EPR and laser flash photolysis studies of the reaction of nitric oxide with water soluble NO trap Fe(II)-proline-dithiocarbamate complex.

Diethyl-dithiocarbamate (DETC) chelating ferrous iron is used during EPR detection of nitric oxide (.NO) as a precursor of spin traps for the quantification of released .NO both in vitro and in vivo. This method is based on the high affinity of water insoluble iron-dithiocarbamate complexes towards .NO. The nitrosyl-iron-dithiocarbamate complex NOFe(DETC)2 is formed with characteristic triplet EPR spectrum. In the present paper we have studied the reaction of water soluble Fe(II)-proline-dithiocarbamate complex, Fe(PDTC)2, with nitric oxide using both EPR spectroscopy and laser flash photolysis. It has been found that the treatment of the Fe(PDTC)2 complex either by authentic .NO dissolved in aqua buffer solutions or by different .NO donors results in the quantitative appearance of an EPR signal of a stable mononitrosyl complex NOFe(PDTC)2 with a g-factor giso = 2.04 and a hyperfine splitting constant aN = 12.5 G. The laser flash photolysis method has been used to study the kinetics of .NO trapping by Fe(PDTC)2. Nitric oxide release from a light sensitive .NO donor, piridazinofuroxan, was induced by a short flash of UV light generated by a XeCl eximer laser. The rate constant of the reaction of .NO with Fe(PDTC)2 was found to be (1.1 +/- 0.3).10(8) M-1s-1, manifesting a high efficiency of .NO trapping by Fe(PDTC)2.