A protein modification reagent used to convert primary amine groups into protected sulfhydryls (-SH). The sulfhydryl is readily made available for use in subsequent reactions by treatment with hydroxylamine. After the simple deprotection step is performed to create the thioacetylated peptide, the free sulfhydryl containing peptide can subsequently be conjugated to make a hapten-carrier conjugate. MW: 231.23. Purity ≥94% GC