Oxygen in S phase of a cell cycle

Abstract

It isgenerally agreed that the S phase is radioresistant because of its deficiency of molecularoxygen. This conclusion is based on the oxygenenhancement ratio (OER) and not by measur-ing the actual molecular oxygen content in eachphase of the cell cycle (Table 1).The OER is calculated by radiation dosedelivered under hypoxic and under aeratedcondition to achieve the same biological endpoint. The OER at high doses yield a valuebetween 2?3 and 3?5 for X-rays and g rays.We abstracted the data from the literature. It isinteresting to note in Figure 1, as the cell ages,water proton NMR Spin Lattice relaxation time(T