Coronavirus Pleomorphism

The coronavirus is always idealized as a spherical capsid with radially protruding

spikes. However, histologically, in the tissues of infected patients, capsids in cross section

are elliptical, and only sometimes spherical [B.W. Neuman, J Virol, 80, 7918 (2006)]. This

capsid ellipticity implies that coronaviruses are oblate or prolate or both. We call this

diversity of shapes, pleomorphism. Recently, the rotational diffusivity of the spherical

coronavirus in suspension was calculated, from first principles, using general rigid beadrod

theory [M.A. Kanso, Phys Fluids, 32, 113101 (2020)]. We did so by beading the

spherical capsid, and then also by replacing each of its bulbous spikes with a single bead.

In this paper, we use energy minimization for the spreading of the spikes, charged

identically, over the oblate or prolate capsids. We use general rigid bead-rod theory to

explore the role of such coronavirus cross-sectional ellipticity on its rotational diffusivity,

the transport property around which its cell attachment revolves. We learn that

coronavirus ellipticity drastically decreases its rotational diffusivity, be it oblate or prolate.