Petrov A I, Khalil D N, Kazaryan R L, Savintsev I V, Sukhorukov B I
Institute of Theoretical and Experimental Biophysics Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
Bioelectrochemistry. 2002 Nov;58(1):75-85. doi: 10.1016/s1567-5394(02)00130-5.
Complex formation of native and denatured DNA, single-stranded polyribonucleotides poly(A) and poly(U), as well as double-stranded poly(A).poly(U) with dodecylamine (DDA) and dodecyltrimethylammonium bromide (DTAB) has been studied by UV-, CD-, IR-spectroscopy and fluorescence analysis of hydrophobic probe pyrene. DDA and DTAB were shown to bind cooperatively with DNA and polyribonucleotides, resulting in the formation of complexes containing hydrophobic micelle-like clusters. Critical aggregation concentration (CAC) of DDA and DTAB shifts sharply to lower values (30-50 times) in the presence of DNA and polynucleotides as compared to critical micelle concentration (CMC) of free DDA and DTAB in solution. The analysis of binding isotherms within the frame of the model of cooperative binding of low-molecular ligands to linear polymers allowed us to determine the thermodynamic parameters of complex formation and estimate the contribution of electrostatic interaction of positively charged heads of amphiphiles with negatively charged phosphate groups of DNA and polyribonucleotides, and hydrophobic interaction of aliphatic chains to complex stability. Electrostatic interaction was shown to make the main contribution to the stability of DNA complexes with DDA, while preferential contribution of hydrophobic interactions is characteristic of DTAB complexes with DNA. The opposite effect of DDA and DTAB on the thermal stability of DNA double helix was demonstrated from UV-melting of DNA-while DTAB stabilizes the DNA helix, DDA, to the contrary, destabilizes it. The destabilizing effect of DDA seems to originate from the displacement of intramolecular hydrogen bonds in complementary Watson-Crick A.T and G.C base pairs with intermolecular H-bonds between unsubstituted DDA amino groups and proton-accepting sites of nucleic bases.
通过紫外光谱、圆二色光谱、红外光谱以及疏水探针芘的荧光分析，研究了天然和变性DNA、单链多聚核糖核苷酸聚腺苷酸（poly(A)）和聚尿苷酸（poly(U)）以及双链聚腺苷酸-聚尿苷酸（poly(A).poly(U)）与十二烷基胺（DDA）和十二烷基三甲基溴化铵（DTAB）的复合物形成情况。结果表明，DDA和DTAB与DNA和多聚核糖核苷酸协同结合，形成了含有疏水胶束样簇的复合物。与溶液中游离DDA和DTAB的临界胶束浓度（CMC）相比，在DNA和多核苷酸存在的情况下，DDA和DTAB的临界聚集浓度（CAC）急剧下降至较低值（30 - 50倍）。在低分子配体与线性聚合物协同结合模型框架内对结合等温线进行分析，使我们能够确定复合物形成的热力学参数，并估算两亲性物质带正电荷的头部与DNA和多聚核糖核苷酸带负电荷的磷酸基团之间的静电相互作用以及脂肪链的疏水相互作用对复合物稳定性的贡献。结果表明，静电相互作用对DNA与DDA形成的复合物稳定性起主要作用，而疏水相互作用的优先贡献是DTAB与DNA形成的复合物的特征。通过DNA的紫外熔解实验证明了DDA和DTAB对DNA双螺旋热稳定性的相反影响——DTAB使DNA螺旋稳定，而DDA则相反，使其不稳定。DDA的去稳定作用似乎源于未取代的DDA氨基与核酸碱基的质子接受位点之间的分子间氢键取代了互补的沃森-克里克A.T和G.C碱基对中的分子内氢键。
