In the version of this technique applied to cellular imaging, a needle with a sharp tip (radius of curvature 10-50 nm) is scanned over the cell surface at a pressing force on the order of 0.1 to 10 pN, and the height of the needle is recorded at each position, thus generating a topographic image of the soft cell surface. The major advantage of AFM as compared to other microscopic techniques is that it provides a better resolution than optical microscopy and yet allows the observation of living cells, which is impossible with electron microscopy. In order to study the cell-surface distribution of specific membrane proteins by AFM, immunogold labeling was applied to provide specificity. This approach was successfully applied to study distinct hierarchical levels of the cell surface distribution of class I and class II MHC molecules in immunocompetent cells [59,60].
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.