Biotin-PEG3-NHS ester

Biotin-PEG3-NHS ester is a PEG-based bioconjugation linker designed for efficient attachment of biotin tags to primary amines in PROTAC-related workflows. Its NHS ester functionality enables robust coupling under mild conditions, while the PEG spacer improves solubility and reduces steric constraints between the biotin handle and target-binding modules. The linker is well suited for preparing biotinylated PROTAC constructs for downstream affinity enrichment, characterization, and pull-down studies; detailed structural and reactivity guidance is provided below.

Structure: The linker contains a poly(ethylene glycol) spacer terminating in an N-hydroxysuccinimide ester, coupled to a biotin moiety. It features amide-forming ester reactivity, ether-rich PEG segments, and heteroatom-rich functional groups that enhance hydrophilicity and conformational flexibility.

Reactivity: The NHS ester reacts with primary amines via nucleophilic acyl substitution to form stable amide bonds, typically using buffered aqueous or mixed solvent systems at conditions that maintain NHS ester integrity. Common approaches include activating the amine-bearing partner, controlling pH to favor amine nucleophilicity, and using mild bases or amine-free buffers to minimize hydrolysis. No special catalysts are required; efficient coupling depends on minimizing water exposure and promptly quenching unreacted ester.