Other fluorophores report the unusual fluorescence signal

(A and B) Ionic current (A) and fluorescence (B) traces recorded from oocytes expressing Kv1.5 A397C channels labeled with PyMPO. Voltage clamp pulses were applied from −80 to +60 mV in 10-mV increments (100 ms duration) from a holding potential of −80 mV (only traces at −60, −30, 0, and +30 mV are shown). (C) Mean G-V and F-V relations for Kv1.5 A397C labeled with PyMPO ( = 4). Boltzmann fits of the data gave and values for G-V and F-V relations of 2.3 ± 1.9 and 17.8 ± 1.3 mV (G-V), respectively, and −6.5 ± 2.5 and 22.2 ± 1.7 mV (F-V), respectively. (D) Mean values for the time constants of the dequenching component of fluorescence measured from PyMPO attached to A397C and the time constants of the associated ionic current activation. The time constants show similar voltage dependence at test voltages ranging from +10 to +60 mV.Copyright information:Taken from "Voltage Clamp Fluorimetry Reveals a Novel Outer Pore Instability in a Mammalian Voltage-gated Potassium Channel"The Journal of General Physiology 2008;132(2):209-222.Published online Jan 2008PMCID:PMC2483330.