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Prof. Amitabha Chattopadhyay - Membrane dipole potential: A novel approach to explore membrane organization and function

 

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Amitabha Chattopadhyay

Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad, India

Membrane dipole potential: A novel approach to explore  membrane organization and function

Biological membranes are complex, soft matter-like organized molecular assemblies of lipids and proteins that provide cells their individual identity by morphological compartmentalization.  Membrane dipole potential has emerged as an important property of model and biological membranes since it provides useful insight in the function of membrane proteins and receptors in the context of the lipid microenvironment.  The origin of membrane dipole potential is the electrostatic potential difference within the membrane due to the nonrandom arrangement (orientation) of amphiphile dipoles and solvent (water) dipoles at the membrane interface.  Although the concept of membrane dipole potential was originally conceptualized in the 70's, its application in the area of membrane biology and biophysics was slow, initially due to lack of proper experimental approaches to measure it.  In this talk, I will focus on the origin and concept of membrane dipole potential and its measurement using electrochromic fluorescent probes, and highlight interesting applications in a number of cases from work done by us.  An important observation was that membrane cholesterol increases membrane dipole potential.1 Interestingly, we demonstrated that biosynthetic and evolutionary precursors of cholesterol, differing with cholesterol merely in a double bond, fails to increase membrane dipole potential.2  We further showed that cholesterol and ent-cholesterol share comparable ability in increasing membrane dipole potential.  In contrast, epi-cholesterol displays a drastic reduction in membrane dipole potential.3  Taken together, these results imply that an extremely subtle change in sterol structure can significantly alter the dipolar field at the membrane interface.  We have recently extended the concept of membrane dipole potential to other organized molecular assemblies such as micelles and showed that dipole potential measurements could provide novel insights into micellar processes associated with dipolar reorganization.4,5  In a recent work, we developed a ratiometric fluorescence microscopic imaging technique to measure dipole potential in cellular membranes.6  Our results indicate that dipole potential measurements in cellular membranes could reveal interesting differences in membrane organization in cases such as acute and chronic depletion of membrane cholesterol.6  Taken together, these results show that subtle changes in membrane dipole potential could be crucial in understanding the modulation of membrane lipids, and the interplay between membrane lipids and proteins in the spatiotemporally complex cellular milieu.

Selected publications

1.    Haldar, S.; Kanaparthi, R. K.; Samanta, A.; Chattopadhyay, A. Biophys. J. 2012, 102, 1561-1569
2.    Singh, P.; Haldar, S.; Chattopadhyay, A. Biochim. Biophys. Acta 2013, 1828, 917-923
3.    Bandari, S.; Chakraborty, H.; Covey, D. F.; Chattopadhyay, A. Chem. Phys. Lipids 2014, 184, 25-29
4.    Sarkar, P.; Chattopadhyay, A. Chem. Phys. Lipids 2015, 191, 91-95
5.    Sarkar, P.; Chattopadhyay, A. Chem. Phys. Lipids 2016, 195, 34-38
6.    Sarkar, P.; Chakraborty, H.; Chattopadhyay, A. Sci. Rep. 2017, 7, 4484

 

Contact: Evert Haanappel (evert.haanappel@ipbs.fr)

Note for visitors: Please come with a valid identity card



 

20 May

11:00 - 12:00

Seminar room - IPBS - Campus 205