Calcium & Other Ion Indicators

Zinquin is an UV-excitable, blue fluorescent zinc indicator. Zinquin ethyl ester is membrane-permeable and is hydrolyzed into Zinquin free acid once entering cells.

5-(and-6)-Carboxy-2′,7′-dichlorofluorescein diacetate, succinimidyl ester is a useful fluorescent tracer that can passively diffuse into cells and covalently label intracellular proteins, resulting in long-term cell labeling. The reagent itself is colorless and nonfluorescent but becomes brightly green fluorescent once it is hydrolyzed by intracellular esterases.

5(6)-CFDA, SE (full name: 5-(and-6)-Carboxyfluorescein diacetate, succinimidyl ester, also known as CFSE) is a useful fluorescent tracer that can passively diffuse into cells and covalently label intracellular proteins, resulting in long-term cell labeling. The reagent itself is colorless and non-fluorescent but becomes brightly green fluorescent once it is hydrolyzed by intracellular esterases.

Ready-to-use solution of Pluronic® F-127, a nonionic detergent useful for solubilizing hydrophobic compounds like AM esters of calcium indicator dyes to facilitate cell loading.

Ionomycin is commonly used to modify intracellular calcium concentrations and to calibrate fluorescent calcium indicators. It is also known for its antiproliferative effects.

Ready-to-use solution of Pluronic® F-127, a nonionic detergent useful for solubilizing hydrophobic dye molecules such as AM esters of calcium indicator dyes to facilitate cell loading.

MQAE (N-(Ethoxycarbonylmethyl)-6-methoxyquinolinium bromide) is an improved chloride indicator that has greater sensitivity to chloride than SPQ, and higher fluorescence quantum yield.

TPEN (Tetrakis-(2-pyridylmethyl)ethylenediamine) is an excellent heavy metal chelator while it does not affect calcium, magnesium, sodium, or potassium concentrations. Thus, TPEN is a useful tool to identify effects of heavy metals (zinc, iron, copper, manganese, etc.) on fluorescent indicators for other ions.

Flubi-2 is the hydrolyzed product of the site-directed fluorogenic probe Flubida-2 (#51022) and can be used as a standard for calibration.

The fluorescence of SPQ is specifically quenched by chloride via collision. Therefore, chloride concentration is measured by monitoring the degree of fluorescence decrease.

The pKa of 5-carboxy-2′,7′-dichlorosulfonefluorescein is near 4 and thus the dye is potentially an excellent pH indicator for acidic organelles.

6-CFDA is membrane-permeant and thus can be loaded into cells via incubation. Once inside cells, 6-CFDA is hydrolyzed by intracellular esterases to 6-carboxyfluorescein.

Flubida-2 has been used to detect pH at a specific site in a cell such as cell organelles by directing the probe to where avidin fusion proteins are located. The probe is a conjugate of biotin and fluorescein diacetate, which is nonfluorescent until the probe has entered the cells and hydrolyzed by endoesterases.

5-CFDA is membrane-permeant and thus can be loaded into cells via incubation. Once inside cells, 5-CFDA is hydrolyzed by intracellular esterases to 5-carboxyfluorescein (see 50015).

This dye can be used as a low pH indicator similar to 51015, and is also useful as a general green fluorescent label.

5-(and-6)-carboxy-2′,7′-dichlorofluorescein is similar to carboxyfluorescein (51013), but has lower pK_a. It is useful for detecting pH in more acidic environment.