Dresden 2006 – scientific programme
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AKB: Biologische Physik
AKB 40: Poster Session II
AKB 40.47: Poster
Wednesday, March 29, 2006, 16:30–19:30, P3
Nanoindentation studies of full and empty viral capsids and the effects of capsid protein mutations on elasticity and strength — •Irena L. Ivanovska1, Jean Philippe Michel2, M. M. Gibbons3, W. S. Klug3, C. M. Knobler2, Gijs. J.L. Wuite1, and Christoph F. Schmidt1 — 1Dept. Physics, Vrije Universiteit, Amsterdam, NL — 2Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA 90095-1569, USA — 3Department of Mechanical and Aerospace Engineering, University of California Los Angeles, Los Angeles, CA 90095-1597, USA
The elastic properties of capsids of the cowpea chlorotic mottle virus (CCMV) have been examined at pH 4.8 by nano-indentation measurements with an atomic force microscope. Studies have been carried out on wild-type capsids, both empty and containing the RNA genome, as well as on full capsids of a salt-stable mutant and empty capsids of the subE mutant. Full capsids resisted indentation more than empty capsids but all of the capsids were highly elastic. There was an initial reversible linear regime that persisted up to indentations varying between 20 and 30 % and applied forces of 0.6 to 1.0 nN; it was followed by a steep drop in force that was associated with irreversible deformation. A single point mutation in the capsid protein increased the capsid stiffness. The experiments are compared with calculations by finite element analysis of the deformation of a homogeneous elastic thick shell. These calculations capture the features of the reversible indentation region, and allow Young’s moduli and relative strengths to be estimated for the empty capsids.