Laboratory for Fluorescence Dynamics, University of California at Irvine, Irvine, CA, USA.
J Membr Biol. 2011 May;241(1):1-10. doi: 10.1007/s00232-011-9348-8. Epub 2011 Apr 6.
Methyl-β-cyclodextrins (MβCDs) are molecules that are extensively used to remove and to load cholesterol (Chol) from artificial and natural membranes; however, the mechanism of Chol extraction by MβCD from pure lipids or from complex mixtures is not fully understood. One of the outstanding questions in this field is the capability of MβCD to remove Chol from lipid domains having different packing. Here, we investigated the specificity of MβCD to remove Chol from coexisting macrodomains with different lipid packing. We used giant unilamellar vesicles (GUVs) made of 1,2-dioleoylphosphatidylcholine:1,2-dipalmitoylphatidylcholine:free cholesterol, 1:1:1 molar ratio at 27°C. Under these conditions, individual GUVs present Chol distributed into lo and ld phases. The two phases can be distinguished and visualized using Laurdan generalized polarization and two-photon excitation fluorescence microscopy. Our data indicate that MβCD removes Chol preferentially from the more disordered phase. The process of selective Chol removal is dependent on the MβCD concentration. At high concentrations, MβCD also removes phospholipids.
甲基-β-环糊精(MβCD)是一种广泛用于从人工和天然膜中去除和加载胆固醇(Chol)的分子;然而,MβCD 从纯脂质或复杂混合物中提取 Chol 的机制尚未完全理解。该领域的一个突出问题是 MβCD 从具有不同堆积的脂质域中去除 Chol 的能力。在这里,我们研究了 MβCD 从具有不同脂质堆积的共存大分子中去除 Chol 的特异性。我们使用了由 1,2-二油酰基-sn-甘油-3-磷酸胆碱:1,2-二月桂酰基-sn-甘油-3-磷酸胆碱:游离胆固醇,摩尔比为 1:1:1 在 27°C 下制成的巨大单层囊泡(GUVs)。在这些条件下,单个 GUVs 呈现出分布在 lo 和 ld 相中的 Chol。可以使用 Laurdan 广义极化和双光子激发荧光显微镜来区分和可视化这两个相。我们的数据表明,MβCD 优先从更无序的相中去除 Chol。选择性 Chol 去除的过程取决于 MβCD 的浓度。在高浓度下,MβCD 也会去除磷脂。