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.