A radioimmunoassay method for quantification of alpha-tropomyosin in heart homogenates.

A new, extremely sensitive, solid phase radioimmunoassay has been developed to quantify tropomyosin levels in heart tissue homogenates. Specific antibody was coupled to Sepharose 4B and saturation levels of [125I]tropomyosin bound. Release of radiolabel into the supernatant portion occurred when heart homogenates, authentic tropomyosin or tropomyosin in the presence of homogenate were added to these immunobeads. Quantification of the amount of tropomyosin was based on the level of release effected by standard tropomyosin with and without homogenate. The assay was determined to be highly specific and sensitive for tropomyosin. Picomolar quantities of the protein were readily detectable. Linearity extended well over the range of 5-200 ng tropomyosin in the homogenate. The method can be applied to other proteins for quantification during embryonic development.