ONLINE - A water window on membrane biochemistry & physics: from water to neurons
CIC nanoGUNE Seminars
- Speaker
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Sylvie Roke, École Polytechnique Fédérale de Lausanne (EPFL)
- When
-
2021/04/12
13:00 - Place
- nanoGUNE online webinar
- Add to calendar
-
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**A water window on membrane biochemistry & physics: from water to neurons **
S. Roke*
Laboratory for fundamental BioPhotonics (LBP), Institute of Bio-engineering
(IBI), and Institute of Materials Science (IMX), School of Engineering (STI),
and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique
Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland,
*[sylvie.roke@epfl.ch ](mailto:sylvie.roke@epfl.ch)
**Abstract:** Lipid cell membranes are essential for life: They are a dynamic
compartmentalized environment, a localized space for proteins to perform their
functions, and select what enters the cell. Although recognized as an
essential building block, water is usually treated as a background for
biology. However, water is a crucial mediator of chemical change and
determines the structure of the membrane. The study of lipid membranes is
generally pursued by following either a top-down approach, introducing labels
to living cell membranes or a bottom-up approach with well-controlled but
over-simplified membrane monolayer or supported membrane models. In the first
approach molecular level hydration information is lost, while in the second
approach the connection with real bilayer membranes is limited.
Recent work in our laboratory offers an alternative path that ultimately
envisions bringing together both top-down and bottom-up approaches. By using
intermediate nano-, micro- and macroscale free-floating membrane systems in
combination with novel nonlinear optical spectroscopy and imaging methods, we
advance the understanding of realistic membranes on a more fundamental level,
yet allowing for the complexity of living systems [1]. In this presentation I
will first introduce high throughput wide-field second harmonic imaging, which
enables the label-free imaging of interfacial (< 1 nm thick) water [2], with a
spatial resolution of ~370 nm and using ~100 ms acquisition times per image.
We obtain information about the orientational order of water and use this
interfacial response to create spatiotemporal membrane potential maps of free
standing lipid membranes in solution [3]. These maps are then used to quantify
divalent – membrane interactions, which show surprisingly heterogeneous
behavior that deviates from predictions by mean field. Finally, I will show
how water in operating ion channels can be SH imaged and understood [4], and
how this can be used to directly visualize neuronal activity in brain cells
[5].
**References **
[1] - Chemistry of Lipid Membranes from Models to Living Systems: A
Perspective of Hydration, Surface Potential, Curvature, Confinement and
Heterogeneity, Halil I. Okur, Orly B. Tarun, S. Roke, J. Am. Chem. Soc.,
(2019), 141, 31, 12168.
[2] - Optical Imaging of Surface Chemistry and Dynamics in Confinement, C.
Macias-Romero, I. Nahalka, H. I. Okur, S. Roke, Science (2017) 357, 784.
[3] - A label-free and charge-sensitive dynamic imaging of lipid membrane
hydration on millisecond time scales, O. Tarun, C. Hannesschläger, P. Pohl,
and S. Roke, Proc. Nat. Acad. Sci. USA (2018) 115, 4081.
[4] - Transient domains of ordered water induced by divalent ions lead to
lipid membrane curvature fluctuations, O.B. Tarun, H.I. Okur, P. Rangamani, S.
Roke, Commun. Chem. (2020) 3 (1), 1-8.
[5] - Spatiotemporal Imaging of Water in Operating Voltage-Gated ion Channels
Reveals the Slow Motion of Interfacial Ions, O. B. Tarun, M. Y. Eremchev, A.
Radenovic, and S. Roke, Nano Lett. (2019), 19, 7608.
[6] - Membrane water for probing neuronal membrane potentials and ionic fluxes
at the single cell level, M. Didier, O. Tarun, P. Jourdain, P. Magistretti, S.
Roke, Nat. Commun. (2018), 9, 5287
**Host:** A. Bittner
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ONLINE nanoGUNE: Sylvie Roke; École Polytechnique Fédérale de Lausanne
(EPFL) \- CIC nanoGUNE
When: Apr 12, 2020 11:00 AM
**Register in advance for this meeting:**