Molecular mass and volume in radiation target theory

Radiation target analysis is based on the action of ionizing radiation dire ctly on macromolecules. Interactions of this radiation with the molecules l eads to considerable structural damage and consequent loss of biological ac tivity. The radiation sensitivity is dependent on the size of the macromole cules. There has been confusion and discrepancy as to whether the molecular mass or the molecular volume was the determinant factor in the sensitivity . Some proteins are known to change their hydrodynamic volume at low pH, an d this characteristic can be utilized to compare the radiation sensitivitie s of these proteins in the two stales. The results show that the radiation sensitivity of proteins depends on the mass of the molecule and is independ ent of the molecular volume/shape.