Abstract: Polynucleotides are labeled with chemiluminescent acridine esters or luminescent lanthanides. Labelling is preferably carried out by incorporating a functional group into a nucleotide or polynucleotide at the C4 position of the pyrimidine portion or the C6 position of the purine portion and bonding a chemiluminescent acridine ester or a luminescent lanthanide to the functional group. The labeled polynucleotides are useful for direct detection of homologous polynucleotide sequences.

Abstract: There is described an enzyme inhibitor labelled immunoassay for measuring the concentration of an analyte in a sample wherein the substrate for the enzyme forms at least a part of the sample. In a particular embodiment the sample comprises or consists of a milk sample and the inhibitor label is capable of inhibiting the activity of an enzyme capable of clotting milk. Examples are given of suitable inhibitors. The assay described may be used to measure the concentration of progestogens or oestrogens in milk using the techniques of heterogeneous or homogeneous enzyme inhibitor labelled immunoassay. The results of such an assay give an indication of the fertility of a milk producing domestic animal (e.g. a cow) and may be used to diagnose pregnancy of such an animal. Particular compounds for use in the assay are described, as is a kit of reagents for use in the assay.

Abstract: A heterogeneous binding assay in which a liquid component and a granular particulate solid phase are incubated together for a predetermined period of time. To prevent unwanted unit gravity sedimentation of the granular particulate solid phase during incubation the density of the liquid component is controlled such that it is substantially equal to the density of the granular particulate solid phase, thus preventing sedimentation. The density may be controlled by adding a density modifying medium such as a colloidal suspension of silica particles coated with polyvinylpyrrolidine. After incubation, the density of the liquid component may be reduced allowing unit gravity sedimentation and hence separation of the solid phase from the liquid component. The assay is particularly applicable to immunoassay (for example radioimmunoassay and immunoradiometric assay). Immunoradiometric assays for human growth hormone, thyroid stimulating hormone and alphafetoprotein are described.