Laurdan in fluid bilayers: Position and structural sensitivity
Laurdan in fluid bilayers: Position and structural sensitivity
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DOI：
10.1007/s10895-005-0059-3
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发表时间：
2006-05-01
影响因子：
2.7
通讯作者：
Lamy, M. Teresa
中科院分区：
文献类型：
--
作者：
De Vequi-Suplicy, Cintia C.;Benatti, Carlos R.;Lamy, M. Teresa
Laurdan（2-二甲氨基-6-月桂酰萘）是一种广泛用于脂质系统的疏水性荧光探针。该探针被证明对脂相高度敏感，并且这种敏感性与探针微环境的极性和粘度有关。在本研究中，Laurdan 被纳入 1,2-二棕榈酰-sn-甘油-3-[磷酸-rac-(1-甘油)] (DPPG) 和 DLPC (1,2-二月桂酰-sn-甘油-3-磷酸胆碱) 中，前者在 41 摄氏度左右发生相变，后者在所有研究温度下均处于流体相。通过分解成两个高斯带（短波长带和长波长带，分别对应于非弛豫激发态和水弛豫激发态）来分析劳丹荧光发射的温度依赖性。正如预期的那样，Laurdan 荧光对 DPPG 凝胶-流体转变高度敏感。然而，研究表明，尽管双层相不发生变化，但 DLPC 中的劳丹荧光也取决于温度。这与类似亲水性探针 Prodan（2-二甲氨基-6-丙酰萘）在相同温度范围内游离于水溶液中时获得的相当相似的荧光发射形成对比。因此，劳丹荧光似乎高度依赖于脂质双层堆积，即使对于流体膜也是如此。 Laurdan 荧光各向异性和在 DLPC 流体脂质双层中不同位置掺入的自旋标记支持了这一点。后者既用作双层堆积的结构探针，又用作劳丹荧光猝灭剂。结果证实了 Laurdan 荧光发射对膜填充的高灵敏度，并表明 Laurdan 在膜中的位置相当浅。
Laurdan (2-dimethylamino-6-lauroylnaphthalene) is a hydrophobic fluorescent probe widely used in lipid systems. This probe was shown to be highly sensitive to lipid phases, and this sensitivity related to the probe microenvironment polarity and viscosity. In the present study, Laurdan was incorporated in 1,2-dipalmitoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DPPG), which has a phase transition around 41 degrees C, and DLPC (1,2-dilauroyl-sn-glycero-3-phosphocholine), which is in the fluid phase at all temperatures studied. The temperature dependence of Laurdan fluorescent emission was analyzed via the decomposition into two gaussian bands, a short- and a long-wavelength band, corresponding to a non-relaxed and a water-relaxed excited state, respectively. As expected, Laurdan fluorescence is highly sensitive to DPPG gel-fluid transition. However, it is shown that Laurdan fluorescence, in DLPC, is also dependent on the temperature, though the bilayer phase does not change. This is in contrast to the rather similar fluorescent emission obtained for the analogous hydrophilic probe, Prodan (2-dimethylamino-6-propionylnaphthalene), when free in aqueous solution, over the same range of temperature. Therefore, Laurdan fluorescence seems to be highly dependent on the lipid bilayer packing, even for fluid membranes. This is supported by Laurdan fluorescence anisotropy and spin labels incorporated at different positions in the fluid lipid bilayer of DLPC. The latter were used both as structural probes for bilayer packing, and as Laurdan fluorescence quenchers. The results confirm the high sensitivity of Laurdan fluorescence emission to membrane packing, and indicate a rather shallow position for Laurdan in the membrane.