6-Carboxy-X-rhodamine N-succinimidyl ester is widely used as a fluorescent labeling reagent in biochemical and cellular research. It is particularly effective for labeling proteins, peptides, and antibodies due to its reactive succinimidyl ester group, which forms stable amide bonds with primary amines. This compound is valued for its bright fluorescence and photostability, making it ideal for fluorescence microscopy, flow cytometry, and other imaging techniques. It is often employed in live-cell imaging to track molecular interactions and cellular processes in real time. Additionally, it is used in fluorescence resonance energy transfer (FRET) studies to investigate protein-protein interactions and conformational changes. Its compatibility with various biological systems and high sensitivity makes it a versatile tool in molecular and cell biology research.