Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
J Phys Chem B. 2011 Dec 22;115(50):14963-8. doi: 10.1021/jp205881f. Epub 2011 Nov 29.
To clarify the influence of cis and trans double bonds on conformational disordering of unsaturated hydrocarbon-chain of lipids in bilayer formed in the binary system with water, calorimetric study was conducted for systems of unsaturated monoacylglycerols; monoolein (MO), monovaccenin (MV), and monoelaidin (ME). Heat capacities of the binary systems were measured by adiabatic calorimetry. The observed entropies of transition (Δ(trs)S) from lamellar phase (L(α)) to fluid isotropic (FI) phase are very small and depend on lipids: Δ(trs)S of MO/water, MV/water, and ME/water were ca. 0.8 J K(-1) (mol of lipid) (-1), ca. 0.9 J K(-1) (mol of lipid) (-1), and ca. 0.4 J K(-1) (mol of lipid) (-1), respectively. These show that the conformational disordering of the hydrocarbon chain over gauche and trans conformations is suppresed in L(α) phase. Through the comparison of Δ(trs)S among the binary systems, the suppresed conformational disordering of hydrocarbon chain in the bilayer is discussed.
为了阐明顺式和反式双键对水形成的双层中非饱和烃链构象无序的影响，对不饱和单酰基甘油体系进行了量热研究；单油酸甘油酯（MO）、单葵酸甘油酯（MV）和单亚油酸甘油酯（ME）。通过绝热量热法测量二元体系的热容。从层状相（L（α））到各向同性流体相（FI）的转变熵（Δ（trs）S）非常小，且取决于脂质：MO/水、MV/水和 ME/水的 Δ（trs）S 分别约为 0.8 J K（-1）（摩尔脂质）（-1）、约 0.9 J K（-1）（摩尔脂质）（-1）和约 0.4 J K（-1）（摩尔脂质）（-1）。这表明在 L（α）相中，烃链的构象无序性受到 gauche 和 trans 构象的抑制。通过比较二元体系中的Δ（trs）S，讨论了双层中非饱和烃链的抑制构象无序性。
