Byrne C D, de Mello A J
School of Chemical Sciences, University of East Anglia, Norwich, NR4 7TJ, UK.
Biophys Chem. 1998 Mar 9;70(3):173-84. doi: 10.1016/s0301-4622(97)00091-4.
Time-integrated and time-resolved fluorescence spectroscopies have been used to probe the photophysical properties of ethidium bromide (Eb) complexed to calf thymus DNA (ct-DNA). Fluorescence decay profiles are obtained using the technique of time-correlated single photon counting (TCSPC), and subsequently analysed using conventional sum-of-exponential (SOE) routines and also the maximum entropy method (MEM). Through use of these methods and simulated decay data, it is demonstrated that the kinetics of Eb in the presence of ds-DNA are best described by a generic model consisting of three exponential terms. At all DNA:Eb ratios and NaCl concentrations studied, free Eb is detected. Furthermore, Eb is found to interact with ds-DNA through two mechanisms, each distinguishable by its fluorescence decay time. Eb is shown to interact with DNA through classic intercalation, and also through binding at secondary sites. The component decay times are shown to be a function of NaCl concentration but independent of DNA:Eb molar ratio.
时间积分荧光光谱法和时间分辨荧光光谱法已被用于探测与小牛胸腺DNA（ct-DNA）复合的溴化乙锭（Eb）的光物理性质。使用时间相关单光子计数（TCSPC）技术获得荧光衰减曲线，随后使用传统的指数和（SOE）程序以及最大熵方法（MEM）进行分析。通过使用这些方法和模拟衰减数据，证明在双链DNA存在下Eb的动力学最好用由三个指数项组成的通用模型来描述。在所研究的所有DNA:Eb比率和NaCl浓度下，均检测到游离的Eb。此外，发现Eb通过两种机制与双链DNA相互作用，每种机制可通过其荧光衰减时间来区分。结果表明，Eb通过经典嵌入以及在二级位点结合与DNA相互作用。组分衰减时间显示为NaCl浓度的函数，但与DNA:Eb摩尔比无关。
