5-(and-6)-Carboxyrhodamine 110-X, succinimidyl ester (5(6)-CR 110-X, SE) readily couples to a primary or secondary amine. The dye is a superior alternative to 5(6)-SFX because of its exceptional phototostability and fluorescence insensitivity to pH between 4-9.    &lamba;Ex/&lamba; Em (MeOH) = 502/524 nm  Orange red solid soluble in DMSO or DMF.  Store at -20°C and protect from light  C31H28N4O8  MW: 584.58