Partitioning and Binding of Fluorophore Quenchers to Membranes

Determination of Partitioning and Binding of Fluorophore Quenchers to Membranes 

In systems where only dynamic quenching occurs, then steady-state fluorescence intensities can be measured instead of lifetimes/101 103-,07) In experiments where comparisons are being made (i.e., for a comparison of different experimental conditions or types of membrane), it is important that the lifetime of the fluorophore (r0) is not affected by the experimental conditions. Fluorescence intensities can be obtained much more rapidly and without specialized instrumentation. Blatt and Sawyer(101) have employed a relationship essentially the same as Eq. (5.20) in this way. They have pointed out that since the quenching mechanism is collisional, the partition coefficient that is derived is a partition coefficient of the quencher into the immediate environment of the fluorophore and is therefore a local Kp. It is therefore possible to investigate the partition coefficient gradient across the lipid bilayer by using a series of probes, such as the anthroylstearates,(108) located at different depths. In their method, Eq. (5.20) has the form 

In addition to the partition coefficient, the bimolecular quenching constant (km) is obtained from quenching experiments. 1 1 7-IIX i and, in principle, this can be used to obtain the lateral diffusion constant of the quencher by using the Smoluchowski equation  

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