The Effect of Axial Ligands on the Redox Potential of Blue Copper Proteins
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Blue copper proteins are crucial components in most electron transfer chains. These proteins coordinate a single copper atom which oscillates between Cu<sup>+1</sup> and Cu<sup>+2</sup> states upon receiving or donating a single electron. One method used to determine a protein?s role in electron transport chain is the evaluation of its redox potentials. The theory behind this research project is based from a trend that the redox potential of a blue copper protein correlates to the hydrophobicity of the amino acid residues coordinating at the axial ligand position. Therefore, we can predict a blue copper protein?s biophysical properties solely from its amino acid sequence. Blue copper proteins display a large range of redox potentials, which vary between +200mV and +600mV. Proteins with hydrophobic axial ligands such as Valine or Leucine have a high redox potential, around +580 mV. Contrarily, proteins with more hydrophilic axial ligands such as Glutamine, have redox potentials nearer to +200mV. If this trend does indeed correlate with the hydrophobicity of the axial ligand, then it can be used as a molecular marker to estimate the redox properties of blue copper proteins for which only amino acid sequence information is available.