EFFECTIVE FLUORESCENT AND 125-IODINE LABELING OF PROTEINS WITH A NEW LABELING REAGENT

A new fluorescent labelling reagent, which was previously developed fo r the labelling of polysaccharides, was also applied to the labelling of non-glycosilated proteins, aspartate aminotransferase and tumor nec rosis factor-alpha. Both proteins were labelled over a range of fluore scent substitutions (0.2 to 1.6 fluorescent moieties per protein molec ule) without loss of biological activity. The fluorescent reagent can also be initially labelled with (125)-iodine. The specific radioactivi ty and biologic activity of labelled tumor necrosis factor-alpha were equivalent to that prepared by a conventional technique for radioiodin ation. It is demonstrated that this new derivative chemistry may be ap plicable to the non-destructive labelling of a wide range of proteins in addition to polysaccharides.