Stereochemistry of nitrosylmetalloporphyrins. Nitrosyl-.alpha.,.beta.,.gamma.,.delta.-tetraphenylporphinato(1-methylimidazole)iron and nitrosyl-.alpha.,.beta.,.gamma.,.delta.-tetraphenylporphinato(4-methylpiperidine)manganese

Piciulo, P.L.; Rupprecht, G. A.; Scheidt, W. Robert

doi:10.1021/ja00823a067

Cited by 102 publications

(56 citation statements)

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“…As has been noted [55], this prediction is well supported by the structures of nitrosyl complexes of Mn II (TPP), Fe II (TPP), and Co II (TPP), with respective M-N-O bond angles of 176.2°, 142.1°, and 128.5° [56,57]. The first is consistent with the cationic nitrosonium adduct, Mn I (TPP)(NO + ), the latter with that of the nitroxyl complex Co III (TPP)(NO À ), while the adduct with Fe II (TPP) is intermediate and has substantial radical character on the NO ligand.…”

Section: The Enemark/feltham Bonding Extremesupporting

confidence: 70%

Coordination chemistry of the HNO ligand with hemes and synthetic coordination complexes

Farmer

Sulc

2005

Journal of Inorganic Biochemistry

138

179

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Section: The Enemark/feltham Bonding Extremesupporting

confidence: 70%

Coordination chemistry of the HNO ligand with hemes and synthetic coordination complexes

Farmer

Sulc

2005

Journal of Inorganic Biochemistry

138

179

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“…To date, all synthetic (por)Mn(NO)-containing compounds of the {MnNO} 6 class (i.e., Mn II NO) that have been characterized by X-ray crystallography display linear Mn-NO groups [48,49,134,135]. The expected and observed linearity of the MnNO bonds is supported by the spectroscopic characterization of several low-spin (por)Mn(NO)-containing compounds [44,46,128,136].…”

Section: The Nitric Oxide Complexmentioning

confidence: 88%

Crystal structures of manganese- and cobalt-substituted myoglobin in complex with NO and nitrite reveal unusual ligand conformations

Zahran

Chooback

Copeland

et al. 2008

Journal of Inorganic Biochemistry

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Nitrite is now recognized as a storage pool of bioactive nitric oxide (NO). Hemoglobin (Hb) and myoglobin (Mb) convert, under certain conditions, nitrite to NO. This newly discovered nitrite reductase activity of Hb and Mb provides an attractive alternative to mammalian NO synthesis from the NO synthase pathway that requires dioxygen. We recently reported the X-ray crystal structure of the nitrite adduct of ferric horse heart Mb, and showed that the nitrite ligand binds in an unprecedented O-binding (nitrito) mode to the d(5) ferric center in Mb(III)(ONO) [D.M. Copeland, A. Soares, A.H. West, G.B. Richter-Addo, J. Inorg. Biochem. 100 (2006) 1413-1425]. We also showed that the distal pocket in Mb allows for different conformations of the NO ligand (120 degrees and 144 degrees ) in Mb(II)NO depending on the mode of preparation of the compound. In this article, we report the crystal structures of the nitrite and NO adducts of manganese-substituted hh Mb (a d(4) system) and of the nitrite adduct of cobalt-substituted hh Mb (a d(6) system). We show that the distal His64 residue directs the nitrite ligand towards the rare nitrito O-binding mode in Mn(III)Mb and Co(III)Mb. We also report that the distal pocket residues allow a stabilization of an unprecendented bent MnNO moiety in Mn(II)MbNO. These crystal structural data, when combined with the data for the aquo, methanol, and azide MnMb derivatives, provide information on the role of distal pocket residues in the observed binding modes of nitrite and NO ligands to wild-type and metal-substituted Mb.

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“…We have carried out calculations for both the five-liganded system with NO as the fifth ligand and the six-liganded systems with the Im of the proximal histidine as the sixth ligand. We have used available x-ray structural data on the five-liganded (27) and six-liganded (28) (1), the decrease in the 14N, hyperfine interaction being primarily a result of the weakening of the Fe-NE bonding, involving a decreased amount of NE orbital admixtures in the d-2-type molecular orbital. Another notable feature of our results is that the '4NNo hyperfine interaction constant is smaller in the completely severed five-liganded NO-heme system than in the six-liganded case, in keeping with experimental observation (2, 9) in this respect.…”

Section: Methodsmentioning

confidence: 99%

Origin of observed changes in ¹⁴ N hyperfine interaction accompanying R → T transition in nitrosylhemoglobin

Mun

Chang

Das

1979

Proc. Natl. Acad. Sci. U.S.A.

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Theoretical investigations of electronic distributions in eight different structural forms of nitrosylhemoglobin were carried out to study the changes in 14N hyperfine interaction observed with the transition from R to T structures under the influence of inositol hexaphosphate or changing pH. Four of the eight forms studied consisted of protonated and deprotonated N ros in the proximal imidazole ligand with linear and bent Fe-N-0 structures. Two other forms had a straight Fe-N-O structure and Fe-Im bond stretched by 0.5 and 1.0 .A. The other two systems we have studied are five-liganded NO-heme with bent and straight Fe-N-O structures. Our investigations show that arrangements of energy levels did not differ significantly among all the structures, the unpaired electron always occupying an antibonding orbital with d.2 symmetry. The protonated and deprotonated systems with either linear or bent Fe-N-O structure showed substantial hyperfine interaction of the 14N nuclei of the NO group and the Nf atom of the proximal imidazole, indicating that a 9-line electron spin resonance hyperfine pattern (R structure) would be expected in all four cases. On the other hand, the extensions of the Fe-Im bond produce a sizeable decrease in the 14Nf hyperfine interaction, indicating that an extension beyond 1.0 A\ would provide a 3-line hyperfine pattern close to that found for the five-liganded NO-heme system. Our results thus provide quantitative support for the model of severe extension or cleavage of the Fe-N, bond proposed in the literature for explaining the R-to-T transition of the a-chain of nitrosylhemoglobin.The study of the properties of nitrosylhemoglobin (NO-Hb) has assumed major importance (1-4) in recent years for two main reasons. First, it is a six-liganded hemoglobin derivative that is paramagnetic with spin 1/2, which makes it amenable for electron paramagnetic resonance (EPR) studies (2-10). Such studies allow one to follow the changes in the electron distribution over the molecule associated with transitions between R and T states, considered to be of crucial importance in the explanation of cooperativity (11) in the oxygen-binding properties of hemoglobin. The second reason is that, in contrast to oxyhemoglobin and carbonmonoxyhemoglobin, NO-Hb shows a pronounced R-to-T transition (12,13) in the presence of inositol hexaphosphate, this transition being also rather sensitive to changes (5, 9, 10) in pH of the surrounding environment. One of the properties of NO-Hb that is a sensitive indicator of changes of structure under the influence of inositol hexaphosphate or changes in pH is the splitting produced (3-10) in EPR spectra by 14N hyperfine interactions. Thus, in NO-Hb A, in the presence of inositol hexaphosphate or at low pH one finds for the aY chain a 3-line hyperfine pattern associated with the hyperfine interaction of the '4N nucleus of NO. On increasing the pH beyond 8.0, even in the presence of inositol hexaphosphate one sees a change (5) from the 3-line to a 9-line pattern, indicating that th...

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Stereochemistry of nitrosylmetalloporphyrins. Nitrosyl-.alpha.,.beta.,.gamma.,.delta.-tetraphenylporphinato(1-methylimidazole)iron and nitrosyl-.alpha.,.beta.,.gamma.,.delta.-tetraphenylporphinato(4-methylpiperidine)manganese

Cited by 102 publications

References 1 publication

Coordination chemistry of the HNO ligand with hemes and synthetic coordination complexes

Coordination chemistry of the HNO ligand with hemes and synthetic coordination complexes

Crystal structures of manganese- and cobalt-substituted myoglobin in complex with NO and nitrite reveal unusual ligand conformations

Origin of observed changes in ¹⁴ N hyperfine interaction accompanying R → T transition in nitrosylhemoglobin

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Stereochemistry of nitrosylmetalloporphyrins. Nitrosyl-.alpha.,.beta.,.gamma.,.delta.-tetraphenylporphinato(1-methylimidazole)iron and nitrosyl-.alpha.,.beta.,.gamma.,.delta.-tetraphenylporphinato(4-methylpiperidine)manganese

Cited by 102 publications

References 1 publication

Coordination chemistry of the HNO ligand with hemes and synthetic coordination complexes

Coordination chemistry of the HNO ligand with hemes and synthetic coordination complexes

Crystal structures of manganese- and cobalt-substituted myoglobin in complex with NO and nitrite reveal unusual ligand conformations

Origin of observed changes in 14 N hyperfine interaction accompanying R → T transition in nitrosylhemoglobin

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Origin of observed changes in ¹⁴ N hyperfine interaction accompanying R → T transition in nitrosylhemoglobin