NEW INSIGHTS INTO THE ROLES OF METALS IN NITRIC OXIDE DELIVERY

The biochemistry of organic nitroso compounds (E-NO, E = RS, RO, R2N, R) is connected to that of nitric oxide. These organic derivatives can serve either as sources of NO in vivo or produce similar effects as NO such as vasodilation. In contrast to free NO, these organic derivatives are stable towards dioxygen. Release of NO from many organonitroso compounds requires a reducing equivalent, implicating redox active metalloenzymes. Thus in many cases the “stored ” NO in its carrier molecules has to go through certain release-and-capture cycles to execute its various biological functions. The transport of NO in biological systems is via S-nitrosothiols, part of sulfur-containing proteins. Employing monovalent nickel and copper beta-diketiminates and tris(pyrazolyl)-borates as models for these metal ions in metalloenzymes, we find that the E-NO bonds of O-nitroso (RO-NO), N-nitroso compounds (R2N-NO), and S-nitroso (RS-NO) are readily cleaved to form well defined metal complexes [Ni](II)-E. In the case of the most biologically relevant Cu complexes, we observe an important contrast to all previousl