Synthesis of conjugates for a barbiturate screening assay.

Novel derivatives of barbiturates functionalized with free carboxylic acids were designed and synthesized. Coupling of 5-cyclopentyl-5-carboxycrotylbarbituric acid via its active ester to an aminofluorescein derivative produced a fluorescent tracer. Conjugation of the 5-cyclopentenyl-5-carboxyethylbarbituric acid via its mixed anhydride to thyroglobulin allowed for subsequent development of a polyclonal antibody which was evaluated for binding in a fluorescence polarization immunoassay format with various barbiturates. The binding studies showed good cross-reactivity of a variety of barbiturates containing both aromatic and aliphatic 5-substituents with the tested antisera. The relationship between the immunogen architecture, the chemical structure of the binding analytes, and the characteristics of the antisera is also presented.