PE/Atto 594-conjugated anti-horse primary antibodies are tandem-dye immunoreagents designed for red-shifted fluorescence detection in multicolor flow cytometry and imaging applications. Produced by immunizing hosts such as goat, rabbit, or mouse with purified horse immunoglobulins, these antibodies are affinity-purified and conjugated to a tandem complex of R-phycoerythrin (R-PE) and Atto 594. This tandem conjugate utilizes Förster resonance energy transfer (FRET): R-PE absorbs light at 488 nm and transfers energy to the acceptor dye Atto 594, which subsequently emits at approximately 617 nm. The resulting emission is significantly red-shifted compared with PE alone (578 nm), enabling improved spectral separation in multicolor panels.

Atto 594, as the acceptor fluorophore, exhibits high quantum yield, excellent photostability, and minimal pH sensitivity across a broad range (pH 2–10). The tandem complex maintains the high brightness of R-PE (extinction coefficient ≈ 1.96 × 10⁶ M⁻¹cm⁻¹) while providing emission in the orange/red region with minimal spectral overlap with FITC (green), PE (orange), and APC (far-red). Extensive cross-adsorption against immunoglobulins from mouse, rat, rabbit, and human reduces nonspecific binding. These conjugates should be stored at 4°C, protected from light, and should not be frozen.

Applications

PE/Atto 594 conjugates are primarily employed in flow cytometry and fluorescence-activated cell sorting (FACS) for high-parameter immunophenotyping of equine leukocytes. The distinct emission at 617 nm is compatible with standard orange/red detection channels and permits simultaneous detection with FITC (525 nm), PE (578 nm), PerCP (675 nm), and APC (660 nm) in multicolor panels, although appropriate compensation and instrument-specific spectral configuration should be established experimentally. In immunofluorescence microscopy, the bright orange-red emission enables antigen localization in tissue sections and cultured cells with reduced background autofluorescence compared with shorter wavelengths. Additional applications include high-content screening, multiplex bead-based assays (e.g., Luminex®), and fluorescent Western blotting. Typical working dilutions range from 1:50 to 1:500 for flow cytometry and 1:100 to 1:1,000 for immunofluorescence. These reagents are intended for research use only and are not for diagnostic procedures.