PBFI (Figure 3.4) is the K+ analog of the Na+ indicator SBFI. Unfortunately, the K+/Na+ selectivity of PBFI is less than the Na+/K+ selectivity of SBFI.  Despite its relatively poor K+/Na+ selectivity, PBFI has been used with some success in cellular experiments because the intracellular K+ concentration is much greater than that of Na+.

PBFI structure

Figure 3.4 PBFI structure


PBFI shares SBFI’s shortcomings of ultraviolet excitation, difficulty in loading the AM ester, and poor brightness. Asante Potassium Green-2 successfully addresses all of these problems.

PBFI is available in the K+ salt form and the acetoxymethyl (AM) ester form. While PBFI has been used for a number of years, we encourage researchers to use Asante Potassium Green-2  for improved performance.


Excitation: 340/390 nm (excitation maxima at 517 nm)

Emission: 500 nm

kd: 5 mM

Solubility: H20 (salt form)  DMSO (AM form)

Molecular Weight: 1175 g/mol