The Effects of Added Agar on the Radiation Sensitivity of Trypsin in Solution

Abstract

A previous study in this series was concerned with the effects of radiation on the two-component system, trypsin plus the gel-forming substance agar. In firm gels the inactivation of trypsin was greatly depressed from that observed for a comparable concentration of trypsin in solution alone. With much smaller concentrations of agar, large pH effects were observed, suggesting the occurrence of fairly specific agar-trypsin complexes (1). The present experiments were designed to investigate further the changes in trypsin radiosensitivity caused by the addition of very small amounts of agar. In particular, this report is concerned with the extent of complex formation and the effects of trypsin-agar interactions on the kinetics of inactivation of the enzyme. An important finding is that, even in such a relatively simple system, three classes of trypsin molecules with widely differing properties can be demonstrated. This raises important questions concerning the relevance of studies in model systems to an understanding of radiobiological mechanisms in cells.