Selective and Efficient Cysteine Conjugation by Maleimides in the Presence of Phosphine Reductants

Sulfhydryl functions of thiol-containing amino acids are prime attachment sites for conjugation of labels, ligands, or drugs to proteinaceous compounds. Usually the thiol is offered a xenobiotic electrophilic moiety from the molecule to be attached such as a maleimido function. As sulfhydryls tend t...

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Bibliographic Details
Published in:Bioconjugate chemistry 2016-10, Vol.27 (10), p.2260-2265
Main Authors: Henkel, Maik, Röckendorf, Niels, Frey, Andreas
Format: Article
Language:English
Subjects:
Amino acids
Cysteine - chemistry
Maleimides - chemistry
Molecules
Organic chemicals
Organophosphorus Compounds - chemistry
Oxidation
Phosphines - chemistry
Reducing Agents - chemistry
Sulfonic Acids - chemistry
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Summary:Sulfhydryl functions of thiol-containing amino acids are prime attachment sites for conjugation of labels, ligands, or drugs to proteinaceous compounds. Usually the thiol is offered a xenobiotic electrophilic moiety from the molecule to be attached such as a maleimido function. As sulfhydryls tend to oxidize into disulfides they must be reduced before conjugation. A popular thiol reduction reagent in biosciences is the substituted phosphine tris­(2-carboxyethyl)­phosphine (TCEP). Yet, phosphines are nucleophilic, too, and thus potentially compete with thiols for the electron-poor alkene moiety of maleimide resulting in complex product mixtures. To overcome this shortcoming we developed a method to eliminate excess reducing agent in the reaction mixture by selective oxidation of the phosphine with azidobenzoic acid before coupling. This results in a selective and efficient labeling of cysteines by maleimides.
ISSN:1043-1802
1520-4812
DOI:10.1021/acs.bioconjchem.6b00371