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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

Time-resolved spectroscopy of the fluorescence quenching of a donor acceptor pair by halothane  

NASA Astrophysics Data System (ADS)

Donor (anthracene) sensitized acceptor (perylene) fluorescence is quenched more efficiently by halothane than is intrinsic perylene fluorescence. The underlying process of dynamic fluorescence quenching is investigated by time-resolved fluorescence spectroscopy.

Sharma, A.; Draxler, S.; Lippitsch, M. E.

1992-04-01

3

Picosecond time-resolved fluorescence spectroscopy of phytochrome and stentorin  

NASA Astrophysics Data System (ADS)

Phytochrome is a tetrapyrrole chromoprotein. It serves as a sensitive photosensor for red lightmediated gene expression and other developmental/morphological responses in plants. In this paper photochemical dynamics of the phytochrome molecule have been described in terms of photoisomerization of the tetrapyrrole chromophore in its singlet excited state and subsequent thermal processes in the Pr Pfr phototransformation of phytochrome. Stentorin acts as the photosensor molecule in the ciliate Stentor coeruleus. This unicellular protozoan is most sensitive to red light (610-620 urn). Stentor also senses the direction of light propagation as evidenced by their light-avoiding and negative phototactic swimming behaviors. This aneural photosensory phenomenon is triggered by the photoreceptor stentorin. The possible involvement of a light-induced transient proton release from the photoreceptor as the primary mechanism of light-signal processing has been discussed on the basis of picosecond fluorescence decays and time-resolved fluorescence spectra of stentorin in solution. An initial sensory signal generated by the primary photoprocess of stentorin then triggers subsequent transduction steps that include calcium ion influx from the extracellular medium. Calcium ion influx from the extracellular medium to the cytosol causes the Stentor cell to reverse its ciliary beating and subsequently steer away from the light trap. II.

Song, Pill-Soon

1991-05-01

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

Fluorescence imaging and time-resolved spectroscopy of steroid using confocal synchrotron radiation microscopy  

NASA Astrophysics Data System (ADS)

The Confocal Synchrotron Radiation Microscope at Daresbury was used in a study of the transport and distribution of the steroid Coumestrol in single Leydig cells. The broad spectrum of synchrotron radiation in combination with UV compatible microscope optics affords the extension of confocal microscopy from the visible to the UV region down to about 200 nm. Consequently fluorescent molecules with absorption bands in the UV can be imaged. In addition the pulsed nature of the light source allows us to perform time-resolved fluorescence spectroscopy experiments on microscopic volumes. Coumestrol is a naturally fluorescing plant steroid exhibiting estrogenic activity. In physiological environments it has an absorption peak in the UV at 340 nm and it emits around 440 nm. First results indicate that the Coumestrol transport through the cell membrane is diffusion limited. The weak fluorescence observed in the nuclei of the Leydig cells may be due to fluorescence quenching arising from the interaction of the Coumesterol with nuclear components. However, micro-volume time-resolved fluorescence spectroscopy experiments on cell nuclei have revealed the same decay behavior for Coumesterol in both the cytoplasm and nucleus of the cells.

Gerritsen, Hans C.; van der Oord, C. J. R.; Levine, Yehudi K.; Munro, Ian H.; Jones, Gareth R.; Shaw, D. A.; Rommerts, Fokko F.

1994-08-01

6

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

7

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

PubMed

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. PMID:24689603

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

2014-03-01

8

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

E-print Network

module attached to it, which enables broadband excitation of the sample. This setup allows rapid acquisition (250 ms for fluorescence decay at a wavelength) of time resolved fluorescence data with a high spectral (as low as 0.5 nm) and temporal (as low...

Trivedi, Chintan A.

2010-07-14

9

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

PubMed

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

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

2014-08-01

10

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

PubMed Central

The goal of this study is to determine the potential of time-resolved laser-induced fluorescence spectroscopy (TR-LIFS) as an adjunctive tool for delineation of brain tumor from surrounding normal tissue in order to assist the neurosurgeon in near-complete tumor excision. A time-domain TR-LIFS prototype apparatus (gated photomultiplier detection, fast digitizer) was used for recording tissue autofluorescence in normal cortex (NC), normal white matter (NWM), and various grades of gliomas intraoperatively. Tissue fluorescence was induced with a pulsed nitrogen laser (337nm, 700ps), and the intensity decay profiles were recorded in the 360-to550-nm spectral range (10-nm interval). Histopathological analysis (hematoxylin & eosin) of the biopsy samples taken from the site of TR-LIFS measurements was used for validation of spectroscopic results. Preliminary results on 17 patients demonstrate that normal cortex (N=16) and normal white matter (N=3) show two peaks of fluorescence emission at 390nm(lifetime=1.80.3ns) and 460nm(lifetime=0.80.1ns). The 390-nm emission peak is absent in low-grade glioma (N=5; lifetime=1.1ns) and reduced in high-grade glioma (N=9; lifetime=1.70.4ns). The emission characteristics at 460nm in all tissues correlated with the nicotinamide adenine dinucleotide fluorescence (peak: 440to460nm; lifetime: 0.8to1.0ns). These findings demonstrate the potential of using TR-LIFS as a tool for enhanced delineation of brain tumors during surgery. In addition, this study evaluates similarities and differences between TR-LIFS signatures of brain tumors obtained in vivo and those previously reported in ex vivo brain tumor specimens. PMID:20459282

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

2010-01-01

11

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

12

Microenvironments of 8-anilino-1-naphthalenesulfonate at the heptane-water interface: time-resolved total internal reflection fluorescence spectroscopy  

Microsoft Academic Search

Picosecond time-resolved total internal reflection fluorescence spectroscopy was applied to study the microenvironments of 8-anilino-1-naphthalenesulfonate molecules at the heptane-water interface. By analyzing the fluorescence decay profiles, it was found that the fluorophores in the vicinity of the interface are present in two different solvated structures. One of them is located up to a few nanometers from the interface, and the

K. Bessho; T. Uchida; A. Yamauchi; T. Shioya; N. Teramae

1997-01-01

13

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; Vay, Ignacio; Bonanca, Paula; Jimnez, M. C.; Miranda, Miguel A.

2014-09-01

14

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.; Fssel, S.; Nanke, R.; Fehre, J.; Wirth, M.; Baretton, G.; Schreiber, J.

2011-03-01

15

TIME-RESOLVED VIBRATIONAL SPECTROSCOPY  

SciTech Connect

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

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

2009-05-14

16

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

2014-12-12

17

Energy transfer processes in chlorophyll f-containing cyanobacteria using time-resolved fluorescence spectroscopy on intact cells.  

PubMed

We examined energy transfer dynamics in the unique chlorophyll (Chl) f-containing cyanobacterium Halomicronema hongdechloris. The absorption band of Chl f appeared during cultivation of this organism under far-red light. The absorption maximum of Chl f in organic solvents occurs at a wavelength of approximately 40 nm longer than that of Chl a. In vivo, the cells display a new absorption band at approximately 730 nm at 298 K, which is at a significantly longer wavelength than that of Chl a. We primarily assigned this band to a long wavelength form of Chl a. The function of Chl f is currently unknown. We measured the fluorescence of cells using time-resolved fluorescence spectroscopy in the picosecond-to-nanosecond time range and found clear differences in fluorescence properties between the cells that contained Chl f and the cells that did not. After excitation, the fluorescence peaks of photosystem I and photosystem II appeared quickly but diminished immediately. A unique fluorescence peak located at 748 nm subsequently appeared in cells containing Chl f. This finding strongly suggests that the Chl f in this alga exists in photosystem I and II complexes and is located close to each molecule of Chl a. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy. PMID:24792349

Tomo, Tatsuya; Shinoda, Toshiyuki; Chen, Min; Allakhverdiev, Suleyman I; Akimoto, Seiji

2014-09-01

18

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

19

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

PubMed

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

Dang, Wei; Mao, Pengcheng; Weng, Yuxiang

2013-07-01

20

Development of a dual-modal tissue diagnostic system combining time-resolved fluorescence spectroscopy and ultrasonic backscatter microscopy  

NASA Astrophysics Data System (ADS)

We report a tissue diagnostic system which combines two complementary techniques of time-resolved laser-induced fluorescence spectroscopy (TR-LIFS) and ultrasonic backscatter microscopy (UBM). TR-LIFS evaluates the biochemical composition of tissue, while UBM provides tissue microanatomy and enables localization of the region of diagnostic interest. The TR-LIFS component consists of an optical fiber-based time-domain apparatus including a spectrometer, gated multichannel plate photomultiplier, and fast digitizer. It records the fluorescence with high sensitivity (nM concentration range) and time resolution as low as 300 ps. The UBM system consists of a transducer, pulser, receiving circuit, and positioning stage. The transducer used here is 45 MHz, unfocused, with axial and lateral resolutions 38 and 200 ?m. Validation of the hybrid system and ultrasonic and spectroscopic data coregistration were conducted both in vitro (tissue phantom) and ex vivo (atherosclerotic tissue specimens of human aorta). Standard histopathological analysis of tissue samples was used to validate the UBM-TRLIFS data. Current results have demonstrated that spatially correlated UBM and TR-LIFS data provide complementary characterization of both morphology (necrotic core and calcium deposits) and biochemistry (collagen, elastin, and lipid features) of the atherosclerotic plaques at the same location. Thus, a combination of fluorescence spectroscopy with ultrasound imaging would allow for better identification of features associated with tissue pathologies. Current design and performance of the hybrid system suggests potential applications in clinical diagnosis of atherosclerotic plaque.

Sun, Yang; Park, Jesung; Stephens, Douglas N.; Jo, Javier A.; Sun, Lei; Cannata, Jonathan M.; Saroufeem, Ramez M. G.; Shung, K. Kirk; Marcu, Laura

2009-06-01

21

Development of a dual-modal tissue diagnostic system combining time-resolved fluorescence spectroscopy and ultrasonic backscatter microscopy.  

PubMed

We report a tissue diagnostic system which combines two complementary techniques of time-resolved laser-induced fluorescence spectroscopy (TR-LIFS) and ultrasonic backscatter microscopy (UBM). TR-LIFS evaluates the biochemical composition of tissue, while UBM provides tissue microanatomy and enables localization of the region of diagnostic interest. The TR-LIFS component consists of an optical fiber-based time-domain apparatus including a spectrometer, gated multichannel plate photomultiplier, and fast digitizer. It records the fluorescence with high sensitivity (nM concentration range) and time resolution as low as 300 ps. The UBM system consists of a transducer, pulser, receiving circuit, and positioning stage. The transducer used here is 45 MHz, unfocused, with axial and lateral resolutions 38 and 200 microm. Validation of the hybrid system and ultrasonic and spectroscopic data coregistration were conducted both in vitro (tissue phantom) and ex vivo (atherosclerotic tissue specimens of human aorta). Standard histopathological analysis of tissue samples was used to validate the UBM-TRLIFS data. Current results have demonstrated that spatially correlated UBM and TR-LIFS data provide complementary characterization of both morphology (necrotic core and calcium deposits) and biochemistry (collagen, elastin, and lipid features) of the atherosclerotic plaques at the same location. Thus, a combination of fluorescence spectroscopy with ultrasound imaging would allow for better identification of features associated with tissue pathologies. Current design and performance of the hybrid system suggests potential applications in clinical diagnosis of atherosclerotic plaque. PMID:19566223

Sun, Yang; Park, Jesung; Stephens, Douglas N; Jo, Javier A; Sun, Lei; Cannata, Jonathan M; Saroufeem, Ramez M G; Shung, K Kirk; Marcu, Laura

2009-06-01

22

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

SciTech Connect

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

Wilden, A.; Modolo, G.; Lange, S.; Sadowski, F.; Bosbach, D. [Foschungszentrum Juelich GmbH, IEK-6, Juelich (Germany); Beele, B.B.; Panak, P.J. [Ruprecht-Karls-Universitaet Heidelberg, Physikalisch Chemisces Institut - PCI, Heidelberg (Germany); Karlsruher Institut fuer Technologie - INE, Karlsruhe (Germany); Skerencak-Frech, A.; Geist, A. [Karlsruher Institut fuer Technologie - INE, Karlsruhe (Germany); Iqbal, M. [University of Twente, Laboratory of Molecular Nanofabrication, Enschede (Netherlands); Department of Chemistry, University of Sargodha, Sargodha 40100 (Pakistan); Verboom, W. [University of Twente, Laboratory of Molecular Nanofabrication, Enschede (Netherlands)

2013-07-01

23

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

PubMed

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

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

2014-08-01

24

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

25

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

Microsoft Academic Search

To date only a small number of studies have investigated the chemical speciation of complexes and the fluorescence properties of metal ions whose emitted fluorescence lifetime is in the range of only few nanoseconds. This is due to a lack of advanced methods which allow the conduction of these measurements. In the current study we set up a new time-resolved

S. Lehmann; G. Geipel; G. Grambole; G. Bernhard

2009-01-01

26

Highly Time Resolved Measurements of OH during POPCORN Using Laser-Induced Fluorescence Spectroscopy  

Microsoft Academic Search

Tropospheric hydroxyl radical (OH) concentrations were measured by laser-induced fluorescence (LIF) during the POPCORN field campaign in August 1994 at a rural site in the North East of Germany. Ambient air spectra were recorded by tuning the laser wavelength over a spectral region covering the Q11(3), Q21(3), and P11(1) rotational transitions of the (0-0) band in the A-X system of

F. Holland; U. Aschmutat; M. Heling; A. Hofzumahaus; D. H. Ehhalt

1998-01-01

27

Nondestructive Evaluation of Tissue Engineered Articular Cartilage Using Time-Resolved Fluorescence Spectroscopy and Ultrasound Backscatter Microscopy  

PubMed Central

The goal of this study is to evaluate the ability of a bimodal technique integrating time-resolved fluorescence spectroscopy (TRFS) and ultrasound backscatter microscopy (UBM) for nondestructive detection of changes in the biochemical, structural, and mechanical properties of self-assembled engineered articular cartilage constructs. The cartilage constructs were treated with three chemical agents (collagenase, chondroitinase-ABC, and ribose) to induce changes in biochemical content (collagen and glycosaminoglycan [GAG]) of matured constructs (4 weeks); and to subsequently alter the mechanical properties of the construct. The biochemical changes were evaluated using TRFS. The microstructure and the thickness of the engineered cartilage samples were characterized by UBM. The optical and ultrasound results were validated against those acquired via conventional techniques including collagen and GAG quantification and measurement of construct stiffness. Current results demonstrated that a set of optical parameters (e.g., average fluorescence lifetime and decay constants) showed significant correlation (p<0.05) with biochemical and mechanical data. The high-resolution ultrasound images provided complementary cross-section information of the cartilage samples morphology. Therefore, the technique was capable of nondestructively evaluating the composition of extracellular matrix and the microstructure of engineered tissue, demonstrating great potential as an alternative to traditional destructive assays. PMID:22010819

Responte, Donald; Xie, Hongtao; Liu, Jing; Fatakdawala, Hussain; Hu, Jerry; Athanasiou, Kyriacos A.

2012-01-01

28

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 5180 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 Frster 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

29

Synchrotron-excited time-resolved fluorescence spectroscopy of adenosine, protonated adenosine and 6 N, 6 N-dimethyladenosine in aqueous solution at room temperature  

Microsoft Academic Search

The fluorescence behavior of adenosine in neutral solution has been studied by time-resolved spectroscopy using synchrotron excitation and timecorrelated single photon counting, and by decay time measurements. Three emissions have been identified and correlated with three excitation spectra. The assignment of these transitions has been made by comparison with similar measurements on 6N, 6N-dimethyladenosine (6 DMA), and on adenosine in

J.-P. Ballini; M. Daniels; P. Vigny

1988-01-01

30

Time-resolved photoelectron spectroscopy of liquids.  

PubMed

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

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

2010-11-01

31

Time-resolved multiple probe spectroscopy  

SciTech Connect

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

Greetham, G. M.; Sole, D.; Clark, I. P.; Parker, A. W.; Pollard, M. R.; Towrie, M. [Central Laser Facility, Science and Technology Facilities Council, Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell, Oxfordshire, OX11 0QX (United Kingdom)

2012-10-15

32

Interaction of Cm(III) and Am(III) with human serum transferrin studied by time-resolved laser fluorescence and EXAFS spectroscopy.  

PubMed

The complexation of Cm(III) with human serum transferrin was investigated in a pH range from 3.5 to 11.0 using time-resolved laser fluorescence spectroscopy (TRLFS). At pH ? 7.4 Cm(III) is incorporated at the Fe(III) binding site of transferrin whereas at lower pH a partially bound Cm(III) transferrin species is formed. At physiological temperature (310 K) at pH 7.4, about 70% of the partially bound and 30% of the incorporated Cm(III) transferrin species are present in solution. The Cm(III) results obtained by TRLFS are in very good agreement with Am(III) EXAFS results, confirming the incorporation of Am(III) at the Fe(III) binding site at pH 8.5. PMID:24626477

Bauer, Nicole; Frhlich, Daniel R; Panak, Petra J

2014-05-14

33

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

34

Time-resolved Raman spectroscopy for in situ planetary mineralogy.  

PubMed

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

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

2010-09-10

35

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

E-print Network

stack. The resulting electron cloud is proximity focused on a cross delay line anode, which allows (SPAD) or electron-multiplying camera using model samples (fluorescent beads, quantum dots and live photo electron per detected photon, which are then multiplied up to 107 times by a 3-microchannel plate

Michalet, Xavier

36

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

37

State Transitions in the Green Alga Scenedesmus Obliquus Probed by Time-Resolved Chlorophyll Fluorescence Spectroscopy and Global Data Analysis  

PubMed Central

Decay-associated fluorescence spectra of the green alga Scenedesmus obliquus have been measured by single-photon timing with picosecond resolution in various states of light adaptation. The data have been analyzed by applying a global data analysis procedure. The amplitudes of the decay-associated spectra allow a determination of the relative antenna sizes of the photosystems. We arrive at the following conclusions: (a) The fluorescence kinetics of algal cells with open PS II centers (F0 level) have to be described by a sum of three exponential components. These decay components are attributed to photosystem (PS) I (? ? 85 ps, ?maxem ? 695-700 nm), open PS II ?-centers (? ? 300 ps, ?maxem = 685 nm), and open PS II ?-centers (? ? 600 ps, ?maxem = 685 nm). A fourth component of very low amplitude (? ? 2.2-2.3 ns, ?maxem = 685 nm) derives from dead chlorophyll. (b) At the Fmax level of fluorescence there are also three decay components. They originate from PS I with properties identical to those at the F0 level, from closed PS II ?-centers (? ? 2.2 ns, ?maxem = 685 nm) and from closed PS ?-centers (? ? 1.2 ns, ?maxem = 685 nm). (c) The major effect of light-induced state transitions on the fluorescence kinetics involves a change in the relative antenna size of ?- and ?-units brought about by the reversible migration of light-harvesting complexes between ?-centers and ?-centers. (d) A transition to state II does not measurably increase the direct absorption cross-section (antenna size) of PS I. Our data can be rationalized in terms of a model of the antenna organization that relates the effects of state transitions and light-harvesting complex phosphorylation with the concepts of PS II ?,?-heterogeneity. We discuss why our results are in disagreement with those of a recent lifetime study of Chlorella by M. Hodges and I. Moya (1986, Biochim. Biophys. Acta., 849:193-202). PMID:19431709

Wendler, Joachim; Holzwarth, Alfred R.

1987-01-01

38

Time resolved fluorescence tomography of turbid media based on lifetime  

E-print Network

Time resolved fluorescence tomography of turbid media based on lifetime contrast Anand T. N. Kumar-based analysis of the entire temporal fluorescence response from a turbid medium. Simulations are used to show, (170.3650) Lifetime-based sensing, (170.6920) Time-resolved imaging, (170.7050) Turbid media References

Kumar, Anand T.N.

39

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

NASA Astrophysics Data System (ADS)

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

Pellegrino, F.

40

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

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

2014-11-01

41

Complex formation of neptunium(V) with 4-hydroxy-3-methoxybenzoic acid studied by time-resolved laser-induced fluorescence spectroscopy with ultra-short laser pulses  

NASA Astrophysics Data System (ADS)

The complex formation of neptunium(V) with 4-hydroxy-3-methoxybenzoic acid (vanillic acid) was studied by time-resolved laser-induced fluorescence spectroscopy with ultra-short laser pulses using the fluorescence properties of 4-hydroxy-3-methoxybenzoic acid. A 2:1 complex of neptunium(V) with 4-hydroxy-3-methoxybenzoic acid was found. The stability constant of this complex was determined to be log ?210 = 7.33 0.10 at an ionic strength of 0.1 mol/l (NaClO 4) and at 21 C. The determination of the stability constant required an investigation of the excited-state proton transfer of 4-hydroxy-3-methoxybenzoic acid over the whole pH range. It was realized that 4-hydroxy-3-methoxybenzoic acid undergoes excited-state reactions only at pH values below 5. At pH values above 5 stability constants can be determined without kinetic calculation of the proton transfer.

Vulpius, D.; Geipel, G.; Baraniak, L.; Bernhard, G.

2006-03-01

42

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, Sebastio; Moriyama, Lilian Tan; Kurachi, Cristina

2014-01-01

43

Time-resolved nanosecond fluorescence lifetime imaging and picosecond infrared spectroscopy of combretastatin A-4 in solution and in cellular systems  

NASA Astrophysics Data System (ADS)

Fluorescence lifetime images of intrinsic fluorescence obtained with two-photon excitation at 630 nm are shown following uptake of a series of E-combretastatins into live cells, including human umbilical vein endothelial cells (HUVECs) that are the target for the anticancer activity of combretastatins. Images show distribution of the compounds within the cell cytoplasm and in structures identified as lipid droplets by comparison with images obtained following Nile red staining of the same cells. The intracellular fluorescent lifetimes are generally longer than in fluid solution as a consequence of the high viscosity of the cellular environment. Following incubation, the intracellular concentrations of a fluorinated derivative of E-combretastatin A-4 in HUVECs are between two and three orders of magnitude higher than the concentration in the surrounding medium. Evidence is presented to indicate that at moderate laser powers (up to 6 mW), it is possible to isomerize up to 25% of the combretastatin within the femtolitre focal volume of the femtosecond laser beam. This suggests that it may be possible to activate the E-combretastatin (with low cellular toxicity) to the Z-isomer with high anticancer drug activity using two-photon irradiation. The isomerization of Z- and E-combretastatins by 266 nm irradiation has been probed by ultrafast time-resolved infrared spectroscopy. Results for the E-isomer show a rapid loss of excess vibrational energy in the excited state with a lifetime of 7 ps, followed by a slower process with a lifetime of 500 ps corresponding to the return to the ground state as also determined from the fluorescence lifetime. In contrast, the Z-isomer, whilst also appearing to undergo a rapid cooling of the initial excited state, has a much shorter overall excited state lifetime of 14 ps. DedicationThis paper is dedicated to the memory of Professor Christopher G Morgan (1949-2011). He was a valued colleague and friend at the University of Salford and made significant contributions to the development and applications of fluorescence lifetime imaging.

Bisby, Roger H.; Botchway, Stanley W.; Greetham, Greg M.; Hadfield, John A.; McGown, Alan T.; Parker, Anthony W.; Scherer, Kathrin M.; Towrie, Mike

2012-08-01

44

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

NASA Astrophysics Data System (ADS)

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

Vaudelle, Fabrice; L'huillier, Jean-Pierre

2013-09-01

45

Proceedings of BiOS, Photonics West 2001, No.4252-27, San Jose, 2001. Time-Resolved Fluorescence Spectroscopy of Dopamine  

E-print Network

Spectroscopy of Dopamine in the Single Cells Michiaki Mabuchi1 , Jun-ichi Shimada2 , Koichi Okamoto3 , Yoichi 606-8501, Japan Abstract Dopamine hydrochloric acid salt in aqueous solution was excited at 266 nm Al2 observation of dopamine in the living cells. In addition, it is needed to detect the dopamine fluorescence

Okamoto, Koichi

46

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

47

Attosecond time-resolved photoelectron spectroscopy of surfaces  

E-print Network

-IR-delay dependent (or "streaked") photoemission spectra that show periodic shifts in measured photoelectron energiesAttosecond time-resolved photoelectron spectroscopy of surfaces Uwe Thumm and Chang-hua Zhang-wave-function localization and including the dynamical plasmon response to the motion of the photoelectron. Keywords

Thumm, Uwe

48

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 ?rHm, ?rSm, and ?rCp,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 . At T = 200 C two chloride ligands are present in the inner coordination sphere of Am(III) at a distance of 2.78 . PMID:24383499

Skerencak-Frech, Andrej; Frhlich, Daniel R; Rothe, Jrg; Dardenne, Kathy; Panak, Petra J

2014-01-21

49

Time-resolved laser fluorescence spectroscopy and extended X-ray absorption spectroscopy investigations of the N3- complexation of Eu(III), Cm(III), and Am(III) in an ionic liquid: differences and similarities.  

PubMed

The complexation of the lanthanide Eu(III) and the actinides Cm(III) and Am(III) by N3- was investigated by application of time-resolved laser fluorescence spectroscopy (TRLFS) and X-ray absorption spectroscopy (XAFS) in the ionic liquid solution of C4mimTf2N (1-butyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imide). TRLFS measurements show that the interaction of azide with Eu(CF3SO3)3 and Eu(ClO4)3 results in both dynamic luminescence quenching by collisional encounters of N3- with Eu(III) and static luminescence quenching by inner-sphere complexation of Eu(III) by N3-. Hereby, the complexation of Eu-triflate by azide starts at a lower N3- concentration as compared to the perchlorate salt. The authors ascribe this phenomenon to a stronger bonding of ClO4- toward the metal ion than triflate, as well as to a stronger electrostatic repulsion of N3- by the perchlorate ligand. In both actinide samples (Cm(ClO4)3, Am(ClO4)3), the complexation with azide exhibits a clear kinetic hindrance. Nevertheless, mixed actinide-perchlorate-azide complexes are formed after several days in C4mimTf2N. The different reaction kinetics for the Ln- and An-complexation by azide may provide the opportunity for an effective separation of lanthanides from actinides in the nuclear fuel cycle by the use of N-based extractants in ionic liquid solution. PMID:18459761

Stumpf, S; Billard, I; Gaillard, C; Panak, P J; Dardenne, K

2008-06-01

50

A 0.18-um CMOS Array Sensor for Integrated Time-Resolved Fluorescence Detection  

PubMed Central

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

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

2010-01-01

51

Time-resolved diffuse optical spectroscopy: a differential absorption approach.  

PubMed

A method is presented for the estimate of spectral changes in the absorption properties of turbid media from time-resolved diffuse optical spectroscopy. The method relies on the hypothesis of constant scattering over the wavelength range of interest, but no limitations come from the sample size and shape as the method is derived directly from the Beer-Lambert law. The effects of a moderate spectral dependence of the scattering properties and of the non-ideal instrument response function were investigated theoretically, and the results were confirmed experimentally, showing that the method can be profitably applied in cases of practical interest. PMID:21073789

Taroni, Paola; Bassi, Andrea; Spinelli, Lorenzo; Cubeddu, Rinaldo; Pifferi, Antonio

2010-11-01

52

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

53

Time-resolved x-ray photoelectron spectroscopy at FLASH  

NASA Astrophysics Data System (ADS)

The technique of time-resolved pump-probe x-ray photoelectron spectroscopy using the free-electron laser in Hamburg (FLASH) is described in detail. Particular foci lie on the macrobunch resolving detection scheme, the role of vacuum space-charge effects and the synchronization of pump and probe lasers. In an exemplary case study, the complete Ta 4f core-level dynamics in the layered charge-density-wave (CDW) compound 1T-TaS2 in response to impulsive optical excitation is measured on the sub-picosecond to nanosecond timescale. The observed multi-component dynamics is related to the intrinsic melting and reformation of the CDW as well as to extrinsic pump-laser-induced vacuum space-charge effects.

Hellmann, S.; Sohrt, C.; Beye, M.; Rohwer, T.; Sorgenfrei, F.; Marczynski-Bhlow, M.; Kallne, M.; Redlin, H.; Hennies, F.; Bauer, M.; Fhlisch, A.; Kipp, L.; Wurth, W.; Rossnagel, K.

2012-01-01

54

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

55

Time-resolved Spectroscopy through Laser-heated Copper Foils  

NASA Astrophysics Data System (ADS)

The volumetric heating of a thin copper target has been studied with time resolved x-ray spectroscopy. The copper target was heated by a plasma produced using the Lawrence Livermore National Laboratory's Compact Multipulse Terawatt (COMET) laser. A variable spaced grating spectrometer coupled to an x-ray streak camera measured soft x-ray emission (800--1450 eV) from the back of the copper target to characterize the bulk heating of the target. Radiation hydrodynamic simulations were modeled in 2-dimensions using the HYDRA code. The target conditions calculated by HYDRA were post-processed with the atomic kinetics code CRETIN to generate synthetic emission spectra. A comparison between the experimental and simulated spectra indicates the presence of specific ionization states of copper and the corresponding electron temperatures and ion densities throughout the laser-heated copper target.

Cone, Kelly Vivian

56

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

57

Time-resolved photoelectron spectroscopy of wavepackets through a conical intersection in NO2  

E-print Network

and electronic modes are coupled. Time-resolved photoelectron spectra probe the entire configuration spaceTime-resolved photoelectron spectroscopy of wavepackets through a conical intersection in NO2 studies of the time-resolved femtosecond photoelectron spectroscopy of quantum wavepackets through

Arasaki, Yasuki

58

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

59

Noninvasive multimodal evaluation of bioengineered cartilage constructs combining time-resolved fluorescence and ultrasound imaging.  

PubMed

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; Leach, J Kent; Marcu, Laura

2011-04-01

60

Time-resolved spectroscopy of the pulsating CV GW Lib  

E-print Network

We present time-resolved optical spectroscopy of the dwarf nova GW Librae during its rare April 2007 super-outburst and compare these with quiescent epochs. The data provide the first opportunity to track the evolution of the principal spectral features. In the early stages of the outburst, the optically thick disc dominates the optical and the line components show clear orbital radial velocity excursions. In the course of several weeks, optically thin regions become more prominent as strong emission lines replace the broad disc absorption. Post-outburst spectroscopy covering the I-band illustrates the advantages of CaII relative to the commonly used Balmer lines when attempting to constrain binary parameters. Due to the lower ionisation energy combined with smaller thermal and shear broadening of these lines, a sharp emission component is seen to be moving in between the accretion disc peaks in the CaII line. No such component is visible in the Balmer lines. We interpret this as an emission component origina...

van Spaandonk, L; Marsh, T R; Torres, M A P

2009-01-01

61

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

62

Exploiting Molecular Biology by Time-Resolved Fluorescence Imaging  

NASA Astrophysics Data System (ADS)

Many contemporary biological investigations rely on highly sensitive in vitro assays for the analysis of specific molecules in biological specimens, and the main part of these assays depends on high-sensitivity fluorescence detection techniques for the final readout. The analyzed molecules and molecular interactions in the specimen need to be detected in the presence of other highly abundant biomolecules, while the analyzed molecules themselves are only present at nano-, pico-, or even femtomolar concentration.A short scientific rationale of fluorescence is presented. It emphasizes the use of fluorescent labels for sensitive assays in life sciences and specifies the main properties of an ideal fluorophore. With fluorescence lifetimes in the microsecond range and fluorescence quantum yield of 0.4 some water soluble complexes of Ruthenium like modified Ru(sulfobathophenanthroline) complexes fulfill these properties. They are outstanding fluorescent labels for ultrasensitive assays as illustrated in two examples, in drug discovery and in point of care testing.We discuss the fundamentals and the state-of-the-art of the most sensitive time-gated fluorescence assays. We reflect on how the imaging devices currently employed for readout of these assays might evolve in the future. Many contemporary biological investigations rely on highly sensitive in vitro assays for the analysis of specific molecules in biological specimens, and the main part of these assays depends on high-sensitivity fluorescence detection techniques for the final readout. The analyzed molecules and molecular interactions in the specimen need to be detected in the presence of other highly abundant biomolecules, while the analyzed molecules themselves are only present at nano-, pico-, or even femtomolar concentration.A short scientific rationale of fluorescence is presented. It emphasizes the use of fluorescent labels for sensitive assays in life sciences and specifies the main properties of an ideal fluorophore. With fluorescence lifetimes in the microsecond range and fluorescence quantum yield of 0.4 some water soluble complexes of Ruthenium like modified Ru(sulfobathophenanthroline) complexes fulfil these properties. They are outstanding fluorescent labels for ultrasensitive assays as illustrated in two examples, in drug discovery and in point of care testing.We discuss the fundamentals and the state-of-the-art of the most sensitive time-gated fluorescence assays. We reflect on how the imaging devices currently employed for readout of these assays might evolve in the future.

Mller, Francis; Fattinger, Christof

63

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 m) 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

64

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

65

Quantitative Time-Resolved Fluorescence Spectrum of the Cortical Sarcoma and the Adjacent Normal Tissue  

Microsoft Academic Search

The difference in time-resolved fluorescence spectrum between the cortical sarcoma and the adjacent normal tissue was studied\\u000a in both experimental and theoretical ways. The Clinical data were obtained in vivo using a time-resolved fluorescence spectrometer employing a single fiber-optic probe for excitation and detection. Tissue\\u000a was modeled as s-180 sarcoma tumor surrounded with normal muscle and was mediated by the

Yuezhi Li; Mingzhao Li; Tao Xu

2007-01-01

66

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

67

Time-resolved fluorescence measurements using stroboscopic excitation  

NASA Astrophysics Data System (ADS)

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

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

2005-08-01

68

Time resolved spectroscopy of the variable brown dwarf Kelu-1  

E-print Network

We report the results of observations designed to investigate the spectroscopic signatures of dust clouds on the L2 brown dwarf Kelu-1. Time resolved medium resolution spectra show no significant evidence of variability in the dust sensitive TiO, CrH and FeH bandheads on the timescale of 1--24 hours. We do however report periodic variability in the psuedo-equivelent width of H-alpha consistent with the 1.8 hour rotation period previously reported for this object Clarke, Tinney & Tolley (2002). Near-contemporaneous I-band photometry shows evidence for non-periodic variability at the level of 2%.

F. J. Clarke; C. G. Tinney; S. T. Hodgkin

2003-01-09

69

Time-resolved spectroscopy of InGaN  

SciTech Connect

The authors have used time-resolved photoluminescence (PL), with 400 nm (3.1 eV) excitation, to examine In{sub x}Ga{sub 1{minus}x}N/GaN light-emitting diodes (LEDs) before the final stages of processing at room temperature. They have found dramatic differences in the time-resolved kinetics between dim, bright and super bright LED devices. The lifetime of the emission for dim LEDs is quite short, 110 {+-} 20 ps at photoluminescence (PL) maximum, and the kinetics are not dependent upon wavelength. This lifetime is short compared to bright and super bright LEDs, which the authors have examined under similar conditions. The kinetics of bright and super bright LEDs are clearly wavelength dependent, highly non-exponential, and are on the nanosecond time scale (lifetimes are in order of 1 ns for bright and 10 ns for super bright LED at the PL max). The nonexponential PL kinetics can be described by a stretched exponential function, indicating significant disorder in the material. Typical values for {beta}, the stretching coefficient, are 0.45--0.6 for bright LEDs, at the PL maxima at room temperature. The authors attribute this disorder to indium alloy fluctuations. From analysis of the stretched exponential kinetics they estimate the potential fluctuations to be approximately 75 meV in the super bright LED. Assuming a hopping mechanism, the average distance between indium quantum dots in the super bright LED is estimated to be 20 {angstrom}.

Pophristic, M.; Long, F.H.; Tran, C.; Ferguson, I.T.

2000-07-01

70

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

PubMed

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

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

2013-12-01

71

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

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

72

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

NASA Astrophysics Data System (ADS)

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

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

2009-05-01

73

Effects of tissue optical properties on time-resolved fluorescence measurements from brain tumors: an experimental and computational study  

NASA Astrophysics Data System (ADS)

Time-Resolved Laser-Induced Fluorescence Spectroscopy (tr-LIFS) offers the potential for intra-operative diagnosis of primary brain tumors. However, both the intrinsic properties of endogenous fluorophores and the optical properties of brain tissue could affect the fluorescence measurements from brain. Scattering has been demonstrated to increase, for instance, detected lifetimes by 10-20% in media less scattering than the brain. The overall goal of this study is to investigate experimentally and computationally how optical properties of distinct types of brain tissue (normal porcine white and gray matter) affect the propagation of the excitation pulse and fluorescent transients and the detected fluorescence lifetime. A time-domain tr-LIFS apparatus (fast digitizer and gated detection) was employed to measure the propagation of ultra-short pulsed light through brain specimens (1-2.5-mm source-detector separation; 0.100-mm increment). A Monte Carlo model for semi-infinite turbid media was used to simulate time-resolved light propagation for arbitrary source-detector fiber geometries and optical fiber specifications; and to record spatially- and temporally resolved information. We determined a good correlation between experimental and computational results. Our findings provide means for quantification of time-resolved fluorescence spectra from healthy and diseased brain tissue.

Butte, Pramod V.; Vishwanath, Karthik; Pikul, Brian K.; Mycek, Mary-Ann; Marcu, Laura

2003-07-01

74

Time-resolved fluorescence imaging of solvent interactions in microfluidic devices.  

PubMed

We present the application of wide-field time-resolved fluorescence imaging methods for the study of solvent interactions and mixing in microfluidic devices. Time-resolved imaging of fluorescence polarization anisotropy allows us to image the local viscosity of fluorescence in three dimensions in order to directly monitor solvent mixing within a microfluidic channel. This provides a viscosity image acquisition time of the order of minutes, and has been applied to a steady-state laminar flow configuration. To image dynamic fluid mixing in real-time, we demonstrate high-speed fluorescence lifetime imaging at 12.3 Hz applied to DASPI, which directly exhibits a solvent viscosity-dependant fluorescence lifetime. These two methods facilitate a high degree of quantification of microfluidic flow in 3-D and/or at high speed, providing a tool for studying fluid dynamics and for developing enhanced microfluidic assays. PMID:19498640

Benninger, Richard; Hofmann, Oliver; McGinty, James; Requejo-Isidro, Jose; Munro, Ian; Neil, Mark; Demello, Andrew; French, Paul

2005-08-01

75

Proceedings of the Fourteenth International Conference on Time-Resolved Vibrational Spectroscopy (TRVS XIV)  

E-print Network

Abstracts of presentations made at the Fourteenth International Conference on Time-Resolved Vibrational Spectroscopy (TRVS XIV) held May 9-14, 2009 in Meredith, New Hampshire. TRVS is a series of biennial conferences ...

Tokmakoff, Andrei

2011-08-31

76

Time-resolved fluorescence studies on the single tryptophan in bovine brain S-100a protein  

NASA Astrophysics Data System (ADS)

The fluorescence emission of the single tryptophan in bovine brain S-lOOa protein has been studied by using time-resolved laser fluorescence spectroscopy. The tryptophan fluorescence emission was isolated by a Schott 0-54 cut-off filter at right angles to the excitation direction by a Hamamatsu R955P photomultiplier. With excitation at 295 nm, the fluorescence decay of S-lOOa protein in 25 mM Tris buffer was best represented by a sum of three exponential terms regardless of solvent conditions. At 20C and pH 7.2, the three components of lifetime for apo-S-lOOa protein were (tau)1~0.43 ns, (tau)2~1.24 ns, and (tau)3~4.05 ns. The corresponding fluorescence contributions of each component were 31%, 31% and 38%, respectively. When the protein was saturated with Mg2, the lifetimes increased slightly and the contribution of the shortest fluorescence component ((tau)1) to the total emission intensity increased slightly at the expense of the other two components. Binding of Ca2+ to S-lOOa protein resulted in a significant decrease of (tau)1, and a substantial increase of (tau)2 and (tau)3, and an increase of the average of the three lifetimes. Under this condition the fractional fluorescence contributions associated with (tau)2 and (tau)3 increased very significantly at the expense of the shortest component. The fluorescence decay behavior of each of he S-lOOa samples was relatively insensitive to the variation of temperature (4~20C). At pH 8.2 and pH 8.4, the decay behavior of the protein in response to binding of Ca2+ and Mg2+, and changes of temperature was very similar to those observed at pH 7.2. The triple exponential decay kinetics of the single tryptophan in S-lOOa protein could be rationalized by the existence of multiple local conformers.

Wang, Chien-Kao; Mani, Rajam S.; Kay, Cyril M.; Cheung, Herbert C.

1990-05-01

77

The application of time-resolved luminescence spectroscopy to a remote uranyl sensor  

SciTech Connect

Time resolved luminescence spectroscopy is an effective method for the determination of a wide range of uranyl concentrations in aqueous samples. We have applied this technique to the development of a remote sensing device using fiber optic cables coupled with a micro flow cell in order to probe for uranyl in aqueous samples. This sensor incorporates a Nafion membrane through which UO{sub 2}{sup 2+} can diffuse in to a reaction/analysis chamber which holds phosphoric acid, a reagent which enhances the uranyl luminescence intensity and lifetime. With this device, anionic and fluorescing organic interferences could be eliminated, allowing for the determination of uranyl over a concentration range of 10{sup 4} to 10{sup {minus}9}M. 17 refs., 5 figs.

Varineau, P.T.; Duesing, R.; Wangen, L.E.

1991-01-01

78

Optical characterization of Pseudomonas fluorescens on meat surfaces using time-resolved fluorescence  

NASA Astrophysics Data System (ADS)

A scanning optical system for the detection of bacteria on meat surfaces based on fluorescence lifetime and intensity measurements is described. The system detects autofluorescent light emitted by naturally occurring fluorophores in bacteria. The technique only requires minimal sample preparation and handling, thus the chemical properties of the specimen are preserved. This work presents the preliminary results obtained from a time-resolved fluorescence imaging system for the characterization of a nonpathogenic gram-negative bacteria, Pseudomonas fluorescens. Initial results indicate that the combination of fluorescence lifetime and intensity measurements provides a means for characterizing biological media and for detecting microorganisms on surfaces.

Bouchard, Alain; Frechette, Julie; Vernon, Marcia L.; Cormier, Jean-Franois; Beaulieu, Rene M.; Valle, Ral; Mafu, Akier A.

2006-01-01

79

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

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

80

Doktorarbeit Time-Resolved Photoelectron Spectroscopy in the Gaseous and Liquid Phase  

E-print Network

absorption spectroscopy in a liquid cell. The requirements for this thesis are a basic understanding in moPhD Thesis Doktorarbeit Time-Resolved Photoelectron Spectroscopy in the Gaseous and Liquid Phase (TRPES) which is sensitive to electronic and vibrational dynamics. In this tech- nique we use a short

Kersting, Roland

81

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

82

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

PubMed

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

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

2013-01-01

83

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 ~400600 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 probebased 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

84

Time-resolved fluorescence study of azurin variants: conformational heterogeneity and tryptophan mobility.  

PubMed Central

Time-resolved fluorescence and time resolved fluorescence anisotropy studies have been performed on wild-type azurin from Pseudomonas aeruginosa and two variants to study the mobility of Trp48. The two azurin variants in which the microenvironment of Trp48 was changed comprised the single mutations Ile7Ser and Phe110Ser. The experiments were performed on the holo-Cu(I), holo-Cu(II), and apo- forms at various pH values, viscosities, and temperatures; two distinct parts of the emission spectrum were selected for detection. Two prominent subnanosecond lifetimes in the fluorescence decays of the Cu(II) proteins could be observed. The decay of apo-azurin also consists of more than one component. The occurrence of more than one component in the fluorescence decays is explained by conformational heterogeneity. The anisotropy decay results appeared to be different for wild-type and mutated azurins. Phe110Ser and Ile7Ser azurin show more mobility of the Trp48 residue, as reflected in the order parameter. PMID:9788939

Kroes, S J; Canters, G W; Gilardi, G; van Hoek, A; Visser, A J

1998-01-01

85

Advancements in Time-Resolved X-Ray Laser Induced Time-of-Flight Photoelectron Spectroscopy.  

National Technical Information Service (NTIS)

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-...

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

2005-01-01

86

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

87

Time-resolved IR laser-assisted XUV photoelectron spectroscopy of metal surfaces  

E-print Network

Time-resolved IR laser-assisted XUV photoelectron spectroscopy of metal surfaces C.-H. Zhang and U by an XUV pulse of length X into the field of a delayed IR laser pulse with carrier period TL allows of the emitted photoelectrons (PEs) oscillates with period TL as a function of the XUV-IR pulse delay, leading

Thumm, Uwe

88

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

89

Viability of Saccharomyces cerevisiae incorporated within silica and polysaccharide hosts monitored via time-resolved fluorescence.  

PubMed

The viability of Saccharomyces cerevisiae in biocompatible polymers under different growth conditions and studied using time-resolved fluorescence techniques is presented. Two fluorophores, the viscosity sensitive probe 4-(4-(dimethylamino)styryl)-N-methyl-pyridiniumiodine (DASPMI) and the yeast viability stain 2-chloro-4-(2,3-dihydro-3-methyl-(benzo-1,3-thiazol-2-yl)-methylidene)-1-phenylquinolinium iodide (FUN-1) are used to elucidate information on the incorporated yeast cell viability. Variations in cell viscosity, which are indicative of the cell state, were obtained using DASPMI. Prior to observing FUN-1 in yeast cells using fluorescence lifetime imaging, its photophysics in solution and heterogeneous media were investigated. Time-resolved emission spectra were measured and analysed to associate lifetimes to the spectral emission. Preliminary results show that monitoring the fluorescence lifetime of FUN-1 may give a useful insight into cellular metabolism. The results indicate that both fluorophores may be used to monitor the entrapped yeast cell viability, which is important for in vitro studies and applications, such as that in the biofuel industry, where Saccharomyces cerevisiae are required to remain active in high ethanol environments. PMID:24145860

Holmes-Smith, A Sheila; Hollas, Alexis C; McLoskey, David; Hungerford, Graham

2013-12-01

90

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

NASA Astrophysics Data System (ADS)

We present results of application of a time-resolved optical system for imaging of fluorescence excited in an inclusion containing indocyanine green (ICG), and located in optically turbid medium. The developed imaging system enabled simultaneous acquisition of fluorescence and diffusive reflectance. Eight independent time-resolved measurement channels based on time-correlated single photon counting technique were applied. In four of these channels, used for the fluorescence detection, sets of filters were applied in order to block the excitation light. Fast optomechanical switches allowed us to illuminate sequentially nine different spots on the surface of the studied object and finally 44 pixels maps at excitation and emission wavelengths were obtained. A liquid phantom used in this study consists of the fish tank filed with a solution ofmilk and water with black ink added to obtain optical properties in the range of the optical properties typical for the living tissue. A gel ball of a diameter of 5 mm with precisely controlled concentration of ICG was immersed in the liquid. The measurements were performed for inclusion located at different depths and for various ICG concentrations in the gel ball and in the surrounding liquid. The recorded distributions of times of arrival (DTA) of fluorescence photons and times of flight (DTOF) of diffusely reflected photons were analyzed by calculation of their statistical moments. We observed specific changes in moments of the measured DTAs as a function of depth of immersion of the fluorescent inclusion in the medium. We noted also that the changes of moments depend significantly on concentration of the dye in the fluorescence inclusion as well as in the surrounding liquid.

Kacprzak, M.; Liebert, A.; Sawosz, P.; ?o?ek, N.; Milej, D.; Maniewski, R.

2010-03-01

91

A time-resolved 128x128 SPAD camera for laser Raman spectroscopy  

NASA Astrophysics Data System (ADS)

In this paper we present a time-gated single-photon avalanche diode (SPAD) array, the first of its kind to be integrated with a newly developed time-resolved laser Raman spectrometer. Time-resolved Raman spectra from various highly fluorescent minerals were successfully observed using our SPAD array; these spectra were obscured by an overwhelming fluorescence background when measured using a traditional continuous wave green laser. The system has photon detection efficiency (PDE) of 5 % at 5 V excess bias with on-chip microlenses. The dark count rate (DCR) of this SPAD is 1.8 kHz at 5 V excess bias. However, thanks to the nanosecond scale time-gating, noise rate per frame is effectively reduced to ~10-3 counts at 40 kHz laser repetition rate.

Maruyama, Yuki; Blacksberg, Jordana; Charbon, Edoardo

2012-06-01

92

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

93

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

94

Application of Time-Resolved Fluorescence for Direct and Continuous Probing of Release from Polymeric Delivery Vehicles  

PubMed Central

Though accurately evaluating the kinetics of release is critical for validating newly designed therapeutic carriers for in vivo applications, few methods yet exist for release measurement in real time and without the need for any sample preparation. Many of the current approaches (e.g. chromatographic methods, absorption spectroscopy, or NMR spectroscopy) rely on isolation of the released material from the loaded vehicles, which require additional sample purification and can lead to loss of accuracy when probing fast kinetics of release. In this study we describe the use of time-resolved fluorescence for in situ monitoring of small molecule release kinetics from biodegradable polymeric drug delivery systems. This method relies on the observation that fluorescent reporters being released from polymeric drug delivery systems possess distinct excited-state lifetime components, reflecting their different environments in the particle suspensions, i.e., confined in the polymer matrices or free in the aqueous environment. These distinct lifetimes enable real-time quantitative mapping of the relative concentrations of dye in each population to obtain precise and accurate temporal information on the release profile of particular carrier/payload combinations. We found that fluorescence lifetime better distinguishes subtle differences in release profiles, (e.g. differences associated with dye loading) than conventional steady-state fluorescence measurements, which represent the averaged dye behavior over the entire scan. Given the method's applicability to both hydrophobic and hydrophilic cargo, it could be employed to model the release of any drug-carrier combination. PMID:23792808

Viger, Mathieu L.; Sheng, Wangzhong; McFearin, Cathryn L.; Berezin, Mikhail Y.; Almutairi, Adah

2013-01-01

95

Time Resolved Optical Spectroscopy Experiments on the 500 kA XP Pulsed-Power Generator  

Microsoft Academic Search

Recent experiments on the 500 kA XP pulsed-power generator at Cornell University have explored the properties of optical spectra emitted by single exploding wires and wire-arrays carrying less than 13 kA and 50 kA per wire, respectively. We are studying the wire's time resolved visible spectra in order to identify the levels of current per wire that visible spectroscopy might

K. S. Bell; S. A. Pikuz; T. A. Shelkovenko; R. D. McBride; I. C. Blesener; P. F. Knapp; D. A. Hammer; J. B. Greenly; Y. Maron

2008-01-01

96

Time-resolved Raman spectroscopy of polytetrafluoroethylene under laser-driven shock compression  

NASA Astrophysics Data System (ADS)

Nanosecond time-resolved Raman spectroscopy has been performed to study polymer films, polytetrafluoroethylene, under laser-driven shock compression at about 2.3 GPa. A vibrational line at 1895 cm-1, which is attributed to the symmetric stretching mode of a C2F4 monomer produced by depolymerization, appears under the shock compression, and its intensity increases along the propagation of the shock wave.

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

1999-08-01

97

Time-resolved remote Raman and fluorescence spectrometers for planetary exploration  

NASA Astrophysics Data System (ADS)

At the University of Hawaii, we have developed compact time-resolved (TR) Raman, and fluorescence spectrometers suitable for planetary exploration under NASA's Mars Instrument Development Program. The compact Raman and fluorescence spectrometers consist of custom miniature spectrographs based on volume holographic gratings, and custom miniature intensified CCD cameras. These spectrographs have been interfaced with a regular 50 mm camera lens as well as with a three and a half inch diameter telescope for remotely interrogating minerals, water, water-ice and dry ice. Using a small frequency-doubled Nd:YAG pulsed laser (35 mJ/pulse, 20 Hz) and 50 mm camera lens, TRRaman and LINF spectra of minerals, and bio-minerals can be measured within 30 s under super-critical CO2, and with 3.5-inch telescope these samples can be interrogated to 50 m radial distance during day time and nighttime. The fluorescence spectrograph is capable of measuring TR- laser-induced fluorescence excited with 355 nm laser in the spectral range 400-800 nm spectral range. The TR-fluorescence spectra allow measurement of LINF from rare-earths and transition-metal ions in time domain, and also assist in differentiating between abiogenic minerals from organic and biogenic materials based on the fluorescence lifetime. Biological materials are also identified from their characteristic short-lived (<10 ns) laser-induced fluorescence lifetime. These instruments will play important role in planetary exploration especially in NASA's future Mars Sample Return Mission, and lander and rover missions.

Sharma, Shiv K.; Misra, Anupam K.; Acosta, Tayro E.; Lucey, Paul G.

2012-06-01

98

Micelle growth of cationic gemini surfactants studied by NMR and by time-resolved fluorescence quenching.  

PubMed

The micelle growth of a series of five cationic gemini surfactants has been investigated by time-resolved fluorescence quenching (TRFQ) and by two NMR techniques, line width analysis and diffusometry. The surfactant series was designed such that the effect of a number of variables could be assessed: length of the spacer unit, presence of ester bonds in the tails close to the head groups, and presence of a hydroxyl group in the spacer. For the gemini with long spacer, the micelles remained relatively small in size upon an increase of the concentration. The gemini surfactants with short spacer, on the other hand, showed a considerable micellar growth as the concentration was raised. It is of particular interest that the relatively simple line width analysis of one dimensional (1)H NMR spectra gave qualitatively the same results as the more sophisticated TRFQ and NMR diffusometry techniques. PMID:23746684

Tehrani-Bagha, Ali Reza; Holmberg, Krister; Nydn, Magnus; Nordstierna, Lars

2013-09-01

99

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

PubMed

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

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

2009-01-01

100

A CMOS Time-Resolved Fluorescence Lifetime Analysis Micro-System  

PubMed Central

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

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

2009-01-01

101

Unraveling the mechanism of NO ligand photoisomerism by time-resolved infrared spectroscopy  

NASA Astrophysics Data System (ADS)

UV-Vis- and infrared femtosecond spectroscopy makes it possible to reveal all different steps of photochemical reactions after the electronic excitation. The electronic relaxations are observed in the UV-Vis spectral range whereas the nuclear motions are monitored in the infrared spectral range. We used femtosecond time-resolved infrared spectroscopy to demonstrate the photoisomerization of the NO ligand photoinduced by a visible femtosecond pulse in a Na2[Fe(CN)5NO]2H2O single crystal occurs in about 350 fs. The analysis of data makes it possible to unravel the mechanism leading to the photoisomerization of the NO ligand.

Gall, Geoffrey; Nicoul, Matthieu; Woike, Theo; Schaniel, Dominik; Freysz, Eric

2012-11-01

102

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

NASA Astrophysics Data System (ADS)

Fluorescence, fluorescence excitation, time-resolved fluorescence spectroscopic, time-dependent fluorescence anisotropy, and time-dependent (TD) DFT studies were carried out to elucidate the excitation energies, fluorescence decay kinetics, and excitation transfer dynamics of calix[4]arene. We found that TD DFT calculations help to analyze the absorption spectra by elucidating the variation of the oscillator strengths with the excitation energies of various conformers involved and to clarify their relative importance. The TD DFT calculations imply that a cone-shaped conformer plays the most important role in the absorption spectrum. Fluorescence in a methanol solvent has a lifetime of 3.11 0.1 ns and the decay kinetics is not found to have particular propensity with respect to solvent polarity. When the molecules in a glass matrix at 77 K were excited by short laser pulses, fluorescence anisotropy was observed. From the time-dependent fluorescence anisotropy, we derived the energy transfer rate constant and fluorescence anisotropy decay time, respectively: ket=1.7109 s-1, ?h=0.59 ns.

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

2013-01-01

103

Non-contact characterization of bacteria by time-resolved fluorescence  

NASA Astrophysics Data System (ADS)

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

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

2004-07-01

104

Picosecond time-resolved infrared spectroscopy of rhodium and iridium azides.  

PubMed

Picosecond time-resolved infrared spectroscopy was used to elucidate early photochemical processes in the diazido complexes M(Cp*)(N3)2(PPh3), M = Rh (), Ir (), using 266 nm and 400 nm excitation in THF, CH2Cl2, MeCN and toluene solutions. The time-resolved data have been interpreted with the aid of DFT calculations on vibrational spectra of the singlet ground states and triplet excited states and their rotamers. While the yields of phototransformations via N2 loss are low in both complexes, cleaves a N3 ligand under 266 nm excitation. The molecular structure of is also reported as determined by single crystal X-ray diffraction. PMID:25182870

Portius, Peter; Meijer, Anthony J H M; Towrie, Michael; Crozier, Benjamin F; Schiager, Ingrid

2014-11-12

105

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

106

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

107

Generalized magic angle for time-resolved spectroscopy with laser pulses of arbitrary ellipticity  

NASA Astrophysics Data System (ADS)

We present a general approach for calculating the magic-angle condition for time-resolved spectroscopy of isotropic samples. Allowing for arbitrary static polarizations and propagation directions of each pulse enables us to retrieve not only the known magic-angle conditions for linear and circular polarization, but also analogous conditions for anisotropy-free spectroscopy using elliptically polarized laser pulses. The results are exemplified on transient absorption and transferred to coherent two-dimensional spectroscopy. Furthermore we derive for transient absorption spectroscopy the relation between the measurable anisotropy and the molecular structure, i.e., the angle between the pumped and probed transition dipole moments (TDMs). The impact of multiple spectrally overlapping signals is considered and discussed on the example of a molecule with a two-fold degenerate TDM.

Schott, Sebastian; Steinbacher, Andreas; Buback, Johannes; Nuernberger, Patrick; Brixner, Tobias

2014-06-01

108

A study of the reaction Li+HCl by the technique of time-resolved laser-induced fluorescence spectroscopy of Li (2 2PJ-2 2S1/2, ?=670.7 nm) between 700 and 1000 K  

NASA Astrophysics Data System (ADS)

A kinetic study is presented of the reaction between lithium atoms and hydrogen chloride over the temperature range 700-1000 K. Li atoms are produced in an excess of HCl and He bath gas by pulsed photolysis of LiCl vapor. The concentration of the metal atoms is then monitored in real time by the technique of laser-induced fluorescence of Li atoms at ?=670.7 nm using a pulsed nitrogen-pumped dye laser and box-car integration of the fluorescence signal. Absolute second-order rate constants for this reaction have been measured at T=700, 750, 800, and 900 K. At T=1000 K the reverse reaction is sufficiently fast that equilibrium is rapidly established on the time scale of the experiment. A fit of the data between 700 and 900 K to the Arrhenius form, with 2? errors calculated from the absolute errors in the rate constants, yields k(T)=(3.81.1)10-10 exp[-(883218)/T] cm3 molecule-1 s-1. This result is interpreted through a modified form of collision theory which is constrained to take account of the conservation of total angular momentum during the reaction. Thereby we obtain an estimate for the reaction energy threshold, E0=8.21.4 kJ mol-1 (where the error arises from uncertainty in the exothermicity of the reaction), in very good agreement with a crossed molecular beam study of the title reaction, and substantially lower than estimates of E0 from both semiempirical and ab initio calculations of the potential energy surface.

Plane, John M. C.; Saltzman, Eric S.

1987-10-01

109

Synthesis of a terbium fluorescent chelate and its application to time-resolved fluoroimmunoassay.  

PubMed

A new nonadentate ligand, N, N, N1, N1-[2,6-bis(3'-aminomethyl-1'-pyrazolyl)-4-phenylpyridine]tetrakis(acetic acid) (BPTA) for a Tb3+ fluorescent complex was synthesized. The Tb3+ complex is strongly fluorescent, having a large fluorescence quantum yield of 1.00 and very long fluorescence lifetime of 2.681 ms in 0.05 M borate buffer of pH 9.1. Streptavidin (SA) was labeled with BPTA by using its succinimidyl monoester, and the BPTA-Tb(3+)-labeled SA was used in sandwich-type time-resolved fluoroimmunoassay (TR-FIA) of alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA) in human sera. The Tb(3+)-labeled SA was also used in competitive-type TR-FIA of bensulfuron-methyl (BSM) in water. The detection limits of these assays are 42 pg/mL for AFP, 70 pg/mL for CEA, and 0.4 ng/mL for BSM. In addition, a new simultaneous measurement method for AFP and CEA in a human serum sample was developed by using 4,4'-bis(1",1",2",2",3",3" -heptafluoro-4",6"-hexanedion-6"-ly)chlorosulfo- o-terphenyl (BHHCT)-Eu(3+)-labeled anti-AFP antibody, biotinylated anti-CEA antibody, and BPTA-Tb(3+)-labeled SA. The concentrations of AFP and CEA in 39 human serum samples were determined, and the results were compared with those of the independently determined AFP and CEA by TR-FIA with a single-label method. A good correlation was obtained with the correlation coefficients of 0.991 for AFP and 0.994 for CEA. PMID:11338604

Yuan, J; Wang, G; Majima, K; Matsumoto, K

2001-04-15

110

The use of time-resolved fluorescence in gel-based proteomics for improved biomarker discovery  

NASA Astrophysics Data System (ADS)

This paper describes a new platform for quantitative intact proteomics, entitled Cumulative Time-resolved Emission 2-Dimensional Gel Electrophoresis (CuTEDGE). The CuTEDGE technology utilizes differences in fluorescent lifetimes to subtract the confounding background fluorescence during in-gel detection and quantification of proteins, resulting in a drastic improvement in both sensitivity and dynamic range compared to existing technology. The platform is primarily designed for image acquisition in 2-dimensional gel electrophoresis (2-DE), but is also applicable to 1-dimensional gel electrophoresis (1-DE), and proteins electroblotted to membranes. In a set of proof-of-principle measurements, we have evaluated the performance of the novel technology using the MicroTime 100 instrument (PicoQuant GmbH) in conjunction with the CyDye minimal labeling fluorochromes (GE Healthcare, Uppsala, Sweden) to perform differential gel electrophoresis (DIGE) analyses. The results indicate that the CuTEDGE technology provides an improvement in the dynamic range and sensitivity of detection of 3 orders of magnitude as compared to current state-of-the-art image acquisition instrumentation available for 2-DE (Typhoon 9410, GE Healthcare). Given the potential dynamic range of 7-8 orders of magnitude and sensitivities in the attomol range, the described invention represents a technological leap in detection of low abundance cellular proteins, which is desperately needed in the field of biomarker discovery.

Sandberg, AnnSofi; Buschmann, Volker; Kapusta, Peter; Erdmann, Rainer; Wheelock, sa M.

2010-02-01

111

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

NASA Astrophysics Data System (ADS)

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

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

2001-12-01

112

Time-resolved photoelectron spectroscopy of coupled electron-nuclear motion  

SciTech Connect

We investigate pump-probe electron detachment spectroscopy in a model system which is ideally suited to study coupled electronic and nuclear wave-packet dynamics. Time-resolved photoelectron spectra are calculated within the adiabatic approximation and a discretization of the detachment continuum. These spectra are compared to those which derive from a non-Born-Oppenheimer description and a numerically exact treatment of the detachment process. In this way it is possible to identify the influence of non-adiabatic effects on the spectra in a systematic way and also to test commonly applied approximations.

Falge, Mirjam; Engel, Volker [Institut fuer Physikalische und Theoretische Chemie and Roentgen Research Center for Complex Material Systems, Universitaet Wuerzburg, Am Hubland, 97074 Wuerzburg (Germany); Graefe, Stefanie [Institute for Theoretical Physics, Vienna University of Technology, Wiedner Hauptstr. 8-10, A-1040 Vienna (Austria)

2011-05-14

113

Time resolved spectroscopy of the multiperiodic pulsating subdwarf B star PG1605+072  

E-print Network

We present results for the 2m spectroscopic part of the MultiSite Spectroscopic Telescope campaign, which took place in May/June 2002. In order to perform an asteroseismological analysis on the multiperiodic pulsating subdwarf B star PG 1605+072 we used over 150 hours of time resolved spectroscopy in order to search for and analyse line profile variations by using phase binning. We succeeded in finding variations in effective temperature and gravity for four modes. A pilot analysis using the \\textit{BRUCE} and \\textit{KYLIE} programs and assuming strong rotation and low inclination favours models with $l=1$ or $l=2$ with $m\\leq0$.

A. Tillich; U. Heber; S. J. O'Toole

2006-12-19

114

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

115

Simultaneous detection of sulfamethazine and sulfaquinoxaline using a dual-label time-resolved fluorescence immunoassay.  

PubMed

A dual-label time-resolved fluoroimmunoassay (TRFIA) was introduced for the simultaneous quantification of sulfamethazine (SM2) and sulfaquinoxaline (SQX). Lanthanide (Eu(3+) and Sm(3+))-labelled antibodies were used because lanthanides have higher stabilities and narrower emission spectra than most fluorescent dyes. The sensitivity of the TRFIA for SM2 was 0.02ngml(-1), and the average recoveries and the intra- and inter-assay CVs were 77.2-107.6%, 5.4-10.5%, and 6.0-11.2%, respectively. The sensitivity of the TRFIA for SQX was 0.04ngml(-1); and the average recoveries and the intra- and inter-assay CVs were 74.1-102.8%, 4.6-10.9%, and 8.7-11.2%, respectively. The method was used to analyse chicken tissue and egg samples, and the results agreed well with the results of HPLC and enzyme-linked immunosorbent assay (ELISA) analyses, with correlation coefficients (R(2)) of 0.9415-0.9724. The TRFIA developed is a simple, fast and sensitive method for the high-throughput simultaneous screening of SM2 and SQX in edible animal tissues. PMID:23782396

Le, Tao; Yan, Peifeng; Liu, Jin; Wei, Shu

2013-01-01

116

Structure and function of the photoreceptor stentorins in Stentor coeruleus. II. Primary photoprocess and picosecond time-resolved fluorescence.  

PubMed

Stentorin serves as the photoreceptor for the photophobic and negative phototactic responses in Stentor coeruleus. Two forms of the stentorin have been isolated and purified. The strongly fluorescent form, stentorin I at pH 7.8, exhibited nearly exponential fluorescence decay monitored at 620 nm, having two comparable lifetime decay components of 2.53 ns (47%) and 5.95 ns (53%). Stentorin I showed no significant time-resolved fluorescence emission spectra in the picosecond-nanosecond time scales. The weakly fluorescent form, stentorin II, exhibited an ultrafast fluorescence decay component (10 ps) at an emission wavelength of 630 nm and pH 7.8. The amplitudes of the multi-component fluorescence in stentorin II were found to be emission wavelength-dependent. Furthermore, the fluorescence emission spectrum was time-resolvable in the picosecond time scales. Effects of pH and pD on the fluorescence decay kinetics and time-resolved spectra of stentorins I and II have also been investigated. Results are suggestive of proton dissociation as a primary photoprocess from the excited state of stentorin II. PMID:2378902

Song, P S; Kim, I H; Florell, S; Tamai, N; Yamazaki, T; Yamazaki, I

1990-08-01

117

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

PubMed

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

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

2011-01-01

118

Time-resolved detection of fluorescent light during inflow of ICG to the braina methodological study  

NASA Astrophysics Data System (ADS)

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

Milej, Daniel; Gerega, Anna; ?o?ek, Norbert; Weigl, Wojciech; Kacprzak, Micha?; Sawosz, Piotr; M?czewska, Joanna; Fronczewska, Katarzyna; Mayzner-Zawadzka, Ewa; Krlicki, Leszek; Maniewski, Roman; Liebert, Adam

2012-10-01

119

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

120

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

121

Structures of reaction intermediates of bovine cytochrome c oxidase probed by time-resolved vibrational spectroscopy.  

PubMed

Structures of reaction intermediates of bovine cytochrome c oxidase (CcO) in the reactions of its fully reduced form with O2 and fully oxidized form with H2O2 were investigated with time-resolved resonance Raman (RR) and infrared spectroscopy. Six oxygen-associated RR bands were observed for the reaction of CcO with O2. The isotope shifts for an asymmetrically labeled dioxygen, (16)O(18)O, has established that the primary intermediate of cytochrome a3 is an end-on type dioxygen adduct and the subsequent intermediate (P) is an oxoiron species with Fe=O stretch (nu(Fe=O)) at 804/764 cm(-1) for (16)O2/(18)O2 derivatives, although it had been long postulated to be a peroxy species. The P intermediate is converted to the F intermediate with nu(Fe=O) at 785/751 cm(-1) and then to a ferric hydroxy species with nu(Fe-OH) at 450/425 cm(-1) (443/417 cm(-1) in D2O). The rate of reaction from P to F intermediates is significantly slower in D2O than in H2O. The reaction of oxidized CcO with H2O2 yields the same oxygen isotope-sensitive bands as those of P and F, indicating the identity of intermediates. Time-resolved infrared spectroscopy revealed that deprotonation of carboxylic acid side chain takes place upon deligation of a ligand from heme a3. UV RR spectrum gave a prominent band due to cis C=C stretch of phospholipids tightly bound to purified CcO. PMID:11132644

Kitagawa, T

2000-11-01

122

LIBS vs TRELIBS - The Relative Merits Of Laser-Induced Breakdown Spectroscopy Versus Time Resolved Laser-Induced Breakdown Spectroscopy  

NASA Astrophysics Data System (ADS)

LIBS - Laser-Induced Breakdown Spectroscopy - and TRELIBS - Time REsolved Laser-Induced Breakdown Spectroscopy - are relatively new techniques for obtaining analytical emissions from solid, liquid and gaseous samples. A pulsed laser is focused on the surface of a solid or liquid sample or focused in a gaseous sample, creating a transient plasma. Sample analytes emit characteristic radiation for upwards to tens of micro-seconds. The event is monitored spectrophotometically using LIBS, where the whole event is analyzed, or by TRELIBS, where the time resolution of the plasma event is analyzed.

Cadwell, L.; Belliveau, J.; Huwell, L.; Griffin, H.

1986-07-01

123

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

PubMed

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

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

2012-08-01

124

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

125

Proof Of Forster Energy Transfer Between Fad And Fmn In Cytochrome P450 Reductase By Time-Resolved Red-Edge Spectroscopy.  

NASA Astrophysics Data System (ADS)

By use of steady state and time-resolved fluorescence techniques Forster energy transfer between the cofactors, FAD and FMN, in cytochrome-P450 reductase is observed. Red-edge spectroscopy allowed us to assign the actual rate constant of transfer as apparent in the anisotropy decay of the holoenzyme. The same approach was used in biflavinyl compounds entrapped in polymethylmetacrylate. As anticipated the fluorescence depolarisation of this system showed a great similarity with the enzyme system. From the results the interflavin distance in the enzyme was estimated between 1.6 and 2.4 nm.

Bastiaens, P. I.; Bonants, P. J.; van Hoek, A.; Muller, F.; Visser, A. J.

1988-06-01

126

Comprehensive photophysical behaviour of ethynyl fluorenes and ethynyl anthracenes investigated by fast and ultrafast time-resolved spectroscopy.  

PubMed

Detailed investigations by time-resolved transient absorption and fluorescence spectroscopies with nano- and femtosecond time resolutions are carried out with the aim of characterising the lowest excited singlet and triplet states of three ethynyl fluorenes (1-3) and three ethynyl anthracenes (4-6) in solvents of different polarity. The solvent is found to modify the deactivation pathways of the lowest excited singlet state of compounds 1-4, thus changing their fluorescence, intersystem crossing and internal conversion efficiencies. The fluorescence and triplet yields gradually decrease, while the internal conversion quantum yield increases upon increasing the solvent dielectric constant. These experimental results, coupled with the marked fluorosolvatochromic effect, point to the involvement of an emitting state with a charge-transfer (CT) character, strongly stabilised by polar solvents. This is proved by ultrafast spectroscopic studies in which two transients, distinguished by characteristic spectral shapes assigned to locally excited (LE) and CT states, are detected, the CT state being the longer lived and fluorescent one in highly polar solvents. The intramolecular LE?CT process, operative in highly polar media, becomes particularly fast (up to ?300 fs) in the case of the NO(2) derivative 1. No push-pull character is found for 5 and 6, which exhibit different photophysical behaviour; indeed, the solvent polarity does not modify significantly the dynamics of the lowest excited singlet states. Quantum mechanical calculations at the TDDFT level are also used to determine the state order and nature of the lowest excited singlet and triplet states and to rationalise the different photophysical behaviour of fluorine and anthracene derivatives, particularly concerning the intersystem crossing process. PMID:22287155

Carlotti, Benedetta; Flamini, Rebecca; Spalletti, Anna; Marrocchi, Assunta; Elisei, Fausto

2012-02-01

127

Development of a time-resolved fluorometric method for observing hybridization in living cells using fluorescence resonance energy transfer.  

PubMed Central

We previously showed that a specific kind of mRNA (c-fos) was detected in a living cell under a microscope by introducing two fluorescently labeled oligodeoxynucleotides, each labeled with donor or acceptor, into the cytoplasm, making them hybridize to adjacent locations on c-fos mRNA, and taking images of fluorescence resonance energy transfer (FRET) (A. Tsuji, H. Koshimoto, Y. Sato, M. Hirano. Y. Sei-Iida, S. Kondo, and K. Ishibashi, 2000, Biophys. J. 78:3260-3274). On the formed hybrid, the distance between donor and acceptor becomes close and FRET occurs. To observe small numbers of mRNA in living cells using this method, it is required that FRET fluorescence of hybrid must be distinguished from fluorescence of excess amounts of non-hybridizing probes and from cell autofluorescence. To meet these requirements, we developed a time-resolved method using acceptor fluorescence decays. When a combination of a donor having longer fluorescence lifetime and an acceptor having shorter lifetime is used, the measured fluorescence decays of acceptors under FRET becomes slower than the acceptor fluorescence decay with direct excitation. A combination of Bodipy493/503 and Cy5 was selected as donor and acceptor. When the formed hybrid had a configuration where the target RNA has no single-strand part between the two fluorophores, the acceptor fluorescence of hybrid had a sufficiently longer delay to detect fluorescence of hybrid in the presence of excess amounts of non-hybridizing probes. Spatial separation of 10-12 bases between two fluorophores on the hybrid is also required. The decay is also much slower than cell autofluorescence, and smaller numbers of hybrid were detected with less interference of cell autofluorescence in the cytoplasm of living cells under a time-resolved fluorescence microscope with a time-gated function equipped camera. The present method will be useful when observing induced expressions of mRNA in living cells. PMID:11423432

Tsuji, A; Sato, Y; Hirano, M; Suga, T; Koshimoto, H; Taguchi, T; Ohsuka, S

2001-01-01

128

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

129

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

PubMed

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 (37)K 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 10(5) in resonant photon detection measurements. The hyperfine structure of (37)K and its isotope shift relative to the stable (39)K were determined using 5 10(4) s(-1) (37)K ions injected into the BECOLA beam line. The obtained hyperfine coupling constants A((2)S1/2) = 120.3(1.4) MHz, A((2)P1/2) = 15.2(1.1) MHz, and A((2)P3/2) = 1.4(8) MHz, and the isotope shift ??(39, 37) = -264(3) MHz are consistent with the previously determined values, where available. PMID:25273722

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

130

Excited state dynamics of nanocrystalline VO2 with white light continuum time resolved spectroscopy  

NASA Astrophysics Data System (ADS)

In an attempt to use ultrafast pump probe spectroscopy technique with white light continuum to reveal wavelength dependent dynamics of VO2, bandgap needs to be opened. Therefore, nanostructured amorphous and crystalline VO2 thin films were prepared with pulsed DC magnetron reactive sputtering. The mean diameters of grains were measured as 220.1 nm and 440.1 nm for amorphous and crystalline VO2 thin films, respectively. Temperature dependent resistance measurements show that nanocrystalline VO2 thin film exhibit metal insulator phase transition. The films exhibited dual band gaps (2.3 eV, <0.6 eV for amorphous films and 1.3 eV, 1.8 eV for crystalline film). Increased band gaps made it possible to perform time resolved transmission and reflection experiments with white light continuum at fluences above and below photo induced phase transition threshold. Although transmission chance due to photo induced phase transition of VO2 in the literature usually takes places at infrared region of the spectrum, transmission chance was observed in visible as low as 630 nm in broadband probe spectra. It was observed that measured time scales depend on not only pump fluence but also probe wavelength. Experiments gave the evidence of the long-lived lower energy non-equilibrium state related to the photo induced phase.

Krm, Ula?; Yaglioglu, H. Gul; Kkz, Betl; Oksuzoglu, R. Mustafa; Y?ld?r?m, Mustafa; Ya?c?, A. Murat; Pekdemir, Sami; Elmali, Ayhan

2014-12-01

131

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

132

Multiple regimes of carrier cooling in photoexcited graphene probed by time-resolved terahertz spectroscopy  

NASA Astrophysics Data System (ADS)

Energy relaxation and cooling of photoexcited charge carriers in graphene has recently attracted significant attention due to possible hot carrier effects, large quantum efficiencies, and photovoltaic applications. However, the details of these processes remain poorly understood, with many conflicting interpretations reported. Here we use time-resolved terahertz spectroscopy to explore multiple relaxation and cooling regimes in graphene in order to elucidate the fundamental physical processes which occur upon photoexcitation of charge carriers. We observe a novel negative terahertz photoconductivity that results from the unique linear dispersion and allows us to measure the electron temperature with ultrafast time resolution. Additionally, we present measurements of the relaxation dynamics over a wide range of excitation fluence. By varying the pump photon energy, we demonstrate that cooling dynamics of photoexcited carriers depend on the amount of energy deposited in the graphene system by the pump pulse, not the number of absorbed photons. The data suggest that fundamentally different regimes are encountered for different excitation fluences. These results may provide a unifying framework for reconciling various measurements of energy relaxation and cooling in graphene.

Frenzel, A. J.; Gabor, N. M.; Herring, P. K.; Fang, W.; Kong, J.; Jarillo-Herrero, P.; Gedik, N.

2013-03-01

133

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

134

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

PubMed

Mild hypothermia (HT(32C-33C)) is an effective neuroprotective strategy for a variety of acute brain injuries. However, the wide clinical adaptation of HT(32-33C) 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 0.15C 1.1C for the in vitro experiments and 0.5C 1.6C for the in vivo measurements. PMID:24817622

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

2014-05-01

135

A compact time-resolved system for near infrared spectroscopy based on wavelength space multiplexing  

NASA Astrophysics Data System (ADS)

We designed and developed a compact dual-wavelength and dual-channel time-resolved system for near-infrared spectroscopy studies of muscle and brain. The system employs pulsed diode lasers as sources, compact photomultipliers, and time-correlated single photon counting boards for detection. To exploit the full temporal and dynamic range of the acquisition technique, we implemented an approach based on wavelength space multiplexing: laser pulses at the two wavelengths are alternatively injected into the two channels by means of an optical 22 switch. In each detection line (i.e., in each temporal window), the distribution of photon time-of-flights at one wavelength is acquired. The proposed approach increases the signal-to-noise ratio and avoids wavelength cross-talk with respect to the typical approach based on time multiplexing. The instrument was characterized on tissue phantoms to assess its properties in terms of linearity, stability, noise, and reproducibility. Finally, it was successfully tested in preliminary in vivo measurements on muscle during standard cuff occlusion and on the brain during a motor cortex response due to hand movements.

Re, Rebecca; Contini, Davide; Caffini, Matteo; Cubeddu, Rinaldo; Spinelli, Lorenzo; Torricelli, Alessandro

2010-11-01

136

Time Resolved Optical Spectroscopy Experiments on the 500 kA XP Pulsed-Power Generator  

NASA Astrophysics Data System (ADS)

Recent experiments on the 500 kA XP pulsed-power generator at Cornell University have explored the properties of optical spectra emitted by single exploding wires and wire-arrays carrying less than 13 kA and 50 kA per wire, respectively. We are studying the wire's time resolved visible spectra in order to identify the levels of current per wire that visible spectroscopy might provide a means to measure magnetic field strength[1]. We have also investigated the dependence of single wire visible spectra on the current, which was measured using a calibrated non-integrating Rogowski coil. PCDs and XRDs were employed to gather information about the temporal structure of the wire radiation. 1. E. Stambulchik, K. Tsigutkin, and Y. Maron. Phys. Rev. Lett. 98, 225001 (2007). This research was supported by DOE grant DE-FG03-98ER54496, Sandia National Laboratories contract AO258, and the NNSA Stockpile Stewardship Academic Alliances program under DOE Cooperative Agreement DE-FC03-02NA00057.

Bell, K. S.; Pikuz, S. A.; Shelkovenko, T. A.; McBride, R. D.; Blesener, I. C.; Knapp, P. F.; Hammer, D. A.; Greenly, J. B.; Maron, Y.

2008-11-01

137

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

138

Structural characteristic of folding/unfolding intermediate of pokeweed anti-viral protein revealed by time-resolved fluorescence.  

PubMed

The structural feature of unfolding intermediate of pokeweed anti-viral protein (PAP) was characterized using time-resolved fluorescence spectroscopic methods to elucidate protein folding/unfolding process. CD and fluorescence spectra consistently demonstrated that the unfolding of PAP completed at 4 M of guanidine hydrochloride (GuHCl). The fluorescence resonance energy transfer (FRET) and time-resolve fluorescence depolarization analysis of Trp208 and Trp237 located in the C-terminal domain of PAP suggested that peculiar unfolding intermediate populated before reaching to the unfolding state. The FRET distance of Trp237 to Tyr182 was extended to more than 28 with keeping the compact conformation in the unfolding intermediate state populated in the presence of 2 M GuHCl. On the other hand, Trp208 maintained the energy transfer pair with Tyr72 near the active site, although the rotational freedom was increased a little. There results suggest that the most distinguished structural feature of the unfolding intermediate of PAP is the separation of C-terminal domain from N-terminal domain. FRET and fluorescence depolarization studies also showed that C-terminal domain would be more separated to liberate the segmental motions of Trp208 and Trp237 distinctly at the unfolding state. PMID:23319009

Matsumoto, Shuzo; Taniguchi, Yuka; Fukunaga, Yukihiro; Nakashima, Hiromichi; Watanabe, Keiichi; Yamashita, Shoji; Nishimoto, Etsuko

2013-05-01

139

Time-Resolved Spectroscopy of Accretion Disks in Algol - Type Binaries.  

NASA Astrophysics Data System (ADS)

Accretion disks are associated with such diverse objects as planetary systems, Be stars and spiral galaxies. However, their structure is poorly defined by existing observational data. This study was an attempt to gather specific structural information about the disks in Algol-type binary systems. In Algol-type binaries mass transfer from the secondary star forms a gaseous disk which surrounds the hotter companion. During the primary eclipse both the central star and the disk undergo a brief occultation. Conventional photographic spectroscopy cannot record the rapid spectral changes which give information on the size, velocities, and physical conditions of the disk. In this study, time -resolved spectroscopy was obtained with modern TV-type multiplexed detectors. A small survey of short-period (< 4 days) Algol systems showed that accretion disks are rare. The system RW Tauri had the most persistent disk, on which most of the results are based. The disk is highly unstable, forming and reforming in less than one orbit. The disk is smaller than previously believed, rarely exceeding 1.5 times the radius of its central star. The electron densities are typically 10('11) to 10('12) cm('-3). The trailing side of the disk appears to be approximately isothermal and of nearly constant density with a size set by an ionization limit rather than an actual physical edge. The conditions on the disk are definitely non-LTE. The leading side of the disk has a high density concentration near the star and shows evidence it is collapsing to the orbital plane. The disk rotation is highly non-Keplerian in nature. On one occasion the highest rotational velocity was at the outer edge. The emission line widths are at least twice that expected from orbital motion. The nearly Gaussian line profiles suggest turbulence. However, it would be required to be highly supersonic. No acceptable explanation for the line widths was found.

Kaitchuck, Ronald Harold

140

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

NASA Astrophysics Data System (ADS)

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

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

141

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 5075% 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

142

SPECTROSCOPY IN CRYOCRYSTALS AND MATRICES Time-resolved CARS measurements of the vibrational decoherence of I2 isolated  

E-print Network

SPECTROSCOPY IN CRYOCRYSTALS AND MATRICES Time-resolved CARS measurements of the vibrational succeeded in making measurements on packets prepared at vibrations as high as v 14, and as a function of tempera- ture, for T 17­33 K. TRCARS measurements are well suited for the preparation of vibrational

Apkarian, V. Ara

143

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

144

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

145

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

PubMed Central

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

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

2012-01-01

146

Time-resolved Optical Spectroscopy of the Classical Nova V723 Cas  

NASA Astrophysics Data System (ADS)

We present the results of time-resolved optical spectroscopy of the classical nova and super-soft X-ray source V723 Cas (Nova Cas 1995). The spectra were obtained at the Steward Observatory Bok 2.3-m telescope (range: 4180-5320 Angstroms) on Kitt Peak and at the MDM Observatory Hilter 2.4-m telescope (range: 4000-7500 Angstroms) in 2007, 2008, and 2010. Both sets of spectra were obtained at a spectral resolution of about 2 Angstroms. Exposure times of the individual spectra were about 20 minutes which is short compared to the 16.6-hour binary orbital period, thus minimizing velocity smearing of spectral features. V723 Cas is an unusual system, being an active super-soft X-ray source for more than 15 years since the 1995 outburst, in contrast to the median X-ray turn off time of only 1.4 years. This may be indicative of steady hydrogen burning on the white dwarf due to renewed accretion (Ness et al. 2008, AJ, 135, 1328). Phasing the individual spectra to the 16.6-hour binary photometric orbital period (Goranskij et al. 2007, Ast. Bull. 62, 125), we find that the Balmer emission lines exhibit a double-peaked accretion disk line profile convolved with a variable Gaussian emission line S-wave component. The He II 4686 emission line exhibits phase-dependent line profile variations as well. We have modeled both emission line profiles with a double-peaked accretion disk line component assuming different disk properties and an independent Gaussian component. The results of our line profile modeling compared to the orbital photometric behavior of V723 Cas are presented and we discuss the interpretation of our synoptic observations in the context of the post-outburst evolution of super-soft X-ray sources and this unusual classical nova.

Vonderharr, Thomas; Woodward, C. E.; Wagner, R. M.; Schwarz, G.; Helton, L. A.; Hamilton-Drager, C.; Recine, K. A.

2011-05-01

147

Nanosecond rapid freezing of liquid benzene under shock compression studied by time-resolved coherent anti-Stokes Raman spectroscopy.  

PubMed

Nanosecond time-resolved coherent anti-Stokes Raman spectroscopy is used to investigate the shock-induced liquid-solid phase transition and crystallization of liquid benzene. Temporal evolution of the Raman shift of the ring-breathing and C-H stretching modes is investigated. A metastable supercompressed state and a liquid-solid phase transition are observed under shock compression. Time-resolved Raman spectra reveal that the liquid state is initially a metastable state and rapidly transforms to the solid state within 25 ns under shock compression at 4.2 GPa. PMID:16468888

Matsuda, Akitaka; Kondo, Ken-ichi; Nakamura, Kazutaka G

2006-02-01

148

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 ) 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

149

Soft x-ray imaging system for picosecond time-resolved absorption spectroscopy using a femtosecond-laser-plasma source  

SciTech Connect

We have developed an imaging system for time-resolved soft x-ray absorption spectroscopy. The system consists of a femtosecond-laser-plasma x-ray source for time-resolved measurements and an x-ray microscope with critical illumination for imaging. The temporal and spatial resolutions were 23 ps and better than 12.5 {mu}m, respectively. We applied this system to the measurement of an aluminum ablation plume induced by irradiation with a 120 fs laser pulse. The shift of the L-shell photoabsorption edge in the expanding plume was observed in the spatiotemporally resolved absorbance spectrum. The space- and time-resolved x-ray absorption spectrum of an expanding laser ablation plume was clearly obtained using the developed system.

Okano, Yasuaki; Oguri, Katsuya; Nishikawa, Tadashi; Nakano, Hidetoshi [NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198 (Japan)

2006-04-15

150

Understanding THz and IR Signals beneath Time-Resolved Fluorescence from Excited-State Ab Initio Dynamics.  

PubMed

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

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

2014-10-22

151

The fate of alkane radical cations in liquid and solid hydrocarbons. Time-resolved fluorescence detected magnetic resonance  

SciTech Connect

Time-resolved fluorescence detected magnetic resonance (FDMR) is used to observe alkane radical cations generated by electron radiolysis in liquid and solid alkane solutions. The ease of observation of the alkane radical cations (on the time scale of tens to hundreds of nanoseconds) depends strongly on the alkane under study as well as the conditions of temperature and concentration. Ion-molecule reactions such as proton transfer or H-atom transfer are responsible for the very transient nature of the alkane radical cations and possibly account for much of the diversity of hydrocarbon radiation chemistry.

Werst, D.W.; Bakker, M.G.; Trifunac, A.D. (Argonne National Lab., IL (USA))

1990-01-03

152

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 Brling; Georg Noga

2011-01-01

153

Intramolecular deactivation of substituted quinolinium cations. Time-resolved fluorescence and semi-empirical calculations  

NASA Astrophysics Data System (ADS)

The fluorescence quenching of N-alkylated quinolinium ions with and without a sulfonato group at the chain end is investigated by measurement of their fluorescence lifetimes. The presence of the sulfonato group leads to a reduction of the fluorescence lifetime from 21.78 0.12 ns for N-ethylquinolinium cation to 0.31 0.05 ns for the sulfonatoethyl compound in CH 3CN. The high intramolecular quenching efficiency depends on the alkyl chain length in CH 3CN. However, in H 2O as solvent, there is no preferential quenching of fluorescence by the sulfonato group, which is strongly solvated. Semi-empirical calculations of sulfonatoalkylquinolinium betaines support the proposal of intramolecular ring formation as the cause of the strong quenching effects. The chain-length dependence of the fluorescence decay in CH 3CN is correlated with the different orientations of an interacting oxygen lone pair with the aromatic ? system.

Lanig, H.; Hof, M.; Stahl, T.; Schneider, F. W.

1994-08-01

154

Conductivity of ZnO Nanowires, Nanoparticles, and Thin Films Using Time-Resolved Terahertz Spectroscopy  

E-print Network

Conductivity of ZnO Nanowires, Nanoparticles, and Thin Films Using Time-Resolved Terahertz. ZnO properties were measured directly for thin films and were extracted from measurements of nanowire samples. Annealing significantly reduces the intrinsic carrier concentration in the ZnO films

155

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

156

Time-resolved fluorescence spectroscopic study of crude petroleum oils: influence of chemical composition.  

PubMed

The fluorescence of crude petroleum oils is sensitive to changes in chemical composition and many different fluorescence methods have been used to characterize crude oils. The use of fluorescence lifetimes to quantitatively characterize oil composition has practical advantages over steady-state measurements, but there have been comparatively few studies in which the lifetime behavior is correlated with gross chemical compositional data. In this study, the fluorescence lifetimes for a series of 23 crude petroleum oils with American Petroleum Institute (API) gravities of between 10 and 50 were measured at several emission wavelengths (450-785 nm) using a 380 nm light emitting diode (LED) excitation source. It was found that the intensity average fluorescence lifetime (tau) at any emission wave-length does not correlate well with either API gravity or aromatic concentration. However, it was found that tau is strongly negatively correlated with both the polar and sulfur concentrations and positively correlated with the corrected alkane concentration. This indicates that the fluorescence behavior of crude petroleum oils is governed primarily by the concentration of quenching species. All the strong lifetime-concentration correlations are nonlinear and show a high degree of scatter, especially for medium to light oils with API gravities of between 25 and 40. The degree of scatter is greatest for oils where the concentrations (wt %) of the polar fraction is approximately 10 +/- 4%, the asphaltene component is approximately 1 +/- 0.5%, and sulfur is 0.5 +/- 0.4%. This large degree of scatter precludes the use of average fluorescence lifetime data obtained with 380 nm excitation for the accurate prediction of the common chemical compositional parameters of crude petroleum oils. PMID:15165340

Ryder, Alan G

2004-05-01

157

Equilibrium between quenched and nonquenched conformations of the major plant light-harvesting complex studied with high-pressure time-resolved fluorescence  

Microsoft Academic Search

Nonphotochemical quenching (NPQ) of chlorophyll fluorescence plays an important role in the protection of plants against excessive light. Fluorescence quenching of the major light-harvesting complex (LHCII) provides a model system to study the mechanism of NPQ. The existence of both quenched and nonquenched states of LHCII has been postulated. We used time-resolved fluorescence and hydrostatic pressure to study differences between

Oort van B. F; Arie van Hoek; Alexander V. Ruban; Herbert van Amerongen

2007-01-01

158

Redox-linked conformational changes in bovine heart cytochrome c oxidase: picosecond time-resolved fluorescence studies of cyanide complex.  

PubMed

Picosecond time-resolved fluorescence studies are carried out on cyanide-inhibited and heat-modified cytochrome c oxidase in aqueous lauryl maltoside surfactant solution, as well as in an aqueous vesicle, to understand the conformational changes associated with electron transfer and proton pumping activity of the enzyme. The tryptophan fluorescence decay profiles follow a four exponential model, which also matches the lifetime maxima obtained in a maximum entropy method analysis. The fast lifetime components are highly affected by the reduction and chemical modification of the enzyme. Changes in these lifetime components are related to the conformational changes in the vicinity of the heme centers of the enzyme. The cyanide-inhibited enzyme in the oxidized form shows a fluorescence decay profile similar to that of the native oxidized form, indicating that the conformational changes due to cyanide binding are very small. However, reduction of the cyanide-inhibited enzyme that leaves cyanide bound heme alpha3 oxidized causes a large increase in the fluorescence lifetimes, which indicates very significant conformational changes due to electron transfer to the dinuclear Cu(A) and heme alpha centers. A comparison of the tryptophan fluorescence decay of various other modified forms of the enzyme leads us to propose that the possible site of conformational coupling is located near heme alpha instead of the binuclear heme alpha3-Cu(B) center. PMID:10958323

Das, T K; Mazumdar, S

2000-01-01

159

Time-resolved fluorescence reveals two binding sites of 1,8-ANS in intact human oxyhemoglobin.  

PubMed

Time-resolved fluorescence of 1,8-anilinonaphthalene sulfonate (1,8-ANS) fluorescent probe bound to intact human oxyhemoglobin (HbO2) is investigated. Fluorescence emission spectra of 1,8-ANS in a potassium buffer solution (pH 7.4) of HbO2 undergo a substantial blue shift during first 6 ns after pulsed optical excitation at 337.1 nm. Nonexponential fluorescence kinetics of 1,8-ANS in the HbO2 solution are studied by the decay time distribution and conventional multiexponential analyses for a set of emission wavelength range of lambdaem = 455-600 nm. These fluorescence decays contain components with mean decay times of <0.5 ns, 3.1-5.5 ns, and 12.4-15.1 ns with spectrally-dependent relative contributions. The shortest decay component is assigned to free 1,8-ANS molecules in the bulk buffer environment, whereas the two longer decay components are assigned to two types of binding sites of 1,8-ANS in the HbO2 molecule presumably differing by polarity and accessibility to water molecules. The results represent the first experimental evidence of heterogeneous binding of 1,8-ANS to intact human oxyhemoglobin. PMID:11233644

Parul, D A; Bokut, S B; Milyutin, A A; Petrov, E P; Nemkovich, N A; Sobchuk, A N; Dzhagarov, B M

2000-11-01

160

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

E-print Network

and Liposomes Ismael Moya, Mariuccia Silvestri,§ Olivier Vallon,| Gianfelice Cinque, and Roberto Bassi*, LURE conformation of the Lhc proteins. Upon incorporation of Lhc proteins into liposomes, a quenching of chlorophyll in the liposomes, and therefore the probability of protein-protein interactions, a further decrease of fluorescence

161

Time-resolved FTIR spectroscopy for monitoring protein dynamics exemplified by functional studies of Ras protein bound to a lipid bilayer  

E-print Network

online 22 August 2011 Keywords: Infrared Time-resolved Difference spectroscopy Rapid scan Step scan infrared (FTIR) difference spectroscopy is a valuable tool for monitoring the dynamics of protein reactions in 25% of human tumors. We show the first time- resolved measurements of membrane anchored Ras

Gerwert, Klaus

162

Intense square-flash source for time-resolved absorption spectroscopy  

NASA Astrophysics Data System (ADS)

This paper describes a compact xenon flash source and associated circuit designed as an absorption background source for time-resolved spectroscopic measurements. The output is a square wave of nearly constant intensity for a period of 250 ?s. Its spectral emissivity is roughly equivalent to a blackbody of 12 000 K, depending on the voltage used, except for a cutoff in the far ultraviolet by the quartz envelope. The lamp jacket is simple and inexpensive to replace and refill.

Paur, Richard J.; Dorsett, John L.; Bair, Edward J.

1982-03-01

163

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

NASA Astrophysics Data System (ADS)

Preterm infants are highly susceptible to ischemic brain injury; consequently, continuous bedside monitoring to detect ischemia before irreversible damage occurs would improve patient outcome. In addition to monitoring cerebral blood flow (CBF), assessing the cerebral metabolic rate of oxygen (CMRO2) would be beneficial considering that metabolic thresholds can be used to evaluate tissue viability. The purpose of this study was to demonstrate that changes in absolute CMRO2 could be measured by combining diffuse correlation spectroscopy (DCS) with time-resolved near-infrared spectroscopy (TR-NIRS). Absolute CBF was determined using bolus-tracking TR-NIRS to calibrate the DCS measurements. Cerebral venous blood oxygenation (SvO2) was determined by multiwavelength TR-NIRS measurements, the accuracy of which was assessed by directly measuring the oxygenation of sagittal sinus blood. In eight newborn piglets, CMRO2 was manipulated by varying the anesthetics and by injecting sodium cyanide. No significant differences were found between the two sets of SvO2 measurements obtained by TR-NIRS or sagittal sinus blood samples and the corresponding CMRO2 measurements. Bland-Altman analysis showed a mean CMRO2 difference of 0.02680.8340 mL O2/100 g/min between the two techniques over a range from 0.3 to 4 mL O2/100 g/min.

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

2013-02-01

164

Development and evaluation of a time-resolved near-infrared fluorescence finite element model  

NASA Astrophysics Data System (ADS)

In this work a generalization of the approach allowing time-domain (TD) excitation and fluorescence data to be generated using a finite element model (FEM) is introduced. This new functionality allows simulation of temporal point-spread functions (TPSF) for a heterogeneous scattering and absorbing media of arbitrary geometry. In the first part of this paper, the approach used to develop a computationally efficient model for solving the time-dependent diffusion equation for excitation and fluorescence data is presented. In the second part, a detailed theoretical evaluation of the method is given by comparing the developed FEM simulations with analytical and Monte Carlo data. The total fluence (intensity data), shows qualitative match whereas meantime of flight is almost identical among the three models for both excitation and emission data. The results show that the model is reliable and warrants its use for future TD applications where diffusion modelling can be used.

Zhu, Qun; Leblond, Frederic; El-Ghussein, Fadi; Pogue, Brian W.; Dehghani, Hamid

2011-02-01

165

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 Pulgarn, J A; Alan Molina, A; Martnez Ferreras, F

2014-07-15

166

Application of time-resolved fluorescence to the determination of metabolites  

NASA Astrophysics Data System (ADS)

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.

Murillo Pulgarn, J. A.; Alan Molina, A.; Martnez Ferreras, F.

2014-07-01

167

Ferryl intermediates of catalase captured by time-resolved Weissenberg crystallography and UV-VIS spectroscopy.  

PubMed

Various enzymes use semi-stable ferryl intermediates and free radicals during their catalytic cycle, amongst them haem catalases. Structures for two transient intermediates (compounds I and II) of the NADPH-dependent catalase from Proteus mirabilis (PMC) have been determined by time-resolved X-ray crystallography and single crystal microspectrophotometry. The results show the formation and transformation of the ferryl group in the haem, and the unexpected binding of an anion during this reaction at a site distant from the haem. PMID:8901874

Gouet, P; Jouve, H M; Williams, P A; Andersson, I; Andreoletti, P; Nussaume, L; Hajdu, J

1996-11-01

168

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

169

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

170

Laguerre-based method for analysis of time-resolved fluorescence data: application to in-vivo characterization and diagnosis of atherosclerotic lesions  

NASA Astrophysics Data System (ADS)

We report the application of the Laguerre deconvolution technique (LDT) to the analysis of in-vivo time-resolved laser-induced fluorescence spectroscopy (TR-LIFS) data and the diagnosis of atherosclerotic plaques. TR-LIFS measurements were obtained in vivo from normal and atherosclerotic aortas (eight rabbits, 73 areas), and subsequently analyzed using LDT. Spectral and time-resolved features were used to develop four classification algorithms: linear discriminant analysis (LDA), stepwise LDA (SLDA), principal component analysis (PCA), and artificial neural network (ANN). Accurate deconvolution of TR-LIFS in-vivo measurements from normal and atherosclerotic arteries was provided by LDT. The derived Laguerre expansion coefficients reflected changes in the arterial biochemical composition, and provided a means to discriminate lesions rich in macrophages with high sensitivity (>85%) and specificity (>95%). Classification algorithms (SLDA and PCA) using a selected number of features with maximum discriminating power provided the best performance. This study demonstrates the potential of the LDT for in-vivo tissue diagnosis, and specifically for the detection of macrophages infiltration in atherosclerotic lesions, a key marker of plaque vulnerability.

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

2006-03-01

171

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

172

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

SciTech Connect

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

France, Kevin; Froning, Cynthia S. [Center for Astrophysics and Space Astronomy, University of Colorado, 389 UCB, Boulder, CO 80309 (United States); Linsky, Jeffrey L. [JILA, University of Colorado and NIST, 440 UCB, Boulder, CO 80309 (United States); Tian, Feng [Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80309 (United States); Roberge, Aki, E-mail: kevin.france@colorado.edu [Exoplanets and Stellar Astrophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2012-05-10

173

Molecular analysis of mitotic chromosome condensation using a quantitative time-resolved fluorescence microscopy assay.  

PubMed

Chromosomes condense during mitotic entry to facilitate their segregation. Condensation is typically assayed in fixed preparations, limiting analysis of contributing factors. Here, we describe a quantitative method to monitor condensation kinetics in living cells expressing GFP fused to a core histone. We demonstrate the utility of this method by using it to analyze the molecular requirements for the condensation of holocentric chromosomes during the first division of the Caenorhabditis elegans embryo. In control embryos, the fluorescence intensity distribution for nuclear GFP:histone changes during two distinct time intervals separated by a plateau phase. During the first interval, primary condensation converts diffuse chromatin into discrete linear chromosomes. After the plateau, secondary condensation compacts the curvilinear chromosomes to form shorter bar-shaped structures. We quantitatively compared the consequences on this characteristic profile of depleting the condensin complex, the mitosis-specific histone H3 kinase Aurora B, the centromeric histone CENP-A, and CENP-C, a conserved protein required for kinetochore assembly. Both condensin and CENP-A play critical but distinct roles in primary condensation. In contrast, depletion of CENP-C slows but does not prevent primary condensation. Finally, Aurora B inhibition has no effect on primary condensation, but slightly delays secondary condensation. These results provide insights into the process of condensation, help resolve apparent contradictions from prior studies, and indicate that CENP-A chromatin has an intrinsic role in the condensation of holocentric chromosomes that is independent of its requirement for kinetochore assembly. PMID:17005720

Maddox, Paul S; Portier, Nathan; Desai, Arshad; Oegema, Karen

2006-10-10

174

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 5257 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 5257, 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 5257 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

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

2014-01-01

175

Time-resolved wavelength modulation spectroscopy measurements of HO2 kinetics  

E-print Network

. Reports of detection sensitivities close to the detector shot-noise limit have appeared under favorable with FM spectroscopy,6 and transient FM spectroscopy has now found applications in the spectroscopy- tected with an InGaAs photodiode detector capable of simultaneously monitoring ac WMS and dc I0 com

176

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 1.010(-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

177

Effects of ligand binding on the conformation and internal dynamics in specific regions of porcine pancreatic phospholipase A2 with tryptophan as a probe: a study combining time-resolved fluorescence spectroscopy and site-directed mutagenesis (same as p. 100)  

NASA Astrophysics Data System (ADS)

Exploration of the effect of ligand-protein interactions on conformational substates and internal dynamics in different regions of phospholipase A2 from porcine pancreas (PLA2), was performed by combining site-directed mutagenesis and time-resolved fluorescence measurements. The single tryptophan residue (Trp-3) in the wild type protein was replaced by a phenylalanine residue, whereafter Trp was substituted either for leucine-31 ,located in the calcium binding loop, or for phenylalanine-94, located at the "back side" of the enzyme, in a-helix E (Dijkstra et al., J. Mol. Biol., 147, 97-123, 1981). Analyses by the Maximum Entropy Method (MIEM) of the total fluorescence intensity decays, provide in each case a distribution of separate lifetime classes, which can be interpreted as reflecting the existence of discrete conformational substates in slow exchange with respect to the time-scale of the decay kinetics. The fluorescence decay of the W94 mutant is dominated by an extremely short excited state lifetime of ~60 ps, probably arising from the presence of two proximate disulfide bridges. Time-resolved fluorescence anisotropy studies show that the Trp residue near the NH2 terminus (Trp-3) undergoes a more limited rotational motion than the Trp-3 1 located in the calcium binding loop. The widest angular rotation is observed at position 94, in a-helix E. Calcium binding displays the strongest influence on the lifetime distribution of Trp-31: a major local conformation corresponding to a lifetime class with a barycenter value of ~5.5 ns and contributing to ~50% of the decay is selected. The conformations giving rise to the short lifetimes ((tau)1 and (tau)2 lifetime classes) become less important. The contribution of the third lifetime class (c3) stays at a constant value of 30%. In the presence of calcium, the amplitude of motion is wider than without the ion. There is virtually no effect of calcium binding on the lifetime distribution of the Trp residue at the 3 or the 94 position. Binding of the monomeric substrate analog n-dodecylphosphocholine (C12PN) in the presence of calcium hardly affects neither the Trp-3 excited state population distribution, nor its rotational dynamics. The binding of C12PN monomers to the W31 mutant further increases the contribution of the t4lifetime class at the expense of c2. A more restricted rotation of the Trp-31 residue is also induced. The binding of the micellar substrate analog n-hexadecylphosphocholine (C16PN) in the presence of calcium is very efficient in modifying the lifetime distribution of Trp-3. Essentially, one major broad lifetime population (centered at ~2.6 ns) is revealed by MEM analysis of the total intensity decay. The internal motion is slowed down and the angle of rotation is much smaller in this conformation. Neither the excited state lifetime distribution of Trp-31 nor its dynamics are affected by micelle binding relative to monomer binding. In conclusion, by placing a single Tip-residue at strategic positions along the peptide chain of PLA2, relevant to the binding of biological ligands, an excellent model system for the study of selective perturbations of conformational substates and internal dynamics is provided.

Kuipers, Oscar; Vincent, Michel; Brochon, Jean-Claude; Verheij, Bert; de Haas, Gerard; Gallay, Jacques

1990-05-01

178

Effects of ligand binding on the conformation and internal dynamics in specific regions of porcine pancreatic phospholipase A2 with tryptophan as a probe: a study combinging time-resolved fluorescence spectroscopy and site-directed mutagenesis (same as p. 628)  

NASA Astrophysics Data System (ADS)

Exploration of the effect of ligand-protein interactions on conformational substates and internal dynamics in different regions of phospholipase A2 from porcine pancreas (PLA2), was performed by combining site-directed mutagenesis and time-resolved fluorescence measurements. The single tryptophan residue (Trp-3) in the wild type protein was replaced by a phenylalanine residue, whereafter Tip was substituted either for leucine-3 1 ,located in the calcium binding ioop, or for phenylalanine-94, located at the "back side" of the enzyme, in a-helix E (Dijkstra et al., J. Mol. Biol., 147, 97-123, 1981). Analyses by the Maximum Entropy Method (MEM) of the total fluorescence intensity decays, provide in each case a distribution of separate lifetime classes, which can be interpreted as reflecting the existence of discrete conformational substates in slow exchange with respect to the time-scale of the decay kinetics. The fluorescence decay of the W94 mutant is. dominated by an extremely short excited state lifetime of ~60 ps, probably arising from the presence of two proximate disulfide bridges. Time-resolved fluorescence anisotropy studies show that the Trp residue near the NH2 terminus (Trp-3) undergoes a more limited rotational motion than the Trp-3 1 located in the calcium binding loop. The widest angular rotation is observed at position 94, in a-helix E. Calcium binding displays the strongest influence on the lifetime distribution of Trp-3 1: a major local conformation corresponding to a lifetime class with a barycenter value of -5.5 ns and contributing to ~50% of the decay is selected. The conformations giving rise to the short lifetimes (?1 and ?2 lifetime classes) become less important. The contribution of the third lifetime class (c3) stays at a constant value of 30%. In the presence of calcium, the amplitude of motion is wider than without the ion. There is virtually no effect of calcium binding on the lifetime distribution of the Trp residue at the 3 or the 94 position. Binding of the monomeric substrate analog n-dodecylphosphocholine (C12PN) in the presence of calcium hardly affects neither the Trp-3 excited state population distribution, nor its rotational dynamics. The binding of C12PN monomers to the W31 mutant further increases the contribution of the ?4 lifetime class at the expense of c2. A more restricted rotation of the Trp-3 1 residue is also induced. The binding of the micellar substrate analog n-hexadecylphosphocholine (C16PN) in the presence of calcium is very efficient in modifying the lifetime distribution of Trp-3. Essentially, one major broad lifetime population (centered at ~2.6 ns) is revealed by MEM analysis of the total intensity decay. The internal motion is slowed down and the angle of rotation is much smaller in this conformation. Neither the excited state lifetime distribution of Trp-31 nor its dynamics are affected by micelle binding relative to monomer binding. In conclusion, by placing a single Tip-residue at strategic positions along the peptide chain of PLA2, relevant to the binding of biological ligands, an excellent model system for the study of selective perturbations of conformational substates and internal dynamics is provided.

Kuipers, Oscar; Vincent, Michel; Brochon, Jean-Claude; Verheij, Bert; de Haas, Gerard; Gallay, Jacques

1990-05-01

179

Non-adiabatic and time-resolved photoelectron spectroscopy for molecular systems  

E-print Network

We quantify the non-adiabatic contributions to the vibronic sidebands of equilibrium and explicitly time-resolved non-equilibrium photoelectron spectra for a vibronic model system of Trans-Polyacetylene. Using exact diagonalization, we directly evaluate the sum-over-states expressions for the linear-response photocurrent. We show that spurious peaks appear in the Born-Oppenheimer approximation for the vibronic spectral function, which are not present in the exact spectral function of the system. The effect can be traced back to the factorized nature of the Born-Oppenheimer initial and final photoemission states and also persists when either only initial, or final states are replaced by correlated vibronic states. Only when correlated initial and final vibronic states are taken into account, the spurious spectral weights of the Born-Oppenheimer approximation are suppressed. In the non-equilibrium case, we illustrate for an initial Franck-Condon excitation and an explicit pump-pulse excitation how the vibronic ...

Flick, Johannes; Rubio, Angel

2014-01-01

180

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

181

Ascertaining free histidine from mixtures with histidine-containing proteins using time-resolved photoluminescence spectroscopy.  

PubMed

The use of photoluminescent probes for differentiating free amino acids from biomolecules containing the same amino acids is challenging. Photoluminescent probes generally present similar emission spectra when in the presence of either free-amino acids or protein containing those same amino acids. Probes based on cyclometalated iridium(III) complexes Ir(L)2(sol)2 (where L is 2-phenylpyridine, 2-(2,4-difluorophenyl)pyridine, or benzo[h]quinolone, and sol is a solvent molecule) present long-lived emission when bound to histidine. This emission is tuned by the microenvironment around the complex and therefore its lifetime is different for free histidine (487 ns) than from histidine-containing proteins such as bovine serum albumin (average lifetime > 700 ns). As a proof-of-concept we demonstrate that free histidine can be discerned from a mixture with histidine-containing proteins by using time-resolved photoluminescence decays. In the presence of multiple sources of histidine, iridium(III) probes display a multiexponential decay, which can be fitted by nonlinear least-squares methods to separate the different components. Because the pre-exponential factor of the 487 ns lifetime is proportional to the concentration of free histidine, we can use it to assess the amount of free histidine in solution even in the presence of proteins such as bovine serum albumin. We also show that iridium(III) probes displaying different photoluminescence maxima can be produced by modifying the ancillary ligands of the metal complex. PMID:25313943

Huang, Kewei; Jiang, Chengmin; Mart, Angel A

2014-11-13

182

Infrared absorption of CH3SO2 detected with time-resolved Fourier-transform spectroscopy  

NASA Astrophysics Data System (ADS)

A step-scan Fourier-transform spectrometer coupled with a 6.4m multipass absorption cell was employed to detect time-resolved infrared absorption spectra of the reaction intermediate CH3SO2 radical, produced upon irradiation of a flowing gaseous mixture of CH3I and SO2 in CO2 at 248nm. Two transient bands with origins at 1280 and 1076cm-1 were observed and are assigned to the SO2-antisymmetric and SO2-symmetric stretching modes of CH3SO2, respectively. Calculations with density-functional theory (B3LYP/aug-cc-pVTZ and B3P86/aug-cc-pVTZ) predicted the geometry, vibrational, and rotational parameters of CH3SO2 and CH3OSO. Based on predicted rotational parameters, the simulated absorption band of the SO2-antisymmetric stretching mode that is dominated by the b-type rotational structure agrees satisfactorily with experimental results. In addition, a band near 1159cm-1 observed at a later period is tentatively attributed to CH3SO2I. The reaction kinetics of CH3+SO2?CH3SO2 and CH3SO2+I ?CH3SO2I based on the rise and decay of absorption bands of CH3SO2 and CH3SO2I agree satisfactorily with previous reports.

Chu, Li-Kang; Lee, Yuan-Pern

2006-06-01

183

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

184

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. We report the first time-resolved soft x-ray spectroscopy of solution-phase molecular dynamics. Changes in ligand-field splitting and spin-state populations in 3d orbitals of the Fe{sup II} complex are directly probed via transient absorption changes of the Fe L{sub 2} and L{sub 3} edges following photo-induced metal-to-ligand charge transfer. With the emergence of high-flux ultrafast soft x-ray sources, details on interplay between atomic structure, electronic states, and spin contributions will be revealed. Our experimental approach opens the door to femtosecond soft x-ray investigations of liquid phase chemistry that have previously been inaccessible.

Huse, N.; Kim, T.-K.; Khalil, M.; Jamula, L.; McCusker, J.K.; Schoenlein, R.W.

2008-08-01

185

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

186

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

187

Time-resolved Spectroscopy of the Polar EU Cancri in the Open Cluster Messier 67  

NASA Astrophysics Data System (ADS)

We present time-resolved spectroscopic and polarimetric observations of the AM Her system EU Cnc. EU Cnc is located near the core of the old open cluster Messier 67; new proper motion measurements indicate that EU Cnc is indeed a member of the star cluster, and this system therefore is useful to constrain the formation and evolution of magnetic cataclysmic variables. The spectra exhibit two-component emission features with independent radial velocity variations as well as time-variable cyclotron emission indicating a magnetic field strength of 41 MG. The period of the radial velocity and cyclotron hump variations are consistent with the previously known photometric period, and the spectroscopic flux variations are consistent in amplitude with previous photometric amplitude measurements. The secondary star is also detected in the spectrum. We also present polarimetric imaging measurements of EU Cnc that show a clear detection of polarization, and the degree of polarization drops below our detection threshold at phases when the cyclotron emission features are fading or not evident. The combined data are all consistent with the interpretation that EU Cnc is a low-state polar in the cluster Messier 67. The mass function of the system gives an estimate of the accretor mass of M WD >= 0.68 M ? with M WD ? 0.83 M ? for an average inclination. We are thus able to place a lower limit on the progenitor mass of the accreting white dwarf of >=1.43 M ?. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Williams, Kurtis A.; Howell, Steve B.; Liebert, James; Smith, Paul S.; Bellini, Andrea; Rubin, Kate H. R.; Bolte, Michael

2013-05-01

188

Molecular dynamics in low vibrational states investigated by fs time-resolved coherent anti-Stokes Raman spectroscopy technique  

NASA Astrophysics Data System (ADS)

The molecular dynamics process is investigated in this paper using a broadband fs time-resolved coherent anti-Stokes Raman spectroscopy (CARS) technique. By varying the timing of laser pulses, low vibrational states are started and studied on both the electronically excited B( 3?0 u+) state and ground X( 1?0 g+) state of iodine in the gas phase at room temperature. According to change the pump wavelength or Stokes pulse as well as the wavelength of the detection window for the CARS signal, dynamics on different potential-energy surfaces can be accessed and detected by the CARS spectroscopy. Results show that the period of the oscillation is decreased for the excited B( 3?0 u+) state as the wavelength of the pump pulses is increased, while it is increased for the ground X( 1?0 g+) state with the increase of the Stokes wavelength.

He, Ping; Li, Sining; Fan, Rongwei; Xia, Yuanqin; Yu, Xin; Yao, Yong; Chen, Deying

2011-09-01

189

An investigation of coordinatively unsaturated metal carbonyls using time-resolved infrared spectroscopy  

SciTech Connect

This dissertation details the work done implementing a state of the art (100 ns temporal response with sub wavenumber frequency resolution) time resolved infrared (TRIR) spectrophotometer to study the reactive chemical species produced by pulsed laser photolysis which are proposed to be related to the key intermediates generated in thermal reactions. Photolysis (308 nm XeCl Excimer laser) of ambient temperature isooctane solutions of Ru[sub 3](CO)[sub 12] produced an intermediate proposed to be the Ru[sub 3](CO)[sub 11] species observed by M.S. Wrighton in low temperature matrices. This intermediate was found to react with CO with a second order rate constant, K[sub co], of 2.4 x 10[sup 9] M[sup [minus]1]s[sup [minus]1]. It was also found to react with donating solvents, such as THF, even more rapidly. The reaction with THF, k[sub L], was found to be 6.1 x 10[sup 9] M[sup [minus]1]s[sup [minus]1]. The rate of dissociation, k[sub L], was 2 x 10[sup 6] s[sup [minus]1]. It is of interest that the associative rates are approaching the calculated diffusion controlled limits for bimolecular reactions in isooctane (k[sub d] = 1.3 x 10[sup 10] M[sup [minus]1]s[sup [minus]1]). The second project discussed concerns the nature of intermediates produced in the migratory insertion reaction of CO with the model compounds CH[sub 3]Mn(CO)[sub 5] and CpFe(CO)[sub 2]CH[sub 3]. It was found that the nominally coordinatively unsaturated intermediates were solvated, especially in more donating solvents such as THF. The acyl intermediates, CH[sub 3]COMn(CO)[sub 4](S) and CpFe(CO)(S)COCH[sub 3], were relatively unreactive in cyclohexane, having K[sub co] values of 5.6 x 10[sup 3] M[sup [minus]1]s[sup [minus]1] and <10[sup 5] M[sup [minus]1]s[sup [minus]1], respectively. Rates for isomerization to the corresponding methyl compounds were 6.0 s[sup [minus]1] and 5.7 x 10[sup 4] s[sup [minus]1].

Ryba, D.W.

1992-01-01

190

Reaction kinetics on model catalysts: Molecular beam methods and time-resolved vibrational spectroscopy  

Microsoft Academic Search

Reaction kinetics on nanometer-scale particles are different from perfect single crystal surfaces. In heterogeneous catalysts this fact is empirically made use of in order to maximize the catalytic performance. Molecular beam experiments combined with vibrational spectroscopy on structurally well-defined model catalysts can provide detailed insight into the underlying reaction kinetics at the microscopic level. We critically review the recent developments,

Jrg Libuda

2005-01-01

191

Rotational and Translational Dynamics of Rhodamine 6G in a Pyrrolidinium Ionic Liquid: A Combined Time-Resolved Fluorescence Anisotropy Decay and NMR Study  

SciTech Connect

NMR spectroscopy and time-resolved fluorescence anisotropy decay (TRFAD) are two of the most commonly used methods to study solute-solvent interactions. However, only a few studies have been reported to date using a combined NMR and TRFAD approach to systematically investigate the overall picture of diffusional and rotational dynamics of both the solute and solvent. In this paper, we combined NMR and TRFAD to probe fluorescent rhodamine dyes in a pyrrolidinium-based room temperature ionic liquid (RTIL), an emergent environmentally-friendly solvent type used in several energy-related applications. A specific interaction of the R6G cation and [Tf2N]- anion was identified, resulting in near-stick boundary condition rotation of R6G in this RTIL. The diffusional rates of the R6G solute and [C4mpyr][Tf2N] solvent derived from 1H NMR suggest the rates are proportional to their corresponding hydrodynamic radii. The 1H and 13C NMR studies of self-rotational dynamics of [C4mpyr][Tf2N] showed that the self-rotational correlation time of [C4mpyr]+ is 47 2 ps at 300 K. At the same temperature, we find that the correlation time for N-CH3 rotation in [C4mpyr]+ is 77 2 ps, comparable to overall molecular reorientation. This slow motion is attributed to properties of the cation structure.

Guo, Jianchang [ORNL; Han, Kee Sung [ORNL; Mahurin, Shannon Mark [ORNL; Baker, Gary A [ORNL; Hillesheim, Patrick C [ORNL; Dai, Sheng [ORNL; Hagaman, Edward {Ed} W [ORNL; Shaw, Robert W [ORNL

2012-01-01

192

Identification of Pregnane X Receptor Ligands Using Time-Resolved Fluorescence Resonance Energy Transfer and Quantitative High-Throughput Screening  

PubMed Central

Abstract The human pregnane X nuclear receptor (PXR) is a xenobiotic-regulated receptor that is activated by a range of diverse chemicals, including antibiotics, antifungals, glucocorticoids, and herbal extracts. PXR has been characterized as an important receptor in the metabolism of xenobiotics due to induction of cytochrome P450 isozymes and activation by a large number of prescribed medications. Developing methodologies that can efficiently detect PXR ligands will be clinically beneficial to avoid potential drugdrug interactions. To facilitate the identification of PXR ligands, a time-resolved fluorescence resonance energy transfer (TR-FRET) assay was miniaturized to a 1,536-well microtiter plate format to employ quantitative high-throughput screening (qHTS). The optimized 1,536-well TR-FRET assay showed Z?-factors of ?0.5. Seven- to 15-point concentrationresponse curves (CRCs) were generated for 8,280 compounds using both terbium and fluorescein emission data, resulting in the generation of 241,664 data points. The qHTS method allowed us to retrospectively examine single concentration screening datasets to assess the sensitivity and selectivity of the PXR assay at different compound screening concentrations. Furthermore, nonspecific assay artifacts such as concentration-based quenching of the terbium signal and compound fluorescence were identified through the examination of CRCs for specific emission channels. The CRC information was also used to define chemotypes associated with PXR ligands. This study demonstrates the feasibility of profiling thousands of compounds against PXR using the TR-FRET assay in a high-throughput format. PMID:19505231

Shukla, Sunita J.; Nguyen, Dac-Trung; MacArthur, Ryan; Simeonov, Anton; Frazee, William J.; Hallis, Tina M.; Marks, Bryan D.; Singh, Upinder; Eliason, Hildegard C.; Printen, John; Austin, Christopher P.; Inglese, James

2009-01-01

193

Time resolved spectroscopy and gain studies of Fullerenes C60 and C70.  

PubMed

The fluorescence decay time of Fullerenes C60 and C70 in pure form as well as in mixture with Coumarin C440 and Quinizarine dyes are studied. Results indicate that the decay of pure fullerenes is constant throughout the solute concentration and it is also independent of excitation wavelength, whereas in the case of mixture with dyes different behavior is noticed. We have also calculated the Stern-Volmer quenching constant and optical gain of both the fullerenes from which it is found that the optical gain is positive for Fullerene C70 only in a very narrow range of concentration. PMID:23747380

Qaiser, Darakhshan; Khan, Mohd Shahid; Singh, R D; Khan, Zahid H

2013-09-01

194

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

195

Fiber-based cryogenic and time-resolved spectroscopy of PbS quantum dots  

E-print Network

PbS quantum dots are promising active emitters for use with high-quality Si nanophotonic devices in the telecommunications-band. Measurements of low quantum dot densities are limited both because of low fluorescence levels and the challenges of single photon detection at these wavelengths. Here, we report on methods using a fiber taper waveguide to efficiently extract PbS quantum dot photoluminescence. Temperature dependent ensemble measurements reveal an increase in emitted photons concomitant with an increase in excited-state lifetime from 58.9 ns at 293 K to 657 ns at 40 K. Measurements are also performed on quantum dots on high-$Q$ ($>10^5$) microdisks using cavity-resonant, pulsed excitation.

Matthew T. Rakher; Ranojoy Bose; Chee Wei Wong; Kartik Srinivasan

2010-12-01

196

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.pelegrin@inserm.fr In oncology, simultaneous inhibition of epidermal growth factor receptor (EGFR) and HER2 by monoclonal EGFR/HER2 heterodimers on cell surface in order to shed some light on the mechanism of such therapies

Paris-Sud XI, Université de

197

Effect of dynamical spectral weight redistribution on effective interactions in time-resolved spectroscopy  

NASA Astrophysics Data System (ADS)

The redistribution of electrons in an ultrafast pump-probe experiment causes significant changes to the spectral distribution of the retarded interaction between electrons and bosonic modes. We study the influence of these changes on pump-probe photoemission spectroscopy for a model electron-phonon coupled system using the nonequilibrium Keldysh formalism. We show that spectral rearrangement due to the driving field preserves an overall sum rule for the electronic self-energy, but modifies the effective electron-phonon scattering as a function of energy. Experimentally, this pump-modified scattering can be tracked by analyzing the fluence or excitation energy dependence of population decay rates and transient changes in dispersion kinks.

Kemper, A. F.; Sentef, M. A.; Moritz, B.; Freericks, J. K.; Devereaux, T. P.

2014-08-01

198

Complete momentum and energy resolved TOF electron spectrometerfor time-resolved photoemission spectroscopy  

SciTech Connect

Over the last decade, high-resolution Angle-Resolved Photoemission Spectroscopy (ARPES) has emerged as a tool of choice for studying the electronic structure of solids, in particular, strongly correlated complex materials such as cuprate superconductors. In this paper we present the design of a novel time-of-flight based electron analyzer with capability of 2D in momentum space (kx and ky) and all energies (calculated from time of flight) in the third dimension. This analyzer will utilize an improved version of a 2D delay linedetector capable of imaging with<35 mm (700x700 pixels) spatial resolution and better than 120 ps FWHM timing resolution. Electron optics concepts and optimization procedure are considered for achieving an energy resolution less than 1 meV and an angular resolution better than 0.11.

Hussain, Zahid; Lebedev, G.; Tremsin, A.; Siegmund, O.; Chen, Y.; Shen, Z.X.; Hussain, Z.

2007-08-12

199

In situ time-resolved X-ray near-edge absorption spectroscopy of selenite reduction by siderite.  

PubMed

The reduction-oxidation reaction between aqueous selenite (SeO(3)(2-)) and siderite (FeCO(3(s))) was monitored by in situ, time-resolved X-ray absorption near-edge structure (XANES) spectroscopy at the selenium K edge in a controlled electrochemical environment. Spectral evolutions showed that more than 60% of selenite was reduced at the siderite surface after 20 h of experiment, at which time the reaction was still incomplete. Fitting of XANES spectra by linear combination of reference spectra showed that selenite reaction with siderite is essentially a two-step process, selenite ions being immobilized on siderite surface prior to their reduction. A kinetic model of the reduction step is proposed, allowing to identify the specific contribution of surface reduction. These results have strong implications for the retention of selenite by corrosion products in nuclear waste repositories and in a larger extent for the fate of selenium in the environment. PMID:22954023

Badaut, V; Schlegel, M L; Descostes, M; Moutiers, G

2012-10-01

200

Mixture models for two-dimensional baseline correction, applied to artifact elimination in time-resolved spectroscopy.  

PubMed

Baseline correction and artifact removal are important pre-processing steps in analytical chemistry. We propose a correction algorithm using a mixture model in combination with penalized regression. The model is an extension of a method recently introduced for baseline estimation in the case of one-dimensional data. The data are modeled as a smooth surface using tensor product P-splines. The weights of the P-splines regression model are computed from a mixture model where a datapoint is either allocated to the noise around the baseline, or to the artifact component. The method is broadly applicable for anisotropic smoothing of two-way data such as two-dimensional gel electrophoresis and two-dimensional chromatography data. We focus here on the application of the approach in femtosecond time-resolved spectroscopy, to eliminate strong artifact signals from the solvent. PMID:23522106

de Rooi, Johan J; Devos, Olivier; Sliwa, Michel; Ruckebusch, Cyril; Eilers, Paul H C

2013-04-10

201

Time-resolved optical resonant absorption spectroscopy of Cr metallic vapor in air using a broadband LED light source  

NASA Astrophysics Data System (ADS)

In this work, we show the feasibility of applying time-resolved broadband optical absorption spectroscopy using an LED light source as a valuable diagnostic tool for characterizing the electrical arc's current-interruption process. With our setup we have shown the capability of following in a single measurement the time evolution of the diffusion of chromium (Cr) neutral atoms around and after current zero of an electrical arc that was ignited between two Cu-Cr contacts. This is achieved by analyzing the absorption spectrum of CrI resonance lines near the central wavelength of the broadband LED at 425 nm, and using the so-called fast-kinetics acquisition mode of the spectrometer, with a time resolution of 415 s. As a result, by relying on the optical thinness of our lines, we could estimate the time evolution of the ground-state population of neutral Cr atoms outside the contact gap.

Horvath, B.; Lamara, T.

2013-08-01

202

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

203

Time Resolved Spectroscopy, High Sensitivity Power Spectrum & a Search for the X-Ray QPO in NGC 5548  

NASA Astrophysics Data System (ADS)

Controversy surrounds the EXOSAT discovery of a QPO (period ~500 s) in NGC 5548 due to the data being plagued by high background and instrumental systematics. If the NGC 5548 QPO is real, the implications for the physics of the X-ray emission mechanism and inner-most disk/black-hole system are enormous. AXAF provides the first opportunity to settle the issue, capable of yielding power spectra with unprecedented sensitivity, pushing the limit on finding new features. Using HETG/ACIS we will also perform time-resolved spectroscopy of the ionized absorption features and Fe-K emission line, search for energy-dependent time lags in the continuum, between the continuum and spectral features, and between the spectral features. These data will provide powerful constraints on models of AGN.

Yaqoob, Tahir

1999-09-01

204

Monitoring the effect of a control pulse on a conical intersection by time-resolved photoelectron spectroscopy.  

PubMed

We have previously shown how femtosecond angle- and energy-resolved photoelectron spectroscopy can be used to monitor quantum wavepacket bifurcation at an avoided crossing or conical intersection and also how a symmetry-allowed conical intersection can be effectively morphed into an avoided crossing by photo-induced symmetry breaking. The latter result suggests that varying the parameters of a laser to modify a conical intersection might control the rate of passage of wavepackets through such regions, providing a gating process for different chemical products. In this paper, we show with full quantum mechanical calculations that such optical control of conical intersections can actually be monitored in real time with femtosecond angle- and energy-resolved photoelectron spectroscopy. In turn, this suggests that one can optimally control the gating process at a conical intersection by monitoring the photoelectron velocity map images, which should provide far more efficient and rapid optimal control than measuring the ratio of products. To demonstrate the sensitivity of time-resolved photoelectron spectra for detecting the consequences of such optical control, as well as for monitoring how the wavepacket bifurcation is affected by the control, we report results for quantum wavepackets going through the region of the symmetry-allowed conical intersection between the first two (2)A' states of NO(2) that is transformed to an avoided crossing. Geometry- and energy-dependent photoionization matrix elements are explicitly incorporated in these studies. Time-resolved photoelectron angular distributions and photoelectron images are seen to systematically reflect the effects of the control pulse. PMID:21290062

Arasaki, Yasuki; Wang, Kwanghsi; McKoy, Vincent; Takatsuka, Kazuo

2011-05-21

205

Ultrafast time-resolved absorption spectroscopy of geometric isomers of xanthophylls  

NASA Astrophysics Data System (ADS)

This paper presents an ultrafast optical spectroscopic investigation of the excited state energies, lifetimes and spectra of specific geometric isomers of neoxanthin, violaxanthin, lutein, and zeaxanthin. All- trans- and 15,15'- cis-?-carotene were also examined. The spectroscopy was done on molecules purified by HPLC frozen immediately to inhibit isomerization. The spectra were taken at 77 K to maintain the configurations and to provide better spectral resolution than seen at room temperature. The kinetics reveal that for all of the molecules except neoxanthin, the S 1 state lifetime of the cis isomers is shorter than that of the all- trans isomers. The S 1 excited state energies of all the isomers were determined by recording S 1 ? S 2 transient absorption spectra. The results obtained in this manner at cryogenic temperatures provide an unprecedented level of precision in the measurement of the S 1 energies of these xanthophylls, which are critical components in light-harvesting pigment-protein complexes of green plants.

Niedzwiedzki, Dariusz M.; Enriquez, Miriam M.; LaFountain, Amy M.; Frank, Harry A.

2010-07-01

206

Ultrafast Time-resolved Absorption Spectroscopy of Geometric Isomers of Xanthophylls.  

PubMed

This paper presents an ultrafast optical spectroscopic investigation of the excited state energies, lifetimes and spectra of specific geometric isomers of neoxanthin, violaxanthin, lutein, and zeaxanthin. All-trans- and 15,15'-cis-beta-carotene were also examined. The spectroscopy was done on molecules purified by HPLC frozen immediately to inhibit isomerization. The spectra were taken at 77 K to maintain the configurations and to provide better spectral resolution than seen at room temperature. The kinetics reveal that for all of the molecules except neoxanthin, the S(1) state lifetime of the cis-isomers is shorter than that of the all-trans isomers. The S(1) excited state energies of all the isomers were determined by recording S(1) --> S(2) transient absorption spectra. The results obtained in this manner at cryogenic temperatures provide an unprecedented level of precision in the measurement of the S(1) energies of these xanthophylls, which are critical components in light-harvesting pigment-protein complexes of green plants. PMID:20689726

Niedzwiedzki, Dariusz M; Enriquez, Miriam M; Lafountain, Amy M; Frank, Harry A

2010-07-19

207

Five-dimensional optical instrumentation: combining polarimetry with time-resolved integral-field spectroscopy  

NASA Astrophysics Data System (ADS)

We present implementations of optical instrumentation that records five dimensions of light: polarization state as a function of wavelength, two spatial dimensions, and time. We focus on the optimal integration of polarimetry within microlens-based integral-field spectroscopy. The polarimetric analyzer (or beam-splitter) and dispersing element could be implemented separately, but also amalgamated in the form of a polarization grating. We present optimizations for stacking the polarization-split spectra on a 2D detector. The polarimetric modulation can be performed in the temporal, the spatial or the spectral domain. Temporal modulation could be set up with achromatic optics conform the Stokes definition scheme, but a wide wavelength range generally demands a "polychromatic" modulation approach for which the modulation efficiency for all or some of the Stokes parameters is optimized at every wavelength. Spectral modulation (full-Stokes or optimized for linear polarization) yields instruments without any moving parts, for which all polarization information is obtained in one shot. We present first results from two polarimetric IFU instruments; the ExPo pIFU and LOUPE. The first is based on a rapid polychromatic modulator consisting of two FLCs and two fixed retarders, while the latter is based on spectral modulation for linear polarization. In addition to applications within astronomy and planetary science, we discuss remote-sensing applications for such instruments.

Rodenhuis, M.; Snik, F.; van Harten, G.; Hoeijmakers, J.; Keller, C. U.

2014-05-01

208

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

209

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

PubMed

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 (B?)(1)B1/()(1)A2, 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 (B?)(1)B1 diabatic state is presented. Signatures of the oscillatory motion on the (B?)(1)B1/()(1)A2 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 (c?)(3)B2 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. PMID:24880274

Wilkinson, Iain; Boguslavskiy, Andrey E; Mikosch, Jochen; Bertrand, Julien B; Wrner, Hans Jakob; Villeneuve, David M; Spanner, Michael; Patchkovskii, Serguei; Stolow, Albert

2014-05-28

210

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/()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/()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.; Wrner, Hans Jakob; Villeneuve, David M.; Spanner, Michael; Patchkovskii, Serguei; Stolow, Albert

2014-05-01

211

Synthesis and Characterization of Time-resolved Fluorescence Probes for Evaluation of Competitive Binding to Melanocortin Receptors  

PubMed Central

Probes for use in time-resolved fluorescence competitive binding assays at melanocortin receptors based on the parental ligands MSH(4), MSH(7), and NDP-?-MSH were prepared by solid phase synthesis methods, purified, and characterized. The saturation binding of these probes was studied using HEK-293 cells engineered to overexpress the human melanocortin 4 receptor (hMC4R) as well as the human cholecystokinin 2 receptor (hCCK2R). The ratios of non-specific binding to total binding approached unity at high concentrations for each probe. At low probe concentrations, receptor-mediated binding and uptake was discernable, and so probe concentrations were kept as low as possible in determining Kd values. The Eu-DTPA-PEGO-MSH(4) probe exhibited low specific binding relative to non-specific binding, even at low nanomolar concentrations, and was deemed unsuitable for use in competition binding assays. The Eu-DTPA-PEGO probes based on MSH(7) and NDP-?-MSH exhibited Kd values of 273.9 nM and 4.20.48 nM, respectively, for binding with hMC4R. These probes were employed in competitive binding assays to characterize the interactions of hMC4R with monovalent and divalent MSH(4), MSH(7), and NDP-?-MSH constructs derived from squalene. Results from assays with both probes reflected only statistical enhancements, suggesting improper ligand spacing on the squalene scaffold for the divalent constructs. The Ki values from competitive binding assays that employed the MSH(7)-based probe were generally lower than the Ki values obtained when the probe based on NDP-?-MSH was employed, which is consistent with the greater potency of the latter probe. The probe based on MSH(7) was also competed with monovalent, divalent, and trivalent MSH(4) constructs that previously demonstrated multivalent binding in competitive binding assays against a variant of the probe based on NDP-?-MSH. Results from these assays confirm multivalent binding, but suggest a more modest increase in avidity for these MSH(4) constructs than was previously reported. PMID:23890524

Alleti, Ramesh; Vagner, Josef; Dehigaspitiya, Dilani Chathurika; Moberg, Valerie E.; Elshan, N. G. R. D.; Tafreshi, Narges K.; Brabez, Nabila; Weber, Craig S.; Lynch, Ronald M.; Hruby, Victor J.; Gillies, Robert J.; Morse, David L.; Mash, Eugene A.

2013-01-01

212

Synthesis and characterization of time-resolved fluorescence probes for evaluation of competitive binding to melanocortin receptors.  

PubMed

Probes for use in time-resolved fluorescence competitive binding assays at melanocortin receptors based on the parental ligands MSH(4), MSH(7), and NDP-?-MSH were prepared by solid phase synthesis methods, purified, and characterized. The saturation binding of these probes was studied using HEK-293 cells engineered to overexpress the human melanocortin 4 receptor (hMC4R) as well as the human cholecystokinin 2 receptor (hCCK2R). The ratios of non-specific binding to total binding approached unity at high concentrations for each probe. At low probe concentrations, receptor-mediated binding and uptake was discernable, and so probe concentrations were kept as low as possible in determining Kd values. The Eu-DTPA-PEGO-MSH(4) probe exhibited low specific binding relative to non-specific binding, even at low nanomolar concentrations, and was deemed unsuitable for use in competition binding assays. The Eu-DTPA-PEGO probes based on MSH(7) and NDP-?-MSH exhibited Kd values of 273.9nM and 4.20.48nM, respectively, for binding with hMC4R. These probes were employed in competitive binding assays to characterize the interactions of hMC4R with monovalent and divalent MSH(4), MSH(7), and NDP-?-MSH constructs derived from squalene. Results from assays with both probes reflected only statistical enhancements, suggesting improper ligand spacing on the squalene scaffold for the divalent constructs. The Ki values from competitive binding assays that employed the MSH(7)-based probe were generally lower than the Ki values obtained when the probe based on NDP-?-MSH was employed, which is consistent with the greater potency of the latter probe. The probe based on MSH(7) was also competed with monovalent, divalent, and trivalent MSH(4) constructs that previously demonstrated multivalent binding in competitive binding assays against a variant of the probe based on NDP-?-MSH. Results from these assays confirm multivalent binding, but suggest a more modest increase in avidity for these MSH(4) constructs than was previously reported. PMID:23890524

Alleti, Ramesh; Vagner, Josef; Dehigaspitiya, Dilani Chathurika; Moberg, Valerie E; Elshan, N G R D; Tafreshi, Narges K; Brabez, Nabila; Weber, Craig S; Lynch, Ronald M; Hruby, Victor J; Gillies, Robert J; Morse, David L; Mash, Eugene A

2013-09-01

213

Two-dimensional subpicosecond time-resolved fluorescence anisotropy: Optical Kerr-gating with the excitation of alternating polarizations of light  

NASA Astrophysics Data System (ADS)

We have developed a subpicosecond time-resolved fluorescence anisotropy (TRFA) that newly implements a photoelastic modulator to alternate the polarizations of an excitation laser light. The setup facilitates virtually simultaneous detection of the parallel I? and the perpendicular I? emission from a photoexcited molecule of interest by means of an ultra-short (optical Kerr-gating) shutter and a spectrograph coupled with a charge-coupled device. From a set of I?(?,t) and I?(?,t) that comprise 2-D (two-dimensional) information on both a full range of spectra and subpicosecond time-resolved fluorescence decays, the 2-D TRFA, R(?,t), is directly given with better accuracy. To claim the merit of the technique we carried out a test for 2-D TRFA of Coumarin 153 in methanol.

Fujiwara, Takashige; Romano, Natalie C.; Lim, Edward C.

2014-03-01

214

A study of collisional quenching and radiation-trapping kinetics for Rb(5p) in the presence of methane and ethane using time-resolved fluorescence  

Microsoft Academic Search

An experimental study using time-resolved fluorescence techniques together with theoretical simulations has been conducted and used to determine the quenching cross-sections of rubidium-methane and rubidium-ethane. Radiation trapping was significant under many of the experimental conditions (temperatures 40-130 C and pressures 50-700 Torr) and a detailed analysis of the interplay between radiation trapping and quenching kinetics was carried out. Modifications of

Nathan D. Zameroski; Wolfgang Rudolph; Gordon D. Hager; David A. Hostutler

2009-01-01

215

A study of collisional quenching and radiation-trapping kinetics for Rb(5p) in the presence of methane and ethane using time-resolved fluorescence  

Microsoft Academic Search

An experimental study using time-resolved fluorescence techniques together with theoretical simulations has been conducted and used to determine the quenching cross-sections of rubidiummethane and rubidiumethane. Radiation trapping was significant under many of the experimental conditions (temperatures 40130 C and pressures 50700 Torr) and a detailed analysis of the interplay between radiation trapping and quenching kinetics was carried out. Modifications of

Nathan D Zameroski; Wolfgang Rudolph; Gordon D Hager; David A Hostutler

2009-01-01

216

Photoexcited State Properties of H2-Porphyrin/C60-Based Rotaxanes as Studied by Time-Resolved EPR Spectroscopy  

PubMed Central

Light-driven intramolecular electron transfer (ET) and energy transfer (EnT) processes in two rotaxanes, the first containing two free base porphyrins and C60 fullerene moieties incorporated around a Cu(I)bisphenanthroline core ((H2P)2-Cu(I)(phen)2-C60) and a second rotaxane lacking the fullerene moiety ((H2P)2-Cu(I)(phen)2) were studied by X-band (9.5 GHz) time-resolved electron paramagnetic resonance (TREPR) spectroscopy. The experiments were performed in a frozen toluene and ethanol, and different phases of the nematic liquid crystal (E-7). It is demonstrated that the ET and EnT processes in the (H2P)2-Cu(I)(phen)2-C60 rotaxane in different media result in formation of the same charge separated state, namely (H2P)2+-Cu(I)(phen)2?-C60, while photoexcitation of the (H2P)2-Cu(I)(phen)2 rotaxane does not induce noticeable transfer processes in these matrices. The results are discussed in terms of the high conformational mobility of the rotaxanes, which enables changes in the molecular topography and resultant modification of the rates and routes of photoinduced processes occurring in these systems. The parameters of the transfer processes are compared with those obtained in our previous study of (ZnP)2-Cu(I)(phen)2-C60 and (ZnP)2-Cu(I)(phen) rotaxanes under the same experimental conditions. PMID:21528881

Jakob, Manuela; Berg, Alexander; Levanon, Haim; Schuster, David I.; Megiatto, Jackson D.

2011-01-01

217

Carrier dynamics of composite and nanolayered films of zinc phthalocyanine and C60 measured by time-resolved terahertz spectroscopy  

NASA Astrophysics Data System (ADS)

We present a study of charge transfer and carrier dynamics in films of zinc phthalocyanine (ZnPc) and buckmisnsterfullerene (C60) investigated by time-resolved terahertz spectroscopy (TRTS). These films are model structures for charge generation layers in organic photovoltaics and their intrinsic properties are therefore of interest. We compare two classes of films: composite films of ZnPc and C60 prepared by co-evaporation and layered ZnPc/C60 films prepared by alternating deposition. We find evidence for a short-lived charge transfer state of C60 that decays within several picoseconds of excitation. In contrast, both composite and multi-layered films have a long-lived THz absorption that depends on the composition and structure of the fims. The optimum composition for charge transfer within composite films is a 1:1 blend of ZnPc and C60. Amongst the layered films, there is an increase in charge photogeneration with decreasing layer thickness with a sample having ultrathin (2 nm) exhibiting the strongest THz absorption. A much stronger THz absorption signal was obtained from the layered structure than for the best composite film, even both structures contain similar fractions of ZnPc and C60 .

Lane, Paul A.; Melinger, Joseph S.; Esenturk, Okan; Heilweil, Edwin J.

2009-08-01

218

Time-resolved vibrational spectroscopy detects protein-based intermediates in the photosynthetic oxygen-evolving cycle  

PubMed Central

Photosynthetic oxygen production by photosystem II (PSII) is responsible for the maintenance of aerobic life on earth. The production of oxygen occurs at the PSII oxygen-evolving complex (OEC), which contains a tetranuclear manganese (Mn) cluster. Photo-induced electron transfer events in the reaction center lead to the accumulation of oxidizing equivalents on the OEC. Four sequential photooxidation reactions are required for oxygen production. The oxidizing complex cycles among five oxidation states, called the Sn states, where n refers to the number of oxidizing equivalents stored. Oxygen release occurs during the S3-to-S0 transition from an unstable intermediate, known as the S4 state. In this report, we present data providing evidence for the production of an intermediate during each S state transition. These protein-derived intermediates are produced on the microsecond to millisecond time scale and are detected by time-resolved vibrational spectroscopy on the microsecond time scale. Our results suggest that a protein-derived conformational change or proton transfer reaction precedes Mn redox reactions during the S2-to-S3 and S3-to-S0 transitions. PMID:16632606

Barry, Bridgette A.; Cooper, Ian B.; De Riso, Antonio; Brewer, Scott H.; Vu, Dung M.; Dyer, R. Brian

2006-01-01

219

Time-resolved resonance Raman spectroscopy of excited singlet and triplet states of free-base meso-tetraphenylporphyrin  

SciTech Connect

Two-color time-resolved resonance Raman spectroscopy has been used to probe the lowest excited singlet (S[sub 1]) and triplet (T[sub 1]) states of free-base meso-tetraphenylporphyrin and meso-tetrakis(4-sulphonatophenyl)porphyrin in solution at room temperature. The spectra were recorded using 532-nm excitation pulses and time-delayed probe pulses ([Delta]T = 0-30 ns, 447 and 460 nm) near [lambda][sub max] of the S[sub 1] and T[sub 1] states. Significant shifts in frequency of the porphyrin core vibrations were observed upon excitation to either the S[sub 1] or T[sub 1] state. Several of the strongest polarized bands in the spectra of both excited states, including [nu][sub 1], [nu][sub 2], [nu][sub 4], [nu][sub 6], and [phi][sub 4], are assigned, and the information they give on the differences in electron distribution in the ground, S[sub 1], and T[sub 1] states is discussed. 16 refs., 3 figs., 1 tab.

Bell, S.E.J.; Hegarty, M.; McGarvey, J.J. (Queens Univ., Belfast (United Kingdom)); Al-Obaidi, A.H.R.; Hester, R.E. (Univ. of York (United Kingdom))

1993-11-11

220

Picosecond Dynamics of G-Protein Coupled Receptor Activation in Rhodopsin from Time-Resolved UV Resonance Raman Spectroscopy  

PubMed Central

The protein response to retinal chromophore isomerization in the visual pigment rhodopsin is studied using picosecond time-resolved UV resonance Raman spectroscopy. High signal-to-noise Raman spectra are obtained using a 1 kHz Ti:Sapphire laser apparatus that provides <3 ps visible (466 nm) pump and UV (233 nm) probe pulses. When there is no time delay between the pump and probe events, tryptophan modes W18, W16, and W3 exhibit decreased Raman scattering intensity. At longer pump-probe time delays of +5 and +20 ps, both tryptophan (W18, W16, W3, and W1) and tyrosine (Y1 + 2xY16a, Y7a, Y8a) peak intensities drop by up to 3%. These intensity changes are attributed to decreased hydrophobicity in the microenvironment near at least one tryptophan and one tyrosine residue that likely arise from weakened interaction with the ?-ionone ring of the chromophore following cis-to-trans isomerization. Examination of the crystal structure suggests that W265 and Y268 are responsible for these signals. These UV Raman spectral changes are nearly identical to those observed for the rhodopsinto-Meta I transition, implying that impulsively driven protein motion by the isomerizing chromophore during the 200 fs primary transition drives key structural changes that lead to protein activation. PMID:12731857

Kim, Judy E.; Pan, Duohai; Mathies, Richard A.

2005-01-01

221

DC-magnetoencephalography and time-resolved near-infrared spectroscopy combined to study neuronal and vascular brain responses.  

PubMed

The temporal relation between vascular and neuronal responses of the brain to external stimuli is not precisely known. For a better understanding of the neuro-vascular coupling changes in cerebral blood volume and oxygenation have to be measured simultaneously with neuronal currents. With this motivation modulation dc-magnetoencephalography was combined with multi-channel time-resolved near-infrared spectroscopy to simultaneously monitor neuronal and vascular parameters on a scale of seconds. Here, the technique is described, how magnetic and optical signals can be measured simultaneously. In a simple motor activation paradigm (alternating 30 s of finger movement with 30 s of rest for 40 min) both signals were recorded non-invasively over the motor cortex of eight subjects. The off-line averaged signals from both modalities showed distinct stimulation related changes. By plotting changes in oxy- or deoxyhaemoglobin as a function of magnetic field a characteristic trajectory was created, which was similar to a hysteresis loop. A parametric analysis allowed quantitative results regarding the timing of coupling: the vascular signal increased significantly slower than the neuronal signal. PMID:17664619

Sander, T H; Liebert, A; Mackert, B M; Wabnitz, H; Leistner, S; Curio, G; Burghoff, M; Macdonald, R; Trahms, L

2007-06-01

222

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

PubMed

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. PMID:25381495

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

2014-11-01

223

Light-induced activation of bacterial phytochrome Agp1 monitored by static and time-resolved FTIR spectroscopy.  

PubMed

Phytochromes, which regulate many biological processes in plants, bacteria, and fungi, can exist in two stable states, Pr and Pfr, that can be interconverted by light, via a number of intermediates such as meta-Rc. Herein we employ FTIR spectroscopy to study the Pr-to-Pfr conversion of the bacteriophytochrome Agp1 from Agrobacterium tumefaciens. Static FTIR Pfr/Pr and meta-Rc/Pr difference spectra are disentangled in terms of cofactor and protein structural changes. Guided by DFT calculations on cofactor models, the chromophore conformational changes can be grouped into structural adjustments of the cofactor-protein interactions localized in the C-D dipyrrole moiety, that is, the photoisomerisation site, and in the A-B dipyrrole moiety including the protein attachment site. Whereas changes at the C and D rings appear to be largely completed in the meta-Rc state, the structural changes in the A-B unit occur during the transition from meta-Rc to Pfr, concomitant with the main protein structural changes, as demonstrated by static and time-resolved FTIR difference spectroscopy. We employ this technique to monitor, for the first time, the dynamics of the photocycle of phytochrome on the millisecond timescale. By extending the studies to genetically engineered protein variants of Agp1, we further demonstrate that H250 and D197 as well as the PHY domain are essential for formation of the Pfr state. Based on the IR spectroscopic and available crystallographic data we discuss the role of critical amino acid residues for the protein-cofactor interactions during the photoinduced reaction cycle. PMID:20333618

Piwowarski, Patrick; Ritter, Eglof; Hofmann, Klaus-Peter; Hildebrandt, Peter; von Stetten, David; Scheerer, Patrick; Michael, Norbert; Lamparter, Tilman; Bartl, Franz

2010-04-26

224

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, Gnter; Namboodiri, Vinu; Materny, Arnulf

2014-04-01

225

Steady-State and Time-Resolved Fluorescence Spectroscopic Studies on Interaction of the N-terminal Region with the Hairpin Loop of the Phytocystain Scb  

Microsoft Academic Search

The steady-state and time-resolved fluorescece spectroscopy is one of the most powerful method to detect and analyze subtle\\u000a conformation change and interaction between peptide elements in protein. Phytocystatin Scb isolated from sunflower seeds includes\\u000a a single Trp residue at position 85. In an attempt to investigate the interaction of the N-terminal region of Scb with the\\u000a first and second hairpin

Keiko Doi-Kawano; Etsuko Nishimoto; Yoshiaki Kouzuma; Daisuke Takahashi; Shoji Yamashita; Makoto Kimura

2009-01-01

226

Steady-State and Time-Resolved Fluorescence Studies of Reverse Micelles in Liquids and Supercritical Solvents.  

NASA Astrophysics Data System (ADS)

This thesis begins (Chapter 1) with a review of micelle formation in liquids and supercritical fluids. Chapter 2 follows with a brief discussion of fluorescence spectroscopy. In Chapter 3, we 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. Following from this work we wondered if the continuous phase (alkane) density could be used to control the internal dynamics within a reverse micelle. To answer this question, we focus on: (1) the effects of water loading, temperature, and fluid density on solute partitioning (Chapter 4) and determine the density effects on micellar aggregates; (2) the effects of solute structure on the distribution of probe molecules within reverse micelles (Chapter 4); and (3) the effects of fluid density, water concentration, and temperature on the reorganizational dynamics within AOT reverse micelles (Chapter 5). In this thesis, simple thermodynamic measurements and nanosecond solvent relaxation experiments are used to account for this partitioning and water reorganization in AOT reverse micelles, respectively. In Chapter 6, we report preliminary results on excited-state deprotonation reactions in AOT reverse micelles maintained in sub-critical propane. This particular system 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. Chapter 7 summarizes the thesis and proposes future work in this area.

Zhang, Jing

227

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

228

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

229

Femtosecond time-resolved transient absorption spectroscopy of CH3NH3PbI3 perovskite films: evidence for passivation effect of PbI2.  

PubMed

CH3NH3PbI3 perovskite layered films deposited on substrates with and without a titania support structure have been prepared and studied using time-resolved femtosecond transient absorption (fs-TA) spectroscopy in the visible light range (450-800 nm). The electron injection dynamics from the photoexcited perovskite layers to the neighboring film structures could be directly monitored via the transient bleaching dynamics of the perovskite at ?750 nm and thus systematically studied as a function of the layer-by-layer architecture. In addition, for the first time we could spectrally distinguish transient bleaching at ?750 nm from laser-induced fluorescence that occurs red-shifted at ?780 nm. We show that an additional bleach feature at ?510 nm appears when PbI2 is present in the perovskite film. The amplitudes of the PbI2 and perovskite TA peaks were compared to estimate relative amounts of PbI2 in the samples. Kinetic analysis reveals that perovskite films with less PbI2 show faster relaxation rates than those containing more PbI2. These fast dynamics are attributed to charge carrier trapping at perovskite grain boundaries, and the slower dynamics in samples containing PbI2 are due to a passivation effect, in line with other recently reported work. PMID:25145978

Wang, Lili; McCleese, Christopher; Kovalsky, Anton; Zhao, Yixin; Burda, Clemens

2014-09-01

230

Time Resolved Spectroscopy of SGR J1550-5418 Bursts Detected with Fermi/Gamma-Ray Burst Monitor  

NASA Astrophysics Data System (ADS)

We report on a time-resolved spectroscopy of the 63 brightest bursts of SGR J1550-5418, detected with the Fermi/Gamma-ray Burst Monitor during its 2008-2009 intense bursting episode. We performed spectral analysis down to 4 ms timescales 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 the flux reaching ~1 at the highest fluxes. Using a two blackbody 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 the lines of constant luminosity at the lowest fluxes, R 2vpropkT -4, with a break at the higher fluxes (F > 10-5.5 erg s-1 cm-2). The area of the high-kT component increases with the flux while its temperature decreases, which we interpret as being due to an adiabatic cooling process. The area of the low-kT component, on the other hand, appears to saturate at the highest fluxes, toward R max ? 30 km. Assuming that crust quakes are responsible for soft gamma repeater (SGR) bursts and considering R max as the maximum radius of the emitting photon-pair plasma fireball, we relate this saturation radius to a minimum excitation radius of the magnetosphere, and we put a lower limit on the internal magnetic field of SGR J1550-5418, B int >~ 4.5 1015 G.

Younes, G.; Kouveliotou, C.; van der Horst, A. J.; Baring, M. G.; Granot, J.; Watts, A. L.; Bhat, P. N.; Collazzi, A.; Gehrels, N.; Gorgone, N.; G??, 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.

2014-04-01

231

Ultrafast excited-state dynamics in photochromic N-salicylideneaniline studied by femtosecond time-resolved REMPI spectroscopy  

NASA Astrophysics Data System (ADS)

Ultrafast processes in photoexcited N-salicylideneaniline have been investigated with femtosecond time-resolved resonance-enhanced multiphoton ionization spectroscopy. The ion signals via the S1(n,?*) state of the enol form as well as the proton-transferred cis-keto form emerge within a few hundred femtoseconds after photoexcitation to the first S1(?,?*) state of the enol form. This reveals that two ultrafast processes, excited-state intramolecular proton transfer (ESIPT) reaction and an internal conversion (IC) to the S1(n,?*) state, occur on a time scale less than a few hundred femtoseconds from the S1(?,?*) state of the enol form. The rise time of the transient corresponding to the production of the proton-transferred cis-keto form is within 750 fs when near the red edge of the absorption is excited, indicating that the ESIPT reaction occurs within 750 fs. The decay time of the S1(?,?*) state of the cis-keto form is 8.9 ps by exciting the enol form at 370 nm, but it dramatically decreases to be 1.5-1.6 ps for the excitation at 365-320 nm. The decrease in the decay time has been attributed to the opening of an efficient nonradiative channel; an IC from S1(?,?*) to S1(n,?*) of the cis-keto form promotes the production of the trans-keto form as the final photochromic products. The two IC processes may provide opposite effect on the quantum yield of photochromic products: IC in the enol form may substantially reduce the quantum yield, but IC in the cis-keto form increase it.

Okabe, Chie; Nakabayashi, Takakazu; Inokuchi, Yoshiya; Nishi, Nobuyuki; Sekiya, Hiroshi

2004-11-01

232

Fluorescence lifetime spectroscopy for guided therapy of brain tumors  

Microsoft Academic Search

This study evaluates the potential of time-resolved laser induced fluorescence spectroscopy (TR-LIFS) as intra-operative tool for the delineation of brain tumor from normal brain. Forty two patients undergoing glioma (WHO grade I-IV) surgery were enrolled in this study. A TR-LIFS prototype apparatus (gated detection, fast digitizer) was used to induce in-vivo fluorescence using a pulsed N2 laser (337 nm excitation,

Pramod V. Butte; Adam N. Mamelak; Miriam Nuno; Serguei I. Bannykh; Keith L. Black; Laura Marcu

2011-01-01

233

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; Khler, J

2014-12-21

234

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

PubMed

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

2001-02-01

235

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

E-print Network

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

236

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

Microsoft Academic Search

The protein myosin transforms chemical energy, in the form of ATP, into mechanical force in muscle. The rotational motions of myosin play a central role in all models of muscle contraction. I investigated the rotations of myosin in contracting muscle using time- resolved phosphorescence anisotropy (TPA), a technique sensitive to rotations on the microsecond time scale. I developed the hardware,

David Ward Hayden

1997-01-01

237

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

238

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

239

Excited-state dynamics of normal and doubly N-confused type hexaphyrin derivatives studied by time-resolved fluorescence measurements  

NASA Astrophysics Data System (ADS)

The excited-state dynamics of two expanded porphyrin derivatives which have six pyrrole rings of normal and doubly N-confused types was studied by time-resolved fluorescence and transient absorption measurements. We have found that their dynamics is very different due to four substituents in the doubly N-confused hexaphyrin derivative. The bleaching recovery of the free-base doubly N-confused hexaphyrin shows the double exponential function with time constants of ? = 80 10 ps and 47 10 ps. The fluorescence decay curve, on the other hand, shows single-exponential function. To explain such behavior, we propose a model that the recovery process originates from two conformers in the S 1 state. It is plausible that the two excited-state conformers are deactivated independently to the ground state with radiative and nonradiative processes, respectively.

Ryu, Jang-Hyun; Ito, Fuyuki; Nagamura, Toshihiko; Nakamura, Kiyohisa; Furuta, Hiroyuki; Shibata, Yutaka; Itoh, Shigeru

2007-08-01

240

Excitation relaxation dynamics and energy transfer in fucoxanthin-chlorophyll a/c-protein complexes, probed by time-resolved fluorescence.  

PubMed

In algae, light-harvesting complexes contain specific chlorophylls (Chls) and keto-carotenoids; Chl a, Chl c, and fucoxanthin (Fx) in diatoms and brown algae; Chl a, Chl c, and peridinin in photosynthetic dinoflagellates; and Chl a, Chl b, and siphonaxanthin in green algae. The Fx-Chl a/c-protein (FCP) complex from the diatom Chaetoceros gracilis contains Chl c1, Chl c2, and the keto-carotenoid, Fx, as antenna pigments, in addition to Chl a. In the present study, we investigated energy transfer in the FCP complex associated with photosystem II (FCPII) of C. gracilis. For these investigations, we analyzed time-resolved fluorescence spectra, fluorescence rise and decay curves, and time-resolved fluorescence anisotropy data. Chl a exhibited different energy forms with fluorescence peaks ranging from 677 nm to 688 nm. Fx transferred excitation energy to lower-energy Chl a with a time constant of 300fs. Chl c transferred excitation energy to Chl a with time constants of 500-600fs (intra-complex transfer), 600-700fs (intra-complex transfer), and 4-6ps (inter-complex transfer). The latter process made a greater contribution to total Chl c-to-Chl a transfer in intact cells of C. gracilis than in the isolated FCPII complexes. The lower-energy Chl a received excitation energy from Fx and transferred the energy to higher-energy Chl a. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy. PMID:24530875

Akimoto, Seiji; Teshigahara, Ayaka; Yokono, Makio; Mimuro, Mamoru; Nagao, Ryo; Tomo, Tatsuya

2014-09-01

241

Application of time-resolved fluorescence for imaging-based multisample and multianalyte detection in single microtiter wells.  

PubMed

Enzyme-linked immunosorbent assays are routinely used in laboratories around the world and ensure highly specific protein detection. Often, more than one analyte needs to be determined in a single sample and numerous protein arrays for multianalyte detection of a single sample have been developed to address this problem. They have the potential to analyze several dozen or even more analytes in an assay volume of usually around 100?L. However, due to the presence of numerous different antibodies, these multianalyte sandwich immunoassays suffer from undesired cross-reactivities between the antibodies which lead to a loss of assay specificities. Here, we present an assay principle which allows, e.g., a detection of an analyte in a sample volume of only 1?L in a normal 96-microtiter well plate, so that up to 100 analytes can be determined from a 100?L sample volume, but in separate wells. This eliminates antibody cross-reactivities. The assay is based on the biotinylated time-resolved fluorophore EuLH used as a PEG11-dye conjugate in combination with ExtrAvidin to ensure high signal-to-background ratios. The model protein epidermal growth factor (EGF) was detected with the established sandwich immunoassay and showed assay parameters comparable to commercially available ones. Furthermore, the assay principle enables a spatial resolution of the assay signal. Here, we demonstrated the application of the new detection system for universal imaging-based analysis of individual spots in one single 96-microtiter well by applying it to multisample and also multianalyte detections. In the case of the multisample analysis approach, a considerable reduction of the required sample volume to only 1?L in a single 96 microtiter well could be achieved. PMID:25192791

Dobslaff, K; Zuchner, T

2014-11-01

242

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

243

Multichannel, time-resolved picosecond laser ultrasound imaging and spectroscopy with custom complementary metal-oxide-semiconductor detector  

SciTech Connect

This paper presents a multichannel, time-resolved picosecond laser ultrasound system that uses a custom complementary metal-oxide-semiconductor linear array detector. This novel sensor allows parallel phase-sensitive detection of very low contrast modulated signals with performance in each channel comparable to that of a discrete photodiode and a lock-in amplifier. Application of the instrument is demonstrated by parallelizing spatial measurements to produce two-dimensional thickness maps on a layered sample, and spectroscopic parallelization is demonstrated by presenting the measured Brillouin oscillations from a gallium arsenide wafer. This paper demonstrates the significant advantages of our approach to pump probe systems, especially picosecond ultrasonics.

Smith, Richard J.; Light, Roger A.; Johnston, Nicholas S.; Pitter, Mark C.; Somekh, Mike G. [Institute of Biophysics, Imaging and Optical Science, University of Nottingham, Nottinghamshire NG7 2RD (United Kingdom); Sharples, Steve D. [Applied Optics Group, Electrical Systems and Optics Research Division, University of Nottingham, Nottinghamshire NG7 2RD (United Kingdom)

2010-02-15

244

Homodimerization of Amyloid Precursor Protein at the Plasma Membrane: A homoFRET Study by Time-Resolved Fluorescence Anisotropy Imaging  

PubMed Central

Classical FRET (Frster Resonance Energy Transfer) using two fluorescent labels (one for the donor and another one for the acceptor) is not efficient for studying the homodimerization of a protein as only half of the homodimers formed can be identified by this technique. We thus resorted to homoFRET detected by time-resolved Fluorescence Anisotropy IMaging (tr-FAIM). To specifically image the plasma membrane of living cells, an original combination of tr-FAIM and Total Internal Reflection Fluorescence Lifetime Imaging Microscope (TIRFLIM) was implemented. The correcting factor accounting for the depolarization due to the high numerical aperture (NA) objective, mandatory for TIRF microscopy, was quantified on fluorescein solutions and on HEK293 cells expressing enhanced Green Fluorescence Protein (eGFP). Homodimerization of Amyloid Precursor Protein (APP), a key mechanism in the etiology of Alzheimers disease, was measured on this original set-up. We showed, both in epifluorescence and under TIRF excitation, different energy transfer rates associated with the homodimerization of wild type APP-eGFP or of a mutated APP-eGFP, which forms constitutive dimers. This original set-up thus offers promising prospects for future studies of protein homodimerization in living cells in control and pathological conditions. PMID:22973448

Devauges, Viviane; Marquer, Catherine; Lecart, Sandrine; Cossec, Jack-Christophe; Potier, Marie-Claude; Fort, Emmanuel; Suhling, Klaus; Leveque-Fort, Sandrine

2012-01-01

245

Microfluidic space-domain time-resolved emission spectroscopy of terbium(III) and europium(III) chelates with pyridine-2,6-dicarboxylate.  

PubMed

This article describes the utilization of laminar microflows for time-resolved emission measurements with steady-state excitation and detection. Passing a laminar flow through a short illuminated section of a microchannel provided a means for pulsed-like photoexcitation of the moieties carried by the fluid. Imaging the microchannel flows carrying thus photoexcited chelates of lanthanide ions allowed us to extract their excited-state lifetimes from the spatial distribution of the changes in the emission intensity. The lifetime values obtained using this space-domain approach agreed well with the lifetimes from time-domain measurements. This validated space-domain microfluidic approach reveals a means for miniaturization of time-resolved emission spectroscopy. PMID:23550512

Nuez, Vicente; Upadhyayula, Srigokul; Millare, Brent; Larsen, Jillian M; Hadian, Ali; Shin, Sanghoon; Vandrangi, Prashanthi; Gupta, Sharad; Xu, Hong; Lin, Adam P; Georgiev, Georgi Y; Vullev, Valentine I

2013-05-01

246

Excited states of C{sub 70} and the intersystem crossing process studied by picosecond time-resolved spectroscopy in the visible and near-IR region  

SciTech Connect

The photophysical properties of C{sub 70} excited states were investigated by some time-resolved spectroscopic techniques. The absorption bands of singlet excited state ({sup 1}C{sub 70}{sup *}) and triplet excited state ({sup 3}C{sub 70}{sup *}) in the visible region were observed by time-resolved absorption spectroscopy using a streak camera. The intersystem crossing rate constant k{sub isc} from {sup 1}C{sub 70}{sup *} to {sup 3}C{sub 70}{sup *} was determined to be 1.25 x 10{sup 9} s{sup -1} by the analysis of the absorption-time profiles considering the overlap of the decay of {sup 1}C{sub 70}{sup *} and the growth of {sup 3}C{sub 70}{sup *}, where the curve fitting was carried out by using the decay rate constant of {sup 1}C{sub 70}{sup *} (1.61 x 10{sup 9} s{sup -1}) determined by the picosecond time-resolved emission spectroscopy. The picosecond time-resolved near-IR spectra of {sup 3}C{sub 70}{sup *} were obtained by the pump-probe technique, using a probe beam based on the broad-band optical parametric generation (OPG) of a {beta}-barium borate (BBO) crystal pumped by 532-nm laser pulse. The lowest transition band of the T-T absorption of {sup 3}C{sub 70}{sup *} was found in the near-IR region (960 nm) by the new technique. 28 refs., 10 figs.

Watanabe, Akira; Ito, Osamu [Tohoku Univ., Sendai (Japan)] [Tohoku Univ., Sendai (Japan); Watanabe, Motoyuki; Saito, Haruhisa; Koishi, Musubu [Hamamatsu Photonics K.K. (Japan)] [Hamamatsu Photonics K.K. (Japan)

1996-06-20

247

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

248

The triplet state of a platinum acetylide chromophore examined by time-resolved infrared spectroscopy and density functional theory  

NASA Astrophysics Data System (ADS)

To understand platinum acetylide molecular structure changes upon conversion to the triplet state, we measured time-resolved infrared (TRIR) spectra of the platinum acetylide complex trans-bis(tributylphosphine)bis(4-ethynyl-1-(2-phenylethynyl)benzene)platinum (abbreviated as PE2). We used density functional theory (DFT) methods to calculate the geometry, molecular orbitals and vibrational spectra of the ground and lowest energy triplet state of PE2. Solutions of PE2 were excited upon ns pulsed laser excitation at 355 nm and TRIR spectra were collected. The TRIR data show cumulenic vibrations in the triplet state as well as evidence for photoproduct formation. The DFT results support the experimental data, suggesting PE2's triplet state has quinone character.

Cooper, Thomas M.; Blaudeau, Jean-Philippe; Hall, Benjamin C.; Rogers, Joy E.; McLean, Daniel G.; Liu, Yonglin; Toscano, John P.

2004-12-01

249

Steady-state and time-resolved two-photon fluorescence microscopy: a versatile tool for probing cellular environment and function  

NASA Astrophysics Data System (ADS)

In the last decade, the two-photon fluorescence laser-scanning microscopy (TPLSM) has become an indispensable tool for the bioscientific and biomedical research. TPLSM techniques as well as their applications are currently experiencing a dramatic evolution and represent the focus of many biophysical research projects. In this work, we compare in detail two steady-state TPLSM techniques, i.e. single-beam scanning microscopy combined with point-detection (SB-PMT) and multi-beam scanning microscopy combined with synchronous detection (MB-CCD), as far as their technical characteristics relevant for the bioscientific research are concerned, i.e. optical performance and imaging speed. We demonstrate that the SB-PMT technique is more adequate for deep-tissue imaging (few 100 ?m depth) than the MB-CCD technique, whereas only the MB-CCD technique enables high-speed imaging for characterizing the dynamics of fast biological phenomena. Novel applications of these techniques are additionally discussed. Moreover, we employ a time-resolved TPLSM technique, i.e. biexponential fluorescence lifetime imaging based on the cellular fluorescence of the nicotinamide pyridine dinucleotides NADH and NADPH, which allows us to probe for the first time the redox cellular metabolism of MIN6 cells (mutated insulin producing pancreatic ?-cells) as well as to show the potential of this method for the specific and dynamic investigation of NADH- and NADPH-dependent cellular processes.

Denicke, Stefan; Ehlers, Jan-Eric; Niesner, Raluca; Quentmeier, Stefan; Gericke, Karl-Heinz

2007-09-01

250

Zeptomole detection sensitivity of prostate-specific antigen in a rapid microtitre plate assay using time-resolved fluorescence.  

PubMed

Prostate-specific antigen (PSA) was detected in microtitre wells coated with a PSA-specific antibody using biotinylated antibody and streptavidin-coated, highly fluorescent 107 nm nanoparticles, which contained more than 30000 europium ions entrapped by beta-diketones. PSA was monitored directly on the surface of a well without any additional enhancement step. The sensitivity of the assay was 1.6 ng/L, corresponding to 50 fmol/L or 250 zeptomoles (250 x 10(-21) mol/L) of PSA. The high specific activity and low non-specific binding of the streptavidin-coated nanoparticles improved the sensitivity of the PSA assay 100-fold compared to the conventional europium-labelled streptavidin tracer in the same assay format. Additionally, the streptavidin-coated nanoparticle label made very rapid assays possible, due to the high affinity of the streptavidin-biotin complex and a high number of binding sites available for tracing the biotinylated antibody on the surface. Due to the inherent problems of tracing analyte with a complex of biotinylated antibody and streptavidin-coated nanoparticles, the streptavidin-coated nanoparticles reacting with the surface-captured analyte and biotinylated antibody was favoured and factors influencing this are discussed. This universal labelling technology can be applied to detect any biotinylated molecule, either in solution or on a solid phase, in order to improve detection sensitivities in many areas of biochemical analysis, such as cyto- and histochemistry, multianalyte DNA-chip assays and single-particle assays. PMID:11114110

Hrm, H; Soukka, T; Lnnberg, S; Paukkunen, J; Tarkkinen, P; Lvgren, T

2000-01-01

251

Lifetime fluorescence spectroscopy for in situ investigation of osteogenic differentiation  

NASA Astrophysics Data System (ADS)

Time-Resolved Laser-Induced Fluorescence Spectroscopy (TR-LIFS) represents a potential tool for the in-situ characterization of bioengineered tissues. In this study, we evaluate the application of TR-LIFS to non-intrusive monitoring of matrix composition during osteogenetic differentiation. Human adipose-derived stem cells, harvested from 3 patients, were induced in osteogenic media for 3, 5, and 7 weeks. Samples were subsequently collected and probed for time-resolved fluorescence emission with a pulsed nitrogen laser. Fluorescence parameters, derived from both spectral- and time-domain, were used for sample characterization. The samples were further analyzed using Western blot analysis and computer-based densitometry. A significant change in the fluorescence parameters was detected for samples beyond 3 weeks of osteogenic differentiation. The spectroscopic observations: 1) show increase of collagen I when contrasted against the time-resolved fluorescence spectra of commercially available collagens; and 2) are in agreement with Western blot analysis that demonstrated significant increase in collagen I content between 3- vs. 5-weeks and 3- vs. 7-weeks and no changes for collagens III, IV, and V. Our results suggest that TR-LIFS can be used as a non-invasive means for the detection of specific collagens in maturing connective tissues.

Marcu, Laura; Elbarbary, Amir; Zuk, Patricia; De Ugarte, Daniel A.; Benhaim, Prosper; Kurt, Hamza; Hedrick, Marc H.; Ashjian, Peter

2003-07-01

252

Direct observation of back energy transfer in blue phosphorescent materials for organic light emitting diodes by time-resolved optical waveguide spectroscopy  

PubMed Central

We demonstrate a high-sensitive transient absorption technique for detection of excited states in an organic thin film by time-resolved optical waveguide spectroscopy. By using a laser beam as a probe light, we detect small change in the transient absorbance which is equivalent to 10?7 absorbance unit in a conventional method. This technique was applied to organic thin films of blue phosphorescent materials for organic light emitting diodes. We directly observed the back energy transfer from emitting guest molecules to conductive host molecules. PMID:23526833

Hirayama, H.; Sugawara, Y.; Miyashita, Y.; Mitsuishi, M.; Miyashita, T.

2013-01-01

253

Time-resolved surface-enhanced IR-absorption spectroscopy of direct electron transfer to cytochrome c oxidase from R. sphaeroides.  

PubMed

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

2013-12-17

254

Afterglow studies of H3+(v=0) recombination using time resolved cw-diode laser cavity ring-down spectroscopy  

NASA Astrophysics Data System (ADS)

The recombination of spectroscopically identified H3+(v=0) ions with thermal electrons has been studied in pulsed afterglow plasma by means of an infrared cavity ring-down spectrometer (CRDS). Time-resolved measurements of the H3+(v=0) density were carried out in helium buffer gas with small admixtures of argon and hydrogen. The gas temperature was ~330 K, and the total pressure ranged from 8 to 16 mbar. The CRDS signal on the [nu]2=3<--0 transition of H3+ ([lambda]=1.4 [mu]m) was monitored as a function of time during the discharge afterglow. Since the absorption cross-section is known, the decay of the H3+(v=0) number density and hence, the recombination coefficient can be deduced. At hydrogen number densities [H2]=11014 to 81014 cm-3 the measured recombination rate coefficient was found to be [alpha]=(1.6+/-0.6)10-7 cm3 s-1.

Macko, P.; Bn, G.; Hlavenka, P.; Plasil, R.; Poterya, V.; Pysanenko, A.; Votava, O.; Johnsen, R.; Glosk, J.

2004-04-01

255

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

256

Development of filtration-based time-resolved fluorescence assay for the high-throughput screening of urotensin II receptor antagonist.  

PubMed

The time-resolved fluorescence (TRF) receptor binding assay has many advantages over the traditional radioligand binding assay in terms of sensitivity and reproducibility for the screening of receptor ligands. The TRF-based urotensin receptor (UT) binding assay with an automatic vacuum filtration system was developed and evaluated for the high-throughput screening of UT receptor antagonists. For this assay development, the human recombinant urotensin II (UII) was modified by labeling europium at its N-terminal position (Eu-UII) and used as a fluorescent tracer. The microsomal membrane fraction of UT receptor was prepared from HEK293 cells stably expressing the human UT receptor. The 50% inhibitory concentration (IC(50)) values of UII from competition binding assays with Eu-UII were 2.76 nM, which is very similar to that of fluorescence polarization (FP)-based UT receptor binding experiment (2.18 nM). Comparing with the FP-based receptor binding assay for UII (Z' factor, 0.36), the current TRF assay presented improved Z' factor (0.76) with a relatively higher signal-to-background ratio (1.5 and 2.1, respectively). The known high-affinity UT receptor antagonists, palosuran and SB657510, exhibited IC(50) values of 23.6 and 73.4 nM, respectively, which were consistent with the IC(50) values from FP-based receptor binding assay (30.6 and 78.7 nM, respectively). These results suggest that our filtration-based TRF UT receptor binding assay can achieve the desired sensitivity with higher reproducibility to adapt for the high-throughput screening of compound libraries. PMID:21561377

Oh, Kwang-Seok; Lee, Sunghou; Lee, Byung Ho

2011-10-01

257

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

258

Photophysical properties of 2,5-diphenyl-1,6,6a-trithiapentalene revealed by time-resolved spectroscopy  

Microsoft Academic Search

The fluorescence decay from S2(?, ?*) state of 2,5-diphenyl-1,6,6a-trithiapentalene (DP-TTP) in cyclohexane, tetrahydrofuran and acetonitrile solutions of a quantum yield of ?0.020.04 were measured. The results indicate that, the dominant process of radiationless deactivation of the S2 state, is internal conversion to the S1 state. Upon laser pulse excitation (?ex=532 nm) from the S1(n, ?*) state, DP-TTP in deoxygenated benzonitrile,

Maged A El-Kemary

2001-01-01

259

Infrared absorption of C6H5SO2 detected with time-resolved Fourier-transform spectroscopy  

NASA Astrophysics Data System (ADS)

C6H5SO2 radicals were produced upon irradiation of three flowing mixtures: C6H5SO2Cl in N2, C6H5Cl and SO2 in CO2, and C6H5Br and SO2 in CO2, with a KrF excimer laser at 248nm. A step-scan Fourier-transform spectrometer coupled with a multipass absorption cell was employed to record the time-resolved infrared (IR) absorption spectra of reaction intermediates. Two transient bands with origins at 1087.7 and 1278.2cm-1 are assigned to the SO2-symmetric and SO2-antisymmetric stretching modes, respectively, of C6H5SO2. Calculations with density-functional theory (B3LYP/aug-cc-pVTZ and B3P86/aug-cc-pVTZ) predict the geometry and vibrational wave numbers of C6H5SO2 and C6H5OSO. The vibrational wave numbers and IR intensities of C6H5SO2 agree satisfactorily with the observed new features. Rotational contours of IR spectra of C6H5SO2 simulated based on predicted molecular parameters agree satisfactorily with experimental results for both bands. The SO2-symmetric stretching band is dominated by a- and c-type rotational structures and the SO2-antisymmetric stretching band is dominated by a b-type rotational structure. When C6H5SO2Cl was used as a precursor of C6H5SO2, C6H5SO2Cl was slowly reproduced at the expense of C6H5SO2, indicating that the reaction Cl +C6H5SO2 takes place. When C6H5Br/SO2/CO2 was used as a precursor of C6H5SO2, features at 1186 and 1396cm-1 ascribable to C6H5SO2Br were observed at a later period due to secondary reaction of C6H5SO2 with Br. Corresponding kinetics based on temporal profiles of observed IR absorption are discussed.

Chu, Li-Kang; Lee, Yuan-Pern

2007-04-01

260

Reaction dynamics of O(1D) + HCOOD/DCOOH investigated with time-resolved Fourier-transform infrared emission spectroscopy  

NASA Astrophysics Data System (ADS)

We investigated the reaction dynamics of O(1D) towards hydrogen atoms of two types in HCOOH. The reaction was initiated on irradiation of a flowing mixture of O3 and HCOOD or DCOOH at 248 nm. The relative vibration-rotational populations of OH and OD (1 ? v ? 4, J ? 15) states were determined from time-resolved IR emission recorded with a step-scan Fourier-transform spectrometer. In the reaction of O(1D) + HCOOD, the rotational distribution of product OH is nearly Boltzmann, whereas that of OD is bimodal. The product ratio [OH]/[OD] is 0.16 0.05. In the reaction of O(1D) + DCOOH, the rotational distribution of product OH is bimodal, but the observed OD lines are too weak to provide reliable intensities. The three observed OH/OD channels agree with three major channels of production predicted with quantum-chemical calculations. In the case of O(1D) + HCOOD, two intermediates HOC(O)OD and HC(O)OOD are produced in the initial C-H and O-D insertion, respectively. The former undergoes further decomposition of the newly formed OH or the original OD, whereas the latter produces OD via direct decomposition. Decomposition of HOC(O)OD produced OH and OD with similar vibrational excitation, indicating efficient intramolecular vibrational relaxation, IVR. Decomposition of HC(O)OOD produced OD with greater rotational excitation. The predicted [OH]/[OD] ratio is 0.20 for O(1D) + HCOOD and 4.08 for O(1D) + DCOOH; the former agrees satisfactorily with experiments. We also observed the v3 emission from the product CO2. This emission band is deconvoluted into two components corresponding to internal energies E = 317 and 96 kJ mol-1 of CO2, predicted to be produced via direct dehydration of HOC(O)OH and secondary decomposition of HC(O)O that was produced via decomposition of HC(O)OOH, respectively.

Huang, Shang-Chen; Nghia, N. T.; Putikam, Raghunath; Nguyen, Hue M. T.; Lin, M. C.; Tsuchiya, Soji; Lee, Yuan-Pern

2014-10-01

261

BL1.4.2: Time-resolved FTIR spectroscopy at up to 5 nanosecond resolution demonstrated  

E-print Network

Transform Infrared Spectroscopy (FTIR) acquires scans on the time scale of one second, so the very fast pulses of a synchrotron source are not noticed. However, using the step-scan capabilities and fast states), environmental science (adsorbates, bacteria, soil chemistry, bioremediation), biological

262

Comparative time-resolved photoconductivity and absorption spectroscopy studies on dark secondary reactions following the photoreduction of benzophenone by triethylamine  

Microsoft Academic Search

The dark secondary reactions following the photoreduction of benzophenone by triethylamine constitute an example of tricky reactions involving radicals throughout proton, hydrogen atom and electron transfer. In this work, nanosecond transient absorption spectroscopy is used to detect the influence of hydrogen bonding ability of the solvent on these reactions by means of adding water or methanol to acetonitrile solutions. The

M. Dossot; X. Allonas; P. Jacques

1999-01-01

263

Identification of an emitting molecular species by time-resolved fluorescence applied to the excited state dynamics of pigment yellow 101.  

PubMed

Time-resolved fluorescence (TRF) with a resolution higher than the periods of vibrations may provide the vibrational spectrum of an emitting species by directly recording the vibrational wave packet motions in time. We applied high-resolution TRF to investigate the excited-state dynamics of pigment yellow 101 (P.Y.101). The TRF spectra of P.Y.101 in dichloromethane showed that upon photoexcitation of the enol isomer, dynamics occur in the S1 state to form a product in two time constants at 30 and 140 fs. TRF signals were modulated due to the vibrational wave packet motions in the excited states, which provided the vibrational spectra of the emitting species. Depending on the emission wavelength, two different vibrational spectra were evident. With the help of theoretical calculations, the two spectra were assigned to the enol and keto isomers of P.Y.101 in the S1 state, leading to the conclusion that P.Y.101 undergoes ultrafast excited-state intramolecular proton transfer (ESIPT) with a quantum yield close to 1. Visible-pump infrared-probe transient absorption spectra were recorded to corroborate this conclusion. PMID:24718423

Lee, Seung Noh; Park, Jaeheung; Lim, Manho; Joo, Taiha

2014-05-28

264

Time-resolved characterization of a filamentary argon discharge at atmospheric pressure in a capillary using emission and absorption spectroscopy  

NASA Astrophysics Data System (ADS)

An argon/nitrogen (0.999/0.001) filamentary pulsed discharge operated at atmospheric pressure in a quartz tube is characterized using voltage-current measurements, microphotography, optical emission spectroscopy (OES) and absorption spectroscopy. Nitrogen is applied as a sensor gas for the purpose of OES diagnostic. The density of argon metastable atoms Ar(3P2) is determined using tunable diode laser absorption spectroscopy (TDLAS). Using a plasma chemical model the measured OES data are applied for the characterization of the plasma conditions. Between intense positive pulses the discharge current oscillates with a damped amplitude. It is established that an electric current flows in this discharge not only through a thin plasma filament that is observed in the discharge image but also through the whole cross section of the quartz tube. A diffuse plasma fills the quartz tube during a time between intense current pulses. Ionization waves are propagating in this plasma between the spike and the grounded area of the tube producing thin plasma channels. The diameter of these channels increases during the pause between the propagation of ionization waves probably because of thermal expansion and diffusion. Inside the channels electron densities of 2 1013 cm-3, argon metastable densities 1014 cm-3 and a reduced electric field about 10 Td are determined.

Schrter, Sandra; Pothiraja, Ramasamy; Awakowicz, Peter; Bibinov, Nikita; Bke, Marc; Niermann, Benedikt; Winter, Jrg

2013-11-01

265

Implementation of time-resolved step-scan fourier transform infrared (FT-IR) spectroscopy using a kHz repetition rate pump laser.  

PubMed

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)(3)Cl(2) 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

2011-05-01

266

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

PubMed

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 100 100 ?m(2) and the flux amounts to 10(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. PMID:21721681

Wernet, Philippe; Gaudin, Jrme; Godehusen, Kai; Schwarzkopf, Olaf; Eberhardt, Wolfgang

2011-06-01

267

Nonresonant ionization of oxygen molecules by femtosecond pulses: Plasma dynamics studied by time-resolved terahertz spectroscopy  

SciTech Connect

We show that optical pump-terahertz probe spectroscopy is a direct experimental tool for exploring laser-induced ionization and plasma formation in gases. Plasma was produced in gaseous oxygen by focused amplified femtosecond pulses. The ionization mechanisms at 400- and 800-nm excitation wavelengths differ significantly being primarily of a multiphoton character in the former case and a strong-field process in the latter case. The generation of the plasma in the focal volume of the laser and its expansion on subnanosecond time scale is directly monitored through its density-dependent susceptibility. A Drude model used to evaluate the plasma densities and electron-scattering rates successfully captures the observations for a wide range of pump intensities. In addition, rotational fingerprints of molecular and ionic species were also observed in the spectra.

Mics, Zoltan; Kadlec, Filip; Kuzel, Petr; Jungwirth, Pavel; Bradforth, Stephen E.; Apkarian, V. Ara [Institute of Physics, Academy of Sciences of the Czech Republic, and Center for Biomolecules and Complex Molecular Systems, Na Slovance 2, 182 21 Prague 8 (Czech Republic); Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic (Czech Republic); Center for Biomolecules and Complex Molecular Systems, Flemingovo nam. 2, 166 10 Prague 6 (Czech Republic); Department of Chemistry, University of Southern California, Los Angeles, California 90089 (United States); Department of Chemistry, University of California, Irvine, California 92697 (United States)

2005-09-08

268

Short-lived Phenoxyl Radicals Formed from Green-Tea Polyphenols and Highly Reactive Oxygen Species: An Investigation by Time-Resolved EPR Spectroscopy.  

PubMed

Polyphenols are effective antioxidants and their behavior has been studied in depth. However, a structural characterization of the species formed immediately upon hydrogen-atom transfer (HAT), a key reaction of oxidative stress, has not been achieved. The reaction of catechin and green-tea polyphenols with highly reactive O-centered H-abstracting species was studied at the molecular level and in real time by using time-resolved electron paramagnetic resonance (EPR) spectroscopy. This mirrors the reaction of highly reactive oxygen species with polyphenols. The results show that all phenolic OH groups display essentially identical reactivity. Accordingly, there is no site specificity for HAT and initial antioxidative events are demonstrated to be largely ruled by statistical (entropic) factors. PMID:25345684

Neshchadin, Dmytro; Batchelor, Stephen N; Bilkis, Itzhak; Gescheidt, Georg

2014-11-24

269

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

270

Observation of femtosecond-laser-induced ablation plumes of aluminum using space- and time-resolved soft x-ray absorption spectroscopy  

SciTech Connect

The dynamics of the laser ablation plume expansion of aluminum was investigated by using space- and time-resolved soft x-ray absorption spectroscopy. Blueshifts of the Al L-shell photoabsorption edge indicating the state of aluminum were observed in the plumes, which were generated by irradiating an aluminum target with 120 fs near-infrared pulses at an intensity of 10{sup 14} W/cm{sup 2}. The spatiotemporal evolution of the plumes exhibited a multilayer structure consisting of vaporized aluminum and condensed aluminum particles, following the expansion of plasma, with expansion velocities of 10{sup 4} m/s for the atomic state and 10{sup 3} m/s for the condensed state.

Okano, Yasuaki; Oguri, Katsuya; Nishikawa, Tadashi; Nakano, Hidetoshi [NTT Basic Research Laboratories, Nippon Telegraph and Telephone Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198 (Japan)

2006-11-27

271

Time-Resolved Multidistance Near-Infrared Spectroscopy of the Adult Head: Intracerebral and Extracerebral Absorption Changes from Moments of Distribution of Times of Flight of Photons  

NASA Astrophysics Data System (ADS)

We report on multidistance time-resolved diffuse reflectance spectroscopy of the head of a healthy adult after intravenous administration of a bolus of indocyanine green. Intracerebral and extracerebral changes in absorption are deduced from moments (integral, mean time of flight, and variance) of the distributions of times of flight of photons (DTOFs), recorded simultaneously at four different source-detector separations. We calculate the sensitivity factors converting depth-dependent changes in absorption into changes of moments of DTOFs by Monte Carlo simulations by using a layered model of the head. We validate our method by analyzing moments of DTOFs simulated for the assumed changes in absorption in different layers of the head model.

Liebert, Adam; Wabnitz, Heidrun; Steinbrink, Jens; Obrig, Hellmuth; Mller, Michael; MacDonald, Rainer; Villringer, Arno; Rinneberg, Herbert

2004-05-01

272

Stagnation layers at the collision front between two laser-induced plasmas: A study using time-resolved imaging and spectroscopy  

NASA Astrophysics Data System (ADS)

When two dense laser-induced plasmas collide a stagnation layer may form at the interface region. The degree of stagnation depends on the so-called collisionality parameter given by the ratio of the geometric scale length of the experiment (in effect the initial plasma-plasma separation) to the ion-ion mean free path. Our experiments confirm that both target geometry and elemental composition strongly influence the collision process and degree of stagnation. In particular, we show that moving from flat to wedge-shaped targets and from aluminium to calcium results in a decrease in the value of the collisionality parameter accompanied by a concomitant reduction in the degree of stagnation. Time-resolved emission imaging was employed to track the size and shape of the stagnation layer which acts as a signature of hard versus soft stagnation. Characterization of the stagnation layer in terms of electron density and temperature has been performed using optical emission spectroscopy.

Dardis, J.; Costello, J. T.

2010-08-01

273

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

274

Ultrafast time-resolved pump-probe spectroscopy of PYP by a sub-8 fs pulse laser at 400 nm.  

PubMed

Impulsive excitation of molecular vibration is known to induce wave packets in both the ground state and excited state. Here, the ultrafast dynamics of PYP was studied by pump-probe spectroscopy using a sub-8 fs pulse laser at 400 nm. The broadband spectrum of the UV pulse allowed us to detect the pump-probe signal covering 360-440 nm. The dependence of the vibrational phase of the vibrational mode around 1155 cm(-1) on the probe photon energy was observed for the first time to our knowledge. The vibrational mode coupled to the electronic transition observed in the probe spectral ranges of 2.95-3.05 and 3.15-3.35 eV was attributed to the wave packets in the ground state and the excited state, respectively. The frequencies in the ground state and excited state were determined to be 1155 1 and 1149 1 cm(-1), respectively. The frequency difference is due to change after photoexcitation. This means a reduction of the bond strength associated with ?-?* excitation, which is related to the molecular structure change associated with the primary isomerization process in the photocycle in PYP. Real-time vibrational modes at low frequency around 138, 179, 203, 260, and 317 cm(-1) were also observed and compared with the Raman spectrum for the assignment of the vibrational wave packet. PMID:23534531

Liu, Jun; Yabushita, Atsushi; Taniguchi, Seiji; Chosrowjan, Haik; Imamoto, Yasushi; Sueda, Keiichi; Miyanaga, Noriaki; Kobayashi, Takayoshi

2013-05-01

275

Elementary reconstitution of the water splitting light reaction in photosynthesis. 1. Time-resolved fluorescence and electron spin resonance studies of chlorophyll a dihydrate photoreaction with water in nonpolar solutions  

Microsoft Academic Search

The path of (Chl a 2HO)\\/sub n\\/ hydrated chlorophyll a in its photoreaction with water is studied by means of time-resolved fluorescence and electron spin resonance techniques. It is shown that the observed ESR effects are primarily attributable to the weakly fluorescent aggregates of chlorophyll a dihydrate, (Chl a 2HO)\\/sub n greater than or equal to 2\\/. By contrast, monomeric

F. K. Fong; M. Kusunoki; L. Galloway; T. G. Matthews; F. E. Lytle; A. J. Hoff; F. A. Brinkman

1982-01-01

276

Comparison of TiO? and ZnO solar cells sensitized with an indoline dye: time-resolved laser spectroscopy studies of partial charge separation processes.  

PubMed

Time-resolved laser spectroscopy techniques in the time range from femtoseconds to seconds were applied to investigate the charge separation processes in complete dye-sensitized solar cells (DSC) made with iodide/iodine liquid electrolyte and indoline dye D149 interacting with TiO2 or ZnO nanoparticles. The aim of the studies was to explain the differences in the photocurrents of the cells (3-4 times higher for TiO2 than for ZnO ones). Electrochemical impedance spectroscopy and nanosecond flash photolysis studies revealed that the better performance of TiO2 samples is not due to the charge collection and dye regeneration processes. Femtosecond transient absorption results indicated that after first 100 ps the number of photoinduced electrons in the semiconductor is 3 times higher for TiO2 than for ZnO solar cells. Picosecond emission studies showed that the lifetime of the D149 excited state is about 3 times longer for ZnO than for TiO2 samples. Therefore, the results indicate that lower performance of ZnO solar cells is likely due to slower electron injection. The studies show how to correlate the laser spectroscopy methodology with global parameters of the solar cells and should help in better understanding of the behavior of alternative materials for porous electrodes for DSC and related devices. PMID:24568536

Sobu?, Jan; Burdzi?ski, Gotard; Karolczak, Jerzy; Idgoras, Jess; Anta, Juan A; Zi?ek, Marcin

2014-03-11

277

Pathways and timescales of primary charge separation in the photosystem II reaction center as revealed by a simultaneous fit of time-resolved fluorescence and transient absorption.  

PubMed

We model the dynamics of energy transfer and primary charge separation in isolated photosystem II (PSII) reaction centers. Different exciton models with specific site energies of the six core pigments and two peripheral chlorophylls (Chls) in combination with different charge transfer schemes have been compared using a simultaneous fit of the absorption, linear dichroism, circular dichroism, steady-state fluorescence, transient absorption upon different excitation wavelengths, and time-resolved fluorescence. To obtain a quantitative fit of the data we use the modified Redfield theory, with the experimental spectral density including coupling to low-frequency phonons and 48 high-frequency vibrations. The best fit has been obtained with a model implying that the final charge separation occurs via an intermediate state with charge separation within the special pair (RP(1)). This state is weakly dipole-allowed, due to mixing with the exciton states, and can be populated directly or via 100-fs energy transfer from the core-pigments. The RP(1) and next two radical pairs with the electron transfer to the accessory Chl (RP(2)) and to the pheophytin (RP(3)) are characterized by increased electron-phonon coupling and energetic disorder. In the RP(3) state, the hole is delocalized within the special pair, with a predominant localization at the inactive-branch Chl. The intrinsic time constants of electron transfer between the three radical pairs vary from subpicoseconds to several picoseconds (depending on the realization of the disorder). The equilibration between RP(1) and RP(2) is reached within 5 ps at room temperature. During the 5-100-ps period the equilibrated core pigments and radical pairs RP(1) and RP(2) are slowly populated from peripheral chlorophylls and depopulated due to the formation of the third radical pair, RP(3). The effective time constant of the RP(3) formation is 7.5 ps. The calculated dynamics of the pheophytin absorption at 545 nm displays an instantaneous bleach (30% of the total amplitude) followed by a slow increase of the bleaching amplitude with time constants of 15 and 12 ps for blue (662 nm) and red (695 nm) excitation, respectively. PMID:15980183

Novoderezhkin, Vladimir I; Andrizhiyevskaya, Elena G; Dekker, Jan P; van Grondelle, Rienk

2005-09-01

278

Pathways and Timescales of Primary Charge Separation in the Photosystem II Reaction Center as Revealed by a Simultaneous Fit of Time-Resolved Fluorescence and Transient Absorption  

PubMed Central

We model the dynamics of energy transfer and primary charge separation in isolated photosystem II (PSII) reaction centers. Different exciton models with specific site energies of the six core pigments and two peripheral chlorophylls (Chls) in combination with different charge transfer schemes have been compared using a simultaneous fit of the absorption, linear dichroism, circular dichroism, steady-state fluorescence, transient absorption upon different excitation wavelengths, and time-resolved fluorescence. To obtain a quantitative fit of the data we use the modified Redfield theory, with the experimental spectral density including coupling to low-frequency phonons and 48 high-frequency vibrations. The best fit has been obtained with a model implying that the final charge separation occurs via an intermediate state with charge separation within the special pair (RP1). This state is weakly dipole-allowed, due to mixing with the exciton states, and can be populated directly or via 100-fs energy transfer from the core-pigments. The RP1 and next two radical pairs with the electron transfer to the accessory Chl (RP2) and to the pheophytin (RP3) are characterized by increased electron-phonon coupling and energetic disorder. In the RP3 state, the hole is delocalized within the special pair, with a predominant localization at the inactive-branch Chl. The intrinsic time constants of electron transfer between the three radical pairs vary from subpicoseconds to several picoseconds (depending on the realization of the disorder). The equilibration between RP1 and RP2 is reached within 5 ps at room temperature. During the 5100-ps period the equilibrated core pigments and radical pairs RP1 and RP2 are slowly populated from peripheral chlorophylls and depopulated due to the formation of the third radical pair, RP3. The effective time constant of the RP3 formation is 7.5 ps. The calculated dynamics of the pheophytin absorption at 545 nm displays an instantaneous bleach (30% of the total amplitude) followed by a slow increase of the bleaching amplitude with time constants of 15 and 12 ps for blue (662 nm) and red (695 nm) excitation, respectively. PMID:15980183

Novoderezhkin, Vladimir I.; Andrizhiyevskaya, Elena G.; Dekker, Jan P.; van Grondelle, Rienk

2005-01-01

279

Fluorescence spectroscopy and imaging for noninvasive diagnostics: applications to early cancer detection in the lung  

NASA Astrophysics Data System (ADS)

Tissue fluorescence spectroscopy and imaging are being investigated as potential methods for non-invasive detection of pre-neoplastic change in the lung and other organ systems. A substantial contribution to tissue fluorescence is known to arise from endogenous cellular fluorophores. Using steady-state and time-resolved fluorescence spectroscopy and imaging, we characterized the endogenous fluorescence properties of immortalized and carcinogen-transformed human bronchial epithelial cells. Non-invasive sensing of endogenous molecular biomarkers associated with human bronchial pre-neoplasia will be discussed.

Mycek, Mary-Ann; Urayama, Paul; Zhong, Wei; Sloboda, Roger D.; Dragnev, Konstantin H.; Dmitrovsky, Ethan

2003-10-01

280

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

281

Diffusion and molecular interactions in a methanol/polyimide system probed by coupling time-resolved FTIR spectroscopy with gravimetric measurements.  

PubMed

In this contribution the diffusion of methanol in a commercial polyimide (PMDA-ODA) is studied by coupling gravimetric measurements with in-situ, time-resolved FTIR spectroscopy. The spectroscopic data have been treated with two complementary techniques, i.e., difference spectroscopy (DS) and least-squares curve fitting (LSCF). These approaches provided information about the overall diffusivity, the nature of the molecular interactions among the system components and the dynamics of the various molecular species. Additional spectroscopic measurements on thin film samples (about 2 ?m) allowed us to identify the interaction site on the polymer backbone and to propose likely structures for the H-bonding aggregates. Molar absorptivity values from a previous literature report allowed us to estimate the population of first-shell and second-shell layers of methanol in the polymer matrix. In terms of diffusion kinetics, the gravimetric and spectroscopic estimates of the diffusion coefficients were found to be in good agreement with each other and with previous literature reports. A Fickian behavior was observed throughout, with diffusivity values markedly affected by the total concentration of sorbed methanol. PMID:24809042

Musto, Pellegrino; Galizia, Michele; La Manna, Pietro; Pannico, Marianna; Mensitieri, Giuseppe

2014-01-01

282

Single molecule fluorescence saturation spectroscopy  

NASA Astrophysics Data System (ADS)

Saturation spectroscopy is a powerful method to investigate photophysical parameters of single fluorescent molecules. Nevertheless, the impact of a gradual increase, over a broad range, of the laser excitation on the intramolecular dynamics is not completely understood, particularly concerning their fluorescence emission (the so-called brightness). As we have presented in a previous paper [1], we interpret the evolution of the brightness with the laser power by cascade absorption of two and three photons within a five-level molecular system. This multi-photon consecutive absorption leads us to reconsider the common expression of the saturation curve of fluorescent molecule. Furthermore, this multi-photon absorption process also affects the observation volume of microscope. So, in this paper we propose to interpret the size increase of the confocal observation volume according to simulations based upon two often used expressions of the Point Spread Functions (PSF) in fluorescence microscopy.

Jaffiol, Rodolphe; Winckler, Pascale

2014-03-01

283

Investigation of Cu-doped Li2B4O7 single crystals by electron paramagnetic resonance and time-resolved optical spectroscopy  

NASA Astrophysics Data System (ADS)

A low-temperature study of the thermoluminescent dosimeter material, lithium tetraborate (Li2B4O7) doped by Cu, has been carried out by the methods of electron paramagnetic resonance (EPR) and time-resolved polarization spectroscopy using 4-20 eV synchrotron radiation and 1 s Xe flash lamp pulses in the region 3-6 eV. The observed EPR spectra of an unpaired hole with strong d-character and characteristic hyperfine splittings can be ascribed to Cu2+ substituted at a Li lattice site and displaced due to relaxation. The results on the Cu+-related luminescence strongly support the conclusion about a low-symmetry position of copper impurity ions in the lithium tetraborate lattice. The temperature dependence of the decay kinetics of the Cu+-related 3.35 eV emission indicates a triplet nature for the relaxed excited state of the Cu+ centres. An off-centre position of the Cu+ ion in the relaxed excited state is suggested.

Corradi, G.; Nagirnyi, V.; Kotlov, A.; Watterich, A.; Kirm, M.; Polgr, K.; Hofstaetter, A.; Meyer, M.

2008-01-01

284

Photodissociation of gaseous acetyl chloride at 248 nm by time-resolved Fourier-transform infrared spectroscopy: the HCl, CO, and CH2 product channels.  

PubMed

In one-photon dissociation of gaseous acetyl chloride at 248 nm, time-resolved Fourier-transform infrared emission spectroscopy is used to detect the fragments of HCl, CO, and CH(2) in the presence of Ar or O(2). The high-resolution spectra of HCl and CO are analyzed to yield the corresponding internal energy deposition of 8.9 +/- 1.1 and 6.2 +/- 0.9 kcal/mol. The presence of the CH(2) fragment is verified by detecting the CO(2) product resulting from the reaction of CH(2) and the added O(2). The probability of the HCl formation via a hot Cl reaction with the precursor is examined to be negligible by performing two experiments, the CH(3)COCl pressure dependence and the measurement of Br(2) with Cl reaction. The HCl elimination channel under the Ar addition is verified to be slowed by 2 orders of magnitude, as compared to the Cl elimination channel. The observed fragments are proposed to dissociate on the hot ground electronic state via collision-induced internal conversion. A two-body dissociation channel is favored leading to HCl and CH(2)CO, followed by secondary dissociation. PMID:20568795

Liu, Yu-Ting; Tsai, Ming-Tsang; Liu, Chia-Yun; Tsai, Po-Yu; Lin, King-Chuen; Shih, Y H; Chang, A H H

2010-07-15

285

Study on vibrational relaxation dynamics of phenol-water complex by picosecond time-resolved IR-UV pump-probe spectroscopy in a supersonic molecular beam  

NASA Astrophysics Data System (ADS)

A comparative study of vibrational energy relaxation (VER) between the monohydrated complexes of phenol-d0 and phenol-d1 is investigated in a supersonic molecular beam. The direct time-resolved measurement of energy redistribution from the phenolic OH/OD stretching mode of the phenol-d0-H2O/phenol-d1-D2O is performed by picosecond IR-UV pump-probe spectroscopy. Two complexes follow the same relaxation process that begins with the intramolecular vibrational energy redistribution (IVR) and the intermolecular vibrational energy redistribution (IVR), which is followed by the vibrational predissociation (VP). The difference in the relaxation lifetimes between them is discussed by anharmonic force field and RRKM calculations. Anharmonic analysis implies that intra- (IVR) and intermolecular (IVR) relaxations occur in parallel in the complexes. The RRKM-predicted dissociation (VP) lifetimes show qualitative agreement with the observed results, suggesting that VP takes place after the statistical energy distribution in the complexes.

Miyazaki, Yasunori; Inokuchi, Yoshiya; Ebata, Takayuki; Petkovi?, Milena

2013-06-01

286

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

287

Photo-induced spin-state conversion in solvated transition metal complexes probed via time-resolved soft X-ray spectroscopy.  

PubMed

Solution-phase photoinduced low-spin to high-spin conversion in the Fe(II) 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 (1)A(1) --> (1)MLCT (metal-to-ligand charge transfer) excitation at 560 nm, changes in the iron L(2)- and L(3)-edges were observed concomitant with formation of the transient high-spin (5)T(2) 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 approximately 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 A 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. PMID:20426414

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

2010-05-19

288

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 (2.34.4 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

289

Lifetime measurement of the T =23 537 cm sup minus 1 , J =9/2 odd-parity level in Nd II using time-resolved collinear fast-beam laser spectroscopy  

SciTech Connect

Time-resolved collinear fast-beam laser spectroscopy has been used to measure the lifetime of the {ital T}=23 537 cm{sup {minus}1}, {ital J}=9/2 odd-parity (abbreviated as (23 537){degree}{sub 9/2}) level in Nd II. Nanosecond pulsed excitation was achieved with the Doppler switching technique. The fast ions were selectively excited from the metastable 4{ital f}{sup 4}5{ital d} {sup 6}{ital K}{sub 9/2} level to the (23 537){degree}{sub 9/2} level by the light of a cw dye laser. The decay of the resonance fluorescence photons emitted in the transition to the ground 4{ital f}{sup 4}6{ital s} {sup 6}{ital I}{sub 7/2} level, as a function of the flight distance, was observed. The decay length was scaled into the decay time by the ion velocity, which was determined using the optical resonance itself. The lifetime is 27.7(9) ns.

Wei, S.; Lu Fuquan; Wu Songmao; Shi Peixiong; Yang Jianjun; Song Linggen; Jiayong, T. (Department of Nuclear Science, Fudan University, Shanghai, People's Republic of China (CN)); Fujia, Y. (Department of Nuclear Science, Fudan University, Shanghai, People's Republic of China Chinese Center of Advanced Science and Technology (World Laboratory), Beijing, People's Republic of China)

1991-02-01

290

Fluorescence Spectroscopy in a Shoebox  

NASA Astrophysics Data System (ADS)

This article describes construction of a simple, inexpensive fluorometer. It utilizes a flashlight or sunlight source, highlighter marker ink, bowl of water with mirror as dispersing element, and colored cellophane sheets as filters. The human eye is used as a detector. This apparatus is used to demonstrate important concepts related to fluorescence spectroscopy. Using ink from a highlighter marker, one can demonstrate the difference between light scattering and fluorescence emission, the need for an intense light source, phenomenon of the Stokes shift, the choice of filters, the preferred geometry of excitation source and emission detector, and the low detection limits that can be achieved by fluorescence measurements. By reflecting the fluorescence emission from a compact disk, it can be seen that the light emitted by molecules is not monochromatic. Furthermore, a spectrofluorometer is constructed using gratings made from a DVD or a CD. The shoebox fluorometer and spectrofluorometer can serve as useful teaching aids in places where commercial instruments are not available, and it avoids the black box problem of modern instruments.

Farooq Wahab, M.

2007-08-01

291

Photodissociation of gaseous CH{sub 3}COSH at 248 nm by time-resolved Fourier-transform infrared emission spectroscopy: Observation of three dissociation channels  

SciTech Connect

Upon one-photon excitation at 248 nm, gaseous CH{sub 3}C(O)SH is dissociated following three pathways with the products of (1) OCS + CH{sub 4}, (2) CH{sub 3}SH + CO, and (3) CH{sub 2}CO + H{sub 2}S that are detected using time-resolved Fourier-transform infrared emission spectroscopy. The excited state {sup 1}(n{sub O}, {pi}{sup *}{sub 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 Multiplication-Sign 10{sup -10} cm{sup 3} molecule{sup -1} s{sup -1}. Among the primary dissociation products, a fraction of the CH{sub 2}CO moiety may undergo further decomposition to CH{sub 2}+ CO, of which CH{sub 2} is confirmed by reaction with O{sub 2} producing CO{sub 2}, CO, OH, and H{sub 2}CO. 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 [Department of Chemistry, National Taiwan University, Taipei 106, Taiwan (China) and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan (China)

2013-01-07

292

Gas-phase photodissociation of CH{sub 3}COCN at 308 nm by time-resolved Fourier-transform infrared emission spectroscopy  

SciTech Connect

By using time-resolved Fourier-transform infrared emission spectroscopy, the fragments of HCN(v= 1, 2) and CO(v= 1-3) are detected in one-photon dissociation of acetyl cyanide (CH{sub 3}COCN) at 308 nm. The S{sub 1}(A'), {sup 1}(n{sub O}, {pi}*{sub CO}) state at 308 nm has a radiative lifetime of 0.46 {+-} 0.01 {mu}s, long enough to allow for Ar collisions that induce internal conversion and enhance the fragment yields. The rate constant of Ar collision-induced internal conversion is estimated to be (1-7) x 10{sup -12} cm{sup 3} molecule{sup -1} s{sup -1}. The measurements of O{sub 2} dependence exclude the production possibility of these fragments via intersystem crossing. The high-resolution spectra of HCN and CO are analyzed to determine the ro-vibrational energy deposition of 81 {+-} 7 and 32 {+-} 3 kJ/mol, respectively. With the aid of ab initio calculations, a two-body dissociation on the energetic ground state is favored leading to HCN + CH{sub 2}CO, in which the CH{sub 2}CO moiety may further undergo secondary dissociation to release CO. The production of CO{sub 2} in the reaction with O{sub 2} confirms existence of CH{sub 2} and a secondary reaction product of CO. The HNC fragment is identified but cannot be assigned, as restricted to a poor signal-to-noise ratio. Because of insufficient excitation energy at 308 nm, the CN and CH{sub 3} fragments that dominate the dissociation products at 193 nm are not detected.

Yeh, Yu-Ying; Chao, Meng-Hsuan; Tsai, Po-Yu; Chang, Yuan-Bin; Tsai, Ming-Tsang; Lin, King-Chuen [Department of Chemistry, National Taiwan University, Taipei 106, Taiwan (China) and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan (China)

2012-01-28

293

Subpicosecond oxygen trapping in the heme pocket of the oxygen sensor FixL observed by time-resolved resonance Raman spectroscopy.  

PubMed

Dissociation of oxygen from the heme domain of the bacterial oxygen sensor protein FixL constitutes the first step in hypoxia-induced signaling. In the present study, the photodissociation of the heme-O2 bond was used to synchronize this event, and time-resolved resonance Raman (TR(3)) spectroscopy with subpicosecond time resolution was implemented to characterize the heme configuration of the primary photoproduct. TR(3) measurements on heme-oxycomplexes are highly challenging and have not yet been reported. Whereas in all other known six-coordinated heme protein complexes with diatomic ligands, including the oxymyoglobin reported here, heme iron out-of-plane motion (doming) occurs faster than 1 ps after iron-ligand bond breaking; surprisingly, no sizeable doming is observed in the oxycomplex of the Bradyrhizobium japonicum FixL sensor domain (FixLH). This assessment is deduced from the absence of the iron-histidine band around 217 cm(-1) as early as 0.5 ps. We suggest that efficient ultrafast oxygen rebinding to the heme occurs on the femtosecond time scale, thus hindering heme doming. Comparing WT oxy-FixLH, mutant proteins FixLH-R220H and FixLH-R220Q, the respective carbonmonoxy-complexes, and oxymyoglobin, we show that a hydrogen bond of the terminal oxygen atom with the residue in position 220 is responsible for the observed behavior; in WT FixL this residue is arginine, crucially implicated in signal transmission. We propose that the rigid O2 configuration imposed by this residue, in combination with the hydrophobic and constrained properties of the distal cavity, keep dissociated oxygen in place. These results uncover the origin of the "oxygen cage" properties of this oxygen sensor protein. PMID:17446273

Kruglik, Sergei G; Jasaitis, Audrius; Hola, Klara; Yamashita, Taku; Liebl, Ursula; Martin, Jean-Louis; Vos, Marten H

2007-05-01

294

Supercritical Angle Fluorescence Correlation Spectroscopy  

PubMed Central

We explore the potential of a supercritical angle (SA) objective for fluorescence correlation spectroscopy (FCS). This novel microscope objective combines tight focusing by an aspheric lens with strong axial confinement of supercritical angle fluorescence collection by a parabolic mirror lens, resulting in a small detection volume. The tiny axial extent of the detection volume features an excellent surface sensitivity, as is demonstrated by diffusion measurements in model membranes with an excess of free dye in solution. All SA-FCS measurements are directly compared to standard confocal FCS, demonstrating a clear advantage of SA-FCS, especially for diffusion measurements in membranes. We present an extensive theoretical framework that allows for accurate and quantitative evaluation of the SA-FCS correlation curves. PMID:17827221

Ries, Jonas; Ruckstuhl, Thomas; Verdes, Dorinel; Schwille, Petra

2008-01-01

295

Time-resolved fluorescence studies of tryptophan mutants of Escherichia coli glutamine synthetase: conformational analysis of intermediates and transition-state complexes.  

PubMed Central

Single tryptophan-containing mutants of low adenylylation state Escherichia coli glutamine synthetase have been studied by frequency-domain fluorescence spectroscopy in the presence of various substrates and inhibitors. At pH 6.5, the Mn-bound wild-type enzyme (wild type has two tryptophans/subunit) and the mutant enzymes exhibit heterogeneous fluorescence decay kinetics; the individual tryptophans are adequately described by a triple exponential decay scheme. The recovered lifetime values are 5.9 ns, 2.6 ns, and 0.4 ns for Trp-57 and 5.8 ns, 2.3 ns, and 0.4 ns for Trp-158. These values are nearly identical to the previously reported results at pH 7.5 (Atkins, W.M., Stayton, P.S., & Villafranca, J.J., 1991, Biochemistry 30, 3406-3416). In addition, Trp-57 and Trp-158 both exhibit an ATP-induced increase in the relative fraction of the long lifetime component, whereas only Trp-57 is affected by this ligand at pH 7.5. The transition-state analogue L-methionine-(R,S)-sulfoximine (MSOX) causes a dramatic increase in the fractional intensity of the long lifetime component of Trp-158. This ligand has no effect on the W158S mutant protein and causes a small increase in the fractional intensity of the long lifetime component of the W158F mutant protein. Addition of glutamate to the ATP complex, which affords the gamma-glutamylphosphate-ADP complex, results in the presence of new lifetime components at 7, 3.2, and 0.5 ns for Trp-158, but has no effect on Trp-57. Similar results were obtained when ATP was added to the MSOX complex; Trp-57 exhibits heterogeneous fluorescence decay with lifetimes of 7, 3.5, and 0.8 ns. Decay kinetics of Trp-158 are best fit to a nearly homogeneous decay with a lifetime of 5.5 ns in the MSOX-ATP inactivated complex. These results provide a model for the sequence of structural and dynamic changes that take place at the Trp-57 loop and the central loop (Trp-158) during several intermediate stages of catalysis. PMID:1363912

Atkins, W. M.; Villafranca, J. J.

1992-01-01

296

Local structural investigations and speciation of uranium in Sr2P2O7 by time resolved emission spectroscopy and Sr K-edge EXAFS  

NASA Astrophysics Data System (ADS)

To probe the speciation and local structure around the uranium atom in strontium pyrophosphate, time resolved emission and Sr K edge EXAFS study was done. From the photoluminescence data it was observed that uranium was present as uranyl at two different sites. By performing time resolved luminescence, the two uranyl species could be identified. From the EXAFS data it was observed that on doping with uranium, the average Sr-O and Sr-P bond lengths increased. The correlation between the EXAFS and luminescence data confirmed the incorporation of the actinide ion at regular lattice positions of Sr ion in the pyrophosphate matrix.

Mohapatra, M.; Yadav, A. K.; Jha, S. N.; Bhattacharyya, D.; Godbole, S. V.; Natarajan, V.

2014-05-01

297

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.; lsner, Andreas; Mhl, Sven; Bluhm, Hendrik; Gessner, Oliver

2014-09-01

298

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 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. 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; Olsner, Andreas; Mhl, Sven; Bluhm, Hendrik; Gessner, Oliver

2014-09-01

299

Time-resolved spectroscopy in LiCaAlF6 doped with Cr3+: dynamical Jahn-Teller effect and thermal shifts associated with the 4T2 excited state  

Microsoft Academic Search

This work investigates the centre distribution of the Cr3 + impurity, the dynamical Jahn-Teller effect in the first 4T2 excited state and the thermal shifts of the absorption and emission peaks in LiCaAlF6:Cr3 + by means of time-resolved emission spectroscopy. The electronic and vibrational fine structure observed in both the absorption and emission spectra at low temperature are assigned according

M. N. Sanz-Ortiz; F. Rodrguez; R. Valiente

2010-01-01

300

Oligomerization of epidermal growth factor receptors (EGFR) on A431 cells studied by time-resolved fluorescence imaging microscopy: a stereochemical model for tyrosine kinase receptor activation  

Microsoft Academic Search

The aggregation states of the epidermal growth factor receptor (EGFR) on single A431 human epidermoid carcinoma cells were assessed with two new techniques for determining fluorescence resonance en- ergy transfer: donor photobleaching fluorescence reso- nance energy transfer (pbFRET) microscopy and fluo- rescence lifetime imaging microscopy (FLIM). Fluorescein-(donor) and rhodamine-(acceptor) labeled EGF were bound to the cells and the extent of

Th. W. J. Gadella; T. M. Jovin

1995-01-01

301

Structural kinetics of myosin by transient time-resolved FRET  

E-print Network

Structural kinetics of myosin by transient time-resolved FRET Yuri E. Nesmelova,1,2 , Roman V technique, ðTR?2 FRET (transient time-resolved FRET), which resolves protein structural states with a fluorescence instrument that uses a pulsed laser and direct waveform recording to acquire an accurate

Thomas, David D.

302

Time-resolved fluorescence of 2-aminopurin ea s a probe of base flipping in M.HhaI-DNA complexes  

Microsoft Academic Search

DNA base flipping is an important mechanism in molecular enzymology, but its study is limited by the lack of an accessible and reliable diagnostic technique. A series of crystalline complexes of a DNA methyltransferase, M.HhaI, and its cognate DNA, in which a fluorescent nucleobase analogue, 2-aminopurine (AP), occupies defined positions with respect the target flipped base, have been pre- pared

Robert K. Neely; Dalia Daujotyte; Saulius Grazulis; Steven W. Magennis; David T. F. Dryden; Saulius Klimas; Anita C. Jones

303

Development of soft x-ray time-resolved photoemission spectroscopy system with a two-dimensional angle-resolved time-of-flight analyzer at SPring-8 BL07LSU  

SciTech Connect

We have developed a soft x-ray time-resolved photoemission spectroscopy system using synchrotron radiation (SR) at SPring-8 BL07LSU and an ultrashort pulse laser system. Two-dimensional angle-resolved measurements were performed with a time-of-flight-type analyzer. The photoemission spectroscopy system is synchronized to light pulses of SR and laser using a time control unit. The performance of the instrument is demonstrated by mapping the band structure of a Si(111) crystal over the surface Brillouin zones and observing relaxation of the surface photo-voltage effect using the pump (laser) and probe (SR) method.

Ogawa, Manami; Yamamoto, Susumu; Nakamura, Fumitaka; Yukawa, Ryu; Fukushima, Akiko; Harasawa, Ayumi; Kakizaki, Akito; Matsuda, Iwao [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Chiba 277-8581 (Japan); Kousa, Yuka; Kondoh, Hiroshi [Department of Chemistry, Keio University, Yokohama 223-8522 (Japan); Tanaka, Yoshihito [RIKEN/SPring-8 Center, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan)

2012-02-15

304

Oligomerization of epidermal growth factor receptors on A431 cells studied by time-resolved fluorescence imaging microscopy. A stereochemical model for tyrosine kinase receptor activation  

PubMed Central

The aggregation states of the epidermal growth factor receptor (EGFR) on single A431 human epidermoid carcinoma cells were assessed with two new techniques for determining fluorescence resonance energy transfer: donor photobleaching fluorescence resonance energy transfer (pbFRET) microscopy and fluorescence lifetime imaging microscopy (FLIM). Fluorescein-(donor) and rhodamine-(acceptor) labeled EGF were bound to the cells and the extent of oligomerization was monitored by the spatially resolved FRET efficiency as a function of the donor/acceptor ratio and treatment conditions. An average FRET efficiency of 5% was determined after a low temperature (4 degrees C) incubation with the fluorescent EGF analogs for 40 min. A subsequent elevation of the temperature for 5 min caused a substantial increase of the average FRET efficiency to 14% at 20 degrees C and 31% at 37 degrees C. In the context of a two-state (monomer/dimer) model for the EGFR, these FRET efficiencies were consistent with minimal average receptor dimerizations of 13, 36, and 69% at 4, 20, and 37 degrees C, respectively. A431 cells were pretreated with the monoclonal antibody mAb 2E9 that specifically blocks EGF binding to the predominant population of low affinity EGFR (15). The average FRET efficiency increased dramatically to 28% at 4 degrees C, indicative of a minimal receptor dimerization of 65% for the subpopulation of high affinity receptors. These results are in accordance with prior studies indicating that binding of EGF leads to a fast and temperature- dependent microclustering of EGFR, but suggest in addition that the high affinity functional subclass of receptors on quiescent A431 cells are present in a predimerized or oligomerized state. We propose that the transmission of the external ligand-binding signal to the cytoplasmic domain is effected by a concerted relative rotational rearrangement of the monomeric units comprising the dimeric receptor, thereby potentiating a mutual activation of the tyrosine kinase domains. PMID:7790353

1995-01-01

305

Time-resolved fluorescence up-conversion study of radiative recombination dynamics in III-nitride light emitting diodes over a wide bias range  

NASA Astrophysics Data System (ADS)

The technique of femtosecond fluorescence up-conversion was employed to explore the transient photoluminescence and carrier decay dynamics in c-plane (In,Ga)N multi-quantum-well light emitting diodes over a wide bias range. By investigating the bias dependence of initial transient photoluminescence intensity and the luminescence lifetime, the field and carrier density effects on the radiative recombination coefficient were revealed for both low and high current injection conditions, and in good agreement with the theory.

You, Guanjun; Liu, Jie; Jiang, Zhenyu; Zhu, Yiming; Chen, Aping; Hu, Yong; Xiong, Feng; Henderson, Ron H.; Zhuang, Songlin; Xu, Jian

2013-09-01

306

Interaction of uranium(VI) with nitrogen containing model ligands studied by laser-induced fluorescence spectroscopy  

Microsoft Academic Search

The complexation of uranium(VI) with two nitrogen containing organic ligands, representing model substances for humic acid building blocks, has been investigated at pH values between 1.5 and 4.5 and an ionic strength of 0.1M (NaClO4). Using two independent fluorescence spectroscopic methods, time-resolved laser-induced fluorescence spectroscopy (TRLFS) and TRLFS with ultrafast pulses (fs-TRLFS), the complex formation of uranium(VI) with anthranilic and

B. Raditzky; K. Schmeide; S. Sachs; G. Geipel; G. Bernhard

2010-01-01

307

Wavelength-dependent photochemistry in Cr(CNPh)6: a study of photosubstitution and photoinduced electron transfer using time-resolved spectroscopy.  

PubMed

The wavelength dependence of photosubstitution, photoinduced electron transfer, and the time-resolved spectra of Cr(CNPh)6, a compound having low-lying MLCT states, were investigated. Photosubstitution quantum yields increase with increasing excitation energy while photoinduced electron transfer quantum yields decrease with increasing excitation energy. At the lowest excitation energy used (532 nm, or 18,800 cm(-1)), the quantum yields for both electron transfer and photosubstitution reach the same maximum value, 0.29. Picosecond time-resolved absorption spectra at 355 and 532 nm excitation wavelengths show two features: a bleach signal centered at 400 nm and an excited state absorption (ESA) in the 600 nm region. The ESA signal is much weaker for 532 nm excitations than for 355 nm excitations. Following a 355 nm flash, the bleach and ESA decay exponentially with the same lifetime of 23 micros. This implies a simple ligand dissociation followed by recombination. Bleach recovery kinetics after a 532 nm flash are more complicated: two or three exponential components are required to fit the data. Cr(CNPh)6 exhibits two photochemical mechanisms: at high excitation energy, a simple charge neutral dissociation occurs; at low energy, it is proposed that a phenylisocyanide radical anion dissociates, forming a radical pair that is responsible for the observed substitution and electron transfer reactivity, and the complicated nanosecond kinetics. The primary processes for both reactions occur in less than 20 ps. PMID:11229574

Shaw, L E; Langford, C H

2000-02-01

308

Time-Resolved Fluorescence Imaging Reveals Differential Interactions of N-Glycan Processing Enzymes across the Golgi Stack in Planta1[W][OA  

PubMed Central

N-Glycan processing is one of the most important cellular protein modifications in plants and as such is essential for plant development and defense mechanisms. The accuracy of Golgi-located processing steps is governed by the strict intra-Golgi localization of sequentially acting glycosidases and glycosyltransferases. Their differential distribution goes hand in hand with the compartmentalization of the Golgi stack into cis-, medial-, and trans-cisternae, which separate early from late processing steps. The mechanisms that direct differential enzyme concentration are still unknown, but the formation of multienzyme complexes is considered a feasible Golgi protein localization strategy. In this study, we used two-photon excitation-Frster resonance energy transfer-fluorescence lifetime imaging microscopy to determine the interaction of N-glycan processing enzymes with differential intra-Golgi locations. Following the coexpression of fluorescent protein-tagged amino-terminal Golgi-targeting sequences (cytoplasmic-transmembrane-stem [CTS] region) of enzyme pairs in leaves of tobacco (Nicotiana spp.), we observed that all tested cis- and medial-Golgi enzymes, namely Arabidopsis (Arabidopsis thaliana) Golgi ?-mannosidase I, Nicotiana tabacum ?1,2-N-acetylglucosaminyltransferase I, Arabidopsis Golgi ?-mannosidase II (GMII), and Arabidopsis ?1,2-xylosyltransferase, form homodimers and heterodimers, whereas among the late-acting enzymes Arabidopsis ?1,3-galactosyltransferase1 (GALT1), Arabidopsis ?1,4-fucosyltransferase, and Rattus norvegicus ?2,6-sialyltransferase (a nonplant Golgi marker), only GALT1 and medial-Golgi GMII were found to form a heterodimer. Furthermore, the efficiency of energy transfer indicating the formation of interactions decreased considerably in a cis-to-trans fashion. The comparative fluorescence lifetime imaging of several full-length cis- and medial-Golgi enzymes and their respective catalytic domain-deleted CTS clones further suggested that the formation of protein-protein interactions can occur through their amino-terminal CTS region. PMID:23400704

Schoberer, Jennifer; Liebminger, Eva; Botchway, Stanley W.; Strasser, Richard; Hawes, Chris

2013-01-01

309

Intramolecular charge transfer of 4-(dimethylamino)benzonitrile probed by time-resolved fluorescence and transient absorption: No evidence for two ICT states and a ??* reaction intermediate  

NASA Astrophysics Data System (ADS)

For the double exponential fluorescence decays of the locally excited (LE) and intramolecular charge transfer (ICT) states of 4-(dimethylamino)benzonitrile (DMABN) in acetonitrile (MeCN) the same times ?1 and ?2 are observed. This means that the reversible LE?ICT reaction, starting from the initially excited LE state, can be adequately described by a two state mechanism. The most important factor responsible for the sometimes experimentally observed differences in the nanosecond decay time, with ?1(LE)fluorescence response functions with a time resolution of 0.5 ps/channel in 1200 channels reliable kinetic and thermodynamic data can be obtained. The arguments presented in the literature in favor of a ??* state with a bent CN group as an intermediate in the ICT reaction of DMABN are discussed. From the appearance of an excited state absorption (ESA) band in the spectral region between 700 and 800 nm in MeCN for N,N-dimethylanilines with CN, Br, F, CF3, and C(=O)OC2H2 p-substituents, it is concluded that this ESA band cannot be attributed to a ??* state, as only the C-CtrpbndN group can undergo the required 120 bending.

Zachariasse, Klaas A.; Druzhinin, Sergey I.; Kovalenko, Sergey A.; Senyushkina, Tamara

2009-12-01

310

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

311

Kinetic study of the absolute rate constant for the reaction between Rb and N sub 2 O by time-resolved atomic resonance absorption spectroscopy  

SciTech Connect

The authors present a kinetic study of the reaction Rb + N{sub 2}O {r arrow} Rb + N{sub 2}O {ital k}{sub N{sub 2}O} by direct spectroscopic monitoring of ground state atomic rubidium in the time domain. Rb(5{sup 2}{ital S}{sub 1/2}) was generated by the pulsed irradiation of rubidium halide vapors at elevated temperatures in the presence of low concentrations of N{sub 2}O and excess helium buffer gas. Digitized decay profiles of the atom during reaction were recorded photoelectrically in the single-shot mode by time-resolved atomic resonance absorption spectroscopic measurements of the optically resolved Rydberg transitions at {lambda} = 420.2 nm (Rb(6{ital p}({sup 2}{ital P}{sub 3/2}))) {l arrow} Rb(5{ital s}({sup 2}{ital S}{sub 1/2})) which were analyzed by computer.

Husain, D.; Ji, B. (Cambridge Univ. (UK))

1990-03-01

312

Infrared Spectroscopic Discrimination between the Loop and ?-Helices and Determination of the Loop Diffusion Kinetics by Temperature-Jump Time-Resolved Infrared Spectroscopy for Cytochrome c  

PubMed Central

The infrared (IR) absorption of the amide I band for the loop structure may overlap with that of the ?-helices, which can lead to the misassignment of the protein secondary structures. A resolution-enhanced Fourier transform infrared (FTIR) spectroscopic method and temperature-jump (T-jump) time-resolved IR absorbance difference spectra were used to identify one specific loop absorption from the helical IR absorption bands of horse heart cytochrome c in D2O at a pD around 7.0. This small loop consists of residues 7085 with Met-80 binding to the heme Fe(III). The FTIR spectra in amide I? region indicate that the loop and the helical absorption bands overlap at 1653 cm?1 at room temperature. Thermal titration of the amide I? intensity at 1653 cm?1 reveals that a transition in loop structural change occurs at lower temperature (Tm = 45C), well before the global unfolding of the secondary structure (Tm ? 82C). This loop structural change is assigned as being triggered by the Met-80 deligation from the heme Fe(III). T-jump time-resolved IR absorbance difference spectra reveal that a T-jump from 25C to 35C breaks the Fe-S bond between the Met-80 and the iron reversibly, which leads to a loop (1653 cm?1, overlap with the helical absorption) to random coil (1645 cm?1) transition. The observed unfolding rate constant interpreted as the intrachain diffusion rate for this 16 residue loop was ?3.6 106 s?1. PMID:17557782

Ye, Manping; Zhang, Qing-Li; Li, Heng; Weng, Yu-Xiang; Wang, Wei-Chi; Qiu, Xiang-Gang

2007-01-01

313

Time-resolved fluorescence measurements of KrF emission produced by vacuum ultraviolet photolysis of KrF2 and Kr/F2 mixtures  

NASA Astrophysics Data System (ADS)

Vacuum ultraviolet (VUV) light radiation was used to produce electronically excited KrF excimers (in D-, B- and C-states) by the photolysis of KrF2 and F2/Kr mixtures at various excitation wavelengths. The excited KrF photoproduct quantum yield was measured over the excitation wavelength range of 120 to 200 nm, and a quantum efficiency of 0.11 was estimated at the peak absorption wavelength of 159 nm for KrF2. The collision-free fluorescence lifetime of the B-X transition near 248 nm was determined to be 9.5 0.6 ns when the KrF2 was excited with the 159 nm light. Near gas kinetic rate constants were measured for the quenching of KrF B-X emission by KrF2 and CO2. Using the threshold wavelength needed for the production of excited KrF photofragments, an upper bound for the bond dissociation energy of KrF2 was determined to be 1.03 0.05 eV.

Tiee, J. J.; Quick, C. R.; Hsu, A. H.; Hof, D. E.

1990-01-01

314

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

315

Time-resolved non-contact fluorescence diffuse optical tomography measurements with ultra-fast time-correlated single photon counting avalanche photodiodes  

NASA Astrophysics Data System (ADS)

The design and fabrication of time-correlated single photon counting (TCSPC) avalanche photodiodes (APDs) and associated quenching circuits have made significant progresses in recent years. APDs with temporal resolutions comparable to microchannel plate photomultiplier tubes (MCP-PMTs) are now available. MCP-PMTs were until these progresses the best TCSPC detectors with timing resolutions down to 30ps. APDs can now achieve these resolutions at a fraction of the cost. Work is under way to make the manufacturing of TCSPC APDs compatible with standard electronics fabrication practices. This should allow to further reduce their cost and render them easier to integrate in complex multi-channel TCSPC electronics, as needed in diffuse optical tomography (DOT) systems. Even if their sensitive area is much smaller than that of the ubiquitous PMT used in TCSPC, we show that with appropriate selection of optical components, TCSPC APDs can be used in time-domain DOT. To support this, we present experimental data and calculations clearly demonstrating that comparable measurements can be obtained with APDs and PMTs. We are, to our knowledge, the first group using APDs in TD DOT, in particular in non-contact TD fluorescence DOT.

Brub-Lauzire, Yves; Robichaud, Vincent; Lapointe, ric

2007-07-01

316

Lifetime measurement of the T=23 537 cm-1, J=9\\/2 odd-parity level in Nd ii using time-resolved collinear fast-beam laser spectroscopy  

Microsoft Academic Search

Time-resolved collinear fast-beam laser spectroscopy has been used to measure the lifetime of the T=23 537 cm-1, J=9\\/2 odd-parity [abbreviated as (23 537)9\\/2] level in Nd ii. Nanosecond pulsed excitation was achieved with the Doppler switching technique. The fast ions were selectively excited from the metastable 4f45d 6K9\\/2 level to the (23 537)9\\/2 level by the light of a cw

Shi Wei; Lu Fuquan; Wu Songmao; Shi Peixiong; Yang Jianjun; Song Linggen; Tang Jiayong; Yang Fujia

1991-01-01

317

Lifetime measurement of the T =23 537 cm sup minus 1 , J =9\\/2 odd-parity level in Nd II using time-resolved collinear fast-beam laser spectroscopy  

Microsoft Academic Search

Time-resolved collinear fast-beam laser spectroscopy has been used to measure the lifetime of the {ital T}=23 537 cm⁻¹, {ital J}=9\\/2 odd-parity (abbreviated as (23 537)°) level in Nd II. Nanosecond pulsed excitation was achieved with the Doppler switching technique. The fast ions were selectively excited from the metastable 4{ital f}⁴5{ital d} ⁶{ital K} level to the (23 537)° level by

S. Wei; Lu Fuquan; Wu Songmao; Shi Peixiong; Yang Jianjun; Song Linggen; T. Jiayong; Y. Fujia

1991-01-01

318

In vivo measurement of tissue oxygenation by time-resolved luminescence spectroscopy: advantageous properties of dichlorotris(1, 10-phenanthroline)-ruthenium(II) hydrate  

NASA Astrophysics Data System (ADS)

Measuring tissue oxygenation in vivo is of interest in fundamental biological as well as medical applications. One minimally invasive approach to assess the oxygen partial pressure in tissue (pO2) is to measure the oxygen-dependent luminescence lifetime of molecular probes. The relation between tissue pO and the probes' luminescence lifetime is governed by the Stern-Volmer equation. Unfortunately, virtually all oxygen-sensitive probes based on this principle induce some degree of phototoxicity. For that reason, we studied the oxygen sensitivity and phototoxicity of dichlorotris(1, 10-phenanthroline)-ruthenium(II) hydrate [Ru(Phen)] using a dedicated optical fiber-based, time-resolved spectrometer in the chicken embryo chorioallantoic membrane. We demonstrated that, after intravenous injection, Ru(Phen)'s luminescence lifetime presents an easily detectable pO dependence at a low drug dose (1 mg/kg) and low fluence (120 mJ/cm2 at 470 nm). The phototoxic threshold was found to be at 10 J/cm2 with the same wavelength and drug dose, i.e., about two orders of magnitude larger than the fluence necessary to perform a pO measurement. Finally, an illustrative application of this pO measurement approach in a hypoxic tumor environment is presented.

Huntosova, Veronika; Gay, Sandrine; Nowak-Sliwinska, Patrycja; Rajendran, Senthil Kumar; Zellweger, Matthieu; van den Bergh, Hubert; Wagnires, Georges

2014-07-01

319

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

320

Time-resolved optical spectroscopy of the pulsating DA white dwarf HS 0507+0434B. New constraints on mode identification and pulsation properties  

NASA Astrophysics Data System (ADS)

We present a detailed analysis of time-resolved optical spectra of the ZZ Ceti white dwarf, HS 0507+0434B. Using the wavelength dependence of observed mode amplitudes, we deduce the spherical degree, l, of the modes, most of which have l=1. The presence of a large number of combination frequencies (linear sums or differences of the real modes) enabled us not only to test theoretical predictions but also to indirectly infer spherical and azimuthal degrees of real modes that had no observed splittings. In addition to the above, we measure line-of-sight velocities from our spectra. We find only marginal evidence for periodic modulation associated with the pulsation modes: at the frequency of the strongest mode in the lightcurve, we measure an amplitude of 2.6+/-1.0 km s-1, which has a probability of 2% of being due to chance; for the other modes, we find lower values. Our velocity amplitudes and upper limits are smaller by a factor of two compared to the amplitudes found in ZZ Psc. We find that this is consistent with expectations based on the position of HS 0507+0434B in the instability strip. Combining all the available information from data such as ours is a first step towards constraining atmospheric properties in a convectionally unstable environment from an observational perspective. The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

Kotak, R.; van Kerkwijk, M. H.; Clemens, J. C.

2002-06-01

321

Dynamics of the reactions of O(1D) with CD3OH and CH3OD studied with time-resolved Fourier-transform IR spectroscopy  

NASA Astrophysics Data System (ADS)

We investigated the reactivity of O(1D) towards two types of hydrogen atoms in CH3OH. The reaction was initiated on irradiation of a flowing mixture of O3 and CD3OH or CH3OD at 248 nm. Relative vibration-rotational populations of OH and OD (1 <= v <= 4) states were determined from their infrared emission recorded with a step-scan time-resolved Fourier-transform spectrometer. In O(1D) + CD3OH, the rotational distribution of OD is nearly Boltzmann, whereas that of OH is bimodal; the product ratio [OH]/[OD] is 1.56 +/- 0.36. In O(1D) + CH3OD, the rotational distribution of OH is nearly Boltzmann, whereas that of OD is bimodal; the product ratio [OH]/[OD] is 0.59 +/- 0.14. Quantum-chemical calculations of the potential energy and microcanonical rate coefficients of various channels indicate that the abstraction channels are unimportant and O(1D) inserts into the C-H and O-H bonds of CH3OH to form HOCH2OH and CH3OOH, respectively. The observed three channels of OH are consistent with those produced via decomposition of the newly formed OH or the original OH moiety in HOCH2OH or decomposition of CH3OOH. The former decomposition channel of HOCH2OH produces vibrationally more excited OH because of incomplete intramolecular vibrational relaxation, and decomposition of CH3COOH produces OH with greater rotational excitation, likely due to a large torque angle during dissociation. The predicted [OH]/[OD] ratios are 1.31 and 0.61 for O(1D) + CD3OH and CH3OD, respectively, at collision energy of 26 kJ mol-1, in satisfactory agreement with the experimental results. These predicted product ratios vary weakly with collision energy.

Huang, Chong-Kai; Xu, Zhen-Feng; Nakajima, Masakazu; Nguyen, Hue M. T.; Lin, M. C.; Tsuchiya, Soji; Lee, Yuan-Pern

2012-10-01

322

Direct Observation of the Kinetically Relevant Site of CO Hydrogenation on Supported Ru Catalyst at 700 K by Time-Resolved FT-IR Spectroscopy  

SciTech Connect

Time-resolved FT-IR spectra of carbon monoxide hydrogenation over alumina-supported ruthenium particles were recorded on themillisecond time scale at 700 K using pulsed release of CO and a continuous flow of H2/N2 (ratio 0.067 or 0.15, 1 atm total pressure). Adsorbed carbon monoxide was detected along with gas phase products methane (3016 and 1306 cm-1), water (1900 +- 1300 cm-1), and carbon dioxide (2348 cm-1). Aside from adsorbed CO, no other surface species were observed. The rate of formation of methane is 2.5 +- 0.4 s-1 and coincides with the rate of carbon dioxide growth (3.4 +- 0.6 s-1), thus indicating that CH4 and CO2 originate from a common intermediate. The broad band of adsorbed carbon monoxide has a maximum at 2010 cm-1 at early times (36 ms) that shifts gradually to 1960 cm-1 over a period of 3 s as a result of the decreasing surface concentration of CO. Kinetic analysis of the adsorbed carbon monoxide reveals that surface sites absorbing at the high frequency end of the infrared band are temporally linked to gas phase product growth. Specifically, a (linear) CO site at 2026 cm-1 decays with a rate constant of 2.9 +- 0.1 s-1, which coincides with the rise constant of CH4. This demonstrates that the linear CO site at 2026 cm-1 is the kinetically most relevant one for the rate-determining CO dissociation step under reaction conditions at 700 K.

Frei, Heinz; Wasylenko, Walter; Frei, Heinz

2008-06-04

323

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.

324

Mini review of ultrafast fluorescence polarization spectroscopy [invited].  

PubMed

A mini review is presented on the theory, experiment, and application of the ultrafast fluorescence polarization dynamics and anisotropy with examples of two important medical dyes, namely Indocyanine Green and fluorescein. The time-resolved fluorescence polarization spectra of fluorescent dyes were measured with the excitation of a linearly polarized femtosecond laser pulse, and detected using a streak camera. The fluorescence emitted from the dyes is found to be partially oriented (polarized), and the degree of polarization of emission decreases with time. The decay of the fluorescence component polarized parallel to the excitation beam was found to be faster than that of the perpendicular one. Based on the physical model on the time-resolved polarized emission spectra in nanosecond range first described by Weber [J. Chem. Phys.52, 1654 (1970)], a set of first-order linear differential equations was used to model fluorescence polarization dynamics and anistropy of dye in picoseconds range. Using this model, two important decay parameters were identified separately: the decay rate of total emission intensity and the decay rate of the emission polarization affected by the rotation of fluorescent molecules causing the transfer of emission polarization from one orthogonal component to another. These two decay rates were separated and extracted from the measured time-resolved fluorescence polarization spectra. The emission polarization difference among dyes arising from different molecular volumes was used to enhance the image contrast. PMID:23400053

Pu, Yang; Wang, Wubao; Dorshow, Richard B; Das, Bidyut B; Alfano, Robert R

2013-02-10

325

Steady-state and time-resolved spectroscopy of 2,2'-bipyridine-3,3'-diol in solvents and cyclodextrins: polarity and nanoconfinement effects on tautomerization.  

PubMed

The ground- and excited-state tautomerization of the 2,2'-bipyridine-3,3'-diol molecule (BP(OH)(2)) was studied in different solvents and in confined nanocavities of cyclodextrins (CDs) using steady-state and lifetime spectroscopic measurements. In all solvents, a dizwitterion (DZ) tautomer is produced in the excited state after intramolecular double-proton transfer. This tautomer is stabilized in the ground state in water only and produces two unique absorption peaks in the region of 400-450 nm. The DZ tautomer fluoresces in the green and as the solvent polarity increases, the fluorescence peak is blue-shifted (498 nm in cyclohexane versus 462 nm in water), and the fluorescence lifetime gets shorter (3.10 ns in cyclohexane versus 0.65 ns in water). The results indicate the sensitivity of this tautomer to solvent polarity, particularly the solvent's hydrogen-bonding capability. In water, another photoinduced tautomerization mechanism takes place via a water network solvating each of the two hydrogen-bonding centers of the molecule. The second tautomer is detected as a small shoulder in the blue side of the fluorescence peak and has a lifetime of 5.40 ns. Using BP(OH)(2) to probe the nanocavities of aqueous CDs reveals the degree of hydrophobicity of the cavities and the different mechanisms of probe encapsulation. As the cavity size decreases in the order gamma-CD to beta-CD to alpha-CD, the cavity is more hydrophobic, which is reflected in an intensity decrease of the absorbance of the DZ tautomer and a red shift in its fluorescence peak. The measured lifetimes show the same trend and reveal how the probe interacts with the CD moiety. In gamma-CD, the probe is located near the secondary rim of the CD annulus, whereas in alpha-CD, the probe is completely sequestered between two CDs, and the hydrophobicity is close to that observed in cyclohexane. In beta-CD and its derivatives, the spectral changes and the measured lifetimes indicate that the CD cavity gets more hydrophobic as a result of methyl substitution of the primary and secondary hydroxyls of the beta-CD rims. In the fully methylated 2,3,6-tri-O-methyl-beta-CD, the probe is exposed to water near the secondary rim due to the steric effect at the entrance rim that prevents the probe from full encapsulation. PMID:20000557

Abou-Zied, Osama K

2010-01-21

326

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

327

Non-destructive analysis of anthocyanins in cherries by means of LambertBeer and multivariate regression based on spectroscopy and scatter correction using time-resolved analysis  

Microsoft Academic Search

In high-value sweet cherry (Prunus avium), the red coloration determined by the anthocyanins content is correlated with the fruit ripeness stage and market value. Non-destructive spectroscopy has been introduced in practice and may be utilized as a tool to assess the fruit pigments in the supply chain processes. From the fruit spectrum in the visible (Vis) wavelength range,

Manuela Zude; Michael Pflanz; Lorenzo Spinelli; Carsten Dosche; Alessandro Torricelli

328

Infrared absorption of C{sub 6}H{sub 5}SO{sub 2} detected with time-resolved Fourier-transform spectroscopy  

SciTech Connect

C{sub 6}H{sub 5}SO{sub 2} radicals were produced upon irradiation of three flowing mixtures: C{sub 6}H{sub 5}SO{sub 2}Cl in N{sub 2}, C{sub 6}H{sub 5}Cl and SO{sub 2} in CO{sub 2}, and C{sub 6}H{sub 5}Br and SO{sub 2} in CO{sub 2}, with a KrF excimer laser at 248 nm. A step-scan Fourier-transform spectrometer coupled with a multipass absorption cell was employed to record the time-resolved infrared (IR) absorption spectra of reaction intermediates. Two transient bands with origins at 1087.7 and 1278.2 cm{sup -1} are assigned to the SO{sub 2}-symmetric and SO{sub 2}-antisymmetric stretching modes, respectively, of C{sub 6}H{sub 5}SO{sub 2}. Calculations with density-functional theory (B3LYP/aug-cc-pVTZ and B3P86/aug-cc-pVTZ) predict the geometry and vibrational wave numbers of C{sub 6}H{sub 5}SO{sub 2} and C{sub 6}H{sub 5}OSO. The vibrational wave numbers and IR intensities of C{sub 6}H{sub 5}SO{sub 2} agree satisfactorily with the observed new features. Rotational contours of IR spectra of C{sub 6}H{sub 5}SO{sub 2} simulated based on predicted molecular parameters agree satisfactorily with experimental results for both bands. The SO{sub 2}-symmetric stretching band is dominated by a- and c-type rotational structures and the SO{sub 2}-antisymmetric stretching band is dominated by a b-type rotational structure. When C{sub 6}H{sub 5}SO{sub 2}Cl was used as a precursor of C{sub 6}H{sub 5}SO{sub 2}, C{sub 6}H{sub 5}SO{sub 2}Cl was slowly reproduced at the expense of C{sub 6}H{sub 5}SO{sub 2}, indicating that the reaction Cl+C{sub 6}H{sub 5}SO{sub 2} takes place. When C{sub 6}H{sub 5}Br/SO{sub 2}/CO{sub 2} was used as a precursor of C{sub 6}H{sub 5}SO{sub 2}, features at 1186 and 1396 cm{sup -1} ascribable to C{sub 6}H{sub 5}SO{sub 2}Br were observed at a later period due to secondary reaction of C{sub 6}H{sub 5}SO{sub 2} with Br. Corresponding kinetics based on temporal profiles of observed IR absorption are discussed.

Chu, L.-K.; Lee, Y.-P. [Department of Applied Chemistry, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan (China); and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan (China)

2007-04-07

329

A core-shell-type fluorescent nanosphere possessing reactive poly(ethylene glycol) tethered chains on the surface for zeptomole detection of protein in time-resolved fluorometric immunoassay.  

PubMed

To increase the sensitivity and to depress the nonspecific binding in biochemical assays, a new core-shell-type fluorescent nanosphere (106.7 nm) covalently conjugated with antibody was prepared. The core-shell-type nanosphere was constructed by dispersion radical polymerization of styrene in the presence of heterotelechelic poly(ethylene glycol) (PEG) macromonomer, which has a polymerizable vinylbenzyl group at one end and a primary amino group at the other chain end and used as well as a surfactant. The resulting nanosphere had PEG tethered chains on the surface, which possesses a primary amino group at the distal end of the PEG chain (NH(2) nanosphere). The fluorescent NH(2) nanosphere was constructed by incorporating fluorescent europium chelates with beta-diketonate ligands in the core of the NH(2) nanosphere by means of a physical entrapment method. The primary amino groups on the fluorescent NH(2) nanosphere were then converted to maleimide groups using a hetero cross-linker. The resulting nanosphere had maleimide groups on the surface (maleimide nanosphere), onto which proteins having SH group in the molecule could be covalently conjugated quantitatively without any denaturation of the proteins under the milder reaction condition. The applicability of the fluorescent nanosphere was tested in a model sandwich immunoassay for alpha-fetoprotein (AFP) determination. Anti-human AFP Fab' fragment was covalently conjugated onto the maleimide nanosphere (Fab' nanosphere), and it was used for the solid-phase time-resolved fluorometric immunoassay of AFP. The detection limit (mean + 2 SD) was 0.040 pg/mL or 57.1 zmol (57.1 x 10(-)(21) mol, M(w,AFP) = 70000) for AFP. The imprecision (concentration CV) over the whole assay range was 1.1% (100 pg/mL) - 17.1% (0.1 pg/mL), even though with this conjugation of antibody to the nanosphere, the nonspecific binding was practically negligible (0.0008%) and even when approximately 1.9 x 10(9) particles of the Fab' nanosphere were applied to the microtitration well. PMID:14615991

Matsuya, Takeshi; Tashiro, Shigeru; Hoshino, Nobuhiro; Shibata, Naoya; Nagasaki, Yukio; Kataoka, Kazunori

2003-11-15

330

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 2.23THz due to coherent excitation of an A_{1g} phonon mode. A distinct, additional frequency of 2.05THz 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

331

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

332

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

333

A von Hamos x-ray spectrometer based on a segmented-type diffraction crystal for single-shot x-ray emission spectroscopy and time-resolved resonant inelastic x-ray scattering studies  

SciTech Connect

We report on the design and performance of a wavelength-dispersive type spectrometer based on the von Hamos geometry. The spectrometer is equipped with a segmented-type crystal for x-ray diffraction and provides an energy resolution in the order of 0.25 eV and 1 eV over an energy range of 8000 eV-9600 eV. The use of a segmented crystal results in a simple and straightforward crystal preparation that allows to preserve the spectrometer resolution and spectrometer efficiency. Application of the spectrometer for time-resolved resonant inelastic x-ray scattering and single-shot x-ray emission spectroscopy is demonstrated.

Szlachetko, J. [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Institute of Physics, Jan Kochanowski University, 25-406 Kielce (Poland); Nachtegaal, M.; Boni, E. de; Willimann, M.; Safonova, O.; Sa, J.; Smolentsev, G.; Szlachetko, M.; Bergamaschi, A.; Schmitt, B.; David, C.; Luecke, A. [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Bokhoven, J. A. van [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Institute for Chemical and Bioengineering, ETH Zurich, 8093 Zuerich (Switzerland); Dousse, J.-Cl.; Hoszowska, J.; Kayser, Y. [Department of Physics, University of Fribourg, 1700 Fribourg (Switzerland); Jagodzinski, P. [University of Technology, Kielce (Poland)

2012-10-15

334

Time-resolved in situ detection of CO in a shock tube using cavity-enhanced absorption spectroscopy with a quantum-cascade laser near 4.6m.  

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

335

Strong carotenoid-to-peptide interaction immediately after triplet excitation triggering conformational changes in photo-reaction center-bound 15- cis-spheroidene as revealed by submicrosecond time-resolved Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Intermolecular interactions and structural changes of 15- cis-spheroidene in the binding pocket of reaction center from Rhodobacter sphaeroides 2.4.1 have been studied by submicrosecond time-resolved Raman spectroscopy at physiological temperature. Immediately after triplet excitation, strong enhancement of the 13-methyl asymmetric deformation Raman line of the carotenoid (Car) at 1458 cm -1 has been observed. The intensity enhancement can be explained in terms of the severe steric interaction between the Car 13-methyl group and the peptide C dbnd O oxygen of Gly M178 caused by the isomerization of the bound 15- cis-spheroidene toward all- trans. Subsequent conformational changes of the Car have also been observed.

Wang, Peng; Fu, Li-Min; Zhang, Jian-Ping; Kakitani, Yoshinori; Ishii, Hidekazu; Nagae, Hiroyoshi; Koyama, Yasushi

2008-06-01

336

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; Pot, Luca; Trivella, Maria Giovanna; L'Abbate, Antonio; Puzzuoli, Stefano

2011-03-01

337

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy  

PubMed Central

Monitoring the dynamics of protonation and protein backbone conformation changes during the function of a protein is an essential step towards understanding its mechanism. Protonation and conformational changes affect the vibration pattern of amino acid side chains and of the peptide bond, respectively, both of which can be probed by infrared (IR) difference spectroscopy. For proteins whose function can be repetitively and reproducibly triggered by light, it is possible to obtain infrared difference spectra with (sub)microsecond resolution over a broad spectral range using the step-scan Fourier transform infrared technique. With ~102-103 repetitions of the photoreaction, the minimum number to complete a scan at reasonable spectral resolution and bandwidth, the noise level in the absorption difference spectra can be as low as ~10-4, sufficient to follow the kinetics of protonation changes from a single amino acid. Lower noise levels can be accomplished by more data averaging and/or mathematical processing. The amount of protein required for optimal results is between 5-100 g, depending on the sampling technique used. Regarding additional requirements, the protein needs to be first concentrated in a low ionic strength buffer and then dried to form a film. The protein film is hydrated prior to the experiment, either with little droplets of water or under controlled atmospheric humidity. The attained hydration level (g of water / g of protein) is gauged from an IR absorption spectrum. To showcase the technique, we studied the photocycle of the light-driven proton-pump bacteriorhodopsin in its native purple membrane environment, and of the light-gated ion channel channelrhodopsin-2 solubilized in detergent. PMID:24998200

Lrenz-Fonfra, Vctor A.; Heberle, Joachim

2014-01-01

338

Proton transfer and protein conformation dynamics in photosensitive proteins by time-resolved step-scan Fourier-transform infrared spectroscopy.  

PubMed

Monitoring the dynamics of protonation and protein backbone conformation changes during the function of a protein is an essential step towards understanding its mechanism. Protonation and conformational changes affect the vibration pattern of amino acid side chains and of the peptide bond, respectively, both of which can be probed by infrared (IR) difference spectroscopy. For proteins whose function can be repetitively and reproducibly triggered by light, it is possible to obtain infrared difference spectra with (sub)microsecond resolution over a broad spectral range using the step-scan Fourier transform infrared technique. With -10(2)-10(3) repetitions of the photoreaction, the minimum number to complete a scan at reasonable spectral resolution and bandwidth, the noise level in the absorption difference spectra can be as low as -10(-) (4), sufficient to follow the kinetics of protonation changes from a single amino acid. Lower noise levels can be accomplished by more data averaging and/or mathematical processing. The amount of protein required for optimal results is between 5-100 g, depending on the sampling technique used. Regarding additional requirements, the protein needs to be first concentrated in a low ionic strength buffer and then dried to form a film. The protein film is hydrated prior to the experiment, either with little droplets of water or under controlled atmospheric humidity. The attained hydration level (g of water / g of protein) is gauged from an IR absorption spectrum. To showcase the technique, we studied the photocycle of the light-driven proton-pump bacteriorhodopsin in its native purple membrane environment, and of the light-gated ion channel channelrhodopsin-2 solubilized in detergent. PMID:24998200

Lrenz-Fonfra, Vctor A; Heberle, Joachim

2014-01-01

339

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

340

Adaptive optics for fluorescence correlation spectroscopy.  

PubMed

Fluorescence Correlation Spectroscopy (FCS) yields measurement parameters (number of molecules, diffusion time) that characterize the concentration and kinetics of fluorescent molecules within a supposedly known observation volume. Absolute derivation of concentrations and diffusion constants therefore requires preliminary calibrations of the confocal Point Spread Function with phantom solutions under perfectly controlled environmental conditions. In this paper, we quantify the influence of optical aberrations on single photon FCS and demonstrate a simple Adaptive Optics system for aberration correction. Optical aberrations are gradually introduced by focussing the excitation laser beam at increasing depths in fluorescent solutions with various refractive indices, which leads to drastic depth-dependent bias in the estimated FCS parameters. Aberration correction with a Deformable Mirror stabilizes these parameters within a range of several tens of ?m into the solution. We also demonstrate, both theoretically and experimentally, that the molecular brightness scales as the Strehl ratio squared. PMID:22274266

Leroux, Charles-Edouard; Wang, Irne; Derouard, Jacques; Delon, Antoine

2011-12-19

341

High-Pressure Fluorescence Correlation Spectroscopy  

PubMed Central

We demonstrate that a novel high-pressure cell is suitable for fluorescence correlation spectroscopy (FCS). The pressure cell consists of a single fused silica microcapillary. The cylindrical shape of the capillary leads to refraction of the excitation light, which affects the point spread function of the system. We characterize the influence of these beam distortions by FCS and photon-counting histogram (PCH) analysis and identify the optimal position for fluorescence fluctuation experiments in the capillary. At this position within the capillary, FCS and photon-counting histogram experiments are described by the same equations as used in standard FCS experiments. We report the first experimental realization of fluorescence fluctuation spectroscopy under high pressure. A fluorescent dye was used as a model system for evaluating the properties of the capillary under pressure. The autocorrelation function and the photon count distribution were measured in the pressure range from 0 to 300 MPa. The fluctuation amplitude and the diffusion coefficient show a small pressure dependence. The changes of these parameters, which are on the order of 10%, are due to the pressure changes of the viscosity and the density of the aqueous medium. PMID:14507734

Mller, Joachim D.; Gratton, Enrico

2003-01-01

342

A Direct Interaction between the Sigma-1 Receptor and the hERG Voltage-gated K+ Channel Revealed by Atomic Force Microscopy and Homogeneous Time-resolved Fluorescence (HTRF).  

PubMed

The sigma-1 receptor is an endoplasmic reticulum chaperone protein, widely expressed in central and peripheral tissues, which can translocate to the plasma membrane and modulate the function of various ion channels. The human ether--go-go-related gene encodes hERG, a cardiac voltage-gated K(+) channel that is abnormally expressed in many human cancers and is known to interact functionally with the sigma-1 receptor. Our aim was to investigate the nature of the interaction between the sigma-1 receptor and hERG. We show that the two proteins can be co-isolated from a detergent extract of stably transfected HEK-293 cells, consistent with a direct interaction between them. Atomic force microscopy imaging of the isolated protein confirmed the direct binding of the sigma-1 receptor to hERG monomers, dimers, and tetramers. hERG dimers and tetramers became both singly and doubly decorated by sigma-1 receptors; however, hERG monomers were only singly decorated. The distribution of angles between pairs of sigma-1 receptors bound to hERG tetramers had two peaks, at ?90 and ?180 in a ratio of ?2:1, indicating that the sigma-1 receptor interacts with hERG with 4-fold symmetry. Homogeneous time-resolved fluorescence (HTRF) allowed the detection of the interaction between the sigma-1 receptor and hERG within the plane of the plasma membrane. This interaction was resistant to sigma ligands, but was decreased in response to cholesterol depletion of the membrane. We suggest that the sigma-1 receptor may bind to hERG in the endoplasmic reticulum, aiding its assembly and trafficking to the plasma membrane. PMID:25266722

Balasuriya, Dilshan; D'Sa, Lauren; Talker, Ronel; Dupuis, Elodie; Maurin, Fabrice; Martin, Patrick; Borgese, Franck; Soriani, Olivier; Edwardson, J Michael

2014-11-14

343

Genetic algorithms optimization approach supported by the first-order derivative and Newton-Raphson methods: Application to fluorescence spectroscopy  

NASA Astrophysics Data System (ADS)

The application of genetic algorithms (GA) optimization approach supported by the first-order derivative (FOD) and Newton-Raphson (NR) methods to time-resolved polarized fluorescence spectroscopy, is discussed. It is demonstrated that the application of both methods to ?2 function reduces the number of adjustable model parameters. The combination of GA-optimizer with the FOD and NR methods improves considerably the efficiency of global analysis of kinetic and polarized fluorescence decays for solutions and organized media, including the case of excited-state processes.

Fisz, J. J.; Buczkowski, M.; Budzi?ski, M. P.; Kolenderski, P.

2005-05-01

344

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

345

Rotationally resolved fluorescence spectroscopy of molecular iodine  

NASA Astrophysics Data System (ADS)

Vibration-electronic spectroscopy of I2 vapor is a common, important experiment in physical chemistry lab courses. We use narrow bandwidth diode-pumped solid state (DPSS) lasers to excite specific rotational levels; these lasers are surprisingly stable and are now available at low cost. We also use efficient miniature fiber-optic spectrometers to resolve rotational fluorescence patterns in a vibrational progression. The resolution enables thorough and accurate analysis of spectroscopic constants for the ground electronic state. The high signal-to-noise ratio, which is easily achieved, also enables students to precisely measure fluorescence band intensities, providing further insight into vibrational wavefunctions and the molecular potential function. We will provide a detailed list of parts for the apparatus as well as modeling algorithms with statistical evaluation to facilitate widespread adoption of these experimental improvements by instructors of intermediate and advanced lab courses.

Lemon, Christopher; Canagaratna, Sebastian; Gray, Jeffrey

2008-03-01

346

Time-resolved fluorometric determination of terbium in aqueous solution  

Microsoft Academic Search

The fluorescent properties of water-soluble binary and ternary complexes of terbium(III) were studied and their applications in time-resolved fluorometric analysis were tested. Solutions composed of different ..beta..-diketones, tri-n-octylphosphine oxide as the synergistic agent, and Triton X-100 as the detergent were optimized to maximize fluorescence emission in Tb measurement. The results were then compared with seven published methods which included the

Hemmilae

1985-01-01

347

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

348

Guest-host interactions investigated by time-resolved X?ray spectroscopies and scattering at MHz rates: solvation dynamics and photoinduced spin transition in aqueous Fe(bipy)3(2+).  

PubMed

We have studied the photoinduced low spin (LS) to high spin (HS) conversion of [Fe(bipy)(3)](2+) in aqueous solution. In a laser pump/X-ray probe synchrotron setup permitting simultaneous, time-resolved X-ray diffuse scattering (XDS) and X-ray spectroscopic measurements at a 3.26 MHz repetition rate, we observed the interplay between intramolecular dynamics and the intermolecular caging solvent response with better than 100 ps time resolution. On this time scale, the initial ultrafast spin transition and the associated intramolecular geometric structure changes are long completed, as is the solvent heating due to the initial energy dissipation from the excited HS molecule. Combining information from X-ray emission spectroscopy and scattering, the excitation fraction as well as the temperature and density changes of the solvent can be closely followed on the subnanosecond time scale of the HS lifetime, allowing the detection of an ultrafast change in bulk solvent density. An analysis approach directly utilizing the spectroscopic data in the XDS analysis effectively reduces the number of free parameters, and both combined permit extraction of information about the ultrafast structural dynamics of the caging solvent, in particular, a decrease in the number of water molecules in the first solvation shell is inferred, as predicted by recent theoretical work. PMID:22970732

Haldrup, K; Vank, G; Gawelda, W; Galler, A; Doumy, G; March, A M; Kanter, E P; Bordage, A; Dohn, A; van Driel, T B; Kjr, K S; Lemke, H T; Canton, S E; Uhlig, J; Sundstrm, V; Young, L; Southworth, S H; Nielsen, M M; Bressler, C

2012-10-11

349

Genesis of Gold Clusters from Mononuclear Gold Complexes on TiO[subscript 2]: Reduction and Aggregation of Gold Characterized by Time-Resolved X-Ray Absorption Spectroscopy  

SciTech Connect

Mononuclear gold complexes bonded to TiO{sub 2} were synthesized from Au(CH{sub 3}){sub 2}(C{sub 5}H{sub 7}O{sub 2}), and their decomposition and conversion into gold nanoclusters on the TiO{sub 2} surface were characterized by time-resolved X-ray absorption and infrared spectroscopies as the temperature of the sample in flowing helium was ramped up. Mass spectra of the evolved gases were also measured during this process. The results show (a) the onset of formation of CH{sub 4} as a decomposition product, (b) the reduction of Au{sup III} to Au{sup 0}, and (c) the formation of Au-Au bonds, all occurring in approximately the same temperature range (about 335-353 K), indicating that the reduction and aggregation of the supported gold are simultaneous processes facilitated by the removal of methyl ligands initially bonded to the gold. IR spectra recorded during the treatment indicate that water on the TiO{sub 2} surface may be involved in the process by reacting with methyl groups bonded to Au{sup III} to give CH{sub 4}.

Fierro-Gonzalez, Juan C.; Gates, Bruce C. (UCD)

2010-07-19

350

APD detectors for biological fluorescence spectroscopy  

NASA Astrophysics Data System (ADS)

Fluorescence spectroscopy is a very convenient and widely used method for studying the molecular background of biological processes [L. Salom, J.L. Cazeil, A. Lopez, J.F. Tocanne, Eur. Biophys. J. 27 (1998) 391-402]. Chromophores are included in the structure under study and a flash of laser light induces fluorescence (Fluorescence Recovery After Photo-bleaching), the decay of which yields information on the polarity, the speed of rotation, and the speed of diffusion as well as on the temporal and spatial evolution of interactions between molecular species. The method can even be used to study living cells [J.F. Tocanne, L. Czanne, A. Lopez, Prog. Lipid Res. 33 (1994) 203-237, L. Cezanne, A. Lopez, F. Loste, G. Parnaud, O. Saurel, P. Demange, J.F. Tocanne, Biochemistry 38 (1999) 2779-2786]. This is classically performed with a PM-based system. For biological reasons a decrease of the excitation of the cells is highly desirable. Because the fluorescence response then becomes fainter a significant improvement in detector capability would be welcome. We present here results obtained with an Avalanche Photo Diode (APD)-based system. The small sensitive area of detection allows a very significant improvement in signal/noise ratio, improvement in gain, and the opening-up of a new parameter space. With these new detectors we can begin the study of information transmission between cells through morphine receptors. This work involves both electronics engineers and biophysicists, so results and techniques in both fields will be presented here.

Mazres, S.; Borrel, V.; Magenc, C.; Courrech, J. L.; Bazer-Bachi, R.

2006-11-01

351

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

352

Temperature dependence of the absolute third-order rate constant for the reaction between K + O/sub 2/ + N/sub 2/ over the range 680-1010K studied by time-resolved atomic resonance absorption spectroscopy  

SciTech Connect

The authors present a direct kinetic study of the third-order recombination reaction K + O/sub 2/ + N/sub 2/ ..-->.. KO/sub 2/ + N/sub 2/ across the temperature range 680-1010K. K(4/sup 2/S/sub 1/2/) was generated by pulsed irradiation and monitored by time-resolved atomic resonance absorption spectroscopy in the ''single shot mode'' in the presence of O/sub 2/ and N/sub 2/ using the Rydberg transition at lambda = 404 nm (K(5/sup 2/P/sub J/) left arrow K(4/sup 2/S/sub 1/2/)). While the resulting data for k/sub 4/ can be empirically expressed within this temperature range by the form k/sub 4/(680-1010K) = (6.63 +- 0.66 X 10/sup -23/)(T/K)/sup -2.6 +-0.28/ cm/sup 6/ molecule /sup -2/ s/sup -1/, a full extrapolation based on the unimolecular rate theory was carried out in order to extend the data to flame temperatures (2000K), given the importance of potassium additives in flame inhibition. The full extrapolation across the range 200-2000K can be expressed to within 10% by ln(k/sub 4//cm/sup 6/ molecule /sup -2/ s/sup -1/) = -0.2558 (ln(T/K)/sup 2/ + 1.361 ln (T/K) - 66.14. These results are compared with data derived from measurements on a fast flow reactor which show a much smaller temperature dependence and indicate an extrapolated value for k/sub 4/ at flame temperatures significantly higher than derived from the present investigations.

Husain, D.; Lee, Y.H.

1987-05-01

353

Glucose Recognition in Vitro Using Fluorescent Spectroscopy  

SciTech Connect

Diabetes is a disease that affects over 16 million people in the USA at a cost of 100 billion dollars annually. The ability to regulate insulin delivery in people with Type 1 diabetes is imperative as is the need to manage glucose levels in all people with this disease. Our current method for monitoring glucose is a (FDA approved) minimally invasive enzymatic sensor that can measure glucose levels in vivo for three days. We are focused on developing a noninvasive implantable glucose sensor that will be interrogated by an external device. The material must be robust, easy to process, biocompatible and resistant to biofouling. In this Presentation we will discuss the development of a new polymeric matrix that can recognize physiological levels of glucose in vitro using fluorescent spectroscopy.

Noronha, G; Heiss, A M; Reilly, J R; Vachon, Jr, D J; Cary, D R; Zaitseva, N P; Reibold, R A; Lane, S M; Peyser, T A; Satcher, J H

2001-04-25

354

The standard deviation in fluorescence correlation spectroscopy.  

PubMed Central

The standard deviation (SD) in fluorescence correlation spectroscopy (FCS) has been mostly neglected in applications. However, the knowledge of the correct SD is necessary for an accurate data evaluation, especially when fitting theoretical models to experimental data. In this work, an algorithm is presented that considers the essential features of FCS. It allows prediction of the performance of FCS measurements in various cases, which is important for finding optimal experimental conditions. The program calculates the SD of the experimental autocorrelation function online. This procedure leads to improved parameter estimation, compared to currently used theoretical approximations for the SD. Three methods for the calculation of the SD are presented and compared to earlier analytical solutions (D. E. Koppel. 1974. Phys. Rev. A. 10:1938-1945.), calculation directly from fluorescence intensity values, by averaging several FCS measurements, or by dividing one measurement into a set of shorter data packages. Although the averaging over several measurements yields accurate estimates for the SD, the other two methods are considerably less time consuming, can be run online, and yield comparable results. PMID:11371471

Wohland, T; Rigler, R; Vogel, H

2001-01-01

355

Development of a single-shot CCD-based data acquisition system for time-resolved X-ray photoelectron spectroscopy at an X-ray free-electron laser facility.  

PubMed

In order to utilize high-brilliance photon sources, such as X-ray free-electron lasers (XFELs), for advanced time-resolved photoelectron spectroscopy (TR-PES), a single-shot CCD-based data acquisition system combined with a high-resolution hemispherical electron energy analyzer has been developed. The system's design enables it to be controlled by an external trigger signal for single-shot pump-probe-type TR-PES. The basic performance of the system is demonstrated with an offline test, followed by online core-level photoelectron and Auger electron spectroscopy in 'single-shot image', 'shot-to-shot image (image-to-image storage or block storage)' and `shot-to-shot sweep' modes at soft X-ray undulator beamline BL17SU of SPring-8. In the offline test the typical repetition rate for image-to-image storage mode has been confirmed to be about 15?Hz using a conventional pulse-generator. The function for correcting the shot-to-shot intensity fluctuations of the exciting photon beam, an important requirement for the TR-PES experiments at FEL sources, has been successfully tested at BL17SU by measuring Au 4f photoelectrons with intentionally controlled photon flux. The system has also been applied to hard X-ray PES (HAXPES) in `ordinary sweep' mode as well as shot-to-shot image mode at the 27?m-long undulator beamline BL19LXU of SPring-8 and also at the SACLA XFEL facility. The XFEL-induced Ti 1s core-level spectrum of La-doped SrTiO3 is reported as a function of incident power density. The Ti 1s core-level spectrum obtained at low power density is consistent with the spectrum obtained using the synchrotron source. At high power densities the Ti 1s core-level spectra show space-charge effects which are analysed using a known mean-field model for ultrafast electron packet propagation. The results successfully confirm the capability of the present data acquisition system for carrying out the core-level HAXPES studies of condensed matter induced by the XFEL. PMID:24365935

Oura, Masaki; Wagai, Tatsuya; Chainani, Ashish; Miyawaki, Jun; Sato, Hiromi; Matsunami, Masaharu; Eguchi, Ritsuko; Kiss, Takayuki; Yamaguchi, Takashi; Nakatani, Yasuhiro; Togashi, Tadashi; Katayama, Tetsuo; Ogawa, Kanade; Yabashi, Makina; Tanaka, Yoshihito; Kohmura, Yoshiki; Tamasaku, Kenji; Shin, Shik; Ishikawa, Tetsuya

2014-01-01

356

Time-resolved blue-green fluorescence of sugar beet ( Beta vulgaris L.) leaves. Spectroscopic evidence for the presence of ferulic acid as the main fluorophore of the epidermis  

Microsoft Academic Search

Sugar beet (Beta uulgaris L.) leaves emit blue-green fluorescence when excited with ultraviolet light. Comparative spectral analysis showed that the blue-green fluorescence of leaves, on both the adaxial and the abaxial side, was dominated by the blue-green fluorescence of the epidermis. A detailed investigation of the adaxial epidermis and of possible candidates for its blue-green fluorescence was carried out. The

Fermn Morales; Zoran G. Cerovic; Ismael Moya

1996-01-01

357

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

358

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

359

Planetary Surface Analysis Using Fast Laser Spectroscopic Techniques: Combined Microscopic Raman, LIBS, and Fluorescence Spectroscopy  

NASA Astrophysics Data System (ADS)

In situ exploration of planetary surfaces has to date required multiple techniques that, when used together, yield important information about their formation histories and evolution. We present a time-resolved laser spectroscopic technique that could potentially collect complementary sets of data providing information on mineral structure, composition, and hydration state. Using a picosecond-scale pulsed laser and a fast time-resolved detector we can simultaneously collect spectra from Raman, Laser Induced Breakdown Spectroscopy (LIBS), and fluorescence emissions that are separated in time due to the unique decay times of each process. The use of a laser with high rep rate (40 KHz) and low pulse energy (1 ?J/pulse) allows us to rapidly collect high signal to noise Raman spectra while minimizing sample damage. Increasing the pulse energy by about an order of magnitude creates a microscopic plasma near the surface and enables the collection of LIBS spectra at an unusually high rep rate and low pulse energy. Simultaneously, broader fluorescence peaks can be detected with lifetimes varying from nanosecond to microsecond. We will present Raman, LIBS, and fluorescence spectra obtained on natural mineral samples such as sulfates, clays, pyroxenes and carbonates that are of interest for Mars mineralogy. We demonstrate this technique using a photocathode-based streak camera detector as well as a newly-developed solid state Single Photon Avalanche Diode (SPAD) sensor array based on Complementary Metal-Oxide Semiconductor (CMOS) technology. We will discuss the impact of system design and detector choice on science return of a potential planetary surface mission, with a specific focus on size, weight, power, and complexity. The research described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA).

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

2011-12-01

360

Fluorescence spectroscopy for noninvasive glucose measurement  

NASA Astrophysics Data System (ADS)

The interaction between gold nanoparticles and glucose and its effect on the fluorescence spectrum of nanoparticles were investigated experimentally. It was observed after this interaction the intensity of fluorescence peak becomes weaker and red shifted.

Bagheri, Z.; Massudi, R.; Ghanavi, J.; Latifi, H.

2013-06-01

361

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

362

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

363

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

364

TOPICAL REVIEW: Single-molecule fluorescence spectroscopy of biomolecular folding  

Microsoft Academic Search

Single-molecule fluorescence spectroscopy is emerging as an important tool for studying biomolecular folding dynamics. Its usefulness stems from its ability to directly map heterogeneities in folding pathways and to provide information about the energy landscape of proteins and ribonucleic acid (RNA) molecules. Single-molecule fluorescence techniques relevant for folding studies, including methods for trapping and immobilizing molecules, are described and compared

Gilad Haran

2003-01-01

365

Time-domain laser-induced fluorescence spectroscopy apparatus for clinical diagnostics  

NASA Astrophysics Data System (ADS)

We report the design and development of a compact optical fiber-based apparatus for in situ time-resolved laser-induced fluorescence spectroscopy (tr-LIFS) of biological systems. The apparatus is modular, optically robust, and compatible with the clinical environment. It incorporates a dual output imaging spectrograph, a gated multichannel plate photomultiplier (MCP-PMT), an intensified charge-coupled-device (ICCD) camera, and a fast digitizer. It can accommodate various types of light sources and optical fiber probes for selective excitation and remote light delivery/collection as required by different applications. The apparatus allows direct recording of the entire fluorescence decay with high sensitivity (nM range fluorescein dye concentration with signal-to-noise ratio of 46) and with four decades dynamic range. It is capable of resolving a broad range of fluorescence lifetimes from hundreds of picoseconds (as low as 300 ps) using the MCP-PMT coupled to the digitizer to milliseconds using the ICCD. The data acquisition and analysis process is fully automated, enabling fast recording of fluorescence intensity decay across the entire emission spectrum (0.8 s per wavelength or 40 s for a 200 nm wavelength range at 5 nm increments). The spectral and temporal responses of the apparatus were calibrated and its performance was validated using fluorescence lifetime standard dyes (Rhodamin B, 9-cyanoanthracene, and rose Bengal) and tissue endogenous fluorophores (elastin, collagen, nicotinamide adenine dinucleotide, and flavin adenine dinucleotide). Fluorescence decay lifetimes and emission spectra of all tested compounds measured with the current tr-LIFS apparatus were found in good agreement with the values reported in the literature. The design and performance of tr-LIFS apparatus have enabled in vivo studies of atherosclerotic plaques and brain tumors.

Fang, Qiyin; Papaioannou, Thanassis; Jo, Javier A.; Vaitha, Russel; Shastry, Kumar; Marcu, Laura

2004-01-01

366

Multiphoton excited fluorescence spectroscopy of biomolecular systems  

Microsoft Academic Search

Recent work on the emerging application of multiphoton excitation to fluorescence studies of biomolecular dynamics and structure is reviewed. The fundamental principles and experimental techniques of multiphoton excitation are outlined, fluorescence lifetimes, anisotropy and spectra in membranes, proteins, hydrocarbons, skin, tissue and metabolites are featured, and future opportunities are highlighted.

David J. S. Birch

2001-01-01

367

Multiphoton cascade absorption in single molecule fluorescence saturation spectroscopy.  

PubMed

Saturation spectroscopy is a relevant method to investigate photophysical parameters of single fluorescent molecules. Nevertheless, the impact of a gradual increase, over a broad range, of the laser excitation on the intramolecular dynamics is not completely understood, particularly concerning their fluorescence emission (the so-called brightness). Thus, we propose a comprehensive theoretical and experimental study to interpret the unexpected evolution of the brightness with the laser power taking into account the cascade absorption of two and three photons. Furthermore, we highlight the key role played by the confocal observation volume in fluorescence saturation spectroscopy of single molecules in solution. PMID:23521543

Winckler, Pascale; Jaffiol, Rodolphe

2013-05-01

368

Quantum dots fluorescence quantum yield measured by Thermal Lens Spectroscopy.  

PubMed

An essential parameter to evaluate the light emission properties of fluorophores is the fluorescence quantum yield, which quantify the conversion efficiency of absorbed photons to emitted photons. We detail here an alternative nonfluorescent method to determine the absolute fluorescence quantum yield of quantum dots (QDs). The method is based in the so-called Thermal Lens Spectroscopy (TLS) technique, which consists on the evaluation of refractive index gradient thermally induced in the fluorescent material by the absorption of light. Aqueous dispersion carboxyl-coated cadmium telluride (CdTe) QDs samples were used to demonstrate the Thermal Lens Spectroscopy technical procedure. PMID:25103802

Estupin-Lpez, Carlos; Dominguez, Christian Tolentino; Cabral Filho, Paulo E; Fontes, Adriana; de Araujo, Renato E

2014-01-01

369

Time-resolved fluorometric determination of terbium in aqueous solution  

SciTech Connect

The fluorescent properties of water-soluble binary and ternary complexes of terbium(III) were studied and their applications in time-resolved fluorometric analysis were tested. Solutions composed of different ..beta..-diketones, tri-n-octylphosphine oxide as the synergistic agent, and Triton X-100 as the detergent were optimized to maximize fluorescence emission in Tb measurement. The results were then compared with seven published methods which included the use of the following respective solutions, ethylenediamine-N,N'-bis((o-hydroxy-phenyl)acetic acid), dipicolinic acid, iminodiacetic acid with Tiron, EDTA with Tiron, EDTA with 2,3-dihydroxynaphthalene, EDTA with sulfosalicylic acid, and EDTA with salicylate. Fluorinated aliphatic ..beta..-diketones showed the most promising properties in acidic solution. They were especially suitable for use in time-resolved fluorometric analyses where Tb was used as the label after being conjugated to the analyte via bifunctional complexones. An acidic pH is required for Tb release before conversion into a fluorescent chelate. The applicability of the developed measurement solutions to the measurement of Eu was also tested. 22 references, 3 figures, 7 tables.

Hemmilae, I.

1985-07-01

370

Fluorescence spectroscopy of gastrointestinal tumors using ?-ALA  

NASA Astrophysics Data System (ADS)

In the recent study delta-aminolevulinic acid/Protoporphyrin IX (?-ALA/PpIX) is used as fluorescent marker for dysplasia and tumor detection in esophagus and stomach. The ?-ALA is administered per os six hours before measurements at dose 20mg/kg weight. High-power light-emitting diode at 405 nm is used as an excitation source. Special opto-mechanical device is built to use the light guide of standard video-endoscopic system (Olimpus Corp.). Through endoscopic instrumental channel a fiber is applied to return information about fluorescence to microspectrometer (USB4000, OceanOptics Inc.). The fluorescence detected from tumor sites has very complex spectral origins. It consists of autofluorescence, fluorescence from exogenous fluorophores and re-absorption from the chromophores accumulated in the tissue investigated. Mucosa autofluorescence lies at 450-600 nm region. The fluorescence of PpIX is clearly pronounced at the 630-710 nm region. Deep minima in the tumor fluorescence signals are observed in the region 540-575 nm, related to hemoglobin re-absorption. Such high hemoglobin content is an indication of the tumors neovascularisation and it is clearly pronounced in all dysplastic and tumor sites investigated. The lack of fluorescence peaks in the red spectral area for normal mucosa is an indication for selective accumulation of ?-ALA/PpIX only in abnormal sites and gives high contrast when lesion borders are determined from clinicians during video observation in the process of diagnostic procedure. Very good correlation between fluorescence signals and histology examination results of the lesions investigated is achieved.

Borisova, E. G.; Vladimirov, B. G.; Angelov, I. G.; Avramov, L. A.

2007-03-01

371

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

372

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

373

Impurity studies in fusion devices using laser-fluorescence-spectroscopy  

SciTech Connect

Resonance fluorescence excitation of neutral atoms using tunable radiation from dye lasers offers a number of unique advantages for impurity studies in fusion devices. Using this technique, it is possible to perform local, time-resolved measurements of the densities and velocity distributions of metallic impurities in fusion devices without disturbing the plasma. Velocities are measured by monitoring the fluorescence intensity while tuning narrow bandwidth laser radiation through the Doppler - broadened absorbtion spectrum of the transition. The knowledge of the velocity distribution of neutral impurities is particularly useful for the determination of impurity introduction mechanisms. The laser fluorescence technique will be described in terms of its application to metallic impurities in fusion devices and related laboratory experiments. Particular attention will be given to recent results from the ISX-B tokamak using pulsed dye lasers where detection sensitivities for neutral Fe of 10/sup 6/ atoms/cm/sup 3/ with a velocity resolution of 600 m/sec (0.1 eV) have been achieved. Techniques for exciting plasma particles (H,D) will also be discussed.

Husinsky, W.R.

1980-08-01

374

Molecular origin of time-dependent fluorescence shifts in proteins  

Microsoft Academic Search

Time-resolved fluorescence spectroscopy is used increasingly to probe molecular motions at the aqueous interfaces of biological macromolecules and membranes. By recording the time variation of the fluorescence frequency, thermal atomic fluctuations in the vicinity of the chromophore can be probed. From such fluorescence Stokes shift (FSS) experiments, it has been inferred that water motions in the hydration layer are slowed

Lennart Nilsson; Bertil Halle

2005-01-01

375

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

376

Fluorescence spectroscopy characteristics of nasopharyngeal carcinoma cells  

NASA Astrophysics Data System (ADS)

The spectroscopic characteristics of autofluorescence for the nasopharyngeal carcinoma in vitro and nasopharyngeal carcinoma cells (CNE cells) were investigated, respectively. The characteristics of fluorescence agree with the results that deduced from the nasopharyngeal carcinoma in vivo, and the optimal excitation-emission wavelength was found at 350-500 nm. Secondly, the selectivity and optimal time for optical diagnosis of nasopharyngeal carcinoma by using the new photosensitizer of Hematoporphyrin Monomethyl Ether (HMME) has been demonstrated and determined by incubated CNE cells with HMME. The fluorescence emission peaks of 615 and 675 nm characterized the selective accumulation of HMME in CNE cells, and the optimal time for optical diagnostics with HMME was about 140 mins after clinic intravenous administration. Moreover, when the concentration of HMME in CNE cells below 32 ?g/mL, the fluorescence intensity versus HMME concentration reveals an obvious linearity. Finally, the fluorescence intensity of CNE cells increases linearly with concentration over the entire range up to 9.0E+05 cells/mL. These results can be used to helpfully improve the accuracy of optical diagnosis for nasopharyngeal carcinoma.

Li, Buhong; Zhang, Zhenxi; Xie, Shusen; Lin, Huiyun

2005-01-01

377

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

378

X-ray Fluorescence Spectroscopy of Novel Materials  

Microsoft Academic Search

This review focuses on the capabilities and potential of soft x-ray fluorescence spectroscopy for the study of the electronic\\u000a structure and chemical bonding of novel materials. The basic principle of x-ray fluorescence measurements using synchrotron\\u000a radiation and the corresponding instrumentation issues are outlined. Particular attention is given to x-ray spectroscopic\\u000a studies of the electronic structure and characterization of nanostructures, thin

E. Z. Kurmaev

2005-01-01

379

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

380

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

381

Diagnostic fluorescence spectroscopy of oral mucosa  

NASA Astrophysics Data System (ADS)

Autofluorescence characteristics of normal, dysplastic, and malignant squamous tissues from the oral cavity were measured with a spectrofluorometer in the excitation range of 250 - 500 nm and emission range of 350 - 750 nm. Fluorescence excitation-emission matrices (EEM) were obtained from samples collected from patients in the clinic and in the operating room. The same samples were submitted for histopathological examination following spectroscopic measurements. The contour plots obtained from the EEMs of the samples showed consistent differences between normal and abnormal tissues. All the abnormal samples showed enhanced red region (> 600 nm) fluorescence with a prominent peak at 635 nm, when excited by 410 nm light. A ratio contour plot (abnormal/normal) enhanced spectral differences in the red region. A fiber-optic based spectrofluorometer for EEM measurements is being developed for further investigations.

Roy, Krishnendu; Bottrill, Ian; Ingrams, Duncan R.; Pankratov, Michail M.; Rebeiz, Elie E.; Woo, Peak; Kabani, Sadru; Shapshay, Stanley M.; Manoharan, Ramasamy; Itzkan, Irving; Feld, Michael S.

1995-05-01

382

Time resolved laser-induced plasma dynamics  

NASA Astrophysics Data System (ADS)

The structure and evolution of the laser-induced vapor plume and shockwave were measured from femtosecond time resolved shadowgraph images. By changing the wavelength of the probe beam (400 and 800 nm), differences in the opacity of the vapor plume were measured as a function of delay time from the ablation laser pulse. The evolution of the temperature and electron number density during and after the ablation laser pulse were determined and compared for ablation in argon and helium background gases. A laser supported detonation wave (LSD) observed for ablation in argon, blocks the incoming laser energy and generates a high-pressure region above the vapor plume.

Mao, Xianglei; Wen, Sy-bor; Russo, Richard E.

2007-05-01

383

"FluSpec": A Simulated Experiment in Fluorescence Spectroscopy  

ERIC Educational Resources Information Center

The "FluSpec" educational software package is a fully contained tutorial on the technique of fluorescence spectroscopy as well as a simulator on which experiments can be performed. The procedure for each of the experiments is also contained within the package along with example analyses of results that are obtained using the software.

Bigger, Stephen W.; Bigger, Andrew S.; Ghiggino, Kenneth P.

2014-01-01

384

Fluorescence correlation spectroscopy based upon two-photon excitation  

NASA Astrophysics Data System (ADS)

Fluorescence correlation spectroscopy (FCS) is a powerful tool for measurement of biological dynamic processes. In this studying, a two-photon excitation fluorescence correlation spectroscopy (TP-FCS) system was set up depending on a part of optical block and detector of the multi-photon excitation fluorescence microscope (MPLFM). The phenomenon "photon-burst" was observed from the TP-FCS system. Meanwhile, the diffusion coefficient of rhodamine B molecule in sucrose aqueous solution was calculated. It was proved that TP-FCS is especially suited for integration into MPEFM accordingly to yield a hybride-technology with the peculiarities of the individual technique and the advantage of mutual synergistic effects. The fusion of both techniques seems to be reasonable and desirable to reduce costs.

Liu, Yafeng; Chen, Tongsheng; Luo, Qingming

2003-12-01

385

Fluorescence lifetime-based sensing and imaging  

Microsoft Academic Search

Time-resolved fluorescence spectroscopy is presently regarded as a research tool in biochemistry, biophysics and chemical physics. However, time-resolved methods can also be used for chemical sensing. Lifetime-based sensing has several advantages over intensity-based methods. Since the lifetime is independent of the total probe intensity, its measurement can provide quantitative sensing of many analytes without the requirement for wavelength-ratiometric probes. Analytes

Henryk Szmacinski; Joseph R. Lakowicz

1995-01-01

386

Time Resolved Deposition Measurements in NSTX  

SciTech Connect

Time-resolved measurements of deposition in current tokamaks are crucial to gain a predictive understanding of deposition with a view to mitigating tritium retention and deposition on diagnostic mirrors expected in next-step devices. Two quartz crystal microbalances have been installed on NSTX at a location 0.77m outside the last closed flux surface. This configuration mimics a typical diagnostic window or mirror. The deposits were analyzed ex-situ and found to be dominantly carbon, oxygen, and deuterium. A rear facing quartz crystal recorded deposition of lower sticking probability molecules at 10% of the rate of the front facing one. Time resolved measurements over a 4-week period with 497 discharges, recorded 29.2 {micro}g/cm{sup 2} of deposition, however surprisingly, 15.9 {micro}g/cm{sup 2} of material loss occurred at 7 discharges. The net deposited mass of 13.3 {micro}g/cm{sup 2} matched the mass of 13.5 {micro}g/cm{sup 2} measured independently by ion beam analysis. Monte Carlo modeling suggests that transient processes are likely to dominate the deposition.

C.H. Skinner; H. Kugel; A.L. Roquemore; J. Hogan; W.R. Wampler; the NSTX team

2004-08-03

387

Time-resolved interaction of polar solvents with excited pyrylium cations  

NASA Astrophysics Data System (ADS)

The time-resolved fluorescence spectra of two pyrylium-ion derivatives have been investigated. In the temperature range 77 to 190 K, a red-shift of the fluorescence spectra of the order of 25-70 nm is observed and assigned to a fast solvent relaxation process. Time-resolved experiments carried out at 160 K showed a rapid decrease of the emission from the non-relaxed excited state at short wavelengths and a corresponding build-up of the emission of the relaxed one at longer wavelengths. At 120 K emission from the non-relaxed electronic state is predominant.

Wintgens, Veronique; Pouliquen, Joseph; Valat, Pierre; Kossanyi, Jean; Canonica, Silvio; Wild, Urs P.

1986-01-01

388

Application of photoacoustic, photothermal and fluorescence spectroscopies in signal enhancement and the kinetics, chemistry and photophysics of several dyes  

SciTech Connect

Modified photoacoustic and photothermal spectroscopies are applied in analytical studies of liquid and solid systems. Quenching of benzophenone by potassium iodide is used to demonstrate application of time resolved photothermal spectroscopies in study of fast (submicrosecond) deexcitation processes. Inherently weak X-ray photoacoustic signals at a synchrotron are enhanced by the introduction of a volatile liquid into a gas-microphone photoacoustic cell. Traditionally, photoacoustic signals have been detected either by gas coupling with a microphone or with a piezoelectric detector. However, optically detected photoacoustic signals have been used in the determination of physical properties of a liquid sample system and are successfully applied to the study of deexcitation processes of a number of dye molecules. Photothermal beam deflection photoacoustic (PBDPA), fluorescence and absorbance measurements are utilized to study the chemistry and photophysics of cresyl violet in aqueous, aqueous micellar and methanolic solutions. A concentration dependence of the fluorescence quantum yield of cresyl violet is investigated. Aspects of chemistry and photophysics relating to potential use of several diazo dyes as photothermal sensitizing dyes in photodynamic therapy are explored experimentally and discussed. Photothermal beam deflection, fluorescence and absorbance measurements are again utilized. The dyes are found to have a number of interesting chemical and photophysical properties. They are also determined to be ideal photothermal sensitizing dye candidates.

Isak, S.J.

1992-06-01

389

Fluorescence Lifetime Correlation Spectroscopy (FLCS): Concepts, Applications and Outlook  

PubMed Central

Fluorescence Lifetime Correlation Spectroscopy (FLCS) is a variant of fluorescence correlation spectroscopy (FCS), which uses differences in fluorescence intensity decays to separate contributions of different fluorophore populations to FCS signal. Besides which, FLCS is a powerful tool to improve quality of FCS data by removing noise and distortion caused by scattered excitation light, detector thermal noise and detector after pulsing. We are providing an overview of, to our knowledge, all published applications of FLCS. Although these are not numerous so far, they illustrate possibilities for the technique and the research topics in which FLCS has the potential to become widespread. Furthermore, we are addressing some questions which may be asked by a beginner user of FLCS. The last part of the text reviews other techniques closely related to FLCS. The generalization of the idea of FLCS paves the way for further promising application of the principle of statistical filtering of signals. Specifically, the idea of fluorescence spectral correlation spectroscopy is here outlined. PMID:23202928

Kapusta, Peter; Machan, Radek; Benda, Ales; Hof, Martin

2012-01-01

390

Recent applications of fluorescence correlation spectroscopy in live systems.  

PubMed

Fluorescence correlation spectroscopy (FCS) is a widely used technique in biophysics and has helped address many questions in the life sciences. It provides important advantages compared to other fluorescence and biophysical methods. Its single molecule sensitivity allows measuring proteins within biological samples at physiological concentrations without the need of overexpression. It provides quantitative data on concentrations, diffusion coefficients, molecular transport and interactions even in live organisms. And its reliance on simple fluorescence intensity and its fluctuations makes it widely applicable. In this review we focus on applications of FCS in live samples, with an emphasis on work in the last 5 years, in the hope to provide an overview of the present capabilities of FCS to address biologically relevant questions. PMID:24726724

Mach?, Radek; Wohland, Thorsten

2014-10-01

391

Fluorescence Correlation Spectroscopy of Finite-Sized Particles  

PubMed Central

A theory is presented to study fluorescence correlation spectroscopy for particles with size comparable to the beam waist of the observation volume. Analytical correlation curves are derived for some experimentally interesting particle geometries. It is found that the finiteness of the particle generally decreases the value of the correlation amplitude and increases the correlation time compared to a point particle model. Furthermore, not only the size but also the distribution of fluorophores affects the shape of the correlation function. This is experimentally demonstrated with surface and internally labeled fluorescent spheres. In addition, experiments are performed on fluorescent spheres of different radii to validate the model by comparing the results to theoretical predictions. PMID:18065475