Journal: The Journal of General Physiology

Article Title: Dual Effects of Adp and Adenylylimidodiphosphate on Cftr Channel Kinetics Show Binding to Two Different Nucleotide Binding Sites

doi:

Figure Lengend Snippet: Calibration of the solution exchange rate by chloride concentration jumps and photolysis of caged ATP. (A) Current through endogenous calcium-activated chloride channels in the presence of 500 μM free calcium and at two different chloride concentrations in the bath. Chloride concentration in the pipette is 150 mM, the holding potential is set to 0 mV. A slow inactivation of the calcium-induced current is seen that is negligible on the time scale of the solution exchange. Bars indicate the presence of calcium and the chloride concentration of the bath solution; the arrow indicates zero current. (B) Current steps in response to a chloride jump shown at a higher time resolution. The traces are from the recording shown in A at the position marked by the asterisk. The broken lines represent fitted functions simulating mixing of the two chloride concentrations by continuous dilution of a fixed solution volume. Time constants for the solution mixing are 16 ms for the jump from 120 to 10 mM chloride and 37 ms for the jump back to 120 mM. (C) Photolysis of 450 μM NPE-ATP with a 10-ns laser pulse of 275 mJ/cm 2 and 308 nm wavelength generates an exponentially rising current. In this example, the exponential time constant is 1,280 ms. The vertical arrow signifies the application of the UV light pulse, which is also visible from the artifact induced by the discharge of the excimer laser, the horizontal arrow indicates zero current.

Article Snippet: As was obvious from the slow rise times seen with a 10-ns pulse, the pulse duration could safely be extended to several milliseconds using a low-power continuous wave He/Cd laser of 325-nm wavelength (Kimmon Electric Co., Ltd.) without compromising the time resolution of the current signal.

Techniques: Concentration Assay, Transferring