Spin trapping nitric oxide from neuronal nitric oxide synthase: A look at several iron-dithiocarbamate complexes

The free radical, nitric oxide (center dot NO), is responsible for a myriad of physiological functions. The ability to verify and study center dot NO in vivo is required to provide insight into the events taking place upon its generation and in particular the flux of center dot NO at relevant cellular sites. With this in mind, several iron-chelates (Fe2+(L)(2)) have been developed, which have provided a useful tool for the study and identification of center dot NO through spin-trapping and electron paramagnetic resonance (EPR) spectroscopy. However, the effectiveness of center dot NO detection is dependent on the Fe2+(L)(2) complex. The development of more efficient and stable Fe2+(L)(2) chelates may help to better understand the role of center dot NO in vivo. In this paper, we present data comparing several proline derived iron-dithiocarbamate complexes with the more commonly used spin traps for center dot NO, Fe2+-di(N-methyl-D-glutamine-dithiocarbamate) (Fe2+(MGD)(2)) and Fe2+-di(N-(dithiocarboxy)sarcosine) (Fe2+(DTCS)(2)). We evaluate the apparent rate constant (k(app)) for the reaction of center dot NO with these Fe2+(L)(2) complexes and the stability of the corresponding Fe2+(NO)(L)(2) in presence of NOS I.