Very high frequency electron paramagnetic resonance of 2,2,6,6-tetramethyl-1-piperidinyloxy in 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine liposomes: partitioning and molecular dynamics.
Very high frequency electron paramagnetic resonance of 2,2,6,6-tetramethyl-1-piperidinyloxy in 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine liposomes: partitioning and molecular dynamics.
复制标题
1,2-二棕榈酰-sn-甘油-3-磷脂酰胆碱脂质体中2,2,6,6-四甲基-1-哌啶氧基的甚高频电子顺磁共振：分配和分子动力学。
DOI：
10.1016/s0006-3495(95)80417-0
复制
发表时间：
1995
影响因子：
3.4
通讯作者：
Morse2nd,PD
中科院分区：
文献类型：
--
作者：
Smirnov,AI;Smirnova,TI;Morse2nd,PD
利用甚高频电子顺磁共振（EPR）研究了1,2-二棕榈酰- n-甘油-3-磷脂酰胆碱组成的大单层脂质体（LUV）中2,2,6,6，-四甲基胡椒碱-1-氧基（TEMPO）硝基自由基的分配和分子动力学。在94.3 GHz的微波频率下进行的实验完全分解了水相和烃相的TEMPO EPR谱。采用精确的计算机模拟方法结合Levenberg-Marquardt优化方法对两相的TEMPO EPR谱进行了分析。从模拟中提取的光谱参数给出了TEMPO探针在LUV烃相和水相之间的实际划分，并允许分析探针在LUV烃相中的皮秒旋转动力学。在甚高频EPR实验中，LUV-TEMPO体系中的相变表现为TEMPO探针的分划和旋转相关次数的急剧变化。相变温度（40.5 +/- 0.2和32.7 +/- 0.5℃）与先前报道的差示扫描微量热数据一致。利用现有的动态变窄氮氧化物光谱理论表达式对谱线宽度进行了分析。结果表明，TEMPO探针在各向同性介质中的各向异性布朗扩散可以很好地描述其运动，而不受波纹结构（P β′）或流体双层结构（L α）相中存在的更大的烃链的限制。
Partitioning and molecular dynamics of 2,2,6,6,-tetramethylpiperedine-1-oxyl (TEMPO) nitroxide radicals in large unilamellar liposomes (LUV) composed from 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine were investigated by using very high frequency electron paramagnetic resonance (EPR) spectroscopy. Experiments carried out at a microwave frequency of 94.3 GHz completely resolved the TEMPO EPR spectrum in the aqueous and hydrocarbon phases. An accurate computer simulation method combined with Levenberg-Marquardt optimization was used to analyze the TEMPO EPR spectra in both phases. Spectral parameters extracted from the simulations gave the actual partitioning of the TEMPO probe between the LUV hydrocarbon and aqueous phases and allowed analysis of picosecond rotational dynamics of the probe in the LUV hydrocarbon phase. In very high frequency EPR experiments, phase transitions in the LUV-TEMPO system were observed as sharp changes in both partitioning and rotational correlation times of the TEMPO probe. The phase transition temperatures (40.5 +/- 0.2 and 32.7 +/- 0.5 degrees C) are in agreement with previously reported differential scanning microcalorimetry data. Spectral line widths were analyzed by using existing theoretical expressions for motionally narrowed nitroxide spectra. It was found that the motion of the small, nearly spherical, TEMPO probe can be well described by anisotropic Brownian diffusion in isotropic media and is not restricted by the much larger hydrocarbon chains existing in ripple structure (P beta') or fluid bilayer structure (L alpha) phases.