Iodoacetyl tandem mass tag reagents enable selective labeling of cysteine-containing peptides for multiplexed sample quantitation using LC-MS/MS analysis. Similar to iodoacetamide, iodoTMT reagents react specifically with reduced cysteines (Cys) in peptides and proteins and enable quantitation of the relative abundance of cysteine modifications, such as S-nitrosylation and the oxidation of disulfide bonds. IodoTMT reagents irreversibly label free sulfhydryl groups on cysteine residues, in contrast to previous reversible cysteine-reactive TMT (cysTMT) reagents.

To selectively analyze the cysteine-labeled peptides, the sample may be enriched using Immobilized Anti-TMT Antibody Resin (Cat. No. 90076) and TMT Elution Buffer (Cat. No. 90104). This approach of selective thiol-labeling and affinity enrichment is similar to isotope-coded affinity tags (ICAT method) but allows for affinity enrichment with a non-biological tag and higher multiplex quantitation.

Features of iodoTMT reagents
• Specific—only reacts with sulfhydryl groups (reduced, unmodified cysteine residues)
• Irreversible—labeled proteins and peptides are not susceptible to reducing agents
• Flexible—options for duplex isotopic (MS) or sixplex isobaric (MS/MS) quantitation
• Versatile—can be used to study cysteine modifications (e.g., di-sulfide bridges, S-nitrosylation)