engleski

Collapsing elastic shells: viruses, pollen grains, footballs and bathyscaphes

Spherical shells are ubiquitous – think e.g. of balloons, balls, Christmas tree decorations, pressure vessels for gas storage, Citroën suspension spheres, chocolate pralines, coconuts... On a micrometer scale, pollen grains are, often spherical, shells containing sensitive interior, vegetative and generative cells, whose preservation is essential for fertilization. Viruses are thousand times smaller, but can again be thought of as spherical, geodesic-dome like structures assembled from identical proteins, which contain and protect the DNA or RNA molecule in their interiors. Biological spherical shells often need to function on a border of stability, i.e. need to be sufficiently strong to protect their interior, yet sufficiently labile to activate and release the interior once they reach a suitable environment. In case of viruses this happens once they enter the cell, and in case of pollen grains once they land on a stigma of a flowering plant. In order to function properly these shells need to conform to specific mechanical requirements. These include the resistance of shells to the pressure from the inside, as is the case in case of bacteriophage which densely pack their DNA pushing against the virus protein coating, but also to the pressure from the outside, as is the case in pollen grains which crumple and deform upon desiccation. A classical theory of shell elasticity can be profitably applied to such systems, as will be shown.

pollen, pressure, elasticity, aperture, collapse, desiccation, harmomegathy

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