Book of Abstracts: Albany 2005
Energetics and Structure of DNA and RNA in Viral Capsids
We shall first describe our theoretical work on the energetic and structural characteristics of DNA packing in a viral capsid, focusing on the forces involved in packaging (a huge length of) DNA within the (very small) protein capsid of a bacteriophage. Using a simple free energy functional comprising the contributions of DNA-DNA interactions, DNA bending, and the surface energy of the DNA bundle, we show that DNA injection (or, equivalently, the reverse process of DNA loading) takes place in two distinct stages, with a corresponding change in the structure of the encapsidated DNA condensate. The theoretical calculations will be compared to experimental results.
In the second part of the talk we shall describe a statistical-thermodynamic model for the budding of animal viruses through the cell membrane. The model takes into account the binding energy between the membrane anchored spike (glyco-) proteins and the viral capsid, the elastic curvature energy of the lipid-protein membrane around the nascent viral particle, the ?line energy? associated with the membrane rim of the partially enveloped virion, and entropic contributions resulting from the different compositions of the curved and planar membrane regions. For realsistic molecular interaction constants the model predicts that the virion envelope is generally ?saturated? with spike proteins, and that the bud size distribution is bimodal, consisting of either barely wrapped or fully enveloped capsids.
Finally, time permitting we hope to present some new theoretical results concerning RNA folding and packing in viral capsids.
Department of Physical Chemistry and the Fritz Haber Research Center