Abstract: A polypeptide-labeled analyte analog for use in an immunoassay is prepared which is capable of binding with a polypeptide partner to provide enzymatic activity such as a ribonuclease or .beta.-galactosidase activity. The polypeptide analog provides a highly sensitive, immunoassay method for determining the amount of an analyte in a sample containing a known analyte in an unknown concentration. To carry out an immunoassay, there is brought together in a medium a sample, the polypeptide-labeled analog of the analyte, an antibody specific for said analyte, a polypeptide partner capable of non-covalently binding with the polypeptide-labeled analyte analog to form a complex having catalytic activity, and a substrate capable of being converted to a reporter molecule by the catalytic activity of said complex.

Abstract: A highly sensitive, immunoassay method for determining the amount of an analyte in a sample containing a known analyte in an unknown concentration is provided. Sample; a polypeptide-labeled analog of the analyte, an antibody specific for said analyte, a polypeptide partner capable of non-covalently binding with the polypeptide-labeled analyte to form a complex having catalytic activity, and a substrate capable of being converted to a reporter molecule by the catalytic activity of said complex are brought together in a medium. The polypeptide-labeled analyte analog is capable of competitively binding to the antibody and the polypeptide partner, the antibody inhibiting the formation of a catalytically active complex in the absence of analyte, and the concentration of the antibody, polypeptide partner and polypeptide-labeled analyte are such as to cause varying amounts of analyte to be directly related to the conversion of the substrate to the reporter molecule.

Abstract: A highly sensitive, immunoassay method for determining the amount of an analyte in a sample containing a known analyte in an unknown concentration is provided. Sample; a polypeptide-labeled analog of the analyte, an antibody specific for said analyte, a polypeptide partner capable of non-covalently binding with the polypeptide-labeled analyte to form a complex having catalytic activity, and a substrate capable of being converted to a reporter molecule by the catalytic activity of said complex are brought together in a medium. The polypeptide-labeled analyte analog is capable of competitively binding to the antibody and the polypeptide partner, the antibody inhibiting the formation of a catalytically active complex in the absence of analyte, and the concentrations of the antibody, polypeptide partner and polypeptide-labeled analyte are such as to cause varying amounts of analyte to be directly related to the conversion of the substrate to the reporter molecule.

Abstract: Folic acid derivatives, such as radiolabeled pteroyltyrosine, are conveniently synthesized from either pteroic acid or by the direct condensation of 6-formylpterin with p-aminobenzoyltyrosine methyl ester. The radioiodinated derivatives are particularly useful in competitive protein binding and radioimmuno-assays of folate compounds.

Abstract: Folic acid derivatives, such as radiolabeled pteroyltyrosine, are conveniently synthesized from either pteroic acid or by the direct condensation of 6-formylpterin with p-aminobenzoyltyrosine methyl ester. The radioiodinated derivatives are particularly useful in competitive protein binding and radioimmuno-assays of folate compounds.

Abstract: Folic acid derivatives, such as radiolabeled pteroyltyrosine, are conveniently synthesized from either pteroic acid or by the direct condensation of 6-formylpterin with p-aminobenzoyltyrosine methyl ester. The radioiodinated derivatives are particularly useful in competitive protein binding and radioimmuno-assays of folate compounds.

Abstract: Folic acid derivatives, such as radiolabeled pteroyltyrosine, are conveniently synthesized from either pteroic acid or by the direct condensation of 6-formylpterin with p-aminobenzoyltyrosine methyl ester. The radioiodinated derivatives are particularly useful in competitive protein binding and radioimmuno-assays of folate compounds.

Abstract: A reactor/separator device is provided for use in automated solid phase immunoassay. The device is a column, fitted at the bottom portion thereof with a water impermeable disc which can hold immunoabsorbents immobilized antisera, ion exchange resins and the like. When the contents of the column supported by the disc are brought into contact with an aqueous phase containing reagents or reactants by centrifugal force, a chemical reaction is initiated. After reaction, centrifugally applied pressure forces the aqueous phase through the filter disc making it water permeable and separating a desired component for subsequent analysis.