Thiol Reactants and Conjugates

Thiol reactive reagents and conjugates are designed to selectively label free sulfhydryl (-SH) groups, most commonly found on cysteine residues in proteins and peptides. These reagents react rapidly and efficiently through thiol-specific chemistries such as maleimide addition, haloacetamide alkylation, or Michael addition to activated electrophiles, forming stable covalent thioether bonds. Because cysteine is relatively rare and often site-specific, thiol-reactive reagents enable highly controlled and targeted modification of biomolecules. These reagents are widely used for protein labeling, antibody conjugation, fluorescent tagging, PEGylation, and the development of bioconjugates for imaging, diagnostics, and therapeutic applications.