An unnatural amino acid that forms a covalent bond with a proximal cysteine can be introduced into proteins, facilitating a variety of applications. Natural proteins often rely on the disulfide ...

Most sulfenic acids enjoy only a fleeting existence, quickly undergoing disulfide bond formation or further oxidation to sulfinic (–SO 2 H) or sulfonic (–SO 3 H) acids.

Thanks to the chemistry of its thiol group, cysteine has long been the go-to amino acid when researchers want to modify a protein. It’s easy to pluck off cysteine’s thiol proton and replace it ...

These new bonds were only discovered in 2016, and are formed when the end of a lysine side-chain is linked to the end of a cysteine side-chain with an oxygen atom linking them together.