2 : DNA 187 DNA 1 EG &G PARC M273 Model 270,HOPG GC, Ag/ AgCl HOPG Union Carbide Corporation,ZYH HOPG, GC ( %),, cm 2 ECAFM NanoScope I

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1 EL ECTROCHEMISTR Y Vol 5 No 2 May 1999 DNA 3 ( ) ( HOPG), (DPV) ( ECAFM) DNA (CT DNA), DNA HOPG, DNA, HOPG ECAFM DNA, AFM, DNA CT DNA HOPG DNA DNA, DNA DNA,HOPG,,ECAFM,, DNA DNA, DNA [1 8 ], DNA ( PG), ( GC) [1,3,4,7 ] DPV, DNA ( 0 9 V 1 2 V, vs SCE) (0 9 V) DNA G, (1 2 V) DNA A [1,4 ] HOPG,HOPG SPM,HOPG DNA,, HOPG DNA DPV ECAFM DNA DNA HOPG DNA, DNA, ; ( ) China Academic Journal Electronic Publishing House All rights reserved

2 2 : DNA 187 DNA 1 EG &G PARC M273 Model 270,HOPG GC, Ag/ AgCl HOPG Union Carbide Corporation,ZYH HOPG, GC ( %),, cm 2 ECAFM NanoScope IIIa SPM (Digital Instruments, Inc ), Si 3 N 4, 200 m, 0 12 N/ m [9 ] 0 1 mol/ L NaAC (p H 7 6) 1 SSC (p H 7 0) DNA ( Huame) (A 260 / A 280 = 1 86), DNA DNA min, N 2 O HOPG DNA 1 DNA Fig 1 Differential pulse voltammogram of ssdna ( 278 mg/ dm 3 ), 0 1 mmol/ L NaAC DPV DNA buffer, p H 7 6 Pulse amplitude 20 mv, HOPG, pulse width 60 ms DNA ( 1) DNA, ( G) [1 (A), ] : China Academic Journal Electronic Publishing House All rights reserved

3 A G DNA DNA,, DNA DNA,, DNA, HOPG,,HOPG DNA,DNA DNA, G A,, DNA, G A, 2 DNA 3 DNA Fig 2 Differential pulse voltammogrma of dsdna Fig 3 Differential pulse voltammogram of ssdna a) pre-polarized at 0 4 V for 15 min b) no a) no pre-polarization b) pre-polarized at 0 4 polarization, other conditions as Fig 1 v for 15 min, other conditions as Fig China Academic Journal Electronic Publishing House All rights reserved

4 2 : DNA 189 ( 0 3 V vs Ag/ AgCl 15 min) DNA DPV ( 2) DNA, ( 3) DNA DNA - HOPG,, DNA,, DNA, DNA ( ), DNA DNA, DNA, ( DNA G A ), [4,10 ], G Brabec PG DNA G A Yao, Brett GC, DNA [4,7 ], 2 2 HOP G DNA ECAFM [11,12 HOPG AFM STM SPM ] DNA ECAFM, AFM 4 DNA ECAFM Fig 4 ECAFM images of dsdna at a concentration of 0 3 g/ dm 3, SSC buffer, p H7 0 NanoScope EC Contact AFM Scan size m Setpoint V Scan rate Hz Number of samples 256 Data type Height Z range mn 5 DNA ECAFM Fig 5 ECAFM images of dsdna, several min later than Fig 4 NanoScope EC Contact AFM Scan size m Setpoint V Scan rate Hz Number of samples 256 Data type Height Z range nm China Academic Journal Electronic Publishing House All rights reserved

190 1999, STM DNA [13 ], DNA HOPG CT DNA ECAFM ( 4), DNA, DNA DNA,,DNA ( 5) DNA, + 0 4-0 6 V ( vs Ag/ 6 DNA ECAFM ( ) AgCl), E2 Fig 6 ECAFM images of dsdna at a concentration of 0 03 g/ dm 3, SSC

5 , STM DNA [13 ], DNA HOPG CT DNA ECAFM ( 4), DNA, DNA DNA,,DNA ( 5) DNA, V ( vs Ag/ 6 DNA ECAFM ( ) AgCl), E2 Fig 6 ECAFM images of dsdna at a concentration of 0 03 g/ dm 3, SSC buffer, p H7 0 CAFM, NanoScope EC Contact AFM,ECAFM CT DNA Scan size m Setpoint V, CT Scan rate Hz DNA DNA Number of samples 256 Data type Height, ( 6) Z range nm DNA 2 3 DNA DNA 12 h, 7 ; UV DNA 300 mg/ L, p H 7 4, 8 DNA 0 1 mol/ L NaAC Fig 8 UV/ Vis reflection spectroscopy of dsdna on Fig 7 UV/ Vis reflection spectroscopy of supporting electrolyte on GCE GCE China Academic Journal Electronic Publishing House All rights reserved

6 2 : DNA DNA 10 dsdna R/ R E Fig 9 UV/ Vis reflection spectroscopy of ssdna on = 350 nm GCE Fig 10 Relative reflectance change curve as the function of potential for dsdna ( R/ R = ( R ( E w ) - R ( E 0 ) ) / R ( E 0 ) ), ( - R/ R) DNA, E V (vs SCE), E w 0 7 V 1 1 V (vs SCE), nm, 7,8,9 DNA, DNA DNA, 10,11 DNA ( 9),DNA, 325 nm ; 0 5 V 0 9 V (vs SCE) ( 11), DNA, DNA ( 8) ( 10), DNA DNA DNA 11 ssdna R/ R E, = 350 mm Fig 11 Relative reflectance change curve as the func2 325 nm, tion of potential for ssdna DNA 260 nm 65 nm, DNA 3,HOPG DNA, China Academic Journal Electronic Publishing House All rights reserved

7 DNA DNA, DNA HOPG ECAFM DNA DNA : AFM Oxidation and Adsorption of Deoxyribonucleic Acid at Highly Ordered Pyrolytic Graphite and Glass Carbon Electrode Zhou Jianzhang Wu Lingling Luo Jin Lin Zhonghua 3 ( S tate Key L ab f or Phys Chem of the Solid S urf, Dept of Chem, Inst of Phys Chem, Xiamen U niv, Xiamen ) Abstract It is shown that calf thymus DNA (CT DNA) can be adsorbed at highly or2 dered pyrolytic grap hite ( HOP G) elect rode and detected by differential pulse voltammet ry (DPV) and elect rochemical atomic force microscopy ( ECAFM) It is found t hat cont rolled potential pre - polarization influences largely t he 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 pattern of adsorption of DNA at HOPG electrode that fits best with the experimental data is proposed The results aslo shows that UV/ Vis reflection spectroscopy, which has not been used in studying elec2 trochemical behavior of DNA, is more sensitive than voltammetry in the investigation of DNA ad2 sorption Key words DNA, HOPG, Pre-polarization, Oxidation, ECAFM, UV/ Vis reflec2 tion spect roscopy Reference s 1 Brabec V, Dryhurst G Electrochemical behaviour of natural and biosynthetic polynucleotides at the pyrolytic graphite electrode : A new probe for studies of polynucleotide structure and reactions J Electroanal Chem, 1978, 89 :161 ; Brabec V, Electrochemical oxidation of polyadenylic acid at graphite electrodes J Electroanal Chem, 1978, 91 : China Academic Journal Electronic Publishing House All rights reserved

8 2 : DNA Wu J T et al Electrochemical behaviours of DNA at mercury film electrode Bioelectrochem Bioenerg 1997, 44 :151 3 Yao T et al The anodic voltammetry of deoxyribonucleic acid at a glassy carbon electorde Bull Chem Soc Japan, 1978, 51 : Brabec V, Koudelka J 314-electrochemical oxidation of nucleic acids andproteins at graphite electrode : Quali2 tive aspects Bioelectrochem Bioenerg, 1980, 7 :69 ; Brabec V, Koudelka J, 394- Oxidation of deoxyribonu2 cleic acid at carbon electrodes : The effect of the quality of the deoxyribonucleic acid sample Bioelectrochem Bioenerg, 1980, 7 :793 5 Pang D W et al Modification of glassy carbon and gold electrodes with DNA J Electroanal Chem, 1996, 403 :183 6 Brabec V 133- nucleic acid analysis by voltammetry at carbon electrodes Bioelectrochem Bioenerg, 1981, 8 : Brett C M A et al On the adsorption and electrochemical oxidation of DNA at glassy carbon electrodes J Elec2 troanal Chem, 1994, 366 :225 8 Palecek E et al Biopolymer- modified electrodes in the voltammetric determination of nucleic acids and proteins at the submicrogram level Anal Chimica Acta, 1993, 273 :175 9 Luo J et al In situ electronic spectroscopic techniques for interfacial electrochemistry Chem Res Chinese Univ, 1996, 12 : Gyal R N, Dryhurst G Redox chemistry of guanine and 8-oxyguanine and a comparison of the peroxidase-cat2 alyzed and electrochemical oxidation of 8-oxyguanine J Electroanal Chem, 1982, 135 :75 11 Engel A Biological applications of scanning probe microscopes Annu Rev Biophys Chem, 1991, 20 :79 12 Bloomfield V A, Arscott P G Nucleic Acids and Molecular Biology Eckstein F, Liley D M J ( eds ), Springer, Berlin, Heidelberg, 1991,5 :39 13 Malfoy B, Reynaud J A Electrochemical Investigation of Nucleic Acid Behaviour Part I Native Calf Thymus DNA J Electroanal Chem, 1976, 67 : China Academic Journal Electronic Publishing House All rights reserved

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