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 E PR detection of nitric oxide ((NO)-N-.) as a precursor of spin traps f or the quantification of released (NO)-N-. both in vitro and in vivo. This method is based on the high affinity of water insoluble iron-dith iocarbamate complexes towards (NO)-N-.. The nitrosyl-iron-dithiocarbam ate complex NOFe(DETC)(2) is formed with characteristic tripler EPR sp ectrum. In the present paper we have studied the reaction of water sol uble Fe(II)-proline-dithiocarbamate complex, Fe(PDTC)(2), with nitric oxide using both EPR spectroscopy and laser flash photolysis. It has b een found that the treatment of the Fe(PDTC)(2) complex either by auth entic (NO)-N-. dissolved in aqua buffer solutions or by different (NO) -N-. donors results in the quantitative appearance of an EPR signal of a stable mononitrosyl complex NOFe(PDTC)(2) with a g-factor g(iso)=2. 04 and a hyperfine splitting constant a(N)=12.5 G. The laser flash pho tolysis method has been used to study the kinetics of (NO)-N-. trappin g by Fe(PDTC)(2). Nitric oxide release from a light sensitive (NO)-N-. donor, piridazinofuroxan, was induced by a short flash of UV light ge nerated by a XeCl eximer laser. The rate constant of the reaction of ( NO)-N-. with Fe(PDTC)(2) was found to be (1.1 +/- 0.3) . 10(8) M(-1) s (-1), manifesting a high efficiency of (NO)-N-. trapping by Fe(PDTC)(2 ). (C) 1996 Academic Press, Inc.