Fina Biosolutions now offers CRM₁₉₇ pre-labeled with maleimide, allowing for the easy conjugation of thiolated antigens.  FinaBio’s CRM₁₉₇, EcoCRM®, is labeled with ~15 maleimides.  The labeled protein is provided frozen, ready to thaw and conjugate to a thiol-containing antigen.

Examples of antigens that have been conjugated to EcoCRM®-maleimide include cysteine-peptides, thiol-labeled oligosaccharides, polysaccharides and proteins.  Depending on the nature of the antigen, gel filtration or spin filters can be used to purify the conjugate. 

EcoCRM®-maleimide
        ~15 Maleimide/CRM₁₉₇
        5 mg/ml
        PBS + 5% sucrose, pH 6.8
        Store at <-20°C

Note:  Use within 1 hr after thawing.  The buffer is a pH compromise as CRM₁₉₇ will denature in acidic buffers while the maleimide linker will hydrolyze in basic buffers.   Care should be taken to keep the conjugation pH between 6.8 and 7.8.  We recommend familiarity with thiol-ether conjugation.  See GT Hermanson, Bioconjugate Techniques.