Abstract: Disclosed is a high throughput compatible assay that is useful for the identification of specific antagonists of TRAF-receptor interactions. The modular flexibility of the assay makes it possible to introduce simple modifications in order to measure the interaction of any TNF receptor cytoplasmic domain (or TRAF-binding protein) with any of the six TRAF proteins, TRAF1, TRAF2, TRAF3, TRAF4, TRAF5 and TRAF6.

Abstract: An arrangement for the investigation of hydrophilic macromolecules (1) in an aqueous solution having a solid carrier surface (5) onto which a lipid film (24) is disposed, wherein the molecules (1) to be investigated are bound, by means of a molecular coupling system (20), to the lipid film (24) and thus are immobilized, is characterized in that the molecular coupling system (20) comprises at least two, preferably three molecular or nuclear components (21, 22, 23), which can be coupled to each other, of which a first component (21) is bound to the lipid film (24) and a second component (22) is bound to a hydrophilic macromolecule (1) to be investigated. In this way, it is rendered possible to immobilize and investigate any hydrophilic macromolecules, wherein the coating of the solid carrier surface should be able to be carried out in an as easy as possible and reversible manner.

Abstract: Methods, compositions and articles of manufacture are provided for conducting specific binding assays to determine the concentration or presence of at least one analyte in a sample. At least two dendrimer-reagent preparations with different analyte specificities may be immobilized on a solid phase. Alternatively, at least one dendrimer-reagent preparation having multiple specificities may be immobilized on a solid phase. Immobilization is facilitated by coupling specific binding assay reagents such as polypeptide receptors or analytes with water soluble polymers. Such water soluble polymers, for example star polymers such as dendrimers, provide production advantages of lot-to-lot uniformity and homogeneity, and can enhance sensitivity due to low non-specific binding to the solid phase.

Abstract: The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

Abstract: A biologically recognizing layer on a solid phase consisting of biologically recognizing molecules comprising regions which recognize a substance to be analyzed and regions which do not recognize a substance to be analyzed.The biologically recognizing molecules are aligned on a suitably modified surface by means of molecular regions which do not recognize the substance to be analyzed. The biologically recognizing molecules are cross-linked with the aligning surface and are consequently covalently altered. The molecular regions recognizing the substance to be analyzed are not altered by the covalent bonding and retain their bonding activity.The layer is produced in a novel two-stage method. In the first step, the biologically recognizing molecules, the aligning molecules and carrier molecules are adsorbed. In the second step, the molecules are covalently anchored by cross-linking. Cross-linking is brought about by photolytic activation of a water soluble reagent bonded to the carrier molecules.

Abstract: For the qualitative or/and quantitative detection of a substance to be determined in a test sample with the aid of an immunoassay or nucleic acid hybridization assay the following components are used:a) a capture reagent which enables a specific detection of the substance to be determined by means of two different binding sites 1) if desired together with further test components and 2) is bound or is capable of binding to an active solid phase via a specific binding pair one partner of which is linked to the capture reagent and the second partner of which is coupled to an active solid phaseb) an active solid phase andc) an inactive solid phase which substantially corresponds to the active solid phase but to which the capture reagent cannot bind,wherein the test sample is either firstly brought into contact with the inactive solid phase alone and only later with the active solid phase, or is simultaneously brought into contact with the active and inactive solid phase during which the capture reagent and if des

Abstract: Methods are provided for conducting specific binding assays to determine the concentration or presence of at least one analyte in a sample. Dendrimer-reagent preparations with particular analyte specificities are mixed in solution with a sample to form dendrimer-reagent-sample complexes. The complexes are then immobilized on a solid phase. Immobilization is facilitated by coupling specific binding assay reagents such as polypeptide receptors or analytes with water soluble polymers. Such water soluble polymers, for example star polymers such as dendrimers, provide production advantages of lot-to-lot uniformity and homogeneity, and can enhance sensitivity due to low non-specific binding to the solid phase.

Abstract: The present invention encompasses a capture membrane comprising a porous filter membrane having a hapten bound directly or indirectly to the membrane wherein complexes formed by specific binding having an anti-hapten bound to a binding member of the specifically binding complex are removed from a solution by the hapten as the solution passes through the membrane. In the preferred embodiment biotin is the hapten and avidin or streptavidin is the anti-hapten.

Abstract: A chromatographic strip positive readout binding assay device and method suitable for quick, sensitive and reliable field testing for small molecules such as environmental contaminants, drugs of abuse, therapeutic drugs and hormones. The detectable label is not attached to either the analyte or to the analyte receptor. Low affinity binding pairs can be used in the positive readout binding assay.

Abstract: The present invention includes novel rubella assays employing a Rubella virus capture reagent and a solid phase material containing a reaction site comprising a polymeric cation substance. A test sample suspected of containing Rubella antibody may be contacted with the capture reagent to form a capture reagent/analyte complex. The complex is then contacted to the positively charged solid phase to attract, attach, and immobilize the capture reagent/analyte complex.

Abstract: The invention concerns a binding matrix containing a carrier material with an oxidic surface and a solid phase reactant covalently bound thereto via anchor groups which is capable of binding to at least one free reaction partner, which is characterized in that the solid phase reactant forms a diluted and essentially laterally homogeneous binding layer on the surface of the carrier material and that the anchor groups are silane groups and are linked to the solid phase reactant via a spacer molecule.

Abstract: The invention relates to novel purified human immunoglobulin E binding factors (IgE-BFs), its individual optionally glycosylated proteins, and fragments thereof, processes for the purification of IgE-BFs, novel monoclonal antibodies to lymphocyte cellular receptors for IgE (Fc.sub..epsilon. R) crossreacting with IgE-BFs, derivatives thereof, processes for the preparation of these antibodies and their derivatives, hybridoma cell lines that produce these antibodies, processes for the preparation of said hybridoma cell lines, the use of the monoclonal antibodies and their derivatives for the qualitative and quantitative determination of IgE-BFs, test kits containing the monoclonal antibodies and/or their derivatives, the use of the monoclonal antibodies for the purification of IgE-BFs, the use of purified IgE-BFs, its individual optionally glycosylated proteins and/or fragments thereof for the prevention and/or treatment of allergy, and to pharmaceutical preparations containing them.

Abstract: The present invention provides a novel carbamazepine hydrazide compound suitable for covalent attachment to a polymer particle reagent, having the general formula ##STR1## The present invention also provides a novel carbamazepine acid compound suitable for attachment to proteins for the production of carbamazepine immunogens. The carbamazepine antigen of the present invention has the following general structure: ##STR2## where X is C=O, CH.sub.2 or SO.sub.2 ; Y is C=O, CH.sub.2, SO.sub.2 ; R is an alkyl and P is a protein or a hapten.

Abstract: Liposome reagents used in assays to detect the presence or amount of an analyte in a test sample, particularly where the analyte is antiphospholipid antibodies are described. The liposome reagents comprise a liposome, a ligand chosen to bind specifically with the analyte and associated with the liposome membrane, and a haptenated component associated with the membrane of the liposome where the hapten is chosen to bind specifically to a receptor bound to a solid phase or to a label compound that is an element of a signal detection system and where the liposome reagent is prepared so that during the assay the linkage between the solid phase and ligand of the liposome reagent is maintained.

Abstract: A surface of specific reactivity is formed by adsorbing a modified block polymeric surfactant of the Pluronic-type, i.e., containing pendant poly(ethylene oxide) blocks attached at an end to poly(propylene oxide) center blocks and with specifically reactive groups at the unattached ends of the poly(ethylene oxide) blocks, upon a hydrophobic surface.

Abstract: An immunochemical method is provided for the detection and determination of an analyte. The zeta potential of a latex-particle loaded with an immunologically active substance is measured before and after bringing the loaded latex-particle into contact with an analyte. The difference in zeta potential is correlated with changes of zeta potential for known concentrations of the analyte in order to determine the presence and amount of the analyte.

Abstract: A method for increasing the binding activity of specific binding members bound to a solid phase material, e.g., a particle, that has been sterically stabilized. This increase in binding activity is brought about by degrading a steric stabilizer on the surface of the solid phase material. The method involves both immobilizing a specific binding member on the surface of a solid phase material and degrading a steric stabilizer on the surface of that solid phase material. In the preferred embodiment, the method involves the immobilization of a specific binding member on the surface of the sterically stabilized solid phase material, with subsequent degradation of the steric stabilizer.

Abstract: Immunoassay methods and reagents for the specific quantification of amitriptyline or nortriptyline in a test sample are disclosed employing antibodies prepared with amitriptyline or nortriptyline derivatives of the Formula III: ##STR1## wherein for amitriptyline, R is CH.sub.3, and for nortriptyline, R is H. The present invention also describes the synthesis of unique fluorescein tracers of the structure of Formula IV and Formula V: ##STR2## wherein for a specific amitriptyline immunoassay, W.sub.1 is a heteroatom linked to the aromatic ring at the 2 or 3 position, and for a specific nortriptyline immunoassay, W.sub.2 is two heteroatoms linked together and attached to the aromatic ring at the 2 or 3 position, and wherein Q is a detectable moiety, preferably fluorescein or a fluorescein derivative.

Abstract: In a method for measuring a specified component in a specimen by reacting the specimen with a first reagent formed by binding a substance active to the specified component, with carrier particles and a second reagent formed by labelling a substance active to the specified component with a first label, and measuring the substances in the complexes obtained in the reaction, there is disclosed a method featured by labelling the carrier particles with a second label different from the first label, and detecting the second label and then the first label utilizing the detection of the second label as a trigger.This method enables a highly precise measurement without the influence of noise components in the detection of specified trace components in the specimen, utilizing an antigen-antibody reaction or a nucleic acid hybridization.

Abstract: Inter alia, a process for the selective removal of salivary .alpha.-amylase from a sample comprising salivary .alpha.-amylase and pancreatic .alpha.-amylase characterized in that there is used a monoclonal antibody against salivary .alpha.-amylase, which is immobilized or is coupled to a physically separable or seperate support and which exhibits a binding affinity towards salivary .alpha.-amylase of at elast 1.times.10.sup.7 l/m and a cross-reactivity with pancreatic .alpha.-amylase of less than 1% is disclosed. The remaining pancreatic .alpha.-amylase may be assayed.

Abstract: A moist unitary non-laminar chromogen agar color reactive test sheet for use in a simplified enzyme-linked immunosorbent assay (ELISA) for the diagnosis of viral, fungal, bacterial and parasitic diseases. The diagnostic test is designed for use in non-laboratory settings where the usual equipment and supplies, including running water, may not be available. The test sheet comprises chromogen agar paper (CAP) impregnated with an enzyme substrate, and electron acceptor, if needed, in agar. It is applied over a conjugate in the form of a species specific enzyme-linked anti-immunoglobulin bound to an antibody-antigen coating of a previously prepared test plate. After incubation to cause a color reaction, the results are read and interpreted in comparison with known standards.

Abstract: Water soluble reagents are claimed, comprising a water-soluble polymeric carrier molecule having attached thereto more than one connecting moiety wherein the connecting moiety is derived from divinyl sulfone, and wherein each connecting moiety is attached to a reactive functional group on the polymeric molecule, and wherein the reagents are capable of reaction with a molecular species having a functional group which is reactive towards the terminal vinyl group of the more than one connecting moiety and the molecular species is selected from the group consisting of labelling species, marking species, and targeting species.

Abstract: A method of preparing functionalized particles including (a) treating an activated substrate (CPG) with a bifunctional cross-linking agent containing a cleavable bond so as to immobilize the cross-linking agent, (b) conjugating an activated particle (P) with the immobilized cross-linking agent, and (c) cleaving the cleavable bond so as to separate the particle (P) from the substrate (CPG). The functionalized particles subsequently can be conjugated to biologically active molecules for use in assay methods.

Abstract: A surface of specific reactivity is formed by adsorbing a modified block polymeric surfactant of the Pluronic-type, i.e., containing pendant poly(ethylene oxide) blocks attached at an end to poly(propylene oxide) center blocks and with specifically reactive groups at the unattached ends of the poly(ethylene oxide) blocks, upon a hydrophobic surface.

Abstract: N-acyldipeptides of formula I ##STR1## wherein R represents a rest of formula ##STR2## and R.sub.4, Y, m, n and Z have the meaning as defined in the description, R.sub.1 represents hydrogen, a 1-10 C. alkyl, an optionally substituted methyl or benzyl,R.sub.2 represents a --CO--A group,wherein A has the meanings as defined in the description,R.sub.3 represents a --(CH.sub.2).sub.p --CO--W group,wherein p and W have the meaning as defined in the description.

Abstract: New method for the detection of specific binding agents and their corresponding bindable substances by employing a label which is a latex particle which can be visually detected.

Abstract: In a known method of immunodiffusion, a sample containing a first agent such as an antigen is introduced into a well in a lamina of agarose gel containing a second agent such as a complementary antibody. The first agent diffuses through the gel and becomes releasably bound to the second agent and, when the concentrations of agents are optimal, the agents form an extended matrix incorporating light-scattering aggregates. The size of the visible matrix enables the concentration of one of the agents to be assessed when that of the other agent is known. Each aggregate comprises very large numbers of the molecules of the agents. The invention provides an improved method in which the second agent is attached to carrier means in the gel so that the carrier means constitutes part of the visible aggregations. The carrier means may constitute the gel itself and/or it may constitute particulate material such as polystyrene particles.

Abstract: The invention relates to a novel process for preparing immunoconjugates consisting of haptens which are sparingly soluble or insoluble in aqueous solution and proteins/polypeptides using special solvents, in particular diethylene glycol monoalkyl ethers.

Abstract: A method and device for measuring the binding affinity of a receptor to a ligand. According to one aspect of the invention, arrays of polymers are synthesized or immobilized on a substrate (212). The array of polymers is exposed to a fluorescently-labelled receptor in solutions of varying concentration. The fluorescence intensity of the labelled receptor is measured by way of, e.g., a photon counter using a confocal microscope (316). Binding affinity is determined through analysis of the relationship between fluorescence intensity and the solution concentration of the receptor. On-rates are measured as a kinetic increase in surface fluorescence intensity, and the on-rate constant rate extracted from fits to the data.

Abstract: Allergens are contained in strictly controlled and reproducible amounts on solid supports to provide a progressive release of the allergen perlingually and sublingually. The compositions are prepared by dissolving an allergen in a polar solvent to obtain a mother solution; preparing dilutions of different predetermined concentrations; fractionating each of the dilutions into sub-dilutions; and impregnating a pharmaceutically acceptable solid support with each sub-dilution, each impregnation step being followed by drying in forced, dried air at a temperature not greater than 30.degree. C.; and applying a protective coating onto the composition.

Abstract: A polymeric latex composition having a hydrophobe incorporated therein can be prepared using a novel latex "loading" method. This method includes providing a loadable latex, providing a hydrophobe dissolved in a water-miscible organic solvent, heating the loadable latex to about 30.degree. to about 90.degree. C. and gradually adding the hydrophobe solution to the heated loadable latex under conditions to keep the hydrophobe in solution and to "load" it into the latex particles. In preferred embodiments, the latex is surfactant-free and has particles which have outer reactive groups which are capable of reacting with free amine or sulfhydryl groups of a biological compound. Such latices can be used to prepare water-insoluble biological reagents having a biological compound attached to the particles.

Abstract: A process for covalently bonding biopolymer, such as protein, to an organic polymer surface coated with hydrophilic nonionic polymer having groups reactive with the biopolymer and having a cloud point in the reaction medium that is at least 5.degree. C. above the temperature at which the coated organic polymer surface is to be used, which comprises reacting biopolymer with the surface in an aqueous reaction medium, at a temperature not less than 5.degree. C. below the cloud point; but not above a temperature at which the biopolymer is deleteriously affected, and preferably not above about 100.degree. C., the product comprises a biopolymer immobilized on a hydrophilic solid surface having a nonionic polymer and a hydrophilic layer, coupled thereto via biopolymer-reactive groups of the nonionic polymer, and accordingly has low spontaneous adsorption of proteins and other biopolymers through electrostatic attraction and/or hydrophobic interaction.

Abstract: Modified proteins for carrying hapten are provided. These carriers are prepared by blocking the amino groups of the original protein and then introducing amino groups into the carboxyl groups of the original protein. The blocking groups may be eliminated at the later stage to regenerate the amino groups of the original protein. The modified protein or polypeptide carrier have the three-dimensional structures different from the original proteins so that they are used in immunoassay while carrying low molecular weight haptens without the fear of forming antibodies for the original proteins. The modified protein carrier may also be used in the passive agglutination immunoassay without the need of absorbing the anti-hapten antibodies by the hapten-carrying carriers.

Abstract: A device for immunological techniques is prepared containing a macroporous hydrophobic synthetic polymer cloth having antibodies or antigens directly adsorbed therein and directly absorbed and immobilized thereon. The cloth has a thickness of more than about 200 .mu.m and has spaces between fibres exceeding about 20 .mu.m in diameter, and preferably has a Frazier Air permeability, in CFM/ft.sup.2 at 0.5" H.sub.2 O of from about 215 to about 750 for thickness of from about 11 to about 40 mils such that it can accommodate a large volume of liquid per surface area, that it has a large surface area, and that it has minimum flow resistance. In immunoassays antibodies may be directly adsorbed therein and directly absorbed and immobilized thereon, and specific antigens from a selected test sample, may then be captured by the antibodies, to be detected conventionally.

Abstract: Highly fluorescent latex microspheres have a diameter of less than five hundred angstroms and have more than five thousand fluorescent markers per sphere. The microspheres are prepared by reacting an acrylic latex bead with a diamine and a fluorescent amine at elevated pH to attach a spacer arm and a marker, respectively, to the bead by transacylation of ester terminations on the surface of the bead. A protein such as avidin or an immunoglobulin may then be conjugated to the spacer arm. A single fluorescent microsphere is visible using standard fluorescent microscopy. Therefore the microspheres may be utilitzed not only to visualize cell surface antigens but also DNA encoding for single genes, by means of a biotinylated DNA probe.

Abstract: A biochemical reagent comprises an oligosaccharide, preferably one which has been liberated from an immunogenic glycoprotein or proteoglycan, which is immobilized on a carrier via an intermediate spacer molecule such as a lipid. The lipid molecule should preferably have at least two long lipid tails so that the oligosaccharide is held in spaced relationship to the carrier where is exhibits antibody-binding ability which is almost indistinguishable from that of the original glycoprotein or proteoglycan. The reagent has its application in biochemical testing of oligosaccharides and systems which bind to them.

Abstract: Antigens, immunogens, inocula, antibodies, and particularly diagnostic methods and systems relating to Epstein-Barr virus nuclear antigen (EBNA) are disclosed. The diagnostic methods and systems utilize a synthetic, random copolymer polypeptide containing about 8 to about 40 amino acid residues that includes the overlapping five and six amino acid residue sequences--Gly--R.sup.1 --Gly--R.sup.2 --Gly-- (i)wherein R.sup.1 and R.sup.2 are amino acid residues selected from Ala, Asn, Arg, Gly, Leu, Pro, Ser, and Thr with the provision that R.sup.1 and R.sup.2 are not both Gly; and--Gly--Ala--Gly--Gly--Ala--Gly--. (ii)The polypeptide contains at least 50 mole percent Gly residues. The diagnostic method and system are particularly useful for assaying for the stage of mononucleois disease, and the presence of nasopharynegeal carcinoma.

Abstract: Antigens, immunogens, inocula, antibodies, and particularly diagnostic methods and systems relating to Epstein-Barr virus nuclear antigen (EBNA) are disclosed. The diagnostic methods and systems utilize a synthetic, random copolymer polypeptide containing about 8 to about 40 amino acid residues that includes the overlapping five and six amino acid residue sequences(i) --Gly--R.sup.1 --Gly--R.sup.2 --Gly--wherein R.sup.1 and R.sup.2 are amino acid residues selected from Ala, Asn, Arg, Gly, Leu, Pro, Ser, and Thr with the provision that R.sup.1 and R.sup.2 are not both Gly; and(ii) --Gly--Ala--Gly--Gly--Ala--Gly--.The polypeptide contains at least 50 mole percent Gly residues. The diagnostic method and system are particularly useful for assaying for the stage of mononucleois disease, and the presence of nasopharynegeal carcinoma.

Abstract: Histamine derivatives, immunogen conjugates comprising histamine or said histamine derivatives coupled to immunogenic carrier materials and antibodies prepared against such immunogen conjugates are disclosed. Such antibodies are useful in immunoassays for determining histamine release in biological fluids.

Abstract: The present invention provides a vaccine for stimulating or enhancing in a subject to whom the vaccine is administered, production of antibodies directed against 9-O-acetyl GD3 ganglioside comprising an amount of purified 9-O-acetyl GD3 ganglioside effective to stimulate or enhance antibody productionThis invention was made with government support under Grant Numbers CA-40532 and CA-43971, National Cancer Institute, Department of Health and Human Services. Accordingly, the U.S. Government has certain rights in the invention.

Abstract: An agent or device for the determination of antigen or antibody comprising capsules of a water-insoluble, dye-permeable polymer or a liquor-pool covered by said polymer, an antien, antibody or hapten immobilized on the surface of said polymer, and a dye solution enclosed or held in said capsules or liquor-pool, and a method for determining antigen or antibody using said agent or device, which can be conveniently used for the serodiagnosis of various diseases.

Abstract: An agglutination method for the detection of antibodies against streptococcal deoxyribonuclease B is described, in which carrier-bound antibodies against streptococcal DNase B are mixed with a solution of streptococcal DNase which contains a protease inhibitor, and the sample in which the antibodies are to be detected, as well as an agent suitable for this method.

Abstract: The present invention provides a process for the determination of an analyte in a body fluid, in which there are used two binding components capable of specifically binding with one another, one of the binding components being enzyme-labelled and not carrier-fixed and the other binding component being carrier-fixed. The process contains a step in which the binding components are incubated with one another so that binding reaction takes place. The amount of enzyme-labelled binding component not bound to the carrier-fixed binding component is a measure of the concentration of the analyte which is determined by allowing the labelling enzyme to act upon a substrate producing a detection signal.

Abstract: A method for assaying of Chlamydia includes adhering Chlamydia antigen to amidine modified latex particles, binding of adhered antigen to an anti-Chlamydia antibody conjugated to an enzyme, separating the particles from the liquid phase of the assay and detecting bound enzyme by color development when the separated particles are contacted with a substrate for the enzyme. The invention includes a kit of materials for preforming an assay in accordance with the method of the invention.

Abstract: An assay for an analyte wherein sample is applied to a support capable of binding proteins by essentially only hydrogen bonding and fixed on the support. Analyte may be determined on the support by use of a suitable tracer. A preferred support is amphiphilic cellulose acetate. In an immunoassay, it is possible to determine analyte without use of a supported ("capture") antibody.

Abstract: An improved heterogeneous immunoassay is provided which includes the utilization of support materials capable of reversible immobilization of proteinaceous binding partners of biological material of interest and the removal of labeled complexes from these supports through the use of release reagents permitting the subsequent solution phase determination of the amount of label.

Abstract: Peptide fragments of certain apolipoproteins have been found to be both immunogenic and capable of eliciting antibodies with highly apolipoprotein-specific immunoreactivity. These antibodies, in labeled and unlabeled form, as well as the labeled synthetic peptide fragments, are useful in the production of immunodiagnostic procedures and kits for quantitating type-specific apolipoproteins. Both competitive assays and immunometric assays are disclosed.

Abstract: Methods and materials for preparing specific binding reagents with a multiplicity of relatively noninterfering label moieties are described. By spacing the labels at the surface of a specific reagent with bulking agent, increased sensitivity can be achieved without interference between individual labeling entities.

Abstract: Samples e.g. transfusion blood, are assayed for antibodies to retroviruses, e.g. AIDS virus, using an insolubilized antigen comprising retrovirus antigens bound to globulin, the globulin itself being bound to an inert solid support; and an immunoglobulin which contains specific antibody to the retrovirus antigens and which is labelled with a revealing label, and the soluble phase is then separated from the insoluble phase and the quantity of revealing label associated with either the soluble or the insoluble phase determined.The sue of labelled antibody in competition with test sera for binding on the insolublized antigen permits better identification of antibody containing specimens. The retroviruses may be a human T-lymphotropic retrovirus HTLV-I, II or III or a new retrovirus isolate CBL-1 etiologically related to AIDS.

Abstract: The performance of double receptor, specific binding assays is improved by use of a receptor complex having the structureA.sub.BL (BL).sub.n A.sub.1wherein BL is a binding ligand, A.sub.BL is a receptor specific for binding ligand, A.sub.1 is a receptor, BL is covalently bonded to A.sub.1 and A.sub.BL is reversibly bonded to BL. Generally A.sub.BL is absorbed onto an insoluble surface and A.sub.1 is an antibody to the substance being assayed. The complex has particular utility in coated tube and rechargeable radioimmunoassay systems.