Preparation and Characterization of Three Fluorescent Labels for Proteins, Suitable for Structural Studies

Three 7-aminocoumarin derivatives, 7-carboxymethyl-amino-4-trifluoromethyl-2 H-1-benzopyran-2-one [2], 7-carboxymethylamino-4-methyl-2 H-1-benzopyran-k2-one [4], and 7-dimethylamino-4-formyl-2 H-1-benzopyran-2-one [6], were prepared. The reagents can be attached to primary amino groups of proteins. The labeled derivatives are stable and are characterized by a strong absorption band in the near uv (300-400 nm) and an emission band in the blue region (440-510 nm) with a large Stokes′ shift. The spectral characteristics of these probes make them useful in applications of dynamic nonradiative excitation energy transfer measurements for conformational studies and analytical procedures based on simultaneous detection of labeled components in mixtures.