Indoles fluorescence intensities

Neither Fj nor F2 alone gave the characteristic fluorescence of fa and nicked fa in the presence of L-serine and pyridoxal phosphate. However, titration of a fixed amount of F2 with F2 gave rise to a fluorescence intensity 80-90% that of nicked fa at a stoichiometric ratio of Ft to F2. Moreover, both the excitation and emission spectra of the stoichiometric mixture were the same as for nicked fa. In addition, the same specific quenching of this fluorescence was shown in recombined Fj and F2 as in nicked fa. Further, the dissociation constants for L-serine and for indole were determined to be the same within experimental error for recombined Fj and F2, as for nicked fa. No significant differences were found between nicked fa and reconstituted Fj F2 in the intrinsic fluorescence of the aromatic residues, or in the sedimentation coefficients or the 200-250 nm CD spectra. From the foregoing independent lines of evidence, F2 and F2 combine to produce a structure very similar to that of nicked fa. 

A fluorescence emission spectrum is a record of fluorescence intensity vs wavelength for a constant intensity of exciting light. Excitation and emission spectra for a flavin and for the indole ring of tryptophan are both given in Fig. 23-13. The heights of the... 

The fluorescence intensity of quinoline derivatives has been found to increase dramatically with an increase in the molecular weight of the host polystyrene. " This is attributed to a decrease in the free volume in the polymer matrix restricting molecular rotation/motion of the fluorophore. Similar effects have been observed for juliodinemalononitrUe in different stereo-regular poly(methyl methacrylates), and temperature effects on the luminescence properties of indole and coumaric acid derivatives in different polymer matrices showed abrupt changes in emission intensity at temperatures which correspond to the onset of local relaxation processes in the polymer. ... 

Fluorescence intensity of the pyridoxal phosphate group at the active site of tryptophan synthetase changes on addition of serine and indole, the substrates. 

The indolyl moiety is also a good donor for the CT interaction [9], and quenching of its fluorescence upon formation of the CT complex with the nicotinamide group has been reported [10]. It is noteworthy that the fluorescence intensities of indole and indolyl 3-acetic acid decrease as any of the present azacyclophanes was added. The binding constant with respect to the host molecules increases in the following order ... 

Change-transfer complexes of solute-alcohol stoichiometry 1 2 have been reported by Walker, Bednar, and Lumry3 for indole and certain methyl derivatives (M) in mixtures of associating solvents n-butanol and methanol (Q) with n-pentane these authors introduced the term exciplex to describe the emitter of the red-shifted structureless fluorescence band which increases in intensity with the alcohol content of the mixed solvent. The shift of the exciplex band to longer wavelengths as the solvent polarity is increased, described by Eq. (15), confirms the dipolar nature of the complex that must have the structure M+Q2. No emission corresponding to the 1 1 complex is observed in these systems which indicates (but does not prove) that the photo-association involves the alcohol dimer. The complex stoichiometry M+Q determined from (Eqs. 9, 10, and 12)... 

A fluorescence spectrum is characteristic of a given compound. It is observed as a result of radiative emission of the energy absorbed by the molecule. The observed spectrum does not depend on the wavelength of the exciting light, except that the spectrum will be more intense if irradiation occurs at the absorption maximum. The spectral intensity is called the quantum efficiency and is usually abbreviated as . The quantum yield or quantum efficiency, d>, which is solvent dependent, is the ratio Approximate values of quantum efficiencies are as follows naphthalene, 0.1 anthracene, 0.3 indole, 0.5 and fluorescein, 0.9. 

The IR spectra of all LC fractions from both Synthoil and shale oil contain a very intense feature at 750 cm and a less intense band at 820 cm". These bands, together with a strong feature at 3495 cm", are indicative of N-H stretching vibrations, thus implying the presence of amines and/or N-heterocyclics in substantial quantities in these samples. Indeed, previous analyses (26) of Synthoil have demonstrated the presence of relatively high concentrations of indole (210 ppm) and 3-methyhndole (130 ppm). However, a careful examination of MI fluorescence spectra of indole and a number of substituted indoles shows no match with any of the major unknown bands in the MI fluorescence spectra of the various Synthoil and shale oil fractions (27). Thus, it remains to identify the unknown fluorescent constituents of these samples, and the identities of the compounds responsible for the intense N-H absorptions in the FTIR spectra remain to be established. 

Indole derivatives have been used for fluorescence (FL), chemiluminescence (CL) and bioluminescence assays. Various indole derivatives were synthesized and their CL characteristics were investigated. However, indole derivatives have not been frequently used compared to the typical FL and CL reagents such as dansyl chloride, fluorescein, luminol and acridinium esters in terms of emission wavelength and intensity. For the selective and highly sensitive FL and CL assays, indole derivatives, which have a long emission wavelength of more than 600 nm and have strong CL intensity, should be developed. 

Fusion of a benzene ring to a heterocyclic nucleus causes a bathochromic shift and increases the intensity of absorption. Thus, quinoline, isoquinoline, indole and quinolium and isoqumolium ions fluoresce in the ultra-violet. Acridine, acridone and carbazole exhibit visible fluorescence. Porphyrin18 and some of its derivatives are characterized by narrow well-defined vibrational bands and their fluorescence bands are in the red region of the spectrum. 

The far-u.v. region has been used to study phosphate interactions in aqueous solutions. Phosphorus is now regularly estimated by (a) absorption spectroscopy using the band at 436 nm produced by vanadomolybdophosphate, b) by flame-emission spectroscopy using the emission band at 528 nm produced by HPO, and (c) by fluorimetry using the intense green-blue fluorescence produced by a transient indole-peroxyphosphoric acid. ... 

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