Date : 2011. 5. 26, 5:00 PM Place : Mogam Hall, Bldg.500 -Abstract-   A cell is crowded with a high content of macromolecules occupying up to 40 % of the total volume, and crowding effects on structure and function of biomolecules have been of great interest in recent years. In this presentation, two biological implications of crowding are discussed: change in the reaction rate of protein-protein associations and structural alteration of chromosomes. Using computer simulations, it is shown that the crowding effect on protein-protein association becomes qualitatively different depending on the intrinsic rate of protein-protein association. The competing effects of reduced diffusion and increased recollision between associating proteins determine the overall crowding effect. In the crowded nucleus, structural alterations of chromosomes due to crowding have been investigated, using a polymer model of chromosome. Non-monotonic crowding dependence of chromosome structure and its possible implications will be discussed.