Atomic Force Microscopy: High Resolution Imaging and Force Spectroscopy in Biology

Authors

• EK Dimitriadis

Abstract

Atomic force microscopy (AFM) is a non-optical microscopy that employs a physically sharp (nm) probe (tip) to trace topographical features at sub-nm resolution. The probe can also be used to apply and/or measure forces with sensitivity of a few pN. A major advantage, compared to other high-resolution imaging (e.g., EM), of AFM is that with minimal sample preparation and without the need for special staining, biological samples can be examined in ambient and under physiological buffer conditions. Furthermore, force spectroscopy can be used to map material properties at the nanoscale, to observe antigen-antibody binding events and to study protein folding and unfolding under the forces applied by the tip. AFM can also be combined with optical techniques, such as fluorescence (e.g. TIRFM and confocal) or Raman spectroscopy, for co-localized observations. We present a few typical applications of the technology including high resolution imaging of protein and protein-DNA complexes (e.g. complexes of HIV Tat protein and amyloid-β peptide or HIV-Integrase/DNA stable synaptic complex (SSC)), co-localized AFM with fluorescence (e.g. shedding of microdomains by cholesterol-enriched macrophages), and force spectroscopy to map elastic properties at high resolution (e.g. cartilage). The facility operates four instruments each designed with certain applications in mind. Two are equipped with micro-incubators for live cell/tissue experiments and with fluorescence capabilities (epi-, TIRF, confocal) that allow simultaneous registration of AFM and fluorescence images for high resolution chemical identification. The AFM facility is open to a wide range of collaborative projects.

Scientific Focus Area: Biomedical Engineering and Biophysics

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