Disruptive quencher

The term "disruptive quencher" is applied to the case in which all exciton contacts with the quencher results in completely effective quenchingIt is not at all clear that this property is applicable to Cu quenching. The case of a non-dlsruptive quencher is much harder to analyze and does not lead to a convenient expression for the excitation decay, analogous to eqn. (18). Based on classical diffusion equations it seems plausible that the disruptive quencher model is applicable so long as the quenching rate at the quenched site is of the same order of magnitude as the transfer rate from that lattice site to neighboring sites. ... 

In eqn. (18) N refers to the number of lattice sites between disruptive quenchers. Since these quenchers are placed randomly on the lattice there will be a distribution of N for a given mole... 

In the ratiometric method, the fluorescence intensity of the liposomes containing pyranine (F) and in the presence of the quencher DPX was determined at 520 nm upon excitation at two wavelengths 460 nm (of the charged unprotonated pyranine) and 415 nm (of the pH-independent isosbestic wavelength that describe the total pyranine concentration). The ratio of is described as F. The ratiometric measurement is used to determine the intraliposome aqueous phase pH (18,22). Then nigericin (or nonactine) at final concentration of 5pM was added to disrupt the pH and/or ammonium ion gradient that induce complete gradient collapse and the measurement at the above two excitations was repeated, and indeed it demonstrated a shift of the intraliposome aqueous pH to be identical to the extraliposome medium pH (10). 

FIGURE 2.5 FRET quench readout principle. In the intact peptidic substrate (amino acids symbolized by X, Y and Z) labeled with a fluorophore (dye) and a quencher (Q) at the opposite sites of the scissile bond, the fluorescence emission is quenched through an energy transfer (ET) from the fluorophore to the quencher. After cleavage of the substrate between amino acids X and Y by a protease, the energy transfer is disrupted and an increase in fluorescence emission is observed (light gray arrow). An increase of fluorescence intensity over time dependent on the enzymatic velocity is recorded. 

A method for the detection of single base mismatches (single nucleotide polymorphism, SNPs) with DNA microarrays is described that does not require labelling of the sample DNA. The method is based on the disruption of FRET between a fluorophore attached to the immobilised probe, and a quencher sequence complementary except for an artificial mismatch. Typically, a universal... 

The NaCl effect upon the proton-transfer reactions in the excited state of 2-naphthol has been studied by Harris and Selinger [41]. They have reported that the enhancement of the fluorescence of 2-naphthol is due either to a disruption of the water structure by the high concentration of Na and Cl ions or to an increase in the activity coefficient of the excited 2-naphthol. In previous works [53,106,107], it is shown that NaCl is a very weak quencher there is a weak quenching ability for CT, but no ability for Na. The NaCl effect on the proton dissociation reactions in water at 300 K has been studied by means of nanosecond and picosecond spectroscopy with fluorimetry [108]. The proton dissociation rate constant k decreases with an increase of [NaCl] according to the equation... 

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