Fisher K A, Whitfield S L, Thomson R E, Yanagimoto K C, Gustafsson M G, Clarke J
Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0130.
Biochim Biophys Acta. 1990 Apr 30;1023(3):325-34. doi: 10.1016/0005-2736(90)90123-6.
We investigated the feasibility of using the scanning tunneling microscope (STM) as a morphometric tool to measure the thickness of biomembranes. Planar monolayers of oriented purple membrane (PM) were prepared, nitrogen-dried or freeze-etched, and coated with metal. PM thickness was quantified by STM and transmission electron microscopy. STM calibration and the effect of contamination-mediated surface deformation on measurements of PM thickness were evaluated. The thickness of PM attached to mica and glass and the effect of papain on PM thickness were also examined. The apparent thickness of enzymatically modified PM increased after papain treatment. The mean thickness of both nitrogen-dried PM on mica and freeze-etched PM on glass was 4.6 nm. After papain treatment PM thickness on mica increased to 4.8 nm and on glass to 5.4 nm. These results demonstrate that STM analysis of metal-coated planar membrane monolayers can be used to measure changes in average membrane thickness at sub-nanometer resolution.
我们研究了使用扫描隧道显微镜（STM）作为形态测量工具来测量生物膜厚度的可行性。制备了取向紫膜（PM）的平面单层，进行氮干燥或冷冻蚀刻，然后镀上金属。通过STM和透射电子显微镜对PM厚度进行量化。评估了STM校准以及污染介导的表面变形对PM厚度测量的影响。还研究了附着在云母和玻璃上的PM的厚度以及木瓜蛋白酶对PM厚度的影响。木瓜蛋白酶处理后，经酶修饰的PM的表观厚度增加。云母上氮干燥的PM和玻璃上冷冻蚀刻的PM的平均厚度均为4.6纳米。木瓜蛋白酶处理后，云母上的PM厚度增加到4.8纳米，玻璃上的增加到5.4纳米。这些结果表明，对镀金属的平面膜单层进行STM分析可用于在亚纳米分辨率下测量平均膜厚度的变化。
