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3237214 
Journal Article 
Nitric oxide transfer from the NO-donor S-nitroso-N-acetylpenicillamine to monomers and dimers of water-soluble iron-porphyrins 
Vilhena, FSDS; Louro, SRW 
2004 
Yes 
Journal of Inorganic Biochemistry
ISSN: 0162-0134
EISSN: 1873-3344 
98 
3 
459-468 
WOS:000220269300005 
The nitrosylation of two water-soluble iron-porphyrins, the
anionic Fe(Ill)-meso-tetrakis(p-sulfonatophenyl)porphyrin (FeT-PPS4) and the cationic Fe(Ill)-
meso-tetrakis(4-N-methylpyridiniumyl)porphyrin (FeTMPyP), by the nitric oxide donor S-nitroso-N-
acetylpenicillamine (SNAP) was studied using optical absorption spectroscopy. The influence of
ionic and non-ionic micelles on rates of nitric oxide transfer was investigated. Initially, the
effect of the micelles on the pH-dependent equilibrium between monomeric and mu-oxo-dimeric
species of the iron-porphyrins was examined. It is not affected in micelle-porphyrin systems with
electric charges identical in sign. The non-ionic micelles of polidocanol induce a small negative
pK shift. In contrast, the dimerization equilibrium of porphyrins in oppositely charged micellar
phases is displaced to lower pH by similar to2 units. Nitric oxide binding to monomers and mu-
oxo-dimers was examined at pH 5.0 and 8.0, respectively. Contrary to nitrosylation by NO gas,
SNAP induces reductive nitrosylation. There was no observed NO-Fe(III)porphyrin intermediate.
Nitrosylation rates were obtained and compared in aqueous buffer and in micellar systems.
Monomers nitrosylate much faster than mu-oxo-dimers. Oppositely charged micelles prevent
nitrosylation of the iron-porphyrins or considerably enhance nitrosylation times. Nitrosylation
rates are comparable to transnitrosylation rates between several S-nitrosothiols and thiol-
containing proteins, suggesting biological relevance for the process. (C) 2003 Elsevier Inc. All
rights reserved. 
iron-porphyrins; nitric oxide; SNAP; reductive nitrosylation; micelles; optical absorption; spectrophotometry; kinetic measurements