Electrochemical Studies of the Recognition Interaction of Rhodamine B with DNA

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【刊名】Chinese Chemical Letters


The recognition interaction of DNA molecule is of great importance in drug composition,carcinogenic mechanism and gene mutation. The interaction of small organicmolecules with DNA and the investigation of their effect on DNA molecule structure andfunction are hot topics in recent years1,2. Rhodamine B (RB) belongs to xanthene dyes,with azoxyanthrone as the parent structure, which has been widely used in detectingmetal ions in luminescent analysis3. In this paper the electrochemical behaviors of RBand its recognition interactions with DNA were investigated using electrochemicaltechniques. The result showed that an electrochemical non-active complex was formed,and the recognition interaction was carefully studied. Figure 1 shows the UV-Vis spectra of RB and RB-DNA interaction system. Overthe scan range of 300 nm-700 nm, RB has a maximum absorbance at 553.9 nm (Curve 1).After the addition of DNA, the maximum wavelength did not change while the peakabsorbance decreased apparently (Curve 2). The more the addition of DNA was, thelarger the decrease of the peak absorbance and the result was in good agreement withwhat Wang4 had studied. These results indicated that RB had entered into the groove ofDNA and had strongly interacted with DNA in groove-binding model. In 0.2 mol/L of pH 7.5 B-R buffer solution, RB had an irreversible oxidation peak at+0.92V (vs. SCE) at a glassy carbon (GC) electrode (Curve 1 in Figure 2). The halfpeak width W1/2 of this oxidation peak was 71 mV. According to the formula:W1/2=62.5/(1-α)n mV (25 °C) The following equation was deduced: (1-α)n=0.88 (1) From formula (1) together with formula (2), n was calculated as 3, illustrating thatthe oxidation process of RB at GC electrode was three electrons irreversible adsorptionwave under this experimental conditions. In pH 7.5 B-R buffer solution, RB had an oxidation peak and no reduction peak.After the addition of DNA, the peak current of RB decreased apparently without the shiftof the peak potential (Curve 2 in Figure 2), further illustrating that an interaction hadbeen happened between RB and DNA, and an electrochemical non-active complex wasformed, which resulted in the decrease of the peak current of RB. Figure 1 UV-Vis absorption spectra of RB interaction with DNAAccording to Laviron5 theory: Ep=E0-RTln(ksRT/αnF)/anF+RTlnv/αnF (2)where Ep (V) is the peak potential, E0(V)the electrode reaction formal potential, ks(s-1)the electrode reaction stand rate constant, a the charge transfer constant, n the reactionelectron number, F (C·mol-1) Faraday's constant, R (J·mol-1·K-1) gas constant, T(K) theabsolute temperature, v (V/s) the scan rate. From the slope of the plot of Ep vs. lnv the an value can be determined and from theintercept the ks can be calculated if the E0 value is known. The value of E0 in formula(2) can be determined from the intercept of Ep vs. v plot on the ordinate by extrapolatingthe line to v=0. According to this method, the a and ks were calculated in the absenceand presence of DNA. The results were 0.71, 1.27 s-1 and 0.73, 1.33 s-1, respectively.Obviously, whether RB interaction with DNA or not the a and ks value almost had notchanged, so RB and DNA formed an electrochemical non-active complex.AcknowledgmentsThe work was supported by the National Natural Science Foundation of China (Grant No.20375020).Electrochemical Studies of the Recognition Interaction of Rhodamine B with DNA1. R. T. Liu, J. H. Yang, X. Wu, T. Wu. Anal. Chim. Acta, 2001, 448(1), 85. 2. H. L.Wu, W. Y. Li, X. W. He, H. Liang, P. Y. Yang. Chin. J. Chem., 2003, 21(3), 305. 3. J. X. Gao. Chemistry (in Chinese), 1997, (8), 38. 4. X. M. Wang, S. J. Gong, Y. Li. Modern Science Instrument (in Chinese), 2001, 2, 46. 5. E. Laviron. J. Electroanal. Chem., 1997,101, 19.