Golaś T, Miller M, Shugar D
Chem Biol Interact. 1980 May;30(2):209-22. doi: 10.1016/0009-2797(80)90127-1.
Thermal transition profiles were recorded for a variety of natural and synthetic DNA and double-stranded RNA preparations in the presence of tetramethylammonium (TMA+) and tetraethylammonium (TEA+) cations. Double-stranded RNAs of natural origin, with GC contents of 50% exhibited the same profiles and Tm values as native DNA containing normal bases. Hence the tetraalkylammonium cations liquidate not only the effects of base composition, and the difference in stability between A-T and A-U base pairs (further confirmed by measurements with uracil-containing DNA from phage PBS-2), but also that of the 2'OH. In the presence of TMA+ cations, there is very marked enhancement of the stability of U-U base pairs in poly(rU) and poly(Um). In 2.4 M TEA, the 1:1 complex of poly(G) with poly (C) formed readily and melted reversibly with a Tm as low as 87 degrees C. At concentrations of TMA and TEA for which dTm/dXGC = 0, the Tm values for various phage DNA preparations containing atypical bases (phages T2, T4, phi e, phi W-14, PBS-2) differ appreciably from those with 'normal bases'. Analysis of these findings indicates that the selective interaction of TMA and TEA cations with A-T base pairs occurs in the minor groove of the DNA helix. The overall results show that the action of these quaternary ammonium cations is not due exclusively to preferential binding to A-T base pairs, but must involve other factors, including modifications of solvent structure. They also underline the utility of TMA and TEA solvent systems for placing in evidence transition profiles not accessible in other solvent systems.
在四甲基铵（TMA⁺）和四乙基铵（TEA⁺）阳离子存在的情况下，记录了多种天然和合成的DNA以及双链RNA制剂的热转变曲线。天然来源的双链RNA，GC含量为50%，其曲线和熔解温度（Tm）值与含有正常碱基的天然DNA相同。因此，四烷基铵阳离子不仅消除了碱基组成的影响以及A - T和A - U碱基对之间稳定性的差异（用来自噬菌体PBS - 2的含尿嘧啶DNA进行测量进一步证实），还消除了2'-OH的影响。在TMA⁺阳离子存在的情况下，聚（rU）和聚（Um）中U - U碱基对的稳定性有非常显著的增强。在2.4 M TEA中，聚（G）与聚（C）的1:1复合物很容易形成并且以低至87℃的Tm可逆地熔化。在dTm/dXGC = 0的TMA和TEA浓度下，含有非典型碱基的各种噬菌体DNA制剂（噬菌体T2、T4、φe、φW - 14、PBS - 2）的Tm值与含有“正常碱基”的制剂有明显差异。对这些发现的分析表明，TMA和TEA阳离子与A - T碱基对的选择性相互作用发生在DNA螺旋的小沟中。总体结果表明，这些季铵阳离子的作用并非仅仅归因于与A - T碱基对的优先结合，而是必须涉及其他因素，包括溶剂结构的改变。它们还强调了TMA和TEA溶剂系统在揭示其他溶剂系统中无法获得的转变曲线方面的实用性。
