SATA is a short-chain (2.8 angstroms spacer arm) reagent for covalent modification of primary amines with a protected sulfhydryl, simulating a crosslinking reagent.SATA reacts with primary amines at pH 7-9 and the resulting modified molecule contains a protected reactive group, which can be deprotected to give the reactive thiol by treatment with hydroxylamine-HCl.Before deprotection, the modified molecule can be stored indefinitely.Sulfhydryl groups are important in protein chemistry modification, but are not always present in the molecule of interest.