Stubbs C D, Williams B W, Boni L T, Hoek J B, Taraschi T F, Rubin E
Department of Pathology and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107.
Biochim Biophys Acta. 1989 Nov 17;986(1):89-96. doi: 10.1016/0005-2736(89)90276-9.
The change in the fluorescence properties of dioleoyl-N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)phosphatidylethanola mine (N-NBD-PE) as an indicator of the (liquid-crystalline) bilayer-to-non-bilayer hexagonalII (HII) phase transition has been investigated. Lipid bilayer systems which are known to undergo the bilayer-to-HII phase transition on addition of Ca2+ were compared with systems which can undergo aggregation and fusion but not HII phase formation. The former included Ca2+-triggered non-bilayer transitions in cardiolipin and in phosphatidylethanolamine mixed with phosphatidylserine. The latter type of system investigated included the addition of polylysine to cardiolipin and Ca2+ to phosphatidylserine. Freeze-fracture electron microscopy was used to confirm that under the experimental conditions used, the formation of HII phase was occurring in the first type of system, but not in the second, which was stable in the bilayer state. It was found that the fluorescence intensity of N-NBD-PE (at 1 mol% of the phospholipids) increased in both types of system, irrespective of the formation of the HII phase. A dehydration at the phospholipid head group is a common feature of the formation of the HII phase, the interaction of divalent cations with phosphatidylserine and the interaction of polylysine with lipid bilayers, suggesting that this may be the feature which affects the fluorescence properties of the NBD. The finding of a fluorescence intensity increase in systems lacking HII phase involvement clearly indicates that the effect is not unique to the formation of the HII phase. Thus, while offering high sensitivity and the opportunity to follow kinetics of lipid structural changes, changes in the N-NBD-PE fluorescence properties should be interpreted with caution in the study of the bilayer-to-HII phase transition.
研究了二油酰 - N -（7 - 硝基苯并 - 2 - 恶唑 - 1,3 - 二氮杂萘 - 4 - 基）磷脂酰乙醇胺（N - NBD - PE）荧光性质的变化，以此作为（液晶态）双层到非双层六方II（HII）相转变的指标。将已知在添加Ca2+时会发生双层到HII相转变的脂质双层系统，与能够发生聚集和融合但不会形成HII相的系统进行了比较。前者包括心磷脂以及与磷脂酰丝氨酸混合的磷脂酰乙醇胺中由Ca2+触发的非双层转变。研究的后一种系统类型包括向心磷脂中添加聚赖氨酸以及向磷脂酰丝氨酸中添加Ca2+。冷冻断裂电子显微镜用于确认在所使用的实验条件下，第一种系统类型中发生了HII相的形成，而第二种系统中未发生，第二种系统在双层状态下是稳定的。结果发现，无论HII相是否形成，两种系统类型中N - NBD - PE（占磷脂的1 mol%）的荧光强度均增加。磷脂头部基团的脱水是HII相形成、二价阳离子与磷脂酰丝氨酸的相互作用以及聚赖氨酸与脂质双层相互作用的共同特征，这表明这可能是影响NBD荧光性质的特征。在未涉及HII相形成的系统中发现荧光强度增加，清楚地表明这种效应并非HII相形成所特有。因此，虽然N - NBD - PE荧光性质的变化在研究双层到HII相转变时提供了高灵敏度以及追踪脂质结构变化动力学的机会，但在解释时应谨慎。
