Fluorescent derivatization reagents for thiols bearing a new type of fluorophores: 7-fluoro-2,1,3-benzoselenadiazole-4-sulfonate and 7-fluoro-2,1,3-benzothiadiazole-4-sulfonate.

7-Fluoro-2, 1, 3-benzoselenadiazole-4-sulfonate (SBSeD-F) and 7-fluoro-2, 1, 3-benzothiadiazole-4-sulfonate (SBThD-F) were synthesized and proposed as the water-soluble fluorescent derivatization reagents for thiols bearing a new type of fluorophores (benzoselenadiazole and benzothiadiazole). The maximum excitation wavelengths of the derivatives of cysteine with SBSeD-F (340 nm) and SBThD-F (315 nm) were shorter than that with ammonium 7-fluoro-2, 1, 3-benzoxadiazole-4-sulfonate (SBD-F) (365 nm), respectively, while the maximum emission wavelength with SBSeD-F (542 nm) was longer than those with SBThD-F (517 nm) and SBD-F (514 nm). The time required for the quantitative derivatization of cysteine with SBSeD-F or SBThD-F was less than 24 h at pH 10.0 and 60°C, while the derivatization was achieved within 1 h with SBD-F. The appropriate derivatization condition was settled with 2 mM SBSeD-F or SBThD-F as 24 h reaction at 60°C in 0.1 M borate buffer (pH 10.0) in the presence of 0.5 mM EDTA.(Communicated by Masanori OTSUKA, M. J. A., May 12, 2003)