Solute fluorescence

Bis(3,4-diethyl-2-pyrrolylmethyl)-3,4-dietliyl-l//-pyrrole (2), prepared in situ from the di-t-butylester of the 5,5 -dicarboxylic acid (/), reacts with 4//-1,2,4-triazole-3,5-dialdehyde (3) in di-chloromethane in the presence of trifluoroacetic acid and 2,3-dichloro-5,6-dicyano-/)-benzoquino-ne as an oxidation reagent. Dark blue crystals are obtained after chromatographic purification. The dark violet chloroform solution fluoresces purple at 360 nm and gives the NMR experiments 39. Which compound and which tautomer of it has been formed ... 

Chelerythrine crystallises from alcohol in colourless, prismatic leaflets, m.p. 207°, containing one molecule of alcohol. The alkaloid absorbs carbon dioxide from the air, becoming yellow. The solutions fluoresce blue when the alkaloid is contaminated with its oxidation product, which is formed by mere exposure of solutions to air. The salts, which are quaternary, are intensely yellow. The hydrochloride, B. HCl. HjO, forms citron-yellow needles, and the sulphate, B. H2SO4.2HjO, golden-yellow needles, sparingly soluble in water the platinichloride, B2. HaPtCl. ... 

Properties of luciferin. The crystals are microscopic needles, which melt with decomposition at 205-210°C (Bitler and McElroy, 1957). It is a quite stable luciferin compared with some other luciferins, such as Cypridina luciferin and the luciferins of krill and dinoflagellates. It is not significantly affected by lOmM H2SO4 and lOmM NaOH at room temperature in air. The absorption spectral data of luciferin are shown in Fig. 1.3 (McElroy and Seliger, 1961). The molar absorption coefficient of the 328 nm peak in acidic solutions and that of the 384 nm peak in basic solutions are both 18,200 (Morton et al., 1969). Luciferin is fluorescent, showing an emission maximum at 537 nm in both acidic and basic conditions, although the intensity of the fluorescence is lower in acidic solution than in basic solution (fluorescence quantum yields 0.62 in basic condition, and 0.25 in acidic condition Morton et al., 1969). The chemical synthesis... 

Cerenkov radiation accounts for a very minor part of the energy loss of fast electrons. Its main importance is for monitoring purposes and establishment of a reference time, since it is produced almost instantaneously with the passage of the particle. Katsumura et al. (1985) have observed a very fast rise of solute fluorescence attributable to the Cerenkov effect the G value for this process is estimated to be -0.02. 

M. R. Eftink and C. A. Ghiron, Anal. Biochem. 114, 199 (1981), review solute fluorescence quenching of proteins in the study of structure and dynamics. 

Determination of aluminium in water for injection as a fluorescent complex Determination of stability of peptide drugs in solution Fluorescent derivatives and flow injection analysis... 

It is found that radical cations of 1,3,5-trixybenzene derivatives in solution fluoresce... 

A remarkable number of organic compounds luminesce when subjected to consecutive oxidation-reduction (or reduction-oxidation) in aprotic solvents1-17 under conditions where anion radicals are oxidized or cation radicals are reduced. In many instances, the emission is identical with that of the normal solution fluorescence of the compound employed. In these instances the redox process has served to produce neutral molecules in an excited electronic state. These consecutive processes which result in emission are not special examples of oxidative chemiluminescence, but are more properly classified as electron transfer luminescence in solution since the sequence oxidation-reduction can be as effective as reduction-oxidation.8,10,12 A simple molecular orbital diagram, although it is a zeroth-order approximation of what might be involved under some conditions, provides a useful starting... 

The name lepidopterene refers to the hydrocarbon 113 (L) whose butterflylike molecular shape was first revealed by X-ray diffraction analysis [129,130]. The structured electronic absorption spectra of lepidopterenes around 270 nm closely resemble that of 9,10-dihydroanthracene (see Figure 31). However, in terms of excited state properties, lepidopterenes have very little in common with 9,10-dihydroanthracene, which in solution fluoresces with a quantum yield of 0.16. By contrast, photoexcitation of lepidopterenes leads mainly to intramolecular exciplexes of 7i-chromophorically substituted anthracenes in an adiabatic process, for which both the molecular topology... 

Crystallises in pale yellow leaflets, which contain 2 mols. of water slightly soluble in water its neutral solution fluoresces blue, its acid solution violet, and its alkaline solution green on heating it decolorises at 230°. (B., 33, 675 D.R.P., 117005.)... 

In higher concentration ranges some aromatic hydrocarbons form dimers. Several distinct types of reaction have been found. Pyrene solutions fluoresce violet when dilute and blue when stronger, and the behavior has been attributed to process 5 followed by 9 (29). 

Fluorescence Correlation Spectroscopy and Fluorescence Burst Analysis. Several nanoscopic chemical imaging approaches work very well for measurements of chemical kinetics, interactions, and mobility in solution. Fluorescence correlation spectroscopy (FCS) measures the temporal fluctuations of fluorescent markers as molecules diffuse or flow in solution through a femtoliter focal volume.54 Their average diffusive dwell times reveal their diffusion coefficients, and additional faster fluctuations can reveal chemical reactions and their kinetics if the reaction provides fluorescence modulation. Cross-correlation of the fluorescence of two distinguishable fluorophore types can very effectively reveal chemical binding kinetics and equilibria at nanomolar concentrations. 

Apart from Eu3+ and Tb3+, few studies have been reported on optical properties of lanthanide ions doped in ZnS nanociystals. Bol et al. (2002) attempted to incorporate Er3"1" in ZnS nanociystal by ion implantation. They annealed the sample at a temperature up to 800 °C to restore the crystal structure around Er3"1", but no Er3"1" luminescence was observed. Schmidt et al. (1998) employed a new synthesis strategy to incorporate up to 20 at% Er3"1" into ZnS (1.5-2 nm) cluster solutions which were stabilized by (aminopropyl)triethoxysilane (AMEO). Ethanolic AMEO-stabilized Er ZnS clusters in solutions fluoresce 200 times stronger at 1540 nm than that of ethanolic AMEO-Er complexes. This is explained by the very low phonon energies in ZnS QDs, and indicates that Er3+ ions are trapped inside chalcogenide clusters. However the exact position of Er3+ in ZnS clusters remains unknown. Further spectroscopic and structural analyses are required in order to obtain more detailed information. 

The absorption spectrum of free ANS in solution fluorescence excitation spectrum of the ANS-BSA complex do not overlap as a result of molecular interaction between ANS and BSA (Figure 8.4). Energy transfer occurs between Trp residues of the BSA and ANS molecules bound to the protein affecting the fluorescence excitation spectrum... 

The maximum absorption per chain for light polarized parallel to the PDA chains is at least as intense as for PA. The measured dichroic ratio is about 120 [117,118]. It may be smaller in other PDAs for instance, about 25 in pTS [123]. As for trans-PA, solid PDAs are not fluorescent (there is a small solution fluorescence). 

In spite of the overall similarity of the fluorescence emission of cyclobutanone to other cyclic alkanones in the vapor phase (broad emission maximum near 400 nm), Hemminger, Rusbult, and Lee (17) report that the solution fluorescence emission of cyclobutanone is exceptional in two important ways (a) (excitation near 310 nm in cyclohexane) is about 1 x 10-4, or nearly 1/20th of the vapor-phase value, and (b) the fluorescence... 

The problem was solved by the development of multifunctional detectors, where more than one property of the solute is concurrently measured while it is situated in a single sensor cell. This arrangement reduces both the cost of the detector and also the extracolumn dispersion as only one cell is employed and only the normal column detector connection is necessary. The first multifunctional detector was developed by DuPont and was a bifunctional detector that simultaneously measured UV absorption and solute fluorescence. 

Moreover, the studies on nanoaperture-enhanced fluorescence point out that for a properly tailored aperture, count rates per molecule greater than a few hundred thousands photons per second were readily obtained, whereas for a single molecule in open solution, fluorescence saturation prevents the count rate from exceeding a few tens of kilocounts per second. This allows for fast and reliable screening for single molecules. 

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