Friday, February 8, 2008
DNA packing and interactions in vitro and in viro
National Institutes of Health
The goal of this work is to connect the direct measurement of forces between DNA double helices in vitro with the action of these forces in viro, within the hard walls of a viral capsid. We use x-ray diffraction and osmotic stress to measure forces between DNA in solutions of different salt type and concentration. In this way, we have built a physics of molecular assembly in vitro. DNA-organizing forces include electrostatic, bending fluctuation, and – most important at the densities typical of viral packing – solvation/hydration. These forces mix. Molecular configuration is restrained by soft collisions between double helices mediated by hydration and electrostatic repulsion. The additional constraint posed by a hard shell of a capsid restricts the DNA polymer to a fixed volume. The DNA organizes near the wall so as to fit its constraint as well as DNA-DNA interactions. By modeling and by x-ray diffraction of DNA in the virus, we now connect in vitro force measurements with in viro packing.
Refreshments at 4:00 PM. Seminar begins at 4:10 PM.
Building 8, Room 241
For further information, please call (909) 869-4014