Studies on Peptides. CXXV. 3-(3-p-Methoxybenzylthiopropionyl)-thiazolidine-2-thione and Its Analogs as Reagents for the Introduction of the Mercapto Group into Peptides and Proteins

A new SH-introducing reagent, 3-(3-p-methoxybenzylthiopropionyl) thiazolidine-2-thione (MTPTT), was prepared by condensation of 3-p-methoxybenzylthiopropionic acid and thiazolidine-2-thione using DCC. Reaction of MTPTT with peptides can be monitored by following the disappearance of the pale yellow color of the reagent. As an example, synthetic human growth hormone-releasing factor (hGRF-40) was treated with MTPTT, followed by 1M trifluoromethanesulfonic acid-thioanisole/trifluoroacetic acid. The resulting HS-CH2CH2-CO-(hGRF-40) was conjugated with bovine serum albumin (BSA) by using a newly introduced heterobifunctional conjugating reagent, 2, 4-dinitrophenyl p-(β-nitrovinyl) benzoate for antigen preparation. Four other similar SH-introducing reagents were also prepared.