In article <[email protected]>, [email protected] says... > > At Sun, 07 Aug 2011 04:04:41 +0000, DK wrote: > > I actually didn't know that "regular" fluorescein has carboxy group. > > What I meant was its carboxy derivative has another COO- on the same > > ring. Fluorescein does bleach rather easily, so this might be a turn > > off. > > Stupid me. The carboxy group I thought of is part of the chromophore. But > that probably means that activating a second carboxy group for coupling > (by eg a carbodiimide method) might result in a mess. That might be the > reason, why fluorescin usually is used as isothiocyante (FITC) for > labelling. > > Your suggestion with the food colorings might be worth a try. > > Thnkns! > > Wo > > > > > Another thought: food coloring dyes. Of what Wikipedia lists, two > > (erythrosine and tartrazine) are carboxylates. They should be very > > cheap! > > > > DK
FITC is used as the isothiocyanate group is very reactive towards primary amines, allowing protein modification under mild conditions. The resulting thiourea, however, has a somewhat limited stability. Erythrosine btw is tetraiodo-fluoresceine. If you plan experiments involving fluorescent labelling, your first stop should be the the Molecular Probes Handbook (http://www.invitrogen.com/site/us/en/home/References/Molecular-Probes- The-Handbook.html). For a more systematic introduction, you may also consider "Biophysical Chemistry of Proteins" (Springer 2011) by yours truely. _______________________________________________ Methods mailing list [email protected] http://www.bio.net/biomail/listinfo/methods
