Pacific Blue (dye)
Pacific Blue, or systematically 3-carboxy-6,8-difluoro-7-hydroxycoumarin, is a fluorophore used in cell biology. Its excitation maximum lies at 401 nm, while its emission maximum is at 452 nm. Even at pH around 7, its fluorescence remains very high. Pacific Blue is a member of the group of Pacific dyes, which includes Pacific Orange, Pacific Green, and Pacific Blue. These fluorescent dyes all have an absorption maximum between 400 and 410 nm, but with different emission spectra: this allows simultaneous excitation with one laser, producing emission at maxima of 551nm, 500 nm and 455 nm , respectively (note: absorption and emission maxima may vary depending on the manufacturer). In flow cytometry Pacific Blue (as well as other Pacific dyes) usually absorbs at 405 nm, disallowing simultaneous use with other fluorophores which share similar excitation and/or emission spectra, such as BV421 or V450. Usage. For purposes of immunohistochemistry or targeted staining in general, Pacific Blue is used as its reactive forms which enable binding to targeting antibodies. Reactive forms in usage are Pacific Blue succinimidyl ester or Pacific Blue C5-Maleimide.