COA, but not N₂A, results in S-phase arrest of cell cycle.

Cells were incubated under aerobic and anaerobic conditions, N₂A or COA, for 4 days. Insert: representative FACS analysis of cell cycle for K562 cells incubated under different atmospheres. Arrows indicate center of S-phase. Main Figure: phase distribution of viable cells. Mean ± SD from 3 independent experiments is shown. Empty bars - G₀/G₁ phase, black bars - S phase and grey bars - G₂/M phase.