Kinoshita K, Yamazaki M
Department of Physics, Faculty of Science, Shizuoka University, Japan.
Biochim Biophys Acta. 1996 Oct 23;1284(2):233-9. doi: 10.1016/s0005-2736(96)00136-8.
We have investigated the effects of several water-soluble organic solvents which also have a high solubility for alkanes, on the structure and phase behavior of multilamellar vesicles of dipalmitoylphosphatidylcholine (DPPC-MLV). Of these solvents, we selected five organic solvents; such as, acetonitrile, acetone, propionaldehyde, ethanol, and tetrahydrofuran. The main transition temperature of DPPC-MLV decreased with an increase in acetonitrile concentration from 0% to 6.0%(v/v) acetonitrile, and increased above 6.0%(v/v). X-ray diffraction data indicated that a phase transition from L beta', to L beta I phase (interdigitated gel phase) in DPPC-MLV, occurred at 5.0%(v/v) and DPPC-MLV were completely in the L beta I phase above 6.0%(v/v) acetonitrile at 20 degrees C. Results of the excimer method (Yamazaki, M. et al. (1992) Biochim. Biophys. Acta 1106, 94-98) supported the above results; the ratio of excimer to monomer fluorescence intensity (E/M) of pyrene-PC in DPPC-MLV rapidly decreased at 5.1%(v/v) and E/M became very low above 6.0%(v/v) acetonitrile. By the excimer method, we have found that other organic solvents; such as, acetone, propionaldehyde, and tetrahydrofuran, induced a phase transition from L beta', to L beta I phase in DPPC-MLV. Threshold concentrations of acetone, ethanol, propionaldehyde, and tetrahydrofuran for this phase transition at 20 degrees C were 9.4%(v/v), 5.5%(w/v), 3.5%(w/v), and 3.7%(w/v), respectively. Substitution of H2O by D2O (deuterium oxide) increased the threshold concentrations of all the organic solvents. A mechanism of these phase transitions and the effect of the substitution of H2O by D2O is proposed and discussed; a concept of the chi parameter, which is an interaction energy parameter between the surface segments of DPPC-MLV and solvents, may explain these phenomena reasonably.
我们研究了几种对烷烃也有高溶解度的水溶性有机溶剂对二棕榈酰磷脂酰胆碱多层囊泡（DPPC-MLV）的结构和相行为的影响。在这些溶剂中，我们选择了五种有机溶剂，即乙腈、丙酮、丙醛、乙醇和四氢呋喃。随着乙腈浓度从0%增加到6.0%（v/v），DPPC-MLV的主要转变温度降低，而在6.0%（v/v）以上则升高。X射线衍射数据表明，在20℃下，DPPC-MLV中从Lβ'相向LβI相（交错凝胶相）的相变发生在5.0%（v/v）时，且在乙腈浓度高于6.0%（v/v）时，DPPC-MLV完全处于LβI相。准分子法（Yamazaki, M.等人，（1992年）《生物化学与生物物理学报》1106，94 - 98）的结果支持了上述结果；DPPC-MLV中芘-PC的准分子与单体荧光强度之比（E/M）在5.1%（v/v）时迅速下降，且在乙腈浓度高于6.0%（v/v）时E/M变得非常低。通过准分子法，我们发现其他有机溶剂，如丙酮、丙醛和四氢呋喃，可诱导DPPC-MLV从Lβ'相向LβI相转变。在20℃下，丙酮､乙醇､丙醛和四氢呋喃发生这种相变的阈值浓度分别为9.4%（v/v）、5.5%（w/v）、3.5%（w/v）和3.7%（w/v）。用重水（D2O）替代H2O会增加所有有机溶剂的阈值浓度。本文提出并讨论了这些相变的机制以及用D2O替代H2O的影响；χ参数的概念，即DPPC-MLV表面片段与溶剂之间的相互作用能参数，可以合理地解释这些现象。
