Conjugated polymer-based fluorescence turn-on sensor for nitric oxide

A turn-on fluorescent sensor for NO (g) in solution was synthesized using a bipyridyl-substituted poly(p-phenylene vinylene) derivative (CP1) as the sensory scaffold. The action of NO (g) upon the CP1-Cu(II) complex reduces it to the CP1-Cu(I) complex with a concomitant 2.8-fold increase in emission intensity. The reagent is selective for NO (g) versus other biological reactive nitrogen species, except for nitroxyl, and has a detection sensitivity limit of 6.3 nM. [structure: see text]     

Improved native UV laser induced fluorescence detection for single cell analysis in poly(dimethylsiloxane) microfluidic devices

Single cell analytics is a key method in the framework of proteom research allowing analyses, which are not subjected to ensemble-averaging, cell-cycle or heterogeneous cell-population effects. Our previous studies on single cell analysis in poly(dimethylsiloxane) microfluidic devices with native label-free laser induced fluorescence detection [W. Hellmich, C. Pelargus, K. Leffhalm, A. Ros, D. Anselmetti, Electrophoresis 26 (2005) 3689] were extended in order to improve separation efficiency and detection sensitivity. Here, we particularly focus on the influence of poly(oxyethylene) based coatings on the separation performance. In addition, the influence on background fluorescence is studied by the variation of the incident laser power as well as the adaptation of the confocal volume to the microfluidic channel dimensions. Last but not least, the use of carbon black particles further enhanced the detection limit to 25 nM, thereby reaching the relevant concentration ranges necessary for the label-free detection of low abundant proteins in single cells. On the basis of these results, we demonstrate the first electropherogram from an individual Spodoptera frugiperda (Sf9) cell with native label-free UV-LIF detection in a microfluidic chip.     

Ultraviolet laser induced fluorescence of human aorta

Laser induced fluorescence from normal human aorta is studied with u.v. excitations of 305 to 310 nm, observing emission from 320 to 500 nm. In this region LIF lineshapes are strongly dependent on the excitation wavelength, suggesting that at least two fluorophores are being observed. The short wavelength fluorophore, peaking at 34Onm, is identified as tryptophan, while the longer wavelength fluorophore, peaking at 387 nm, is associated with collagen and elastin. In addition, fluorescence time decays of each component are measured with a time correlated photon counting system. A four-exponential fit of each decay is necessary to extract fluorescence lifetimes, which range from 33 ps to 8.6 ns.     

Attogram detection limits using laser induced fluorescence

Laser induced fluorescence has produced outstanding detection limits in liquid phase analysis. This paper presents a general method for optimizing detection limits as a function of sample volume.     

Determination of lead in water using laser ablation–laser induced fluorescence

The detection sensitivity of laser-induced breakdown spectroscopy (LIBS) is improved by coupling it with a laser-induced fluorescence method. A waterjet sample containing 500 ppm of Pb as an analyte was ablated by a 266 nm, frequency-quadrupled Q-switchedNd:YAG laser at an energy of ~ 260 μJ. After a short delay the resulting plume was re-excited with a 283.306 nm, nanosecond pulse dye laser at energies ranging from 45 to 100 nJ. The limit of detection (LOD) of lead in water was determined both by the single-pulse LIBS technique and Laser Ablation coupled with Laser-Induced Fluorecence (LA–LIF) method. It was found to be 75 ppm in the case of single-pulse LIBS and 4.3 ppm for LA–LIF. When the resonant pulse was detuned from the transition wavelength the LA–LIF signal disappeared demonstrating the resonant selectivity of this technique.     

Triggered dye release via photodissociation of nitric oxide from designed ruthenium nitrosyls: turn-ON fluorescence signaling of nitric oxide delivery

Two new fluorescein-tethered nitrosyls derived from designed tetradentate ligands with carboxamido-N donors have been synthesized and characterized by spectroscopic techniques. These two diamagnetic {Ru-NO}(6) nitrosyls, namely, [(Me(2)bpb)Ru(NO)(FlEt)] (1-FlEt, Me(2)bpb = 1,2-bis(pyridine-2-carboxamido)5-dimethylbenzene, FlEt = fluorescein ethyl ester) and [((OMe)(2)IQ1)Ru(NO)(FlEt)] (2-FlEt, (OMe)(2)IQ1 = 1,2-bis(isoquinoline-1-carboxamido)-4,5-dimethoxybenzene), display NO stretching frequencies (ν(NO)) at 1846 and 1832 cm(-1) in addition to their FlEt carbonyl stretching frequencies (ν(CO)) at 1715 and 1712 cm(-1), respectively. Coordination of the dye ligand enhances the absorptivity and NO photolability of these two nitrosyls in the visible region (450-600 nm) of light. Exposure to visible light promotes rapid loss of NO from both {Ru-NO}(6) nitrosyls to generate Ru(III) photoproducts in dry aprotic solvents, such as MeCN and DMF. The FlEt(-) moiety remains bound to the paramagnetic Ru(III) center in such cases, and hence, the photoproducts exhibit very weak fluorescence from the dye unit. In the presence of water, the Ru(III) photoproducts undergo further aquation and loss of the FlEt(-) moiety via protonation. These steps lead to turn-ON fluorescence (from the free FlEt unit) and provide a visual signal of the NO photorelease from 1-FlEt and 2-FlEt in aqueous media.     

High sensitivity laser induced fluorescence detection in capillary zone electrophoresis

Laser induced fluorescence is used for the detection of labeled amino acids. A preliminary comparison is made of three fluorescence pre-column labeling reagents, ortho-phthaldialdehyde, naphthalene dicarboxaldehyde, and fluorescein isothiocyanate, and data on phenylalanine detection limits are given.     

Determination of uranium in silicate rocks using laser induced fluorescence

A rapid method for fluorimetric estimation of uranium in silicate rocks is described. The fluorescence of uranyl complex is induced by laser beam in the ultraviolet region provided by nitrogen laser tube. The emission spectrum is quite intense and relatively persistent. For direct estimation of uranium in geological silicate materials without prior extraction, the interference of certain cations and anions that might be present in silicate rocks on uranium determination was studied. The limit of detection is 0.5 ppb.     

Pulsed microchip laser induced fluorescence for in situ tracer experiments

A compact system for remote and non intrusive in situ analysis of fluorescent tracers using a newly developed pulsed microchip laser coupled to fiber optics was used for in situ rhodamine determinations. By using a crystal doubling in front of the microchip Nd-YAG laser, it is possible to obtain 532 nm at 5 kHz with an energy of 0.6 μJ in a 0.5 ns pulse. Using fiber optics and a passive optode, it was possible to analyze remotely the fluorescence of rhodamine with a compact detection system (monochromator and photomultiplier). Limits of detection down to 10^–10–10^–11 mol/L can be reached depending on the rhodamine studied. Such a laser can be directly implanted in the optode avoiding laser losses when exciting in the U.V. Received: 30 July 1997 / Revised: 6 October 1997 / Accepted: 10 October 1997     

Pulsed microchip laser induced fluorescence for in situ tracer experiments

A compact system for remote and non intrusive in situ analysis of fluorescent tracers using a newly developed pulsed microchip laser coupled to fiber optics was used for in situ rhodamine determinations. By using a crystal doubling in front of the microchip Nd-YAG laser, it is possible to obtain 532 nm at 5 kHz with an energy of 0.6 μJ in a 0.5 ns pulse. Using fiber optics and a passive optode, it was possible to analyze remotely the fluorescence of rhodamine with a compact detection system (monochromator and photomultiplier). Limits of detection down to 10^–10–10^–11 mol/L can be reached depending on the rhodamine studied. Such a laser can be directly implanted in the optode avoiding laser losses when exciting in the U.V. Received: 30 July 1997 / Revised: 6 October 1997 / Accepted: 10 October 1997     

IR multiple-photon excitation distribution probed by IR fluorescence

Vibrational fluorescence induced by IR multiple-photon excitation of hexafluorocyclobutene was measured as a function of laser frequencies. The width and shift of the inhomogeneous broadened fluorescence bands represent the excitation energy. The contrasting shapes of the excitation and previously measured chemical yield spectra are explained by the Poisson distribution of the molecules in the quasicontinuum.     

Vacuum UV laser induced scission of simian virus 40 DNA

Abstract— The effect of vacuum UV-laser irradiation on Simian virus 40 (SV40) DNA I was studied in vitro. Following exposure of SV40 DNA I to an argon fluoride (ArF) laser (LD = 193 nm), single-strand breaks occur in either strand of the double-stranded superhelical molecule (DNA I) and convert it to the DNA II conformation. Upon increased irradiation times, additional breaks occur in already scissioned strands resulting in the production of smaller fragments as analyzed by alkaline sucrose centrifugation. These results suggest that short periods of irradiation lead to conformational alterations of SV40 DNA I.     

The heat of formation of the nitric oxide dimer and its UV spectrum

(NO)₂ was detected at ambient temperature in compressed gaseous NO. From the temperature dependence of the UV absorption intensity the enthalpy cha

Abstract

We have shown that van der Waals molecules may be conveniently detected at ambient temperature in a short optical path cell by applying simple high pre     

Graphene oxide modifications induced by excimer laser irradiations

The properties of graphene oxide foils were modified by excimer laser irradiation at different fluences and times. The irradiations were performed in air and in vacuum using a pulsed UV laser operating at 248-nm wavelength and 23-ns pulse duration. Measurements of ablation yield, microscope surface morphology and Raman spectroscopy were performed. The residual surface shows a significant oxygen reduction due to the removing of functional oxygen groups, a thickness reduction due to the removal of graphene layers depending on the used laser shots and a presence of defects in the graphene sheets as evident by the Raman spectroscopy investigation.     

A laser induced fluorescence study of vibrational energy transfer in dideuteromethane

V—V and V—T/R rates of ν₁, ν₂, ν₃, ν₆, ν₈, and ν₉ of CH₂D₂ were measured and are reported. The deactivation efficiencies of rare gas collision partners were measured and calculated by SSH theory, the results are reported and discussed. Possible V—V pathways are presented and discussed.     

UV laser induced proton-transfer of protein molecule in the gas phase produced by droplet-beam laser ablation

Droplet-beam laser-ablation mass-spectrometry was applied for a study of the UV-laser induced proton-transfer reaction of protonated lysozyme hydrated clusters in the gas phase. Protonated lysozyme hydrated clusters were produced by irradiation of an IR laser onto a droplet-beam of an aqueous solution of lysozyme and were subsequently irradiated by a UV laser. It is found that H⁺ and H₃O⁺ are produced through photodissociation of protonated lysozyme hydrated clusters. The mechanism of the proton-transfer reaction is discussed.     

Determination of phosphorus in steel by the combined technique of laser induced breakdown spectrometry with laser induced fluorescence spectrometry

Laser induced breakdown spectrometry (LIBS) combined with laser induced fluorescence spectrometry (LIFS) has been applied for detection of trace-level phosphorus in steel. The plasma induced by irradiation of Nd:YAG laser pulse for ablation was illuminated by the 3rd harmonic of Ti:Sapphire laser tuned to one of the resonant lines for phosphorus in the wavelength region of 253–256 nm. An excitation line for phosphorus was selected to give the highest signal-to-noise ratio. Fluorescence signals, P213.62 and P214.91 nm, were observed with high selectivity at the contents as low as several tens µg g^− 1. Fluorescence intensities were in a good linear correlation with the contents. Fluorescence intensity ratio of a collisionally assisted line (213.62 nm) to a direct transition line (214.91 nm) was discussed in terms of the analytical conditions and experimental results were compared with a calculation based on rate equations. Since the fluorescence signal light in the wavelength range longer than 200 nm can be transmitted relatively easily, even through fiber optics of moderate length, LIBS/LIFS would be a versatile technique in on-site applications for the monitoring of phosphorus contents in steel.     

IR/UV and UV/UV double-resonance study of guaiacol and eugenol dimers

Guaiacol (2-methoxyphenol) and eugenol (4-allyl-2-methoxyphenol) molecules are biologically active phenol derivatives with an intramolecular -OH...OCH3 hydrogen bond (H bond). Pulsed supersonic expansions of mixtures of either of the two molecules with He yield weakly bound homodimers as well as other higher-order complexes. A number of complementary and powerful laser spectroscopic techniques, including UV-UV and IR-UV double resonances, have been employed to interrogate the species formed in the expansion in order to get information on their structures and spectroscopic properties. The interpretation of the spectra of eugenol dimer is complex and required a previous investigation on a similar but simpler molecule both to gain insight into the possible structures and support the conclusions. Guaiacol (2-methoxyphenol) has been used for that purpose. The combination of the broad laser study combined with ab initio calculations at the Becke 3 Lee-Yang-Parr/6-31+Gd level has provided the isomer structures, the potential-energy wells, and shed light on the inter- and intramolecular interactions involved. Guaiacol homodimer has been shown to have a single isomer whereas eugenol dimer has at least two. The comparison between the computed geometries of the dimers, their respective energies, and the vibrational normal modes permits the identification of the spectra.     

A laser induced fluorescence study of vibrational energy transfer processes in cyclopropane

Results of infrared laser induced fluorescence studies on cyclopropane are presented. Molecules were excited from the ground state to the v₁₀ level of cyclopropane using a Q-switched CO₂ laser operating on either the P(14) or P(20) transition of the 9.6 μ branch. Fluorescence was observed from the v₆, v₈, v₁₀ + v₁₁ and v₅ + v₁₀ levels of cyclopropane. The self-deactivation of vibrationally excited cyclopropane through V → T/R processes was found to have a rate of 8.0 ± 1.5 ms^?1 torr^?1. Deactivation by rare gas collisions was also studied with comparison to simple V → T and V → R theories. V → V equilibration processes are discussed involving the v₆, v₈, v₁₀, v₁₁, and v₁₀ + v₁₁ levels.