THEORETICAL APPROACHES IN CELL BIOLOGY
PHYSICS OF ACTIVE, EVOLVING SYSTEMS

The living cell is an active, self-organized medium comprising molecular processes fuelled by energy. Our group is interested in the organization, flow and processing of mass (molecules), mechanical stress, energy (mitochondria) and information (signaling) in living cells and tissues. These fluxes are coupled via interconnected networks of molecules engaged in biochemical reactions played out in this active dynamical medium. 

A proper understanding of such processes appears to involve new physical principles arising as a consequence of the novel response of cellular systems to local active (energy consuming) forces which maintain it away from equilibrium. These active forces arising from (i) the coupled dynamics of the cytoskeleton, motors and cytoskeletal regulatory proteins, and (ii) the active dynamics of fission and fusion of organelles, regulate the flux of mass, stress, energy and information. We have been engaged in developing a theoretical framework, called active hydrodynamics, to address situations where activity plays a significant role. Using this framework we study the mechanical response, pattern formation, symmetry breaking,  hydrodynamic instabilities and information optimization in both in-vivo and in-vitro reconstituted active systems.

Specifically we have been working on (details on next page)

  • Organization of signaling platforms and endocytosis on the cell membrane through  interaction with active cortical actin
  • Golgi and Mitochondrial morphogenesis and remodeling
  • Chromatin organization and active mechanics in the nucleus
  • Actomyosin dynamics and Cytokinesis in fission yeast
  • Tissue dynamics

In addition, I am currently working on

(i) Nonequilibrium phenomena in solids

        Dynamics of solid state transformations - Martensites
        Driven Solids
        Non-affine deformations in solids under shear
        Onset of Plasticity
       
(ii) Soft Matter Physics : Equilibrium and Nonequilibrium

       Ordering transitions on membranes and shape changes
       Active membranes, polymers, liquid crystals, solids
       Soft rheology
       Statistical Mechanics of biomolecules
      
(iii) Nonequilibrium statistical mechanics of driven interacting systems

Selected Publications

1. K. Gowrishankar, S. Ghosh, S. Saha, Ruma, C., S. Mayor, M. Rao, (2012), Active remodeling of cortical actin regulates spatiotemporal organization of cell surface molecules, Cell 149 : 1353-1367.

2. Abhishek Chaudhuri, Bhaswati Bhattacharya, Kripa Gowrishankar, Satyajit Mayor and Madan Rao, (2011), Spatiotemporal regulation of chemical reactions by active cytoskeletal remodeling, Proc. Nat. Acad. Sc. 108 : 14825-14830.

3. D. Goswami, K. Gowrishankar, S. Bilgrami, S. Ghosh, R. Raghupathy, R. Chadda, R. Vishwakarma, M. Rao and S. Mayor, (2008), Nanoclusters of GPI-anchored proteins are formed by cortical actin-driven activity, Cell 135:1085-1097.

4. S. Ramaswamy and M. Rao, (2007), Active filament hydrodynamics : instabilities, boundary conditions and rheology, New J. Phys. 9:423.

5. Y. Hatwalne, S. Ramaswamy, M. Rao, and R.A. Simha, (2004), Rheology of active-particle suspensions, Phys. Rev. Lett. 92:118101.

6. S. Mayor and M. Rao, (2004), Rafts: Scale-dependent, active lipid organization at the cell surface, Traffic 5:231-240.

7. P. Sharma P, R. Varma, RC Sarasij, Ira, K. Gousset, G. Krishnamoorthy, M. Rao and S. Mayor, (2004), Nanoscale organization of multiple GPI-Anchored proteins in living cell  membranes, Cell 116:577-589.

8. M. Rao and Sarasij RC, (2001), Active fusion and fission processes on a fluid membrane, Phys. Rev. Lett. 87:128101.

Simons Centre for the Study of Living Machines