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%.
Highlights
Environmental moisture is a key factor that influences the biological activity of different families of viruses, and, the spread and the transmission of many virus-mediated infectious diseases
We study the wetting of individual adsorbed Tobacco Mosaic Virions (TMV) at varying relative humidities by atomic force microscopy (AFM)
In our experiments on Tobacco Mosaic virions (TMV) samples performed at high relative humidity (RH), we found a strong contrast between regions containing extended water droplets and the remaining part of the surface whenever we recorded the second excited mode during multifrequency experiments [21,22]
Summary
Environmental moisture is a key factor that influences the biological activity of different families of viruses, and, the spread and the transmission of many virus-mediated infectious diseases. Much work has been focused on this correlation for the case of human viruses. Biological assays correlated the seasonality and infectivity of human Influenza A and Norovirus with the total amount of water vapor present in the air, i.e., with the absolute humidity [1,2,3,4]. The mechanisms through which environmental water vapor affects the spreading of human viruses have not been determined unequivocally; they can be expected to depend on the virus structure at the molecular level [6]. Yang and coworkers proposed that variations in RH modify the pH of aerosols made up of micrometer-sized droplets containing hydrated virus particles and trigger conformational changes in glycoproteins at the surface of enveloped viruses that affect infectivity [7]
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