The quenching constant for the iodide quenching of the fluorescence of riboflavin phosphate was measured at pH 5 and at pH 8. The value of the constant at the lower pH (where the phosphate group is unionized), k' = 23 M~ , was independent of the ionic strength, |i. The ratio k"/k' = f (k" the quenching constant at pH 8, where the phosphate group carries a single negative charge) was found to he...

An important consideration in the design of oligonucleotide probes for homogeneous hybridization assays is the efficiency of energy transfer between the fluorophore and quencher used to label the probes. We have determined the efficiency of energy transfer for a large number of combinations of commonly used fluorophores and quenchers. We have also measured the quenching effect of nucleotides on...

ce has become one of the most powerful methods for assessing photosynthetic performance in plant physiological experiments (Horton and Bowyer, 1990; Krause and Weis, 1991). This has resulted almost entirely from the development of methods to distinguish photochemical and nonphotochemical quenching of fluorescence. Moreover, it is now clear that the process of nonphotochemical quenching itself i...

Platinum tetrakis(2,4,6-triethylphenyl)porphyrin (Pt-1) was synthesized and its structural (X-ray), electrochemical and photophysical properties were fully characterized. Comparative studies of Pt-1 and its unsubstituted analog PtTPP show the effect of sterically congesting ortho-substituents on the dynamics of the triplet excited states. Lowered quenching rates by 3-4 times were observed for P...

In this study, we have carried out a characterization of the quenching effect produced by some commonly encountered metal ions (Co2+, Cu2+, Ni2+, Pb2+, Cd2+, As5+) on the photoluminescence of water suspensions of open-cage fullerene quantum dots prepared with a modified Hummers method. The response to heavy-metal ions occurs through a selective quenching of the PL emission and modifications of ...