Fluorescence self-quenching

Phillips RL, Kim IB, Tolbert LM, Bunz UHF (2008) Fluorescence self-quenching of a mannosylated poly(p-phenyleneethynylene) induced by concanavalin A. J Am Chem Soc 130 6952-6954... 

Just as photoassociation may be inferred from the observation of fluorescence self-quenching, so may the negative temperature coefficient of KM be adopted as a criterion of excimer dissociation in the absence of excimer fluorescence. The application of Eq. (31) to data obtained for the selfquenching of anthracene in the vapor phase leads to a value of — AHa 7.6... 

Thin films only exhibited very weak fluorescence. This suggests the formation of strong interchain interaction in the solid state, leading to fluorescence self-quenching. 

Other MW enhancers have been described. Peptides with oligonucleotides as enhancers were attached to substrates for a polarization assay with caspase-3 (Lopez-Calle et al., 2002). As strepta-vidin has four binding sites, fluorescence self-quenching effects between the dye molecules can occur with increasing binding degree resulting in depolarization (Pope et al., 1999). The alternative MW enhancer approaches may overcome this limitation. 

Protein disulfide isomerase (PDI), a homo-dimeric protein (Mr 110 kDa) widely distributed across eukaryotic cells. PDI catalyzes the isomerization and rearrangement of disulfide bonds in the endoplasmic reticulum. Furthermore, S-denitrosation activity of PDI has been described. Recently, a direct, continuous, sensitive assay of PDI based on fluorescence self quenching has been described [B. Wflkin-son, H. F. Gilbert, Biochim. Biophys. Acta... 

Pattanayak V, Gifford LK, Lu P, Gewirtz AM (2008) Observed versus predicted structure of fluorescent self-quenching reporter molecules (SQRM) caveats with respect to the use of "stem-loop" oligonucleotides as probes for mRNA folding. RNA 14 657-665... 

The experimental principle is illustrated in Fig. 3. The interaction of the polymer with the liposomal membranes causes the perturbation of the bilayer. This perturbation follows the leakage of calcein from the liposome. Calcein in high concentration in the liposome is self-quenched, but has strong fluorescence intensity by the leak from the liposome. Therefore, the extent of the membrane interaction can be estimated quantitatively from the fluorescence spectroscopy. 

In the equation, the subscripts 1 and 2 refer to the reference compound and the compound of interest, respectively, is the intensity of the fluorescent signal of each compound measured as peak height in centimeters, 8 is the molar absorptivity, c is the concentration in moles per liter, and is the fluorescence quantum yield. In this application, i is set at 1.00. The concentrations of the solutions that were tested ranged from 10 to 10 M. The solutions run at the higher concentrations were all checked for self-quenching, but none was found. All measurements, except the fluorescence-versus-solvent study, were made in 0.1-N phosphate buffer, pH 7.4. Slit settings on the Perkin-Elmer MPF-2A were 10 mp (nm) for both emission and excitation monochromators. 

Poly(methyl methacrylate) [PMMA] is an excellent polymer for studying photoresist dissolution because of its minimal swelling characteristic. For this work, PMMA molecules were labelled with phenanthrene (Phe) dye since its fluorescence is quenched by MEK. In addition, this dye has the advantage of forming few excimers (23-241 which results in self-quenching. Thus, the reduction in fluorescence intensity of PMMA-Phe is virtually solely due to MEK quenching. Consequently, the permeation of MEK into a PMMA film can be monitored from fluorescence intensity decay. 

The value of the quantum yield of fluorescence of TIN in the PMMA film (calculated using the total film absorbance at the excitation wavelength) decreases from 1.2 x 10-3 to 5.0 x 10"4 when the concentration of TIN is increased from 0.07 mole% to 5.0 mole%. This suggests that the TIN molecules are involved in a concentration-dependent, self-quenching process. 

The dependence of the fluorescence quantum yields and lifetimes of these stabilizers on the nature of the solvent suggests that the excited-state, non-radiative processes are affected by solvation. In polar, hydroxylic solvents, values of the fluorescence quantum yield for the non proton-transferred form are significantly lower, and the fluorescence lifetimes are shorter, than those calculated for aprotic solvents. This supports the proposal of the formation, in alcoholic solvents, of an excited-state encounter complex which facilitates ESIPT. The observed concentration dependence of the fluorescence lifetime and intensity of the blue emission from TIN in polymer films provides evidence for a non-radiative, self-quenching process, possibly due to aggregation of the stabilizer molecules. 

The fluorescence quenching occurs when dye molecules are close to the metal. The energy from the first excited fluorophores can be consumed through a non-radiative path to the metal. A spacing layer is usually required to avoid this energy transfer process. In addition, the concentration of the dispersed dye molecules should be suitable to avoid self quenching [34, 81]. 

If Q is identical to M (self-quenching without formation of products), (MM) is called an excimer (excited dimer) with its own fluorescence spectrum and lifetime (Section 4.4.1). 

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