Introduce free sulfhydryl groups into a protein of interest to allow the modified protein to react with a variety of sulfhydryl-selective products.

• Adds a protected sulfhydryl that can be deprotected by hydroxylamine
• Allows long-term storage of the sulfhydryl-modified molecule
• Forms cleavable disulfide bonds with other sulfhydryl-containing molecules
• Reacts with primary amines (e.g., lysine residues proteins) to form stable amide bonds
• Preserves protein activity with its mild, non-denaturing reaction conditions

Sulfhydryl groups are added through a covalent linkage to yield a stable product, yet the reaction conditions will not denature the protein in order to preserve protein activity. In addition, the sulfhydryl group is protected to allow for long-term storage of the modified protein. Deprotection is accomplished through the use of a hydroxylamine, rather than a reducing agent to eliminate the presence of a second sulfhydryl that could quench or compete with subsequent reactions.