A NEW FLUORESCENCE REACTION IN PROTEIN CYTOCHEMISTRY - FORMATION OF NAPHTHALIMIDE FLUOROPHORES FROM PRIMARY AMINO-GROUPS AND 1,8-NAPHTHALICANHYDRIDE DERIVATIVES

In this work we describe the formation of fluorescent naphthalimide de rivatives as a new cytochemical method for revealing protein amino gro ups. The reaction is based on the condensation of 1,8-naphthalic anhyd rides in organic solvents with primary aliphatic amines. Under optimal violet-blue (436 nm) excitation, a strong yellow-green emission is ob served in specific cell components from blood smears treated with 3-am ino-1,8-naphthalic anhydride in N,N-dimethylformamide, which were the most suitable reagent and solvent for microscopic studies. Cytoplasmic granules of mammalian eosinophils and avian heterophils showed the hi ghest fluorescence reaction, which was abolished by blocking procedure s for amino groups. Spectrofluorometric analysis confirmed the emissio n characteristics of the naphthalimides produced from n-butylamine and gelatine. Taking into account the chemical reactivity of 1,8-naphthal ic anhydrides and present results, the reaction can be considered sele ctive for lysine andarginine residues of proteins.