Mechanical limits of viral capsids
- *Fachbereich Physik, Philipps-Universität Marburg, D-35032 Marburg, Germany; and
- †Center for Theoretical Biological Physics, University of California at San Diego, La Jolla, CA 92093-0374
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Edited by David R. Nelson, Harvard University, Cambridge, MA, and approved April 23, 2007 (received for review December 22, 2006)
Abstract
We studied the elastic properties and mechanical stability of viral capsids under external force-loading with computer simulations. Our approach allows the implementation of specific geometries corresponding to specific phages, such as φ29 and cowpea chlorotic mottle virus. We demonstrate how, in a combined numerical and experimental approach, the elastic parameters can be determined with high precision. The experimentally observed bimodality of elastic spring constants is shown to be of geometrical origin, namely the presence of pentavalent units in the viral shell. We define a criterion for capsid breakage that explains well the experimentally observed rupture. From our numerics we find a crossover from γ2/3 to γ1/2 for the dependence of the rupture force on the Föppl-von Kármán number, γ. For filled capsids, high internal pressures lead to a stronger destabilization for viruses with buckled ground states versus viruses with unbuckled ground states. Finally, we show how our numerically calculated energy maps can be used to extract information about the strength of protein–protein interactions from rupture experiments.
Footnotes
- ‡To whom correspondence should be addressed. E-mail: peter.lenz{at}physik.uni-marburg.de
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Author contributions: P.L. designed research; M.B. performed research; and M.B. and P.L. wrote the paper.
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The authors declare no conflict of interest.
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This article is a PNAS Direct Submission.
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This article contains supporting information online at www.pnas.org/cgi/content/full/0611472104/DC1.
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↵ § Anderson, T. F. (1950) J. Appl. Phys. 21:70 (abstr.).
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↵ ¶ The simpler discretization scheme used in refs. 12, 18, and 19 also has the drawback that it does not yield the correct small γ values of K l (data not shown).
- Abbreviations:
- CCMV,
- cowpea chlorotic mottle virus;
- FvK,
- Föppl-von Kármán;
- SFM,
- scanning force microscopy.
- © 2007 by The National Academy of Sciences of the USA
