Chandrasekaran S, Krishnamoorthy C R, Jones R L, Smith J C, Wilson W D
Biochem Biophys Res Commun. 1984 Jul 31;122(2):804-9. doi: 10.1016/s0006-291x(84)80105-9.
In a low salt buffer (0.011 M Na+) stopped-flow kinetic results for the SDS driven dissociation of an ethidium-Poly d(G-C) X d(G-C) complex are 8.7, 23, and 58.5 s-1 at 20, 30, and 40 degrees C, respectively. These results predict that in NMR experiments at high field strengths, ethidium should be in slow exchange among polymer binding sites. This has been found to be the case for both 31P (109 MHz) and 1H (imino proton spectra in H2O at 270 MHz) experiments. At higher salt, and/or higher temperature, and/or lower field, the bound and free peaks are no longer resolved in the NMR spectra. Good agreement is obtained between the stopped-flow kinetic results and the coalescence temperature observed in NMR experiments. Imino protons in base pairs on both sides of the intercalated ethidium are shifted approximately one ppm upfield while only the phosphate groups at the intercalation site experience large chemical shifts.
在低盐缓冲液（0.011 M Na⁺）中，通过停流动力学得到的结果表明，在20、30和40摄氏度下，十二烷基硫酸钠（SDS）驱动的溴化乙锭 - 聚d（G - C）×d（G - C）复合物解离的速率分别为8.7、23和58.5 s⁻¹。这些结果预测，在高场强的核磁共振（NMR）实验中，溴化乙锭在聚合物结合位点之间应处于缓慢交换状态。对于³¹P（109 MHz）和¹H（270 MHz下H₂O中的亚氨基质子光谱）实验，情况确实如此。在较高盐浓度、较高温度和/或较低场强下，核磁共振谱中结合峰和游离峰不再能分辨。停流动力学结果与核磁共振实验中观察到的聚结温度之间取得了良好一致性。插入的溴化乙锭两侧碱基对中的亚氨基质子向上场移动约1 ppm，而只有插入位点的磷酸基团经历较大的化学位移。
