Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada A1B 3X7.
Langmuir. 2010 Jul 20;26(14):12104-11. doi: 10.1021/la1014362.
Variable-pressure deuterium nuclear magnetic resonance ((2)H NMR) has been used to study the pressure-temperature phase diagram of bicellar mixtures containing 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC). Spectra were obtained for DMPC-d(54)/DHPC (3:1), DMPC-d(54)/DHPC (4.4:1), DMPC/DHPC-d(22) (3:1), and DMPC/DHPC-d(22) (4.4:1) in the range 10-68 degrees C at ambient pressure, 66 MPa, 102 MPa, and 135 MPa. Isotropic-to-nematic and nematic-to-lamellar transition temperatures were found to rise with pressure at approximately 0.15 and approximately 0.14 degrees C/MPa, respectively, for DMPC-d(54)/DHPC (3:1) and at at approximately 0.19 and approximately 0.18 degrees C/MPa, respectively, for DMPC-d(54)/DHPC (4.4:1). Pressure had little effect on the range of DMPC-d(54) chain orientational order through the nematic phase temperature range, but the behavior of chain orientational order at the nematic-to-lamellar transition was found to vary slightly with pressure. Comparison of differential scanning calorimetry (DSC) observations with ambient-pressure (2)H NMR observations of DMPC-d(54) in the bicellar mixtures suggests that absorption of heat persists for a few degrees above the onset of axially symmetric DMPC-d(54) reorientation.
变压氘核磁共振((2)H NMR)已被用于研究含有 1,2-二肉豆蔻酰-sn-甘油-3-磷酸胆碱(DMPC)和 1,2-二己酰基-sn-甘油-3-磷酸胆碱(DHPC)的双分子层混合物的压力-温度相图。在环境压力、66 MPa、102 MPa 和 135 MPa 下，在 10-68°C 的范围内获得了 DMPC-d(54)/DHPC(3:1)、DMPC-d(54)/DHPC(4.4:1)、DMPC/DHPC-d(22)(3:1)和 DMPC/DHPC-d(22)(4.4:1)的光谱。对于 DMPC-d(54)/DHPC(3:1)，各向同性-向列相和向列-层状相转变温度分别约以 0.15 和 0.14°C/MPa 的速率随压力升高，对于 DMPC-d(54)/DHPC(4.4:1)，各向同性-向列相和向列-层状相转变温度分别约以 0.19 和 0.18°C/MPa 的速率随压力升高。压力对 DMPC-d(54)链取向有序性在向列相温度范围内的范围影响不大，但在向列-层状相转变处链取向有序性的行为随压力略有变化。比较差示扫描量热法(DSC)观察与双分子层混合物中 DMPC-d(54)的环境压力((2)H NMR)观察表明，轴向对称 DMPC-d(54)重取向开始后，吸收热量会持续几度。
