SPQ is used to measure membrane chloride transport mechanisms.

Instructions
a. Solution preparation:
1. Preparation of SPQ stock solution: Dissolve SPQ powder in water or buffer to prepare a stock solution of at least 1 mg/mL. For example, weigh 10 mg of SPQ and add it to 10 mL of water or buffer.
2. Preparation of working solution: Dilute SPQ stock solution with Krebs-HEPES buffer (20 mM HEPES, 128 mM NaCl, 2.5 mM KCl, 2.7 mM CaCl2, 1 mM MgCl2, 16 mM glucose, pH 7.4) to prepare a 5-10 µM working solution for later use.
Note: The stock solution needs to be stored at -20℃ or -80℃. Please avoid repeated freezing and thawing. The diluted working solution should be prepared and used as soon as possible.
b. Operation steps:
1. Cultivate the cells to be tested to an appropriate density, about 8-10×10^6 cells/mL.
2. Wash the cells 3 times with Krebs-HEPES buffer.
3. Add 5-10 µM SPQ in Krebs-HEPES buffer to the cells and incubate at 37°C for 1 hour.
4. Wash the cells 5 times with Krebs-HEPES buffer to remove the residual dye outside the cells.
5. Observe the cells using a fluorescence microscope with an excitation wavelength of 344 nm and an emission wavelength of 443 nm.

The above information is based on published literature. Experimental procedures should be appropriately modified to meet specific research demands.

H2O: 20 mg/mL (71.09 mM), Sonication is recommended.