Berlin 2008 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 15: Single Molecules
BP 15.8: Vortrag
Mittwoch, 27. Februar 2008, 16:00–16:15, C 243
(Non-) linear deformation of viral shells — •Wouter H. Roos1, Charlotte Uetrecht2, Norman Watts3, Paul Wingfield3, Alasdair Steven3, Albert Heck2, and Gijs J. L. Wuite1 — 1Natuur- en Sterrenkunde, Vrije Universiteit, Amsterdam, Niederlande — 2Bijvoet Instituut, Universiteit Utrecht, Niederlande — 3NIH, Bethesda, USA
Nanoindentation techniques are increasingly being applied to study the mechanical properties of complex protein assemblies such as viral shells (capsids). Numerical simulations guided by the Föppl- von Kármán (FvK) number γ (a dimensionless number relating the "in-plane" elasticity of the shell to its "out-of-plane" bending rigidity) have been able to explain indentation results on capsids with γ < 150 (linear response) and γ > 700 (buckling transition). Yet for shells with a γ between those values a non-linear, but continuous response is expected. Here we report nanoindentation experiments with an atomic force microscope on capsids of the Hepatitis B Virus (HBV) to investigate this intermediate response regime. HBV was chosen as a model system because its capsids can form in a smaller T=3 and a bigger T=4 configuration that have FvK values within our region of interest. We demonstrate that the HBV T=3 capsid shows a subtle non-linear behaviour while the T=4 capsid reacts strongly non-linear, but continuously to deformation. Both non-linear responses can be understood in relation to their FvK values. At large indentations HBV undergoes permanent plastic deformation indicating a rearrangement of capsid proteins. The presented results demonstrate the surprising strength of continuum elastic theory to describe these nanometre sized objects.