5-CR110-PEO4 SE (full name: 5-Carboxyrhodamine 110-PEO4-propionate, succinimidyl ester, single isomer) is an excellent green fluorescent rhodamine dye for labeling amines. The dye has better solubility than the parent dye 5-CR110 SE and its long PEG spacer should reduce any steric effect of the dye on the molecule to be labeled. Carboxyrhodamine 110 and its derivatives are, in general, significantly more photostable than any other known green fluorescent dyes including Alexa Fluor® 488. In addition, their spectra are unaffected by pH change from 4 to 9. Unlike Alexa Fluor® 488, which is readily degraded under alkaline conditions, CR110 and its derivatives are highly stable under both acidic and basic conditions. As a result, CR110 and its derivatives are superior alternatives to other green fluorescent dyes for applications where only a single dye is required for the labeling.
