What are the differences between calcium ion indicators: Cal 520, Cal 520FF, and Cal 520N?
Posted April 9, 2018
All three of these Ca2+ indicators differ mainly by their dissociation constant (Kd):
- Cal 520® AM has a Kd of 320 nM
- Cal 520FF™ AM has a Kd of 9.8 μM
- Cal 520N™ AM has a Kd of 90 μM
Ca2+ indicators that have a very low Kd value are high-affinity chelators and have a greater tendency to bind Ca2+. When the Kd value is high, it is a low-affinity chelator.
A variety of ion indicators are available for detecting intracellular Ca2+ over a broad range (e.g., less than 50 nM to more than 50 μM). Higher affinity indicators, such as Cal 520® AM, are designed to quantify Ca2+ levels in the cytosol. Whereas, lower affinity indicators can be optimized for measuring Ca2+ in subcellular compartments with higher Ca2+ concentrations (e.g., ER).