The reaction mechanism of general anesthetics studied by electron spin resonance and fluorescence measurement technique

本文研究了全身麻醉药和温度对多层脂质体（MLV）电子自旋共振（ESR）谱的影响。脂质体由DMPC、DOPC或EYPC组成，分别用5-DSA或16-DSA标记。在10 ~ 50 ℃不同温度下测定了ESR谱。16-DSA标记的MLV与5-DSA标记的MLV相比，其光谱呈现三个尖锐信号。5-DSA和16-DSA的序参量S值的差异表明，5-DSA和16-DSA的氮氧自由基在膜双层中的位置不同。麻醉药对膜流动性指标S和τ值无明显影响。因此，麻醉剂保留在脂质双层表面，而不作用于自旋标记氮氧自由基所处的内部疏水区和表面相对亲水区。麻醉药在低温范围内使S和τ值降低，表明膜流动性增加，但随着温度升高，这种作用减弱。这些结果表明，脂质体膜的流动性随温度的升高而增加，而与麻醉剂的存在无关，并且麻醉剂增加了膜的流动性，特别是在低温下，并使饱和脂肪酸的相变温度向较低温度移动。

We investigated the effects of general anesthetics and the temperature on electron spin resonance (ESR) spectra of multilamellar liposome (MLV). Liposomes were composed of DMPC, DOPC or EYPC, labeled with 5-DSA or 16-DSA. The ESR spectra were measured at different temperatures from 10 to 50 ℃. The spectra of MLV labeled by 16-DSA showed three sharp signals compared with 5-DSA. The difference of order parameter S value of 5-DSA and 16-DSA suggested that the nitroxide radical location of 5-DSA and 16-DSA were different in the membrane bilayr. The anesthetics did not alter the S and τ values, which are index of the fluidity of membrane. Therefore it is suggested that anesthetics remain on the surface of lipid bilayr and do not act both the inside hydrophobic area and relatively surface hydrophilic area that the nitroxide radical of spin label located. The anesthetics decreased S and τ values in the low temperature range, suggesting an increase of membrane fluidity, but the effects decreased as the temperature rose. These results suggest that the fluidity of liposome membrane increases with rise of the temperature irrespective of the presence of anesthetics and that the anesthetics increases the fluidity of the membrane especially at the low temperature and shifts the phase transition temperature of saturated fatty acid to a lower temperature.