나노과학기술대학원에서는 김용운 박사 (Korea Institute for Advanced Study) 세미나를

개최하오니 관심 있는분들의 많은 참석바랍니다.

 * 일시/장소  : 4월 12일(월) 오전 11시~ , 자연과학동(E6) 2층세미나실 2502호  

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Title : Understanding cooperativity in biological systems: Swimming bacteria and DNA packaging 

Abstract:

Rapidly increasing attention to life science nowadays makes it challenging and promising that physics interfaces with biological sciences and nanotechnology, at the outside the conventional boundaries of the scientific disciplines. In particular, it is of great interest from a physical point of view that using unique features like self-organization and conformational flexibility, biological systems display various cooperative phenomena. Here I will introduce a couple of examples of the cooperative phenomena and my contributions to its understanding. The first one is bacteria swimming, especially, using cilia, that clearly demonstrates very different principles of propulsion on the micro/nano-meter scale fromthe macroscopic world. Nonlinear deformation of the soft object in response to hydrodynamic flow is a key factor to have net propulsion by breaking time-reversal symmetry. Furthermore, phase locking between swimming objects is found to occur autonomously, yielding significantly enhanced swimming efficiency. This finding provides an interesting physical explanation on self-organized synchronization and its role in bacteria swimming. Secondly, I will discuss condensation of charged biopolymers, which is in fact surprising and puzzling phenomena in sharp contrast with the common sense

that like charges always repel. For example, DNA is a highly, negatively charged biopolymer, but these likely-charged DNA usually form strongly condensed phases. According to several recent experiments, DNA condensations are effectively driven by short stiff polyamines such as spermine and spermidine. A novel energetic bridging mechanism explaining the prevailing role of polyamines on the charged biopolymer condensation will be presented.