Energy Transfer in Relation to Water-content in Solid Proteins

Summary Transfer of excitation energy from one chromophore to another in a protein molecule has been measured in thin, transparent films of a protein with various amounts of hydration water. The decrease in transfer efficiency accompanying the adsorption of water was found to be of the same magnitude as that expected from the molecular expansion connected with the hydration. The influence of the water on the radiosensitivity of some biological materials is far more drastic than the decrease in transfer efficiency measured here. Although this decrease may be expected to be much greater in DNA than in the protein investigated, it is certainly not great enough to explain the total biological effect, as it has been assumed by a few authors. Other rôles played by water in this connection are discussed in relation to possible effects of excitations on macromolecules.