Simultaneous trichromatic fluorescence detection of proteins on Western blots using an amine-reactive dye in combination with alkaline phosphatase- and horseradish peroxidase-antibody conjugates.

Three-color fluorescence detection methods are described based upon covalently coupling the dye 2-methoxy-2,4-diphenyl-2(2H)-furanone (MDPF) to proteins immobilized on poly(vinylidene difluoride) (PVDF) membranes, followed by detection of target proteins using alkaline-phosphatase-conjugated reporter molecules in combination with the fluorogenic substrate 9H-(1,3-dichloro-9,9-dimethylacridin-2-one-7-yl) phosphate (DDAO-phosphate) as well as horseradish peroxidase-conjugated reporter molecules in combination with the new fluorogenic substrate Amplex Gold reagent. This results in all proteins in the profile being visualized as fluorescent blue signal, those detected specifically with the alkaline phosphatase conjugate appearing as fluorescent red signal and those detected specifically with the horseradish peroxidase conjugate appearing as fluorescent yellow signal. Using conventional secondary antibodies, two different targets may be identified as long as primary antibodies generated from two different species are used in the analysis. However, Zenon antibody labeling technology eliminates this restriction, permitting the simultaneous use of two different mouse monoclonal antibodies or two different rabbit polyclonal antibodies in the same electroblotting experiment. The trichromatic detection system is broadly compatible with UV epi-illuminators combined with photographic or charge-coupled device (CCD) cameras, and xenon-arc sources equipped with appropriate excitation/emission filters. Alternatively, the enzyme conjugates may be detected using a laser-based gel scanner. The trichromatic method permits detection of low nanogram amounts of protein and allows for unambiguous identification of two different target proteins relative to the entire protein profile on a single electroblot, precluding any requirement for running replicate gels that would otherwise require separate visualization of total proteins and subsequent alignment with multiple chemiluminescent or colorimetric signals generated on different electroblots.