tetrametilrodamina

Tetramethylrhodamine is a red-emitting fluorophore belonging to the rhodamine family and widely used as a fluorescent label in biochemistry and cell biology. The name also appears in reference to TAMRA, the carboxytetramethylrhodamine derivative, which is common in bioconjugation applications. The core consists of a xanthene chromophore with four methyl substituents on the amine groups, contributing to brightness and photostability. In solution the dye is typically cationic and can equilibrate with a nonfluorescent lactam form depending on pH and solvent.

Spectral properties of tetramethylrhodamine place its absorption in the green-yellow region and its emission in the orange-red region. Typical excitation is around 540–565 nm and emission around 580–590 nm, producing bright fluorescence that is well separated from green-emitting dyes. The dye offers high extinction coefficients and substantial quantum yield, making it a reliable fluorophore for multicolor imaging. It is moderately pH-dependent, with fluorescence diminishing under strongly acidic conditions.

Applications and derivatives of tetramethylrhodamine are widespread in fluorescence microscopy, flow cytometry, and molecular labeling. It is available in various reactive forms for covalent attachment, including NHS esters for amines, maleimides for thiols, and other handles suitable for click chemistry. The carboxylated TAMRA derivative is especially common for peptide and protein labeling, and TMR/TAMRA dyes are often used in FRET pairs with appropriate partners.

Availability and handling: tetramethylrhodamine and its derivatives are commercially available from multiple suppliers in free dye and conjugatable forms. As with other fluorophores, standard laboratory safety practices apply, and working concentrations are typically in the micromolar to nanomolar range for imaging and labeling experiments.