U. C. Davis, Biological Sciences

Disulfide Bonds

Under oxidizing conditions, two cysteine molecules (or cysteine residues in a polypeptide or protein) can dimerize through formation of a disulfide bond. The structure of two cysteine residues connected by such a link is shown below. This cysteine dimer is sometimes referred to in as a cystine residue when it is found in a protein. Disulfide bonds in proteins do not participate directly in initial formation of protein structure but can be important in stabilizing such structures against denaturation. Disulfide bonds can be broken by addition of reducing agents. The most common agents for this purpose are ß-mercaptoethanol (BME) or dithiothritol (DTT).

Disulfide Bond

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Aliphatic AA	Aromatic AA	Polar but Uncharged AA
G, A, V, L, I, P	F, Y, W	S, T, N, Q

Suflur Containing AA	Charged AA
C, M	D, E, H, K, R

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