Nitric Oxide-forming Reaction between the Iron-N-Methyl-d-glucamine Dithiocarbamate Complex and Nitrite

Abstract

The objective of this study was to elucidate the origin of the nitric oxide-forming reactions from nitrite in the presence of the iron-N-methyl-D-glucamine dithiocarbamate complex ((MGD) 2 Nitric oxide (NO) 1 has many important physiological roles which include that of a cytotoxic mediator of the immune system, regulation of vasomotor tone in the cardiovascular system, and as a neurotransmitter in the central nervous system (1, 2). NO is thought to be identical to the endothelium-derived relaxing factor (1), and its insufficiency is believed to contribute to the pathogenesis of vascular disease such as atherosclerosis, hypertension, and myocardial ischemia. As a result, much attention has been focused on the potential therapeutic ability of nitrovasodilators (e.g. nitroglycerin and nitroprusside) (3) and the anti-cancer drug hydroxyurea (4) to release NO.In order to understand the mechanisms by which NO, a diffusable free radical with a short lifetime, mediates various biological processes, accurate methods for its measurement are required. Several methods for the quantitation of NO such as chemiluminescence (1), methemoglobin formation (5), and electron paramagnetic resonance (EPR) spectroscopy of nitrosylmetal complexes (6) have been developed (7). Production of NO can also be indirectly assessed by measuring the nitric oxide oxidation product, nitrite, with the Griess reaction.EPR spectroscopy is the only specific general technique available for the detection and measurement of radical production, but has severe quantum mechanical limitations for diatomic molecules. EPR methods have been developed which stabilize NO as a polyatomic adduct using endogenous and exogenous spin traps (8 -14). Conventional nitrone-and nitroso-based spin traps are not capable of trapping NO as stable radical adducts, and nitromethane is an effective spin trap only at very alkaline pH values (15). The diethyldithiocarbamate (DETC) ferrous complex is a commonly used spin trap for NO (16), and the resultant (DETC) 2 Fe 2ϩ

Nitrite as the major source of nitric oxide production by Arabidopsis thaliana in response to Pseudomonas syringae

“…3C). In wild-type plants, this increased Å NO production was difficult to detect in the absence of SOD, because of the pre-existing basal Å NO levels that reacted with O À 2 [29]. However, the addition of SOD revealed a significant difference in Å NO production between control and inoculated wild-type plants (Figs.…”

Endogenous Superoxide Production and the Nitrite/Nitrate Ratio Control the Concentration of Bioavailable Free Nitric Oxide in Leaves

“…It has been shown before that NO can be synthesized nonenzymatically from nitrite through its direct interaction with Fe 2ϩ -dithiocarbamate complexes (37). Clearly, that cannot be the case for hydrophobic complexes, such as Fe 2ϩ -DETC, localized in intracellular membrane compartments to which nitrite does not have access.…”

“…Clearly, that cannot be the case for hydrophobic complexes, such as Fe 2ϩ -DETC, localized in intracellular membrane compartments to which nitrite does not have access. However, the reaction was shown to take place for water-soluble Fe 2ϩ -dithiocarbamate complexes, such as Fe 2ϩ -MGD (37). Thus, the possibility exists that the MNIC-MGD complexes in the leaf preparations are formed via this nonenzymatic mechanism of nitrite reduction by the Fe 2ϩ -MGD complexes in the medium and not via the intracellular NO generation by NR.…”

Multi-photon excitation in uncaging the small molecule bioregulator nitric oxide

“…The two-photon absorption cross section of this complex was determined to be 682 GM at 775 nm. Both SPE at 365 nm and TPE at 775 nm led to NO release which was detected by electron paramagnetic resonance (EPR) spectroscopy using Fe(MGD) 2 (MGB = N-methyl-D-glucamine dithiocarbamate) as a trapping agent to give the EPR active Fe(MGD) 2 (NO) [64]. Since the fluorescent ligand was also released from the metal cluster as the result of the photolabilization of NO followed by oxidative secondary reactions, as previously seen with PPIX-RSE and Fluor-RSE [18,60], the net fluorescence from the solution increased as the photoreaction progressed.…”