The maleimide linkers react specifically with sulfhydryl groups when the pH is between 6.5 and 7.5. The reaction forms a stable thioether linkage. When pH is higher than 8.5, the maleimide linkers readily react with primary amines. Maleimides do not react with tyrosines, histidines or methionines.
AxisPharm provide a broad range of maleimide linkers with various functional groups, such as Mal-PEG-azide, Mal-PEG-alkyne, Mal-PEG-NHS ester, Mal-PEG-TCO, Mal-PEG-BCN, Mal-PEG-DBCO and Mal-PEG-fluorescent dye probes, Mal-PEG-folate and Mal-PEG-biotin, etc.