Current Research Interests:  

Biological machines are naturally occuring molecular devices that  transform one form of energy (usually, chemical or electro-chemical energy) into another form of energy (most often, mechanical energy required for directed molecular motion). This class of machines includes wide variety of molecular motors, for  example,  cytoskeletal motor proteins (kinesin, dynein, etc), DNA/RNA  helicases/polymerases,  ATP synthase, flagellar motors, etc.  Molecular pumps  (e.g., sodium/potassium pumps, proton pumps, etc), which drive active transport against concentration gradient, constitute another major class of biological machines. What distinguishes these molecular machines from their macroscopic counterparts  is (a) high viscous drag (low-Reynold's number) and (b) strong thermal fluctuations (Brownian motion). 

We develop simple theoretical models to understand the roles of "noise" and "nonlinearity" in the operation of these natural nano-machines. Deep insights gained from the investigations of these machines not only help in understanding  their biological functions in terms of their structure and dynamics  (and, hence,  the causes of diseases leading, eventually to the possibility of controlling the diseases arising from malfunctioning of the biomolecular machines ) but are also likely to find applications in biological routes to  nano-technology.

(i) Cytoskeleton and associated molecular motors: We are interested mainly in the  (de-)polymerization of cytoskeletal filaments (particularly, microtubules) and in the directed transport by the cytoskeleton-associated motors. We have derived the steady-state distribution of the lengths of the microtubules in the presence of  catastrophe-suppressing drugs and MT-depolymerizing motor proteins.  Our main aim is to understand how the operational mechanisms of the individual motors depend on their (a) architectural design, and (b) mechano-chemical cycle. We have already modelled the dynamics of single-headed kinesins KIF1A and MT-depolymerizing kinesins MCAK and Kip3p.

(ii) Molecular motors associated with nucleic acids: Our main aim is to understand how the operational mechanisms of the individual helicase, nucleic-acid translocase and polymerase machines depend on their architectural design and on the nature of their mechano-chemical cycle. We have developed models of NS3 helicase of Hepatitis C virus (HCV), RNA polymerases (DNA-dependent RNA polymerase) and ribosomes of E-coli bacteria.

(II) Molecular motor traffic:

(i) Cytoskeletal motor traffic: Steric interactions of cytoskeletal motors are  believed to play crucial roles  in sub-cellular vesicular traffic and in the self-organization of the  cytoskeleton as well as the organelles. We calculate the effects of the mechano-chemistry of individual motors and their steric interactions as well as those of their attachments to- / detachments from the track on the collective transport of intracellular cargo. So far we have developed theoretical models for traffic of single-headed kinesins KIF1A. 

Main  goal of my research is to understand the interplay of structure and dynamics in the equilibrium and non-equilibrium phenomena exhibited by systems consisting of a macroscopically large number of interacting constituents, using the modern concepts and techniques of statistical mechanics. The interacting constituents need not  necessarily be atoms and molecules in a solid or liquid (e.g., condensed matter) but can also be cells (e.g., neurons in the brain) or multi-cellular organisms (e.g., bacteria in bacterial colonies) or species in an eco-system or vehicles in a traffic. In such a broader context inter-constituent interaction is synonymous with their influence on each other. Therefore. although my primary interest is in physics, most of my works are of inter-disciplinary nature.

Office Location: FB 385
Phone: 91-512-259 7039(O), 259 8465(R)
Fax: 91-512-259 0914
Department of Physics
Indian Institute of Technology
Kanpur 208016, India.