One of the most important effects of water on earth is that surfaces in air adsorb small amounts of water, usually in the form of a thin film. Real surfaces, especially the rather soft biomolecular surfaces, are covered by highly curved micro-and nanostructures, which induce more complex wetting geometries, such as films, droplets, and filaments. This effect, though ubiquitous, has not yet been investigated on the nanoscale. We have approached the situation by combining a soft proteinous surface, made up from very resilient tubular plant viruses, with ionic liquids. Their low vapor pressure allowed us to observe nanoscale wetting patterns at very high spatial resolution with AFM (atomic force microscopy), SEM (scanning electron microscopy) and STEM (scanning transmission electron microscopy). We found droplets, filaments and layers, with meniscus diameters down to below 10 nm. All geometries are comparable with results obtained on the microscale, and with standard macroscale wetting models.

Metals and polymers are probably the most important construction materials, but also have many more functions, e.g., for electronics. The interaction of metal ions with tobacco mosaic virus (TMV) was originally used for the preparation of heavy metal isomorphic replacement for structural analysis. Metal ions can also be the precursors for metal clusters, particles, and layers. Various strategies have been developed, which allow the creation of metal layers on the external surface of TMV. Such layers can be made as metal tubes, enveloping a complete virion. An alternative strategy is adsorption of metal nanoparticles. If a dense coating of TMV is achieved, again a tube results. Nanoscale tubes have various physical properties that depend on size, crystallinity, uniformity, but especially on the nature of the metal. Polymer coatings are as yet rarely investigated, though they can be prepared quite easily.Here, a series of exemplary protocols is provided, which covers all of these different concepts.

Some of the best nucleating agents in nature are ice-nucleating proteins, which boost ice growth better than any other material. They can induce immersion freezing of supercooled water only a few degrees below 0 °C. An open question is whether this ability also extends to the deposition mode, i.e., to water vapor. In this work, we used three proteins, apoferritin, InaZ (ice nucleation active protein Z), and myoglobin, of which the first two are classified as ice-nucleating proteins for the immersion freezing mode. We studied the ice nucleation ability of these proteins by differential scanning calorimetry (immersion freezing) and by environmental scanning electron microscopy (deposition freezing). Our data show that InaZ crystallizes water directly from the vapor phase, while apoferritin first condenses water in the supercooled state, and subsequently crystallizes it, just as myoglobin, which is unable to nucleate ice.

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