Mapping microscopic viscosity using molecular rotors

DIPC Seminars

Marina K. Kuimova (Imperial College London, UK)
Donostia International Physics Center (DIPC).Paseo Manuel de Lardizabal, 4 , Donostia
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Mapping microscopic viscosity using molecular rotors Mapping microscopic viscosity using molecular rotors Marina K. Kuimova Department of Chemistry, Imperial College London, Exhibition Road, London, SW7 2AZ, UK e-mail: Viscosity is one of the main factors which influence diffusion in condensed media. In a cell viscosity can play a role in several diffusion mediated processes, such as drug delivery, signalling and mass transport. Previously, alterations in viscosity in cells and organs have been linked to malfunction; however, mapping viscosity on a single-cell scale remains a challenge. We have imaged viscosity inside lipid mono- and bi-layers, in cells and in atmospheric aerosol particles using fluorescent probes, called molecular rotors [1]. In molecular rotors the speed of rotation about a sterically hindered bond is viscosity-dependent [1]. This approach enabled us to demonstrate that viscosity distribution in a cell is highly heterogeneous and that the local microviscosity in hydrophobic cell domains can be up to 100 times higher than that of water [2-5]. These conclusions have been confirmed by monitoring the decay and reaction rates of short-lived excited state of molecular oxygen, singlet oxygen, on a single cell level [3]. We also determine particle viscosity of complex, atmospherically relevant organic aerosols and monitor its temporal changes in real time, over time scales relevant for the atmosphere. References [1] M. K. Kuimova, Phys Chem Chem Phys, 2012, 14, 12671 [2] M. K. Kuimova, G. Yahioglu, J. A. Levitt, K. Suhling, J. Amer. Chem. Soc., 2008, 130, 6672 [3] M. K. Kuimova, S. W. Botchway, A. W. Parker, M. Balaz, H. A. Collins, H. L. Anderson, K. Suhling, P. R. Ogilby, Nature Chem., 2009, 1, 69-73 [4] N. A. Hosny, G. Mohamedi, P. Rademeyer, J. Owen, Y. Wu, M-X. Tang, R. J. Eckersley, E. Stride and M. K. Kuimova, Proc. Nat. Acad. Sci. USA, 2013, 110, 9225–9230 [5] I. Lopez-Duarte, T. T. Vu, M. A. Izquierdo, J. A. Bull, M. K. Kuimova. Chem. Commun., 2014, DOI: 10.1039/C3CC47530A