TAMRA-X contains a seven-atom aminohexanoyl spacer (known as ‘X’) between TAMRA fluorophore and the succinimidyl ester. The ‘X’ spacer separates the fluorophore from the biomolecule to which it is conjugated, potentially reducing the quenching that typically occurs upon conjugation. We recommend this TAMRA-X derivative as the preferred dye for preparing TAMRA-labeled proteins when the fluorescence quenching of the labeling dye by protein is a serious problem.
Wazawa T, et al.(2000). Spectral fluctuation of a single fluorophore conjugated to a protein molecule. Biophys J 78, 1561-9; Moore KJ, et al. (1999). Single molecule detection technologies in miniaturized high throughput screening: fluorescence correlation spectroscopy. J Biomol Screen 4, 335-54.