PHYSICAL AND CHEMICAL INTERACTIONS BETWEEN NITRIC-OXIDE AND NITROXIDES

The physical and chemical interactions of nitric oxide ((NO)-N-.) with stable nitroxides have been studied in both aqueous and membrane environments, The ESR spectrum of 3-carbamoyl-2,2,5,5-tetramethyl-3-pyrroline-1-yloxy (CTPO) was observed to broaden upon exposure to (NO)-N-.. This effect can be explained by invoking Heisenberg spin exchange as has been previously reported for molecular oxygen. No loss of total spin was observed negating the possibility of a chemical reaction between (NO)-N-. and CTPO. The extent of signal broadening was proportional to the concentration of (NO)-N-. and can thus be used to monitor (NO)-N-. concentration. We have used this method to observe the partitioning of (NO)-N-. into model membranes. We also report the use of multiquantum ESR to detect directly the effects of (NO)-N-. on the membrane bound spin label 12-doxylstearic acid. This methodology may prove useful for detecting (NO)-N-. in both aqueous and lipid environments and for examining the physical properties of (NO)-N-. within biological membranes.