Diene-Containing Lipids as Probes for Phase-Transition Behavior of Lipids in Liposomes
作者:Shinji Takeoka、Hidetaka Iwai、Hiroyuki Ohno、Eishun Tsuchida
DOI:10.1246/bcsj.62.102
日期:1989.1
The absorption maximum (λmax) of 1,2-bis(2,4-octadecadienoyl)-sn-glycero-3-phosphorylcholine (DODPC), dispersed in an aqueous medium as liposomes, showed blue shift from 256.8 nm to 241.8 nm when these liposomes were cooled down from liquid crystalline state to gel state. The blue shift is explained to be due to stronger interaction between diene groups at gel state. This diene-containing lipid is examined to be an excellent membrane probe because it is typical phospholipid and miscible with several lipids. Furthermore, the dienoyl groups are known to be settled in the definite positions in bilayer membrane by suitable chemical modification. Phase transition behaviors of various 2,4-octadecadienoyl-containing phosphorylcholines as analogs for DODPC have also been investigated. Although they had similar spectral shifts at gel-to-liquid crystalline phase-transition temperature, their phase-transition temperatures and magnitude of λmax shifts were revealed to be related directly and therefore be governed by the different packing of the diene groups in bilayer membrane. DODPC was mixed with 1,2-dipalmitoyl-sn-glycero-3-phosphorylcholine, or cholesterol, and phase behaviors of these mixed liposomes were also examined. Phase-transition of the mixed liposomes was detected easily by the shift of its λmax with high sensitivity. Results were quite comparable to those obtained from other measurements, such as DSC, NMR, and so on.
1,2-bis(2,4-octadecadienoyl)-sn-glycero-3-phosphorylcholine (DODPC)在水相介质中以脂质体形式分散,其吸收最大值(λmax)从256.8 nm蓝移到241.8 nm,当这些脂质体从液晶态冷却到胶态时。蓝移被解释为由于在胶态下二烯基之间的相互作用增强。该含二烯基的脂质被认为是优秀的膜探针,因为它是一种典型的磷脂,并且可以与多种脂质混溶。此外,已知二烯酰基通过适当的化学修饰固定在双层膜的特定位置。各种含2,4-十八烯酸的磷酰胆碱作为DODPC的类似物的相变行为也进行了研究。尽管它们在胶态到液晶态相变温度时具有相似的光谱位移,但它们的相变温度和λmax位移的幅度被证明与双层膜中二烯基的不同排列直接相关。因此,DODPC与1,2-二棕榈酰-sn-甘油-3-磷酸胆碱或胆固醇混合,这些混合脂质体的相行为也得到了研究。混合脂质体的相变通过其λmax的位移被高灵敏度地检测到。结果与通过其他测量方法(如DSC、NMR等)获得的结果相当。