Nanoscale Wetting of Single Viruses

Abstract

The epidemic spread of many viral infections is mediated by the environmental conditions and influenced by the ambient humidity. Single virus particles have been mainly visualized by atomic force microscopy (AFM) in liquid conditions, where the effect of the relative humidity on virus topography and surface cannot be systematically assessed. In this work, we employed multi-frequency AFM, simultaneously with standard topography imaging, to study the nanoscale wetting of individual Tobacco Mosaic virions (TMV) from ambient relative humidity to water condensation (RH > 100%). We recorded amplitude and phase vs. distance curves (APD curves) on top of single virions at various RH and converted them into force vs. distance curves. The high sensitivity of multifrequency AFM to visualize condensed water and sub-micrometer droplets, filling gaps between individual TMV particles at RH > 100%, is demonstrated. Dynamic force spectroscopy allows detecting a thin water layer of thickness ⁓1 nm, adsorbed on the outer surface of single TMV particles at RH < 60%.

Structural Insights into Plant Viruses Revealed by Small-Angle X-ray Scattering and Atomic Force Microscopy

“…A variation in the intermittent contact mode is multi-frequency AFM, in which the cantilever is oscillated at several frequencies simultaneously and the amplitude and phase images at these frequencies are analyzed separately. AFM images acquired at higher frequencies and lower amplitudes tend to better distinguish surface regions with different properties, thus providing more morphological detail on the surface of the virion ( Figure 5 ) [ 72 , 73 ].…”

“…A variation in the intermittent contact mode is multi-frequency AFM, in which the cantilever is oscillated at several frequencies simultaneously and the amplitude and phase images at these frequencies are analyzed separately. AFM images acquired at higher frequencies and lower amplitudes tend to better distinguish surface regions with different properties, thus providing more morphological detail on the surface of the virion (Figure 5) [72,73]. A variation in the intermittent contact mode is multi-frequency AFM, in which the cantilever is oscillated at several frequencies simultaneously and the amplitude and phase images at these frequencies are analyzed separately.…”

Modelling Virus Contact Mechanics under Atomic Force Imaging Conditions

“…Atomic force microscopy (AFM) is currently the only method capable of imaging small virus morphology in real-time under environmental conditions, with a spatial resolution routinely reaching 3-5 nm [22,3,6,43,5]. The study of single virus particles by atomic force microscopy and force spectroscopy has led to insights in virus mechanics and its relationship with the virus structure and the chemical environment [24,7,26,35,20,17,44].…”