Ca2 Indicator Photobleaching

One of the most threatening impacts to Ca2+ indicators is photobleaching. Photobleaching is defined as the irreversible damage caused by the generation of a less fluorescent species of the FP. It results in a decrease of fluorescence signal over time. The more resistant a Ca2+ indicator is to photobleaching, the longer it can provide reliable and useful information about the measured Ca2+ signals (Thomas, Tovey et al. 2000).
The SNR is defined as the difference between the level of the desired signal to the level of background noise. Brightness, dynamic range and kinetics one the one hand and features of the signal on the other hand play a crucial role. "SNR increases when the fluorescence can be integrated in space and time" (Badura, Sun et al. 2014). …show more content…
In neurons, the basal Ca2+ concentration typically varies between 50 and 200 nM, while during action potential firing Ca2+ concentration can reach 1 to 10 µM (Badura, Sun et al. 2014). High Ca2+ affinity in GECIs with a Kd close to the basal Ca2+ concentration allow high SNR monitoring of small Ca2+ transients, but also saturate at high concentrations and may perturb the cell´s intrinsic Ca2+-dependent processes (Griesbeck 2004). An optimal sensor will span the entire range of likely Ca2+ concentrations in a linear way. A key parameter of an indicators dynamic range is nH. NH is related to the binding stoichiometry of the