exciton domains of strongly coupled pigments. Exciton relaxations within a domain and exciton transfers between domains are treated on the basis of Redfield theory and generalized Förster theory, respectively. The excitonic couplings between the pigments are calculated by a quantum chemical/electrostatic method (Poisson-TrEsp). Starting with previously published values, a refined set of site energies of the pigments is obtained through optimization cycles of the fits of stationary optical spectra of PS II. Satisfactorily agreement between the experimental and simulated spectra is obtained for the absorption spectrum including its temperature dependence and the linear dichroism spectrum of PS II core complexes (PS II-CC). Furthermore, the refined site energies well reproduce the temperature dependence of the time-resolved fluorescence spectrum of PS II-CC, which is characterized by the emergence of a 695 nm fluorescence peak upon cooling down to 77 K and the decrease of its relative intensity upon further cooling below 77 K. The blue shift of the fluorescence band upon cooling below 77 K is explained by the existence of two red-shifted chlorophyll pools emitting at around 685 and 695 nm. The former pool is assigned to Chl45 or Chl43 in CP43 (Chl numbering according to the nomenclature of Loll et al. Nature2005, 438, 1040) while the latter is assigned to Chl29 in CP47. The 695 nm emitting chlorophyll is suggested to attract excitations from the peripheral light-harvesting complexes and might also be involved in photoprotection. PMID:23537277

2013-01-01

37

Time Resolved Single Molecule Spectroscopy  

NASA Astrophysics Data System (ADS)

A new method based on the calculation of autocorrelation functions for spectra measured at a high acquisition rate is developed to study spectral dynamics of single molecules. The technique allows for spectroscopy with time resolutions down to the luminescence lifetime. The method is used to study spectral diffusion in two-photon excitation spectra of diphenyloctatetraene molecules doped in an n-tetradecane crystal matrix. The diffusion is light induced, and is absent in one-photon excitation spectra. It has a ``steplike'' time behavior, different from gradual diffusion observed in glasses.

Plakhotnik, Taras; Walser, Daniel

1998-05-01

38

Complexation of curium(III) by adenosine 5?-triphosphate (ATP): A time-resolved laser-induced fluorescence spectroscopy (TRLFS) study  

Microsoft Academic Search

The complex formation of curium(III) with adenosine 5?-triphosphate (ATP) was determined by time-resolved laser-induced fluorescence spectroscopy (TRLFS). The interaction between soluble species of curium(III) with ATP was studied at trace Cm(III) concentrations (3×10?7M). The concentrations of ATP were varied between 6.0×10?7 and 1.5×10?4M in the pH range of 1.5–7.0 using 0.154M NaCl as background electrolyte.Three Cm–ATP species, MpHqLr, could be

Henry Moll; Gerhard Geipel; Gert Bernhard

2005-01-01

39

Time-resolved fluorescence decay measurements for flowing particles  

DOEpatents

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.

Deka, C.; Steinkamp, J.A.

1999-06-01

40

Time-resolved fluorescence decay measurements for flowing particles  

DOEpatents

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.

Deka, Chiranjit (Miami, FL); Steinkamp, John A. (Los Alamos, NM)

1999-01-01

41

Modification of energy-transfer processes in the cyanobacterium, Arthrospira platensis, to adapt to light conditions, probed by time-resolved fluorescence spectroscopy.  

PubMed

In cyanobacteria, the interactions among pigment-protein complexes are modified in response to changes in light conditions. In the present study, we analyzed excitation energy transfer from the phycobilisome and photosystem II to photosystem I in the cyanobacterium Arthrospira (Spirulina) platensis. The cells were grown under lights with different spectral profiles and under different light intensities, and the energy-transfer characteristics were evaluated using steady-state absorption, 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. The direct energy transfer from the phycobilisome to photosystem I and energy transfer from photosystem II to photosystem I were modified depending on the light quality, light quantity, and cultivation period. However, the total amount of energy transferred to photosystem I remained constant under the different growth conditions. We discuss the differences in energy-transfer processes under different cultivation and light conditions. PMID:23605291

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

2013-11-01

42

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

PubMed Central

Abstract. 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-?m axial, 65-?m 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. PMID:23117798

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

2012-01-01

43

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

PubMed

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-?m axial, 65-?m 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. PMID:23117798

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; Farwell, D Gregory; Marcu, Laura

2012-11-01

44

APPLICATIONS OF LASERS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Laser microscope for time-resolved fluorescence spectroscopy  

NASA Astrophysics Data System (ADS)

A description is given of a new automated laser fluorescence microscope. The fluorescence is excited by picosecond YAG:Nd laser pulses at a repetition frequency of 5 kHz. The spatial resolution of the microspectrofluorimeter is 1 ?m. The temporal resolution of the system, based on counting single photons, is in the subnanosecond range. A report is given of the application of this microfluorimeter in determination of the spectral and temporal characteristics of hematoporphyrin in a single cell.

Vardanyan, A. G.; Kamalov, Valey F.; Koroteev, Nikolai I.; Lobanov, O. V.

1989-09-01

45

A space-and time-resolved single-photon counting detector for fluorescence microscopy and spectroscopy  

E-print Network

(SPAD) or electron-multiplying camera using model samples (fluorescent beads, quantum dots and live, quantum dot, live cell 1. INTRODUCTION The exquisite sensitivity of light detectors currently used in wide rejection of background sources (Rayleigh or Raman scattering, optics autofluorescence) has recently allowed

Michalet, Xavier

46

Fulvic acid complexation of Eu(III) and Cm(III) at elevated temperatures studied by time-resolved laser fluorescence spectroscopy.  

PubMed

The interaction of Eu(III) and Cm(III) with three different aquatic fulvic acids (FA) was studied as a function of the temperature (T = 20-80 °C) in 0.1 M NaCl solution by time-resolved laser fluorescence spectroscopy. The speciation of both trivalent metal ions was determined by peak deconvolution of the recorded fluorescence spectra. For each studied metal ion-FA system only one complexed species is formed under the given experimental conditions. The stability constants at 20, 40, 60 and 80 °C (log??'(T)) were determined according to the charge neutralization model. The log??' (20 °C) for the different FAs show similar values (log??(20 °C) = 5.60-6.29). The stability constants increase continuously with increasing temperature by approximately 0.3-1.0 orders of magnitude. The reaction enthalpies and entropies are derived from the integrated Van't Hoff equation. The results show that all investigated complexation reactions are endothermic and entropy-driven. PMID:25207846

Fröhlich, Daniel R; Skerencak-Frech, Andrej; Gast, Michael; Panak, Petra J

2014-11-01

47

Time-resolved fluorescence lifetime for cutaneous melanoma detection  

PubMed Central

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

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

2014-01-01

48

TIME-RESOLVED TERAHERTZ TRANSMISSION SPECTROSCOPY OF DIELECTRICS  

E-print Network

Republic. Using the method of time-domain terahertz-transmission spectroscopy we measured the far-infrared Terahertz pulses; far infrared; time-resolved spectroscopy INTRODUCTION The time-domain terahertzTIME-RESOLVED TERAHERTZ TRANSMISSION SPECTROSCOPY OF DIELECTRICS PETR KUZEL AND JAN PETZELT

KuÂ?el, Petr

49

Ultrafast time-resolved vibrational spectroscopies of carotenoids in photosynthesis.  

PubMed

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

Hashimoto, Hideki; Sugisaki, Mitsuru; Yoshizawa, Masayuki

2015-01-01

50

Conformational States of the Rapana thomasiana Hemocyanin and Its Substructures Studied by Dynamic Light Scattering and Time-Resolved Fluorescence Spectroscopy  

PubMed Central

Hemocyanins are dioxygen-transporting proteins freely dissolved in the hemolymph of mollusks and arthropods. Dynamic light scattering and time-resolved fluorescence measurements show that the oxygenated and apo-forms of the Rapana thomasiana hemocyanin, its structural subunits RtH1 and RtH2, and those of the functional unit RtH2e, exist in different conformations. The oxygenated respiratory proteins are less compact and more asymmetric than the respective apo-forms. Different conformational states were also observed for the R. thomasiana hemocyanin in the absence and presence of an allosteric regulator. The results are in agreement with a molecular mechanism for cooperative dioxygen binding in molluscan hemocyanins including transfer of conformational changes from one functional unit to another. PMID:15533921

Georgieva, Dessislava; Schwark, Daniel; Nikolov, Peter; Idakieva, Krassimira; Parvanova, Katja; Dierks, Karsten; Genov, Nicolay; Betzel, Christian

2005-01-01

51

Seventh international conference on time-resolved vibrational spectroscopy  

SciTech Connect

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.

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

1997-04-01

52

Motor Oil Classification Based on Time-Resolved Fluorescence  

PubMed Central

A time-resolved fluorescence (TRF) technique is presented for classifying motor oils. The system is constructed with a third harmonic Nd:YAG laser, a spectrometer, and an intensified charge coupled device (ICCD) camera. Steady-state and time-resolved fluorescence (TRF) measurements are reported for several motor oils. It is found that steady-state fluorescence is insufficient to distinguish the motor oil samples. Then contour diagrams of TRF intensities (CDTRFIs) are acquired to serve as unique fingerprints to identify motor oils by using the distinct TRF of motor oils. CDTRFIs are preferable to steady-state fluorescence spectra for classifying different motor oils, making CDTRFIs a particularly choice for the development of fluorescence-based methods for the discrimination and characterization of motor oils. The two-dimensional fluorescence contour diagrams contain more information, not only the changing shapes of the LIF spectra but also the relative intensity. The results indicate that motor oils can be differentiated based on the new proposed method, which provides reliable methods for analyzing and classifying motor oils. PMID:24988439

Mu, Taotao; Chen, Siying; Zhang, Yinchao; Guo, Pan; Chen, He; Meng, Fandong

2014-01-01

53

Subnanosecond, time-resolved, broadband infrared spectroscopy using synchrotron radiation  

E-print Network

Subnanosecond, time-resolved, broadband infrared spectroscopy using synchrotron radiation R. P. S-probe infrared spectroscopy has been developed at the National Synchrotron Light Source of Brookhaven National­hole recombination dynamics for an HgCdTe semiconductor film in the far- and mid-infrared range is presented. © 2002

Tanner, David B.

54

Time-resolved laser-induced fluorescence system  

NASA Astrophysics Data System (ADS)

Fluorescence methods are being used increasingly in the measurement of species concentrations in gases, liquids and solids. Laser induced fluorescence is spontaneous emission from atoms or molecules that have been excited by laser radiation. Here we present a time resolved fluorescence instrument that consists of a 5 ?J Nitrogen laser (337.1 nm), a sample holder, a quartz optical fiber, a spectrometer, a PMT and a PC that allows the measurement of visible fluorescence spectra (350-750 nm). Time response of the system is approximately 5 ns. The instrument has been used in the measurement of colored bond paper, antifreeze, diesel, cochineal pigment and malignant tissues. The data acquisition was achieved through computer control of a digital oscilloscope (using General Purpose Interface Bus GPIB) and the spectrometer via serial (RS232). The instrument software provides a graphic interface that lets make some data acquisition tasks like finding fluorescence spectra, and fluorescence lifetimes. The software was developed using the Lab-View 6i graphic programming package and can be easily managed in order to add more functions to it.

Bautista, F. J.; De la Rosa, J.; Gallegos, F. J.

2006-02-01

55

Portable optical oxygen sensor based on time-resolved fluorescence.  

PubMed

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 ratio ?0/?100 measures sensitivity of the sensing film, where ?0 and ?100 represent the detected fluorescence lifetimes from the sensing film exposed to 100% nitrogen and 100% oxygen, respectively. 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. PMID:25402987

Chu, Cheng-Shane; Chu, Ssu-Wei

2014-11-10

56

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

Microsoft Academic Search

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

Elena Vetrova; N. Kudryasheva; K. Cheng

2006-01-01

57

Time-resolved terahertz spectroscopy of bulk and nanoscale semiconductors  

Microsoft Academic Search

The nature of charge carrier dynamics and conduction in bulk and nanoscale semiconducting materials is investigated with time-resolved terahertz (THz) spectroscopy (TRTS). This powerful technique uses picosecond (10-12 s) pulses of far-infrared light to map the electrodynamic response of a photoexcited material in the 0.2 - 3 THz (1012 Hz) frequency range on ultrafast time scales. We show how TRTS

David G. Cooke

2007-01-01

58

Combined time-resolved laser fluorescence spectroscopy and extended X-ray absorption fine structure spectroscopy study on the complexation of trivalent actinides with chloride at T = 25-200 °C.  

PubMed

The complexation of trivalent actinides (An(III)) with chloride is studied in the temperature range from 25 to 200 °C by spectroscopic methods. Time-resolved laser fluorescence spectroscopy (TRLFS) is applied to determine the thermodynamic data of Cm(III)-Cl(-) complexes, while extended X-ray absorption fine structure spectroscopy (EXAFS) is used to determine the structural data of the respective Am(III) complexes. The experiments are performed in a custom-built high-temperature cell which is modified for the respective spectroscopic technique. The TRLFS results show that at 25 °C the speciation is dominated mainly by the Cm(3+) aquo ion. Only a minor fraction of the CmCl(2+) complex is present in solution. As the temperature increases, the fraction of this species decreases further. Simultaneously, the fraction of the CmCl2(+) complex increases strongly with the temperature. Also, the CmCl3 complex is formed to a minor extent at T > 160 °C. The conditional stability constant log ?'2 is determined as a function of the temperature and extrapolated to zero ionic strength with the specific ion interaction theory approach. The log ?°2(T) values increase by more than 3 orders of magnitude in the studied temperature range. The temperature dependency of log ?°2 is fitted by the extended van't Hoff equation to determine ?rH°m, ?rS°m, and ?rC°p,m. The EXAFS results support these findings. The results confirm the absence of americium(III) chloride complexes at T = 25 and 90 °C ([Am(III)] = 10(-3) m, [Cl(-)] = 3.0 m), and the spectra are described by 9-10 oxygen atoms at a distance of 2.44-2.48 Å. At T = 200 °C two chloride ligands are present in the inner coordination sphere of Am(III) at a distance of 2.78 Å. PMID:24383499

Skerencak-Frech, Andrej; Fröhlich, Daniel R; Rothe, Jörg; Dardenne, Kathy; Panak, Petra J

2014-01-21

59

Examining Electron-Boson Coupling Using Time-Resolved Spectroscopy  

NASA Astrophysics Data System (ADS)

Nonequilibrium pump-probe time-domain spectroscopies can become an important tool to disentangle degrees of freedom whose coupling leads to broad structures in the frequency domain. Here, using the time-resolved solution of a model photoexcited electron-phonon system, we show that the relaxational dynamics are directly governed by the equilibrium self-energy so that the phonon frequency sets a window for “slow” versus “fast” recovery. The overall temporal structure of this relaxation spectroscopy allows for a reliable and quantitative extraction of the electron-phonon coupling strength without requiring an effective temperature model or making strong assumptions about the underlying bare electronic band dispersion.

Sentef, Michael; Kemper, Alexander F.; Moritz, Brian; Freericks, James K.; Shen, Zhi-Xun; Devereaux, Thomas P.

2013-10-01

60

A sensitive time-resolved fluorescent immunoassay for metallothionein protein.  

PubMed

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

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

2003-01-15

61

Differential Hydration of Tricyanomethanide Observed by Time Resolved Vibrational Spectroscopy  

PubMed Central

The degenerate transition corresponding to asymmetric stretches of the D3h tricyanomethanide anion, C(CN)3-, in aqueous solution was investigated by linear FTIR spectroscopy, femtosecond pump-probe spectroscopy, and 2D IR spectroscopy. Time resolved vibrational spectroscopy shows that water induces vibrational energy transfer between the degenerate asymmetric stretch modes of tricyanomethanide. The frequency-frequency correlation function and the vibrational energy transfer show two significantly different ultrafast time scales. The system is modeled with molecular dynamics simulations and ab-initio calculations. A new model for theoretically describing the vibrational dynamics of a degenerate transition is presented. Microscopic models, where water interacts axially and radially with the ion, are suggested for the transition dipole reorientation mechanism. PMID:22934602

Kuroda, Daniel G.; Singh, Prabhat K.; Hochstrasser, Robin M.

2012-01-01

62

Steady State and Time-Resolved Fluorescence Studies of a Hemagglutinin from Moringa oleifera  

Microsoft Academic Search

The saccharide binding and conformational characterization of a hemagglutinin, a low molecular weight protein from the seeds\\u000a of Moringa oleifera was studied using steady state and time resolved fluorescence. The lectin binds sugars LacNAc (K\\u000a a?=?1380 M?1) and fructose (K\\u000a a?=?975 M?1), as determined by the fluorescence spectroscopy. It has a single tryptophan per monomer which is exposed on the surface\\u000a and

Uma V. Katre; C. G. Suresh; M. Islam Khan; Sushama M. Gaikwad

2008-01-01

63

Application of In-Situ High Energy-Resolution Fluorescence Detection and Time-Resolved X-Ray Spectroscopy: Catalytic Activation of Oxygen over Supported Gold Catalysts  

NASA Astrophysics Data System (ADS)

Life-time-broadening reduction in high-energy-resolution fluorescence detected XAS produced spectra of unprecedented detail. Au L3 edge spectra of a Au/Al2O3 catalyst under various reaction conditions showed the interaction of oxygen with the gold particles on this catalyst. A reaction path on the gold particle in the oxidation of CO was established.

van Bokhoven, Jeroen A.; Tromp, Moniek; Glatzel, Pieter; Safonova, Olga

2007-02-01

64

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)

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.

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

2013-06-01

65

Time resolved spectroscopy of GRB030501 using INTEGRAL  

E-print Network

The Gamma-ray instruments on-board INTEGRAL offer an unique opportunity to perform time resolved analysis on GRBs. The imager IBIS allows accurate positiioning of GRBs and broad band spectral analysis, while SPI provides high resolution spectroscopy. GRB 030501 was discovered by the INTEGRAL Burst Alert System in the ISGRI field of view. Although the burst was fairly weak (fluence F = 3.5 * 10^-6 erg cm^-2 in the 20-200 keV energy band) it was possible to perform time resolved spectroscopy with a resolution of a few seconds. The GRB shows a spectrum in the 20 - 400 keV range which is consistent with a spectral photon index of -1.7. No emission line or spectral break was detectable in the spectrum. Although the flux seems to be correlated with the hardness of the GRB spectrum, there is no clear soft to hard evolution seen over the duration of the burst. The INTEGRAL data have been compared with results from the Ulysses and RHESSI experiments.

V. Beckmann; J. Borkowski; T. J. -L. Courvoisier; D. Goetz; R. Hudec; F. Hroch; N. Lund; S. Mereghetti; S. E. Shaw; C. Wigger

2003-07-03

66

UV extended supercontinuum source for time resolved and steady state spectroscopy for biological and chemical molecules  

NASA Astrophysics Data System (ADS)

The spectrum of the supercontinuum generated by a femtosecond Ti:Sapphire laser beam in photonic crystal fiber (PCF) is increased into the UV using small core diameter PCF with zero dispersion wavelength (ZDW) shorter 600 nm. A flat spectrum is generated that spans from 350 to 1000 nm. The SC was used as an excitation source for fluorescence spectroscopy. Fluorescence spectra can be detected from dye molecules, and native molecules in tissues samples with excitation from wavelengths extracted from ultrafast SC light in the spectral range between 350 to 500 nm using narrow bandpass filters. A Streak Camera was used for time-resolved fluorescence measurements.

Alfano, R. R.; Kartazaev, V.; Zeylikovich, I.; Das, B.; Nolan, D.

2010-02-01

67

Multidimensional Time-Resolved Spectroscopy of Vibrational Coherence in Biopolyenes  

NASA Astrophysics Data System (ADS)

Multidimensional femtosecond time-resolved vibrational coherence spectroscopy allows one to investigate the evolution of vibrational coherence in electronic excited states. Methods such as pump-degenerate four-wave mixing and pump-impulsive vibrational spectroscopy combine an initial ultrashort laser pulse with a nonlinear probing sequence to reinduce vibrational coherence exclusively in the excited states. By carefully exploiting specific electronic resonances, one can detect vibrational coherence from 0 cm-1 to over 2,000 cm-1 and map its evolution. This review focuses on the observation and mapping of high-frequency vibrational coherence for all-trans biological polyenes such as β-carotene, lycopene, retinal, and retinal Schiff base. We discuss the role of molecular symmetry in vibrational coherence activity in the S1 electronic state and the interplay of coupling between electronic states and vibrational coherence.

Buckup, Tiago; Motzkus, Marcus

2014-04-01

68

Thermally activated delayed fluorescence of fluorescein derivative for time-resolved and confocal fluorescence imaging.  

PubMed

Compared with fluorescence imaging utilizing fluorophores whose lifetimes are in the order of nanoseconds, time-resolved fluorescence microscopy has more advantages in monitoring target fluorescence. In this work, compound DCF-MPYM, which is based on a fluorescein derivative, showed long-lived luminescence (22.11 ?s in deaerated ethanol) and was used in time-resolved fluorescence imaging in living cells. Both nanosecond time-resolved transient difference absorption spectra and time-correlated single-photon counting (TCSPC) were employed to explain the long lifetime of the compound, which is rare in pure organic fluorophores without rare earth metals and heavy atoms. A mechanism of thermally activated delayed fluorescence (TADF) that considers the long wavelength fluorescence, large Stokes shift, and long-lived triplet state of DCF-MPYM was proposed. The energy gap (?EST) of DCF-MPYM between the singlet and triplet state was determined to be 28.36 meV by the decay rate of DF as a function of temperature. The ?E(ST) was small enough to allow efficient intersystem crossing (ISC) and reverse ISC, leading to efficient TADF at room temperature. The straightforward synthesis of DCF-MPYM and wide availability of its starting materials contribute to the excellent potential of the compound to replace luminescent lanthanide complexes in future time-resolved imaging technologies. PMID:24936960

Xiong, Xiaoqing; Song, Fengling; Wang, Jingyun; Zhang, Yukang; Xue, Yingying; Sun, Liangliang; Jiang, Na; Gao, Pan; Tian, Lu; Peng, Xiaojun

2014-07-01

69

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

E-print Network

Theory of time-resolved Raman scattering and fluorescence emission from semiconductor quantum dots description of time-resolved Raman scattering and fluorescence emission of a coupled phonon-quantum dot system spectra of an InGaAs/GaAs-quantum dot are calculated for stationary and pulsed optical excitation

Nabben, Reinhard

70

Shock wave induced decomposition of RDX: time-resolved spectroscopy.  

PubMed

Time-resolved optical spectroscopy was used to examine chemical decomposition of RDX crystals shocked along the [111] orientation to peak stresses between 7 and 20 GPa. Shock-induced emission, produced by decomposition intermediates, was observed over a broad spectral range from 350 to 850 nm. A threshold in the emission response of RDX was found at about 10 GPa peak stress. Below this threshold, the emission spectrum remained unchanged during shock compression. Above 10 GPa, the emission spectrum changed with a long wavelength component dominating the spectrum. The long wavelength emission is attributed to the formation of NO2 radicals. Above the 10 GPa threshold, the spectrally integrated intensity increased significantly, suggesting the acceleration of chemical decomposition. This acceleration is attributed to bimolecular reactions between unreacted RDX and free radicals. These results provide a significant experimental foundation for further development of a decomposition mechanism for shocked RDX (following paper in this issue). PMID:18642891

Patterson, James E; Dreger, Zbigniew A; Miao, Maosheng; Gupta, Yogendra M

2008-08-14

71

Noninvasive Multimodal Evaluation of Bioengineered Cartilage Constructs Combining Time-Resolved Fluorescence and Ultrasound Imaging  

PubMed Central

A multimodal diagnostic system that integrates time-resolved fluorescence spectroscopy, fluorescence lifetime imaging microscopy, and ultrasound backscatter microscopy is evaluated here as a potential tool for assessing changes in engineered tissue composition and microstructure nondestructively and noninvasively. The development of techniques capable of monitoring the quality of engineered tissue, determined by extracellular matrix (ECM) content, before implantation would alleviate the need for destructive assays over multiple time points and advance the widespread development and clinical application of engineered tissues. Using a prototype system combining time-resolved fluorescence spectroscopy, FLIM, and UBM, we measured changes in ECM content occurring during chondrogenic differentiation of equine adipose stem cells on 3D biodegradable matrices. The optical and ultrasound results were validated against those acquired via conventional techniques, including collagen II immunohistochemistry, picrosirius red staining, and measurement of construct stiffness. Current results confirm the ability of this multimodal approach to follow the progression of tissue maturation along the chondrogenic lineage by monitoring ECM production (namely, collagen type II) and by detecting resulting changes in mechanical properties of tissue constructs. Although this study was directed toward monitoring chondrogenic tissue maturation, these data demonstrate the feasibility of this approach for multiple applications toward engineering other tissues, including bone and vascular grafts. PMID:21303258

Fite, Brett Z.; Decaris, Martin; Sun, Yinghua; Sun, Yang; Lam, Adrian; Ho, Clark K.L.

2011-01-01

72

TIME-RESOLVED RAMAN SPECTROSCOPY OF MARS ANALOG MINERALS AND ORGANICS. J. Blacksberg1 Y. Maruyama1  

E-print Network

are present. The primary chal- lenge is that fluorescence often makes conventional 532 nm Raman spectroscopy that builds on the widely used 532 nm Raman tech- nique to provide a means for performing Raman spec- troscopyTIME-RESOLVED RAMAN SPECTROSCOPY OF MARS ANALOG MINERALS AND ORGANICS. J. Blacksberg1 , Y. Maruyama

Rossman. George R.

73

PERSPECTIVE www.rsc.org/pps | Photochemical & Photobiological Sciences Time-resolved methods in biophysics. 3. Fluorescence lifetime correlation  

E-print Network

in biophysics. 3. Fluorescence lifetime correlation spectroscopy Ingo Gregor and J¨org Enderlein* Received 18th decade. Today, FCS has become an important spectroscopic technique that is used in numerous biophysical is derived from the lecture given at the X School of Pure and Applied Biophysics "Time- resolved

Enderlein, Jörg

74

Time-resolved terahertz spectroscopy of bulk and nanoscale semiconductors  

NASA Astrophysics Data System (ADS)

The nature of charge carrier dynamics and conduction in bulk and nanoscale semiconducting materials is investigated with time-resolved terahertz (THz) spectroscopy (TRTS). This powerful technique uses picosecond (10-12 s) pulses of far-infrared light to map the electrodynamic response of a photoexcited material in the 0.2 - 3 THz (1012 Hz) frequency range on ultrafast time scales. We show how TRTS can be used to extract the complex conductivity of a material induced by a femtosecond pump pulse, just picoseconds after excitation. A case study of a standard III-V semiconductor, GaAs, is presented to establish a baseline for TRTS in the Ultrafast Spectroscopy lab at the University of Alberta. Fundamental conduction mechanisms are investigated in dilute nitride and bismide alloys of GaAs, materials of interest for optoelectronic devices. We find that while both nitrogen and bismuth incorporation reduces the fundamental energy bandgap of GaAs, bismuth does so without deteriorating the electrical properties whereas nitrogen severely reduces the electron mobility, limiting its usefulness in future devices. This is the first measurement of electron mobility in GaAsBi, and the results should have a significant impact on the optoelectronic device community. The inherent sensitivity of the THz pulse to the conductivity of a material, sub-picosecond resolution, and noncontact nature make time-resolved terahertz spectroscopy an ideal technique for investigating carrier capture dynamics in semiconductor nanostructures. In this work, we demonstrate how THz pulses can be used to monitor this capture process directly in both quantum dot and quantum wire structures. We further show how the THz polarization can be used to probe a photoconductive anisotropy arising from a linear ordering of both quantum wire and dot-chain systems. Finally, we investigate how the confinement of charge carriers influences the electrodynamics of silicon films by varying the degree of structural disorder. A transition from free to localized behaviour is observed from bulk, crystalline silicon to silicon nanocrystals embedded in glass. The transition from metal-to-insulator can be observed directly as a suppression of the low frequency real conductivity, and can be explained using a model based on carrier backscattering.

Cooke, David G.

75

FRONTIER, MAGNETIC, ELLIPSOMETRIC AND TIME-RESOLVED INFRARED SPECTROSCOPY (FIS + MET)  

E-print Network

spectroscopy, including the very far-infrared and sub-THz. Sample environments include extreme pressuresFRONTIER, MAGNETIC, ELLIPSOMETRIC AND TIME-RESOLVED INFRARED SPECTROSCOPY (FIS + MET) SCIENTIFIC-resolved Frontier Infrared Spectroscopy (FIS) and Magnetic, Ellipsometric and Time-Resolved Infrared Spectroscopy

Ohta, Shigemi

76

Optical Shock Generation Integrated with Time-resolved Spectroscopy  

NASA Astrophysics Data System (ADS)

A detailed understanding of how materials respond to ballistic shock-loading is critical for the design and development of new protective materials. However, nonlinear viscoelastic deformation present in polymers during and immediately following a ballistic impact event is not currently well understood. The dynamic mechanical responses of materials during shock-loading are quite complex, with large amplitude compressions resulting in strain rates of 10^6 s-1 and pressures exceeding several GPa. The mechanical properties of multilayered thin films are measured using impulsive stimulated thermal scattering, a laser-based photoacoustic technique. Since the data can be acquired on a single shot basis, the measurement is compatible with laser shock loading. To this end, a novel pairing of optical shock generation and time-resolved spectroscopy is used, providing an insightful tool for studying the material response to large-amplitude short-time mechanical transients. Laser-induced shock loading has been synchronized with ISTS measurement of acoustic waves so that dynamical evolution of mechanical properties in laser-shocked materials can be examined. The results could complement those from a recent gas gun-ISTS combination that permits measurement of acoustic and mechanical properties during steady-state shock loading. This work is supported by the U.S. Army Research Office.

Saini, G.; Pezeril, T.; Kooi, S. E.; Thomas, E. L.; Nelson, K. A.

2007-06-01

77

Time-resolved fluorescence spectroscopic investigation of cationic polymer/DNA complex formation  

NASA Astrophysics Data System (ADS)

Since DNA is not internalized efficiently by cells, the success of gene therapy depends on the availability of carriers to efficiently deliver genetic material into target cells. Gene delivery vectors can be broadly categorized into viral and non-viral ones. Non-viral gene delivery systems are represented by cationic lipids and polymers rely on the basics of supramolecular chemistry termed "self-assembling": at physiological pH, they are cations and spontaneously form lipoplexes (for lipids) and polyplexes (for polymers) complexing nucleic acids. In this scenario, cationic polymers are commonly used as non-viral vehicles. Their effectiveness is strongly related to key parameters including DNA binding ability and stability in different environments. Time-resolved fluorescence spectroscopy of SYBR Green I (DNA dye) was carried out to characterize cationic polymer/DNA complex (polyplex) formation dispersed in aqueous solution. Both fluorescence amplitude and lifetime proved to be very sensitive to the polymer/DNA ratio (N/P ratio, +/-).

D'Andrea, Cosimo; Bassi, Andrea; Taroni, Paola; Pezzoli, Daniele; Volonterio, Alessandro; Candiani, Gabriele

2011-07-01

78

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

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

79

Time-resolved Optical Spectroscopy of Sco X-1  

NASA Astrophysics Data System (ADS)

We present an analysis of time-resolved, medium resolution (1.5Å) optical (6200--7100Å) spectroscopy of the low mass X-ray binary Sco X-1. The spectra were obtained during 2000 April 07--10 UT on the 1.5-m telescope at Cerro Tololo Inter-American Observatory. A complete orbital cycle of Sco X-1 was sampled in 40 spectra with orbital phase resolution of ?0.03. In addition to a new radial velocity curve of the H? emission line, we present the first Doppler tomograms of Sco X-1. The H? line profile exhibits several interesting features that have not been seen in previously published spectra of Sco X-1: (1) The main emission component is a strong, narrow peak blue-shifted by ? -200 km s-1 (quoted velocities are relative to the rest wavelength of H? ). This component traces an S-wave as a function of orbital phase in the trailed spectrogram. (2) A narrow absorption feature, reminiscent of an inverse P Cygni profile, is located redward of the H? emission peak, at ? +150 km s-1. The depth and velocity of this feature vary considerably during the orbit. (3) A broad (? V?500 km s-1) wing of H? emission is visible redward of the absorption feature, at ? +600 km s-1. These three features provide valuable clues about the structure of the disk and accretion flow in Sco X-1. Cerro Tololo Inter-American Observatory is operated by AURA, Inc. under cooperative agreement with the NSF.

Hoard, D. W.; Wachter, S.

2000-10-01

80

Monitoring tissue metabolism via time-resolved laser fluorescence  

NASA Astrophysics Data System (ADS)

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.

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

1999-05-01

81

Time-resolved fluorescence microscopy for probing mitochondrial metabolites  

NASA Astrophysics Data System (ADS)

A novel set-up for time-gated (nanosecond) detection of fluorescence spectra and images of microscopic samples was recently developed. The apparatus was now used to measure the fluorescence of mitochondrial coenzymes (NADH, flavins) and a marker molecule (rhodamine 123) in endothelial cells from calf aorta. In these cultivated cells the electron transport chain was inhibited at various sites of the inner mitochondrial membrane. It could be shown that the fluorescence intensity of the free coenzyme NADH depended on the site of inhibition. In addition, an increased energy transfer from mitochondrial coenzymes (NADH, flavins) to rhodamine 123 molecules was observed, if the inhibition occurred in complex I (NADH- coenzyme Q reductase) or complex III (coenzyme QH2-cytochrome c reductase) of the respiratory chain. The diagnostic potential of these findings are discussed.

Gschwend, Michael H.; Strauss, Wolfgang S. L.; Schneckenburger, Herbert; Steiner, Rudolf W.

1996-01-01

82

Instrument response standard in time-resolved fluorescence.  

PubMed

The fluorescence of LDS 798 dye in aqueous solution has a very short lifetime of 24 ps, independent of excitation wavelength. The time response of common photon counting detectors depends on the wavelength of the registered photon. In lifetime measurements, the instrument response function (IRF) is usually approximated by the temporal profile of the scattered excitation light. Because lambda(Exc) is typically much shorter than lambda(Em), a systematic error may be present in these measurements. We demonstrate that the fluorescence decay of LDS 798 is a better approximation of IRF, in particular, for avalanche photodiodes used in the near infrared spectral region. PMID:19334909

Luchowski, Rafal; Gryczynski, Zygmunt; Sarkar, Pabak; Borejdo, Julian; Szabelski, Mariusz; Kapusta, Peter; Gryczynski, Ignacy

2009-03-01

83

Instrument response standard in time-resolved fluorescence  

NASA Astrophysics Data System (ADS)

The fluorescence of LDS 798 dye in aqueous solution has a very short lifetime of 24ps, independent of excitation wavelength. The time response of common photon counting detectors depends on the wavelength of the registered photon. In lifetime measurements, the instrument response function (IRF) is usually approximated by the temporal profile of the scattered excitation light. Because ?Exc is typically much shorter than ?Em, a systematic error may be present in these measurements. We demonstrate that the fluorescence decay of LDS 798 is a better approximation of IRF, in particular, for avalanche photodiodes used in the near infrared spectral region.

Luchowski, Rafal; Gryczynski, Zygmunt; Sarkar, Pabak; Borejdo, Julian; Szabelski, Mariusz; Kapusta, Peter; Gryczynski, Ignacy

2009-03-01

84

Ultrafast time-resolved spectroscopy of xanthophylls at low temperature.  

PubMed

Many of the spectroscopic features and photophysical properties of xanthophylls and their role in energy transfer to chlorophyll can be accounted for on the basis of a three-state model. The characteristically strong visible absorption of xanthophylls is associated with a transition from the ground state S0 (1(1)Ag-) to the S2 (1(1)Bu+) excited state. The lowest lying singlet state denoted S1 (2(1)Ag-), is a state into which absorption from the ground state is symmetry forbidden. Ultrafast optical spectroscopic studies and quantum computations have suggested the presence of additional excited singlet states in the vicinity of S1 (2(1)Ag-) and S2 (1(1)Bu+). One of these is denoted S* and has been suggested in previous work to be associated with a twisted molecular conformation of the molecule in the S1 (2(1)Ag-) state. In this work, we present the results of a spectroscopic investigation of three major xanthophylls from higher plants: violaxanthin, lutein, and zeaxanthin. These molecules have systematically increasing extents of pi-electron conjugation from nine to eleven conjugated carbon-carbon double bonds. All-trans isomers of the molecules were purified by high-performance liquid chromatography (HPLC) and studied by steady-state and ultrafast time-resolved optical spectroscopy at 77 K. Analysis of the data using global fitting techniques has revealed the inherent spectral properties and ultrafast dynamics of the excited singlet states of each of the molecules. Five different global fitting models were tested, and it was found that the data are best explained using a kinetic model whereby photoexcitation results in the promotion of the molecule into the S2 (1(1)Bu+) state that subsequently undergoes decay to a vibrationally hot S1 (1(1)Ag-) state and with the exception of violaxanthin also to the S* state. The vibrationally hot S1 (1(1)Ag-) state then cools to a vibrationally relaxed S1 (2(1)Ag-) state in less than a picosecond. It was also found that a portion of the S* population is converted into S1 (2(1)Ag-) during deactivation, but this process and the relative yield of S* was found to depend on temperature, consistent with it being associated with a twisted conformation of the xanthophyll. The results of the global fitting suggest that subpopulations of twisted conformers of xanthophylls already exist in the ground state prior to photoexcitation. PMID:18293955

Cong, Hong; Niedzwiedzki, Dariusz M; Gibson, George N; Frank, Harry A

2008-03-20

85

Time-resolved optical spectroscopy measurements of shocked liquid deuterium  

NASA Astrophysics Data System (ADS)

Time-resolved optical spectroscopy has been used to measure the shock pressure steadiness, emissivity, and temperature of liquid deuterium shocked to 22-90 GPa. The shock was produced using magnetically accelerated flyer plate impact, and spectra were acquired with a suite of four fiber-optic-coupled spectrometers with streak camera detectors. The shock pressure changes by an average of -1.2% over the 10-30 ns cell transit time, determined from the relative changes in the shock front self-emission with time. The shock front reflectivity was measured from 5140Å and 5320Å laser light reflected from the D2 shock. The emissivity inferred from the reflectivity measurements was in reasonably good agreement with quantum molecular dynamics simulation predictions. The spectral radiance wavelength dependence was found to agree well (average normalized ?2=1.6 ) with a Planckian multiplied by the emissivity. The shock front temperature was determined from the emissivity and the wavelength-dependent shock self-emission. Thirty-seven temperature measurements spanning the 22-90 GPa range were accumulated. The large number of temperature measurements enables a comparison of the scatter in the data with expectations for a Gaussian distribution. This facilitates determination of uncertainties that incorporate both apparatus contributions and otherwise unquantified systematic effects that cause self-emission variations from one experiment to another. Agreement between temperatures determined from the absolute spectral radiance and from the relative shape of the spectrum further substantiates the absence of systematic biases. The weighted mean temperature uncertainties were as low as ±3-4% , enabling the discrimination between competing models for the D2 equation of state (EOS). The temperature results agree well with models that predict a maximum compression of ˜4.4 . Softer models that predict approximately sixfold compression are inconsistent with the data to a very high statistical confidence level. Previous analysis [D. Saumon and T. Guillot, Astrophys. J. 609, 1170 (2004)] of Jupiter’s internal structure has shown that the core mass is restricted to be less than approximately three times the mass of the Earth, if EOS models consistent with these temperature measurements are employed.

Bailey, J. E.; Knudson, M. D.; Carlson, A. L.; Dunham, G. S.; Desjarlais, M. P.; Hanson, D. L.; Asay, J. R.

2008-10-01

86

Time-Resolved Spectroscopy of Active Binary Stars  

NASA Technical Reports Server (NTRS)

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.

Brown, Alexander

2000-01-01

87

Analysis of time-resolved fluorescence anisotropy decays.  

PubMed Central

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

Cross, A J; Fleming, G R

1984-01-01

88

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

NASA Astrophysics Data System (ADS)

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.

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

2006-10-01

89

Fluorescence quenching and time-resolved fluorescence studies on Momordica charantia (bitter gourd) seed lectin.  

PubMed

Chemical modification studies implicated tryptophan (Trp) residues in the sugar binding activity of Momordica charantia lectin (MCL) [Mazumdar, T., Gaur, N. & Surolia, A. (1981) Eur. J. Biochem. 113, 463-470]. In the present study, the accessibility and environment of Trp residues in MCL were investigated by intrinsic fluorescence quenching and time-resolved fluorescence. The emission lamda max of native MCL in the absence as well as in the presence of 0.1 M lactose was around 335 nm, which shifted to 365 nm in the presence of 8 M urea, suggesting that the Trp residues which are predominantly buried in the hydrophobic core of the native lectin get exposed to the aqueous environment upon denaturation. At a quencher concentration of 0.5 M, the extent of quenching observed for the native MCL with acrylamide, I- and Cs+ was 46%, 17% and 12%, respectively. In the presence of 0.1 M lactose this quenching was smaller, suggesting that the sugar ligand provides a partial protection to the Trp residues. In time-resolved fluorescence measurements, the decay curves could be fitted well to a biexponential function with the estimated life times 0.92 ns and 4.64 ns for the native protein and 1.15 ns and 5.1 ns in the presence of 0.1 M lactose. All these results are consistent with the involvement of Trp residues in the sugar-binding activity of MCL. PMID:9739456

Padma, P; Komath, S S; Swamy, M J

1998-08-01

90

Fluorophore Conjugated Silver Nanoparticles: A Time-resolved Fluorescence Correlation Spectroscopic Study  

PubMed Central

Fluorescence detection is a central component in biological research. In recent years there has been a growing interest in the interactions of fluorophores with metallic surfaces or particles. A single-stranded oligonucleotide was chemically bound to a single 50 nm diameter silver particle and a Cy5-labeled complementary single-stranded oligonucleotide was hybridized with the particle-bound oligonucleotide. The bound Cy5 molecules on the silver particles were spatially separated from the silver surface by the hybridized DNA duplex chains, which were about 8 nm in length, to reduce the competitive quenching. We use fluorescence lifetime correlation spectroscopy (FLCS) with picosecond time-resolved detection to separate the fluorescence correlation spectroscopy (FCS) contributions from fluorophores and metal-conjugated fluorophores. The single Cy5-labeled 50 nm silver particles displayed a factor of 15-fold increase in emission signal and 5-fold decrease in emission lifetimes in solution relative to the Cy5-DNA in the absence of metal. Lifetime measurements support the near-field interaction mechanism between the fluorophore and silver nanoparticle. In this study, FLCS is being applied to a system where the brightness and the fluorescent lifetime of the emitting species are significantly different. Our measurements suggest that FLCS is a powerful method for investigating the metal-fluorophore interaction at the single molecule level and to separate two different species from a mixture solution emitting at the same wavelength. Additionally, the highly bright Cy5-DNA-Ag molecules offer to be excellent probes in high background biological samples. PMID:19609374

Ray, Krishanu; Zhang, Jian; Lakowicz, Joseph R.

2009-01-01

91

Solving the structure of reaction intermediates by time-resolved synchrotron x-ray absorption spectroscopy  

E-print Network

Solving the structure of reaction intermediates by time-resolved synchrotron x-ray absorption present a robust data analysis method of time-resolved x-ray absorption spectroscopy experiments suitable for chemical speciation and structure determination of reaction intermediates. Chemical speciation is done

Frenkel, Anatoly

92

Time-Resolved Fluorescence Analysis of the Photosystem II Antenna Proteins in Detergent Micelles and Liposomes  

E-print Network

Time-Resolved Fluorescence Analysis of the Photosystem II Antenna Proteins in Detergent Micelles of the light-harvesting complexes (Lhc) of photosystem II (Lhcb) in order to obtain information apparatus of higher plants is composed of two photosystems (PS),1 PSI and PSII, each consisting of a core

93

An alternative fluorescence enhancement solution for use in lanthanide-based time-resolved fluoroimmunoassays.  

PubMed

Time-resolved fluoroimmunoassays that make use of lanthanide chelates as labels require the addition of an enhancement solution to elicit the formation of a fluorescent lanthanide complex. All solutions previously described are based on 2-naphthoyltrifluoroacetone (NTA), a beta-diketone. Currently, this compound is not commercially available. We report here the properties and performance of an enhancement solution prepared with a commercially available beta-diketone, thenoyltrifluoroacetone. Use of this solution in a commercial time-resolved fluoroimmunoassay gave results essentially identical to those obtained with the NTA-based solution, although fluorescence emission was approximately 27% lower. The lower fluorescence yield did not, however, significantly reduce assay sensitivity. We conclude that this solution represents a viable and highly economical alternative to the preparation currently in use, particularly for laboratories wishing to develop their own assays based on lanthanide fluorescence. PMID:3690848

Keelan, J A; France, J T; Barling, P M

1987-12-01

94

Binding of 7-methoxy-4-(aminomethyl)-coumarin to wild-type and W128F mutant cytochrome P450 2D6 studied by time-resolved fluorescence spectroscopy  

PubMed Central

Enzyme structure and dynamics may play a main role in substrate binding and the subsequent steps in the CYP (cytochrome P450) catalytic cycle. In the present study, changes in the structure of human CYP2D6 upon binding of the substrate are studied using steady-state and time-resolved fluorescence methods, focusing not only on the emission of the tryptophan residues, but also on emission of the substrate. As a substrate, MAMC [7-methoxy-4-(aminomethyl)-coumarin] was selected, a compound exhibiting native fluorescence. As well as the wild-type, the W128F (Trp128?Phe) mutant of CYP2D6 was studied. After binding, a variety of energy transfer possibilities exist, and molecular dynamics simulations were performed to calculate distances and relative orientations of donors and acceptors. Energy transfer from Trp128 to haem appeared to be important; its emission was related to the shortest of the three average tryptophan fluorescence lifetimes observed for CYP2D6. MAMC to haem energy transfer was very efficient as well: when bound in the active site, the emission of MAMC was fully quenched. Steady-state anisotropy revealed that besides the MAMC in the active site, another 2.4% of MAMC was bound outside of the active site to wild-type CYP2D6. The tryptophan residues in CYP2D6 appeared to be less accessible for the external quenchers iodide and acrylamide in presence of MAMC, indicating a tightening of the enzyme structure upon substrate binding. However, the changes in the overall enzyme structure were not very large, since the emission characteristics of the enzyme were not very different in the presence of MAMC. PMID:16190863

Stortelder, Aike; Keizers, Peter H. J.; Oostenbrink, Chris; De Graaf, Chris; De Kruijf, Petra; Vermeulen, Nico P. E.; Gooijer, Cees; Commandeur, Jan N. M.; Van Der Zwan, Gert

2005-01-01

95

Time-Resolved Infrared Spectroscopy on the U12IR Beamline at the J.D. LaVeigne  

E-print Network

) was recently completed and commissioned. Its key purposes are for time-resolved and far infrared spectroscopiesTime-Resolved Infrared Spectroscopy on the U12IR Beamline at the NSLS J.D. LaVeigne , G.L. Carr , R for performing time-resolved infrared spectroscopy has been developed at the NSLS, primarily at beamline U12IR

Tanner, David B.

96

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

NASA Astrophysics Data System (ADS)

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.

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

2010-02-01

97

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

Microsoft Academic Search

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

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

2010-01-01

98

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

ERIC Educational Resources Information Center

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…

Gutow, Jonathan H.

2005-01-01

99

Femtosecond time-resolved Raman spectroscopy using stimulated Raman scattering  

Microsoft Academic Search

Femtosecond Raman spectroscopy has been developed to investigate ultrafast photoinduced structural changes of materials. Vibrational modes in the photogenerated transient species are measured by stimulated Raman scattering using a Raman pump pulse with narrow bandwidth and a femtosecond supercontinuum probe pulse. The Raman signal can be measured without slowing the temporal response and broadening the spectrum, because the temporal and

Masayuki Yoshizawa; Makoto Kurosawa

2000-01-01

100

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

PubMed Central

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

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

2014-01-01

101

Comparison of a Time-Resolved Fluorescence Immunoassay and an Enzyme-Linked Immunosorbent Assay for the Analysis of Atrazine  

E-print Network

for the Analysis of Atrazine in Water Gerry J. Reimer,,§ Shirley J. Gee, and Bruce D. Hammock*, CanTest, Ltd of California, Davis, California 95616 Immunoassays for atrazine based on a time-resolved fluorescent label and an enzyme label were optimized and utilized to measure atrazine in water. The time-resolved fluorescent

Hammock, Bruce D.

102

TIME-RESOLVED INFRARED SPECTROSCOPY IN THE U121R BEAMLINE AT THE NSLS  

SciTech Connect

A facility for performing time-resolved infrared spectroscopy has been developed at the NSLS, primarily at beamline U12IR. The pulsed IR light from the synchrotron is used to perform pump-probe spectroscopy. The authors present here a description of the facility and results for the relaxation of photoexcitations in both a semiconductor and superconductor.

CARR,G.L.; LAVEIGNE,J.D.; LOBO,R.P.S.M.; REITZE,D.H.; TANNER,D.B.

1999-07-19

103

Time-Resolved Polarization Imaging By Pump-Probe (Stimulated Emission) Fluorescence Microscopy  

Microsoft Academic Search

We report the application of pump-probe fluorescence microscopy in time-resolved polarization imaging. We derived the equations governing the pump-probe stimulated emission process and characterized the pump and probe laser power levels for signal saturation. Our emphasis is to use this novel methodology to image polarization properties of fluorophores across entire cells. As a feasibility study, we imaged a 15-?m orange

Ch. Buehler; C. Y. Dong; P. T. C. So; E. Gratton

2000-01-01

104

Picosecond time-resolved fluorescence depolarization of p-terphenyl at high pressures  

NASA Astrophysics Data System (ADS)

Picosecond time-resolved fluorescence depolarization was measured at high pressures for p-terphenyl (PTP) in n-octane and 1-butanol. The rotational reorientation time ( ?R) was deduced from these measurements and studied as a function of solvent viscosity. The viscosity dependence of ?R was compared with the results predicted by hydrodynamic models. A faster deviation than predicted from the modified SED slip hydrodynamic model was observed.

Ito, Naoki; Kajimoto, Okitsugu; Hara, Kimihiko

2000-02-01

105

Multicolor Photometry and Time-resolved Spectroscopy of Two sdBV Stars  

NASA Astrophysics Data System (ADS)

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.

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

106

Speciation of uranyl species in nitric acid medium by time-resolved laser-induced fluorescence  

NASA Astrophysics Data System (ADS)

The aim of this work is the development of an on-line analytical procedure for uranyl trace determination in the nuclear fuel reprocessing process using time-resolved laser-induced fluorescence. Because the uranyl fluorescence spectrum is strongly affected by the nitrate concentration, knowledge of composition of the medium is necessary to normalize measurements. This paper reports the assumptions made on the spectral distortion, leading to a spectral deconvolution model. Uranyl complex formation constants are obtained from the spectral deconvolution and validate the method. In this way, spectral distortion allows the determination of the nitrate concentration with good accuracy.

Couston, Laurent; Pouyat, Dominique; Moulin, Christophe; Decambox, Pierre

1995-03-01

107

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

PubMed Central

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

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

2012-01-01

108

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

109

Nanoparticle metrology standards based on the time-resolved fluorescence anisotropy of silica colloids  

NASA Astrophysics Data System (ADS)

We demonstrate nanoparticle size measurement using time-resolved fluorescence anisotropy decay in relation to establishing a nanometrology standard. The rotational correlation time equivalent to the isotropic Brownian rotation of a fluorescent 6-methoxyquinolinium dye attached to amorphous silica nanoparticles was determined in three different LUDOXLUDOX is a registered trademark of DuPont Corporation. colloids from the complex fluorescence anisotropy decay observed. Once competing depolarization and nanoparticle aggregation had been taken into account, good agreement was found of 4.0 ± 0.4 nm, 6.4 ± 0.5 nm and 11.0 ± 1.6 nm corresponding to the manufacturer's reported particle radii of 3.5 nm, 6 nm and 11 nm, for LUDOX SM30, AM30 and AS40 respectively. We describe the measurement science required for acquisition and interpretation of fluorescence anisotropy decay data in order to determine nanoparticle size while highlighting the limitations and useful range of measurement.

Apperson, Kathleen; Karolin, Jan; Martin, Robert W.; Birch, David J. S.

2009-02-01

110

System for time-resolved spectroscopy using a semiconductor picosecond laser  

Microsoft Academic Search

Optical time-resolved spectroscopy using optical fibers opens up new possibilities for research on highly scattering materials. We present a system that measures the time of fligh distribution of light propagating through such materials. The system employs a picosecond semiconductor laser, a photon counter using an avalanche photodiode working in Geiger mode and standard, gradient index profile, multimode fibers. We present

Jerzy Plucinski; Pawel Wierzba; Risto A. Myllylae

2001-01-01

111

THE JOURNAL OF CHEMICAL PHYSICS 139, 124113 (2013) Time-resolved broadband Raman spectroscopies: A unified  

E-print Network

THE JOURNAL OF CHEMICAL PHYSICS 139, 124113 (2013) Time-resolved broadband Raman spectroscopies in molecules can be studied by an electronically off-resonant Raman process induced by a probe pulse of the technique that involve either spontaneous or stimulated Raman detection and different pulse configurations

Mukamel, Shaul

112

Atomic cesium 6h states observed by time-resolved FTIR spectroscopy  

NASA Astrophysics Data System (ADS)

The infrared emission spectra of Cs resulting from the laser ablation of CsI tablets in a vacuum were recorded using time-resolved Fourier-transform spectroscopy in the 1200-1600 cm-1 range with a resolution of 0.017 cm-1. The 6h level of Cs was observed. The probabilities of transitions between the observed levels are calculated.

Civiš, S.; Kubelík, P.; Jelínek, P.; Chernov, V. E.; Knyazev, M. Yu

2011-11-01

113

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

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

114

Time-resolved fluorescence lifetime imaging microscopy using a picosecond pulsed tunable dye laser system  

NASA Astrophysics Data System (ADS)

The design and implementation of a time-resolved fluorescence lifetime imaging microscope (TRFLIM) for the biomedical sciences are described. The measurement of fluorescence lifetimes offers many benefits, among which is that they are independent of local signal intensity and concentration of the fluorophore and they provide visualization of the molecular environment in a single living cell. Unlike single photon counting, which employs a photomultiplier as the detector, TRFLIM uses a nanosecond-gated multichannel plate image intensifier providing a two-dimensional map of the spatial distribution of fluorescent lifetime in the sample under observation. Picosecond laser pulses from a tunable dye laser are delivered to the fluorophore inside living cells on the stage of a fluorescent microscope. Images of the fluorescence emission at various times during the decay of the fluorescence are collected using a high-speed gated image intensifier and the lifetimes are calculated on a pixel-by-pixel basis. Lifetimes measured by TRFLIM are compared with those measured by conventional methods.

Periasamy, Ammasi; Wodnicki, Pawel; Wang, Xue F.; Kwon, Seongwook; Gordon, Gerald W.; Herman, Brian

1996-10-01

115

A self-normalized, full time-resolved method for fluorescence diffuse optical tomography.  

PubMed

A full time-resolved scheme that has been previously applied in diffuse optical tomography is extended to time-domain fluorescence diffuse optical tomography regime, based on a finite-element-finite-time-difference photon diffusion modeling and a Newton-Raphson inversion framework. The merits of using full time-resolved data are twofold: it helps evaluate the intrinsic performance of time-domain mode for improvement of image quality and set up a valuable reference to the assessment of computationally efficient featured-data-based algorithms, and provides a self-normalized implementation to preclude the necessity of the scaling-factor calibration and spectroscopic-feature assessments of the system as well as to overcome the adversity of system instability. We validate the proposed methodology using simulated data, and evaluate its performances of simultaneous recovery of the fluorescent yield and lifetime as well as its superiority to the featured-data one in the fidelity of image reconstruction. PMID:18711549

Gao, Feng; Zhao, Huijuan; Zhang, Limin; Tanikawa, Yukari; Marjono, Andhi; Yamada, Yukio

2008-08-18

116

Development of Time Resolved Fluorescence Resonance Energy Transfer-based Assay for FXR Antagonist Discovery  

PubMed Central

FXR (farnesoid X receptor, NRIH4), a nuclear receptor, plays a major role in the control of cholesterol metabolism. FXR ligands have been investigated in preclinical studies for targeted therapy against metabolic diseases, but have shown limitations. Therefore, there is a need for new agonist or antagonist ligands of FXR, both for potential clinical applications, as well as to further elucidate its biological functions. Here we describe the use of the X-ray crystal structure of FXR complexed with the potent small molecule agonist GW4064 to design and synthesize a novel fluorescent, high-affinity probe (DY246) for time resolved fluorescence resonance energy transfer (TR-FRET) assays. We then used the TR-FRET assay for high throughput screening of a library of over 5,000 bioactive compounds. From this library, we identified 13 compounds that act as putative FXR transcriptional antagonists. PMID:23688559

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

2013-01-01

117

Simultaneous reference and differential waveform acquisition in time-resolved terahertz spectroscopy.  

PubMed

We present a new method for data acquisition in time-resolved terahertz spectroscopy experiments. Our approach is based on simultaneous collection of reference and differential THz scans. Both the optical THz generation beam and the pump beam are modulated at two different frequencies that are not harmonic with respect to each other. Our method allows not only twice as fast data acquisition but also minimization of noise connected to slowly varying laser power fluctuations and timing instabilities. Our use of the nonlinear crystal N-benzyl-2-methyl-4-nitroaniline (BNA) enables time-resolved THz spectroscopy to beyond 5 THz, thereby highlighting that the presented method is especially valuable at higher frequencies where phase errors in the data acquisition become increasingly important. PMID:19997441

Iwaszczuk, Krzysztof; Cooke, David G; Fujiwara, Masazumi; Hashimoto, Hideki; Jepsen, Peter Uhd

2009-11-23

118

Fluorescence Spectroscopy  

NSDL National Science Digital Library

This resource, part of the Spectroscopy Lab Suite, simulates optical transitions in a Fluorescent light. In this illustration, the transitions between bands in the phosphor coating of the light are shown. The phosphor is excited by discharge in a mercury gas. The energy levels and transitions in the phosphor material can be changed.

Zollman, Dean

2010-05-21

119

A Global Fit Approach to Time-Resolved Gamma-Ray Spectroscopy  

Microsoft Academic Search

We propose a general method for time resolved gamma-ray spectroscopy of astrophysical transients -- the Global Fit Analysis (GFA). Instead of parameterizing individual spectra and analyzing spectral evolution of a transient in terms of numerous individual spectral fit parameters we define a spectral evolution model with a set of constant global parameters and just a few (N=1-2) time-dependent variables. In

A. Chernenko

2002-01-01

120

Near-infrared time-resolved spectroscopy system for tissue oxygenation monitor  

NASA Astrophysics Data System (ADS)

We have developed a three-wavelength (759,797, and 833 nm) time-resolved spectroscopy (TRS) system as a tissue oxygenation monitor employing a time-correlated single photon counting method. This system achieved a high data acquisition rate and system miniaturization maintaining a high sensitivity and time resolution. Our system succeeded in accurately measuring concentrations of oxy-(HbO2) and deoxyhemoglobin (Hb) by means of TRS data observation through studies using a phantom model and living tissue.

Oda, Motoki; Yamashita, Yutaka; Nakano, Tetsuhisa; Suzuki, Akihiro; Shimizu, Keiji; Hirano, Isuke; Shimomura, Fumihiko; Ohmae, Etsuko; Suzuki, Toshihiko; Tsuchiya, Yutaka

2000-11-01

121

Photoinduced Phase Transitions by Time-Resolved Far-Infrared Spectroscopy in V2O3  

Microsoft Academic Search

Using time-resolved far-infrared spectroscopy, we observe multiple routes for photoinduced phase transitions in V2O3. This includes (i) a photothermal antiferromagnetic to paramagnetic transition and (ii) an incipient strain-generated paramagnetic metal to paramagnetic insulator transition, which manifests as coherent oscillations in the far-infrared conductivity. The ˜100ps conductivity oscillation results from coherent acoustic phonon modulation of the bandwidth W. Our results indicate

M. K. Liu; B. Pardo; J. Zhang; M. M. Qazilbash; Sun Jin Yun; Z. Fei; Jun-Hwan Shin; Hyun-Tak Kim; D. N. Basov; R. D. Averitt

2011-01-01

122

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

Microsoft Academic Search

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 (â200 ps) is

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

2000-01-01

123

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

Microsoft Academic Search

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 \\\\(~200 ps\\\\) is

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

2000-01-01

124

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

PubMed Central

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

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

1991-01-01

125

Binding and relaxation behavior of Coumarin-153 in lecithin-taurocholate mixed micelles: A time resolved fluorescence spectroscopic study  

NASA Astrophysics Data System (ADS)

The microenvironment of the bile salt-lecithin mixed aggregates has been investigated using steady state and picosecond time resolved fluorescence spectroscopy. The steady state spectra show that the polarity of the bile salt is higher compared to lecithin vesicles or the mixed aggregates. We have observed slow solvent relaxation in bile salt micelles and lecithin vesicles. The solvation time is gradually slowed down due to gradual addition of the bile salt in lecithin vesicles. Addition of bile salt leads to the tighter head group packing in lecithin. Thus, mobility of the water molecules becomes slower and consequently the solvation time is also retarded. We have observed bimodal slow rotational relaxation time in all these systems.

Chakrabarty, Debdeep; Chakraborty, Anjan; Seth, Debabrata; Hazra, Partha; Sarkar, Nilmoni

2005-09-01

126

Conformational changes induced in the Tet repressor protein TetR(B) upon operator or anhydrotetracycline binding as revealed by time-resolved fluorescence spectroscopy on single tryptophan mutants.  

PubMed

We have analyzed the tryptophan (trp) fluorescence-decay kinetics of single trp mutants of the Tet repressor protein in the free, the tet operator and anhydrotetracycline (atc)-bound states. The position of the single trp varies between residues 164 and 171, in close proximity to one entrance of the tetracycline-binding pocket. A good fit of the trp fluorescence decay needed generally three exponentials. The decay times vary with detection wavelength, the extent of this variation being correlated to the variation of the emission maximum. Quenching experiments with neutral (acrylamide), cationic (N-methylpyridinium chloride) and anionic quencher (KI) support the interpretation of the three fluorescence components within a conformer model. Operator and atc binding change the ratio of the relative amplitudes of the medium- and long-lived component, thus pointing to structural changes as indicated also by the changes in decay time. Since the fluorescence decay is different between the free, atc- and operator-bound states we conclude that the protein structure is different in each of these three states. The fluorescence quenching constants reflect not only the variation in solvent exposure with position, but also the fact that the net surface charge in this region is negative, because the quenching constants by the cationic quencher are up to 10-fold higher. The atc fluorescence appears to decay monoexponentially with about the same decay time for all mutants, except W170, in which the trp residue sterically interferes with atc. PMID:10911727

Kunz, M; Kintrup, M; Hillen, W; Schneider, S

2000-07-01

127

Serological Responses to Experimental Norwalk Virus Infection Measured Using a Quantitative Duplex Time-Resolved Fluorescence Immunoassay ?  

PubMed Central

A quantitative duplex time-resolved fluorescence assay, dissociation-enhanced lanthanide fluorescent immunoassay (DELFIA), was developed to measure Norwalk virus (NV)-specific IgA and IgG antibodies simultaneously. The duplex assay showed superior performance by detecting seroconversion following experimental NV infection at an earlier time point than a reference total immunoglobulin enzyme-linked immunosorbent assay (ELISA). PMID:21593238

Kavanagh, Owen; Estes, Mary K.; Reeck, Amanda; Raju, Ravikiran M.; Opekun, Antone R.; Gilger, Mark A.; Graham, David Y.; Atmar, Robert L.

2011-01-01

128

Serological responses to experimental Norwalk virus infection measured using a quantitative duplex time-resolved fluorescence immunoassay.  

PubMed

A quantitative duplex time-resolved fluorescence assay, dissociation-enhanced lanthanide fluorescent immunoassay (DELFIA), was developed to measure Norwalk virus (NV)-specific IgA and IgG antibodies simultaneously. The duplex assay showed superior performance by detecting seroconversion following experimental NV infection at an earlier time point than a reference total immunoglobulin enzyme-linked immunosorbent assay (ELISA). PMID:21593238

Kavanagh, Owen; Estes, Mary K; Reeck, Amanda; Raju, Ravikiran M; Opekun, Antone R; Gilger, Mark A; Graham, David Y; Atmar, Robert L

2011-07-01

129

Time-resolved fluorescence polarization anisotropy and optical imaging of Cybesin in cancerous and normal prostate tissues  

E-print Network

Time-resolved fluorescence polarization anisotropy and optical imaging of Cybesin in cancerous. The fluorescence polarization difference imaging technique based on the polarization preservation of Cybesin polarization difference imaging 1. Introduction Prostate cancer has a high incidence and mortality rate in men

Larson-Prior, Linda

130

Time-resolved optical emission spectroscopy on three-dimensionally integrated micro-solution plasma  

NASA Astrophysics Data System (ADS)

Time-averaged and time-resolved optical emission spectroscopy (OES) has been performed on three-dimensionally integrated micro-solution plasma (3D IMSP). In comparison with that of a conventional solution plasma generated in pure water vapor bubbles, the OES spectrum of our 3D IMSP, which is generated in Ar gas bubbles surrounded with water, shows more pronounced optical emission of OH radicals than of H and O radicals. In addition, time-resolved OES shows that the optical emission of OH radicals is sustained even after the emission of H and Ar almost disappears. The mechanisms of these phenomena are discussed by considering the dissociative recombination of H2O+ and/or H3O+ with low-temperature electrons.

Shirafuji, Tatsuru; Ogura, Yuhei; Himeno, Yuta

2014-01-01

131

Noninvasive assessment of breast cancer risk using time-resolved diffuse optical spectroscopy  

NASA Astrophysics Data System (ADS)

Breast density is a recognized strong and independent risk factor for breast cancer. We propose the use of time-resolved transmittance spectroscopy to estimate breast tissue density and potentially provide even more direct information on breast cancer risk. Time-resolved optical mammography at seven wavelengths (635 to 1060 nm) is performed on 49 subjects. Average information on breast tissue of each subject is obtained on oxy- and deoxyhemoglobin, water, lipids, and collagen content, as well as scattering amplitude and power. All parameters, except for blood volume and oxygenation, correlate with mammographic breast density, even if not to the same extent. A synthetic optical index proves to be quite effective in separating different breast density categories. Finally, the estimate of collagen content as a more direct means for the assessment of breast cancer risk is discussed.

Taroni, Paola; Pifferi, Antonio; Quarto, Giovanna; Spinelli, Lorenzo; Torricelli, Alessandro; Abbate, Francesca; Villa, Anna; Balestreri, Nicola; Menna, Simona; Cassano, Enrico; Cubeddu, Rinaldo

2010-11-01

132

Applications of Phasors to In Vitro Time-Resolved Fluorescence Measurements  

PubMed Central

The phasor method of treating fluorescence lifetime data provides a facile and convenient approach to characterize lifetime heterogeneity and to detect the presence of excited state reactions, such as solvent relaxation and Förster Resonance Energy Transfer. The method utilizes a plot of M sin(?) versus M cos(?), where M is the modulation ratio and ? is the phase angle taken from frequency domain fluorometry. A principle advantage of the phasor method is that it provides a model-less approach to time-resolved data, amenable to visual inspection. Although the phasor approach has been recently applied to Fluorescence Lifetime Imaging Microscopy it has not been extensively utilized for cuvette studies. In the present study we explore the applications of the method to in vitro samples. The phasors of binary and ternary mixtures of fluorescent dyes demonstrates the utility of the method for investigating complex mixtures. Data from excited state reactions, such as dipolar relaxation in membrane and protein systems and also energy transfer from the tryptophan residue to the chromophore in EGFP, are also presented. PMID:21078290

Štefl, Martin; James, Nicholas G.; Ross, Justin A.; Jameson, David M.

2010-01-01

133

A multi-analytical investigation of semi-conductor pigments with time-resolved spectroscopy and imaging  

NASA Astrophysics Data System (ADS)

We present the non-invasive study of historical and modern Zn- and Cd-based pigments with time-resolved fluorescence spectroscopy, fluorescence multispectral imaging and fluorescence lifetime imaging (FLIM). Zinc oxide and Zinc sulphide are semiconductors which have been used as white pigments in paintings, and the luminescence of these pigments from trapped states is strongly dependent on the presence of impurities and crystal defects. Cadmium sulphoselenide pigments vary in hue from yellow to deep red based on their composition, and are another class of semiconductor pigments which emit both in the visible and the near infrared. The Fluorescence lifetime of historical and modern pigments has been measured using both an Optical Multichannel Analyser (OMA) coupled with a Nd:YAG nslaser, and a streak camera coupled with a ps-laser for spectrally-resolved fluorescence lifetime measurements. For Znbased pigments we have also employed Fluorescence Lifetime Imaging (FLIM) for the measurement of luminescence. A case study of FLIM applied to the analysis of the painting by Vincent Van Gogh on paper - "Les Bretonnes et le pardon de Pont-Aven" (1888) is presented. Through the integration of complementary, portable and non-invasive spectroscopic techniques, new insights into the optical properties of Zn- and Cd-based pigments have been gained which will inform future analysis of late 19th] and early 20th C. paintings.

Nevin, A.; Cesaratto, A.; D'Andrea, C.; Valentini, Gianluca; Comelli, D.

2013-05-01

134

Tryptophan dynamics of the FK506 binding protein: time-resolved fluorescence and simulations.  

PubMed Central

The FK506-binding protein (FKBP12) is important in the immunosuppressant action of FK506 and rapamycin. We have investigated Trp side chain dynamics in FKBP12, with and without a bound immunosuppressant, by measuring the Trp time-resolved fluorescence anisotropy decay r(t). The r(t) for W59 in aqueous uncomplexed FKBP12 at 20 degrees C is well described by a single exponential with a recovered initial anisotropy, r(eff)o, of 0.192 and an overall rotational correlation time for the protein, phi p, of 4.7 ns; r(eff)o = 0.214 and phi p = 4.2 ns for the FKBP12/FK506 complex. Using an expression for the order parameter squared, namely S2 = r(eff)o/rTo, where rTo is the vitrified steady-state excitation anisotropy, we recovered an S2 of 0.75 for W59 fluorescence in uncomplexed FKBP12 and S2 approximately equal to 1 in the FKBP12/FK506 complex. Results obtained for the FKBP12/rapamycin complex are similar to those found for the FKBP12/FK506 complex. Minimum perturbation mapping simulations were performed on the free and complexed forms of FKBP12 and the results were generally in agreement with the experimental data. Images FIGURE 5 FIGURE 6 PMID:8785272

Silva, N D; Prendergast, F G

1996-01-01

135

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

SciTech Connect

Steady-state and time-resolved spectroscopies were employed to study the photodissociation of both the neutral (HS-CH{sub 2}-COOH) and doubly deprotonated ({sup -}S-CH{sub 2}-COO{sup -}) 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 S{sub 1} and S{sub 2} 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 {pi}{sub CO}{sup *}(leftarrow)n{sub 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 {alpha}-thiol-substituted acyl radical ({alpha}-TAR, S-CH{sub 2}-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 {alpha}-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.

Attar, Andrew R.; Blumling, Daniel E.; Knappenberger, Kenneth L. Jr. [Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306 (United States)

2011-01-14

136

Time-resolved spectroscopy of plasma resonances in highly excited silicon and germanium  

SciTech Connect

The dynamics of the electron-hole plasma in silicon and germanium samples irradiated by 20 ps. 532 nm laser pulses has been investigated in the near infrared by the time-resolved picosecond optical spectroscopy. The experimental reflectivities and transmission are compared with the predictions of the thermal model for degenerate carrier distributions through the Drude formalism. Above a certain fluence, a significant deviation between measured and calculated values indicates a strong increase of the recombination rate as soon as the plasma resonances become comparable with the band gaps. These new plasmon-aided recombination channels are particularly pronounced in germanium. 15 refs., 8 figs.

Huang, C.Y.; Malvezzi, A.M.; Bloembergen, N.; Kurz, H.

1985-01-01

137

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

SciTech Connect

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.

Materny, Arnulf; Konradi, Jakow; Namboodiri, Vinu; Namboodiri, Mahesh; Scaria, Abraham [Jacobs University Bremen, School of Science and Engineering Campus Ring 1, 28759 Bremen (Germany)

2008-11-14

138

Multi-channel time-resolved system for functional near infrared spectroscopy  

NASA Astrophysics Data System (ADS)

We have designed a compact dual wavelength multi-channel time-resolved system for functional near infrared spectroscopy. The system enables 16 sources and up to 64 collection points, with a minimum acquisition time of 5 ms per channel. Performances of the system have been tested on tissue phantoms in terms of linearity, noise, stability and reproducibility. Preliminary measurements on volunteers have been performed to validate the instrument capability to acquire in vivo maps of the hemodynamic parameters in the muscle during arterial occlusion and in the adult head during a finger tapping experiment.

Contini, Davide; Torricelli, Alessandro; Pifferi, Antonio; Spinelli, Lorenzo; Paglia, Floriano; Cubeddu, Rinaldo

2006-06-01

139

Time-resolved photoacoustic spectroscopy using fiber Bragg grating acoustic transducers  

Microsoft Academic Search

An acoustic transducer based on a fiber Bragg grating (FBG) is presented\\u000a and characterized for use in time-resolved laser-induced photoacoustic\\u000a spectroscopy (PAS) on solid samples. The photoacoustic wave was\\u000a generated by pulsed laser excitation of immobilized carbon black or\\u000a erbium oxide powder, and detected by recording either the transmission\\u000a or reflection spectrum of a clamped fiber Bragg grating (FBG). The

Qingxin Yang; Jack Barnes; Hans-Peter Loock; David Pedersen

2007-01-01

140

Time resolved single molecule spectroscopy of semiconductor quantum dot/conjugated organic hybrid nanostructures  

NASA Astrophysics Data System (ADS)

Single molecule studies on CdSe quantum dots functionalized with oligo-phenylene vinylene ligands (CdSe-OPV) provide evidence of strong electronic communication that facilitate charge and energy transport between the OPV ligands and the CdSe quantum dot core. This electronic interaction greatly modify, the photoluminescence properties of both bulk and single CdSe-OPV nanostructure thin film samples. Size-correlated wide-field fluorescence imaging show that blinking suppression in single CdSe-OPV is linked to the degree of OPV coverage (inferred from AFM height scans) on the quantum dot surface. The effect of the complex electronic environment presented by photoexcited OPV ligands on the excited state property of CdSe-OPV is measured with single photon counting and photon-pair correlation spectroscopy techniques. Time-tagged-time-resolved (TTTR) single photon counting measurements from individual CdSe-OPV nanostructures, show excited state lifetimes an order of magnitude shorter relative to conventional ZnS/CdSe quantum dots. Second-order intensity correlation measurements g(2)(tau) from individual CdSe-OPV nanostructures point to a weak multi-excitonic character with a strong wavelength dependent modulation depth. By tuning in and out of the absorption of the OPV ligands we observe changes in modulation depth from g(2) (0) ? 0.2 to 0.05 under 405 and 514 nm excitation respectively. Defocused images and polarization anisotropy measurements also reveal a well-defined linear dipole emission pattern in single CdSe-OPV nanostructures. These results provide new insights into to the mechanism behind the electronic interactions in composite quantum dot/conjugated organic composite systems at the single molecule level. The observed intensity flickering , blinking suppression and associated lifetime/count rate and antibunching behaviour is well explained by a Stark interaction model. Charge transfer from photo-excitation of the OPV ligands to the surface of the CdSe quantum dot core, mixes electron/holes states and lifts the degeneracy in the band edge bright exciton state, which induces a well define linear dipole behaviour in single CdSe-OPV nanostructures. The shift in the electron energies also affects Auger assisted hole trapping rates, suppress access to dark states and reduce the excited state lifetime.

Odoi, Michael Yemoh

141

Time-resolved spectroscopy of the Mercury 6 3P1 state  

NASA Technical Reports Server (NTRS)

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.

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

1981-01-01

142

Four-way modeling of 4.2 K time-resolved excitation emission fluorescence data for the quantitation of polycyclic aromatic hydrocarbons in soil samples.  

PubMed

A screening method for the soil analysis of 15 Environmental Protection Agency-polycyclic aromatic hydrocarbons (EPA-PAHs) is reported. The new method is based on the collection of 4.2 K fluorescence time-resolved excitation-emission cubes (TREECs) via laser-excited time-resolved Shpol'skii spectroscopy. 4.2 K fluorescence TREECs result from the superposition of fluorescence time-resolved excitation emission matrices recorded at different time windows from the laser excitation pulse. Potential interference from unknown sample concomitants is handled by processing the four-way 4.2 K fluorescence TREEC data arrays with either parallel factor analysis (PARAFAC) or unfolded partial least-squares/residual-trilinearization(U-PLS/RTL). The sensitivity of the two approaches makes possible to determine PAHs at the ng g(-1) to pg g(-1) concentration level with no need for sample pre-concentration. Its selectivity eliminates sample clean-up steps and chromatographic separation. These features reduce PAH loss, analysis time and cost. The method is environmentally friendly as the complete screening of the 15 EPA-PAHs takes only 250 ?L of organic solvent per sample. PMID:23158330

Goicoechea, Hector C; Yu, Shenjiang; Moore, Anthony F T; Campiglia, Andres D

2012-11-15

143

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

PubMed

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

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

2014-01-01

144

Monitoring cellular stress responses using integrated high-frequency impedance spectroscopy and time-resolved ELISA.  

PubMed

We have developed a lab-on-a-chip system for continuous and non-invasive monitoring of microfluidic cell cultures using integrated high-frequency contactless impedance spectroscopy. Electrically insulated microfabricated interdigitated electrode structures were embedded into four individually addressable microchambers to reliably and reproducibly detect cell-substrate interactions, cell viability and metabolic activity. While silicon nitride passivated sensor substrates provided a homogeneous cell culture surface that minimized cell orientation along interdigitated electrode structures, the application of high-frequency AC fields reduced the impact of the 300 nm thick passivation layer on sensor sensitivity. The additional implementation of multivariate data analysis methods such as partial least square (PLS) for high-frequency impedance spectra provided unambiguous information on intracellular pathway activation, up and down-regulation of protein synthesis as well as global cellular stress responses. A comparative cell analysis using connective tissue fibroblasts showed that high-frequency contactless impedance spectroscopy and time-resolved quantification of IL-6 secretion using ELISA provided similar results following stimulation with circulating pro-inflammatory cytokines IL-1? and TNF?. The combination of microfluidics with contactless impedance sensing and time-resolved quantification of stress factor release will provide biologist with a new tool to (a) establish a variety of uniform cell culture surfaces that feature complex biochemistries, micro- and nanopatterns; and (b) to simultaneously characterize cell responses under physiologically relevant conditions using a complementary non-invasive cell analysis method. PMID:25137192

Charwat, Verena; Joksch, Martin; Sticker, Drago; Purtscher, Michaela; Rothbauer, Mario; Ertl, Peter

2014-10-21

145

Realtime correction of probe pulse in subpicosecond time-resolved transient absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Due to its breakthrough the electro-optical time response limitation for picosecond dynamics of processes, many research groups around the world operating in different fields from physics and chemistry to biology, medicine and material science, utilize laser setups capable of providing subpicosecond pulses and femtosecond-level time delay lines. However the signal amount of Femto-picosecond Dynamics is about at an altitude of 1%, but the fluctuation of femtosecond probe pulse at its best can only reach about 5%. Real-time correct the probe pulse is the only effective way to realize subpicosecond time-resolved detection precision of transient absorption spectroscopy. So in this paper, reference pulse was drawn into the measurement equipment through different methods to dispel the fluctuation of probe pulse. Firstly, in the case of Subpicosecond time-resolved transient absorption spectroscopy, probe and reference beams have the same spectral distribution and derived from the same source to measure the variation of transmittance in the excited volume. Secondly probe pulse is spatially and temporally overlapped to the excitation pulse, reference pulse spatially overlapped but temporally anticipated in respect to the excitation pulse. Finally reference pulse passes through the sample in a different position. The detector can be a CCD camera or a double photodiode. The results shown that when reference pulse passes through the sample in a different position and detected by CCD, the correction results can reach to 1%. Which meet the femto-picosecond dynamics precise requirement.

Zhang, Su-jan; Duan, Cun-li; Feng, Xiao-qiang; He, Jun-fang

2011-06-01

146

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

PubMed Central

The prolactin receptor (PRLR) is emerging as a therapeutic target in oncology. Knowledge-based drug design led to the development of a pure PRLR antagonist (Del1-9-G129R-hPRL) that was recently shown to prevent PRL-induced mouse prostate tumorogenesis. In humans, the first gain-of-function mutation of the PRLR (PRLRI146L) was recently identified in breast tumor patients. At the molecular level, the actual mechanism of action of these two novel players in the PRL system remains elusive. In this study, we addressed whether constitutive PRLR activation (PRLRI146L) or PRLR blockade (antagonist) involved alteration of receptor oligomerization and/or of inter-chain distances compared to unstimulated and PRL-stimulated PRLR. Using a combination of various biochemical and spectroscopic approaches (co-IP, blue native electrophoresis, BRET1), we demonstrated that preformed PRLR homodimers are altered neither by PRL- or I146L-induced receptor triggering, nor by antagonist-mediated blockade. These findings were confirmed using a novel time-resolved fluorescence resonance energy transfer (TR-FRET) technology that allows monitoring distance changes between cell surface tagged receptors. This technology revealed that PRLR blockade or activation did not involve detectable distance changes between extracellular domains of receptor chains within the dimer. This study merges with our previous structural investigations suggesting that the mechanism of PRLR activation solely involves intermolecular contact adaptations leading to subtle intramolecular rearrangements. PMID:22649370

Tallet, Estelle; Fernandez, Isabelle; Zhang, Chi; Salsac, Marion; Gregor, Nathalie; Ayoub, Mohammed Akli; Pin, Jean Philippe; Trinquet, Eric; Goffin, Vincent

2011-01-01

147

Poly(?-amino ester)-DNA complexes: time-resolved fluorescence and cellular transfection studies.  

PubMed

A large number of different polymers have been developed and studied for application as DNA carriers for non-viral gene delivery, but the DNA binding properties are not understood. This study describes the efficiency of nanoparticle formation by time-resolved fluorescence measurements for poly(?-amino esters), cationic biodegradable polymers with DNA complexation and transfection capability. From the large library of poly(?-amino esters) ten polymers with different transfection efficacies were chosen for this study. The binding constants for nanoparticle formation were determined and compared to with the same method. Although the DNA binding efficiency of the amine groups are similar for both types of polymers, the overall binding constants are an order of magnitude smaller for poly(?-amino esters) than for 25 kDa polyethylenimines, yet poly(?-amino esters) show comparable DNA transfection efficacy with polyethylenimines. Within this series of polymers the transfection efficacy showed increasing trend in association with relative efficiency of nanoparticle formation. PMID:21699928

Vuorimaa, Elina; Ketola, Tiia-Maaria; Green, Jordan J; Hanzlíková, Martina; Lemmetyinen, Helge; Langer, Robert; Anderson, Daniel G; Urtti, Arto; Yliperttula, Marjo

2011-09-01

148

Poly(?-amino ester) - DNA complexes: time-resolved fluorescence and cellular transfection studies  

PubMed Central

A large number of different polymers have been developed and studied for application as DNA carriers for non-viral gene delivery, but the DNA binding properties are not understood. This study describes the efficiency of nanoparticle formation by time-resolved fluorescence measurements for poly(?-amino esters), cationic biodegradable polymers with DNA complexation and transfection capability. From the large library of poly(?-amino esters) ten polymers with different transfection efficacies were chosen for this study. The binding constants for nanoparticle formation were determined and compared to polyethylene imines with the same method. Although the DNA binding efficiency of the amine groups are similar for both types of polymers, the overall binding constants are an order of magnitude smaller for poly(?-amino esters) than for 25 kDa polyethylenimines, but yet poly(?-amino esters) show comparable DNA transfection efficacy with polyethyleneimines. Within this series of polymers the transfection efficacy showed increasing trend in association with relative efficiency of nanoparticle formation. PMID:21699928

Vuorimaa, Elina; Ketola, Tiia-Maaria; Green, Jordan J.; Hanzlíková, Martina; Lemmetyinen, Helge; Langer, Robert; Anderson, Daniel G.; Urtti, Arto; Yliperttula, Marjo

2011-01-01

149

Rapid and sensitive detection of biological warfare agents using time-resolved fluorescence assays.  

PubMed

We have achieved sensitive, rapid and reproducible detection of three biological threat agents in a variety of biological and environmental matrices using the DELFIA time-resolved fluorometry (TRF) assay system (Perkin-Elmer Life Sciences, Akron, OH). Existing ELISA assays for the detection of Francisella tularensis, Clostridium botulinum A/B neurotoxin (BotNT A/B), and Staphylococcus aureus enterotoxin B (SEB) were converted to TRF assays. They use 100 microl of positive control or unknown per test well and require just over 2 h to run. Fluorescent signal read time is a fraction of a second per well. The assay format consists of a capture ELISA utilizing a biotinylated capture antibody, prebound to a streptavidin-coated 96-well plate and a lanthanide (Europium, Eu3+)-labeled detector antibody. The bound Eu-labeled detector antibody produces a fluorescent signal upon the addition of an enhancement solution. The signal results from the dissociation of the Europium from the antibody, creating a micelle, thus amplifying the signal nearly one million-fold. Sensitivities achieved by these assays were between 4 and 20 pg/ml in buffer. Additionally, we have tested this system in different matrices such as serum, urine, dirt, and sewage. Concentration curves generated from standard solutions produced a wide linear range making serial dilutions of unknown samples unnecessary. DELFIA TRF assays are significantly better in terms of sensitivity, linear range, and run time than standard capture ELISAs and should facilitate early detection of potential biological warfare agents in clinical and environmental samples. PMID:12009202

Peruski, Anne Harwood; Johnson, Linwood Hill; Peruski, Leonard Francis

2002-05-01

150

X-ray crystal structure and time-resolved spectroscopy of the blue carotenoid violerythrin.  

PubMed

Violerythrin, a blue-colored carotenoid, has been investigated by X-ray crystallography and steady-state and ultrafast time-resolved absorption spectroscopy. The X-ray crystal structure of violerythrin shows that the molecule is nearly planar with the terminal rings positioned in the s-trans conformation. The steady-state and time-resolved spectroscopic data of violerythrin do not differ significantly from those of other carbonyl carotenoids with long (N > 10) pi-electron conjugated chains. This indicates that while the four carbonyl groups in violerythrin are critical for generating the bathochromic shift that leads to the blue color of the molecule, no dramatic changes attributable to a charge-transfer state known to affect the excited-state properties of carotenoids with short polyene chains occur. This may be due to the symmetric distribution of the carbonyl groups, which would preclude such an effect. The structural requirements for a blue, neutral, carotenoid are a planar, symmetric, cross-conjugated chromophore, containing at least 30 pi-electrons, a central polyene chain with 9 or 10 conjugated carbon-carbon double bonds connected at each end by an s-trans or trans bond to two identical, cyclic end groups, each possessing a conjugated keto group further cross-conjugated to another keto group, or a double bond in a quinoid type structure. PMID:20545330

Polívka, Tomás; Frank, Harry A; Enriquez, Miriam M; Niedzwiedzki, Dariusz M; Liaaen-Jensen, Synnøve; Hemming, Joanna; Helliwell, John R; Helliwell, Madeleine

2010-07-01

151

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

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

152

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

PubMed

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

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

2012-04-01

153

Space and time-resolved laser-induced breakdown spectroscopy using charge-coupled device detection.  

PubMed

Space and time-resolved studies of laser induced plasmas in air at atmospheric pressure are presented. Photovoltaic solar cells have been used as samples. The second harmonic (532 nm) of a Nd : YAG laser at an irradiance of 18 x 10(12) W/cm(2) has been used. The precise focus of the beam allows a microanalysis at a 0.02 mm(2) surface area working in single-shot mode. The use of an intensified charge-coupled device (CCD) detector has allowed time-resolved studies in both imaging or spectroscopy modes. The two-dimensional capability of the CCD has enabled the study of atomic and ionic species distribution along the plume. Most data have been recorded using single-laser shot experiments. Spectral lines have been assigned to transitions in atomic components of the material under investigation in the neutral or ionic states of the corresponding atoms. Effects of delay in improving spectral resolution and some examples of spectral characterization of species as a function of its decay are shown. PMID:15045450

Vadillo, J M; Milán, M; Laserna, J J

1996-04-01

154

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

NASA Astrophysics Data System (ADS)

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.

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

1995-04-01

155

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

PubMed Central

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 ?mol /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 ?mol/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 ?-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

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

156

Time-resolved study of hot dense germanium by L -shell absorption spectroscopy  

SciTech Connect

We have used time-resolved 2{ital p}-3{ital d} absorption spectroscopy to probe the ionization degree of a germanium plasma heated by the soft x rays emitted from the rear side of laser-irradiated gold targets. We have determined the average ionization degree and the distribution of ion stages as a function of time during the expanding, cooling phase of the plasma. They have been compared with collisional-radiative distributions based on hydrodynamic simulations of the plasma parameters. Results show a slow decrease of the ionization degree from {l angle}{ital Z}{r angle}=11.5 to 10.0 during a 3-ns period after gold heating. Comparison with theoretical spectra show matter densities around 0.01 g/cm{sup 3} and temperatures of about 50 eV.

Bruneau, J.; Decoster, A.; Desenne, D.; Dumont, H.; Le Breton, J.; Boivineau, M.; Perrine, J.; Bayle, S.; Louis-Jacquet, M. (Centre d'Etudes de Limeil-Valenton, 94195 Villeneuve Saint Georges, France (FR) ); Geindre, J.; Chenais-Popovics, C.; Gauthier, J. (Laboratoire de Physique des Milieux Ionises, Ecole Polytechnique, 91128 Palaiseau, (France))

1991-07-15

157

Label-Free Toxin Detection by Means of Time-Resolved Electrochemical Impedance Spectroscopy  

PubMed Central

The real-time detection of trace concentrations of biological toxins requires significant improvement of the detection methods from those reported in the literature. To develop a highly sensitive and selective detection device it is necessary to determine the optimal measuring conditions for the electrochemical sensor in three domains: time, frequency and polarization potential. In this work we utilized a time-resolved electrochemical impedance spectroscopy for the detection of trace concentrations of Staphylococcus enterotoxin B (SEB). An anti-SEB antibody has been attached to the nano-porous aluminum surface using 3-aminopropyltriethoxysilane/glutaraldehyde coupling system. This immobilization method allows fabrication of a highly reproducible and stable sensing device. Using developed immobilization procedure and optimized detection regime, it is possible to determine the presence of SEB at the levels as low as 10 pg/mL in 15 minutes. PMID:22315560

Chai, Changhoon; Takhistov, Paul

2010-01-01

158

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

SciTech Connect

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.

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

2004-01-21

159

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

NASA Astrophysics Data System (ADS)

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 ?s 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.

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

2014-11-01

160

Time-Resolved Spectroscopy and Near Infrared Imaging for Prostate Cancer Detection: Receptor-targeted and Native Biomarker  

NASA Astrophysics Data System (ADS)

Optical spectroscopy and imaging using near-infrared (NIR) light provides powerful tools for non-invasive detection of cancer in tissue. Optical techniques are capable of quantitative reconstructions maps of tissue absorption and scattering properties, thus can map in vivo the differences in the content of certain marker chromophores and/or fluorophores in normal and cancerous tissues (for example: water, tryptophan, collagen and NADH contents). Potential clinical applications of optical spectroscopy and imaging include functional tumor detection and photothermal therapeutics. Optical spectroscopy and imaging apply contrasts from intrinsic tissue chromophores such as water, collagen and NADH, and extrinsic optical contrast agents such as Indocyanine Green (ICG) to distinguish disease tissue from the normal one. Fluorescence spectroscopy and imaging also gives high sensitivity and specificity for biomedical diagnosis. Recent developments on specific-targeting fluorophores such as small receptor-targeted dye-peptide conjugate contrast agent offer high contrast between normal and cancerous tissues hence provide promising future for early tumour detection. This thesis focus on a study to distinguish the cancerous prostate tissue from the normal prostate tissues with enhancement of specific receptor-targeted prostate cancer contrast agents using optical spectroscopy and imaging techniques. The scattering and absorption coefficients, and anisotropy factor of cancerous and normal prostate tissues were investigated first as the basis for the biomedical diagnostic and optical imaging. Understanding the receptors over-expressed prostate cancer cells and molecular target mechanism of ligand, two small ICG-derivative dye-peptides, namely Cypate-Bombesin Peptide Analogue Conjugate (Cybesin) and Cypate-Octreotate Peptide Conjugate (Cytate), were applied to study their clinical potential for human prostate cancer detection. In this work, the steady-state and time-resolved fluorescence spectroscopy of Cybesin (Cytate) in solution, and in cancerous and normal prostate tissues were studied. It was found that more Cybesin (Cytate) was uptaken in the cancerous prostate tissue than those in the normal tissue. The preferential uptake of Cybesin (Cytate) in cancerous tissue was used to image and distinguish cancerous areas from the normal tissue. To investigate rotational dynamics and fluorescence polarization anisotropy of the contrast agents in prostate tissues, an analytical model was used to extract the rotational times and polarization anisotropies, which were observed for higher values of Cybesin (Cytate)-stained cancerous prostate tissue in comparison with the normal tissue. These reflect changes of microstructures of cancerous and normal tissues and their different binding affinity with contrast agents. The results indicate that the use of optical spectroscopy and imaging combined with receptor-targeted contrast agents is a valuable tool to study microenvironmental changes of tissue, and detect prostate cancer in early stage.

Pu, Yang

161

TIME RESOLVED FLUORESCENCE RESONANCE ENERGY TRANSFER (TR-FRET) TO ANALYZE THE DISRUPTION OF EGFR/HER2 DIMERS: A NEW METHOD TO EVALUATE  

E-print Network

1 TIME RESOLVED FLUORESCENCE RESONANCE ENERGY TRANSFER (TR-FRET) TO ANALYZE THE DISRUPTION OF EGFR Running title: TR-FRET to quantify HER dimers and evaluate mAb efficiency Address correspondence to: André. Here, we describe a time resolved fluorescence resonance energy transfer (TR- FRET) method to quantify

Paris-Sud XI, Université de

162

Lanthanide labeling of a potent protease activated receptor-2 agonist for time-resolved fluorescence analysis  

PubMed Central

Protease activated receptor-2 (PAR2) is one of four G-protein coupled receptors (GPCRs) that can be activated by exogenous or endogenous proteases, which cleave the extracellular amino-terminus to expose a tethered ligand and subsequent G-protein signaling. Alternatively, PAR2 can be activated by peptide or peptidomimetic ligands derived from the sequence of the natural tethered ligand. Screening of novel ligands that directly bind to PAR2 to agonize or antagonize the receptor has been hindered by the lack of a sensitive, high-throughput, affinity binding assay. In this report we describe the synthesis and use of a modified PAR2 peptidomimetic agonist, 2-furoyl-LIGRLO-(diethylenetriaminepentaacetic acid)-NH2 (2-f-LIGRLO-dtpa), designed for lanthanide-based time resolved fluorescence screening. We first demonstrate that 2-f-LIGRLO-dtpa is a potent and specific PAR2 agonist across a full spectrum of in vitro assays. We then show that 2-f-LIGRLO-dtpa can be utilized in an affinity binding assay to evaluate the ligand-receptor interactions between known high potency peptidomimetic agonists (2-furoyl-LIGRLO-NH2, 2-f-LIGRLO; 2-aminothiazol-4-yl-LIGRL-NH2, 2-at-LIGRL and; 6-aminonicotinyl-LIGRL-NH2, 6-an-LIGRL) and PAR2. A separate N-terminal peptidomimetic modification (3-indoleacetyl-LIGRL-NH2, 3-ia-LIGRL) that does not activate PAR2 signaling was used as a negative control. All three peptidomimetic agonists demonstrated sigmoidal competitive binding curves, with the more potent agonists (2-f-LIGRLO and 2-at-LIGRL) displaying increased competition. In contrast, the control peptide (3-ia-LIGRL) displayed limited competition for PAR2 binding. In summary, we have developed a Europium-containing PAR2 agonist that can be used in a highly sensitive affinity binding assay to screen novel PAR2 ligands in a high-throughput format. This ligand can serve as a critical tool in the screening and development of PAR2 ligands. PMID:22994402

Hoffman, Justin; Flynn, Andrea N.; Tillu, Dipti V.; Zhang, Zhenyu; Patek, Renata; Price, Theodore J.; Vagner, Josef; Boitano, Scott

2012-01-01

163

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

SciTech Connect

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.

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

2008-06-04

164

Advancements in time-resolved x-ray laser induced time-of-flight photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

Time-resolved soft x-ray photoelectron spectroscopy is used to probe the non-steady-state evolution of the valence band electronic structure of laser heated ultra-thin (50 nm) metal foils and bulk semiconductors. Single-shot soft x-ray laser induced time-of-flight photoelectron spectroscopy with picosecond time resolution was used in combination with optical measurements of the disassembly dynamics that have shown the existence of a metastable liquid phase in fs-laser heated metal foils persisting 4-5 ps. This metastable phase is studied using a 527 nm wavelength 400 fs laser pulse containing 0.3 - 2.5 mJ laser energy focused in a large 500 × 700 ?m2 spot to create heated conditions of 0.2 - 1.8 × 1012 W cm-2 intensity. The unique LLNL COMET compact tabletop soft x-ray laser source provided the necessary high photon flux, highly monoenergetic, picosecond pulse duration, and coherence for observing the evolution of changes in the valence band electronic structure of laser heated metals and semiconductors with picosecond time resolution. This work demonstrates the continuing development of a powerful new technique for probing reaction dynamics and changes of local order on surfaces on their fundamental timescales including phenomena such as non-thermal melting, chemical bond formation, intermediate reaction steps, and the existence of transient reaction products.

Nelson, A. J.; Dunn, J.; Widmann, K.; Ao, T.; Ping, Y.; Hunter, J.; Ng, A.

2005-09-01

165

Time-resolved tuned diode laser absorption spectroscopy of pulsed plasma  

NASA Astrophysics Data System (ADS)

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].

Adámek, P.; Do, H. T.; ?ada, M.; Hubi?ka, Z.; Hippler, R.

2014-05-01

166

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

PubMed Central

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

Lin, Wenwei; Chen, Taosheng

2013-01-01

167

Manganese-doped ZnSe quantum dots as a probe for time-resolved fluorescence detection of 5-fluorouracil.  

PubMed

Quantum dots (QDs) are generally used for the conventional fluorescence detection. However, it is difficult for the QDs to be applied in time-resolved fluorometry due to their short-lived emission. In this paper, high-quality Mn-doped ZnSe QDs with long-lived emission were prepared using a green and rapid microwave-assisted synthetic approach in aqueous solution. Fluorescence lifetime of the Mn-doped ZnSe QDs was extended as long as 400 ?s, which was 10,000 times higher than that of conventional QDs such as CdS, CdSe, and CdTe. The QDs exhibited an excellent photostability over 35 h under continuous irradiation at 260 nm. Capped with mercaptopropionic acid (MPA), the Mn-doped ZnSe QDs were used for the time-resolved fluorescence detection of 5-fluorouracil (5-FU) with the detection limit of 128 nM. The relative standard deviation for seven independent measurements of 1.5 ?M 5-FU was 3.8%, and the recovery ranged from 93% to 106%. The results revealed that the Mn-doped ZnSe QDs could be a good candidate as a luminescence probe for highly sensitive time-resolved fluorometry. PMID:22026809

Zhu, Dong; Chen, Yun; Jiang, Liping; Geng, Jun; Zhang, Jianrong; Zhu, Jun-Jie

2011-12-01

168

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

NASA Astrophysics Data System (ADS)

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 37K at the BEam COoler and LAser spectroscopy (BECOLA) facility at the National Superconducting Cyclotron Laboratory at Michigan State University. A 1.29 ?s bunch width from the buncher and a bunch repetition rate of 2.5 Hz led to a background suppression factor of 3.1 × 105 in resonant photon detection measurements. The hyperfine structure of 37K and its isotope shift relative to the stable 39K were determined using 5 × 104 s-1 37K ions injected into the BECOLA beam line. The obtained hyperfine coupling constants A(2S1/2) = 120.3(1.4) MHz, A(2P1/2) = 15.2(1.1) MHz, and A(2P3/2) = 1.4(8) MHz, and the isotope shift ??39, 37 = -264(3) MHz are consistent with the previously determined values, where available.

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

2014-09-01

169

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

PubMed Central

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

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

2012-01-01

170

In vivo time-resolved spectroscopy of the human bronchial early cancer autofluorescence  

NASA Astrophysics Data System (ADS)

Time-resolved measurements of tissue autofluorescence (AF) excited at 405 nm were carried out with an optical-fiber-based spectrometer in the bronchi of 11 patients. The objectives consisted of assessing the lifetime as a new tumor/normal (T/N) tissue contrast parameter and trying to explain the origin of the contrasts observed when using AF-based cancer detection imaging systems. No significant change in the AF lifetimes was found. AF bronchoscopy performed in parallel with an imaging device revealed both intensity and spectral contrasts. Our results suggest that the spectral contrast might be due to an enhanced blood concentration just below the epithelial layers of the lesion. The intensity contrast probably results from the thickening of the epithelium in the lesions. The absence of T/N lifetime contrast indicates that the quenching is not at the origin of the fluorescence intensity and spectral contrasts. These lifetimes (6.9 ns, 2.0 ns, and 0.2 ns) were consistent for all the examined sites. The fact that these lifetimes are the same for different emission domains ranging between 430 and 680 nm indicates that there is probably only one dominant fluorophore involved. The measured lifetimes suggest that this fluorophore is elastin.

Uehlinger, Pascal; Gabrecht, Tanja; Glanzmann, Thomas; Ballini, Jean-Pierre; Radu, Alexandre; Andrejevic, Snezana; Monnier, Philippe; Wagnières, Georges

2009-03-01

171

Steady state and time-resolved fluorescence study of isoquinoline: reinvestigation of excited state proton transfer.  

PubMed

In the present work we report some hitherto unnoticed features in the steady state and time-resolved measurements of isoquinoline in water and trifluoroethanol (TFE). Absorption spectra reveal that in water, neutrals as well cationic species are present. Emission spectrum shows structured features at shorter wavelengths accompanied with a broad band around 375 nm, which correspond to neutrals and cations respectively. However, time-resolved data indicate that protonation does not take place in the excited state in water. On the contrary, in stronger hydrogen bonding solvent TFE, distribution of decay components is observed and at longer wavelengths a small rise time is present. This is ascribed to neutral and cation-like species present in the ground as well as in the excited state. The difference in the results is explained in terms of different excited state potential energy surfaces for water and TFE; particularly, the presence of a rather small barrier for protonation in case of TFE. PMID:22690918

Joshi, Neeraj Kumar; Joshi, Hem Chandra; Gahlaut, Richa; Tewari, Neeraj; Rautela, Ranjana; Pant, Sanjay

2012-07-12

172

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

PubMed

Mild hypothermia (HT(32°C-33°C)) is an effective neuroprotective strategy for a variety of acute brain injuries. However, the wide clinical adaptation of HT(32-33°C) 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. PMID:24817622

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

2014-05-01

173

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

174

a Study of the Hydroxycyclohexadienyl Radical Absorption Using Time-Resolved Resonance Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

Thus far there has been little understanding of the vibrational spectra, structure and electronic absorption of hydroxycyclohexadienyl radicals in water. They are primary chemical species formed on interaction of radiation with aqueous solutions containing aromatic molecules. We have applied time- resolved resonance Raman (TR-RR) spectroscopy to structurally identify isomers of cyclohexadienyl radicals formed in the pulse radiolysis, using aqueous benzoate solutions as a model system. An early ESR study ((Eiben, K; Fessenden, R.W.; J. Phys. Chem. 1971, 75, 1186-1201) has shown that a mixture of three benzoate hydroxycyclohexadienyl radical isomers: ortho-, meta- and para- are formed upon electron irradiation of N_{2}O saturated benzoate solution. Their collective transient absorption is believed to exhibit a single broad band in the near UV region (?_{max} = 330 nm, ?_{330} = 3800 M^{-1}cm^{-1}). To extract the single isomeric contribution to this collective absorption, we applied TR-RR at various wavelengths within the broad transient absorption range looking for the characteristic indication of each individual isomer. Raman signals of various para-substituted benzoates were also collected to aid in the vibrational studies of the aforementioned benzoate hydroxycyclohexadienyl radicals.

O'Donnell, Deanna M.; Tripathi, G. N. R.; Brinkmann, Nicole R.

2009-06-01

175

Optical analysis of cirrhotic liver by near infrared time resolved spectroscopy  

NASA Astrophysics Data System (ADS)

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.

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

1999-10-01

176

Two-photon resonances in femtosecond time-resolved four-wave mixing spectroscopy: ?-carotene  

NASA Astrophysics Data System (ADS)

Femtosecond time-resolved pump-degenerate four-wave mixing (pump-DFWM) spectroscopy has been used to study the ultrafast dynamics of ?-carotene involving several electronic and vibrational states. An initial pump pulse, resonant with the S0-to-S2 transition, excites the molecular system and a DFWM process, resonant with the S1-to-Sn 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 S1 state, nonresonant DFWM signal of the ground S0 state and vibrational hot S0? state, and the two-photon resonant DFWM signal of the ground S0 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 ?-carotene. For comparison, a two-pulse pump-probe experiment was performed measuring the transient absorption at the wavelength of the DFWM experiment.

Namboodiri, V.; Namboodiri, M.; Flachenecker, G.; Materny, A.

2010-08-01

177

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

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

178

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

PubMed Central

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

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

2010-01-01

179

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

NASA Technical Reports Server (NTRS)

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.

McLaren, Ian A.; Wrobel, Jacek D.

1997-01-01

180

Time resolved spectroscopy of SGR J1550-5418 bursts detected with Fermi/GBM  

E-print Network

We report on time-resolved spectroscopy of the 63 brightest bursts of SGR J1550-5418, detected with Fermi/Gamma-ray Burst Monitor during its 2008-2009 intense bursting episode. We performed spectral analysis down to 4 ms time-scales, to characterize the spectral evolution of the bursts. Using a Comptonized model, we find that the peak energy, E_peak, anti-correlates with flux, while the low-energy photon index remains constant at -0.8 up to a flux limit F~10^-5 erg s-1 cm-2. Above this flux value the E_peak-flux correlation changes sign, and the index positively correlates with flux reaching 1 at the highest fluxes. Using a two black-body model, we find that the areas and fluxes of the two emitting regions correlate positively. Further, we study here for the first time, the evolution of the temperatures and areas as a function of flux. We find that the area-kT relation follows lines of constant luminosity at the lowest fluxes, R^2 \\propto kT^-4, with a break at higher fluxes ($F>10^-5.5 erg s-1 cm-2). The are...

Younes, G; van der Horst, A J; Baring, M G; Granot, J; Watts, A L; Bhat, P N; Collazzi, A; Gehrels, N; Gorgone, N; Gogus, E; Gruber, D; Grunblatt, S; Huppenkothen, D; Kaneko, Y; von Kienlin, A; van der Klis, M; Lin, L; Mcenery, J; van Putten, T; Wijers, R A M J

2014-01-01

181

Rapid and sensitive detection of biological warfare agents using time-resolved fluorescence assays  

Microsoft Academic Search

We have achieved sensitive, rapid and reproducible detection of three biological threat agents in a variety of biological and environmental matrices using the DELFIA time-resolved fluorometry (TRF) assay system (Perkin-Elmer Life Sciences, Akron, OH). Existing ELISA assays for the detection of Francisella tularensis, Clostridium botulinum A\\/B neurotoxin (BotNT A\\/B), and Staphylococcus aureus enterotoxin B (SEB) were converted to TRF assays.

Anne Harwood Peruski; Linwood Hill Johnson III; Leonard Francis Peruski Jr

2002-01-01

182

Energy transfer in photosystem I. Time resolved fluorescence of the native photosystem I complex and its core complex  

NASA Astrophysics Data System (ADS)

Energy transfer within isolated spinach photosystem I (PS I) complexes with different antenna size were studied using time-resolved picosecond and steady-state fluorescence spectroscopy. In both the native PS I complexes and the PS I core complexes lacking the outer chlorophyll a/ b antenna we observed a fast dominating emission component ? 35 ps at room temperature which is associated with the trapping process by the reaction centre. In the native PS I complex there also appears a 120 ps component which was not observed in the PS I core complex. This component most likely represents an energy transfer from low energy pigments in the light-harvesting complex I antenna and into the core. Due to a very fast energy equilibration (< 10 ps) it was not possible to resolve the energy transfer at room temperature. At 77 K, however, it was possible to follow the energy transfer from F690 to F720 with a transfer time of ? 35 ps within the native PS I complex and slightly longer, 78 ps, in the PS I core complex. The native PS I complex also exhibited in the region 700-740 nm a 102 ps component which originates from F720 and represents energy transfer from F720 to P700 at 77 K. At low temperatures the PS I core complex exhibited a component of 161 ps which is associated with F720 and has the same function as the 102 ps component of the native PS I complex. We conclude that the F720 emission originates from pigments in the core antenna system. This emission also increases at low temperature. In the native PS I complex there is an initial increase in the F720 emission as the temperature is lowered but at 77 K the F735 emission originating from LHC I dominates.

Pålsson, Lars-Olof; Tjus, Staffan E.; Andersson, Bertil; Gillbro, Tomas

1995-05-01

183

Time-Resolved Emission Study of a Thiophene-Modified Fluorescent Nucleoside in Solution and within Multiply-Modified Oligodeoxynucleotides  

E-print Network

Steady-state and time-resolved emission techniques were employed to study the photophysical properties of 5-(thien-2-yl)-2'-deoxyuridine (dUTh), an isomorphic fluorescent nucleoside analog. We found that the emission lifetime of dUTh is dependent upon the solvent viscosity and obeys the F\\"orster-Hoffman relation over a wide range of temperatures in 1-propanol, a glass-forming liquid. Upon incorporation into oligodeoxynucleotides, the average emission lifetime significantly increases, and the decay is non-exponential. We use a non-radiative decay model that takes into account the twist angle of the thiophene ring to fit the time-resolved emission decay curves.

Mary Noe; Yuval Erez; Itay Presiado; Yitzhak Tor; Dan Huppert

2014-12-15

184

Time-resolved spectroscopy on epitaxial graphene in the infrared spectral range: relaxation dynamics and saturation behavior  

E-print Network

1 Time-resolved spectroscopy on epitaxial graphene in the infrared spectral range: relaxationC, and in the far infrared range for the quasi-intrinsic graphene layers. In addition graphene samples performed in a wide spectral range, namely from the near-infrared

Boyer, Edmond

185

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

PubMed

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

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

2014-09-25

186

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

SciTech Connect

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.

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

2010-05-02

187

Steady-state and time-resolved fluorescence studies on the conjugation of Rose Bengal to gold nanorods  

NASA Astrophysics Data System (ADS)

This work examines the fluorescence properties of Rose Bengal (RB) molecules conjugated to cetyltrimethylammonium bromide (CTAB) - coated gold nanorods (GNRs) by performing steady-state and time-resolved fluorescence measurements. We show that the quantum yield and fluorescence lifetime can be significantly modified by the electromagnetic coupling of RB to GNRs but the overall fluorescence signal depends also on the environmental conditions in which RB molecules reside - in solution or on solid substrate. For example, we have observed the increase of fluorescence intensity after binding RB to GNRs (RB@GNR) as result of both non-radiative rate decrease and contribution from the electromagnetic coupling of RB to GNRs. For RB@GNRs conjugates deposited on solid substrate we can provide evidence for a clear metal-enhanced fluorescence (MEF) mechanism by observing the decrease of fluorescence lifetime of RB from an average of 2.1 ± 0.36 ns, when complexed to CTAB solely, to 1.6 ± 0.26 ns, when conjugated to GNRs, together with the increase of fluorescence intensity. Our findings contribute to the development and evaluation of novel fluorescent tags based on plasmonic nanoparticles for biomedical applications.

Gabudean, Ana-Maria; Groza, Raluca; Maniu, Dana; Astilean, Simion

2014-09-01

188

Ns-scale time-resolved laser induced fluorescence imaging for detection of fecal contamination on apples  

NASA Astrophysics Data System (ADS)

Our laboratory has been utilizing fluorescence techniques as a potential means for detection of quality and wholesomeness of food products. A system with a short pulse light source such as a laser coupled with a gated detector can be used to harvest fluorescence in ambient light conditions from biological samples with relatively low fluorescence yields. We present a versatile multispectral laser-induced fluorescence (LIF) imaging system capable of ns-scale time resolved fluorescence. The system is equipped with a tunable pulse laser system that emits in the visible range from 410 nm to 690 nm. Ns-scale, time-dependent multispectral fluorescence emissions of apples contaminated with a range of diluted cow feces were acquired. Four spectral bands, F670, F680, F685 and F730, centered near the emission peak wavelengths of the major constituents responsible for the red fluorescence emissions from apples artificially contaminated with cow feces were examined to determine a suitable single red fluorescence band and optimal ns-gate window for detection of fecal contamination on apples. The results based on the ns decay curves showed that 670 nm with 10 nm full width at half maximum (FWHM) at a gate-delay of 4 ns from the laser excitation peak provided the greatest differences in time-dependent fluorescence responses between feces contaminated spots and apples surfaces.

Kim, Moon S.; Lefcourt, Alan M.; Chen, Yud-Ren

2004-11-01

189

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

PubMed Central

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

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

190

Vacuum ultraviolet luminescence of wide band-gap solids studied using time-resolved spectroscopy with synchrotron radiation  

NASA Astrophysics Data System (ADS)

Some highlights of the time-resolved vacuum ultraviolet (VUV) luminescence spectroscopy of solids using synchrotron radiation (SR) are outlined, including studies of the unique phenomenon crossluminescence (CL) and the contribution of time-resolved VUV spectroscopy to the understanding of 5d-4f transitions of rare earth ions in solids. The main properties of CL studied at different SR sources are described and some unclear aspects of CL are pointed out. The results of recent studies of some CL-active nanosize materials are presented. We describe the time-resolved experiments which led to the discovery of 5d-4f luminescence in the deep VUV region (near 10 eV) of Gd3+ and Lu3+ ions incorporated into some wide band-gap fluoride hosts. The results of high-resolution (?? ˜ 0.5 Å) studies of 5d-4f emission and 4f-5d excitation spectra of Gd3+ and Lu3+, which allowed the detailed analysis of electron-lattice coupling in these systems, are presented. Possible new developments in the femtosecond time-resolved spectroscopy of solids with a free electron laser are discussed.

Makhov, V. N.

2014-04-01

191

Steady state and time-resolved fluorescence investigation of the specific binding of two chlorin derivatives with human serum albumin.  

PubMed

The specific binding of two model drugs for photodynamic therapy, namely chlorin p6 and purpurin 18 in the vicinity of Sudlow's Site I of HSA has been investigated by monitoring the intrinsic fluorescence of single tryptophanyl residue and by competitive binding with warfarin. The distance from the tryptophanyl residue has been ascertained by FRET from Trp to the chlorins and has been found to indicate a binding to Sudlow's Site I. The principal driving force for the interaction is found to be the hydrophobic effect. The main mechanism of protein fluorescence quenching was static. Time-resolved fluorescence results of competitive binding with warfarin are found to confirm that they bind to the warfarin binding site. PMID:17705527

Patel, Sunita; Datta, Anindya

2007-09-01

192

Conformation and dynamics of abasic sites in DNA investigated by time-resolved fluorescence of 2-aminopurine.  

PubMed

Abasic sites are highly mutagenic lesions in DNA that arise as intermediates in the excision repair of modified bases. These sites are generated by the action of damage-specific DNA glycosylases and are converted into downstream intermediates by the specific activity of apurinic/apyrimidinic endonucleases. Enzymes in both families have been observed in crystal structures to impose deformations on the abasic-site DNA, including DNA kinking and base flipping. On the basis of these apparent protein-induced deformations, we propose that altered conformation and dynamics of abasic sites may contribute to the specificity of these repair enzymes. Previously, measurements of the steady-state fluorescence of the adenine analogue 2-aminopurine (2AP) opposite an abasic site demonstrated that binding of divalent cations could induce a conformational change that increased the accessibility of 2AP to solute quenching [Stivers, J. T. (1998) Nucleic Acids Res. 26, 3837-44]. We have performed time-resolved fluorescence experiments to characterize the states involved in this conformational change. Interpretation of these studies is based on a recently developed model attributing the static and dynamic fluorescence quenching of 2AP in DNA to aromatic stacking and collisional interactions with neighboring bases, respectively (see the preceding paper in this issue). The time-resolved fluorescence results indicate that divalent cation binding shifts the equilibrium of the abasic site between two conformations: a "closed" state, characterized by short average fluorescence lifetime and complex decay kinetics, and an "open" state, characterized by monoexponential decay with lifetime approximately that of the free nucleoside. Because the lifetime and intensity decay kinetics of 2AP incorporated into DNA are sensitive primarily to collisional interactions with the neighboring bases, the absence of dynamic quenching in the open state strongly suggests that the fluorescent base is extrahelical in this conformation. Consistent with this interpretation, time-resolved quenching studies reveal that the open state is accessible to solute quenching by potassium iodide, but the closed state is not. Greater static quenching is observed in the abasic site when the fluorescent base is flanked by 5'- and 3'-thymines than in the context of 5'- and 3'-adenines, indicating that 2AP is more stacked with the neighboring bases in the former sequence. These results imply that the conformation of the abasic site varies in a sequence-dependent manner. Undamaged sequences in which the abasic site is replaced by thymine do not exhibit an open state and have different levels of both static and dynamic quenching than their damaged homologues. These differences in structure and dynamics may be significant determinants of the high specific affinity of repair enzymes for the abasic site. PMID:11170417

Rachofsky, E L; Seibert, E; Stivers, J T; Osman, R; Ross, J B

2001-01-30

193

Highly Sensitive Time-Resolved Fluoroimmunoassay of Human Immunoglobulin E by Using a New Europium Fluorescent Chelate as a Label  

Microsoft Academic Search

A new europium fluorescent chelate, 4,4?-bis(1?,1?, 1?,2?,2?,3?,3?-heptafluoro-4?,6?-hexanedione-6?-yl)-chlorosulfo-o-terphenyl (BHHCT)–Eu3+, was used as a label for highly sensitive time-resolved fluoroimmunoassay of human IgE. Two assay formats were employed in the analysis. In the first format, an immunoconjugate of rabbit anti-human IgE antibody–human IgE-biotinylated goat anti-human IgE antibody–BHHCT- Eu3+-labeled SA (or BHHCT–Eu3+-labeled BSA–SA; BSA, bovine serum albumin; SA, streptavidin) was used for measurement.

Jingli Yuan; Guilan Wang; Hiroko Kimura; Kazuko Matsumoto

1997-01-01

194

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

SciTech Connect

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.

Tripathi, G.N.R.

1983-01-01

195

Time-resolved multicolor two-photon excitation fluorescence microscopy of cells and tissues  

NASA Astrophysics Data System (ADS)

Multilabeling which maps the distribution of different targets is an indispensable technique in many biochemical and biophysical studies. Two-photon excitation fluorescence (TPEF) microscopy of endogenous fluorophores combining with conventional fluorescence labeling techniques such as genetically encoded fluorescent protein (FP) and fluorescent dyes staining could be a powerful tool for imaging living cells. However, the challenge is that the excitation and emission wavelength of these endogenous fluorophores and fluorescent labels are very different. A multi-color ultrafast source is required for the excitation of multiple fluorescence molecules. In this study, we developed a two-photon imaging system with excitations from the pump femtosecond laser and the selected supercontinuum generated from a photonic crystal fiber (PCF). Multiple endogenous fluorophores, fluorescent proteins and fluorescent dyes were excited in their optimal wavelengths simultaneously. A time- and spectral-resolved detection system was used to record the TPEF signals. This detection technique separated the TPEF signals from multiple sources in time and wavelength domains. Cellular organelles such as nucleus, mitochondria, microtubule and endoplasmic reticulum, were clearly revealed in the TPEF images. The simultaneous imaging of multiple fluorophores of cells will greatly aid the study of sub-cellular compartments and protein localization.

Zheng, Wei

2014-11-01

196

Spectral and time-resolved fluorescence signature of four weed species as affected by selected herbicides  

Microsoft Academic Search

In the present study we show for the first time the suitability of the laser-induced fluorescence technique to evaluate in vivo herbicide-induced damages as revealed by changes of fluorescence spectra and lifetime. Four herbicides of different modes of action (glyphosate, bromoxynil, mesotrione, and amitrole) were selected and applied to four weed species (Stellaria media, Setaria viridis, Chenopodium album, and Viola

Mauricio Hunsche; Kathrin Bürling; Georg Noga

2011-01-01

197

Novel flashlamp-based time-resolved fluorescence microscope reduces autofluorescence for 30-fold contrast enhancement in environmental samples  

NASA Astrophysics Data System (ADS)

The abundance of naturally fluorescing components (autofluorophors) encountered in environmentally sourced samples can greatly hinder the detection and identification of fluorescently labeled target using fluorescence microscopy. Time-resolved fluorescence microscopy (TRFM) is a technique that reduces the effects of autofluorescence through precisely controlled time delays. Lanthanide chelates have fluorescence lifetimes many orders of magnitude greater than typical autofluorophors, and persist in their luminescence long after autofluorescence has ceased. An intense short pulse of (UV) light is used to excite fluorescence in the sample and after a short delay period the longer persisting fluorescence from the chelate is captured with an image-intensified CCD camera. The choice of pulsed excitation source for TRFM has a large impact on the price and performance of the instrument. A flashlamp with a short pulse duration was selected for our instrument because of the high spectral energy in the UV region and short pulse length. However, flash output decays with an approximate lifetime of 18?s and the TRFM requires a long-lived chelate to ensure probe fluorescence is still visible after decay of the flash plasma. We synthesized a recently reported fluorescent chelate (BHHCT) and conjugated it to a monoclonal antibody directed against the water-borne parasite Giardia lamblia. Fluorescence lifetime of the construct was determined to be 339?s +/- 14?s and provided a 45-fold enhancement of labeled Giardia over background using a gate delay of 100?s. Despite the sub-optimal decay characteristics of the light pulse, flashlamps have many advantages compared to optical chopper wheels and modulated lasers. Their low cost, lack of vibration, ease of interface and small footprint are important factors to consider in TRFM design.

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

2003-07-01

198

Transient photoconductivity in GaAs as measured by time-resolved terahertz spectroscopy Matthew C. Beard, Gordon M. Turner, and Charles A. Schmuttenmaer  

E-print Network

. INTRODUCTION Ultrafast carrier dynamics in semiconductors have been of great interest for the last few decades absorption. Time-resolved THz spectroscopy TRTS is a noncontact electrical probe capable of determiningTransient photoconductivity in GaAs as measured by time-resolved terahertz spectroscopy Matthew C

199

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

PubMed

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

Abe, Fumiyoshi

2013-12-15

200

Characterization of time-resolved fluorescence response measurements for distributed optical-fiber sensing.  

PubMed

A distributed optical-fiber sensing system based on pulsed excitation and time-gated photon counting has been used to locate a fluorescent region along the fiber. The complex Alq3 and the infrared dye IR-125 were examined with 405 and 780 nm excitation, respectively. A model to characterize the response of the distributed fluorescence sensor to a Gaussian input pulse was developed and tested. Analysis of the Alq3 fluorescent response confirmed the validity of the model and enabled the fluorescence lifetime to be determined. The intrinsic lifetime obtained (18.2±0.9 ns) is in good agreement with published data. The decay rate was found to be proportional to concentration, which is indicative of collisional deactivation. The model allows the spatial resolution of a distributed sensing system to be improved for fluorophores with lifetimes that are longer than the resolution of the sensing system. PMID:21102661

Sinchenko, Elena; Gibbs, W E Keith; Davis, Claire E; Stoddart, Paul R

2010-11-20

201

ANG-2 for quantitative Na(+) determination in living cells by time-resolved fluorescence microscopy.  

PubMed

Sodium ions (Na(+)) play an important role in a plethora of cellular processes, which are complex and partly still unexplored. For the investigation of these processes and quantification of intracellular Na(+) concentrations ([Na(+)]i), two-photon coupled fluorescence lifetime imaging microscopy (2P-FLIM) was performed in the salivary glands of the cockroach Periplaneta americana. For this, the novel Na(+)-sensitive fluorescent dye Asante NaTRIUM Green-2 (ANG-2) was evaluated, both in vitro and in situ. In this context, absorption coefficients, fluorescence quantum yields and 2P action cross-sections were determined for the first time. ANG-2 was 2P-excitable over a broad spectral range and displayed fluorescence in the visible spectral range. Although the fluorescence decay behaviour of ANG-2 was triexponential in vitro, its analysis indicates a Na(+)-sensitivity appropriate for recordings in living cells. The Na(+)-sensitivity was reduced in situ, but the biexponential fluorescence decay behaviour could be successfully analysed in terms of quantitative [Na(+)]i recordings. Thus, physiological 2P-FLIM measurements revealed a dopamine-induced [Na(+)]i rise in cockroach salivary gland cells, which was dependent on a Na(+)-K(+)-2Cl(-) cotransporter (NKCC) activity. It was concluded that ANG-2 is a promising new sodium indicator applicable for diverse biological systems. PMID:25311309

Roder, Phillip; Hille, Carsten

2014-12-12

202

Time-resolved fluorescence-based assay for rapid detection of Escherichia coli.  

PubMed

Fast and simple detection of pathogens is of utmost importance in health care and the food industry. In this article, a novel technology for the detection of pathogenic bacteria is presented. The technology uses lytic-specific bacteriophages and a nonspecific interaction of cellular components with a luminescent lanthanide chelate. As a proof of principle, Escherichia coli-specific T4 bacteriophage was used to infect the bacteria, and the cell lysis was detected. In the absence of E. coli, luminescent Eu(3+)-chelate complex cannot be formed and low time-resolved luminescence signal is monitored. In the presence of E. coli, increased luminescence signal is observed as the cellular contents are leached to the surrounding medium. The luminescence signal is observed as a function of the number of bacteria in the sample. The homogeneous assay can detect living E. coli in bacterial cultures and simulated urine samples within 25min with a detection limit of 1000 or 10,000 bacterial cells/ml in buffer or urine, respectively. The detection limit is at the clinically relevant level, which indicates that the method could also be applicable to clinical settings for fast detection of urine bacteria. PMID:25233000

Kulpakko, Janne; Kopra, Kari; Hänninen, Pekka

2015-02-01

203

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

PubMed

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

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

2014-01-01

204

Europium chelate labels in time-resolved fluorescence immunoassays and DNA hybridization assays  

Microsoft Academic Search

Like many analytical methodologies, immunoassays and nucleic acid hybridization assays rely on the reaction between an analyte of interest and a specific reagent. The analyte concentration is then deduced by measuring either the amount of analyte-reagent complex formed (product) or the amount of residual reagent. The authors describe the application of fluorescent rare-earth chelates to immunoassay and DNA probing.

Eleftherios P. Diamandis; Theodore K. Christopoulos

1990-01-01

205

Near-infrared time-resolved spectroscopy of the cataclysmic variable YY Draconis  

Microsoft Academic Search

Time-resolved near-infrared (8100-8600 A) spectrophotometry and Johnson B-band CCD photometry of the cataclysmic binary YY Dra are presented. The spectra show the presence of the Na I doublet in absorption from the secondary, as well as sharp and broad Ca II emission lines. The sharp Ca II emission lines appear to originate on or near the secondary star because they

Mario Mateo; Paula Szkody; Peter Garnavich

1991-01-01

206

Generation of femtosecond VUV pulses and their application to time resolved spectroscopy in the gas phase  

NASA Astrophysics Data System (ADS)

We describe a laser system capable of producing tunable femtosecond VUV pulses around 100 nm by two-photon near-resonant four-wave difference-frequency mixing in argon. Two colour pump-probe ionization experiments allow the characterization of the VUV pulses as well as time-resolved studies of highly excited molecular systems (CS 2 , toluene, HDO) in a supersonic jet.

Wittmann, M.; Wick, M. T.; Steinkellner, O.; Farmanara, P.; Stert, V.; Radloff, W.; Korn, G.; Hertel, I. V.

2000-01-01

207

Time-Resolved Terahertz Spectroscopy with Free-Space Electro-Optic Sampling  

Microsoft Academic Search

We present a time-resolved ultrafast measurement in terahertz (THz) frequency region by means of the free-space electro-optic sampling. The fast delay scan technique is used to suppress the noise with low frequency and to improve the signal-to-noise ratio of the system. The transmission spectra of different materials are obtained. The optical properties of these materials in a THz region are

Zhang Liang-Liang; Zhao Guo-Zhong; Zhong Hua; Hu Ying; Zhang Cun-Lin

2004-01-01

208

The measurement of the phosphorescence and singlet oxygen fluorescence time-resolved waveforms of Photofrin(II) and Talaporfin sodium with pulsed excitation  

NASA Astrophysics Data System (ADS)

In order to investigate the interaction between the triplet state T I and ground state oxygen 3O II during pulsed excitation photodynamic therapy (PDT), we measured the phosphorescence and singlet oxygen 1O II fluorescence time-resolved waveform. The phosphorescence time-resolved waveform from clinical photosensitizers has not been obtained because this signal was buried in the photosensitizer fluorescence. We constructed the experimental setup with a spectral and temporal filter to select the phosphorescence signals from the Photofrin(II) (R) and Talaporfin sodium solution. The lifetimes and spectrums of the measured luminescence coincided with the phosphorescence characteristics, respectively. We obtained the phosphorescence time-resolved waveforms from the clinical photosensitizer solutions successfully. The 1O II fluorescence time-resolved waveforms from these photosensitizers were measured with an IR-PMT with a photon counter. The fluorescence time-resolved waveforms of each photosensitizer were also obtained by the authors. We could consequently describe sequential generation of three time-resolved waveforms throughout the photosensitive reaction in the clinical photosensitizers. We think we may evaluate the photoseisitizer characteristics by these waveforms.

Hakomori, Shiho; Ohmori, Sayaka; Masuda, Kensuke; Yamamoto, Kojiro; Arai, Tsunenori

2007-02-01

209

Time resolved laser induced fluorescence of the NH radical in low pressure NâO flames  

Microsoft Academic Search

Total removal rate constants from the NH(\\/ital A\\/³\\/product\\/\\/sub \\/ital i\\/\\/) electronic state have been obtained in low pressure (\\/similar to\\/14-Torr) NâO 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(A³\\/product\\/\\/sub u\\/) is significantly greater than that for other radicals CH(A²\\/Delta\\/ and

Richard A. Copeland; Michael L. Wise; Karen J. Rensberger; David R. Crosley

1989-01-01

210

Time-resolved infrared fluorescence from an IR multiphoton dissociation product of trifluoroacetic anhydride  

NASA Astrophysics Data System (ADS)

Infrared multiphoton dissociation of trifluoroacetic anhydride by a pulse CO 2 yields CF 3COF, C 2F 4 and CO 2 as the major, and COF 2, CO and C 2F 6 as minor photoproducts. Infrared fluorescence from a photoproduct, COF 2, is observed. The intermolecular V ? V and V ? T relaxation rate constants are calculated to be 8×10 4 and 3×10 4 s -1 Torr -1, respectively.

Kumar, Awadhesh; Vatsa, R. K.; Naik, P. D.; Rama Rao, K. V. S.; Mittal, J. P.

1992-12-01

211

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

PubMed

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 ?g L(-1) and 1.66 ?g 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. PMID:24662756

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

2014-07-15

212

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

NASA Astrophysics Data System (ADS)

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 ?v?3 and ?v?5. 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 ?v?3 and ?v?5 targets to select patients for therapy with RGD chemotherapy conjugates.

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

213

Using Time-Resolved Fluorescence to Measure Serum Venom-Specific IgE and IgG  

PubMed Central

We adapted DELFIA™ (dissociation-enhanced lanthanide fluoroimmunoassay), a time resolved fluorescence method, to quantitate whole venom specific and allergenic peptide-specific IgE (sIgE), sIgG1 and sIgG4 in serum from people clinically allergic to Australian native ant venoms, of which the predominant cause of allergy is jack jumper ant venom (JJAV). Intra-assay CV was 6.3% and inter-assay CV was 13.7% for JJAV sIgE. DELFIA and Phadia CAP JJAV sIgE results correlated well and had similar sensitivity and specificity for the detection of JJAV sIgE against intradermal skin testing as the gold standard. DELFIA was easily adapted for detecting sIgE to a panel of other native ant venoms. PMID:21304970

van Eeden, Pauline E.; Wiese, Michael D.; Aulfrey, Susan; Hales, Belinda J.; Stone, Shelley F.; Brown, Simon G. A.

2011-01-01

214

Using time-resolved fluorescence to measure serum venom-specific IgE and IgG.  

PubMed

We adapted DELFIA™ (dissociation-enhanced lanthanide fluoroimmunoassay), a time resolved fluorescence method, to quantitate whole venom specific and allergenic peptide-specific IgE (sIgE), sIgG(1) and sIgG(4) in serum from people clinically allergic to Australian native ant venoms, of which the predominant cause of allergy is jack jumper ant venom (JJAV). Intra-assay CV was 6.3% and inter-assay CV was 13.7% for JJAV sIgE. DELFIA and Phadia CAP JJAV sIgE results correlated well and had similar sensitivity and specificity for the detection of JJAV sIgE against intradermal skin testing as the gold standard. DELFIA was easily adapted for detecting sIgE to a panel of other native ant venoms. PMID:21304970

van Eeden, Pauline E; Wiese, Michael D; Aulfrey, Susan; Hales, Belinda J; Stone, Shelley F; Brown, Simon G A

2011-01-01

215

Sensitive and simple detection of Escherichia coli strain based on time-resolved fluorescence DNA hybridization assay.  

PubMed

A two-probe tandem DNA hybridization assay based on time-resolved fluorescence was employed to detect Escherichia coli strain. The amino modified capture probe was covalently immobilized on the common glass slide surface. The Eu(TTA)(3)(5-NH(2)-phen) with the characteristics of long lifetime and intense luminescence was labeled with reporter probe. The original extracted DNA samples without the purification and amplification process were directly used in the hybridization assay. The concentration of capture probe, hybridization temperature, hybridization and washing time were optimized. The detection limit is about 1.49x10(3) CFU mL(-1) E. coli cells, which is comparable to the value of most microbiology methods. The proposed method has the advantages of easy operation, satisfactory sensitivity and specificity, which can provide a promising technique for monitoring the microorganisms. PMID:20226937

Ruan, Min; Niu, Cheng-Gang; Qin, Pin-Zhu; Zeng, Guang-Ming; Yang, Zhao-Hui; He, Hui; Huang, Jing

2010-04-01

216

Photon counting technique applied to time-resolved laser-induced fluorescence measurements on a stabilized discharge  

SciTech Connect

A novel approach to perform time-resolved laser-induced fluorescence (LIF) measurements in plasma discharges is presented. The LIF technique relies on a photon counting method associated with a sinusoidal potential modulation on a floating electrode located in the plasma to ensure time coherence. By tuning the modulation frequency, resonance can be reached with the discharge current in order to guarantee repeatable measurement conditions. Time-averaged characteristics of the discharge (such as T{sub e}, n{sub e}, V{sub p}, and V{sub ion}) remain unaffected by the modulation. As an example, the association of the photon counting method with the modulation system is employed to determine the time evolution of several ion velocity groups inside an E × B discharge. Interesting features of the velocity oscillations are examined and pave the way for more focused studies.

Vaudolon, J.; Balika, L.; Mazouffre, S. [ICARE Laboratory - CNRS, 1C Av. de la Recherche Scientifique, Orleans (France)] [ICARE Laboratory - CNRS, 1C Av. de la Recherche Scientifique, Orleans (France)

2013-07-15

217

Time-Resolved Terahertz Spectroscopy with Free-Space Electro-Optic Sampling  

NASA Astrophysics Data System (ADS)

We present a time-resolved ultrafast measurement in terahertz (THz) frequency region by means of the free-space electro-optic sampling. The fast delay scan technique is used to suppress the noise with low frequency and to improve the signal-to-noise ratio of the system. The transmission spectra of different materials are obtained. The optical properties of these materials in a THz region are shown. The broadening of spectrum and chirping phenomena are illustrated. We find that polystyrene is an excellent material for the THz application.

Zhang, Liang-Liang; Zhao, Guo-Zhong; Zhong, Hua; Hu, Ying; Zhang, Cun-Lin

2004-11-01

218

High spectral resolution time-resolved optical spectroscopy of V893 Sco  

E-print Network

We present high resolution time-resolved optical spectra of the high inclination short orbital period dwarf nova V893 Sco. We performed spectral analysis through radial velocity measurements, Doppler mapping, and ratioed Doppler maps. Our results indicate that V893 Sco's accretion disk is dissimilar to WZ Sge's accretion disk, and does not fit any of the current accretion disk models. We derive the system parameters M1 and i, and present evidence for V893 Sco as a very young cataclysmic variable and an ER UMa star. We advance the hypothesis that all ER UMa stars may be newly formed cataclysmic variables.

E. Mason; W. Skidmore; S. B. Howell; R. E. Mennickent

2001-10-10

219

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

NASA Technical Reports Server (NTRS)

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.

Szmacinski, Henryk

2003-01-01

220

Full Genotyping of a Highly Polymorphic Human Gene Trait by Time-Resolved Fluorescence Resonance Energy Transfer  

PubMed Central

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

Totè, Edoardo; Lamperti, Marco; Bondani, Maria; Salerno, Domenico; Cassina, Valeria; Nardo, Luca

2014-01-01

221

Time-resolved energy loss spectroscopy of energetic heavy ion beams generating a dense plasma  

NASA Astrophysics Data System (ADS)

At the Gesellschaft für Schwerionenforschung (GSI) Darmstadt, intense beams of energetic heavy ions have been used to generate hot dense plasmas by impact on solid targets. Recently, we have measured time evolution of the energy loss of intense beams (10 9-10 10 particles/pulse) of 190 MeV/u 238U as well as of 300 MeV/u 86Kr in cryogenic crystals of neon and xenon, respectively. For this purpose, a new time resolving energy loss spectrometer has been set up. We observed continuous reduction in the energy loss due to hydrodynamic motion of the ion beam heated target matter. These are the first measurements of this kind. Two-dimensional hydrodynamic simulations were also carried out using the above beam and target parameters. Good agreement has been found between the experimental results and the simulations.

Varentsov, D.; Spiller, P.; Funk, U. N.; Hoffmann, D. H. H.; Kozyreva, A.; Tahir, N.; Constantin, C.; Dewald, E.; Jacoby, J.; Neuner, U.; Udrea, S.; Bock, R.

2001-03-01

222

Time-Resolved X-ray Spectroscopy of the Massive Binary delta Ori  

NASA Astrophysics Data System (ADS)

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.

Nichols, Joy S.; Naze, Y.; Corcoran, M. F.; Pollock, A.; Moffat, A. F.; Ignace, R.; Waldron, W. L.; Evans, N. R.

2014-01-01

223

Limitations of Time-Resolved Fluorescence Suggested by Molecular Simulations: Assessing the Dynamics of T cell Receptor Binding Loops  

PubMed Central

Time-resolved fluorescence anisotropy (TRFA) has a rich history in evaluating protein dynamics. Yet as often employed, TRFA assumes that the motional properties of a covalently tethered fluorescent probe accurately portray the motional properties of the protein backbone at the probe attachment site. In an extensive survey using TRFA to study the dynamics of the binding loops of a ?? T cell receptor, we observed multiple discrepancies between the TRFA data and previously published results that led us to question this assumption. We thus simulated several of the experimentally probed systems using a protocol that permitted accurate determination of probe and protein time correlation functions. We found excellent agreement in the decays of the experimental and simulated correlation functions. However, the motional properties of the probe were poorly correlated with those of the backbone of both the labeled and unlabeled protein. Our results warrant caution in the interpretation of TRFA data and suggest further studies to ascertain the extent to which probe dynamics reflect those of the protein backbone. Meanwhile, the agreement between experiment and computation validates the use of molecular dynamics simulations as an accurate tool for exploring the molecular motion of T cell receptors and their binding loops. PMID:23260055

Scott, Daniel R.; Vardeman, Charles F.; Corcelli, Steven A.; Baker, Brian M.

2012-01-01

224

A time-resolved fluorescence immunoassay for the ultrasensitive determination of diethylstilbestrol based on the double-codified gold nanoparticles.  

PubMed

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

Wang, Longjun; Zhang, Yuanfu; Liu, Guofu; Zhang, Chunyan; Wang, Shuhao

2014-11-01

225

Time Resolved Photoelectron Spectroscopy of Thioflavin T Photoisomerization; A Simulation Study  

PubMed Central

The excited state isomerization of thioflavin T (ThT) is responsible for the quenching of its fluorescence in a non-restricted environment. The fluorescence quantum yield increases substantially upon binding to amyloid fibers. Simulations reveal that the variation of the twisting angle between benzothiazole and benzene groups (?1) is responsible for the sub-picosecond fluorescence quenching. The evolution of the twisting process can be directly probed by photoelectron emission with energies ? ? 1.0 eV before the molecule reaches the ?1-twisted configuration (~300 fs). PMID:23517370

Ren, Hao; Fingerhut, Benjamin P.; Mukamel, Shaul

2013-01-01

226

Time-resolved fluorescence resonance energy transfer kinase assays using physiological protein substrates: Applications of terbium–fluorescein and terbium–green fluorescent protein fluorescence resonance energy transfer pairs  

Microsoft Academic Search

Fluorescence-based kinase assays using peptide substrates are an established format for high-throughput screening and profiling of kinases. Among fluorescence-based formats, time-resolved fluorescence resonance energy transfer (TR-FRET) using a lanthanide donor species has advantages over other fluorescent formats in being resistant to many types of optical interference such as autofluorescent compounds, scattered light from precipitated compounds, or colored compounds that absorb

Steven M. Riddle; Kevin L. Vedvik; George T. Hanson; Kurt W. Vogel

2006-01-01

227

Wavelength dependence of electronic relaxation in isolated adenine using UV femtosecond time-resolved photoelectron spectroscopy.  

PubMed

Electronic relaxation pathways in photoexcited nucleobases have received much theoretical and experimental attention due to their underlying importance to the UV photostability of these biomolecules. Multiple mechanisms with different energetic onsets have been proposed by ab initio calculations yet the majority of experiments to date have only probed the photophysics at a few selected excitation energies. We present femtosecond time-resolved photoelectron spectra (TRPES) of the DNA base adenine in a molecular beam at multiple excitation energies between 4.7-6.2 eV. The two-dimensional TRPES data is fit globally to extract lifetimes and decay associated spectra for unambiguous identification of states participating in the relaxation. Furthermore, the corresponding amplitude ratios are indicative of the relative importance of competing pathways. We adopt the following mechanism for the electronic relaxation of isolated adenine; initially the S(2)(??*) state is populated by all excitation wavelengths and decays quickly within 100 fs. For excitation energies below ?5.2 eV, the S(2)(??*)?S(1)(n?*)?S(0) pathway dominates the deactivation process. The S(1)(n?*)?S(0) lifetime (1032-700 fs) displays a trend toward shorter time constants with increasing excitation energy. On the basis of relative amplitude ratios, an additional relaxation channel is identified at excitation energies above 5.2 eV. PMID:20961159

Evans, Nicholas L; Ullrich, Susanne

2010-10-28

228

Multiplexed measurements by time resolved spectroscopy using colloidal CdSe/ZnS quantum dots  

SciTech Connect

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.

Kaiser, U.; Jimenez de Aberasturi, D.; Malinowski, R.; Amin, F.; Parak, W. J.; Heimbrodt, W., E-mail: Wolfram.Heimbrodt@physik.uni-marburg.de [Department of Physics and Materials Sciences Center, Philipps-University of Marburg, Renthof 5, D-35032 Marburg (Germany)

2014-01-27

229

Exciton dynamics in electroluminescent polymers studied by femtosecond time-resolved photoluminescence spectroscopy  

NASA Astrophysics Data System (ADS)

We report measurements of the time-resolved photoluminescence from unoriented films of poly[2-methoxy,5-(2'-ethyl-hexyloxy)-p-phenylenevinylene] (MEH-PPV) and poly(p-phenylenevinylene) (PPV). An extremely rapid luminescence rise is observed over the entire spectral region measured. A broad high-energy luminescence tail can be seen for very short times after excitation. A redshift of the luminescence with time is also observed and is larger in MEH-PPV than in PPV. The measured decay times of the photoluminescence indicate that the nonradiative decay of singlet excitons is more rapid in MEH-PPV than in PPV, lowering its photoluminescence efficiency. We attribute the differences between the materials to the reduced crystallinity of MEH-PPV compared to PPV. This increases the density of conformational defects and thus reduces the effective conjugation length of the polymer chains. These defects also provide a more efficient nonradiative decay channel. Polarized measurements of the luminescence were performed and provide insight into the ultrafast dynamics of the excitons.

Hayes, G. R.; Samuel, I. D. W.; Phillips, R. T.

1995-10-01

230

Multiplexed measurements by time resolved spectroscopy using colloidal CdSe/ZnS quantum dots  

NASA Astrophysics Data System (ADS)

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.

Kaiser, U.; Jimenez de Aberasturi, D.; Malinowski, R.; Amin, F.; Parak, W. J.; Heimbrodt, W.

2014-01-01

231

Diffusion optical spectroscopy of cancerous and normal prostate tissues in time-resolved and frequency domain  

NASA Astrophysics Data System (ADS)

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.

Zhou, Kenneth J.; Pu, Yang; Chen, Jun

2014-03-01

232

Photoinduced Bimolecular Electron Transfer Investigated by Femtosecond Time-Resolved Infrared Spectroscopy  

E-print Network

Spectroscopy Omar F. Mohammed,, Natalie Banerji, Bernhard Lang, Erik T. J. Nibbering,*, and Eric Vauthey-12489 Berlin, Germany ReceiVed: September 18, 2006; In Final Form: October 30, 2006 Ultrafast infrared transient absorption spectroscopy is used to study the photoinduced bimolecular electron transfer reaction

Candea, George

233

A comparative study on bulk and nanoconfined water by time-resolved optical Kerr effect spectroscopy.  

PubMed

The low frequency (nu < 500 cm(-1)) vibrational spectra of hydrated porous silica are specifically sensitive to the hydrogen bond interactions and provide a wealth of information on the structural and dynamical properties of the water contained in the pores of the matrix. We investigate systematically this spectral region for a series of Vycor porous silica samples (pore size approximately equal 4 nm) at different levels of hydration, from the dry matrix to completely filled pores. The spectra are obtained as the Fourier transforms of time-resolved heterodyne detected optical Kerr effect (HD-OKE) measurements. The comparison of these spectra with that of bulk water enables us to separately extract and analyze the spectral contributions of the first and second hydration layers, as well as that of bulk-like inner water. We conclude that the extra water entering the pores above approximately equal 10% water/silica weight ratio behaves very similarly to bulk water. At lower levels of hydration, corresponding to two complete superficial water layers or less, the H-bond bending and stretching bands, characteristic of the tetrahedral coordination of water in the bulk phase, progressively disappear: clearly in these conditions the H-bond connectivity is very different from that of liquid water. A similar behavior is observed for the structural relaxation times measured from the decay of the time-dependent HD-OKE signal. The value for the inner water is very similar to that of the bulk liquid; that of the first two water layers is definitely longer by a factor approximately equal 4. These findings should be carefully taken into account when employing pore confinement to extend towards lower temperatures the accessible temperature range of supercooled water. PMID:24640497

Taschin, Andrea; Bartolini, Paolo; Marcelli, Agnese; Righini, Roberto; Torre, Renato

2013-01-01

234

TIME-RESOLVED SPECTROSCOPY OF THE POLAR EU CANCRI IN THE OPEN CLUSTER MESSIER 67  

SciTech Connect

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 }.

Williams, Kurtis A. [Department of Physics and Astronomy, Texas A and M University-Commerce, P.O. Box 3011, Commerce, TX 75429 (United States); Howell, Steve B. [NASA Ames Research Center, P.O. Box 1, M/S 244-30, Moffett Field, CA 94035 (United States); Liebert, James; Smith, Paul S. [Steward Observatory, University of Arizona, Tucson, AZ (United States); Bellini, Andrea [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Rubin, Kate H. R. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Bolte, Michael, E-mail: kurtis.williams@tamuc.edu, E-mail: steve.b.howell@nasa.gov, E-mail: jamesliebert@gmail.com, E-mail: psmith@as.arizona.edu, E-mail: bellini@stsci.edu, E-mail: rubin@mpia.de, E-mail: bolte@ucolick.org [UCO/Lick Observatory, University of California, 1156 High St., Santa Cruz, CA 95064 (United States)

2013-05-15

235

Developments in time-resolved ultrafast imaging and spectroscopy at terahertz frequencies  

E-print Network

Prior to the advent of high energy pulsed femtosecond lasers, the field of terahertz (THz) spectroscopy was stagnated by the lack of both high power THz sources and sensitive THz detectors. Over the past few years, it has ...

Teo, Stephanie M

2014-01-01

236

The H + OCS hot atom reaction - CO state distributions and translational energy from time-resolved infrared absorption spectroscopy  

NASA Technical Reports Server (NTRS)

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.

Nickolaisen, Scott L.; Cartland, Harry E.

1993-01-01

237

Fluorescence Correlation Spectroscopy  

NSDL National Science Digital Library

This paper, which was previously published as part of an online biophysics textbook, provides detailed information about concepts related to fluorescence correlation spectroscopy. Sections of the document include writing on experimental realization, theoretical concepts, and applications of this technology.

Haustein, Elke

238

Utilization of fluorescence polarization and time resolved fluorescence resonance energy transfer assay formats for SAR studies: Src kinase as a model system.  

PubMed

High-throughput screening (HTS), a major component of lead identification, often utilizes fluorescence-based assay technologies. For example, HTS kinase assays are formatted using a variety of fluorescence-based assay technologies including, but not limited to, dissociation enhanced lanthanide fluoroimmunoassay (DELFIA), time-resolved fluorescence resonance energy transfer (TR-FRET), and fluorescence polarization (FP). These assays offer tremendous advantages such as a nonradioactive format, ease of automation, and excellent reproducibility. Fluorescence-based assays frequently used for lead identification can also be useful for structure activity relationship (SAR) studies during lead optimization. An important issue when assessing an assay to be used for SAR is the ability of the assay to discriminate high-affinity small molecule inhibitors (pM-nM) from low-affinity inhibitors (microM-mM). The purpose of this study was to utilize HTS-friendly assay formats for SAR by developing TR-FRET, FP, and DELFIAassays measuring Src kinase activity and to define the theoretical lower limit of small molecule inhibitor detection achievable with these assay formats. The authors show that 2 homogeneous assay formats, TR-FRET and FP, allowed for the development of Src kinase assays with a lower limit of detection of K(i) = 0.01 nM. This study indicates that assay technologies typically used for HTS can be used during lead optimization by providing quantitative measurements of compound activity critical to driving SAR studies. PMID:15452339

Newman, Miki; Josiah, Serene

2004-09-01

239

Light-induced switching of HAMP domain conformation and dynamics revealed by time-resolved EPR spectroscopy.  

PubMed

HAMP domains are widely abundant signaling modules. The putative mechanism of their function comprises switching between two distinct states. To unravel these conformational transitions, we apply site-directed spin labeling and time-resolved EPR spectroscopy to the phototactic receptor/transducer complex NpSRII/NpHtrII. We characterize the kinetic coupling of NpHtrII to NpSRII along with the activation period of the transducer and follow the transient conformational signal. The observed transient shift towards a more compact state of the HAMP domain upon light-activation agrees with structure-based calculations. It thereby validates the two modeled signaling states and integrates the domain's dynamics into the current model. PMID:25240192

Klose, Daniel; Voskoboynikova, Natalia; Orban-Glass, Ioan; Rickert, Christian; Engelhard, Martin; Klare, Johann P; Steinhoff, Heinz-Jürgen

2014-11-01

240

Local structure of reaction intermediates probed by time-resolved x-ray absorption near edge structure spectroscopy  

SciTech Connect

A method for the analysis of time-resolved x-ray absorption near edge structure (XANES) spectra is proposed. It combines principal component analysis of the series of experimental spectra, multidimensional interpolation of theoretical XANES as a function of structural parameters, and ab initio XANES calculations. It allows to determine the values of structural parameters for intermediates of chemical reactions and the concentrations of different states as a function of time. This approach is tested using numerically generated data and its possibilities and limitations are discussed. The application of this method to a reaction with methylrhenium trioxide catalyst in solution, for which experimental data were measured using stopped-flow energy-dispersive x-ray absorption spectroscopy technique, is demonstrated. Possibilities and limitations of this experimental technique are also discussed.

Smolentsev, G.; Soldatov, A. V. [Center for Nanoscale Structure of Matter and Faculty of Physics, Southern Federal University, Rostov-on-Don 344090 (Russian Federation); Guilera, G. [ALBA Synchrotron, Barcelona 08193 (Spain); Tromp, M. [University of Southampton, Southampton SO17 1BJ (United Kingdom); Pascarelli, S. [European Synchrotron Radiation Facility, Grenoble 38000 (France)

2009-05-07

241

Measurement of orientational relaxation times of OH in a flame using picosecond time-resolved polarization spectroscopy  

NASA Astrophysics Data System (ADS)

Picosecond time-resolved polarization spectroscopy in the ultraviolet has been used to measure relaxation times of the laser-induced optical anisotropy of OH in an atmospheric pressure flame. OH radicals were produced in the post flame gases of a methane/air flame. Transient signals from absorption in theA2?-X2? (0-0) electronic transition were studied by pump-probe experiments using different P- and Q-branch transitions. A theoretical approach has been developed to interpret experimentally observed transient signals in terms of the relaxations of molecular orientation and alignment. The observed effective relaxation times for these flame conditions are of the order of 240-590 ps depending on the rotational state. We found slightly larger values for the relaxation times of molecular orientation than for molecular alignment. These results are relevant to the interpretation and modeling of four-wave mixing spectra.

Dreizler, A.; Tadday, R.; Suvernev, A. A.; Himmelhaus, M.; Dreier, T.; Foggi, P.

1995-06-01

242

Measurement of orientational relaxation times of OH in a flame using picosecond time-resolved polarization spectroscopy  

NASA Astrophysics Data System (ADS)

Picosecond time-resolved polarization spectroscopy in the ultraviolet has been used to measure relaxation times of the laser-induced optical anisotropy of OH in an atmospheric pressure flame. OH radicals were produced in the post flame gases of a methane/air flame. Transient signals from absorption in theA 2?-X 2? (0-0) electronic transition were studied by pump-probe experiments using different P- and Q-branch transitions. A theoretical approach has been developed to interpret experimentally observed transient signals in terms of the relaxations of molecular orientation and alignment. The observed effective relaxation times for these flame conditions are of the order of 240-590 ps depending on the rotational state. We found slightly larger values for the relaxation times of molecular orientation than for molecular alignment. These results are relevant to the interpretation and modeling of four-wave mixing spectra.

Dreizler, A.; Tadday, R.; Suvernev, A. A.; Himmelhaus, M.; Dreier, T.; Foggi, P.

1995-06-01

243

Transient Bond Scission of Polytetrafluoroethylene under Laser-Induced Shock Compression Studied by Nanosecond Time-Resolved Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

Nanosecond time-resolved Raman spectroscopy has been performed to study polymer films, polytetrafluoroethylene (PTFE), under laser driven shock compression at laser power density of 4.0 GW/cm2. The CF2 stretching mode line of PTFE showed a higher shift (18 cm-1) at delay time of 9.3 ns due to the shock compression and corresponding pressure was estimated to be approximately 2.3 GPa. A new vibrational line at 1900 cm-1 appeared only under shock compression and was assigned to the C=C stretching in transient species such as a monomer (C2F4) produced by the shock-induced bond scission. Intensity of the new line increased with increasing delay time along propagation of the shock compression.

Nakamura, Kazutaka G.; Wakabayashi, Kunihiko; Kondo, Ken-ichi

2002-07-01

244

Photoluminescence and time-resolved spectroscopy in multiferroic BiFeO3: Effects of electric fields and sample aging  

NASA Astrophysics Data System (ADS)

We report photoluminescence and time-resolved spectroscopy in bismuth ferrite excited with a 325 nm source. The direct-bandgap recombinations near 2.55 eV and indirect-bandgap transitions near 2.67 eV are presented as functions of applied in-plane electric field with recombination time in the microsecond regime. The applied field moves some conduction electrons away from the Brillouin zone center, increasing significantly the intensity of indirect-gap recombination. An aging phenomenon is manifest in specimens stored for more than twelve months under ambient conditions. Effect of external magnetic field on the surface phase transition is negligible up to H = 0.5 T.

Anshul, Avneesh; Kumar, Ashok; Gupta, Bipin K.; Kotnala, R. K.; Scott, J. F.; Katiyar, R. S.

2013-06-01

245

Determination of s-d exchange coupling in GaMnN by time-resolved Kerr rotation spectroscopy  

NASA Astrophysics Data System (ADS)

Coherent electron-spin dynamics in Ga1-xMnxN has been investigated by time-resolved Kerr rotation spectroscopy. The effective electron g factor shows a linear increase with the Mn concentration due to the s-d exchange coupling between the conduction electrons and the d-shell electrons of Mn3+ impurities. The magnitude and sign of the s-d exchange constant are determined precisely to be N0? =+0.23±0.02eV, indicative of a ferromagnetic s-d exchange coupling in GaMnN. The determined N0? is consistent with the typical value found in most diluted magnetic semiconductors and reveals that GaMnN is indeed not an exception.

Hsu, Wei-Ting; Hsieh, Ting-Yen; Chen, Hsin-Feng; Huang, Feng-Wen; Chen, Po-Cheng; Sheu, Jinn-Kong; Chang, Wen-Hao

2014-09-01

246

Detection of anthrax protective antigen (PA) using europium labeled anti-PA monoclonal antibody and time-resolved fluorescence.  

PubMed

Inhalation anthrax is a rare but acute infectious disease following adsorption of Bacillus anthracis spores through the lungs. The disease has a high fatality rate if untreated, but early and correct diagnosis has a significant impact on case patient recovery. The early symptoms of inhalation anthrax are, however, non-specific and current anthrax diagnostics are primarily dependent upon culture and confirmatory real-time PCR. Consequently, there may be a significant delay in diagnosis and targeted treatment. Rapid, culture-independent diagnostic tests are therefore needed, particularly in the context of a large scale emergency response. The aim of this study was to evaluate the ability of monoclonal antibodies to detect anthrax toxin proteins that are secreted early in the course of B. anthracis infection using a time-resolved fluorescence (TRF) immunoassay. We selected monoclonal antibodies that could detect protective antigen (PA), as PA83 and also PA63 and LF in the lethal toxin complex. The assay reliable detection limit (RDL) was 6.63×10(-6)?M (0.551ng/ml) for PA83 and 2.51×10(-5)?M (1.58ng/ml) for PA63. Despite variable precision and accuracy of the assay, PA was detected in 9 out of 10 sera samples from anthrax confirmed case patients with cutaneous (n=7), inhalation (n=2), and gastrointestinal (n=1) disease. Anthrax Immune Globulin (AIG), which has been used in treatment of clinical anthrax, interfered with detection of PA. This study demonstrates a culture-independent method of diagnosing anthrax through the use of monoclonal antibodies to detect PA and LF in the lethal toxin complex. PMID:24857756

Stoddard, Robyn A; Quinn, Conrad P; Schiffer, Jarad M; Boyer, Anne E; Goldstein, Jason; Bagarozzi, Dennis A; Soroka, Stephen D; Dauphin, Leslie A; Hoffmaster, Alex R

2014-06-01

247

Time-resolved Fluorescence Resonance Energy Transfer (TR-FRET) to Analyze the Disruption of EGFR/HER2 Dimers  

PubMed Central

In oncology, simultaneous inhibition of epidermal growth factor receptor (EGFR) and HER2 by monoclonal antibodies (mAbs) is an efficient therapeutic strategy but the underlying mechanisms are not fully understood. Here, we describe a time-resolved fluorescence resonance energy transfer (TR-FRET) method to quantify EGFR/HER2 heterodimers on cell surface to shed some light on the mechanism of such therapies. First, we tested this antibody-based TR-FRET assay in NIH/3T3 cell lines that express EGFR and/or HER2 and in various tumor cell lines. Then, we used the antibody-based TR-FRET assay to evaluate in vitro the effect of different targeted therapies on EGFR/HER2 heterodimers in the ovarian carcinoma cell line SKOV-3. A simultaneous incubation with Cetuximab (anti-EGFR) and Trastuzumab (anti-HER2) disturbed EGFR/HER2 heterodimers resulting in a 72% reduction. Cetuximab, Trastuzumab or Pertuzumab (anti-HER2) alone induced a 48, 44, or 24% reduction, respectively. In contrast, the tyrosine kinase inhibitors Erlotinib and Lapatinib had very little effect on EGFR/HER2 dimers concentration. In vivo, the combination of Cetuximab and Trastuzumab showed a better therapeutic effect (median survival and percentage of tumor-free mice) than the single mAbs. These results suggest a correlation between the extent of the mAb-induced EGFR/HER2 heterodimer reduction and the efficacy of such mAbs in targeted therapies. In conclusion, quantifying EGFR/HER2 heterodimers using our antibody-based TR-FRET assay may represent a useful method to predict the efficacy and explain the mechanisms of action of therapeutic mAbs, in addition to other commonly used techniques that focus on antibody-dependent cellular cytotoxicity, phosphorylation, and cell proliferation. PMID:21282108

Gaborit, Nadège; Larbouret, Christel; Vallaghe, Julie; Peyrusson, Frédéric; Bascoul-Mollevi, Caroline; Crapez, Evelyne; Azria, David; Chardès, Thierry; Poul, Marie-Alix; Mathis, Gérard; Bazin, Hervé; Pèlegrin, André

2011-01-01

248

Photoinduced bimolecular electron transfer investigated by femtosecond time-resolved infrared spectroscopy.  

PubMed

Ultrafast infrared transient absorption spectroscopy is used to study the photoinduced bimolecular electron transfer reaction between perylene in the first singlet excited state and 1,4-dicyanobenzene in acetonitrile and dichloromethane. Following vibrational marker modes on both donor and acceptor sides in real time provides direct insight into the structural dynamics during the reaction. A band narrowing on a time scale of a few tens of picoseconds observed on the antisymmetric CN stretching vibration of the dicyanobenzene radical anion indicates that a substantial part of the excess energy is channeled into vibrational modes of the product, despite the fact that the reaction is weakly exergonic. An additional narrowing of the same band on a time scale of several hundreds of picoseconds observed in acetonitrile only is interpreted as a signature of the dissociation of the geminate ion pairs into free ions. PMID:17181320

Mohammed, Omar F; Banerji, Natalie; Lang, Bernhard; Nibbering, Erik T J; Vauthey, Eric

2006-12-28

249

Photosynthetic Dioxygen Formation Monitored by Time-Resolved X-Ray Spectroscopy  

SciTech Connect

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.

Haumann, Michael; Dau, Holger [Freie Universitaet Berlin, Inst. f. Experimentalphysik, Arnimallee 14, D-14195 Berlin (Germany)

2007-02-02

250

Structural dynamics of membrane proteins - time-resolved and surface-enhanced IR spectroscopy  

NASA Astrophysics Data System (ADS)

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.

Heberle, Joachim

2013-03-01

251

Development of a High Harmonic Beamline for Time-Resolved XUV Spectroscopy  

NASA Astrophysics Data System (ADS)

In order to better understand bond breaking and other photochemical processes it is critical to determine the valence electron dynamics occurring during such phenomena. Extreme ultraviolet (XUV) light induces transitions between narrowly confined core electronic states and valence states. Thus ultrafast XUV absorption provides a route to determine electron distributions during chemical change. We present the design of our new femtoseconds XUV absorption spectrometer. The XUV pulses are generated in a rare gas cell in a high harmonic generation (HHG) process. Strong laser field HHG yields a promising probe source in the 10-100 eV spectral range, making it an ideal tool for XUV absorption spectroscopy of molecules containing 3d transition metals with M2,3 edges between 40-70 eV. The femtosecond duration pulses intrinsically produced by HHG allow for the necessary temporal resolution. We plan to study organometallic molecules such as the transition metal carbonyls which undergo ligand dissociation under the influence of ultraviolet light. After UV excitation a radiationless non-Born-Oppenheimer processes occur before dissociation. The understanding of these non-Born-Oppenheimer dynamics is important to the general field of photocatalysis. This work is supported by the Office of Science Early Career Research Program.

Sistrunk, Emily; Grilj, Jakob; Guehr, Markus

2012-06-01

252

Excited state dynamics in SO2. I. Bound state relaxation studied by time-resolved photoelectron-photoion coincidence spectroscopy  

NASA Astrophysics Data System (ADS)

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.

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

253

Solvatochromism and time-resolved fluorescence of the antitumor agent mitoxantrone and its analogues in solution and in DNA  

SciTech Connect

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.

Su Lin; Struve, W.S. (Ames Lab., IA (United States))

1991-03-21

254

Time-resolved Spectroscopy and Multi-color Photometry Of The Pulsating and Short-period Binary Subdwarf B Star Feige 48  

NASA Astrophysics Data System (ADS)

Pulsating subdwarf B (sdB) stars can be used as probes of the helium fusing cores of horizontal branch stars. To probe these stars, asteroseismology must be able to observationally associate pulsation frequencies with modes. 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 RV and multicolor measurements has also been shows as an effective means of constraining mode identifications. I will present results for Feige 48 using both time-resolved spectroscopy and multicolor photometry and attempts to constrain their pulsation modes using the atmospheric codes BRUCE and KYLIE.

Reed, Mike; Baran, A.; O'Toole, S.

2012-05-01

255

Probing the hydrogen-bond network of water via time-resolved soft x-ray spectroscopy  

SciTech Connect

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.

Huse, Nils; Wen, Haidan; Nordlund, Dennis; Szilagyi, Erzsi; Daranciang, Dan; Miller, Timothy A.; Nilsson, Anders; Schoenlein, Robert W.; Lindenberg, Aaron M.

2009-04-24

256

Time-resolved, multi-color photometry and spectroscopy of Virgo 4 (OU Vir): a high orbital inclination, short orbital period dwarf nova  

E-print Network

We present multi-color photometry and time resolved spectroscopy of OU Vir. The analysis of the quiescent light curve shows that OU Vir is characterized by i) strong cycle-to-cycle brightness variations, and ii) hot spot modulated light curve with grazing eclipse of the impact region. Colors are derived both in- and out- of eclipse. The time-resolved spectroscopy allows us to produce the radial velocity curve from the H$\\alpha$ accretion disk emission line which possibly reveals only weak evidence for hot spot line emission. The hot spot is believed to be a turbulent optically thick region, producing mostly continuum emission.

E. Mason; S. B. Howell; P. Szkody; T. E. Harrison; J. A. Holtzman; D. W. Hoard

2002-10-09

257

Time-resolved, multi-color photometry and spectroscopy of Virgo 4 (OU Vir) a high orbital inclination, short orbital period dwarf nova  

E-print Network

We present multi-color photometry and time resolved spectroscopy of OU Vir. The analysis of the quiescent light curve shows that OU Vir is characterized by i) strong cycle-to-cycle brightness variations, and ii) hot spot modulated light curve with grazing eclipse of the impact region. Colors are derived both in- and out- of eclipse. The time-resolved spectroscopy allows us to produce the radial velocity curve from the H$\\alpha$ accretion disk emission line which possibly reveals only weak evidence for hot spot line emission. The hot spot is believed to be a turbulent optically thick region, producing mostly continuum emission.

Mason, E; Szkody, P; Harrison, T E; Holtzman, J A; Hoard, D W

2002-01-01

258

Effect of sphere to rod transition on the probe microenvironment in sodium dodecyl sulphate micelles: A time resolved fluorescence anisotropy study  

Microsoft Academic Search

The effect of different hydrotropic salts on the microenvironment at the anionic head group region of sodium dodecyl sulphate (SDS) micelle has been studied through time-resolved fluorescence anisotropy measurements of a solubilized probe, coumarin-153 (C153). The organic cations of the hydrotropic salts used in this study, i.e. aniline hydrochloride (AHC) and o-, m- and p-toluidine hydrochlorides (OTHC, MTHC and PTHC,

Teena Goel; Manoj Kumbhakar; Tulsi Mukherjee; Haridas Pal

2010-01-01

259

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)

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.

Zheng, Wei; Li, Dong; Qu, Jianan Y.

2010-05-01

260

Fluorescence Spectroscopy of Neoplastic and Non-Neoplastic Tissues  

PubMed Central

Abstract Fast and non-invasive, diagnostic techniques based on fluorescence spectroscopy have the potential to link the biochemical and morphologic properties of tissues to individual patient care. One of the most widely explored applications of fluorescence spectroscopy is the detection of endoscopically invisible, early neoplastic growth in epithelial tissue sites. Currently, there are no effective diagnostic techniques for these early tissue transformations. If fluorescence spectroscopy can be applied successfully as a diagnostic technique in this clinical context, it may increase the potential for curative treatment, and thus, reduce complications and health care costs. Steady-state, fluorescence measurements from small tissue regions as well as relatively large tissue fields have been performed. To a much lesser extent, time-resolved, fluorescence measurements have also been explored for tissue characterization. Furthermore, sources of both intrinsic (endogenous fluorophores) and extrinsic fluorescence (exogenous fluorophores) have been considered. The goal of the current report is to provide a comprehensive review on steady-state and time-resolved, fluorescence measurements of neoplastic and non-neoplastic, biologic systems of varying degrees of complexity. First, the principles and methodology of fluorescence spectroscopy are discussed. Next, the endogenous fluorescence properties of cells, frozen tissue sections and excised and intact bulk tissues are presented; fluorescence measurements from both animal and human tissue models are discussed. This is concluded with future perspectives. PMID:10933071

Ramanujam, Nirmala

2000-01-01

261

Testing the Physical Mechanisms of Gamma-Ray Bursts with Multi-Instrument Time-Resolved Spectroscopy  

NASA Astrophysics Data System (ADS)

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).

Briggs, Michael S.; Preece, Robert E.

2001-12-01

262

Testing the Physical Mechanisms of Gamma-Ray Bursts with Multi-Instrument Time-Resolved Spectroscopy  

NASA Technical Reports Server (NTRS)

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).

Briggs, Michael S.; Preece, Robert E.

2001-01-01

263

Two-photon resonances in femtosecond time-resolved four-wave mixing spectroscopy: beta-carotene.  

PubMed

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(0)-to-S(2) transition, excites the molecular system and a DFWM process, resonant with the S(1)-to-S(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(1) state, nonresonant DFWM signal of the ground S(0) state and vibrational hot S(0)* state, and the two-photon resonant DFWM signal of the ground S(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. PMID:20707538

Namboodiri, V; Namboodiri, M; Flachenecker, G; Materny, A

2010-08-01

264

Two-photon resonances in femtosecond time-resolved four-wave mixing spectroscopy: {beta}-carotene  

SciTech Connect

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.

Namboodiri, V.; Namboodiri, M.; Flachenecker, G.; Materny, A. [Center of Functional Materials and Nanomolecular Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen (Germany)

2010-08-07

265

Communication: Ultrafast time-resolved ion photofragmentation spectroscopy of photoionization-induced proton transfer in phenol-ammonia complex  

NASA Astrophysics Data System (ADS)

Photoionization-induced proton transfer (PT) in phenol-ammonia (PhOH-NH3) complex has been studied using ultrafast time-resolved ion photofragmentation spectroscopy. Neutral PhOH-NH3 complexes prepared in a free jet are photoionized by femtosecond [1+1] resonance-enhanced multiphoton ionization via the S1 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-NH3]+ 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.

Shen, Ching-Chi; Tsai, Tsung-Ting; Ho-Wei, Jr.; Chen, Yi-Wei; Cheng, Po-Yuan

2014-11-01

266

Time-resolved and photoluminescence spectroscopy of ?-Al?O? nanowires for promising fast optical sensor applications.  

PubMed

Herein, we have demonstrated the high yield facile growth of Al2O3 nanowires of uniform morphology with different polymorph phases (e.g. ?, ? and ?) via a hydrothermal method with varying calcination temperatures. The synthesized ?-Al2O3 nanowires were well characterized by XRD, FTIR, SEM/EDAX, AFM and HRTEM techniques. Microstructural analysis confirmed that the dimensions of the individual ?-Al2O3 nanowires are approximately in the ranges 5-20 nm in width and 40-150 nm in length, and the aspect ratio is up to 20. AFM results evidenced the uniform distribution of the nanowires with controlled morphology. Furthermore, UV-vis spectroscopic data reveal that the estimated optical band gap of the ?-Al2O3 nanowires was ~5.16 eV. The photoluminescence spectrum exhibits blue emission upon excitation at a wavelength of 252 nm. Time-resolved spectroscopy demonstrates that these nanowires illustrate a decay time of ~2.23 nanoseconds. The obtained photoluminescence results with a decay time of nanoseconds suggest that the ?-Al2O3 phase could be an exceptional choice for next generation fast optical sensors. PMID:25300301

Gangwar, Jitendra; Gupta, Bipin Kumar; Kumar, Pawan; Tripathi, Surya Kant; Srivastava, Avanish Kumar

2014-12-01

267

Time-resolved spectroscopy of the charge-transfer gap in Sr2CuO2Cl2  

NASA Astrophysics Data System (ADS)

We present energy- and time-resolved pump-probe spectroscopy near the charge-transfer gap in the undoped cuprate compound Sr2CuO2Cl2. Upon photoexcitation, an increase in absorption is observed for energies below 1.95 eV, whereas a decrease occurs above 1.95 eV. Overall, the spectral weight is not conserved over the probe range of 1.6-2.3 eV. No hole-burning is observable at the pump energy Epump = 2.1 eV. The transient spectral changes appear as one spectral unit instantaneously after the excitation, and they decay, again as one spectral unit, on a picosecond time scale. The photoinduced response relates simply to the thermal response, indicating a common boson-mediated origin. These results support a theoretical model that places the gap energy near 1.5 eV, well below the peak in the charge-transfer absorption spectrum.ootnotetextK. M. Shen et al., Phys. Rev. B 75, 075115 (2007). In this model, the photoexcited state decays rapidly to the gap energy via phonon emission, and the presence of the additional phonons then has the same effect on the charge-transfer absorption as an increase in the equilibrium lattice temperature.

Dodge, J. Steven; Schumacher, Andreas; Miller, Lance; Chemla, Daniel

2008-03-01

268

Fast CCD camera for x-ray photon correlation spectroscopy and time-resolved x-ray scattering and imaging  

SciTech Connect

A new, fast x-ray detector system is presented for high-throughput, high-sensitivity, time-resolved, x-ray scattering and imaging experiments, most especially x-ray photon correlation spectroscopy (XPCS). After a review of the architectures of different CCD chips and a critical examination of their suitability for use in a fast x-ray detector, the new detector hardware is described. In brief, its principal component is an inexpensive, commercial camera - the SMD1M60 - originally designed for optical applications, and modified for use as a direct-illumination x-ray detector. The remainder of the system consists of two Coreco Imaging PC-DIG frame grabber boards, located inside a Dell Power-edge 6400 server. Each frame grabber sits on its own PCI bus and handles data from 2 of the CCD's 4 taps. The SMD1M60 is based on a fast, frame-transfer, 4-tap CCD chip, read out at12-bit resolution at frame rates of up to 62 Hz for full frame readout and up to 500 Hz for one-sixteenth frame readout. Experiments to characterize the camera's suitability for XPCS and small-angle x-ray scattering (SAXS) are presented. These experiments show that single photon events are readily identified, and localized to within a pixel index or so. This is a sufficiently fine spatial resolution to maintain the speckle contrast at an acceptable value for XPCS measurements. The detective quantum efficiency of the SMD1M60 is 49% for directly-detected 6.3 keV x rays. The effects of data acquisition strategies that permit near-real-time data compression are also determined and discussed. Overall, the SMD1M60 detector system represents a major improvement in the technology for time-resolved x-ray experiments, that require an area detector with time-resolutions in few-milliseconds-to-few-seconds range, and it should have wide applications, extending beyond XPCS.

Falus, P.; Borthwick, M.A.; Mochrie, S.G.J. [Department of Physics, Yale University, New Haven, Connecticut 06520 and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Departments of Physics and Applied Physics, Yale University, New Haven, Connecticut 06520 (United States)

2004-11-01

269

Micro-systems for time-resolved fluorescence analysis using CMOS single-photon avalanche diodes and micro-LEDs   

E-print Network

Fluorescence based analysis is a fundamental research technique used in the life sciences. However, conventional fluorescence intensity measurements are prone to misinterpretation due to illumination and fluorophore ...

Rae, Bruce R.

2009-01-01

270

Time-resolved photometry and spectroscopy of the new deeply-eclipsing SW Sextantis star HS 0728+6738  

NASA Astrophysics Data System (ADS)

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.

Rodríguez-Gil, P.; Gänsicke, B. T.; Barwig, H.; Hagen, H.-J.; Engels, D.

2004-09-01

271

Nanosecond fluorescence spectroscopy  

SciTech Connect

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.

Leskovar, B.

1985-03-01

272

Electron-hole recombination on ZnO(0001) single-crystal surface studied by time-resolved soft X-ray photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

Time-resolved soft X-ray photoelectron spectroscopy (PES) experiments were performed with time scales from picoseconds to nanoseconds to trace relaxation of surface photovoltage on the ZnO(0001) single crystal surface in real time. The band diagram of the surface has been obtained numerically using PES data, showing a depletion layer which extends to 1 ?m. Temporal evolution of the photovoltage effect is well explained by a recombination process of a thermionic model, giving the photoexcited carrier lifetime of about 1 ps at the surface under the flat band condition. This lifetime agrees with a temporal range reported by the previous time-resolved optical experiments.

Yukawa, R.; Yamamoto, S.; Ozawa, K.; Emori, M.; Ogawa, M.; Yamamoto, Sh.; Fujikawa, K.; Hobara, R.; Kitagawa, S.; Daimon, H.; Sakama, H.; Matsuda, I.

2014-10-01

273

Nonlinear spectroscopy in the near-field: time resolved spectroscopy and subwavelength resolution non-invasive imaging  

NASA Astrophysics Data System (ADS)

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.

Namboodiri, Mahesh; Khan, Tahirzeb; Karki, Khadga; Kazemi, Mehdi Mohammad; Bom, Sidhant; Flachenecker, Günter; Namboodiri, Vinu; Materny, Arnulf

2014-04-01

274

Time-resolved OES of nanosecond pulsed discharges in N$_{2}$ and N$_{2}$/H$_{2}$O mixtures]{Time-resolved optical emission spectroscopy of nanosecond pulsed discharges in atmospheric pressure N$_{2}$ and N$_{2}$/H$_{2}$O mixtures  

E-print Network

In this contribution, nanosecond pulsed discharges in N$_{2}$ and N$_{2}$/0.9% H$_{2}$O at atmospheric pressure (at 300 K) are studied with time-resolved imaging, optical emission spectroscopy and Rayleigh scattering. A 170 ns high voltage pulse is applied across two pin-shaped electrodes at a frequency of 1 kHz. The discharge consists of three phases: an ignition phase, a spark phase and a recombination phase. During the ignition phase the emission is mainly caused by molecular nitrogen (N$_{2}$(C-B)). In the spark and recombination phase mainly atomic nitrogen emission is observed. The emission when H$_{2}$O is added is very similar, except the small contribution of H$_{\\alpha}$ and the intensity of the molecular N$_{2}$(C-B) emission is less.

van der Horst, R M; van Veldhuizen, E M; Bruggeman, P J

2014-01-01

275

Unravelling the conformations of di-(perylene bisimide acrylate) by combining time-resolved fluorescence-anisotropy experiments and molecular modelling.  

PubMed

We compare the results from time-resolved fluorescence anisotropy experiments and molecular modelling on perylene bisimide acrylate dimers which allows us to connect the observed spectral signatures unambiguously with the non-stacked and two (parallel and anti-parallel) stacked conformations. For the parallel stacked conformation the experimental data can be reproduced quantitatively using a model that assumes structural relaxation in the electronically excited state of the stacked aggregate. For the non-stacked conformation we find quantitative agreement between experiment and modelling only if a fast hopping of the electronic excitation between the perylene bisimide subunits is taken into account. PMID:25358077

Spreitler, F; Sommer, M; Hollfelder, M; Thelakkat, M; Gekle, S; Köhler, J

2014-12-21

276

Organization and dynamics of tryptophan residues in tetrameric and monomeric soybean agglutinin: studies by steady-state and time-resolved fluorescence, phosphorescence and chemical modification.  

PubMed

We have investigated the organization and dynamics of tryptophan residues in tetrameric, monomeric and unfolded states of soybean agglutinin (SBA) by selective chemical modification, steady-state and time-resolved fluorescence, and phosphorescence. Oxidation with N-bromosuccinimide (NBS) modifies two tryptophans (Trp 60 and Trp 132) in tetramer, four (Trp 8, Trp 203 and previous two) in monomer, and all six (Trp 8, Trp 60, Trp 132, Trp 154, Trp 203 and Trp 226) in unfolded state. Utilizing wavelength-selective fluorescence approach, we have observed a red-edge excitation shift (REES) of 10 and 5 nm for tetramer and monomer, respectively. A more pronounced REES (21 nm) is observed after NBS oxidation. These results are supported by fluorescence anisotropy experiments. Acrylamide quenching shows the Stern-Volmer constant (K(SV)) for tetramer, monomer and unfolded SBA being 2.2, 5.0 and 14.6 M(-1), respectively. Time-resolved fluorescence studies exhibit biexponential decay with the mean lifetime increasing along tetramer (1.0 ns) to monomer (1.9 ns) to unfolded (3.6 ns). Phosphorescence studies at 77 K give more structured spectra, with two (0,0) bands at 408.6 (weak) and 413.2 nm for tetramer. However, a single (0,0) band appears at 411.8 and 407.2 nm for monomer and unfolded SBA, respectively. The exposure of hydrophobic surface in SBA monomer has been examined by 8-anilino-1-naphthalenesulfonate (ANS) binding, which shows approximately 20-fold increase in ANS fluorescence compared to that for tetramer. The mean lifetime of ANS also shows a large increase (12.0 ns) upon binding to monomer. These results may provide important insight into the role of tryptophans in the folding and association of SBA, and oligomeric proteins in general. PMID:19383525

Molla, Anisur R; Maity, Shyam S; Ghosh, Sanjib; Mandal, Dipak K

2009-07-01

277

Time-resolved Fourier transform infrared spectroscopy of the polarizable proton continua and the proton pump mechanism of bacteriorhodopsin.  

PubMed Central

Nanosecond-to-microsecond time-resolved Fourier transform infrared (FTIR) spectroscopy in the 3000-1000-cm(-1) region has been used to examine the polarizable proton continua observed in bacteriorhodopsin (bR) during its photocycle. The difference in the transient FTIR spectra in the time domain between 20 ns and 1 ms shows a broad absorption continuum band in the 2100-1800-cm(-1) region, a bleach continuum band in the 2500-2150-cm(-1) region, and a bleach continuum band above 2700 cm(-1). According to Zundel (G., J. Mol. Struct. 322:33-42), these continua appear in systems capable of forming polarizable hydrogen bonds. The formation of a bleach continuum suggests the presence of a polarizable proton in the ground state that changes during the photocycle. The appearance of a transient absorption continuum suggests a change in the polarizable proton or the appearance of new ones. It is found that each continuum has a rise time of less than 80 ns and a decay time component of approximately 300 micros. In addition, it is found that the absorption continuum in the 2100-1800-cm(-1) region has a slow rise component of 190 ns and a fast decay component of approximately 60 micros. Using these results and those of the recent x-ray structural studies of bR(570) and M(412) (H. Luecke, B. Schobert, H.T. Richter, J.-P. Cartailler, and J. K., Science 286:255-260), together with the already known spectroscopic properties of the different intermediates in the photocycle, the possible origins of the polarizable protons giving rise to these continua during the bR photocycle are proposed. Models of the proton pump are discussed in terms of the changes in these polarizable protons and the hydrogen-bonded chains and in terms of previously known results such as the simultaneous deprotonation of the protonated Schiff base (PSB) and Tyr185 and the disappearance of water molecules in the proton release channel during the proton pump process. PMID:11159463

Wang, J; El-Sayed, M A

2001-01-01

278

Carrier dynamics in bulk ZnO. II. Transient photoconductivity measured by time-resolved terahertz spectroscopy  

E-print Network

thin-film transistor,4 and electron-transport material in nanostructured solar cells.5­7 Electron to improving their perfor- mance. Carrier dynamics in ZnO bulk crystals, thin films, nano- wiresCarrier dynamics in bulk ZnO. II. Transient photoconductivity measured by time-resolved terahertz

279

Separation of indocyanine green boluses in the human brain and scalp based on time-resolved in-vivo fluorescence measurements  

NASA Astrophysics Data System (ADS)

Non-invasive detection of fluorescence from the optical tracer indocyanine green is feasible in the adult human brain when employing a time-domain technique with picosecond resolution. A fluorescence-based assessment may offer higher signal-to-noise ratio when compared to bolus tracking relying on changes in time-resolved diffuse reflectance. The essential challenge is to discriminate the fluorescence originating from the brain from contamination by extracerebral fluorescence and hence to reconstruct the bolus kinetics; however, a method to reliably perform the necessary separation is missing. We present a novel approach for the decomposition of the fluorescence contributions from the two tissue compartments. The corresponding sensitivity functions pertaining to the brain and to the extracerebral compartment are directly derived from the in-vivo measurement. This is achieved by assuming that during the initial and the late phase of bolus transit the fluorescence signal originates largely from one of the compartments. Solving the system of linear equations allows one to approximate time courses of a bolus for each compartment. We applied this method to repetitive measurements on two healthy subjects with an overall 34 boluses. A reconstruction of the bolus kinetics was possible in 62% of all cases.

Jelzow, Alexander; Wabnitz, Heidrun; Obrig, Hellmuth; Macdonald, Rainer; Steinbrink, Jens

2012-05-01

280

In-situ analysis of fruit anthocyanins by means of total internal reflectance, continuous wave and time-resolved spectroscopy  

NASA Astrophysics Data System (ADS)

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.

Zude, Manuela; Spinelli, Lorenzo; Dosche, Carsten; Torricelli, Alessandro

2009-08-01

281

Conformation Transition in Silk Protein Films Monitored by Time-Resolved Fourier Transform Infrared Spectroscopy:  Effect of Potassium Ions on Nephila Spidroin Films †  

Microsoft Academic Search

We used time-resolved Fourier transform infrared spectroscopy (FTIR) to follow a conformation transition in Nephila spidroin film from random coil and\\/or helical structures to ‚-sheet induced by the addition of KCl from 0.01 to 1.0 mol\\/L in D2O. Time series difference spectra showed parallel increases in absorption at 1620 and 1691 cm-1, indicating formation of ‚-sheet, together with a coincident

Xin Chen; David P. Knight; Zhengzhong Shao; Fritz Vollrath

2002-01-01

282

A high-throughput time-resolved mini-silicon photomultiplier with embedded fluorescence lifetime estimation in 0.13 ?m CMOS.  

PubMed

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

Tyndall, David; Rae, Bruce R; Li, David Day-Uei; Arlt, Jochen; Johnston, Abigail; Richardson, Justin A; Henderson, Robert K

2012-12-01

283

Non-invasive measurement of blood glucose level by time-resolved transmission spectroscopy: A feasibility study  

NASA Astrophysics Data System (ADS)

An optical spectroscopic method is investigated theoretically for in vivo measurement of blood glucose concentration. This method is based on dynamic dual wavelength (610 nm and 810 nm) time-resolved measurements under a condition of artificial blood flow kinetics in a human finger. The influence of glucose concentration on absorption and reduced scattering coefficients of the whole blood is simulated using the T-matrix method. The scattering centers, RBC aggregation, under the artificial — kinetics condition are modeled as spheroid. The modified parametric slopes were derived from the Laplace transformed data of the time-resolved transmittance. The results show that an appropriate selection of the Laplace parameter can lead to enhanced sensitivity for glucose measurement.

Sun, Meixiu; Chen, Nanguang

2012-03-01

284

Manifestation of electron-electron interactions in time-resolved ultrafast pump-probe spectroscopy in C60 : Theory  

Microsoft Academic Search

The electron-electron interaction (EEI) is at the core of modern physics from high-temperature superconductivity to giant magnetoresistance. Nanostructures, in general, and C60 , in particular, open a new frontier for the study of the electron correlation effect in quasi-zero-dimensional materials. Here, a direct investigation of the time-resolved pump-probe signal in C60 shows that the on-site electron-electron interaction manifests itself in

G. P. Zhang; Thomas F. George

2007-01-01

285

Manifestation of electron-electron interactions in time-resolved ultrafast pump-probe spectroscopy in C60  

Microsoft Academic Search

The electron-electron interaction EEI is at the core of modern physics from high-temperature supercon- ductivity to giant magnetoresistance. Nanostructures, in general, and C60, in particular, open a new frontier for the study of the electron correlation effect in quasi-zero-dimensional materials. Here, a direct investigation of the time-resolved pump-probe signal in C60 shows [1] that the on-site electron-electron interaction manifests itself

Guoping Zhang; Thomas F. George

2010-01-01

286

Lattice Relaxation Effect Associated with Core Holes in Ionic Crystals Studied by Time-Resolved Luminescence Spectroscopy  

NASA Astrophysics Data System (ADS)

Auger-decay-free core luminescence in RbF, CsF, CsCl, CsBr and BaF2 has been studied under monochromatic vacuum ultraviolet light excitation using a time-resolved technique. Luminescence spectra associated with core holes are carefully separated from those originating in the valence-band excitation. Based on the spectral shape and energy range of the luminescence bands, a lattice relaxation effect following the core hole creation is discussed.

Matsumoto, Tamao; Kan'no, Ken-ichi; Itoh, Minoru; Ohno, Nobuhito

1996-05-01

287

Time-resolved measurement of atomic emission enhancement by fs ns dual-pulsed laser-induced breakdown spectroscopy  

Microsoft Academic Search

Time-resolved measurement of atomic emission enhancement is performed by using a 500-fs KrF laser pulse incident upon a high density supersonic O2 gas jet, synchronized with an orthogonal ns frequency-doubled Nd:YAG laser pulse. The ultra-short pulse serves as an igniter of the gas jet, and the subsequent ns-laser pulse significantly enhances the atomic emission. Analysis shows that the contributions to

Li-Xin Yan; Yong-Sheng Zhang; Guo-Xin Zheng; Jing-Ru Liu; Jian-Ping Cheng; Min Lü

2006-01-01

288

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

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 (?2) and new non-Gaussian (?) 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

Das, Anuradha; Das, Suman; Biswas, Ranjit

2015-01-21

289

Employing time-resolved terahertz spectroscopy to analyze carrier dynamics in thin-film Cu{sub 2}ZnSn(S,Se){sub 4} absorber layers  

SciTech Connect

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.

Guglietta, Glenn W.; Baxter, Jason B. [Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States); Choudhury, Kaushik Roy; Caspar, Jonathan V. [DuPont Central Research and Development, Experimental Station, Wilmington, Delaware 19880 (United States)

2014-06-23

290

Time-resolved measurement of atomic emission enhancement by fs ns dual-pulsed laser-induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

Time-resolved measurement of atomic emission enhancement is performed by using a 500-fs KrF laser pulse incident upon a high density supersonic O2 gas jet, synchronized with an orthogonal ns frequency-doubled Nd:YAG laser pulse. The ultra-short pulse serves as an igniter of the gas jet, and the subsequent ns-laser pulse significantly enhances the atomic emission. Analysis shows that the contributions to the enhancement effect are made mainly by the bremsstrahlung radiation and cascade ionization.

Yan, Li-Xin; Zhang, Yong-Sheng; Zheng, Guo-Xin; Liu, Jing-Ru; Cheng, Jian-Ping; Lü, Min

2006-10-01

291

Direct on-strip analysis of size- and time-resolved aerosol impactor samples using laser induced fluorescence spectra excited at 263 and 351 nm.  

PubMed

We report a novel atmospheric aerosol characterization technique, in which dual wavelength UV laser induced fluorescence (LIF) spectrometry marries an eight-stage rotating drum impactor (RDI), namely UV-LIF-RDI, to achieve size- and time-resolved analysis of aerosol particles on-strip. The UV-LIF-RDI technique measured LIF spectra via direct laser beam illumination onto the particles that were impacted on a RDI strip with a spatial resolution of 1.2mm, equivalent to an averaged time resolution in the aerosol sampling of 3.6 h. Excited by a 263 nm or 351 nm laser, more than 2000 LIF spectra within a 3-week aerosol collection time period were obtained from the eight individual RDI strips that collected particles in eight different sizes ranging from 0.09 to 10 ?m in Djibouti. Based on the known fluorescence database from atmospheric aerosols in the US, the LIF spectra obtained from the Djibouti aerosol samples were found to be dominated by fluorescence clusters 2, 5, and 8 (peaked at 330, 370, and 475 nm) when excited at 263 nm and by fluorescence clusters 1, 2, 5, and 6 (peaked at 390 and 460 nm) when excited at 351 nm. Size- and time-dependent variations of the fluorescence spectra revealed some size and time evolution behavior of organic and biological aerosols from the atmosphere in Djibouti. Moreover, this analytical technique could locate the possible sources and chemical compositions contributing to these fluorescence clusters. Advantages, limitations, and future developments of this new aerosol analysis technique are also discussed. PMID:24745745

Wang, Chuji; Pan, Yong-Le; James, Deryck; Wetmore, Alan E; Redding, Brandon

2014-04-11

292

Trp aporepressor engineered for fluorescence spectroscopy  

NASA Astrophysics Data System (ADS)

The tryptophan repressor from Escherichia coli binds to the trp operator in the presence of L- tryptophan, thereby inhibiting the biosynthesis of L-tryptophan. Site-directed mutagenesis was used to change tryptophan-19 and tryptophan-99 to leucine and methionine, respectively. This mutant protein without tryptophan in its amino acid sequence has wild-type repressor activity and is a suitable model for fluorescence studies of corepressor binding. Both steady-state and time-resolved fluorescence spectroscopy have been used to compare the binding of L- tryptophan, indole-3-propionic acid, indole-3-butyric acid, and indole. In all cases, binding to the mutant aporepressor results in a large blue shift and a change in the intensity of the ligand fluorescence. The decay of the total fluorescence intensity from the complex indicates the presence of three distinct bound states of the ligand. The distribution of ligand binding modes is influenced by the substituent at the 3-position of the indole ring. The rotational correlation time of the complexes formed with L-tryptophan or indole-3-propionic acid indicate that the protein is present as a dimer, whereas with indole or indole-3-butyric acid the correlation times are much lower, suggesting that the protein is present as a monomer.

Millar, David P.; Hochstrasser, Remo A.; Chapman, David; Youderian, Philip

1992-04-01

293

Steady-state and time-resolved fluorescence studies of reverse micelles in liquids and supercritical solvents  

SciTech Connect

The authors investigate the effects of temperature, salt concentration, and water loading on the internal dynamics of AOT Aerosol-OT, sodium bis (2-ethylhexyl sulfosuccinate) micelles in liquid heptane, using ANS-like (anilino-naphthalene sulfate) fluorescent probes. The important results from these experiments are that: (1) the molecular geometry of the probe is the predominant factor controlling partitioning even at high water loadings; (2) the photophysics of ANS is strongly dependent on the water content and temperature and corresponds to changes in local polarity and viscosity; (3) addition of electrolytes changes the dynamic fluorescence which is in turn related to the changes in internal microenvironments; and (4) a nanosecond solvent relaxation process occurs within reverse micelles. It was wondered if the continuous phase (alkane) density could be used to control the internal dynamics within a reverse micelle. To answer this question, research focused on: (1) the effects of water loading, temperature, and fluid density on solute partitioning and determination of the density effects on micellar aggregates; (2) the effects of solute structure on the distribution of probe molecules within reverse micelles; and (3) the effects of fluid density, water concentration, and temperature on the reorganizational dynamics within AOT reverse micelles. Simple thermodynamic measurements and nanosecond solvent relaxation experiments are used to account for this partitioning and water reorganization in AOT reverse micelles, respectively. Results on excited-state deprotonation reactions in AOT reverse micelles maintained in sub-critical propane, provides a useful model for density-controlled deprotonation reactions within reverse micelles. Preliminary work shows that the continuous phase density can be used to control reactions within reverse micelles formed in near- and supercritical alkanes.

Zhang, Jing.

1992-01-01

294

Time-Resolved Surface-Enhanced IR-Absorption Spectroscopy of Direct Electron Transfer to Cytochrome c Oxidase from R. sphaeroides  

PubMed Central

Time-resolved surface-enhanced IR-absorption spectroscopy triggered by electrochemical modulation has been performed on cytochrome c oxidase from Rhodobacter sphaeroides. Single bands isolated from a broad band in the amide I region using phase-sensitive detection were attributed to different redox centers. Their absorbances changing on the millisecond timescale could be fitted to a model based on protonation-dependent chemical reaction kinetics established previously. Substantial conformational changes of secondary structures coupled to redox transitions were revealed. PMID:24359742

Schwaighofer, Andreas; Steininger, Christoph; Hildenbrandt, David M.; Srajer, Johannes; Nowak, Christoph; Knoll, Wolfgang; Naumann, Renate L.C.

2013-01-01

295

Time-Resolved IR-Absorption Spectroscopy of Hot-Electron Dynamics in Satellite and Upper Conduction Bands in GaP  

NASA Technical Reports Server (NTRS)

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.

Cavicchia, M. A.; Alfano, R. R.

1995-01-01

296

Investigation of verbal and visual working memory by multi-channel time-resolved functional near-infrared spectroscopy  

NASA Astrophysics Data System (ADS)

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.

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

297

Tracking Local Conformational Changes of Ribonuclease A Using Picosecond Time-Resolved Fluorescence of the Six Tyrosine Residues  

PubMed Central

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 (?1 = 1.7 ns, ?2 = 180 ps, and ?3 = 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 ?1 to Tyr-76 (R = 12.8 Å), ?2 to Tyr-115 (R = 6.9 Å), and ?3 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

Noronha, Melinda; Lima, João C.; Paci, Emanuele; Santos, Helena; Maçanita, António L.

2007-01-01

298

Time-Resolved FT-IR Spectroscopy of CO Hydrogenation overSupported Ru Catalyst at 700K  

SciTech Connect

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.

Wasylenko, Walter; Frei, Heinz

2006-02-13

299

A digital spectrometer approach to obtaining multiple time-resolved gamma-ray spectra for pulsed spectroscopy  

NASA Astrophysics Data System (ADS)

Neutron-induced gamma-ray emission and its detection using a pulsed neutron generator system is an established analytical technique for quantitative multi-element analysis. Traditional gamma-ray spectrometers used for this type of analysis are normally operated either in coincidence mode - for counting prompt gamma-rays following inelastic neutron scattering (INS) events when the neutron generator is ON, or in anti-coincidence mode - for counting prompt gamma-rays from thermal neutron capture (TNC) processes when the neutron generator is OFF. We have developed a digital gamma-ray spectrometer for concurrently measuring both the INS and TNC gamma-rays using a 14 MeV pulsed neutron generator. The spectrometer separates the gamma-ray counts into two independent spectra together with two separate sets of counting statistics based on the external gate level. Because the TNC gamma-ray yields are time dependent, additional accuracy in analyzing the data can be obtained by acquiring multiple time-resolved gamma-ray spectra at finer time intervals than simply ON or OFF. For that purpose we are developing a multi-gating system that will allow gamma-ray spectra to be acquired concurrently in real time with up to 16 time slots. The conceptual system design is presented, especially focusing on considerations for tracking counting statistics in multiple time slots and on the placement of pulse heights into multiple spectra in real time.

Tan, H.; Mitra, S.; Fallu-Labruyere, A.; Hennig, W.; Chu, Y. X.; Wielopolski, L.; Warburton, W. K.

2007-10-01

300

Probing the interactions of hemoglobin with antioxidant flavonoids via fluorescence spectroscopy and molecular modeling studies  

Microsoft Academic Search

Steady state and time resolved fluorescence spectroscopy, combined with molecular modeling computations, have been used to explore the interactions of two therapeutically important flavonoids, fisetin (3,7,3?,4?-OH-flavone) and 3-hydroxyflavone (3-HF), with normal human hemoglobin (HbA). Distinctive ‘two color’ fluorescence signatures and fairly high fluorescence anisotropy (r=0.12–0.28) of fisetin and 3-HF reveal their specific interactions with HbA. Binding constants estimated from the

Sudip Chaudhuri; Sandipan Chakraborty; Pradeep K. Sengupta

2011-01-01

301

Structural characterisation and time-resolved luminescence spectroscopy of nanocrystalline X2-Lu2SiO5:Pr3+ powders  

NASA Astrophysics Data System (ADS)

Nanocrystalline X2 lutetium oxyorthosilicate (X2-Lu2SiO5) doped with Pr3+ was synthesized by the sol-gel route. The product was characterised with X-ray diffraction and transmission electron microscopy to confirm the crystal structure and analyse the morphology on the nanoscale. The luminescence spectroscopy and the excited state dynamics were investigated by time-resolved VUV spectroscopy using synchrotron radiation. Fast and efficient host-to-impurity energy transfer was observed. The temperature dependence of the decay dynamics was investigated. In view of a potential application as a scintillator, the X-ray excited luminescence of the X2-Lu2SiO5 nanopowder was studied. Excitation and relaxation processes occurring in nanocrystalline Lu2SiO5:Pr3+ are analysed and discussed.

Trevisani, M.; Ivanovskikh, K. V.; Grillet, N.; Piccinelli, F.; Bettinelli, M.

2013-04-01

302

Time-resolved plasma spectroscopy of thin foils heated by a relativistic-intensity short-pulse laser.  

PubMed

Time-resolved K-shell x-ray spectra are recorded from sub-100 nm aluminum foils irradiated by 150-fs laser pulses at relativistic intensities of Ilambda(2)=2 x 10(18) W microm(2)/cm(2). The thermal penetration depth is greater than the foil thickness in these targets so that uniform heating takes place at constant density before hydrodynamic motion occurs. The high-contrast, high-intensity laser pulse, broad spectral band, and short time resolution utilized in this experiment permit a simplified interpretation of the dynamical evolution of the radiating matter. The observed spectrum displays two distinct phases. At early time, < or =500 fs after detecting target emission, a broad quasicontinuous spectral feature with strong satellite emission from multiply excited levels is seen. At a later time, the He-like resonance line emission is dominant. The time-integrated data is in accord with previous studies with time resolution greater than 1 ps. The early time satellite emission is shown to be a signature of an initial large area, high density, low-temperature plasma created in the foil by fast electrons accelerated by the intense radiation field in the laser spot. We conclude that, because of this early time phenomenon and contrary to previous predictions, a short, high-intensity laser pulse incident on a thin foil does not create a uniform hot and dense plasma. The heating mechanism has been studied as a function of foil thickness, laser pulse length, and intensity. In addition, the spectra are found to be in broad agreement with a hydrodynamic expansion code postprocessed by a collisional-radiative model based on superconfiguration average rates and on the unresolved transition array formalism. PMID:12513417

Audebert, P; Shepherd, R; Fournier, K B; Peyrusse, O; Price, D; Lee, R W; Springer, P; Gauthier, J-C; Klein, L

2002-12-01

303

Time-resolved x-ray photoelectron spectroscopy techniques for real-time studies of interfacial charge transfer dynamics  

SciTech Connect

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.

Shavorskiy, Andrey; Hertlein, Marcus; Guo Jinghua; Tyliszczak, Tolek [Advanced Light Source, Lawrence Berkeley National Laboratory (United States); Cordones, Amy; Vura-Weis, Josh [Department of Chemistry, University of California Berkeley (United States); Siefermann, Katrin; Slaughter, Daniel; Sturm, Felix; Weise, Fabian; Khurmi, Champak; Belkacem, Ali; Weber, Thorsten; Gessner, Oliver [Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory (United States); Bluhm, Hendrik [Chemical Sciences Division, Lawrence Berkeley National Laboratory (United States); Strader, Matthew; Cho, Hana; Coslovich, Giacomo; Kaindl, Robert A. [Materials Sciences Division, Lawrence Berkeley National Laboratory (United States); Lin, Ming-Fu [Department of Chemistry, University of California Berkeley (United States); Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory (United States); and others

2013-04-19

304

Time-resolved x-ray photoelectron spectroscopy techniques for real-time studies of interfacial charge transfer dynamics  

NASA Astrophysics Data System (ADS)

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.

Shavorskiy, Andrey; Cordones, Amy; Vura-Weis, Josh; Siefermann, Katrin; Slaughter, Daniel; Sturm, Felix; Weise, Fabian; Bluhm, Hendrik; Strader, Matthew; Cho, Hana; Lin, Ming-Fu; Bacellar, Camila; Khurmi, Champak; Hertlein, Marcus; Guo, Jinghua; Tyliszczak, Tolek; Prendergast, David; Coslovich, Giacomo; Robinson, Joseph; Kaindl, Robert A.; Schoenlein, Robert W.; Belkacem, Ali; Weber, Thorsten; Neumark, Daniel M.; Leone, Stephen R.; Nordlund, Dennis; Ogasawara, Hirohito; Nilsson, Anders R.; Krupin, Oleg; Turner, Joshua J.; Schlotter, William F.; Holmes, Michael R.; Heimann, Philip A.; Messerschmidt, Marc; Minitti, Michael P.; Beye, Martin; Gul, Sheraz; Zhang, Jin Z.; Huse, Nils; Gessner, Oliver

2013-04-01

305

Development of a time-resolved fluorescence immunoassay for herpes simplex virus type 1 and type 2 IgG antibodies.  

PubMed

Enzyme-linked immunosorbent assays (ELISA) specific for anti-HSV glycoprotein G (gG) are most commonly used in the clinical diagnosis of HSV infection. But most of them are qualitative and with narrow detection ranges. A novel time-resolved fluoroimmunoassay (TRFIA) methodology was developed for the quantitative determination of HSV IgG in human serum. The assay was based on an indirect immunoassay format, and performed in 96-well microtiter plates. HSV-1 and HSV-2 were used as the coating antigens. Eu(3+) -labeled goat anti-(human IgG) polyclonal antibodies were used as tracers. The fluorescence intensity of each well was measured and serum HSV IgG levels quantified against a calibration curve. The detection range of the novel TRFIA was between 5 and 500?AU/mL. Assay sensitivity was 0.568?AU/mL. The intra- and inter-assay coefficients of variation were 0.59-3.63% and 3.65-6.81%, respectively. Analytical recovery, dilution tests and serum panel tests were performed using TRFIA and the results proved satisfactory. There were no statistically significant differences in sensitivity and specificity between the TRFIA and commercial ELISAs. An effective, sensitive and accurate quantitative HSV type 1 and type 2 IgG TRFIA was successfully developed and provided diagnostic value in clinical use. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25377426

Liang, Qian-Ni; Zhou, Jian-Wei; Liu, Tian-Cai; Lin, Guan-Feng; Dong, Zhi-Ning; Chen, Zhen-Hua; Chen, Juan-Juan; Wu, Ying-Song

2014-11-01

306

Pressure effects on the lateral distribution of cholesterol in lipid bilayers: a time-resolved spectroscopy study.  

PubMed Central

The effects of hydrostatic pressure and temperature on the phase behavior and physical properties of the binary mixture palmitoyloleoylphosphatidylcholine/cholesterol, over the 0-40 molar % range of cholesterol compositions, were determined from the changes in the fluorescence lifetime distribution and anisotropy decay parameters of the natural lipid trans-parinaric acid (t-PnA). Pressurized samples were excited with a Ti-sapphire subpicosecond laser, and fluorescence decays were analyzed by the quantified maximum entropy method. Above the transition temperature (T(T) = -5 degrees C), at atmospheric pressure, two liquid-crystalline phases, alpha and beta, are formed in this system. At each temperature and cholesterol concentration below the transition pressure, the fluorescence lifetime distribution pattern of t-PnA was clearly modulated by the pressure changes. Pressure increased the fraction of the liquid-ordered beta-phase and its order parameter, but it decreased the amount of cholesterol in this phase. Palmitoyloleoylphosphatidylcholine/cholesterol phase diagrams were also determined as a function of temperature and hydrostatic pressure. PMID:9545048

Tauc, P; Mateo, C R; Brochon, J C

1998-01-01

307

Hydrogen transfer dynamics in a photoexcited phenol/ammonia (1:3) cluster studied by picosecond time-resolved UV-IR-UV ion dip spectroscopy  

NASA Astrophysics Data System (ADS)

The picosecond time-resolved IR spectra of phenol/ammonia (1:3) cluster were measured by UV-IR-UV ion dip spectroscopy. The time-resolved IR spectra of the reaction products of the excited state hydrogen transfer were observed. From the different time evolution of two vibrational bands at 3180 and 3250cm-1, it was found that two isomers of hydrogenated ammonia radical cluster •NH4(NH3)2 coexist in the reaction products. The time evolution was also measured in the near-IR region, which corresponds to 3p-3s Rydberg transition of •NH4(NH3)2; a clear wavelength dependence was found. From the observed results, we concluded that (1) there is a memory effect of the parent cluster, which initially forms a metastable product, •NH4-NH3-NH3, and (2) the metastable product isomerizes successively to the most stable product, NH3-•NH4-NH3. The time constant for OH cleaving, the isomerization, and its back reaction were determined by rate-equation analysis to be 24, 6, and 9ps, respectively.

Ishiuchi, Shun-ichi; Sakai, Makoto; Daigoku, Kota; Hashimoto, Kenro; Fujii, Masaaki

2007-12-01

308

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)

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.

Mo, Weirong; Chan, Tryphena S. S.; Chen, Ling; Chen, Nanguang

2009-11-01

309

Implementation of Time-Resolved Step-Scan Fourier Transform Infrared (FT-IR) Spectroscopy Using a kHz Repetition Rate Pump Laser  

PubMed Central

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

MAGANA, DONNY; PARUL, DZMITRY; DYER, R. BRIAN; SHREVE, ANDREW P.

2011-01-01

310

Applications of immunomagnetic capture and time-resolved fluorescence to detect outbreak Escherichia coli O157 and Salmonella in alfalfa sprouts  

NASA Astrophysics Data System (ADS)

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.

Tu, Shu-I.; Gordon, Marsha; Fett, William F.; Gehring, Andrew G.; Irwin, Peter L.

2004-03-01

311

Single-State Electronic Structure Measurements Using Time-Resolved X-Ray Laser Induced Photoelectron Spectroscopy  

Microsoft Academic Search

We demonstrate single-shot x-ray laser induced time-of-flight photoelectron spectroscopy on semiconductor and metal surfaces with picosecond time resolution. The LLNL COMET compact tabletop x-ray laser source provides the necessary high photon flux (>10¹²\\/pulse), monochromaticity, picosecond pulse duration, and coherence for probing ultrafast changes in the city, chemical and electronic structure of these materials. Static valence band and shallow core-level photoemission

A J Nelson; J Dunn; T van Buuren

2004-01-01

312

Femtosecond time-resolved photoelectron spectroscopy with a vacuum-ultraviolet photon source based on laser high-order harmonic generation  

SciTech Connect

A laser-based tabletop approach to femtosecond time-resolved photoelectron spectroscopy with photons in the vacuum-ultraviolet (VUV) energy range is described. The femtosecond VUV pulses are produced by high-order harmonic generation (HHG) of an amplified femtosecond Ti:sapphire laser system. Two generations of the same setup and results from photoelectron spectroscopy in the gas phase are discussed. In both generations, a toroidal grating monochromator was used to select one harmonic in the photon energy range of 20-30 eV. The first generation of the setup was used to perform photoelectron spectroscopy in the gas phase to determine the bandwidth of the source. We find that our HHG source has a bandwidth of 140 {+-} 40 meV. The second and current generation is optimized for femtosecond pump-probe photoelectron spectroscopy with high flux and a small spot size at the sample of the femtosecond probe pulses. The VUV radiation is focused into the interaction region with a toroidal mirror to a spot smaller than 100 x 100 {mu}m{sup 2} and the flux amounts to 10{sup 10} photons/s at the sample at a repetition rate of 1 kHz. The duration of the monochromatized VUV pulses is determined to be 120 fs resulting in an overall pump-probe time resolution of 135 {+-} 5 fs. We show how this setup can be used to map the transient valence electronic structure in molecular dissociation.

Wernet, Philippe; Gaudin, Jerome; Godehusen, Kai; Schwarzkopf, Olaf; Eberhardt, Wolfgang [Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin (Germany)

2011-06-15

313

Atomic resolution mapping of the excited-state electronic structure of Cu2O with time-resolved x-ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

We have used time-resolved soft x-ray spectroscopy to investigate the electronic structure of optically excited cuprous oxide at the OK edge and the CuL3 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 Cu3d and O2p orbital contributions. The 2.1 eV optical band gap of Cu2O significantly exceeds the one eV shift in the CuL3 - and OK -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.

Hillyard, P. W.; Kuchibhatla, S. V. N. T.; Glover, T. E.; Hertlein, M. P.; Huse, N.; Nachimuthu, P.; Saraf, L. V.; Thevuthasan, S.; Gaffney, K. J.

2009-09-01

314

Time-resolved soft-x-ray spectroscopy of a magnetic octupole transition in nickel-like xenon, cesium, and barium ions  

SciTech Connect

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.

Trabert, E; Beiersdorfer, P; Brown, G V; Boyce, K; Kelley, R L; Kilbourne, C A; Porter, F S; Szymkowiak, A

2005-11-11

315

Atomic resolution mapping of the excited-state electronic structure of Cu2O with time-resolved x-ray absorption spectroscopy  

SciTech Connect

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.

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

316

Application of External-Cavity Quantum Cascade Infrared Lasers to Nanosecond Time-Resolved Infrared Spectroscopy of Condensed-Phase Samples Following Pulse Radiolysis  

SciTech Connect

Pulse radiolysis, utilizing short pulses of high-energy electrons from accelerators, is a powerful method for rapidly generating reduced or oxidized species and other free radicals in solution. Combined with fast time-resolved spectroscopic detection (typically in the ultraviolet/visible/near-infrared), it is invaluable for monitoring the reactivity of species subjected to radiolysis on timescales ranging from picoseconds to seconds. However, it is often difficult to identify the transient intermediates definitively due to a lack of structural information in the spectral bands. Time-resolved vibrational spectroscopy offers the structural specificity necessary for mechanistic investigations but has received only limited application in pulse radiolysis experiments. For example, time-resolved infrared (TRIR) spectroscopy has only been applied to a handful of gas-phase studies, limited mainly by several technical challenges. We have exploited recent developments in commercial external-cavity quantum cascade laser (EC-QCL) technology to construct a nanosecond TRIR apparatus that has allowed, for the first time, TRIR spectra to be recorded following pulse radiolysis of condensed-phase samples. Near single-shot sensitivity of DeltaOD <1 x 10(-3) has been achieved, with a response time of <20 ns. Using two continuous-wave EC-QCLs, the current apparatus covers a probe region from 1890-2084 cm(-1), and TRIR spectra are acquired on a point-by-point basis by recording transient absorption decay traces at specific IR wavelengths and combining these to generate spectral time slices. The utility of the apparatus has been demonstrated by monitoring the formation and decay of the one-electron reduced form of the CO(2) reduction catalyst, [Re(I)(bpy)(CO)(3)(CH(3)CN)](+), in acetonitrile with nanosecond time resolution following pulse radiolysis. Characteristic red-shifting of the nu(CO) IR bands confirmed that one-electron reduction of the complex took place. The availability of TRIR detection with high sensitivity opens up a wide range of mechanistic pulse radiolysis investigations that were previously difficult or impossible to perform with transient UV/visible detection.

Grills, D.C.; Cook, A.R.; Fujita, E.; George, M.W.; Miller, J.R.; Preses, J.M.; Wishart, J.F.

2010-06-01

317

Subunit-Selective Interrogation of CO Recombination in Carbonmonoxy Hemoglobin by Isotope-Edited Time-resolved Resonance Raman Spectroscopy  

PubMed Central

Hemoglobin is an allosteric tetrameric protein made up of ?? hetero-dimers. The ? and ? chains are similar, but are chemically and structurally distinct. To investigate dynamical differences between the chains, we have prepared tetramers in which the chains are isotopically distinguishable, via reconstitution with 15N-heme. Ligand recombination and heme structural evolution, following HbCO dissociation, was monitored with chain selectivity by resonance Raman (RR) spectroscopy. For ? but not for ? chains, the frequency of the ?4 porphyrin breathing mode increased on the microsecond time scale. This increase is a manifestation of proximal tension in the Hb T-state, and its time course is parallel to the formation of T contacts, as determined previously by UVRR spectroscopy. Despite the localization of proximal constraint in the ? chains, geminate recombination was found to be equally probable in the two chains, with yields of 39 ± 2 %. We discuss the possibility that this equivalence is coincidental, in the sense that it arises from the evolutionary pressure for cooperativity, or that it reflects mechanical coupling across the ?? interface, evidence for which has emerged from UVRR studies of site-mutants. PMID:19245215

Balakrishnan, Gurusamy; Zhao, Xiaojie; Podstawska, Edyta; Proniewicz, Leonard M.; Kincaid, James R.; Spiro, Thomas G.

2009-01-01

318

On time resolved gas temperature measurements in a pulsed dc plasma using quantum cascade laser absorption spectroscopy  

NASA Astrophysics Data System (ADS)

With a time resolution of 33 µs, the gas temperature in a pulsed dc air plasma admixed with 0.8% NO has been measured by quantum cascade laser absorption spectroscopy (QCLAS). For this purpose, the temperature dependent intensity ratios of two absorption structures of NO at 1900 cm-1 (5.26 µm) have been used. The QCLAS system worked in the Intra Pulse Mode with a pulse repetition frequency of 30 kHz leading to a spectrum recorded each 33 µs. In a low pressure discharge, the influence of nonlinear absorption phenomena causing strong distorted absorption structures of NO has been taken into account by a calibration routine based on tabulated line strengths. Different mean plasma currents have been applied to the discharge leading to gas temperature values ranging from about 300 K up to about 500 K.

Hübner, M.; Marinov, D.; Guaitella, O.; Rousseau, A.; Röpcke, J.

2012-11-01

319

Homogeneous Time-Resolved Fluorescence-Based Assay to Monitor Extracellular Signal-Regulated Kinase Signaling in a High-Throughput Format  

PubMed Central

The extracellular signal-regulated kinases (ERKs) are key components of multiple important cell signaling pathways regulating diverse biological responses. This signaling is characterized by phosphorylation cascades leading to ERK1/2 activation and promoted by various cell surface receptors including G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs). We report the development of a new cell-based Phospho-ERK1/2 assay (designated Phospho-ERK), which is a sandwich proximity-based assay using the homogeneous time-resolved fluorescence technology. We have validated the assay on endogenously expressed ERK1/2 activated by the epidermal growth factor as a prototypical RTK, as well as various GPCRs belonging to different classes and coupling to different heterotrimeric G proteins. The assay was successfully miniaturized in 384-well plates using various cell lines endogenously, transiently, or stably expressing the different receptors. The validation was performed for agonists, antagonists, and inhibitors in dose–response as well as kinetic analysis, and the signaling and pharmacological properties of the different receptors were reproduced. Furthermore, the determination of a Z?-factor value of 0.7 indicates the potential of the Phospho-ERK assay for high-throughput screening of compounds that may modulate ERK1/2 signaling. Finally, our study is of great interest in the current context of investigating ERK1/2 signaling with respect to the emerging concepts of biased ligands, G protein-dependent/independent ERK1/2 activation, and functional transactivation between GPCRs and RTKs, illustrating the importance of considering the ERK1/2 pathway in cell signaling PMID:25002860

Ayoub, Mohammed Akli; Trebaux, Julien; Vallaghe, Julie; Charrier-Savournin, Fabienne; Al-Hosaini, Khaled; Gonzalez Moya, Arturo; Pin, Jean-Philippe; Pfleger, Kevin D. G.; Trinquet, Eric

2014-01-01

320

Surface vibrational relaxation of N2 studied by CO2 titration with time-resolved quantum cascade laser absorption spectroscopy  

NASA Astrophysics Data System (ADS)

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 ?3 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 ?1 = (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, ?1 = (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.

Marinov, D.; Lopatik, D.; Guaitella, O.; Hübner, M.; Ionikh, Y.; Röpcke, J.; Rousseau, A.

2012-05-01

321

Spatial density profile of electrons near the LaAlO{sub 3}/SrTiO{sub 3} heterointerface revealed by time-resolved photoluminescence spectroscopy  

SciTech Connect

The depth profile of the electron density near the LaAlO{sub 3}/SrTiO{sub 3} heterointerface has been studied by means of time-resolved photoluminescence (PL) spectroscopy. A broad blue PL band is observed at 2.9?eV, originating from the two-carrier radiative recombination of interface-induced electrons and photoexcited holes. The PL lifetime of LaAlO{sub 3}/SrTiO{sub 3} heterointerface is dominated by the three-carrier Auger recombination of electrons and holes and is sensitive to electron density. We tuned the probing depth by changing the excitation photon energy and evaluated the carrier-density profile using the relation between the carrier density and the PL lifetime. Our non-contact probe method based on PL spectroscopy indicates that the carriers are confined within several nanometers in depth near the LaAlO{sub 3}/SrTiO{sub 3} heterostructures.

Yamada, Yasuhiro, E-mail: yamada.yasuhiro.6c@kyoto-u.ac.jp; Kanemitsu, Yoshihiko [Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Sato, Hiroki K. [SLAC National Accelerator Laboratory, Stanford Institute for Materials and Energy Sciences, Menlo Park, California 94025 (United States); Department of Advanced Materials Science, The University of Tokyo, Kashiwa, Chiba 277-8561 (Japan); Hikita, Yasuyuki [SLAC National Accelerator Laboratory, Stanford Institute for Materials and Energy Sciences, Menlo Park, California 94025 (United States); Hwang, Harold Y. [SLAC National Accelerator Laboratory, Stanford Institute for Materials and Energy Sciences, Menlo Park, California 94025 (United States); Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305 (United States)

2014-04-14

322

Sensitivity correction for the influence of the fat layer on muscle oxygenation and estimation of fat thickness by time-resolved spectroscopy  

NASA Astrophysics Data System (ADS)

Near-infrared spectroscopy (NIRS) has been used for noninvasive assessment of oxygenation in living tissue. For muscle measurements by NIRS, the measurement sensitivity to muscle (S) is strongly influenced by fat thickness (FT). In this study, we investigated the influence of FT and developed a correction curve for S with an optode distance (3 cm) sufficiently large to probe the muscle. First, we measured the hemoglobin concentration in the forearm (n=36) and thigh (n=6) during arterial occlusion using a time-resolved spectroscopy (TRS) system, and then FT was measured by ultrasound. The correction curve was derived from the ratio of partial mean optical path length of the muscle layer to observed mean optical path length . There was good correlation between FT and at rest, and could be used to estimate FT. The estimated FT was used to validate the correction curve by measuring the forearm blood flow (FBF) by strain-gauge plethysmography (SGP_FBF) and TRS (TRS_FBF) simultaneously during a reactive hyperemia test with 16 volunteers. The corrected TRS_FBF results were similar to the SGP_FBF results. This is a simple method for sensitivity correction that does not require use of ultrasound.

Ohmae, Etsuko; Nishio, Shinichiro; Oda, Motoki; Suzuki, Hiroaki; Suzuki, Toshihiko; Ohashi, Kyoichi; Koga, Shunsaku; Yamashita, Yutaka; Watanabe, Hiroshi

2014-06-01

323

Photodissociation of gaseous CH3COSH at 248 nm by time-resolved Fourier-transform infrared emission spectroscopy: Observation of three dissociation channels  

NASA Astrophysics Data System (ADS)

Upon one-photon excitation at 248 nm, gaseous CH3C(O)SH is dissociated following three pathways with the products of (1) OCS + CH4, (2) CH3SH + CO, and (3) CH2CO + H2S that are detected using time-resolved Fourier-transform infrared emission spectroscopy. The excited state 1(nO, ?*CO) has a radiative lifetime of 249 ± 11 ns long enough to allow for Ar collisions that induce internal conversion and enhance the fragment yields. The rate constant of collision-induced internal conversion is estimated to be 1.1 × 10-10 cm3 molecule-1 s-1. Among the primary dissociation products, a fraction of the CH2CO moiety may undergo further decomposition to CH2 + CO, of which CH2 is confirmed by reaction with O2 producing CO2, CO, OH, and H2CO. Such a secondary decomposition was not observed previously in the Ar matrix-isolated experiments. The high-resolution spectra of CO are analyzed to determine the ro-vibrational energy deposition of 8.7 ± 0.7 kcal/mol, while the remaining primary products with smaller rotational constants are recognized but cannot be spectrally resolved. The CO fragment detected is mainly ascribed to the primary production. A prior distribution method is applied to predict the vibrational distribution of CO that is consistent with the experimental findings.

Hu, En-Lan; Tsai, Po-Yu; Fan, He; Lin, King-Chuen

2013-01-01

324

Calibration of diffuse correlation spectroscopy with a time-resolved near-infrared technique to yield absolute cerebral blood flow measurements  

PubMed Central

A primary focus of neurointensive care is the prevention of secondary brain injury, mainly caused by ischemia. A noninvasive bedside technique for continuous monitoring of cerebral blood flow (CBF) could improve patient management by detecting ischemia before brain injury occurs. A promising technique for this purpose is diffuse correlation spectroscopy (DCS) since it can continuously monitor relative perfusion changes in deep tissue. In this study, DCS was combined with a time-resolved near-infrared technique (TR-NIR) that can directly measure CBF using indocyanine green as a flow tracer. With this combination, the TR-NIR technique can be used to convert DCS data into absolute CBF measurements. The agreement between the two techniques was assessed by concurrent measurements of CBF changes in piglets. A strong correlation between CBF changes measured by TR-NIR and changes in the scaled diffusion coefficient measured by DCS was observed (R2 = 0.93) with a slope of 1.05 ± 0.06 and an intercept of 6.4 ± 4.3% (mean ± standard error). PMID:21750781

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

2011-01-01

325

Statistical Time-Resolved Spectroscopy: A higher fraction of short-period binaries for metal-rich F-type dwarfs in SDSS  

E-print Network

Stellar multiplicity lies at the heart of many problems in modern astrophysics, including the physics of star formation, the observational properties of unresolved stellar populations, and the rates of interacting binaries such as cataclysmic variables, X-ray binaries, and Type Ia supernovae. However, little is known about the stellar multiplicity of field stars in the Milky Way, in particular about the differences in the multiplicity characteristics between metal-rich disk stars and metal-poor halo stars. In this study we perform a statistical analysis of ~15,000 F-type dwarf stars in the Milky Way through time-resolved spectroscopy with the sub-exposures archived in the Sloan Digital Sky Survey. We obtain absolute radial velocity measurements through template cross-correlation of individual sub-exposures with temporal baselines varying from minutes to years. These sparsely sampled radial velocity curves are analyzed using Markov chain Monte Carlo techniques to constrain the very short-period binary fraction...

Hettinger, T; Strader, J; Bickerton, S J; Beers, T C

2015-01-01

326

Solid-phase nano-extraction and laser-excited time-resolved Shpol'skii spectroscopy for the analysis of polycyclic aromatic hydrocarbons in drinking water samples.  

PubMed

A unique method for screening polycyclic aromatic hydrocarbons in drinking water samples is reported. Water samples (500 microl) are mixed and centrifuged with 950 microl of a commercial solution of 20 nm gold nanoparticles for pollutants extraction. The precipitate is treated with 2 microl of 1-pentanethiol and 48 microl of n-octane, and the supernatant is then analyzed via laser-excited time-resolved Shpol'skii spectroscopy. Fifteen priority pollutants are directly determined at liquid helium temperature (4.2 K) with the aid of a cryogenic fiber-optic probe. Unambiguous pollutant determination is carried out via spectral and lifetime analysis. Limits of detection are at the parts-per-trillion level. Analytical recoveries are similar to those obtained via high-performance liquid chromatography. The simplicity of the experimental procedure, use of microliters of organic solvent, short analysis time, selectivity, and excellent analytical figures of merit demonstrate the advantages of this environmentally friendly approach for routine analysis of numerous samples. PMID:19100235

Wang, Huiyong; Yu, Shenjiang; Campiglia, Andres D

2009-02-15

327

Analysis of time resolved femtosecond and femtosecond/picosecond coherent anti-Stokes Raman spectroscopy: Application to toluene and Rhodamine 6G  

NASA Astrophysics Data System (ADS)

The third-order polarization for coherent anti-Stokes Raman scattering (CARS) from a pure state is described by 48 terms in perturbation theory, but only 4 terms satisfy the rotating wave approximation. They are represented by Feynman dual time-line diagrams and four-wave mixing energy level diagrams. In time-resolved (tr) fs and fs/ps CARS from the ground vibrational state, one resonant diagram, which is the typical CARS term, with three field interactions—pump, Stokes, followed by probe—on the ket is dominant. Using the separable, displaced harmonic oscillators approximation, an analytic result is obtained for the four-time correlation function in the CARS third-order polarization. Dlott's phenomenological expression for off-resonance CARS from the ground vibrational state is derived using a three-state model. We calculated the tr fs and fs/ps CARS for toluene and Rhodamine 6G (R6G), initially in the ground vibrational state, to compare with experimental results. The observed vibrational features and major peaks for both tr fs and fs/ps CARS, from off-resonance (for toluene) to resonance (for R6G) pump wavelengths, can be well reproduced by the calculations. The connections between fs/ps CARS, fs stimulated Raman spectroscopy, and impulsive stimulated scattering for toluene and R6G are discussed.

Niu, Kai; Lee, Soo-Y.

2012-02-01

328

Photo-Induced Spin-State Conversion in Solvated Transition Metal Complexes Probed via Time-Resolved Soft X-ray Spectroscopy  

SciTech Connect

Solution-phase photoinduced low-spin to high-spin conversion in the FeII polypyridyl complex [Fe(tren(py)3)]2+ (where tren(py)3 is tris(2-pyridylmethyliminoethyl)amine) has been studied via picosecond soft X-ray spectroscopy. Following 1A1 --> 1MLCT (metal-to-ligand charge transfer) excitation at 560 nm, changes in the iron L2- and L3-edges were observed concomitant with formation of the transient high-spin 5T2 state. Charge-transfer multiplet calculations coupled with data acquired on low-spin and high-spin model complexes revealed a reduction in ligand field splitting of 1 eV in the high-spin state relative to the singlet ground state. A significant reduction in orbital overlap between the central Fe-3d and the ligand N-2p orbitals was directly observed, consistent with the expected ca. 0.2 Angstrom increase in Fe-N bond length upon formation of the high-spin state. The overall occupancy of the Fe-3d orbitals remains constant upon spin crossover, suggesting that the reduction in sigma-donation is compensated by significant attenuation of pi-back-bonding in the metal-ligand interactions. These results demonstrate the feasibility and unique potential of time-resolved soft X-ray absorption spectroscopy to study ultrafast reactions in the liquid phase by directly probing the valence orbitals of first-row metals as well as lighter elements during the course of photochemical transformations.

Huse, Nils; Kim, Tae Kyu; Jamula, Lindsey; McCusker, James K.; de Groot, Frank M. F.; Schoenlein, Robert W.

2010-04-30

329

Soft X-ray Laser Microscopy of Lipid Rafts towards GPCR-Based Drug Discovery Using Time-Resolved FRET Spectroscopy  

PubMed Central

Many signaling molecules involved in G protein-mediated signal transduction, which are present in the lipid rafts and believed to be controlled spatially and temporally, influence the potency and efficacy of neurotransmitter receptors and transporters. This has focus interest on lipid rafts and the notion that these microdomains acts as a kind of signaling platform and thus have an important role in the expression of membrane receptor-mediated signal transduction, cancer, immune responses, neurotransmission, viral infections and various other phenomena due to specific and efficient signaling according to extracellular stimuli. However, the real structure of lipid rafts has not been observed so far due to its small size and a lack of sufficiently sophisticated observation systems. A soft X-ray microscope using a coherent soft X-ray laser in the water window region (2.3–4.4 nm) should prove to be a most powerful tool to observe the dynamic structure of lipid rafts of several tens of nanometers in size in living cells. We have developed for the X-ray microscope a new compact soft X-ray laser using strongly induced plasma high harmonic resonance. We have also developed a time-resolved highly sensitive fluorescence resonance energy transfer (FRET) system and confirmed protein-protein interactions coupled with ligands. The simultaneous use of these new tools for observation of localization of G-protein coupled receptors (GPCRs) in rafts has become an important and optimum tool system to analyze the dynamics of signal transduction through rafts as signaling platform. New technology to visualize rafts is expected to lead to the understanding of those dynamics and innovative development of drug discovery that targets GPCRs localized in lipid rafts.

Baba, Motoyoshi; Kozasa, Tohru; Hamakubo, Takao; Kuroda, Hiroto; Masuda, Kazuyuki; Yoneya, Shin; Kodama, Tatsuhiko

2011-01-01

330

CHICKEN DISEASE CHARACTERIZATION BY FLUORESCENCE SPECTROSCOPY  

Technology Transfer Automated Retrieval System (TEKTRAN)

Fluorescence spectroscopy was used to characterize chicken carcass spectra. Spectral signatures of three different disease categories of poultry carcasses (airsacculitis, cadaver, and septicemia) were obtained from fluorescence emission measurements in the wavelength range of 360 to 600 nm with 330 ...

331

Using time-resolved Ru L-edge X-ray absorption spectroscopy to capture photoinduced transient electronic structure in a solar cell dye molecule  

NASA Astrophysics Data System (ADS)

Understanding the electronic structure of transition metal dye molecules used in dye-sensitized solar cells (DSSC) is critical for determining the functioning of these devices. Ru^II dyes such as Ru(dcbpy)2(NCS)2 (termed RuN3) have been components in some of the most effective DSSCs. We use synchrotron-based picosecond Ru L-edge X-ray absorption spectroscopy (XAS) to monitor changes the changes in the electronic structure of RuN3^4- that accompany the ^1A1 to ^3MLCT conversion initiated with a 400 nm light pulse. The results are interpreted by simulating the Ru L3 X-ray absorption spectra of the ^1A1 and ^3MLCT states with time-dependent density functional theory (TD-DFT). We observe the formation of the Ru^III oxidation state of RuN3^4- within the 70 ps time resolution of our experiment. The TD-DFT simulation allows us to assign a spectral feature in the Ru L-edge spectrum as a probe of the electronic structure of the NCS ligands due to overlap between Ru 4d and NCS ?* orbitals. A 1.2 eV blue shift in this feature between ground and ^3MLCT state corresponds to depletion in charge density on the NCS ligands in the excited state. We will discuss in detail the local electronic structure around the Ru atom in the transient ^3MLCT state measured by time-resolved XAS.

van Kuiken, Benjamin; Lynch, Michael; Khalil, Munira; Huse, Nils; Cho, Hana; Strader, Matthew; Schoenlein, Robert

2012-02-01

332

Stark-assisted population control of coherent CS(2) 4f and 5p Rydberg wave packets studied by femtosecond time-resolved photoelectron spectroscopy.  

PubMed

A two-color (3+1(')) pump-probe scheme is employed to investigate Rydberg wave packet dynamics in carbon disulfide (CS(2) (*)). The state superpositions are created within the 4f and 5p Rydberg manifolds by three photons of the 400 nm pump pulse, and their temporal evolution is monitored with femtosecond time-resolved photoelectron spectroscopy using an 800 nm ionizing probe pulse. The coherent behavior of the non-stationary superpositions are observed through wavepacket revivals upon ionization to either the upper (12) or lower (32) spin-orbit components of CS(2) (+). The results show clearly that the composition of the wavepacket can be efficiently controlled by the power density of the excitation pulse over a range from 500 GWcm(2) to 10 TWcm(2). The results are consistent with the anticipated ac-Stark shift for 400 nm light and demonstrate an effective method for population control in molecular systems. Moreover, it is shown that Rydberg wavepackets can be formed in CS(2) with excitation power densities up to 10 TWcm(2) without significant fragmentation. The exponential 1e population decay (T(1)) of specific excited Rydberg states are recovered by analysis of the coherent part of the signal. The dissociation lifetimes of these states are typically 1.5 ps. However, a region exhibiting a more rapid decay ( approximately 800 fs) is observed for states residing in the energy range of 74 450-74 550 cm(-1), suggestive of an enhanced surface crossing in this region. PMID:17902914

Knappenberger, Kenneth L; Lerch, Eliza-Beth W; Wen, Patrick; Leone, Stephen R

2007-09-28

333

Time-resolved visible and infrared difference spectroscopy for the study of photosystem I with different quinones incorporated into the A1 binding site.  

PubMed

Room (298K) and low (77K) temperature time-resolved visible and infrared difference spectroscopy has been used to study photosystem I particles with phylloquinone (2-methyl-3-phytyl-1,4-naphthoquinone), menadione (2-methyl-1,4-naphthoquinone) and plastoquinone 9 (2,3-dimethyl-5-prenyl-l,4-benzoquinone), incorporated into the A1 binding site. Concentrated samples in short path-length (~5?m) sample cells are typically used in FTIR experiments. Measurements were undertaken using standard "dilute" samples at 298K, and concentrated (~5×) samples at both 298 and 77K. No concentration induced alterations in the flash-induced absorption changes were observed. Concentrated samples in short path-length cells form a transparent film at 77K, and could therefore be studied spectroscopically at 77K without addition of a cryoprotectant. At 298K, for photosystem I with plastoquinone 9/menadione/phylloquinone incorporated, P700(+)FA/B(-) radical pair recombination is characterized by a time constant of 3/14/80ms, and forward electron transfer from A1A(-) to Fx by a time constant of 211/3.1/0.309?s, respectively. At 77K, for concentrated photosystem I with menadione/phylloquinone incorporated, P700(+)A1(-) radical pair recombination is characterized by a time constant of 240/340?s, with this process occurring in 58/39% of the PSI particles, respectively. The origin of these differences is discussed. Marcus electron transfer theory in combination with kinetic modeling is used to simulate the observed electron transfer time constants at 298K. This simulation allows an estimate of the redox potential for the different quinones in the A1 binding site. PMID:25534606

Makita, Hiroki; Zhao, Nan; Hastings, Gary

2015-03-01

334

Structural Changes and Thermal Stability of Charged LiNixMnyCozO2 Cathode Materials Studied by Combined In Situ Time-Resolved XRD and Mass Spectroscopy.  

PubMed

Thermal stability of charged LiNixMnyCozO2 (NMC, with x + y + z = 1, x:y:z = 4:3:3 (NMC433), 5:3:2 (NMC532), 6:2:2 (NMC622), and 8:1:1 (NMC811)) cathode materials is systematically studied using combined in situ time-resolved X-ray diffraction and mass spectroscopy (TR-XRD/MS) techniques upon heating up to 600 °C. The TR-XRD/MS results indicate that the content of Ni, Co, and Mn significantly affects both the structural changes and the oxygen release features during heating: the more Ni and less Co and Mn, the lower the onset temperature of the phase transition (i.e., thermal decomposition) and the larger amount of oxygen release. Interestingly, the NMC532 seems to be the optimized composition to maintain a reasonably good thermal stability, comparable to the low-nickel-content materials (e.g., NMC333 and NMC433), while having a high capacity close to the high-nickel-content materials (e.g., NMC811 and NMC622). The origin of the thermal decomposition of NMC cathode materials was elucidated by the changes in the oxidation states of each transition metal (TM) cations (i.e., Ni, Co, and Mn) and their site preferences during thermal decomposition. It is revealed that Mn ions mainly occupy the 3a octahedral sites of a layered structure (R3?m) but Co ions prefer to migrate to the 8a tetrahedral sites of a spinel structure (Fd3?m) during the thermal decomposition. Such element-dependent cation migration plays a very important role in the thermal stability of NMC cathode materials. The reasonably good thermal stability and high capacity characteristics of the NMC532 composition is originated from the well-balanced ratio of nickel content to manganese and cobalt contents. This systematic study provides insight into the rational design of NMC-based cathode materials with a desired balance between thermal stability and high energy density. PMID:25420188

Bak, Seong-Min; Hu, Enyuan; Zhou, Yongning; Yu, Xiqian; Senanayake, Sanjaya D; Cho, Sung-Jin; Kim, Kwang-Bum; Chung, Kyung Yoon; Yang, Xiao-Qing; Nam, Kyung-Wan

2014-12-24

335

Sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy setup for pulsed and constant wave X-ray light sources  

NASA Astrophysics Data System (ADS)

An apparatus for sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy studies with pulsed and constant wave X-ray light sources is presented. A differentially pumped hemispherical electron analyzer is equipped with a delay-line detector that simultaneously records the position and arrival time of every single electron at the exit aperture of the hemisphere with ˜0.1 mm spatial resolution and ˜150 ps temporal accuracy. The kinetic energies of the photoelectrons are encoded in the hit positions along the dispersive axis of the two-dimensional detector. Pump-probe time-delays are provided by the electron arrival times relative to the pump pulse timing. An average time-resolution of (780 ± 20) ps (FWHM) is demonstrated for a hemisphere pass energy Ep = 150 eV and an electron kinetic energy range KE = 503-508 eV. The time-resolution of the setup is limited by the electron time-of-flight (TOF) spread related to the electron trajectory distribution within the analyzer hemisphere and within the electrostatic lens system that images the interaction volume onto the hemisphere entrance slit. The TOF spread for electrons with KE = 430 eV varies between ˜9 ns at a pass energy of 50 eV and ˜1 ns at pass energies between 200 eV and 400 eV. The correlation between the retarding ratio and the TOF spread is evaluated by means of both analytical descriptions of the electron trajectories within the analyzer hemisphere and computer simulations of the entire trajectories including the electrostatic lens system. In agreement with previous studies, we find that the by far dominant contribution to the TOF spread is acquired within the hemisphere. However, both experiment and computer simulations show that the lens system indirectly affects the time resolution of the setup to a significant extent by inducing a strong dependence of the angular spread of electron trajectories entering the hemisphere on the retarding ratio. The scaling of the angular spread with the retarding ratio can be well approximated by applying Liouville's theorem of constant emittance to the electron trajectories inside the lens system. The performance of the setup is demonstrated by characterizing the laser fluence-dependent transient surface photovoltage response of a laser-excited Si(100) sample.

Shavorskiy, Andrey; Neppl, Stefan; Slaughter, Daniel S.; Cryan, James P.; Siefermann, Katrin R.; Weise, Fabian; Lin, Ming-Fu; Bacellar, Camila; Ziemkiewicz, Michael P.; Zegkinoglou, Ioannis; Fraund, Matthew W.; Khurmi, Champak; Hertlein, Marcus P.; Wright, Travis W.; Huse, Nils; Schoenlein, Robert W.; Tyliszczak, Tolek; Coslovich, Giacomo; Robinson, Joseph; Kaindl, Robert A.; Rude, Bruce S.; Ölsner, Andreas; Mähl, Sven; Bluhm, Hendrik; Gessner, Oliver

2014-09-01

336

Sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy setup for pulsed and constant wave X-ray light sources.  

PubMed

An apparatus for sub-nanosecond time-resolved ambient-pressure X-ray photoelectron spectroscopy studies with pulsed and constant wave X-ray light sources is presented. A differentially pumped hemispherical electron analyzer is equipped with a delay-line detector that simultaneously records the position and arrival time of every single electron at the exit aperture of the hemisphere with ~0.1 mm spatial resolution and ~150 ps temporal accuracy. The kinetic energies of the photoelectrons are encoded in the hit positions along the dispersive axis of the two-dimensional detector. Pump-probe time-delays are provided by the electron arrival times relative to the pump pulse timing. An average time-resolution of (780 ± 20) ps (FWHM) is demonstrated for a hemisphere pass energy E(p) = 150 eV and an electron kinetic energy range KE = 503-508 eV. The time-resolution of the setup is limited by the electron time-of-flight (TOF) spread related to the electron trajectory distribution within the analyzer hemisphere and within the electrostatic lens system that images the interaction volume onto the hemisphere entrance slit. The TOF spread for electrons with KE = 430 eV varies between ~9 ns at a pass energy of 50 eV and ~1 ns at pass energies between 200 eV and 400 eV. The correlation between the retarding ratio and the TOF spread is evaluated by means of both analytical descriptions of the electron trajectories within the analyzer hemisphere and computer simulations of the entire trajectories including the electrostatic lens system. In agreement with previous studies, we find that the by far dominant contribution to the TOF spread is acquired within the hemisphere. However, both experiment and computer simulations show that the lens system indirectly affects the time resolution of the setup to a significant extent by inducing a strong dependence of the angular spread of electron trajectories entering the hemisphere on the retarding ratio. The scaling of the angular spread with the retarding ratio can be well approximated by applying Liouville's theorem of constant emittance to the electron trajectories inside the lens system. The performance of the setup is demonstrated by characterizing the laser fluence-dependent transient surface photovoltage response of a laser-excited Si(100) sample. PMID:25273702

Shavorskiy, Andrey; Neppl, Stefan; Slaughter, Daniel S; Cryan, James P; Siefermann, Katrin R; Weise, Fabian; Lin, Ming-Fu; Bacellar, Camila; Ziemkiewicz, Michael P; Zegkinoglou, Ioannis; Fraund, Matthew W; Khurmi, Champak; Hertlein, Marcus P; Wright, Travis W; Huse, Nils; Schoenlein, Robert W; Tyliszczak, Tolek; Coslovich, Giacomo; Robinson, Joseph; Kaindl, Robert A; Rude, Bruce S; Ölsner, Andreas; Mähl, Sven; Bluhm, Hendrik; Gessner, Oliver

2014-09-01

337

Complexity of Lipid Domains and Rafts in Giant Unilamellar Vesicles Revealed by Combining Imaging and Microscopic and Macroscopic Time-Resolved Fluorescence  

PubMed Central

The application of fluorescence lifetime imaging microscopy to study gel/fluid and raftlike lipid domains in giant unilamellar vesicles (GUVs) is demonstrated here. Different regions of the ternary dipalmitoylphosphatidylcholine/dioleoylphosphatidylcholine/cholesterol phase diagram were studied. The head-labeled phospholipid Rhodamine-dioleoylphosphatidylethanolamine (Rhod-DOPE) was used as a fluorescent probe. Gel/fluid and liquid-ordered (lo)/liquid-disordered (ld) phase separation were clearly visualized upon two-photon excitation. Fluorescence intensity decays in different regions of a GUV were also obtained with the microscope in fixed laser-beam configuration. The ensemble behavior of the system was studied by obtaining fluorescence intensity decays of Rhod-DOPE in nongiant vesicle suspensions. The fingerprints for gel/fluid coexistence and for the presence of lo raftlike phase, based on fluorescence lifetime imaging microscopy histograms and images, and on the fluorescence intensity decay parameters of Rhod-DOPE, are presented. The presence of three lipid phases in one single GUV is detected unequivocally. From the comparison of lifetime parameters, it can be concluded that the lo phase is formed in the binary dipalmitoylphosphatidylcholine/cholesterol but not in the dioleoylphosphatidylcholine/cholesterol mixture. The domains apparent in fluorescence intensity images have a more complex substructure revealed by analysis of the lifetime data. The potential applications of this combined imaging/microscopic/macroscopic methodology are discussed. PMID:17449668

de Almeida, Rodrigo F. M.; Borst, JanWillem; Fedorov, Alexander; Prieto, Manuel; Visser, Antonie J. W. G.

2007-01-01

338

Time-Resolved FTIR Difference Spectroscopy for the Study of Photosystem I Particles with Plastoquinone9 Occupying the A 1 Binding Site †  

Microsoft Academic Search

In photosystem I from plants and cyanobacteria a phylloquinone molecule, called A1, functions as the secondary electron acceptor. In cyanobacteria, genes that encode for proteins involved in phylloquinone biosynthesis can be deleted. Here, we have studied three different gene deletion mutants called menB, menD, and menE mutants. In these mutants, plastoquinone-9 occupies the A1 binding site. Using time-resolved, step-scan FTIR

K. M. Priyangika Bandaranayake; Ruili Wang; T. Wade Johnson; Gary Hastings

2006-01-01

339

Development of a cyanovirin-N-HIV-1 gp120 binding assay for high throughput screening of natural product extracts by time-resolved fluorescence.  

PubMed

The unique, high-affinity binding of cyanovirin-N (CV-N), a potent anti-human immunodeficiency virus (HIV) protein, to the HIV envelope glycoprotein gp120, was exploited to develop an HTS assay in an attempt to discover small-molecule mimetics of CV-N. A competition binding assay was developed using CV-N labeled with europium (Eu(3+)). The labeling protocol did not significantly alter the gp120 binding properties or the antiviral activity of CV-N. This report describes the assay development, validation, and results of screening a large library of aqueous and organic natural product extracts. The extracts were incubated with immobilized recombinant gp120 in 96-well plates prior to the addition of Eu(3+)-labeled CV-N. Following a wash step, bound CV-N was measured by dissociation-enhanced time-resolved fluorometry of Eu(3+). The assay proved to be robust, rapid, and reproducible, and was used to screen over 50,000 natural product extracts, and has resulted in the identification of several aqueous natural product extracts that inhibited CV-N-gp120 binding and also had anti-HIV activity. PMID:10894760

McMahon, J B; Beutler, J A; O'Keefe, B R; Goodrum, C B; Myers, M A; Boyd, M R

2000-06-01

340

Time resolved single photon imaging in Nanometer Scale CMOS technology   

E-print Network

Time resolved imaging is concerned with the measurement of photon arrival time. It has a wealth of emerging applications including biomedical uses such as fluorescence lifetime microscopy and positron emission tomography, ...

Richardson, Justin Andrew

2010-06-28

341

Cervical cancer detection by time-resolved spectra of blood components  

NASA Astrophysics Data System (ADS)

Fluorescence spectral techniques are very sensitive, and hence they are gaining importance in cancer detection. The biomarkers indicative of cancer could be identified and quantified by spectral or time domain fluorescence spectroscopy. The results of an investigation of time-resolved spectra of cellular components of blood obtained from cervical cancer patients and normal controls are given. The cancer indicative biomarker in this paper is porphyrin; it has a fluorescence decay time of 60% more in samples of cancer patients than those of normal controls. Based on such measurements, a randomized set comprising samples from cancer patients and controls (N=27 in total) could be classified with sensitivity (92%) and specificity (86%).

Kalaivani, Rudran; Masilamani, Vadivel; AlSalhi, Mohamad Saleh; Devanesan, Sandhanasamy; Ramamurthy, P.; Palled, Siddanna R.; Ganesh, K. M.

2014-05-01

342

Effect of nanosize micelles of ionic and neutral surfactants on the photophysics of protonated 6-methoxyquinoline: Time-resolved fluorescence study.  

PubMed

The excited state dynamic studies have been carried out to investigate the effects of micellar surface charge on the photophysics of protonated 6-methoxyquinoline (6MQ(+)) in anionic, sodium dodecylsulphate (SDS), cationic, cetyltrimethylammonium bromide (CTAB) and neutral, triton X-100 (TX100) surfactant at premicellar, micellar and postmicellar concentrations in aqueous phase at room temperature. At premicellar concentrations of SDS, there is a slight decrease in emission intensity and at micellar and postmicellar concentrations, increase in emission intensity and blue shift of spectrum has been observed. The blue shift in fluorescence spectrum and slight increase in quantum yield are attributed to incorporation of solute molecule to the micelles. Edge excitation red shift (EERS) in fluorescence maximum of 6MQ(+) has been observed in all the surfactant solutions studied. The EERS has been ascribed in terms of solvent relaxation process. In SDS surfactant system, due to heterogeneous restricted motion of solvent molecules, the solvent viscosity increases which results in an increase in net magnitude of EERS. The fluorescence decay components of 6MQ(+) fit with multi exponential functions in all the micellar systems studied. The location of the probe molecule in micellar systems is justified by a variety of spectral parameters such as refractive index, dielectric constant, ET (30), EERS, average fluorescence decay time, radiative and non radiative rate constants, and rotational relaxation time. PMID:25434640

Tej Varma, Y; Joshi, Sunita; Pant, Debi D

2015-03-01

343

Effect of electric fields on the decay branching ratio of {sup 1}P{sup e} doubly excited states in helium measured by time-resolved fluorescence  

SciTech Connect

We have measured the lifetimes of {sup 1}P{sup e} (n=9-12) doubly excited states in static electric fields (1-6 kV/cm) by observing the decay of the fluorescence signal as a function of time. The effects of the field on these helium states below the second ionization threshold are twofold: their excitation becomes possible due to the Stark mixing with the optically allowed {sup 1}P{sup o} series, and their lifetime is strongly modified by the opening of the autoionization channel, not accessible in zero field. Although the electric field represents only a tiny perturbation of the atomic potential, a substantial shortening of the lifetimes below 100 ps is observed. This is the simplest quantum system where the ratio of autoionization to fluorescence decay probability can be effectively controlled by an electric field of moderate strength.

Zitnik, Matjaz; Mihelic, A.; Bucar, K. [Jozef Stefan Institute, P. O. Box 3000, SI-1001 Ljubljana (Slovenia); Penent, F.; Lablanquie, P. [LCP-MR, Universite Pierre et Marie Curie 6 and CNRS (UMR 7614), 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Richter, R. [Sincrotrone Trieste, I-340 12 Trieste (Italy); Alagia, M. [INFM-TASC, Padriciano 99, I-340 12 Trieste (Italy); Stranges, S. [Dipartimento di Chimica, Universita di Roma 'La Sapienza' and INFM Unit, 00185 Rome (Italy)

2006-11-15

344

Electronic energy migration on different time scales: concentration dependence of the time-resolved anisotropy and fluorescence quenching of Lumogen Red in poly(methyl methacrylate).  

PubMed

Electronic energy transfer plays an important role in many types of organic electronic devices. Forster-type theories of exciton diffusion provide a way to calculate diffusion constants and lengths, but their applicability to amorphous polymer systems must be evaluated. In this paper, the perylenediimide dye Lumogen Red in a poly(methyl methacrylate) host matrix is used to test theories of exciton motion over Lumogen Red concentrations (C(LR)'s) ranging from 1 x 10(-4) to 5 x 10(-2) M. Two experimental quantities are measured. First, time-resolved anisotropy decays in films containing only Lumogen Red provide an estimate of the initial energy transfer rate from the photoexcited molecule. Second, the Lumogen Red lifetime decays in mixed systems where the dyes Malachite Green and Rhodamine 700 act as energy acceptors are measured to estimate the diffusive quenching of the exciton. From the anisotropy measurements, it is found that theory accurately predicts both the C(LR)(-2) concentration dependence of the polarization decay time tau(pol), as well as its magnitude to within 30%. The theory also predicts that the diffusive quenching rate is proportional to C(LR)(alpha), where alpha ranges between 1.00 and 1.33. Experimentally, it is found that alpha = 1.1 +/- 0.2 when Malachite Green is used as an acceptor, and alpha = 1.2 +/- 0.2 when Rhodamine 700 is the acceptor. On the basis of the theory that correctly describes the anisotropy data, the exciton diffusion constant is projected to be 4-9 nm(2)/ns. By use of several different analysis methods for the quenching data, the experimental diffusion constant is found to be in the range of 0.32-1.20 nm(2)/ns. Thus the theory successfully describes the early time anisotropy data but fails to quantitatively describe the quenching experiments which are sensitive to motion on longer time scales. The data are consistent with the idea that orientational and energetic disorder leads to a time-dependent exciton migration rate, suggesting that simple diffusion models cannot accurately describe exciton motion within this system. PMID:20170138

Colby, Kathryn A; Burdett, Jonathan J; Frisbee, Robert F; Zhu, Lingyan; Dillon, Robert J; Bardeen, Christopher J

2010-03-18

345

Acetylene weak bands at 2.5 $?$m from intracavity Cr2+:ZnSe laser absorption observed with time-resolved Fourier transform spectroscopy  

E-print Network

The spectral dynamics of a mid-infrared multimode Cr^2+:ZnSe laser located in a vacuum sealed chamber containing acetylene at low pressure is analyzed by a stepping-mode high-resolution time-resolved Fourier transform interferometer. Doppler-limited absorption spectra of C_2H_2 in natural isotopic abundance are recorded around 4000 cm^-1 with kilometric absorption path lengths and sensitivities better than 3 10^-8 cm-1. Two cold bands are newly identified and assigned to the n_1+n_4^1 and n_3+n_5^1 transitions of ^12C^13CH_2. The n_1+n_5^1 band of ^12C_2HD and fourteen ^12C_2H_2 bands are observed, among which for the first time n_2+2n_4^2+n_5^-1.

Véronique Girard; Robert Farrenq; Evgeni Sorokin; Irina T. Sorokina; Guy Guelachvili; Nathalie Picqué

2006-12-01

346

Fluorescence spectroscopy of rhodopsins: insights and approaches.  

PubMed

Fluorescence spectroscopy has become an established tool at the interface of biology, chemistry and physics because of its exquisite sensitivity and recent technical advancements. However, rhodopsin proteins present the fluorescence spectroscopist with a unique set of challenges and opportunities due to the presence of the light-sensitive retinal chromophore. This review briefly summarizes some approaches that have successfully met these challenges and the novel insights they have yielded about rhodopsin structure and function. We start with a brief overview of fluorescence fundamentals and experimental methodologies, followed by more specific discussions of technical challenges rhodopsin proteins present to fluorescence studies. Finally, we end by discussing some of the unique insights that have been gained specifically about visual rhodopsin and its interactions with affiliate proteins through the use of fluorescence spectroscopy. This article is part of a Special Issue entitled: Retinal Proteins - You can teach an old dog new tricks. PMID:24183695

Alexiev, Ulrike; Farrens, David L

2014-05-01

347

Time resolved techniques: An overview  

SciTech Connect

Synchrotron sources provide exceptional opportunities for carrying out time-resolved x-ray diffraction investigations. The high intensity, high angular resolution, and continuously tunable energy spectrum of synchrotron x-ray beams lend themselves directly to carrying out sophisticated time-resolved x-ray scattering measurements on a wide range of materials and phenomena. When these attributes are coupled with the pulsed time-structure of synchrotron sources, entirely new time-resolved scattering possibilities are opened. Synchrotron beams typically consist of sub-nanosecond pulses of x-rays separated in time by a few tens of nanoseconds to a few hundred nanoseconds so that these beams appear as continuous x-ray sources for investigations of phenomena on time scales ranging from hours down to microseconds. Studies requiring time-resolution ranging from microseconds to fractions of a nanosecond can be carried out in a triggering mode by stimulating the phenomena under investigation in coincidence with the x-ray pulses. Time resolution on the picosecond scale can, in principle, be achieved through the use of streak camera techniques in which the time structure of the individual x-ray pulses are viewed as quasi-continuous sources with {approximately}100--200 picoseconds duration. Techniques for carrying out time-resolved scattering measurements on time scales varying from picoseconds to kiloseconds at present and proposed synchrotron sources are discussed and examples of time-resolved studies are cited. 17 refs., 8 figs.

Larson, B.C.; Tischler, J.Z.

1990-06-01

348

Time Resolved 3D Molecular Tracking in Live Cells  

PubMed Central

We report a method for tracking individual quantum dot (QD) labeled proteins inside of live cells that uses four overlapping confocal volume elements and active feedback once every 5 milliseconds to follow three dimensional molecular motion. This method has substantial advantages over 3D molecular tracking methods based upon CCD cameras, including increased Z tracking range (10 ?m demonstrated here), substantially lower excitation powers (15 ?W used here), and the ability to perform time-resolved spectroscopy (such as fluorescence lifetime measurements or fluorescence correlation spectroscopy) on the molecules being tracked. In particular, we show for the first time fluorescence photon anti-bunching of individual QD labeled proteins in live cells and demonstrate the ability to track individual dye labeled nucleotides (Cy5-dUTP) at biologically relevant transport rates. To demonstrate the power of these methods for exploring the spatio-temporal dynamics of live cells, we follow individual QD-labeled IgE receptors both on and inside rat mast cells. Trajectories of receptors on the plasma membrane reveal three dimensional, nano-scale features of the cell surface topology. During later stages of the signal transduction cascade, clusters of QD labeled IgE-Fc?RI were captured in the act of ligand-mediated endocytosis and tracked during rapid (~950 nm/s) vesicular transit through the cell. PMID:20957984

Wells, Nathan P.; Lessard, Guillaume A.; Goodwin, Peter M.; Phipps, Mary E.; Cutler, Patrick J.; Lidke, Diane S.; Wilson, Bridget S.; Werner, James H.

2010-01-01

349

Comparison of microenvironments of aqueous sodium dodecyl sulfate micelles in the presence of inorganic and organic salts: a time-resolved fluorescence anisotropy approach.  

PubMed

Microenvironments of aqueous sodium dodecyl sulfate (SDS) micelles was examined in the presence of additives such as sodium chloride and p-toluidine hydrochloride (PTHC) by monitoring the fluorescence anisotropy decays of two hydrophobic probes, 2,5-dimethyl-1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DMDPP) and coumarin 6 (C6). It has been well-established that SDS micelles undergo a sphere-to-rod transition and that their mean hydrodynamic radius increases from 19 to 100 A upon the addition of 0.0-0.7 M NaCl at 298 K. A similar size and shape transition is induced by PTHC at concentrations that are 20 times lower compared to that of NaCl. This study was undertaken to find out how the microviscosity of the micelles is influenced under these circumstances. It was noticed that the microviscosity of the SDS/NaCl system increased by approximately 45%, whereas there was a less than 10% variation in the microviscosity of the SDS/PTHC system. The large increase in the microviscosity of the former system with salt concentration has been rationalized on the basis of the high concentration of sodium ions in the headgroup region of the micelles and their ability to strongly coordinate with the water present in this region, which decreases the mobility of the probe molecules. PMID:16262297

Dutt, G B

2005-11-01

350

Time-resolved spectral characterization of ring cavity surface emitting and ridge-type distributed feedback quantum cascade lasers by step-scan FT-IR spectroscopy.  

PubMed

We present the time-resolved comparison of pulsed 2nd order ring cavity surface emitting (RCSE) quantum cascade lasers (QCLs) and pulsed 1st order ridge-type distributed feedback (DFB) QCLs using a step-scan Fourier transform infrared (FT-IR) spectrometer. Laser devices were part of QCL arrays and fabricated from the same laser material. Required grating periods were adjusted to account for the grating order. The step-scan technique provided a spectral resolution of 0.1 cm(-1) and a time resolution of 2 ns. As a result, it was possible to gain information about the tuning behavior and potential mode-hops of the investigated lasers. Different cavity-lengths were compared, including 0.9 mm and 3.2 mm long ridge-type and 0.97 mm (circumference) ring-type cavities. RCSE QCLs were found to have improved emission properties in terms of line-stability, tuning rate and maximum emission time compared to ridge-type lasers. PMID:24663557

Brandstetter, Markus; Genner, Andreas; Schwarzer, Clemens; Mujagic, Elvis; Strasser, Gottfried; Lendl, Bernhard

2014-02-10

351

Rate constant for the reaction of OH with methyl iodide, a re-determination by flash photolysis of water vapour and time resolved resonance fluorescence of OH  

NASA Astrophysics Data System (ADS)

Methyl iodide is a major source gas for atmospheric iodine, and it is mainly emitted from the ocean. Aqueous-phase reactions, such as hydrolysis and exchange reactions with chloride control its emissions to the atmosphere, where its lifetime is limited to less than a week, mainly by photolysis. A minor contribution to the loss processes in the troposphere is the gas-phase reaction with OH radicals, that has been investigated by several authors. On the other hand, this reaction turned out to be uncertain in spite of interest in nuclear safety after the International Phebus Fission Product programme, initiated in 1988. Some of the most important observed phenomena with regard to the chemistry of iodine were not predicted, clearly showing the need for carrying out rate constant determinations for the reactions of I2 and CH3I with OH, which is a major oxidant product from the air radiolysis under accident conditions. We have measured the rate constant for the reaction OH + CH3I - H2O + CH2I in He at 260 mbar in the temperature range from 298 to 362 K. OH radicals were produced by flash photolysis of H2O in the vacuum-UV at wavelengths > 115 nm using a Xe flash lamp with a MgF2 window. Time profiles of OH radicals are monitored by resonance fluorescence of the A2 ? - X2 ? transition at 308 nm, induced by the emission from a microwave discharge of a flow of He and H2O, a few Torr each. The signal is monitored by photon counting and multichannel scaling, collecting the counts from 50 flashes each, obtaind by pulsed photolysis of various mixtures of H2O and CH3I under slow-flow conditions. Decays of OH in the presence of CH3I are observed to be exponential, and the decay rates are found to be linearly dependent on the concentration of CH3I. Rate constants, k ± 2? (in units of 10-14 cm3 s-1) of 4.14±0.20, 6.33±0.68, 7.31±1.18 and 8.24±1.60 at 298, 326, 352 and 362 K, respectively, are obtained from linear regressions and lead to an Arrhenius expression of k = 1.5×10-12 exp (-1067 K / T) cm3 s-1 . These rate constants are significantly below the present IUPAC recommendation. The consequence is an even smaller contribution of the OH reaction to tropospheric degradation. Acknowledgements: Shaoliang Zhang and Rafal Strekowski wish to thank the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) for support and Cornelius Zetzsch acknowledges funding within the research unit HALOPROC of the German Science Foundation

Zhang, Shaoliang; Strekowski, Rafal; Zetzsch, Cornelius

2010-05-01

352

Interaction of fisetin with human serum albumin by fluorescence, circular dichroism spectroscopy and DFT calculations: binding parameters and conformational changes  

Microsoft Academic Search

The interaction between fisetin, an antioxidant and neuroprotective flavonoid, and human serum albumin (HSA) is investigated by means of fluorescence (steady-state, synchronous, time-resolved) and circular dichroism (CD) spectroscopy. The formation of a 1:1 complex with a constant of about 105M?1 was evidenced. Förster's resonance energy transfer and competitive binding with site markers warfarin and ibuprofen were considered and discussed. Changes

Iulia Matei; Sorana Ionescu; Mihaela Hillebrand

2011-01-01

353

Measurement of Intrinsic Dirac Fermion Cooling on the Surface of the Topological Insulator Bi2Se3 Using Time-Resolved and Angle-Resolved Photoemission Spectroscopy  

E-print Network

We perform time- and angle-resolved photoemission spectroscopy of a prototypical topological insulator (TI) Bi[subscript 2]Se[subscript 3] to study the ultrafast dynamics of surface and bulk electrons after photoexcitation. ...

Wang, Y. H.

354

Extraction of masked fluorescence peaks through synchronous fluorescence spectroscopy  

NASA Astrophysics Data System (ADS)

Fluorescence spectroscopy has been demonstrated as a viable tool for noting subtle biochemical changes that occur during early-stage cervical cancer progression. Due to multiple fluorophore contributions, the individual fluorophore activities often get masked due to overlapping spectra of neighboring fluorophores. Recently synchronous fluorescence spectroscopy has been demonstrated as an efficient technique for investigation of such non-dominant fluorophores. With synchronous fluorescence spectroscopy individual fluorophore responses are highlighted as sharp peaks by choosing appropriate offsets during signal acquisition. Such peaks may, however be missed due to absorption effects. By correcting the measured synchronous fluorescence spectrum with elastic scattering data, it was observed that the masked fluorophores are highlighted while the broader bands are sharpened. Interestingly, fluorophore activities of protoporphyrin, collagen, NADH, FAD and porphyrin can now be studied using this technique, as compared to only collagen and NADH seen earlier. The results have been verified using tissue phantoms with known fluorophores and scatterers. Use of normalized synchronous spectra has led to enhancement of several fluorophore responses. It was also observed that among the different offsets, the lower ones show sharper features, whereas the larger offsets show a broadband response. Among the different offsets 120nm is found optimal for further investigation.

Devi, Seema; Mozumder, Meghdoot; Ghosh, Nirmalya; Pradhan, Asima

2012-03-01

355

Ultrafast Fluorescence Spectroscopy via Upconversion: Applications to Biophysics  

PubMed Central

This chapter reviews basic concepts of nonlinear fluorescence upconversion, a technique whose temporal resolution is essentially limited only by the pulse width of the ultrafast laser. Design aspects for upconversion spectrophotofluorometers are discussed, and a recently developed system is described. We discuss applications in biophysics, particularly the measurement of time-resolved fluorescence spectra of proteins (with subpicosecond time resolution). Application of this technique to biophysical problems such as dynamics of tryptophan, peptides, proteins, and nucleic acids is reviewed. PMID:19152860

Xu, Jianhua; Knutson, Jay R.

2012-01-01

356

Dual-Color Fluorescence Cross-Correlation Spectroscopy on a  

E-print Network

Dual-Color Fluorescence Cross-Correlation Spectroscopy on a Single Plane Illumination Microscope fluorescence correlation spectroscopy (SPIM-FCS) is a new method for imaging FCS in 3D samples, providing to two-color fluorescence cross-correlation spectroscopy (SPIM-FCCS), which allows to measure molecular

Garbe, Christoph S.

357

Time-resolved in situ detection of CO in a shock tube using cavity-enhanced absorption spectroscopy with a quantum-cascade laser near 4.6 µm.  

PubMed

Cavity-enhanced absorption spectroscopy (CEAS) using a mid-infrared DFB quantum-cascade laser is reported for sensitive time-resolved (10 ?s) in situ CO measurements in a shock tube. Off-axis alignment and fast scanning of the laser wavelength were used to minimize coupling noise in a low-finesse cavity. An absorption gain factor of 91 was demonstrated, which enabled sub-ppm detection sensitivity for gas temperatures of 1000-2100K in a 15 cm diameter shock tube. This substantial improvement in detection sensitivity compared to conventional single-pass absorption measurements, shows great potential for the study of reaction pathways of high-temperature combustion kinetics mechanisms in shock tubes. PMID:25322031

Sun, Kai; Wang, Shengkai; Sur, Ritobrata; Chao, Xing; Jeffries, Jay B; Hanson, Ronald K

2014-10-01

358

Time-resolved study of the symmetric SN2-reaction I Roland Wester,a)  

E-print Network

Time-resolved study of the symmetric SN2-reaction I� ¿CH3I Roland Wester,a) Arthur E. Bragg, Alison presented here, in which we attempt the first time- resolved investigation of a bimolecular SN2-reaction, California 94720 Received 2 May 2003; accepted 22 August 2003 Time-resolved photoelectron spectroscopy

Neumark, Daniel M.

359

Distinguishing bulk and surface electron-phonon coupling in the topological insulator Bi(2)Se(3) using time-resolved photoemission spectroscopy.  

PubMed

We report time- and angle-resolved photoemission spectroscopy measurements on the topological insulator Bi(2)Se(3). We observe oscillatory modulations of the electronic structure of both the bulk and surface states at a frequency of 2.23 THz due to coherent excitation of an A(1g) phonon mode. A distinct, additional frequency of 2.05 THz is observed in the surface state only. The lower phonon frequency at the surface is attributed to the termination of the crystal and thus reduction of interlayer van der Waals forces, which serve as restorative forces for out-of-plane lattice distortions. Density functional theory calculations quantitatively reproduce the magnitude of the surface phonon softening. These results represent the first band-resolved evidence of the A(1g) phonon mode coupling to the surface state in a topological insulator. PMID:25375740

Sobota, J A; Yang, S-L; Leuenberger, D; Kemper, A F; Analytis, J G; Fisher, I R; Kirchmann, P S; Devereaux, T P; Shen, Z-X

2014-10-10

360

Time-resolved surface infrared spectroscopy during atomic layer deposition of TiO{sub 2} using tetrakis(dimethylamido)titanium and water  

SciTech Connect

Atomic layer deposition of titanium dioxide using tetrakis(dimethylamido)titanium (TDMAT) and water vapor is studied by reflection-absorption infrared spectroscopy (RAIRS) with a time resolution of 120?ms. At 190?°C and 240?°C, a decrease in the absorption from adsorbed TDMAT is observed without any evidence of an adsorbed product. Ex situ measurements indicate that this behavior is not associated with an increase in the impurity concentration or a dramatic change in the growth rate. A desorbing decomposition product is consistent with these observations. RAIRS also indicates that dehydroxylation of the growth surface occurs only among one type of surface hydroxyl groups. Molecular water is observed to remain on the surface and participates in reactions even at a relatively high temperature (110?°C) and with long purge times (30?s)

Sperling, Brent A., E-mail: brent.sperling@nist.gov; Hoang, John; Kimes, William A.; Maslar, James E. [Chemical Sciences Division, National Institute of Standards and Technology, 100 Bureau Dr., Stop 8320, Gaithersburg, Maryland 20899-8320 (United States); Steffens, Kristen L. [Biomolecular Measurement Division, National Institute of Standards and Technology, 100 Bureau Dr., Stop 8362, Gaithersburg, Maryland 20899-8362 (United States); Nguyen, Nhan V. [Semiconductor and Dimensional Metrology Division, National Institute of Standards and Technology, 100 Bureau Dr., Stop 8120, Gaithersburg, Maryland 20899-8120 (United States)

2014-05-15

361

Time-resolved diffuse optical spectroscopy up to 1700 nm by means of a time-gated InGaAs/InP single-photon avalanche diode.  

PubMed

We present a new compact system for time-domain diffuse optical spectroscopy of highly scattering media operating in the wavelength range from 1100 nm to 1700 nm. So far, this technique has been exploited mostly up to 1100 nm: we extended the spectral range by means of a pulsed supercontinuum light source at a high repetition rate, a prism to spectrally disperse the radiation, and a time-gated InGaAs/InP single-photon avalanche diode working up to 1700 nm. A time-correlated single-photon counting board was used as processing electronics. The system is characterized by linear behavior up to absorption values of about 3.4 cm(-1) where the relative error is 17%. A first measurement performed on lipids is presented: the absorption spectrum shows three major peaks at 1200 nm, 1400 nm, and 1700 nm. PMID:22800436

Bargigia, Ilaria; Tosi, Alberto; Bahgat Shehata, Andrea; Della Frera, Adriano; Farina, Andrea; Bassi, Andrea; Taroni, Paola; Dalla Mora, Alberto; Zappa, Franco; Cubeddu, Rinaldo; Pifferi, Antonio

2012-08-01

362

Ultrafast free-carrier dynamics in Cu2ZnSnS4 single crystals studied using femtosecond time-resolved optical spectroscopy  

NASA Astrophysics Data System (ADS)

We studied the dynamics of photogenerated carriers in Cu2ZnSnS4 (CZTS) single crystals using femtosecond transient reflectivity (TR) and optical pump-THz probe transient absorption (THz-TA) spectroscopy. The TR and THz-TA decay dynamics consistently showed that free carriers have long lifetimes of up to a few nanoseconds. The excitation-photon-energy-dependent TR measurements revealed a slow picosecond energy relaxation of free carriers to the band edge in CZTS. The relaxation and recombination dynamics of free carriers were affected by nonradiative recombinations at the surface. Our results revealed a global feature of energy relaxation and recombination processes of free carriers in CZTS single crystals.

Phuong, L. Q.; Okano, M.; Yamada, Y.; Yamashita, G.; Morimoto, T.; Nagai, M.; Ashida, M.; Nagaoka, A.; Yoshino, K.; Kanemitsu, Y.

2014-12-01

363

Distinguishing Bulk and Surface Electron-Phonon Coupling in the Topological Insulator Bi2Se3 Using Time-Resolved Photoemission Spectroscopy  

NASA Astrophysics Data System (ADS)

We report time- and angle-resolved photoemission spectroscopy measurements on the topological insulator Bi2Se3. We observe oscillatory modulations of the electronic structure of both the bulk and surface states at a frequency of 2.23 THz due to coherent excitation of an A1g phonon mode. A distinct, additional frequency of 2.05 THz is observed in the surface state only. The lower phonon frequency at the surface is attributed to the termination of the crystal and thus reduction of interlayer van der Waals forces, which serve as restorative forces for out-of-plane lattice distortions. Density functional theory calculations quantitatively reproduce the magnitude of the surface phonon softening. These results represent the first band-resolved evidence of the A1g phonon mode coupling to the surface state in a topological insulator.

Sobota, J. A.; Yang, S.-L.; Leuenberger, D.; Kemper, A. F.; Analytis, J. G.; Fisher, I. R.; Kirchmann, P. S.; Devereaux, T. P.; Shen, Z.-X.

2014-10-01

364

In vivo swine myocardial tissue characterization and monitoring during open chest surgery by time-resolved diffuse near-infrared spectroscopy  

NASA Astrophysics Data System (ADS)

Cardiovascular diseases are the main cause of death in industrialized countries. Worldwide, a large number of patients suffering from cardiac diseases are treated by surgery. Despite the advances achieved in the last decades with myocardial protection, surgical failure can still occur. This is due at least in part to the imperfect control of the metabolic status of the heart in the various phases of surgical intervention. At present, this is indirectly controlled by the electrocardiogram and the echographic monitoring of cardiac mechanics as direct measurements are lacking. Diffuse optical technologies have recently emerged as promising tools for the characterization of biological tissues like breast, muscles and bone, and for the monitoring of important metabolic parameters such as blood oxygenation, volume and flow. As a matter of fact, their utility has been demonstrated in a variety of applications for functional imaging of the brain, optical mammography and monitoring of muscle metabolism. However, due to technological and practical difficulties, their potential for cardiac monitoring has not yet been exploited. In this work we show the feasibility of the in-vivo determination of absorption and scattering spectra of the cardiac muscle in the 600-1100 nm range, and of monitoring myocardial tissue hemodynamics by time domain near-infrared spectroscopy at 690 nm and 830 nm. Both measurements have been performed on the exposed beating heart during open chest surgery in pigs, an experimental model closely mimicking the clinical cardio-surgical setting.

Spinelli, Lorenzo; Contini, Davide; Farina, Andrea; Torricelli, Alessandro; Pifferi, Antonio; Cubeddu, Rinaldo; Ascari, Luca; Potì, Luca; Trivella, Maria Giovanna; L'Abbate, Antonio; Puzzuoli, Stefano

2011-03-01

365

Time-Resolved Quantitative Measurement of OH HO2 and CH2O in Fuel Oxidation Reactions by High Resolution IR Absorption Spectroscopy.  

SciTech Connect

Combined with a Herriott-type multi-pass slow flow reactor, high-resolution differential direct absorption spectroscopy has been used to probe, in situ and quantitatively, hydroxyl (OH), hydroperoxy (HO 2 ) and formaldehyde (CH 2 O) molecules in fuel oxidation reactions in the reactor, with a time resolution of about 1 micro-second. While OH and CH 2 O are probed in the mid-infrared (MIR) region near 2870nm and 3574nm respectively, HO 2 can be probed in both regions: near-infrared (NIR) at 1509nm and MIR at 2870nm. Typical sensitivities are on the order of 10 10 - 10 11 molecule cm -3 for OH at 2870nm, 10 11 molecule cm -3 for HO 2 at 1509nm, and 10 11 molecule cm -3 for CH 2 O at 3574nm. Measurements of multiple important intermediates (OH and HO 2 ) and product (CH 2 O) facilitate to understand and further validate chemical mechanisms of fuel oxidation chemistry.

Huang, Haifeng; Rotavera, Brandon; Taatjes, Craig A.

2014-08-01

366

Fluorescence spectroscopy for diagnosis of esophageal cancer  

NASA Astrophysics Data System (ADS)

Laser-induced fluorescence spectroscopy was employed to measure fluorescence emission of normal and malignant tissue during endoscopy in patients with esophageal adenocarcinoma. A nitrogen/dye laser tuned at 410 nm was used for excitation source. The fluorescence lineshape of each spectrum was determined and sampled at 15 nm intervals from 430 nm to 716 nm. A calibration set from normal and malignant spectra were selected. Using stepwise discriminate analysis, significant wavelengths that separated normal and malignant spectra were selected. The intensities at these wavelengths were used to formulate a classification model using linear discriminate analysis. The model was used to classify additional tissue spectra from 26 malignant and 108 normal sites into either normal or malignant spectra with a sensitivity of 100 percent and specificity of 98 percent.

Panjehpour, Masoud; Overholt, Bergein F.; Vo-Dinh, Tuan; Farris, Christie; Schmidhammer, James L.; Sneed, Rick E.; Buckley, Paul F., III

1994-07-01

367

Scanning fluorescence correlation spectroscopy on biomembranes.  

PubMed

Fluorescence correlation spectroscopy (FCS) is a powerful quantitative method to study dynamical properties of biophysical systems. It exploits the temporal autocorrelation of fluorescence intensity fluctuations originating from a tiny volume (~fL). A theoretical model function can be then fitted to the measured auto-correlation curve to obtain physical parameters such as local concentration and diffusion time. However, the application of FCS on membranes is coupled to several difficulties like accurate positioning and stability of the set-up. In this book chapter, we explain the theoretical framework of point FCS and Scanning FCS (SFCS), which is a variation especially suitable for membrane studies. We present a list of materials necessary for SFCS studies on Giant Unilamellar Vesicles (GUVs). Finally, we provide simple protocols for the preparation of GUVs, calibration of the microscope setup, and acquisition and analysis of SFCS data to determine diffusion coefficients and concentrations of fluorescent particles embedded in lipid membranes. PMID:25331137

Hermann, Eduard; Ries, Jonas; García-Sáez, Ana J

2015-01-01

368

Detection of the covalent intermediate of UDP-N-acetylglucosamine enolpyruvyl transferase by solution-state and time-resolved solid-state NMR spectroscopy.  

PubMed

Uridine diphosphate-N-acetylglucosamine (UDP-NAG) enolpyruvyl transferase from Enterobacter cloacae catalyzes the transfer of an enolpyruvyl moiety from phosphoenolpyruvate (PEP) to the 3-hydroxyl of UDP-NAG to form enolpyruvyl UDP-NAG and inorganic phosphate. Indirect evidence for the involvement of a covalent intermediate, in which the C-2 of O-phosphothioketal moiety is attached to Cys-115, in the reaction catalyzed by UDP-NAG enolpyruvyl transferase has been reported by Wanke and Amrhein [Wanke, C., & Amrhein, N. (1993) Eur. J. Biochem. 218, 861-870]. In the enzyme from Escherichia coli, a noncovalent tetrahedral intermediate in which the C-2 of PEP is attached to the 3-OH of UDP-NAG via an ether linkage has been isolated by Marquardt et al. [Marquardt, J.L., Brown, E.D., Walsh, C.T., & Anderson, K.S. (1993) J. Am. Chem. Soc. 115, 10398-10399]. In this study, we provide direct evidence for the formation of a covalent O-phosphothioketal enzyme intermediate from UDP-NAG enolpyruvyl transferase of E. cloacae overexpressed in E. coli. The intermediate was obtained by incubation of the enzyme with [2,3-13C2]PEP and UDP-NAG and was characterized by solution-state 1D 13C and 31P NMR, 13C DEPT NMR, and 1H[13C]2D HMQC NMR spectroscopy. The 13C NMR spectra showed two coupled resonances at 29.3 and 88.7 ppm which were assigned to the C-3 and C-2 of the covalent intermediate, and the 13C DEPT confirmed that C-3 was a methyl group and C-2 was quaternary.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7999765

Ramilo, C; Appleyard, R J; Wanke, C; Krekel, F; Amrhein, N; Evans, J N

1994-12-20

369

Role of local structure and dynamics of small ligand migration in proteins: a study of a mutated truncated hemoprotein from Thermobifida fusca by time resolved MIR spectroscopy.  

PubMed

Carbon monoxide recombination dynamics in a mutant of the truncated hemoglobin from Thermobida fusca (3F-Tf-trHb) has been analyzed by means of ultrafast Visible-pump/MidIR-probe spectroscopy and compared with that of the wild-type protein. In 3F-Tf-trHb, three topologically relevant amino acids, responsible for the ligand stabilization through the formation of a H-bond network (TyrB10 TyrCD1 and TrpG8), have been replaced by Phe residues. X-ray diffraction data show that Phe residues in positions B10 and G8 maintain the same rotameric arrangements as Tyr and Trp in the wild-type protein, while Phe in position CD1 displays significant rotameric heterogeneity. Photodissociation of the ligand has been induced by exciting the sample with 550 nm pump pulses and the CO rebinding has been monitored in two mid-IR regions respectively corresponding to the ?(CO) stretching vibration of the iron-bound CO (1880-1980 cm(-1)) and of the dissociated free CO (2050-2200 cm(-1)). In both the mutant and wild-type protein, a significant amount of geminate CO rebinding is observed on a subnanosecond time scale. Despite the absence of the distal pocket hydrogen-bonding network, the kinetics of geminate rebinding in 3F-Tf-trHb is very similar to the wild-type, showing how the reactivity of dissociated CO toward the heme is primarily regulated by the effective volume and flexibility of the distal pocket and by caging effects exerted on the free CO on the analyzed time scale. PMID:25019316

Patrizi, Barbara; Lapini, Andrea; Di Donato, Mariangela; Marcelli, Agnese; Lima, Manuela; Righini, Roberto; Foggi, Paolo; Baiocco, Paola; Bonamore, Alessandra; Boffi, Alberto

2014-08-01

370

The role of water H-bond imbalances in B-DNA substate transitions and peptide recognition revealed by time-resolved FTIR spectroscopy.  

PubMed

The conformational substates B(I) and B(II) of the phosphodiester backbone in B-DNA are thought to contribute to DNA flexibility and protein recognition. We have studied by rapid scan FTIR spectroscopy the isothermal B(I)-B(II) transition on its intrinsic time scale. Correlation analysis of IR absorption changes occurring within seconds after a reversible incremental growth of the DNA hydration shell identifies water populations w(1) (PO(2)(-)-bound) and w(2) (non-PO(2)(-)-bound) exhibiting weaker and stronger H-bonds, respectively, than those dominating in bulk water. The B(II) substate is stabilized by w(2). The water H-bond imbalance of 3-4 kJ mol(-1) is equalized at little enthalpic cost upon formation of a contiguous water network (at 12-14 H(2)O molecules per DNA phosphate) of reduced ?(OH) bandwidth. In this state, hydration water cooperatively stabilizes the B(I) conformer via the entropically favored replacement of w(2)-DNA interactions by additional w(2)-water contacts, rather than binding to B(I)-specific hydration sites. Such water rearrangements contribute to the recognition of DNA by indolicidin, an antimicrobial 13-mer peptide from bovine neutrophils which, despite little intrinsic structure, preferentially binds to the B(I) conformer in a water-mediated induced fit. The FTIR spectra resolve sequential steps leading from PO(2)(-)-solvation to substate transition and eventually to base stacking changes in the complex. In combination with CD-spectral titrations, the data indicate that, in the absence of a bulk aqueous phase, as in molecular crowded environments, water relocation within the DNA hydration shell allows for entropic contributions similar to those assigned to water upon DNA ligand recognition in solution. PMID:21446714

Khesbak, Hassan; Savchuk, Olesya; Tsushima, Satoru; Fahmy, Karim

2011-04-20

371

Time-resolved experiments on light diffusion in anisotropic random media  

PubMed

Multiple light scattering in isotropic and anisotropic media is studied experimentally with an optical gating technique, as commonly used in fluorescence spectroscopy. The experimental setup permits an accurate analysis of the propagation of a short light pulse through disordered or partially ordered media. The diffusion constant of some isotropic systems is reported, and the anisotropy in the diffusion constant for light diffusion through liquid crystals is observed. For the time-resolved data, good agreement with diffusion theory is found in all cases, including the liquid crystal in the nematic phase. PMID:11102019

Wiersma; Muzzi; Colocci; Righini

2000-11-01

372

Plasmon-controlled fluorescence: a new paradigm in fluorescence spectroscopy  

PubMed Central

Fluorescence spectroscopy is widely used in biological research. Until recently, essentially all fluorescence experiments were performed using optical energy which has radiated to the far-field. By far-field we mean at least several wavelengths from the fluorophore, but propagating far-field radiation is usually detected at larger macroscopic distances from the sample. In recent years there has been a growing interest in the interactions of fluorophores with metallic surfaces or particles. Near-field interactions are those occurring within a wavelength distance of an excited fluorophore. The spectral properties of fluorophores can be dramatically altered by near-field interactions with the electron clouds present in metals. These interactions modify the emission in ways not seen in classical fluorescence experiments. In this review we provide an intuitive description of the complex physics of plasmons and near-field interactions. Additionally, we summarize the recent work on metal–fluorophore interactions and suggest how these effects will result in new classes of experimental procedures, novel probes, bioassays and devices. PMID:18810279

Lakowicz, Joseph R.; Ray, Krishanu; Chowdhury, Mustafa; Szmacinski, Henryk; Fu, Yi; Zhang, Jian; Nowaczyk, Kazimierz

2009-01-01

373

Diagnosing breast cancer using diffuse reflectance spectroscopy and intrinsic fluorescence spectroscopy  

E-print Network

Using diffuse reflectance spectroscopy and intrinsic fluorescence spectroscopy, we have developed an algorithm that successfully classifies normal breast tissue, fibrocystic change, fibroadenoma, and infiltrating ductal ...

Fitzmaurice, Maryann

374

Time-resolved photon migration in bi-layered tissue models.  

PubMed

In this article, we describe a novel Monte Carlo code for time-integrated and time-resolved photon migration simulations of excitation and fluorescent light propagation (with reabsorption) in bi-layered models of biological tissues. The code was experimentally validated using bi-layered, tissue-simulating phantoms and the agreement between simulations and experiment was better than 3%. We demonstrate the utility of the code for quantitative clinical optical diagnostics in epithelial tissues by examining design characteristics for clinically compatible waveguides with arbitrarily complex source-detector configurations. Results for human colonic tissues included a quantitative comparison of simulation predictions with time-resolved fluorescence data measured in vivo and spatio-temporal visualizations of photon migration characteristics in tissue models in both two- and three-dimensions for source-detector configurations, including variable waveguide spacing, numerical aperture, and diameter. These results were then extended from surface point spectroscopy to imaging modalities for both time-gated (fluorescence lifetime) and steady-state (fluorescence intensity) experimental conditions. To illustrate the flexibility of this computational approach, time-domain results were extended to simulate predictions for frequency-domain instrumentation. This work is the first demonstration and validation of a time-domain, multi-wavelength photon transport model with these capabilities in layered turbid-media. PMID:19498772

Vishwanath, Karthik; Mycek, Mary-Ann

2005-09-19

375

Using the finite-difference time-domain pulse propagation method to simulate time-resolved THz experiments  

E-print Network

Using the finite-difference time-domain pulse propagation method to simulate time-resolved THz The finite-difference time-domain FDTD method has been applied to time-resolved THz spectroscopy TRTS experiments. Time-resolved THz spectroscopy utilizes an optical pump pulse to excite the sample, followed

376

Noninvasive skin fluorescence spectroscopy for diabetes screening.  

PubMed

The development of cost-effective, simple, and reproducible tests for diabetes screening represents a priority of modern medicine in light of the increasing prevalence of diabetes mellitus. Besides fasting plasma glucose, the oral glucose tolerance test, and glycated hemoglobin A1c, several tests have been proposed, among them the assessment of skin fluorescence spectroscopy (SFS). This article comments on the article by Olson and coauthors published in this issue of Journal of Diabetes Science and Technology and comprehensively reviews related available information. Overall, SFS seems to represent an easy-to-use, noninvasive tool that adds value to existing tests for diabetes screening. PMID:23911182

Stirban, Alin

2013-07-01

377

Two-Photon Fluorescence Correlation Spectroscopy  

NASA Technical Reports Server (NTRS)

We will describe a two-photon microscope currently under development at the NASA Glenn Research Center. It is composed of a Coherent Mira 900 tunable, pulsed Titanium:Sapphire laser system, an Olympus Fluoview 300 confocal scanning head, and a Leica DM IRE inverted microscope. It will be used in conjunction with a technique known as fluorescence correlation spectroscopy (FCS) to study intracellular protein dynamics. We will briefly explain the advantages of the two-photon system over a conventional confocal microscope, and provide some preliminary experimental results.

Zimmerli, Gregory A.; Fischer, David G.

2002-01-01

378

Thermal stability in the blended lithium manganese oxide - Lithium nickel cobalt manganese oxide cathode materials: An in situ time-resolved X-Ray diffraction and mass spectroscopy study  

NASA Astrophysics Data System (ADS)

Thermal stabilities of a series of blended LiMn2O4 (LMO)-LiNi1/3Co1/3Mn1/3O2 (NCM) cathode materials with different weight ratios were studied by in situ time-resolved X-ray diffraction (XRD) combined with mass spectroscopy in the temperature range of 25 °C-580 °C under helium atmosphere. Upon heating, the electrochemically delithiated LMO changed into Mn3O4 phase at around 250 °C. Formation of MnO with rock-salt structure started at 520 °C. This observation is in contrast to the previous report for chemically delithiated LMO in air, in which a process of ?-MnO2 transforming to ?-MnO2 was observed. Oxygen peak was not observed in all cases, presumably as a result of either consumption by the carbon or detection limit. CO2 profile correlates well with the phase transition and indirectly suggests the oxygen release of the cathode. Introducing NCM into LMO has two effects: first, it makes the high temperature rock-salt phase formation more complicated with more peaks in CO2 profile due to different MO (M = Ni, Mn, Co) phases; secondly, the onset temperature of CO2 release is lowered, implying lowered oxygen release temperature. Upon heating, XRD patterns indicate the NCM part reacts first, followed by the LMO part. This confirms the better thermal stability of LMO over NCM.

Hu, Enyuan; Bak, Seong Min; Senanayake, Sanjaya D.; Yang, Xiao-Qing; Nam, Kyung-Wan; Zhang, Lulu; Shao, Minhua

2015-03-01

379

Time-Resolved Ultraviolet Spectroscopy of the SW Sex Star DW UMa: Confirmation of a Hidden White Dwarf and the UV Counterpart to Phase 0.5 Absorption Events  

E-print Network

We present time-resolved, ultraviolet (UV) spectroscopy of the SW Sex star DW UMa in the high state. We confirm that, shortward of 1500 \\AA, the high-state, UV continuum level is lower than the white dwarf (WD)-dominated low-state level. We also do not see the WD contact phases in the high state eclipse light curves. These results confirm our earlier finding that the WD in this system is hidden from view in the high state. Based on this, we caution that eclipse mapping of high-inclination SW Sex stars in the high state may yield incorrect or misleading results. In the context of DW UMa, we demonstrate explicitly that distance estimates obtained by recent eclipse mapping studies cannot be reconciled with the WD-dominated low-state spectrum. We also show that the fluxes of the UV emission lines in the high state drop near orbital phase 0.5. This is the first detection of a UV counterpart to the class-defining phase 0.5 absorption seen in the optical emission lines of SW Sex stars.

Christian Knigge; Sofia Araujo-Betancor; Boris T. Gaensicke; Knox S. Long; Paula Szkody; D. W. Hoard; R. I. Hynes; V. S. Dhillon

2004-10-12

380

Time-Resolved Ultraviolet Spectroscopy of the SW Sex Star DW UMa: Confirmation of a Hidden White Dwarf and the UV Counterpart to Phase 0.5 Absorption Events  

E-print Network

We present time-resolved, ultraviolet (UV) spectroscopy of the SW Sex star DW UMa in the high state. We confirm that, shortward of 1500 \\AA, the high-state, UV continuum level is lower than the white dwarf (WD)-dominated low-state level. We also do not see the WD contact phases in the high state eclipse light curves. These results confirm our earlier finding that the WD in this system is hidden from view in the high state. Based on this, we caution that eclipse mapping of high-inclination SW Sex stars in the high state may yield incorrect or misleading results. In the context of DW UMa, we demonstrate explicitly that distance estimates obtained by recent eclipse mapping studies cannot be reconciled with the WD-dominated low-state spectrum. We also show that the fluxes of the UV emission lines in the high state drop near orbital phase 0.5. This is the first detection of a UV counterpart to the class-defining phase 0.5 absorption seen in the optical emission lines of SW Sex stars.

Knigge, C; Gänsicke, B T; Long, K S; Szkody, P; Hoard, D W; Hynes, R I; Dhillon, V S; Knigge, Christian; Araujo-Betancor, Sofia; Gaensicke, Boris T.; Long, Knox S.; Szkody, Paula

2004-01-01

381

Time-resolved Ultraviolet Spectroscopy of the SW Sex Star DW UMa: Confirmation of a Hidden White Dwarf and the Ultraviolet Counterpart to Phase 0.5 Absorption Events  

NASA Astrophysics Data System (ADS)

We present time-resolved ultraviolet (UV) spectroscopy of the SW Sex star DW UMa in the high state. We confirm that shortward of 1500 Å, the high-state UV continuum level is lower than the white dwarf (WD) dominated low-state level. We also do not see the WD contact phases in the high-state eclipse light curves. These results confirm our earlier finding that the WD in this system is hidden from view in the high state. On the basis of this, we caution that eclipse mapping of high-inclination SW Sex stars in the high state may yield incorrect or misleading results. In the context of DW UMa, we demonstrate explicitly that distance estimates obtained by recent eclipse-mapping studies cannot be reconciled with the WD-dominated low-state spectrum. We also show that the fluxes of the UV emission lines in the high state drop near orbital phase 0.5. This is the first detection of a UV counterpart to the class-defining phase 0.5 absorption seen in the optical emission lines of SW Sex stars. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS5-26555.

Knigge, Christian; Araujo-Betancor, Sofia; Gänsicke, Boris T.; Long, Knox S.; Szkody, Paula; Hoard, D. W.; Hynes, R. I.; Dhillon, V. S.

2004-11-01

382

Fluorescence fluctuation spectroscopy for clinical applications  

NASA Astrophysics Data System (ADS)

Fluorescence correlation spectroscopy (FCS) and the related techniques of brightness analysis have become standard tools in biological and biophysical research. By analyzing the statistics of fluorescence emitted from a restricted volume, a number of parameters including concentrations, diffusion coefficients and chemical reaction rates can be determined. The single-molecule sensitivity, spectral selectivity, small sample volume and non-perturbative measurement mechanism of FCS make it an excellent technique for the study of molecular interactions. However, its adoption outside of the research laboratory has been limited. Potential reasons for this include the cost and complexity of the required apparatus. In this work, the application of fluorescence fluctuation analysis to several clinical problems is considered. Optical designs for FCS instruments which reduce the cost and increase alignment tolerance are presented. Brightness analysis of heterogenous systems, with application to the characterization of protein aggregates and multimer distributions, is considered. Methods for FCS-based assays of two clinically relevant proteins, von Willebrand factor and haptoglobin, are presented as well.

Olson, Eben

383

[A new measurement method of time-resolved spectrum].  

PubMed

A new method for measuring time-resolved spectrum (TRS) is brought forward. Programming with assemble language controlled the micro-control-processor (AT89C51), and a kind of peripheral circuit constituted the drive circuit, which drived the stepping motor to run the monochromator. So the light of different kinds of expected wavelength could be obtained. The optical signal was transformed to electrical signal by optical-to-electrical transform with the help of photomultiplier tube (Hamamatsu 1P28). The electrical signal of spectrum data was transmitted to the oscillograph. Connecting the two serial interfaces of RS232 between the oscillograph and computer, the electrical signal of spectrum data could be transmitted to computer for programming to draw the attenuation curve and time-resolved spectrum (TRS) of the swatch. The method for measuring time-resolved spectrum (TRS) features parallel measurement in time scale but serial measurement in wavelength scale. Time-resolved spectrum (TRS) and integrated emission spectrum of Tb3+ in swatch Tb(o-BBA)3 phen were measured using this method. Compared with the real time-resolved spectrum (TRS). It was validated to be feasible, credible and convenient. The 3D spectra of fluorescence intensity-wavelength-time, and the integrated spectrum of the swatch Tb(o-BBA)3 phen are given. PMID:17514939

Shi, Zhi-gang; Huang, Shi-hua; Liang, Chun-jun; Lei, Quan-sheng

2007-02-01

384

Time-resolved FRET reveals the structural mechanism of SERCAPLB Xiaoqiong Dong a  

E-print Network

Time-resolved FRET reveals the structural mechanism of SERCA­PLB regulation Xiaoqiong Dong May 2014 Keywords: Phospholamban SERCA Phosphorylation FRET a b s t r a c t We have used time-resolved fluorescence resonance energy transfer (TR-FRET) to characterize the inter- action between phospholamban (PLB

Thomas, David D.

385

Time-resolved Mueller matrix imaging polarimetry  

Microsoft Academic Search

We present a new method of time-resolved Mueller matrix imaging polarimetry for spatial and temporal characterization of the polarization effects in backscattering from turbid media. The technique allows measuring the time evolution of spatially varying polarization patterns of diffusely backscattered light with picosecond resolution. A series of time-resolved polarization patterns are obtained at various time delays, are analyzed in sequence,

Ihor Berezhnyy; Aristide Dogariu

2004-01-01

386

Optimizing Disinfection Pretreatment using Excitation-emission Matrix Fluorescence Spectroscopy  

Microsoft Academic Search

Excitation-emission matrix fluorescence spectroscopy (EEM) can be used to characterize organic matter present in water samples. When excited, the intensity of fluorescence emitted can be used to generate a representation of organic matter makes it possible to localize fluorescence centers related to particular groups, which can ‘fingerprint’ a sample. The technique is applicable to wastewater samples to identify contributors of

Katherine Y. Bell; Juan Sánez; Martha J. M. Wells

2012-01-01

387

Investigation of the role of protonation of benzophenone and its derivatives in acidic aqueous solutions using time-resolved resonance Raman spectroscopy: how are ketyl radicals formed in aqueous solutions?  

PubMed

The formation mechanism of ketyl radicals and several other selective photoreactions of benzophenone and its derivatives are initiated by the protonation of their triplet state and have been investigated using nanosecond time-resolved resonance Raman spectroscopy (ns-TR(3)) in solutions of varying conditions. Evidence is found that the ketyl radical is generated by the combined action of a ketone protonation and a subsequent electron transfer based on the results from previous studies on the photochemistry and photophysics of benzophenone and the ns-TR(3) results reported here for benzophenone, 1,4-dibenzoylbenzene, 3-(hydroxymethyl)benzophenone, and ketoprofen in neutral and acidic solution. In order to better understand the role of the protonated ketone, results are summarized for some selective photochemical reactions of benzophenone and its derivatives induced by protonation in acidic solutions. For the parent benzophenone, the protonation of the ketone leads to the photohydration reactions at the ortho- and meta-positions of the benzene ring in acidic aqueous solutions. For 3-(hydroxymethyl)benzophenone, the protonation promotes an interesting photoredox reaction to become very efficient and the predominant reaction in a pH = 2 aqueous solution. While for ketoprofen, the protonation can initiate a solvent-mediated excited-state intramolecular proton transfer (ESIPT) from the carboxyl group to the carbonyl group that then leads to a decarboxylation reaction in a pH = 0 acidic aqueous solution. We briefly discuss the key role of the protonation of the ketone in the photochemistry of these aromatic ketones. PMID:25141023

Li, Ming-De; Huang, Jinqing; Liu, Mingyue; Li, Songbo; Ma, Jiani; Phillips, David Lee

2015-02-12

388

Electrochemistry, Chemical Reactivity, and Time-Resolved Infrared Spectroscopy of Donor–Acceptor Systems [(Qx)Pt(papy)] (Q = Substituted o-Quinone or o-Iminoquinone; pap = Phenylazopyridine)  

PubMed Central

The donor–acceptor complex [(O,NQ2–)Pt(pap0)] (1; pap = phenylazopyridine, O,NQ0 = 4,6-di-tert-butyl-N-phenyl-o-iminobenzoquinone), which displays strong ?-bonding interactions and shows strong absorption in the near-IR region, has been investigated with respect to its redox-induced reactivity and electrochemical and excited-state properties. The one-electron-oxidized product [(O,NQ•–)Pt(pap0)](BF4) ([1]BF4) was chemically isolated. Single-crystal X-ray diffraction studies establish the iminosemiquinone form of O,NQ in [1]+. Simulation of the cyclic voltammograms of 1 recorded in the presence of PPh3 elucidates the mechanism and delivers relevant thermodynamic and kinetic parameters for the redox-induced reaction with PPh3. The thermodynamically stable product of this reaction, complex [(O,NQ•–) Pt(PPh3)2](PF6) ([2]PF6), was isolated and characterized by X-ray crystallography, electrochemistry, and electron paramagnetic resonance spectroscopy. Picosecond time-resolved infrared spectroscopic studies on complex 1b (one of the positional isomers of 1) and its analogue [(O,OQ2–)Pt(pap0)] (3; O,OQ = 3,5-di-tert-butyl-o-benzoquinone) provided insight into the excited-state dynamics and revealed that the nature of the lowest excited state in the amidophenolate complex 1b is primarily diimine-ligand-based, while it is predominantly an interligand charge-transfer state in the case of 3. Density functional theory calculations on [1]n+ provided further insight into the nature of the frontier orbitals of various redox forms and vibrational mode assignments. We discuss the mechanistic details of the newly established redox-induced reactivity of 1 with electron donors and propose a mechanism for this process. PMID:24400886

2014-01-01

389

TWO-COLOR FLUORESCENCE (CROSS-)CORRELATION SPECTROSCOPY ON A SELECTIVE PLANE ILLUMINATION MICROSCOPE  

E-print Network

TWO-COLOR FLUORESCENCE (CROSS-)CORRELATION SPECTROSCOPY ON A SELECTIVE PLANE ILLUMINATION: Imaging fluorescence cross-correlation spectroscopy, selective plane illumination microscopy, quantitative imaging, EMCCD camera ABSTRACT: Fluorescence correlation spectroscopy (FCS) is a useful technology

Garbe, Christoph S.

390

A fluorescence lifetime spectroscopy study of matrix metalloproteinases -2 and -9 in human atherosclerotic plaque  

PubMed Central

Matrix metalloproteinase (MMP) -2 and -9 play important roles in the progression of atherosclerosis. This study aims to determine whether MMP-2 and -9 content in the fibrotic caps of atherosclerotic plaque is correlated with plaque autofluorescence. A time-resolved laser-induced fluorescence spectroscopy (TR-LIFS) system was used to measure the autofluorescence and assess the biochemical composition of human plaques obtained from carotid endarterectomy. Results presented here demonstrate for the first time the ability to characterize the biochemical composition as it relates to MMP-2 and -9 content in the atherosclerotic plaque cap using a label-free imaging technique implemented with a fiberoptic TR-LIFS system. PMID:21770037

Phipps, Jennifer E.; Hatami, Nisa; Galis, Zorina S.; Baker, J. Dennis; Fishbein, Michael C.; Marcu, Laura

2011-01-01

391

Standoff Raman spectrometry for the non-invasive detection of explosives precursors in highly fluorescing packaging.  

PubMed

Noninvasive standoff deep Raman spectroscopy has been utilised for the detection of explosives precursors in highly fluorescing packaging from 15m. To our knowledge this is the first time standoff deep Raman spectroscopy of concealed substances in highly fluorescing coloured packaging is demonstrated. Time-resolved Raman spectroscopy, spatially offset Raman spectroscopy and time-resolved spatially offset Raman spectroscopy have been compared to identify their selectivity towards the deep layers of a sample. The selectivity of time-resolved Raman spectroscopy towards the concealed chemical substances was found to be comparable to that of spatially offset Raman spectroscopy. However, time-resolved Raman spectroscopy did not require precise translation of the laser excitation beam onto the surface of the interrogated packaging as in the case of spatially offset Raman spectroscopy. Our results confirm that standoff time-resolved spatially offset Raman spectroscopy has significantly higher selectivity towards the deep layers of a sample when compared to the other deep Raman spectroscopy modes. The developed spectrometer was capable of detecting the concealed substances within 5s of data acquisition. By using time-resolved spatially Raman spectroscopy, a Raman spectrum that is representative of the content alone was acquired without the use of sophisticated algorithms to eliminate the spectral contributions of the packaging material within the acquired spectrum as in the case of time-resolved Raman spectroscopy and spatially offset Raman spectroscopy. PMID:23200353

Izake, Emad L; Sundarajoo, Shankaran; Olds, William; Cletus, Biju; Jaatinen, Esa; Fredericks, Peter M

2013-01-15

392

Europium Uptake and Partitioning in Oat (Avena sativa) Roots as studied By Laser-Induced Fluorescence Spectroscopy and Confocal Microscopy Profiling Technique  

SciTech Connect

The uptake of Eu3+ by elongating oat plant roots was studied by fluorescence spectroscopy, fluorescence lifetime measurement, as well as laser excitation time-resolved confocal fluorescence profiling technique. The results of this work indicated that the initial uptake of Eu(III) by oat root was most evident within the apical meristem of the root just proximal to the root cap. Distribution of assimilated Eu(III) within the roots differentiation and elongation zone was non-uniform. Higher concentrations were observed within the vascular cylinder, specifically in the phloem and developing xylem parenchyma. Elevated levels of the metal were also observed in the root hairs of the mature root. The concentration of assimilated Eu3+ dropped sharply from the apical meristem to the differentiation and elongation zone and then gradually decreased as the distance from the root cap increased. Fluorescence spectroscopic characteristics of the assimilated Eu3+ suggested that the Eu3+ exists a s inner-sphere mononuclear complexes inside the root. This work has also demonstrated the effectiveness of a time-resolved Eu3+ fluorescence spectroscopy and confocal fluorescence profiling techniques for the in vivo, real-time study of metal[Eu3+] accumulation by a functioning intact plant root. This approach can prove valuable for basic and applied studies in plant nutrition and environmental uptake of actinide radionuclides.

Fellows, Robert J.; Wang, Zheming; Ainsworth, Calvin C.

2003-11-15

393

Time-Resolved Photoluminescence and Photovoltaics  

SciTech Connect

The time-resolved photoluminescence (TRPL) technique and its ability to characterize recombination in bulk photovoltaic semiconductor materials are reviewed. Results from a variety of materials and a few recent studies are summarized and compared.

Metzger, W. K.; Ahrenkiel, R. K.; Dippo, P.; Geisz, J.; Wanlass, M. W.; Kurtz, S.

2005-01-01

394

Electronic nose to detect volatile compound profile and quality changes in 'spring Belle' peach (Prunus persica L.) during cold storage in relation to fruit optical properties measured by time-resolved reflectance spectroscopy.  

PubMed

The aim of this research was to study the relationships between electronic nose (E-nose) pattern, maturity class of peaches assessed at harvest by means of absorption coefficient at 670 nm (?(a)670) measured in fruit pulp by time-resolved reflectance spectroscopy (TRS), and quality evolution during a 4 week cold storage. 'Spring Belle' peaches were measured for ?(a)670 by TRS, ranked according to decreasing ?(a)670 value, divided into three TRS maturity classes (less (LeM), medium (MeM), and more (MoM) mature), and randomized into 9 samples of 30 fruit each, so that fruits from the whole ?(a)670 range were present in each sample. At harvest and after 1, 2, 3, and 4 weeks of storage at 0 and 4 °C, fruits of each sample were evaluated for firmness, expressible juice, ?(a)670, and ethylene production. LeM and MoM peaches of each sample were analyzed for aroma pattern by a commercial electronic nose and by static HS-GC and for sugar (glucose, fructose, sucrose, and sorbitol) and organic acid (quinic, malic, and citric acids) compositions by HPLC. Principal component analysis (PCA) of electronic nose data emphasized the ability of the E-nose to assess the ripening stage of fruit associated with maturity class, storage time, and storage temperature. The sensors having the highest influence on the pattern were W5S in PC-1, W1S in PC-2, and W2S in PC-3. From linear correlation analysis between PCs and firmness, flavor, and volatile compounds, it was found that PC-1 was related to ethylene production and volatile compounds (mainly acetate esters and ethanol); the highest PC-1 scores were found for fruit belonging to the MoM class after 2 weeks of storage at 4 °C, which showed the rise in ethylene production coupled with the highest total volatile production and sugar and acid composition of ripe peach fruits. PC-2 correlated with hexanal, ethyl acetate, and sugar composition, and PC-3 was mainly related to flavor compounds; both functions significantly changed with cold storage time in different ways according to storage temperature and maturity class. PMID:23020286

Rizzolo, Anna; Bianchi, Giulia; Vanoli, Maristella; Lurie, Susan; Spinelli, Lorenzo; Torricelli, Alessandro

2013-02-27

395

Time-resolved cathodoluminescence and photoluminescence of nanoscale oxides  

Microsoft Academic Search

The nanostructured oxide materials such as ZnO, ZrO2, and Y3Al5O12 (YAG) are perspective materials for transparent scintillating and\\/or laser ceramics. The luminescence properties of single crystals, nanopowders and ceramic were compared. Nominally pure and rare-earth doped nanopowders and ceramics have been studied by means of time-resolved luminescence spectroscopy.The fast blue luminescence band was studied in ZnO ceramics sintering from different

L. Grigorjeva; D. Millers; A. Kalinko; V. Pankratov; K. Smits

2009-01-01

396

Detection of colorectal cancer using time-resolved autofluorescence spectrometer  

NASA Astrophysics Data System (ADS)

As we know Quantum mechanics is a mathematical theory that can describe the behavior of objects that are at microscopic level. Time-resolved autofluorescence spectrometer monitors events that occur during the lifetime of the excited state. This time ranges from a few picoseconds to hundreds of nanoseconds. That is an extremely important advance as it allows environmental parameters to be monitored in a spatially defined manner in the specimen under study. This technique is based on the application of Quantum Mechanics. This principle is applied in our project as we are trying to use different fluorescence spectra to detect biological molecules commonly found in cancerous colorectal tissue and thereby differentiate the cancerous and non-cancerous colorectal polyps more accurately and specifically. In this paper, we use Fluorescence Lifetime Spectrometer (Edinburgh Instruments FL920) to measure decay time of autofluorescence of colorectal cancerous and normal tissue sample. All specimens are from Department of Colorectal Surgery, Singapore General Hospital. The tissues are placed in the time-resolved autofluorescence instrument, which records and calculates the decay time of the autofluorescence in the tissue sample at the excitation and emission wavelengths pre-determined from a conventional spectrometer. By studying the decay time,?, etc. for cancerous and normal tissue, we aim to present time-resolved autofluorescence as a feasible technique for earlier detection of malignant colorectal tissues. By using this concept, we try to contribute an algorithm even an application tool for real time early diagnosis of colorectal cancer for clinical services.

Fu, Sheng; Kwek, Leong-Chuan; Chia, Teck-Chee; Lim, Chu-Sing; Tang, Choong-Leong; Ang, Wuan-Suan; Zhou, Miao-Chang; Loke, Po-Ling

2006-04-01

397

Effect of probe pressure on cervical fluorescence spectroscopy measurements  

E-print Network

Fluorescence spectroscopy is a promising technology for detection of epithelial precancers and cancers. While age and menopausal status influence measurements in the cervix, other variables do not significantly affect the ...

Nath, Audrey

398

Native fluorescence spectroscopy of thymus and fat tissues  

NASA Astrophysics Data System (ADS)

Fluorescence spectroscopy of the human thymus gland and surrounding mediastinal fat were measured to evaluate this approach in distinguishing between thymus and fat tissues during therapeutic surgery for myasthenia gravis disease.

Tang, Gui C.; Oz, Mehmet C.; Reid, V.; Steinglass, K.; Ginsberg, Mark D.; Jacobowitz, Larry; Alfano, Robert R.

1993-08-01

399

Quantitative Determination of DNA-Ligand Binding Using Fluorescence Spectroscopy  

ERIC Educational Resources Information Center

The effective use of fluorescence spectroscopy for determining the binding of the intercalcating agent crhidium bromide to DNA is being described. The analysis used simple measurement techniques and hence can be easily adopted by the students for a better understanding.

Healy, Eamonn F.

2007-01-01

400

Fluorescence Lifetime Techniques in Medical Applications  

PubMed Central

This article presents an overview of time-resolved (lifetime) fluorescence techniques used in biomedical diagnostics. In particular, we review the development of time-resolved fluorescence spectroscopy (TRFS) and fluorescence lifetime imaging (FLIM) instrumentation and associated methodologies which allows for in vivo characterization and diagnosis of biological tissues. Emphasis is placed on the translational research potential of these techniques and on evaluating whether intrinsic fluorescence signals provide useful contrast for the diagnosis of human diseases including cancer (gastrointestinal tract, lung, head and neck, and brain), skin and eye diseases, and atherosclerotic cardiovascular disease. PMID:22273730

Marcu, Laura

2012-01-01

401

Multimodal, multiplex, Raman spectroscopy of alcohol in diffuse, fluorescent media  

E-print Network

Multimodal, multiplex, Raman spectroscopy of alcohol in diffuse, fluorescent media Scott T. Mc spectrometer to detect alcohol in a lipid tissue phantom solution. Keywords: Raman Spectroscopy, Tissue in solutions of a lipid tissue phantom. At high lipid concentrations, our instrument detects Raman signatures

Pitsianis, Nikos P.

402

Low-temperature and time-resolved spectroscopic characterization of the LOV2 domain of Avena sativa phototropin 1  

NASA Astrophysics Data System (ADS)

The phototropins are plant 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 residue in light, oxygen or voltage (LOV) domains. The spectroscopic properties of the LOV2 domain of phototropin 1 of Avena sativa (oat) have been investigated by means of low-temperature absorption and fluorescence spectroscopy and by time-resolved fluorescence spectroscopy. The low-temperature absorption spectrum of the LOV2 domain showed a fine structure around 473 nm, indicating heterogeneity in the flavin binding pocket. The fluorescence quantum yield of the flavin cofactor increased from 0.13 to 0.41 upon cooling the sample from room temperature to 77 K. A pronounced phosphorescence emission around 600 nm was observed in the LOV2 domain between 77 and 120 K, allowing for an accurate positioning of the flavin triplet state in the LOV2 domain at 16900 cm-1. Fluorescence from the cryotrapped covalent adduct state was extremely weak, with a fluorescence spectrum showing a maximum at 440 nm. Time-resolved fluorescence experiments utilizing a synchroscan streak camera revealed a singlet-excited state lifetime of the LOV2 domain of 2.4 ns. FMN dissolved in aqueous solution showed a pH-dependent lifetime ranging between 2.9 ns at pH 2.0 to 4.7 ns at pH 8.0. No spectral shifting of the flavin emission was observed in the LOV2 domain nor in FMN in aqueous solution.

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

2004-09-01

403

Low-temperature and time-resolved spectroscopic characterization of the LOV2 domain of Avena sativa phototropin  

SciTech Connect

The phototropins are plant 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 residue in light, oxygen or voltage (LOV) domains. The spectroscopic properties of the LOV2 domain of phototropin 1 of Avena sativa (oat) have been investigated by means of low-temperature absorption and fluorescence spectroscopy and by time-resolved fluorescence spectroscopy. The low-temperature absorption spectrum of the LOV2 domain showed a fine structure around 473 nm, indicating heterogeneity in the flavin binding pocket. The fluorescence quantum yield of the flavin cofactor increased from 0.13 to 0.41 upon cooling the sample from room temperature to 77 K. A pronounced phosphorescence emission around 600 nm was observed in the LOV2 domain between 77 and 120 K, allowing for an accurate positioning of the flavin triplet state in the LOV2 domain at 16900 cm{sup -1}. Fluorescence from the cryotrapped covalent adduct state was extremely weak, with a fluorescence spectrum showing a maximum at 440 nm. Time-resolved fluorescence experiments utilizing a synchroscan streak camera revealed a singlet-excited state lifetime of the LOV2 domain of 2.4 ns. FMN dissolved in aqueous solution showed a pH-dependent lifetime ranging between 2.9 ns at pH 2.0 to 4.7 ns at pH 8.0. No spectral shifting of the flavin emission was observed in the LOV2 domain nor in FMN in aqueous solution.

Gauden, Magdalena; Crosson, Sean; van Stokkum, I.H.; Grondelle, Rienkvan; Moffat, Keith; Kennis, John T. (UC)

2004-12-13

404

Complexation of Cm(iii) with the recombinant N-lobe of human serum transferrin studied by time-resolved laser fluorescence spectroscopy (TRLFS).  

PubMed

The complexation of Cm(iii) with the recombinant N-lobe of human serum transferrin (hTf/2N) is investigated in the pH range from 4.0 to 11.0 using TRLFS. At pH ? 7.4 a Cm(iii) hTf/2N species is formed with Cm(iii) bound at the Fe(iii) binding site. The results are compared with Cm(iii) transferrin interaction at the C-lobe and indicate the similarity of the coordination environment of the C- and N-terminal binding sites with four amino acid residues of the protein, two H2O molecules and three additional ligands (e.g. synergistic anions such as carbonate) in the first coordination sphere. Measurements at c(carbonate)tot = 0.23 mM (ambient carbonate concentration) and c(carbonate)tot = 25 mM (physiological carbonate concentration) show that an increase of the total carbonate concentration suppresses the formation of the Cm(iii) hTf/2N species significantly. Additionally, the three Cm(iii) carbonate species Cm(CO3)(+), Cm(CO3)2(-) and Cm(CO3)3(3-) are formed successively with increasing pH. In general, carbonate complexation is a competing reaction for both Cm(iii) complexation with transferrin and hTf/2N but the effect is significantly higher for the half molecule. At c(carbonate)tot = 0.23 mM the complexation of Cm(iii) with transferrin and hTf/2N starts at pH ? 7.4. At physiological carbonate concentration the Cm(iii) transferrin species II forms at pH ? 7.0 whereas the Cm(iii) hTf/2N species is not formed until pH > 10.0. Hence, our results reveal significant differences in the complexation behavior of the C-terminal site of transferrin and the recombinant N-lobe (hTf/2N) towards trivalent actinides. PMID:25483018

Bauer, N; Smith, V C; MacGillivray, R T A; Panak, P J

2014-12-23

405

Time-resolved optical spectrometer based on a monolithic array of high-precision TDCs and SPADs  

NASA Astrophysics Data System (ADS)

We present a compact time-resolved spectrometer suitable for optical spectroscopy from 400 nm to 1 ?m wavelengths. The detector consists of a monolithic array of 16 high-precision Time-to-Digital Converters (TDC) and Single-Photon Avalanche Diodes (SPAD). The instrument has 10 ps resolution and reaches 70 ps (FWHM) timing precision over a 160 ns full-scale range with a Differential Non-Linearity (DNL) better than 1.5 % LSB. The core of the spectrometer is the application-specific integrated chip composed of 16 pixels with 250 ?m pitch, containing a 20 ?m diameter SPAD and an independent TDC each, fabricated in a 0.35 ?m CMOS technology. In front of this array a monochromator is used to focus different wavelengths into different pixels. The spectrometer has been used for fluorescence lifetime spectroscopy: 5 nm spectral resolution over an 80 nm bandwidth is achieved. Lifetime spectroscopy of Nile blue is demonstrated.

Tamborini, Davide; Markovic, Bojan; Di Sieno, Laura; Contini, Davide; Bassi, Andrea; Tisa, Simone; Tosi, Alberto; Zappa, Franco

2013-12-01

406

Laser-induced fluorescence spectroscopy in tissue local necrosis detection  

NASA Astrophysics Data System (ADS)

The recent effort leads to reliable imaging techniques which can help to a surgeon during operations. The fluorescence spectroscopy was selected as very useful online in vivo imaging method to organics and biological materials analysis. The presented work scopes to a laser induced fluorescence spectroscopy technique to detect tissue local necrosis in small intestine surgery. In first experiments, we tested tissue auto-fluorescence technique but a signal-to-noise ratio didn't express significant results. Then we applied a contrast dye - IndoCyanine Green (ICG) which absorbs and emits wavelengths in the near IR. We arranged the pilot experimental setup based on highly coherent extended cavity diode laser (ECDL) used for stimulating of some critical areas of the small intestine tissue with injected ICG dye. We demonstrated the distribution of the ICG exciter with the first file of shots of small intestine tissue of a rabbit that was captured by high sensitivity fluorescent cam.

Cip, Ondrej; Buchta, Zdenek; Lesundak, Adam; Randula, Antonin; Mikel, Bretislav; Lazar, Josef; Veverkova, Lenka

2014-03-01

407

Time-resolved multiphoton imaging of basal cell carcinoma  

NASA Astrophysics Data System (ADS)

We investigated human cutaneous basal cell carcinoma ex-vivo samples by combined time resolved two photon intrinsic fluorescence and second harmonic generation microscopy. Morphological and spectroscopic differences were found between malignant skin and corresponding healthy skin tissues. In comparison with normal healthy skin, cancer tissue showed a different morphology and a mean fluorescence lifetime distribution slightly shifted towards higher values. Topical application of delta-aminolevulinic acid to the lesion four hours before excision resulted in an enhancement of the fluorescence signal arising from malignant tissue, due to the accumulation of protoporphyrines inside tumor cells. Contrast enhancement was prevalent at tumor borders by both two photon fluorescence microscopy and fluorescence lifetime imaging. Fluorescence-based images showed a good correlation with conventional histopathological analysis, thereby supporting the diagnostic accuracy of this novel method. Combined morphological and lifetime analysis in the study of ex-vivo skin samples discriminated benign from malignant tissues, thus offering a reliable, non-invasive tool for the in-vivo analysis of inflammatory and neoplastic skin lesions.

Cicchi, R.; Sestini, S.; De Giorgi, V.; Stambouli, D.; Carli, P.; Massi, D.; Pavone, F. S.

2007-02-01

408

Spectral and time-resolved studies on ocular structures  

NASA Astrophysics Data System (ADS)

Measurements of endogeous fluorophores open the possibility for evaluation of metabolic state at the eye. For interpretation of 2-dimensional measurements of time-resolved auto fluorescence in 2 separate spectral ranges at the human eye, comparing measurements were performed on porcine eyes. Determining excitation and emission spectra, attention was drawn of proof of coenzymes NADH and FAD in isolated anatomical structures cornea, aqueous humor, lens, vitreous, neuronal retina, retinal pigment epithelium (RPE), choroid, and sclera. All these structures exhibit auto fluorescence, highest in lens. Excitation at 350 nm results in local fluorescence maxima at 460 nm, corresponding to NADH, in all structures. This short-wave excitation allows metabolic studies only at the anterior eye, because of the limited transmission of the ocular media. During excitation at 446 nm the existence of FAD is expressed by local fluorescence maxima at 530 nm. The composition fluorescence spectra allow no discrimination between single ocular structures. Approximating the dynamic fluorescence by a double exponential function, the shortest lifetimes were detected in RPE and neuronal retina. The histograms of mean lifetime t M cover each other on lens with cornea and also on sclera with choroid. Despite the lifetimes are close between RPE and neuronal retina, the relative contributions Q I are wide different. The gradient of trend lines in cluster diagrams of amplitudes ? II vs. ? I allows a discrimination of ocular structures.

Schweitzer, D.; Jentsch, S.; Schenke, S.; Hammer, M.; Biskup, C.; Gaillard, E.

2007-07-01

409

Fluorescence correlation spectroscopy and its potential for intracellular applications  

Microsoft Academic Search

Fluorescence correlation spectroscopy (FCS) is a time-averaging fluctuation analysis of small molecular ensembles, combining\\u000a maximum sensitivity with high statistical confidence. Among a multitude of physical parameters that are, in principle, accessible\\u000a by FCS, it most conveniently allows to determine local concentrations, mobility coefficients, and characteristic rate constants\\u000a of fast-reversible and slow-irreversible reactions of fluorescently labeled biomolecules at very low (nanomolar)

Petra Schwille

2001-01-01

410

Time-Resolved Conformational Dynamics in Hydrocarbon Chains  

SciTech Connect

Internal rotation about carbon-carbon bonds allows N,N-dimethyl-2-butanamine (DM2BA) and N,N-dimethyl-3-hexanamine (DM3HA) to assume multiple conformeric structures. We explore the equilibrium composition and dynamics between such conformeric structures using Rydberg fingerprint spectroscopy. Time constants for conformeric interconversion of DM2BA (at 1.79 eV of internal energy) are 19 and 66 ps, and for DM3HA (1.78 eV) 23 and 41 ps. For the first time, a time-resolved and quantitative view of conformational dynamics of flexible hydrocarbon molecules at high temperatures is revealed.

Minitti, Michael P.; Weber, Peter M. [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States)

2007-06-22

411

Structural kinetics of myosin by transient time-resolved FRET.  

PubMed

For many proteins, especially for molecular motors and other enzymes, the functional mechanisms remain unsolved due to a gap between static structural data and kinetics. We have filled this gap by detecting structure and kinetics simultaneously. This structural kinetics experiment is made possible by a new technique, (TR)(2)FRET (transient time-resolved FRET), which resolves protein structural states on the submillisecond timescale during the transient phase of a biochemical reaction. (TR)(2)FRET is accomplished with a fluorescence instrument that uses a pulsed laser and direct waveform recording to acquire an accurate subnanosecond time-resolved fluorescence decay every 0.1 ms after stopped flow. To apply this method to myosin, we labeled the force-generating region site specifically with two probes, mixed rapidly with ATP to initiate the recovery stroke, and measured the interprobe distance by (TR)(2)FRET with high resolution in both space and time. We found that the relay helix bends during the recovery stroke, most of which occurs before ATP is hydrolyzed, and two structural states (relay helix straight and bent) are resolved in each nucleotide-bound biochemical state. Thus the structural transition of the force-generating region of myosin is only loosely coupled to the ATPase reaction, with conformational selection driving the motor mechanism. PMID:21245357

Nesmelov, Yuri E; Agafonov, Roman V; Negrashov, Igor V; Blakely, Sarah E; Titus, Margaret A; Thomas, David D

2011-02-01

412

Design of time-resolved fluorometer based on immunochromatography  

NASA Astrophysics Data System (ADS)

This paper introduces the design of a novel time-resolved fluorometer based on immunochromatograghy. Different from the other time-resolved fluorometers, it tests the immunochromatographic strip which is labeled with lanthanide ions and their chelates. This instrument can provide a rapid, quantitative measurement of analytes present in samples without any washing steps and it can be used to carry out point-of-care test (POCT). The immunochromatograghy-based timeresolved fluorometer is composed of a specific optical sensor, a scanning stage, a signal processing system and a computer control system. The light from UV LED is focused on the test strip by a condense lens group in the optical sensor. If the labels are present in samples, the fluorescence at 613nm will be exited (when Eu3+chelate is used for marking substance). After a delay of some microseconds, the fluorescence will be collected by the optical sensor and converted into electronic signal by a photomultiplier tube (PMT). The concentration of the sample can be calculated through the standard working curve of this instrument. By testing, the sensitivity is several ng/ml level (when Eu3+chelate is used for marking substance), test linear range is from several ng/ml to 103 ng/ml, in which correlation coefficient is 99.97%.

Ren, Bingqiang; Huang, Lihua; Huang, Huijie

2008-12-01

413

Pancreatic tissue assessment using fluorescence and reflectance spectroscopy  

NASA Astrophysics Data System (ADS)

The ability of multi-modal optical spectroscopy to detect signals from pancreatic tissue was demonstrated by studying human pancreatic cancer xenografts in mice and freshly excised human pancreatic tumor tissue. Measured optical spectra and fluorescence decays were correlated with tissue morphological and biochemical properties. The measured spectral features and decay times correlated well with expected pathological differences in normal, pancreatitis and adenocarcinoma tissue states. The observed differences between the fluorescence and reflectance properties of normal, pancreatitis and adenocarcinoma tissue indicate a possible application of multi-modal optical spectroscopy to differentiating between the three tissue classifications.

Chandra, Malavika; Heidt, David; Simeone, Diane; McKenna, Barbara; Scheiman, James; Mycek, Mary-Ann

2007-07-01

414

Time-resolved reaction yield detected magnetic resonance (RYDMR)  

NASA Astrophysics Data System (ADS)

Novel time-resolved reaction yield detected magnetic resonance studies are reported on exciplex systems consisting of pyrene and dicyanobenzene. It is shown that the fluorescence from the systems, observed under the action of a static and a resonant magnetic field, exhibits a marked variation in time, including oscillations, after the creation of the exciplex. This variation is characteristically different between the three isomers of the dicyanobenzene molecule. In a theoretical analysis, the major experimental features are reproduced and it is suggested that oscillations observed in the fluorescence decay curves may correlate with ST 0 mixing quantum beats. This experiment provides a new method for studying the spin evolution inside radical pair systems and for estimating the lifetime of the spin-correlated radical pair.

Batchelor, S. N.; McLauchlan, K. A.; Shkrob, I. A.

1991-06-01

415

Single molecule fluorescence spectroscopy of mutants of the Discosoma red fluorescent protein DsRed  

NASA Astrophysics Data System (ADS)

We studied the emission of mutants of the red fluorescent protein DsRed by room temperature single molecule fluorescence spectroscopy. Bulk samples of the DsRed variant E8 show mixed green and red fluorescence of equivalent intensities individually spectrally similar to arrested green and mature red fluorescent forms of DsRed. Investigations at the single molecule level indicate that, like DsRed, E8 is not monomeric at single molecule concentrations. The entities visualized are composed of green and red emitting proteins without a fixed ratio of green to red fluorescing units. We find indications for only weak, if any, fluorescence resonance energy transfer (FRET) between red and green chromophores within one E8 entity.

Blum, Christian; Subramaniam, Vinod; Schleifenbaum, Frank; Stracke, Frank; Angres, Brigitte; Terskikh, Alexey; Meixner, A. J.

2002-08-01

416

Detecting rearrangements of shaker and NaChBac in real-time with fluorescence spectroscopy in patch-clamped mammalian cells.  

PubMed

Time-resolved fluorescence detection of site-directed probes is a major tool in the investigation of structure-function relationships of voltage-dependent ion channels. However, the technique has been limited so far to the Xenopus-oocyte system making it difficult to study proteins, like, e.g., the prokaryotic sodium channel NaChBac, whose expression in oocytes is insufficient or whose physiological functions are distorted in oocytes. To expand the application of site-directed fluorescence detection to these proteins, we used two techniques-semiconfocal epifluorescence and total internal reflection fluorescence-to detect time-resolved fluorescence changes from site-directed labeled proteins expressed in mammalian cells under patch-clamp conditions, and investigated the characteristics and limitations of the techniques. The voltage-sensitive dye, di-8-ANEPPS, was used to monitor control of the membrane voltage in epifluorescence and total internal reflection fluorescence. Fluorescence changes in patch-clamped cells were recorded from a Shaker channel mutant (M356C) labeled in the S3-S4 linker using semiconfocal epifluorescence. The gating kinetics and fluorescence changes were in accordance with previous studies using fluorescence spectroscopy in Xenopus-oocyte systems. We applied our technique to the prokaryotic sodium channel NaChBac. Voltage-dependent protein-rearrangements of S4 could be detected that are independent of inactivation. Comparison of the S3-S4 linker regions revealed structural differences to the KvAP voltage sensor. The results from the NaChBac channel point to structural requirements for the S3-