The Role of Singlet Oxygen in Photooxidation of Excitable Cell Membranes

Giant nerve axons from lobsters were photooxidized by visible light from a Xe arc using eosin Y, rose bengal and methylene blue as sensitizers. The degree of modification was assayed as the rate constant for block of sodium channels during illumination. Protection or enhancement of modification was tested for several reagents known to interact with singlet oxygen. Deuterium oxide enhanced the modification up to 57% while sodium azide protected up to 60%. β ‐Carotene, triethylamine and DABCO exerted no effect. From a consideration of the probable low polarity environment of the sensitization sites and diffusional restrictions on reagents it is concluded that intramembranously created singlet oxygen plays a significant role in membrane modification.