Singlet oxygen can be generated by many chemical, biological, and photochemical processes, including energy transfer from an electronically excited photosensitizer to oxygen. We study it and other reactive intermediates and novel products in photochemical and other oxidation reactions by spectroscopic and kinetic methods, trapping, and isolation of novel products. We observe its weak infrared emission with an ultrasensitive germanium diode. If the sensitizer is excited by a short laser pulse, the emission can be measured as a function of time. Many short-lived products are directly characterized by low-temperature NMR spectroscopy. Many novel synthetically useful reactions result from this work.
Oxygen-dependent photosensitized toxic effects are extremely common in nature. A particularly exciting application of this type of chemistry is the use of a photosensitizer, light, and oxygen to kill tumor cells selectively in humans. Studies of the mechanism and preparation of more effective sensitizers are in progress.
We are also studying the antimicrobial action of human white cells. Foreign microorganisms are trapped ("phagocytosed") by the white cells. Oxygen is involved in this process, and we have evidence that a reactive species is hypochlorous acid, which can be assayed by suitable traps.
In summary, we use a wide range of techniques to show the role of key oxidants in chemical systems that are important to organic, biological, and medical science.
[ Department * Faculty * Current Organic Research * Organic Research Interests ]
Last Revision: 10/26/95 // mk