It shows that calf thymus DNA(CT DNA) can be adsorbed at a highly ordered pyrolytic graphite (HOPG) electrode and detected by differential pulse voltammetry (DPV) and electrochemical atomic force microscopy (ECAFM). It is found that controlled potential pre-polarization influences largely the adsorption of dsDNA while it has little influence on ssDNA. It is demonstrated that ECAFM is useful to exploit adsorption of DNA at HOPGE. The mode of adsorption of DNA at the HOPG electrode that fits best with the experimental data is proposed.

The electrochemical ex situ SERS spectra indicate that under atmosphere,the conformation of most of helices on gold substrate is B-form,but A-form conformation also exists. The band intensities of the in situ SERS spectra of oligonucleotide probes and their hybridized helices decrease substantially when the potentials are made more positive, especially for two ring vibration modes of the out-of-plane contribution of adenine,which indicates that conversion of the vertical adsorption orientation to flattened adsorption orientation occurs when the potential is changed from negative to more positive potentials according to SERS ‘surface selection rules’. _ 2002 Elsevier Science B.V. All rights reserved.

The present work used mainly electrochemical in situ time-resolved UV-vis subtractive reflectance spectroscopy to study the electron transfer process of cytochrome c in the presence of promoter (the equal molar mixture of guanine and cytosine). Two new absorption bands 450 and 500 nm and two bipolar bands 250 and 300 nm are observed in the spectra with different time resolutions. In addition, the intensity of another band 420 nm changes with the time resolutions. All the results show that the electron transfer of cytochrome c is accompanied by significant conformational rearrangement.

The redox process of poly-o-phenylenediamine (PoPD) film in strong acid solution has been studied by in situ resonance Raman spectroscopy, in situ UV-vis subtractive reflectance spectroscopy and cyclic voltammetry. A marked potential-dependent spectral change is observed in the in situ resonance Raman spectra, which reveals that at least three redox states of PoPD are formed in the redox process and the structure of PoPD is dominated by a ladder polymer with phenazine rings. The three kinds of PoPD display different resonance Raman enhancement effects, which is verified by the in situ UV-vis subtractive reflectance spectra. The ex situ resonance Raman spectra indicate that the electronic structure of the PoPD molecule is evidently influenced by protonation and that the most stable state of PoPD is its semi-oxidized state. Finally, a possible reaction scheme of the electrochromic process of PoPD film in strong acid solution is proposed.