The invention relates generally to synthetic non-antibody protein scaffolds (synNAPS) that differentially detect or quantitate a target insecticidal protein in a complex biological matrix comprising the target protein and a non-target insecticidal protein and to methods of using the synNAPS in immunoassays, and more particularly to monoclonal antibodies and immunoassays for the differential detection and quantitation of a wild-type crystal protein, such as a wild-type-Cry1Ab, from Bacillus thuringiensis and hybrid crystal proteins, which comprise all or a significant portion of the wild-type Cry protein in complex biological samples comprising both the wild-type Cry protein and one or more of the hybrid Cry proteins.