Solubility of nitric oxide (NO) in lipid aggregates as monitored by nuclear magnetic resonance

Nitric oxide (NO) is known as a multifaceted bioregulatory agent and an environmental pollutant. We investigated the role of nitric oxide in phospholipid solutions by NMR techniques. A mixture of lipids dissolved in a ternary solvent was used. 31P NMR spectra of this mixture before and after exposure to nitric oxide were recorded. Nitric oxide is a strongly paramagnetic molecule which is able to increase the spin-lattice relaxation rates, and, after its addition, we observed a strong signal broadening at certain solvent concentrations. Many pure phospholipids, dispersed in organic solvents, can form reversed micelles by spontaneous self-association. These results suggest that the lipids form a colloidal dispersion in a homogeneous organic ternary mixture, where the NO solubility increases strongly and produces a broadening of the 31P NMR signal.