Abstract

Structure and mechanics are intimately linked: from macroscopic to nanoscopic length-scales, from single particles to whole systems. Here I will show how microscopic force sensor arrays, or Beds of Nails, have been used to probe material properties of cells and the sub-cellular cytoskeleton. These arrays allow for studying the dynamics of rhythmic Cardiac Cell contractions and the process of biopolymer network formation. Going to a smaller scale, I will discuss force spectroscopy measurements on viruses. This is an increasingly popular technique to study the material properties of macromolecular assemblies such as viral shells (capsids) [1]. I present a combined imaging and force spectroscopy approach to study the structure and mechanics of various viral particles. The force characterisation studies are performed by Atomic Force Microscopy (AFM) nanoindentation: literally squeezing single viral nanoparticles yields detailed insights on their structure and mechanical properties. In addition to this Virus Squeezer, high resolution AFM imaging of the viral nano-particles before and after indentation gives a complete picture of the response of such nanocontainers to mechanical stress. Using examples showing how pre-stress can strengthen viral shells [2], how single capsomeres (the viral structural units) can be removed out of the icosahedral capsid lattice without disrupting the overall structure, and how conformational changes can lead to a considerable reinforcement of the capsid [3], I exemplify the amazing wealth of varieties nature developed to create robust protein containers to protect the viral genome. Finally, I show how by using modelling approaches we extract additional information out of our experimental data. References [1] W. H. Roos, R. Bruinsma, G. J. L. Wuite. Nature Physics (2010), 6:733 [2] M. Baclayon, G. K. Shoemaker, C. Uetrecht, S. Crawford, M. Estes, B. Prasad, A.J. Heck, G.J. Wuite, W.H. Roos. Nano Letters (2011), 11:4865 [3] W. H. Roos, I. Gertsman, E. R. May, C. L. Brooks III , J. E. Johnson, G. J. L. Wuite Proc. Natl. Acad. Sci. U. S. A. (2012), 109: 2342