Acta Phys. -Chim. Sin. ›› 2012, Vol. 28 ›› Issue (05): 1127-1133.doi: 10.3866/PKU.WHXB201203073

• ELECTROCHEMISTRY AND NEW ENERGY • Previous Articles     Next Articles

Effect of pH and Au Nanoparticles on Cytochrome c Investigated by Electrochemistry and UV-Vis Absorption Spectroscopy

WANG Yan-Yan1, JIANG Yan-Xia1, SUSHAAndrei2, ROGACH Andrey2, SUN Shi-Gang1   

  1. 1. Key Laboratory of Physical Chemistry of Solid Surface, Department of Chemistry, College of Chemistry and Chemistry Engineering, Xiamen University, Xiamen 361005, Fujian Province, P. R. China;
    2. Department of Physics and Materials Science, City University of Hong Kong, Hong Kong, P. R. China
  • Received:2012-01-13 Revised:2012-02-29 Published:2012-04-26
  • Contact: JIANG Yan-Xia
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (20833005, 20873116, 60936003, 21021002).

Abstract: In this paper, gold nanoparticles (NPs) with an average size of (4.7 ± 0.6) nm, capped with mercaptopropionic acid (MPA) ligand, are prepared. The effect of pH and Au NPs on cytochrome c (Cyt c) is investigated by electrochemistry and UV-Vis absorption spectroscopy. UV-Vis absorption spectra indicate that the structures of Cyt c and Cyt c-Au NPs complex do not change appreciably between pH=7.5 and pH=3.0, but their Soret band positions change markedly at pH=2.0, indicating that low pH value induces a conformational change in Cyt c. Cyclic voltammetry (CV) result shows that Au NPs capped with MPA enhance electron transfer between Cyt c and the electrode. The data also reveals that the biocompatibility of Au NPs is improved when citric acid ligand is replaced with MPA. The change in pH value causes a change of peak currents in CV and a shift of peak potential. When pH value deviates from 7.0, levels of electroactive Cyt c decrease. Significant pH change induces irreversible denaturing of Cyt c. The pH at which Cyt c-Au NPs complex denatures completely is one unit higher than that of Cyt c. Combining the results from UV-Vis spectroscopy and CV, we find that addition of Au NPs makes adsorbing state Cyt c more vulnerable to pH.

Key words: Au nanoparticle, Cytochrome c, pH value, Cyclic voltammetry, UV-Vis absorption spectroscopy