Iron-containing Biomolecules

Structure of myoglobin (Protein Data Bank DOI 10.2210/pdblmbn/pdb) and detail of the heme of hemoglobin. 

This removes one of the common reactions of iron complexes in the beaker , and is an example of the role and importance of the enveloping biopolymer in the natural system. 

Whereas oxygen binding in humans and many other animals involves heme units, not all life-forms bind and carry dioxygen in this way. Hemerythrin is a nonheme iron protein used by sipunculid and brachiopod marine invertebrates for oxygen transfer and/or storage. 

The geometry at the iron centres of the bridged dinuclear unit in hemerythrin in its dioxygen-free deoxy (left) and oxygenated oxy (right) forms, with changes upon dioxygen coordination shown. 

Once dioxygen arrives at a cell it is reduced to water in order to yield the energy necessary to convert adenosine diphosphate (ADP) to adenosine triphosphate (ATP), the energy carrier for cell processes. This oxygen burning (8.1) is mediated in turn by a series of metalloenzymes, such as cytochrome oxidase, which contains one heme Fe and one Cu in the active site. 

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One large class of non-heme iron-containing biomolecules involves proteins and enzymes containing iron-sulfur clusters. Iron-sulfur clusters are described in Sections 1.7 (Bioorganometallic Chemistry) and 1.8 (Electron Transfer) as well as in Section 3.6 (Mossbauer Spectroscopy). See especially Table 3.2 and the descriptive examples discussed in Section 3.6.4. Iron-sulfur proteins include rubredoxins, ferrodoxins, and the enzymes aconitase and nitrogenase. The nitrogenase enzyme was the subject of Chapter 6 in the hrst edition of this text—see especially Section 6.3 for a discussion of iron-sulfur clusters. In this... 

Polysaccharides are used as structural units and as stored energy sources. Proteins are used to construct muscle and enzymes that also contain metals such as zinc, manganese, and iron. There are many other important biomolecules present at lower concentrations such as DNA and RNA, which are also released into the soil solution. All can be the source of smaller molecules in the soil solution. 

There are a number of enzymes that catalyse the dismutation of superoxide in vivo, viz. the superoxide dismutases [50,51], They are metalloproteins which contain copper, zinc, manganese or iron as the prosthetic group. The enzyme catalase exists in vivo to degrade hydrogen peroxide within cells to form water and oxygen [43]. As stated earlier, there are barely detectable amounts of these two enzymes in the synovial fluid of arthritic patients and hence both superoxide radicals and hydrogen peroxide are potential mediators of damage to the biomolecules of the synovial fluid. 

NRVS represents the ultimate limit in vibrational selectivity, because it reveals the vibrational spectrum of an individual probe atom even when embedded in a complex enviromnent such as a biomolecule containing thousands of other atoms. Fe NRVS is thus an exquisite probe for the stmcture and dynamics of the immediate coordination sphere of the iron, which is the heart of the reactivity of numerous important proteins. 

In particular we refer to high-potential iron proteins (HP) and to cubane-like model complexes, which are the only examples of JT effect in biomolecules containing metal clusters we have found in literature " ... 

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