Sauer B B, Flint R A, Justice J B, Trowbridge C G
Arch Biochem Biophys. 1984 Nov 1;234(2):580-4. doi: 10.1016/0003-9861(84)90307-2.
A liquid membrane electrode selective for ethidium ion was used to measure free ethidium in mixtures with calf thymus DNA. Electrode response was unaffected by variation in ionic strength from 1 mM to 0.5 M, and was not degraded over the temperature range studied. DNA-ethidium binding isotherms obtained with the electrode at 17.4, 25.4, 30.1, and 40.6 degrees C were fitted to a single class of excluded sites model for v ranging from 0.01 to 0.16. van't Hoff analysis of these data yielded delta H = -8300 cal/mol ethidium bound (in 0.5 M KCl, 10 mM Tris buffer, pH 10, 1 mM EDTA). Direct calorimetric measurements of the heat of complex formation led to a value of -7600 cal/mol at 25 degrees C in the same medium; the two results were not significantly different at the 95% confidence level. The agreement supports the validity of the ethidium selective electrode, and illustrates its utility in the study of ligand binding to nucleic acids and related materials.
使用对乙锭离子具有选择性的液膜电极来测量与小牛胸腺DNA混合液中的游离乙锭。电极响应不受离子强度从1 mM变化到0.5 M的影响，并且在所研究的温度范围内不会降解。在17.4、25.4、30.1和40.6摄氏度下用该电极获得的DNA - 乙锭结合等温线符合v范围为0.01至0.16的单一类别的排除位点模型。对这些数据进行范特霍夫分析得出，结合的乙锭的ΔH = -8300 cal/mol（在0.5 M KCl、10 mM Tris缓冲液、pH 10、1 mM EDTA中）。在相同介质中，直接量热法测量复合物形成的热在25摄氏度时得出的值为-7600 cal/mol；在95%置信水平下，这两个结果没有显著差异。该一致性支持了乙锭选择性电极的有效性，并说明了其在研究配体与核酸及相关物质结合方面的实用性。
