Direct effects of radiation on the avidin-biotin system. Absence of energy transfer

Frozen solutions of biotinylated glucose-6-phosphate dehydrogenase and fluorescently tagged avidin were exposed to high energy ionizing radiation. Parallel experiments with peroxidase coupled to streptavidin and with biotinylated phycoerythrin were also performed. The loss of function of each compound was analyzed according to target theory. Target analysis revealed that the radiation-sensitive mass associated with the enzymatic activity and that associated with the fluorescence were unchanged by irradiation in the strongly coupled state. Therefore the noncovalent bonds between biotin and avidin do not permit the transfer of radiation-deposited energy in amounts sufficient to destroy the activity of apposing molecule.