Lobo Brian A, Koe Gary S, Koe Janet G, Middaugh C Russell
Department of Pharmaceutical Chemistry, University of Kansas, 2095 Constant Ave., Lawrence, KS 66047, USA.
Biophys Chem. 2003 May 1;104(1):67-78. doi: 10.1016/s0301-4622(02)00339-3.
A better understanding of the nature of the interaction between various cationic lipids used for gene delivery and DNA would lend insight into their structural and physical properties that may modulate their efficacy. We therefore separated the protonation and binding events which occur upon complexation of 1:1 DOTAP (1,2-dioleoyl-3-trimethylammonium propane):DOPE (1,2-dioleoylphosphatidylethanolamine) liposomes to DNA using proton linkage theory and isothermal titration calorimetry (ITC). The enthalpy of DOPE protonation was estimated as -45.0+/-0.7 kJ/mol and the intrinsic binding enthalpy of lipid to DNA as +2.8+/-0.3 kJ/mol. The pK(a) of DOPE was calculated to shift from 7.7+/-0.1 in the free state to 8.8+/-0.1 in the complex. At physiological ionic strength, proton linkage was not observed upon complex formation and the buffer-independent binding enthalpy was +1.0+/-0.4 kJ/mol. These studies indicate that the intrinsic interaction between 1:1 DOTAP/DOPE and DNA is an entropy-driven process and that the affinities of cationic lipids that are formulated with and without DOPE for DNA are controlled by the positive entropic changes that occur upon complex formation.
更好地理解用于基因递送的各种阳离子脂质与DNA之间相互作用的本质，将有助于深入了解它们可能调节其功效的结构和物理性质。因此，我们使用质子键合理论和等温滴定量热法（ITC）分离了1:1 DOTAP（1,2 - 二油酰基 - 3 - 三甲基铵丙烷）：DOPE（1,2 - 二油酰基磷脂酰乙醇胺）脂质体与DNA复合时发生的质子化和结合事件。DOPE质子化的焓估计为-45.0±0.7 kJ/mol，脂质与DNA的固有结合焓为+2.8±0.3 kJ/mol。计算得出DOPE的pK(a)从游离状态下的7.7±0.1变为复合物中的8.8±0.1。在生理离子强度下，复合物形成时未观察到质子键合，且与缓冲液无关的结合焓为+1.0±0.4 kJ/mol。这些研究表明，1:1 DOTAP/DOPE与DNA之间的固有相互作用是一个熵驱动的过程，并且含有和不含有DOPE的阳离子脂质对DNA的亲和力由复合物形成时发生的正熵变化控制。
