Protein binding assays, radioisotopic

In an attempt to overcome some of the diflSculties mentioned above, radioisotopic competitive protein binding assays (CPBA) were devel-... 

Immunoassays, specific protein-binding assays, and radioisotope tests are sometimes used for the determination of water-soluble vitamins. These are the only feasible and practical methods for the quantification of certain vitamins in physiological samples. The principle of competitive protein binding (CPB) using labeled radioactive or fluorescent tracer is still routinely applied to quantification of serum vitamin... 

Protein-binding assays The radioisotope dilation assay (RIDA) has been employed for determining vitamin B12 in foods, using radiolabeled Bi2 and hog intrinsic factor (IP), the most specific Bi2-binding protein. Several kits for the RIDA method are commercially available. A very good correlation coefficient has been found between the microbiological method and the RIDA method, but a radioisotope is used and radioisotope facilities and apparatuses are necessary for the RIDA method. The direct... 

One other class of biochemical proteins that offers a similar advantage in clinical biochemistry is antibodies, which are highly specific for interaction with other proteins (i.e. with antigens) and bind with a high affinity. The combination of antibodies with radioisotopes produces very sensitive and very specific assays. This system has been used particularly for measuring the concentrations of hormones (see below) peptides and cytokines. 

---