Widely used in bioconjugation, this compound efficiently labels primary amine groups on proteins, peptides, and amine-modified nucleic acids, enabling fluorescent detection in biological systems. Its high fluorescence quantum yield and photostability make it ideal for sensitive imaging applications such as fluorescence microscopy, flow cytometry, and immunohistochemistry. The carboxyl group enhances water solubility and allows for further chemical modifications, improving compatibility with aqueous biological environments. It is especially useful in multicolor labeling experiments due to its distinct emission spectrum in the orange-red region, which minimizes overlap with other common fluorophores. Additionally, the N-succinimidyl ester group ensures rapid and selective reaction under mild conditions, making it a preferred choice for labeling biomolecules without affecting their activity.