Minasyan S H, Tavadyan L A, Antonyan A P, Davtyan H G, Parsadanyan M A, Vardevanyan P O
Laboratory of Liquid-Phase Oxidation and Free-Radical Reactions, Institute of Chemical Physics named after A.B. Nalbandyan, NAS of Armenia, Sevak St., 5/2, 375014, Yerevan, Armenia.
Bioelectrochemistry. 2006 Jan;68(1):48-55. doi: 10.1016/j.bioelechem.2005.03.006.
The interaction of ethidium bromide (EtBr) with calf thymus DNA is investigated electrochemically with the use of differential pulse voltammetry (DPV) at two different ionic strengths of a solution (0.154 M and 0.02 M [Na+], pH 7.0). It is revealed that EtBr binds with DNA in more than one way. The appropriate values of constants (K) and number site sizes (n) of EtBr binding to DNA are determined. The values of binding constants are equal to 1.9 x 10(6) and 5.6 x 10(5) M(-1), and number site sizes to 9 and 3.6 for strong interactions at ionic strengths of solutions 0.02 and 0.154 M Na+ at 28 degrees C, respectively. For a weaker interaction, these parameters are equal to 7 x 10(4) and 8 x 10(4) M(-1) and 1.5 and 1 at the mentioned ionic strengths of solutions, respectively. Thus, EtBr interacts with DNA in more than one way--intercalative and electrostatic at low ionic strength, and semi-intercalative and electrostatic at a higher strength of the solution. These results are in good accordance with the ones obtained by spectroscopic (absorption and fluorimetric) methods.
利用差分脉冲伏安法（DPV）在两种不同离子强度（0.154 M和0.02 M [Na⁺]，pH 7.0）的溶液中，对溴化乙锭（EtBr）与小牛胸腺DNA的相互作用进行了电化学研究。结果表明，EtBr与DNA的结合方式不止一种。确定了EtBr与DNA结合的常数（K）和结合位点数目（n）的合适值。在28℃下，溶液离子强度为0.02 M Na⁺和0.154 M Na⁺时，强相互作用的结合常数分别为1.9×10⁶和5.6×10⁵ M⁻¹，结合位点数目分别为9和3.6。对于较弱的相互作用，在上述溶液离子强度下，这些参数分别为7×10⁴和8×10⁴ M⁻¹以及1.5和1。因此，EtBr与DNA的相互作用方式不止一种——在低离子强度下为插入和静电作用，在较高溶液强度下为半插入和静电作用。这些结果与通过光谱（吸收和荧光）方法获得的结果非常一致。
