ABSTRACT

Wavelength-selective fluorescence comprises a set of approaches based on the red edge effect in fluorescence spectroscopy which can be used to directly monitor the environment and dynamics around a fluorophore in a complex biological system. A shift in the wavelength of maximum fluorescence emission toward higher wavelengths, caused by a shift in the excitation wavelength toward the red edge of absorption band, is termed red edge excitation shift (REES). This effect is mostly observed with polar fluorophores in motionally restricted media such as very viscous solutions or condensed phases where the dipolar relaxation time for the solvent shell around a fluorophore is comparable to or longer than its fluorescence lifetime. REES arises from slow rates of solvent relaxation (reorientation) around an excited state fluorophore which is a function of the motional restriction imposed on the solvent molecules in the immediate vicinity of the fluorophore. Utilizing this approach, it becomes possible to probe the mobility parameters of the environment itself (which is represented by the relaxing solvent molecules) using the fluorophore merely as a reporter group. Further, since the ubiquitous solvent for biological systems is water, the information obtained in such cases will come from the otherwise 'optically silent' water molecules. This makes REES and related techniques extremely useful since hydration plays a crucial modulatory role in a large number of important cellular events, including lipid-protein interactions and ion transport. The application of REES and related techniques (wavelength-selective fluorescence approach) as a powerful tool to monitor organization and dynamics of cytoskeletal proteins such as spectrin, and of probes and peptides bound to membranes, micelles, and reverse micelles will be the focus of the talk.

ABOUT THE SPEAKER

Prof. Amitabha Chattopadhyay received B.Sc. with Honors in Chemistry from St. Xavier's College (Calcutta) and M.Sc. from IIT Kanpur. He obtained his Ph.D. from the State University of New York (SUNY) at Stony Brook, and was a Postdoctoral Fellow at the University of California, Davis. He subsequently joined the Centre for Cellular and Molecular Biology (CCMB) in Hyderabad and is now an Outstanding Scientist (Director level) there. 

Prof. Chattopadhyay's work is focused on monitoring organization, dynamics and function of biological membranes in healthy and diseased conditions. His group has developed and applied novel, innovative and sensitive techniques (such as the wavelength-selective fluorescence approach) using fluorescence spectroscopy for monitoring solvent relaxation in membranes, membrane-mimetic media, and proteins. These pioneering studies have led to a better understanding of the dynamics of hydration of membranes and proteins. Another seminal contribution of Prof. Chattopadhyay's group focuses on the role of membrane cholesterol in regulating the organization, dynamics and function of G-protein coupled receptors such as the serotonin1A receptor. His work showed, for the first time, that membrane cholesterol is necessary for the function of G-protein coupled receptors such as the serotonin1A receptor. His work has also provided novel insight in the role of membrane cholesterol in the entry of pathogens into host cells. Prof. Chattopadhyay has used fluorescence-based microscopic approaches such as Fluorescence Recovery After Photobleaching (FRAP), Fluorescence Correlation Spectroscopy (FCS), and Fluorescence Resonance Energy Transfer (FRET) to provide novel insight into organization, dynamics and function of membrane-bound receptors. Overall, his work has contributed significantly to the understanding of membrane organization and dynamics, and the interplay between membrane lipids and proteins, especially in neuronal membranes. 

Prof. Chattopadhyay was awarded the prestigious Shanti Swarup Bhatnagar Award, Ranbaxy Research Award, and currently is a J.C. Bose Fellow of the Dept. of Science and Technology, Govt. of India. He is an elected Fellow of the Royal Society of Chemistry, and all the Indian Academies of Science, the Andhra Pradesh Akademi of Sciences, and West Bengal Academy of Science and Technology. Prof. Chattopadhyay is currently on the editorial boards of a large number of reputed international journals that includes Biophysical Journal, The Journal of Physical Chemistry, Journal of Nanochemistry and BBA-Biochemistry. He has mentored a number of students for PhD. Prof. Chattopadhyay has authored close to 200 research publications (total citations > 5700, h-index 40), a monograph, and national and international patents. He has delivered more than 400 invited lectures all over the world including keynote and plenary lectures. Prof. Chattopadhyay has organized a number of international conferences on the broad theme of biological membranes including a thematic meeting of the Biophysical Socoety. Prof. Chattopadhyay has been instrumental in designing and teaching courses related to biomembranes and fluorescence spectroscopy for Ph.D. students in India and other parts of the world. In recent years, Prof. Chattopadhyay has been involved with science awareness programs among high school and college students. Prof. Chattopadhyay is an Adjunct Professor at the Special Centre for Molecular Medicine, Jawaharlal Nehru University (New Delhi), the Indian Institute of Science Education and Research (Mohali), Institute of Life Sciences (Hyderabad) and Honorary Faculty at the Jawaharlal Nehru Centre for Advanced Scientific Research (Bangalore). He serves as the first Dean of Biological Sciences of the Academy of Scientific and Innovative Research.