“Homogeneous” enzyme immunoassay. A new immunochemical technique

Addition of morphine antibodies to a conjugate of morphine and lysozyme resulted in inhibition of lysozyme activity. Addition of free morphine to a mixture of the conjugate and morphine antibodies reduced the inhibition of enzyme activity in proportion to the quantity of free morphine added. As little as 1 × 10−9 M morphine could be detected in this manner. The method constitutes a powerful new immunochemical technique for the quantitative determination of haptens.