Huang T H, Blume A, Das Gupta S K, Griffin R G
School of Physics, Georgia Institute of Technology, Atlanta 30332.
Biophys J. 1988 Jul;54(1):173-9. doi: 10.1016/S0006-3495(88)82942-4.
The interaction of UO2(2+) with dipalmitoylphosphatidylcholine (DPPC) has been studied as a function of temperature and composition using nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), and monolayer studies. Computer simulations of the 31P-NMR powder spectra of DPPC dispersions in the presence of various concentrations of UO2(2+) are consistent with the binding stoichiometry of [UO2(2+)]/[DPPC] = 1:4 at [UO2(2+)]/[DPPC] less than 0.3. This complex undergoes a phase transition to the liquid crystalline phase at T'm = 50 +/- 3 degrees C with a breadth delta T'm = 7 +/- 3 degrees C. This broad transition gradually disappears at higher UO2(2+) concentrations, suggesting the presence of yet another UO2(2+)/DPPC complex (or complexes) whose NMR spectra are indistinguishable from those of the 1:4 UO2(2+)/DPPC species. The temperature-dependent 13C powder spectra of 2(1-13C) DPPC dispersions in the presence of 1.2 mol ratio of UO2(2+) show that this higher order complex (complexes) also undergoes a phase transition to the liquid crystalline state at T'm +/- = 58 +/- 3 degrees C with a breadth delta T"m = 15 +/- 5 degrees C. The NMR spectra indicate that exchange among these various UO2(2+)/DPPC complexes is slow. In addition, computer simulations of the 31P-, 13C-, and 2H-NMR powder spectra show that axial diffusion of the DPPC molecules about their long axes is quenched by addition of UO2(2+) and acyl chain isomerization is the dominant motional mode. The isomerization is best described as two-site hopping of the greater than C-D bond at a rate of approximately 10(6) s-1, a motional mode which is expected for a kink diffusion.
利用核磁共振（NMR）光谱、差示扫描量热法（DSC）和单分子层研究，研究了UO₂²⁺与二棕榈酰磷脂酰胆碱（DPPC）的相互作用与温度和组成的关系。在存在不同浓度UO₂²⁺的情况下，对DPPC分散体的³¹P-NMR粉末光谱进行计算机模拟，结果表明，当[UO₂²⁺]/[DPPC]小于0.3时，[UO₂²⁺]/[DPPC]的结合化学计量比为1:4。该配合物在T'm = 50±3℃时发生向液晶相的相变，相变宽度ΔT'm = 7±3℃。在较高的UO₂²⁺浓度下，这种宽的转变逐渐消失，这表明存在另一种UO₂²⁺/DPPC配合物，其NMR光谱与1:4 UO₂²⁺/DPPC物种的光谱无法区分。在1.2摩尔比的UO₂²⁺存在下，2(1-¹³C) DPPC分散体的温度依赖性¹³C粉末光谱表明，这种高阶配合物在T'm± = 58±3℃时也发生向液晶态的相变，相变宽度ΔT"m = 15±5℃。NMR光谱表明，这些不同的UO₂²⁺/DPPC配合物之间的交换很慢。此外，对³¹P-、¹³C-和²H-NMR粉末光谱的计算机模拟表明，添加UO₂²⁺会抑制DPPC分子绕其长轴的轴向扩散，酰基链异构化是主要的运动模式。异构化最好描述为大于C-D键的双位点跳跃，速率约为10⁶ s⁻¹，这是扭结扩散预期的运动模式。
