PHASE-EQUILIBRIA OF MEMBRANE-LIPIDS FROM ACHOLEPLASMA-LAIDLAWII - IMPORTANCE OF A SINGLE LIPID FORMING NONLAMELLAR PHASES
PHASE-EQUILIBRIA OF MEMBRANE-LIPIDS FROM ACHOLEPLASMA-LAIDLAWII - IMPORTANCE OF A SINGLE LIPID FORMING NONLAMELLAR PHASES
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DOI：
10.1021/bi00371a037
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发表时间：
1986-11-18
期刊：
影响因子：
2.9
通讯作者：
WIESLANDER, A
中科院分区：
文献类型：
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作者：
LINDBLOM, G;BRENTEL, I;WIESLANDER, A
生物膜中双层结构重组的基础是水中脂质形成的不同聚集体结构。用不同的核磁共振技术研究了来自酰基链修饰的拉氏无胆甾原体膜的所有单个脂质和几种体内极性脂质混合物的相平衡。除了单葡糖基甘油二酯（MGDG）之外，所有二油酰基（DO）极性脂质都形成层状液晶（L α）。阶段而已。DOMGDG的相图揭示了反立方（III）、反六边形（HII）和L α。阶段。在DOMGDG和二油酰二葡萄糖基二甘油酯（DODGDG）的混合物中，DOMGDG和低水合或高温增强了III（或HII）相的形成。对于所有极性DO脂质的体内混合物，L α的转变。通过低水合作用或高温（50 ℃）促进III相的形成。C）。磷脂被纳入该III阶段。同样地，III和HII相在类似的温度下在具有不同程度的酰基链不饱和度的一系列体内混合物中形成。然而，它们的解链温度（Tm）以预期的方式变化。所有的立方相和六方相，除了III相与DOMGDG，存在于与过量的水平衡。MGDG和DGDG的最大水合作用是相似的，并且随着酰基链不饱和度的增加而增加，但基本上低于例如，卵磷脂在立方相中的脂质的平移扩散是快速的，这意味着双连续结构。然而，它们在冷冻断裂电镜照片中的外观是不同的。DOMGDG的III相属于Ia3d空间群。结果表明，A. Laidlawii脂质的浓度严重依赖于MGDG浓度。
A basis of the reorganization of the bilayer structure in biological membranes is the different aggregate structures formed by lipids in water. The phase equilibria of all individual lipids and several in vivo polar lipid mixtures from acyl chain modified membranes of Acholeplasma laidlawii were investigated with different NMR techniques. All dioleoyl (DO) polar lipids, except monoglucosyldiglyceride (MGDG), form lamellar liquid crystalline (L.alpha.) phases only. The phase diagram of DOMGDG reveals reversed cubic (III), reversed hexagon (HII), and L.alpha. phases. In mixtures of DOMGDG and dioleoyldiglucosyldiglyceride (DODGDG), the formation of an III (or HII) phase is enhanced by DOMGDG and low hydration or high temperatures. For in vivo mixtures of all polar DO lipids, a transition for an L.alpha. to an III phase is promoted by low hydration or high temperaturs (50.degree. C). The phospholipids are incorporated in this III phase. Likewise, III and HII phases are formed at similar temperatures in a series of in vivo mixtures with different extents of acyl chain unsaturation. However, their melting temperatures (Tm) vary in an expected manner. All cubic and hexagonal phases, except the III phase with DOMGDG, exist in equilibrium with excess water. The maximum hydration of MGDG and DGDG is similar and increases with acyl chain unsaturation but is substantially lower than that for, e.g., phosphatidylcholine. The translational diffusion of the lipids in the cubic phases is rapid, implying bicontinuous structures. However, their appearances in freeze-fracture electron microscope pictures are different. The III phase of DOMGDG belongs to the Ia3d space group. It is concluded that the formation of nonlamellar phases by A. laidlawii lipids depends critically upon the MGDG concentration.