Theoretical Problems in Biophysics and Condensed Matter

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0231631NelsonThis award supports fundamental theoretical research and education centered on problems in biophysics, soft condensed matter and the physics of vortices in Type II superconductors. The PI will study the architecture of virus shells in an effort to understand why small viruses are round and large ones are faceted. The faceting may be related to a buckling transition of the twelve 5-fold disclinations embedded in icosahedral arrays of protein capsomers. Theoretical advance could allow experimental determinations of elastic parameters from structural data. The PI will explore localization effects due to polynucleotide sequence variation on motor protein arrays such as RNA polymerases translating along a DNA strand. Sequential polymerization of single strand binding proteins such as Rec A and the maximum pull out force of DNA hybrids will be studied as well. In addition, problems in soft matter condensed matter physics will also be attacked, these include determining crystalline ground states on the torus and for colloids adsorbed onto negatively curved "plumber's nightmare" phases. Finally, work will continue on vortex matter in superconductors by exploring the unusual response (related to the transverse Meissner effect) of an entangled flux liquid with a dilute concentration of columnar pins to a tilted magnetic field. Methods will include analytical approaches to statistical mechanics and dynamics, numerical diagonalization of evolution operators and computer simulations of model systems inspired by problems in biology, soft condensed matter and vortex physics. Investigations of buckling in viral shells will exploit extensive experience with floating mesh discretizations of the nonlinear elastic equations which describe thin spherical shells. The PI will seek to benefit from close contact and vigorous interactions with the experimental community. This award supports graduate and higher level training in condensed matter theory. The work may also impact fields other than condensed matter physics. Understanding deformations of viral shells could identify weaknesses (such as ridgelines or grain boundaries) which would allow attack on harmful infectious agents. Explorations of how sequence randomness affects protein interactions with DNA and RNA might influence the design of artificial genetic circuits in bacteria. A comprehensive theory of defect arrays on curved surfaces could guide the construction of new materials with bicontinuous lipid phases as templates. Finally, understanding vortex interactions with columnar defects is useful for applications in high magnetic fields. %%%This award supports fundamental theoretical research and education at the interface between condensed matter physics and biology. The research is centered on problems in biophysics, soft condensed matter and the physics of vortices in Type II superconductors. The work in the former area includes the study of virus structures and various problems on motion in a random potential that are inspired by experiments on the binding and motion of RNA polymerize along a DNA nucleotide sequence. This award also supports graduate and higher level training in theoretical condensed matter physics with a bent toward problems at the interface with biology. The results of this work may have impact in other fields, notably in molecular and cellular biosciences.***