Methoxytrityl-S-dPEG®₄-acid

Product number 10301, Methoxytrityl-S-dPEG®4-acid, permits introduction of a protected thiol-dPEG® spacer/linker onto a molecule by reaction with a free amine. The methoxytrityl (Mmt) protected thiol deprotects under mild conditions using dilute trifluoroacetic acid (TFA) with a scavenger.


Thiolation is a useful reaction in the chemistry toolbox, but free thiols are not always available. Various means exist to introduce thiols into molecules or onto surfaces. These thiols frequently are introduced with a protecting group attached to shield the thiol from exposure to reactive conditions until the thiol reactivity is needed.

PEGylation refers to the covalent addition of polyethylene glycol (PEG) to a compound or surface. PEGylated compounds include proteins, peptides, dyes or other labels, and small molecule drugs. Peptide synthesis frequently employs PEGylation to enhance solubility of the peptide, because the amphiphilic character of PEG imparts tremendous water solubility to peptides. Moreover, peptide PEGylation prolongs in vivo circulation of peptide conjugates by both increasing the peptide's hydrodynamic volume and protecting the peptide from proteolysis. Additionally, PEGylation reduces or eliminates antigenicity of the conjugated peptide. Our single molecular weight PEG products (known as "discrete PEG" and sold under the dPEG® trademark) provide all of the benefits of traditional, dispersed PEG without the analytical headache that comes from having an intractable mixture of conjugates, each with different PEG chain lengths.

PN10301 permits our customers to insert a short (16 atom, 18.3Å) dPEG® into a peptide chain using familiar solid phase or solution phase chemistry. The dPEG® can be inserted at the N-terminus of a peptide chain or on any amino acid side chain with an exposed free amine. In addition, the short dPEG® spacer can be used simply to provide additional distance in a synthetic construct where steric hindrance is a problem. The amphiphilic nature of dPEG® means that the construct will gain some degree of water solubility while remaining soluble in organic solvent. The Mmt protecting group removes relatively easily with a dilute solution of TFA that also contains a scavenger such as triethylsilane (TES) or triisopropylsilane (TIPS). Once the thiol group is deprotected, it can be reacted with another thiol to form a disulfide bond or with any thiol-reactive group such as maleimide, bromoacetamide, alkene (thiol-ene reaction) or alkyne (thiol-yne reaction).

Upon activation, PN10301 reacts with any free amine, whether on a peptide, protein, surface, or other molecule. This allows for a broad range of situations where this product can be employed to convert an amine to a thiol. However, because deprotection of the Mmt group requires the use of TFA, PN10301 is not recommended for protein modification.

If you need bulk product in a larger package size than our standard sizes, please contact us for a quote. Our commercial capabilities permit us to manufacture this product at any scale that you need.

Application References:

Hermanson, G. T. Chapter 18, PEGylation and Synthetic Polymer Modification. Bioconjugate Techniques, 3rd edition. Academic Press: New York, 2013, 787-838.

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