The effects of 2H2O on the phase transition of large unilamellar vesicle (LUV) suspensions as detected by ultrasound spectroscopy and electron spin resonance.
The effects of 2H2O on the phase transition of large unilamellar vesicle (LUV) suspensions as detected by ultrasound spectroscopy and electron spin resonance.
复制标题
通过超声波光谱和电子自旋共振检测到 2H2O 对大单层囊泡 (LUV) 悬浮液相变的影响。
DOI：
10.1016/0005-2736(89)90126-0
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Dunn,F
中科院分区：
文献类型：
--
作者：
Ma,LD;Magin,RL;Bacic,G;Dunn,F
研究了水在大型单层囊泡(LUV)悬浮液分子动力学中的重要性，在LUV悬浮液中，越来越多的水被2H2O取代。用双晶声干涉仪测定了二棕榈酰磷脂酰胆碱、二棕榈酰磷脂酰胆碱和二棕榈酰磷脂酰甘油混合物(LuVS：4：1(w/w))在其磷脂相变附近的每波长超声吸收系数(αλ)随温度和频率的变化。并用电子自旋共振(ESR)和差示扫描量热法(DSC)对该体系进行了表征。当水含量增加时，体系的相变温度从42.0℃提高到42.9℃(表明相变激活能增大)，αλ在相变时的幅值增大。然而，αλ在相变处的最大值与频率的函数不随2H2O的加入而改变，这表明导致超声吸收的事件的松弛时间没有受到影响。随着2H2O的加入，转变活化能增大，表明膜/水界面附近磷脂的迁移率发生了变化。用位于膜/水界面的氮氧化物自旋探针(5-DOxyl stesteate和CAT16)对LuV进行的电子自旋共振(ESR)实验表明，LuV在2H2O中的膜/水界面有比在H2O中的LuV更宽的裂解。这些结果表明，2H2O改变了膜/水界面区域磷脂的流动性和/或结构。对于位于双层C-12位置的探针PC-12-十二烷基硬脂酸酯来说，这种差异在Amax中看不到。
The importance of water in the molecular dynamics of large unilamellar vesicle (LUV) suspensions, in which increasing portions of the water were replaced by2H2O, was investigated. Determinations of the ultrasonic absorption coefficient per wavelength, αλ, were performed as a function of temperature and frequency for LUVs (LUVs: 4:1 (w/w) mixture of dipalmitoylphosphatidylcholine, DPPC, and dipalmitoylphosphatidylglycerol, DPPG) in the vicinity of their phospholipid phase transition, using a double crystal acoustic interferometer. Electron spin resonance (ESR) and differential scanning calorimetry (DSC) were also employed to probe this system. When increasing portions of the aqueous content of the LUV suspensions were replaced by2H2O the phase transition temperature increased from 42.0°C to 42.9°C (indicating an increase in the activation energy of the transition), and the amplitude of αλ at the phase transition increased. However,αλmaxas a function of frequency at the phase transition did not change with the addition of2H2O, indicating that the relaxation time of the event responsible for the absorption of ultrasound was unaffected. The increase in the activation energy of the transition with the addition of2H2O suggested that the mobility of phospholipids near the membrane/aqueous interface was changed. Electron spin resonance (ESR) experiments on LUVs with nitroxide spin probes positioned at the membrane/aqueous interface (5-doxyl stearate and CAT16) showed that LUVs in2H2O have a broader splitting,Amax, at the membrane/aqueous interface than do LUVs in H2O. These results suggest that2H2O changes the mobility and/or structure of the phospholipids in the region of the membrane/aqueous interface. This difference inAmaxwas not seen for the probe PC-12-doxyl stearate, which resides at the C-12 position of the bilayer.