To elucidate the stabilization process which occurs during the maturation of Herpes Simplex Virus Type 1 (HSV1) nuclear capsids, we used biochemical and nanoindentation approaches to analyze the structural and mechanical properties of these capsids. From our AFM measurements we conclude that HSV1 capsids are stabilized after removal of the scaffolding proteins, and that this stabilization is triggered by the packaging of DNA, however it is independent of the actual presence of DNA. Read more in PNAS.

Herpes Simplex capsid imaged by atomic force microscopy, revealing the capsomers on top of the icosahedral capsid. Hexons can clearly be distinguished as well as the three holes left by the pentons, which were removed by Guanidine .

AFM images of a T=3 and T=4 Hepatitis B viral capsid. The lateral height profiles show the differences in diameter [PNAS, 2008, 105, 9216].

In addition to the importance of Hepatitis B virus (HBV) in human health, there is growing interest in adapting HBV and other viruses for drug delivery and other nanotechnological applications. In both of these contexts a precise biophysical characterization of these large macromolecular particles is fundamental. HBV capsids are particularly interesting as they exhibit two distinct icosahedral geometries, T=3 and T=4, nominally composed of 90 and 120 dimers. The figure shows atomic force microscopy (AFM) images of both morphologies. Nanoindentation experiments by AFM indicate that both capsids have similar stabilities and the measurements yielded a Young’s modulus of approx. 0.3 GPa.  Furthermore, it was shown that no material fatigue can be observed upon multiple indentations at small forces. Read more on the AFM and the related mass spectrometry measurements [PNAS 2008, 105, 9216].

More on the AFM and related modelling approaches.....