Abstract: Heterogeneous assays for different analytes in a single biological sample are performed simultaneously in a multiplexed assay that combines flow cytometry with the use of magnetic particles as the solid phase and yields an individual result for each analyte. The particles are distinguishable from each other by characteristics that permit them to be differentiated into groups, each group carrying an assay reagent bonded to the particle surface that is distinct from the assay reagents of particles in other groups. The magnetic particles facilitate separation of the solid and liquid phases, permitting the assays to be performed by automated equipment. Assays are also disclosed for the simultaneous detection of antibodies of different classes and a common antigen specificity or of a common class and different antigen specificities.

Abstract: A compound of a general structure: D—B—M wherein: B is selected from the group consisting of derivatives of naturally occurring nitrogenous bases having a C—H group at positions 5 or 8, and derivatives of nitrogenous base-analogs having a C—H group at positions 5 or 8; D is at least one derivatizing group, including hydrogen; and M is a maleimide derivative.