5-CR6G, SE is the purified single isomer of 5(6)-CR6G, SE. It is preferred for some complicated biological applications where reproducibility is more critical than material cost since the minor positional difference between 5-CR6G and 6-CR6G might significantly affect some biological properties of the underlying conjugates.
Hung SC, et al. (1997). Optimization of spectroscopic and electrophoretic properties of energy transfer primers. Anal Biochem 252, 78-88; Hung SC, et al. (1996). Energy transfer primers with 5- or 6-carboxyrhodamine-6G as acceptor chromophores. Anal Biochem 238, 165-70.