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Updated: May 14, 2026

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry
Published on: July 20, 2016
DNA-maleimide: an improved maleimide compound for electrophoresis-based titration of reactive thiols in a specific
Satoshi Hara1, Tatsuya Nojima, Kohji Seio
1Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta 4259-R1-8, Midori-ku, Yokohama 226-8503, Japan.
Background:
Thiol-mediated redox regulation of proteins plays a key role in many cellular processes.
Methods:
To understand the redox status of cysteinyl thiol groups of the desired proteins, we developed a new maleimide reagent: a maleimide-conjugated single strand DNA, DNA-maleimide (DNA-Mal).
Results:
DNA-Mal labelled proteins run as a distinct band on SDS-PAGE, with a discrete 9.32 kDa mobility shift per label regardless of the protein species or electrophoretic conditions.
Conclusions:
DNA-Mal labels free thiols like standard maleimide reagents, but possesses practical advantages in titration of the number and relative content of free thiols in a protein.
General Significance:
The versatility of DNA molecule enhances the application of DNA-Mal in a broader range of cysteine containing proteins.
