We are an interdisciplinary research group whose primary interests are to explore and understand science that is happening at the nanometer regime and within picoNewton (pN) to nanoNewton (nN) force range. We use both experimental techniques, like Dynamic Force Spectroscopy, Forster Resonance Energy Transfer, Time-Resolved Emission Spectroscopy etc. for single molecule and ensemble measurements as well as computational approaches like Molecular Dynamics and Steered Molecular Dynamics. We utilize our knowledge of chemistry and instrumentation on biological phenomena that are controlled by mechanical forces. Mechanical forces play major role in biology, e.g., in protein synthesis, cell division, embryonic-development, cell-adhesion, wound-healing etc. Here a mechanical force acts as a stimulus to transduce a signal through mechano-responsive proteins. While for most cases, the proteins that orchestrate these mechanotransduction is known, very little is known about how forces regulate the chemical and physical properties of the system for transduction. Our research therefore aims to:
(1) Understand the biophysical properties of mechano-responsive proteins in hearing: In hearing, sound waves first generate oscillations in the inner-ear fluid, which thus deflect inner-ear hair-cells and stereocillia. The stereocilia are linked together by a pair of proteins at their tips. Upon deflection, these interacting proteins at tip-links are elastically stretched, which leads to the opening of ion-channels in stereocillia. Open channels can now allow ions to move-in and change the polarity of the cells. Nerve cells attached to hair-cells thereafter sense this electrical change that is conveyed to the brain. The brain interprets this as sound. We are particularly interested in (a) understanding the binding kinetics of the proteins forming tip-links against tensile force and their reproducibility, (b) measuring the molecular elasticity of these proteins etc. We will further extend these studies with mutant proteins leading to deafness or Usher Syndrome.
(2) Develop mechanically activated smart polymers: We often find that biology has mastered and engineered the non-covalent interactions to convert polymers into smart materials. In order to develop such smart mechano-active materials, quantitative understandings of non-covalent weak interactions are essential. Our research goal here is to quantitatively estimate the magnitude and kinetics of pi-pi, pi-cation and pi-anion interactions and at the single molecule level and design a rule of thumb. The better understanding of such pi-interactions would help us in rational drug design and lead optimization in medicinal chemistry. This study will also open up new directions in protein-folding related issues and new dimensions in supramolecular & host-guest chemistry.
- Sabyasachi Rakshit and Sanjeevi Sivasankar; Phys. Chem. Chem. Phys. (Invited Review); Accepted.
- Biomechanics of Cell Adhesion: How Force Regulates the Lifetime of Adhesive Bonds at the Single Molecule Level.
Sabyasachi Rakshit, Yunxiang Zhang, Kristine Manibog, Omer Shafraz and Sanjeevi Sivasankar Proc. Natl. Acad. Sci. U.S.A, 2012; 109(46); 18815-20. Ideal, Catch And Slip Bonds In Cadherin Adhesion. (Recommended by Faculty1000)
- Sabyasachi Rakshit and Sanjeevi Sivasankar; Soft Matter, 2011; 7 (6); 2348-51. Cross-Linking of A Charged Polysaccharide Using Polyions As Electrostatic Staples.
- Sabyasachi Rakshit and Sukumaran Vasudevan; ACS Nano, 2008; 2 (7); 1473-79. Resonance Energy Transfer from β-Cyclodextrin Capped ZnO:MgO Nanocrystals to Included Nile Red Guest Molecules in Aqueous Media.
- Sabyasachi Rakshit and Sukumaran Vasudevan; J. Phys. Chem. C.; 2008; 112(12); 4531-4537. Trap State Dynamics in Visible Light Emitting ZnO:MgO Nanocrystals.