Associate Professor, Soft Nano Laboratory, Physical Sciences Division, Institute of Advanced Study in Science and Technology (IASST), India

Biography: Dr. Sarathi Kundu did his M.Sc. from Visva-Bharati University, West Bengal. He completed his Ph.D. work from Saha Institute of Nuclear Physics, Kolkata in 2006 and the degree is conferred by Jadavpur University. He did is Post-Doctoral research work from University of Paris Sud, France. He was Visiting Faculty Fellow in S.N. Bose National Centre for Basic Sciences, Kolkata and Visiting Scientist in KEK, Japan. At present he is Associate Professor in IASST, Guwahati. Dr. Kundu has been working on soft matter physics with emphasis on thin films of fatty acids, lipids, proteins, polymers, nanomaterials, etc. He is interested to explore structures and properties using scattering, spectroscopic and microscopic methods. Dr. Kundu has published nearly 55 journal papers and several conference papers so far.

Speech Title: Structures, interactions and related properties of polymer and polymer nanocomposites
Abstract: Biological functions of biopolymers like proteins strongly depend upon their structures which can be modified in the presence of different ions around them and hence the effect of ionic strength, nature of ions, temperature, pH, concentration, nanoparticles, etc. strongly affect the protein-protein interactions. Among different proteins, globular proteins like BSA, HSA, lysozyme can be considered as charged colloidal particles and both the short-range attraction and long-range electrostatic repulsion exists among the protein molecules in solution and hence Derjaguin-Landau-Verway-Overbeek (DLVO) potential can be applied to obtain the interaction nature and to explain the phase behaviors. In addition, one, two or three attractive or repulsive Yukawa form potentials were also used to explain the nature of interactions. Small angle neutron scattering (SANS) study shows that for the different counter ions and for the equal ionic strength, the interactions are largely modified by the tri-valent and di-valent ions and comparatively less by the mono-valent ions. Below the isoelectric point, protein has a net positive surface charge although local charge inhomogeneity presents and as a result interaction nature modifies. In the presence of different ions, cold gelation behaviors of proteins have also been studied which indicates the fractal structure formation after gelation. Structures and interactions among proteins and nanoparticles in solution have also been explored with the temperature variation. In the presence of charged polymers, conformational changes of globular proteins may occur depending upon the charge states of the polyelectrolytes. Protein-polyelectrolyte complexes (PPC) show modified behaviors than that of pure protein/polymer. Protein and protein films are also used as templates to form metallic nanostructures of different shapes and sizes which are also used for modifying both optical and electrical properties.