Jain P, Sen S, Risbud S H
Department of Chemical Engineering and Materials Science, University of California at Davis, Davis, California 95616, USA.
J Chem Phys. 2009 Jul 14;131(2):025102. doi: 10.1063/1.3170927.
(31)P NMR spectroscopy has been used to elucidate the role of glass-forming sugars in the preservation of dipalmitoylphosphatidylcholine (DPPC) lipid bilayers. (31)P wideline NMR spectra of freeze-dried pure DPPC, DPPC/trehalose, DPPC/glucose, and DPPC/hydroxyethyl starch (HES) mixtures collected in the temperature range of 25-80 degrees C have been simulated to obtain quantitative information about rotational dynamics and orientation of the lipid head groups in these media. In the case of pure DPPC, DPPC/glucose, and DPPC/HES, the gel-to-liquid crystalline phase transition of DPPC bilayer is characterized by a sudden increase in the rate of rotational diffusion of the PO(4) head groups near 40 degrees C. The corresponding rotational jump frequency increases from a few kilohertz in the gel phase to at least several megahertz in the liquid crystalline phase. On the other hand, in the case of DPPC/trehalose mixture the temperature of this onset of rapid head group dynamics is increased by approximately 10 degrees C. Trehalose reduces the lipid head group motions most effectively in the temperature range of T < or = 50 degrees C relevant for biopreservation. Additionally, and possibly more importantly, trehalose is found to strongly restrict any change in the orientation of the diffusion axis of the PO(4) head groups during the phase transformation. This unique ability of trehalose to maintain the dynamical and orientational rigidity of lipid head groups is likely to be responsible for its superior ability in biopreservation.
磷-31核磁共振光谱已被用于阐明玻璃态形成糖在二棕榈酰磷脂酰胆碱（DPPC）脂质双层保存中的作用。对在25至80摄氏度温度范围内收集的冻干纯DPPC、DPPC/海藻糖、DPPC/葡萄糖和DPPC/羟乙基淀粉（HES）混合物的磷-31宽线核磁共振光谱进行了模拟，以获得有关这些介质中脂质头部基团旋转动力学和取向的定量信息。在纯DPPC、DPPC/葡萄糖和DPPC/HES的情况下，DPPC双层从凝胶态到液晶态的相变特征是在40摄氏度附近PO(4)头部基团的旋转扩散速率突然增加。相应的旋转跳跃频率从凝胶态的几千赫兹增加到液晶态的至少几兆赫兹。另一方面，在DPPC/海藻糖混合物的情况下，这种头部基团快速动力学开始的温度提高了约10摄氏度。在与生物保存相关的T≤50摄氏度温度范围内，海藻糖最有效地降低了脂质头部基团的运动。此外，可能更重要的是，发现在相变过程中海藻糖强烈限制了PO(4)头部基团扩散轴取向的任何变化。海藻糖维持脂质头部基团动力学和取向刚性的这种独特能力可能是其在生物保存中具有卓越能力的原因。
