Biological inactivation by singlet oxygen: distinguishing O2(1 delta g) and O2(1 sigma g+)

Experiments were performed to determine whether bacterial inactivation in the separated-surface-sensitizer system for singlet oxygen generation is due to O2(1 delta g) or O2(1 sigma g+). The rates of inactivation of Gram-negative Salmonella typhimurium LT-2 and a nonpigmented strain of Gram-positive Sarcina lutea were found to increase linearly with the concentration of 1 delta g. The gas phase lifetime of the inactivating agent was found to be within the range of values expected for the gas phase lifetime of 1 delta g rather than 1 sigma g+. These measurements conclusively demonstrate that bacterial inactivation in this system is due predominantly to 1 delta g. Therefore, studies of bacterial inactivation with this singlet oxygen generating system can be used to assess the role of singlet oxygen in various biological and medically relevant situations.