Research Interest:
Physical and analytical methods for the determination of molecular structure and interaction of biological interests; membrane structure and dynamics using nuclear magnetic resonance, fluorescence spectroscopy and differential scanning calorimetry.

Phospholipids play an important role in the architecture of biological membranes. This structural role of phospholipids reflects their physical properties which are determined by their ability to self-assemble into a variety of supra molecular assemblies, including the well-known phospholipid bilayers which are present in every living cell of every organism. Over the past two decades, there has been considerable interest in the bilayer as a model for molecular ordering and dynamics in biological membranes. The focus of our research efforts has been on the effect of the addition of an extrinsic element such as an anesthetic or a tranquilizer (alcohol, chlorpromazine) on the structure and motional behavior of membrane lipids.

We have been successful in using techniques such as nuclear magnetic resonance spectroscopy (NMR), fluorescence anisotropy, quenching and lifetime measurements as well as differential scanning calorimetry (DSC) to elucidate the properties of bilayer membranes. Both phosphorus NMR and deuterium NMR (involving selective deuterium substitution) have been essential to a description of conformation, spatial distribution, and lipid motion in bilayer forming systems. These properties may be studied by simple spectral acquisition, line shape analyses, relaxation rate measurements and saturation transfer experiments. Fluorescence spectroscopy offers several advantages for the study of membrane dynamics. Among these are the high sensitivity of the technique and the virtual absence of perturbation of the membrane structure even if fluorescent probes are employed. In study cases such as those with the tranquilizer chlorpromazine, no fluorescent probes are necessary as chlorpromazine itself is highly fluorescent. Also important are the responsiveness of fluorescence parameters to the physical properties of the environment and the possibility of resolving spectroscopic parameters arising from sample heterogeneity. The technique of DSC has been of primary importance in studies of lipid phase transitions in model as well as biological membranes. In particular, the bilayer gel-to-liquid crystalline or chain-melting phase transition has been the most intensively studied lipid phase transition. From a DSC trace, a number of important parameters such as the phase transition temperature and the enthalpy of the transition may be determined. The molecular basis for the thermotropic phase behavior of many lipid systems is just beginning to be understood, offering a very exciting area of scientific investigation.

Students involved in our research would acquaint themselves with the biochemical and biophysical aspects of cellular structure and function. They would be exposed to various general as well as specialized techniques in the laboratory, instrumentation, and computer analysis of data. Among others, a state-of-the-art laser fluorescence spectrophotometer, a high field 400 MHz NMR, a DSC and a micro-titration calorimeter are available in our laboratory in support of the research project.

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