Electrochemical and UV-Visible Spectroscopic Studies of Self-Organized Gold Nanoparticle~Cytochrome C Superstructures

The addition of the protein, cytochrome c (cyt. c), to gold nanoparticles in solution results in self-organization of cyt. c into multilayered protein superstructures (abbreviated as Au~cyt. c superstructures) and stabilizes the thousands of organized cyt. c proteins to unfolding both when encapsulated in porous solids and when remaining in solution.  Our research has shown that the electrochemical characteristics of superstructure-assembled cyt. c are enhanced compared to cyt. c alone and vary as the ratio of cyt. c to Au varies.  In order to determine whether the enhanced electrochemical properties are directly related to the multiple protein layers of the superstructures staying intact at the electrode surface, the protein superstructures were stripped from the electrode surface and measured with UV-visible spectroscopy.   The UV-visible absorbance of the cyt. c Soret peak, and subsequent calculated cyt. c electrode surface coverage, varied as the ratio of gold to protein varied.  These results support the idea that at an optimal ratio of gold to protein when forming superstructures, the cyt. c electrochemical properties are enhanced and are related to multiple proteins remaining active within superstructures at the electrode surface.  These results may prove useful to those developing bioanalytical devices when a good understanding of the interaction between protein and material surface is needed.