Protonex™ Red 670 maleimide is a highly effective tool for generating target-specific conjugates aimed at monitoring pH-dependent biological processes. This fluorophore demonstrates pH-sensitive fluorescence, with low intensity at basic pH and enhanced fluorescence at acidic pH. When conjugated to surface-bound receptors or antibodies, Protonex™ Red 670 remains non-fluorescent due to the neutral extracellular pH. Upon internalization through the endosomal pathway, where the pH becomes more acidic, the dye exhibits a significant increase in fluorescence intensity. Excitation at 632 nm (He-Ne laser) or 647 nm (red laser) induces red emission, making it ideal for tracking receptor or antibody activation and intracellular trafficking in live cells.

Protonex™ Red 670 maleimide is commonly employed for labeling biomolecules containing free thiol (SH) groups, including antibodies, proteins, thiol-modified oligonucleotides, and small-molecule ligands. Maleimide functional groups form stable thioether bonds with sulfhydryl groups, facilitating robust and consistent labeling of biomolecules for various experimental applications, including flow cytometry, fluorescence microscopy, and live-cell imaging.