5-ROX-PEO8 SE (full name: 5-Carboxy-X-rhodamine-PEO8-propionate, succinimidyl ester) has an approximately 32 Angstrom water-soluble PEG spacer that separates the red fluorescent ROX dye and the amine-reactive SE group. &lamba;Ex/&lamba; Em(MeOH) = 568/595 nm Dark red solid soluble in DMSO or DMF Store at -20°C and protect from light C56H70N4O16 MW: 1055.17