PROTEIN BINDING ASSAYS

摘要

The subject invention concerns novel compositions for use in immunoassays, as well as immunoassays employing such novel compositions. The compositions comprise discrete charged colloidal particles comprised of small molecules which particles are capable of retaining their discrete character in an aqueous medium and composed of aggregates of lipophilic and/or amphiphilic organic molecules to which are bound non-covalently a label capable of producing a detectible signal and a ligand or an analog of the ligand capable of competing with a ligand for a ligand receptor. The discrete colloidal particle serves as a hub or nucleus for retaining the ligand or its analog and the label within a limited locus. The compositions are prepared by individually covalently bonding the ligand and the label, when not naturally lipophilic, to a lipophilic (includes amphiphilic) compound, normally a phospholipid. Depending upon the nature of the particle, the amphiphilic conjugated ligand and label are combined with the particle or alternatively may be combined with the compounds employed for preparing the particle under particle forming conditions. Particles are then obtained having the analog of the ligand and the label bound to the particle. The compositions find use in immunoassays where an interaction between the label and receptor provides a means for modulating a detectible signal. The interaction can be as a result of quenching or modification of fluorescence, where the label is a fluorescer, steric inhibition of the approach of a signal modifier to the label, such as a label receptor or with an enzyme label, an antienzyme or enzyme inhibitor, the inhibition of cleavage of an enzyme labile bond or the cooperative interaction of two labels, such as two enzymes, where the product of one enzyme is a substrate of another enzyme.