Fluorescence quencher

I ndole Carboxy groups, chlorinated compounds, Dimethylformamide 51-53 

Tryptophan Acrylamide, histidin, succinimide, trifluoroacetamide, iodide, disulfides 55-58 59, 60 

Quinolinium ions and their betains Chloride, bromide, iodide 67-69 

Thus from the plot of this ratio versus the quencher concentration and by knowing 6a separately, the bimolecular quenching constant, kq, can be determined. The 

Example of application of solute quenching in protein studies One of the main aims in biophysical studies of the stracture and function of proteins is to identify the protein domains which are responsible for the interaction of the entire protein with physiologically relevant binding partners. Proteins usually contain several tryptophan residues, which may be distributed among the different protein domains. Since each of these tryptophan residues is located in a distinct environ- 

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Fluorescence measurement using this probe does not require a fluorescence quencher or washing process to suppress the fluorescence emission from nonbinding probes and nonspecific binding probes, which would be advantageous for the detection of mRNAs with poly(A) tracts in cells. 

Enzyme structure may be studied by fluorescence spectroscopy [238-244]. Excitation in the 280-310 nm absorption bands of proteins, usually results in fluorescence from tryptophan (Trp) residues in the 310-390 nm region. The fluorescence from the Trp residues is a convenient marker for protein denaturation and large decreases or red-shifts in fluorescence are observed when proteins are denatured. These changes are most often due to the exposure of the Trp residues that are buried in the protein and may be due to the changes in the proximities of specific residues that may act as fluorescence quenchers. Fluorescence emission characterization of the immobilized... 

The energies calculated for the electron transfer from electron-rich olefins to excited conjugated iminium salts are energetically favourable118. Thus, electron-rich olefins are excellent fluorescence quenchers of 2-phenyl- 1-pyrrolinium perchlorate 133119. The... 

Few chemical sensing mechanisms (other than bulk quenching) have been described for neutral molecules nevertheless, many small analytes of interest are uncharged glucose, for example. Of course, most carbohydrates are neither fluorescent nor are they fluorescence quenchers novel signal transduction mechanisms are required. 

T. Ando and H. Miyata, Pyruvate as a fluorescence quencher Anew specttoscopic assay for pyruvate reactions, Anal. Biochem. 129, 170-175 (1983). 

In protein molecules with two or more tryptophan residues, it is necessary to obtain first the fluorescence decay curves for the individual residues. For this purpose, additional spectroscopic information is necessary. One can use the dependence of the decay curves on emission wavelength, apply selective fluorescence quenchers, or selectively modify one of the tryptophan residues. The results of Brochon et al. for the lac repressor(44) and those of Beechem et al. for alcohol dehydrogenase(45) provide evidence in favor of such approaches. 

This equation is a good approximation to the description of the relaxa-tional spectral shifts occurring with variations of xR and xF, which are brought about by temperature changes and effects of collisional fluorescence quenchers. Using this equation, xR can be easily determined if xF, v0, and vs are known for the system (the chromophore and its environment) under study. The last two values may be obtained not only from time-resolved spectra but also from steady-state spectra at the lowest (v0)and highest (vE) temperatures. The latter measurement is difficult to achieve with such labile... 

D. B. Chalpin and A. M. Kleinfeld, Interaction of fluorescence quenchers with the -(9-anthroyloxy) fatty acid membrane probes, Biochim. Biophys. Acta 731, 465 174 (1983). 

Here, is the rate constant for radiative decay (fluorescence), while k r is the combined rate constant for aU non-radiative decay processes, is virtually constant and is an inherent property of the material in question, and for this material is significantly greater than k r, given the high fluorescence efficiency. When a fluorescence quencher, such as TNT, is introduced, km increases because an additional efficient non-radiative pathway now exists. This, via Eq. (4), makes r smaller. 

Fig. 5. Illustration of the 5 -nucleotidase (TaqMan) assay for allele discrimination. (A) The allele discrimination assay employs two unlabeled PCR primers and two doubly fluorescent labeled PCR probes for visuaUzation of a mutant allele. The target sequence is initially denatured and amplified in the presence of each of the primers and probes. Increasing polymerization in the presence of a thermostable polymerase which contains a 5 proofreading function allows cleavage of one fluorescent indicator from an appropriate probe during the cycling reaction. (B) Probes are designed with a fluorescent reporter and a quencher moiety. AmpUfication reactions are spiked with additional fluorescent quenchers in order to render the reaction initially dark to the photomultipUer mbe or diode. The probes are designed...

Nemzek and Ware [7] have studied the fluorescence decay of 1,2-benzanthracene (and naphthalene) in 1,2-propanediol or purified mineral oil by the single photon counting technique over the temperature range 10—45°C. The fluorescence lifetimes, t0, were measured. In further experiments, which included a heavy atom fluorescence quencher, carbon tetrabromide in concentration [Q] 0.05—0.29 mol dm-3, no longer could the decay be characterised by an exponential with a constant lifetime. However, the decay of fluorescence was well described by an expression of the form... 

Online chromatographic detection by fluorescence can add to the characterization of DOM and help to study complex formation between DOM and paramagnetic metal ions known to be effective fluorescence quenchers (Saar and Weber, 1982 Schmitt et al., 2002). 

The choice of the mobile phase is very important, as fluorescence is sensitive to fluorescence quenchers. Highly polar solvents, buffers, and halide ions quench fluorescence. The pH of the mobile phase is also important to fluorescence efficiency for example, quinine and quinidine only display fluorescence in strongly acidic conditions, whereas oxybarbiturates are only fluorescent in a strongly alkaline solution [67,68]. Due to the stability of the chromatographic sorbents, the use of very acidic or basic mobile phase may not be possible. One alternative is to alter the effluent pH postcolumn. Postcolumn addition of sulfuric acid has been used for the assay of ethynodiol diacetate and mestranol in tablets [69]. Another example is the determination of tetracycline antibiotics in capsules and syrup where EDTA and calcium chloride were added to enhance fluorescence [70]. 

Even more straightforward evidence in favor of recombination to the triplet state was obtained by heavy-atom substitution into the fluorescence quencher, which also enhances the rate of spin conversion. By measuring the transient absorption of both ion radicals and the triplet products of their recombination, it was demonstrated that the quantum yield of triplets increases when the charge separation yield 9(0) decreases as a result of heavy-atom substitution [225]. As was shown in Figure 3.76, triplet state is faster than to the singlet state, while the quantum yield of triplets produced from the singlet precursor only increases with ks. Hence these data also indicate that the triplet channel of recombination is the most efficient. 

QSY9 trade name for an efficient xanthene-based fluorescence quencher dye... 

Fig. 4.2.9. Linear PNA-beacons in unhybrid-ized peptide nucleic acids (PNA) the averaged distance between appropriately appended fluorescence donor and fluorescence quencher groups is smaller than in the duplex structure.

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