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Fig. 1.1 Heme pigments are often involved in interaction between reactive oxygen
species and reactive nitrogen species as shown for oxidation of NO by oxygen in
nitrosylmyoglobin with the heme cavity acting as a chemical reactor as suggested by
Frauenfelder et al. (2001) to yield peroxynitrite/nitrate and metmyoglobin. Absorption of
visible light opens up for a parallel reaction pathway initiated by photodissociation of
nitric oxide.
specifically with thiols and may be involved in thiol depletion and accordingly
protein modification (Paolocci et al., 2007). HNO is a unique molecule, as it
may donate a hydrogen atom to a lipid peroxyl radical (LOO
·
):
HNO LOO
·
! NO LOOH
1.11
in a process typical for chain-breaking antioxidants, as discussed in Section 1.4.
·
NO formed, may further react as a radical scavenger and chain breaker in lipid
autoxidation:
·
NO LOO
·
! LOONO ! LONO
2
1.12
The role of the unusual acid/base couple HNO/NO
±
in oxidative processes
should be further explored.
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