Indo-1 Low Affinity (LowAff)

TEFLabs Order Form

Low affinity (formerly designated as “FF”) versions enable studies where a large concentration of calcium is expected. They have two major advantages over their high affinity counterparts. They cause reduced buffering of intracellular calcium and reduced perturbation of calcium transients, and they allow for measurements of shorter-lived transients.

TEFLabs low affinity calcium indicators, based on the effect of fluorines on lowering the affinity of the regular indicators, have an appropriate Kd in the range of 15 μM to 25 μM. Fura-2 LowAff and Indo-1 LowAff were the first low affinity indicators introduced by TEFLabs.

Indo-1 is also available in High Affinity (Indo-1), Near Membrane (Indo-1 NearMem), and Leakage Resistant (Indo-1 LeakRes) versions.


Excitation: 346 nm (high/low Ca2+)
Emission: ratiometric,  475 nm and 405 nm
kd: 26 uM
Solubility: H20 (salt form)  DMSO (AM form)
Molecular Weight:  1046 g/mol (AM form),  862 g/mol (salt form)


Indo-1 lowAff, Indo-1 FF

Figure 6.2 Indo-1 LowAff Structure



Indo-1 LeakRes

Indo-1 NearMem

Asante Calcium Red Low Affinity

Asante Calcium Green Low Affinity

Fluo-2 Low Affinity

Fura-2 Low Affinity