Mendelsohn R, Dluhy R, Curatolo W, Sears B
Chem Phys Lipids. 1982 Jun;30(4):287-95. doi: 10.1016/0009-3084(82)90023-8.
Deuterium magnetic resonance (2H-NMR) and Raman spectroscopy are used to investigate order and fluidity at the terminal methyl position in 16-d3, 16'-d3 dipalmitoylphosphatidyl-choline (16-d6 DPPC) multibilayers. These methods reveal substantial motion and disorder in the gel phase, 5-10 degree C below the gel-liquid crystal phase transition temperature (Tm). The phase transition is sensed in the 2H-NMR spectrum as a reduction in the quadrupole splitting from 14 kHz to approximately 3 kHz. In contrast, the Raman parameter used to characterize the CD3 vibrations is quite insensitive to the melting process, although an analagous parameter does sense disordering at Tm at the 10 and 10' position in 10-d2, 10'-d2 DPPC. The difference in the response of the NMR and Raman parameters may arise because the vibrational spectrum of the CD3 group is inhomogeneously broadened and is therefore quite sensitive to alterations in the local environment around the methyl group. In contrast, the NMR quadrupole splitting is sensitive to both local motion of the methyl group and, near Tm, to motions of the CD2 group induced by transgauche isomerizations further up the chain. The difficulties that arise when results from different spectroscopic techniques are compared are demonstrated.
氘磁共振（2H-NMR）和拉曼光谱被用于研究16-d3、16'-d3二棕榈酰磷脂酰胆碱（16-d6 DPPC）多层膜中末端甲基位置的有序性和流动性。这些方法揭示了在低于凝胶-液晶相转变温度（Tm）5-10摄氏度的凝胶相中存在大量的运动和无序。在2H-NMR谱中，相变表现为四极分裂从14千赫兹降低到约3千赫兹。相比之下，用于表征CD3振动的拉曼参数对熔化过程相当不敏感，尽管类似的参数在10-d2、10'-d2 DPPC的10和10'位置确实能检测到在Tm时的无序。NMR和拉曼参数响应的差异可能是因为CD3基团的振动光谱不均匀展宽，因此对甲基周围局部环境的变化非常敏感。相比之下，NMR四极分裂对甲基的局部运动以及在接近Tm时对链上更远位置的反式-顺式异构化引起的CD2基团的运动都很敏感。展示了比较不同光谱技术结果时出现的困难。
