Sukhorukov B I, Petrov A I, Kazarian R L, Kuvichkin V V
Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, Russia.
Biofizika. 2000 Mar-Apr;45(2):245-53.
The formation of complexes of DNA with dodecylamine, dodecyltrimethylammonium, tetradecyltrimethylammonium, and hexadecyltrimethylammonium was studied using a fluorescent probe pyrene. The dependences of the spectral parameters of the hydrophobic pyrene probe on the concentration of the cationic amphiphile in the presence and absence of DNA were obtained and analyzed. It is shown that, in the absence of DNA, these dependences exhibit only one S-shaped region, which corresponds to the micelle formation of the amphiphile, whereas in the presence of DNA there are two S-shaped regions, which indicates the cooperative formation of two types of DNA-cationic amphiphile complexes. For each of the four cationic amphiphiles, the critical concentrations for the micelle formation in the absence of DNA (C0) and the concentrations at which the first (Cd1) and the second complex with DNA are formed were determined. It was found that the Cd1 value is 15-40 times lower than C0. The Cd1 value does not depend on DNA concentration and is determined only by the length of the hydrocarbon chain and the structure of the amphiphile ionic fragment. The Cd1 value increases as the length of the aliphatic chain decreases and upon replacement of mobile hydrogen atoms in the ammonium fragment by methyl groups. It was shown that hydrophobic clusters of amphiphile arising upon complex formation with DNA play the role of cross-links promoting DNA aggregation, or DNA compactization in the case of dilute solution of high-molecular weight DNA. The structures of the first and second DNA-cationic amphiphile complexes are proposed, and the mechanism and nature of interactions that determine their formation are discussed.
使用荧光探针芘研究了DNA与十二烷基胺、十二烷基三甲基铵、十四烷基三甲基铵和十六烷基三甲基铵形成复合物的情况。获得并分析了在有和没有DNA存在时，疏水性芘探针的光谱参数对阳离子两亲物浓度的依赖性。结果表明，在没有DNA的情况下，这些依赖性仅表现出一个S形区域，这对应于两亲物的胶束形成，而在有DNA存在时则有两个S形区域，这表明形成了两种类型的DNA-阳离子两亲物复合物。对于四种阳离子两亲物中的每一种，都确定了在没有DNA时胶束形成的临界浓度（C0）以及形成第一个（Cd1）和第二个与DNA复合物的浓度。发现Cd1值比C0低15至40倍。Cd1值不依赖于DNA浓度，仅由烃链长度和两亲物离子片段的结构决定。Cd1值随着脂肪链长度的减少以及铵片段中可移动氢原子被甲基取代而增加。结果表明，与DNA形成复合物时产生的两亲物疏水簇起到交联作用，促进DNA聚集，在高分子量DNA稀溶液的情况下则促进DNA压缩。提出了第一个和第二个DNA-阳离子两亲物复合物的结构，并讨论了决定其形成的相互作用的机制和性质。
