Continuous wave electron paramagnetic resonance spectroscopy and two-pulse echo detected spectra of chain-labeled lipids are used to study the dynamics of frozen lipid membranes over the temperature range 77–260 K. Bilayers of ester-linked dihexadecanoylphosphatidylcholine (DPPC) with noninterdigitated chains and ether-linked dihexadecyl phosphatidylcholine (DHPC) with interdigitated chains are considered. Rapid stochastic librations of small angular amplitude are found in both lipid matrices. In noninterdigitated DPPC bilayers, the mean-square angular amplitude, , of the motion increases with temperature and it is larger close to the chain termini than close to the polar/apolar interface. In contrast, in interdigitated DHPC lamellae, is small and temperature and label-position independent at low temperature and increases steeply at high temperature. The rotational correlation time, τ_c, of librations lies in the subnanosecond range for DPPC and in the nanosecond range for DHPC. In all membrane samples, the temperature dependence of resembles that of the mean-square atomic displacement revealed by neutron scattering and a dynamical transition is detected in the range 210–240 K. The results highlight the librational oscillations and the glass-like behavior in bilayer and interdigitated lipid membranes.

中文翻译：

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酯和醚连接的磷脂酰胆碱膜中链标签脂质的低温动力学

连续波电子顺磁共振光谱和链标记的脂质的两脉冲回波检测光谱用于研究77-260 K温度范围内冷冻脂质膜的动力学。考虑了具有叉指链的醚连接的二十六烷基磷脂酰胆碱（DHPC）。在两种脂质基质中都发现了小角度幅度的快速随机释放。在非叉指式DPPC双层中，运动的均方角幅度随温度增加，并且靠近链末端的距离大于靠近极性/非极性界面的距离。相反，在交错的DHPC薄片中，体积小，在低温下温度和标签位置无关，而在高温下急剧增加。的旋转相关时间，τ _Ç，的librations在于在亚纳秒范围为DPPC和在纳秒范围DHPC。在所有膜样品中，温度依赖性类似于中子散射揭示的均方原子位移，并且在210–240 K范围内检测到动态跃迁。结果突出了双层中的自由振动和玻璃状行为和指状脂质膜。