Liang DAI is an assistant professor in the Department of Physics at City University of Hong Kong (CityU). Dr. Dai obtained his BSc degree in physics from University of Science and Technology of China in 2004, and his PhD degree in physics from National University of Singapore in 2009. Before joining CityU, he worked as a research scientist in Singapore-MIT Alliance for Research and Technology (SMART). Dr Dai performs research in soft matter physics and biophysics using multi-scale modeling, from atomistic to coarse-grained, and statistical mechanics, with tight collaboration with experimental groups. In addition to addressing fundamental physics problems in soft matter systems, Dr Dai is interested in practical applications such as DNA sequencing technologies based on nanopores or nanochannels, and design of antimicrobial peptides for antibiotic drugs.
Knotting is a common phenomenon in linear objects ranging from macroscopic ropes to DNA, proteins, and other polymers. Physical understanding of knotting phenomena is very limited due to the complexity of knotting. In recent years, we developed a theoretical model to describe the knotting in DNA and other polymers, and revealed many intriguing knot properties. This theoretical model is based on tubes for knots. The tube model assumes that the polymer segments in a knot core are confined within a virtual tube due to topological entanglements and presents a simplified view of knotted polymer conformations that appear irregular and disordered. To materialize the conceptual tube, we generated a large number of knotted polymer conformations by Monte Carlo simulations and superimposed them to obtain the tube. The tube model converts the complicated knotting problem to a tube confinement problem, which can be better tackled by theory and can be used to derive the shape, fluctuations, and free energy of knots.