Laboratory for Fluorescence Dynamics, Biomedical Engineering Department, University of California, Irvine, 3208 Natural Sciences II, Irvine, CA 92697-2715, USA.
Proc Natl Acad Sci U S A. 2012 May 8;109(19):7314-9. doi: 10.1073/pnas.1118288109. Epub 2012 Apr 23.
Cellular membranes are heterogeneous in composition, and the prevailing theory holds that the structures responsible for this heterogeneity in vivo are small structures (10-200 nm), sterol- and sphingolipid-enriched, of different sizes, highly dynamic denominated rafts. Rafts are postulated to be platforms, which by sequestering different membrane components can compartmentalize cellular processes and regulate signaling pathways. Despite an enormous effort in this area, the existence of these domains is still under debate due to the characteristics of the structures itself: small in size and highly mobile, which from the technical point of view implies using techniques with high spatial and temporal resolution. In this report we measured rapid fluctuations of the normalized ratio of the emission intensity at two wavelengths of Laurdan, a membrane fluorescent dye sensitive to local membrane packing. We observed generalized polarization fluctuations in the plasma membrane of intact rabbit erythrocytes and Chinese hamster ovary cells that can be explained by the existence of tightly packed micro-domains moving in a more fluid background phase. These structures, which display different lipid packing, have different sizes; they are found in the same cell and in the entire cell population. The small size and characteristic high lipid packing indicate that these micro-domains have properties that have been proposed for lipid rafts.
细胞膜在组成上是不均匀的，占主导地位的理论认为，体内造成这种不均匀性的结构是小结构（10-200nm），富含固醇和鞘脂，大小不同，高度动态，被称为筏。筏被假定为平台，通过隔离不同的膜成分，可以分隔细胞过程并调节信号通路。尽管在这一领域进行了巨大的努力，但由于这些结构本身的特点，这些结构的存在仍然存在争议：体积小且高度移动，这从技术角度意味着需要使用具有高空间和时间分辨率的技术。在本报告中，我们测量了膜荧光染料 Laurdan 的两个波长的发射强度归一化比值的快速波动，该染料对局部膜堆积敏感。我们观察到完整兔红细胞和中国仓鼠卵巢细胞的质膜中存在广义偏振波动，这可以用紧密堆积的微域在更流动的背景相中移动来解释。这些显示不同脂质堆积的结构具有不同的大小；它们存在于同一细胞和整个细胞群体中。这些微域的小尺寸和特征的高脂质堆积表明它们具有已被提议用于脂筏的性质。
