Mag-Indo-1 tetrapotassium salt is a cell impermeable fluorescent probe for Mg2+ detection[1].
Mag-Indo-1 tetrapotassium salt can be used to determine the free Mg2+ concentration in the cytoplasmic solutions[1].
Guidelines (Following is our recommended protocol. This protocol only provides a guideline, and should be modified according to your specific needs)[1].
1. Calibrating solutions containing various concentrations of Mg2+ are prepared by mixing different ratios of the two stock solutions: one contains (mM) 150 KCl, 0.1 EGTA and 5 Hepes (pH 7.2 with KOH), and the other contains 100 MgCl2, 0.1 EGTA and 5 Hepes (pH 7.2 with KOH).
2. The calibration curve is constructed using calibrating solutions containing 1 μM Mag-Indo-1 tetrapotassium salt.
3. The 'Mg2+' calibrating solution contained (mM): 130 KCl, 4 EDTA and 5 Hepes (pH 7.2 with KOH).
4. The relationship between the background-corrected value of the fluorescence ratio (R) and the Mg2+ concentration is fitted with the following theoretical equation.
[Mg]=K (R-Rmin)/(Rmax-R), where [Mg] is the concentration of free Mg2+ ion, Rmin is the R value at 0 [Mg2+], and Rmax is the R value at saturating Mg2+. The curve fitting gave Rmin= 0.053, Rmax= 1.57, and K= 5.1 mM.
Note: the specific curve can refer to the reference.
[1]. Ding-Hong Yan, et al. Two Kir2.1 channel populations with different sensitivities to Mg(2+) and polyamine block: a model for the cardiac strong inward rectifier K(+) channel. J Physiol. 2005 Mar 15;563(Pt 3):725-44.