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SAT(PEG)4 Thiolation and PEGylation Reagent

Pegylates and adds protected sulfhydryl groups for later conjugation.

Pierce SAT(PEG)4

Thermo Scientific Pierce SAT(PEG)4 is a long-arm (18.2 angstroms), pegylated form of SATA, a sulfhydryl-addition reagent for covalent modification of primary amines to facilitate controlled, heterobifunctional crosslinking.

SAT(PEG)4 is the abbreviation for N-Succinimidyl S-acetyl(thiotetraethylene glycol), an amine-reactive reagent for PEGylating and adding sulfhydryl groups to proteins and other amine-containing molecules. Like SATA and other S-acetyl (SAT) reagents, SAT(PEG)4 is most frequently used in bioconjugation methods to incorporate sulfhydryl (–SH) groups into proteins as part of a two-step or heterobifunctional crosslinking strategy. The SAT group prevents oxidation of the sulfur atom but is easily removed by treatment with hydroxylamine when the unprotected sulfhydryl group is needed for conjugation. The polyethylene glycol (PEG) spacer arm in SAT(PEG)4 minimizes steric hindrance and provides added solubility to the modified and conjugated molecules.


  • Thiolate and PEGylate primary amines in one step
  • Add sulfhydryl groups for heterobifunctional crosslinking without compromising protein solubility
  • NHS-activated for efficient PEGylation of primary amines at pH 7-9; reaction of NHS-ester group results in formation of stable, irreversible amide bonds
  • Pure compound with defined structure and molecular weight, ensuring reproducible protein-modification effects
  • PEG spacer provides unique advantages, including increased stability, reduced tendency toward aggregation and reduced immunogenicity

Product Details:

Succinimidyl acetyl(thiotetraethyleneglycol); SAT(PEG)4)

Structure and properties of SAT(PEG)4:

  • Functional groups: NHS ester (amine-reactive) and sulfhydryl (protected)
  • Chemical name: N-succinimidyl S-acetyl (thiotetraethyleneglycol) ester
  • Alternative names: dPEG4 SATA; PEG SATA; S-acetyl-dPEG4; PEO SATA; SAT-PEO4, pegylated SATA
  • Spacer arm length: 18.3 angstroms (includes polyethylene glycol units)
  • Molecular weight: 421.46

Specific reactivity to primary amines (e.g., lysine residues in proteins) occurs via the NHS-ester group. Spontaneous reaction in phosphate or other non-amine buffer at pH 7-9 results in formation of stable, covalent, amide bonds. Upon deprotection of the sulfhydryl group with hydroxylamine, molecules that have been modified with SAT(PEG)4 can be reacted with other proteins or surfaces that have been maleimide-activated with heterobifunctional crosslinkers like Sulfo-SMCC or SM(PEG)n Reagents.

Thiolation with SATA, an S-acetyl NHS-ester modification reagent
Reaction and modification scheme for NHS-activated S-acetyl reagents.

Related Resources:

Overview of crosslinking and protein modification
Protein Pegylation and PEG reagent selection guide

Related Products:

SATA – alternative sulfhydryl-addition reagent
SATP – slightly longer version of SATA
Hydroxylamine – deprotects sulfhydryls after SATA modification
Traut's Reagent– small thiolation compound
SPDP – amine-to-sulfhydryl crosslinker

Ordering Information
Product # Description Pkg. Size Instructions MSDS CofA Price
26099 SAT(PEG)4
Formulation: Succinimidyl acetyl(thiotetraethyleneglycol); amber oil liquid
Sufficient For: 237mL of typical 1X (1mM) reaction solution, or approx. 50 uses at 2mg reagent per use
100mg Product Instructions for product #26099 SAT(PEG)4 MSDS for product #26099 SAT(PEG)4 Certificate of Analysis for product #26099 SAT(PEG)4 $297.00

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Instructions | MSDS | CofA
Product Instructions | MSDS | CofA  

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