Santacroce Massimo, Orsini Francesco, Mari Stefania Anna, Marinone Massimo, Lenardi Cristina, Bettè Sara, Sacchi Vellea Franca, Poletti Giulio
Giovanni Esposito Institute of General Physiology and Biological Chemistry, University of Milan, Via Trentacoste 2, Milan, Italy.
Microsc Res Tech. 2008 Jun;71(6):397-402. doi: 10.1002/jemt.20559.
Atomic force microscopy (AFM) was used to investigate the native plasma membrane of Xenopus laevis (X. laevis) oocyte purified by means of ultracentrifugation on sucrose gradient and subsequently adsorbed on mica leaves through a physisorption process. Reproducible AFM topography images were collected, analyzed, and compared. AFM images showed the presence of large single or double bilayer membrane sheets covered with protein complexes. The lateral dimension and height of protein complexes imaged in air showed a normal distribution centred on 15.4 +/- 0.4 nm (mean +/- SE; n = 59) and 3.9 +/- 0.2 nm (mean +/- SE; n = 57), respectively. A density of about 270 protein complexes per square micron was calculated. Less frequently, ordered nanometer domains with densely packed protein complexes arranged in hexagonal patterns were also visualized in AFM images, confirming previously published data. Their lateral dimension and height showed a normal distribution centred on 23.0 +/- 0.4 nm (mean +/- SE; n = 42) and 1.5 +/- 0.6 nm (mean +/- SE; n = 90), respectively. A density of about 870 protein complexes per square micrometer was calculated. Advantages and drawbacks of this new sample preparation for AFM imaging are discussed.
利用原子力显微镜（AFM）对非洲爪蟾（X. laevis）卵母细胞的天然质膜进行了研究。该质膜通过蔗糖梯度超速离心法纯化，随后通过物理吸附过程吸附在云母片上。收集、分析并比较了可重复的AFM形貌图像。AFM图像显示存在覆盖有蛋白质复合物的大的单层或双层膜片。在空气中成像的蛋白质复合物的横向尺寸和高度分别呈正态分布，中心值分别为15.4±0.4 nm（平均值±标准误；n = 59）和3.9±0.2 nm（平均值±标准误；n = 57）。计算得出每平方微米约有270个蛋白质复合物的密度。在AFM图像中较少见的是，还观察到具有以六边形模式排列的密集堆积蛋白质复合物的有序纳米结构域，这证实了先前发表的数据。它们的横向尺寸和高度分别呈正态分布，中心值分别为23.0±0.4 nm（平均值±标准误；n = 42）和1.5±0.6 nm（平均值±标准误；n = 90）。计算得出每平方微米约有870个蛋白质复合物的密度。讨论了这种用于AFM成像的新样品制备方法的优缺点。
