Synthesis, spectral properties, and use of 6-acryloyl-2-dimethylaminonaphthalene (Acrylodan). A thiol-selective, polarity-sensitive fluorescent probe.

Fluorophores processing a 6-acyl-2-dimethylaminonaphthalene moiety show fluorescence that is extremely sensitive to solvent polarity (Weber, G., and Farris, F. J. (1979) Biochemistry 18, 3075-3078). We have synthesized and characterized 6-acryloyl-2-dimethylaminonaphthalene (Acrylodan) which selectively labels thiol moieties in proteins. The quantum yield of this agent is markedly enhanced after reaction with thiols, and as expected, the fluorescent derivatives are very sensitive to dipolar perturbation from their environments. The usefulness of Acrylodan in the study of "hydrophobic" domains, conformational changes, and dipolar relaxation processes in proteins is demonstrated by measurements of fluorescence spectra and lifetimes of a mercaptoethanol adduct dissolved in different solvents and of adducts of this agent with parvalbumin, troponin C, papain, and carbonic anhydrase.