Models carbon monoxide binding

At the present time we have no certain knowledge of the state of the heme in these 450 nm species. We do not know if there are heme aggregates although they are unlikely. It is therefore reasonable to look at systems where the haem is aggregated as well as those where it is not in order to see how the absorption spectra can be mimic-ed. It seems reasonable to assume that the iron is low-spin in the carbon monoxide, isocyanide, and nitric oxide complexes as no high-spin iron complexes of this type are known. In the high-spin or low-spin state it may be that the thiol is weakly bound, if at all, for Fe(II) heme in models or in hemoglobin does not bind to thiols. In an attempt to understand these spectra we shall use a semi-empirical approach based on the theoretical discussion in the previous article (52) and elaborated in what follows immediately. Only Fe(II) complexes will be analysed as the Fe(III) proteins have been previously examined (52). 

The model of carbon monoxide toxicity proposed by Kao and Nanagas (2006) combines the cascade of changes resulting from three primary events - binding to HB, direct cellular injury, and increased NO activity. CO is not a radical but many of the injuries produced by it are those that are caused by oxidative stress, which is secondary to hypoxia. In the model of Kao and Nanagas (2006), the oxidant is NO, which contributes to oxidative damage to the brain and produces the clinical syndrome of delayed neurologic sequelae (Thom et al, 1997). 

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