Legleiter Justin, DeMattos Ronald B, Holtzman David M, Kowalewski Tomasz
Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA.
J Colloid Interface Sci. 2004 Oct 1;278(1):96-106. doi: 10.1016/j.jcis.2004.05.009.
The three-dimensional shapes and sizes of plasma lipoproteins and astrocyte-secreted lipoproteins (ASLPs) were characterized with the aid of in situ atomic force microscopy (AFM), which has the unique ability to study three-dimensional nanostructures under physiological conditions. Apolipoprotein E (apoE) and apolipoprotein J (apoJ) are the two most abundant apolipoproteins produced in the central nervous system (CNS). This study revealed that ASLPs containing apoE3, apoE4, or apoJ significantly differ from high density lipoprotein particles, thought to be their closest analogs in plasma, in aggregation properties, size, and shape. ASLPs were found to be significantly flatter and smaller than their plasma counterparts. Plasma lipoproteins were able to form ordered arrays on a mica surface at high concentration, but ASLPs did not. Rather, they formed amorphous aggregates at similar concentrations. Comprehensive quantitative characterization of particle size and shape was facilitated by two advances in AFM image analysis: (1) automated analysis through image-recognition algorithms, and (2) correction for the finite size of the AFM probe based on geometric modeling. This study and the developed AFM methodologies open the way to further in situ AFM studies of the lipoproteins in general and more specifically of CNS lipoproteins.
借助原位原子力显微镜（AFM）对血浆脂蛋白和星形胶质细胞分泌的脂蛋白（ASLP）的三维形状和大小进行了表征，AFM具有在生理条件下研究三维纳米结构的独特能力。载脂蛋白E（apoE）和载脂蛋白J（apoJ）是中枢神经系统（CNS）中产生的两种最丰富的载脂蛋白。这项研究表明，含有apoE3、apoE4或apoJ的ASLP在聚集特性、大小和形状上与高密度脂蛋白颗粒（被认为是其在血浆中最相似的类似物）有显著差异。发现ASLP比其血浆对应物明显更扁平、更小。血浆脂蛋白在高浓度下能够在云母表面形成有序阵列，但ASLP不能。相反，它们在相似浓度下形成无定形聚集体。AFM图像分析的两项进展有助于对颗粒大小和形状进行全面定量表征：（1）通过图像识别算法进行自动分析，以及（2）基于几何建模对AFM探针的有限尺寸进行校正。这项研究以及所开发的AFM方法为进一步原位AFM研究一般脂蛋白，更具体地说是中枢神经系统脂蛋白开辟了道路。
