Search results for "Fluorescence"
showing 10 items of 2463 documents
BODIPY Dyes Functionalized with Pendant Cyclic and Acyclic Polyamines
2013
The synthesis and characterization of a series of BODIPY derivatives substituted with acyclic and cyclic polyamines, in particular, cyclen and homocyclen, are reported. The 19F NMR, UV/Vis, and fluorescence spectroscopic data of these compounds are discussed. One compound was found to be very selective for CuII ions, which makes it a very promising system for CuII detection.
The Interaction of State Transitions and Chlororespiration in the Xanthophycean Alga Pleurochloris Meiringensis
1990
Wavelength dependent State I-State II-transitions have been shown to exist in chlorophytes and red algae. Little is known about the regulation of energy distribution between the photosystems of chlorophyll c-containing plants. Previously it was shown that in the xanthophycean alga Pleurochloris meiringensis two states of energy distribution could be established [l]: In state “D” light is preferentially transferred to PS II, whereas in state “L” PS I is favoured. These state regulations strictly depend on the intensity and not on the wavelength of prei1lumination. In this paper we give new evidence that chlororespiration is involved in the mechanism of state “L”-state “D”-transitions.
Fluorimetric determination of binding constants between micelles and chemical systems
1991
Abstract A fluorimetric method is adapted to determine the binding constants (K) between different systems and micelles. The method is based on the variation of the fluorescence of the system in the presence of increasing amounts of a surfactant agent. This method permits the determination of binding constants in strong acid or alkaline media. The binding constants of 1-naphthol and 2-(4-alkylamino-2 hydroxyphenyl)benzo-X azoles (X being an O or an S atom, PAS-O and PAS-S) with cationic, anionic, and nonionic surfactants have been determined by the proposed method. Values from 49,100 M−1 for the interaction between PAS-S and CTAB in basic medium to 10 M−1 for the interaction of 1-naphthol w…
Origin of the temperature dependence of the rate of singlet energy transfer in a three-component truxene-bridged dyads
2014
We report a truxene-based dyad built upon one donor (tri-meso-phenylzinc(II)porphyrin) and two acceptors (octa-β-alkylporphyrin free base) in which the donor exhibits free rotation around a Ctruxene-Cmeso single bond at 298 K in fluid solution but not at 77 K in a glass matrix, whereas the acceptors have very limited motion as they are blocked by β-methyl groups. This case is interesting because all the structural and spectroscopic parameters affecting the rate for singlet energy transfer according to a Förster Resonance Energy Transfer are only weakly temperature dependent, leaving only the Dexter mechanism explaining the larger variation in rate of energy transfers with the temperature h…
Bioorthogonal red and far-red fluorogenic probes for wash-free live-cell and super-resolution microscopy
2020
AbstractSmall-molecule fluorophores enable the observation of biomolecules in their native context with fluorescence microscopy. Specific labelling via bioorthogonal tetrazine chemistry confers minimal label size and rapid labelling kinetics. At the same time, fluorogenic tetrazine-dye conjugates exhibit efficient quenching of dyes prior to target binding. However, live-cell compatible long-wavelength fluorophores with strong fluorogenicity have been difficult to realize. Here, we report close proximity tetrazine-dye conjugates with minimal distance between tetrazine and fluorophore. Two synthetic routes give access to a series of cell permeable and impermeable dyes including highly fluorog…
ChemInform Abstract: Fluorescent Chemosensors Containing Polyamine Receptors
2000
Chemosensors have attracted interest in many different scientific fields, such as environmental chemistry, medicine, and the processing and storage of information. These molecular-scale devices have the advantage of working on the same spatial scale as the chemical structures that are responsible for macroscopic behaviour observed in the environment or those associated with health problems. Moreover, they allow the construction of molecular-scale devices for information storage. In this review, we describe a family of chemosensors based on a polyamine receptor and a fluorescent signalling unit. Polyamine receptors are water-soluble ambidentate receptors; they are able to coordinate either m…
Micellar fluorescence enhancement of carbamate pesticides
1990
Abstract Different studies have been carried out on the interaction of carbamate pesticides, such as carbofuran and carbaryl, with nonionic and anionic surfactants. Micellar fluorescence enhancements (MEF) of 15–20 for carbofuran in the presence of fatty alcohol ethylene oxide condensates, and of 3.7–8.6 in the presence of anionic surfactants at neutral pH have been obtained. Carbaryl does not interact with surfactants, but when it is hydrolysed to 1-naphthol, MEF values of the order of 2 are obtained in the presence of nonylphenol ethylene oxide condensates. The experimental parameters have been optimized in order to obtain maximum fluorescence. The mechanisms involved in the fluorescence …
Terrylene in p-terphenyl: single-molecule experiments at room temperature
1999
Abstract This paper reports on fluorescence microscopy and spectroscopy of single terrylene molecules embedded in p -terphenyl at room temperature. The basic photophysical parameters of this crystalline host/guest system such as photostability, single-molecule emission rates and the properties of dispersed fluorescence spectra are reported. The stability of the single-molecule signals allowed the direct observation of singlet–triplet quantum jumps at room temperature, by means of which the underlying intersystem crossing rates can be investigated. The results of earlier investigations at liquid-helium temperatures are reviewed briefly where appropriate. The properties of terrylene in p -ter…
Fluorescent chemosensors based on cyclohexane: selective sensing of succinate and malonate versus their longer or shorter homologues
2008
The sensing properties towards aliphatic α,ω-dicarboxylates of five cyclohexane-based ligands are described. The studied ligands have been designed following the binding site-signalling unit approach and they all possess thiourea groups as recognition moieties. Ligands 1 and 3 containing naphthalene units can be used as fluorescent sensors as they form intra- or intermolecular excimers in the presence of appropriate dicarboxylates. Selective sensing of succinate and malonate versus their longer or shorter homologues has been observed.
Specific dye adsorption at oriented monolayers
2007
We studied the adsorption of water soluble cyanine dyes (pseudoiso-cyanine and “stains-all”) to monomolecular layers of arachidic acid at the water-air interface in a Langmuir trough. Fluorescence microscopy was employed to on-line monitor the formation of J-aggregates upon adsorption. Large two-dimensional monodomain single crystals could be grown by this self-assembly process with optical properties reminiscent of those found and extensively studied for amphiphilic derivatives of the same chromophors [12]. In addition to the necessary Coulombic interaction between subphasedye and target monolayer, we found that details of the crystal morphology also crucially depend on substrate parameter…