P.hd in Solute-solvent interactions in interfaces and inside membrane channels reconstituted into bimolecular lipid membranesTata Institute of Fundamental Research
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P.hd in Solute-solvent interactions in interfaces and inside membrane channels reconstituted into bimolecular lipid membranes
We study the mechanisms of transport of small solutes and water molecules across cell membranes. Our primary interest lies in the physiology of epithelial cells, the cells that line surfaces of the body and are the key transporting cells of organs like the intestine, kidneys and eyes. In many of these epithelial cell systems, it is still not clear as to what the driving forces for water absorption and secretion are. The technical challenge of working with small living structures in vitro requires experimental models dedicated to each cell system and the parameters being measured. Where information is sought at a single membrane level we use artificial planar bilayer membranes with model channels like the antibiotic gramicidin inserted in them.
The primary research interest of the Membrane Biophysics Laboratory is the study of transport processes in cell membranes, particularly the coupled transport of solutes and water molecules. We investigate cellular and molecular mechanisms that underlie physiological processes in epithelial cells, cell layers and artificial planar bilayer membranes with model channels inserted in them using three or four techniques:
Microperfusion electrophysiology of tubular insect epithelial cells, e.g. the Drosophila midgut; analysis of ion-currents and ion-water interactions in ion channels in artificial bimolecular lipid membranes; capacitance probe measurement of transepithelial water transport and fluid transport in insect epithelia using the Ramsay technique
With these techniques, it has been possible to determine the number of water molecules (5 to 7) coupled to a Group IA cation in its transit through an ion channel and also the binding constants for ions inside the channel. The ion-selective microelectrode technique for measuring streaming potentials has the advantage that it makes no presuppositions about the molecular mechanism of ion-water coupling inside carriers like Valinomycin and ion channels. Most of the work has been done on very narrow channels like the antibiotic gramicidin, through which ions and water can permeate selectively, but cannot go past each other. Present work is centered on the effects of lipid bilayer thickness and composition on the conduction process.