The spectroscopic and electrophoretic properties of
proteins labeled with Chromeo
P503 were investigated. Its photobleaching characteristics were determined by continually infusing Chromeo P503-labeled
alpha-lactalbumin into a sheath-flow cuvette and monitored fluorescence as a function of
laser power. The labeled
protein is relatively photo-labile with an optimum excitation power of about 2 mW. The unreacted
reagent is weakly fluorescent but present at much higher concentration than the labeled
protein. The unreacted
reagent undergoes photobleaching at a
laser power more than an order of magnitude higher than the labeled
protein. One-dimensional capillary electrophoresis analysis of Chromeo P503-labeled
alpha-lactalbumin produced concentration detection limits (3sigma) of 12 pM and mass detection limits of 0.7 zmol, but with modest theoretical plate counts of 17,000. The
reagent was employed for the two-dimensional capillary electrophoresis analysis of a homogenate prepared from a
Barrett's esophagus cell line; the separation quality is similar to that produced by
3-(2-furoyl)quinoline-2-carboxaldehyde (FQ), a more commonly used
reagent.