of sol-gel encapsulated Hb, and the patterns observed were con-
sistent with a mechanism whereby NO reacts with the ferric
nitrite derivative to generate N 2 O 3 ( 70 ).
Flavodi-iron proteins containing a distinctive nonheme diiron/
flavin mononucleotide active site, catalyze reductive scavenging
of dioxygen and NO in air sensitive microorganisms. Anaerobic
addition of NO up to one NO per diferrous unit results in forma-
tion of a diiron mononitrosyl complex, whereas further addition
of NO results in two reaction pathways, one of which produces
N 2 O and the diferric site and the other which produces a stable
diiron–dinitrosyl complex. The production of N 2 O upon addition
of NO to the mononitrosyl deflavo-protein was interpreted in
terms of the hyponitrite mechanism( 71 ).
The DFT method was used to study the adsorption of NO on
various metal phthalocyanines, MPc, (M¼Mn, Fe, Co). The NO
adsorption induces significant changes in the geometry and the
electronic structures of the MPc. The geometry of the MN O
grouping was found linear in the case of the Mn center, whereas
bent for Fe and Co phthalocyanines. The observed difference in
the geometry and the electronic structures was interpreted in
terms of the hybridization of NOp* orbitals and d orbitals of
the metal atoms, as well as charge transfer between the NO mol-
ecule and MPc. The calculation and parallel experimental results
have shown that metal phthalocyanines are potential sensor
devices for detecting NO gas( 72 ).
Transition metal complexes binding efficiently enough to elim-
inate NO from some compartments have attracted much interest
because of their potential use as NO acceptors, donors, and/or
carriers important not only in therapy but also in pollution
abatement. Among these complexes the iron(II) ami-
nocarboxylates are characterized by their high solubility in aque-
ous solution and ability of rapid and reversible NO-binding.
These features are useful in reducing both the NO content in
exhaust gases and the NO level in human body during NO medi-
ated pathological events( 73 – 77 ).
The photolabile [Fe NO]^6 iron nitrosyl complexes with a
pentadentate ligand N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-
pyridine-2-carboxamide, PaPy 3 H, and its derivative [(PaPy 3 )Fe
(NO)](ClO 4 ) have been synthesized in which the binding of NO
is reversible and the bound NO is released rapidly under irradi-
ation with visible light( 78 – 80 ).
Among the studied aminocarboxylates, the ethylenediamine-
tetraacetate complex of Fe(II) proved to be the most promising
NO-scavenger and the reaction:
308 ZOFIA STASICKA