Substituted 2-iminothiolanes: reagents for the preparation of disulfide cross-linked conjugates with increased stability

Bioconjug Chem. Nov-Dec 1990;1(6):381-6. doi: 10.1021/bc00006a003.


Much attention has been focused recently on the stability of immunotoxin (antibody-toxin) conjugates linked by a disulfide bridge. Conflicting reports have appeared regarding the in vivo stability of such conjugates prepared with the two most commonly used cross-linking reagents, SPDP and 2-iminothiolane. We have developed (i) a series of reagents based on 2-iminothiolane substituted at the 4- and/or 5-positions (X2ITs) which, based on model studies with simple amines, should show enhanced disulfide stability when conjugated with antibodies or other proteins and (ii) a real-time method for monitoring the rate and extent of conjugation of these reagents with amino groups. Depending upon the substituent, the stability of model-activated disulfides relative to unsubstituted 2-iminothiolane was increased from 5- to 4000-fold as measured by glutathione-induced release of thionitrobenzoic acid. This family of cross-linking reagents should allow the construction of disulfide cross-linked toxin, drug, or enzyme conjugates with enhanced stability in vivo.

MeSH terms

  • Chemical Phenomena
  • Chemistry
  • Cross-Linking Reagents / chemistry*
  • Cyclization
  • Disulfides / chemistry*
  • Dithionitrobenzoic Acid
  • Drug Stability
  • Glycine / chemistry
  • Imidoesters / chemistry*
  • Magnetic Resonance Spectroscopy
  • Nitriles / chemistry
  • Nitrobenzoates
  • Spectrophotometry, Ultraviolet
  • Sulfhydryl Compounds


  • Cross-Linking Reagents
  • Disulfides
  • Imidoesters
  • Nitriles
  • Nitrobenzoates
  • Sulfhydryl Compounds
  • thionitrobenzoic acid
  • methyl 4-mercaptobutyrimidate
  • Dithionitrobenzoic Acid
  • Glycine