Nitric oxide complexes, with

Woolum, J. C., Tiezzi, E., and Commoner, B. (1968). Electron spin resonance of iron-nitric oxide complexes with amino acids, peptides and proteins. Biochim. Biophys. Acta 160, 311-320. 

Nitrosylmyoglobin (NO-Mb) Nitric oxide complex with myoglobin Intact Fe(II) Native Red... 

The isolation of [Fe2(SMe)2(NO)4] from certain preserved vegetables and its implication in diet-related carcinogenesis, underlines the similarities between the iron- sulfur nitrosyl systems and the complexes discussed above. The proto-typic iron-sulfur nitrosyl complexes are Roussin s salts (Section Nitric Oxide Complexes with Sulfur Donors ). [Fe2 (SR)2 (N0)4] complexes are known with a wide range of R groups. They can be synthesized directly from iron(ll) salts, as shown in equation (20), or a variety of other mononuclear iron complex precursors including [Fe(NO)(S2CNMe2)2] (with excess RS ), [Fe(CO)3NO], and [Fe(NO)2(SR)2] . 

Studies related to the mechanisms of nitric oxide reactions with transition metal complexes in this laboratory were supported by grants from the U.S. National Science Foundation, by a Collaborative UC/Los Alamos National Laboratory Research grant, by a grant from the U.S. Japan Cooperative Research Program (Photoconversion/ Photosynthesis) (NSF INT 9116346), and by a grant from the ACS Petroleum Research Fund. We thank the students and postdoctoral fellows at UC Santa Barbara who participated in this research and acknowledge collaborative studies with Dr. David Wink (National Cancer Institute, Bethesda MD, USA), Dr. Mikio Hoshino (RIKEN, Wako-shi, Japan) and Dr. Jon Schoonover (Los Alamos National Laboratory). 

Bec, N., Gorren, A. C., Voelker, C., Mayer, B., Lange, R., Reaction of neuronal nitric-oxide synthase with oxygen at low temperature. Evidence for reductive activation of the oxy-ferrous complex by tetrahydrobiopterin, J. Biol. Chem. 273 (1998), p. 13502-13508... 

Reaction of the manganese tropocoronand complex [Mn(tc-5,5)(NO)] with [Fe(tc-5,5)] results in complete transfer of the NO to the [Fe(tc-5,5)]. Other nitric oxide complexes appear in the sections on nitroprusside (Section S.4.2.2.6 above), on phthalocyanines (Section 5.4.3.7.4 above), and on polynuclear iron-sulfide complexes (Roussin s salts Section 5.4.5.9.2 below) Fe-por-phyrin-NO redox chemistry has been mentioned in Section 5.4.3.7.2 above. 

To separate osmium from ruthenium, the aqueous solution is acidified with nitric acid. While nitric acid oxidizes osmate ion to volatile osmium tetroxide, Os04, it converts ruthenium to a nitric oxide complex. Osmium tetroxide is removed from the solution by distillation in air and collected in an aqueous solution of caustic soda containing ethanol. Osmium tetroxide solution is heated with ammonium chloride, upon which osmium precipitates out as a complex chloride, 0s02(NH3)4Cl2. The precipitate is filtered, washed and decomposed by ignition with hydrogen to yield osmium metal. 

In the process, the iron is reduced to the ferrous form. Ferric cytochrome c is reduced by nitric oxide through a nitrosyl intermediate to produce ferrous cytochrome c and nitrite (Orii and Shimada, 1978). The nitrosyl cytochrome c absorbs at 560 nm, which is slightly higher than the 550-nm peak observed for reduced cytochrome c. Nitric oxide may be an interference in the assay of superoxide from cultured cells by the cytochrome c method. When nitric oxide reacts with cytochrome c, there is an initial decrease in absorbance at 550 nm as the nitrosyl complex is formed followed by a rise in absorbance as the complex decomposes to nitrite and reduced cytochrome c. This is a potential artifact in studies measuring the release of superoxide from cultured endothelial cells or other cells that make nitric oxide. 

Partial replacement of isocyanide in [Cr(CNR)6](PF6)2 or [CrCl(CNPh)5]PF6 by phosphines PR3, bis(diphenylphosphino)ethane (dppe) or bis(diphenylphosphino)methane (dppm) provides two series of mixed-ligand complexes (Scheme 4).22,23 The complexes [Cr(CNR)4(dppe)](PF6)2, which must be cis, have more complicated spectra in the v(CN) region than the complexes [Cr(CNR)4(PR3)2](PF6)2j which are therefore trans (Table 3). Nitric oxide reacts with [Cr(CNR)6](PF6)2 to give [Cr(NO)(CNR)5](PF6)2 from which many mixed nitrosyl isocyanide complexes of Cr1 and Cr° can be derived (Section 35.4.2.6). 

Treatment of the complex with donor molecules such as pyri-dines, phosphines, bipyridyl (2,2 -bipyridine), etc., results in the cleavage of the dimer and formation of diamagnetic five- and six-coordinate adducts.4 Nitric oxide reacts with the complex forming the unstable green mononitrosyl [Co(NO)S4C4(CN)4]-which has one unpaired electron.3 Treatment with Na2S2C2-(CN)2 results in the formation of [CoS6C6(CN6)]3 which can be isolated as the tetraphenylphosphonium salt.14... 

Nitric oxide reacts with an ethanolic solution of [Fe(salen)] [salen = A,7V -ethylenebis(sali-cylideniminato)] at room temperature to give the black complex [Fe(salen)NO]. This compound exhibits185 an S = to S = spin cross-over at 175 K. The corresponding complex of the 5-chloro-salen ligand [Fe(5-Cl-salen)NO], however, shows no sharp spin cross-over transition but a steady decrease in magnetic moment from 3.8 to 0.5 BM over the temperature range 4-100 K, indicative186... 

The preceding discussion illustrates the continuing uncertainty as to the nature of the Lj and La ligands. The properties of low-spin ferricata-lase derivatives are consistent with the presence of histidine at La but, seemingly, the characteristics of the free enzyme and of the low-spin ferrocatalase-nitric oxide complex are not. It could be argued, of course, that the orientation of La, or even its identity, is not invariant in different derivatives, but is mobile or interchangeable. Indeed, Samejima and Kita... 

Binary Nitric Oxide Complexes. A binary iron nitrosyl complex is not known, although described in early reports as [Fe(NO)4], the compound having that stoichiometry is a dimer with an N2O2 bridging ligand (10). 

The chloride dimer [Fe(NO)2Cl]2 also exists, and can be reduced in THF solution to Fe(NO)2 , which is most likely [Fe(NO)2(THF) ]. The brown color of the familiar, so-called, Brown Ring Test for nitrate in which the sample is treated with ferrous sulfate and sulfuric acid is due to the formation of the nitric oxide complex [Fe(H20)5N0] +. 

Nitric oxide reacts with Fen(M4PyTPP), where M4PyTPP = meso-4-pyridyltriphenyl-porphyrinate, to form two nitrosyl complexes, identified by IR spectroscopy.298 The resonance Raman spectrum of the NO-bound ferric derivative of HbN (a haemoglobin from Mycobacterium tuberculosis) showed a shift of vNO from 1914 cm-1 to 1908 cm-1 on forming the B10 Tyr - Phe mutant.299 The resonance Raman spectrum of the iron(II)-NO complex of the haem-regulated eukaryotic initiation factor 2a kinase (HRI) is consistent with a... 

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