Fluorescence quenching, technique

OV-absorbing compounds can be measured by fluorescence quenching as well as by reflectance. The fluorescence quenching technique provides a means of visualizing spots absorbing UV-light... 

Vo-Dinh T, Pal, T. 1992. Development of a fluorescence quenching technique to detect permeation of chemical agent simulants through protective clothing materials. Appl Spectrosc 46(4) 677-681. 

The location of a compound within a lipid bilayer can be studied using X-ray diffraction [167], neutron diffraction [164], fluorescence quenching techniques [163], differential scanning microcalorimetry [164], or NMR techniques [168,169],... 

In our previous paper (H), we introduced a novel experimental method to study the mechanistic details of solvent permeation into thin polymer films. This method incorporates a fluorescence quenching technique (19-20) and laser interferometry ( ). The former, in effect, monitors the movement of vanguard solvent molecules the latter monitors the dissolution process. We took the time differences between these two techniques to estimate both the nascent and the steady-state transition layer thicknesses of PMMA film undergoing dissolution in 1 1 MEK-isoproanol solution. The steady-state thickness was in good agreement with the estimate of Krasicky et al. (IS.). ... 

M. H. Winkler, A fluorescence quenching technique for the investigation of the configurations of binding sites for small molecules, Biochemistry 8, 2586-2590 (1969). 

R. Homan and M. Eisenberg, A fluorescence quenching technique for the measurement of paramagnetic ion concentrations at the membrane/water interface. Intrinsic and X537A-mediated cobalt fluxes across lipid bilayer membranes, Biochim. Biophys. Acta 812, 485—4-92 (1985). 

Let us recall the micellar aqueous system, as this procedure is actually the basic one. The chemistry is based on fatty acids, that build micelles in higher pH ranges and vesicles at pH c. 8.0-8.5 (Hargreaves and Deamer, 1978a). The interest in fatty acids lies also in the fact that they are considered possible candidates for the first prebiotic membranes, as will be seen later on. The experimental apparatus is particularly simple, also a reminder of a possible prebiotic situation the water-insoluble ethyl caprylate is overlaid on an aqueous alkaline solution, so that at the macroscopic interphase there is an hydrolysis reaction that produces caprylate ions. The reaction is very slow, as shown in Figure 7.15, but eventually the critical micelle concentration (cmc) is reached in solution, and thus the first caprylate micelles are formed. Aqueous micelles can actually be seen as lipophylic spherical surfaces, to which the lipophylic ethyl caprylate (EC) avidly binds. The efficient molecular dispersion of EC on the micellar surface speeds up its hydrolysis, (a kind of physical micellar catalysis) and caprylate ions are rapidly formed. This results in the formation of more micelles. However, more micelles determine more binding of the water-insoluble EC, with the formation of more and more micelles a typical autocatalytic behavior. The increase in micelle population was directly monitored by fluorescence quenching techniques, as already used in the case of the... 

Field-enhanced fluorescence quenching techniques have been widely used to study photogeneration during the past two decades (Menzel and Popovic, 1978 Popovic and Menzel, 1979 Popovic, 1982, 1983, 1984 Yokoyama and Mikawa, 1982 Popovic etal., 1985, 1987 Popovic andHor, 1988, 1995 Weiss and Bufbeny, 1988 Niimi and Umeda, 1993 Popovic and Mesbah, 1993 Hor and Popovic, 1994. Fluorescence quenching is not affected by trapping. As with photoacoustical measurements, a fundamental limitation of the technique is... 

Popovic et al. (1985) investigated photogeneration of a series of peiylene diimides by delayed-field and field-induced fluorescence quenching techniques. The results for N.N-bis(phenyl)perylene-3,4.9.10-tetracaiboxyldiimide (PPECI)... 

Hor and Popovic (1994) measured photogeneration efficiencies of dispersions of HOGaPc in poly (vinyl butyral) (PVB) by delayed-field collection and field-induced fluorescence quenching techniques. The HOGaPc polymorph was described as type V. The transport layers contained N,N -diphenyl-N,N -bis(3-methylphenyl)-(l,r-biphenyl)-4,4 -diamine. Like many phthalocyanines, HOGaPc exhibits a linear correlation of the photogeneration and field-induced... 

Ellipticine and several derivatives were able to displace 7,12-dimethyl-benz[a]anthracene from binding to bovine and human serum albumin using the fluorescence-quenching technique (192,193). The site of binding of ellipticines appears to be on the hydrophobic regions of the enzyme. A fast kinetic experimental technique, namely, temperature-jump spectroscopy, has been developed in order to study the interaction of elliptinium, and other molecules, with biological macromolecules (194). 

Since the excited triplet state is observed by use of the fluorescence spectrum, the rates of the proton-transfer reactions involved may be measured by the fluorescence-quenching technique, as described by Hague [1]. Unfortunately, although the triplet state is produced by the kinetic technique of flash photolysis, no rate coefficients have been published. Kinetic results obtained by the fluorescence-quenching technique have been reviewed by Weller [85]. 

The rates of intramolecular proton-transfer reactions, which are not limited by the need for reagents to diffuse together have also been studied by the fluorescence-quenching technique [85], For example, salicylic esters undergo protomeric isomerisation in the upper singlet state... 

Barzykin AV, Tachiya M. (2003) Diffusion of probe molecules in polymer gels as observed by fluorescence quenching techniques. J Phys Chem B 107 2953-2957. 

The DNP-amino acids, after separation into individual spots on the chromatographic plate, can be eluted from the scraped off area by adding 4 ml of water to the material in a small tube. The tube is heated at 50° in a water bath for 15 minutes and centrifuged to clear the solution. The color is read against known standards at 360 nm. Direct estimation of DNP-, PTH-, and DANS-amino acids separated on the thin-layer plate can be performed by fluorescence and fluorescence quenching techniques (P8). It is also possible to convert unmodified amino acids, separated on a silica gel G chromatographic plate, into DNP-amino acids by in situ conversion as was described in Section 4.7.18. The DNP-derivatives can then be developed in the second dimension and the spots analyzed quantitatively. 

Fluorescence quenching techniques (1) provide a battery of useful tools for the study of morphology in complex polymer systems. One of the most important applications of these techniques is to the study of interfaces and interphases in polymer systems. 

There are many different ways of using fluorescence quenching techniques to study the morphology of polymer materials, even those of rather complicated composition. Important considerations are (i) the use of synthesis to introduce the dye as a sensor into a specific phase of the material (ii) the spectroscopic... 

Table 5 also lists rate constants determined using Stem-Volmer fluorescence quenching techniques for water quenching of the 9-phenylxanthyl cation generated from its corresponding alcohol in very strongly acidic aqueous acetonitrile and for the cation tetrafluoroborate salt in acetonitrile [11,28]. Both values are in excellent agreement with the values reported by Minto and Das when the difference in solvent systems is taken into account [8]. 

Volmer fluorescence quenching techniques in strongly acidic aqueous acetonitrile solution [11], The values are all in the range (2-9) x 10 M" s and follow the reactivity order H > Me > t-Pr > c-Pr. This trend suggested a small steric effect toward the attack of water at the 9-position, although the relative rate differences are not very large. 

Aromatic nitriles are strong oxidants in their excited states (see Table I). Since they fluoresce strongly, the involvement of the singlet states can be easily proved by application of fluorescence quenching techniques. In all of the tested cases, it has been found that the Stern Volmer constant obtained from fluorescence analysis and that obtained from the double reciprocal plots of reaction quantum yield vs. quencher concentration are nearly equal, thus proving that the singlet stale is actually involved In the photochemical reaction. Actually it has been observed that a AG < 0 and polar solvents are necessary (although not sufficient, see Section 3) conditions for the photochemical proc-... 

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