Search results for "Fluorescence"
showing 10 items of 2463 documents
Optical determination of pH on surfaces using immobilized Fluorescent dyes.
1993
The attachment of pH-sensitive Fluorescent dyes on to hydroxylapatite for measuring the pH of small volumes is described. Fluorescein and acridine were used, both activated with reactive functions, such as isothiocyanate or succinimidyl ester groups, to enhance the possibility of a covalent linkage to the surface. First investigations were carried out on synthetic hydroxylapatite as the surface material. After the preparation of a particular surface with the fluorescent dye, steady-state and time-resolved fluorescence spectroscopies were employed for estimating the pH value of a solution applied to the surface. In this paper we present the results of our investigations done with both method…
A LASER-INDUCED FLUORESCENCE (LIF) METHOD FOR MONITORING OXYGEN–ALKALI DELIGNIFICATION OF SOFTWOOD KRAFT PULP
2002
ABSTRACT A laser-induced fluorescence (LIF) method for monitoring the oxygen–alkali delignification of pine (Pinus sylvestris) kraft pulp was tested. The fluorescence intensity of the effluent was found to increase systematically during treatment as the lignin content of the pulp decreased. This emission method, compared, for example, to a UV/Vis absorption method, seems to have potential for large-scale applications. Owing both to the complex chemical nature of the effluent from oxygen–alkali delignification and to the complex nature of the fluorescence method, further work on this method is needed before it can be used for industrial purposes.
Bis(pyridylvinyl)diaminobenzenes: synthesis, acidochromism and solvatochromism of the fluorescence
2005
Abstract C2-symmetrical 1,4-distyrylbenzenes with 4-dimethylaminobenzene or pyridine as terminal rings, and propyloxy or dipropylamino groups in the central 2,5-positions were prepared. Solvatochromism of the absorption is small, but more pronounced in the fluorescence spectra. Some compounds exhibit huge Stokes shifts. Acid strongly alters the fluorescence: red shifts and decreasing quantum yields is the general result, but depending on the position and character of the basic sites, a strong recovery of fluorescence efficiency combined with large hypsochromic shifts may result in highly acidic solutions.
Phosphororganische Verbindungen, 113. Chemoselektive gesteuerte Fluoreszenzmarkierung von α-Chymotrypsin
1985
α-Chymotrypsin wird durch die fluoreszierenden Phosphonoylfluoride 1 und 3 inhibiert. Die fluoreszenzmarkierten α-Chymotrypsine 5 und 6 wurden gelelektrophoretisch aufgetrennt. Die Fluoreszenz von 1 und 3 sowie 5 und 6 ist komplementar losungsmittelabhangig. Mit 3 fluoreszenzmarkiertes α-Chymotrypsin ergibt bei der sauren Hydrolyse den fluoreszierenden Serinester 7. Durch reduktive Offnung der SS-Brucken im fluoreszenzmarkierten 6 wird bewiesen, das 1 mit einem Serin der C-Kette reagiert hat. Das gleiche Ergebnis erhalt man, wenn man in 6 die durch Reduktion freigesetzten SH-Gruppen zunachst mit Vinylsulfonen blockiert und dann auftrennt. Organophosphorus Compounds, 113. — Chemoselectively …
Low temperature headspace desorption of volatile organic compounds trapped in air sampling solid-supports
2009
Environmental context. The monitoring of volatile organic compounds (VOCs) in air is of great importance for air quality on both local and global scales. The determination of VOCs can be carried out by gas chromatography–mass spectrometry (GC-MS) after active or passive sampling and (high temperature) thermal desorption. An attractive alternative would be to combine GC-MS with headspace (HS) systems as it allows simpler, faster, low temperature desorption. We present here the first report of HS-GC-MS for the determination of VOCs in air sampled using solid supports. Abstract. The use of a headspace (HS) for low temperature desorption of VOCs, previously sorbed from indoor air on solid supp…
Dispersion management in two-photon microscopy by using diffractive optical elements.
2013
We demonstrate efficient generation of wide-field fluorescence signals in two-photon microscopy exploiting diffractive optical elements and short pulses by using a dispersion-compensated beam delivery optics module. Computer-generated holograms are codified onto a phase-only spatial light modulator, which allows for arbitrary single-shot patterning of the sample. Spatiotemporal shaping of the pulse is mandatory to overcome spatial chirp and pulse-front tilt effects that spread both in space and time the irradiance patterns, thus limiting not only the spatial resolution but also the signal-to-noise ratio in two-photon microscopy. By using a multipass amplifier delivering 30 fs, 0.8 mJ pulses…
Description of x-ray beams using the fluorescence yields of a set of thick targets
1995
Quantitative methods in x-ray fluorescence analysis require a knowledge of the spectral distribution of the fluorescence-exciting beam. The use of XRF yield measurements of a set of thick pure element targets is proposed for the description of a fluorescence-exciting x-ray beam, without the need to obtain its spectral distribution. This new approach is derived theoretically and verified by comparing thin-target yields calculated from XRF yield measurements of thick pure element specimens with those obtained from a calculated spectral distribution. The difference between the two methods of obtaining the thin-target yields is within 9% relative error.
Potential retrieval of biophysical parameters from FLORIS, S3-OLCI and its synergy
2012
The main objective of FLEX is the measurement of vegetation chlorophyll fluorescence (Fs) from space and the exploitation of this signal to better understand the carbon cycle. FLuORescence Imaging Spectrometer (FLORIS) is the main instrument of the FLEX mission concept. ESA's Earth Science Advisory Committee recommended the investigation of the FLEX concept as an in-orbit demonstrator to be flown as a tandem mission with Sentinel-3 (S-3). S-3 is amongst others equipped with the Ocean Land Colour Instrument (OLCI). When flown in tandem these instruments are expected to provide an accurate characterization of key atmospheric and surface parameters to facilitate Fs retrieval for FLORIS. In thi…
2-D differential membrane proteome analysis of scarce protein samples
2006
Proteome studies with small sample amounts are difficult to perform, especially when membrane proteins are the focus of interest. In our study a new method for the analysis of scarce membrane protein samples combining large gel 2-D-CTAB/SDS-PAGE with fluorescence dye saturation labelling (satDIGE) was developed, allowing a highly sensitive differential analysis of different cell states. After Triton X-114 phase partitioning, enriched membrane protein samples of T cells were labelled at cysteine residues using fluorescence dyes and separated by large gel 2D-CTAB/SDS-PAGE. For a differential analysis 3 mug protein was found to be sufficient to detect proteins in a widespread well-separated di…
Identification of Three-Way DNA Junction Ligands through Screening of Chemical Libraries and Validation by Complementary in Vitro Assays
2019
International audience; The human genome is replete with repetitive DNA sequences that can fold into thermodynamically stable secondary structures such as hairpins and quadruplexes. Cellular enzymes exist to cope with these structures whose stable accumulation would result in DNA damage through interference with DNA transactions such as transcription and replication. Therefore, the chemical stabilization of secondary DNA structures offers an attractive way to foster DNA transaction-associated damages to trigger cell death in proliferating cancer cells. While much emphasis has been recently given to DNA quadruplexes, we focused here on three-way DNA junctions (TWJ) and report on a strategy t…