tetraiodofluorescein

Tetraiodofluorescein is a polyiodinated derivative of fluorescein, in which four iodine atoms are substituted on the xanthene dye backbone. By adding four iodine substituents, the molecule becomes considerably heavier and less hydrophilic than fluorescein, and its spectral properties are altered accordingly.

Chemically, tetraiodofluorescein retains the core xanthene framework of fluorescein but with extensive iodination. The heavy-atom effect of the iodine atoms typically shifts the absorption spectrum toward longer wavelengths and can substantially reduce fluorescence quantum yield relative to unsubstituted fluorescein. These changes make tetraiodofluorescein useful in applications that require dyes with distinct spectral characteristics, though its brightness is generally lower than that of fluorescein.

Preparation of tetraiodofluorescein usually involves electrophilic iodination of fluorescein under carefully controlled conditions, followed by purification to remove partially iodinated byproducts. The resulting compound is often more soluble in organic solvents than in water, reflecting its increased hydrophobic character due to the iodine substituents.

Applications of tetraiodofluorescein center on fluorescence-based techniques in research. It is employed as a fluorescent probe or label in specialized assays and imaging settings where its spectral properties provide a useful spectral separation from other dyes. Its reduced fluorescence compared with fluorescein can be advantageous in certain multiplexed assays, acting as a quenched or lower-intensity label.

Safety and handling follow standard precautions for aromatic iodinated dyes: use appropriate personal protective equipment, work in a well-ventilated area, and dispose of waste according to institutional and regulatory guidelines.