BIOPHYSICAL STUDIES WITH SPATIALLY CORRELATED IONS .3. CELL-SURVIVAL STUDIES USING DIATOMIC DEUTERIUM

Diatomic deuterium ions were accelerated at the Radiological Research Accelerator Facility to produce pairs of deuterons (LET = 33 keV/μm) for radiation biology experiments. Cell survival of hydroxyurea-synchronized Chinese hamster V79 cells was determined for pairs of deuterons whose mean separations were varied from less than 0.1 μm to more than 0.2 μm. An enhanced killing of late-S-phase cells was observed, for these separations, beyond that of unassociated (single) deuterons. An enhanced killing was detected also for G1/S transition cells but to a lesser extent. Irradiations were performed with helium ions (LET = 65 keV/μm) at twice the deuteron LET value as an approximation to zero separation of deuteron pairs. The effectiveness of paired deuterons at the separations achieved in these experiments was less than that of the helium ions. The results provide information about the spatial dependence for sublesions to form lethal lesions.