ɑ-Butyric Acid-ω-Maleimidohexanamido PEG , 5000 Dalton

This PEG linker with a maleimide endgroup is applied in sulfhydryl-selective coupling of PEG to proteins and other thiol substrates and for selective scavenging of thiol containing peptides. The maleimide group reacts at about neutral pH with free thiols via a Michael addition to form a stable thioether bond. Carboxy PEGs may be used for conjugation to amine substrates (forming amides) or other nucleophiles (forming esters). However, activation is necessary prior to conjugation. Different PEG carboxy derivatives display a different degree of stability and reactivity of the corresponding active ester. The butyric acid endgroup is directly connected to the PEG chain via a very stable ether linkage. After activation it is used to conjugate the PEG derivative to nucleophilic substrates, mainly amines (to form amides) or hydroxyls/thiols (forming esters). PEG butyric acid active esters are one of the most hydrolytically stable PEG active esters. They can be used for pegylation in aqueous media without the need of a large excess of PEG.

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