
NSF Org: |
CMMI Division of Civil, Mechanical, and Manufacturing Innovation |
Recipient: |
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Initial Amendment Date: | August 30, 2017 |
Latest Amendment Date: | August 30, 2017 |
Award Number: | 1748049 |
Award Instrument: | Standard Grant |
Program Manager: |
Laurel Kuxhaus
CMMI Division of Civil, Mechanical, and Manufacturing Innovation ENG Directorate for Engineering |
Start Date: | June 1, 2017 |
End Date: | August 31, 2020 (Estimated) |
Total Intended Award Amount: | $223,994.00 |
Total Awarded Amount to Date: | $223,994.00 |
Funds Obligated to Date: |
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History of Investigator: |
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Recipient Sponsored Research Office: |
633 CLARK ST EVANSTON IL US 60208-0001 (312)503-7955 |
Sponsor Congressional District: |
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Primary Place of Performance: |
1801 Maple Ave Evanston IL US 60201-3149 |
Primary Place of
Performance Congressional District: |
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Unique Entity Identifier (UEI): |
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Parent UEI: |
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NSF Program(s): | BMMB-Biomech & Mechanobiology |
Primary Program Source: |
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Program Reference Code(s): |
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Program Element Code(s): |
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Award Agency Code: | 4900 |
Fund Agency Code: | 4900 |
Assistance Listing Number(s): | 47.041 |
ABSTRACT
The cells of mammals, birds and reptiles have as their outer edge a thin layer, a cell membrane, that is composed of fatty molecules (lipids). The inside of the cell has a different concentration of charged molecules from the outside of the cell, resulting in an electric field across the membrane that changes its mechanical properties. The mechanical properties of the cell membrane have a profound effect upon how the cell functions. The research will determine by experiment how the mechanical properties of a cell membrane change as the result of exposure to electrical fields. The results of the experiments will be modeled using the engineering methods of 'shell theory' which can model the effects of the curvature of a thin material on its mechanical properties.
An electric potential difference across the plasma membrane is common to all living cells and is essential to physiological functions such as generation of action potentials for cell-to-cell communication. While the basics of cell electrical activity are well established (e.g. the Hodgkin-Huxley model of the action potential), the coupling between voltage and membrane deformation has received limited attention. To fill this void, a combined theoretical and experimental study of biomimetic membranes in externally applied electric fields will be studied. Specifically, the research seeks to determine the relation between membrane voltage, membrane properties such as bending rigidity, tension, and spontaneous curvature, and membrane shape. The project integrates theory and experiment to analyze both the small thermally-driven bilayer undulations and the large buckling-like deformations in an applied electric field. The transformative impact of the project lies in its pioneering research of the dynamic coupling between shape and voltage of biomembranes; our findings will uncover new physics relevant to a broad range of physiological processes involving excitable cells.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Cells and internal cellular organelles are enveloped by membranes composed primarily of lipid bilayers. Many cell biological functions involve membrane structural and morphological changes. These processes depend strongly on the mechanical properties of the lipid bilayer. A key characteristic that has been extensively studied is the bending rigidity, which quantifies the energy needed to change the membrane curvature. In neutral (charge-free) membranes, the bending rigidity is related to the energy cost for compression and expansion of the inner and outer lipid monolayers in the bent bilayer. Biological membranes contain charged lipids, e.g., the fraction of phosphatidylglycerol in bacteria Staphylococcus aureus and Caulobacter crescentus can be as high as 80%. Moreover, an electric potential difference exists across plasma membrane in living systems. Modulation of the transmembrane electric field is often associated with membrane deformation, e.g, electromotility of outer hair cells. External electric fields can have more dramatic effects, e.g, directing neuron growth or causing membrane poration. An important question arises: how do surface charge and transmembranepotential affect the bending rigidity, as well as other membrane properties such as tension and viscosity, of bilayer membranes?
The project funded by this award developed novel experimental methods to answer this question. In the case of membranes containing charged lipids, we were able for the first time to quantify the membrane stiffening in the full range of membrane compositions – from neutral to 100% charged – as well as at different salt concentrations. Our work provides solid foundation for future studies of membrane electromechanics.
The project trained two PhD students in experimental and theoretical membrane biomechanics and fostered interdisciplinary collaborations between applied mathematicians and biophysicists. The project also involved international collaboration thereby training the graduate students as globally-engaged scientists. The research resulted in five publications in peer-reviewed journals. The results were broadly disseminated by numerous presentations at conferences and invited talks.
Last Modified: 10/13/2020
Modified by: Petia Vlahovska
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