SPDP-PEG6-NHS ester
CAS No.: 1818294-32-4
Cat No.: BP-501515
Purity: ≥95%
4.5 
SPDP-PEG6-NHS ester is a heterobifunctional PEG-based linker designed for thiol–amine conjugation in targeted protein degradation workflows. Structurally, it combines a polyethylene glycol spacer of six ethylene glycol units with an NHS ester handle for efficient acylation of primary amines on targeting ligands or other PROTAC components, and a pyridyl disulfide (SPDP) moiety that selectively reacts with accessible thiols to form a stable disulfide-linked intermediate. In PROTAC design, this linker enables modular assembly by first installing the NHS-activated group onto an amine-bearing partner, then coupling the resulting construct to a thiol-containing moiety (e.g., a cysteine- or thiol-functionalized ligand) to generate a conjugate with defined spacing and improved solubility. Its PEG spacer can reduce steric hindrance and help preserve binding interactions, supporting systematic optimization of degradation potency and cooperativity in experimental targeted degradation studies.
Structure of 1818294-32-4
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SPDP-PEG6-NHS ester is a PEG-based bifunctional linker designed for efficient conjugation workflows commonly used in PROTAC construction. It provides a stable NHS ester handle for rapid amide-bond formation with primary amines, while incorporating a thiol-reactive SPDP functionality that enables subsequent formation of disulfide-linked intermediates. This combination supports modular assembly of target-binding ligands and degraders, improving synthetic flexibility and enabling controlled attachment strategies. Detailed structural and reactivity considerations are provided below.
Structure: The molecule contains a polyethylene glycol spacer that imparts hydrophilicity and conformational flexibility, connected to an N-hydroxysuccinimide ester for activated acyl transfer. A thiol-reactive SPDP-derived disulfide-containing motif supports later thiol/disulfide exchange chemistry. Overall, it behaves as an electrophilic linker with ester-based leaving-group reactivity.
Reactivity: The NHS ester reacts with primary amines under mild, typically aqueous-organic buffered conditions to form stable amide bonds via nucleophilic acyl substitution. For PROTAC assembly, the amine-functionalized ligand is first coupled, then the SPDP component is used to generate thiol-bearing intermediates through disulfide exchange. Thiol/disulfide formation is commonly promoted by controlled reducing conditions or thiol nucleophiles, with careful exclusion of competing nucleophiles and moisture to preserve 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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