Coumarin 343

Coumarin 343 is a small hydrophilic dye. It cannot penetrate cell membranes by itself. Coumarin 343 is also known as Coumarin 519. Depending on the pH of the medium, coumarin 343 exists in neutral and anionic forms with an excitation peak at 443 nm and an emission peak at 461 nm. It can be excited using a 445 nm laser and a 510/80 nm bandpass filter.