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Iodoacetic Acid and Iodoacetamide

Rapid carboxymethylation of reduced cysteine residues.

Pierce Iodoacetic Acid (IAA)

Thermo Scientific Pierce Iodoacetic Acid (IAA) can react with several protein functional groups but is typically used for specific S-carboxymethylation of sulfhydryls (reduced cysteines).

Iodoacetic acid reacts with sulfhydryls on cysteines, imidazolyl side chain nitrogens of histidines, the thioether of methionine and the primary amine group of lysines.The rate of reaction and specificity is dependent on the ionization level, which can be manipulated by the pH of the reaction condition.


  • React at slightly alkaline pH for specific S-carboxymethylation of free sulfhydryls
  • React at low pH for specific carboxymethylation of methionines
  • React at high pH to favor carboxymethylation of histidines and lysines
  • Methylate reduced cysteine peptide fragments in protease digests for mass spectrometry

Product Details:

Iodoacetic Acid (IAA) Iodoacetamide (IAM))
  • Chemical name: iodoacetic acid
  • Reactivity: sulfhydryl groups
  • Chemical formula: C2H3IO2
  • CAS number: 64-69-7
  • Molecular weight: 185.95
  • Form: solid, powder
  • Chemical name: iodoacetamide
  • Reactivity: sulfhydryl groups
  • Chemical formula: C2H4INO
  • CAS number: 144-48-9
  • Molecular weight: 184.96
  • Form: solid, powder


  1. Hall, J., et al. (1989). Role of specific lysine residues in the reaction of Rhodobacter sphaeroides cytochrome c2 with the cytochrome bc1 complex. Biochem 28:2568.
  2. Hermason, G.T. (2008). Bioconjugate Techniques, Second Edition. Academic Press. pp. 109-111.

Related Resources:

Overview of crosslinking and protein modification
Sample preparation for mass spectrometry

Related Products:

N-ethylmaleimide – permanently block sulfhydryls
MM(PEG)n – methylate and pegylate sulfhydryls
MMTS – reversibly block sulfhydryls

Ordering Information
Product # Description Pkg. Size Instructions MSDS CofA Price
35603 Iodoacetic Acid
Formulation: Iodoacetic acid
Sufficient For: 27mL of 100mM solution
500mg MSDS for product #35603 Iodoacetic Acid Certificate of Analysis for product #35603 Iodoacetic Acid $80.00

Now available on lifetechnologies.com
90034 Iodoacetamide, Single-Use
Formulation: White solid of 2-iodoacetamide (IAM) in foil-sealed black microtubes (3 x 8 format)
Sufficient For: 24 separate uses for alkylation before mass spectrometry, each with up to 75 protein samples
24 x 9.3mg Product Instructions for product #90034 Iodoacetamide, Single-Use MSDS for product #90034 Iodoacetamide, Single-Use Certificate of Analysis for product #90034 Iodoacetamide, Single-Use $144.00

Now available on lifetechnologies.com

Instructions | MSDS | CofA
Product Instructions | MSDS | CofA  

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