N-(Azido-PEG3)-N-Biotin-PEG4-methyl ester
CAS No.: 2100306-76-9
Cat No.: BP-501139
Purity: 98%
4.5 
N-(Azido-PEG3)-N-Biotin-PEG4-methyl ester is a heterobifunctional PEG-based linker that combines an azide handle with a biotin moiety and a terminal methyl ester. Structurally, it consists of an azido-terminated short polyethylene glycol segment connected to a biotin-conjugation region through an amide linkage, followed by a longer PEG4 spacer that improves aqueous solubility and spatial control. In PROTAC and targeted degradation workflows, the azide group enables bioorthogonal conjugation (e.g., copper-free click chemistry) to install the linker onto an E3 ligase ligand or other binding module, while the biotin functionality can be used for affinity-based capture, localization, or modular assembly with biotin-binding partners. The methyl ester provides a chemically addressable end group that can be leveraged for controlled derivatization or stability tuning during synthesis. This linker is valuable for constructing well-defined, water-compatible PROTAC architectures and for facilitating purification or analytical tracking of assembled conjugates.
Structure of 2100306-76-9
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This PROTAC linker reagent, N-(Azido-PEG3)-N-Biotin-PEG4-methyl ester, combines an azide handle with PEG-based spacing and a biotin motif to support modular assembly of targeted protein degraders. Its flexible polyethylene glycol segments can improve solubility and presentation of reactive termini, while the biotin functionality enables robust conjugation strategies commonly used in proximity-inducing designs. The following sections describe its structure and practical reactivity considerations for linker incorporation into PROTAC constructs.
Structure: The molecule is built from PEG oligomers featuring ether linkages that provide conformational flexibility and improved hydrophilicity. A terminal azide group enables bioorthogonal click chemistry, while a biotin-derived amide region and a methyl ester provide orthogonal functional handles for controlled conjugation and coupling.
Reactivity: The azide is typically used in copper-catalyzed azide–alkyne cycloaddition or related click reactions to join PROTAC fragments under mild, aqueous-compatible conditions. The methyl ester can undergo standard ester-activation or nucleophilic acyl substitution approaches to form amide or related linkages, depending on the coupling partner. Selection of solvent systems and catalysts should follow established click and ester-coupling protocols that preserve sensitive targeting ligands and maintain linker integrity.
* Our calculator is based on the following equation:
Concentration (start) x Volume (start) = Concentration (final) x Volume (final)
It is commonly abbreviated as: C1V1 = C2V2
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