Iodoacetamide (IAA) is an organic compound with the chemical formula ICH2CONH2.

It is commonly used to bind covalently with the thiol group of cysteine so the protein cannot form disulfide bonds.

In comparison with its acid derivative, iodoacetate, iodoacetamide reacts substantially faster.

This observation appears contradictory to standard chemical reactivity, however the presence of a favourable interaction between the positive imidazolium ion of the catalytic histidine and the negatively charged carboxyl-group of the iodoacetate is the reason for the increased relative activity of iodoacetamide.

[4] It is commonly used during the sample preparation for de novo (peptide) sequencing with protein mass spectrometry, but recent critics suggest to avoid the use of it [5]