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Excitation Light (excitation + light)
Selected AbstractsPlasmonic Enhancement or Energy Transfer?ADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Its Potential for Light-Emitting Devices, Lanthanide-Doped Silicate Glasses, On the Luminescence of Gold-, Silver- Abstract With the technique of synchrotron X-ray activation, molecule-like, non-plasmonic gold and silver particles in soda-lime silicate glasses can be generated. The luminescence energy transfer between these species and lanthanide(III) ions is studied. As a result, a significant lanthanide luminescence enhancement by a factor of up to 250 under non-resonant UV excitation is observed. The absence of a distinct gold and silver plasmon resonance absorption, respectively, the missing nanoparticle signals in previous SAXS and TEM experiments, the unaltered luminescence lifetime of the lanthanide ions compared to the non-enhanced case, and an excitation maximum at 300,350,nm (equivalent to the absorption range of small noble metal particles) indicate unambiguously that the observed enhancement is due to a classical energy transfer between small noble metal particles and lanthanide ions, and not to a plasmonic field enhancement effect. It is proposed that very small, molecule-like noble metal particles (such as dimers, trimers, and tetramers) first absorb the excitation light, undergo a singlet-triplet intersystem crossing, and finally transfer the energy to an excited multiplet state of adjacent lanthanide(III) ions. X-ray lithographic microstructuring and excitation with a commercial UV LED show the potential of the activated glass samples as bright light-emitting devices with tunable emission colors. [source] Development of an Optrode for Intramural Multisite Optical Recordings of Vm in the HeartJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2003JONATHAN L. BYARS M.S. Introduction: Optical mapping of transmembrane potential (Vm) is an important tool in the investigation of impulse propagation in the heart. It provides valuable information about spatiotemporal changes of Vm that cannot be obtained by other techniques, but it presently is limited to measurements from the heart surfaces. Therefore, the goal of this work was to develop a technique for intramural multisite optical measurements of Vm using fiberoptic technology. Methods and Results: An optrode, a bundle of thin optical fibers, was developed for measuring intramural optical signals at multiple sites in the heart. The optrode consisted of seven fibers with diameter of 225 ,m arranged in a hexagonal pattern that were used to deliver excitation light to the myocardium, to collect the emitted fluorescence, and to project the light onto a 16 × 16 array of photodiode detectors. Rabbit hearts were stained with the Vm -sensitive dye RH-237. Fluorescence was excited using a 100-W Hg lamp. Intramural action potentials were recorded at multiple sites separated by 2 mm inside the left ventricle. Signal-to-noise (RMS) ratio was 21.2 ± 12 (n = 7) without averaging or ratiometry and with negligible cross-talk (<1.9%) between the neighboring photodiodes. The size of the recording area for an individual fiber was estimated at approximately 0.8 mm. Conclusion: These data demonstrate feasibility of multisite transmural measurements of Vm without signal averaging and ratiometry. This technique might become useful in studies of transmural impulse conduction during arrhythmias and defibrillation. (J Cardiovasc Electrophysiol, Vol. 14, pp. 1196-1202, November 2003) [source] Effects of lodide on the Fluorescence and Activity of the Hydroperoxyflavin Intermediate of Vibrio harveyi Luciferase,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2005Shouqin Huang ABSTRACT The 4a-hydroperoxy-4a,5-dihydroFMN intermediate (II or HFOOH) of Vibrio harveyi luciferase is known to transform from a low quantum yield IIx to a high quantum yield (,max 485 nm, uncorrected) IIy fluorescent species on exposure to excitation light. Similar results were observed with II prepared from the ,H44A luciferase mutant, which is very weak in bioluminescence activity. Because of the rapid decay of the ,H44A II, its true fluorescence was obscured by the more intense 520 nm fluorescence (uncorrected) from its decay product oxidized flavin mononucleotide (FMN). Potassium iodide (KI) at 0.2 M was effective in quenching the FMN fluorescence, leaving the 485 nm fluorescence of II from both the wild-type (WT) and ,H44A luciferase readily detectable. For both II species, the luciferase-bound peroxyflavin was well shielded from KI quenching. KI also enhanced the decay rates of both the WT and ,H44A II. For ,H44A, the transformation of IIx to IIy can be induced by KI in the dark, and it is proposed to be a consequence of a luciferase conformational change. The WT II formed a bioluminescence-inactive complex with KI, resulting in two distinct decay time courses based on absorption changes and decreases of bioluminescence activity of II. [source] Integrated fluorescence sensor based on ring-shaped organic photodiodesPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 7 2010Bernhard Lamprecht Abstract We demonstrate a novel sensor type, which is based on the monolithic integration of luminescent optical sensor spots together with ring-shaped thin-film organic photodiodes on one substrate. The organic photodiodes serve as integrated fluorescence detectors, simplifying the detection system by minimizing the number of required optical components. The proposed concept enables filter-less discrimination between excitation light and generated fluorescence light. The functionality of the concept is demonstrated by an integrated oxygen sensor, exhibiting excellent performance. The sensor spots are excited by an assembled organic light emitting diode. The integrated optical sensor platform is suitable for the parallel detection of multiple parameters. Sensor schemes for the analytical parameters carbon dioxide, temperature and ammonia, are proposed. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Photoluminescence and time-resolved photoluminescence in Cu(In,Ga)Se2 thin films and solar cellsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2009Sho Shirakata Abstract Photoluminescence (PL) and time-resolved PL (TR-PL) studies have been carried out on Cu(In,Ga)Se2 (CIGS) thin films and solar cells (ZnO/CdS/CIGS) to study the recombination of the photo-excited carriers. The CIGS solar cells exhibited intense near-band-edge (NBE) PL compared with the CIGS films by two orders of magnitude. PL decay time of the cell is strongly dependent on the repetition frequency of the excitation light. PL decay time of the cell is longer than that of the corresponding CIGS thin film. The chemical bath deposition of the CdS buffer layer on CIGS leads to changes in PL intensity, defect-related PL and the PL decay time. They are discussed with relation to the substitution of Cd atom at the Cu site at the Cu-deficient surface of CIGS thin film. Under the open circuit condition, NBE-PL is stronger and the decay time is longer compared with those under the short circuit condition. PL of the cell under the load was examined, and PL intensity and PL decay time are related to the photovoltage during PL measurements. Low temperature PL suggests that the Cd diffusion during the CBD process is pronounced for low Ga content CIGS. The authors demonstrate the effectiveness of PL as a powerful non-destructive device and photovoltaic characterization methods of CIGS solar cells. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Laser-induced formation of nonradiative centers observed by two-wavelength excited photoluminescencePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008H. Ogawa Abstract By observing an intensity change of photoluminescence (PL) due to the addition of a below-gap excitation light (BGE effect), a quantitative determination of nonradiative recombination (NRR) centers becomes possible. We observed an irreversible decrease of the BGE effect, together with a distinct PL quenching, when a GaN/AlGaN quantum well was irradiated by a Nd:YAG laser (1.17 eV) in addition to a D2 lamp (4.88 eV). The decrease is considered to be due to the formation of a NRR center at sample surface. An equivalent rate equation analysis explained both of the experimental change rather well. The observation of a defect formation enables us to understand the nature of NRR centers more dynamically, thus it is effective for determining the origin of the defect and optimizing the growth condition in nitride-based materials. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The effect of Polbax extract on lipofuscin accumulation in cultured neonatal rat cardiac myocytesPHYTOTHERAPY RESEARCH, Issue 2 2002Alexei Terman Abstract Polbax®, a water-soluble extract of fresh pollen grains and pistils, was tested for its ability to influence the accumulation of lipofuscin (age pigment) in cultured neonatal rat cardiac myocytes. Exposure for 3 weeks to Polbax at concentrations of 0.1, 1.0 or 10,mg/L decreased lipofuscin accumulation morphometrically assayed using laser scanning microscopy images (green excitation light) of formaldehyde-fixed cells, by 24%, 41% or 43%, respectively. Based on the knowledge that oxidative stress and iron-catalysed peroxidation play an important role in lipofuscinogenesis, we suggest that Polbax may slow lipofuscin formation due to antioxidant activities, perhaps involving intralysosomal dismutation of superoxide produced by autophagocytosed mitochondria and/or iron-chelation. Copyright © 2002 John Wiley & Sons, Ltd. [source] Calmodulin binding to M-type K+ channels assayed by TIRF/FRET in living cellsTHE JOURNAL OF PHYSIOLOGY, Issue 9 2008Manjot Bal Calmodulin (CaM) binds to KCNQ2,4 channels within their carboxy termini, where it regulates channel function. The existing data have not resolved the Ca2+ dependence of the interaction between the channels and CaM. We performed glutathione S-transferase (GST)-pull-down assays between purified KCNQ2,4 carboxy termini and CaM proteins to determine the Ca2+ dependence of the interaction in vitro. The assays showed substantial Ca2+ dependence of the interaction of the channels with wild-type (WT) CaM, but not with dominant-negative (DN) CaM. To demonstrate CaM,channel interactions in individual living cells, we performed fluorescence resonance energy transfer (FRET) between ECFP-tagged KCNQ2,4 channels and EYFP-tagged CaM expressed in CHO cells, performed under total internal reflection fluorescence (TIRF) microscopy, in which excitation light only penetrates several hundred nanometres into the cell, thus isolating membrane events. FRET was assayed between the channels and either WT or DN CaM, performed under conditions of normal [Ca2+]i, low [Ca2+]i or high [Ca2+]i induced by empirically optimized bathing solutions. The FRET data suggest a strong Ca2+ dependence for the interaction between WT CaM and KCNQ2, but less so for KCNQ3 and KCNQ4. FRET between all KCNQ2,4 channels and DN CaM was robust, and not significantly Ca2+ dependent. These data show interactions between CaM and KCNQ channels in living cells, and suggest that the interactions between KCNQ2,4 channels and CaM are likely to have Ca2+ -dependent and Ca2+ -independent components. [source] Efficient UV detection of protein crystals enabled by fluorescence excitation at wavelengths longer than 300,nmACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 4 2010Karsten Dierks It is well known that most proteins and many other biomolecules fluoresce when illuminated with UV radiation, but it is also commonly accepted that utilizing this property to detect protein crystals in crystallization setups is limited by the opacity of the materials used to contain and seal them. For proteins, this fluorescence property arises primarily from the presence of tryptophan residues in the sequence. Studies of protein crystallization results in a variety of setup configurations show that the opacity of the containment hardware can be overcome at longer excitation wavelengths, where typical hardware materials are more transparent in the UV, by the use of a powerful UV-light source that is effective in excitation even though not at the maximum of the excitation response. The results show that under these circumstances UV evaluation of crystallization trials and detection of biomolecular crystals in them is not limited by the hardware used. It is similarly true that a deficiency in tryptophan or another fluorescent component that limits the use of UV light for these purposes can be effectively overcome by the addition of fluorescent prostheses that bind to the biomolecule under study. The measurements for these studies were made with a device consisting of a potent UV-light source and a detection system specially adapted (i) to be tunable via a motorized and software-controlled absorption-filter system and (ii) to convey the excitation light to the droplet or capillary hosting the crystallization experiment by quartz-fibre light guides. [source] Subminute and sensitive determination of the neurotransmitter serotonin in urine by capillary electrophoresis with laser-induced ,uorescence detectionBIOMEDICAL CHROMATOGRAPHY, Issue 7 2004David Arráez Román Abstract In this work, a sub-minute and sensitive capillary electrophoresis with laser-induced ,uorescence (CE-LIF) method was developed for the analysis and quantitation of the neurotransmitter 5-hydroxytryptamine (5-HT) or serotonin in urine. The method involves precolumn derivatization with ,uorescein isothiocyanate isomer I (FITC) using an excitation light from an argon ion laser of 488 nm and a 520 nm band pass emission ,lter. Different variables that affect derivatization (pH, FITC concentration, reaction time and temperature) and separation (buffer concentration, pH, applied voltage and injection time) were studied. The linear dynamic range obtained was between 0 and 188 nm with a detection limit of 16 nm with a RSD between 2 and 9%. The applicability of the proposed method was demonstrated by analysis of 5-HT in human urine, establishing a concentration of 57 nm in control urine. The method was validated by standard-addition methodology. Copyright © 2004 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||