Carbonylacrylic (CBA) is one of ene-thiol click reaction reagents that can react with thiol group to form a stable thiol ether bond via so called ene-thiol Michael addition. Unlike maleimide-thiol adduct, which can hydrolyze at alkaline pH, the reaction between carbonylacrylic and thiol is non-reversible, and therefore the adduct form between CBA and thiol is more stable.