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Mechanisms for the direct electron transfer of cytochrome c induced by multi-walled carbon nanotubes.

Zhao HZ, Du Q, Li ZS, Yang QZ - Sensors (Basel) (2012)

Bottom Line: There are several possible mechanisms that explain the DET of Cyt c.In the presence of MWCNTs, the secondary structure of Cyt c changes, which exposes the active site, then, the orientation of the heme is optimized, revolving the exposed active center to the optimum spatial orientation for DET; and finally, a transition of spin states is induced, providing relatively high energy and a more open microenvironment for electron transfer.These changes at different nano-levels are closely connected and form a complex process that promotes the electron transfer of Cyt c.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Engineering, Peking University, Beijing 100871, China. zhaohuazhang@pku.edu.cn

ABSTRACT
Multi-walled carbon nanotube (MWCNT)-modified electrodes can promote the direct electron transfer (DET) of cytochrome c (Cyt c). There are several possible mechanisms that explain the DET of Cyt c. In this study, several experimental methods, including Fourier transform infrared spectroscopy, circular dichroism, ultraviolet-visible absorption spectroscopy, and electron paramagnetic resonance spectroscopy were utilized to investigate the conformational changes of Cyt c induced by MWCNTs. The DET mechanism was demonstrated at various nano-levels: secondary structure, spatial orientation, and spin state. In the presence of MWCNTs, the secondary structure of Cyt c changes, which exposes the active site, then, the orientation of the heme is optimized, revolving the exposed active center to the optimum spatial orientation for DET; and finally, a transition of spin states is induced, providing relatively high energy and a more open microenvironment for electron transfer. These changes at different nano-levels are closely connected and form a complex process that promotes the electron transfer of Cyt c.

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Cyclic voltammograms corresponding to (A) Cyt c with and without MWCNTs (scan rate: 50 mV/s); (B) Cyt c on the MWCNT-modified GC electrode at various scan rates: 200, 400, 600, 800, and 1,000 mV/s. (C) The dependence of (a) the anodic peak currents and (b) the cathodic peak currents on the scan rates and square root of scan rates. The activation potential window of the electrode is 1.5 V–1.0 V. The supporting electrolyte was 1 M PBS (pH 6.07) containing 0.1 M NaCl.
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f1-sensors-12-10450: Cyclic voltammograms corresponding to (A) Cyt c with and without MWCNTs (scan rate: 50 mV/s); (B) Cyt c on the MWCNT-modified GC electrode at various scan rates: 200, 400, 600, 800, and 1,000 mV/s. (C) The dependence of (a) the anodic peak currents and (b) the cathodic peak currents on the scan rates and square root of scan rates. The activation potential window of the electrode is 1.5 V–1.0 V. The supporting electrolyte was 1 M PBS (pH 6.07) containing 0.1 M NaCl.

Mentions: CV experiments were conducted to clarify the DET between Cyt c and the MWCNT-modified electrode in PBS. As shown in Figure 1(A), a pair of well-defined redox peaks appeared at the MWCNT-modified GC electrode with the formal potential of 46 mV, which is almost in agreement with the reported formal potential of Cyt c on SWCNTs [13]. However, no peaks were apparent at the bare GC electrode. This suggests that the thin layer of MWCNT on the GC electrode assists in the DET from the active site of Cyt c to the electrode and that, in the absence of the MWCNTs, no electron transfer occurs at the electrode. This conclusion is consistent with other results of CNT-modified electrodes [28–33].


Mechanisms for the direct electron transfer of cytochrome c induced by multi-walled carbon nanotubes.

Zhao HZ, Du Q, Li ZS, Yang QZ - Sensors (Basel) (2012)

Cyclic voltammograms corresponding to (A) Cyt c with and without MWCNTs (scan rate: 50 mV/s); (B) Cyt c on the MWCNT-modified GC electrode at various scan rates: 200, 400, 600, 800, and 1,000 mV/s. (C) The dependence of (a) the anodic peak currents and (b) the cathodic peak currents on the scan rates and square root of scan rates. The activation potential window of the electrode is 1.5 V–1.0 V. The supporting electrolyte was 1 M PBS (pH 6.07) containing 0.1 M NaCl.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472837&req=5

f1-sensors-12-10450: Cyclic voltammograms corresponding to (A) Cyt c with and without MWCNTs (scan rate: 50 mV/s); (B) Cyt c on the MWCNT-modified GC electrode at various scan rates: 200, 400, 600, 800, and 1,000 mV/s. (C) The dependence of (a) the anodic peak currents and (b) the cathodic peak currents on the scan rates and square root of scan rates. The activation potential window of the electrode is 1.5 V–1.0 V. The supporting electrolyte was 1 M PBS (pH 6.07) containing 0.1 M NaCl.
Mentions: CV experiments were conducted to clarify the DET between Cyt c and the MWCNT-modified electrode in PBS. As shown in Figure 1(A), a pair of well-defined redox peaks appeared at the MWCNT-modified GC electrode with the formal potential of 46 mV, which is almost in agreement with the reported formal potential of Cyt c on SWCNTs [13]. However, no peaks were apparent at the bare GC electrode. This suggests that the thin layer of MWCNT on the GC electrode assists in the DET from the active site of Cyt c to the electrode and that, in the absence of the MWCNTs, no electron transfer occurs at the electrode. This conclusion is consistent with other results of CNT-modified electrodes [28–33].

Bottom Line: There are several possible mechanisms that explain the DET of Cyt c.In the presence of MWCNTs, the secondary structure of Cyt c changes, which exposes the active site, then, the orientation of the heme is optimized, revolving the exposed active center to the optimum spatial orientation for DET; and finally, a transition of spin states is induced, providing relatively high energy and a more open microenvironment for electron transfer.These changes at different nano-levels are closely connected and form a complex process that promotes the electron transfer of Cyt c.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Engineering, Peking University, Beijing 100871, China. zhaohuazhang@pku.edu.cn

ABSTRACT
Multi-walled carbon nanotube (MWCNT)-modified electrodes can promote the direct electron transfer (DET) of cytochrome c (Cyt c). There are several possible mechanisms that explain the DET of Cyt c. In this study, several experimental methods, including Fourier transform infrared spectroscopy, circular dichroism, ultraviolet-visible absorption spectroscopy, and electron paramagnetic resonance spectroscopy were utilized to investigate the conformational changes of Cyt c induced by MWCNTs. The DET mechanism was demonstrated at various nano-levels: secondary structure, spatial orientation, and spin state. In the presence of MWCNTs, the secondary structure of Cyt c changes, which exposes the active site, then, the orientation of the heme is optimized, revolving the exposed active center to the optimum spatial orientation for DET; and finally, a transition of spin states is induced, providing relatively high energy and a more open microenvironment for electron transfer. These changes at different nano-levels are closely connected and form a complex process that promotes the electron transfer of Cyt c.

Show MeSH
Related in: MedlinePlus