5-Carboxytetramethylrhodamine succinimidyl ester

An amine-reactive fluorescent probe; has been used in double site-directed peptide modification to label proteinase substrates for use in FRET assays; quenches lucifer yellow fluorescence by 90% in uncleaved proteinase substrates, which allows for the detection of enzyme-cleaved substrates by an increase in fluorescence intensity; has also been used in the synthesis of fluorescent derivatives of a variety of compounds, including ampicillin, UDP, and RU486; ex/em = 540-560/580 nm, respectively