A new isoluminol reagent for chemiluminescence labeling of proteins

We report the synthesis and the characterization of N-(4-aminobutyl)-N-ethyl-isoluminol (ABEI) macrocyclic lactone, an activated ester with an unusual macrocyclic structure, and its use for efficient ABEI conjugation to proteins. Compared to the equivalent reagent normally used for chemiluminescence protein labeling, the ABEI macrocyclic lactone displays improved chemical properties, including stability and reactivity. We show the simple synthesis and the use of ABEI macrocyclic lactone for efficient chemiluminescence labeling of monoclonal antibody mixtures currently used in clinical immunodiagnostic assays for the detection of the HIV p24 antigen in patients.