Abstract: The invention disclosed is a method of inhibiting L-tryptophan to serum albumin binding in a biological fluid containing L-tryptophan and serum albumin, comprising adding to the fluid cis-parinaric acid in a molar ratio to serum album of about 0.5:1 to 4.0:1.

Abstract: Spin labels, especially dianionic aromatic spin labels which can bind to the first specific high-affinity bilirubin-binding site on serum albumin, and which are quantitatively displaceable into solution from said site in the presence of bilirubin, can be used in an assay for bilirubin-binding capacity. In the assay, an excess of spin label is mixed with the serum albumin or serum and is titrated with standard bilirubin. ESR spectroscopy indicates a change in the rate of spin label release with addition of bilirubin, giving a value indicative of bilirubin-binding capacity. Novel dianionic aromatic spin labels are also disclosed.

Abstract: Immune lysis of sensitized liposomes containing a marker is employed in an assay method wherein an antigenic material to be determined is reacted with a specific antiserum and the degree of inhibition of the antiserum is detected by the extent of release of a marker when the antiserum reacts with liposomes containing a sensitizer specific to the antiserum.

Abstract: Monitorable drug compositions contain known proportions by weight of a drug e.g. methadone and an isotopic analogue e.g. deuterated methadone. A urine specimen or blood specimen can be tested to reveal whether the proportion of the two constituents in the urine is the same as the proportion in the composition that was prescribed to the patient. A discrepancy will reveal that the patient has supplemented his dosage with drugs obtained from another source.