Abstract: A quantitative determination of a substance is performed in a homogeneous system based on a change in enzyme activity; differences between the activity of a free enzyme and that of an enzyme bound by an aggregation or chemical bonding are observed. A peroxidase-labeled antibody and antigen system is one of of the typical example. Since the reaction is effected in a homogeneous system, the amount of antigen can be easily measured by the difference of enzyme activity.

Abstract: A biological substance is determined with the use of a marker comprising a lanthanide or other metal ion coupled to the biological substance by means of chelate-forming compound. The chelate complex is dissociated by reduction of the ambient pH to a sufficiently low level to liberate the metal ion and the metal ion is then chelated with a separate chelating chromophore with an increase in the pH to a value closer to the optimum for determination of the metal-chelated chromophore by fluorescence spectroscopy, luminometry, colourometry or the like.

Abstract: Surfactants bound to a ligand and dissolved in a single phase aqueous solution form a precipitate when a multivalent antiligand is added to the solution. This invention can be used in an affinity precipitation test procedure (and kit) for detecting the presence or absence of a multivalent antiligand in a sample suspected of containing the multivalent antiligand, in an affinity precipitation inhibition test procedure (and kit) for detecting the presence or absence of a target ligand in a sample suspected of containing the target ligand, and in a process for separating a multivalent antiligand from a crude material containing the multivalent antiligand.

Abstract: The present invention provides methods and compositions for assaying biological samples, such as human serum, for barbiturates. In one aspect, analogs of barbiturates derivatized with fluorescein and analogs of barbiturates derivatized with immunogenic polypeptides are provided. The fluorescent analogs are employed as tracers in a competitive homogeneous immunoassay, i.e., a fluorescence polarization immunoassay, for detecting barbiturates. The immunogenic analogs are employed to make anti-barbiturate antiserum of the invention for use in the immunoassay method. Intermediates for preparing the fluorescent and immunogenic analogs are also provided. Further provided are test kits, comprising a fluorescent tracer and an antiserum according to the invention, for analyzing biological samples by fluorescence polarization immunoassay for the presence of a barbiturate.

Abstract: Apparatus and method for performing a chemiluminescence assay involving the immobilization of a chemiluminescent reaction complex to a solid, porous element. The solid, porous element is preferably treated to provide an immobilizing interaction with the chemiluminescent reaction complex wherein the chemiluminescent reaction complex is thereby immobilized to the solid, porous element. The activating and reading of the chemiluminescent reaction are separately performed by evenly distributing a concentrated chemiluminescent activating solution to form a puddle on the surface of the porous element to which the chemiluminescent reaction complex is immobilized.

Abstract: A method of assaying a ligand in a sample which method includes the steps of contacting the sample with components comprising(a) a specific binding partner to the ligand and, if desired,(b) at least one reagent selected from ligand analogues and specific binding, partners,at least one of the said components (a) and (b) being labelled with an electron-donor or electron-acceptor,and determining whether (and, if desired, the extent to which) transfer of electrons between the said electron-donor or electron-acceptor label and a suitable charge-transfer partner resulting in charge-transfer complex formation is perturbed by ligand complex formation and/or by controlled external influences.

Abstract: In an assay where a ligand or organism is detected by a detector binding protein ("DBP") capable of generating a signal in proportion to the amount of ligand or organism bound to the DBP, the presence of the ligand or organism is confirmed by the use, prior to or concurrently with the DBP, of a confirmatory binding protein ("CBP") which binds to a second site on the ligand or organism, and thereby prevents the DBP from binding to the first site. Thus, a reduction in signal of a predetermined amount indicates the true presence of the ligand or organism, while failure to obtain signal reduction of a predetermined amount indicates that the original signal was a false positive due to assay artifact or detection of related ligands or organisms. In a preferred embodiment, the CBP is a monoclonal antibody and the organism is derived from Chlamydia species.

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 is provided for combining normally interacting reagents in a liquid single reagent and preventing complex formation using a surfactant and then reversing the inhibition by adding a cyclodextrin. The method finds particular use in diagnostic immunoassays. Reagents facilitating the invention are also provided.

Abstract: A quartz crystal microbalance assay in which the binding of analyte to a surface on or near a quartz crystal microbalance (QCM) is detected by a conjugate which comprises an enzyme capable of catalyzing the conversion of a substrate to a product capable of accummulating on or reacting with a surface of the QCM leading to a mass change and, hence, a change in resonant frequency.

Abstract: The presence of an antigenic analyte ligand in a liquid sample is determined by (1) mixing the sample with a fluorescently labeled ligand immunologically complexed onto a solid phase supported antibody capable of exchanging the fluorescently labeled ligand with the analyte ligand in the sample and (2) measuring the fluorescence of the resulting liquid phase without measuring the fluorescence of the resulting solid phase and without separating the resulting solid phase from the resulting liquid phase.

Abstract: The present invention provides for novel homogeneous immunoassay systems involving complement-mediated lysis of marker-encapsulating lipid vesicles (liposomes) for detection of analyte in a fluid sample. These systems do not require the separation of unbound antigens and/or antibody conjugates yet provide highly sensitive procedures for analyte detection. Liposomes containing a marker, are coupled to antibody fragments in a way which confers the liposomes with immunological specificity yet avoids sensitizing the liposomes to complement mediated lysis in the absence of analyte. Antibody sensitized liposomes (the first reagent) are sequentially incubated with an analyte-containing sample, and optionally "dummy" liposomes, which do not contain encapsulated marker, a second antibody (the second reagent), and finally with a complement source such as plasma. Complement is activated by the liposome-antibody-antigen-second antibody complex causing liposome lysis and a concomitant release of marker.

Abstract: The present invention provides a process for the determination of a bindable analyte according to the principle of heterogeneous immunoassay by incubation of a sample solution which contains the analyte with a labelled first receptor specifically bindable with the analyte and present in dissolved phase and a second receptor present in a solid phase which does not cross-react with the first receptor and can fix a complex which contains the analyte and first receptor, separation of the phases after incubation and quantitative measurement of the labelling bound to the solid phase, wherein there is determined the back dissociation velocity of the labelling bound to the solid phase into the dissolved phase and the quotients of the back dissociation velocity and measurement value are used as a measure for the correctness of the test result of the first measurement.

Abstract: Species-linked diamine triacetic acids of the formula ##STR1## wherein T is an organic species containing at least one amine, hydroxyl, or thiol functional group, L is the residue of at least one of those functional groups and R is a two or more atom long covalent bridge, are disclosed. Methods for their preparation, for the preparation of metal chelates from them and for the use of the chelates are also disclosed. In a preferred embodiment, the metal ions employed in the formation of the chelates are rare earth metal ions capable of forming fluorescent chelates which can in turn be employed in fluoroassay techniques.

Abstract: The present invention provides an enzymatically-inactive, immunologically-active .beta.-galactosidase mutein, wherein, in the region between the amino acids 430 and 550, at least one amino acid of the natural sequence is changed to another amino acid and the enzymatic activity does not amount to more than 1%, referred to the native enzyme. The present invention also provides a process for the production of this mutein. Furthermore, the present invention is concerned with the use of this mutein in the immunological determination of serum proteins by the enzyme immunoassay principle.

Abstract: Process for producing an antibody catalyst for a chemical reaction. Chemical reactions in which the antibody catalyst can be used are also disclosed.

Abstract: A quick and simple immunoassay technique applicable to the determination of large molecules like proteins, polynucleotides and others involves labelling competitive immunospecies with an enzyme as signal generator. This enzyme can be converted to the corresponding apo-enzyme form and its regeneration, upon addition of a suitable co-factor, is inhibited by complexation when the labelled specie is reacted with its immunopartner. The degree of complexation is therefore ascertained by measuring the extent of regenerated activity.

Abstract: The method of the present invention employs an enzyme immunoassay for measuring the concentration of an analyte in a sample by indirect colorimetric detection. An incident light beam at a plurality of wavelengths is directed into a liquid solution containing an analyte of interest. The solution is capable of attenuating the amount of light at a first wavelength received from this solution as a function of the increasing concentration of the analyte present. A light signal from the solution at the first wavelength is detected, and light at a second wavelength, at which substantially no attenuation of light signal occurs as the concentration of the analyte increases, is also detected. The ratio of the two respective wavelengths is formed and that ratio is compared with ratios of known amounts of the analyte to determine the amount of the analyte in the sample.

Abstract: Chemiluminescent 1,2-dioxetane compounds are disclosed in which the molecule is stabilized at the 3-position on the dioxetane ring against decomposition prior to the molecule's coming in contact with a labile group-removing substance (e.g., an enzyme that will cleave the labile group to cause the molecule to decompose to form at least one light-emitting fluorophore) and substituted at the 4-position on the dioxetane ring with a fused polycyclic ring-containing fluorophore moiety bearing a labile ring substituent whose point of attachment to the fused polycyclic ring, in relation to this ring's point(s) of attachment to the dioxetane ring, is such that the total number of ring atoms separating these points of attachment, including the ring atoms at the points of attachment, is an odd whole number. These odd pattern substituted compounds decompose to emit light of greater intensity and of a different wavelength than that emitted by the corresponding even pattern substituted isomers.

Abstract: The present invention provides a process for the determination of .alpha.-amylase by cleavage of a substrate in the presence of one or more auxiliary enzymes and measurement of a cleavage product, wherein the reaction is carried out in the presence of monoclonal antibodies against .alpha.-amylase.The present invention also provides a reagent for the determination of .alpha.-amylase containing a substrate, one or more auxiliary enzymes and a system for the measurement of a cleavage product, wherein it also contains at least one monoclonal antibody against .alpha.-amylase.

Abstract: A detectable molecule of the formulaA.sup.3 --(--X--R.sup.1 --E--Det.sup.b).sub.mwhere A.sup.3 is A.sup.2 or a polymer, where A.sup.3 has at least one modifiable reactive group selected from the group consisting of amino, hydroxy, cis OH, halides, aryl, imidazoyl, carbonyl, carboxy, thiol or a residue comprising an activated carbon; --X-- is selected from the group consisting of ##STR1## a C.sub.1 -C.sub.10 branched or unbranched alkyl or aralkyl, which may be substituted by --OH; --Y-- is a direct bond to --E--, or --Y-- is --E--R.sup.2 -- where R is a C.sub.1 -C.sub.10 branched or unbranched alkyl; Z.sub.a is chlorine, bromine or iodine; E is O, NH or an acyclic divalent sulfur atom; Det.sup.b is a chemical moiety capable of being detected, preferably comprising biotin or a metal chelator of the formula: ##STR2## or the 4-hydroxy or acyloxy derivative thereof, where R.sup.3 is C.sub.1 -C.sub.4 alkyl or CH.sub.

Abstract: An immunochemical assay to determine the presence or concentration of antigen or antibodies in a fluid, comprising: (a) forming a ternary complex of a first labelled antibody or antigen, a second labelled antibody or antigen, and the antigen or antibody to be determined; and (b) detecting a signal produced in the presence of at least one substrate, by an interaction between said first label and said second label, enhanced by their proximity to each other bound to the antigenic substance.

Abstract: The present invention is directed to a fluorescence polarization assay for opiate alkaloids and their metabolites, to the various components needed for preparing and carrying out such an assay and to methods of making these components. Specifically, tracers, immunogens and antibodies are disclosed, as well as methods for making them. The tracers and the immunogens are made from substituted opiate alkaloids. A fluorescein moiety is included in the tracers, while a poly(amino acid) forms a part of the immunogens. The assay is conducted by measuring the degree of polarization retention of the fluorescence resulting when a sample mixed with antiserum and tracer is irradiated with plane-polarized light.

Abstract: Processes are disclosed in which light of different wavelengths is simultaneously released from two or more enzymatically decomposable chemiluminescent 1,2-dioxetane compounds, said compounds being configured, by means of the inclusion of a different light emitting fluorophore in each of them, to each emit light of said different wavelengths, by decomposing each of said compounds by means of a different enzyme. Such processes can be used in multi-channel assays--immunoassays, chemical assays and nucleic acid probe assays--to detect the presence or determine the concentration of chemical or biological substances, and in multi-channel chemical/physical probe procedures for studying the microstructures of macromolecules.

Abstract: Human cancer is diagnosed/monitored by measuring the levels of N-[9-(.beta.-D-ribofuranosyl)purin-6-ylcarbamoyl]-L-threonine (t.sup.6 A), in a physiological fluid specimen of a subject by a quantitative immunoassay that employs a monoclonal anti-t.sup.6 A antibody and comparing that level to the level of t.sup.6 A that occurs in corresponding physiological fluid of normal subjects to determine whether the former is substantially elevated over the latter or by comparing that level to the level of t.sup.6 A present in specimens taken from the subject at different times.

Abstract: A new reporter mechanism for biospecific reactions is disclosed. This mechanism involves interligand metal ion transfer in which a metal ion is directly transferred from one chelate complex to another following the occurance of the biospecific reaction. The second chelate complex is separate from and detectably different than the first chelate complex. This invention can take the form of methods of chemical analysis and kits for conducting such methods. In preferred embodiments of this invention the detectable difference is a difference in fluorescence, such as an increase or decrease which occurs as a result of the formation of the second chelate. In further preferred embodiments the difference in fluorescence is detected using fluorescent background rejection methods.

Abstract: Microcapsules labeled with an antigen or antibody contain a liquid containing a fluorescent substance, for example, carboxyfluorescein. The liquid in the microcapsules is prepared so as to have a viscosity different from that of a liquid outside the microcapsules. For example, the microcapsules contain polyvinyl alcohol as a substance for increasing the viscosity. Antigen-antibody reaction is caused by mixing such microcapsules, a sample and a complement, and complement is activated with resulting antigen-antibody complex, whereby the microcapsules are lysed.The reaction mixture is irradiated with exciting light, and the polarization components (I.sub..parallel. and I.sub..perp.) of fluorescence from the reaction mixture are detected. The concentration of a substance to be assayed in the sample is determined by calculating the degree of polarization fluorescence P on the basis of the intensities of the polarization components.

Abstract: The present invention is concerned with novel monoclonal antibodies which define a glycolipid antigen associated with human non-small cell lung carcinomas ("NSCLC") and certain other human carcinomas. The antibodies bind to normal human cells to a much lesser degree than to tumor cells. The antibodies find use in diagnostic methods such as the detection of malignant cells associated with NSCLC and in therapeutic methods. Also disclosed in a novel glycolipid antigen. The invention also comprises a method for determining the presence of a malignant condition in lung tissue and other human tissue. The method involves examining the human tissue for the presence of a glycolipid antigen having the terminal carbohydrate sequence: GalNAc.beta.l.fwdarw.4Gal.beta.l.fwdarw.3GalNAc.beta.l.fwdarw.4Gal.beta.l. fwdarw.R.

Abstract: A method for enzyme immunoassay includes contacting under binding conditions a liquid suspected of containing an analyte, an antianalyte affixed to a solid support and a tracer having an enzyme conjugated thereto. A bound fraction is separated from the liquid and incubated in a second liquid with a masked ligand. The masked ligand is converted by the enzyme on the bound fraction to give free lignad which binds to an antiligand. A signal system, such as a signal enzyme and substrate therefor, or a label-loaded vesicle and vesicle lysing agent, is added to generate a signal used to detect or measure the analyte in the liquid. The invention includes a kit of materials useful in performing the assay of the invention.

Abstract: This disclosure relates to a fluorescence polarization immunoassay method for determining C-reactive protein in liquids, especially in biological fluids such as serum, plasma, spinal fluid, amnionic fluid and urine. This disclosure also relates to novel reagents useful in such fluorescence polarization immunoassays.

Abstract: Hybridomally produced monoclonal IgM antibodies having high affinity are useful for the immunoassay and purification of viral antigens.

Abstract: A process for the detection of antibodies to HTLV III/LAV comprising:(A) mixing an unknown serum sample with a crude HTLV III/LAV viral antigen selected from the group consisting of(1) an antigen comprising P24 core protein and Penv protein;(2) a P24 antigen and(3) a Penv antigen,(B) incubating the resultant mixture from step (A);(C) contacting the mixture of step (B) with a solid substrate coated with antibody to HTLV III/LAV;(D) incubating the mass from step (C);(E) washing the mass from step (D);(F) contacting the mass from step (E) with a labeled antibody to HTLV III/LAV;(G) incubating the mass from step (F);(H) washing the mass from step (G);(I) assaying the label in the mass from step (H);(J) as a negative control, mixing a serum sample known to be negative to HTLV III/LAV antibody with a diluent;(K) subjecting the mass from step (J) to steps (B) to (I);(L) as a positive control, mixing a predetermined amount of the crude HTLV III/LAV viral antigen and the diluent;(M) subjecting the mass from step (L) t

Abstract: Peridinin-chlorophyll-protein complexes are provided for use as fluorescent labels and are particularly useful in diagnostic assays employing as a reagent a fluorescent compound conjugated to a member of a specific binding pair, wherein the pair consists of a biochemical ligand and a receptor and the diagnostic assay comprises a step in which the conjugate binds to its complementary binding-pair member.

Abstract: A method is disclosed to detect the presence of an analyte. The method involves forming a complex comprising the analyte and a binding entity. The binding entity comprises a first partner of an energy transfer system. The complex is then contacted with a reporting entity to form a unit. The reporting entity comprises a second partner of the energy transfer system. The first partner and the second partner are within Furster's radius of each other in the formed unit. The unit is irradiated with energy which can only be absorbed by one of said partners, namely, the energy donor, which then emits fluorescent energy. Some of this energy is absorbed by the other of said partners, namely, the energy acceptor, which also emits fluorescent energy. However, the fluorescent energy of the energy acceptor is of longer wavelength and in addition may be of substantially greater duration than the fluorescent energy of the energy donor.

Abstract: A method for determining the presence of a polynucleotide analyte in a sample suspected of containing the analyte is disclosed. The method comprises combining in an assay medium the sample and first and second polynucleotide reagents complementary to the analyte. Each of the first and second reagents hybridize with a different region of the analyte. The first reagent contains means for rendering the first reagent non-covalently polymerizable. The second reagent contains means for rendering the second reagent detectable. The sample and the first and second reagents are combined in the assay medium under conditions for polymerizing the first reagent wherein the second reagent becomes bound to the polymerized first reagent only when the analyte is present in the sample. A determination is then made as to whether the second reagent has become bound to the polymerized first reagent.

Abstract: A method of determining a ligand of interest in a ligand is described. The method, which makes it possible to detect and quantify a ligand in a liquid, makes use of a biotin-avidin system which can be used to carry out immunoassays in both heterogeneous and homogeneous format. The basic components used in the method are a biotin-labeled substance (which is biotin-lableled ligand or biotin-labeled specific binding partner), biotin-labeled fluorophore, a liquid to be analyzed for the ligand of interest, specific binding partner for the ligand of interest and avidin.

Abstract: Reagents qualitatively and quantitatively measure ligands such as antigens and haptens in biological fluids. The reagents include at least ten dye molecules or at lead one dye polymer having at least ten dye monomers per polymer bound to an antibody through an isothiocyanate group on the dye.

Abstract: Hybrid receptors are provided that comprise (a) the ligand binding domain of a predetermined receptor and (b) a heterologous reporter polypeptide. The hybrid receptors are useful for convenient and large scale assay of biologically active ligands or their antagonists or agonists.

Abstract: Labellable reagents for fluormetric assays comprise a cyclic condensation product of a .beta.-diketone, an aldehyde and an NH.sub.2 -bearing macromolecule, for example an antigen or antibody or a substance having an active group to which an antibody or antigen is linked. The reagents can chelate lanthanide metal ions such as Eu(II) and Tb(III) to form fluorescing complexes which can be used as labelled reagents for fluorometric assay of organic substances, for example antigens, antibodies and other substances occurring in body fluids.

Abstract: This invention provides a class of phycoerythrins useful in diagnostic and detection protocols wherein a fluorescent label is required. The unique spectral properties of the phycoerythrins described herein provide for increased sensitivity and alternative uses in assays employing them.

Abstract: A novel competitive assay for theophylline wherein caffeine-like (7-substituted) labeled conjugates are used to detect the presence and/or amount of theophylline present in a test sample. The use of such conjugates in a competitive assay for theophylline results in improved sensitivity of the assay method. Where the assay method is a nephelometric or turbidimetric inhibition immunoassay procedure, the assay was found to be less temperature dependent than prior art immunoassays.

Abstract: Hybridoma for production of monoclonal antibody to an antigen found on the peptide fragment of the B.beta. chain of human fibrinogen or fibrin I containing amino acid residues 1-42. The hybridoma is formed by fusing an animal myeloma cell, e.g., mouse myeloma cell, with a splenocyte from an animal, e.g., a mouse, immunized with an NH.sub.2 -terminal of human fibrinogen or fibrin I. Hybridoma for production of monoclonal antibody to an antigen found on the peptide fragment of the B.beta. chain of human fibrin II containing amino acid residues 15-42. The hybridoma is formed by fusing an animal, e.g., mouse myeloma cell with a splenocyte from an animal, e.g., mouse, immunized with a NH.sub.2 -terminal of human fibrin II. Diagnostic and therapeutic uses of the monoclonal antibodies are also disclosed.

Abstract: The present invention discloses an assay for nucleic acid which comprises the steps of;(a) providing a probe material comprising;(i) a sequence of nucleic acids complementary to a given target sequence and,(ii) a first ligand chemically linked thereto and capable of a specific binding reaction with an antiligand;(b) contacting the said probe material with an assay system comprising:(i) a suitable mediator, enzyme, substrate system capable of transferring charge to an electrode surface when the enzyme is catalytically active, and;(ii) a second ligand chemically linked to one of said mediator, enzyme or substrate, wherein the second ligand is capable of a competitive binding reaction with the antiligand, and;(iii) the said antiligand, Whereby the said first ligand competes with the said second ligand in a specific binding reaction with the antiligand, and;(c) contacting the above system with a solution suspected of containing the said target sequence whereby the binding of any of the said target sequence presen

Abstract: A method for enzyme immunoassay for a ligand suspected to be present in a liquid sample includes signal amplification by use of at least two hydrolases and a blocked fluoroketone for one of the hydrolases. Ligand present in the liquid binds to an antiligand and a hydrolase-labeled tracer. The resulting bound fraction is separated and the hydrolase in the tracer removes the blocking group from the blocked fluoroketone. The fluoroketone activates or inhibits a second hydrolase which catalyzes the conversion of a substrate to a product. The presence or absence of the ligand in the liquid is indicated by a signal, such as a color change or a rate of color change, associated with the product. The invention includes a new class of hydrolase inhibitors and blocked fluoroketones and a kit of materials useful for performing the method of the invention.

Abstract: Electrochemical detection of mediator level is employed in a method of assay using a redox enzyme and redox substrate to detect conversion to an effective mediator by an assay enzyme label of a compound which is non-mediating under the assay conditions.

Abstract: Improved luminescent lifetime-resolved association assay techniques for detection of analytes in samples using two photophore-labelled probes, the photophores of which have different emissive lifetimes. One of the photophores is excitable by a modulated energy source to an excited state from which energy may be transferred to the other photophore when in close poximity thereto resulting in excitation and emission of the other photophore. Methods according to the invention involve associating the first photophore-labelled probe with the analyte and associating the second photophore-labelled probe with the analyte or first probe in a reaction mixture bringing the photophores in sufficient proximity to allow energy transfer to occur. The reaction mixture is formed, excited by the modulated energy source and monitored for emission of the photophore excited by energy transfer at a time beyond the emissive lifetime of the shorter-lived photophore.

Abstract: Fluorescence ligand binding assay of a sample containing an unknown amount of ligand is performed by making direct intensity measurements. In an immunoassay the sample is in a solution containing dye labeled analyte and an antibody specific to the analyte. Surfactant, added to the solution in an amount sufficient to form micelles, provides markedly different fluorescent intensity from bound and unbound labeled analyte if the surfactant ions and dye ions have the same charge polarity and the analyte moeity has the opposite charge polarity.

Abstract: A monoclonal hybridoma antibody with specificity for an antigen that is present on tumors of epithelial origin; the cell line secreting said antibodies; a process for selecting the cell line; a diagnostic process for detecting the antigen and a therapeutic process for neutrailization of the angtigen.

Abstract: A method for immunoassay for a ligand suspected to be present in a fluid includes use of an enzyme, a metal ion catalyst for an indicator reaction and a blocked modulator for the catalyst. Ligand present in the fluid binds to an antiligand. The resulting bound fraction activates the enzyme to unblock the modulator. The free modulator activates or inhibits the catalyst thereby modulating the rate of an indicator reaction between a substrate and a redox reagent. The presence of absence of the ligand in the fluid is indicated by a signal, such as a color change or a rate of color change, consequent to the indicator reaction. The invention includes a kit of materials useful for performing the method of the invention.

Abstract: Compound having the following structure: ##STR1## R is a direct chain or branched alkylene group comprising 2-8 carbon atoms,n and m are 0 or 1,Y is a carboxylic or phosphonic acid, andX is an active functional group which permits covalent coupling to a bio-organic molecule.