Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, Wisconsin 53705-1691, United States.
J Phys Chem B. 2010 Dec 2;114(47):15554-64. doi: 10.1021/jp107936b. Epub 2010 Nov 9.
We report the use of dynamic light scattering (DLS), small-angle neutron scattering (SANS), and small-angle X-ray scattering (SAXS) to characterize the nanostructure of complexes formed by either single- or double-stranded oligonucleotides with a cationic surfactant (cetyltrimethylammonium bromide, CTAB) in aqueous solution (1 mM Li(2)SO(4)). For single-stranded oligonucleotides 5'-A(20)-3' and 5'-CCCCATTCTAGCAGCCCGGG-3', both the appearance of two Bragg peaks (at 0.14 and 0.28 Å(-1)) in SAXS spectra with a spacing of 1:2 and form factor fits to SANS spectra are consistent with the presence of multilamellar vesicles (with, on average, 6-9 layers with a periodicity of 45-48 Å). Some samples showed evidence of an additional Bragg peak (at 0.20 Å(-1)) associated with periodic packing (with a periodicity of 31 Å) of the oligonucleotides within the lamellae of the nanostructure. The nucleotide composition of the single-stranded oligonucleotides was also found to impact the number and size of the complexes formed with CTAB. In contrast to 5'-A(20)-3' and 5'-CCCCATTCTAGCAGCCCGGG-3', 5'-T(20)-3' did not change the state of aggregation of CTAB (globular micelles) over a wide range of oligonucleotide:CTAB charge ratios. These results support the proposition that hydrophobic interactions, as well as electrostatics, play a central role in the formation of complexes between cationic amphiphiles and single-stranded oligonucleotides and thus give rise to nanostructures that depend on nucleotide composition. In contrast to the single-stranded oligonucleotides, for double-stranded oligonucleotides mixed with CTAB, three Bragg peaks (0.13, 0.23, and 0.25 Å(-1)) in SAXS spectra with a spacing ratio of 1:√3:√4 and characteristic changes in SANS spectra indicate formation of a hexagonal nanostructure. Also, the composition of the double-stranded oligonucleotides did not measurably impact the nanostructure of complexes formed with CTAB, suggesting that electrostatic interactions dominate the formation of these complexes. Overall, these results provide insights into the intermolecular interactions that occur between cationic amphiphiles and oligonucleotides and establish that single and double-stranded oligonucleotides form complexes with cationic surfactants that differ in nanostructure. The results also provide guidance for the design of oligonucleotide complexes with cationic amphiphiles.
我们使用动态光散射（DLS）、小角中子散射（SANS）和小角 X 射线散射（SAXS）来表征在水溶液中（1 mM Li(2)SO(4)）由阳离子表面活性剂（十六烷基三甲基溴化铵，CTAB）与单链或双链寡核苷酸形成的复合物的纳米结构。对于单链寡核苷酸 5'-A(20)-3' 和 5'-CCCCATTCTAGCAGCCCGGG-3'，SAXS 谱中出现两个布拉格峰（在 0.14 和 0.28 Å(-1)处），间距为 1:2，并且对 SANS 谱的形状因子拟合表明存在多层囊泡（平均有 6-9 层，周期性为 45-48 Å）。一些样品显示出与寡核苷酸在纳米结构的层内周期性排列（周期性为 31 Å）相关的附加布拉格峰（在 0.20 Å(-1)处）的证据。单链寡核苷酸的核苷酸组成也被发现影响与 CTAB 形成的复合物的数量和大小。与 5'-A(20)-3' 和 5'-CCCCATTCTAGCAGCCCGGG-3' 相比，5'-T(20)-3' 在很宽的寡核苷酸：CTAB 电荷比范围内没有改变 CTAB 的聚集状态（球状胶束）。这些结果支持了这样的观点，即疏水性相互作用以及静电作用在阳离子两亲物与单链寡核苷酸之间形成复合物中起核心作用，从而导致依赖于核苷酸组成的纳米结构的形成。与单链寡核苷酸相反，对于与 CTAB 混合的双链寡核苷酸，SAXS 谱中出现三个布拉格峰（0.13、0.23 和 0.25 Å(-1)），间距比为 1:√3:√4，以及 SANS 谱中的特征变化表明形成了六方纳米结构。此外，双链寡核苷酸的组成没有可测量地影响与 CTAB 形成的复合物的纳米结构，这表明静电相互作用主导了这些复合物的形成。总体而言，这些结果提供了对阳离子两亲物与寡核苷酸之间发生的分子间相互作用的深入了解，并确定单链和双链寡核苷酸与阳离子表面活性剂形成的复合物在纳米结构上有所不同。结果还为设计与阳离子两亲物的寡核苷酸复合物提供了指导。
