Merocyanin 540

Merocyanin 540 is a fluorescent membrane probe that selectively stains the membranes of a wide variety of electrically excitable cells, but not those of nonexcitable cells (Ex/Em: 540/580 nm)^[1][2]. In Vitro:Guidelines^[1] (Following is our recommended protocol. This protocol only provides a guideline, and should be modified according to your specific needs).
Labeling of Cells:
1. Wash monolayer cultured cells with isotonic saline with or without 1-5 mM CaCl₂ or iso-osmotic sucrose (0.25 M) solutions buffered with 5 mM Tris-Cl (pH 7.4).
2. Expose cells to Merocyanin 540 (1.6 x 10^-5 M) in the appropriate buffer for 10 min at room temperature under ambient lighting conditions.
3. Wash extensively and examine by fluorescence microscopy.
4. For protozoa, place 0.05 mL aliquots of washed cultures containing 100-200 organisms on a microscope slide.
5. Add Merocyanin 540 to a final concentration of 1.0-10 μg/mL.
6. Examine cells by fluorescence microscopy.
7. Incubate single cell suspensions or tissue slices with Merocyanin 540 (1.75-5.25 x 10^-5 M) and examine by fluorescence microscopy as described for attached cells.