Nickel biomolecules

For the known nickel sites in biological systems, four-coordinate square planar, five-coordinate, and six-coordinate octahedral geometries are found.1840-1846 In general, the flexible coordination geometry of nickel causes its coordination properties in metallo-biomolecules to be critically influenced by the protein structure. 

The role of the transition elements in living systems is equally important. Iron is present in biomolecules such as hemoglobin, which transports oxygen from our lungs to other parts of the body. Cobalt is an essential component of vitamin B12. Nickel, copper, and zinc are vital constituents of many enzymes, the large protein molecules that catalyze biochemical reactions. 

This mode of separation, as the name suggests, uses stationary phases with a special affinity for a specific analyte. The affinity ligand immobilized on the stationary phase varies dramatically from peptide, to protein, to oligonucleotide, to monoclonal antibody. In some cases the target molecule is labelled with an affinity tag to simplify the separation. This approach is common in the synthesis of recombinant proteins where the system can be engineered so that the target biomolecule expresses a tag such as polyhistidine. A stationary phase functionalized with aminodiacetic acid and nickel chelate is then used to fish out the required molecule by chelating with the polyhistidine tag. 

Many biomolecules feature metal ions in a mixed donor set, and the area is intensively studied. As an example, the active site of the hydrogenase from thiocapsa roseopersicina features nickel in a mixed 0,N,S donor environment. Definition of the ligand donor set in biopolymers is not always facile, however, so they tend to be overlooked as examples of mixed donor ligands. There are some small biomolecule examples extant. 

Figure 32 shows the amperometric response of the biosensor in the presence of different hydrogen peroxide concentration. As shown a well defined response was observed after hydrogen peroxide addition. The values of KM, 0.96 mM for hemoglobin and 1.37 mM for catalase indicates the immobilized biomolecules into nickel oxide nanoparticles retained their native activity. 

Russell and Hall (this volume) adopt this premise and suggest that life first emerged where dissolved H2 from submarine hot springs redueed dissolved CO2 in the ancient ocean. They propose that iron-nickel sulfide minerals served as catalysts in the generation of essential biomolecules. Other important thermodynamic energy sources, Russell and Hall note, resulted from the strong pH and thermal gradients between the acidic ocean and alkaline hydrothermal fluids. 

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