Fluorescence Mean-Lifetimes of a Series of Small and Bright Fluorescent Dyes

Fluorescence mean-lifetime is a photophysical parameter that is used in basic research and in many fields of applications. However, the parameter is not available in the literature for some small and bright fluorescent dyes, or at least it is difficult to find. Therefore, in the present work, the fluorescence mean-lifetime of some small and bright fluorescent dyes was measured in aqueous buffered solutions. A few more dyes with an already known fluorescence mean-lifetime are also included for comparison. The total list of five classes (scaffolds) and their respective dyes analyzed are as follows: (1) four rhodamines-5(6)-carboxy-X-rhodamine (ROX), Rho 6G 3⁺ (N-[2-(2-aminoethylamino)ethyl]rhodime 6G-amide), Rho 6G 2⁺ (N-(8-amino-3,6-dioxaoctyl)rhodamine 6G-amide), and TAMRA-SE-Gly (a carboxytetramethylrhodamine); (2) four fluoresceins-5-aminofluorescein, 5(6)-carboxyfluorescein (FAM), 6-TET-SE-Gly (a tetrachlorocarboxyfluorescein), and 6-HEX-SE-Gly (a hexachlorocarboxyfluorescein); (3) three pyrenes-8-aminopyrene-1,3,6-trisulfonic acid, 8-hydroxypyrene-1,3,6-trisulfonic acid, and pyrene-1,3,6,8-tetrasulfonic acid; (4) one borondipyrromethene-BODIPY FL (4,4-Difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-propanoic acid); and (5) one acridine-3,6-dimethylaminoacridine (acridine orange). Fluorescence mean-lifetimes were measured in one or more of the following mediums: 100 mM acetic acid/sodium acetate pH 4, water pH ~ 7, and 20 mM potassium tetraborate pH 10.