Please join Yale Chemistry for a Silliman Seminar in theory chemistry with Prof. Michael L. Klein, Laura H. Carnell Professor of Science, Director of the Institute for Computational Molecular Science, and Director of the Temple Materials Institute, from Temple University.
Abstract: Knots have been an enduring fascination since ropes were first fabricated. Knots have also been employed widely as spiritual and aesthetic entities. The mathematical theory of knots has its origins in the 18th and 19th centuries and is now a vibrant area of research in topology.
Experiments have been carried out to determine the relative strengths of different knots in macroscopic fibers and ropes, demonstrating that the break in a knotted rope almost invariably occurs at the point just outside the ‘entrance’ to the knot. Renewed interest in the physical characteristics of knots emerged in the last two decades or so with the realization that both synthetic and natural macromolecules, such as in polymers, proteins (enzymes) and DNA strands, can contain knots.
Knots are of continuing interest to polymer science, in part because of they affect mechanical properties. Knot theory applied to the topology of macromolecules indicates that the simple trefoil or ‘overhand’ knot is likely to be present whenever the polymer molecule is long enough to allow its random walk to sample crossings between different chain segments. Indeed, fragments of DNA have been observed to contain such knots in both experiments and computer simulations.
I will review the history of knots in polymers, including computational studies on the effect of a trefoil knot on the breaking strength of a polymer strand. Also, recent computational results on more complex knots in polyethylene will be reported. Knots weaken a polymer strand significantly, and as with a knotted macroscopic rope, breakage under tension usually occurs at the entrance to the knot.
The Klein Group applies principles from quantum mechanics and statistical thermodynamics to model molecular phenomena with computer simulations. They use or adapt existing software to perform ab initio electronic structure calculations, all-atom and coarse grained classical molecular dynamics and Car-Parrinello and Born-Oppenheimer ab initio molecular dynamics simulations. They also develop new techniques and program code for new hardware like GPGPUs and multi-core CPUs and specific complex problems, for example to enhance sampling of rare events, and develop parameters for realistic coarse grain modeling of meso-scale biophysical applications. Simulations help interpret experimental results and gain understanding from a microscopic perspective; therefore they also collaborate with researchers from several multi-disciplinary research efforts. More information on Prof. Klein’s research can be found here: Michael Klein — EFRC CCM
Hosted by: Prof. Bill Jorgensen
Sponsored by the Mrs. Hepsa Ely Silliman Memorial Fund.