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Surface Enhanced Raman Spectroscopy of Biomolecules

Vibrational spectroscopy (infrared and Raman) is widely acknowledged as an efficient technique to study the conformation of the molecules and to analyze the influence of the molecular environment on the structure of the molecules. Raman spectroscopy has an advantage over IR in the context of investigating biological macromolecules. Water being a poor scatterer of radiation makes the Raman process an excellent tool to investigate phenomena occurring in aqueous medium. Raman spectroscopy, with molecular cross sections in the range of 10-32cm2, is an extremely weak phenomenon (in comparison, fluorescence has a molecular cross section in the range of 10-16 cm2). This turns out to be a handicap in using Raman scattering to study biological macro-molecules in cellular and physiological conditions where they occur in very low concentrations. The problem can, however, be circumvent by applying the Surface Enhanced Raman Spectroscopy (SERS). When a molecule is adsorbed on a noble metal surface great amount of signal enhancement is observed. This surface enhancement is used for the detection of bio-molecules at low concentrations. In our lab the focus is on applying the SERS technique to study the structural characteristics of nucleic acid, proteins and their interactions. Methylation of the DNA and its influence on the protein-DNA interaction is another aspect of the nucleic acids that we are investigating.

Reconstituted membranes

Plasma membrane plays an important role in maintaining the structural integrity and function of the cell. The lipid bilayer is traversed at strategic locations by the transmembrane proteins that play an important role in processes like the signal transduction and intercellular communication. Structural characterization of reconstituted and supported membranes and membrane bound proteins is another area of interest in our lab. The membrane characteristics under various conditions physical and chemical stress are studied with an atomic force microscope. The Interactive forces between molecules are measured with an AFM by scanning with chemically modified tips. We had previously measured the permeability of Rhodamine-6-G across the gap junctions by combining SERS and patch clamp techniques. Work is in progress to measure the permeabilities of other small and non-fluorescent molecules of biological importance.

Metal binding proteins

Metal ions play an important role in maintaining the cellular metabolic balance. The concentration of intra-cellular metal ions is under stringent regulation. Any fluctuation in this delicate balance leads to numerous physiological disorders like the Wilson's disease and Menke's disease. Metal binding proteins and transporters play a very important role in maintaining the intra-cellular levels of metabolically important metal ions and in transporting them to appropriate compartments of the cell. Our lab is engaged in studying such metal binding proteins. As a model system we are using short peptides with the ability to bind to specific metal ions. Development of biosensors with the ability to remove metal ions from the sewage and waste waters is another aspect of our research.

Sponsored Projects

1. Spectroscopic analysis of Toxins and their degradation projects, DRDE (DRDO), Principal Investigator

2. Development of an instrument using immunofluorescence based biosensor for detection of infectious pathogens. DST, Co-Principal Investigator



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