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Electronic and spatial structures of water-soluble dinitrosyl iron complexes with thiol-containing ligands underlying their ability to act as nitric oxide and nitrosonium ion donors.

Vanin AF, Burbaev DSh - J Biophys (2012)

Bottom Line: Similarly, the {(RS(-))(2)Fe(+)(NO(+))(2)}(+) structure describing the distribution of unpaired electron density in M-DNIC corresponds to the low-spin (S = 1/2) state with a d(7) electron configuration of the iron atom and predominant localization of the unpaired electron on MO(d(z2)) and the square planar structure of M-DNIC.On the other side, the formation of molecular orbitals of M-DNIC including orbitals of the iron atom, thiolate and nitrosyl ligands results in a transfer of electron density from sulfur atoms to the iron atom and nitrosyl ligands.Most probably, the S-nitrosating effect of nitrosyl ligands is a result of weak binding of thiolate ligands to the iron atom under conditions favoring destabilization of M-DNIC.

View Article: PubMed Central - PubMed

Affiliation: N. N. Semyonov Institute of Chemical Physics, Russian Academy of Sciences, Kosygin Street 4, Moscow 119991, Russia.

ABSTRACT
The ability of mononuclear dinitrosyl iron commplexes (M-DNICs) with thiolate ligands to act as NO donors and to trigger S-nitrosation of thiols can be explain only in the paradigm of the model of the [Fe(+)(NO(+))(2)] core ({Fe(NO)(2)}(7) according to the Enemark-Feltham classification). Similarly, the {(RS(-))(2)Fe(+)(NO(+))(2)}(+) structure describing the distribution of unpaired electron density in M-DNIC corresponds to the low-spin (S = 1/2) state with a d(7) electron configuration of the iron atom and predominant localization of the unpaired electron on MO(d(z2)) and the square planar structure of M-DNIC. On the other side, the formation of molecular orbitals of M-DNIC including orbitals of the iron atom, thiolate and nitrosyl ligands results in a transfer of electron density from sulfur atoms to the iron atom and nitrosyl ligands. Under these conditions, the positive charge on the nitrosyl ligands diminishes appreciably, the interaction of the ligands with hydroxyl ions or with thiols slows down and the hydrolysis of nitrosyl ligands and the S-nitrosating effect of the latter are not manifested. Most probably, the S-nitrosating effect of nitrosyl ligands is a result of weak binding of thiolate ligands to the iron atom under conditions favoring destabilization of M-DNIC.

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Mentions: First, our model provides a natural interpretation for the ability of DNIC with thiol-containing ligands to induce S-nitrosation of thiols due to the presence of nitrosonium ions (NO+) in the DNIC [Fe+(NO+)2] core. As mentioned above, this formula reflects the distribution of spin electron density within the core. Actually, the electron density (i.e., part of paired electrons) is transferred from sulfur atoms to iron and NO+ ligands due to high π-donor activity of sulfur atoms of thiol-containing ligands thereby decreasing their positive charge and attenuating the hydrolytic effect of hydroxyl ions. The ability of nitrosyl ligands to induce S-nitrosation of thiols diminishes, correspondingly, and reappears upon decomposition of DNIC or after attaining a chemical equilibrium between DNIC and its constituent components (Scheme 2), that is, during the release of thiol-containing ligands from DNIC. As a result, the electron density on nitrosyl ligands gradually disappears as a result of which the latter are converted into nitrosonium ions and thus acquire a positive charge. Only one nitrosyl ligand remains in the form of NO+, whereas the second ligand accepts an electron from iron to be converted into a neutral NO molecule. This mechanism underlies the ability of DNIC to act as NO and NO+ donors.


Electronic and spatial structures of water-soluble dinitrosyl iron complexes with thiol-containing ligands underlying their ability to act as nitric oxide and nitrosonium ion donors.

Vanin AF, Burbaev DSh - J Biophys (2012)

© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3306989&req=5

Mentions: First, our model provides a natural interpretation for the ability of DNIC with thiol-containing ligands to induce S-nitrosation of thiols due to the presence of nitrosonium ions (NO+) in the DNIC [Fe+(NO+)2] core. As mentioned above, this formula reflects the distribution of spin electron density within the core. Actually, the electron density (i.e., part of paired electrons) is transferred from sulfur atoms to iron and NO+ ligands due to high π-donor activity of sulfur atoms of thiol-containing ligands thereby decreasing their positive charge and attenuating the hydrolytic effect of hydroxyl ions. The ability of nitrosyl ligands to induce S-nitrosation of thiols diminishes, correspondingly, and reappears upon decomposition of DNIC or after attaining a chemical equilibrium between DNIC and its constituent components (Scheme 2), that is, during the release of thiol-containing ligands from DNIC. As a result, the electron density on nitrosyl ligands gradually disappears as a result of which the latter are converted into nitrosonium ions and thus acquire a positive charge. Only one nitrosyl ligand remains in the form of NO+, whereas the second ligand accepts an electron from iron to be converted into a neutral NO molecule. This mechanism underlies the ability of DNIC to act as NO and NO+ donors.

Bottom Line: Similarly, the {(RS(-))(2)Fe(+)(NO(+))(2)}(+) structure describing the distribution of unpaired electron density in M-DNIC corresponds to the low-spin (S = 1/2) state with a d(7) electron configuration of the iron atom and predominant localization of the unpaired electron on MO(d(z2)) and the square planar structure of M-DNIC.On the other side, the formation of molecular orbitals of M-DNIC including orbitals of the iron atom, thiolate and nitrosyl ligands results in a transfer of electron density from sulfur atoms to the iron atom and nitrosyl ligands.Most probably, the S-nitrosating effect of nitrosyl ligands is a result of weak binding of thiolate ligands to the iron atom under conditions favoring destabilization of M-DNIC.

View Article: PubMed Central - PubMed

Affiliation: N. N. Semyonov Institute of Chemical Physics, Russian Academy of Sciences, Kosygin Street 4, Moscow 119991, Russia.

ABSTRACT
The ability of mononuclear dinitrosyl iron commplexes (M-DNICs) with thiolate ligands to act as NO donors and to trigger S-nitrosation of thiols can be explain only in the paradigm of the model of the [Fe(+)(NO(+))(2)] core ({Fe(NO)(2)}(7) according to the Enemark-Feltham classification). Similarly, the {(RS(-))(2)Fe(+)(NO(+))(2)}(+) structure describing the distribution of unpaired electron density in M-DNIC corresponds to the low-spin (S = 1/2) state with a d(7) electron configuration of the iron atom and predominant localization of the unpaired electron on MO(d(z2)) and the square planar structure of M-DNIC. On the other side, the formation of molecular orbitals of M-DNIC including orbitals of the iron atom, thiolate and nitrosyl ligands results in a transfer of electron density from sulfur atoms to the iron atom and nitrosyl ligands. Under these conditions, the positive charge on the nitrosyl ligands diminishes appreciably, the interaction of the ligands with hydroxyl ions or with thiols slows down and the hydrolysis of nitrosyl ligands and the S-nitrosating effect of the latter are not manifested. Most probably, the S-nitrosating effect of nitrosyl ligands is a result of weak binding of thiolate ligands to the iron atom under conditions favoring destabilization of M-DNIC.

No MeSH data available.