Microscopy Imaging of Membrane Domains in Model and Cellular Systems

Seminar by Dr. Luis Bagatolli, Dept. of Biochemistry and Molecular Biology, University of Southern Denmark.

Abstract

Biological membranes are sheet like structures mainly composed of lipids and proteins. These structures are only two (lipid) molecules thick (thickness ~ 60 Å (6 nm) to 100 Å (10 nm) depending on the particular membrane). Such membranes typically define enclosed spaces or compartments in which cells may maintain a chemical or biochemical environment that differs from the outside. All the communication from the inside to the outside of the cell obviously may cross the membranes. Our main research interest is to study the lateral distribution and dynamics of particular molecules (particularly lipids and proteins) in different artificial lipid membrane’s model systems (liposomes and supported bilayers) and particular biological membranes (such as skin stratum corneum lipid membranes and pulmonary surfactant membranes). These last parameters are very important to understand general aspects of membrane function. For example it is well known that changes in the lateral structure of membranes (by changing composition, temperature, pH or ionic strength) may induce changes in the mechanical properties of the membrane that in turn may affect the biochemical/biological response of the membrane. The main techniques we use in these studies are based in Fluorescence spectroscopy/microscopy (including confocal fluorescence microscopy, multiphoton excitation fluorescence microscopy and second harmonic generation microscopy). Fluorescence spectroscopy measure the light emitted by particular molecules (fluorescent molecules or probes). In some cases the emitted light (fluorescence) is sensitive to the molecular environment of the probe. In the case of fluorescence microscopy an additional spatial correlation is obtained (fluorescence image). 

References

1) J. Brewer, J. Bernardino de la Serna , K. Wagner and L.A. Bagatolli. “Multiphoton excitation fluorescence microscopy in planar membrane systems”, 2010, Biochim. Biophys. Acta. 1798(7):1301- 1308.

2) L.A. Bagatolli, J.H. Ipsen, A.C. Simonsen and O.G. Mouritsen “An outlook on organization of lipids in membranes: Searching for a realistic connection with the organization of biological membranes”, 2010 Prog. Lipid Res.

3) M. Fidorra, A. Garcia, J. Ipsen, S. Hartel and L.A. Bagatolli “Lipid domains in giant unilamellar vesicles and their correspondence with equilibrium thermodynamic phases: A quantitative fluorescence microscopy imaging approach”, 2009 Biochim. Biophys. Acta 1788(10):2142- 2149.

4) U. Bernchou, J. R. Brewer, H. S. Midtiby, J. H. Ipsen, L. A. Bagatolli and A. C. Simonsen, “Texture of lipid bilayer domains” 2009, Journal of the American Chemical Society 131(40):14130-143