JenKem Technology provides high quality activated polyethylene glycol derivatives (PEGs) with high purity and low polydispersity for Thiol PEGylation or Sulfhydyl PEGylation.

Methoxy PEG Maleimide is selective for thiol groups on cystein side chains. Y-shape PEG Maleimide is more selective, due to its sterically bulky structure. The bulky structure of JenKem Technology’s proprietary Y-shape branched PEG derivatives, consisting of two linear methoxy PEG chains attached to a central core with an active maleimide group, may help to reduce the number of attachment sites to a protein molecule.

Methoxy PEG Vinylsulfone is a sulfhydryl reactive PEG that reacts at high pH. Methoxy PEG Thiol polydisperse or monodisperse PEGs are thiol reactive towards the SH groups on cysteine side chains under mild reaction conditions. PolyLactide PEG Maleimide (PLA PEG Maleimide) is a biodegradable thiol reactive PEG co-polymer usually employed for controlled drug release.

Activated PEG products for thiol PEGylation with molecular weights, branching, and functional groups not listed in our online catalog may be available by custom synthesis. Please inquire at about pricing and availability of custom PEGs for thiol PEGylation, and PEGylation services.

JenKem Technology provides GMP grade PEG derivatives and bulk orders via

Scheme of Thiol PEGylation with JenKem® Y-PEG-MAL

custom synthesis, offering the opportunity to match customers’ special quality requirements. JenKem Technology is capable of development and synthesis of a wide range of GMP PEG derivatives in 200g to 40 kg or greater batches, under ISO 9001 and ISO 13485 certified quality management system, following ICH Q7A guidelines. In 2020 JenKem Technology will start to use High Purity (> 99%) mPEG Raw Materials to manufacture GMP grade Methoxy PEG Derivatives. For inquiries on cGMP production of PEG derivatives please contact us at

For global distribution, please visit link. Click the buttons below to order directly from JenKem Technology:

Y-shaped  PEG Maleimide
≥ 95% Y-shape PEG Maleimide reacts with thiol groups at pH 5.0-6.5. JenKem proprietary Y-shape PEGs are more selective, due to their sterically bulky structure.[1]
U-shaped Branched PEG Maleimide
≥ 95% MPEG2 Maleimide  with superior quality; reacts with thiol groups on cystein side chains, such as thiols on certolizumab [28]
Linear Methoxy PEG Maleimide
≥ 95% Methoxy PEG Maleimide from JenKem Technology is a thiol reactive PEG derivative selective for thiol groups on cysteine side chains. Methoxy PEG Maleimide undergoes thiol PEGylation reactions with thiol-containing molecules at pH 5.0-6.5. [2-4], [15-20].
Linear Methoxy PEG Iodoacetamide
≥ 90% Methoxy PEG Iodoacetamide from JenKem Technology is a PEG derivative reacting with thiol groups on cysteine side chains.
Linear Methoxy PEG Vinylsulfone
≥ 90% Methoxy PEG Vinylsulfone are high quality products for sulfhydryl PEGylation. Methoxy Vinylsulfone PEG products are special thiol PEGylation PEGs that react at high pH. [5]
Linear Methoxy PEG Thiol
≥ 95% Methoxy PEG Thiol is a high quality activated PEG product for thiol pegylation. Methoxy PEG Thiol PEGylates the thiol groups on cysteine side chains under mild reaction conditions.[6-9], [21-25].
≥ 90% Methoxy PEG5 Thiol and Methoxy PEG6 Thiol monodisperse Methoxy PEG Thiol products for thiol PEGylation in mild conditions. [10]
Linear Methoxy PEG Acrylate
≥ 90% Substitution Methoxy PEG Acrylate a thiol-reactive PEG, reacting with sulfhydryl groups via Michael addition reactions. Acrylate groups are typically involved in vinyl photopolymerization or co-polymerization. [33]
≥ 90% Purity Methoxy PEG5 Acrylate and Methoxy PEG6 Acrylate monodisperse Methoxy PEG Acrylate products for thiol PEGylation. [34]
Biodegradable PolyLactide PEG Maleimide Co-Polymers (PLA PEG Maleimide)
≥90% MAL-PEG5000-b-PLA20K, Maleimide Polyethylene Glycol Polylactide block copolymer, PEG MW 5000, PLA MW 20000, Substitution (Maleimide) ≥ 70%. Biodegradable PEG for controlled release applications.
≥90% MAL-PEG2000-b-PLA2000, Maleimide Polyethylene Glycol Polylactide block copolymer, PEG MW 2000, PLA MW 2000, Substitution (Maleimide) ≥ 70%. Biodegradable PEG for controlled release applications.
Homobifunctional Activated PEG for Thiol PEGylation


> 90% Maleimide PEG Maleimide. Selective crosslinker for thiol groups on cystein side chains. [11]
≥ 95% Thiol PEG Thiol. Thiol reactive PEG crosslinker, reacts with HS groups on cysteine side chains under mild reaction conditions. [12], [26].
> 90% Vinylsulfone PEG Vinylsulfone. Sulfhydryl reactive homobifunctional PEG crosslinker [13, 14, 27].
> 90% Tosylate PEG Tosylate. Tosylate PEG Tosylate (diTosylate PEG, diToluenesulfonyl PEG, or PEG (Tosylate)2) is employed for amine and thiol pegylation.
≥ 95% PEG diAcrylate. Thiol reactive PEG crosslinker. [29-32]
Monodisperse Heterobifunctional PEGs Functionalized with Thiol
Heterobifunctional PEGs Functionalized with Thiol Reactive Groups
Multiarm Homofunctional PEGs Functionalized with Thiol Reactive Groups
Multiarm Heterobifunctional PEGs Functionalized with Thiol Reactive Groups


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Founded in 2001 by experts in PEG synthesis and PEGylation, JenKem Technology specializes exclusively in the development and manufacturing of high quality polyethylene glycol (PEG) products and derivatives, and related custom synthesis and PEGylation services. JenKem Technology is ISO 9001 and ISO 13485 certified, and adheres to ICH Q7 guidelines for GMP manufacture. The production of JenKem® PEGs is back-integrated to in-house polymerization from ethylene oxide, enabling facile traceability for regulated customers. JenKem Technology caters to the PEGylation needs of the pharmaceutical, biotechnology, medical device and diagnostics, and emerging chemical specialty markets, from laboratory scale through large commercial scale.