NSP [³H]-, (N-Succininidynl[2,3-³H]propionate)

³H succinimidyl propionate is used to labeled proteins with tritium. Succinimidyl propionate is supplied in benzene, which must be removed immediately prior to use. This can be accomplished by subjecting the reagent to a gentle stream of dry nitrogen. The dried reagent should be immediately redissolved in a small amount of dry tetrahydrofuran (THF). The volume of THF should be kept to a minimum so that it is never greater than 10% of the labeling reaction.

The protein to be labeled should be dissolved in the volume of buffer so that, after addition of the succinimidyl propionate in THF, the final protein concentration is 2 mg/mL. Both 0.2 M potassium phosphate buffer pH 7.5 and 0.05 M borate buffer pH 8.0 have been shown to be suitable buffers. Add the protein to the succinimidyl propionate at 0-2 °C and mix. The reaction should be allowed to proceed for at least two hours and may be left over night at 4 °C. At that time, the reagent is either conjugated or hydrolyzed. Dialysis or gel filtration is recommended to separate labeled protein from hydrolysis products. The protein may then be further purified and analyzed by conventional methods. Protein specific activities of 0.1 - 25 mCi/mg have been obtained post-labeling by our laboratories.