6-Maleimidocaproic acid sulfo-NHS
CAS No.: 103848-61-9
Cat No.: BP-500764
Purity: ≥98%
4.5 
6-Maleimidocaproic acid sulfo-NHS is a heterobifunctional linker combining a sulfonated N-hydroxysuccinimide (sulfo-NHS) ester with a terminal maleimide group separated by a caproic acid spacer. The sulfo-NHS ester enables efficient, aqueous-compatible conjugation to primary amines on proteins or targeting ligands (e.g., lysine residues) to form stable amide bonds, while the maleimide selectively reacts with thiols (such as cysteine or engineered thiol handles) via a rapid thio-Michael addition to generate a robust thioether linkage. In PROTAC and targeted protein degradation workflows, this linker is useful for modular assembly: it can install a thiol-reactive handle on one component and an amine-reactive handle on another, facilitating controlled conjugation of ligands, E3-recruiting moieties, or carrier scaffolds. Its water solubility and orthogonal chemistries support reproducible construct generation for studying degrader potency, stoichiometry, and structure–activity relationships.
Structure of 103848-61-9
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6-Maleimidocaproic acid sulfo-NHS, is designed to enable efficient, modular construction of PROTACs through robust amide-bond formation and subsequent thiol-directed conjugation. Its bifunctional architecture supports linking of targeting ligands and warheads under widely used bioconjugation chemistries, improving synthetic flexibility and reproducibility. The maleimide handle provides selective reactivity toward cysteine thiols, while the sulfo-NHS ester promotes rapid coupling to primary amines. Detailed structural and reactivity considerations are provided below.
Structure: The molecule contains a sulfonated N-hydroxysuccinimide ester for amine acylation and a maleimide moiety for thiol addition, connected via a flexible aliphatic caproic acid spacer. Key functional groups include an activated carboxylate ester and a conjugated maleimide double bond, enabling controlled conjugation.
Reactivity: For PROTAC assembly, the sulfo-NHS ester is typically reacted with primary amines on targeting ligands to form stable amide bonds under mildly basic aqueous buffer conditions. After amide formation, the resulting intermediate is coupled via the maleimide group to thiols (commonly cysteine residues) through a Michael-type addition, often requiring near-neutral pH and avoidance of competing thiols. Standard bioconjugation solvents and buffers are used, with purification steps to remove hydrolyzed activated ester.
* 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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