Figure 2. The QV5 construct reports the ATP/ADP ratio.
Application of ATP in the constant presence of three different concentrations of ADP demonstrates the increasing effective affinities of the sensor for ATP with increasing concentrations of ADP. The QV5 construct fluorescence response to ATP application in the presence of 5 μM, 50 μM, and 500 μM shows a half-maximal response at 1 μM, 10 μM, and 100 μM ATP respectively, corresponding to a half-maximal response when the ratio R equals ~0.2.