Fluorescent protein tracers: the unreacted fluorescent material in fluorescein conjugates and studies of conjugates with other green fluorochromes.

Abstract

Protein conjugates with fluorescein isocyanate and isothiocyanate contain unreacted fluorescent material (U.F.M.) which contributes to specific immunological staining but is troublesome because it also stains non-specifically. Attempts have been made to find an alternative to fluorescein isocyanate and isothiocyanate conjugates, with similar green fluorescence but free from U.F.M. and more easily prepared. Conjugates were made with fluorescein and certain derivatives of fluorescein in the form of the acid chlorides, `reactive' dyes, a dichlorocyclopropyl derivative of a stilbene sulphonic acid (R 8065/1, Geigy), and 3-hydroxypyrene 5-8-10 trisulphonic acid; none proved satisfactory. At the present time, green fluorescent protein tracers are probably best prepared from fluorescein isothiocyanate.