Abstract: This invention provides a hydrophilic specific binding assay reagent which is prepared by a process comprising the steps of reacting a partner of a specific binding pair and at least one hydrophilic substance with haloalkyl moieties associated with the surface of a solid phase and recovering the reagent so prepared from any unreacted binding partner. Preferably, the alpha-haloalkyl is chloromethyl and the at least one hydrophilic substance comprises at least one protein, such as albumin, and at least one non-proteinaceous amine to which the solid phase is impermeable, such as tris (hydroxymethyl) aminomethane. The specific binding assay reagent of the invention can be combined with other reagents to provide an assay composition.

Abstract: A specific binding enzyme-resistant ligand assay test material, which material comprises (a) a solid phase incorporated with one partner of a specific binding pair comprising said ligand or a binding analog thereof and a specific binding protein therefor; (b) a conjugate comprising the other partner of said specific binding pair incorporated with a substance which protects the specific binding protein of said pair from enzyme inactivation when bound with its partner; and (c) an active protein-inactivating enzyme. Also a specific binding method of assaying for an enzyme-resistant ligand in a sample, which method uses the above test material and which results in a reduction in interference caused by non-specific protein.