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Lipid Bilayer Mechanics in a Pipette with Glass-Bilayer Adhesion

Ursell, Tristan and Agrawal, Ashutosh and Phillips, Rob (2011) Lipid Bilayer Mechanics in a Pipette with Glass-Bilayer Adhesion. Biophysical Journal, 101 (8). pp. 1913-1920. ISSN 0006-3495.

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Electrophysiology is a central tool for measuring how different driving forces (e.g., ligand concentration, transmembrane voltage, or lateral tension) cause a channel protein to gate. Upon formation of the high resistance seal between a lipid bilayer and a glass pipette, the so-called “giga-seal”, channel activity can be recorded electrically. In this article, we explore the implications of giga-seal formation on the mechanical state of a lipid bilayer patch. We use a mechanical model for the free energy of bilayer geometry in the presence of glass-bilayer adhesion to draw three potentially important conclusions. First, we use our adhesion model to derive an explicit relationship between applied pressure and patch shape that is consistent with the Laplace-Young Law, giving an alternative method of calculating patch tension under pressure. With knowledge of the adhesion constant, which we find to be in the range ~0.4–4 mN/m, and the pipette size, one can precisely calculate the patch tension as a function of pressure, without the difficultly of obtaining an optical measurement of the bilayer radius of curvature. Second, we use data from previous electrophysiological experiments to show that over a wide range of lipids, the resting tension on a electrophysiological patch is highly variable and can be 10–100 times higher than estimates of the tension in a typical cell membrane. This suggests that electrophysiological experiments may be systematically altering channel-gating characteristics and querying the channels under conditions that are not the same as their physiological counterparts. Third, we show that reversible adhesion leads to a predictable change in the population response of gating channels in a bilayer patch.

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Additional Information:© 2011 by the Biophysical Society. Published by Elsevier Inc. Received 11 March 2011; Accepted 30 August 2011. Editor: Reinhard Lipowsky. Available online 12 October 2011. We thank Paul Blount for kindly providing us with the bilayer shape data. The authors thank Rod MacKinnon and Daniel Schmidt for stimulating discussion and critical reading of the early manuscript, as well as helpful comments from an anonymous reviewer. We are grateful for the following funding sources: T.U. for the Genentech Bio-X Postdoctoral Fellowship, and T.U., A.A., and R.P. for the National Institutes of Health Director’s Pioneer Award, the Howard Hughes Medical Institute Collaborative Innovation Award, and National Institutes of Health Award R01 GM084211.
Funding AgencyGrant Number
Genentech Bio-X Postdoctoral FellowshipUNSPECIFIED
NIH Director’s Pioneer AwardUNSPECIFIED
Howard Hughes Medical Institute (HHMI) Collaborative Innovation AwardUNSPECIFIED
NIHR01 GM084211
Issue or Number:8
Record Number:CaltechAUTHORS:20111111-151109702
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Official Citation:Tristan Ursell, Ashutosh Agrawal, Rob Phillips, Lipid Bilayer Mechanics in a Pipette with Glass-Bilayer Adhesion, Biophysical Journal, Volume 101, Issue 8, 19 October 2011, Pages 1913-1920, ISSN 0006-3495, 10.1016/j.bpj.2011.08.057.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:27758
Deposited By: Tony Diaz
Deposited On:12 Nov 2011 00:23
Last Modified:03 Oct 2019 03:26

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