Issue 36, 2013

Molecular rheometry: direct determination of viscosity in Lo and Ldlipid phases via fluorescence lifetime imaging

Abstract

Understanding of cellular regulatory pathways that involve lipid membranes requires the detailed knowledge of their physical state and structure. However, mapping the viscosity and diffusion in the membranes of complex composition is currently a non-trivial technical challenge. We report fluorescence lifetime spectroscopy and imaging (FLIM) of a meso-substituted BODIPY molecular rotor localised in the leaflet of model membranes of various lipid compositions. We prepare large and giant unilamellar vesicles (LUVs and GUVs) containing phosphatidylcholine (PC) lipids and demonstrate that recording the fluorescence lifetime of the rotor allows us to directly detect the viscosity of the membrane leaflet and to monitor the influence of cholesterol on membrane viscosity in binary and ternary lipid mixtures. In phase-separated 1,2-dioleoyl-sn-glycero-3-phosphocholine-cholesterol–sphingomyelin GUVs we visualise individual liquid ordered (Lo) and liquid disordered (Ld) domains using FLIM and assign specific microscopic viscosities to each domain. Our study showcases the power of FLIM with molecular rotors to image microviscosity of heterogeneous microenvironments in complex biological systems, including membrane-localised lipid rafts.

Graphical abstract: Molecular rheometry: direct determination of viscosity in Lo and Ld lipid phases via fluorescence lifetime imaging

Supplementary files

Article information

Article type
Paper
Submitted
08 May 2013
Accepted
09 Jul 2013
First published
09 Jul 2013
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2013,15, 14986-14993

Molecular rheometry: direct determination of viscosity in Lo and Ld lipid phases via fluorescence lifetime imaging

Y. Wu, M. Štefl, A. Olzyńska, M. Hof, G. Yahioglu, P. Yip, D. R. Casey, O. Ces, J. Humpolíčková and M. K. Kuimova, Phys. Chem. Chem. Phys., 2013, 15, 14986 DOI: 10.1039/C3CP51953H

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