Dynamic force microscopy for imaging of viruses under physiological conditions

Abstract

Dynamic force microscopy (DFM) allows imaging of the structure and the assessment of the function of biological specimens in their physiological environment. In DFM, the cantilever is oscillated at a given frequency and touches the sample only at the end of its downward movement. Accordingly, the problem of lateral forces displacing or even destroying bio-molecules is virtually inexistent as the contact time and friction forces are reduced. Here, we describe the use of DFM in studies of human rhinovirus serotype 2 (HRV2) weakly adhering to mica surfaces. The capsid of HRV2 was reproducibly imaged without any displacement of the virus. Release of the genomic RNA from the virions was initiated by exposure to low pH buffer and snapshots of the extrusion process were obtained. In the following, the technical details of previous DFM investigations of HRV2 are summarized.

Scanning Force Microscopy as Applied to Conformational Studies in Macromolecular Research

“…[86] Yet, SFM allows one to trace the course of dynamic process of RNA macromolecules release and removal from viral capsid directly in real time regime in situ. [87,88] Such experiments have been performed recently with adsorbed viral particles exposed to aqueous buffer solutions of different pH. [87,88] Observations of Dynamic Processes in Real Time Regime…”

“…[87,88] Such experiments have been performed recently with adsorbed viral particles exposed to aqueous buffer solutions of different pH. [87,88] Observations of Dynamic Processes in Real Time Regime…”

Imaging morphological details and pathological differences of red blood cells using tapping-mode AFM

“…In contrast to contact-mode AFM, where the tip mechanically contacts the sample permanently while it scans over the surface (Mueller et al, 1995), in DFM the cantilever touches the sample only at the end of its downward movement. Thus, the advantage of DFM is that lateral friction forces during imaging are significantly reduced, thereby minimizing sample damage by the scanning cantilever (Kienberger et al, 2004). Imaging of biological specimens has therefore significantly benefited from the development of DFM, since soft samples are less deformed and specimens weakly adhered to surfaces are not so easily displaced by the scanning cantilever (Kienberger et al, 2003).…”

Material Properties of Viral Nanocages Explored by Atomic Force Microscopy

“…In AFM, one of the most commonly used surfaces to immobilize particles is mica which also has been used successfully to immobilize viral particles [32]. Muscovite mica, an often used type of mica, constitutes of layers of (Si,Al) 2 O 5 ionically bound to a central layer of Al 2 (OH) 2 .…”