Nakagawa Kouichi
RI Research Center, Fukushima Medical University, 1 Hikarigaoka, Fukushima 960-1295, Japan.
Langmuir. 2003 Jun 10;19(12):5078-5082. doi: 10.1021/la026813d.
The molecular dynamics of aliphatic spin probes in a unique triglyceride membrane were investigated by continuous wave electron paramagnetic resonance (CW EPR) and saturation recovery spectroscopic methods. Rotational diffusion coefficients (R and R) obtained by a slow-motional EPR spectral simulation for 7-doxylstearic acid (7-DSA), 12-doxylstearic acid (12-DSA), and 16-doxylstearic acid (16-DSA) in the membrane at various temperatures were obtained. The activation energies calculated using R values for 7-, 12-, and 16-DSA in the membrane were 19 ± 0.9, 24 ± 1.2, and 37 ± 1.8 kJ/mol, respectively. The higher activation energy implies that the perpendicular motion of 16-DSA is more sensitive to temperature. As the nitroxide group of the spin probe was moved further down the stearic chain, electron spin-lattice relaxation times (T) became shorter. The shorter T indicates more flexibility around the probe moiety. Also, T for the DSAs became shorter when the temperature increased. The values of T obtained were consistent with perpendicular diffusion coefficients. In addition, no significant difference in T between the HO and the DO solutions was observed for the different DSAs. Therefore, it is concluded that steric effects and the local rotational mobility of the nitroxide moiety influence the T's obtained.
通过连续波电子顺磁共振（CW EPR）和饱和恢复光谱方法，研究了脂肪族自旋探针在独特甘油三酯膜中的分子动力学。通过慢运动EPR光谱模拟，获得了不同温度下膜中7-脱氧硬脂酸（7-DSA）、12-脱氧硬脂酸（12-DSA）和16-脱氧硬脂酸（16-DSA）的旋转扩散系数（R和R）。利用膜中7-DSA、12-DSA和16-DSA的R值计算得到的活化能分别为19±0.9、24±1.2和37±1.8 kJ/mol。较高的活化能意味着16-DSA的垂直运动对温度更敏感。随着自旋探针的氮氧基团沿硬脂酸链向下移动，电子自旋-晶格弛豫时间（T）变短。较短的T表明探针部分周围的柔韧性更高。此外，当温度升高时，DSA的T也变短。获得的T值与垂直扩散系数一致。此外，对于不同的DSA，在HO和DO溶液之间未观察到T有显著差异。因此，可以得出结论，空间位阻效应和氮氧基团的局部旋转流动性会影响所获得的T值。
