engleski

Elasticity of viral capsids

Although often called „ spherical“ icosahedral viruses are rarely spherical. The general trend is that smaller viruses are more spherical, while larger viruses often show pronounced icosahedral shape with flattened icosahedral faces [1]. This can be explained in rather general context of energetics and equilibrium shapes of elastic icosadeltahedral shells [2]. The existence of twelve disclinations, i.e. protein pentamers, at icosahedron vertices in otherwise six-fold coordinated shell consisting of 10(T-1) protein hexamers (T is the Caspar-Klug triangulation number of the shell) induces the so-called buckling of the shell that results in conical portions of the shell surface surrounding the twelve protein pentamers [2]. The buckling takes place only for sufficiently large shells thus making them more aspherical. These considerations can explain the shapes of viruses and offer an additional insight in energetics of viral assembly [3]. Even more insight is obtained by studying the bacteriophage viral capsids [4] that withstand the huge internal pressure (~50 atm) of the tightly wound double-stranded DNA molecule [5]. I shall present a simple application of the theory of shell elasticity to virus capsids both under internal pressure acting from its DNA molecule and under external mechanical pressure [6] that may be induced by osmotic pressure of the external solution (dissolved polyethylene glycol) [7]. The predictions of these studies nicely connect to quantities that have been and that yet may be measured. [1] T.S. Baker, N.H. Olson, and S.D. Fuller, Microbiol. Mol. Biol. Rev. 63, 862 (1999). [2] J. Lidmar, L. Mirny, and D.R. Nelson, Phys. Rev. E 68, 051910 (2003). [3] A. Šiber and R. Podgornik, Phys. Rev. E 76, 061906 (2007). [4] A. Šiber, Phys. Rev. E 73, 061915 (2006). [5] A. Šiber, M. Dragar, V.A. Parsegian, and R. Podgornik, in press in Eur. Phys. J. E. [6] A. Šiber and R. Podgornik, sent to publication. [7] A. Evilevitch, L. Lavelle, C.M. Knobler, E. Raspaud, and W.M. Gelbart, Proc. Natl. Acad. Sci. 100, 9292 (2003).

virus; elasticity

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