35] Radiation inactivation and target size analysis of interferons

Abstract

This chapter discusses the radiation inactivation and target size analysis of interferons. There has been a resurgence of interest in an alternative technique of molecular size determination––radiation inactivation. This is undoubtedly stimulated by the unique principles and properties of this approach; that the loss of biological activity resulting from molecular damage is related to the mass of the structure, and the fact that the results are independent of the presence of other molecules. The size measurement obtained from radiation inactivation must be interpreted as the mass of a biologically active unit. The fact that the target molecules are hit at random, depending only on their mass, and that the energy is confined to a single covalent structure leads to an important characteristic of the target analysis. The study of a particular activity is independent of the presence of other molecules in the preparation if they are not functional in the assay conditions. Thus, purification is not required. A sequela of this fact is that a single irradiated sample can be monitored for as many independent biological functions as desired, and target sizes for each activity can be obtained simultaneously. Enzymes of known size that are present in the preparation can be monitored as an internal control.